JPH07242419A - Satisfactorily soluble germanium oxide powder - Google Patents

Abstract

PURPOSE:To improve the solubility of water-soluble hexagonal GeO2 powder to ethylene glycol. CONSTITUTION:This GeO2 powder has >=5,000ppm surface OH groups measured by the Karl Fischer method and >=5X10<15>groups/cm<2> density of the surface OH groups to the specific surface area measured by the BET method. This GeO2 powder is obtd. by hydrolyzing GeCl4 kept at a low temp. of <0 deg.C. When this GeO2 powder is dissolved as a polyethylene terephthalate polymn. catalyst in ethylene glycol, dissolution is finished in a time corresponding to half or less of the time required to dissolve the conventional product.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a water-soluble germanium oxide (GeO ₂ ) powder used as a polymerization catalyst in the production of polyethylene terephthalate, and more particularly to a GeO ₂ powder having an improved dissolution rate in ethylene glycol.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
Is widely used as synthetic fiber, film, container material, etc. Industrial production methods of polyethylene terephthalate include a transesterification method using dimethyl terephthalate as a raw material and a direct esterification method using terephthalic acid as a raw material. In any case, first, 2 mol of ethylene glycol is allowed to act on 1 mol of this raw material, and bis (β-hydroxyethyl) terephthalate (that is, bisethylene glycol of terephthalic acid) is subjected to a transesterification reaction or a direct esterification reaction. Monoester) monomer is produced and this monomer is melt-polycondensed under reduced pressure in a two-step reaction process. All of these reactions are usually performed without the use of a solvent.

Of these, the esterification reaction between terephthalic acid and ethylene glycol proceeds without the use of a catalyst due to the autocatalytic action of terephthalic acid, but the transesterification reaction between dimethyl terephthalate and ethylene glycol and bis ( The melt polycondensation reaction of β-hydroxyethyl) terephthalate monomer requires the addition of a catalyst. P
The GeO ₂ powder used as a polymerization catalyst for ET exhibits a catalytic action for both the transesterification reaction and the melt polycondensation reaction.

When GeO ₂ powder is used as a PET polymerization catalyst, the powder is dissolved in ethylene glycol which is a liquid reaction component in advance and used for the reaction. Therefore, in order to dissolve the catalyst in ethylene glycol in a short time, fine GeO ₂ particles having an average primary particle size of about 1 μm or less.
The powder is used as a catalyst.

GeO ₂ includes water-soluble crystals having a hexagonal α-quartz type structure and insoluble crystals having a tetragonal rutile type structure. The water-soluble crystals dissolve 0.453 g in 100 g of water at 25 ° C, whereas the water solubility of the insoluble crystals under the same conditions is 0.23 mg, which is 1/1000 or less. P
What is used as a polymerization catalyst for ET is a powder of water-soluble crystals of GeO ₂ . In the following, this water-soluble crystal powder is simply referred to as GeO ₂ powder.

Fine GeO used as a PET polymerization catalyst
_Two powders (that is, water-soluble GeO ₂ powders) are produced by reacting GeCl ₄ (germanium tetrachloride) with water to hydrolyze it. Since this hydrolysis reaction is an exothermic reaction, it is usual to carry out the reaction at a temperature of about 0 to 10 ° C. while cooling with ice. Specifically, liquid GeCl ₄ is added dropwise to the ice water over several minutes while stirring. The temperature at the start of dropping is 0 ° C., and the amount of ice is set so as not to exceed 10 ° C. at the end. After completion of the dropping, stirring is continued for about 30 to 60 minutes to ripen the crystals. As a result, the hydrolysis is completed, and the grain size of the precipitated GeO ₂ crystal becomes more uniform. Then, the precipitate is thoroughly washed, filtered, and dried under reduced pressure to obtain a GeO ₂ powder product.

[0007]

However, the conventional GeO ₂ powder thus produced does not have sufficient solubility (dissolution rate) in ethylene glycol, and the amount of GeO ₂ powder (eg ethylene Dissolution of GeO ₂ powder 0.1 g) in 50 mL of glycol usually required a dissolution time of 1 hour or more. Since it takes a long time to dissolve the catalyst significantly impairs the productivity of PET production, a GeO ₂ powder having excellent solubility that can be dissolved in ethylene glycol in a short time has been desired.

Therefore, an object of the present invention is to provide a highly soluble GeO ₂ powder which has a high dissolution rate in ethylene glycol and which is optimal as a PET polymerization catalyst.

[0009]

[Means for Solving the Problems] The inventors of the present invention have conducted repeated studies on the relationship between the surface characteristics of GeO ₂ powder and the solubility in ethylene glycol in order to achieve the above object. As a result, the hydroxyl groups (OH) existing on the surface of the GeO ₂ powder are
It was found that the group) contributes to the dissolution in ethylene glycol, and the dissolution rate is remarkably increased when the amount of the surface OH groups and the density thereof per unit surface area are above a certain value. Such high G and high density of OH groups
It was also found that the eO ₂ powder can be obtained by hydrolyzing GeCl _{4 at} a temperature lower than 0 ° C.

According to the present invention, the surface OH group amount measured by the Karl Fischer method is 5000 ppm or more, and the surface OH group density relative to the specific surface area measured by the BET method is 5 × 10 ^15.
The gist is a water-soluble GeO ₂ powder excellent in solubility in ethylene glycol, characterized in that the number of particles / cm ² or more.

The Karl Fischer method is generally known as a method for quantifying water, but when it is applied to an anhydrous oxide such as the GeO ₂ powder of the present invention, the amount of surface OH groups is measured. Therefore, in the present invention, the amount of OH groups obtained from the measurement value obtained by titrating a sample of GeO ₂ powder by the Karl Fischer method is used as the amount of surface OH groups. This measurement can be carried out by titration using a commercially available Karl Fischer reagent, and GeO
_{Since the two} powders are colorless, the end point can be determined by either the visual method (change to reddish brown) or the electric current method. Since the Karl Fischer method automatic titrator utilizing the electric current method is commercially available, it is possible to easily perform the measurement using this apparatus.

The GeO ₂ powder of the present invention has a surface OH group content thus determined of not less than 5000 ppm (= 0.5% by weight). Furthermore, the specific surface area (cm ² / g) of the GeO ₂ powder was calculated by the BET method,
When the surface OH group density per unit surface area is calculated, the surface OH group density is 5 × 10 ¹⁵ / cm ² or more. Therefore, compared to conventional GeO ₂ powder,
It shows excellent solubility in ethylene glycol, which means that the dissolution rate in ethylene glycol is more than doubled (dissolution time is less than half). This improvement in solubility in ethylene glycol cannot be obtained unless both the total amount of surface OH groups and the density thereof are high as described above, and only one of the amount and density of surface OH groups satisfies the above condition. In some cases, the solubility in ethylene glycol is not improved.

Since the rate of dissolution in ethylene glycol tends to increase as the amount of surface OH groups and the density thereof increase, the GeO ₂ powder of the present invention preferably has a surface OH group content.
8,000 ppm or more, particularly 10,000 ppm or more, and the surface OH group density is preferably 8 × 10 ¹⁵ pieces / cm ² or more. The specific surface area is measured by the BET method using commercially available BE using N ₂ gas or the like.
It can be carried out using a T method measuring device.

Generally, the finer the powder, the larger the specific surface area, and therefore the amount of OH groups on the surface tends to increase. Therefore, even with the conventional GeO ₂ powder, for example, the average primary particle size is 0.3
With very fine powder of less than μm, the surface OH group content is 5000
Sometimes exceeded ppm. However, with such a fine powder having a large specific surface area, on the contrary, the surface OH group density per unit surface area was low and did not reach 5 × 10 ¹⁵ / cm ² . On the other hand, in the conventional relatively coarse GeO ₂ powder having an average primary particle size of more than 1 μm, the surface OH group density may exceed 5 × 10 ¹⁵ particles / cm ² because the specific surface area is relatively small. However, the amount of surface OH groups never reached 5000 ppm. Therefore, with the conventional GeO ₂ powder, it took time to dissolve ethylene glycol regardless of the particle size.

According to the present invention, as described later, by hydrolyzing GeCl _{4 at} a lower temperature than before, the surface OH group amount is 5000 ppm or more and the surface OH group density per unit surface area is 5 × 10 5. GeO ₂ powder having a large amount and high density of surface OH groups of ¹⁵ / cm ² or more is obtained, and the solubility in ethylene glycol is improved. The reason why the amount and density of the surface OH groups are both increased by carrying out hydrolysis at a low temperature in this way has not been fully clarified, but the lower the reaction temperature, the more the dehydration due to heat after hydrolysis is suppressed, structure water or Ge (O to GeO ₂ in the crystal
It is speculated that this is because a large amount of OH groups remain as the H) ₄ phase. Further, when the amount and density of surface OH groups are high, the solubility in ethylene glycol is good because water-soluble GeO ₂
Dissolution of crystals occurs through the solvation of ethylene glycol to the surface OH groups, and if the surface OH groups are present in a large amount and at a high density, a larger amount of ethylene glycol will be solvated and the dissolution rate will be faster. Conceivable.

The average primary particle size of the GeO ₂ powder of the present invention is
It is not particularly limited as long as the above-mentioned amount and density of surface OH groups are satisfied, but it is usually within the range of 0.1 to 5.0 μm in average primary particle diameter calculated from the specific surface area obtained by the BET method, preferably 0.5 to 2.0. It is in the range of μm.

The GeO ₂ powder of the present invention is produced by hydrolyzing GeCl ₄ in the same manner as the conventional method for producing GeO ₂ powder described above except that the hydrolysis of GeCl ₄ is performed at a temperature lower than 0 ° C. can do.

Since the hydrolysis reaction is carried out at a temperature lower than 0 ° C.,
GeCl ₄ (liquid with a melting point of -51.8 ° C) used is a refrigerant
(E.g. alcohol, freon, methyl chloride, ammonia,
Cool to below 0 ° C by indirect cooling with liquid nitrogen, etc. or direct cooling with dry ice.
The cooling temperature of GeCl ₄ is preferably as low as possible unless the reaction mixture is solidified by dropping, and is preferably -10 ° C or lower, more preferably -20 ° C or lower.

On the other hand, the water to which GeCl ₄ is dripped is also added with an appropriate freezing point depressant (eg alcohol such as ethanol, sodium chloride) so that it does not solidify even at a temperature lower than 0 ° C. Cool to a temperature of 0 ° C. or lower by adding ice or external cooling with a refrigerant. The cooled GeCl ₄ is added dropwise to the cooled water with stirring. During the dropping and during the subsequent aging, the temperature of the reaction mixture was kept at 0 ° C. by external cooling or ice.
Keep it cooler. The dropping rate of GeCl ₄ is set so that the temperature of the reaction mixture does not rise above 0 ° C.
The lower the reaction temperature at this time, the larger the amount of surface OH groups in the generated GeO ₂ powder tends to be.

Except for this reaction temperature, other reaction conditions may be the same as conventional ones. For example, the weight ratio of water / GeCl ₄ is usually in the range of 1 to 10 and the dropping time is not limited, but considering the reaction efficiency, it is about 1 to 30 minutes and the stirring speed is 100 to 1000 rpm. The aging time after the reaction is up to about 2 hours.

[0021] Thereafter, precipitate was washed thoroughly, after filtration, when completely dehydrated and dried by heating, GeO ₂ of the present invention
A powder is obtained. In order to prevent loss due to melting,
It is also preferable to perform washing at the lowest possible temperature (eg, 5 ° C or lower). Drying conditions are, for example, 80 mmHg, 11
It is carried out by vacuum drying at 0 ° C.

[0022]

EXAMPLES Examples will be shown below, but these do not limit the present invention.

Example 1 While stirring 1 L of water at 0 ° C. at 300 rpm, 300 g of GeCl ₄ cooled to about −40 ° C. by cooling with dry ice was dropped into this water over 5 minutes, and GeCl _{4 was} added. Was hydrolyzed. At the end of this addition, the temperature of the reaction mixture was -15 ° C. Then, stirring was continued for 30 minutes while maintaining the reaction mixture at −10 ° C. or lower by cooling with dry ice to ripen the precipitated GeO ₂ powder to obtain a GeO ₂ suspension. Then, GeO ₂ was filtered through a Buchner funnel, and the conductivity of the filtrate was 1000 Ω · cm, p
The product was recovered by washing with water at 5 ° C or lower until H became 4, and then filtering again. Then 10 mm at 80 mm Hg and 110 ° C.
After drying under reduced pressure for an hour, dried GeO ₂ powder was obtained.

The obtained GeO ₂ powder had a hexagonal α-quartz type crystal structure as a result of examination by X-ray diffractometry.
Specific surface area of 3.0 m ² / g, average primary particle size of 0.5
The surface OH group content measured by Karl Fischer automatic titrator is 11,000 ppm, and therefore the surface OH group density is
It was 13 × 10 ¹⁵ pieces / cm ² . 1 g of this GeO ₂ powder was added to 200 mL of ethylene glycol, the liquid was heated and boiled without stirring, and the time from the start of boiling until the dissolution of the GeO ₂ powder was required (hereinafter referred to as the ethylene glycol dissolution time).
The total amount was dissolved in 16 minutes (total amount dissolution was visually determined).

(Example 2) The cooling temperature of GeCl ₄ was -20 ° C.
GeO ₂ was prepared in the same manner as in Example 1 except that
Got the powder. The temperature of the reaction mixture is -10 ° C at the end of dropping,
During aging, the temperature was -5 ° C. The obtained GeO ₂ powder has a specific surface area of 3.5 m ² / g, an average primary particle size of 0.4 μm and a surface OH.
Base amount is 9,000 ppm, surface OH group density is 9.1 × 10 ¹⁵ units / cm ²
And the ethylene glycol dissolution time was 28 minutes.

(Example 3) The cooling temperature of GeCl ₄ was -10 ° C.
GeO ₂ was prepared in the same manner as in Example 1 except that
Got the powder. The temperature of the reaction mixture is -8 ° C at the end of dropping,
During aging, the temperature was -5 ° C. The obtained GeO ₂ powder has a specific surface area of 3.1 m ² / g, an average primary particle size of 0.46 μm and a surface OH.
Base amount is 7,000 ppm, surface OH group density is 8.0 × 10 ¹⁵ units / cm ²
And the ethylene glycol dissolution time was 34 minutes.

(Example 4) The cooling temperature of GeCl ₄ was -4 ° C.
GeO ₂ was prepared in the same manner as in Example 1 except that
Got the powder. The temperature of the reaction mixture is -4 ° C at the end of the dropping,
During aging, the temperature was -5 ° C. The obtained GeO ₂ powder has a specific surface area of 3.1 m ² / g, an average primary particle size of 0.56 μm and a surface OH.
Base amount is 5,400 ppm, surface OH group density is 6.1 × 10 ¹⁵ units / cm ²
And the ethylene glycol dissolution time was 41 minutes.

(Comparative Example 1) A GeO ₂ powder was obtained in the same manner as in Example 1 except that the cooling temperature of GeCl ₄ was changed to 0 ° C. The temperature of the reaction mixture was 5 ° C. at the end of dropping and 9 ° C. during aging. The obtained GeO ₂ powder has a specific surface area of 3.7.
m ² / g, average primary particle size 0.38 μm, surface OH group content 3,80
The surface OH group density was 0 ppm, the concentration was 3.6 × 10 ¹⁵ groups / cm ² , and the ethylene glycol dissolution time was 71 minutes.

Reference Example 1 Two commercially available water-soluble GeO ₂
With respect to the powders A and B, various measurements were performed in the same manner as in Example 1. As a result, GeO ₂ powder A has a specific surface area of 7.79.
m ² / g, average primary particle size 0.182 μm, surface OH group content
The surface OH group density was 5,400 ppm, 2.45 × 10 ¹⁵ groups / cm ² , and the ethylene glycol dissolution time was 93 minutes. On the other hand, GeO ₂ powder B has a specific surface area of 1.36 m ² / g, an average primary particle diameter of 1.043 μm, a surface OH group amount of 3,200 ppm, a surface OH group density of 8.28 × 10 ¹⁵ particles / cm ² , The glycol dissolution time was 110 minutes. That is, these commercially available powders satisfied only one condition of the amount of surface OH groups and the density thereof specified in the present invention, but it took a very long time to dissolve in ethylene glycol. Therefore, in order to improve the solubility in ethylene glycol, it is understood that both the amount of surface OH groups and the density thereof must satisfy the conditions defined in the present invention.

[0030]

EFFECT OF THE INVENTION Surface OH group content is 5000 ppm or more, surface OH
The GeO ₂ powder of the present invention having a group density of 5 × 10 ¹⁵ units / cm ² or more exhibits excellent solubility in ethylene glycol, which is less than half the dissolution time in ethylene glycol compared to the conventional product. As a result, when GeO ₂ powder is used as a PET polymerization catalyst, the dissolution time of the catalyst in ethylene glycol is reduced to half or less, and PET productivity is improved. In addition to the ethylene glycol, the GeO ₂ powder of the present invention exhibits a higher solubility in water and various alcohol solvents than conventional products. Therefore, the GeO ₂ powder of the present invention is useful not only as a PET polymerization catalyst but also for other uses in which it is dissolved in water or an alcohol solvent.

Claims (1)

[Claims] 1. Surface O measured by the Karl Fischer method
Water solubility with excellent solubility in ethylene glycol, characterized by an H group content of 5000 ppm or more and a surface OH group density of 5 × 10 ¹⁵ / cm ² or more relative to the specific surface area measured by the BET method. Germanium oxide powder.