JPH11116237A - Production of crystalline aluminum hydroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high purity aluminum hydroxide by adding a supersaturated aluminate solution into a mixed suspension of a mother liquor having specific concentration of total sodium hydroxide and aluminum with a crystalline aluminum hydroxide to perform crystallization reaction. SOLUTION: The mother liquor having 50-700 g/l total sodium hydroxide concentration and 0-300 g/l aluminum concentration is fed to a crystallization reaction vessel and the temp. is setted to a prescribed temp. in a range of 10-200 deg.C. Next the crystalline aluminum hydroxide is charged into the crystallization reaction vessel, controlled to have a prescribed concentration and kept as it is for 1-48 hr to dissolve a part of aluminum hydroxide and after that, the crystalline aluminum hydroxide is crystallized by mixing the supersaturated sodium aluminate solution intermittently, continuously and peridically with at least >=3 hr, preferably >= 12 hr interval and setting to a crystallization temp. to perform the crystallization reaction and the liquid after the crystallization is used for an etchant for an etching process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method wherein a seed crystal is charged into a crystallization reaction tank, and a supersaturated sodium aluminate solution is intermittently continued at intervals of at least 3 hours (preferably 12 hours or more). The present invention relates to a method for producing crystalline aluminum hydroxide having high mechanical strength, which is supplied periodically to crystallize crystalline aluminum hydroxide from a supersaturated sodium aluminate solution.

[0002]

2. Description of the Related Art The surface of an aluminum plate used as a support of a lithographic printing plate is etched with an aqueous solution of caustic soda before and after mechanically or electrochemically roughening the surface. In addition, for example, nitric acid and hydrochloric acid are used in the step of electrochemically roughening the surface of the aluminum plate, and sulfuric acid is used in the anodic oxidation step, and various treatment liquids are used for the surface treatment of the aluminum support. Have been. Depending on the aluminum ion concentration in the treatment solution used for such a surface treatment, the surface shape of the treated aluminum support after the treatment greatly varies, and the effect of the aluminum ion concentration in the solution on the quality of the aluminum support is significant. large.

As described above, the aluminum ion concentration in the processing solution has a great effect on the quality of the aluminum support for a printing plate. Therefore, it is important to keep the aluminum ion concentration in the processing solution constant at a predetermined concentration. . Conventionally, in order to keep the aluminum ion concentration constant, the processing solution in the treatment system is discharged to the outside of the system to keep the aluminum ion concentration constant, or as described in JP-A-57-192300. It has been common practice to use a resin to adsorb aluminum ions in a treatment solution to an ion exchange resin and keep the aluminum ion concentration constant. However, the method of adjusting the outside of the system so as to keep the aluminum ion concentration constant by discharging the processing solution in the processing system out of the system requires that the processing solution be discharged out of the system, and the amount of the processing solution used is reduced. There is a problem that the number of waste liquids becomes extremely large, and the load of waste liquid treatment is large.

The aluminum sash material is also etched with caustic soda in a process of matting the surface of the material or forming an anodic oxide film to improve the durability. Due to the large volume of the solution, it is necessary to recover the aluminum hydroxide from the etching solution. In addition, as a result of various surface treatments such as surface strengthening treatment by anodic oxidation using sulfuric acid, the necessity of recovering aluminum hydroxide from sludge generated by neutralizing waste liquid and the concentration of aluminum ion in the surface treatment agent The recovery of aluminum ions and the like performed for management is a problem that is the same as the case of waste liquid treatment in the surface treatment step of the aluminum support for a printing plate.

As described above, in the process of manufacturing alumina, the process of manufacturing a lithographic printing plate, and the process of manufacturing an aluminum sash, the process of controlling the aluminum ion concentration is an important problem.

[0006] In the process of producing alumina from bauxite, the process of obtaining a purified sodium aluminate solution from a supersaturated sodium aluminate solution to produce aluminum hydroxide has heretofore been carried out by the sedimentation method using a thickener as described above. A method of sedimenting crystals to remove impurities from a supersaturated sodium aluminate solution has been used.However, since the crystals of the impurities are fine, a long time is required for sedimentation, and a large sedimentation area is required. is there. In addition, very fine crystals of impurities (those which can be regarded as almost liquid) cannot be sufficiently removed, so that it takes as long as 42 to 72 hours to crystallize the aluminum hydroxide, and moreover, the purified sodium aluminate solution Poor purity and poor crystal deposition rate. Furthermore, in order to separate sodium ions and aluminum ions from the sodium aluminate solution, the present inventors have previously proposed the diffusion of aluminum ions out of the system by diffusion dialysis using an ion-exchange membrane (Japanese Unexamined Patent Publication No. 1-200992).
Publication). However, in the case of diffusion dialysis,
Removal of insoluble metals such as iron adhering to the membrane and scale of aluminum hydroxide etc. adhere to the waste liquid side after diffusion dialysis. However, there is a problem that the number increases.

A method for obtaining an aluminum hydroxide crystal and a sodium aluminate solution from a supersaturated sodium aluminate solution by a crystallization method, particularly, a method for crystallizing aluminum hydroxide from a supersaturated sodium aluminate solution by a crystallization method and after crystallization As a method for maintaining the aluminum ion concentration of an etching solution or the like at a predetermined concentration by reusing the above solution as an etching solution in the etching step, a method as described in JP-A-5-279020 is known. . However, particulate crystalline aluminum hydroxide which is a general industrial product (generally 1 μm to 150 μm unless otherwise specified)
m. ) And JP-A-5-279020
When the crystalline aluminum hydroxide obtained by the method described in the publication is pump-circulated in the form of a slurry, a part of the secondary crystal may be broken into the primary crystal or the primary crystal may be further reduced due to an external force received from the pump. Hereinafter, when no error occurs, the crystalline aluminum hydroxide may be simply referred to as aluminum hydroxide. Also, when aluminum hydroxide is used as an abrasive, general industrial products such as aluminum hydroxide and JP-A-5-2790
When aluminum hydroxide obtained by the method described in Japanese Patent Publication No. 20 is used as a polishing agent, the polishing life is extremely short compared to polishing agents other than aluminum hydroxide, and the consumption of aluminum hydroxide becomes enormous. There was a problem.

[0008]

The problem to be solved by the present invention in producing aluminum hydroxide and purified sodium aluminate solution by a hydrolysis reaction from a supersaturated sodium aluminate solution is to reduce the strength of the aluminum hydroxide. The goal is to obtain high purity aluminum hydroxide that is improved and meets a wider need. Further, in the case where the surface of a lithographic printing plate aluminum plate is subjected to an etching treatment using sodium hydroxide, or a surface treatment is carried out using various treatment solutions of acids and alkalis, the problem to be solved by the present invention is as follows. To keep the quality of surface etching and surface treatment good and uniform, keep the aluminum ion concentration in the treatment solution at a predetermined concentration and effectively use aluminum hydroxide discharged from the surface treatment process in large quantities. Is to re-use it.

[0009]

The above objects can be attained by the method for producing aluminum hydroxide of the present invention and the method for treating the surface of a printing support using the method. (A) In a method for producing crystalline aluminum hydroxide in which aluminum hydroxide is crystallized by a hydrolysis reaction from a supersaturated sodium aluminate solution, the total caustic soda concentration is 50 to 700 g / l and the aluminum concentration is 0 to 0.
After maintaining the liquid temperature of the mixed suspension of the mother liquor and the crystalline aluminum hydroxide of 300 g / liter at a temperature of 10 ° C. to 200 ° C. for at least 1 to 48 hours, the supersaturated sodium aluminate solution is kept for at least 3 hours ( Preferably 1
A method for producing crystalline aluminum hydroxide, characterized in that it is supplied intermittently at regular intervals at intervals of 2 hours or more) and is subjected to a crystallization reaction at a crystallization reaction temperature. (B) In a method for producing crystalline aluminum hydroxide in which aluminum hydroxide is crystallized by a hydrolysis reaction from a supersaturated sodium aluminate solution, the crystalline aluminum hydroxide is etched in advance to obtain an average particle diameter (median diameter).
After the thing of 1 μm to 50 μm (preferably 15 μm) is put into the crystallization reaction tank as an initial seed crystal, a supersaturated sodium aluminate solution is provided at intervals of at least 3 hours (preferably 12 hours or more). A method for producing crystalline aluminum hydroxide, characterized in that aluminum hydroxide is crystallized at a crystallization reaction temperature by continuously and intermittently supplying the aluminum hydroxide.

(C) In a method for producing crystalline aluminum hydroxide, in which aluminum hydroxide is crystallized by a hydrolysis reaction from a supersaturated sodium aluminate solution, the crystalline aluminum hydroxide is pulverized and etched in advance to obtain an average particle size. (Median diameter) 1 μm to 50 μm (preferably 15 μm
μm) as an initial seed crystal and charged into the crystallization reaction tank, and then a supersaturated sodium aluminate solution is continuously intermittently provided with an interval of at least 3 hours (preferably 12 hours or more). A method for producing crystalline aluminum hydroxide, comprising periodically supplying and crystallizing aluminum hydroxide at a crystallization reaction temperature to crystallize aluminum hydroxide. (D) In a method for producing crystalline aluminum hydroxide, in which aluminum hydroxide is crystallized by a hydrolysis reaction from a supersaturated sodium aluminate solution, a method in which crystalline aluminum hydroxide is powdered in advance at 80 ° C. to 200 ° C. After maintaining the temperature for at least 1 hour to 48 hours, the initial seed crystal is introduced into the crystallization reaction tank, and then the supersaturated sodium aluminate solution is intermittently spaced at least 3 hours (preferably 12 hours or more). A method for producing crystalline aluminum hydroxide, wherein the aluminum hydroxide is supplied continuously and periodically to crystallize aluminum hydroxide. (E) In a method for producing crystalline aluminum hydroxide, in which aluminum hydroxide is crystallized by a hydrolysis reaction from a supersaturated sodium aluminate solution, a crystal aluminum hydroxide which is hard to be etched as a seed crystal is used as an initial seed crystal. After charging into the precipitation reaction tank, the supersaturated sodium aluminate solution is supplied for at least 3 hours (preferably 12 hours or more).
A method for producing crystalline aluminum hydroxide, wherein the aluminum hydroxide is supplied intermittently at regular intervals to crystallize aluminum hydroxide.

(F) In the surface treatment of the aluminum plate, a part of the treatment solution containing the sodium aluminate solution to be circulated for the surface etching treatment and neutralization of waste acid and waste alkali discharged from the surface treatment step of the aluminum plate A method of mixing aluminum sludge containing non-crystalline aluminum hydroxide as a main component, which is produced, is adjusted to a supersaturated sodium aluminate solution, and aluminum hydroxide is crystallized from the supersaturated sodium aluminate solution by a hydrolysis reaction. The aluminum is separated from a part of the processing solution containing the sodium aluminate solution to be recycled and used outside the system, and crystallization is previously performed in the surface treatment method of the aluminum support in which the aluminum ion concentration in the processing solution is maintained at a predetermined concentration. In the reaction vessel, the total caustic soda concentration is 50 to 700 g / liter, and the aluminum concentration is 0 to 300 g / liter. The mother liquor and the crystallized aluminum hydroxide are charged, and the solution temperature is maintained at a temperature of 10 ° C. to 200 ° C. for at least 1 to 48 hours. Then, the supersaturated sodium aluminate solution is added for at least 3 hours (preferably 12 At a crystallization reaction temperature, crystallize aluminum hydroxide, and etch the liquid after crystallization in the etching process. A surface treatment method for an aluminum support, which is reused as a liquid.

(G) In the surface treatment method for an aluminum support for maintaining the aluminum ion concentration in the surface treatment solution at a predetermined concentration as described in (f) above, on the surface of the aluminum material, the crystalline aluminum hydroxide is etched in advance. After the initial seed crystal having an average particle diameter (median diameter) of 1 μm to 50 μm (preferably 15 μm) is charged into the crystallization reaction tank, a supersaturated sodium aluminate solution is added for at least 3 hours (preferably 12 μm). At a crystallization reaction temperature to cause crystallization reaction, crystallize aluminum hydroxide, and re-use the solution after crystallization as an etching solution. A surface treatment method for an aluminum support for a printing plate, which is used. (H) In the surface treatment of the aluminum material, the above (f)
In the surface treatment method for an aluminum support, wherein the aluminum ion concentration in the surface treatment solution is kept at a predetermined concentration, crystalline aluminum hydroxide is pulverized and etched in advance to have an average particle diameter (median diameter) of 1 μm to 50 μm (desirably). 15 μm) as an initial seed crystal was charged into the crystallization reactor, and then a supersaturated sodium aluminate solution was intermittently continued at intervals of at least 3 hours (preferably 12 hours or more). The aluminum support for the printing plate is characterized in that the crystallization reaction is carried out at a crystallization reaction temperature, the crystallization reaction is carried out, the aluminum hydroxide is crystallized, and the liquid after crystallization is reused as an etching solution. Surface treatment method.

(I) In the surface treatment of an aluminum material, the method of (f), wherein the aluminum ion concentration in the surface treatment solution is maintained at a predetermined concentration, wherein the aluminum support has a predetermined concentration. 8
After being kept at a temperature of 0 ° C. to 200 ° C. for at least 1 hour to 48 hours, the initial seed crystal is introduced into a crystallization reaction tank, and then a supersaturated sodium aluminate solution is added for at least 3 hours (preferably 12 hours or more). A surface of an aluminum support for a printing plate, characterized in that aluminum hydroxide is crystallized and the crystallized solution is reused as an etching solution while being supplied intermittently and periodically at intervals. Processing method. (J) In the surface treatment of the aluminum material, (f)
In the surface treatment method for an aluminum support for maintaining the aluminum ion concentration in the surface treatment solution at a predetermined concentration according to the above, after the crystalline aluminum hydroxide which is difficult to be etched is charged into a crystallization reaction tank as an initial seed crystal A supersaturated sodium aluminate solution is intermittently and periodically supplied at intervals of at least 3 hours (preferably 12 hours or more) to crystallize aluminum hydroxide and to remove the liquid after crystallization. A method for treating a surface of an aluminum support for a printing plate, wherein the method is reused as an etching solution.

(K) Neutralization of a part of a treatment solution containing a sodium aluminate solution to be circulated for surface etching and waste acid and waste alkali discharged from the surface treatment step of the aluminum plate during the surface treatment of the aluminum plate. A method of mixing aluminum sludge containing non-crystalline aluminum hydroxide as a main component, which is produced, is adjusted to a supersaturated sodium aluminate solution, and aluminum hydroxide is crystallized from the supersaturated sodium aluminate solution by a hydrolysis reaction. The aluminum is separated from a part of the processing solution containing the sodium aluminate solution to be recycled and used outside the system, and the surface treatment method of the aluminum support for maintaining the aluminum ion concentration in the processing solution at a predetermined concentration is previously crystallized. In the reaction vessel, the total caustic soda concentration is 50 to 700 g / liter and the aluminum concentration is 0 to 30. The mother liquor and a crystalline aluminum hydroxide which is g / liter was charged, the solution temperature 10 ° C. to 200 DEG
After holding at a temperature of at least 1 hour to 48 hours,
The supersaturated sodium aluminate solution is supplied intermittently and continuously at intervals of at least 3 hours (preferably 12 hours or more), and the crystallization reaction is performed at the crystallization reaction temperature. Wherein the solution after crystallization is reused as an etching solution in an etching step. (L) In the surface treatment of the aluminum material, the above (k)
In the surface treatment method for an aluminum support for maintaining the aluminum ion concentration in the surface treatment solution at a predetermined concentration according to the above, the seed crystal according to any one of the above (g) to (j) is crystallized in advance. After that, the supersaturated sodium aluminate solution is supplied intermittently at regular intervals for at least 3 hours (preferably at intervals of 12 hours or more), and the crystallization reaction is performed at the crystallization reaction temperature. A method of crystallizing aluminum hydroxide and reusing the solution after crystallization as an etching solution.

In the present invention, aluminum hydroxide having a ring-shaped internal structure is formed by periodically changing the crystal growth rate at intervals of at least 3 hours (preferably 12 hours or more), thereby forming the ring inside the crystal. Is generated. Aluminum hydroxide having such an annual ring-shaped internal structure has a dense portion that is hardly etched and has very few defects, and a sparse portion having relatively many defects is periodically present. For this reason, the aluminum hydroxide crystal is a crystal having a crystal structure that does not progress cracks at the time of fracture and has high strength against external force and is hard to be etched by a sodium hydroxide solution as described with reference to FIG. Means FIG.
Was manufactured by supplying a sample CR-4000TYPE which is an example of an aluminum hydroxide crystal having a ring-shaped internal structure used for crystallization of the aluminum hydroxide of the present invention and a supersaturated sodium aluminate solution continuously overnight. CR-400
When 0 is dissolved in a sodium hydroxide solution having a concentration of 100 g / liter (the initial aluminum concentration is zero equivalent / liter) at a temperature of 65 ° C., the relationship between the weight loss expressed as a percentage of the weight loss of dissolution / percentage of the original sample and the time is shown. It is a graph shown. FIG.
More specifically, the sample CR-4000TYPE of the present invention was CR-40.
It can be seen that the film is hardly etched by the caustic soda solution from 00.

[0016]

DETAILED DESCRIPTION OF THE INVENTION The method for producing aluminum hydroxide according to the present invention (a) will be described. In the production method described in the above (a), a mother liquor having a composition having a total caustic soda concentration of 50 to 700 g / l and an aluminum concentration of 0 to 300 g / l is charged into the crystallization reaction tank, and the liquid temperature is raised to 10 to 200 ° C. The temperature is set to a predetermined temperature between ℃ and the crystallized aluminum hydroxide is charged to this tank to obtain a predetermined concentration, and is maintained for a predetermined time to partially dissolve the aluminum hydroxide. The soda solution is intermittently and periodically supplied at intervals of at least 3 hours (preferably 12 hours or more), set to the crystallization reaction temperature, and subjected to the crystallization reaction.

Next, the method for producing aluminum hydroxide described in the above (b) will be described. In the manufacturing method described in (b), aluminum hydroxide is etched in a caustic soda solution in a seed crystal dissolving step. By etching in a caustic soda solution, the aluminum hydroxide is broken into primary crystals or a portion having many defects is dissolved, and as a result, aluminum hydroxide which is hard to be etched is obtained, and furthermore, at least 3 hours (preferably 12 hours) At intervals of the above), supersaturated sodium aluminate is supplied intermittently and periodically to set the crystallization reaction temperature, and by crystallization reaction, when supersaturated sodium aluminate is not supplied, It is presumed that denser aluminum hydroxide with higher strength is obtained because the growth becomes slow. Also,
In the manufacturing method described in (c), the crystalline aluminum hydroxide is crushed in advance to a predetermined size before the step of etching in a caustic soda solution in the manufacturing method described in (b), and the etching is easily performed. After being brought into a state, the aluminum hydroxide is etched in a caustic soda solution in a seed crystal dissolving step, and as a result, aluminum hydroxide which is hard to be etched is obtained. Further, at intervals of at least 3 hours (preferably 12 hours or more), supersaturated sodium aluminate is supplied intermittently and periodically to set the crystallization reaction temperature, and the crystallization reaction is performed. When supersaturated sodium aluminate is not supplied, it is presumed that the growth becomes slow, so that a dense aluminum hydroxide having higher strength can be obtained. Further, in the manufacturing method described in (d), the aluminum hydroxide is heated to a predetermined temperature in an electric furnace with the aluminum hydroxide in powder form, and is maintained at that temperature. As a result, aluminum hydroxide that is difficult to be etched is obtained. In addition, at least 3
At intervals of time (preferably 12 hours or more), supersaturated sodium aluminate is supplied intermittently and regularly, and the crystallization reaction temperature is set. When soda is not supplied, the growth is slowed down, and it is assumed that denser aluminum hydroxide with higher strength is obtained.

As described above, by etching aluminum hydroxide in a caustic soda solution in the seed crystal dissolving step by the processing method described in the above (b) to (c), aluminum hydroxide which is hard to be etched is obtained. It is inferred. Aluminum hydroxide that is difficult to be etched as described above, or aluminum hydroxide that is presumed to be difficult to be etched, is used as an initial seed crystal in a crystallization reaction tank from a supersaturated sodium aluminate solution by a hydrolysis reaction to form aluminum hydroxide. By crystallizing,
Aluminum hydroxide with few defects and high strength against external force is obtained.Moreover, supersaturated sodium aluminate is supplied intermittently and the crystallization reaction temperature is set. When soda is not supplied, since the growth is slow, crystalline aluminum hydroxide having fewer defects and strong strength against external force can be obtained.

In the method for treating the surface of an aluminum plate or the surface of an aluminum material according to the present invention, a part of a treatment solution containing a sodium aluminate solution to be circulated and used for a surface etching treatment and waste acid discharged from the surface treatment step; By applying the method of the present invention to a supersaturated sodium aluminate solution prepared from aluminum sludge containing non-crystalline aluminum hydroxide as a main component generated during the neutralization of waste alkali to produce aluminum hydroxide, Aluminum hydroxide with high purity and high purity that meets wider needs can be obtained. In the method for surface treating an aluminum plate or the method for treating an aluminum material, the supersaturated sodium aluminate solution described in
By applying the method described in Japanese Patent No. 279020 to remove impurities from the supersaturated sodium aluminate solution, and applying the method of the present invention to produce aluminum hydroxide, it is stronger and more suitable for a wider range of needs. Thus, highly pure aluminum hydroxide can be obtained.

In the surface treatment method of an aluminum plate or the surface treatment of an aluminum material, as described above, obtaining a homogeneous and high-purity aluminum hydroxide from a supersaturated sodium aluminate solution means that a homogeneous and high-purity water solution is simultaneously obtained. This means that the aluminum oxide solution is recovered, and thus greatly contributes to the stabilization of the entire surface treatment process. Also, the recovered aluminum hydroxide, for example, when used as an abrasive, can be adapted to a wide range of needs because it has a longer life and superior quality than aluminum hydroxide which is a general industrial product. .

In the step of producing aluminum hydroxide from bauxite of the present invention shown in FIG. 1, impurities are removed from the sodium aluminate solution produced in the flash tank 42 by using a centrifugal sedimentation machine equipped with a separation plate, and the supply liquid stock tank 45A is removed. After the primary storage, the supersaturated sodium aluminate solution is intermittently and periodically added to the crystallization reaction tank 45 at intervals of at least 3 hours (preferably 12 hours) as a supersaturated sodium aluminate solution. The seed crystal was separately adjusted in advance in a seed crystal dissolving tank 46, and the seed crystal was added to the crystallization reaction tank 45. Then, a supersaturated sodium aluminate solution was continuously added intermittently. In the precipitation reaction tank 45, supersaturated sodium aluminate is hydrolyzed to crystallize aluminum hydroxide. The techniques for adjusting the seed crystal described in the above (a) to (c) are techniques for adjusting the seed crystal performed in the seed crystal dissolving tank 46. In the method described in (d), the aluminum hydroxide is heated in the air in a powder state. In the step of producing aluminum hydroxide from bauxite of the present invention shown in FIG. 2, a seed crystal which is hardly etched and prepared in advance is added as an initial seed aluminum hydroxide to crystallize aluminum hydroxide. [This is an application example of the method for producing aluminum hydroxide described in (e). The reference numerals in FIG. 2 are the same as those in FIG.

Next, referring to FIG. 3, the above (f) to (i)
The surface treatment method for an aluminum support for a printing plate of the present invention described in the above section will be described. In the etching treatment in the etching treatment tank 11 of the surface treatment method of the present invention shown in FIG. 3, the treatment liquid is prepared in the liquid preparation tank 5, and the prepared processing liquid passes through the liquid supply pipe 12 using the liquid supply pump 4. Is sent to the spray 3 in the etching tank 11. The etching treatment liquid from the liquid preparation tank 5 can be further sent to the dissolution tank 34 through the liquid supply pipe 13 branched from the liquid supply pipe 12. The amount of liquid supply and the timing of liquid supply can be adjusted by operating a valve (not shown) provided in the middle of the pipe, so that at least 3 hours (preferably 12
It is possible to supply and add supersaturated sodium aluminate intermittently at regular intervals (at least an hour).

The liquid preparation tank 5 and the etching tank 11 are connected by a liquid supply pipe 12 and a return pipe 14.
The etching treatment liquid is circulated between them. During the etching treatment, the sodium hydroxide component in the treatment liquid decreases by the reaction, the aluminum ion content increases, and the water evaporates and decreases. Amounts and ingredient concentrations vary. For this reason, although the sodium hydroxide solution and the water are supplied to the processing liquid in the liquid preparation tank 5 through the supply pipes 21 and 22, respectively, the aluminum ions in the processing liquid are supplied by the supply liquid without removing the increasing aluminum ions. It is wasteful to maintain at a predetermined concentration.

For this reason, a part of the circulating treatment liquid in the liquid preparation tank 5 is supplied to the dissolution tank 34 through the liquid supply pipe 13 in a timely manner to remove aluminum ions from the system. On the other hand, the aluminum sludge 16 converts pH of waste alkali 30 and waste acid 31, 32, 33 discharged from each surface treatment step to pH.
Neutralization is performed in the adjusting tank 27 and coagulation and precipitation are performed in the coagulation and sedimentation tank 28. Further, solid-liquid separation is performed by a filter press 29, and the solid is separated and sent to a dissolution tank 34 as needed.

In the dissolving tank 34, the etching solution, aluminum sludge 16 and water 19 are mixed as required to adjust supersaturated sodium aluminate. If necessary, impurities such as calcium are added to the slide thickener 36 and the filter 35. Removed. The supersaturated sodium aluminate solution from which impurities have been removed is intermittently and periodically added to the crystallization reaction tank 7 at intervals of at least 3 hours (preferably 12 hours or more). Supply and add. In the surface treatment method for an aluminum support for a printing plate of the present invention described in the above (f) to (i), the above (a) to (c) may be carried out in a separately provided crystallization dissolution tank (not shown). After the seed crystal prepared by the method described in (1) is added to the crystallization reaction tank 7, the supersaturated sodium aluminate solution is intermittently continuously provided at least for 3 hours (preferably 12 hours or more). Aluminum hydroxide is crystallized from the sodium aluminate solution by a hydrolysis reaction in the crystallization reaction tank 7 by supplying and adding periodically, and the aluminum ion concentration is reduced by the crystallization. It becomes a mixed recovery liquid. A mixture of a treatment solution mainly containing sodium hydroxide and crystals of aluminum hydroxide is sent to a thickener 8 by a liquid sending pipe 17, and the crystallized aluminum hydroxide is syneresis in a drum filter 9 through a pipe 18. , Collected in the hopper 10. On the other hand, the processing liquid mainly containing a sodium hydroxide solution passes through the recovery pipe 20 as a recovery liquid, and is returned to the liquid preparation tank 5 after concentration adjustment as necessary. On the other hand, the aluminum hydroxide collected in the hopper 10 is supplied to the polishing liquid adjusting tank 47 as needed as an abrasive in the mechanical roughening step. In the surface treatment method for an aluminum support for a printing plate of the present invention described in (j), the seed crystal to be added to the crystallization reaction tank 7 is a previously prepared hard-to-etch seed crystal, and the above (f) to It is the same as the surface treatment method of the aluminum support for a printing plate of the present invention described in (i).

[0026]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. Example 1 The results of the case where the surface treatment of the aluminum plate was performed while modifying the aluminum hydroxide sludge under the following conditions using the apparatus having the arrangement shown in FIG. Aluminum surface treatment conditions Aluminum plate width: 1000 mm Processing speed: 50 m / min Crystallization conditions Crystallization tank temperature: 55 ° C Crystallized liquid concentration: Total NaOH 100 g / liter Aluminum 15 to 20 g / liter (change periodically) Crystallized seed crystal concentration: 100 g / l Initial seed crystal condition Aluminum hydroxide: H-W (trade name; manufactured by Showa Denko KK) Seed crystal solution concentration: Total NaOH 100 g / l Aluminum 20 g / l seed crystal solution Temperature: 75 ° C. In FIG. 5, aluminum hydroxide HW, which is a general industrial raw material, was previously prepared as the initial seed crystal conditions, and total NaOH (100 g) was prepared.
/ Liter), and a crystal structure when a seed crystal (aluminum hydroxide) treated in a mother liquor of aluminum (0 g / liter) at 75 ° C. for 10 minutes is grown while periodically changing the concentration of the crystallization liquid. Cross section scanning electron microscope (SE
M) A photograph is shown. From this photograph, it can be seen that the crystalline aluminum hydroxide obtained in this example had an annual ring-shaped internal structure.

COMPARATIVE EXAMPLE 1 For the purpose of comparison with Example 1, aluminum hydroxide, which is a general industrial product, was used as an initial seed crystal under the conditions shown in FIG. Table 1 shows the results when the surface treatment of the aluminum plate was performed while the aluminum sludge was modified. Aluminum surface treatment conditions Aluminum plate width: 1000 mm Processing speed: 50 m / min Crystallization conditions Precipitation tank temperature: 55 ° C. Crystallized liquid temperature: Total NaOH 100 g / L Aluminum 20 g / L (continuous supply for 24 hours) Crystal concentration: 100 g / L Initial seed crystal conditions Aluminum hydroxide: HW (manufactured by Showa Denko KK) Seed solution concentration: Total NaOH 100 g / L Aluminum 20 g / L Seed solution temperature: 75 ° C

[0028]

[Table 1]

FIG. 6 shows that, as the initial seed crystal condition, aluminum hydroxide HW, which is a general industrial raw material, was previously prepared.
A seed crystal (aluminum hydroxide) treated at 75 ° C. for 10 minutes in a mother liquor of H (100 g / l) and aluminum (0 g / l) was continuously supersaturated for 24 hours so that the concentration of the crystallization liquid was always constant. Supply sodium aluminate,
5 shows an SEM photograph of a cross section showing a crystal structure when a crystal is grown. SE of cross section showing aluminum hydroxide crystal structure
The M photograph shows that after embedding aluminum hydroxide in a resin and buffing, etching with about 10% solution of caustic soda for 10 minutes, washing with 10% solution of nitric acid for 1 minute, and crystal after washing with water by SEM It was taken. As is clear from this photograph, the aluminum hydroxide obtained in this comparative example does not show an annual ring-shaped internal structure.

[0030]

The crystalline aluminum hydroxide obtained by the method of the present invention for crystallizing aluminum hydroxide from a supersaturated sodium aluminate solution by a hydrolysis reaction according to the present invention has an unprecedented strength. The secondary crystals are not easily broken by external force. This has made it possible to use the aluminum hydroxide obtained in a wider range as an industrial raw material. In the surface treatment method of the aluminum material or the aluminum support for a printing plate of the present invention, the crystalline aluminum hydroxide obtained by the above method is used as an abrasive for surface treatment of the aluminum material or the aluminum plate. As a result, the polishing life was greatly increased as compared with the general industrial material aluminum hydroxide. As described above, the present invention greatly contributes to improving the quality of crystalline aluminum hydroxide and reducing the cost of equipment for surface treatment of an aluminum material or an aluminum plate.

[Brief description of the drawings]

FIG. 1 is a schematic structural diagram of a new alumina production step by an aluminum hydroxide production method of the present invention using a seed crystal prepared in advance by the method of the present invention.

FIG. 2 is a schematic configuration diagram of a new alumina production process by an aluminum hydroxide production method of the present invention using a seed crystal that is difficult to be etched.

FIG. 3 is a schematic configuration diagram of a surface treatment step of an aluminum support for a printing plate by the method for producing a sodium aluminate solution of the present invention.

FIG. 4 is a graph comparing the solubility of aluminum hydroxide produced by the methods of Example 1 and Comparative Example 1 of the present invention in a sodium hydroxide solution.

FIG. 5: Aluminum hydroxide H, a common industrial product
3 is a scanning microscope (SEM) photograph showing a crystal structure of a cross section of a seed crystal when -W is treated with caustic soda and then grown according to Example 1.

FIG. 6: Aluminum hydroxide H, a general industrial product
5 is an SEM photograph showing a crystal structure of a cross section of a seed crystal when -W is subjected to a caustic soda treatment and then subjected to crystal growth according to Comparative Example 1.

[FIGS. 1 and 2]

 Reference Signs List 40 ball mill 41 digester 42 flash tank 44 centrifugal settler with separator plate 45 crystallization reaction tank 45A supply liquid stock tank 46 seed crystal dissolution tank [Fig. 3] 5 liquid preparation tank 7 crystallization reaction tank 8 thickener 9 drum filter 10 hydroxylation Aluminum hopper 11 Etching treatment tank 15 Electrolytic treatment tank 20 Recovered liquid 25 Anodizing tank 28 Coagulation settling tank 29 Filter press 34 Dissolution tank 35 Filter 36 Sludge thickener 38 Evaporation tube 47 Polishing liquid preparation tank

Claims (12)

[Claims] 1. A method for producing a crystalline aluminum hydroxide, wherein aluminum hydroxide is crystallized from a supersaturated sodium aluminate solution by a hydrolysis reaction, wherein the total caustic soda concentration is 50 to 700 g / l and the aluminum concentration is 0 to 300 g / l. After maintaining the liquid temperature of the mixed liquor of mother liquor and crystalline aluminum hydroxide at 10 ° C. to 200 ° C. for at least 1 to 48 hours, the supersaturated sodium aluminate solution is added for at least 3 hours. A method of producing a crystalline aluminum hydroxide, comprising: intermittently intermittently mixing, periodically mixing, and causing a crystallization reaction at a crystallization reaction temperature. 2. In a method for producing crystalline aluminum hydroxide, wherein aluminum hydroxide is crystallized from a supersaturated sodium aluminate solution by a hydrolysis reaction, the crystalline aluminum hydroxide is etched in advance to obtain an average particle diameter (median diameter). An initial seed crystal having a size of 1 μm to 50 μm is used as an initial seed crystal, and the supersaturated aluminate solution is intermittently and continuously mixed at intervals of at least 3 hours to be crystallized at a crystallization reaction temperature. For producing crystalline aluminum hydroxide. 3. A method for producing crystalline aluminum hydroxide in which aluminum hydroxide is crystallized from a supersaturated sodium aluminate solution by a hydrolysis reaction, wherein the crystalline aluminum hydroxide is pulverized in advance to obtain an average particle diameter (median diameter). 1
The initial seed crystal having a diameter of 50 μm to 50 μm is used as the initial seed crystal, and the supersaturated aluminate solution is intermittently and continuously mixed at intervals of at least 3 hours to form a crystal at the crystallization reaction temperature. A method for producing crystalline aluminum hydroxide, which is characterized by: 4. A method for producing crystalline aluminum hydroxide, wherein aluminum hydroxide is crystallized from a supersaturated sodium aluminate solution by a hydrolysis reaction. After holding at a temperature of at least 1 hour to 48 hours as an initial seed crystal in a crystallization reaction tank, a supersaturated sodium aluminate solution is intermittently and periodically intermittently spaced at least 3 hours. A method for producing a crystalline aluminum hydroxide, comprising: supplying the aluminum hydroxide to the solution and crystallizing the aluminum hydroxide. 5. A method for producing a crystalline aluminum hydroxide, wherein aluminum hydroxide is crystallized from a supersaturated sodium aluminate solution by a hydrolysis reaction. After being charged into a crystallization reaction tank, a supersaturated sodium aluminate solution is supplied intermittently at regular intervals of at least 3 hours to crystallize aluminum hydroxide. Surface treatment method for aluminum support. 6. In the surface treatment of an aluminum plate, a part of a treatment solution containing a sodium aluminate solution to be circulated for surface etching treatment and neutralization of waste acid and waste alkali discharged from the surface treatment step of the aluminum plate. The resulting solution is mixed with aluminum sludge containing non-crystalline aluminum hydroxide as a main component to adjust the solution to a supersaturated sodium aluminate solution, and then hydrated by a hydrolysis reaction from the supersaturated sodium aluminate solution in a crystallization reactor. Aluminum is crystallized, and aluminum is separated out of the system from a part of the processing solution containing the sodium aluminate solution to be recycled,
In the surface treatment method for an aluminum support, in which the aluminum ion concentration in the treatment liquid is maintained at a predetermined concentration, a mother liquor having a total caustic soda concentration of 50 to 700 g / l and an aluminum concentration of 0 to 300 g / l in a crystallization reaction tank in advance. Liquid temperature of the mixed suspension of
C. to 200.degree. C. for at least 1 hour to 48 hours, and then continuously supply the supersaturated sodium aluminate solution intermittently at intervals of at least 3 hours at a crystallization reaction temperature. A surface treatment method for an aluminum support, wherein a crystallization reaction is performed to crystallize aluminum hydroxide, and a liquid after crystallization is reused as an etching liquid in an etching step. 7. A method for surface treatment of an aluminum support according to claim 6, wherein the surface treatment of the aluminum plate is carried out by etching the crystalline aluminum hydroxide in advance. After the initial seed crystal having an average particle diameter (median diameter) of 1 μm to 50 μm is charged into the crystallization reaction tank, the supersaturated sodium aluminate solution is intermittently continued at intervals of at least 3 hours. Aluminum for a printing plate, characterized in that it is supplied periodically and is subjected to a crystallization reaction at a crystallization reaction temperature to crystallize aluminum hydroxide and reuse the solution after crystallization as an etching solution in an etching step. Surface treatment method for the support. 8. A method for surface treating an aluminum support according to claim 6, wherein the surface treatment of the aluminum plate is carried out by pulverizing crystalline aluminum hydroxide in advance. An initial seed crystal having an average particle diameter (median diameter) of 1 μm to 50 μm is charged into the crystallization reaction tank, and then at least 3 μm.
The supersaturated sodium aluminate solution is intermittently and periodically supplied at intervals of time, and a crystallization reaction is performed at a crystallization reaction temperature to crystallize aluminum hydroxide and to remove the liquid after crystallization. A surface treatment method for an aluminum support for a printing plate, which is reused as an etching solution in an etching step. 9. The method of claim 6, wherein the aluminum ion concentration in the surface treatment solution is maintained at a predetermined concentration during the surface treatment of the aluminum plate. ~ 20
After the thing kept at a temperature of 0 ° C. for at least 1 to 48 hours is introduced into a crystallization reaction tank as an initial seed crystal, the supersaturated sodium aluminate solution is intermittently continued at intervals of at least 3 hours. Wherein the aluminum hydroxide is supplied periodically to crystallize the aluminum hydroxide, and the solution after the crystallization is reused as an etching solution in the etching step. 10. A method of treating a surface of an aluminum plate according to claim 6, wherein the aluminum ion concentration in the surface treatment solution is maintained at a predetermined concentration. Is introduced into the crystallization reaction tank as an initial seed crystal, and then the supersaturated sodium aluminate solution is intermittently and periodically supplied at intervals of at least 3 hours to crystallize aluminum hydroxide. A method for treating the surface of an aluminum support for a printing plate, wherein the solution after crystallization is reused as an etching solution in an etching step. 11. In the surface treatment of an aluminum plate, a part of a treatment solution containing a sodium aluminate solution to be circulated for surface etching and a waste liquid and a waste alkali discharged from the surface treatment step of the aluminum plate are generated during neutralization. By a method of mixing aluminum sludge containing non-crystalline aluminum hydroxide as a main component to adjust to a supersaturated sodium aluminate solution, from the supersaturated sodium aluminate solution to crystallize aluminum hydroxide by a hydrolysis reaction,
In a surface treatment method for an aluminum support in which aluminum is separated out of a part of a treatment solution containing a sodium aluminate solution to be recycled and kept at a predetermined concentration of aluminum ions in the treatment solution, a crystallization reaction tank is used in advance. Then, a mother liquor having a total caustic soda concentration of 50 to 700 g / l and an aluminum concentration of 0 to 300 g / l and crystalline aluminum hydroxide are charged, and the liquid temperature is maintained at a temperature of 10 ° C to 200 ° C for at least 1 to 48 hours. After the holding, the supersaturated sodium aluminate solution is supplied intermittently and continuously at intervals of at least 3 hours, and is crystallized at a crystallization reaction temperature to crystallize aluminum hydroxide. A method for treating a surface of an aluminum support for a printing plate, wherein the solution after crystallization is reused as an etching solution in an etching step. 12. The surface treatment method for an aluminum support according to claim 11, wherein the aluminum ion concentration in the surface treatment solution is maintained at a predetermined concentration during the surface treatment of the aluminum material. After introducing the seed crystal according to any one of the above into a crystallization reaction tank, the supersaturated sodium aluminate solution is intermittently and periodically supplied at intervals of at least 3 hours, and aluminum hydroxide is supplied. Wherein the solution after crystallization is reused as an etching solution in an etching step.