JP2011046829A - Manufacturing method for aromatic copolymerized polyester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To economically manufacture an aromatic copolymerized polyester excellent in transparency, color tone and clarity and with suppressed variation of quality. <P>SOLUTION: The method continuously manufactures the aromatic copolymerized polyester containing terephthalic acid as a main dicarboxylic acid component and containing ethylene glycol and neopentyl glycol as main glycolic acid components. In the method a slurry containing terephthalic acid, ethylene glycol and neopentyl glycol is prepared in a slurry preparation tank, and the slurry is continuously fed to an esterification reaction tank. An esterification reaction is performed using a plurality of esterification reaction tanks connected to each other in series, and subsequently, a polycondensation reaction is performed in a polycondensation reaction tank. A germanium compound is added during the time from the slurry preparation tank to the first esterification reaction tank, and a cobalt compound is added during the time from the last esterification reaction tank to the polycondensation reaction tank. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a continuous process for producing an aromatic copolymer polyester having excellent transparency and color tone and high clarity.

  Polyesters typified by polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), etc. are excellent in mechanical properties and chemical properties. Depending on the respective properties, for example, for clothing and industrial materials It is used in a wide range of fields, such as textile fibers, packaging, magnetic tape, optical films and sheets, hollow molded bottles, casings for electrical and electronic parts, and other engineering plastic molded articles.

  In recent years, due to the diversification of the market, copolymer polyesters using neopentyl glycol as a glycol component have attracted attention (for example, see Patent Documents 1 and 2). Such copolyesters are characterized by being amorphous and having a high glass transition point, and are more excellent in moldability and transparency than homopolyesters, and their use in the various fields described above is expanding.

  In Patent Document 1, a specific amount of an antimony compound, a germanium compound, a cobalt compound, and a phosphorus compound is included. In Patent Document 2, a specific amount of a titanium compound, a germanium compound, a cobalt compound, and a phosphorus compound is included. However, it is disclosed that the color tone of the copolyester can be improved, but with the expansion of the market, for example, in the field of containers that require a high-class feeling such as cosmetic containers and optical molded articles, etc. There is a demand for transparency, and there is an increasing demand for further improvements in color tone and clarity.

JP 2004-123984 A JP 2004-137292 A

  The inventor of the present invention has been invented in view of the above-described state of the art, and has a method for continuously producing an aromatic copolyester having excellent transparency, color tone, clarity, and suppressed quality fluctuation. The purpose is to provide.

The present invention has finally been completed as a result of diligent research to achieve the above object.
That is, the present invention has the following configurations (1) to (5).
(1) A method for continuously producing an aromatic copolyester having terephthalic acid as a main dicarboxylic acid component and ethylene glycol and neopentyl glycol as a main glycolic acid component, comprising terephthalic acid, ethylene glycol, and A slurry containing neopentyl glycol is prepared in a slurry preparation tank, the slurry is continuously supplied to the esterification reaction tank, and an esterification reaction is performed using a plurality of serially connected esterification reaction tanks. In the method of performing the polycondensation reaction in the condensation reaction tank, the germanium compound is added between the slurry preparation tank and the first esterification reaction tank, and the cobalt compound is added between the last esterification reaction tank and the polycondensation reaction tank. The polyester oligomer cal at the outlet of the first esterification reactor The xyl end group concentration is 1000 to 4000 eq / ton, the hydroxyl end group concentration is 1000 to 5000 eq / ton, and the carboxyl end group concentration of the polyester oligomer where the cobalt compound is added is 100 to 650 eq / ton. And having a hydroxyl end group concentration of 1000 to 3000 eq / ton.
(2) The addition amount of the germanium compound and the cobalt compound is such that the residual amount of germanium atoms in the resulting aromatic copolymer polyester is 20 to 100 ppm and the residual amount of cobalt atoms is 3 to 30 ppm. The method according to (1), wherein
(3) The method according to (1) or (2), wherein a phosphorus compound is added from the slurry preparation tank to the polycondensation reaction tank.
(4) The method according to (3), wherein the addition amount of the phosphorus compound is such that the residual amount of phosphorus atoms in the resulting aromatic copolymer polyester is 15 to 50 ppm.
(5) The method according to any one of (1) to (4), wherein a glycol component containing neopentyl glycol is additionally supplied from the esterification reaction tank before the polycondensation reaction tank.

  The method for producing an aromatic copolymer polyester of the present invention is an economically excellent method for producing an aromatic copolymer polyester having high transparency, color tone and clarity, and high homogeneity with suppressed variation in quality. It can be manufactured stably. Therefore, the aromatic copolyester obtained by the production method of the present invention is a molded product having severe requirements for transparency, color tone and clarity, for example, a container required for a high-class feeling such as a cosmetic container, and an optical molding. It can be suitably used as a raw material for the body.

The aromatic copolymer polyester of the present invention will be described in detail below.
The dicarboxylic acid component in the aromatic copolyester of the present invention (hereinafter sometimes simply referred to as copolyester) comprises terephthalic acid as the main constituent. The ratio of the terephthalic acid component to the total dicarboxylic acid component is preferably 70 mol% or more, more preferably 85 mol% or more, particularly preferably 95 mol% or more, and most preferably 100 mol%.

  Examples of other dicarboxylic acid components that can be used with terephthalic acid include (1) aromatic dicarboxylic acids such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4′-dicarboxylic acid, and diphenoxyethanedicarboxylic acid. (2) Aliphatic dicarboxylic acids such as adipic acid, sebacic acid, succinic acid and glutaric acid, and (3) alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid.

  The copolymerized polyester of the present invention may further be copolymerized with an acid component other than the dicarboxylic acid component, and examples of the acid component include oxyacids such as p-oxybenzoic acid and oxycaproic acid. . In the present invention, the dicarboxylic acid component and the acid component other than the dicarboxylic acid component also include ester-forming derivatives such as alkyl esters having about 1 to 4 carbon atoms in the raw material stage before polymerization.

  The glycol component in the copolymerized polyester of the present invention is mainly composed of ethylene glycol (EG) and neopentyl glycol (NPG). The ratio of the total amount of EG and NPG to the total glycol component is preferably 70 mol% or more, more preferably 85 mol% or more, particularly preferably 95 mol% or more, and most preferably 100 mol%. It is preferable that the ratio of EG is 60 to 99 mol% and the ratio of NPG is 1 to 40 mol% with respect to all glycol components. When the proportion of NPG is less than 1 mol%, the degree of crystallinity of the polyester increases and transparency tends to deteriorate. For this reason, the haze value when formed into a molded product tends to increase. On the other hand, when the ratio of NPG exceeds 40 mol%, the degree of polymerization is difficult to increase, and it takes a long time to reach a predetermined intrinsic viscosity. Therefore, the color tone tends to deteriorate due to the heat history during that time. Moreover, when there is too much quantity of NPG, a predetermined intrinsic viscosity may not be reached. The lower limit of the ratio of EG is more preferably 65 mol%, particularly preferably 68 mol%. On the other hand, the upper limit of the ratio of EG is more preferably 95 mol%, particularly preferably 90 mol%.

  Further, the lower limit value of the ratio of NPG to the total glycol component is preferably 5 mol%, more preferably 10 mol%. On the other hand, the upper limit of the ratio of NPG is preferably 35 mol%, and more preferably 32 mol%.

  The copolyester of the present invention preferably has all glycol components composed of EG and NPG. However, it does not impair the transparency and color tone of the present invention, and imparts other functions or properties to the polyester. In order to improve the above, other glycol components other than EG and NPG may be used up to 30 mol% based on the total glycol components.

  Other glycol components include (1) aliphatic glycols such as trimethylene glycol, tetramethylene glycol, 1,4-cyclohexanedimethanol, pentamethylene glycol, hexamethylene glycol, and (2) 1,3-cyclohexanedimethyl. Examples include alicyclic glycols such as methanol, and (3) aromatic glycols such as p-xylylene glycol and m-xylylene glycol. Of these, 1,4-cyclohexanedimethanol is preferred. In addition, these glycol components may be used alone or in combination of two or more at an arbitrary ratio.

  In the production of the copolymerized polyester of the present invention, a germanium compound is added as a polycondensation catalyst. Examples of germanium compounds suitable as the polycondensation catalyst include crystalline germanium dioxide, amorphous germanium dioxide, germanium tetraethoxide, germanium tetra n-butoxide, and the like. Among these, crystalline germanium dioxide and amorphous germanium dioxide are preferred, and amorphous germanium dioxide is particularly preferred.

  The addition amount of the germanium compound is appropriately determined so that the content of germanium atoms in the copolyester is 20 to 100 ppm. The content of germanium atoms is preferably 30 to 80 ppm, and more preferably 40 to 60 ppm. If the content of germanium atoms is less than the above range, the polycondensation activity is insufficient and the productivity of polycondensation is lowered, which is not preferable. On the other hand, if it exceeds the above range, the clarity and color tone of the aromatic polyester obtained is deteriorated and it is disadvantageous economically, which is not preferable. It is necessary to determine the addition amount of the germanium compound in consideration of the fact that about 40% of the addition amount is removed from the system in a reduced pressure environment at the time of copolymerization polyester polymerization depending on the polymerization apparatus and polymerization conditions. Therefore, it is necessary to carry out several trial experiments and determine the addition amount. The actual amount of germanium compound added is 30 to 170 ppm, preferably 50 to 140 ppm, based on germanium atoms.

  When other polycondensation catalysts such as antimony compounds and titanium compounds are used in combination as in Patent Documents 1 and 2, for example, when antimony compounds are used in combination, transparency and clarity are deteriorated, and when titanium compounds are used in combination, the color tone is deteriorated. This is not preferable.

  Further, when the copolymerized polyester of the present invention is produced, a cobalt compound is added as a polycondensation catalyst and for improving the color tone. The cobalt compound has the effect of reducing the color b value. Examples of the cobalt compound include cobalt acetate, cobalt chloride, cobalt benzoate, and cobalt chromate. Of these, cobalt acetate is preferred.

  The addition amount of the cobalt compound is selected so that the content of cobalt atoms in the copolyester is 3 to 30 ppm. The content of cobalt atoms is preferably 5 to 25 ppm, and more preferably 5 to 20 ppm. If the content of cobalt atoms is less than the above range, the color tone improving effect is lowered, which is not preferable. On the other hand, if the above range is exceeded, the reduction of cobalt metal may cause the copolyester to darken or become bluish, the color L value may be less than 50, or the color b value may be less than −2, Product value is reduced. The cobalt compound remains in the copolyester without removing almost 100% of the addition amount from the system even under a reduced pressure environment during the copolyester polymerization. Therefore, the actual addition amount of the cobalt compound is 3 to 30 ppm, preferably 5 to 25 ppm, based on the cobalt atom.

  Further, when the copolymerized polyester of the present invention is produced, a phosphorus compound is added as a stabilizer and for improving the clarity. Examples of the phosphorus compound include phosphoric acid, phosphorous acid, phosphonic acid, and derivatives thereof. Preferred examples include phosphoric acid, trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, monomethyl phosphate, dimethyl phosphate, monobutyl phosphate, dibutyl phosphate, phosphorous acid, phosphorous acid Examples include trimethyl, tributyl phosphite, methylphosphonic acid, dimethyl methylphosphonate, dimethyl ethylphosphonate, dimethyl phenylphosphonate, diethyl phenylphosphonate, and diphenyl phosphonate. Among these, trimethyl phosphate, triethyl phosphate and phosphoric acid are particularly preferable.

  The phosphorus compound is presumed to act as follows from the viewpoint of improving the color tone of the copolyester of the present invention.

  Oxygen acid having phosphorus as a central element has a tetrahedral structure in which four total of OH and H are coordinated around the phosphorus atom. When orthophosphoric acid is condensed, condensed phosphoric acid such as polyphosphoric acid and metaphosphoric acid is produced. These condensed phosphoric acids have the property of being easily coordinated to metal ions. Therefore, if a phosphorus compound and free metal ions (in the present invention, ions such as germanium and cobalt) are present in the polyester polymerization reaction system, the phosphorus compound reacts preferentially with the metal ions.

  By reacting the germanium compound with the phosphorus compound at a specific molar ratio, the germanium compound is stabilized, and the color b value can be reduced while maintaining the catalytic activity. At this time, if an excessive amount of the phosphorus compound is present, it may react with the germanium compound to form an insoluble compound in the copolymer polyester, thereby reducing the clarity of the copolymer polyester.

  Further, the reaction between the phosphorus compound and the cobalt compound can increase the bluing effect on the copolyester by the cobalt compound, and the color b value can be reduced. At this time, if the phosphorus compound is present in excess, the heat resistance of the polyester itself deteriorates, and the color b value increases. On the other hand, when the amount of the phosphorus compound is small, it does not react with the cobalt compound, so that the effect of imparting blue to the polyester is reduced. In addition, since the free germanium compound increases, the color b value increases.

  The addition amount of the phosphorus compound is appropriately selected so that the phosphorus atom content in the copolyester is 15 to 50 ppm. The phosphorus atom content is preferably 20 to 40 ppm. If the phosphorus atom content exceeds the above range, it is not preferable because the polycondensation activity may be lowered or an insoluble compound in the copolyester may be formed. On the other hand, if it is less than the above range, the color tone improving effect is lowered, which is not preferable. It is necessary to determine the addition amount of the phosphorus compound in consideration of the fact that about 30% of the addition amount is removed from the system in a reduced pressure environment at the time of copolymerization polyester polymerization depending on the polymerization apparatus and polymerization conditions. Therefore, it is necessary to carry out several trial experiments and determine the addition amount. The actual addition amount of the phosphorus compound is 20 to 70 ppm, preferably 25 to 60 ppm, based on the phosphorus atom.

  The copolymer polyester of the present invention has an absorbance of 0.004 or less when a solution obtained by dissolving 5 g of the copolymer polyester in 50 g of a mixed solvent of phenol / tetrachloroethane (mass ratio 60:40) is measured at a wavelength of 657 nm and an optical path length of 10 mm. It is preferable that The absorbance is more preferably 0.0035 or less, and further preferably 0.003 or less. The lower limit is most preferably 0, but is preferably 0.001 in terms of cost performance.

  Thus, a highly transparent molded object can be obtained stably by making light absorbency low. For example, in Patent Documents 1 and 2, the haze value of a stepped molded plate is described as a measure of the transparency of the molded body of the copolyester disclosed in these documents. The mold temperature is evaluated at 20 ° C. However, copolymer polyesters obtained by the methods of these documents may not always provide a molded article with high transparency. As a result of intensive studies on the cause, the present inventors have found that the temperature variation of the mold and the transparency of the molded product are caused by fine particles insoluble in the polyester present in the copolyester. In other words, by reducing the amount of fine particles insoluble in the copolyester that are present in the copolyester in minute amounts, the mold temperature fluctuates and is stable and transparent even when the temperature becomes higher than the set value. It has been found that a molded article with high properties can be obtained.

  Therefore, it is preferable that the amount of germanium atoms and cobalt atoms insoluble in the copolymerized polyester determined by the following method is 3 ppm or less and 5 ppm or less, respectively.

[Method for quantification of germanium atom and cobalt atom insoluble in copolymer polyester]
30 g of sample copolymer polyester pellets and 300 ml of a mixed solution of parachlorophenol / tetrachloroethane (3/1: weight ratio) were put into a round bottom flask equipped with a stirrer, and the pellet was stirred at 100 to 105 ° C. for 2 hours. Dissolve. The solution was allowed to cool to room temperature, and a polytetrafluoroethylene membrane filter (Advantec PTFE membrane filter, product name: T100A047A) having a diameter of 47 mm / pore size of 1.0 μm was used, and the total amount was under a pressure of 0.15 MPa. Use to filter out foreign objects. The effective filtration diameter is 37.5 mm. After completion of the filtration, the product is subsequently washed with 300 ml of chloroform, and then dried under reduced pressure at 30 ° C. for a whole day and night. The amount of germanium atoms and cobalt atoms is quantified on the filtration surface of the membrane filter with a scanning X-ray fluorescence analyzer (manufactured by RIGAKU, ZSX100e, Rh tube 4.0 kW). The quantification is performed on a portion having a diameter of 30 mm at the center of the membrane filter. The calibration curve of the fluorescent X-ray analysis method is obtained using a polyethylene terephthalate resin with known amounts of germanium atoms and cobalt atoms, and the apparent amounts of germanium atoms and cobalt atoms are displayed in ppm. The measurement is carried out by measuring Al-Kα ray intensity under the conditions of PHA (wave height analyzer) 100-300, using pentaerythritol as a spectral crystal, PC (proportional counter) as a detector, with an X-ray output of 50 kV-70 mA. . The contents of germanium atoms and cobalt atoms in the polyethylene terephthalate resin for the calibration curve are quantified by the method described later.

  More preferably, the amount of insoluble germanium atoms is 2 ppm or less, and the amount of cobalt atoms is 4 ppm or less. The amount of these metal atoms is a measure of the amount of insoluble components of these metal compounds relative to the copolyester. Therefore, when this amount exceeds the above range, the clarity of the copolyester is lowered, which leads to deterioration of the transparency and appearance of the molded article. Further, in the production process of the copolyester, the polymer filter used for increasing the clarity of the copolyester is clogged, and the life of the filter is shortened.

  The copolymer polyester of the present invention preferably has a color L value of 58% or more and a color b value of 0 ± 1. It is preferable that this characteristic and the above-described absorbance characteristic are simultaneously satisfied.

  The color L value is more preferably 59% or more, and further preferably 60% or more. The color L value is a measure of the lightness of the copolyester. If the color L value is less than the above value, dullness occurs in the molded article and the clear feeling is lowered, which is not preferable. For example, when a conventionally known antimony compound is used as a polycondensation catalyst, precipitation of antimony metal occurs due to reduction of the antimony compound in the polycondensation step, resulting in a low color L value and dullness.

  On the other hand, the color b value is more preferably 0 ± 0.8. The color b value is a measure of the blueness and yellowness of the copolyester. If the b value increases on the positive side, the yellowishness increases. Conversely, if the b value increases on the negative side, the blueness increases. For example, when a titanium compound is used as the polycondensation catalyst, deterioration of the copolymerized polyester increases and the b value increases. Further, by adding appropriate amounts of the cobalt compound and the phosphorus compound, an increase in the b value caused by the deterioration of the copolymerized polyester can be suppressed by bluing. When the compounding quantity of a cobalt compound and a phosphorus compound becomes excessive, b value will fall too much and blue will become strong. Therefore, a colorless and transparent molded article can be obtained by setting the L value and the b value in the above ranges. For example, in a conventionally known production method in which a titanium compound is used as a polycondensation catalyst and bluished with a cobalt compound and a phosphorus compound, the blending amount of the cobalt compound and the phosphorus compound is increased because the yellowness of the copolyester is increased. It is necessary to increase, and if the blending amount is increased, the L value decreases, so that both characteristics cannot be satisfied.

  The copolyester of the present invention preferably has an intrinsic viscosity (IV) of 0.60 to 1.2 dl / g. The lower limit of the intrinsic viscosity is more preferably 0.65 dl / g, and particularly preferably 0.70 dl / g. If the intrinsic viscosity is less than the above range, the mechanical properties of the molded product tend to deteriorate.

  On the other hand, the upper limit of the intrinsic viscosity is more preferably 1.1 dl / g, and particularly preferably 1.05 dl / g. If the intrinsic viscosity exceeds the above range, the resin temperature tends to be high when melted by a molding machine or the like, and thermal decomposition tends to be severe. Problems such as yellow coloring are likely to occur.

  When the copolymerized polyester of the present invention is molded into a stepped molded plate, the haze value at a thickness of 5 mm of the stepped molded plate when molded at a mold temperature of 40 ° C. is 5% or less, preferably 3% or less. Preferably it is 2% or less, Most preferably, it is 1.5% or less. When the haze value exceeds the above range, the transparency of the molded product is deteriorated, and there are cases where it cannot be used in applications where the requirement for transparency is severe.

  In the present invention, the above-described copolymer polyester is produced by a continuous polycondensation method. The continuous polycondensation method is advantageous in terms of quality uniformity and economy compared to the batch method.

  Specifically, a slurry containing terephthalic acid, ethylene glycol, and neopentyl glycol is prepared in a slurry preparation tank, and the slurry is continuously supplied to the esterification reaction tank, and a plurality of the esterification reaction tanks connected in series. An aromatic copolymer polyester is continuously produced by carrying out an esterification reaction using, followed by a polycondensation reaction in a polycondensation reaction tank. By performing the esterification reaction step using a multistage apparatus in which a plurality of esterification reaction vessels are connected in series, the effects of the present invention can be efficiently and stably expressed.

  In the production method of the present invention, the germanium compound is added between the slurry adjustment tank and the first esterification reaction tank, and the cobalt compound is added between the last esterification reaction tank and the polycondensation reaction tank. By such an addition method, it is possible to reduce the amount of germanium atoms and cobalt atoms that are insoluble in the copolyester evaluated by the above-described method. Since germanium atoms and cobalt atoms insoluble in the copolyester are coarse particles having a maximum diameter of 2 μm or more, the amount of germanium atoms or cobalt atoms insoluble in the copolyester is reduced to clarify the copolymer polyester obtained. The degree is increased. In addition, if the amount of germanium atoms and cobalt atoms insoluble in the copolymerized polyester increases, clogging of the filter for filtering oligomers and polymers installed in the copolymerized polyester production process increases, so germanium insoluble in the copolymerized polyester. By reducing the amount of the compound and the cobalt compound, it is possible to suppress an increase in pressure due to clogging of these filters, and it is possible to extend the filter life.

  Moreover, in the manufacturing method of this invention, the carboxyl terminal group density | concentration of the polyester oligomer of the first esterification reaction tank exit is 1000-4000 eq / ton, and the hydroxyl terminal group density | concentration is 1000-5000 eq / ton. Preferably, the carboxyl end group concentration is 1200 to 3500 eq / ton, the hydroxyl end group concentration is 1200 to 4800 eq / ton, more preferably the carboxyl end group concentration is 1400 to 3000 eq / ton, and the hydroxyl end group concentration Is 1400-4600 eq / ton. As a result, even if a germanium compound is added to the first esterification reaction vessel, the amount of germanium atoms insoluble in the copolymerized polyester can be reduced, and production can be stabilized over a long period of time. When the carboxyl end group concentration is less than the above range, it is not preferable to add the germanium compound to the first esterification reaction tank because the amount of germanium atoms insoluble in the copolymerized polyester increases. Moreover, since esterification reaction time increases and it leads to the increase in the byproduct amount of diethylene glycol, it is not preferable. Furthermore, it leads to a decrease in polycondensation activity and increases the polycondensation time, which is not preferable. Conversely, when the above range is exceeded, piping clogging such as transfer lines due to oligomers may occur, which is not preferable. When the hydroxy end group concentration is less than the above range, the germanium compound used as a catalyst is not completely dissolved in the oligomer system and becomes a foreign substance, causing a decrease in transparency as a polymer. On the contrary, when the hydroxy terminal group concentration of the oligomer exceeds the above range, it is necessary to add an excessive amount of glycol, resulting in poor productivity.

  When the germanium compound is added to the slurry preparation tank, there is no restriction on the lower limit of the carboxyl end group concentration with respect to the increase in the amount of germanium atoms insoluble in the copolyester, but the above range is in view of stabilization of production. It is preferable to carry out.

  Moreover, in the manufacturing method of this invention, the carboxyl terminal group density | concentration of the polyester oligomer of the location which adds a cobalt compound is 100-650 eq / ton, and a hydroxyl terminal group density | concentration is 1000-3000 eq / ton. Preferably, the carboxyl end group concentration is 150 to 600 eq / ton, the hydroxyl end group concentration is 1200 to 2800 eq / ton, more preferably the carboxyl end group concentration is 200 to 550 eq / ton, and the hydroxyl end group concentration Is 1400-2600 eq / ton. When the carboxyl end group exceeds the above range, the amount of cobalt atoms insoluble in the copolymer polyester is increased, and the clarity of the copolymer polyester is deteriorated. On the other hand, when the amount is less than the above range, the esterification reaction time increases, leading to an increase in the amount of by-produced diethylene glycol, which is not preferable. Moreover, since it leads to the fall of polycondensation activity and polycondensation time increases, it is not preferable. When the hydroxyl end group concentration is less than the above range, the germanium compound used as a catalyst is not completely dissolved in the oligomer system and becomes a foreign substance, resulting in a decrease in transparency as a polymer. When the hydroxyl end group concentration exceeds the above range, the glycol component in the oligomer is large, the polymerization time becomes long, and the productivity is inferior, such as causing bumping in the vacuum process in the polycondensation.

  In the production method of the present invention, it is preferable to add the phosphorus compound between the slurry preparation tank and the polycondensation reaction tank. Thereby, the effect by addition of the phosphorus compound mentioned above is expressed. Although the addition time of a phosphorus compound is not limited, It is preferable to add after adding a germanium compound. Thereby, the direct reaction of a germanium compound and a phosphorus compound is suppressed.

  By doing so, the amount of germanium compound and cobalt compound insoluble in the copolymer polyester can be reduced, and the reason why the clarity of the copolymer polyester is increased is not clear, but the copolymer polyester oligomer end group, It seems that the reaction between the cobalt compound, the germanium compound, and the phosphorus compound is changed to suppress the formation of coarse particles made of the germanium compound and the cobalt compound that are insoluble in the copolyester.

An example of the production method of the present invention is shown below.
A slurry of a mixed glycol composed of 1.02 to 3.0 mol, preferably 1.5 to 2.5 mol of EG and NPG is prepared per mol of terephthalic acid, and this is continuously used in the esterification reaction step. To supply. The esterification reaction is carried out using a multistage apparatus in which a plurality of esterification reaction tanks are connected in series while removing water generated by the reaction from the system using a rectification column. The temperature of the esterification reaction is 240 to 290 ° C, preferably 245 to 280 ° C, and the pressure is normal pressure to 290 KPa, preferably 20 to 190 KPa. Ultimately, it is desirable that the esterification reaction rate reaches 90% or more, preferably 93% or more. The pressure is a gauge pressure.

  After the esterification reaction, it is transferred to a polycondensation reaction tank to carry out polycondensation. The number of reaction tanks in the polycondensation step is not limited, but generally a three-stage system of initial polycondensation, intermediate polycondensation and late polycondensation is adopted. As for the polycondensation reaction conditions, the reaction temperature of the first stage polycondensation is 250 to 290 ° C., preferably 260 to 280 ° C., and the pressure is 10 to 2.7 KPa, preferably 2.7 to 0.27 KPa. The temperature of the final stage polycondensation reaction is 265 to 300 ° C, preferably 275 to 295 ° C, and the pressure is 1.3 to 0.13 KPa, preferably 0.65 to 0.065 KPa. When carried out in three or more stages, the reaction conditions for the intermediate stage polycondensation reaction are conditions between the reaction conditions for the first stage and the reaction conditions for the last stage. The degree of increase in intrinsic viscosity achieved in each of these polycondensation reaction steps is preferably distributed smoothly.

  In the production method of the present invention, NPG is preferably added to the reaction system in two or more portions. In the production method disclosed in the above-mentioned patent document, the entire amount of NPG is supplied in the slurry preparation. However, when it is carried out by this method, in the case of continuous production over a long period, There has been a problem that the fluctuation of the NPG content of the product becomes large. The present inventors have examined such problems and found that the fluctuation can be suppressed by adding a part of EG and NPG separately after the second esterification reaction tank. The number of divisions, the division addition ratio, and the addition location are not limited, but it is preferable to add 2 to 10% by mass of the total amount to the second esterification reaction tank. 4-8 mass% is more preferable. Thereby, it is guessed that the fluctuation | variation of the distillation rate to the outside of the system of NPG after a 2nd esterification reaction tank is suppressed.

  In the production method of the present invention, in the esterification reaction step, the esterification reaction tank temperature at which NPG is dividedly supplied after the second esterification reaction tank is set to 5 to 5 from the esterification reaction temperature of the previous reaction tank. It is preferable to lower by 15 ° C. Thereby, foaming of the esterification reaction product in the esterification reaction tank that supplies NPG in a divided manner is suppressed, and a stable operation is possible for a long period of time. Usually, when the esterification reaction is carried out in a plurality of reaction vessels, it is carried out by increasing the temperature in the reaction vessel according to the progress of the reaction. In this case, the inside of the esterification reaction vessel is divided by NPG supply. Foaming increases and polyester oligomers are scattered in the piping to the distillation column and the distillation column installed in the reaction tank, and the operation cannot be performed.

  In the production method of the present invention, it is preferable to increase the clarity by filtering the oligomer or polymer through a filter in the production process of the copolyester. The opening, structure, capacity, installation location, etc. of the filter are not particularly limited.

  In the production method of the present invention, the novel NPG is preferably supplied to the polyester production process after being filtered through a filter having an average pore diameter of 20 μm or less as a molten solution or a mixed solution with ethylene glycol. Since NPG is solid at room temperature, it is usually packaged and distributed in paper bags. When handled with solid NPG, there is a problem that foreign matters are mixed in and the clarity of the resulting copolymer polyester is lowered. However, the filter suppresses the contamination of foreign matters and improves the clarity of the copolymer polyester. The average pore diameter of the filter is more preferably 15 μm or less, and further preferably 10 μm or less. The lower limit of the average pore diameter is about 1 μm from the viewpoint of the degree of clarity and the operability of filtration. The form and capacity of the filter are not limited. What is necessary is just to select suitably in consideration of the clarity, operativity, etc. of copolyester. The installation location is not limited. What is necessary is just to install in the arbitrary places between the supply tank of NPG and the manufacturing apparatus of copolyester.

  In the above filtration, molten NPG may be directly filtered, or may be filtered as a mixed solution of ethylene glycol mixed with novel ethylene glycol or recovered glycol. In the present invention, the latter implementation is preferred.

  Handling NPG in a molten state leads to an improvement in the measurement accuracy of NPG supply. The melting of NPG may be performed by installing a melting tank in the production facility for copolymerized polyester, or NPG may be purchased in a molten state.

  In the present invention, the above intrinsic viscosity may be obtained directly by the melt polycondensation method described above, or an intrinsic viscosity lower than the target intrinsic viscosity may be obtained by the melt polycondensation method. You may raise to the target intrinsic viscosity legally. You may mix | blend additives, such as various antioxidant and a lubrication agent, with the copolyester of this invention.

  As described above, the copolyester obtained by the production method of the present invention is highly excellent in transparency, color tone and clarity, and has high homogeneity. Therefore, the copolyester is extruded or injection molded. The obtained molded article has good color tone, excellent transparency and clarity, and can be suitably used as a molded article for containers and optical members that require a high-class feeling such as a cosmetic container.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, these Examples illustrate this invention and are not limited. The properties of the copolyester were measured according to the following method.

1. Intrinsic viscosity (IV)
0.1 g of copolymer polyester sample was precisely weighed, dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane = 3/2 (mass ratio), and measured at 30 ° C. using an Ostwald viscometer.

2. Oligomer carboxyl end group concentration The oligomer was pulverized by a handy mill (pulverizer) without exhibiting drying. A sample of 1.00 g was precisely weighed and 20 ml of pyridine was added. Several grains of zeolite were added and dissolved by boiling for 15 minutes. Immediately after boiling and refluxing, 10 ml of pure water was added and allowed to cool to room temperature. Titration with N / 10-NaOH was performed using phenolphthalein as an indicator. Do the same for the blank without the sample. When the oligomer did not dissolve in pyridine, the reaction was carried out in benzyl alcohol. AVo (eq / ton) is calculated according to the following equation.
AVo = (A−B) × 0.1 × f × 1000 / W
(A = drop constant (ml), B = blank drop constant (ml), f = factor N / 10-NaOH, W = weight of sample (g))

3. Oligomer hydroxyl end group concentration The oligomer was pulverized by a handy mill (pulverizer) without exhibiting drying. 0.5 g of the sample was precisely weighed and added to a mixed solution of 1.02 g of acetic anhydride and 10 ml of pyridine, and reacted at 95 ° C. for 1.5 hours. Distilled water (10 ml) was added to the reaction product and allowed to cool at room temperature. Subsequently, it was titrated with an N / 10 sodium hydroxide solution (solution: water / methanol = 5/95 (volume ratio)) using phenolphthalein as an indicator. In addition, the oligomer hydroxyl value was calculated | required from following Formula.
OHV (eq / ton) = ((BA) × f) / (Wg × 10 ³ ) × 10 ⁶
(A = drop constant (ml), B = blank drop constant (ml), f = factor N / 10-NaOH, W = weight of sample (g))

4). Composition ratio of copolymerized polyester Approximately 5 mg of copolymerized polyester sample was dissolved in 0.7 ml of a mixed solution of deuterated chloroform and trifluoroacetic acid (volume ratio 9/1) and ¹ H-NMR (manufactured by varian, UNITY50) was used. Asked.

5). Absorbance of copolymerized polyester solution The absorbance of a solution obtained by dissolving 5 g of a copolymerized polyester sample in 50 g of a mixed solvent of phenol / tetrachloroethane (mass ratio 60:40) at a wavelength of 657 nm and an optical path length of 10 mm was determined.

6). Color tone The color of the copolymerized polyester chip was measured using a color meter (manufactured by Nippon Denshoku Co., Ltd., Model 1001DP) to determine the color L value and the color b value. The polyester chip size was measured for 2.0 to 3.5 mmΦ × 2.5 to 3.5 mm.

7). Using a haze value injection molding machine (M-150C-DM, manufactured by Meiki Seisakusho), the copolymerized polyester is melted at 280 ° C., and a stepped molding plate having a thickness of 2 to 11 mm is molded at a mold temperature of 40 ° C. And the haze value (%) was measured for the site | part of thickness 5mm with the haze meter (Nippon Denshoku make, Model NDH2000).

8). Elemental analysis Elemental analysis was carried out by the following method.

(A) Analysis of Sb 1 g of a sample was wet-decomposed with a mixed solution of sulfuric acid / hydrogen peroxide solution. Next, sodium nitrite was added to make Sb atoms Sb ^5+, and brilliant green was added to form a blue complex with Sb. After extracting this complex with toluene, the absorbance at a wavelength of 625 nm was measured using an absorptiometer (manufactured by Shimadzu Corporation, UV-150-02), and colorimetric determination of Sb was performed.

(B) Analysis of Ge 2 g of sample was incinerated and decomposed with a platinum crucible, and further 5 ml of a 10% by mass sodium hydrogen carbonate solution was added and evaporated, and then hydrochloric acid was added and evaporated to dryness. The temperature was raised from 400 ° C. to 950 ° C. in an electric furnace and left for 30 minutes to melt the residue. The melt was dissolved by heating in 10 ml of water and transferred to a germanium distillation apparatus. The inside of the platinum crucible was washed twice with 7.5 ml of ion exchange water, and this washing solution was also transferred to a germanium distillation apparatus. Next, 35 ml of hydrochloric acid was added and distilled to obtain 25 ml of a distillate. An appropriate amount was taken from the distillate, and hydrochloric acid was added so that the final concentration was 1.0 to 1.5 mol / L. Further, 2.5 ml of a 0.25 mass% polyvinyl alcohol solution and 5 ml of a 0.04 mass% phenylfluorene (2,3,7-trihydroxy-9-phenyl-6-fluorene) solution were added, and ion-exchanged water was added. To 25 ml. The produced yellow complex with Ge was measured for absorbance at a wavelength of 505 nm with an absorptiometer (manufactured by Shimadzu Corporation, UV-150-02), and colorimetric determination of Ge was performed.

(C) Co analysis 1 g of a sample was incinerated and decomposed with a platinum crucible, and 6 mol / L hydrochloric acid was added to evaporate to dryness. This was dissolved in 1.2 mol / L hydrochloric acid, and the luminescence intensity was measured using an ICP emission spectrometer (ICPS-2000, manufactured by Shimadzu Corporation). Co in the sample was quantified from a calibration curve prepared in advance.

(D) Analysis of P Phosphorus can be obtained by dry ash decomposition of 1 g of sample in the presence of sodium carbonate, or by wet decomposition with a mixed solution of sulfuric acid / nitric acid / perchloric acid or a mixed solution of sulfuric acid / hydrogen peroxide. The compound was orthophosphoric acid. Next, the molybdate is reacted in a 1 mol / L sulfuric acid solution to form phosphomolybdic acid, and this is reduced with hydrazine sulfate. The heteropoly blue produced is absorbed by an absorptiometer (manufactured by Shimadzu Corporation, UV-150-02). Absorbance at a wavelength of 830 nm was measured, and colorimetric determination of P was performed.

(E) Analysis of Ti 1 g of a sample was incinerated and decomposed with a platinum crucible, and sulfuric acid and potassium hydrogen sulfate were added and heated and melted. This melt was dissolved in 2 mol / L sulfuric acid, hydrogen peroxide solution was added, and the absorbance at a wavelength of 420 nm was measured with an absorptiometer (manufactured by Shimadzu Corporation, UV-150-02). From a calibration curve prepared in advance, Ti in the sample was colorimetrically determined.

9. Quantitative determination method for germanium atom and cobalt atom insoluble in copolymer polyester 30 g of sample copolymer polyester pellets and 300 ml of parachlorophenol / tetrachloroethane (3/1: weight ratio) mixed solution were put into a round bottom flask with a stirrer, and the pellets Is stirred and dissolved in the mixed solution at 100 to 105 ° C. for 2 hours. The solution was allowed to cool to room temperature, and a polytetrafluoroethylene membrane filter (Advantec PTFE membrane filter, product name: T100A047A) having a diameter of 47 mm / pore size of 1.0 μm was used, and the total amount was under a pressure of 0.15 MPa. Use to filter out foreign objects. The effective filtration diameter was 37.5 mm. After completion of the filtration, the product is subsequently washed with 300 ml of chloroform, and then dried under reduced pressure at 30 ° C. for a whole day and night. The amount of germanium atoms and cobalt atoms on the filtration surface of the membrane filter was quantified with a scanning X-ray fluorescence analyzer (RIGAKU, ZSX100e, Rh tube 4.0 kW). The quantification was performed on a portion having a diameter of 30 mm at the center of the membrane filter. The calibration curve of the X-ray fluorescence analysis was determined using a polyethylene terephthalate resin with known amounts of germanium atoms and cobalt atoms, and the apparent amounts of germanium atoms and cobalt atoms were expressed in ppm. The measurement was carried out by measuring the intensity of Al-Kα rays under the conditions of PHA (wave height analyzer) 100-300 using X-ray output 50 kV-70 mA and using pentaerythritol as a spectroscopic crystal and PC (proportional counter) as a detector. . The contents of germanium atoms and cobalt atoms in the polyethylene terephthalate resin for the calibration curve were quantified by the above method.

10. The number of coarse particles in the copolyester The filtration surface of the membrane filter after filtration obtained by the method for determining germanium atoms and cobalt atoms insoluble in the copolyester was filtered with a scanning electron microscope at a magnification of 1000 times. The total number of coarse foreign matters having a maximum diameter of 2 μm or more was counted.

Example 1
(1) Slurry preparation To a slurry preparation tank, terephthalic acid / ethylene glycol / neopentyl glycol / water is continuously supplied at a mass ratio of 1.00 / 0.53 / 0.31 / 0.025 while stirring. A glycol slurry of terephthalic acid was prepared. Neopentyl glycol is melted in a neopentyl glycol melting tank, and ethylene glycol and water mixed in a mixing tank so as to have the above composition are filtered through a filter having an average pore diameter of 5 μm, and then a slurry is prepared. It was supplied to the tank. Furthermore, the crystalline germanium dioxide was continuously supplied to the slurry preparation tank as a 0.8 g / L aqueous solution so that the residual germanium atomic weight was 50 ppm with respect to the produced copolymerized polyester.

(2) Esterification Reaction As the esterification reaction apparatus, a continuous esterification reaction apparatus composed of a three-stage complete mixing tank having a stirrer, a distillation tower, a raw material charging port and a product outlet was used. Along with 1651 kg / hour of the terephthalic acid glycol slurry prepared in (1) above, the slurry was supplied to the first esterification reaction tank, and the esterification reaction was carried out at an absolute pressure of 122 kpa, a temperature of 258 ° C., and an average residence time of 6 hours.

  The reaction solution was taken out so that the liquid level in the first esterification reaction tank was constant, and charged into the second esterification reaction tank. A glycol mixture of ethylene glycol / neopentyl glycol = 75/25 (mass ratio) is charged at 50 kg / hour from another inlet of the second esterification reaction tank, absolute pressure 122 kpa, temperature 247 ° C., average residence time 1 The esterification reaction was carried out in 5 hours. The carboxyl end group concentration and hydroxy end group concentration of the oligomer at the outlet of the first esterification reaction tank were 1950 eq / ton and 2500 eq / ton on average, respectively.

  The reaction solution was taken out so that the liquid level in the second esterification reaction tank was constant, and charged into the third esterification reaction tank. From another supply port, triethyl phosphate was made into a 65 g / L ethylene glycol solution and continuously supplied to the third ester reaction tank so that the amount of residual phosphorus atoms was 30 ppm with respect to the resulting copolymerized polyester. The esterification reaction was carried out at normal pressure, a temperature of 253 ° C., and an average residence time of 1.0 hour. The carboxyl end group concentration and hydroxy end group concentration of the third esterification reaction vessel outlet oligomer were 340 eq / ton and 1700 eq / ton on average, respectively.

  Cobalt acetate dihydrate as a 50 g / L ethylene glycol solution in an in-line mixer provided in the transfer line from the third esterification reaction tank to the first polycondensation reaction tank. It supplied continuously so that it might be set to 10 ppm.

(3) Polycondensation reaction The reaction liquid is taken out so that the liquid level in the third esterification reaction tank becomes constant, and is put into the first polycondensation reaction tank, pressure 5.3 kpa, temperature 261 ° C., average residence time. The first polycondensation reaction was performed in 1.5 hours.

  The reaction solution was taken out so that the liquid level in the first polycondensation reaction tank was constant, and charged into the second polycondensation reaction tank. The second polycondensation reaction was performed at a pressure of 0.45 kpa, a temperature of 272 ° C., and an average residence time of 1.2 hours.

  The reaction solution was taken out so that the liquid level of the second polycondensation reaction product was constant, and charged into the third polycondensation reaction tank. The degree of vacuum (pressure) was adjusted so that the average intrinsic viscosity of the reaction product was 0.74 at a temperature of 272 ° C. and an average residence time of 1.2 hours. The pressure ranged from 0.06 to 0.15 kpa.

  The copolymerized polyester was taken out in a strand shape so that the liquid level in the third polycondensation reaction was constant, the copolymerized polyester was cooled with water and solidified, and pelletized with a strand cutter. A filter having an average pore diameter of 20 μm was installed at the outlet of the third polycondensation reaction tank, and the copolymerized polyester was filtered.

  Cobalt acetate dihydrate as a 50 g / L ethylene glycol solution in an in-line mixer provided in the transfer line from the third esterification reaction tank to the first polycondensation reaction tank. It supplied continuously so that it might be set to 10 ppm.

  The composition of the obtained copolyester is, on average, terephthalic residue // ethylene glycol residue / neopentyl glycol residue / diethylene glycol residue (byproduct) = 100 // 69/30/1 (molar ratio) Met. Table 1 shows the characteristic values of the obtained copolyester.

The copolymer polyester obtained in this example has a low absorbance of the copolymer polyester solution,
The haze value of the stepped molded plate was small. Also, the color tone was good. Furthermore, since the amount of germanium and cobalt atoms insoluble in the copolyester was low, the amount of coarse foreign matter was small and the clarity was high. In addition, the average value of the copolyester characteristics when continuously operated for 10 days is 30 mol%, and the variation range of the neopentyl glycol content when measured every 12 hours is ± 2 mol%, and the quality variation is small. The homogeneity was high.

  The copolymerized polyester obtained in this example was extruded or injection molded to obtain a molded body. The obtained molded product has good color tone, excellent transparency and clarity, is of high quality, and is suitably used as a molded product for containers and optical members that require a high-class feeling such as cosmetic containers. I was able to.

Examples 2-5
In Example 1, the carboxyl end group concentration and the hydroxyl end group concentration of the oligomer at the first esterification reaction vessel outlet / cobalt addition site were adjusted to the values shown in Table 1 by adjusting the raw material input ratio and reaction conditions. Except for the above, a copolyester was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1. The copolyesters obtained in Examples 2 to 5 and the molded articles obtained using the same were good as in Example 1.

Examples 6-11
In Example 1, a copolymerized polyester was obtained in the same manner as in Example 1 except that the germanium content, cobalt content, and phosphorus content were changed to the amounts shown in Table 1, respectively. The evaluation results are shown in Table 1. The copolyesters obtained in Examples 6 to 11 and the molded articles obtained using the same were good as in Example 1.

Examples 12-14
In Example 1, a copolymerized polyester was obtained in the same manner as in Example 1, except that the addition location of the germanium compound, cobalt compound, and phosphorus compound was changed. The evaluation results are shown in Table 1. The copolyesters obtained in Examples 12 to 14 and the molded articles obtained using the same were good as in Example 1.

Example 15
In Example 1, a copolymer polyester was obtained in the same manner as in Example 1 except that the glycol mixture composed of ethylene glycol / neopentyl glycol was not supplied to the second esterification reaction tank. The evaluation results are shown in Table 1. The obtained copolyester has the same quality as the copolyester obtained in Example 1 in terms of color tone, absorbance of the copolyester solution, and stepped molded plate haze value, and is high quality. The average value of the copolyester characteristics when operated continuously for the day was the same, but the variation range of the neopentyl glycol content when measured every 12 hours was ± 4 mol%, and the method of Example 1 The fluctuation range became wider than.

Comparative Examples 1 and 2
In Example 1, it carried out like Example 1 except having changed the addition place of a germanium compound and a cobalt compound, respectively. The evaluation results are shown in Table 2. The copolyesters obtained in Comparative Examples 1 and 2 and the molded articles obtained using them were inferior to those of the Examples.

Comparative Examples 3-10
In Example 1, the carboxyl end group concentration and the hydroxyl end group concentration of the oligomer at the first esterification reaction vessel outlet / cobalt addition site were adjusted to the values shown in Table 2 by adjusting the raw material charging ratio and reaction conditions. Except for this, the same procedure as in Example 1 was performed. The evaluation results are shown in Table 2. The copolyesters obtained in Comparative Examples 3 to 10 and the molded articles obtained using the same were inferior to those of Examples.

  By the production method of the present invention, it is possible to stably produce a highly homogenous aromatic copolyester having excellent transparency, color tone and clarity, and with suppressed variation in quality by a highly economical method. it can. Therefore, the aromatic copolyester obtained by the production method of the present invention is a molded product having severe requirements for transparency, color tone and clarity, for example, a container required for a high-class feeling such as a cosmetic container, and an optical molding. It can be suitably used as a raw material for the body.

Claims (5)

  A method for continuously producing an aromatic copolyester having terephthalic acid as a main dicarboxylic acid component and ethylene glycol and neopentyl glycol as a main glycolic acid component, comprising terephthalic acid, ethylene glycol, and neopentyl glycol The slurry is prepared in a slurry preparation tank, the slurry is continuously supplied to the esterification reaction tank, the esterification reaction is performed using a plurality of serially connected esterification reaction tanks, and then the polycondensation reaction tank In the method of carrying out the polycondensation reaction, a germanium compound is added between the slurry preparation tank and the first esterification reaction tank, and a cobalt compound is added between the last esterification reaction tank and the polycondensation reaction tank. , Polyester oligomer carboxy at the outlet of the first esterification reactor The end group concentration is 1000 to 4000 eq / ton, the hydroxyl end group concentration is 1000 to 5000 eq / ton, and the carboxyl end group concentration of the polyester oligomer where the cobalt compound is added is 100 to 650 eq / ton. And the hydroxyl end group concentration is 1000 to 3000 eq / ton.   The addition amount of the germanium compound and the cobalt compound is such that the remaining amount of germanium atoms in the obtained aromatic copolymer polyester is 20 to 100 ppm and the remaining amount of cobalt atoms is 3 to 30 ppm. The method according to claim 1.   The method according to claim 1 or 2, wherein the phosphorus compound is added from the slurry preparation tank to the polycondensation reaction tank.   The method according to claim 3, wherein the amount of the phosphorus compound added is such that the residual amount of phosphorus atoms in the aromatic copolymer polyester obtained is 15 to 50 ppm.   The method according to any one of claims 1 to 4, wherein a glycol component containing neopentyl glycol is additionally supplied from the esterification reaction tank before the polycondensation reaction tank.