JPH05163337A - Production of polyester - Google Patents

Abstract

PURPOSE:To produce a polyester which can give a molding of excellent transparency by bringing a polycondensate, obtained by using crystalline GeO2 in a state of aqueous colloid as a catalyst, into contact with saturated steam. CONSTITUTION:A process for producing a polyester comprising an acid component based on an aromatic dicarboxylic acid and a glycol component based on ethylene glycol, wherein polycondensation is effected by using a catalyst comprising crystalline GeO2 in a state of aqueous colloid and the obtained polycondensate is brought into contact with saturated steam (desirably at 130 deg.C or above for 2 hr or shorter). The resulting copolyester has low internal haze, is reduced in the deposition of oligomers on a drum or a mold even when melt- molded for a long time, and can give a highly transparent molding because of low diffused reflection on its surface.

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 transparency.

[0002]

2. Description of the Related Art Polyester is widely used in fibers, films, bottles, industrial resins and the like because of its excellent mechanical, physical and chemical properties.

In the application of flat or three-dimensional molded products such as films and bottles, many products require transparency depending on the field of use.

Regarding the transparency, in addition to the internal structure of the material such that the material itself has good light transmittance, a material (molded article) in which the surface of the molded article does not have irregularities and diffuse reflection of light does not occur on the surface There are two factors that relate to the surface properties of.

Regarding the former, it goes without saying that foreign matter is not mixed in during the production of polyester, but it is necessary that the catalyst to be used does not exist as particles, or if it does exist, its particle size is extremely small. For this reason, even in the prior art, the type of catalyst used for the polycondensation reaction and the like is carefully selected according to the purpose and application.

For example, antimony compounds, which are the catalysts most widely used at present in polyethylene terephthalate type polyesters, are satisfactory in terms of reaction activity, but have low solubility in polyesters and are present as particles in the polymer. At the time of melt molding, there is a drawback that antimony is reduced depending on the material of the molding apparatus and deposited as a metal on the surface of the molded product.

On the other hand, the catalytic titanium compound has a higher reaction activity, a small amount of it used as a catalyst is sufficient, and it has a high solubility in a polymer, so that particles are hardly formed in the polymer. Gives a molded article with excellent transparency. However, the reaction activity may accelerate the decomposition reaction of the polymer at the time of melt molding, and the molded product may be colored.

By the way, a germanium compound has a solubility lower than that of a titanium compound in polyester, but it has a better solubility than an antimony compound, and therefore has been widely used in a field requiring transparency. However, due to the recent sophistication of the required quality, the transparency of this catalyst is becoming insufficient, and as a result, improvement is required.

On the other hand, regarding the surface property of the molded product which controls the second factor of transparency, a molded product having a fairly clean surface can be obtained depending on the finishing degree of the surface of the cooling drum during film formation and the surface of the mold during molding. ing. However, if the molding is continued for a long time continuously, the oligomers precipitated from the polymer will adhere to the cooling drum and the mold, and this will transfer to the film or molded product to form irregularities on the molded product surface. ,
The same unfavorable result occurs when light is diffusely reflected and transparency is reduced. As a method for preventing this, for example, Japanese Patent Laid-Open No. 3-
As disclosed in Japanese Patent No. 47830, there has been proposed a method of suppressing regeneration of an oligomer during melt molding by partial hydrolysis of a polymer or deactivation of a catalyst by water treatment.

[0010]

However, the recent demand for high transparency has not reached the level that can be sufficiently met by the conventional techniques.

Therefore, as a result of earnest studies, the inventors of the present invention can achieve this object for the first time by using a catalyst which has been subjected to a specific treatment, and treating the polymer under special conditions at the polymerization stage. They have found the present invention and reached the present invention.

[0012]

[Means for Solving the Problems] That is, in the present invention, when a polyester having an aromatic dicarboxylic acid as a main acid component and ethylene glycol as a main glycol component is produced, crystalline germanium dioxide treated with a hydrocolloid is used as a catalyst. After the condensation reaction, the obtained polymer is brought into contact with saturated steam, which is a method for producing a polyester.

In the present invention, the "polyester" means a polyester having an aromatic dicarboxylic acid as a main acid component and ethylene glycol as a main glycol component. As used herein, "mainly" means that ethylene aromatic dicarboxylate units account for 85 mol% or more.
The 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. The "glycol" constituting the polyester is an alkylene glycol,
Especially ethylene glycol.

The third component which can be copolymerized is an aromatic dicarboxylic acid which constitutes the polyester, a dicarboxylic acid other than ethylene 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. Acid, tetralindicarboxylic acid, hexahydroterephthalic acid and the like; aliphatic dicarboxylic acids such as malonic acid, succinic acid, adipic acid, sebacic acid and the like. 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 cyclohexane diol, etc .; aliphatic oxycarboxylic acids such as glycolic acid,
Hydroacrylic acid, 3-oxypropionic acid, etc .; Alicyclic oxycarboxylic acids, such as asiatic acid, quinobaic acid, etc .; Aromatic oxycarboxylic acids, such as salicylic acid, m-
Examples thereof include oxybenzoic acid, p-oxybenzoic acid, mandelic acid and atrolactic acid.

Further, within the range where 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, tricarballylic acid, gallic acid and the like may be copolymerized, and if necessary, monofunctional compounds such as o-benzoylbenzoic acid and naphthoic acid. May be added.

The germanium catalyst used in the present invention is hydrocolloid-treated crystalline germanium dioxide. The transparency of the polymer is poor when used as a mere crystalline germanium dioxide powder or in a slurry state of ethylene glycol or the like.

Examples of the water colloid treatment method include the following methods. Crystalline germanium dioxide is dispersed in a large amount of ion-exchanged water so as to have a concentration of about 0.1 to 1 wt%, and is near the boiling point of water, for example, 80 to 100.
Heat treatment is performed at a temperature of several degrees Celsius for several hours, for example, 3 to 10 hours. It is also possible to distill water during the heat treatment to adjust the concentration.

The hydrocolloidal germanium dioxide treated by the method of the present invention has an infrared absorption spectrum of 515,55.
There is absorption at 1,587,872,955 cm ^-1 , and the hexagonal crystalline state before treatment is maintained, and the hydrate (500,
It is not in the state of 780 cm ^-1 ). Then, it exhibits the Tyndall phenomenon, which is a characteristic of hydrocolloid solutions.

The polyester obtained in the present invention can be produced by these known means under the same conditions as those generally known except that hydrocolloid-treated germanium dioxide is used as a polymerization catalyst.

For example, a method in which an acid and a glycol are directly esterified and then melt polycondensed in the presence of a suitable catalyst, or a lower alkyl ester of an acid and a glycol are subjected to transesterification reaction 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 cooling medium such as water, cutting into a suitable size, and chipping. The chips may have a rectangular parallelepiped shape, a cylindrical shape, or a dice shape.

The polyester of the present invention may be subjected to solid phase polymerization at a temperature below the melting point depending on the purpose to reduce the amount of oligomers in the polymer. Moreover, the effect of the method of the present invention is more remarkable when the polymer has a lower oligomer content.

The solid phase polymerization may be carried out under an inert gas flow or under vacuum (under reduced pressure), and may be applied in a continuous system or a batch system. Further, it may be a packed tower type, a horizontal clinker type, or a tumbler type.

In the present invention, it is necessary to bring the polymer into contact with saturated steam after the polycondensation reaction. With superheated steam, the effect of suppressing oligomer regeneration during melt molding is small. The minimum contact time varies depending on the particle size and crystal state of the polymer, but may be any time sufficient for water vapor to penetrate into the polymer particles. For example, in the case of saturated steam at 130 ° C., 40 minutes or more is sufficient, and in the case of 160 ° C. or more, 20 minutes or more is usually sufficient. On the other hand, if the contact time is too long, the hydrolysis of the polymer proceeds too much, which may affect the physical properties of the molded product in some cases.

Generally, it is 2 hours or less at 130 ° C., 1
It is preferably 1 hour or less at 60 ° C. At other temperatures, thermodynamically, the time for water vapor to diffuse inside the polymer will be selected accordingly.

[0026]

EFFECT OF THE INVENTION The polyester produced by the method of the present invention has a low internal haze of the polymer, little oligomer adhesion to the drum or mold even after long-term melt molding, and little irregular reflection of light on the surface of the molded article. High transparency is obtained as.

[0027]

EXAMPLES The present invention will be supplemented by the following examples. In addition, "part" in an Example means a weight part. Moreover, the measuring method of the characteristic used in the Example is shown below.

1) Intrinsic viscosity: [η] phenol / tetrachloroethane (weight ratio 60/40)
It was calculated from the solution viscosity measured at 35 ° C. using the mixed solvent of.

2) Transparency of molded product: The polymer was dried at 160 ° C. for 5 hours, and then injection molding machine Dynamelter M-1000M manufactured by Meiki Seisakusho was used.
A preform weighing 50 g is formed at a cylinder temperature of 295 ° C., and this is blow-drawn to obtain a bottle having an internal volume of 1.5 liters and a body wall thickness of 0.3 mm. Cut off this straight body part,
The haze of the bottle body was measured with a haze meter to determine the transparency of the molded product.

3) Oligomer (abbreviated as Cy-3) A polymer or a preform of a molded bottle was sampled, dissolved in a fluoroisopropanol / chloroform (50/50) mixed solvent, further diluted with chloroform, and a Millipore filter was used. The content of the cyclic trimer in the filtered filtrate is quantified using ALC / GPX744 manufactured by Waters.

The haze resulting from the unevenness of the bottle surface caused by the transfer of the die deposit to the bottle cannot be evaluated unless it is continuously molded for a long period of time. Therefore, the amount of oligomer before and after molding was used as a substitute.

[0032]

Reference Example 1 Crystalline germanium dioxide powder was directly dispersed in ethylene glycol so as to be 20% by weight and subjected to a sand grinder to obtain a germanium dioxide ethylene glycol slurry. Typical particle size is 4-6
μm (hereinafter referred to as “slurry Ge”).

[0033]

[Reference Example 2] (Water colloid treatment) Crystalline germanium dioxide powder was blended in pure water so as to be 0.6% by weight, and 100% of this was added.
After stirring at ℃ for 6 hours and boiling under circulation, a part of water was distilled off to finally obtain a 0.76 wt% liquid.

The infrared absorption spectrum of this product is 515,
It has absorptions at 551,587,872,955 cm ^-1, and exhibits a typical hexagonal crystalline germanium dioxide pattern. However, although the appearance of the liquid was transparent and no particles were observed, the liquid was extremely pale milky white and exhibited the Tyndall phenomenon, so it was found that the crystals were micronized to a colloidal state. (This is hereinafter referred to as "water colloid Ge").
The crystalline germanium dioxide as it is is hereinafter referred to as “powder Ge”.

[0035]

Examples 1 to 4 and Comparative Examples 1 to 5 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 part of trimethyl phosphate was added, and further various catalysts shown in Table 1 were added in predetermined amounts, and polycondensation reaction was carried out at 270 ° C.
A polymer having an intrinsic viscosity of 0.51 was obtained.

This was pelletized and solid phase polymerization was carried out at 215 ° C. until the intrinsic viscosity became 0.76 (Cy-3 amount, 0.2
6 wt%), and steam treatment was performed under the conditions shown in Table 1. Various properties of molded products obtained by melt-molding this polymer are shown in the same table.

Even if the same germanium dioxide is used, the slurry Ge and the powder Ge have an oligomer regeneration suppressing effect, but the internal haze is 1% or more, and the total transparency is inferior to that of the water colloid Ge.

Titanium acetate has a good haze, but has almost no effect of suppressing oligomers. It can be pointed out that antimony trioxide has an extremely bad haze.

[0039]

[Table 1]

[0040]

Example 5 In Example 1, 216 parts of naphthalene-2,6-dicarboxylic acid was used instead of 166 parts of terephthalic acid,
When the same procedure as in Example 1 was carried out except that the melt polymerization temperature was 290 ° C., the haze of the molded product was 0.8%, and Cy−
The amount of 3 regenerations was 0.01 wt%.

Claims (3)

[Claims] 1. A method for producing a polyester comprising an aromatic dicarboxylic acid as a main acid component and ethylene glycol as a main glycol component, which is obtained by carrying out a polycondensation reaction using a hydrocolloid-treated crystalline germanium dioxide as a catalyst. A method for producing a polyester, which comprises contacting the polycondensate with saturated steam. 2. The method for producing a polyester according to claim 1, wherein terephthalic acid is used as the aromatic dicarboxylic acid. 3. The method for producing a polyester according to claim 1, wherein the condition for contacting with saturated steam is 130 ° C. or higher and 2 hours or shorter.