KR940011777B1 - Process for preparation of polyester - Google Patents

Abstract

The producing method of a polyethylene terephthalate having a good transparency free of an whitening agent is characterized by reacting a dimethyl terephthalate (A) with an ethylene glycol (B) in the presence of 0.1-10 X 10-4 mole of an ester exchange catalyst of manganese acetate and cobalt acetate w.r.t. (A), 0.1-10 X 10-4 mole of a condensation polymerizing catalyst of antimony trioxide and/or di-n-butyl tin malate w.r.t. (A), and 0.01-0.5 wt.% of a diethyl ewter of 3,5-di-tertbutyl-4-hydroxy benzyl phosphonic acid of formula (I) w.r.t. (A+B).

Description

Manufacturing method of polyester with excellent transparency

The present invention relates to a method for producing a polyester that is a thermoplastic material, and more particularly, to a method for producing a polyester having excellent transparency by adding a polymerization catalyst and thermal stability to the polymerization process.

Generally, polyethylene terephthalate as a polyester can be industrially produced by transesterification using dimethylene terephthalate and direct polycondensation using terephthalic acid. Currently, high-quality polyethylene terephthalate is prepared by using dimethylene terephthalate. The transesterification method to be used is widely applied by industrial companies.

However, the polymerization of such polyesters is accompanied with side reactions, and even if less side reactions occur, it adversely affects the physical properties of the polyester. Therefore, it is necessary to suppress side reactions generated in the manufacturing process to produce a polyester polymer having excellent transparency. Can be.

In other words, the polyester polymer requires transparency as a final product. When pyrolysis occurs in the manufacturing process, coloration occurs and the color develops, firstly yellow, then brown again, and finally black. Coloring materials in this phenomenon are predicted to be unsaturated aliphatic polymers with molecular weights ranging from 300 to 1000 (LHBuxbaum, Ang, Chem. Int. Ed., 7, 182 (1968)), and coloring materials are also incorporated into the polyester chain. It is known to be chemically bound (HAPohl, J. Amer. Chem. Soc., 73, 5669 (1951)).

This coloration phenomenon is caused by the catalyst and shows the difference in coloration or degree depending on the type and concentration of the catalyst. That is, as a transesterification catalyst, catalysts such as manganese, lead, cadmium, and cobalt are colored (H. Zimmermann, faserforsch.u.Textiltech., 13, 481 (1962)), and catalysts such as calcium and magnesium It does not cause coloring but has a low catalytic activity (K. Tonita, H. Ida, Polym., 16, 185 (1975)).

In addition, as a polycondensation catalyst, the antimony catalyst causes some of the catalyst to be reduced during the polymerization to cause a gray color (US Pat. No. 3,732,182), and the titanium catalyst acts as a yellow color. It has a low disadvantage.

In order to solve the problem of color in polyester, a manufacturing method using calcium acetate and cobalt acetape as transesterification catalyst, antimonitrioxide as condensation polymerization catalyst, and phosphoric acid as heat stabilizer (US Pat. No. 4,058,507) Polyethylene terephthalate by using zinc acetate as a transesterification catalyst, tetrabutylate as a polycondensation catalyst, magnesium acetate as the heat stabilizer, manganese acetate, and isopropyl titanate (US Pat. No. 4,128,533). It is known that they can be obtained, but these methods were also not satisfactory in transparency.

Accordingly, an object of the present invention is to prepare polyethylene terephthalate having excellent transparency by adding a transesterification catalyst, a polycondensation catalyst and a heat stabilizer in the production of polyethylene terephthalate using dimethyl terephthalate and ethylene glycol as raw materials.

Hereinafter, the present invention will be described in detail.

In the present invention, in the preparation of polyethylene terephthalate using dimethyl terephthalate and ethylene glycol as raw materials, manganese acetate and cobalt acetate are used as a transesterification catalyst, and antimony trioxide and di-n-butyl tin maleate are used as condensation polymerization catalysts. Or a mixture thereof, characterized in that a diethyl ester of 3,5-di-tert-butyl-4-hydroxy benzyl phosphonic acid of the following structural formula (I) is added as a heat stabilizer.

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

The present invention is characterized by mixing a transesterification catalyst, a polycondensation catalyst and a heat stabilizer component as an existing basic raw material, the dimethyl terephthalate and ethylene glycol as the basic raw material is used so that the molar ratio of 1.8: 1.

In addition, the manganese acetate and cobalt acetate used as the transesterification catalyst in the present invention uses 0.1-10 x 10 ^-4 moles of dimethyl terephthalate, and the antimony trioxide or di-n-butyl tin maleate as a polycondensation catalyst. Or 0.1-10 × 10 ^-4 mol of these mixtures relative to dimethylterephthalate. At this time, a diethyl ester of 3,5-di-tert-butyl hydroxy-4-hydroxybenzyl phosphonic acid represented by the above formula (I) as a heat stabilizer together with the polycondensation catalyst was added at 0.01 to 0.5% by weight based on the polymer. use.

Here, if the amount of the transesterification catalyst is less than 0.1 × 10 ^-4 moles, the transesterification reaction is delayed and the color becomes poor. If the transesterification catalyst is more than 10 × 10 ^-4 moles, the reduction of the catalyst occurs and the color changes. do. On the other hand, if the addition amount of the polycondensation catalyst, and the yellow color change while pyrolysis is promoted with a delay is 0.1 × 10 ^-4 viscosity increase of the polymer it is less than obtained by mole in excess of the 10 × 10 ^-4 mol of the polymerization rate is faster or transesterification Like the reaction, the reduction reaction of the catalyst is promoted to give a color, causing a problem in transparency.

Under these catalyst conditions, yellowing of the polymer of the polymer may occur if the thermal stabilizer is not added with diethyl ester of 3,5-di-tert-butyl-4-hydroxy benzyl phosphonic acid or less than 0.01% by weight of the polymer. If the amount exceeds 0.5% by weight, the thermal stabilizer itself is thermally decomposed due to the excessive amount of the thermal stabilizer.

As described above, the polyester polymer obtained by the present invention has excellent transparency, and thus, when melted and fabricated to prepare fibers, films, molded articles, especially beverage bottles, etc., an excellent product can be obtained. In addition, in the present invention, by using a catalyst and a heat stabilizer, the effect of promoting the polymerization rate of the polyester and preventing the thermal decomposition can be obtained together with the effect of lowering the content of the terminal glass carboxyl group of the general polyester. In addition, the present invention has the effect of producing a polymer having excellent transparency without the use of a whitening agent (whitening agent) as a color improving agent in the polymerization process of the polyester.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by Examples.

In salsi example, the specific reaction method is as follows.

[Ester exchange reaction]

Ethylene glycol and dimethyl terephthalate were added in a molar ratio of 2,014g, 1,159g in a transesterification device equipped with a reflux device, a condenser, a stirring device, and a heating device. When it reaches to ℃, the side reactant methanol begins to distill, and reaches 230 ℃ to reach an esterification rate of about 90 ~ 98%. At this time, the reaction time takes about 4 to 6 hours.

[Condensation polymerization reaction]

The oligomer obtained from the transesterification reaction was placed in a stainless steel reactor equipped with an ethylene glycol condenser, a stirring device, a decompression device, and a heating device, and then a condensation polymerization catalyst and a heat stabilizer were added. Raise. The final reaction temperature is 270 to 285 ° C., and the reduced pressure is maintained at 0.2 torr or less. At this time, the condensation polymerization time takes about 1 hour 30 minutes to 4 hours to obtain a polymer having an intrinsic viscosity of 0.6 to 0.8 dl / g.

[Measurement of Physical Properties of Polymers]

(1) Intrinsic Viscosity Measurement: A polymer was prepared with a mixed solution of phenol and tetrachloroethane at a solution concentration of 0.5 g / dl, and then obtained by calculating the intrinsic viscosity using a ubelob viscometer in a 20 ° C incubator.

(2) Method for measuring terminal free carboxyl group: 0.1-0.2 g of polymer and benzyl alcohol are placed in a tube, dissolved by heating, and then added to a beaker containing 10 ml of chloroform. Phenolphthalein was added to this solution, and it calculated by using titration of 0.1N caustic soda solution dissolved in benzyl alcohol.

(3) Method of measuring color value: The color of the finally obtained polymer measured L (Lighness) and b (Yellowness) using the color difference meter.

[Examples 1-3, Comparative Examples 1-3]

As an ester exchange catalyst was manganese acetate using 10 × 10 ^-4 mol and cobalt acetate 0.6 × 10 ^-4 mol based on dimethyl terephthalate, a polycondensation catalyst was used for antimony trioxide 0.2 × 10 ^-4 mol. In this case, polyethylene terephthalate was prepared by diethyl ester of 3,5-di-tertary butyl-4-hydroxy benzyl phosphonic acid as a heat stabilizer as described in Table 1 below.

Example 4

As transesterification catalyst, 0.5 × 10 ⁻⁴ mol of manganese acetate and 0.6 × 10 ⁻⁴ mol of cobalt acetate were used, and 0.5 × 10 ⁻⁴ mol of antimonitrioxide was used as the polycondensation catalyst. In this case, the polyethylene terephthalate was prepared by adding 0.05 wt% of the thermal stabilizer used in Example 1 to the polymer.

[Examples 5 and 6]

As a transesterification catalyst, manganese acetate 0.7 × 10 ⁻⁴ mol and cobalt acetate 0.4 × 10 ⁻⁴ mol in Example 5 were used, and in Example 6 manganese acetate 1 × 10 ⁻⁴ mol, cobalt acetate 0.6 × 10 ^{− 4} moles were used. As a condensation polymerization catalyst, in Example 5, antimony trioxide 1.5 × 10 ⁻⁴ mol was used, and in Example 6, antimony trioxide 2 × 10 ⁻⁴ mol and di-n-butyltin maleate 0.1 × 10 ⁻⁴ Moles were used. In this case, the thermal stabilizer used in Example 1 was used, but in Example 5, 0.1 wt% was added to the polymer, and in Example 6, 0.05 wt% was added to prepare polyethylene terephthalate.

Example 7,8

1 × 10 ^-4 mol of manganese acetate and 0.8 × 10 ^-4 mol of cobalt acetate were used as the transesterification catalyst, and 2 × 10 ^-4 mol of antimonytrioxide was used as the polycondensation catalyst and di-n-butyl Tinmalate was used in Example 7 at 0.1 × 10 ⁻⁴ mol and in Example 8 at 0.05 × 10 ⁻⁴ mol, respectively. In this case, the polyethylene terephthalate was prepared by adding 0.05 wt% of the thermal stabilizer used in Example 1 to the polymer.

[Comparative Example 4,5]

As a transesterification catalyst manganese acetate 0.05 × 10 ^-4, and the use of cobalt acetate, 0.05 × 10 ^-4 mol, the shaft as a polymerization catalyst, and antimony trioxide 0.05 × 10 ^-4 mol, di -n- butyl tinmal rate is 4 to compare Was not used, and 0.05 × 10 ^-4 mol was used in Comparative Example 5. At this time, polyethylene terephthalate was prepared without adding a heat stabilizer.

[Comparative Example 6,7]

As a transesterification catalyst manganese acetate 4 × 10 ^-4 mol, it was used as the cobalt acetate 4 × 10 ^-4 mole, the shaft as a polymerization catalyst, and antimony trioxide 4 ×× 10 ^-4 mol, di -n- butyl tinmal rate comparison It was not used in Example 6, and 3x10 ^-4 mol was used in Comparative Example 7. At this time, polyethylene terephthalate was prepared without adding a heat stabilizer.

Comparative Example 8

Was used as magnesium acetate 6 × 10 ^-4 mol, 1 × 10 ^-4 mol of manganese acetate, isopropyl titanium carbonate 1.5 × 10 ^-4 mol as an ester exchange catalyst, a polycondensation catalyst was prepared a polyethylene terephthalate without using a separate .

Comparative Example 9

As an ester exchange catalyst using zinc acetate 1 × 10 ^-4 mol, and the di -n- butyl tinmal rate 1 × 10 ^-4 mol was used as the polycondensation catalyst. At this time, 3 × 10 ^-4 mol of triphenyl phosphate was added to dimethyl terephthalate as a heat stabilizer to prepare polyethylene terephthalate.

Comparative Example 10

2 x 10 ^-4 mol of calcium acetate and 0.5 x 10 ^-4 mol of cobalt acetate were used as the transesterification catalyst, and 2 x 10 ^-4 mol of antimony trioxide was used as the polycondensation catalyst. In this case, polyethylene terephthalate was prepared by adding 0.7 × 10 ⁻⁴ mol of dimethyl terephthalate as a stabilizer.

Experimental methods and results of the Examples and Comparative Examples are shown in the table below.

TABLE 1

TABLE 2

Claims (4)

In the production of polyethylene terephthalate using dimethyl terephthalate and ethylene glycol as raw materials, manganese acetate and cobalt acetate are used as a transesterification catalyst, and antimony trioxide, di-n-butyl tin maleate or theirs is used as a condensation polymerization catalyst. A mixture is used, and a method for producing a polyester characterized in that a diethyl ester of 3,5-di-tert-butyl-4-hydroxy benzyl phosphonic acid of the following structural formula (I) is added as a heat stabilizer. The method according to claim 1, wherein the transesterification catalyst is added in an amount of 0.1 to 10 x 10 ^-4 moles to dimethyl terephthalate. The method of claim 1, wherein the polycondensation catalyst is added in an amount of 0.1 to 10 x 10 ^-4 moles to dimethyl terephthalate. The method according to claim 1, wherein the heat stabilizer is added in an amount of 0.01 to 0.5% by weight based on the polymer.