Method for manufacturing polyester compositions

Abstract

The present invention provides a method for producing a polyester composition that suppresses the generation of aggregates originating from added catalysts and particles, thereby preventing blockage of the filtration filter or molten polymer channel during melt molding of the polyester composition, and improving the quality and durability of the resulting molded product. [Solution] A method for producing a polyester composition in a polycondensation batch process that uses dicarboxylic acids or their ester-forming derivatives and diols as the main raw materials, wherein the addition of a polymerization catalyst or the like is started when the liquid temperature of the intermediate bis-2-hydroxyethyl terephthalate (BHT) obtained by the ester reaction of the raw materials is 240 to 270°C, the minimum liquid temperature of the BHT until the addition is completed is 220°C or higher, and the decrease in liquid temperature during the addition is within 30°C from the addition start temperature.

Description

Technical Field

[0001] The present invention relates to a method for producing a polyester composition. More specifically, it relates to a method for producing a polyester composition to which a reaction catalyst and particles are added.

Background Art

[0002] Due to its excellent properties such as durability and processability, polyester is widely used in various fields including fiber and film applications. Regarding this polyester, a catalyst represented by antimony trioxide or the like is added to promote the polymerization reaction, or in particular for fiber applications, particles represented by titanium dioxide or the like are generally known to be contained for the purpose of imparting functions such as mold release properties and gas barrier properties.

[0003] Regarding polymerization catalysts and particles, it is generally known that aggregates are generated depending on the environment such as the presence of ions or particles with opposite charges in the same system because they are ionized or the particles themselves have a charge. These aggregates lead to defects, quality deterioration, and reduced durability of molded products using the polyester composition. Moreover, even if trying to capture these aggregates with a filter or the like, if the amount is large, the filter will quickly become clogged, which can also hinder the molding process. <( Therefore, it is necessary to devise ideas and take measures to prevent the generation of aggregates.

[0004] Various studies have been made on suppressing the aggregation of reaction catalysts and particles. For example, Patent Document 1 and Patent Document 2 propose optimizing the temperature after adding the reaction catalyst. Also, Patent Document 3 proposes preheating as a pretreatment for the slurry of titanium dioxide and glycol components.

[0005] As described above, various studies have been made on avoiding the generation of aggregates derived from reaction catalysts and particles, but further improvement is required.

Prior Art Documents

[0006] [Patent Document 1] Japanese Patent Application Publication No. 59-164325 [Patent Document 2] Special Publication No. 60-66859 [Patent Document 3] Japanese Patent Application Laid-Open No. 62-119228 [Overview of the project] [Problems that the invention aims to solve]

[0007] Patent documents 1 and 2 propose optimizing the temperature after adding the reaction catalyst, while patent document 3 proposes preheating as a pretreatment for the slurry of titanium dioxide and glycol components. However, the improvements achievable through temperature control alone were insufficient, so we thoroughly examined the reaction catalyst and particle addition conditions for further improvement.

[0008] The present invention, viewed in light of the background art, aims to provide a method for producing a polyester composition that optimizes the temperature of the entire addition process, from the start of addition of reaction catalysts and particles to during and after addition, thereby suppressing the generation of aggregates originating from these reaction catalysts and particles, preventing blockage of the filter or molten polymer channel during melt molding of the polyester composition, and improving the quality and durability of the resulting molded product. [Means for solving the problem]

[0009] As a result of diligent research to solve the aforementioned problems, the inventors discovered a correlation between the addition temperature of the reaction catalyst and particles and the increase in filtration pressure of the filter when filtering the polyester composition, leading to the present invention.

[0010] In other words, the present invention can be achieved by a method for producing a polyester composition using dicarboxylic acid or its ester-forming derivative, and diol as the main raw materials, wherein, in a batch process of polycondensation in which a polymerization catalyst and a co-catalyst or only the polymerization catalyst are added in the stage from obtaining the intermediate bis-2-hydroxyethyl terephthalate by the ester reaction of the main raw materials until the polymerization reaction is started, the addition of the polymerization catalyst etc. is started when the liquid temperature of BHT in the polymerization reactor is 240 to 270°C, and regarding the decrease in the liquid temperature of BHT during or after the addition of the polymerization catalyst etc., the minimum temperature after the decrease in liquid temperature is 220°C or higher, and the range of liquid temperature decrease is within 30°C from the temperature at which the polymerization catalyst is added. [Effects of the Invention]

[0011] According to the present invention, the formation of aggregates derived from the added catalyst or particles can be suppressed, thereby preventing blockage of the filter or molten polymer channel during melt molding of the polyester composition, and improving the quality and durability of the resulting molded product. [Modes for carrying out the invention]

[0012] The present invention relates to a polycondensation process for producing a polyester composition using dicarboxylic acids or their ester-forming derivatives and diols as the main raw materials. When the liquid temperature of the intermediate bis-2-hydroxyethyl terephthalate (hereinafter referred to as BHT), obtained by the esterification reaction of the aforementioned raw materials, reaches 240-270°C, the addition of the polymerization catalyst and / or co-catalyst (hereinafter referred to as polymerization catalyst, etc.) is started.

[0013] By setting the liquid temperature of BHT to 240°C or higher when starting the addition of polymerization catalysts, the melt viscosity of BHT can be sufficiently reduced, and the polymerization catalysts can be uniformly dispersed in the BHT. This shortens the dissolution time and suppresses the formation of aggregates of the polymerization catalysts. In addition, it is possible to prevent the liquid temperature after adding polymerization catalysts from falling below the melting point of BHT and solidifying, thereby avoiding equipment problems and other issues.

[0014] Furthermore, by keeping the liquid temperature of BHT below 270°C when starting the addition of polymerization catalysts, thermal degradation of BHT can be suppressed, and the resulting polyester composition can be kept in good condition. In addition, because the controllability of the stirring torque in the reaction step after adding polymerization catalysts can be maintained, variations in polycondensation reaction time between batches can be suppressed, and the amount of carboxyl groups in the resulting polyester composition can be reduced, thereby improving its heat resistance.

[0015] To further improve the quality of the resulting polyester composition, the liquid temperature of BHT at the start of adding the polymerization catalyst is preferably 245 to 265°C, and more preferably 245 to 260°C.

[0016] In addition to the liquid temperature of BHT at the start of adding the polymerization catalyst, the minimum liquid temperature of BHT until the addition of the polymerization catalyst is completed shall be 220°C or higher.

[0017] By setting the minimum liquid temperature of the BHT to 220°C or higher, the melt viscosity of the BHT can be sufficiently reduced, allowing the polymerization catalyst and other components to be uniformly dispersed in the BHT, thereby suppressing the formation of aggregates. In addition, it is possible to prevent the BHT from solidifying when its liquid temperature falls below its melting point, thus avoiding equipment troubles and other issues.

[0018] To further improve the quality of the resulting polyester composition, it is preferable to set the minimum temperature of the BHT solution to 230°C or higher, and more preferably to 235°C or higher.

[0019] In addition to the liquid temperature of BHT when starting the addition of the polymerization catalyst etc. (hereinafter referred to as the starting BHT liquid temperature) and the lowest temperature, the liquid temperature drop width of BHT during the addition of the polymerization catalyst etc. shall be within 30°C from the starting BHT liquid temperature. By setting the liquid temperature drop width within 30°C from the starting BHT liquid temperature, the increase width of the melt viscosity of BHT can be reduced, the polymerization catalyst etc. can be uniformly dispersed in BHT, and the generation of aggregates can be suppressed. In addition, since the controllability of the liquid temperature in the reaction process after adding the polymerization catalyst etc. can be maintained, the variation in the polycondensation reaction time between batches can be suppressed, the amount of carboxyl groups in the obtained polyester composition can be suppressed, and the heat resistance can also be improved.

[0020] To further improve the quality of the obtained polyester composition, it is preferable that the liquid temperature drop width is within 25°C from the starting BHT liquid temperature, more preferably within 20°C from the starting BHT liquid temperature.

[0021] Regarding the polymerization reaction catalyst, general antimony compounds, titanium compounds, germanium compounds, etc. are preferably used, but are not limited thereto. Regarding the co-catalyst, general phosphorus compounds, alkali metal compounds, alkaline earth metal compounds, etc. are preferably used, but are not limited thereto.

[0022] In the method for producing the polyester composition of the present invention, when the liquid temperature of BHT in the intermediate obtained by the ester reaction of the raw materials is 250 to 265°C, the addition of inorganic particles or organic particles (hereinafter referred to as particles etc.) is started, and the lowest liquid temperature until the addition is completed is preferably 220°C or higher, and the liquid temperature drop width during the addition is within 40°C from the liquid temperature at the start of the addition.

[0023] Regarding the inorganic particles, general titanium compounds, silicon compounds, zirconium compounds, etc. are preferably used, but are not limited thereto. Regarding the organic particles, calcium compounds, etc. are preferably used, but are not limited thereto.

[0024] In the method for producing the polyester composition of the present invention, it is preferable to add a polymerization catalyst or particles when the liquid temperature of the intermediate BHT obtained by the esterification reaction of the raw materials has risen.

[0025] Furthermore, in light of the growing awareness of environmental impact in recent years, it is preferable to use raw materials obtained by recycling polyester waste and unused polyester compositions generated in the polyester product manufacturing process. Specific examples include the reuse of waste derived from PET bottles and other polyethylene terephthalate products, or bis-2-hydroxyethyl terephthalate, terephthalic acid, or dimethyl terephthalate obtained from such polyethylene terephthalate product waste through a depolymerization process.

[0026] Furthermore, in the method for producing the polyester composition of the present invention, chemical substances commonly used in the esterification and polycondensation reactions of polyesters can be used without particular limitation, as long as they do not impair the objectives of the present invention. Also, as long as they do not impair the objectives of the present invention, there is no problem in adopting a method of preheating and adding polymerization catalysts, etc., in order to reduce the range of liquid temperature drop. [Examples]

[0027] The present invention will be described in more detail below with reference to examples. The physical properties were measured using pellets of the polyester composition obtained by the method described later.

[0028] (1) Polycondensation reaction time In the polycondensation reaction process, the time at which the pressure in the reaction vessel was reduced was defined as zero, and the time from when the predetermined viscosity (predetermined stirrer power value) was reached until the pressure reduction was stopped was defined as the polycondensation reaction time. The time required for each process, including the polycondensation reaction time, is managed to ensure that one batch fits within a predetermined cycle time in order to efficiently carry out production. Therefore, in this invention, the judgment was made based on the cycle time according to the following criteria, with ◎ and ○ being considered passing grades. ◎: 180 minutes or less. ○: More than 180 minutes to less than 220 minutes. ×: Over 220 minutes.

[0029] (2) Carboxylate group The polyester composition pellets obtained according to the present invention were dissolved by heat treatment at 100°C for 30 minutes while stirring under immersion in an o-cresol preparation solution. After cooling to 25°C, the amount of carboxyl groups was measured using an automatic titrator. The evaluation was performed according to the following criteria, with ◎ and ○ indicating a pass. ◎: 24 equivalents / ton or less. ○: More than 24 equivalents / ton to less than 30 equivalents / ton. ×: More than 30 equivalents / ton.

[0030] (3) Filterability The polyester composition pellets obtained according to the present invention were dried to a moisture content of 150 ppm or less. These dried pellets were melted and extruded using an extruder heated to 300°C, and the polyester composition was passed through a 5μ mesh nonwoven fabric filter at a rate of 10 g / min. The difference between the pressure at the start of feeding and the pressure after 1 kg of polyester composition had passed was measured. The evaluation was performed according to the following criteria, with ◎ and ○ indicating a pass. ◎: 0.4MPa / kg or less. ○: More than 0.4MPa / kg to less than 1.0MPa / kg. ×: Exceeds 1.0 MPa / kg.

[0031] Example 1 With 2000 kg of BHT already loaded, a slurry of 1300 kg of terephthalic acid and 560 kg of ethylene glycol was supplied over 3 hours to an esterification reaction vessel maintained at a temperature of 245°C, and the esterification reaction was carried out while distilling off the water generated during the esterification reaction from the reaction system. Next, an amount of BHT equivalent to 45% by mass in the esterification reactor was transferred to the polycondensation reactor. Simultaneously with the transfer of BHT, heating of the polycondensation reactor was started, and after the transfer was complete, 0.01% by mass of an 85% aqueous solution of phosphoric acid was added. When the BHT liquid temperature rose to 260°C, a slurry containing 0.03% by mass of antimony trioxide and 0.01% by mass of cobalt acetate tetrahydrate dispersed in 150 kg of ethylene glycol was added to the polycondensation reactor at a rate of 125-135 kg / min as a polymerization catalyst. The lowest temperature of the BHT liquid during the addition of the polymerization catalyst was 241°C.

[0032] Next, an ethylene glycol slurry containing 13% by mass of titanium dioxide with a uniform particle size distribution was added to the polycondensation reactor at a rate of 45-55 kg / min when the BHT liquid temperature rose to 255°C, so that the resulting polyester composition contained 2% by mass of titanium dioxide. At this time, the lowest temperature of the BHT liquid was 220°C. Subsequently, the pressure was reduced to 50 Pa while distilling off ethylene glycol from the polycondensation reactor. When the agitator power value reached a predetermined value, the polycondensation reaction vessel was purged with nitrogen to return to atmospheric pressure, stopping the polycondensation reaction. The reaction product was then pressurized with nitrogen to discharge it in strand form, cooled, and immediately cut to obtain pellets of the polyester composition. The polycondensation reaction time from the start of reduced pressure to reaching the predetermined stirrer power value was 191 minutes. The resulting polyester composition had a carboxyl group content of 25.3 equivalents / ton and a filterability of 0.47 MPa / kg.

[0033] Examples 2-4 The procedure was the same as in Example 1, except that the starting temperature for adding polymerization catalysts, etc., was changed. The results are shown in Tables 1 and 2.

[0034] Examples 5, 6 The procedure was the same as in Example 1, except that the starting temperature for adding particles was changed. The results are shown in Tables 1 and 2.

[0035] Example 7 With 2000 kg of BHT already loaded, a slurry of 1300 kg of terephthalic acid and 560 kg of ethylene glycol was supplied over 3 hours to an esterification reaction vessel maintained at a temperature of 245°C, and the esterification reaction was carried out while distilling off the water generated during the esterification reaction from the reaction system. Next, an amount of BHT equivalent to 45% by mass in the esterification reactor was transferred to the polycondensation reactor. Simultaneously with the transfer of BHT, heating of the polycondensation reactor was started, and after the transfer was complete, 0.01% by mass of an 85% aqueous solution of phosphoric acid was added. When the BHT liquid temperature rose to 260°C, a slurry containing 0.03% by mass of antimony trioxide and 0.01% by mass of cobalt acetate tetrahydrate dispersed in 150 kg of ethylene glycol was added to the polycondensation reactor at a rate of 125-135 kg / min as a polymerization catalyst. The lowest temperature of the BHT liquid during the addition of the polymerization catalyst was 241°C. Next, the pressure was reduced to 50 Pa while distilling off ethylene glycol from the polycondensation reactor. When the agitator power value reached a predetermined value, the polycondensation reaction vessel was purged with nitrogen to return to atmospheric pressure, stopping the polycondensation reaction. The reaction product was then pressurized with nitrogen to discharge it in strand form, cooled, and immediately cut to obtain pellets of the polyester composition. The polycondensation reaction time from the start of reduced pressure to reaching the predetermined stirrer power value was 201 minutes. The amount of carboxyl groups in the resulting polyester composition was 26.2 equivalents / ton, and the filterability was 0.42 MPa / kg.

[0036] Example 8 The procedure was carried out in the same manner as in Example 7, except that the starting temperature for adding polymerization catalysts, etc., was changed. The results are shown in Tables 1 and 2.

[0037] Example 9 The procedure was carried out in the same manner as in Example 7, except that the addition rate of ethylene glycol slurry, which is a polymerization catalyst, was changed to 135-145 kg / min to alter the range of liquid temperature drop. The results are shown in Tables 1 and 2.

[0038] Example 10 The procedure was carried out in the same manner as in Example 7, except that the starting temperature for adding the polymerization catalyst was changed, and the addition rate of the ethylene glycol slurry, which is the polymerization catalyst, was changed to 135-145 kg / min to alter the range of liquid temperature drop. The results are shown in Tables 1 and 2.

[0039] [Table 1]

[0040] [Table 2]

[0041] Comparative Example 1 The procedure was the same as in Example 7, except that the starting temperature for adding the polymerization catalyst was changed to 230°C. The results are shown in Tables 3 and 4. Under these conditions, the temperature of the BHT in the polycondensation reactor dropped to 205°C, causing the BHT to solidify, making further testing impossible.

[0042] Comparative Example 2 The procedure was the same as in Example 7, except that the starting temperature for adding polymerization catalysts, etc., was changed to 280°C. The results are shown in Tables 3 and 4. Under these conditions, the minimum temperature of the BHT solution was high at 265°C, and the high temperature at the start of the polycondensation reaction made it impossible to control the stirring torque thereafter, resulting in a significant delay in the polycondensation reaction time.

[0043] Comparative Example 3 The procedure was the same as in Example 7, except that the addition rate of ethylene glycol slurry, which is a polymerization catalyst, was changed to 150-160 kg / min to alter the range of liquid temperature drop. The results are shown in Tables 3 and 4.

[0044] [Table 3]

[0045] [Table 4]

Claims

1. Using dicarboxylic acids or their ester-forming derivatives and diols as the main raw materials, In a polycondensation batch process for producing polyester compositions, When the liquid temperature of the intermediate bis-2-hydroxyethyl terephthalate obtained by the esterification reaction of the raw materials is 240 to 270°C, the addition of the polymerization reaction catalyst and / or co-catalyst is started. A method for producing a polyester composition, characterized in that the minimum liquid temperature of bis-2-hydroxyethyl terephthalate until the addition is completed is 220°C or higher, and the decrease in liquid temperature during the addition is within 30°C from the liquid temperature at the start of addition.

2. When the liquid temperature of the intermediate bis-2-hydroxyethyl terephthalate obtained by the esterification reaction of the aforementioned raw materials is 250 to 265°C, the addition of inorganic or organic particles is started. The minimum temperature of the bis-2-hydroxyethyl terephthalate solution until the addition is complete is 220°C or higher, and the temperature drop during the addition is within 40°C from the initial temperature. A method for producing the polyester composition according to claim 1, characterized in that it is as described above.

3. A method for producing a polyester composition according to claim 1 or 2, characterized in that a polymerization reaction catalyst and / or co-catalyst, as well as inorganic or organic particles, are added when the liquid temperature of the intermediate bis-2-hydroxyethyl terephthalate obtained by the esterification reaction of the raw materials is elevated.

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