KR930004619B1 - Process for preparation of polyester - Google Patents

Abstract

The polyester is prepared by (1) reacting terephthalic acid and ethylene glycol, (2) adding glycol-soluble antimony compound (A) and tin compound (B) as a polymerization catalyst, phosphorus compound (C) as a stabilizer and cobalt compound (D) as a coloring agent into the reactant and (3) polycondensting the mixture. The addition amount of each component is satisfied by the equations of 200 < A+B+D <= 300 (A >= 100) (I), 0.3 < (B+D)/C <= 1.8 (II) and 1 < B/ D <= 1.5 (III). In the equations, A,B,C and D are the content (PPM, particles per million) of each compound to polymer. The polyester has an improved color balance and transparence.

Description

Manufacturing method of polyester with good transparency

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyester having good color tone and excellent transparency. In particular, in the preparation of polyethylene terephthalate (hereinafter referred to as “polyester”) by reacting ethylene glycol and terephthalic acid, a glycol soluble antimony compound and tin The present invention relates to a method for producing a polyester having good transparency, wherein the compound is used as a polymerization catalyst, the phosphorus compound is used as a stabilizer, and the cobalt compound is used as a color tone improving agent.

In general, polyester has a wide range of mechanical and chemical properties, and thus is widely used in clothing, sheet, fishing net, cloth net and tire cord, in addition to film, blow molding.

In addition, it is known that the polyester is usually produced industrially by the following two-step reaction.

That is, a polycondensation obtained by polymerizing a terephthalic acid or a lower alkyl ester derivative thereof and ethylene glycol by heat-reacting a bisglycol ester of terephthalic acid or a oligomer thereof and polycondensation of the resulting bisglycol ester or terpolymer of terephthalic acid. Since it consists of a synthesis reaction, the use of various catalysts and stabilizers has been proposed for the said two kinds of reactions.

For example, sodium, lithium, calcium, magnesium, manganese, zinc, tin and the like have been used as catalysts for the ester reaction, and antimony compounds, germanium compounds, titanium compounds and the like have been proposed as stabilizers in the polycondensation reaction.

Of these, antimony compounds are inexpensive and have excellent catalytic activity, but they require a large amount of catalyst and have the disadvantage of blackening the polymer due to precipitation of antimony metals during the reaction. Germanium compounds have excellent reactivity and have excellent transparency and gloss. On the other hand, it is difficult to increase the degree of polymerization due to poor solubility and remain insoluble in the reaction, or fly out of the reactant by sublimation during the reaction, and the heat resistance decreases when used in excess, and the titanium compound has a drawback that the reactant is colored.

Therefore, the method of using a conventionally well-known catalyst and stabilizer was not satisfactory in obtaining polyester which is excellent in transparency and a good color tone. In particular, polyesters used for films and blow moldings are highly required for transparency and gloss. Antimony compounds, which are commonly used industrially, are inadequate because of the disadvantage of blackening polymers. The use of germanium catalysts is disclosed in Japanese Unexamined Patent Publications No. 55-40704 and No. 52-49292.

However, since germanium catalysts are very expensive, they must be reduced in order to obtain price competitiveness in industrial use, so that germanium and antimony compounds can be used in parallel, as described in US Pat. No. 3,795,639, Germanium and titanium compounds are used together as in 6175, or germanium and magnesium compounds are used together as described in Japanese Patent Application No. 48-37759, as well as in combination with germanium and calcium compounds as in US Pat. No. 3,842,043. Has been proposed to maintain transparency and to lower the production cost thereof.

In addition, to improve transparency without using germanium at all, titanium compounds are used to improve transparency, such as Japanese Pat. No. 49-35461 and Japanese Pat. No. 49-33998, but the color tone is poor. In the case of -53333, an antimony compound was used alone as a polymerization catalyst, and tetraethylene glycol was added to the reaction of the production step to improve crystallinity by reducing crystallization. However, there was a disadvantage of reducing the mechanical strength of the final molded product. In 51-134786, antimony compound was used, cobalt compound was added as a color tone improving agent, and bromine compound was used in parallel.

Accordingly, the present invention provides a glycol-soluble antimony compound (A) and a tin compound (A) as a polymerization catalyst in the production of polyesters having terephthalic acid and ethylene glycol as main raw materials for producing polyester having good transparency and good color like glass. B), and a phosphorus compound (C) as a stabilizer and a cobalt compound (D) as a color tone improving agent, wherein each addition amount satisfies the formulas (I), (II) and (III). It is an ester manufacturing method.

(Wherein A, B, C and D represent the content (PPM) of each compound in the polymer).

The characteristic of the polyester production method of the present invention is to obtain a polyester having excellent transparency and good color tone by using a small amount in addition of cobalt compound and phosphorus compound in joint use of glycol soluble antimony compound and tin compound as a polymerization catalyst. .

When antimony compound and tin compound are used in polyester production, it is generally put into the ester reaction stage in order to shorten the reaction of polyester (Japanese Patent Office 55-5530). As a known fact, a large amount of cobalt compound is added.

In addition, in the case of producing polyester by adding a tin compound to the polycondensation reaction step, it has been proposed in Japanese Patent Application No. 55-5535 that the main raw material is diethyl terephthalic acid and no color tone improving agent is added. The reason that the tin compound is not added to the polycondensation reaction is that the tin compound is difficult to completely dissolve in glycol, and that the tin compound forms a sediment when the temperature is lower than 150 ° C., so that it is not evenly distributed in the reactant.

Therefore, in the present invention, an antimony compound and a tin compound are used as the catalyst, but the content of the catalyst and the color tone improving agent is 210 to 300 ppm. However, as the catalyst, the antimony compound was 100 ppm or more, and when the antimony compound was 100 ppm or less, the transparency decreased.

In the present invention, when the glycol soluble antimony compound and the tin compound are used as a polymerization catalyst, they are dissolved in glycol in advance, but the concentration is 2.5% and 1.0% or less, respectively, and the temperature of the input tank is maintained at 150 ° C. or higher so that they can be evenly distributed in the reaction product. It is.

Antimony compounds used in the present invention include antimony acetate, antimony trichloride, antimony trifluoride, antimony trioxide, and the like, and tin compounds include monobutyl tin oxide, dibutyl tin oxide, and the like.

The amount of catalyst used is about 100-250 ppm. If the catalyst is less than 100ppm it is difficult to increase the degree of polymerization and the color tone is poor, it is necessary to add an excess cobalt compound to compensate for this, the excess cobalt compound inhibits the transparency. If the content exceeds 250ppm, the transparency and color tone deteriorate as in the case of the antimony compound alone addition, and the excessive amount of stabilizer is added to compensate for this. The ratio of antimony compound and tin compound should be controlled to be 0.26 ~ 1.0. If less than 0.26, the polymer is colored by precipitation of metal antimony. If it is greater than 1, the polymer is yellowed and the polymerization rate is slowed down.

The cobalt compound used in the present invention is suitable for cobalt acetate, and the stabilizer may be phosphoric acid, phosphorous acid, monomethyl phosphate, dimethyl phosphate, trimethyl phosphate, triphenyl phosphate, etc., and phosphoric acid is the best stabilizer used for producing polyester by terephthalic acid. to be.

The amount of phosphorus compound (C) used is determined by the tin compound and cobalt compound as shown in formula (II). If the amount is less than 0.3 in formula (II), transparency decreases and the reactivity is weakened. It becomes

The cobalt compound prevents the polymer from becoming yellow due to the tin compound, but its transparency is weakened as its capacity increases, and as shown in formula (III), the transparency is weakened when the tin compound ratio is 1 or less, and yellow when it is 1.5 or more. It becomes

In carrying out the method of the present invention, it may be carried out in any of the batch process or the continuous polymerization process, but the tin and antimony compounds may be added at a temperature not exceeding 150 ° C., but the cobalt compounds may contain antimony and tin compounds. After complete dissolution, it must be added to the same feeder. In addition, the stabilizer is more preferably prior to the addition of the polymerization catalyst.

Hereinafter, the present invention will be specifically described in Examples.

Intrinsic viscosity in Examples was a value measured with a Wevelrod viscometer at 25 ° C using orthochlorophenol as a solvent, and the polymer color tone was obtained by using a color difference meter at room temperature for the polyester chip after polymerization. The hue L value indicates lightness (the higher the value is good), and the b value indicates yellow and blue color (the lower the value, the better). In addition, the transparency of the polymer is expressed as a solution haze, which is dissolved at 120 ° C. in a phenol / tetrachloroethane (weight ratio: 6/4) mixed solution and measured at room temperature with a haze meter (the lower the value, the better). box).

Example 1

16 kg of terephthalic acid and 93 kg of ethylene glycol were added to the reaction tube and reacted for about 4 hours under a nitrogen atmosphere of 2 kg / cm 2. The end point of the reaction was the amount of water generated during the reaction and discharged through the distillation column was 35.1kg or more. After the reaction was completed, the reaction product was transferred to a polymerization tube, and 28.8 g of phosphoric acid was added, followed by stirring at atmospheric pressure for 5 minutes. Then, 28.8 g of antimony trioxide (2.4% dissolved in ethylene glycol) and 11.52 g monobutyl tin oxide were used as a polymerization catalyst. (0.8% ethylene glycol dissolved content) was mixed and maintained at 175 ° C, 9.6 g of cobalt acetate was added to the polymerization tube, and the reaction was continued. At this time, the pressure in the polymerization tube was 1 mmHg or less and the temperature was 285 ° C. The reaction was completed for 30 hours to complete the polycondensation. The inherent viscosity of the obtained polymer was 0.63, the L value was 59.3, the b value was 0.3, and the haze was 0.5 when melting.

EXAMPLES 2-4

After the ester reaction in the same manner as in Example 1, the polymerization catalyst was added in the same manner, and the amount thereof was changed to carry out condensation polymerization to obtain a polymer.

In the above table, it was found that the increase in the antimony compound, the polymerization catalyst, showed a decrease in L value, and that the polymerization degree of the haze and the polymer was slightly lowered when the total amount of the antimony compound and the tin compound decreased. However, a small amount of phosphorus compound was added even though a small amount of antimony compound was added. Therefore, the reaction time was not significantly affected, and the yellow phenomenon was adjusted to the amount of cobalt compound to be made transparent, and the chemical mechanism was still identified during the reaction. It was not possible, but it clearly showed an increase in transparency.

Comparative Example 1

The ester reaction was completed by the same method as in Example 1, and 28.8 g of phosphoric acid, 28.8 g of antimony trioxide, 11.52 g of tin compound (monobutyl tin oxide) and 9.6 g of cobalt acetate were added simultaneously without dissolving the esterification reaction. .

At this time, the reaction temperature was 285 ℃, the pressure was 1mmHg or less and the reaction time was 3 hours 20 minutes. The inherent viscosity of the produced polymer was 0.642, L value was 51.0, b value was 1.3, and haze was 1.7.

[Comparative Examples 2-4]

After the ester reaction in the same manner as in Example 1, the polymerization method was changed by adding the polymerization catalyst and the addition amount, thereby obtaining a polymer.

In the input method, Comparative Example 2 is the same method as Example 1, Comparative Example 3 is a phosphoric acid and cobalt compound was simultaneously added to the polymerization tube by dissolving the antimony compound at 175 ℃ and tin compound at room temperature. Comparative Example 4 was added in the same manner as in Comparative Example 1.

The above table does not satisfy the formulas (I), (II), and (III) of the present invention, and it can be seen that the color tone and transparency of the polymer vary greatly according to the method of adding the polymerization catalyst. In other words, when the amount of addition of the antimony compound and tin compound as the polymerization catalyst increases, the transparency decreases, and when the phosphorus compound is added together with other polymerization catalysts, the transparency and color tone deteriorate together.

Claims (1)

In preparing polyester using terephthalic acid and ethylene glycol as the main raw materials, glycol soluble antimony compound (A) and tin compound (B) are used as polymerization catalysts, but the concentration is 2.5% by weight or less than 1.0% by weight. It is dissolved and used, the temperature of the input tank is maintained at 150 ° C or higher, and phosphorus compound (C) as a stabilizer and cobalt compound (D) as a color tone improver are added to the polycondensation reaction. After adding the compound, the cobalt compound is added, the phosphorus compound is added before the polymerization catalyst, and the amount of catalyst and stabilizer is satisfied so as to satisfy the formulas (I), (II) and (III). Good method for producing polyester.

(Equations A, B, C, and D each represent the converted amount (PPM) of each compound in the polymer.)