JP3137794B2 - Polyester production method - Google Patents

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, and more particularly to a method for producing a polyester which gives a molded article having excellent heat stability.

[0002]

2. Description of the Related Art Polyester is excellent in mechanical, physical and chemical properties, so that fibers, films,
Widely used for bottles or industrial resins.

[0003] In various polyester production methods, for the purpose of high strength, low carboxylation, low acetaldehyde conversion, low oligomerization, etc., there is a method in which solid polymerization is performed at a temperature lower than the melting point of a polymer after melt polymerization. Solid-phase polymers generally have a high degree of polymerization, but even during solid-state polymerization, the degree of polymerization decreases and the number of terminal carboxyl groups increases due to decomposition during melt molding. Must be manufactured. The deterioration during the melt molding becomes more severe as the polymer becomes higher (higher degree of polymerization and lower carboxyl group concentration), so that it is difficult to obtain a high-performance molded product.

[0004] The main causes of this deterioration are hydrolysis, oxidative decomposition, thermal decomposition, and the like. As methods for preventing such deterioration, dry strengthening before melt molding, drying in an inert gas stream, and the like have been conventionally performed.

[0005]

However, the recent demand for high quality has not reached the level where the prior art can sufficiently cope with it.

Accordingly, the present inventors have made intensive studies and found that this problem can be achieved for the first time by treating the polymer after solid-phase polymerization under special conditions, and reached the present invention.

[0007]

That is, the present invention relates to a method for producing a polyester containing an aromatic dicarboxylic acid as a main acid component and an alkylene glycol as a main glycol component, after melt polymerization and solid phase polymerization. This is a method for producing a polyester, which comprises subjecting the solid phase polymer to ultrasonic treatment in a liquid of a solvent that is insoluble and unreactive with the solid polymer.

[0008] In the present invention, the "polyester" refers to a polyester containing an aromatic dicarboxylic acid as a main acid component and an alkylene glycol as a main glycol component. Here, “main” means that the alkylene aromatic dicarboxylate unit accounts for 85 mol% or more. What contains 15 mol% or less of the third component is a technique to which the present invention can be applied.

Examples of the "aromatic dicarboxylic acid" constituting the polyester include terephthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylketonedicarboxylic acid, diphenoxyethanedicarboxylic acid and the like. Examples of the “alkylene glycol” constituting the polyester include ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol and the like.

As the third component which can be copolymerized, there are aromatic dicarboxylic acids and dicarboxylic acids other than alkylene glycol, diols and oxycarboxylic acids which constitute the polyester. Specifically, in addition to the above compounds, aromatic dicarboxylic acids such as isophthalic acid, diphenylsulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, sodium-sulfoisophthalic acid, and dibromoterephthalic acid; alicyclic dicarboxylic acids such as decalin dicarboxylic acid Acid, tetralindicarboxylic acid, hexahydroterephthalic acid and the like; and aliphatic dicarboxylic acids such as malonic acid, succinic acid, adipic acid and sebacic acid. Examples of the glycol component include aliphatic diols such as trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, diethylene glycol, and triethylene glycol; aromatic diols such as catechol and naphthalene diol;
Resorcinol, 4,4'-dihydroxy-diphenyl-sulfone, bisphenol A ([2,2'-bis (4-hydroxyphenyl) propane]), tetrabromobisphenol A, bishydroxyethoxybisphenol A
An alicyclic diol such as cyclohexanediol; an aliphatic oxycarboxylic acid such as glycolic acid;
Hydroacrylic acid, 3-oxypropionic acid, etc .: alicyclic oxycarboxylic acids, such as asiatic acid, quinovanic acid, etc .; aromatic oxycarboxylic acids, such as salicylic acid, m-
Oxybenzoic acid, p-oxybenzoic acid, mandelic acid, atrolactic acid and the like can be mentioned.

Further, a polyfunctional compound having a valence of 3 or more, for example, glycerin, within a range in which the polyester is substantially linear.
Trimethylolpropane, pentaerythrite, trimellitic acid, trimesic acid, pyromellitic acid, tricarbamic acid, gallic acid, etc. may be copolymerized, and if necessary, monofunctional compounds such as o-benzoylbenzoic acid, naphthoe An acid or the like may be added.

For the production of the polyester of the present invention, conventionally known methods of melt polymerization and solid state polymerization may be used as they are.
For example, in melt polymerization, a method in which an acid and a glycol are directly esterified and then melt-polycondensed in the presence of a suitable catalyst, a transesterification reaction of a lower alkyl ester of an acid and a glycol in the presence of a suitable catalyst, Examples of the method include melt polycondensation. In any case, after the melt polycondensation, the mixture is melt-extruded, cooled in a suitable cooling medium, for example, water, cut into a suitable size, and formed into chips. The tip may be of any shape and may be dice-shaped. After the melt polymerization, the solid-phase polymerization performed at a temperature equal to or lower than the melting point may be performed under an inert gas stream or under a vacuum (under reduced pressure), and may be applied in a continuous system or a batch system. Furthermore,
It may be a packed tower type, a horizontal clinker type or a tumbler type.

In the present invention, after the solid phase polymerization, the obtained polymer is subjected to ultrasonic treatment in an inert liquid. The frequency of the ultrasonic wave may be in a normal frequency range. For example, it can be applied at a frequency of about 20 kHz (lower limit) to 100 kHz or more (upper limit).

Known means can be used as an oscillation source for generating ultrasonic waves. For example, a piezoelectric vibrator using quartz,
An electrostrictive oscillator using barium titanate, an electrostrictive oscillator using nickel or ferrite, a Janowski-Poleman sound wave, or the like can be used.

The intensity of the ultrasonic wave is not particularly limited,
It is preferably about 100 w / cm ^{2 in a} liquid. In some cases, it can be converged and raised to about 2 kw / cm ² .

As the medium, a liquid that does not dissolve the polyester and does not react is used. For example, pure water, low-concentration mineral acid water, low-concentration alcohol water, and the like are exemplified. Of these, water is preferred. Heating promotes the effect.

Conventionally, a method of using ultrasonic waves for producing polyester has been known. For example, JP-A-51-1398
No. 96, No. 53-114894, No. 55-12161
And JP-B-56-47428 disclose a method of obtaining a polyester by adding a solvent subjected to ultrasonic treatment to a polymerization reaction system. However, these are for improving the dispersibility of the additive.

Japanese Patent Application Laid-Open No. 48-52862 discloses that when a molded product is obtained, a soluble component is extracted by ultrasonically treating a polymer in a solvent to obtain a molded product having good heat and dimensional stability. A method of obtaining is disclosed. The purpose is to uniformly extract soluble components from polyester, polyamide and the like in a short period of time, and as a result, heat stability and dimensional stability are improved because low molecular weight substances are extracted.

Further, JP-A-48-44512 discloses that
A method of ultrasonically processing a flow channel in order to prevent deterioration such as gelation and thermal decomposition in a flow channel in melt extrusion of a polymer is disclosed. The purpose of preventing thermal degradation is the same, but the purpose is to process the channel rather than the polymer.

On the other hand, the production method of the present invention relates to a polymer which has an advantage that a polyester which has undergone solid-state polymerization and has only a small amount of thermal deterioration can be obtained by melt-molding the polyester by ordinary drying alone.

Since the treatment is carried out in an inert medium, only the soluble components as in the above-mentioned known documents are not extracted.
In fact, when comparing the polymers before and after the ultrasonic treatment, the amounts of the monomers, oligomers, catalysts, stabilizers and the like hardly changed between the untreated and the treated ones.

The reason why the ultrasonic treatment reduces the decomposition during melt molding is not clear, but during solid phase polymerization, water and glycol produced as a result of the reaction, or aldehydes and other low molecular weight substances generated by the decomposition, After extraction from the solid (pellet), some unknown substance is adsorbed on the pellet because it is dropped off by ultrasonic waves, or the activated surface is stabilized by ultrasonic treatment. For some reason, or for other reasons, it has not been clarified yet. Of course, sonication is a reproducible and very effective modification method.

[0023]

As described above, the polyester obtained by the method of the present invention is less decomposed during melt molding, and a molded article having excellent performance can be obtained.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples.
You. The embodiment is merely an example of the present invention, and the present invention is not limited to the embodiment.
It is not limited to only. In the examples, "parts" refers to parts by weight.
Means The method of measuring the characteristics used in the examples is as follows.
Shown in 1) Intrinsic viscosity (may be expressed as [η]) Phenol / tetrachloroethane (weight ratio 60/40)
Calculated from solution viscosity measured at 35 ° C using mixed solvent of
did. 2) Terminal carboxyl group concentration: COOH A. Conix, Makromol. chem. ,2
6, 226 (1958)). 3) Acetaldehyde: AA According to the Celanese method.

[0025]

Examples 1-4, Comparative Examples 1-2 Terephthalic acid 166
And 74.4 parts of ethylene glycol in an autoclave, and an esterification reaction was carried out at 250 ° C. under a pressure of 3 kg / cm ² G. 0.042 parts of trimethyl phosphate and 0.037 parts of germanium oxide were added to the esterification product, and a polycondensation reaction was performed at 270 ° C. to obtain a polymer having an intrinsic viscosity of 0.51. .

This was pelletized, subjected to solid-state polymerization at 215 ° C. to an intrinsic viscosity of 0.76, and further processed under the conditions shown in Table 1. The properties of this polymer and various properties of a molded product obtained by injection molding at 300 ° C. are shown in the same table.

[0027]

[Table 1]

It was found that the sonicated product had a lower terminal COOH concentration and the amount of acetaldehyde and were more stable than the untreated product.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08G 63/00-63/91

Claims (4)

(57) [Claims] In producing a polyester comprising an aromatic dicarboxylic acid as a main acid component and an alkylene glycol as a main glycol component, the obtained solid phase polymer is subjected to melt polymerization and solid phase polymerization. A method for producing a polyester, comprising sonicating the solid-phase polymer in a liquid having no solubility and having no reactivity. 2. The method according to claim 1, wherein the aromatic dicarboxylic acid is terephthalic acid. 3. The method for producing a polyester according to claim 1, wherein ethylene glycol is used as the alkylene glycol. 4. The method according to claim 1, wherein the liquid is water.