JPS5839167B2 - Polyester manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyethylene terephthalate having excellent color tone and heat resistance.

Polyethylene terephthalate is produced by esterifying or transesterifying terephthalic acid or dimethyl terephthalate with ethylene glycol to form bis(2-hydroxyethyl).
Polyethylene terephthalate chips are produced from a first step reaction to obtain terephthalate or its low polymer, and a second step reaction in which the terephthalate or its low polymer is subjected to polybonding under high temperature and reduced pressure.

The polyethylene terephthalate chips obtained in the second and second steps then undergo a third step of melt spinning, melt film forming, and melt molding to produce useful fibers, films, or other molded products.

Both of these first and second steps can proceed smoothly even on a large scale by adding a catalyst from Hikaraka.
It is a well-known fact that the final products, such as fibers, films, and molded products, can be obtained as products with excellent commercial value.

However, conventionally, the use of cobalt metal, manganese metal, or magnesium metal as a catalyst for producing polyethylene terephthalate, ■ the use of cobalt salt, manganese salt, or magnesium salt, ■ the combined use of cobalt salt and manganese salt, It is known to use cobalt salts and magnesium salts together.

However, when a manganese salt or a magnesium salt is used alone, the color of the produced polymer is yellow even when an appropriate amount of catalyst is added, and the coloration is particularly noticeable when producing a high molecular weight polymer in large quantities.

There is also the problem that coloration increases during the third step of melt extraction.

In addition, the use of cobalt salts in combination has the effect of suppressing coloration caused by manganese salts and magnesium salts, but the softening point decreases, especially when producing high molecular weight polymers in large quantities, and the disadvantages are that the heat resistance, especially the amount of aldehyde generation increases, There is a drawback that as the amount of cobalt salt is increased, the light transmittance of the polymer decreases, impairing transparency.

Furthermore, terephthalic acid, which is the raw material for polyethylene terephthalate today, is often produced by oxidizing p-xylene, and the production of by-product impurities, particularly p-formylbenzoic acid, is unavoidable during this production process.

Furthermore, even if the terephthalic acid is methyl esterified and purified by distillation and recrystallization, it is currently difficult to completely remove aldehyde compounds represented by methyl p-formylbenzoate.

In particular, refining to high purity on a commercial scale poses a problem that imposes a large economic burden.

Polyesters made from terephthalic acid or its dimethyl ester containing such aldehyde compounds tend to be colored yellow, which greatly reduces commercial value, and such coloring is mainly caused by aldehyde compounds, especially p-formylbenzoic acid or derivatives of terephthalic acid. It is estimated that

Therefore, even if terephthalic acid or its dimethyl ester contains an aldehyde compound, it is of great value from an industrial perspective to find an effective catalyst that does not affect the color tone.

Furthermore, the second and third steps mentioned above must be carried out at a high temperature that is at least higher than the melting point of the polyester, and if the polyester is kept at high temperatures, other undesirable reactions such as thermal decomposition will occur, resulting in a decrease in quality and the quality of the product. It is well known that side reactions that impair quality are accelerated.

In particular, as the melting time becomes longer, aldehyde is generated, the molecular weight decreases, and the resin becomes yellowish.

Therefore, it is of great industrial value to find an effective catalyst that suppresses the change in color tone as much as possible in the second and third melting steps.

As already mentioned, many reaction catalysts for the first step have been proposed, but there has been no excellent reaction catalyst that causes little change in color tone of the reaction product from the first to the third step.

The present inventors used the above-mentioned aldehyde-containing terephthalic acid or its dimethyl ester to conduct studies aimed at obtaining polyethylene terephthalate with good color tone without change in color tone during melting or inability to generate aldehyde compounds.As a result, the present invention was achieved. It has been reached.

In the present invention, when producing a polyester from a dicarboxylic acid containing terephthalic acid as a main component or an alkyl ester thereof and a glycol containing ethylene glycol as a main component, the molar ratio of glycol to dicarboxylic acid component is adjusted to 1.
．． 1 to 1.85, and add a glycol-soluble cobalt compound and at least one glycol-soluble magnesium compound and a manganese compound to satisfy the following formulas 1 and 2 until the esterification or transesterification reaction is completed. This is a method for producing polyester characterized by:

10<Co<300 ・・・・・・・・・・・・
・・・・・・・・・125<Co+Me<1000・
2 (in the formula, Co is metal cobal) ppm to polyester, Me is the total purchase of metal magnesium and metal manganese to polyester.

) The first feature of the present invention is that the amount of a specific type of metal compound is used in a specific range, and the second feature is that the molar ratio of glycol to the dicarboxylic acid component is within a specific low range.

Examples of the glycol-soluble cobalt compounds used in the present invention include cobalt chloride, cobalt acetate, cobalt nitrate, cobalt benzoate, cobalt chromate, and cobalt acetylacetonate (■).

■) etc., and the amount added is 1 in terms of cobalt metal equivalent.
0 to 200 ppo+ (versus polyester).

If the amount added is less than 10 pp1, the effect of improving the color tone of the polymer disappears, and if it exceeds 2001) Ilm, the softening point decreases, the heat resistance deteriorates, and the transparency of the polymer decreases.

As glycol-soluble magnesium and manganese compounds, glycol-soluble compounds such as halides, inorganic salts such as nitrates and sulfates, organic acid salts such as acetates, oxalates, and benzoates, and oxides are used. However, two or more selected from these groups may be used in combination.

The amounts of these magnesium compounds and manganese compounds to be added are determined in relation to the cobalt compound used in combination, and the appropriate amounts are within the range of general formula 2 above.

In this case, generally speaking, the higher the amount added, the lower the softening point of the polymer will be suppressed, but if the total amount of magnesium and manganese compounds exceeds 11,000 pp in terms of metal, the softening point will decrease and the color tone will worsen, so the amount used is limited.

Furthermore, if the total amount of magnesium and manganese compounds in terms of metal is less than 25%, the softening point will be lowered, and the transesterification reaction rate will be lowered, resulting in an increase in residual alkoxy groups, making it impossible to obtain a polyester with a high degree of polymerization.

The cobalt compound, magnesium compound, and manganese compound may be added at any stage until the esterification is completed in the case of direct esterification from dicarboxylic acid and glycol; When the transesterification reaction is carried out, any stage may be used as long as the transesterification reaction is completed.

In this case, it is more preferable to add it before the start of the transesterification reaction.

Note that a portion may be added during the process until the polycondensation reaction is completed.

Further, the order in which the compounds are added may be simultaneous, separate, or whichever is added first.

In the present invention, the blending molar ratio of glycol to dicarboxylic acid component must be 1.1 to 1.85, which prevents the softening point of the polyester produced and improves heat resistance due to the generation of aldehyde compounds in the second and third steps. It is possible to prevent the decrease.

In this case, in direct esterification from dicarboxylic acid and glycol, the blending molar ratio of glycol to dicarboxylic acid is more preferably 1.1 to 1.5, and in transesterification reaction between an alkyl ester of dicarboxylic acid and glycol, the alkyl The molar ratio of glycol to ester is more preferably 1.5 to 1585.

The molar ratio of glycol to dicarboxylic acid component is 1.8
If it exceeds 5, the softening point tends to decrease when metal compounds other than cobalt, manganese, and magnesium compounds are not present in the present invention.

Furthermore, if the molar ratio of glycol to dicarboxylic acid component is less than 1.1, the dicarboxylic acid component will be insufficiently dissolved in glycol.

In the present invention, conventionally known polyester polymerization catalysts can be used without any problem, and antimony compounds and germanium compounds can also be used.

For example, if a large amount of commonly used antimony trioxide is used, metallic antimony will precipitate and the resulting polyester will be colored gray, so the amount added is limited.

A germanium compound may be used in combination to eliminate the dullness of polyester caused by these antimony catalysts.

However, addition of a large amount of germanium compounds lowers the softening point and heat resistance of the resulting polyester, so the amount added is limited.

In order to further improve the heat resistance and whitening of the produced polyester, known phosphorus compounds such as phosphoric acid, phosphorous acid and their esters, alkylphosphonic acid, phenylphosphonic acid and their esters may be added. May be added.

There is no particular limit to the amount of these phosphorus compounds added, but if they are used in large quantities, it is desirable to limit the amount used to a necessary and sufficient amount, since polymerization productivity may decrease, the amount of diethylene glycol by-product may increase, etc.

The polyester of the present invention is one in which 80 mol% or more of the repeating units constituting the polyester consist of ethylene terephthalate.

Also, terephthalic acid or its dimethyl ester is p-
Terephthalic acid produced by a xylene oxidation method, such as a nitric acid oxidation method, a one-stage air oxidation method, or a two-stage oxidation method using nitric acid and air, or terephthalic dimethyl ester obtained by esterifying the terephthalic acid with methanol.

Copolymerization components include isophthalic acid, p-β-oxyethoxybenzoic acid, diphenyl ether-4゜4'-dicarboxylic acid, diphenoxyethane-4゜4'-dicarboxylic acid,
Dicarboxylic acid components such as adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid or their alkyl ester derivatives, glycols such as propylene glycol, butanediol, neopentyl glycol, cyclohexane dimetatool, and ethylene oxide adduct of bisphenol A can be used.

The effects achieved by the present invention are listed below.

(1) The amount of aldehyde compounds generated during the melting process is small, and the change in color tone is also small.

(2) A polyester with improved transparency and whitening and less decrease in softening point can be obtained.

(3) Since there is little change in color tone during high-temperature processes, high-temperature polymerization or high-temperature melting is possible, improving productivity.

(4) Even if terephthalic acid or its dimethyl ester raw material containing an aldehyde compound as an impurity is used, a polyester with good color tone and heat resistance can be obtained.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, the measurement method of each characteristic of the polymer in an Example is as follows.

(Polymer color tone) Indicated by Hunter values (L, a, b) using a polymer chip color machine (manufactured by Toyo Rika), L is lightness (the larger the value, the brighter), b is yellow - the hue of the front thread (+ is yellowish) , - is bluish)
represents.

(Intrinsic viscosity) Expressed as a value measured in an orthochlorophenol solvent at 25°C.

(Softening point) A polymer chip was placed in a silicone oil bath and heated at a rate of 68C for 15 minutes.
The point where 11 m is injected is electrically detected.

(Amount of aldehyde generated) Acetaldehyde generated from a polymer melted at 300° C. in a nitrogen stream was collected with cooled methanol and measured by gas chromatography.

(Metal compounds) Quantitative analysis of cobalt, manganese, and magnesium metals is
2 g of polyester was accurately weighed, ignited at 700° C. for 2 hours to incinerate it, and then subjected to atomic absorption spectrometry using a conventional method as a hydrochloric acid solution.

Comparative Examples 1 to 3 1.9 times the mole of ethylene glycol (EG) was added to 100 parts of dimethyl terephthalate (DMT), and Table 1
Cobalt acetate tetrahydrate ((CH3C
OO)2CO-4H20) 0.127 parts, manganese acetate tetrahydrate [(CH3COO)2Mn4H20) 0.1
25 parts, magnesium acetate tetrahydrate [(CH3COO)
0.113 part of 2Mg.4H20) was added as a catalyst, and a transesterification reaction was carried out in a conventional manner (under normal pressure).

Next, 0.03 part of antimony trioxide was added to the product, and polymerization was carried out at 285° C. under a reduced pressure of 1 mmHg or less to obtain a polymer having the intrinsic viscosity shown in Table 1.

The metal content in the obtained polymer is Kobal I'
The content was 300 ppm, the manganese content was 278 ppm, and the magnesium content was 125 ppm.

Although the use of cobalt salt suppresses yellowing of the polymer, it has the drawbacks of lowering the softening point of the polymer and generating a large amount of aldehyde during melting.

As shown in Table 1, when a manganese salt or a magnesium salt is used alone, there is a drawback that the polymer becomes yellow in color.

Comparative Example 4 0.03 parts of antimony trioxide and trimethyl phosphor) were added to the transesterified product in Comparative Example 2.
．． 03 parts were added and polymerized by a conventional method to obtain a polymer having an intrinsic viscosity of 0.65.

The polymer has an L value of 41.2 and a b value of 3.4, and although the addition of the phosphorus compound has an effect of improving the color tone, it still has a yellowish tinge.

Example 1 1.75 times the mole of ethylene glycol was added to 100 parts of dimethyl terephthalate, and manganese acetate tetrahydrate ((C
Hs COO) 2 Mn ・4 H20) O-06
and cobalt acetate tetrahydrate ((CHa COO)
2C.

A transesterification reaction was carried out by a conventional method using 0.01 part of 4H20) as a catalyst.

Next, 0.03 part of antimony trioxide and 0.03 part of trimethyl phosphate were added to the reaction product and polymerized in a conventional manner to obtain a polymer having an intrinsic viscosity of 0.66.

The cobalt content in the polymer was 24 pIn, and the manganese content was 135 pl)m.

As shown in Table 2 below, the resulting polymer had a high softening point of 260.4° C., an L value of 41.6, and a b value of 1.2, and had a high brightness and no yellowish tinge.

After heating this polymer in air at 240°C for 6 hours, the color tone was L value 74.5 and B value 11. 0, and compared to Comparative Example 5, the color tone change is small.

Also, the amount of aldehyde generated during heating and melting at 300°C is 18.
4×10-”mol/100g polymer, Comparative Example 1
It was found that the heat resistance was better compared to samples 3 and 5.

Example 2 In Example 1, 0.025 part of antimony trioxide and 0.004 part of germanium dioxide were added to the transesterification product.
1 part and 0.04 part of trimethyl phosphate were added and polymerized in a conventional manner to obtain a polymer having an intrinsic viscosity of 0.66.

The characteristic values of the polymer are shown in Table 2, and the softening point is 259.
Although the temperature was slightly low at 6°C, the brightness was higher with an L value of 44.2 and a b value of 0.8, less yellowness, and a good color tone.

As shown in Table 2, the color change of the polymer after the deterioration test in air at 240°C conducted in the same manner as in Example 1 was small, and the amount of aldehyde generated during melting at 300°C was also small.

Example 3 In Example 1, magnesium acetate tetrahydrate [(CH2COO)2Mg4H20] was used as the transesterification catalyst.
0.06 part and cobalt acetate tetrahydrate ((CH2CO
O) 2 Co ・4 H20) The same procedure as in Example 1 was carried out except that 0.005 part was added, and the intrinsic viscosity was 0.
65 polymers were obtained.

The cobalt content in the polymer was 12 ppl, the magnesium content was 68111)III, and other characteristic values are shown in Table 2, and the obtained polymer had a high brightness without yellowing and a good color tone.

Further, in the deterioration test conducted in the air at 240° C. in the same manner as in Example 1, the color tone change and the amount of aldehyde generated during melting were small, and the heat resistance was excellent.

Example 4 100 parts of terephthalic acid (TPA) and 1.25 times the mole of ethylene glycol were charged into a reaction vessel, and the amount was 1.5 kg/cv.
The reaction was carried out at 240° C. for 6 hours below tG.

The reaction product was then transferred between polymerizations and cobalt acetate 4
0.01 part of hydrate, 0.04 part of manganese acetate tetrahydrate, 0.02 part of phosphoric acid, and 0.03 part of antimony trioxide were added, and the intrinsic viscosity was 0 at 285°C under reduced pressure of 1 miHg or less.
．． The polymerization reaction was carried out until reaching 65.

The cobalt content in the obtained polymer was 241)IIm, the manganese content was 90 ppm, and the characteristic values of the polymer were as shown in Table 2, a softening point of 259.2°C, an L value of 43.5, and a b value of 2.
2, a polymer with high brightness and no yellow coloring was obtained.

Further, there was little change in color tone after the deterioration test in air at 240°C, and the amount of aldehyde generated during melting was also small.

Comparative Example 5 Example 1 except that 2.2 times the molar amount of ethylene glycol relative to dimethyl terephthalate was used in Example 1.
A polymer having an intrinsic viscosity of 0.66 was obtained in the same manner as above.

The characteristic values of the polymer are shown in Table 2, and the color tone was good, but the softening point was low at 258.2°C.

Furthermore, the color tone changed significantly after the deterioration test in air at 240°C, and a large amount of aldehyde was generated during melting.

Example 5 In Example 1, manganese acetate tetrahydrate ((CH3COO)2Mn-4H20)0.
03 parts, magnesium acetate tetrahydrate ((CH3COO)
2Mg-4H20) 0.02 part and cobalt chloride 6
The same procedure as in Example 1 was carried out except that 0.02 part of aqueous salt [coC12/6H20] was added, and the intrinsic viscosity was 0.65.
obtained a polymer.

The cobalt content in the polymer was 49 parts%, the manganese content was 67 pp11, and the magnesium content was 221) III.It had a high softening point of 259.8°C, and the polymer had a b value of 1.5, and had a good color tone without yellowing. Ta.

Further, the color tone change in the deterioration test at 240C in air conducted in the same manner as in Example 1, and the amount of aldehyde generated during melting were small, indicating excellent heat resistance.

Claims (1)

[Scope of Claims] 1. When producing a polyester from a dicarboxylic acid whose main component is terephthalic acid or its alkyl ester and a glycol whose main component is ethylene glycol, the molar ratio of glycol to dicarboxylic acid component is 1.1 to 1.1.
1.85, and add a glycol-soluble cobalt compound and at least one glycol-soluble magnesium compound and a manganese compound so as to satisfy the following formulas 1 and 2 until the esterification or transesterification reaction is completed. A method for producing polyester characterized by: (In the formula, Co is metal cobal H1lllll vs. polyester,
Me indicates the total ppm of metallic magnesium and metallic manganese versus polyester. )