JP2010030797A - Method for producing alumina dispersion liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an alumina dispersion liquid in which hydrated alumina powder is well dispersed. <P>SOLUTION: The method is for producing an alumina dispersion liquid containing hydrated alumina powder and an aqueous dispersion medium, which has a supplying process to supply the hydrated alumina powder into an aqueous dispersion medium in dispersing equipment and a dispersing process to disperse the hydrated alumina powder in the aqueous dispersion medium by stirring the aqueous dispersion medium with a stirring means with which the dispersing equipment is equipped. The pH value of the aqueous dispersion medium into which the hydrated alumina is supplied is in a range of 3.0-6.0, and effective consumption power for stirring of the stirring means is in a range of 0.01-0.2 kw/m<SP>3</SP>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing an alumina dispersion.

  In the ink jet recording method, a recording liquid such as ink is ejected by various operating principles and adhered to a recording medium such as paper to record images, characters, and the like. In recent years, it has been required to easily output an image comparable to silver salt photography or plate-making multicolor printing by an ink jet recording method.

As an ink jet recording medium used for ink jet recording or the like, there is a medium having a porous ink receiving layer made of an inorganic pigment and a binder on a support. An ink jet recording medium having a porous ink receiving layer can be obtained by coating inorganic fine particles on a support. As the inorganic fine particles, alumina hydrate is preferably used. The porous ink-receiving layer is usually formed by applying an alumina dispersion liquid in which an alumina hydrate powder is dispersed in an aqueous dispersion medium and a coating liquid composed of a polyvinyl alcohol-based binder on a support and then drying. Is formed. The alumina dispersion used at this time was dispersed by putting alumina hydrate powder into an aqueous dispersion medium in a dispersion tank and stirring for a certain time (see Patent Document 1).
Japanese Unexamined Patent Publication No. 2000-071609

  However, with the recent improvement in image quality, the conventional dispersion method as described in Patent Document 1 is further improved in terms of dispersion stability of the alumina hydrate powder in the aqueous dispersion medium. There is a need for improvement. This is because when the dispersion of alumina hydrate in the dispersion is not good, it is difficult to uniformly apply to the resulting recording medium, and it is difficult to obtain a recording medium suitable for high image quality that has recently been required.

  Accordingly, an object of the present invention is to provide a method for producing an alumina dispersion in which alumina hydrate powder is well dispersed.

  The above object is achieved by the present invention described below.

That is, the present invention relates to a method for producing an alumina dispersion containing an alumina hydrate powder and an aqueous dispersion medium, wherein the alumina hydrate powder is charged into an aqueous dispersion medium in a dispersion apparatus. And a dispersion step of dispersing the alumina hydrate powder in the aqueous dispersion medium by stirring the aqueous dispersion medium with stirring means provided in the dispersion device, and the alumina hydrate is charged the pH of the aqueous dispersion medium that is, 3.0 or more and 6.0 or less, the effective power consumption of the stirring of the agitating means, 0.01 kW / ^{m 3} or more, 0.2kw / ^{m 3} or less This is a method for producing an alumina dispersion.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the manufacturing method which manufactures the alumina dispersion liquid which disperse | distributed the alumina hydrate powder favorably.

  The method for producing the alumina dispersion of the present invention will be described in detail.

  FIG. 1 is an example of a schematic diagram of a dispersion apparatus used in the alumina dispersion method of the present invention. The dispersion apparatus includes a dispersion tank 1 having a rotary blade type agitator 2 driven by a stirring motor 3, an alumina hydrate powder charging hopper 4, a powder transporting device 6, a powder charging line 5, and a tank. A discharge valve 7 is provided.

  First, in the charging process, the alumina hydrate powder put in the powder feeding hopper 4 is fed into the dispersion tank 1 through the powder feeding line 5 by the action of the powder transporting device 6. In the dispersion tank 1 in the dispersion apparatus, there is an aqueous dispersion medium adjusted to a predetermined pH. It is preferable that the alumina hydrate powder to be fed is supplied at a constant ratio in an aqueous dispersion medium in a constant stirring state. The input amount of alumina hydrate powder into the aqueous dispersion medium per minute is preferably controlled to 30% by mass or less of the total input amount of alumina hydrate powder into the aqueous dispersion medium. Here, the total input amount is the total mass of the alumina hydrate powder to be added to the aqueous dispersion medium before finally obtaining the alumina dispersion. When the input amount per minute exceeds 30% by mass of the total input amount, the dispersion tends to be unsatisfactory. As an input device for appropriately controlling the input amount, it is preferable to use a suction and transport type powder input device. Examples of the quantitative charging device include a table feeder, a screw feeder, and a vibration feeder. However, since the alumina hydrate powder is fine and very cohesive and easily causes flushing, such a charging apparatus has a problem in stability. On the other hand, the powder feeding device of the suction transportation system can accurately specify the amount of charge per one time or a fixed time and has a strong supply power, so even a highly cohesive powder can be smooth. Can be supplied to. FIG. 1 shows the case where a vacuum pump is used as a suction source, and the alumina hydrate powder in the charging hopper 4 is charged into the powder by the negative pressure generated by the vacuum pump provided in the powder transporting device 6. It is introduced into the dispersion tank via line 5. At this time, it is possible to intermittently charge a certain amount of powder by repeating the vacuum and pressurization cycle in the system. In this example, the powder feeding device of the suction transportation system corresponds to the powder feeding line 5 and the powder transportation device 6. The charging is preferably performed continuously, but may be performed in small portions at regular intervals. As a suction source, a jet type using compressed air or a blower type can be used in addition to the vacuum pump. A vacuum conveyor manufactured by Akabu Engineering Co., Ltd. can be used as a suction transport device using a vacuum pump.

  Further, the stirring means provided in the dispersing apparatus performs stirring so as to reduce coarse particles, but the present inventors have found that if the stirring is performed too strongly, the viscosity tends to increase or the particle size distribution tends to be disrupted. . In addition, when the hydrated alumina powder is peptized in the presence of a peptizer such as an acid, the hydrated alumina powder exists in an agglomerated state, and is peptized and dispersed in an acidic atmosphere. . In the stirring state at that time, it is important that stirring of the entire dispersion is performed without stagnation and excessive stirring share is not applied. Therefore, the stirring at that time requires a stirring share enough to loosen the agglomeration, and it is difficult to obtain a stable dispersion state even if the stirring is too strong or too weak.

The effective power consumption of stirring by the stirring means means the power consumed by subtracting the power consumed during idling in the no-load state from the total power consumed by stirring of the stirring means. It refers to the power consumed per unit volume. Moreover, the average power consumption during stirring is indicated. In the present invention, the effective power consumption of the agitator 0.01 kW / ^{m 3} or more, and a 0.2kw / ^{m 3} or less. The effective power consumption is more preferably 0.02kw / ^{m 3} or more. Further, it is more preferably 0.19 kw / m ³ or less. When the effective power consumption exceeds 0.2 kw / m ³ , the stirring share becomes excessive, the particle size distribution of the resulting dispersion is atomized, the viscosity during stirring increases, and handling becomes difficult. In addition, when the effective power consumption is less than 0.01 kw / m ³ , the flow state of the dispersion is insufficient, and a staying portion is generated in the tank, resulting in poor dispersion.

  Examples of the stirring means used in the present invention include a stirrer and a line mixer. The stirrer is not particularly limited, but an anchor blade, a paddle blade, a full zone blade, a three-blade swept blade, a propeller blade, and the like can be preferably used. In addition, it is preferable to install a baffle plate or the like because stirring becomes more uniform.

  The aqueous dispersion medium charged with the alumina hydrate powder of the present invention has a pH of 3.0 or more and 6.0 or less. When the pH is less than 3.0, the alumina dispersion tends to increase in viscosity, and the corrosiveness becomes strong, making it difficult to handle the dispersion. On the other hand, if the pH exceeds 6.0, the dispersion does not proceed sufficiently or a long time is required for the dispersion, which is not preferable. An acid is preferably added to adjust the pH. The acid is not particularly limited, and for example, any of inorganic acids such as hydrochloric acid, nitric acid, amidosulfuric acid, and organic acids such as acetic acid can be used. Among them, it is preferable to use acetic acid. The amount of acid added is preferably 0.005 equivalents or more and 0.2 equivalents or less with respect to 1 mol of aluminum atoms in the alumina dispersion. Moreover, it is more preferable that it is 0.01 equivalent or more. Moreover, it is more preferable that it is 0.1 equivalent or less. When the amount is less than 0.005 equivalent, not only does it take a long time to disperse, but it also tends to gel when the concentration of the alumina sol is high. An amount exceeding 0.2 equivalent is not preferable because the alumina hydrate may be dissolved.

  The liquid contact part of the tank and the stirring means used in the present invention is preferably made of a material excellent in corrosiveness in an acidic atmosphere, and particularly preferably made of glass lining. That the wetted part is made of glass lining means that the glass is sprayed on the wetted part such as the tank wall surface or the stirring means surface and baked, and the tank wall or stirring means surface is bonded to the glass. Say. Since it is made of glass lining, there is little adhesion of the slurry to the tank wall surface, and even if it adheres, it can be easily removed, so that the yield can be improved.

  The time required for the dispersion treatment is preferably 1 hour or more. Moreover, 24 hours or less are preferable and 12 hours or less are more preferable. By the above dispersion treatment, the secondary particle diameter of the alumina particles can be easily adjusted. An average secondary particle diameter of 50 to 1000 nm is preferable because the alumina hydrate powder obtained by drying the dispersion liquid has a large pore diameter and pore volume and can produce an alumina dispersion liquid with high transparency. In addition, since the alumina hydrate powder obtained by drying the alumina dispersion contains an acid that is a peptizer, it is easily re-peptized when mixed with a binder. It is possible to provide a coating liquid that can form a highly transparent ink-receiving layer even when using.

  According to the method of the present invention, a highly transparent alumina dispersion can be easily produced, and the alumina hydrate powder obtained by drying the dispersion has a large pore diameter and pore volume. When the alumina dispersion obtained by the method of the present invention is appropriately mixed with a binder, applied onto a substrate and dried to form an ink receiving layer, a recording medium having good ink absorbability can be obtained. Moreover, if a transparent base material is used, a transparent recording medium can also be obtained.

The alumina hydrate powder used in the present invention is preferably an alumina hydrate having a boehmite structure represented by the composition formula: AlOOH.xH ₂ O (0 ≦ x <2). The crystal having a boehmite structure in the alumina hydrate powder of the present invention preferably has a crystal thickness (hereinafter referred to as crystal size) of 6 nm or more in a direction perpendicular to the (010) plane. When the crystal size is less than 6 nm, it is difficult to form an ink receiving layer having excellent absorbability. From the X-ray diffraction analysis of the alumina hydrate powder obtained by drying the alumina dispersion liquid to a constant weight at 140 ° C., the crystal size is determined by the diffraction angle 2θ (°) of the peak on the (020) plane and the half width B A value obtained from Schrader's equation (t = 0.9λ / Bcos θ) from (rad). In this equation, t is the crystal size (nm), and λ is the X-ray wavelength (nm).

  FIG. 2 is an example of a schematic diagram of a dispersion apparatus showing another embodiment of the present invention. This disperser is provided with a circulation line with respect to the apparatus shown in FIG. 1, and is preferably used when dispersing more efficiently. In FIG. 2, 8 is a circulation pump, 9 is a line mixer, and 10 is a circulation line.

A predetermined amount of the alumina hydrate powder is put into the dispersion tank, and after the dispersion is started by the action of the rotary stirrer 2, the circulation pump and the line mixer are started as appropriate, and the dispersion liquid is circulated through the circulation line. I do. By performing the circulation, the alumina hydrate powder can be more effectively dispersed, and the dispersion time can be shortened. In that case, it is more preferable to use a line mixer as needed as shown in FIG. A line mixer is used to aid dispersion in a rotary stirrer. In this example, the stirring means so rotary agitator and line mixer, the sum of these effective power consumption, 0.01 kW / ^{m 3} or more, it is necessary to 0.2kw / ^{m 3} or less.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, the content of this invention is not restricted to an Example.

<Example 1>
The apparatus described in FIG. 1 was used. A dispersion tank having a capacity of 10 m ³ was used, and an anchor blade was installed as a rotary stirrer. The liquid contact part of the dispersion tank and the stirrer was made of glass lining.

The dispersion tank was charged with 5700 L (liter) of ion exchange water and 40 L of 90% acetic acid, and the anchor blade was stirred at 60 rpm. While stirring, 1800 kg of Dispersal HP15 (manufactured by SASOL) having a BET specific surface area of 160 m ² / g was supplied into the tank as an alumina hydrate powder.

For supplying the powder, a vacuum suction conveying device, which is a powder feeding device of a suction transportation system, was used. The alumina hydrate powder was sucked by opening and closing the valve in a reduced pressure atmosphere obtained by a vacuum pump, and the powder was put into the tank by the flow of air. The charging was performed continuously at intervals of 10 seconds, 10 kg, and the entire amount of 1800 kg was charged in 30 minutes. The stirring blade rotation speed was 60 revolutions / minute, and a dispersion time of 12 hours was required until good dispersion was obtained. The pH of the aqueous dispersion medium charged with alumina hydrate was 4.1, and the effective power consumption of the stirring means (stirrer) was 0.07 kw / m ³ . In this way, an alumina dispersion was obtained.

  Further, 100 g of the dispersion was suction filtered with a filter paper having a diameter of 9 cm and an opening of 4 μm, and the residue remaining on the filter paper was visually observed to evaluate the dispersion state of the alumina dispersion. As a result, no residue was found on the filter paper, and the dispersion state was very good (evaluation: A).

  Moreover, after discharging the dispersion liquid from the tank, the adhesion state of the alumina hydrate powder in the tank was visually evaluated. As a result, almost no deposits were observed, and a small amount of deposits could be easily removed by applying washing water (evaluation; A).

<Example 2>
Dispersion was carried out in the same manner as in Example 1 except that the rotation speed of the anchor blade was 40 rotations / minute. The effective power consumption at this time was 0.02 kw / m ³ , and a dispersion time of 20 hours was required until good dispersion was obtained.

  Both the dispersion state and the state of adhesion in the tank were as good as those in Example 1 (evaluation: A).

<Example 3>
Dispersion was performed in the same manner as in Example 1 except that the liquid contact part of the dispersion tank and the stirrer was SUS304 (stainless steel). A dispersion time of 12 hours was required until a good dispersion was obtained.

  The dispersion state was as good as that of Example 1 (evaluation: A). The state of adhesion in the tank was evaluated according to the same criteria as in Example 1. As a result, deposits were found on the tank wall surface and the stirrer, and it was difficult to remove the deposits even by applying washing water (evaluation; B ).

<Example 4>
Alumina hydrate powder was charged without hanging a vacuum suction conveyance device by hanging a 600 kg flexible container on the upper part of the tank and opening and closing the damper from the lower part of the container. Three bags of containers were charged in 3 minutes, and dispersion was performed in the same manner as in Example 1. A dispersion time of 12 hours was required until a good dispersion was obtained.

  When the dispersion state was evaluated according to the same criteria as in Example 1, aggregated particles were observed on the filter paper (evaluation; B). The state of adhesion in the tank was evaluated according to the same criteria as in Example 1. As a result, deposits were found on the tank wall surface and the stirrer, and it was difficult to remove the deposits even by applying washing water (evaluation; B ).

<Example 5>
The apparatus described in FIG. 2 was used. As in Example 1, a dispersion tank having a capacity of 10 m ³ was used, an anchor blade was installed as a rotary stirrer, a circulation line for the dispersion was connected, and a circulation pump and a line mixer were installed in the circulation line. As the line mixer, a pipeline homomixer manufactured by Primix Co., Ltd. was used, and the wetted parts of the dispersion tank, the stirrer and the line mixer were made of glass lining. As in Example 1, the alumina hydrate powder was put into the dispersion tank using a vacuum suction transfer device, and after all the powder was put in, the circulation pump and line mixer were started, and the liquid was circulated in the circulation line. Went.

The stirring blade rotation speed was 60 rotations / minute, the line mixer rotation speed was 1000 rotations / minute, and a dispersion time of 6 hours was required until good dispersion was obtained. The pH of the aqueous dispersion medium charged with alumina hydrate was 4.1, and the effective power consumption of the stirring means (stirrer and line mixer) was 0.18 kw / m ³ .

  Both the dispersion state and the state of adhesion in the tank were as good as those in Example 1 (evaluation: A).

<Example 6>
Dispersion was performed in the same manner as in Example 5 except that the effective power consumption of the stirring means was changed to 0.12 kw / m ³ . It took 9 hours to obtain a good dispersion.

  Both the dispersion state and the state of adhesion in the tank were as good as those in Example 1 (evaluation: A).

<Example 7>
Dispersion was carried out in the same manner as in Example 5 except that SUS304 (stainless steel) was used as the wetted part of the dispersion tank and anchor blade. It took 6 hours to obtain a good dispersion.

  The dispersion state was as good as that of Example 1 (evaluation: A). The state of adhesion in the tank was evaluated according to the same criteria as in Example 1. As a result, deposits were found on the tank wall surface and the stirrer, and it was difficult to remove the deposits even by applying washing water (evaluation; B ).

<Example 8>
Dispersion was performed in the same manner as in Example 5 except that a flexible container was used in the same manner as in Example 4 for charging the alumina hydrate powder. It took 6 hours to obtain a good dispersion.

  When the dispersion state was evaluated according to the same criteria as in Example 1, aggregated particles were observed on the filter paper (evaluation; B). The state of adhesion in the tank was evaluated according to the same criteria as in Example 1. As a result, deposits were found on the tank wall surface and the stirrer, and it was difficult to remove the deposits even by applying washing water (evaluation; B ).

<Comparative Example 1>
Dispersion was performed in the same manner as in Example 1 except that the number of rotations of the anchor blade was 20 rotations / minute. The effective power consumption at this time was 0.007 kw / m ³ and the dispersion time was 24 hours.

  When the dispersion state was evaluated according to the same criteria as in Example 1, coarse particles were deposited on the filter paper, and it was very difficult to filter the dispersion (evaluation; C). The state of adhesion in the tank was evaluated according to the same criteria as in Example 1, and was as good as that in Example 1 (evaluation; A).

<Comparative example 2>
Dispersion was performed in the same manner as in Comparative Example 1 except that a flexible container was used in the same manner as in Example 4 for charging the alumina hydrate powder.

  When the dispersion state was evaluated according to the same criteria as in Example 1, coarse particles were deposited on the filter paper, and it was very difficult to filter the dispersion (evaluation; C). The state of adhesion in the tank was evaluated according to the same criteria as in Example 1. As a result, deposits were found on the tank wall surface and the stirrer, and it was difficult to remove the deposits even by applying washing water (evaluation; B ).

<Comparative Example 3>
Dispersion was performed in the same manner as in Example 1 except that the rotation speed of the anchor blade was set to 100 rotations / minute. The effective power consumption at this time was 0.3 kw / m ³ . When dispersed for 6 hours, an increase in the viscosity of the liquid was observed during the dispersion, and it was confirmed that the liquid remained due to insufficient stirring. In addition, it was found that this viscosity hinders the processing of the next step, and the dispersion was stopped.

  In the dispersed state, the portion where stirring was sufficient was good, but coarse particles were confirmed in the liquid retention portion (evaluation; C). The state of adhesion in the tank was evaluated according to the same criteria as in Example 1, and was as good as that in Example 1 (evaluation; A).

<Comparative example 4>
Dispersion was performed in the same manner as in Example 1 except that SUS304 (stainless steel) was used as the liquid contact part of the dispersion tank and the stirrer, and acetic acid was not added. At this time, the pH of the aqueous dispersion medium charged with the alumina hydrate was 7.4, the effective power consumption was 0.07 kw / m ³ , and the dispersion time was 24 hours.

  When the dispersion state was evaluated according to the same criteria as in Example 1, coarse particles were deposited on the filter paper, and it was very difficult to filter the dispersion (evaluation; C). The state of adhesion in the tank was evaluated according to the same criteria as in Example 1. As a result, deposits were found on the tank wall surface and the stirrer, and it was difficult to remove the deposits even by applying washing water (evaluation; B ).

<Comparative Example 5>
Dispersion was carried out in the same manner as in Example 1 except that the acid used was hydrochloric acid. At this time, the pH of the aqueous dispersion medium charged with the alumina hydrate was 2.5. When dispersed for 12 hours, an increase in the viscosity of the liquid was observed during the dispersion, and it was confirmed that the liquid remained due to insufficient stirring. In addition, it was found that this viscosity hinders the processing of the next step, and the dispersion was stopped.

  In the dispersed state, the portion where stirring was sufficient was good, but coarse particles were confirmed in the liquid retention portion (evaluation; C). The state of adhesion in the tank was evaluated according to the same criteria as in Example 1, and was as good as that in Example 1 (evaluation; A).

  The results of Examples 1 to 8 and Comparative Examples 1 to 5 are shown in Table 1.

Comparing the results of Comparative Examples 1-3 and Examples 1-8, the effective power consumption of the stirring means 0.01 kW / ^{m 3} or more, by a 0.2kw / ^{m 3} or less, the dispersion state of the alumina dispersion It turns out that becomes good. Further, when the results of Examples 1 to 8 and Comparative Examples 4 and 5 were compared, the pH of the aqueous dispersion medium into which the alumina hydrate was added was adjusted to 3.0 or more and 6.0 or less, whereby the alumina dispersion liquid It turns out that the dispersion state of becomes favorable. Comparing the results of Example 1 and Example 3, it is possible to suppress the adhesion of the alumina hydrate dispersion to the dispersion tank and the stirring means when the liquid contact part of the dispersion tank and the stirring means is made of glass lining. It is understood that it is preferable. Comparing the results of Example 1 and Example 3, the amount of alumina hydrate powder charged into the aqueous dispersion medium per minute was 30 times the total amount of alumina hydrate powder charged into the aqueous dispersion medium. It can be seen that controlling to less than or equal to mass% is preferable in terms of good dispersion of the alumina dispersion and suppression of adhesion to the tank. It can also be seen that it is preferable that the alumina hydrate powder is charged through a suction and transport type powder charging device in terms of good dispersion of the alumina dispersion and suppression of adhesion to the tank.

It is an example of the schematic of the dispersion apparatus which performs the alumina dispersion | distribution method of this invention. It is an example of the schematic of the dispersion apparatus which performs the alumina dispersion | distribution method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dispersion tank 2 Rotary stirrer 3 Stirring motor 4 Powder input hopper 5 Powder input line 6 Powder transport device 7 Tank discharge valve 8 Circulation pump 9 Line mixer 10 Circulation line

Claims (4)

A method for producing an alumina dispersion containing an alumina hydrate powder and an aqueous dispersion medium,
A charging step of charging the alumina hydrate powder into an aqueous dispersion medium in a dispersing device;
A dispersion step of dispersing the alumina hydrate powder in the aqueous dispersion medium by stirring the aqueous dispersion medium with stirring means provided in the dispersion apparatus;
The pH of the aqueous dispersion medium charged with the alumina hydrate is 3.0 or more and 6.0 or less,
The effective power consumption of the stirring of the agitating means, 0.01 kW / ^{m 3} or more, a manufacturing method of alumina dispersion, characterized in that at 0.2kw / ^{m 3} or less.   The amount of charge per minute of the alumina hydrate powder to the aqueous dispersion medium is controlled to 30% by mass or less of the total amount of charge of the alumina hydrate powder to the aqueous dispersion medium. A method for producing an alumina dispersion.   The method for producing an alumina dispersion liquid according to claim 1 or 2, wherein the alumina hydrate powder is introduced into an aqueous dispersion medium through a suction transportation type powder injection apparatus.   The method for producing an alumina dispersion according to any one of claims 1 to 3, wherein the liquid contact part of the dispersion tank and the stirring means is made of glass lining.

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