RU2804159C1 - Complex catalyst for synthesis of polyethylene terephthalate - Google Patents

Abstract

FIELD: polymers.

SUBSTANCE: invention relates to a method for producing a catalyst for the synthesis of polyethylene terephthalate. A complex catalyst for the synthesis of polyethylene terephthalate based on a guanidine-containing compound and a titanium-containing compound is characterized in that the guanidine-containing compound is guanidine methacrylate, and a titanium-containing compound of tetrabutoxytitanium, with a quantitative ratio of components of 0.5-2 mol: 1 mol, respectively.

EFFECT: obtaining an effective complex catalyst for the synthesis of polyethylene terephthalate, which has the ability to improve the viscosity and colour of the final synthesis product.

1 cl, 3 dwg, 3 tbl

Description

The invention relates to a method for producing complex catalysts intended for the synthesis of polyethylene terephthalate.

Thermoplastic polyester materials, as an important class of polymers, bring great convenience to people's lives. These materials are widely used in the fields of fibers, films, PET bottles, medical materials and engineering plastics. Catalysts are used in the production of polyesters. One of the most common catalysts for the synthesis of polyesters are antimony compounds. For several years now, polyester manufacturers have been trying to abandon antimony catalysts. They pose a danger to the environment. Titanium catalysts are preferred to replace them. As a result of the analysis of patent and technical literature, developments describing various titanium catalysts were identified. The invention of US Pat. No. 5,656,716 describes a catalyst for the production of polyesters consisting primarily of a finely divided high surface area titanium compound selected from hydrated TiO ₂ obtained by hydrolysis and having the composition yTiO ₂ ⋅zH ₂ O. The composite material further includes. (MenO)x, where Me is an alkaline earth metal or an alkali metal. The process inhibitor is a phosphorus-oxygen compound, which is added immediately before, during or after polycondensation. A distinctive feature of the catalysts according to the invention is that the catalytic activity for polyester synthesis does not depend on the duration of storage.

A polyethylene terephthalate resin synthesized using an inorganic Ti-Mg catalyst is described in US patent application 20090280279. Polyethylene terephthalate resins containing a small amount of blue dye and/or additionally containing inorganic Fe ₃ O ₄ or BaSO ₄ particles are synthesized in the presence of an inorganic Ti-Mg catalyst. Mg and phosphorus stabilizer, and the resulting PET resins do not have a yellowish tint and reduce the amount of recovered acetaldehyde and cyclic oligomers after treatment. The production method is based on (a) the use of purified terephthalic acid (TPA) and ethylene glycol (EG) for the sequential process of direct esterification. Before starting the polycondensation process, an inorganic Ti-Mg catalyst and a phosphorus stabilizer are added to the reaction tank, wherein the inorganic Ti-Mg catalyst is added in an amount of 10 to 100 ppm, and the phosphorus compound is added in an amount of 5 to 50 ppm based on the total weight of the resin PET, and the titanium contained in the Ti-Mg catalyst ranges from 5 to 10 ppm based on the total weight of the PET resin and the molar ratio of added titanium to magnesium ranges from 0.1 to 0.2. Before the direct esterification process is completed, blue dye is added to the reaction tank where the direct esterification process takes place. Based on the results of Examples 1 to 7 and Comparative Examples 1 to 3, as shown in Table 15, the following conclusions are drawn: (1) PET resins contain a small amount of blue dye, and Ti-Mg inorganic catalyst used in PET synthesis is also added in as a polycondensation catalyst, and phosphoric acid as a heat stabilizer. The resulting PET is characterized by no yellowish color, excellent transparency and the formation of less recovered acetaldehyde and cyclic trimer after processing. (2) PET resins additionally contain inorganic Fe3O4 particles, which significantly contribute to the relatively high crystallinity.

The titanium/metal catalytic complex is presented in US Pat. No. 5,017,680 (1994). It can be prepared in several ways. (1) Titanium tetraisoproxide (or other titanium alkoxides) is dissolved in ethylene glycol, and a metal salt (Na, K, Li, Mg, etc.) is dissolved in ethylene glycol. Metal salts are added to the titanium alkoxide solution to obtain the desired metal/titanium ratio and stirred at room temperature.

US Patent 6,066,714 (2000), discloses an organic titanium compound, a phosphorus compound, an amine, and a solvent as a catalyst. The method for carrying out the invention is described in the patent: 33 g (0.116 mol) of tetraisopropyl titanate (TYZOR TPT) and 23 g of isopropyl alcohol were charged into a 250 ml flask equipped with a water-cooled refrigerator, stirrer, thermocouple, dropping funnel and nitrogen purge. Stirring was started and 21 g (0.116 mol) of ZELEC TY acid phosphating mass was added dropwise over 10 minutes. The reaction mass was heated to 60°C and kept for 1 hour. after which 15.5 g (0.116 mol) 2-[2-(dimethylamino)ethoxy]ethanol was added dropwise. The reaction mixture was kept for 2 hours. at 60°C and then bottled. The resulting pale yellow liquid contained 5.99% Ti and was dissolved in glycol.

The closest analogue to this development is the invention patent of the People's Republic of China 104725616 (IPC C08G 63/87, C08G 63/183, C08G 63/80, C08G 63/85). The invention describes a method of using organic guanidine catalysis of melt-solid polycondensation for the synthesis of poly(butylene adipate-co-terephthalate). The process utilizes an efficient catalytic system formed by organic guanidine, 4-isopropyl titanate in orthotitanate, or a parent zirconic acid ester. According to the authors of the invention, the catalytic system is capable of accelerating the process of obtaining the final polymer. The main disadvantage of the invention is that the suitability of using the catalytic system in the synthesis of polyethylene terephthalate is not known.

The objective of the present invention is to expand the range of effective complex catalysts for the synthesis of polyethylene terephthalate, which have the ability to improve the viscosity and color of the final synthesis product.

The problem is solved by reacting a guanidine compound with a titanium-containing compound. Moreover, it is preferable to use guanidine methacrylate as a guanidine compound, and tetraisopropoxytitanium or tetraisobutoxytitanium as a titanium compound (Fig. 1), where the structural formulas of a) tetraisopropoxytitanium and b) tetrabutoxytitanium are presented

The proposed method for obtaining a catalytic composition (CC) is carried out as follows:

At the initial stage of the process, the titanium-containing compound is pre-dissolved in ethylene glycol to obtain a highly homogenized mixture. The amount of ethylene glycol is 2% by weight of the titanium-containing compound. Then guanidine methacrylate is introduced into the system in the amount specified in Table 1.

Table 1 Example No. Guanidine compound, mol Titanium compound, mole 1 0.5 1 2 1 1 3 1.5 1 4 2 1

All stages of preparation were carried out at room temperature in a dispersant until a highly homogenized mixture was obtained. The output is a highly homogenized mixture, ready for inclusion in the synthesis of polyesters. The resulting mixture is presented in the present invention under the name CC. As a result of the interaction of the components presented in Table 1, we obtain a complex compound, shown schematically in Figure 2 using tetrabutoxytitanium as an example.

In fig. Figure 2 shows the structure of CC, which includes components in the quantitative ratio - a) 1 mol MAG : 1 mol Ti compound and b) 2 mol MAG : 1 mol Ti compound.

In order to confirm the formation of a complex compound, samples of the studied QC were analyzed using IR spectroscopy (Fig. 3). As the result of the analysis showed, in the IR spectrum of tetrabutoxytitanium after the addition of guanidine methacrylate, new characteristic bands are formed, corresponding to the formation of CC.

The interaction of Ti ions with MAG leads to a redistribution of band intensities in the region of 1260-1500 cm ^-1 , broadening of the peak at 817 cm ^-1 and 1100 cm ^-1 , and the appearance of new absorption peaks in the region of 600-700 cm ^-1 . This indicates the formation of a new coordination compound due to active interaction with the oxygen atom of the carboxylate ion and with the nitrogen atom of the amine group of MAG and titanium ions. An increase in the intensity of the bands of asymmetric and symmetric stretching vibrations of the ionized carboxyl group COO- in the range 1100 cm ^-1 - 900 cm ^-1 and a decrease in the peaks of deformation vibrations of the NH groups of the guanidine fragment in the range 800 - 700 cm ^-1 indicates that in coordination with The metal cation includes both active MAG ligands (carboxylate ion and guanidine). The presence of butoxide groups in the complex compound is confirmed by intense peaks in the region of 2600-2800 cm ^-1 .

Approbation of the catalytic system.

1 mol of terephthalic acid, 2 mol of ethylene glycol, isophthalic acid in an amount of 2% by weight of terephthalic acid and diethylene glycol in an amount of 1.5% by weight of ethylene glycol were introduced into the chemical reactor. CC obtained according to the method described above is introduced into the system, and the amount of introduced catalyst corresponds to a value of 100-250 ppm relative to CC. The installation was heated to 240°C, with intense stirring (500 rpm) in a nitrogen atmosphere for 1 hour. The pressure in the reactor system is 4-5 atm. At the same time, the by-product was distilled off along with EG. After one hour, the temperature in the reaction medium was increased to 260°C. The pressure in the reactor dropped to less than 2 atm. and the process is converted to polycondensation. A stabilizer based on phosphoric acid was introduced into the reaction mixture, the temperature of the reaction medium increased to 290°C and a vacuum was created corresponding to a value of 0.2-0.3 mm Hg. The polycondensation process takes place over 2 hours. The final product of the polycondensation reaction is discharged into cold water in the form of strands. The strands are granulated and subjected to all necessary types of research.

Tables 1 and 2 present the quantitative ratios of all components of PET synthesis and their reduced viscosity. As a comparison, a method for producing PET is presented using a traditional titanium-containing catalyst - tetraisopropoxytitanium, designated in tables 2 and 3 as “An analogous example”.

table 2
Quantitative ratio of components Component name Example by analogy Example 1 Example 2 Example 3 Example 4 TFC 1 mole 1 mole 1 mole 1 mole 1 mole EG 2 mol 2 mol 2 mol 2 mol 2 mol IFC 2% by weight TPA 2% by weight TPA 2% by weight TPA 2% by weight TPA 2% by weight TPA DEG 1.5% by weight of EG 1.5% by weight of EG 1.5% by weight of EG 1.5% by weight of EG 1.5% by weight of EG Tetraisopropoxytitanium 100 ppm 100 ppm 150 ppm 200 ppm 250 ppm Catalyst according to the invention (CC) - 100 ppm 150 ppm 200 ppm 250 ppm Stabilizer 20 ppm 20 ppm 20 ppm 20 ppm 20 ppm

The amount of catalyst and stabilizer is calculated using terephthalic acid.

Table 3
The value of the reduced viscosity of the studied samples Example by analogy Example 1 Example 2 Example 3 Example 4 Reduced viscosity, g/cm3 0.65 0.77 0.78 0.8 0.81 Color: L
A
b 83.7 81.0 80.9 81.0 81.0 2.6 4.32 4.3 4.4 4.2 5.7 16.76 16.7 16.9 16.8

The technical result of the invention is to expand the range of effective complex catalysts for the synthesis of polyethylene terephthalate, which have the ability to increase viscosity and reduce the color of the final synthesis product.

Claims (1)

A complex catalyst for the synthesis of polyethylene terephthalate based on a guanidine-containing compound and a titanium-containing compound, characterized in that the guanidine-containing compound is guanidine methacrylate, and the titanium-containing compound is tetrabutoxytitanium, with a quantitative ratio of components of 0.5-2 mol: 1 mol, respectively.