JPS6135978B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a method for producing polyester using terephthalic acid and ethylene glycol as the main starting materials by a batch method. More specifically, a reactant containing terephthalic acid and ethylene glycol as main components is esterified by a batch method, followed by a polycondensation reaction to produce a high-quality polyester with low diethylene glycol content and good whiteness. It provides a method for manufacturing on time. Conventionally, polyester useful as industrial fibers or films has been produced using dimethyl terephthalate and ethylene glycol as the main raw materials, but recently, advances in the production method of terephthalic acid have made it easier to obtain terephthalic acid at a lower price than dimethyl terephthalate. , a method using terephthalic acid has been investigated. However, when polyester is produced by the batch esterification method, a problem arises in that a large amount of diethylene glycol is produced during the esterification reaction and is copolymerized into the polyester, degrading the quality of the polyester. Various studies have been made to prevent the formation of diethylene glycol, one of which is the addition of an alkali or the like as a diethylene glycol inhibitor. However, when an alkali is added to the reaction system, aggregates are formed, which may shorten the life of the spinning filter during spinning in the fiber manufacturing process.
The spinning or drawing conditions were poor, causing various troubles. On the other hand, if mild reaction conditions are adopted and the reaction is carried out over a long period of time, the diethylene glycol content will be reduced to some extent, but from an industrial standpoint, productivity will drop significantly, so such conditions cannot be adopted. It is not possible. As a result of various studies to solve these problems, the present inventors found that instead of adding one batch of dicarboxylic acid and glycol to the remaining oligomer all at once, they added it gradually, and in that case, one batch was fully reacted. By adopting the conditions described below regarding slurry supply rate with respect to time, reaction pressure and temperature during slurry supply or after completion of supply, polyester with low diethylene glycol content and good whiteness can be produced in a short time, and at the same time They have discovered a manufacturing method that is completely trouble-free during the polymer and fiber manufacturing process. That is, in the present invention, when performing an esterification reaction using terephthalic acid and ethylene glycol or terephthalic acid and ethylene glycol and another third component in a batch method, 10 to 30% of the oligomers produced in one batch are subjected to the esterification reaction. The oligomer is left in the tank, and the oligomer is mixed with a slurry of dicarboxylic acid and glycol in a molar ratio of 1.03 to 1.6 of glycol, mainly ethylene glycol, to dicarboxylic acid, mainly terephthalic acid, or the dicarboxylic acid and glycol. The dicarboxylic acid and glycol are supplied separately, continuously or intermittently, and the supply of the dicarboxylic acid and glycol is completed in 60 to 90% of the time required for one batch of reaction, and the remaining 40 to 10% is React without supply for a time of
The reaction pressure is 1.0 to 3.0Kg/cm ² G during supply, and the reaction pressure is 1.5Kg/cm ² G when reacting without supply.
The present invention relates to a batch esterification method characterized in that the reaction temperature is 235 to 270°C. In the present invention, it is necessary to allow 10 to 30% of the oligomer produced in one batch to remain in the esterification tank. If it is less than 10%, the esterification reaction will take a long time and the diethylene glycol content of the resulting polyester will increase, which is undesirable.
% or more, the reaction time for one batch is somewhat shortened, but the residual amount is large, resulting in low productivity, and the diethylene glycol content is also large, which is not preferable. The amount of remaining oligomer can be adjusted, for example, as shown in FIG. 1, by adjusting the height of the protrusion of the oligomer transfer pipe from the esterification tank to the polymerization tank within the esterification tank. FIG. 1 is an example of an apparatus used in the present invention. In the figure, 1 is the esterification tank, 2 is the polymerization tank, 3 is the slurry supply pipe, 4 is the stirrer, 5 is the liquid level before transferring the oligomer to the polymerization tank, 6 is the liquid level of the remaining oligomer, and 7 is an oligomer transfer pipe, 8 is a rectification column, 9 is a condenser, 10 is a distillate receiving tank, 1
1 is a reflux pipe, 12 is a distillate delivery pipe, and 13 is a polymer extraction pipe. In the present invention, the molar ratio of dicarboxylic acid and glycol added to the reaction system must be 1.03 to 1.6. If it is less than 1.03, it will take a very long time to complete the reaction, and if it is more than 1.6, the diethylene glycol content will be large, which is not preferable. The molar ratio of terephthalic acid (total of other dicarboxylic acids, if any) and ethylene glycol (total of other glycols, if any) is:
Although it is usually constant from the beginning to the end of the preparation, it may change during the preparation, especially when terephthalic acid and ethylene glycol are added without making a slurry. In short, the overall charging molar ratio and the charging molar ratio at intermediate stages (when terephthalic acid and ethylene glycol are added separately and intermittently, It needs to be substantially 1.03 to 1.6, excluding changes in the molar ratio.The method for adding and supplying dicarboxylic acid and glycol is as follows:
Although dicarboxylic acid and glycol are generally mixed and added as a slurry, they may be supplied separately. In the following, for convenience of explanation, a case where both are mixed and supplied as a slurry will be described. In the present invention, the slurry is not added all at once to the remaining oligomers, but is added gradually. The slurry is particularly preferably supplied for 60 to 90% of the time required for one batch of esterification reaction. is 70-80% complete and the remaining 40-10
%, preferably 30 to 20% of the time, the reaction is allowed to proceed without feeding. The time required for one batch of esterification reaction here refers to the time during which the reactants are present in the esterification reaction vessel and the polycondensation reaction vessel, in relation to the subsequent polycondensation reaction time. Shows reaction times that are equal and have no latency. This is important in terms of productivity and polymer quality in the batch esterification process. If the slurry supply is completed in less than 60% of the time required for one batch of esterification reaction, the diethylene glycol content will be large, and if the slurry is completed in 90% or more, it will contain a large amount of unreacted raw materials. Since the polyester is transferred to the polymerization tank in a state in which the ester is present, the degree of polymerization does not increase and it is not possible to obtain polyester of the desired quality. This results in a longer total esterification time and a higher diethylene glycol content. The slurry feeding rate may not be constant. It is preferable to adjust the feed rate appropriately so that the feed rate at the end of the process is relatively high. The pressure during the esterification reaction is 1.0 during slurry supply.
~3.0Kg/cm ² G, and 1.5Kg/cm ² G or less when reacting without supplying slurry. If the pressure during slurry supply is less than 1.0Kg/cm ² G, the esterification reaction time will be long; on the other hand, if the pressure is 3.0Kg/cm ² G or more, the reaction will take a short time, but the diethylene glycol content will be large. Become. If the pressure is 1.5 Kg/cm ² G or more when the reaction is carried out without supplying slurry, the reaction will be completed in a short time, but the diethylene glycol content will be large. During reaction operation, the pressure is 1.0~ throughout the entire reaction period.
It is advantageous to keep the pressure constant between 1.5 Kg/cm ² G, but the diethylene glycol content will be lower if the pressure is lower when the slurry is not being supplied than the esterification reaction pressure when the slurry is being supplied. Become. In most of the esterification reaction, the reaction temperature is 235 to 270°C, except for the start of charging and the period when the esterification rate is 93% to 97% or more. At temperatures below 235°C, the reaction takes a very long time and the diethylene glycol content is not very small. Conversely, if the temperature is 270°C or higher, the reaction time will be short, but the diethylene glycol content will be large. The polyester in the present invention is composed of terephthalic acid and ethylene glycol or terephthalic acid and ethylene glycol and another third component.
This is a polyester in which 80% or more of the repeating structural units are ethylene terephthalate, obtained by performing the esterification reaction and polycondensation reaction batchwise. The third component in the polyester includes isophthalic acid, phthalic acid, adipic acid, sebacic acid, propylene glycol, neopentyl glycol, tetramethylene glycol, 1,4-cyclohexanedimethanol, P-oxybenzoic acid, P-oxyethoxy Difunctional comonomers such as benzoic acid, polyfunctional crosslinking agents such as trimethylolpropane, pentaerythritol, glycerin, and trimesic acid, and monofunctional terminal capping agents such as monomethoxypolyethylene glycol and naphthoic acid are used. Additionally, additives such as other types of polymers such as polystyrene, styrene-methyl methacrylate copolymers, pigments such as titanium oxide, carbon black, UV absorbers, fluorescent brighteners, or insoluble nucleating agents such as kaolin. May contain. The present invention will be specifically described below with reference to Examples. The esterification reactions in Examples and Comparative Examples were carried out until 95 to 97% reaction was achieved, by determining the esterification rate (the esterified proportion of the total terephthalic acid supplied) by quantifying the carboxyl group. The polycondensation reaction was carried out in the same manner as in Example 1 until [η] (intrinsic viscosity dl/g measured at 30°C in orthochlorophenol solvent) reached 0.68 based on the torque indicated by the stirring blade of the polymerization tank. I did it. Furthermore, the diethylene glycol content in the polyester is a value determined by gas chromatography after decomposing the polyester using a conventional method. In addition, the whiteness was determined as a yellowness value using a standard method using a Carl Zeiss Ellehometer using chips of 2 x 4 x 6 mm after the completion of polymerization. It is shown that. Example 1 Terephthalic acid (hereinafter referred to as
TA/EG slurry, which is a mixture of ethylene glycol (hereinafter referred to as EG) at a molar ratio of 1.1 times that of TA (abbreviated as TA), is continuously supplied for 75% of the time required for one batch. Ta. The slurry is supplied while stirring the esterification tank, and the reaction pressure is
The reaction was carried out at 1.5 Kg/cm ² G and a temperature of 245° C. The water produced by the reaction was successively distilled out through a rectification unit attached to the esterification tank, and a portion was refluxed. After the slurry supply was completed, the reaction was continued as it was, and the reaction pressure was gradually reduced to normal pressure at the end of the reaction, and the reaction temperature was also gradually increased to 260°C at the end of the reaction. The total time required for the esterification reaction was 240 minutes, and the esterification rate at this time was 95%. 85% of the oligomer obtained by the reaction was left in the esterification tank.
% was transferred to a polymerization tank. Antimony oxide equivalent to 350 ppm, phosphoric acid equivalent to 100 ppm, cobalt acetate equivalent to 100 ppm, and titanium dioxide equivalent to 0.5% by weight were added to the polyester in a polymerization tank, and the temperature was raised from 245°C to 285°C. At the same time, the pressure was reduced from 760 mmHg to 1 mmHg or less, and the polycondensation reaction was carried out for 180 minutes until [η] became 0.6 dl/g. The obtained polymer was extruded from a polymerization tank for 60 minutes and turned into chips. The time required for the polymerization reaction, including the polymer extrusion time, was 240 minutes. Diethylene glycol (hereinafter abbreviated as DEG) contained in the obtained polymer was 1.6 mol%,
The whiteness was 0.1. Examples 2 to 11 and Comparative Examples 1 to 11 By performing the same operations as in Example 1, various changes were made in the remaining amount of monomer, the charged EG/TA molar ratio, the slurry supply method during the esterification reaction, the esterification reaction temperature, and the pressure. and examined its impact. The results are shown in Table 1 together with the results of Example 1.
As is clear from Table 1, high quality polyester can be obtained in a short time only in the case of the present invention.

【table】

[Table] Example 11 Into an esterification tank in which 15% of the total amount of the oligomer produced in the previous batch remained, 3 EG and TA powders were continuously added from separate charging ports at an EG/TA molar ratio of 1.2. Supply over time, pressure 1.5Kg/cm ² ,
The reaction was carried out at a temperature of 250°C, and the produced water was removed from a rectification column. After the completion of the EG and TA powder supply, the reaction continued as it was, and the reaction pressure was gradually reduced to normal pressure at the end of the reaction and to 260°C at the end of the reaction. The esterification rate at this time was 95%. 15% of the oligomer so obtained remained in the esterification tank and 85% was transferred to the polymerization tank. Polymerization was carried out in the same manner as in Example 1. The polymerization time was 235 minutes, and a polymer with a DEG content of 1.7 mol% and a whiteness of 0.5 was obtained. Comparative Example 12 Into an esterification tank in which 15% of the total amount of the oligomer produced in the previous batch remained, 4 EG and TA powders were continuously added from separate feeding ports at an EG/TA molar ratio of 1 and 2. Supply over time, pressure 1.5Kg/
cm ² and a temperature of 250° C., and immediately polymerization was carried out in the same manner as in Example 1. The polymerization time was 315 minutes, and an unsatisfactory polymer with a DEG content of 4.5 mol% and a whiteness of 3.7 was obtained. Comparative Example 13 A polyester was obtained in the same manner as in Example 1 except that the reaction pressure of 1.5 Kg/cm ² G was maintained even after the oligomer was supplied. The resulting polyester exhibited whiteness 8 times that of the example, and also had a 20% increase in diethylene glycol content.

[Brief explanation of the drawing]

Figure 1 is an example of equipment showing the process from the esterification tank to the polymerization tank, where 1 is the esterification tank, 2 is the polymerization tank, 3 is the slurry supply pipe, 4 is the stirrer, and 5 is the transfer of oligomers to the polymerization tank. 6 is the liquid level of the remaining oligomer, 7 is the oligomer transfer pipe, 8
1 is a rectification column, 9 is a condenser, 10 is a distillate receiving tank, 11 is a reflux pipe, 12 is a distillate delivery pipe, and 13 is a polymer extraction pipe.

Claims (1)

[Claims] 1 When carrying out an esterification reaction of terephthalic acid and ethylene glycol or terephthalic acid and ethylene glycol and other third components by a batch method, 10% of the oligomers produced in one batch are
~30% remains in the esterification reaction tank, and the oligomer is a slurry of a mixture of dicarboxylic acid and glycol with a molar ratio of glycol, mainly ethylene glycol, to dicarboxylic acid, mainly terephthalic acid, of 1.03 to 1.6. Alternatively, the dicarboxylic acid and glycol are supplied separately, continuously or intermittently, and the supply of the dicarboxylic acid and glycol is completed in 60 to 90% of the time required for one batch of reaction, and the remaining React without supplying for 40-10% of the time, and keep the reaction pressure at 1.0 during supply.
~3.0Kg/cm ² G, the reaction pressure when reacting without supply is 1.5Kg/cm ² G or less, the reaction pressure when reacting without supply is lower than the reaction pressure during supply,
A batch esterification method for terephthalic acid, characterized in that the reaction temperature is 235° to 270°C.