KR20010087534A - Manufacturing method of polyester polymer having high transparency - Google Patents

Abstract

PURPOSE: Provided is a process for producing polyester polymer, used for packing and storing food and being excellent in transparency and color, by polycondensing terephthalic acid or ester-forming derivatives thereof and ethylene glycol. CONSTITUTION: The process for producing the polyester polymer comprises the steps of: esterifying the terephthalic acid or the ester-forming derivatives thereof and the ethylene glycol at a temperature of less than 260deg.C and stopping the esterification when the rate of the esterification is 90-92%; polycondensing the resultant and 20-60ppm (based on the polymer) of a phosphorous compound as a heat-stabilizer at a temperature of less than 285deg.C in the presence of 80-150ppm (based on the polymer) of a glycol soluble germanium compound catalyst.

Description

Manufacturing method of polyester polymer having high transparency

The present invention relates to a method for producing a polyester polymer having excellent transparency as a main component of polyethylene terephthalate. In particular, a glycol-soluble germanium compound is used as a polymerization catalyst in the range of 90% to 92% esterification, and as a stabilizer, The present invention relates to a process for producing polyester polymers suitable for producing co-currents, sheets, and various blow molded articles requiring good transparency.

In general, polyester, in particular polyethylene terephthalate (hereinafter referred to as "PET") is widely used as a resin for bottles, fibers, films and sheets because of its excellent mechanical properties, heat resistance and chemical resistance, PET is usually produced industrially by the following two-step reaction.

That is, the first step reaction of forming a bishydroxy ethyl terephthalate or its polymer by heating reaction (typically 200-270 degreeC) of terephthalic acid or its ester formation derivative and ethylene glycol, and the produced bishydroxy ethyl terephthalate Or a second step reaction (typically 280 to 310 ° C.) in which the low polymer is polycondensed to obtain a polymer. Such a reaction is usually smoothly condensed in the presence of various additives such as a catalyst and thermal stability.

For example, in the first stage reaction, one or more kinds of metal compounds such as sodium, lithium, calcium, magnesium, manganese, zinc and tin are selectively used, and in the second stage reaction, phosphorus compound and polycondensation are used as stabilizers. As the catalyst, for example, antimony compounds, titanium compounds, germanium compounds and the like are used.

The antimony compound used as the polycondensation catalyst is low in price and excellent in catalyst activity, but the amount of catalyst added during the polycondensation reaction should be large, and antimony metal precipitates during the reaction to blacken the polymer, and heavy metal components during product molding. Phosphorus antimony precipitates and contaminates the surface and contents of the product. In addition, in the case of the titanium compound, the reaction activity is excellent, but there is a disadvantage in that the obtained polymer is colored, which is not suitable for the production of products requiring excellent color and transparency. In addition, the germanium compound may obtain a polymer having excellent reactivity and excellent transparency and gloss, but has a disadvantage in that coloring and heat resistance are reduced when used in excess.

Various additives and stabilizers are used to compensate for the shortcomings of such polycondensation catalysts, but these components also cause other side reactions during the polymerization of polyesters, which may act as a factor of reducing the color and transparency of the polymer.

That is, these additives are used to obtain a high quality polyester polymer having excellent color and transparency, but since the polycondensation reaction is performed for a long time at a high temperature, various unwanted side reactions (diethylene glycol production and terminal carboxyl group content, internal particle generation) Lowering of transparency and coloring, etc., may cause physical and chemical degradation of the resulting polyester polymer, and the higher the type and content of the additive, the more complicated the reaction mechanism, resulting in unexpected side reactions, resulting in coloring or transparency. It acts as a factor that causes degradation of polyester such as degradation and precipitation of additives.

Conventionally, in order to improve the coloring and transparency problems caused by side reactions, a method of preparing a polyester polymer using a mixture of a lithium compound and a germanium compound as a polycondensation catalyst has been proposed (Korean Patent Application 93-704015). The role of the thermal stabilizer that can sufficiently reduce the reverse reaction and side reactions caused by the catalyst is insufficient, and the method of producing high quality polyester by dividing the esterification reaction which proceeded only in one step into two steps is disclosed in Korean Patent Application No. 91. It was proposed as -4203, but there was a disadvantage in that the productivity decreases as the reaction time increases.

In addition, Japanese Laid-Open Patent Publication No. 11-140175 discloses a method of using a mixed oxide of titanium dioxide and germanium dioxide as a catalyst, and Japanese Patent Laid-Open No. 55-36211 discloses a method using a germanium compound and an amine compound. In Japanese Patent Application Laid-Open No. 61-85435, a method of using a mixed catalyst such as magnesium or manganese, an alkali metal compound, a germanium catalyst, and an antimony catalyst is mainly used as a polycondensation catalyst by mixing antimony or titanium compounds in addition to germanium compounds, Although a method of using various additives and the like has been introduced, it has not substantially overcome the quality deterioration, such as the deposition of metal catalysts or coloring by reverse reactions and side reactions, and the decrease in transparency.

In order to solve the problems described above, the present invention used a glycol-soluble germanium compound having excellent reaction activity as a polycondensation catalyst, and a phosphorus compound was used as a stabilizer to effectively suppress side reactions. It is characterized by providing a method for producing a high quality polyester polymer having excellent transparency.

In addition, another object of the present invention is to use an environment-friendly germanium catalyst, do not use a metal catalyst, eliminating the problems caused by the precipitation of the catalyst during molding, excellent transparency used for packaging and storage of foods It is to provide a method for producing a polyester polymer.

In order to achieve the above object, the present invention provides a method for producing a polyester resin obtained by subjecting terephthalic acid or its ester-forming derivative and ethylene glycol to a polycondensation reaction in the presence of a catalyst, wherein terephthalic acid or its ester-forming derivative and ethylene glycol are 260 ° C. When the reaction rate is 90-92% at a temperature not exceeding, the one-step esterification reaction is completed, and the reactant is transferred to a polycondensation reaction tube, and a thermal stabilizer is added 20 to 60 ppm of phosphorus compound with respect to the polymer, and continuously glycol 80 to 150 ppm of the polymer is added to the polymer using a soluble germanium compound as a polycondensation catalyst, and the polycondensation reaction temperature is not higher than 285 ° C., thereby preventing side reactions due to high temperature reaction. Is achieved.

The glycol soluble germanium compound used as the polycondensation catalyst in the present invention includes glycol soluble germanium dioxide, germanium acetate, germanium oxide, etc., and its content is suitably 80 to 150 ppm relative to the polymer. When the amount of the polycondensation catalyst added is less than 80 ppm, the polymerization time is long, the IV increase rate is significantly reduced, making it difficult to obtain a polymer having a desired molecular weight, and coloring by side reaction products occurs. In addition, when the amount of polycondensation catalyst added exceeds 150 ppm, the polycondensation reaction time is considerably shortened, but the molecular weight is not uniform, and there is a closed end to obtain a colored polymer.

As a stabilizer which is a phosphorus compound used in the present invention, phosphoric acid, triethyl phosphate and triphenyl phosphate are preferable, and its content is suitably 20 to 60 ppm with respect to the polymer. If less than 20 ppm of stabilizer is used, the product by side reaction increases to color the polymer, and the heat resistance is lowered. If the stabilizer is used more than 60 ppm, polycondensation reaction is delayed and side reaction product is increased and there is a closed end.

The measurement regarding the property and general physical properties of the polymer obtained in the present invention was made by the following method.

(1) Intrinsic viscosity is measured by using orthochlorophenol as a solvent at 25 ℃.

(2) The color tone of the polymer was determined using a color difference meter at room temperature for the chip after the polymerization reaction.

The color tone L value represents lightness, and the larger the value, the brighter and transparent the color value, the larger the value, the yellower color and the smaller the value, the blue color.

(3) The transparency of the polymer was expressed as a solution haze. After dissolving at 110 ° C. in a phenol / tetrachloroethane (60/40 weight ratio) mixed solution, the haze was measured at room temperature. In this case, the lower the measurement, the better.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

Example 1

190 g of pure terephthalic acid and 82 g of ethylene glycol were charged to a reaction tube, and reacted for about 4 hours without a catalyst at 250 ° C. under a nitrogen atmosphere of 1.5 Kg / cm 2. Water generated during the reaction was discharged through a distillation column, and the amount of water discharged was calculated to complete the first stage reaction when the reaction rate was 91%. Transfer the reaction product from the first stage reaction to the polymerization tube, add 30 ppm phosphoric acid to the polymer on the elemental basis with thermal stabilizer, and add 90 ppm to the polymer on the germanium element basis with glycol soluble germanium dioxide as polycondensation catalyst. The reaction was carried out, and 1 hour after the start of the reaction, the reaction was carried out at a temperature of 280 ° C. under 0.5 mmHg vacuum to complete the polycondensation. The inherent viscosity of the obtained polymer was 0.635, the L value was 63.4, the b value was -1.5, and the haze was 0.5.

Example 2

In Example 1, 40 ppm of triethyl phosphate was added as a stabilizer to the polymer on the basis of phosphorus element, and the reaction was performed under the same conditions. The inherent viscosity of the obtained polymer was 0.625, the L value was 63.2, the b value was -1.1, and the haze was 0.6.

Example 3

In Example 1, the reaction was carried out using 45 ppm of triphenylphosphate as a stabilizer based on phosphorus element and 120 ppm of glycol soluble germanium acetate as polymer based on elemental germanium as polycondensation catalyst. The inherent viscosity of the obtained polymer was 0.625, the L value was 62.8, the b value was -0.9, and the haze was 0.6.

Comparative Example 1

The reaction was carried out in the same manner as in Example 1 except that 60 ppm of trimethyl phosphate was used as a thermal stabilizer for the polymer based on phosphorus, and 200 ppm was added to the polymer based on antimony triacetate as the polycondensation catalyst. 0.5 mmHg vacuum The reaction was completed at a temperature of 290 ° C. for 2 hours to complete the polycondensation. The inherent viscosity of the obtained polymer was 0.630, the L value was 54.7, the b value was -0.3, and the haze was 0.8.

Comparative Example 2

In Comparative Example 1, 30 ppm of tetraethylammonium hydroxide was added as catalyst to the polymer on the basis of elemental ammonia, and 50 ppm to phosphorus on the basis of phosphorus element as the stabilizer in the two-step reaction. Cobalt acetate was added to the polymer based on the antimony trioxide as a 180 ppm complementary agent on the basis of the antimony element and 45 ppm to the polymer based on the cobalt element to proceed the polymerization. The inherent viscosity of the obtained polymer was 0.630, the L value was 51.7, the b value was -2.2, and the haze was 1.3.

Table 1 shows the results of Examples and Comparative Examples.

Table 1

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Intrinsic viscosity 0.635 0.625 0.625 0.630 0.630 Hue (L / b) 63.4 / -1.5 63.2 / -1.1 62.8 / -0.9 54.7 / -0.3 51.7 / -2.2 Haze (%) 0.5 0.6 0.6 0.8 1.3

From the results of Table 1, the polyester polymer prepared by the polymerization method as in the present invention is an antimony catalyst and a complementary agent (cobalt acetate), side reaction inhibitor (tetra ethylammonium hydroxide) and the like in terms of color tone and transparency (haze). It showed much better color and transparency than the polyester using the conventional antimony catalyst polycondensed. In particular, when using an antimony catalyst, it can be seen that there is a gloss decrease (L value) due to precipitation of the catalyst.

As described in detail above, in the present invention, in the polycondensation of polyesters by esterifying terephthalic acid and ethylene glycol, transparency is achieved only by using glycol-soluble germanium compounds and phosphorus compounds as additives without using any metal catalysts or side reaction inhibitors. It is possible to manufacture polyester polymer with excellent reactivity and color and excellent reactivity. In particular, since the additives of metal components harmful to human body are not used, the polyester polymer can be used in food-forming bottles or hollow containers such as food-storage containers. It is very effective when manufacturing packing sheets.

Claims (3)

In the method for producing a polyester polymer obtained by polycondensation of terephthalic acid or its esterified derivative and ethylene glycol in the presence of a catalyst, the esterification rate of terephthalic acid or its esterified derivative and ethylene glycol at a temperature not exceeding 260 ° C. When 90-92% of the reaction is completed, one-step esterification reaction is completed and transferred to the polycondensation reaction tube. Then, 80 to 150 ppm of the polymer is added to the polymer using the glycol-soluble germanium compound as the polycondensation catalyst, and the phosphorus compound is heat stabilizer. A method of producing a polyester polymer, characterized in that the addition of 20 to 60ppm to the polymer, the polycondensation reaction temperature is not higher than 285 ℃ to suppress side reactions due to high temperature reaction. The method according to claim 1, A method for producing a polyester polymer, wherein the germanium compound used as the polycondensation catalyst is a glycol soluble germanium compound selected from germanium dioxide, germanium acetate or germanium oxide. The method according to claim 1, A method for producing a polyester polymer, characterized in that the phosphorus compound used as a stabilizer is a phosphorus compound selected from phosphoric acid, triethyl phosphate, or triphenyl phosphate.