KR20060077247A - Method for producing polyethyleneterephthalate having improved heat resistance - Google Patents

Abstract

Disclosed is a method for producing polyethylene terephthalate which is excellent in heat resistance and particularly useful as a raw material for industrial synthetic fibers. The polyethylene terephthalate production method comprises the steps of esterifying ethylene glycol and terephthalic acid to prepare an oligomer; And polycondensing the resulting oligomer, adding a phosphorus-based heat stabilizer at the end of the polycondensation reaction, or adding polycarbodiimide immediately before the end of the polycondensation reaction. Here, the phosphorus heat stabilizer is selected from the group consisting of phosphoric acid, phosphorous acid, polyphosphoric acid, trimethyl phosphate, triethyl phosphate, trimethyl phosphine, triphenyl phosphine and mixtures thereof, and the end and polycondensation reaction of the polycondensation reaction It is preferable that phosphorus heat-resistant stabilizer and polycarbodiimide are respectively added just before completion | finish.

Heat resistance, polyethylene terephthalate, polymerization, phosphorus heat stabilizer, polycarbodiimide

Description

Method for producing polyethylene terephthalate having improved heat resistance

The present invention relates to a method for producing polyethylene terephthalate, and more particularly, to a method for producing polyethylene terephthalate, which is excellent in heat resistance and particularly useful as a raw material for industrial synthetic fibers.

As a manufacturing method of polyethylene terephthalate (PET), DMT and terephthalic acid (TPA) using a ester interchange reaction of dimethyl terephthalate (DMT) and ethylene glycol (EG) The TPA method which uses the esterification reaction of with ethylene glycol is known. Dimethyl terephthalate used in the DMT method has better solubility in ethylene glycol than terephthalic acid, so that it is easy to handle, and the initial reaction rate of the transesterification reaction is high, and high molecular weight polymer can be obtained with high purity. Because of its advantages, conventionally, the DMT method has been mainly used for the production of polyethylene terephthalate. However, with the recent production of high purity terephthalic acid, the production cost is low, the manufacturing process is simple, the handling is easy, and the TPA method which can improve the physical properties of the polymer is more suitable for the production of polyethylene terephthalate. It is used universally.

PET fiber manufactured using such polyethylene terephthalate is low in price and excellent in physical properties such as durability, and thus is useful not only for clothing fibers but also for medical and industrial fibers. Accordingly, various attempts have been made to produce industrial PET fibers having excellent heat resistance using polyethylene terephthalate. Methods of improving the heat resistance of PET fibers include a method of modifying the PET polymer which is a raw material of the fiber and a method of post-treatment of the fiber produced by spinning the PET polymer. Same as First, there is a method of improving the heat resistance of a PET polymer by deactivating the metal catalyst used in PET polymerization after completion of the polymerization reaction. The metal catalyst used in the PET polymerization acts as a polymerization catalyst during the polymerization, but after polymerization, a metal catalyst decomposes when heat is applied. For example, U.S. Patent No. 5,898,058 adds a phosphorus thermal stabilizer such as trimethyl phosphate, trimethyl phosphine, phosphoric acid, phosphorous acid, triethylene phosphate, and the like to the PET polymer. A method of preventing is disclosed. Second, there is a method of improving the heat resistance of the PET polymer by inhibiting side reactions that generate impurities such as acetaldehyde, diethylene glycol (DEG), oligomers (Oligomer) during PET polymerization. DEG produced by the side reaction during PET polymerization is inserted into the PET main chain and decomposes the ester bond, so that suppressing the generation of such impurities can improve the heat resistance of PET. In order to suppress such side reactions, the method of adding additives, such as Irgamod-195 by Ciba company typically, to a polymerization reaction is used. Third, there is a method of improving the heat resistance of PET polymer by using a chain extender such as PBO (1,4-Phenylene Bisoxazoline), BO (2,2-Bis-2-Oxazoline), Bruggolen M1251, etc. . The chain extender connects PET polymer molecules to each other to induce crosslinking between polymer chains, thereby improving heat resistance of the PET polymer. Fourth, there is a method of improving the heat resistance of a PET polymer by using a carboxyl capping agent such as polycarbodiimide and sodium benzonate. The carboxyl group protecting group is bonded to the carboxyl group of the PET chain, thereby reducing the activity of the carboxyl group. The carboxyl group of the PET polymer decomposes the main chain by reacting with the main chain of the polymer, thereby lowering the heat resistance of the PET. When the carboxyl group is inactivated, the heat resistance of the PET polymer can be improved. However, polyethylene terephthalate produced by such a method also does not have sufficient satisfactory heat resistance.

Accordingly, an object of the present invention is to provide a method for producing polyethylene terephthalate having excellent heat resistance. Another object of the present invention is to provide a method for producing polyethylene terephthalate which is particularly useful as a raw material for industrial synthetic fibers.

In order to achieve the above object, the present invention comprises the steps of esterifying the ethylene glycol and terephthalic acid to prepare an oligomer; And polycondensation of the resulting oligomer, and at the end of the polycondensation reaction to add a phosphorus-based heat stabilizer, or a polycarbodiimide immediately before the end of the polycondensation reaction provides a method for producing a polyethylene terephthalate. Here, the phosphorus heat stabilizer is selected from the group consisting of phosphoric acid, phosphorous acid, polyphosphoric acid, trimethyl phosphate, triethyl phosphate, trimethyl phosphine, triphenyl phosphine and mixtures thereof, and the end and polycondensation reaction of the polycondensation reaction It is preferable that phosphorus heat-resistant stabilizer and polycarbodiimide are respectively added just before completion | finish.

Hereinafter, the present invention will be described in more detail.

In order to prepare polyethylene terephthalate (PET) according to the present invention, first, an esterification reaction of an ethylene glycol (EG) and a terephthalic acid (TPA) slurry in an esterification reactor prepares an oligomer, and then polycondenses the resulting oligomer. Carry out polycondensation reaction by transferring to poly condensation (PC) reactor, and add a phosphorus heat stabilizer at the end of the polycondensation reaction, or at the end of the polycondensation reaction, a Carboxylic Ending Group (CEG) protecting group Polycarbo diimid is added as a capping agent. In this case, the esterification reaction may be carried out under the same conditions as the esterification reaction of a conventional polyethylene terephthalate manufacturing process, for example, may be carried out at atmospheric pressure and temperature of 260 ℃, the polycondensation reaction is also conventional It may be carried out under the same conditions as the polycondensation reaction, for example, may be carried out in a vacuum and at a temperature of 270 ℃, preferably in the presence of Sb ₂ O ₃ as a polymerization catalyst.

At the end of the polycondensation reaction, specifically, the phosphorus heat stabilizer added 30 minutes before the end of the reaction deactivates the polycondensation metal catalyst which causes the chain decomposition action on the PET polymer, thereby improving the heat resistance of the polymer. It is preferable to add when the polycondensation reaction is almost completed. Such phosphorus heat stabilizers include phosphoric acid, phosphorous acid, polyphosphic acid, trimethyl phosphate (TMP), triethyl phosphate, trimethyl phosphine , Triphenyl phosphine (triphenyl phosphine) and the like can be used alone or in combination. The amount of the phosphorus heat stabilizer is preferably 25 to 500 ppm, more preferably 50 to 150 ppm relative to the PET polymer. If the amount of the phosphorus heat stabilizer is less than 25 ppm, the function of the phosphorus heat stabilizer is not sufficiently exhibited. It is difficult to substantially increase the heat resistance of the polymer, and if it exceeds 500 ppm, it exceeds the saturation point of the stabilizer action, which makes it difficult to obtain additional effects, and the phosphorus-based compound acts as an impurity, which may lower the physical properties of the PET polymer. . The phosphorus heat stabilizer may be dissolved or dispersed in ethylene glycol, and added to the polycondensation reactor in a solution state, wherein the amount of ethylene glycol may be appropriately used in an amount capable of sufficiently dissolving the phosphorus heat stabilizer. For example, it can manufacture and use so that the density | concentration of a phosphorus heat resistant stabilizer may be 10 weight%.

Immediately before the end of the polycondensation reaction, preferably, about 10 minutes after the addition of the phosphorus heat stabilizer, polycarbodiimide is added to the carboxyl end group that lowers the heat resistance and fatigue resistance of the PET polymer. : CEG) to inactivate the carboxyl end groups, thereby improving the heat resistance of the PET polymer. Since the polycarbodiimide functions to inhibit the polycondensation reaction by inactivating the carboxyl end groups of the polymer, it is preferably added at the time when the polycondensation reaction is almost completed, and after the phosphorus heat stabilizer is stabilized, More preferably. Commercially available examples of such polycarbodiimide may include the reagent name Polycarbodiimide of Sigma Aldrich, USA. Since the polycarbodiimide is intended to inactivate the carboxyl end groups, it is preferable to add at least the amount of carboxyl end groups present in the PET polymer. Specifically, the amount of the polycarbodiimide used is preferably 200 to 1000 ppm, more preferably 250 to 500 ppm, and most preferably 350 to 500 ppm relative to the PET polymer. If the amount of the polycarbodiimide is less than 200 ppm, the carboxyl end groups may not be sufficiently inactivated. If the amount of the polycarbodiimide exceeds 1000 ppm, the polycarbodiimide may act as an impurity, which may adversely affect the physical properties of the PET polymer. . The polycarbodiimide may also be dissolved or dispersed in ethylene glycol and added to the polycondensation reactor in a solution state, wherein the amount of ethylene glycol may be appropriately used in an amount capable of sufficiently dissolving polycarbodiimide. For example, it can manufacture and use so that the density | concentration of polycarbodiimide may be 10 weight%. In this way, by adding the phosphorus heat stabilizer and the polycarbodiimide at the end of the polycondensation reaction and immediately before the end of the polycondensation reaction, the heat resistance of the PET polymer can be improved synergistically.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. In the following Examples and Comparative Examples, the heat resistance of the polymer (1) of IV (Intrinsic Viscosity, Intrinsic Viscosity) and CEG (carboxylic end group) of PET polymer before and after heating (130 ° C., 20 hours) in pressurized water The change was evaluated by comparing the change (hydrolysis experiment) and (2) comparing the change of IV and CEG of the PET polymer before and after melting (290 ° C., 30 minutes) in the air atmosphere (melting experiment). The smaller the change, the better the heat resistance stability.

Example 1                     

Ethylene glycol and terephthalic acid were used as the reaction raw materials, and esterification was performed for 2 hours using a 10 kg batch pilot polymerizer for Hyosung Co., Ltd., followed by polycondensation for 4 hours to carry out PET polymer. Prepared. At this time, at the end of the polycondensation reaction, specifically 30 minutes before the end of the reaction, 100 ppm of trimethyl phosphate (manufactured by Aldrich Co., Ltd.) was prepared as a 10 wt% ethylene glycol solution and added to the PET polymer.

Example 2

Instead of adding trimethylphosphate at the end of the polycondensation reaction, 450 ppm of polycarbodiimide (from Aldrich) was added to the PET polymer immediately before the end of the polycondensation reaction, specifically 20 minutes before the end of the reaction. A PET polymer was prepared in the same manner as in Example 1, except for preparing and adding.

Example 3

Immediately before the end of the polycondensation reaction, the PET polymer was prepared in the same manner as in Example 1, except that 450 ppm polycarbodiimide (manufactured by Aldrich) was added to the PET polymer in a 10 wt% ethylene glycol solution and further added thereto. Prepared.

Comparative Example 1

A PET polymer was prepared in the same manner as in Example 1, except that no additive was used.

Comparative Example 2

Instead of adding trimethylphosphate at the end of the polycondensation reaction, except that 450 ppm of polycarbodiimide (from Aldrich) was prepared in 10 wt% ethylene glycol solution and added to the PET polymer at the beginning of the polycondensation reaction, PET polymer was prepared in the same manner as in Example 1.

Comparative Example 3

Instead of adding trimethylphosphate at the end of the polycondensation reaction, except that 100 ppm of trimethyl phosphate (Aldrich's product) was prepared as a 10 wt% ethylene glycol solution and added to the PET polymer at the beginning of the polycondensation reaction. PET polymer was prepared in the same manner as 1.

To evaluate the heat resistance of the PET polymer prepared in Examples and Comparative Examples are shown in Table 1 below.

Hydrolysis experiment Melting experiment Polycondensation reaction time ΔI.V. rate △ CEG rate ΔI.V. rate △ CEG rate Comparative Example 1 4 hours 10 minutes 32% 84% 24% 46% Comparative Example 2 6 hours 20 minutes 30% 79% 22% 45% Comparative Example 3 5 hours 40 minutes 31% 70% 14% 30% Example 1 4 hours 5 minutes 25% 54% `15% 35% Example 2 3 hours 50 minutes 24% 43% 13% 33% Example 3 4 hours 15 minutes 10% 21% 6% 18%

From the above Table 1, even when the polycarbodiimide and the phosphorus heat stabilizer were separately added (Examples 1 and 2), the heat resistance of the obtained PET polymer was improved as compared with the case where no additive was added (Comparative Example 1). When both the polycarbodiimide and the phosphorus heat stabilizer are added at an appropriate time point (Example 3), it can be seen that the heat resistance of the obtained PET polymer is significantly increased. In addition, when the polycarbodiimide and the phosphorus heat resistant stabilizer are added at the beginning of the polycondensation reaction (Comparative Examples 2 and 3), it can be seen that the polycondensation reaction is inhibited and the reaction time is long.

As described above, the polyethylene terephthalate polymer prepared according to the present invention is excellent in heat resistance and is particularly useful as a raw material of industrial synthetic fibers.

Claims (5)

Preparing an oligomer by esterifying ethylene glycol and terephthalic acid; And Polycondensation of the resulting oligomer, a method of producing a polyethylene terephthalate comprising the step of adding a polyphosphorus heat stabilizer at the end of the polycondensation reaction, or just before the end of the polycondensation reaction. The preparation of polyethylene terephthalate according to claim 1, wherein the phosphorus heat stabilizer is selected from the group consisting of phosphoric acid, phosphorous acid, polyphosphoric acid, trimethylphosphate, triethylphosphate, trimethylphosphine, triphenylphosphine and mixtures thereof. Way. The method of claim 1, wherein the amount of the phosphorus heat stabilizer is 25 to 500 ppm based on the polyethylene terephthalate polymer. The method of claim 1, wherein the polycarbodiimide is used in an amount of 200 to 1000 ppm based on the polyethylene terephthalate polymer. The method for producing polyethylene terephthalate according to claim 1, wherein the phosphorus heat stabilizer and the polycarbodiimide are added at the end of the polycondensation reaction and immediately before the end of the polycondensation reaction.