JP2000159872A - Manufacture of polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a polyester capable of polycondensing arom. dicarboxylic acids and ethylene glycols using a highly active catalyst. SOLUTION: In this manufacturing method of a polyester, a catalyst comprising a zinc compd. (i) and a metal compd. (ii) of a metal selected from alkali metals, alkali earth metals, transition metals of the forth row of the periodical table, and aluminum is used as a polycondensation catalyst, in manufacturing a polyester by polycondensation of an arom. dicarboxylic acid or its ester- forming derivative with an aliphatic diol or its ester-forming derivative in the presence of the polycondensation catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyester suitably used for forming films such as bottles, sheets and the like, and more particularly, to an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid at a high polymerization rate. The present invention relates to a method for producing a polyester capable of polycondensing with a diol.

[0002]

BACKGROUND OF THE INVENTION Polyester, especially polyethylene terephthalate (PET), has excellent mechanical strength, heat resistance, transparency and gas barrier properties, and is suitable as a material for beverage filling containers such as juices, soft drinks and carbonated drinks. Used in

[0003] Such polyesters are usually produced using aromatic dicarboxylic acids such as terephthalic acid and aliphatic diols such as ethylene glycol as raw materials.
Specifically, first, a low-order condensate (ester low polymer) is formed by an esterification reaction of an aromatic dicarboxylic acid and an aliphatic diol, and then this low-order condensate is formed in the presence of a polycondensation catalyst. Deglycol reaction (liquid phase polycondensation)
After high molecular weight, it is produced by further performing solid phase polycondensation.

[0004] The polyester thus produced is generally supplied to a molding machine such as an injection molding machine to form a hollow molded article preform, and then the preform is inserted into a mold having a predetermined shape and stretch blow-molded to form a hollow molded article. Molded into containers.

[0005] In the above polyester production method, an antimony compound, a germanium compound and the like have been used as a polycondensation catalyst. However,
When an antimony compound was used, there were some problems in heat resistance and transparency of the obtained polyester as compared with the case where a germanium compound was used.

[0006] In addition, the germanium compound is quite expensive, so there is a problem that the production cost of polyester is high. To reduce the production cost, for example, a process of collecting and reusing the germanium compound scattered at the time of polymerization is used. Are being considered.

Further, although the use of a zinc compound has been proposed (for example, see JP-A-53-542).
In the polycondensation step, a known catalyst was separately added.

The present inventor has conducted intensive studies on polycondensation catalysts for the production of polyesters in view of the prior art as described above. As the polycondensation catalysts, zinc compounds, alkali metals, alkaline earth metals, By using a compound of at least one metal selected from the fourth period transition metal and aluminum, the polyester can be obtained with a higher catalytic activity than when a germanium compound is used, without using an expensive germanium compound. Have found that the present invention can be manufactured, and have completed the present invention.

[0009]

An object of the present invention is to provide a method for producing a polyester capable of polycondensing an aromatic dicarboxylic acid and ethylene glycol with high catalytic activity.

[0010]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for producing a polyester, comprising polycondensing an aromatic dicarboxylic acid or an ester-forming derivative thereof with an aliphatic diol or an ester-forming derivative thereof in the presence of a polycondensation catalyst. In producing polyester, (i) a zinc compound as a polycondensation catalyst, and (ii) a compound of at least one metal selected from alkali metals, alkaline earth metals, transition metals of the fourth period of the periodic table and aluminum. And a catalyst comprising:

The zinc compound (i) is preferably zinc acetate or zinc carbonate. Further, (ii) an alkali metal, an alkaline earth metal, a transition metal of the fourth period of the periodic table,
Examples of the compound of at least one metal selected from aluminum include carbonates, acetates, and phosphates of at least one metal selected from alkali metals, alkaline earth metals, transition metals of the fourth period of the periodic table, and aluminum. Salts or phosphites are preferred.

[0012]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the method for producing the polyester of the present invention will be specifically described. Polycondensation catalyst First, the polycondensation catalyst used in the method for producing a polyester according to the present invention will be described.

In the present invention, a compound of (i) a zinc compound and (ii) at least one metal selected from alkali metals, alkaline earth metals, transition metals of the fourth period of the periodic table, and aluminum are used as the polycondensation catalyst. (Hereinafter also referred to as (ii) a metal compound).

(I) Examples of the zinc compound include carboxylate salts such as zinc acetate, zinc carbonate, zinc acetylacetonate and the like.
Zinc alkoxide and the like can be mentioned, and zinc acetate and zinc carbonate are particularly preferable.

(Ii) The metal compound is a carbonate, acetate or phosphate of at least one metal selected from alkali metals, alkaline earth metals, transition metals of the fourth period of the periodic table and aluminum. Alternatively, phosphite is preferably used.

As the metal compound (ii), specifically, lithium carbonate, sodium carbonate, potassium carbonate,
Magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, aluminum carbonate, lithium acetate,
Sodium acetate, potassium acetate, magnesium acetate, calcium acetate, strontium acetate, barium acetate, aluminum acetate, lithium phosphate, sodium phosphate,
Potassium phosphate, magnesium phosphate, calcium phosphate, strontium phosphate, barium phosphate, aluminum phosphate, lithium phosphite, sodium phosphite,
Examples include potassium phosphite, magnesium phosphite, calcium phosphite, strontium phosphite, barium phosphite, aluminum phosphite, cobalt acetate, manganese acetate, nickel acetate and the like. Of these, sodium phosphate, potassium phosphate, sodium phosphite, and potassium phosphite are particularly preferred.

The above (ii) metal compounds may be used in combination of two or more. (I) in the polycondensation catalyst used in the present invention
The molar ratio of the zinc compound and (ii) the metal compound (i) / (ii) is
It is desirably 50/1 to 1/50, preferably 20/1 to 1/10 in terms of metal atoms.

Such a polycondensation catalyst is capable of reacting an aromatic dicarboxylic acid with (i) a metal atom in the polycondensation catalyst in terms of (i)
0.001 to 0.2 mol% of zinc compound, preferably 0.002 to 0.1
Mol%, (ii) the metal compound is 0.005 to 0.3 mol%, preferably
It is desirable to use it in an amount of 0.010 to 0.2 mol%.

By using such a polycondensation catalyst, polycondensation between an aromatic dicarboxylic acid and an aliphatic diol can be carried out with high polymerization activity. Method for Producing Polyester The method for producing a polyester according to the present invention includes an esterification step and a polycondensation step, and is not particularly limited except for using the above-mentioned polycondensation catalyst.

In such a process, the polycondensation catalyst only needs to be present at the time of the polycondensation reaction. Even if it is added in any one of the polycondensation step, esterification step, raw material slurry preparation step, etc. May be added separately. Alternatively, a catalyst prepared by reacting (i) a zinc compound and (ii) a metal compound in advance may be used.

In the present invention, known additives such as stabilizers, release agents, antistatic agents, dispersants, and coloring agents such as dyes and pigments may be added at any stage during polyester production. Good. These additives may be added by a master batch before molding.

The polyester composition thus obtained is melt-molded and used for bottles, sheets, films and the like.

[Raw Materials Used] In the process for producing a polyester according to the present invention, an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof are used as raw materials.

Examples of the aromatic dicarboxylic acid include terephthalic acid, phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid and the like.

The aliphatic diols include ethylene glycol, trimethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexanemethylene glycol, dodecamethylene glycol and the like.

In the present invention, for example, homopolyethylene terephthalate may be produced using terephthalic acid and ethylene glycol, or terephthalic acid and a dicarboxylic acid other than terephthalic acid, and ethylene glycol and a diol other than ethylene glycol. Using,
Copolyesters can also be produced.

In the present invention, an aliphatic dicarboxylic acid such as adipic acid, sebacic acid, azelaic acid or decane dicarboxylic acid, or an alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid or the like is used as a raw material together with an aromatic dicarboxylic acid. Can also.

Further, together with the aliphatic diol, an alicyclic glycol such as cyclohexane dimethanol, bisphenol, hydroquinone, or an aromatic diol such as 2,2-bis (4-β-hydroxyethoxyphenyl) propane is used as a raw material. You can also.

In the production method of the present invention, either a batch system or a continuous system may be employed. Hereinafter, an example of a continuous manufacturing method will be described, but the present invention is not limited thereto.

[Esterification Step] First, in producing a polyester, an aromatic dicarboxylic acid or an ester-forming derivative thereof is subjected to an esterification reaction with an aliphatic diol or an ester-forming derivative thereof.

Specifically, a slurry containing an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof is prepared. Such a slurry contains 1.005 to 1.4 moles per mole of the aromatic dicarboxylic acid or its ester-forming derivative,
Preferably 1.01 to 1.3 moles of an aliphatic diol or an ester-forming derivative thereof is included. This slurry is continuously supplied to the esterification reaction step.

The esterification reaction is preferably carried out using an apparatus in which two or more reactors are connected in series, and under conditions where the aliphatic diol is refluxed, water produced by the reaction is removed outside the system by a rectification column. It is desirable to perform while doing.

When the esterification reaction step is carried out in multiple stages, the first stage of the esterification reaction is usually carried out at a reaction temperature of 240-400.
270 ° C, preferably 245-265 ° C, pressure 0.2-3kg / cm
² G, preferably 0.5 to ² kg / cm ² G, and the final stage of the esterification reaction is usually performed at a reaction temperature of 250 to 280.
° C, preferably 255-275 ° C, and the pressure is 0-1.5 kg / cm ²
G, preferably 0 to 1.3 kg / cm ² G.

Therefore, when the esterification reaction is carried out in two stages, the first and second stage esterification reaction conditions are within the above ranges, respectively, and when the esterification reaction is carried out in three or more stages, The esterification reaction conditions from the second stage to one stage before the final stage may be any conditions between the reaction conditions of the first stage and the reaction conditions of the final stage.

For example, when the esterification reaction is carried out in three stages, the reaction temperature of the second stage of the esterification reaction is usually 245 to 275 ° C., preferably 250 to 270 ° C., and the pressure is usually 0 to 270 ° C.で あ れ ば² kg / cm ² G, preferably 0.2-1.5 kg / cm ² G.

The esterification reaction rate in each of these stages is not particularly limited, but it is preferable that the degree of increase in the esterification reaction rate in each stage is smoothly distributed, and furthermore, the esterification reaction formation in the final stage is performed. It is generally desirable that the content of the product reaches 90% or more, preferably 93% or more.

By this esterification step, an esterified product (lower condensate) of an aromatic dicarboxylic acid and an aliphatic diol is obtained, and the number average molecular weight of this lower condensate is 500
It is about 5000.

Such an esterification reaction is carried out by using a tertiary amine such as triethylamine, tri-n-butylamine and benzyldimethylamine, a tetraethylammonium hydroxide, a hydroxide such as an aromatic dicarboxylic acid and an aliphatic diol. Quaternary ammonium hydroxides such as tetra-n-butylammonium, tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide, trimethylbenzylammonium hydroxide, and lithium carbonate;
Basic compounds such as sodium carbonate, potassium carbonate and sodium acetate may be added, and the reaction can be carried out in the presence of the above-mentioned polycondensation catalyst.

By subjecting terephthalic acid and ethylene glycol to an esterification reaction in the presence of such a basic compound, for example, polyethylene terephthalate having a small content of dioxyethylene terephthalate component units can be obtained.

The low-order condensate obtained in the above esterification step is then supplied to a polycondensation (liquid-phase polycondensation) step. [Liquid-phase polycondensation step] In the liquid-phase polycondensation step, in the presence of the above-mentioned polycondensation catalyst, the low-order condensate obtained in the esterification step is heated under reduced pressure at a temperature not lower than the melting point of the polyester ( The polycondensation is carried out by heating to a temperature of usually 250 to 280 ° C. In addition, in this polycondensation reaction, it is desirable to carry out while distilling unreacted aliphatic diol out of the reaction system.

The polycondensation reaction may be performed in one stage or may be performed in a plurality of stages. For example, when the polycondensation reaction is performed in multiple stages, the first-stage polycondensation reaction includes:
Reaction temperature 250-290 ° C, preferably 260-280 ° C, pressure 500
To 20 torr, preferably 200 to 30 torr, and the polycondensation reaction in the final stage is performed at a reaction temperature of 265 to 300 ° C, preferably
The reaction is carried out at a temperature of 270 to 295 ° C and a pressure of 10 to 0.1 torr, preferably 5 to 0.5 torr.

When the polycondensation reaction is carried out in three or more stages, the polycondensation reaction from the second stage to the stage before the last stage is as follows:
The reaction is performed under the conditions between the first-stage reaction conditions and the final-stage reaction conditions. For example, when the polycondensation step is performed in three stages, the second stage polycondensation reaction is usually carried out at a reaction temperature.
260-295 ° C, preferably 270-285 ° C, pressure 50-2torr
r, preferably 40 to 5 torr.

In such a polycondensation reaction, as described above, the polycondensation catalyst reacts with the aromatic dicarboxylic acid in an amount of 0.001 to 0.001 in terms of the metal atom in the polycondensation catalyst.
0.2 mol%, preferably 0.002 to 0.1 mol%, (ii) a compound of at least one metal selected from alkali metals, alkaline earth metals, transition metals of the fourth period of the periodic table, and aluminum is 0.005 to 0.3 mol% , Preferably in an amount of 0.010 to 0.2 mol%.

Such a polycondensation catalyst may be present at the time of the polycondensation reaction. Further, the polycondensation reaction is desirably performed in the presence of a stabilizer. Specific examples of the stabilizer include phosphate esters such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, and triphenyl phosphate, triphenyl phosphite, trisdecyl phosphite, and trisnonyl phenyl phosphite. Phosphates such as phosphites, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, dibutyl phosphate, monobutyl phosphate, dioctyl phosphate and the like, and phosphoric acid esters, and organic phosphorus compounds such as polyphosphoric acid. No.

The amount of the organic phosphorus compound to be added is 0.005 to 0.2 mol%, preferably 0.01 to 0.1 mol%, in terms of the phosphorus atom in the organic phosphorus compound, based on the aromatic dicarboxylic acid. It is desirable.

The intrinsic viscosity [IV] of the polyester obtained in the liquid phase polycondensation step as described above is desirably 0.40 to 1.0 dl / g, preferably 0.50 to 0.90 dl / g. In addition, the intrinsic viscosity achieved in each stage except the final stage of the liquid-phase polycondensation step is not particularly limited, but it is preferable that the degree of increase in the intrinsic viscosity in each stage be distributed smoothly.

In the present specification, the intrinsic viscosity is calculated from the solution viscosity measured at 25 ° C. after heating and dissolving 1.2 g of polyester in 15 cc of o-chlorophenol.

The polyester obtained in this liquid phase polycondensation step is usually melt-extruded and formed into particles (chips). [Solid phase polycondensation step] The polyester obtained in this liquid phase polycondensation step may be further subjected to solid phase polycondensation, if desired.

The granular polyester supplied to the solid-phase polycondensation step is preliminarily crystallized by heating to a temperature lower than the temperature at which the solid-phase polycondensation is performed, and then supplied to the solid-phase polycondensation step. Is also good.

Such pre-crystallization is usually carried out by drying the granular polyester in a dry state at 120 to 200 ° C., preferably 130 to 180 ° C.
This can be done by heating to a temperature of ° C for 1 minute to 4 hours. Such pre-crystallization can also be performed by heating the granular polyester at a temperature of 120 to 200 ° C. for 1 minute or more in a steam atmosphere, a steam-containing inert gas atmosphere, or a steam-containing air atmosphere.

The pre-crystallized polyester preferably has a crystallinity of 20 to 50%.

In this pre-crystallization treatment, the so-called solid state polycondensation reaction of the polyester does not proceed, and the intrinsic viscosity of the pre-crystallized polyester is almost the same as the intrinsic viscosity of the polyester after the liquid phase polycondensation. The difference between the intrinsic viscosity of the pre-crystallized polyester and the intrinsic viscosity of the polyester before the pre-crystallization is usually 0.06 dl / g or less.

The solid-phase polycondensation step comprises at least one stage and has a temperature of 190 to 230 ° C., preferably 195 to 225 ° C.,
Pressure 1kg / cm ² G~10torr, 100torr preferably from normal pressure
Under an atmosphere of an inert gas such as nitrogen, argon, or carbon dioxide. As the inert gas used, nitrogen gas is desirable.

The intrinsic viscosity of the granular polyester thus obtained is usually 0.60 to 1.00 dl / g, preferably
Desirably, it is 0.75 to 0.95 dl / g.

[0055]

According to the method for producing a polyester according to the present invention, the polycondensation reaction can be completed in a short time without using a germanium compound which has been conventionally used as a polycondensation catalyst. Therefore, the amount of the expensive germanium compound used can be reduced, and the production cost of the polyester can be reduced.

[0056]

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

[0057]

Example 1 First, ethylene glycol and terephthalic acid were continuously subjected to low-order condensation. The low-order condensation is pre-
0458 parts by weight of the reaction solution (at the time of steady-state operation) is kept in a reactor maintained at 260 ° C. and 0.9 kg / cm ² G in a nitrogen atmosphere, and 6458 parts by weight of high-purity terephthalic acid and 2615 parts by weight / Hour of ethylene glycol was continuously fed under stirring to perform an esterification reaction. In this esterification reaction, a mixed solution of water and ethylene glycol was distilled off.

The esterification reaction product, which is a low-order condensate, was continuously extracted out of the system while controlling the average residence time in the reactor to be 3.5 hours. The number average molecular weight of the low-order condensate of ethylene glycol and terephthalic acid thus obtained was 600 to 1300 (trimer to pentamer).

Next, a polycondensation catalyst was added to the low-order condensate thus obtained, and a liquid phase polycondensation reaction was carried out. In this polycondensation reaction, as a polycondensation catalyst, 0.021 mol% of zinc carbonate, 0.042 mol% of potassium carbonate, and phosphoric acid of potassium carbonate are converted to terephthalic acid units in the lower condensate with respect to zinc atoms. The reaction was carried out at 285 ° C. and 1 torr using an amount of 0.0105 mol% in terms of phosphorus atoms.

The intrinsic viscosity of polyethylene terephthalate [I
Table 1 shows the time (liquid weight time) required until V] reached 0.56 dl / g.

[0061]

Example 2 In Example 1, magnesium carbonate was used in place of potassium carbonate as a polycondensation catalyst, based on terephthalic acid units in the lower condensate in terms of magnesium atoms.
A polycondensation reaction was carried out in the same manner as in Example 1, except that the polycondensation reaction was used in an amount of 0.042 mol%. Time required for the intrinsic viscosity [IV] of polyethylene terephthalate to reach 0.56 dl / g
(Liquid weight time) is shown in Table 1.

[0062]

Example 3 In Example 1, dipotassium hydrogen phosphate was used as a polycondensation catalyst instead of potassium carbonate, based on terephthalic acid units in the lower condensate in terms of potassium atom.
A polycondensation reaction was carried out in the same manner as in Example 1, except that 0.021 mol% was used and phosphoric acid was not used. Table 1 shows the time required for the intrinsic viscosity [IV] of polyethylene terephthalate to reach 0.56 dl / g (liquid weight time).

[0063]

Comparative Example 1 A polycondensation reaction was carried out in the same manner as in Example 1 except that potassium carbonate was not used as a polycondensation catalyst. Time required for the intrinsic viscosity [IV] of polyethylene terephthalate to reach 0.56 dl / g
(Liquid weight time) is shown in Table 1.

[0064]

[Table 1]

As shown in these Examples and Comparative Examples, a polycondensation catalyst comprising (i) a zinc compound and (ii) an alkali metal, an alkaline earth metal, a transition metal in the fourth period of the periodic table and aluminum. In the polyester production methods of Examples 1 to 3 using a catalyst comprising at least one selected metal compound, the polycondensation reaction was performed in a shorter time as compared with Comparative Example 1 using a zinc compound alone as a catalyst. Can be completed.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Junichi Imuta 6-1-2, Waki, Waki-machi, Kuga-gun, Yamaguchi F-term in Mitsui Chemicals, Inc. (reference) 4J029 AA03 AB01 AB04 AB05 AC01 BA01 BA03 BA04 BA05 BA08 BA10 CB04A CB05A CB06A CB10A CC05A JF011 JF021 JF031 JF041 JF111 JF131 JF141 JF161 JF181 JF221 JF311

Claims (3)

[Claims] 1. A method for producing a polyester by esterifying an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof and subjecting the ester to polycondensation in the presence of a polycondensation catalyst. A catalyst comprising: (i) a zinc compound; and (ii) a compound of at least one metal selected from an alkali metal, an alkaline earth metal, a transition metal of the fourth period of the periodic table, and aluminum. Characteristic polyester production method. 2. The method according to claim 1, wherein (i) zinc acetate or zinc carbonate is used as the zinc compound. (Ii) as a compound of at least one metal selected from alkali metals, alkaline earth metals, transition metals of the fourth period of the periodic table and aluminum, alkali metals, alkaline earth metals and the periodic table; At least one selected from the fourth period transition metal and aluminum
3. The process according to claim 1, wherein a carbonate, acetate, phosphate or phosphite of one of the metals is used.