JP3071540B2 - 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 technique for producing a polyester having excellent molded article transparency and high molding performance.

[0002]

2. Description of the Related Art Polyesters are widely used in packaging materials such as fibers, films, bottles, etc., industrial resins and the like because of their excellent mechanical, physical and chemical properties.

[0003] Above all, in recent years, packaging materials, mainly bottles, have grown remarkably, and their required characteristics have become even more severe. In particular, recently, from the viewpoint of improving the appearance of molded articles, polyesters having higher transparency and higher productivity, that is, polyesters excellent in moldability performance, have been strongly demanded. There are two main factors affecting the transparency. The first is a problem of haze inside the molded article, and the second is an optical problem associated with irregular reflection of light due to the adhesion of irregularities or white powder on the surface of the molded article. Regarding the former, the polymerization catalyst mainly used for polyester has a great influence. Commonly used antimony compound catalysts have low solubility in polymers and have high internal haze (poor transparency) because they exist as particles in the polymer. On the other hand, a titanium catalyst has high solubility in a polymer and is excellent in transparency, but has a high activity, a decomposition reaction is easily promoted, and there is a problem of a decrease in the degree of polymerization and a problem of coloring. On the other hand, the germanium catalyst does not have such a high activity and must be used in a large amount. However, the solubility in the polymer is relatively good, and it is possible to obtain a polymer having considerably high transparency. However, the transparency is inferior to that of titanium catalysts, and it has not yet reached the current strict required characteristics. On the other hand, the latter is mainly caused by the oligomer contained in the polyester, and this oligomer bleeds out to the surface during the stretching and heat setting steps during molding, and adheres and accumulates on the mold by long-term continuous molding. By doing so, irregularities occur on the surface of the molded article. Therefore, as a countermeasure, a method such as solid-phase polymerization has conventionally been employed for the purpose of reducing the oligomer content in the polyester, and some effects have actually been obtained. However, even if the absolute value of the oligomer is reduced as described above, the effect is reduced by half because the oligomer is regenerated in the melting at the time of molding, and the effect has not been actually reduced to a satisfactory level. However, recently, a proposal has been made to treat chips once with water as a method of suppressing the regenerated oligomer at the time of melting. [Japanese Unexamined Patent Publication No. 3-47830,
No. 174441). This is because the polymerization catalyst contained in the polyester is deactivated by water treatment, and the effect of this is to suppress the regeneration of the oligomer at the time of melting. There is no known difference.

The inventors of the present invention have studied in detail that, in practice, the generally used antimony catalyst and titanium catalyst have hardly exhibited the effect of suppressing the regeneration of oligomers.
It was found that the effect was exhibited only when certain conditions were satisfied.

[0005]

As a result of intensive studies, the present inventor has found that in the polymerization of polyester, a specific pre-treated germanium catalyst is used, and the obtained polymer is conditioned to obtain a specific polymer. By making the moisture percentage,
The inventors have found that the problems of the internal haze, the surface smoothness, and the adhesion of white powder as described above can be simultaneously solved, a molded article having extremely high transparency can be obtained, and the molding performance can be improved.

[0006]

The present invention relates to a method for producing a polyester whose main repeating unit is ethylene aromatic dicarboxylate as one of polycondensation catalysts.
A polycondensation reaction is performed using at least a germanium compound that has been treated with a water colloid, and contains oligomers (cyclic trimers)
Is obtained by adjusting the moisture content of the polyester to 0.4 to 0.8% by weight.

The present invention will be described.

[0008] In the present invention, the "polyester" refers to a polyester containing an aromatic dicarboxylic acid as a main acid component and ethylene glycol as a main glycol component. Here, "main" means that the ethylene 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.

The “aliphatic glycol” constituting the polyester is specified as ethylene glycol. The effects of the present invention do not appear with tetramethylene glycol or other substances.

As the third component capable of being copolymerized, there are aromatic dicarboxylic acids and dicarboxylic acids other than ethylene 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; aliphatic dicarboxylic acids such as malonic acid, succinic acid, adipic acid and sebacic acid. Further, as the glycol component, aliphatic diols such as trimethylene glycol, tetramethylene glycol,
Pentamethylene glycol, hexamethylene glycol, diethylene glycol, triethylene glycol, etc .; aromatic diols such as catechol, naphthalene diol, resorcin, 4,4'-dihydroxy-diphenyl-sulfone, bisphenol A ([2,2'-bis ( 4-hydroxyphenyl) propane]), tetrabromobisphenol A, bishydroxyethoxybisphenol A, etc .; alicyclic diols, eg, cyclohexanediol; aliphatic oxycarboxylic acids, eg, glycolic acid, hydroacrylic acid, 3-oxypropionic acid Alicyclic oxycarboxylic acids such as asiatic acid, quinovanic acid and the like; aromatic oxycarboxylic acids such as salicylic acid, m-oxybenzoic acid, p-oxybenzoic acid, mandelic acid, and Or the like can be mentioned Rakuchin acid.

Further, a trifunctional or higher polyfunctional compound such as glycerin, trimethylolpropane, pentaerythritol, or the like, as long as the polyester is substantially linear.
Trimellitic acid, trimesic acid, pyromellitic acid, tricarballylic acid, gallic acid and the like may be copolymerized, and if necessary, a monofunctional compound such as o-benzoylbenzoic acid,
Naphthoic acid or the like may be added.

The germanium catalyst used in the present invention is intended for crystalline germanium dioxide which has been treated with a water colloid. In the case of using pure crystalline germanium dioxide powder or a slurry state of ethylene glycol or the like, or using a hydrate of germanium dioxide (or germanium hydroxide), the solubility in the polymer was not sufficiently satisfied, and was obtained. Poor polymer transparency.

The following method is exemplified as a water colloid treatment method. Crystalline germanium dioxide is dispersed in a large amount of ion-exchanged water so as to have a concentration of about 0.1 to 2% by weight, and heat-treated at a boiling point of water, for example, 80 to 100 ° C. for several hours, for example, 3 to 10 hours. During the heat treatment, water can be distilled off to adjust the concentration.

The water-colloidized germanium dioxide treated by the present method has an infrared absorption spectrum of 515, 551, 87.
It has absorptions of 2 and 955 cm ^-1 , maintains a hexagonal crystal state, and is not a hydrate (500, 780 cm ^-1 ). Then, it exhibits the Tyndall phenomenon which is a characteristic of the aqueous colloid liquid.

The polyester can be produced by a generally known method except that water-colloid-treated germanium dioxide is used as a polymerization catalyst.

For example, a method of directly esterifying an acid and a glycol followed by melt polycondensation in the presence of a suitable catalyst, a method of subjecting a lower alkyl ester of an acid to a glycol to a transesterification reaction 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 a rectangular parallelepiped, a cylinder, a die, or a sphere.

In the polyester of the present invention, the oligomer content must be 0.4% by weight or less. This is because, as described above, the oligomer mainly causes a reduction in the smoothness of the molding surface and a white powder, and deteriorates the transparency. The means for reducing the oligomer content is not particularly limited, and may be, for example, a solid phase polymerization method, an extraction method,
Although a hydrolysis method [JP-A-56-118420] and the like can be mentioned, it is generally preferable to use solid-state polymerization from the viewpoint of industrial efficiency, cost efficiency and quality control.

Next, the thus obtained polyester chips having an oligomer content of 0.4% by weight or less are conditioned. As a means for humidity control, it is desirable to use a high-temperature and high-humidity atmosphere from the viewpoint of chip handling and hydrolyzability after treatment. The humidity control condition in this case is preferably carried out at a relative humidity of 80 to 100% from the viewpoint of achieving the target water absorption and the production efficiency. Further, in order to obtain a sufficient oligomer regeneration inhibitory effect, the moisture content in the chip after moisture conditioning should be 0.4%.
It has to be set to 0.8 wt%. If the water content is less than 0.4% by weight, the effect cannot be sufficiently obtained and the transparency is poor. Even if the water content exceeds 0.8 wt%, no further improvement in transparency can be expected, and on the contrary, the loss of processing time only leads to a decrease in production efficiency and in the case of high-temperature processing. Promotes hydrolysis and leads to deterioration of quality.

[0020]

The present invention will be described in more detail with reference to the following examples. In the examples, "parts" indicates parts by weight, and characteristic values were measured by the following methods.

1) Intrinsic viscosity: [η] It was calculated from the solution viscosity measured at 35 ° C. using an orthochlorophenol solvent.

2) Moisture content Immediately after the humidity control, the water adhering to the surface of the obtained polymer chip was quickly and completely removed by air pressure, and 50 g of the chip was dried in a dryer at 160 ° × 16 h. Calculated.

3) Transparency of molded product After drying the polymer at 160 ° C. for 5 hours, a preform of 50 g was molded at a cylinder temperature of 295 ° C. using an injection molding machine Dynamelter M-100DM manufactured by Meiki Seisakusho. This is blow-stretched and processed into a bottle having an inner volume of 1.5 liters and a wall thickness of 0.3 mm. The straight body was cut out and the haze of the bottle body was measured with a haze meter to determine the transparency of the molded product.

4) Oligomer (abbreviated as cy-3) Sampling is performed from a polymer or a preform of a molded bottle, which is dissolved in a mixed solvent of fluoroisopropanol / chloroform (50/50), further diluted with chloroform, and filtered with a Millipore filter. The content of the cyclic trimer of the filtered filtrate was quantified by ALC / GPC744 of Waters.

Fogging caused by irregularities on the bottle surface due to the transfer of the deposits on the bottle to the bottle cannot be evaluated unless continuous molding is performed for a long period of time.

[0026]

REFERENCE EXAMPLE 1 Crystalline germanium dioxide powder was directly dispersed in ethylene glycol so as to be 20% by weight.
A sand grinder treatment was performed to obtain a germanium dioxide slurry of ethylene glycol. Typical particle size is 4-6μm
(This is hereinafter referred to as “slurry Ge”).

[0027]

[Reference Example 2] (hydrocolloid treatment) 0.6% by weight of crystalline germanium dioxide powder in pure water
After stirring at 100 ° C. for 6 hours and boiling under circulation, a part of water was distilled off to finally obtain a liquid of 0.76% by weight.

Its infrared absorption spectrum is 515,
It exhibited typical hexagonal crystalline germanium dioxide patterns with absorptions at 551, 587, 872 and 955 cm ^-1 . However, although the appearance of the solution was transparent and no particles were observed, it was found to be extremely pale milky white and exhibit the Tyndall phenomenon, so that the crystals were refined to a colloidal state (hereinafter referred to as "water colloid Ge"). "). still,
The crystalline germanium dioxide as such is hereinafter referred to as “powder Ge”.

[0029]

Example 1 1700 parts of dimethyl terephthalate, 1100 parts of ethylene glycol, 1.3% of titanium acetate in ethylethylene glycol solution (1% as Ti), and 4.9 parts of diethylene glycol were charged into a transesterification reaction tank.
The transesterification reaction was performed at a temperature of from 〜 ° to 235 °. When no distillate was generated, “water colloid Ge” of Reference Example 2 was changed to 42
Parts (concentration 0.76 wt%), a methylamide phosphate in ethylene glycol solution (5.5% as P).
Five parts were added and transferred to the polymerization reaction tank. The mixture was reacted at 260 to 270 ° C. for about 30 minutes under normal pressure, and then reacted at 265 ° C. under high vacuum (high vacuum of several mmHg or more) for about 2 hours. Thereafter, a large amount of running water was drawn out from the polymerization reactor by a conventional method to obtain a strand type chip. [Η] of this chip was 0.53. The chips were pre-dried at 150 to 160 ° C. for about 3 hours, and then dried under a high vacuum of 0.5 mmHg.
Solid-state polymerization was performed at 10 ° C. for 10 hours. The chip [η] after the solid-phase polymerization was 0.77, and the oligomer in the chip was 0.1.
It was 26 wt%.

3 kg of the chip was placed in a thermo-hygrostat controlled at 90 ° C. × 95% RH, and left for 48 hours to adjust the humidity. The chip [η] after the treatment was 0.76, and the amount of the oligomer was 0.26 wt%.

Using this chip, it was melt molded. Table 1 shows the properties of the molded product.

[0032]

Comparative Example 1 The same treatment as in Example 1 was carried out except that 1.6 parts (concentration: 20 wt%) of "Slurry Ge" was used as a polymerization catalyst.

[0033]

Comparative Example 2 The same treatment as in Example 1 was performed except that 0.3 parts of "powder Ge" was used as a polymerization catalyst.

[0034]

Comparative Example 3 The same treatment as in Example 1 was performed, except that 53 parts of a 1.3 wt% Sb ₂ O ₃ ethylene glycol slurry was used instead of the germanium compound as the polymerization catalyst.

[0035]

Comparative Example 4 The same treatment as in Example 1 was performed except that 4.3 parts of an ethylene glycol solution of titanium acetate (1% as Ti) was further added instead of the germanium compound as the polymerization catalyst. Table 1 also shows the moisture content of the chips of Comparative Examples 1 to 4 after humidity control, [η], and various characteristics of the molded product.

[0036]

Examples 2 to 3 and Comparative Examples 5 to 6 The same procedure as in Example 1 was carried out except that the amounts of oligomers in the polymer and the humidity control conditions were as shown in Table 1. It was shown to.

Table 1 summarizes the results of the above measurements and the like.

[0038]

[Table 1]

[0039]

As described above, the polyester according to the present invention has a low internal haze of the polymer, and has a low oligomer adhesion to the drum and the mold even when melt-molded for a long period of time.
Since there is no irregular reflection from the surface of the molded article, a molded article having excellent transparency can be obtained.

Continuation of the front page (56) References JP-A-3-72524 (JP, A) JP-B-46-42492 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 63 / 78-63/91

Claims (2)

(57) [Claims] When producing a polyester in which the main repeating unit is ethylene aromatic dicarboxylate, a polycondensation reaction is carried out using at least a germanium compound treated with a water colloid as one of the polycondensation catalysts.
A method for producing a polyester in which the content of cyclic trimer oligomer is 0.4% by weight or less, and then the polyester is subjected to a humidity control treatment so that the moisture content is 0.4 to 0.8% by weight. 2. The method according to claim 1, wherein the polyester is subjected to a humidity control treatment in an atmosphere having a relative humidity of 80 to 100%.