JP2000063504A - Production of polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polyester excellent in color and processability when molded and free from a problem of e.g. fouling in spinnerets, a pressure increase in filtration or breakage in thread when manufacturing a molded product for e.g. fiber, film or bottles. SOLUTION: This method is to polycondense a product obtained by subjecting both an aromatic dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative to esterification reaction or transesterification reaction, wherein there is used a complex compound having a hexadentate ligand as a polycondensation catalyst.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing polyester. More specifically, it relates to a method for producing a polyester having excellent moldability and color tone.

[0002]

2. Description of the Related Art Polyester has been widely used in various fields including fibers, films and bottles because of its excellent properties. Among them, polyethylene terephthalate is preferably used because of its excellent mechanical strength, chemical properties, dimensional stability and the like.

Polyethylene terephthalate is generally produced from terephthalic acid or its ester-forming derivative and ethylene glycol. In commercial processes for producing high molecular weight polymers, antimony compounds are widely used as polycondensation catalysts. . However, polymers containing antimony compounds have some unfavorable properties as described below.

For example, it is known that when a polyester obtained by using an antimony catalyst is melt-spun to form a fiber, the residue of the antimony catalyst is deposited around the spinneret holes. If this deposition progresses, it will cause defects in the filament, and therefore it will be necessary to remove it in a timely manner. The deposition of antimony catalyst residue occurs when antimony is present in the polymer in the form of antimony glycolate, which undergoes metamorphism in the vicinity of the base metal, part of which vaporizes and dissipates.
It is thought that this is because the component mainly containing antimony remains in the base.

Further, the antimony catalyst residue in the polymer tends to be relatively large particles, which becomes foreign matter and causes increase in filter pressure of the filter during molding, yarn breakage during spinning, or film breakage during film formation. It has undesirable characteristics such as

From the above background, there is a demand for polyesters having an extremely low antimony content or no antimony content.

Many titanium compounds have been proposed as polymerization catalysts for polyesters other than antimony compounds.
For example, titanium alkoxide (JP-A-52-86496)
JP-A-52-57289, an aliphatic carboxylic acid or a complex salt of a carboxylate with titanium (JP-A-52-57289), an acetylacetone-type complex (JP-A-8-71429), and the like, which have been conventionally proposed. Titanium compounds are excellent in polymerization activity, but on the other hand, there is a problem that the obtained polymer is severely colored.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a polyester which eliminates the above-mentioned drawbacks of the polyester containing an antimony compound.

[0009]

The above-mentioned object of the present invention is a product obtained by an esterification reaction or transesterification reaction with an aromatic dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative. In the method for producing a polyester by polycondensation of the above, it is achieved by a method for producing a polyester, which comprises using a complex compound having a hexadentate ligand as a polycondensation catalyst.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester of the present invention is a polymer synthesized from a dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative, and can be used as a molded article such as a fiber, a film or a bottle. There is no particular limitation as long as it is possible.

Specific examples of such polyesters include polyethylene terephthalate, polytetramethylene terephthalate, polycyclohexylene dimethylene terephthalate, polyethylene-2,6-naphthalene dicarboxylate, polyethylene-1,2-bis ( Two
-Chlorophenoxy) ethane-4,4'-dicarboxylate, polypropylene terephthalate and the like. The present invention is suitable for the most commonly used polyethylene terephthalate or a polyester copolymer mainly composed of polyethylene terephthalate.

Further, these polyesters include dicarboxylic acids such as adipic acid, isophthalic acid, sebacic acid, phthalic acid, 4,4'-diphenyldicarboxylic acid and their ester-forming derivatives, polyethylene glycol and diethylene glycol as copolymerization components. , A dioxy compound such as hexamethylene glycol, neopentyl glycol, polypropylene glycol, an oxycarboxylic acid such as p- (β-oxyethoxy) benzoic acid, and an ester-forming derivative thereof may be copolymerized.

The complex compound in the present invention has 6 ligands.
It must be a bidentate ligand. In the complex, the anion or neutral molecule surrounding the cation is called a ligand, and this ligand has various monodentate or bidentate multidentate ligands depending on the coordination number.

All the ligands in the complex compound of titanium with an aliphatic carboxylic acid or a carboxylic acid salt proposed in JP-A-52-57289 are monodentate or bidentate ligands, and JP-A-8-71429. The acetylacetone type complex proposed in Japanese Patent Publication is also a bidentate ligand. Further, the porphyrin complex proposed in JP-A-61-64722 is a tetradentate ligand. As described above, many ligands have been studied so far with regard to the complex compound. However, when a complex compound composed of a tetradentate or less ligand is used, A polymer having a strong yellow color and having a good color tone could not be obtained.

By using the complex compound having a hexadentate ligand of the present invention as a polycondensation catalyst, a good color tone which cannot be obtained with a complex compound having a tetradentate or lower ligand can be obtained.

Further, among the hexadentate ligands, it is preferable to use a complex compound composed of a tetracarboxylic acid type ligand having the structure of the following formula 1 because the polymerization activity is particularly high and the color tone is good. A specific example of such a hexadentate ligand is ethylenediaminetetraacetic acid.

[0017]

[Chemical 2] Further, the complex compound of the present invention needs to have a hexadentate ligand, but other ligands may be coordinated at the same time in addition to the hexadentate ligand, for example, coordination of water. It may be a compound.

On the other hand, the metal serving as a cation that forms a pair with the ligand is not particularly limited. From the viewpoint of catalytic activity, titanium, zirconium, zinc, tin, aluminum and the like can be mentioned, but titanium having particularly high catalytic activity is preferable.

The addition amount of the complex compound of the present invention depends on the kind of metal atom, but it is preferable to add it so as to be 1 to 500 ppm by weight in terms of metal based on polyester. If the amount added is less than 1 ppm, the catalyst activity will be insufficient, and the resulting polymer will have a low molecular weight and the molded product will have insufficient strength. On the other hand, if it is added in an amount exceeding 500 ppm, foreign matter is liable to be generated, the filtering pressure during molding may be remarkably increased, and the polymer color tone may be deteriorated. More preferably 5-200 ppm, still more preferably 5-
It is 100 ppm.

The complex compound of the present invention may be added as it is to the reaction system of polyester, but if it is added to the reaction system after being mixed with water, an organic solvent or a mixture of water and an organic solvent containing the compound in advance. It is preferable because the generation of foreign matter in the polyester of the compound is further suppressed. In particular, it is preferable to mix the compound with a solvent containing a polyester-forming diol component such as ethylene glycol to form a solution or a slurry and then add it to the reaction system because the generation of foreign substances in the polyester is further suppressed.

Thus, when the complex compound of the present invention is previously mixed with water, an organic solvent or a mixture of water and an organic solvent, the concentration of the complex compound with respect to water, the organic solvent or the mixture of water and the organic solvent is increased. 0.5 to 50% by weight,
A concentration of 1 to 40% by weight is more preferable from the viewpoint of foreign matter generation.

In the present invention, it is preferable to use a cobalt compound in combination with the above complex compound because the polycondensation reaction proceeds more rapidly and the color tone of the obtained polyester is further improved.

The cobalt compound of the present invention is not particularly limited, but specific examples thereof include cobalt acetate tetrahydrate, cobalt nitrate, cobalt chloride, cobalt acetylacetonate and cobalt naphthenate.

The amount of the cobalt compound added is 0.1 in terms of the molar ratio of the metal of the complex compound to the cobalt atom (Ti / Co).
It is preferably set to 20. Within the molar ratio range,
The effect of improving the polymerization activity is high, the effect of improving the polymer color tone is large, and the heat resistance can be maintained well. It is more preferably 1 to 15, and even more preferably 2 to 10.

In the present invention, it is preferable to use a conventionally known phosphorus compound in combination because the color tone becomes good. The phosphorus compound is not particularly limited, for example, phosphoric acid, trimethyl phosphate, triethyl phosphate, phosphoric acid ester such as triphenyl phosphate, phosphorous acid, phosphorous acid ester such as trimethyl phosphite, methylphosphonic acid, Examples thereof include phosphonic acid esters such as phenylphosphonic acid, methylphosphonic acid methyl ester, and phenylphosphonic acid ethyl ester, trimethyl phosphate, triethyl phosphate, and the like.

The amount of the phosphorus compound added is 1 to the polyester obtained, in that the color tone and the polymerization reactivity are improved.
It is preferably 100 ppm. The molar ratio of the complex metal atom to the phosphorus atom (complex metal / phosphorus) is 0.
It is preferable that it is from 2 to 10 because the color tone is particularly good.

In the method for producing a polyester of the present invention, an antimony compound may be used in combination, but when the amount added as an antimony atom is 50 ppm or less relative to the polymer, yarn breakage during spinning of the fiber or film production The breakage during film formation is suppressed, and the transparency is good for bottles and the like, which is preferable. It is more preferably 30 ppm or less, still more preferably 10 ppm or less.

The method for producing the polyester of the present invention will be described using the example of polyethylene terephthalate.

The high molecular weight polyethylene terephthalate used for fibers, films and the like is usually produced by any of the following processes. That is, (1) a process in which low molecular weight polyethylene terephthalate or oligomer is obtained by direct esterification reaction from terephthalic acid and ethylene glycol as raw materials, and further high molecular weight polymer is obtained by polycondensation reaction, (2) dimethyl terephthalate (DMT) ) And ethylene glycol as raw materials, a low molecular weight polymer is obtained by a transesterification reaction, and then a high molecular weight polymer is obtained by a polycondensation reaction thereafter.
Here, the esterification reaction proceeds even without a catalyst, but in the transesterification reaction, usually, a compound such as manganese, calcium, magnesium, zinc, or lithium is used as a catalyst to proceed, and the transesterification reaction is substantially After completion, for the purpose of deactivating the catalyst used in the reaction,
A phosphorus compound is added.

The production method of the present invention comprises (1) or (2)
In the low polymer obtained in the initial or first half of the series of reactions of
The specific complex compound of the present invention is added, and thereafter, the polycondensation reaction in the latter half is allowed to proceed to obtain a high molecular weight polyethylene terephthalate.

The above reaction is carried out in a batch system, a semi-batch system, a continuous system or the like, but the production method of the present invention can be applied to any of these systems.

[0032]

The present invention will be described in more detail with reference to the following examples. The physical property values in the examples were measured by the methods described below.

(1) Intrinsic viscosity of polymer [η] It was measured at 25 ° C. using orthochlorophenol as a solvent.

(2) Metal content in polymer It was determined by fluorescent X-ray.

(3) Color tone of polymer Hunter value (L, a, b) was measured using a color difference meter (SM color computer model SM-3) manufactured by Suga Test Instruments Co., Ltd.
Value).

(4) Amount of carboxyl end group of polymer Method by Maurice et al. [Anal. Chim. Act
a, 22, p363 (1960)].

(5) Fiber Strength and Elongation Using a Tensilon tensile tester manufactured by Toyo Baldwin Co., Ltd., an SS curve was obtained at a test length of 250 mm and a tension rate of 300 mm / min to calculate the strength and elongation.

Example 1 A catalyst-free oligomer prepared by a conventional method from high-purity terephthalic acid and ethylene glycol was prepared at 250 ° C.
Melted, and phosphoric acid was added to the melt so that the content of phosphorus atoms in the finally obtained polyester was 5 ppm, and then ethylenediamine tetraacetic acid titanium salt was added to the polyester. The content was added so as to be 20 ppm, and further cobalt acetate tetrahydrate was added so that the content of cobalt atom was 20 ppm. Then, the reaction system was gradually heated from 250 ° C. to 285 ° C. while the low polymer was stirred at 30 rpm, and the pressure was lowered to 40 Pa. The time required to reach the final temperature and the final pressure was both 60 minutes. When the predetermined stirring torque was reached, the reaction system was purged with nitrogen, returned to normal pressure to stop the polycondensation reaction, discharged into cold water in a strand form, and immediately cut to obtain polyester pellets.

The polymer obtained had an intrinsic viscosity of 0.67, a carboxyl end group content of 20 equivalents / ton, and a polymer color tone of L = 60, a = 0.3 and b = 6.0. In addition, it was confirmed by a fluorescent X-ray analysis that the titanium atomic component content was 10 ppm. Thus, pellets of the polyester composition having good polymerization reactivity and polymer characteristics were obtained.

After the pellets were dried, they were fed to an extruder type spinning machine and melt-spun at a spinning temperature of 295 ° C. At this time, a metal non-woven fabric having an absolute filtration accuracy of 10 μm was used as a filter, and a round hole having a diameter of 0.6 mm was used as a die. Thread discharged from the mouthpiece is 30 cm in length and 25 cm in inner diameter
After gradually cooling with a heating cylinder of φ and temperature of 300 ℃, apply chimney cooling air to cool and solidify the oil, and refuel, then take-off speed 550m
/ Min. This unstretched yarn was stretched at a stretching temperature of 95 ° C. while appropriately changing the stretch ratio so that the stretched yarn has an elongation of 14 to 15%, and then heat treated at a heat treatment temperature of 220 ° C. and a relaxation rate of 2.0%. I got a thread.

In the melt-spinning process, no increase in filtration pressure was observed during spinning, and there was no yarn breakage during stretching, and the polymer was a good moldability.

Examples 2 to 3 and Comparative Examples 1 to 3 Polymers were polymerized and melt-spun in the same manner as in Example 1 except that the kind of complex compound, addition amount, and compound used in combination were changed. The results are shown in Table 1.

The polymer of the present invention showed good progress both in the polymer and in the melt spinning process, but when a complex in which the other ligands were other than the hexadentate ligand was used, the color tone of the obtained polymer was changed. Was worse, and in the case of using antimony trioxide, the spinnability was inferior to that in the case of using the complex compound of the present invention.

[0044]

[Table 1]

[0045]

EFFECTS OF THE INVENTION The polyester obtained by the method for producing a polyester of the present invention has excellent moldability and has problems such as stains on the spinneret, increased filtration pressure, and thread breakage in the production of molded articles for fibers, films, bottles and the like. And a product having a good color tone can be obtained.

Continued front page    F term (reference) 4J029 AA03 AB04 AC01 AD01 AD02                       AE01 AE02 AE03 BA02 BA03                       BA05 BA08 BA10 BD07A                       BF25 CA06 CB04A CB05A                       CB06A CB10A CC06A CG09X                       EA02 HA01 HB01 HB02 JA061                       JA111 JA161 JA251 JB151                       JB171 JC481 JC571 JC581                       JE182 JF181 JF221 JF321                       JF331 JF371 JF571 KB05                       KE02 KE03 KE05

Claims (5)

[Claims] 1. A method for producing a polyester by polycondensing a product obtained by an esterification reaction or an ester exchange reaction with an aromatic dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative, A method for producing a polyester, which comprises using a complex compound having a hexadentate ligand as a polycondensation catalyst. 2. The method for producing a polyester according to claim 1, wherein the hexadentate ligand has a structure of formula 1. [Chemical 1] 3. The method for producing a polyester according to claim 1, wherein the polycondensation catalyst is a titanium complex compound. 4. A polyester according to any one of claims 1 to 3, wherein a cobalt compound is used in combination and the molar ratio of the metal atom to the cobalt atom of the complex compound is 0.1 to 20. Method. 5. The production of polyester according to claim 1, wherein a phosphorus compound is used in combination and the molar ratio of metal atom to phosphorus atom of the complex compound is 0.2 to 10. Method.