JP3434983B2 - Purification method of metal alkoxide - 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 purifying a metal alkoxide which efficiently removes chlorine ions contained in a liquid metal alkoxide at room temperature (25 ° C.).

[0002]

2. Description of the Related Art Dielectric thin films made of metal alkoxide are expected to be used in many applications such as non-volatile memory devices, capacitor devices, surface acoustic wave devices and infrared sensor devices. It is increasing as the degree increases.

An application for a dielectric thin film of a metal alkoxide is, for example, Japanese Patent Application Laid-Open No. 8-157215. In the invention of this publication, a composite alkoxide solution is repeatedly applied and dried on a substrate surface to a predetermined thickness. After manufacturing the thin film laminate, the thin film laminate is heat-treated at a predetermined temperature before firing.

By the way, the metal alkoxide used for the production of such a dielectric thin film needs to have a high purity. For example, when it is used for a dielectric thin film for LSI, it dissolves the metal component of the thin film production apparatus, Regarding chlorine ions that may be incorporated into the dielectric, it is required to remove them to near the detection limit, but the amount of commercially available industrial metal alkoxides or newly homemade metal alkoxides is considerable. Since it contains chlorine ions of, it cannot be used for this purpose as it is.

Generally, as a method for purifying a metal alkoxide, a purification method by distillation is adopted.

[0006]

However, depending on the distillation purification method, it is not easy to remove the chlorine ion in the metal alkoxide to the detection limit or lower.

Therefore, the present inventors have examined the removal of chlorine ions in metal alkoxides by an ion exchange method using an ion exchange resin, but a commercially available anion type compound that usually contains a large amount of water is used. If the ion-exchange resin is used as it is, the metal alkoxide is rapidly hydrolyzed to form a metal oxide, and alcohol is by-produced.

Under the above circumstances, the present invention can suppress the hydrolysis of metal alkoxide within an allowable range and can remove chlorine ions to the detection limit or below, and further, the apparatus and the running. It is an object of the present invention to provide a method for purifying a metal alkoxide which is advantageous from an industrial viewpoint such as cost.

[0009]

The method for purifying a metal alkoxide of the present invention comprises contacting a metal alkoxide containing chlorine ions as impurities and being a liquid at a temperature of 25 ° C. with an anion type ion exchange resin which has been dehydrated in advance. It is characterized by removing chlorine ions.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.

As the metal alkoxide to be purified, various metal alkoxides that are liquid at a temperature of 25 ° C.,
For example, titanium isopropoxide _{Ti (i-OC 3 H 7} ) 4, titanium n- butoxide _{Ti (n-OC 4 H 9} ) 4, zirconium t- butoxide _{Zr (t-OC 4 H 9} ) 4, niobium ethoxide _{nb (OC 2 H 5) 5} , tantalum ethoxide _{Ta (OC 2 H 5) 5} , tantalum n- propoxide _{Ta (n-OC 3 H 7} ) 5, germanium isopropoxide Ge (iO
C ₃ H _{7) 4,} germanium ethoxide _{Ge (OC 2 H 5) 4} , antimony ethoxide _{Sb (OC 2 H 5) 3} , vanadyl ethoxide VO (OC
₂ H ₅ ) ₃ and so on. It is also possible to use a bimetallic alkoxide or a metal complex alkoxide. Among these, alkoxides of titanium and zirconium used as a dielectric material or a ferroelectric material are important.

The metal alkoxide may be a commercially available industrial metal alkoxide, or may be a new home-made product. In either case, the metal alkoxide contains a considerable amount of impurities, and when attention is paid to chlorine ions, for example, it often contains several 10 ppm of chlorine ions.

As the anion type ion exchange resin, OH
Commercially available products include "Diaion" manufactured by Mitsubishi Chemical Co., "Amberlist" manufactured by Rohm and Haas, and "Amberlight" manufactured by Rohm and Haas. , There are products of many companies inside and outside.

In the present invention, a metal alkoxide containing chlorine ions as impurities and liquid at a temperature of 25 ° C. is brought into contact with an anion type ion exchange resin which has been dehydrated in advance to remove the chlorine ions. The contact can be performed in a batch system or a flow system. The temperature at the time of contact treatment is usually room temperature, but heating may be performed as long as the temperature is not higher than the boiling point of the target metal alkoxide and not higher than the durable temperature of the resin.

The anion type ion exchange resin usually contains water in a weight approximately equal to that of the ion exchange resin. Since the presence of such a large amount of water causes rapid hydrolysis of the metal alkoxide, it is necessary to dehydrate the anion type ion exchange resin in advance.

The anion type ion exchange resin is dehydrated by
It is preferable that the water contained in the anion-type ion exchange resin in the water-containing state is replaced with a water-miscible organic solvent to be removed, and then the organic solvent is deaerated and removed. Water-miscible organic solvents include lower alcohols such as
Methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol and t-butanol are preferred. In addition, as the water-miscible organic solvent, ketones, ethers, cellosolves, polyhydric alcohols and the like can be used. In addition, if it is attempted to directly deaerate the water content by depressurizing without substituting with the organic solvent, it becomes necessary to continue drying under reduced pressure for a long time, which is not practical.

Although the degree of dehydration of the anion type ion exchange resin is appropriately determined, it has been found that if the dehydration is completely or almost completely, the removal rate of chlorine ions tends to decrease. Therefore, it is recommended to perform incomplete dehydration treatment to remove chlorine ions while keeping the amount of by-product alcohol within an allowable range. At this time, the residual water content of the anion type ion exchange resin after the dehydration treatment is 8 to 17% by weight (particularly 10 to 1% by weight) with respect to the weight of the ion exchange resin.
5% by weight) is preferred.

The anion type ion exchange resin after use can be regenerated with an alkaline solution and repeatedly used.

<Action> By purifying the metal alkoxide according to the method of the present invention, while suppressing hydrolysis of the metal alkoxide within an allowable range (for example, 10% by weight or less in terms of alcohol), chlorine ions in the metal alkoxide are removed. It can be removed up to the detection limit or lower. Moreover, the method of the present invention is advantageous from an industrial viewpoint such as equipment and running cost.

[0020]

EXAMPLES The present invention will be further described with reference to examples.

Example 1 As a metal alkoxide raw material, Ti (i-OC ₃ H ₇ ) was used.
Titanium isopropoxide (manufactured by Nippon Soda Co., Ltd.) represented by ₄ was prepared. The impurity concentration in this raw material was 1003 wt ppm of water, 8830 wt ppm of organic impurities (isopropanol) and 27 chloride ions of chlorine on a weight basis.
pp m , Na ion 3 ppb, Ca ion 1 ppb, F
e ion 2 ppb, Ni ion 0.8 ppb, Cr ion 2 ppb, Al ion 8 ppb, Mn ion 0.7 p
pb, Zn ion 3 ppb, Ca ion 3 ppb, Co
The ion was 4 ppb.

Anion type ion exchange resin having a water content of 55 to 65% by weight ("DIAION SAT10" manufactured by Mitsubishi Chemical Corporation, spherical, ion type: OH type, exchange capacity:
0.9meq / ml or more, particle size distribution: 1180-300μm is 9
4% or more, effective diameter: 0.40 mm or more, uniform diameter number: 1.6 or less) were prepared.

40 ml of methanol (special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.) was added to an Erlenmeyer flask containing 5 g of the above anion type ion exchange resin, and the mixture was shaken gently for 1 minute and then decanted. After repeating this operation a total of 6 times, methanol was deaerated and removed using a vacuum pump under conditions of 10 Torr and 3 hours at room temperature. The residual water content in the anion-type ion-exchange resin after the dehydration treatment thus obtained was 7.4% by weight based on the weight of the ion-exchange resin.

After the dehydration treatment, the anion type ion exchange resin is placed in an atmosphere in which water does not exist, and the above chlorine ion 2 is added.
It was added to 30 g of titanium isopropoxide containing 7 ppm and stirred for 1 hour.

After that, when the amount of chlorine ions in the purified titanium isopropoxide was measured by an ion chromatograph (Dionex), the amount of chlorine ions in the titanium isopropoxide was reduced to 0.2 ppm or less. The amount of isopropanol produced as a by-product was 4.6% by weight based on the weight of purified titanium isopropoxide.

Example 2 Example 1 was repeated except that the residual water content in the anion type ion exchange resin after dehydration treatment with methanol was changed, and the chlorine ion (Cl ⁻ ) content in purified titanium isopropoxide and The amount of isopropanol (IPA) was measured.

Example 1 (Experiment No. 2) and Example 2
The results of (Experiment Nos. 1, 3, 4) are shown in Table 1 and FIG. The residual water content is% by weight based on the weight of the ion exchange resin.

[0028]

[Table 1] Experiment No. 1 2 3 4 Residual water content (wt%) 5.0 7.4 15.4 37.4 Cl ^- Amount (ppm) 0.6 <0.2 <0.2 <0.2 IPA content (wt%) 1.8 4.6 7.8 59.5

From the above results, when the residual water content in the anion type ion exchange resin after the dehydration treatment is 8 to 17% by weight, particularly 10 to 15% by weight based on the weight of the ion exchange resin, the secondary amount of isopropanol is It can be seen that the amount of chloride ions can be reduced below the permissible limit while suppressing the raw material. When an anion-type ion exchange resin not subjected to dehydration treatment is used, most of titanium isopropoxide is hydrolyzed to produce TiO2 and isopropanol, which may reach the purpose of purifying titanium isopropoxide. Can not.

Examples 3 to 4 As the raw material metal alkoxide, the chloride ion concentration was 28 pp.
m of titanium n-butoxide Ti (n-OC ₄ H ₉ ) ₄ (Example 3),
Example 1 except that zirconium t-butoxide Zr (t-OC ₄ H ₉ ) ₄ (Example 4) having a chlorine ion concentration of 30 ppm was used.
Anion type ion exchange resin "Diaion S
Contact treatment with "AT10" was performed. The results are shown in Table 2.
The by-product alcohol is n-butanol in Example 3 and t-butanol in Example 4.

[0031]

[Table 2]

[0032]

As described in the section of the action, when the metal alkoxide is purified according to the method of the present invention, the hydrolysis of the metal alkoxide is suppressed within the allowable range, but the chlorine ion in the metal alkoxide can be detected at the detection limit. It can be removed to a degree or even less. Moreover, the method of the present invention is advantageous from an industrial viewpoint such as equipment and running cost.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the chlorine ion concentration and the by-produced isopropanol concentration when various amounts of residual water in the anion-type ion exchange resin after dehydration treatment are changed.

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-63-198689 (JP, A) JP-A-63-198688 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C07F 7/28 C07F 7/00

Claims (5)

(57) [Claims] 1. A chlorine ion as an impurity and a temperature of 2
A method for purifying a metal alkoxide, which comprises contacting a metal alkoxide that is liquid at 5 ° C. with an anion-type ion exchange resin that has been dehydrated in advance to remove chlorine ions. 2. A dehydration treatment of an anion type ion exchange resin,
The purification method according to claim 1, wherein the water contained in the anion-type ion exchange resin in a water-containing state is removed by substituting and removing the water with a water-miscible organic solvent, and then degassing and removing the organic solvent. 3. The amount of residual water in the anion type ion exchange resin after dehydration treatment is 8 to 1 with respect to the weight of the ion exchange resin.
The purification method according to claim 2, which is 7% by weight. 4. The organic solvent is a lower alcohol.
The described purification method. 5. The purification method according to claim 1, wherein the metal alkoxide is a titanium or zirconium alkoxide.