Aluminum hydroxide production system and flame retardant

Abstract

To provide an aluminum hydroxide production system capable of producing aluminum hydroxide using a low cost process.SOLUTION: The aluminum hydroxide production system is characterized by comprising raw liquid recovery means of recovering an alkali-aluminate aqueous solution obtained after producing hydrogen by reacting aluminum with an alkaline aqueous solution, crude crystal recovery means of crystallizing and recovering aluminum hydroxide from the recovered raw liquid, and washing means of washing the crude crystal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a system for producing aluminum hydroxide, and more particularly to a production system integrated with a hydrogen production system. [Background technology]

[0002] Aluminum hydroxide is widely used as an industrial raw material. Aluminum hydroxide currently available on the market is manufactured using the Bayer process, using bauxite as a raw material, but much of it in Japan is imported. Patent Document 1 proposes a method for producing aluminum hydroxide via aluminum alkoxide, which is produced by reacting metallic aluminum with alcohol, but the process is complicated and expensive. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-48060 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide an aluminum hydroxide production system that is capable of producing aluminum hydroxide using an inexpensive process. [Means for solving the problem]

[0005] The aluminum hydroxide production system according to the present invention is characterized by comprising: a raw solution recovery means for recovering an aqueous alkali aluminate solution after hydrogen has been produced by reacting aluminum with an alkaline aqueous solution; a crude crystal recovery means for precipitating and recovering aluminum hydroxide from the recovered raw solution; and a washing means for washing the crude crystals.

[0006] Here, aluminum includes both pure aluminum and aluminum alloys. The present invention is characterized in that aluminum hydroxide is produced using an aqueous solution of alkali aluminate, which is generated when hydrogen is produced by reacting aluminum with an aqueous alkali solution, as a stock solution.

[0007] The aluminum used for hydrogen production can be wrought or cast material even if it has a low purity, so the aluminum may be aluminum recovered from aluminum-containing waste using an aluminum recovery system, or may be chips or scraps generated during the manufacturing process of aluminum products.

[0008] There are a wide variety of products that use aluminum, including aluminum beverage cans, packaged products, and various packaging materials. These aluminum-containing wastes can be collected through the separate collection systems run by each local government. Furthermore, collection boxes for aluminum packs or the like may be installed in each facility, supermarket, etc., and a system for regular or irregular collection may be established.

[0009] Aluminum is also used in a variety of industrial applications, including machine parts and vehicle parts. These products are made from raw materials such as aluminum extrusions, rolled aluminum, and cast aluminum, and are manufactured through a machining process. In the present invention, the reaction-finished liquid from hydrogen production using chips and scraps generated in these production processes can also be used as the raw liquid.

[0010] It has been found that the aluminum hydroxide produced in this manner can be satisfactorily used as a flame retardant, as will be described in detail later. Aluminum hydroxide is stable up to about 200°C, but at temperatures above that it decomposes into alumina and water of crystallization, and this reaction has a large endothermic effect. Utilizing this principle, adding aluminum hydroxide to rubber or resin materials creates a self-extinguishing effect, which has the advantage of suppressing smoke and not generating harmful gases. It can also be used as a raw material for flame-retardant back coating agents to impart flame retardancy to textile products. [Effects of the Invention]

[0011] The present invention produces hydrogen using aluminum, which can be used as an energy source for fuel cells and the like, and also produces aluminum hydroxide using the residue, the reaction-terminated liquid, as a stock solution, resulting in an inexpensive and environmentally friendly production system. [Brief explanation of the drawings]

[0012] [Figure 1] An example of an apparatus for obtaining a raw solution and crude crystals for producing aluminum hydroxide is shown below. [Figure 2] The evaluation results of flame retardancy are shown below. DETAILED DESCRIPTION OF THE INVENTION

[0013] An example of the aluminum hydroxide production system according to the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

[0014] The present invention is characterized by its integration with a system for producing hydrogen using aluminum as a raw material, making effective use of the stock solution of aluminum hydroxide.

[0015] FIG. 1 shows a schematic diagram of an example of a hydrogen production system. An aqueous solution of sodium hydroxide with a pH of 13 or higher is poured into reaction tank 1, into which aluminum recovered by the waste recovery system and chips generated during the manufacturing process of products are poured from input tank 2. The generated hydrogen passes through a cleaning tank 7 and is stored in a hydrogen storage tank 6, and is used as fuel for fuel cells and the like. The temperature of the reaction vessel 1 is controlled via a heat exchanger 3 . When the reaction is completed, the aqueous sodium aluminate solution remains in the reaction vessel 1. When this is cooled, aluminum hydroxide precipitates, and the solid and liquid are separated in a filter press 4, and the liquid portion is returned to the reaction vessel 1 and reused. The solid content is collected in a crude crystal collection bucket 5. This crude aluminum hydroxide crystal is washed several times with water and used as a flame retardant or the like.

[0016] In order to compare with a commercially available flame-retardant back-coating paint (Example 1) in which the aluminum hydroxide according to the present invention obtained above was blended, a flame-retardant back-coating paint in which commercially available aluminum hydroxide was blended in the same formulation as in Example 1 was used. The flame retardancy test was carried out based on the JIS L 1091A-1 method for testing the flammability of textile products. The results are shown in the table in Figure 2. It was confirmed that the aluminum hydroxide obtained using the system according to the present invention can be satisfactorily used as a flame retardant. [Explanation of symbols]

[0017] 1 Reaction vessel 2 Loading tank 3 Heat exchanger 4. Filter press 5. Coarse crystal collection bucket 6 Hydrogen storage tank 7. Cleaning Tank

Claims

1. recovering a stock solution of the alkali aluminate aqueous solution after producing hydrogen by reacting aluminum with the alkaline aqueous solution; precipitating and recovering aluminum hydroxide from the recovered stock solution to obtain crude crystals; and washing the crude crystals. The method for producing aluminum hydroxide is characterized in that the aluminum is aluminum derived from aluminum-containing waste or chips or scraps generated in the manufacturing process of aluminum products.

2. A method for producing a flame retardant using the aluminum hydroxide according to claim 1 as a raw material.

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