JP2003313027A - Method of producing boehmite sol, boehmite sol, method of producing recording medium and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a boehmite sol by which a recording medium capable of performing recording of high quality can be produced on information recording by an ink jet process, to provide a boehmite sol, to provide a method of producing a recording medium using the same, and to provide a recording medium. <P>SOLUTION: A boehmite sol used for the production of a recording medium for an ink jet is produced. In this case, amorphous alumina hydrate slurry prepared by neutralization reaction between a basic aluminum chloride aqueous solution and a sodium aluminate aqueous solution, preferably under the condition of ≤40°C is subjected to hydrothermal treatment in an alkali region of pH ≥10 at ≥120°C to form boehmite slurry. Thereafter, the slurry is deflocculated to form a boehmite sol. The viscosity of the boehmite sol in the case the sol concentration is controlled to 20 wt.% expressed in terms of Al<SB>2</SB>O<SB>3</SB>is ≤100 cP. Also the mean fine pore size of pores formed in boehmite fine powder obtained by drying the boehmite sol is ≥15 nm. The volume of the pores is ≥0.5 cc/g. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boehmite sol suitable for manufacturing a recording medium used for recording information by an ink jet method, a method for manufacturing the same, a recording medium using the boehmite sol, and a method for manufacturing the same. is there.

[0002]

2. Description of the Related Art As a recording medium used for recording information by an ink jet method, a recording medium in which an ink receiving layer containing alumina hydrate particles is formed on a substrate is known. The ink receiving layer is a porous layer obtained by applying a coating liquid containing alumina sol on a substrate and then drying the coating liquid. In such an ink receiving layer, if the pore size and the pore volume of the alumina hydrate particles are not sufficiently large, the ink absorption time is long, and overflow or bleeding of the ink occurs. Various characteristics are required.

Heretofore, as a method for producing an alumina sol, conventionally, a method of hydrolyzing aluminum isopropoxide and then peptizing by adding an acid, and an alumina slurry obtained by hydrolyzing aluminum dodoxide are aged. Then, a method for forming a sol is known.

[0004]

However, a recording solution in which a porous layer of alumina hydrate particles is formed on a substrate by applying a coating liquid using a conventional alumina sol on the substrate and then drying the coating liquid is used. In the medium, the alumina hydrate particles have a small pore radius and a small pore volume, and the ink absorbency is insufficient.

Further, when a recording medium is manufactured, if a coating solution is prepared by using the alumina sol obtained by the conventional manufacturing method, it is difficult to uniformly coat the surface of the base material because of its high viscosity. Therefore, conventionally, there is a problem that the recording medium cannot be efficiently manufactured because the sol concentration of the coating liquid has to be lowered.

In view of the above problems, the object of the present invention is to
Provided are a method for producing a boehmite sol, a method for producing a boehmite sol, a method for producing a recording medium using the same, and a recording medium, which are suitable for producing a recording medium capable of performing high-quality recording when information is recorded by an inkjet method. To do.

[0007]

In order to solve the above problems, the inventors of the present invention have repeatedly conducted studies, and as a result, when a recording medium was manufactured using the following boehmite sol, information recording by the ink jet method was performed. At this time, it was found that high-quality recording can be performed and a recording medium can be preferably manufactured.

That is, in the method for producing a boehmite sol of the present invention, an alumina hydrate slurry is prepared by a neutralization reaction between a basic aluminum chloride aqueous solution and a sodium aluminate aqueous solution, and the alumina hydrate slurry is adjusted to pH 10
After the hydrothermal treatment is performed in the above alkaline region and at a temperature of 120 ° C. or higher to obtain a boehmite slurry, the basic aluminum chloride aqueous solution and the aluminate acid are used to peptize the boehmite slurry to obtain a boehmite sol. When adjusting the alumina hydrate slurry by a neutralization reaction with a sodium aqueous solution, the basic aluminum chloride aqueous solution is added to the sodium aluminate aqueous solution.

Although boehmite sols have been commercially available for some time, conventional commercial products have a low sol concentration of 5 to 10% by weight in order to suppress viscosity, and the concentration of these sols is increased. Therefore, there is a problem in that the viscosity increases when concentrated and gels over time. Therefore, when manufacturing a recording medium using a conventional boehmite sol, it is difficult to coat the surface of the substrate with the boehmite sol uniformly and efficiently. However, in the present invention, after the alumina hydrate slurry is prepared, the alumina hydrate slurry is prepared in the alkaline range of pH 10 or higher and at 120
Hydrothermal treatment is performed at a high temperature of ℃ or more to obtain a boehmite slurry in which boehmite is rapidly generated, and the boehmite slurry is peptized to obtain a boehmite sol. Therefore, for example, the sol concentration is 20 wt% in terms of Al ₂ O ₃ conversion concentration.
Even when, the viscosity is 100 cP or less, further 5
A boehmite sol having a viscosity of 0 cP or less can be obtained. Moreover, in the present invention, when the alumina hydrate slurry is prepared by the neutralization reaction between the basic aluminum chloride aqueous solution and the sodium aluminate aqueous solution, the basic aluminum chloride aqueous solution is added to the sodium aluminate aqueous solution, Compared with the case of adding sodium aluminate aqueous solution to basic aluminum chloride aqueous solution, it is possible to increase the concentration of alumina hydrate slurry obtained by neutralization, and to produce high concentration boehmite sol. Are suitable. Therefore, when the boehmite sol according to the present invention is used, the sol concentration in the coating liquid can be kept high even when a coating liquid is prepared by adding a binder or the like when manufacturing a recording medium. When such a coating liquid is used, the higher the sol concentration is, the thicker the coating film can be obtained, and the smaller the volume shrinkage during drying is, which is advantageous in that the film is less likely to be cracked. Furthermore, since the concentration can be increased by filtration and concentration, there is an advantage that an expensive concentration device such as a vacuum concentration device is not required.

Here, the use of the basic aluminum chloride aqueous solution and the sodium aluminate aqueous solution for preparing the alumina hydrate slurry makes it possible to obtain a homogeneous alumina hydrate slurry by the neutralization reaction between them. Because. For example, when aluminum sulfate is used as the Al raw material, sulfate ions remain in the alumina hydrate, and an alumina hydrate slurry suitable for boehmite cannot be obtained. Moreover, when NaOH is used instead of sodium aluminate as an alkali raw material, bayerite (A
1 (OH) ₃ ) is partially formed, and a homogeneous alumina hydrate slurry cannot be obtained.

Further, the hydrothermal treatment of alumina hydrate at 120 ° C. or higher is because when the hydrothermal reaction is carried out under such a high temperature condition, the boehmite crystal grows uniformly and rapidly, and the homogeneous and stable low viscosity is obtained. This is because the boehmite sol can be obtained. On the other hand, when the hydrothermal temperature is 120 ° C. or lower, coarse particles of bayerite are partially generated, so that a homogeneous boehmite sol cannot be prepared. Also,
By boehmite-forming the alumina hydrate slurry at a temperature of 120 ° C. or higher for a short time, a uniform and stable boehmite sol having uniform boehmite particles can be obtained.

Further, the alumina hydrate slurry was adjusted to pH 1
The hydrothermal treatment at 0 or more is because a boehmite sol having a high concentration and a low viscosity can be obtained, and a boehmite sol that can be dried to prepare a boehmite powder having a large pore size and a large pore volume can be obtained. . On the other hand, if the pH is lower than 10, as will be described later as Comparative Example 1, it is not possible to obtain a low-viscosity boehmite sol and a boehmite powder having a sufficient pore size and pore volume.

In the present invention, it is preferable to perform the hydrothermal treatment under the condition that the pH of the boehmite slurry after the hydrothermal treatment is higher than the pH of the alumina hydrate slurry before the hydrothermal treatment. For example, when sodium aluminate in excess of the neutralization equivalent to basic aluminum chloride is used and hydrothermal treatment is performed under the conditions of the present invention, the pH of the slurry after the hydrothermal reaction increases, and boehmite is formed in a short time. And uniform grain growth occurs. The cause has not been clarified yet, but it is considered that the boehmite particles are likely to uniformly grow as the pH increases during the hydrothermal treatment.

Further, in the method for producing a boehmite sol of the present invention, an alumina hydrate slurry prepared by a neutralization reaction between a basic aluminum chloride aqueous solution and a sodium aluminate aqueous solution is used in an alkaline region of pH 10 or more, and
After the hydrothermal treatment is performed at a temperature of 20 ° C. or higher to obtain the boehmite slurry, the boehmite slurry is peptized to obtain the boehmite sol, and the pH of the boehmite slurry after the hydrothermal treatment is subjected to the hydrothermal treatment. It is characterized in that the condition is set to be higher than the pH of the above-mentioned alumina hydrate slurry.

In the present invention, an alumina hydrate slurry can be obtained by adjusting the alumina hydrate slurry by a neutralization reaction between a basic aluminum chloride aqueous solution and a sodium aluminate aqueous solution. If the material slurry is left to stand, part of it crystallizes. Even with such an alumina hydrate slurry, if the hydrothermal treatment is performed under the condition that the pH of the boehmite slurry after the hydrothermal treatment is higher than the pH of the alumina hydrate slurry before the hydrothermal treatment, In a short period of time, generation and uniform grain growth occur. For example, when sodium aluminate in excess of the neutralization equivalent to basic aluminum chloride is used and hydrothermal treatment is performed under the conditions of the present invention, the pH of the slurry after the hydrothermal reaction increases, and boehmite is formed in a short time. And uniform grain growth occurs. The cause has not been clarified yet, but it is considered that the boehmite particles are likely to uniformly grow as the pH increases during the hydrothermal treatment.

Further, in the present invention, after the alumina hydrate slurry is prepared, the alumina hydrate slurry is subjected to hydrothermal treatment in the alkaline region of pH 10 or higher and at a high temperature of 120 ° C. or higher. In order to obtain a boehmite slurry in which boehmite is rapidly generated and to peptize the boehmite slurry to obtain a boehmite sol, for example, even when the sol concentration is 20 wt% in terms of Al ₂ O ₃ conversion, the viscosity is 100 cP or less. Furthermore, a boehmite sol having a low viscosity of 50 cP or less can be obtained. Therefore, when the boehmite sol according to the present invention is used, the sol concentration in the coating liquid can be kept high even when a coating liquid is prepared by adding a binder or the like when manufacturing a recording medium. When such a coating liquid is used, the higher the sol concentration is, the thicker the coating film can be obtained, and the smaller the volume shrinkage during drying is, which is advantageous in that the film is less likely to be cracked. further,
Since the concentration can be increased by filtration and concentration, there is also an advantage that an expensive concentration device such as a vacuum concentration device is not required.

Here, the basic aluminum chloride aqueous solution and the sodium aluminate aqueous solution are used to prepare the alumina hydrate slurry, as described above, because the homogeneous alumina hydrate slurry is obtained by their neutralization reaction. Because you can get In addition, the hydrothermal treatment of amorphous alumina hydrate at 120 ° C. or higher is performed as described above.
This is because the boehmite crystals grow uniformly and quickly, and a homogeneous and stable low-viscosity boehmite sol can be obtained. Furthermore, since the alumina hydrate slurry is boehmite-formed at a temperature of 120 ° C. or higher for a short time, a uniform and stable boehmite sol with uniform boehmite particles can be obtained. Further, since the amorphous alumina hydrate slurry is hydrothermally treated at a pH of 10 or more, it is possible to obtain a boehmite sol having a high concentration and a low viscosity, and a boehmite powder having a large pore size and a large pore volume can be prepared by drying. Boehmite sol can be obtained.

In the present invention, an amorphous alumina hydrate slurry is prepared by a neutralization reaction between the basic aluminum chloride aqueous solution and the sodium aluminate aqueous solution to form the amorphous alumina hydrate slurry. On the other hand, it is preferable to perform the hydrothermal treatment. An amorphous alumina hydrate slurry can be prepared by neutralizing a basic aluminum chloride aqueous solution and a sodium aluminate aqueous solution, but it is better to subject the amorphous alumina hydrate slurry to hydrothermal treatment. A boehmite sol having a high concentration and a low viscosity can be reliably obtained.

In order to produce a recording medium for ink jet using the boehmite sol according to the present invention, for example, a coating solution prepared by mixing a boehmite sol with a binder is applied on a substrate and then dried. Then, a porous layer of boehmite hydrate particles is formed as an ink receiving layer on the surface of the base material.

In the present invention, the neutralization reaction is preferably carried out at 40 ° C. or lower. By carrying out the neutralization reaction at such a low temperature, an amorphous alumina hydrate slurry can be obtained.
On the other hand, when the reaction temperature is 40 ° C. or higher, coarse particles of bayerite and boehmite with low crystallinity are partially generated, so that even if this alumina hydrate slurry is hydrothermally treated, it is a homogeneous and stable boehmite sol. Does not tend to be obtained.

In the present invention, the Cl / Al molar ratio of basic aluminum chloride is preferably in the range of 0.45 to 1.5. With respect to the basicity of aluminum chloride, if the basicity is given, the reaction with sodium aluminate becomes milder than in the case of the normal salt (AlCl ₃ ), so that a homogeneous amorphous alumina hydrate is obtained. In addition, compared with the neutralization reaction of normal salt, the salt (NaC
The amount of l) can be significantly reduced. On the other hand, when the Cl / Al molar ratio is high, that is, when the basicity is low, bayerite is easily generated,
Not preferable.

According to the production method of the present invention, the viscosity is 1 when the sol concentration is 20 wt% in terms of Al ₂ O ₃ conversion concentration.
A boehmite sol of 00 cP or less can be obtained. When a recording medium is manufactured using boehmite sol, a binder is mixed with boehmite sol to prepare a coating liquid, and the coating liquid is applied onto a substrate. Therefore, in the present invention, the sol concentration is Al ₂ O. Viscosity is 5 when 20% by weight in ₃ conversion concentration
It is preferably 0 cP or less. Further, it is preferable that the sol concentration is 18% by weight or more in terms of Al ₂ O ₃ conversion concentration.

Further, in the present invention, a boehmite sol having an average pore size of 15 nm or more and a pore volume of 0.5 cc / g or more formed in the boehmite fine powder obtained by drying the boehmite sol is produced. Preferably. The boehmite powder obtained by drying such a boehmite sol has a pore diameter of 15 nm or more and a pore volume of 0.5 to
It is in the range of 1.0 cc / g and can be suitably used for a recording medium for inkjet paper. Moreover, the pore size distribution of the present boehmite powder is very sharp. Specifically, the volume of the pores within the range of ± 10 nm of the pore diameter at the peak position of the pore diameter distribution occupies 65% or more of the entire pore volume. It is considered that this is because the particle diameters of the boehmite particles are uniform.

In the present invention, the pH of the boehmite sol is preferably 3.5 to 4.5. When the pH is high, the viscosity increases. On the other hand, when the pH is low, Al is partially dissolved, which is not preferable. The acid used as the dispersant for adjusting the pH is not particularly limited, but inorganic acids such as nitric acid and hydrochloric acid, or carboxylic acids such as acetic acid can be preferably used.

[0025]

The present invention will be described in more detail below. The various physical properties relating to the present invention were measured by the following methods.

Identification of crystal form: Alumina hydrate before and after hydrothermal treatment was measured using an X-ray diffractometer (RINT2000 manufactured by Rigaku Denki Co., Ltd.).

Pore volume, average pore size, and pore size distribution of dried sample: boehmite sol dried at 60 ° C. was degassed at 150 ° C. for 2 hours under vacuum exhaust, and then nitrogen adsorption / desorption device (manufactured by Micromeritics). ASAP2
000). The pore volume is 1.
It is a value of 7 to 300 nm, and the pore distribution was determined by the BJH method.

Sol viscosity: After adjusting the sol temperature to 20 ° C., a B type viscometer (manufactured by Tokyo Keiki Seisakusho) NO. It measured using the 1 rotor.

Sol concentration: After adding acid to boehmite sol and heating and dissolving, the Al content is determined by chelate titration method,
Converted to Al ₂ O ₃ concentration.

Transmittance: Boehmite sol having a sol concentration of 0.5% by weight is used in a cell having an optical path length of 10 mm and a wavelength of 530 nm.
The light transmittance of was measured.

In the following, among the studies repeatedly conducted by the inventor of the present application, Examples 1 to 9 and Comparative Examples 1 to 3 will be described. Of these Examples, Examples 1 to 5 and
Table 1 shows the conditions and the evaluation results of Comparative Examples 1 and 2.

[0032]

[Table 1]

[Example 1] 5000 ml of glass beer
Al for car₂O₃Converted concentration = 23.6%, Cl / Al mole
Basic aluminum chloride aqueous solution with a ratio of 0.501
Name: Alphain 83, manufactured by Daimei Chemical Industry Co., Ltd.) and appropriate amount
Of water and stir this aqueous solution with a homomixer.
, Until the pH reaches 10.6, sodium aluminate
Aqueous solution (Al ₂O₃Converted concentration = 1%, Na / Al molar ratio =
2.0) is gradually added at room temperature to give amorphous alumina water.
A Japanese slurry is obtained.

Next, this slurry is subjected to hydrothermal reaction at 150 ° C. for 8 hours using an autoclave. The pH of the slurry (boehmite slurry) after the hydrothermal treatment was measured and found to be 12.0.

Next, the slurry after the hydrothermal reaction is filtered and washed until the electric conductivity of the filtrate becomes 20 μS / cm or less.
To the filter cake thus obtained, 1N nitric acid is added so as to have a pH of 4, and then an appropriate amount of water is added to peptize the mixture to prepare a boehmite sol.

Al of the boehmite sol thus obtained
_{The 2} O ₃ conversion concentration was 20.2%. The viscosity of this boehmite sol was measured and found to be 33 cP. Further, the transmittance is 3. when the sol concentration is 0.5% by weight.
It was 0%. The alumina hydrate obtained by drying the boehmite sol was boehmite (AlOOH), and the average pore diameter was 27.9 nm and the pore volume was 0.753 cc / g. Further, the volume of pores within the range of ± 10 nm of the pore diameter at the peak position of the pore diameter distribution occupied 73% of the total pore volume.

In order to manufacture a recording medium for ink jet recording using the boehmite sol thus manufactured, 100 g of boehmite sol is firstly added with a 10% by weight aqueous solution of polyvinyl alcohol (saponification degree 97%, polymerization degree 1700). 22.2 g are mixed to prepare a coating liquid. Next, this coating solution was applied on a high-quality paper having a thickness of 200 μm by a bar coater so that the film thickness after drying was 20 μm, and dried to form a porous layer of boehmite hydrate particles as an ink receiving layer. The recording paper (recording medium) formed as described above is manufactured.

As a result, no cracks were found in the porous layer. Further, as a result of performing test printing on this recording paper by using an ink jet printer PM700C manufactured by Epson and visually confirming the printing condition, it was confirmed that there was no bleeding or the like and the ink absorbability was large.

Example 2 A boehmite sol was prepared in the same manner as in Example 1 except that the hydrothermal treatment with an autoclave was carried out at 150 ° C. for 10 hours. The obtained sol had an Al ₂ O ₃ conversion concentration of 20.1% and a viscosity of 30 cP.
Met. The alumina hydrate obtained by drying this sol was boehmite, and its average pore diameter was 29.
The pore volume was 4 nm and the pore volume was 0.787 cc / g.

Further, as in Example 1, a coating liquid was prepared to produce a recording paper, and a printing test was conducted on the recording paper. As a result, it was confirmed that there was no bleeding and the ink absorbency was high. Was done.

Example 3 A boehmite sol was prepared in the same manner as in Example 1, except that the hydrothermal treatment in an autoclave was carried out at 170 ° C. for 5 hours. A of the obtained sol
The l ₂ O ₃ conversion concentration was 20.2%, and the viscosity was 28 cP. The alumina hydrate obtained by drying this sol was boehmite and had an average pore diameter of 31.6.
nm, and the pore volume was 0.704 cc / g.

Further, as in Example 1, a coating liquid was prepared to produce a recording paper, and a printing test was conducted on the recording paper. As a result, it was confirmed that there was no bleeding and the ink absorbency was high. Was done.

Example 4 5000 ml glass beer
Al for car₂O₃Converted concentration = 23.0%, Cl / Al mol
Basic aluminum chloride aqueous solution with a ratio = 0.751
Name: Alphain 75, manufactured by Daimei Chemical Industry Co., Ltd.) and appropriate amount
Of water and stir this aqueous solution with a homomixer.
Until the pH reaches 10.2, sodium aluminate
Aqueous solution (Al ₂O₃Converted concentration = 1%, Na / Al molar ratio =
2.0) is gradually added at room temperature to give amorphous alumina water.
A Japanese slurry is obtained. Next, this slurry is autoclaved.
And perform hydrothermal reaction at 170 ° C. for 2 hours. Water heat
The pH of the slurry after the reaction was measured and found to be 11.1.
It was. Next, the slurry after the hydrothermal reaction is treated with the electric conductivity of the filtrate.
Is washed by filtration until 20 μS / cm or less. This
The filter cake obtained in this way was adjusted to pH 4 with 1N
After adding nitric acid, add an appropriate amount of water to peptize and add boehm
Prepare Tosol.

The boehmite sol thus obtained had an Al ₂ O ₃ conversion concentration of 20.2% and a viscosity of 36 cP.
Met. The alumina hydrate obtained by drying this boehmite sol was boehmite, and had an average pore diameter of 24.8 nm and a pore volume of 0.695 cc / g.

Further, a recording liquid was prepared by preparing a coating liquid in the same manner as in Example 1, and a printing test was conducted on the recording paper. As a result, it was confirmed that there was no bleeding and the ink absorption was high. It was

Example 5 A boehmite sol was prepared in the same manner as in Example 1 except that the hydrothermal treatment with an autoclave was carried out at 130 ° C. for 10 hours. The obtained sol had an Al ₂ O ₃ conversion concentration of 20.1% and a viscosity of 45 cP.
Met. The alumina hydrate obtained by drying this sol was boehmite, and its average pore diameter was 20.
It was 1 nm and the pore volume was 0.684 cc / g. Further, the transmittance is 3. when the sol concentration is 0.5% by weight.
It was 4%.

Further, as in Example 1, a coating liquid was prepared to produce a recording paper, and a printing test was conducted on the recording paper. As a result, it was confirmed that there was no bleeding and the ink absorption was high. Was done.

[Example 6] In Example 1 and the like, when the alumina hydrate slurry was prepared by the neutralization reaction between the basic aluminum chloride aqueous solution and the sodium aluminate aqueous solution, aluminate was added to the basic aluminum chloride aqueous solution. Although the sodium aqueous solution was added, in the present embodiment, as described below, the basic aluminum chloride aqueous solution is added to the sodium aluminate aqueous solution.

An aqueous sodium aluminate solution (concentration of Al ₂ O ₃ = 1.3%, N
a / Al molar ratio = 2.0), and while stirring this solution with a stirrer, basic aluminum chloride aqueous solution (Cl / Al molar ratio = 0.501) is added at room temperature until pH becomes 10.4. The mixture was gradually added dropwise to obtain an amorphous alumina hydrate slurry having an Al ₂ O ₃ conversion concentration of 3%.

Next, this slurry is subjected to a hydrothermal reaction at 120 ° C. for 17 hours using an autoclave. The pH of the hydrothermal slurry was measured and found to be 11.7.

Next, the slurry after the hydrothermal reaction was filtered and washed until the electric conductivity of the filtrate became 20 μS / cm or less.
Boehmite sol was prepared by adding 1N nitric acid to the filter cake thus obtained so that the pH was 4, and then peptizing by adding an appropriate amount of water.

Al of the boehmite sol thus obtained
_{The 2} O ₃ conversion concentration was 20.1%. The viscosity of the boehmite sol was measured and found to be 22 cP. Also,
The alumina hydrate obtained by drying this boehmite sol is boehmite and has an average pore diameter of 21.5 n.
m, and the pore volume was 0.895 cc / g.

Further, a recording liquid was prepared by preparing a coating liquid in the same manner as in Example 1, and a printing test was conducted on the recording paper. As a result, it was confirmed that there was no bleeding and the ink absorbency was high. Was done.

The advantage of changing the order of addition as in the present embodiment is that the concentration of the alumina hydrate slurry obtained by neutralization can be increased. That is, in the state of the alumina hydrate slurry, the Al ₂ O ₃ conversion concentration in Examples 1 to 5 and Comparative Examples 1 and ₂ was 1%, but according to this example, it should be increased to 3%. You can It is possible to increase the concentration of the alumina hydrate slurry by filtration concentration, but it is basically preferable to perform the hydrothermal treatment as it is. In the present embodiment, the concentration of the alumina hydrate slurry is increased. As a result, the size of the hydrothermal reaction device can be reduced.

Example 7 In Example 1, an amorphous alumina hydrate slurry was prepared by a neutralization reaction between a basic aluminum chloride aqueous solution and a sodium aluminate aqueous solution, which was hydrothermally treated. An example of using a neutralized slurry in which crystalline is partially mixed in the hydrate slurry will be described below.

First, the amorphous alumina hydrate slurry obtained by the method of Example 6 was allowed to stand at room temperature for 166 hours. When the X-ray diffraction measurement of the alumina hydrate slurry left to stand was performed, a part of the crystalline substance (Bayerite Al (O
It was confirmed that H) ₃ ) was produced.

Using this alumina hydrate slurry, the same treatment as in Example 6 was carried out to obtain a boehmite sol. The pH of the alumina hydrate slurry before hydrothermal treatment is 1
0.4, pH of boehmite slurry after hydrothermal treatment is 1
It was 2.2. The obtained boehmite sol had an Al ₂ O ₃ conversion concentration of 20.3% and a viscosity of 18 cP. Also,
The boehmite obtained by drying this boehmite sol has an average pore diameter of 31.0 nm and a pore volume of 0.695 cc.
/ G.

Further, a recording liquid was prepared by preparing a coating solution in the same manner as in Example 1, and a printing test was conducted on this recording paper. As a result, it was confirmed that there was no bleeding and the ink absorption was high. Was done.

As described above, when the alumina slurry obtained by the neutralization is left to stand, partially crystalline bayerite is produced. However, even if bayerite is produced, if the treatment is carried out under the hydrothermal conditions according to the present invention, the bayerite is produced. Since the light disappears and becomes a single phase of boehmite, boehmite sol can be produced. In this case, the boehmite crystals tend to grow faster than when an amorphous slurry is used.

On the other hand, when the hydrothermal condition of the present invention is not satisfied, that is, when the pH decreases before and after hydrothermal treatment or when the hydrothermal temperature is lower than 120 ° C., the bayerite remains. However, such an example will be described later as Comparative Example 3.

[Embodiment 8] In each of the above embodiments, nitric acid was used as the dispersant, but an example using acetic acid as the dispersant will be described below.

A neutralization reaction and a hydrothermal reaction were carried out in the same manner as in Example 7 to obtain a boehmite cake. P for this cake
4N acetic acid is added so that H becomes 4, and then an appropriate amount of water is added to peptize to prepare a boehmite sol. The obtained boehmite sol had an Al ₂ O ₃ conversion concentration of 20.1% and a viscosity of 16 cP. The average pore diameter of boehmite obtained by drying this boehmite sol was 18.2 n.
m, and the pore volume was 0.766 cc / g.

Further, a coating liquid was prepared in the same manner as in Example 1, a recording paper was manufactured, and a printing test was conducted on the recording paper. As a result, it was confirmed that there was no bleeding and the ink absorption was high. Was done.

Example 9 Next, an example using hydrochloric acid as a dispersant will be described below.

The acid used for deflocculation is 4N acetic acid to 4N
The same treatment as in Example 8 was performed except that the hydrochloric acid was changed to
Prepare boehmite sol.

The obtained boehmite sol had an Al ₂ O ₃ conversion concentration of 20.1% and a viscosity of 18 cP. The average pore diameter of boehmite obtained by drying this boehmite sol was 18.1 nm, and the pore volume was 0.769 cc / g.
Met.

Further, a recording liquid was prepared by preparing a coating solution in the same manner as in Example 1, and a printing test was conducted on this recording paper. As a result, it was confirmed that there was no bleeding and the ink absorbency was high. Was done.

[Comparative Example 1] A basic aluminum chloride solution (trade name: Alfain 83, Daimei Co., Ltd.) having a concentration of Al ₂ O _{3 of} 23.6% and a Cl / Al molar ratio of 0.501 was placed in a glass beaker of 5000 ml. Chemical Industry Co., Ltd.), take an appropriate amount of water, stir this solution with a homomixer,
Sodium aluminate solution (Al ₂ O ₃ conversion concentration = 1%, Na / Al molar ratio = 2.
0) is gradually added at room temperature to obtain an amorphous alumina hydrate slurry. Next, this slurry is hydrothermally reacted at 150 ° C. for 8 hours using an autoclave. The pH of the slurry after the hydrothermal reaction was measured and found to be 4.8.
Next, the slurry after the hydrothermal reaction has a filtrate electric conductivity of 20.
Filter and wash until it becomes μS / cm or less. Next, the filter cake thus obtained is adjusted to pH 4 with 1
After adding N nitric acid, an appropriate amount of water is added to peptize to prepare a boehmite sol.

The Al ₂ O ₃ conversion concentration of the sol thus obtained was 19.1%. When the viscosity of this sol was measured, it was 930 cP. The alumina hydrate obtained by drying this sol was boehmite, but its average pore diameter was 9.0 nm and pore volume was 0.444 cc /.
It was g, and all were small values.

As described above, in Comparative Example 1, since the pH after the neutralization reaction was 9.0 and the pH after the hydrothermal reaction was lowered, the coating was carried out in the same manner as in Example 1. After a liquid was prepared to produce a recording paper, a printing test was conducted on the recording paper. As a result, it was confirmed that bleeding occurred and the ink absorbency was poor.

[Comparative Example 2] An alumina sol was prepared in the same manner as in Example 1 except that the hydrothermal treatment with an autoclave was conducted at 110 ° C for 8 hours. The alumina hydrate obtained by drying this sol has a hydrothermal reaction temperature condition of 11
As low as 0 ℃, boehmite and bayerite (Al (O
H) ₃ ), which is a mixture and was formed together with boehmite, had coarse particles of about several μm, so that a uniform sol could not be prepared.

[Comparative Example 3] Using the slurry of partially crystalline bayerite obtained in Example 7, 110
Alumina sol was prepared in the same manner as in Example 7, except that hydrothermal treatment was performed at 17 ° C for 17 hours. The alumina hydrate obtained by drying this sol was a mixture of bayerite and boehmite, and a uniform sol could not be prepared.

[Other Embodiments] In addition to the above embodiments,
According to repeated examinations by the inventor of the present application, for example, C
The amorphous aluminum produced by the neutralization reaction of a basic aluminum chloride aqueous solution having an l / Al molar ratio of 0.45 to 1.5 and a sodium aluminate aqueous solution, preferably a neutralization reaction at 40 ° C. or lower. PH 1 of alumina hydrate slurry
After hydrothermal treatment in an alkaline region of 0 or more and at a temperature of 120 ° C. or more to obtain a boehmite slurry, the boehmite slurry is peptized to obtain a sol concentration of 20% by weight in terms of Al ₂ O ₃ conversion concentration. And the average pore size of the pores formed in the boehmite fine powder obtained by drying the boehmite sol is 15 nm.
As described above, it was confirmed that a boehmite sol having a pore volume of 0.5 cc / g or more could be produced, and a recording medium capable of high-quality recording could be produced when information was recorded by the inkjet method.

Here, as the recording medium, one having an ink receiving layer formed on paper as a base material, and one having an ink receiving layer formed on a transparent plastic sheet for OHP as a base material, etc. It can be manufactured.

Further, as the boehmite sol used for producing the recording medium, it is preferable that the viscosity is 50 cP or less when the sol concentration is 20 wt% in terms of Al ₂ O ₃ concentration, and the sol concentration is Al ₂ It was confirmed that it is preferably 18% by weight or more in terms of O ₃ conversion concentration.

[0076]

As described above, according to the present invention, when the boehmite sol used for producing the ink jet recording medium is produced, a neutralization reaction between the basic aluminum chloride aqueous solution and the sodium aluminate aqueous solution, preferably 40 ° C. The amorphous alumina hydrate slurry prepared by the neutralization reaction under the following conditions is hydrothermally treated at a pH of 10 or more in an alkaline region and at a temperature of 120 ° C. or more to obtain a boehmite slurry. Since the slurry is peptized to obtain a boehmite sol, it is possible to produce a boehmite sol having a low viscosity even if the sol concentration is high. Such a boehmite sol can efficiently produce a recording medium capable of performing high-quality recording when information is recorded by an inkjet method.

Even if a part of the alumina hydrate slurry prepared by the neutralization reaction between the basic aluminum chloride aqueous solution and the sodium aluminate aqueous solution is crystallized, the pH of the boehmite slurry after hydrothermal treatment is By setting the conditions such that the pH is higher than that of the alumina hydrate slurry before hydrothermal treatment, it is possible to produce a boehmite sol having a low viscosity even if the sol concentration is high. Such a boehmite sol can also efficiently produce a recording medium capable of high-quality recording when information is recorded by the inkjet method.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Minoru Tanaka             2 major, 3685 Minamiminowa Village, Kamiina District, Nagano Prefecture             Meikagaku Kogyo Co., Ltd. F-term (reference) 2C056 FC06                 2H086 BA15 BA33 BA41                 4G076 AA02 AA10 AA21 AB02 AB04                       AB06 BA12 BA15 BA48 BD01                       BD02 CA12 CA15 CA18 DA30                       FA08

Claims (13)

[Claims] 1. An alumina hydrate slurry is prepared by a neutralization reaction between a basic aluminum chloride aqueous solution and a sodium aluminate aqueous solution, and the alumina hydrate slurry is adjusted to pH.
In the alkaline region of 10 or more, and after hydrothermal treatment at a temperature of 120 ° C. or more to obtain a boehmite slurry, when the boehmite slurry is peptized to obtain a boehmite sol, the basic aluminum chloride aqueous solution and the aluminum Production of a boehmite sol characterized by adding the basic aluminum chloride aqueous solution to the sodium aluminate aqueous solution when the alumina hydrate slurry is prepared by a neutralization reaction with the sodium acid aqueous solution. Method. 2. The condition according to claim 1, wherein the pH of the boehmite slurry after the hydrothermal treatment is set to be higher than the pH of the alumina hydrate slurry before the hydrothermal treatment. Manufacturing method of boehmite sol. 3. An alumina hydrate slurry prepared by a neutralization reaction between a basic aluminum chloride aqueous solution and a sodium aluminate aqueous solution, in an alkaline region of pH 10 or more,
In addition, after the hydrothermal treatment is performed at a temperature of 120 ° C. or higher to obtain the boehmite slurry, when the boehmite slurry is peptized to obtain the boehmite sol, the pH of the boehmite slurry after the hydrothermal treatment is the hydrothermal treatment. The method for producing a boehmite sol is characterized in that the condition is set to be higher than the pH of the alumina hydrate slurry before performing. 4. The method according to any one of claims 1 to 3,
After adjusting the amorphous alumina hydrate slurry by a neutralization reaction between the basic aluminum chloride aqueous solution and the sodium aluminate aqueous solution, the hydrothermal treatment is performed on the amorphous alumina hydrate slurry. A method for producing boehmite sol, which is characterized by the above. 5. The method according to any one of claims 1 to 4,
A method for producing boehmite sol, wherein the neutralization reaction is performed at a temperature of 40 ° C. or lower. 6. The method according to any one of claims 1 to 5,
The basic aluminum chloride has a Cl / Al molar ratio of 0.45
To 1.5, a method for producing a boehmite sol. 7. A boehmite sol produced by the method as defined in any one of claims 1 to 6. 8. The sol concentration according to claim 7, wherein the sol concentration is Al ₂ O ₃
A boehmite sol having a viscosity of 100 cP or less when converted to a concentration of 20% by weight. 9. The sol concentration according to claim 8,
The viscosity is 50 cP when 20% by weight is calculated as the concentration of ₂ O _3.
A boehmite sol characterized by being: 10. The boehmite sol according to claim 8, wherein the sol concentration is 18 wt% or more in terms of Al ₂ O ₃ conversion concentration. 11. The boehmite fine powder obtained by drying boehmite sol according to claim 7, wherein the fine pores have an average pore diameter of 15 nm or more and a pore volume of 0.5 cc / g or more. Boehmite sol characterized by being. 12. A boehmite hydrate is hydrated on the surface of the base material by applying a coating solution prepared by mixing a binder to the boehmite sol defined in any one of claims 7 to 11 and then drying the coating solution. A method for producing a recording medium, characterized in that a porous layer is formed of the material particles. 13. A boehmite hydrate is hydrated on the surface of the base material by applying a coating solution prepared by mixing a binder to the boehmite sol defined in any one of claims 7 to 10 and then drying it. A recording medium comprising a porous layer of material particles.