JP2009067943A - Method for production of polyester for monofilament for screen gauze - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for production of polyester monofilaments for screen gauze which can be suitably used for preserving the viscosity of the polyester for a long time and for preventing the reduction of strength of the monofilaments by suppressing oxidative decomposition or thermal decomposition in melt molding caused by catalysts used in ester exchange reaction or esterification reaction and polycondensation reaction. <P>SOLUTION: The invention relates to a method for production of polyester comprising polycondensation of terephthalic acid or its ester forming derivative as a principal acid component, and a diol or its ester forming derivative as a principal glycol component, in the presence of a polycondensation catalyst to obtain the polyester with 0.70-1.30 of the intrinsic viscosity, wherein a trivalent phosphorus compound with 10-200 ppm of phosphorus atom conversion is added during the polymerization reaction with 85-98% of the target intrinsic viscosity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a process for producing a polyester for monofilaments for screens having excellent thermal stability. Specifically, the viscosity of the polyester can be maintained for a long time by suppressing the oxidative degradation caused by the catalyst used in the transesterification reaction or the esterification reaction and the polycondensation reaction, or thermal decomposition in the monofilament melt spinning process. The present invention relates to a method for producing a polyester for monofilaments for screens which is less likely to cause a decrease in strength.

  The monofilaments for screens are specifically used for precision screens and high-mesh screens, and more specifically for application of electrode paste to the front electrode substrate and the back electrode substrate constituting the plasma display. It is a polyester monofilament used for screen wrinkles and screen wrinkles having a weaving density of 355 mesh or more used for compact disc printing or graphic printing, that is, the number of warp and weft yarns is 355 or more per inch.

  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.

  In general, polyethylene terephthalate is produced from terephthalic acid or an ester-forming derivative thereof and ethylene glycol. However, in a commercial process for producing a high molecular weight polyester, an antimony compound, a germanium compound, a titanium compound, etc. as a polycondensation catalyst. Is widely used. These polycondensation catalysts naturally promote polycondensation reaction of polyethylene terephthalate, but also promote side reactions such as oxidative decomposition reaction and thermal decomposition reaction. In particular, when a titanium compound is used as the polycondensation catalyst, the side reaction is greatly accelerated due to its high catalytic activity, and the viscosity of the polyester during the polycondensation reaction is colored yellow, as well as the viscosity due to thermal decomposition in the melt spinning process. A significant drop occurs.

  In recent years, the number of applications that require higher fiber strength compared to conventional products, such as monofilaments for screens, has been increasing. Viscosity polyester is weaker against oxidation and heat than those with low viscosity, and it is extremely difficult to maintain the viscosity for a long time. In other words, maintaining the viscosity leads to maintaining the high strength of monofilaments used for screens. If monofilaments are made of polyester with a significant decrease in viscosity and used for screens, even the heat applied in each step of screen weaving gradually Deterioration progresses and the strength decreases, and as a result, the durability of the cocoon decreases, and the amount of whiskers or powdery scum increases in the screen cocoon weaving process, which is characterized by high-density and high-speed weaving. May lead to yarn breakage during the weaving process. In other words, developing a technique for maintaining the viscosity of polyester for monofilaments for screens for a long period of time is a very important issue in maintaining the high strength of monofilaments.

  In response to such a problem, by adding a phosphorus compound to the catalyst used in the transesterification reaction or esterification reaction and polycondensation reaction, the activity of the catalyst is suppressed or lost (hereinafter referred to as deactivation), and the polymer Studies to reduce color tone deterioration and improve heat resistance have been widely made.

  As a conventional technique, for example, in a polyester using a titanium compound as a catalyst, a polyester having excellent heat resistance can be obtained by defining the addition amount of a titanium compound, a phosphorus compound, and further a magnesium compound, a manganese compound, and a calcium compound. It has been proposed (see Patent Document 1). This technology suppresses side reactions by containing a certain amount of a metal compound used as a catalyst and a phosphorus compound having a catalyst deactivation effect, thereby suppressing deterioration of the color tone of the polymer and improving heat resistance. For example, if a certain amount or more of a phosphorus compound is added at the initial stage of the polycondensation reaction, the deactivation effect of the polycondensation catalyst is too great, delaying the polymerization reaction time, and in some cases the target polymerization It may not reach the degree. When the polycondensation reaction time is delayed, not only the color tone of the polymer deteriorates but also the thermal deterioration progresses, so that it becomes more difficult to maintain high strength and the required strength may not be obtained.

  As another technique, when producing a polyester using an antimony compound, a method for producing a polyester excellent in color tone and thermal stability by adding a phosphorus compound when the polycondensation reaction is completed 30 to 60% is proposed. (See Patent Document 2). Although this technique certainly has an effect of suppressing side reactions, the addition of a certain amount or more of a phosphorus compound at a stage of 30 to 60% of the polycondensation reaction results in too much deactivation effect of the polycondensation catalyst, and the polymerization reaction time is reduced. There may be a delay or, in some cases, the target degree of polymerization may not be reached. When the polycondensation reaction time is delayed, not only the color tone of the polymer deteriorates but also the thermal deterioration progresses, so that it is more difficult to maintain high strength, and the required strength may not be obtained.

In a polyester copolymerized with isophthalic acid or polyethylene glycol, a method of adding a phosphorus compound after completion of the polycondensation reaction in order to solve the delay of the polymerization reaction due to the addition of the phosphorus compound (see Patent Document 3) or a continuous polymerization method Proposed a method of adding a phosphorus compound after completion of the polycondensation reaction (see Patent Document 4). Certainly, when these methods are used, deactivation of the polycondensation catalyst by the phosphorus compound can be prevented, but since the polyester and the phosphorus compound are mixed after the polycondensation reaction is completed, the side reaction that occurs immediately after the completion of the polycondensation reaction cannot be suppressed. Furthermore, deterioration of the polymer in the mixing process is inevitable. Further, when a phosphorus compound is added after the completion of the polycondensation reaction, the dispersibility at that time is extremely poor, and the polymer quality is uneven, and the production process such as a chip forming process or a monofilament forming process may be adversely affected.
JP 2006-188667 A (Claims) Japanese Patent Publication No. 33-3748 (Detailed Description of the Invention) JP-A-48-79896 (Detailed Description of the Invention) JP 2000-510180 (Claims)

  In the present invention, the viscosity of the polyester can be maintained for a long time by suppressing the oxidative decomposition caused by the catalyst used in the transesterification reaction or the esterification reaction and the polycondensation reaction, or thermal decomposition during melt molding, and thereby the strength of the monofilament. The present invention provides a method for producing a polyester for monofilaments for screens which is less likely to be lowered.

  The present invention has arrived at the present invention as a result of intensive studies in order to solve the problems that could not be solved by the above prior art.

  That is, the present invention has an intrinsic viscosity of 0.70 which can be obtained by polycondensation reaction in the presence of a polycondensation catalyst using terephthalic acid or its ester-forming derivative as the main acid component and diol or its ester-forming derivative as the main glycol component. This is a method for producing a polyester of ˜1.30, and can be achieved by adding 10 to 200 ppm of a trivalent phosphorus compound in terms of phosphorus atom during a polymerization reaction of 85 to 98% of the target intrinsic viscosity setting value.

  The polyester for screen filament monofilament obtained by the method of the present invention can suppress thermal decomposition during monofilament melt molding compared to general high-viscosity polyester, thereby obtaining a polyester suitable for screen filament monofilament. it can. That is, in the method of the present invention, the trivalent phosphorus compound is added at the optimal time in the latter half of the polycondensation reaction, so that side reactions are suppressed without delaying the polycondensation reaction, and the added phosphorus compound is uniformly dispersed. Therefore, a larger side reaction suppressing effect can be obtained without affecting the polyester production process. Moreover, since the polycondensation reaction catalyst is deactivated, thermal decomposition during monofilament melt molding can be suppressed.

  The polyester production method of the present invention is synthesized by esterifying or transesterifying a dicarboxylic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof, followed by a polycondensation reaction. Specific examples of the polyester obtained by such a production method include polyethylene terephthalate, polytrimethylene terephthalate, polytetramethylene terephthalate, polycyclohexylene dimethylene terephthalate, polyethylene-2,6-naphthalene dicarboxylate, 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. Specific examples of the copolymerizable compound include dicarboxylic acids such as isophthalic acid, cyclohexanedicarboxylic acid, adipic acid, dimer acid, and sebacic acid, while glycol components include, for example, ethylene glycol, diethylene glycol, butanediol, and neopentyl glycol. , Cyclohexanedimethanol, polyethylene glycol, polypropylene glycol and the like. In addition, titanium dioxide as a matting agent, silica or alumina fine particles as a lubricant, hindered phenol derivatives, coloring pigments and the like as antioxidants may be added as necessary.

  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. In particular, when a titanium compound is used as a polycondensation catalyst, since the side reaction due to heat is strongly activated, a large amount of 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.

  Further, the present inventors have examined the coloring mechanism of the polyester in detail. As a result, the polycondensation reaction of the polyester is substantially completed in the β-hydrogen abstraction of the polyester and the reaction generated by the vinyl end group component and the aldehyde component. It was found that it occurred in large quantities immediately afterwards, and thereafter, a reaction in which a vinyl end group component was formed into polyene proceeded, and it was difficult to suppress even by addition of a phosphorus compound.

  Therefore, by adding a phosphorus compound not after the polyester polycondensation reaction is substantially completed but before the polycondensation reaction is substantially completed, β-hydrogen abstraction and vinyl terminal occurs immediately after the completion of the polycondensation reaction. It has been found that the production of the base component and the aldehyde component can be specifically suppressed. This cannot be achieved by the conventional phosphorus compound or the addition method of the phosphorus compound.

  In the polyester production method of the present invention, the phosphorus compound is added at a stage where the intrinsic viscosity of the polyester is 85% or more and 98% or less of the target intrinsic viscosity. If a phosphorus compound is added at a stage earlier than 85% of the target intrinsic viscosity, the polymerization reaction is delayed, and the polymer color tone and heat resistance are deteriorated, which is not preferable. If a phosphorus compound is added at a stage later than 98% of the target intrinsic viscosity, In addition to not being able to obtain a sufficient catalyst deactivation effect, it not only adversely affects the color tone and heat resistance of the polymer, but is the same as that added after the polymerization of the polyester is substantially completed without uniformly dispersing the phosphorus compound. Thus, it becomes impossible to stably discharge from the polymerization reactor, and the chip shape becomes non-uniform, which affects the operation of the subsequent drying process and melt spinning process, and may cause quality spots, which is not preferable. The step of adding the phosphorus compound is more preferably a step of 90% or more and 97.5% or less of the target intrinsic viscosity, and still more preferably a step of 92% or more and 96% or less.

  The intrinsic viscosity value of the polyester at the time when the phosphorus compound is added may be directly sampled and measured in the limit year by the method described later, or may be calculated from the torque load applied to the stirring blades of the reactor. In addition, the phosphorus compound may be added in several portions or may be continuously added with a feeder or the like. However, in the case of batch polycondensation, when adding the phosphorus compound, the phosphorus compound is added. It may be added alone or in a state dissolved or dispersed in a diol component such as ethylene glycol. However, if a diol component such as ethylene glycol is brought in and added in a large amount, depolymerization of the polyester (polyester main chain cleavage reaction) proceeds, so it is preferable to add the phosphorus compound alone.

  In the present invention, a trivalent phosphorus compound is added. The trivalent phosphorus compound refers to a phosphite compound, a phosphonite compound, a phosphinite compound, a phosphine compound, and an alkyl ester or aryl ester thereof. These trivalent phosphorus compounds convert peroxides (R—O—OH: further promoting side reactions) generated by side reactions into alcohols (R—OH) and turn themselves into pentavalent phosphorus compounds. This particularly suppresses the side reaction of polyester.

  In the present invention, the trivalent phosphorus compound is added in an amount of 10 ppm to 200 ppm in terms of phosphorus atoms. If the amount added is less than 10 ppm, a sufficient catalyst deactivation effect cannot be obtained, which is unfavorable because it adversely affects the polymer color tone and heat resistance. If the amount added exceeds 200 ppm, the polymerization reaction is delayed. As a result, not only the color tone and heat resistance of the polymer deteriorates, but also the phosphorus compound is not uniformly dispersed and cannot be stably discharged from the polymerization reactor, and the chip shape becomes non-uniform so that the subsequent drying process or melt spinning process In addition to affecting the operational aspects, it may cause quality spots, which is not preferable. The addition amount is more preferably 12 ppm or more and 150 ppm or less, and further preferably 15 ppm or more and 100 ppm or less.

  In the polyester production method of the present invention, the intrinsic viscosity of the polyester is 0.70 or more and 1.30 or less. When the intrinsic viscosity is less than 0.70, it is not preferable because the necessary breaking strength cannot be obtained when weaving a high-density screen wrinkle. When the intrinsic viscosity exceeds 1.30, the softness peculiar to polyester is not good. This is not preferable because the generation amount of scum is increased in the screen knit weaving process, which is characterized by high density and high speed weaving. The intrinsic viscosity is more preferably 0.73 or more and 1.00 or less, and further preferably 0.75 or more and 0.80 or less.

  In the method for producing a polyester of the present invention, any of those generally known as polycondensation catalysts may be used, and specific examples include titanium compounds, antimony compounds, germanium compounds, aluminum compounds and the like. . These polycondensation catalysts may be used alone or in combination. Among these, it is preferable to use a titanium compound for the polycondensation catalyst because generation of foreign matters is suppressed. Furthermore, you may use together compounds, such as sodium, potassium, lithium, magnesium, calcium, zinc, cobalt, manganese. 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.

  In the present invention, when a titanium compound is used for the polycondensation catalyst, it is preferably added so as to contain 1 ppm or more and 30 ppm or less in terms of titanium atom with respect to the obtained polyester. It is preferable that the content in terms of titanium atom is 1 ppm or more because the polymer color tone and heat resistance can be kept good without delaying the polycondensation reaction time. Further, it is preferable that the content in terms of titanium atom is 30 ppm or less because the catalyst activity hardly remains and the catalyst deactivation effect by the trivalent phosphorus compound described above can be sufficiently obtained. The content in terms of titanium atom is more preferably 3 ppm or more and 15 ppm or less, and further preferably 4 ppm or more and 10 ppm or less.

  When a titanium compound is used for the polycondensation catalyst, the content of the antimony compound is preferably 30 ppm or less or not contained in terms of antimony atoms. In general, an antimony compound tends to form a metal crystal as compared with other metal compounds, and the crystal may have a bad influence on a subsequent melt-spinning process or screen knot weaving process as a foreign substance. By setting the content of the antimony compound within the specified range of the present invention, it is preferable because the operation of each step can be stabilized.

  When using an antimony compound for a polycondensation catalyst, it is preferable to add it so that it may contain 150 ppm or more and 300 ppm or less in conversion of antimony atom with respect to the polyester obtained.

  When the titanium compound used as a polymerization catalyst as described above is a titanium complex having a polyvalent carboxylic acid and / or hydroxycarboxylic acid and / or nitrogen-containing carboxylic acid as a chelating agent, the viewpoint of thermal stability and color tone of the polymer To preferred. 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.

  The polycondensation catalyst of the present invention is generally a reaction of (1) a dicarboxylic acid component and a diol component in 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. Esterification reaction, (2) Transesterification reaction, which is a reaction between an ester-forming derivative component of dicarboxylic acid and a diol component, (3) Substantially the ester reaction or transesterification reaction is completed, and the resulting polyethylene terephthalate low weight This refers to a polycondensation reaction in which the coalescence is increased in the degree of polymerization by a dediol reaction, and has at least an effect contributing to the reaction promotion of (3). Accordingly, titanium oxide particles generally used for fiber matting agents have substantially no catalytic effect on the above reaction, and can be used as a polycondensation catalyst of the present invention. Is different.

  In the present invention, the phosphorus compound added between the start of the pressure reduction in the polymerization reaction system after the addition of the polycondensation catalyst and before the polyester polycondensation reaction is substantially completed has a melting point of 100 ° C. or higher and 400 ° C. The following is preferable. A melting point of 100 ° C. or higher is preferable because a desired amount of phosphorus compound can be reliably added to the polyester without scattering when adding the phosphorus compound under reduced pressure conditions. Further, it is preferable that the melting point is 400 ° C. or lower because the phosphorus compound is easily adapted to the polyester and has excellent dispersibility, and thus a greater effect can be obtained for the coloring of the polymer and the improvement of heat resistance. The melting point of the phosphorus compound is more preferably 115 ° C. or higher and 350 ° C. or lower, and further preferably 175 ° C. or higher and 300 ° C. or lower.

  The trivalent phosphorus compound added in the present invention is specifically bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol-di-phosphite (melting point) represented by the following formula 1. : 234-240 ° C.) and tris [2-{(2,4,8,10-tetra-t-butyldibenz [d, f] [1,3,2] -dioxaphosphine represented by formula 2 Pin-6-yl) oxy} ethyl] amine (melting point: 190-210 ° C.), 6- [3- (3-tert-butyl-4-hydroxy-5-methyl) propoxy] -2 represented by formula 3 , 4,8,10-tetra-t-butyldibenz [d, f] [1,3,2] -dioxaphosphine (melting point: 115 ° C. to 125 ° C.), tetrakis (2, 4-di-t-butyl-5-methylphenyl) [1,1-bi Eniru] -4,4'-diyl bis phosphonite (mp: 234 to 240 ° C.) are preferred. In these compounds, Formula 1 is ADK STAB PEP-36 (manufactured by ADEKA), Formula 2 is IRGAFOS12 (manufactured by Ciba Specialty Chemicals), Formula 3 is Sumizer-GP (manufactured by Sumitomo Chemical Co., Ltd.), Formula 4 Is available as GSY-P101 (Osaki Industrial Chemical Co., Ltd.). These compounds may be used alone or in combination.

  When adding the phosphorus compound in the present invention, it is preferable to add the phosphorus compound by filling it into a container made of substantially the same component as the polyester obtained in the present invention, which can be dissolved or melted in the polymerization system. When adding a phosphorus compound in a container as described above, the addition of the polymerization compound to the polymerization reactor under reduced pressure prevents the phosphorus compound from scattering and flowing out of the reduced pressure line. And 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. It is. Further, it is more preferable to make an air vent such as a hole in the container. 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 thickness of the container is too thick, it takes a long time for melting and melting, so it is better to reduce the thickness. However, the thickness of the container is ensured so that it does not rupture when the phosphorus compound is enclosed or added. For this purpose, a uniform and non-uniform thickness with a thickness of 10 to 500 μm is preferable.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, the main measured value of the Example was measured with the following method.

(1) Intrinsic viscosity Intrinsic viscosity [η] is a value determined based on the following defining formula.

Ηr in the definition formula is a value obtained by dividing the viscosity at 25 ° C. of a diluted PET solution dissolved in O-chlorophenol having a purity of 98% or more by the viscosity of the solvent itself measured at the same temperature. Is defined. C is the solute weight value in grams in 100 ml of the solution.

(2) Metal content such as phosphorus, titanium, antimony, etc. 6 g of polymer was melted and formed into a plate shape, and the strength was measured by fluorescent X-ray analysis (fluorescence X-ray analyzer 3270 type, manufactured by Rigaku Corporation). It converted into metal content using the analytical curve created beforehand with the sample of.

(3) Polymer heat resistance (gelation rate / measurement of gelled product generation)
After the polymer is dried under reduced pressure at 130 ° C. for 3 hours, 1 g is weighed and dissolved at 300 ° C. for 6 hours under air flow. Next, o-chlorophenol having a purity of 98% or more is added, dissolved for 30 minutes, filtered through a filter having an opening of 20 μm, and the amount of filter supplement is weighed. The value obtained by dividing the amount of supplement by the amount of polymer before the dissolution treatment was defined as the gelation rate. A gel having a calculated gelation rate of 1.0% or less was accepted.

(4) Breaking strength After obtaining a monofilament by the method described later, it was measured according to JIS L1013 (1999).

(5) Strength retention After obtaining a monofilament by the method described later, the breaking strength was measured in accordance with JIS L1013 (1999) without any special treatment, and the same monofilament was measured at 160 ° C. under no load. The breaking strength after 15 minutes of dry heat treatment in the oven is also measured by the same method. The value obtained by dividing the breaking strength when dry heat-treated by the breaking strength when untreated was taken as the strength retention. In addition, the thing with the calculated intensity | strength retention rate of 95% or more was set as the pass.

(6) Discharge stability After the polycondensation reaction is completed, when the obtained polyester is discharged into a strand and made into chips by a cutter, the number of occurrences of strand breakage per unit weight is measured. , 6 to 8 times were evaluated as ◯, 9 times or more were evaluated as ×, and XX and ○ were regarded as acceptable. However, in the case of the batch type, the strands are likely to be disturbed immediately after the start of discharge and immediately before the end of discharge. Therefore, when measuring the number of strand breaks, the measurement range is 1 minute immediately after the start of discharge and immediately before the end of discharge. Excluded from.

(7) Scratch resistance A screen fabric with a width and width of 355 mesh (355 pieces / inch (2.54 cm)), a rotational speed of 350 rpm and a weaving width of 2.54 m and a length of 30 m is used. Weaving anti-continuously, seeking the weaving length up to the point at which the weaving blade part must be stopped due to the contamination of the wings or powdered scum, and normal weaving cannot be maintained. Was ○, 150 to 200 m was taken as ○, less than 150 m was taken as ×, and ○○ and ○ were accepted.

Example 1
About 1950 kg of bis (hydroxyethyl) terephthalate is charged in advance, and 1300 kg of high-purity terephthalic acid (manufactured by Mitsui Chemicals) is added to an esterification reaction tank maintained at a temperature of 245 ° C. and a pressure of 1.8 × 10 ⁵ Pa. 560 kg of slurry (manufactured by Catalyst Co., Ltd.) was sequentially supplied over 3 hours, and after the completion of the supply, an esterification reaction was further performed over 1 hour, and the resulting esterification reaction product 1590 kg was transferred to a polycondensation reaction tank.

  To the esterification reaction product, cobalt acetate is added to the polymer with a citrate chelate titanium compound equivalent to 170 ppm in terms of cobalt atom and 5 ppm in terms of titanium atom, followed by reaction while stirring the low polymer at 30 rpm. The system was gradually heated from 250 ° C. to 290 ° C., and the pressure was reduced to 40 Pa.

When 95% of the predetermined stirring torque (target intrinsic viscosity setting value) is reached (2 hours and 50 minutes after the start of decompression), 25 ppm (as a compound) in terms of phosphorus atoms with respect to the polymer from the top of the reaction can 250 ppm equivalent) bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol-di-phosphite (manufactured by ADKA Corporation, Adekastab PEP-36, melting point 236 ° C., pre-injected with polyethylene terephthalate Were added to a container having a thickness of 200 μm and an internal volume of 50 cm ^{3 and} a container formed in its lid (packed in a container and a lid with a combined weight of 30 g). Thereafter, the reaction is continued, and when the predetermined stirring torque is reached, the reaction system is purged with nitrogen and returned to normal pressure to stop the polycondensation reaction, discharged in a strand form, cooled, and immediately cut to obtain a chip-like polyester. Obtained. The time from the start of decompression to the arrival of the predetermined stirring torque was 3:00 hours. The intrinsic viscosity of the obtained polyester was 0.78. The discharge stability of the polymer was extremely good, and the gelation rate used as an index of heat resistance was 0.3%, and a polyester excellent in thermal stability was obtained. Furthermore, the obtained polyester was made into a monofilament by the following method, and the properties as a monofilament were also measured.

  After melt spinning the polyester obtained by the production method of the present invention using a pressure melter type spinning machine and then cooling and solidifying with cooling air, the monofilament yarn is unstretched at a spinning speed of 850 m / min after applying the oil. Is then wound up 4.39 times between the first hot roller having a surface temperature of 90 ° C. and the second hot roller having a surface temperature of 100 ° C., and 1.3 between the second hot roller and the third hot roller having a surface temperature of 200 ° C. A relaxation time of 4.29% was imparted between the third hot roller and the cooling roller having a surface temperature of room temperature of 07 times and stretched and heat set to obtain a monofilament having a fineness of 13.0 dtex. The breaking strength of the monofilament was 5.8 cN / dtex, and the strength retention was 97%. Sufficient strength and high strength retention can be obtained as a monofilament for use in screens, and the evaluation results in other weaving processes are as shown in Table 1. The amount of scum generation is small and the abrasion resistance is excellent. A good polyester was obtained by the production method.

Examples 2-4
A polyester is obtained by polymerization in the same manner as in Example 1 except that the kind of the trivalent phosphorus compound added at a stage of 85% or more and less than 98% of the target intrinsic viscosity setting value of the polyester is changed to obtain a polyester, and further melt spinning. A monofilament was obtained. The obtained polyester was excellent in ejection stability and heat resistance, and as a monofilament, a polyester having high strength and high strength retention and further excellent abrasion resistance was obtained.

Examples 5-7
A polyester is obtained by polymerization in the same manner as in Example 1 except that the addition amount of the trivalent phosphorus compound added at a stage of 85% or more and less than 98% of the target intrinsic viscosity setting value of polyester is obtained, and further melted. Spinning was performed to obtain a monofilament. The obtained polyester was excellent in ejection stability and heat resistance, and as a monofilament, a polyester having high strength and high strength retention and further excellent abrasion resistance was obtained. In contrast to Example 1, when the addition amount of the phosphorus compound was decreased, the strength retention was slightly inferior, and when it was increased, the dischargeability tended to be slightly inferior.

Examples 8-10
A polyester is obtained by polymerization in the same manner as in Example 1 except that the addition time of the trivalent phosphorus compound added at a stage of 85% or more and less than 98% of the target intrinsic viscosity setting value of the polyester is obtained, and further melted. Spinning was performed to obtain a monofilament. The obtained polyester was excellent in ejection stability and heat resistance, and as a monofilament, a polyester having high strength and high strength retention and further excellent abrasion resistance was obtained. In contrast to Example 1, when the phosphorus compound was added earlier, the heat resistance was slightly inferior, and when it was delayed, the dischargeability was slightly inferior.

Examples 11 and 12
A polyester was obtained by polymerizing in the same manner as in Example 1 except that the intrinsic viscosity of the finally obtained polyester was changed, and further melt-spun to obtain a monofilament. The obtained polyester was excellent in ejection stability and heat resistance, and as a monofilament, a polyester having high strength and high strength retention and further excellent abrasion resistance was obtained. In addition, the level of the intrinsic viscosity showed a remarkable difference with respect to the breaking strength of the monofilament, and the high-viscosity polymer tended to be slightly inferior in heat resistance and strength retention.

Examples 13-15
A polyester was obtained by polymerization in the same manner as in Example 1 except that the addition amount of the citric acid chelate titanium compound was changed, and further melt-spun to obtain a monofilament. The obtained polyester was excellent in ejection stability and heat resistance, and as a monofilament, a polyester having high strength and high strength retention and further excellent abrasion resistance was obtained. In contrast to Example 1, when the addition amount of the titanium compound was decreased, a slight delay was observed in the reaction time, and when it was increased, the heat resistance and the strength retention were slightly inferior.

Example 16
A polyester was obtained by polymerization in the same manner as in Example 1 except that 30 ppm of an antimony compound in terms of antimony atom was added in addition to the citric acid chelate titanium compound, and then a polyester was obtained by melt spinning to obtain a monofilament. The obtained polyester was excellent in ejection stability and heat resistance, and as a monofilament, a polyester having high strength and high strength retention and further excellent abrasion resistance was obtained. In contrast to Example 1, when the antimony compound was added, the abrasion resistance tended to be slightly inferior.

Example 17
A polyester was obtained by polymerization in the same manner as in Example 1 except that no citric acid chelate titanium compound was added and 330 ppm of an antimony compound was added instead of an antimony atom, and a polyester was obtained by melt spinning to obtain a monofilament. The obtained polyester was excellent in ejection stability and heat resistance, and as a monofilament, a polyester having high strength and high strength retention and further excellent abrasion resistance was obtained. Similar to Example 16, when the antimony compound was added, the abrasion resistance tended to be slightly inferior.

Comparative Examples 1-3
A polyester is obtained by polymerization in the same manner as in Example 1 except that the kind of the trivalent phosphorus compound added at a stage of 85% or more and less than 98% of the target intrinsic viscosity setting value of the polyester is changed to obtain a polyester, and further melt spinning. A monofilament was obtained. Although the obtained polyester was excellent in ejection stability, it was poor in heat resistance, low in strength retention even as a monofilament, and other evaluation results are as shown in Table 2. I couldn't.

Comparative Example 4
A polyester is obtained by polymerization in the same manner as in Example 1 except that the trivalent phosphorus compound is not added at a stage of 85% or more and less than 98% of the target intrinsic viscosity setting value of polyester to obtain a polyester, which is further melt-spun and monofilament Got. Although the obtained polyester was excellent in ejection stability, the heat resistance was poor in heat resistance, and the strength retention was low even as a monofilament, and satisfactory results were not obtained.

Comparative Example 5
Polymerization was carried out in the same manner as in Example 1 except that the addition amount of the trivalent phosphorus compound added at a level of 85% or more and less than 98% of the target intrinsic viscosity setting value of the polyester was changed. However, since the amount of the phosphorus compound added was too large, the polycondensation catalyst was deactivated before reaching the target intrinsic viscosity setting value, and the target polyester could not be obtained.

Comparative Example 6
Polymerization was carried out in the same manner as in Example 1 except that the addition amount of the trivalent phosphorus compound added at a level of 85% or more and less than 98% of the target intrinsic viscosity setting value of the polyester was changed. However, since the addition time of the phosphorus compound was too early, the polycondensation catalyst was deactivated before reaching the target intrinsic viscosity setting value, and the target polyester could not be obtained.

Comparative Example 7
A polyester is obtained by polymerization in the same manner as in Example 1 except that a trivalent phosphorus compound is added after the polymerization reaction is substantially completed (after reaching the target intrinsic viscosity), and a polyester is obtained. Got. However, in this method, foreign substances that appear to be aggregates of phosphorus compounds are generated in the polymer, the discharge state is poor, and considerable spots are generated in heat resistance. Further, the monofilament was uneven in strength and strength retention, and was also poor in shaving due to the aggregate of the phosphorus compound.

Comparative Example 8
A polyester was obtained by polymerizing in the same manner as in Example 1 except that the intrinsic viscosity of the finally obtained polyester was changed, and further melt-spun to obtain a monofilament. Although the obtained polyester was excellent in discharge stability and heat resistance, the strength was low as a monofilament, and satisfactory results were not obtained.

Comparative Example 9
A polyester was obtained by polymerization in the same manner as in Example 1 except that the addition amount of the citric acid chelate titanium compound was changed, and further melt-spun to obtain a monofilament. Although the obtained polyester was excellent in ejection stability, the heat resistance was very poor due to the remaining activity as a polycondensation catalyst, and the strength retention was low even as a monofilament, and satisfactory results were obtained. I couldn't.

Claims (5)

  A terephthalic acid or an ester-forming derivative thereof as a main acid component, a diol or an ester-forming derivative thereof as a main glycol component, and having an intrinsic viscosity of 0.70 to 1.30 obtained by polycondensation reaction in the presence of a polycondensation catalyst. A polyester manufacturing method for monofilaments for use in screens, wherein a trivalent phosphorus compound is added in an amount of 10 to 200 ppm in terms of phosphorus atoms during a polymerization reaction of 85 to 98% of the target intrinsic viscosity setting value. Manufacturing method.   The polyester for monofilaments for use in screens according to claim 1, wherein the titanium compound other than the titanium oxide particles is contained in an amount of 1 to 30 ppm in terms of titanium atom, and the content of the antimony compound is 30 ppm or less in terms of antimony atom. Production method.   The melting point of the trivalent phosphorus compound is 100 to 400 ° C, The method for producing a polyester for a screen filament monofilament according to claim 1 or 2.   The trivalent phosphorus compound is bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, tris [2-{(2,4,8,10-tetra-t-butyldibenz [ d, f] [1,3,2] -dioxaphosphin-6-yl) oxy} ethyl] amine, 6- [3- (3-tert-butyl-4-hydroxy-5-methyl) propoxy] -2,4,8,10-tetra-t-butyldibenz [d, f] [1,3,2] -dioxaphosphine, tetrakis (2,4-di-t-butyl-5-methylphenyl) The polyester for monofilaments for screen use according to any one of claims 1 to 3, which is at least one selected from [1,1-biphenyl] -4,4'-diylbisphosphonite. Production method.   The polyester for monofilaments for use in screens according to any one of claims 1 to 4, wherein the trivalent phosphorus compound is added in a container mainly composed of the same polyester as the polyester to be produced. Manufacturing method.