JP2008095078A - Method for manufacturing polyester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a polyester that controls the thermal decomposition reaction of the polyester due to a polymerization catalyst, exhibits a good polymer color tone compared to a conventional product, and shows dramatically small increase in the amount of a carboxyl terminal group as well as dramatically small decrease in the intrinsic viscosity of the polyester when melted at an elevated temperature. <P>SOLUTION: This method for manufacturing the polyester comprises the polycondensation of a dicarboxylic acid or its ester-forming derivative with a diol or its ester-forming derivative in presence of a polycondensation catalyst, furthermore comprising the addition of a 5-valency phosphorus compound in a time period between the start of the operation of applying a reduced pressure after the addition of the polycondensation catalyst and the arrival at a target degree of polymerization of the polyester. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a polyester excellent in color tone and thermal stability. More specifically, the thermal decomposition reaction caused by the catalyst used during the polymerization is suppressed, the color of the polymer is better than that of the conventional product, and the increase in the amount of carboxyl end groups and the decrease in intrinsic viscosity of the polyester when melted at high temperature. The present invention relates to a method for producing a polyester whose amount is remarkably small.

  Polyester is used for various purposes because of its useful functionality, and is used for clothing, materials, and medical use, for example. Among them, polyethylene terephthalate is excellent in terms of versatility and practicality and is preferably used.

  Polyethylene terephthalate is generally produced from terephthalic acid or its ester-forming derivative and ethylene glycol. However, in commercial processes for producing high molecular weight polymers, antimony compounds, germanium catalysts, titanium catalysts, etc. are widely used as polycondensation catalysts. It is used. These polycondensation catalysts naturally promote polycondensation reaction of polyethylene terephthalate, but also promote side reactions such as thermal decomposition reaction and oxidative decomposition reaction. In particular, in the case of using a titanium catalyst, since the catalytic activity is high, the side reaction is also greatly promoted, resulting in a problem that the polymer is colored yellow. It is not preferable that the polymer is yellowish, for example, when polyester is used as the fiber, since the commercial value of the fiber for clothing is impaired.

  In order to solve this problem, studies have been widely made to improve the color tone and heat resistance of a polymer by adding a phosphorus compound together with a polycondensation catalyst. This method suppresses the activity of the polycondensation catalyst with a phosphorus compound to improve the color tone and heat resistance of the polymer. For example, in a method for producing a polyester using a titanium compound as a catalyst, a method of adding phosphoric acid or phosphorous acid as a phosphorus compound (Patent Document 1), and a method of adding a phosphonic acid compound as a phosphorus compound (Patent Document 2) In addition, a method for adding a phosphinic acid compound, a phosphine oxide compound, a phosphonous acid compound, a phosphinic acid compound, and a phosphine compound as a phosphorus compound is disclosed (Patent Document 3). However, when these methods are used, certain effects can be seen in suppressing side reactions. However, when a certain amount or more of a phosphorus compound is added, the polymerization activity of the polycondensation catalyst is excessively suppressed, and the target degree of polymerization is reached. It did not reach or the polymerization reaction time was delayed, resulting in a problem that the color tone of the polymer deteriorated.

  On the other hand, there is a method of limiting the molar ratio (Ti / P) of the titanium compound and the phosphorus compound to a certain range (Patent Document 4). According to this method, although the deactivation of the catalyst of the titanium compound can be prevented, it is not possible to obtain a color tone or heat resistant polyester exceeding a certain level.

  In order to solve this problem, a method of adding a phosphorus compound after completion of the polycondensation reaction has been proposed. For example, a method of adding a phosphorus compound after completion of the polycondensation reaction is disclosed (Patent Document 5). Certainly, if this method is used, deactivation of the polycondensation catalyst by the phosphorus compound can be prevented, but since the phosphorus compound is mixed into the molten polyester reaction system after the polycondensation reaction is completed, the side reaction in the polycondensation reaction is It cannot be suppressed, and deterioration of the polymer in the mixing process is inevitable. In addition, there is a method of adding a phosphorus compound to the melted polyester after the polycondensation under reduced pressure conditions (Patent Document 6), but even in this method, the side reaction in the polycondensation reaction cannot be suppressed, Further, since phosphorus is added under reduced pressure conditions, there is a problem that the phosphorus compound is scattered and not added to the polyester.

Therefore, in the present invention, as a result of diligent studies to solve the above problems, a pentavalent phosphorus compound was added after the addition of the catalyst until the polyester reached the target degree of polymerization after the depressurization of the polymerization reactor was started. It has been found that the object of the present invention can be achieved by a polyester production method characterized by addition.
JP-A-6-100680 (Claims) JP 2004-217855 A (Claims) JP 2004-292657 A (Claims) Japanese Patent Laid-Open No. 2000-256542 (Claims) JP 2004-359907 A (Claims) JP-A-48-79896 (Claims)

  The object of the present invention is to eliminate the above-mentioned conventional problems, that is, to suppress the thermal decomposition reaction caused by the catalyst used at the time of polymerization, the polymer color tone is better than the conventional product, and the carboxyl end group of the polyester at the time of high-temperature melting An object of the present invention is to provide a method for producing polyester in which the amount of increase and the amount of decrease in intrinsic viscosity are remarkably small.

  The object of the present invention is to add a polycondensation catalyst in a process for producing a polyester obtained by polycondensation reaction of a dicarboxylic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof in the presence of a polycondensation catalyst. This can be achieved by a method for producing a polyester characterized in that a pentavalent phosphorus compound is added after the inside of the polymerization reactor is depressurized until the polyester reaches a target degree of polymerization.

  According to the present invention, a pentavalent phosphorus compound is added between the start of pressure reduction in a polymerization reactor after addition of a polycondensation catalyst and the time until the polyester reaches a target degree of polymerization. The polyester obtained by the production method has better polymer color tone than the polyester obtained by the conventional production method, and the increase amount of the carboxyl end group amount and the decrease amount of the intrinsic viscosity of the polyester are drastically reduced. be able to. The polyester obtained by this production method can solve problems such as deterioration in color tone and physical properties in the production process of molded articles for fibers, films and bottles.

  The polyester production method of the present invention is obtained by esterifying or transesterifying a dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative to obtain a low polymer, and then adding a polycondensation catalyst and reducing the pressure. Polyester is obtained by polycondensation under conditions. Specific examples of the polyester obtained by such a method include polyethylene terephthalate, polytrimethylene terephthalate, polytetramethylene terephthalate, polycyclohexylene dimethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, polyethylene. -1,2-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate and the like. The present invention is suitable for polyethylene terephthalate or polyester copolymers mainly containing ethylene terephthalate units, which are most commonly used.

  In the method for producing a polyester of the present invention, after adding a polycondensation catalyst, the pressure in the reactor is reduced and the polycondensation reaction is started until the polyester reaches the target degree of polymerization. It is essential to add. By adding a phosphorus compound in this way, the deactivation of the polycondensation catalyst can be extremely effectively suppressed, and the increase in the color tone and the increase in the carboxyl end groups and the decrease in the intrinsic viscosity of the polyester when melted at a high temperature are dramatically increased. Small polyester can be obtained. Coloring of polyester and deterioration of heat resistance are caused by a side reaction of polyester as clearly shown in a saturated polyester resin handbook (Nikkan Kogyo Shimbun, first edition, P.178-198). In the side reaction of this polyester, carbonyl oxygen is activated by a metal catalyst, and β hydrogen is extracted, thereby generating a vinyl end group component and an aldehyde component. By forming a polyene by this vinyl end group, the polymer is colored yellow, and since an aldehyde component is generated, the main chain ester bond is cleaved, so that the polymer has poor heat resistance. When this main chain ester bond is cleaved, the molecular weight of the polyester is lowered, so that the intrinsic viscosity is lowered, and the terminal of the polyester molecule is replaced with the diol terminal and the carboxyl terminal is increased. In particular, when a titanium compound is used as a polymerization catalyst, the side reaction due to heat is very strongly activated, so that many vinyl end group components and aldehyde components are generated, resulting in a yellow colored polymer having poor heat resistance. The phosphorus compound plays a role of regulating the activity of the polycondensation catalyst by appropriately interacting with the polycondensation catalyst. However, in the conventional method in which the phosphorus compound is added before the start of the polycondensation reaction, it is inevitable to reduce the polycondensation activity as well as the side reaction activity of the polycondensation catalyst. However, according to the present invention, it is possible to keep only the side reaction activity extremely small while sufficiently maintaining the polymerization activity of the polycondensation catalyst. As a result of intensive studies by the present inventors, it was noted that the side reaction of the polyester occurred in the late stage of polycondensation compared to the early stage of polycondensation, and by adding the phosphorus compound after starting the polycondensation reaction, The present inventors have found that a side reaction occurring in the latter stage of polycondensation can be specifically suppressed while maintaining the polycondensation activity. This cannot be achieved by a conventional phosphorus compound or a method of adding a phosphorus compound, for example, a method of adding a phosphorus compound after the polymerization reaction of the polyester is substantially completed.

  Polyester is usually produced by adding a polycondensation catalyst to dicarboxylic acid or its ester-forming derivative and diol or its ester-forming derivative, and then proceeding the polycondensation reaction by reducing the pressure in the reactor. . Polyesters are required to have various degrees of polymerization depending on the application and purpose. Therefore, when the desired degree of polymerization is reached, the polycondensation reaction is stopped by setting the inside of the reactor to normal pressure or pressure, and the polyester is discharged outside the reactor. In the present invention, it is essential to add a pentavalent phosphorus compound between the time when the pressure inside the reactor is reduced and the polycondensation reaction is started until the polyester reaches the target degree of polymerization.

  The phosphorus compound of the present invention may be added at any time during the period from the start of the polycondensation reaction by reducing the pressure in the reactor until the polymerization is substantially completed. It is preferable to add it at a time when the viscosity is 40 to 99% of the intended intrinsic viscosity because side reactions can be suppressed with very little deactivation of the polycondensation catalyst. Preferably it is between 50 and 98%, and particularly preferably between 75 and 98%. The intrinsic viscosity of the polyester at the time when the phosphorus compound is added may be calculated by directly sampling and measuring the viscosity by the method described later, or may be calculated from the torque load applied to the stirring blade of the reactor.

  The phosphorus compound of the present invention may be added in several divided portions, or may be continuously added with a feeder or the like. When a phosphorus compound is added, the phosphorus compound may be added alone, or may be added in a state dissolved or dispersed in a diol component such as ethylene glycol, or a master pellet containing phosphorus at a high concentration. It may be added. However, when a diol component such as ethylene glycol is brought in a large amount and added, polyester depolymerization (polyester main chain cleavage reaction) proceeds, so it is preferable to add a phosphorus compound alone.

  The phosphorus compound of the present invention can be dissolved or melted in a polymerization system, and is preferably added in a container made of a polymer having substantially the same component as the polymer obtained in the present invention. When the phosphorus compound is added to the container as described above and added, the addition of the polymerization reactor under the reduced pressure condition may cause the phosphorus compound to scatter and prevent the phosphorus compound from flowing out to the reduced pressure line. In addition, a desired amount of phosphorus compound can be added to the polymer. The container referred to in the present invention is not limited as long as it contains phosphorus compounds, and includes, for example, an injection-molded container having a lid or a stopper, or a sheet or film formed into a bag shape by sealing or sewing. More preferably, the container described above creates an air vent. When a phosphorus compound is added to a container that has been vented, even if it is added to the polymerization reactor under vacuum conditions, the container bursts due to air expansion and the phosphorus compound flows out to the decompression line, or the upper part of the polymerization reactor. The phosphorus compound can be added to the polymer in a desired amount without adhering to the wall surface. If the container is too thick, it takes longer to dissolve and melt, so it is better to make the container thinner. However, the container should be thick enough not to rupture when the phosphorus compound is sealed or added. For this purpose, a material having a thickness of 10 to 500 μm and uniform thickness is preferable.

  In addition, the phosphorus compound of the present invention may be added alone or as described above, but when mixed with a low polymer of a polyester having an intrinsic viscosity of 0.4 or less and then added to the polyester, scattering of the phosphorus compound can be further prevented. So desirable. In the case of melt mixing, it is more preferable in terms of preventing scattering and uniform addition of the phosphorus compound.

  In the present invention, the phosphorus compound added between the time when the polycondensation reactor is decompressed and the polycondensation reaction is started until the polyester reaches the target degree of polymerization must be a pentavalent phosphorus compound. It is. The pentavalent phosphorus compound means a phosphate compound, a phosphonate compound, a phosphinate compound, or a phosphine oxide compound. These pentavalent phosphorus compounds particularly suppress the side reaction of the polyester by coordinating with the polycondensation catalyst to suppress the catalytic activity.

  Specifically, for example, phosphate compounds such as phosphoric acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, stearyl phosphate, methylphosphonic acid, ethylphosphonic acid, propylphosphonic acid, isopropylphosphonic acid, butylphosphonic acid , Phenylphosphonic acid, benzylphosphonic acid, tolylphosphonic acid, xylylphosphonic acid, biphenylphosphonic acid, naphthylphosphonic acid, anthrylphosphonic acid, 2-carboxyphenylphosphonic acid, 3-carboxyphenylphosphonic acid, 4-carboxyphenylphosphonic Acid, 2,3-dicarboxyphenylphosphonic acid, 2,4-dicarboxyphenylphosphonic acid, 2,5-dicarboxyphenylphosphonic acid, 2,6-dicarboxyphenylphosphonic acid, 3,4-dicarboxyphenylphosphonic acid acid 3,5-dicarboxyphenylphosphonic acid, 2,3,4-tricarboxyphenylphosphonic acid, 2,3,5-tricarboxyphenylphosphonic acid, 2,3,6-tricarboxyphenylphosphonic acid, 2,4, 5-tricarboxyphenylphosphonic acid, 2,4,6-tricarboxyphenylphosphonic acid, methylphosphonic acid dimethyl ester, methylphosphonic acid diethyl ester, ethylphosphonic acid dimethyl ester, ethylphosphonic acid diethyl ester, phenylphosphonic acid dimethyl ester, phenylphosphone Acid diethyl ester, phenylphosphonic acid diphenyl ester, benzylphosphonic acid dimethyl ester, benzylphosphonic acid diethyl ester, benzylphosphonic acid diphenyl ester, lithium (3,5-di-tert-butyl) Ethyl 4-hydroxybenzylphosphonate), sodium (ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate), magnesium bis (3,5-di-tert-butyl-4-hydroxybenzylphosphonate) ), Phosphonate compounds such as calcium bis (3,5-di-tert-butyl-4-hydroxybenzylphosphonate), diethylphosphonoacetic acid, methyl diethylphosphonoacetate and ethyl diethylphosphonoacetate, hypophosphorous acid Sodium hypophosphite, methylphosphinic acid, ethylphosphinic acid, propylphosphinic acid, isopropylphosphinic acid, butylphosphinic acid, phenylphosphinic acid, tolylphosphinic acid, xylylphosphinic acid, biphenylylphosphinic acid, diphenylphosphinic acid, dimethyl Tylphosphinic acid, diethylphosphinic acid, dipropylphosphinic acid, diisopropylphosphinic acid, dibutylphosphinic acid, ditolylphosphinic acid, dixylphosphinic acid, dibiphenylylphosphinic acid, naphthylphosphinic acid, anthrylphosphinic acid, 2-carboxyphenyl Phosphinic acid, 3-carboxyphenylphosphinic acid, 4-carboxyphenylphosphinic acid, 2,3-dicarboxyphenylphosphinic acid, 2,4-dicarboxyphenylphosphinic acid, 2,5-dicarboxyphenylphosphinic acid, 2,6 -Dicarboxyphenylphosphinic acid, 3,4-dicarboxyphenylphosphinic acid, 3,5-dicarboxyphenylphosphinic acid, 2,3,4-tricarboxyphenylphosphinic acid, 2,3,5-tricarboxy Phenylphosphinic acid, 2,3,6-tricarboxyphenylphosphinic acid, 2,4,5-tricarboxyphenylphosphinic acid, 2,4,6-tricarboxyphenylphosphinic acid, bis (2-carboxyphenyl) phosphinic acid, Bis (3-carboxyphenyl) phosphinic acid, bis (4-carboxyphenyl) phosphinic acid, bis (2,3-dicarboxylphenyl) phosphinic acid, bis (2,4-dicarboxyphenyl) phosphinic acid, bis (2 , 5-Dicarboxyphenyl) phosphinic acid, bis (2,6-dicarboxyphenyl) phosphinic acid, bis (3,4-dicarboxyphenyl) phosphinic acid, bis (3,5-dicarboxyphenyl) phosphinic acid, bis (2,3,4-tricarboxyphenyl) phosphinic acid, bis (2, , 5-tricarboxyphenyl) phosphinic acid, bis (2,3,6-tricarboxyphenyl) phosphinic acid, bis (2,4,5-tricarboxyphenyl) phosphinic acid, and bis (2,4,6-tri Carboxyphenyl) phosphinic acid, bis (4-methoxyphenyl) phosphinic acid, methylphosphinic acid methyl ester, dimethylphosphinic acid methyl ester, methylphosphinic acid ethyl ester, dimethylphosphinic acid ethyl ester, ethylphosphinic acid methyl ester, diethylphosphinic acid methyl Esters, ethyl phosphinic acid ethyl ester, diethyl phosphinic acid ethyl ester, phenyl phosphinic acid methyl ester, phenyl phosphinic acid ethyl ester, phenyl phosphinic acid phenyl ester, diphenyl phosphite Acid methyl ester, diphenylphosphinic acid ethyl ester, diphenylphosphinic acid phenyl ester, benzylphosphinic acid methyl ester, benzylphosphinic acid ethyl ester, benzylphosphinic acid phenyl ester, bisbenzylphosphinic acid methyl ester, bisbenzylphosphinic acid ethyl ester, bis Examples include phosphinate compounds such as benzylphosphinic acid phenyl ester, phosphine oxide compounds such as trimethylphosphine oxide, triethylphosphine oxide, tripropylphosphine oxide, triisopropylphosphine oxide, tributylphosphine oxide, and triphenylphosphine oxide. You may use it in combination of seed | species or 2 or more types.

  The phosphorus compound preferably has a weight average molecular weight in the range of 100 to 2,000. When the molecular weight of the phosphorus compound is within the above range, there is little scattering of the phosphorus compound upon addition under reduced pressure conditions, and the phosphorus compound is rapidly and uniformly dispersed in the polyester, so that the aggregated foreign matter derived from phosphorus Occurrence is suppressed. The weight average molecular weight is preferably 150 to 1000, more preferably 200 to 1000.

    The polyester obtained by the production method of the present invention has a phosphorus compound added between the time when the pressure in the reactor is reduced and the polycondensation reaction is started until the polyester reaches the target degree of polymerization. It is preferable to add 1 to 500 ppm in terms of phosphorus atoms because the heat resistance of the polyester can be improved. If the addition amount is less than the above range, the desired effect cannot be achieved. If the addition amount is more than the above range, the polycondensation catalyst is deactivated and the polymerization reaction is delayed, or the reaction proceeds to the target degree of polymerization. The problem that does not occur. The amount of phosphorus added is preferably 10 to 250 ppm, more preferably 20 to 150 ppm.

  In the polyester obtained by the production method of the present invention, a titanium compound, an antimony compound, a germanium compound, an aluminum compound, or the like is used as a polycondensation catalyst. These polycondensation catalysts may be used alone or in combination, or in addition, compounds such as sodium, potassium, lithium, magnesium, calcium, zinc, cobalt and manganese may be used in combination. These polycondensation catalysts are preferably added in an amount of 1 to 1000 ppm in terms of metal atoms with respect to the resulting polyester. Among these, it is preferable to use a titanium compound as a polycondensation catalyst because the effect of improving the color tone is large and the generation of foreign substances is suppressed.

  The polycondensation catalyst of the present invention is generally a reaction for synthesizing a polyester from a dicarboxylic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof, or (1) an ester that is a reaction between a dicarboxylic acid component and a diol component. (2) Transesterification reaction which is a reaction between an ester-forming derivative component of dicarboxylic acid and a diol component, (3) Polyethylene terephthalate low polymer obtained after substantially complete ester reaction or transesterification reaction Is a polycondensation reaction in which the degree of polymerization is increased by a dediol reaction, and has the effect of contributing to at least (3) reaction promotion. Therefore, titanium oxide particles generally used as inorganic particles in fiber matting agents and the like have substantially no catalytic effect on the above reaction and should be used as the polycondensation catalyst of the present invention. It is different from the titanium compound that can be used. It is preferable to add so that it may become 1-30 ppm in conversion of a titanium atom with respect to obtained polyester. When it is 3 to 15 ppm, the thermal stability and color tone of the polymer become better, more preferably 5 to 10 ppm.

  In addition to the polycondensation catalyst, a small amount of phosphorus compound may be added together with the catalyst for the purpose of adjusting the catalytic activity. The phosphorus compound added here is not particularly limited, and is selected from phosphite compounds, phosphonite compounds, phosphinite compounds, phosphine compounds, phosphate compounds, phosphonate compounds, phosphinate compounds, and phosphine oxide compounds. . Of these, the addition of a trivalent phosphorus compound is preferred from the viewpoint of color tone and heat resistance. A trivalent phosphorus compound refers to a phosphite compound, a phosphonite compound, a phosphinite compound, or a phosphine compound. The phosphorus compound added here is different from the phosphorus compound added between the time when the inside of the reactor is depressurized and the polycondensation reaction is started until the polyester reaches the target degree of polymerization. Since the condensation catalyst may be deactivated to cause a polymerization delay or the polycondensation reaction may not proceed to the target degree of polymerization, so that the polyester obtained is 50 ppm or less in terms of phosphorus atoms. It is preferable to add.

  The titanium compound used as the polymerization catalyst is preferably a titanium complex having a polyvalent carboxylic acid and / or hydroxycarboxylic acid and / or nitrogen-containing carboxylic acid as a chelating agent from the viewpoint of thermal stability and color tone of the polymer. Examples of chelating agents for titanium compounds include polyvalent carboxylic acids such as phthalic acid, trimellitic acid, trimesic acid, hemititic acid, pyromellitic acid, and hydroxycarboxylic acids such as lactic acid, malic acid, tartaric acid, and citric acid. As the nitrogen-containing carboxylic acid, ethylenediaminetetraacetic acid, nitrilotripropionic acid, carboxyiminodiacetic acid, carboxymethyliminodipropionic acid, diethylenetriaminopentaacetic acid, triethylenetetraminohexaacetic acid, iminodiacetic acid, iminodipropionic acid Hydroxyethyliminodiacetic acid, hydroxyethyliminodipropionic acid, methoxyethyliminodiacetic acid and the like. These titanium compounds may be used alone or in combination.

The polyester obtained by the production method of the present invention was obtained by drying a polyester having an intrinsic viscosity of 0.66 dlg ⁻¹ under reduced pressure at 150 ° C. for 12 hours and then melting it at 290 ° C. for 60 minutes in a nitrogen atmosphere. It is preferable that the increase is in the range of 1 to 20 equivalents / ton and the decrease in the intrinsic viscosity is in the range of 0.001 to 0.1. This means that the smaller the increase in carboxyl end groups and the decrease in intrinsic viscosity, the smaller the main chain cleavage reaction due to thermal degradation or oxidative degradation, and the better the thermal stability. When the increase in the carboxyl end group or the decrease in the intrinsic viscosity exceeds the above range, viscosity unevenness occurs or the physical properties are deteriorated in the production process of the molded product for fibers, films, bottles and the like. Preferably, the increase in carboxyl end groups is 3 to 15 equivalents / ton, and the decrease in intrinsic viscosity is 0.001 to 0.05, particularly preferably 3 to 10 equivalents / ton, and the decrease in intrinsic viscosity is 0.001 to 0.00. 03.

  In the polyester obtained by the production method of the present invention, the color tone in the chip shape is a hunter value, the L value is 60 to 95, the a value is -6 to 2, and the b value is in the range of -5 to 5, It is preferable from the viewpoint of the color tone of a molded product such as a fiber or a film. More preferably, the L value ranges from 70 to 90, the a value ranges from -5 to 1, and the b value ranges from -3 to 3.

  The polyester obtained by the production method of the present invention is useful as a fiber by forming into a filament by melt extrusion molding or the like and then stretching or spinning.

  In addition to pigments such as titanium oxide and carbon black, conventionally known antioxidants, anti-coloring agents, light resistance agents, antistatic agents, ultraviolet absorbers and the like may be added.

  The method for producing the polyester of the present invention will be described below. Although the example of a polyethylene terephthalate is described as a specific example, it is not limited to this.

  Polyethylene terephthalate is usually produced by one of the following processes.

  That is, (A) a process in which terephthalic acid and ethylene glycol are used as raw materials, a low polymer is obtained by direct esterification reaction, and a high molecular weight polymer is obtained by subsequent polycondensation reaction, and (B) dimethyl terephthalate and ethylene glycol are used as raw materials. In this process, a low polymer is obtained by a transesterification reaction, and a high molecular weight polymer is obtained by a subsequent polycondensation reaction. Here, the esterification reaction proceeds even without a catalyst, but the aforementioned titanium compound may be added as a catalyst. In the transesterification reaction, a compound such as magnesium, manganese, calcium, cobalt, zinc, lithium, or the above-described titanium compound is used as a catalyst, and after the transesterification reaction is substantially completed, it is used for the reaction. For the purpose of inactivating the catalyst, a phosphorus compound may be added. The phosphorus compound added at this point is distinguished from the phosphorus compound added in the present invention.

  The polyester of the present invention can be used as a polycondensation catalyst for the low polymer obtained in any stage of the series of reactions (A) or (B), preferably in the first half of the series of reactions (A) or (B). After adding the above-mentioned titanium compound, antimony compound, and germanium compound, the inside of the reactor is decompressed to obtain a polycondensation reaction. At this time, a pentavalent phosphorus compound is added during the period from when the pressure in the reactor is reduced to when the polyester reaches the target degree of polymerization, thereby obtaining the target polyethylene terephthalate. This reaction can be applied to a batch, semi-batch or continuous mode.

Hereinafter, the present invention will be described in more detail with reference to examples. In addition, the physical-property value in an Example was measured with the following method.
(1) Intrinsic viscosity of polymer IV
Measurement was performed at 25 ° C. using orthochlorophenol as a solvent.
(2) Carboxyl terminal group of polymer Using orthocresol as a solvent, it was measured by titration with an automatic titration apparatus (COM-550, manufactured by Hiranuma Sangyo Co., Ltd.) using a 0.02 N aqueous NaOH solution at 25 ° C.
(3) Color tone of polymer Using a color difference meter (SM color computer model SM-T45, manufactured by Suga Test Instruments Co., Ltd.), it was measured as a Hunter value (L, a, b value).
(4) Δ intrinsic viscosity 290
After the polyester having an intrinsic viscosity of 0.66 dlg ⁻¹ was dried under reduced pressure at 150 ° C. for 12 hours and then heated and melted at 290 ° C. for 60 minutes in a nitrogen atmosphere, the intrinsic viscosity was measured by the method of (1), The difference before and after heating and melting was measured as Δ intrinsic viscosity 290.
(5) Δ carboxyl end group 290
A polyester having an intrinsic viscosity of 0.66 dlg ⁻¹ was dried under reduced pressure at 150 ° C. for 12 hours, then heated and melted at 290 ° C. for 30 minutes in a nitrogen atmosphere, and then the carboxyl end group amount was measured by the method (2) The difference between before and after heating and melting was measured as Δ carboxyl end group 290.
(6) Observation of deposits in the die The amount of deposits around the die holes 72 hours after the start of melt spinning was observed using a long focus microscope. The state in which deposits were hardly recognized was judged as ◯, the state in which deposits were recognized but operable was judged as Δ, and the state in which deposits were found and yarn breakage frequently occurred was judged as ×.
(Creation of container)
<Container 1>
A polyethylene terephthalate sheet was formed by injection molding into a container having a thickness of 0.2 mm and an internal volume of 500 cm ³ and its lid, and an air vent was provided. The combined weight of the container and the lid was 30 g.
<Container 2>
A biaxially stretched polyethylene terephthalate film having a thickness of 0.07 mm was sewn using polyethylene terephthalate fiber as a sewing thread to create a bag having an internal volume of 500 cm ³ with air vent. The weight of the container containing the film and thread was 10 g.

Example 1
About 100 kg of bis (hydroxyethyl) terephthalate is charged in advance, 82.5 kg of high-purity terephthalic acid (manufactured by Mitsui Chemicals) and ethylene glycol are added to an esterification reaction tank maintained at a temperature of 250 ° C. and a pressure of 1.2 × 10 ⁵ Pa. (Manufactured by Nippon Shokubai Co., Ltd.) 35.4 kg of slurry was sequentially supplied over 4 hours, and after completion of the supply, an esterification reaction was carried out over an additional hour, and 101.5 kg of the resulting esterification reaction product was polycondensed. Transferred to.

  To the esterification reaction product, 100 ppm (phosphorus 2,7-di-tert-butyl-4-methylphenyl) pentaerythritol-di-phosphite (Asahi Denka Co., Ltd., ADK STAB PEP-36) was added to the polymer. 10 ppm in terms of atoms) was added. After 5 minutes, a citrate chelate titanium compound equivalent to 10 ppm in terms of titanium atoms was added, and further 5 minutes later, ethylene glycol slurry of titanium oxide particles was added in an amount of 0.3% by weight in terms of titanium oxide particles to the polymer. . After another 5 minutes, the reaction system was decompressed to initiate the reaction. The reactor was gradually heated from 250 ° C. to 290 ° C., and the pressure was reduced to 40 Pa. The time to reach the final temperature and final pressure was both 60 minutes. Diethylphosphonoacetate equivalent to 723 ppm (100 ppm in terms of phosphorus atom) with respect to the polymer from the upper part of the reaction can when 85% of the predetermined stirring torque is reached (at 2 hours 30 minutes from the start of pressure reduction) (Made by Wako Pure Chemical Industries, Ltd., molecular weight 224) was added after filling the container 1. Thereafter, the reaction is continued, and when a predetermined stirring torque (target polymerization degree is set to IV = 0.66) is reached, the reaction system is purged with nitrogen to return to normal pressure to stop the polycondensation reaction, and in a strand form After discharging and cooling, cutting was performed immediately to obtain polymer pellets. The time from the start of decompression to the arrival of the predetermined stirring torque was 2 hours and 50 minutes.

  The obtained polymer was a polyester excellent in color tone and heat resistance.

  The polyester was vacuum-dried at 150 ° C. for 12 hours, then subjected to a spinning machine, melted by a melter, discharged from the spinning pack portion, and taken up at a speed of 1000 m / min. In the melt spinning process, almost no deposits around the nozzle holes and no increase in filtration pressure were observed during spinning.

Examples 2-5
A polyester was polymerized and melt-spun in the same manner as in Example 1 except that the timing of adding the phosphorus compound was changed after the reaction was started. In Examples 2 and 3, the polymerization time was delayed, but the obtained polymer was excellent in color tone. In Examples 2 and 5, although the color tone was slightly yellowish, there was no problem in quality. In all the levels, deposits around the mouthpiece hole during spinning and an increase in filtration pressure were hardly observed.

Examples 6-9
A polyester was polymerized and melt-spun in the same manner as in Example 1 except that the addition amount of the phosphorus compound added after the reaction was started was changed. In Example 6, although the color tone was slightly yellowish, there was no problem in quality at all. In Example 9, although the polymerization time was slightly delayed, the obtained polymer was excellent in color tone. In all the levels, deposits around the mouthpiece hole during spinning and an increase in filtration pressure were hardly observed.

Examples 10-12
In Example 10, the phosphorus compound added before the start of the reaction is added after the start of the reaction. In Example 11, the phosphorus compound added before the start of the reaction is changed to ethyl diethylphosphonoacetate. Then, the polyester was polymerized and melt-spun in the same manner as in Example 1 except that the addition of the phosphorus compound after the start of the reaction was added in two portions. In Example 11, the polymerization time was slightly delayed, but at other levels, there was no polymerization time delay, and a polymer excellent in color tone and heat resistance was obtained. In addition, almost no deposits and increase in filtration pressure around the nozzle holes during spinning were observed.

Examples 13-18
The added species of the phosphorus compound to be added after the reaction was started were orthophosphoric acid (manufactured by Wako Pure Chemical Industries, molecular weight 98, Example 13), dimethyl methylphosphonate (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight 124, Example 14), Triphenyl phosphate (manufactured by Wako Pure Chemical Industries, molecular weight 326, Example 15), bis (4-methoxyphenyl) phosphinic acid (manufactured by ALDRICH, molecular weight 278, Example 16), triphenylphosphine oxide (Tokyo Chemical Industry Co., Ltd.) Ex., Except that the molecular weight was changed to 278, Example 17), stearyl phosphate (mono-, di-ester mixture) (manufactured by Asahi Denka Co., Ltd., AX-71, mixture of molecular weights 350 and 603, Example 18) Polyester was polymerized and melt-spun as in 1. In Examples 13 and 14, the heat resistance was slightly inferior, but the quality was satisfactory. In all the levels, deposits around the mouthpiece hole during spinning and an increase in filtration pressure were hardly observed.

Examples 19-21
In Example 19, the phosphorus compound was filled in the container 1 without air venting, in Example 20, the phosphorus compound was packed in the container 2 provided with air venting, and in Example 21, the phosphorus compound was added directly from the additive charging line without filling the container. The polyester was polymerized and melt-spun in the same manner as in Example 1 except that In Examples 19 and 21, the color tone was slightly yellowish, but there was no problem in quality. In Example 21, the heat resistance was slightly inferior, but the quality was not a problem. In all the levels, deposits around the mouthpiece hole during spinning and an increase in filtration pressure were hardly observed.

Examples 22-28
A polyester was polymerized and melt-spun in the same manner as in Example 1 except that the addition amount of polycondensation catalyst and the added species were changed. In Example 22, although the polymerization time was slightly delayed, the obtained polymer was excellent in color tone. In Examples 23, 24, and 27, the color tone was slightly yellowish, but there was no problem in quality at all. In Example 28, a slight amount of deposit was observed around the die hole during spinning, and an increase in filtration pressure occurred. At other levels, deposits around the mouthpiece hole during spinning and an increase in filtration pressure were hardly observed.

Example 29
Instead of putting the phosphorus compound in a container, it was mixed with a melt of 1 kg of a low polymer polyester (intrinsic viscosity of 0.35) for 20 minutes in a nitrogen atmosphere and then added to the polyester as in Example 1. Polyester was polymerized and melt spun. In Example 29, the amount of the carboxyl end group of the polyester was slightly increased, but the scattering of the phosphorus compound was small, and the b value and the carboxyl end group 290 were good.

Comparative Example 1
A polyester was polymerized and melt-spun in the same manner as in Example 1 except that no phosphorus compound was added after the reaction was started. The obtained polymer was inferior in color tone and heat resistance.

Comparative Example 2
Polyester was polymerized in the same manner as in Example 1 except that the phosphorus compound added after starting the reaction in Example 1 was added before starting the reaction. As a result, the predetermined stirring torque (degree of polymerization) was not reached.

Comparative Examples 3-4
The polyester was polymerized and melt-spun in the same manner as in Example 1 except that the phosphorus compound was added after the polymerization reached a predetermined target torque (after the polymerization reaction was substantially completed). In Comparative Example 3, after reaching a predetermined agitation torque, the phosphorus compound was added and discharged immediately after the addition. In Comparative Example 4, after reaching a predetermined stirring torque (the polymerization reaction was substantially completed), a phosphorus compound was added, and the mixture was stirred and mixed for 10 minutes under reduced pressure, and then discharged. In Comparative Example 3, the obtained polymer was inferior in color tone and had poor heat resistance. In addition, foreign substances that appeared to be aggregates of phosphorus were generated in the polymer, and deposits around the mouthpiece hole were observed during melt spinning, resulting in frequent increases in filtration pressure and yarn breakage. In Comparative Example 4, the obtained polymer had a higher degree of polymerization than the target degree of polymerization, and the color tone and heat resistance were also poor.

Claims (9)

  In a method for producing a polyester obtained by polycondensation reaction of a dicarboxylic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof in the presence of a polycondensation catalyst, A method for producing a polyester comprising adding a pentavalent phosphorus compound between the start of pressure reduction and the time when the polyester reaches a target degree of polymerization.   The method for producing a polyester according to claim 1, wherein the pentavalent phosphorus compound is added in an amount of 1 to 500 ppm in terms of phosphorus atoms with respect to the obtained polyester.   The method for producing a polyester according to claim 1 or 2, wherein the pentavalent phosphorus compound has a weight average molecular weight in the range of 100 to 2,000.   The pentavalent phosphorus compound can be dissolved or melted in a polymerization system, and is added in a container made of a polymer having substantially the same component as the polymer obtained in the polymerization system. The manufacturing method of polyester of any one of 1-3.   The method for producing a polyester according to any one of claims 1 to 4, wherein a titanium compound is used as the polycondensation catalyst.   In the process for producing a polyester obtained by polycondensation reaction of a dicarboxylic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof in the presence of a polycondensation catalyst, before starting the pressure reduction in the polymerization reactor, Alternatively, in terms of phosphorus atom, 1 to 3 in terms of phosphorus atom with respect to the polyester from which trivalent phosphorus compound can be obtained at any point in time from the start of the pressure reduction in the polymerization reactor until the polyester reaches the target degree of polymerization. Adding 50 ppm and adding 10 to 500 ppm of a pentavalent phosphorus compound from the start of pressure reduction in the polymerization reactor until the polyester reaches the target degree of polymerization. A feature of the polyester production method.   After drying at 150 ° C. for 12 hours under reduced pressure, the amount of increase in carboxyl end groups after melting at 290 ° C. for 60 minutes in a nitrogen atmosphere is 1 to 20 equivalents / ton, and the amount of decrease in intrinsic viscosity is 0.01 to 0.1. A polyester produced by the method according to claim 1, wherein the polyester is a polyester.   The method for producing a polyester according to any one of claims 1 to 7, wherein the phosphorus compound is added to the polyester after being mixed with a polyester low polymer having an intrinsic viscosity of 0.4 or less.   A fiber formed by melt spinning the polyester according to claim 7 or 8.