JPH06279580A - Production of polyester - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the quality of polyester melt-molded products. [Structure] A polyester that is melt-polymerized, followed by solid-phase polymerization, and then subjected to ultrasonic treatment in an inert medium such as water to improve the thermal stability of the polyester.

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

[0002]

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

Among various methods for producing polyesters, there are some which undergo solid phase polymerization below the melting point of the polymer after melt polymerization for the purpose of high strength, low carboxylation, low acetaldehyde formation, low oligomerization, and the like. Solid-phase polymers generally have a high degree of polymerization, but even if solid-state polymerization occurs, the degree of polymerization decreases and the number of terminal carboxyl groups increases due to decomposition during melt molding. Must be manufactured. This deterioration during melt molding becomes more severe as the polymer becomes higher (high polymerization degree, low carboxyl group concentration), and thus it becomes difficult to obtain a high-performance molded product.

Hydrolysis, oxidative decomposition, thermal decomposition, etc. are the main causes of this deterioration, and as a method for preventing this, strengthening of drying before melt molding, drying in an inert gas stream, etc. have been conventionally performed.

[0005]

However, the recent demand for high quality has not reached the level that can be sufficiently met by the prior art.

As a result of intensive studies, the present inventors have found that this problem can be achieved for the first time by treating the polymer after solid phase polymerization under special conditions, and arrived at the present invention.

[0007]

[Means for Solving the Problems] That is, the present invention provides a polyester obtained by subjecting 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. The method for producing a polyester comprises sonicating in a liquid of a solvent that is insoluble and non-reactive with the solid phase polymer.

In the present invention, the "polyester" means a polyester containing an aromatic dicarboxylic acid as a main acid component and an alkylene glycol as a main glycol component. Here, "mainly" means that the alkylene aromatic dicarboxylate unit accounts for 85 mol% or more. A technique containing 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 and diphenoxyethanedicarboxylic acid. Examples of the "alkylene glycol" constituting the polyester include ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol and the like.

The third component which can be copolymerized is an aromatic dicarboxylic acid constituting the polyester, a dicarboxylic acid other than alkylene glycol, a diol and an oxycarboxylic acid. Specifically, in addition to the above compounds, aromatic dicarboxylic acids such as isophthalic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, sodium-sulfoisophthalic acid, dibromoterephthalic acid; alicyclic dicarboxylic acids such as decalin dicarboxylic acid. Examples thereof include acids, tetralindicarboxylic acid, hexahydroterephthalic acid and the like; 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.
Resorcin, 4,4'-dihydroxy-diphenyl-sulfone, bisphenol A ([2,2'-bis (4-hydroxyphenyl) propane]), tetrabromobisphenol A, bishydroxyethoxybisphenol A
Alicyclic diols, such as cyclohexanediol, etc .; aliphatic oxycarboxylic acids, such as glycolic acid,
Hydroacrylic acid, 3-oxypropionic acid, etc .: alicyclic oxycarboxylic acid, such as asiatic acid, quinobaic acid, etc .; aromatic oxycarboxylic acid, such as salicylic acid, m-
Examples thereof include oxybenzoic acid, p-oxybenzoic acid, mandelic acid and atrolactic acid.

Further, within the range in which the polyester is substantially linear, a polyfunctional compound having a valence of 3 or more, such as glycerin,
Trimethylolpropane, pentaerythritol, trimellitic acid, trimesic acid, pyromellitic acid, tricarbamic acid, gallic acid, etc. may be copolymerized, and if necessary, a monofunctional compound such as o-benzoylbenzoic acid or naphthoic acid can be used. 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 phase 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 polycondensation is performed in the presence of a suitable catalyst, and a lower alkyl ester of an acid and a glycol are transesterified in the presence of a suitable catalyst, Examples thereof include a method of melt polycondensation. In either case, after melt polycondensation, melt extrusion is performed, followed by cooling in a suitable refrigerant, for example, water, cutting into a suitable size, and chipping. The chips may have any shape or dice shape. Solid phase polymerization performed at a temperature equal to or lower than the melting point after melt polymerization may be performed under an inert gas flow or under 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 ultrasonic waves may be in the 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, and other Janowski-Pallman sound waves can be used.

The intensity of ultrasonic waves is not particularly limited,
About 100 w / cm ^{2 in the} liquid is preferable. In some cases, it can be converged and increased to about ² kw / cm ² .

A liquid which does not dissolve the polyester and does not react is used as a medium. Examples include pure water, low-concentration mineral acid water, low-concentration alcoholic water, and the like. Of these, water is preferred. The effect is promoted by heating.

Conventionally, a method using ultrasonic waves for producing polyester is known. For example, JP-A-51-1398
No. 96, No. 53-114894, No. 55-12161
No. 56-47428 and the like disclose a method of obtaining a polyester by adding an ultrasonically treated solvent to a polymerization reaction system. However, these are for improving the dispersibility of the additive.

Further, in JP-A-48-52862, when a molded product is obtained, soluble components are extracted by subjecting a polymer to ultrasonic treatment in a solvent: a molded product having good heat and dimensional stability. A method of obtaining is disclosed. This is for the purpose of uniformly extracting soluble components from polyester, polyamide and the like in a short time, and since low molecular weight substances are extracted, as a result, thermal stability and dimensional stability are improved.

Further, Japanese Patent Application Laid-Open No. 48-44512 discloses that
There is disclosed a method of ultrasonically processing a channel in order to prevent deterioration such as gelation and thermal decomposition in the channel during melt extrusion of a polymer. The purpose of preventing thermal deterioration is the same, but the channel is processed instead of the polymer.

On the other hand, the production method of the present invention relates to a polymer having an advantage that a polyester which has undergone solid phase polymerization can be obtained by subjecting it to ordinary drying only and melt-molding as it is with little thermal deterioration.

Since the treatment is carried out in an inert medium, it is not the case that only the soluble component as in the above-mentioned known literature is extracted.
In fact, even when the polymers are compared before and after the ultrasonic treatment, the amounts of monomers, oligomers, catalysts, stabilizers, etc. hardly change between the untreated and treated ones.

It is not clear why the ultrasonic treatment reduces decomposition during melt molding, but during solid phase polymerization, water and glycol produced as a result of the reaction, or aldehydes and other low molecular weight products generated by decomposition are After extracting from the solid (pellet), some unknown substance is adsorbed to the pellet because it is removed by ultrasonic waves, or the activated surface is stabilized by ultrasonic treatment. It has not been clarified yet, probably because of other reasons. Of course, ultrasonic treatment is a reproducible and extremely effective modification method.

[0023]

EFFECTS OF THE INVENTION The polyester produced by the method of the present invention is less likely to be decomposed during melt molding, and a molded product having excellent performance can be obtained.

[0024]

The present invention will be specifically described with reference to the following examples. The embodiments are merely examples of the present invention, and the present invention is not limited to the embodiments. “Parts” in the examples means parts by weight. Moreover, the measuring method of the characteristic used in the Example is shown below. 1) Intrinsic viscosity (sometimes referred to as [η]) Phenol / tetrachloroethane (weight ratio 60/40)
It was calculated from the solution viscosity measured at 35 ° C. using the mixed solvent of. 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 were charged into an autoclave, and an esterification reaction was carried out at 250 ° C. under a pressure of 3 kg / cm ² G. To this esterification reaction product, 0.042 parts of trimethyl phosphate and 0.037 parts of germanium oxide were added, and polycondensation reaction was performed at 270 ° C. to obtain a polymer having an intrinsic viscosity of 0.51. .

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

[0027]

[Table 1]

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

Claims (4)

[Claims] 1. When producing a polyester having an aromatic dicarboxylic acid as a main acid component and an alkylene glycol as a main glycol component, a solid polymer obtained after undergoing the steps of melt polymerization and solid phase polymerization A method for producing a polyester, which comprises subjecting the solid phase polymer to ultrasonic treatment in a liquid using a liquid which is insoluble and has no reactivity. 2. The method for producing a polyester 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 for producing a polyester according to claim 1, wherein the liquid is water.