JP2002146002A - Method for producing polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polyester, capable of giving the polyester having a better color tone, less dipropylene glycol content, and less carboxyl end-group content, when compared with conventional polypropylene terephthalate. SOLUTION: This method for producing a polyester comprises subjecting an aromatic dicarboxylic acid consisting mainly of terephthalic acid or its ester-forming derivative to esterification reaction or ester interchange reaction with a diol consisting mainly of propylene glycol, then subjecting the reaction product to polycondensation to produce the polyester of which the repeating unit consists mainly of propylene terephthalate, wherein a titanium compound is used as a catalyst for the esterification reaction, the ester interchange reaction and/or the polycondensation reaction, and further at least one kind of alkaline compound selected from the group consisting of nitrogen-containing compounds, sodium hydroxide, and potassium hydroxide is added to the reaction mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a polyester whose main repeating unit comprises propylene terephthalate. More specifically, the color tone is good, the dipropylene glycol (hereinafter referred to as DPG) content and the terminal carboxyl group (hereinafter referred to as COOH)
The present invention relates to a method for producing polypropylene terephthalate having a low content.

[0002] The DPG referred to herein has the following structural formula.

HO—CH ₂ CH ₂ CH ₂ —O—CH ₂ C
H ₂ CH ₂ -OH

[0004]

2. Description of the Related Art Polypropylene terephthalate (common name: polytrimethylene terephthalate, hereinafter referred to as PTT)
Because of its high crystallization rate and excellent moldability, it is useful as an engineering plastic like polybutylene terephthalate, and is expected to have a large market.

[0005] In recent years, as the production method of inexpensive 1,3-propanediol (hereinafter referred to as PG) has been developed,
TT has been more likely to be manufactured cheaply,
Due to its molecular structure, TT has a lower polymerization reaction rate than polyethylene terephthalate, so that it is difficult to produce a polymer having a molecular weight. As a polymerization catalyst, a titanium compound having low-temperature activity has been mainly used. (For example,
JP-A-51-140992, JP-A-8-1205
21, JP-A-11-172525, etc.).

However, when a titanium compound is used as a catalyst, not only is the polymer colored yellow, but a side reaction is liable to occur during the polymerization reaction, and the decomposition reaction is accelerated (deterioration of the melting heat stability). Increase in DPG amount and COOH
There were problems such as a decrease in hydrolysis resistance due to an increase in the amount.

In order to improve the hydrolysis resistance, thermal stability, color tone and the like of PTT, a method of adding a hindered phenol compound during the polymerization reaction (Japanese Patent Laid-Open No. 51-14209).
No. 8, JP-A-51-142097), a method of polymerizing in the presence of a magnesium compound (JP-A-2000-142975).
159876) and the like,
These methods have problems such as a decrease in productivity as well as polymerization reactivity, and they have not been satisfactory in terms of hydrolysis resistance, heat stability, color tone and the like of the obtained polymer.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing PTT which overcomes the problems of the prior art, has a good color tone, and has a low DPG content and a small amount of COOH.

[0009]

In order to solve the above-mentioned problems, an aromatic dicarboxylic acid containing terephthalic acid (hereinafter referred to as TPA) as a main component or an ester-forming derivative thereof and a diol containing PG as a main component are used. When a product obtained by an esterification reaction or a transesterification reaction is subjected to polycondensation to produce a polyester whose main repeating unit is propylene terephthalate, a titanium compound is used as a catalyst for esterification or transesterification and / or polycondensation. And at least one alkali compound selected from the group consisting of a nitrogen-containing compound, sodium hydroxide and potassium hydroxide is added.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester in which the main repeating unit of the present invention is propylene terephthalate is an aromatic dicarboxylic acid having TPA as a main component or an ester-forming derivative thereof as an acid component, and PG as a glycol component. It is composed of a diol or an ester-forming derivative thereof as a main component.

The polyester of the present invention may contain adipic acid, isophthalic acid, sebacic acid, phthalic acid, or the like as a copolymer component as long as the effects of the present invention are not impaired.
4,4′-diphenyldicarboxylic acid, dicarboxylic acids such as alkali metal salts of sulfoisophthalic acid, phosphonium salts of sulfoisophthalic acid and ester-forming derivatives thereof, polyethylene glycol, diethylene glycol,
Dioxy compounds such as ethylene glycol, hexamethylene glycol and neopentyl glycol, oxycarboxylic acids such as p- (β-oxyethoxy) benzoic acid, and ester-forming derivatives thereof may be copolymerized.

The titanium compound in the present invention is not particularly limited. At least one selected from the group consisting of titanium alkoxide, titanium acylate and titanium chelate
Various kinds of organotitanium compounds are preferable. Specifically, tetra-n-propyl titanate (hereinafter, referred to as TnPT), tetraisopropyl titanate (hereinafter, referred to as TPT), tetra-n-butyl titanate (hereinafter, referred to as TBT), tetra-t- Butyl titanate, tetraphenyl titanate, tetracyclohexyl titanate, tetrabenzyl titanate, tetrastearoxy titanate, tetra-
titanium alkoxide such as n-propyl titanate polymer, tetraisopropyl titanate polymer, tetra-n-butyl titanate polymer, tetra-t-butyl titanate polymer, or a mixed titanate thereof;
Titanium acylate such as tri-n-butoxytitanium stearate and isopropoxystearate, or a mixed titanate thereof, diisopropoxytitanium bisacetylacetonate (hereinafter referred to as TAA), dihydroxy
Titanium chelates such as bis-lacto-titanium and the like, or a mixed titanate thereof are mentioned.

Of these, TnPT, TPT, TBT which are relatively inexpensive, have a low molecular weight and a high content of titanium atoms
Is preferred, and TBT is most preferred. Further, two or more of these titanium compounds may be used in combination.

The titanium compound of the present invention is preferably added to the resulting polyester in an amount of 5 to 500 ppm in terms of titanium atoms. 5 ppm added
If the amount is lower, the catalytic activity is insufficient, and as a result, only a polymer having a low molecular weight is obtained. Also, 500pp
When the amount exceeds m, the color tone of the polymer deteriorates and a side reaction easily occurs during the polymerization reaction, and the DPG amount and the COOH amount may increase. More preferably, 10 to 300 pp
m, more preferably 20 to 150 ppm.

The alkali compound of the present invention must be at least one alkali compound selected from the group consisting of a nitrogen-containing compound, sodium hydroxide and potassium hydroxide.

The added amount of the alkali compound of the present invention is preferably from 10 to 3000 ppm based on the obtained polyester. If the content is less than 10 ppm, the DPG amount or CO by improvement of the polymer color tone and suppression of side reactions during the polymerization reaction are reduced.
It is difficult to obtain the effect of suppressing an increase in the amount of OH, and 3000
When added in excess of ppm, the color tone of the polymer may be deteriorated. 20 to 2000
ppm is more preferred, and even more preferably 50-100.
It is 0 ppm.

In the present invention, these nitrogen-containing compounds,
When at least one alkali compound selected from the group consisting of sodium hydroxide and potassium hydroxide is used, the use of a nitrogen-containing compound is particularly preferable because the resulting polyester has a particularly good color tone.

Preferred examples of the nitrogen-containing compound of the present invention include compounds represented by the following formulas 1 and 2.

[0019]

(Equation 1)

[0020]

(Equation 2) More specifically, examples of the compound of Formula 1 include ammonia, diethylamine, trimethylamine, triethylamine (hereinafter referred to as TEA), tripropylamine, tributylamine, and the like. Examples of the compound of the formula 2 include tetramethylammonium hydroxide, tetraethylammonium hydroxide (hereinafter referred to as EAH), tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylbenzylammonium hydroxide, and the like.

Further, as a compound other than Formula 1 or 2,
A derivative of the compound of Formula 1 or Formula 2, ethylenediamine,
Tetraethylenediamine, hexamethylenediamine, pyridine, quinoline, pyrroline, pyrrolidone, piperidine and the like may be used.

As the nitrogen-containing compound of the present invention, among the above-mentioned compounds, a tertiary amine compound or a quaternary ammonium compound is preferable because the formation of insoluble foreign matters in the obtained polyester is small. More preferably, 28
When the compound volatilizes at a temperature of 0 ° C. or lower, the residual amount in the finally obtained polyester is reduced, and the color tone of the polyester is further improved, which is preferable. Such compounds include tertiary amine compounds such as trimethylamine, TEA, tripropylamine, and tributylamine;
And quaternary ammonium compounds such as tetramethylammonium hydroxide, EAH, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and trimethylbenzylammonium hydroxide.

In the present invention, the amount of the nitrogen-containing compound added is
5 to 10 in terms of nitrogen atom with respect to the obtained polyester
Preferably it is 00 ppm. Further, the content is more preferably from 10 to 800 ppm, particularly preferably from 20 to 500 ppm, in order to improve the effect of suppressing the formation of foreign matters and the color tone of the obtained polyester.

The addition time of the titanium compound in the present invention may be before the start of the esterification reaction, during the esterification reaction, after the esterification reaction, or before the start of the transesterification reaction, during the transesterification reaction, after the transesterification reaction, and / or It is before the start of condensation and the like, but is not particularly limited. Also,
The addition time of the alkali compound is also before the start of the esterification reaction, during the esterification reaction, after the esterification reaction, or before the start of the transesterification reaction, during the transesterification reaction, after the transesterification reaction, and / or before the start of the polycondensation. Although not particularly limited, it is preferable to add the titanium compound before or simultaneously with the addition of the titanium compound from the viewpoint of the effect of suppressing the color tone of the obtained polymer, the DPG amount and the COOH amount.

The titanium compound may be added as it is to the polyester reaction system, or may be added to the reaction system after previously mixing with a diol component forming a polyester such as PG. Further, after previously mixed with water containing an alkali compound, an organic solvent or a mixture of water and an organic solvent, the mixture may be added to the reaction system, and further diluted with a diol component forming a polyester such as PG. May be added. Further, the alkali compound may be added as it is to the polyester reaction system.
And the like, and then added to the reaction system. Further, after mixing with water, an organic solvent or a mixture of water and an organic solvent, the mixture may be added to the reaction system, or may be further diluted with a diol component forming a polyester such as PG and then added to the reaction system. .

The polyester in the present invention is obtained by the following method. For example, (1) dimethyl terephthalate and PG are used as raw materials, a low-polymer is obtained by a transesterification reaction, and further produced by a polycondensation reaction. For example, PTT having a molecular weight or an oligomer thereof may be obtained, and then produced by a subsequent polycondensation reaction. Here, a titanium compound is used as a catalyst for esterification or transesterification and / or polycondensation, and at least one alkali compound selected from the group consisting of nitrogen-containing compounds, sodium hydroxide and potassium hydroxide is added. May be advanced using a small amount of an antimony compound, a tin compound, a germanium compound, or a compound such as manganese, cobalt, zinc, or the like as a catalyst. For the purpose of inactivating the catalyst used in the reaction, a phosphorus compound may be added. In addition, the polycondensation reaction may be carried out by polycondensation using the activity of the titanium compound used in the esterification or transesterification reaction as it is, or may be newly added with a titanium compound, or may be advanced by adding various catalyst compounds. .

[0027] The production method of the present invention comprises the steps of: starting from the initial stage of the series of esterification or transesterification reaction of (1) or (2) and after completion of the reaction; and / or at the beginning of the polycondensation reaction. A compound and an alkali compound are added, and an esterification or transesterification reaction and a polycondensation reaction are further advanced to obtain PTT.

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

[0029]

The present invention will be described in more detail with reference to the following examples. In addition, each characteristic value in an Example was calculated | required by the following method. (1) Intrinsic viscosity of polymer (hereinafter referred to as IV) It was measured at 25 ° C. using orthochlorophenol as a solvent. (2) Metal content in polymer Determined by X-ray fluorescence. (3) Color tone of polymer Using a color difference meter (SM color computer model SM-3) manufactured by Suga Test Instruments Co., Ltd., Hunter values (L, a, b)
Value). (4) DPG content of polymer ¹ H-NMR was measured using VARIAN's UNITYINOVA600, and quantified from the integral ratio of the obtained signals. (5) COOH content of the polymer The method of Maurice et al. [Anal. Chim. Act
a, 22, p363 (1960)]. (6) Presence or absence of insoluble foreign matter (transparency) After the completion of the polymerization operation, the molten polymer in the glass polymerization tube was observed to determine the presence or absence of insoluble foreign matter.

：: No insoluble foreign matter was observed.

X: Insoluble foreign matter is observed.

Example 1 98 parts by weight of high-purity TPA and 61 parts by weight of PG were charged into a reactor, and TBT 0.0
1 part by weight and a mixed solution in which PG was mixed with an aqueous solution containing 20% by weight of EAH in advance (1% as nitrogen atom)
00 ppm) and stirring at 140 to 240 ° C.
The mixture was heated and stirred for a long time, and then further stirred at 240 ° C. until the distilling of water was not observed, thereby allowing the esterification reaction to proceed. After the esterification reaction, TBT
0.075 parts by weight was additionally added.

Thereafter, the temperature of the reaction system was gradually raised from 240 to 260 ° C. while the low polymer was stirred at 30 rpm, and the pressure was lowered to 40 Pa. The time to reach the final temperature and the final pressure was 60 minutes. When the predetermined 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 time from the start of the pressure reduction to the predetermined stirring torque was 3 hours and 15 minutes.

The intrinsic viscosity of the obtained polymer is 0.89,
DPG amount 1.2 mol%, COOH amount 21 equivalents / ton,
The color tone of the polymer was 61.3 in L value, 0.5 in a value, and 6.8 in b value, and no insoluble foreign matter was observed. Also,
Analysis by X-ray fluorescence confirmed that the titanium atomic component was 120 ppm. Thus, polyester pellets having good polymerization reactivity and good polymer characteristics were obtained.

Examples 2 to 11 and Comparative Examples 1 and 2 Except for changing the kind and amount of the metal compound or alkali,
The polymer was polymerized in the same manner as in Example 1. Table 1 shows the results
It was shown to.

[0036] In any of the claims of the present invention, those having good polymer properties were obtained.
Those polymerized without using an alkali compound or those polymerized with antimony trioxide alone have poor polymer color tone,
An increase in the amount of DPG and COOH and insoluble foreign matters were observed.

[0037]

[Table 1]

[0038]

According to the method for producing a polyester of the present invention, a polymer having a good color tone and a small DPG content and a small amount of COOH as compared with conventional PTT can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J029 AA03 AB04 AC01 AC02 AD01 AD02 BA04 CB06A JA173 JB131 JB181 JC023 JC033 JC043 JC233 JC243 JF321 KB04 KB05 KD01 KD07 KE02 KE03

Claims (5)

[Claims] 1. A product obtained by an esterification reaction or a transesterification reaction with an aromatic dicarboxylic acid containing terephthalic acid as a main component or an ester-forming derivative thereof and a diol containing 1,3-propanediol as a main component. To produce a polyester whose main repeating unit is propylene terephthalate, using a titanium compound as a catalyst for esterification or transesterification and / or polycondensation, and further comprising a nitrogen-containing compound, sodium hydroxide and water. A method for producing a polyester, comprising adding at least one alkali compound selected from the group consisting of potassium oxide. 2. The method for producing a polyester according to claim 1, wherein a titanium compound is added in an amount of 5 to 500 ppm in terms of titanium atom to the obtained polyester. 3. The polyester obtained is mixed with at least one alkali compound selected from the group consisting of a nitrogen-containing compound, sodium hydroxide and potassium hydroxide.
The method for producing a polyester according to claim 1, wherein the addition is performed in an amount of 3000 ppm. 4. The polyester according to claim 1, wherein the titanium compound is at least one organic titanium compound selected from the group consisting of titanium alkoxide, titanium acylate and titanium chelate. Manufacturing method. 5. The method according to claim 1, wherein the nitrogen-containing compound is a tertiary amine compound or a quaternary ammonium compound.