Method for producing inorganic molded product

Abstract

To provide a method for producing an inorganic molded product that can save energy.SOLUTION: The method comprises dewatering and molding a mixture of crushed cement-hardened material, a carboxylic acid, and water. The carboxylic acid preferably includes citric acid.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a method for producing an inorganic molded article, and more particularly to a method for producing an inorganic molded article containing a pulverized product of hardened cement. [Background technology]

[0002] Patent Document 1 describes a water-impermeable hardened material containing an inorganic substance and at least one selected from lignin and cellulose. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 095297 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the invention described in Patent Document 1, lignin or cellulose or raw materials containing them are mixed with inorganic substances such as concrete or sand, and then heated under pressure to cause thermal hardening, which requires a considerable amount of energy (heat and pressure).

[0005] An object of the present disclosure is to provide a method for producing an inorganic molded article that can achieve energy savings. [Means for solving the problem]

[0006] In a method for producing an inorganic molded product according to one embodiment of the present disclosure, a mixture of pulverized hardened cement product, a carboxylic acid, and water is dehydrated and molded. Effect of the Invention

[0007] The present disclosure has the advantage of being able to conserve energy. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (1) Overview In the method for producing an inorganic molded product in this embodiment, a mixture of pulverized hardened cement product, carboxylic acid, and water is dehydrated and molded. This causes a reaction between the hydroxyl group of calcium hydroxide contained in the pulverized hardened cement product and the carboxyl group of the carboxylic acid, and the reaction product bonds the pulverized products together as the water dries, thereby obtaining an inorganic molded product.

[0009] A typical method for recycling hardened cement is to produce a plate-shaped inorganic molded product by solidifying pulverized hardened cement with a binder such as resin, but a method that does not use a petroleum-derived binder has been proposed in the invention described in Patent Document 1. However, the invention described in Patent Document 1 requires that a mixture of lignin or cellulose or a raw material containing them and pulverized hardened cement is pressurized and heated to harden, and a considerable amount of energy is consumed for pressurization and heating.

[0010] On the other hand, the method for producing an inorganic molded product of the present embodiment can obtain an inorganic molded product without applying pressure and heat or with almost no application of pressure and heat. Therefore, energy saving can be achieved. Furthermore, the method for producing an inorganic molded product of the present embodiment does not require any equipment for applying pressure and heat, making it easy to produce an inorganic molded product using existing production equipment.

[0011] (2)Details In the method for producing an inorganic molded product in this embodiment, a mixture of pulverized hardened cement, carboxylic acid, and water is dehydrated and molded.

[0012] The hardened cement product is a hardened product of a hydraulic material containing cement. Cement is a powder that hardens by hydration and polymerization with a liquid agent containing water, and examples of the cement include Portland cement, blast furnace cement, silica cement, and fly ash cement.

[0013] Hardened cement products preferably contain 20% by mass or less of wood reinforcing materials such as pulp, aggregates such as sand and fly ash, resin particles, etc., rather than those containing large amounts of sand and gravel like general concrete and mortar. This makes it easier to produce inorganic molded products that are not brittle and have high strength.

[0014] The hardened cement product can be made from waste building materials, including exterior materials such as exterior wall materials and roofing materials. Also, scraps (waste materials) that are discarded during the manufacture of building materials can be used as the hardened cement product. This can reduce waste generation and conserve resources.

[0015] The pulverized hardened cement product can be obtained by pulverizing the hardened cement product with a pulverizer or the like. The average particle size of the pulverized product is preferably 0.1 mm or more. This prevents the pulverized product from agglomerating (forming lumps) in the mixture and makes it easier to mix with water, etc. The average particle size of the pulverized product is preferably 1.5 mm or less. This makes it difficult for large pulverized products to be included in the inorganic molded product, making it easier to produce inorganic molded products that are not brittle and have high strength. The average particle size of the pulverized product can be obtained by measuring the diameters of multiple pulverized products and calculating the arithmetic average.

[0016] The hardened cement product preferably contains a wood reinforcing material such as pulp, etc. This allows the wood reinforcing material to be contained in the inorganic molded product produced, which tends to improve the strength of the inorganic molded product.

[0017] The carboxylic acid is a component that reacts with calcium hydroxide contained in the pulverized cement hardened product. The carboxylic acid preferably contains citric acid. Citric acid can be produced from plants as a raw material, and is therefore preferable because it can reduce the use of fossil resources. As the carboxylic acid, various monocarboxylic acids, dicarboxylic acids, and tricarboxylic acids can be used in addition to citric acid.

[0018] The carboxylic acid is preferably blended at a ratio of 1 part by mass or more per 10 parts by mass of the pulverized product of the hardened cement. This makes it difficult for poor hardening due to a lack of carboxylic acid to occur. The carboxylic acid is preferably blended at a ratio of 5 parts by mass or less per 10 parts by mass of the pulverized product of the hardened cement. This makes it easy to obtain an inorganic molded product with a relatively high specific gravity of 0.7 to 1.0. If the amount of carboxylic acid blended is more than 5 parts by mass, calcium hydroxide in the pulverized product and the carboxylic acid react vigorously to generate water, which evaporates vigorously (water foaming), and the inorganic molded product may become porous. The inorganic molded product that is porous has a low specific gravity of 0.2 to 0.5, which reduces its strength and makes it difficult to maintain a desired shape. The carboxylic acid is more preferably blended at a ratio of 3 parts by mass or more and 5 parts by weight or less per 10 parts by mass of the pulverized product of the hardened cement.

[0019] Water is a medium that makes it easy to uniformly contact the ground hardened cement product with the carboxylic acid. This makes it easy for the calcium hydroxide in the ground product to react with the carboxylic acid, thereby reducing the lack of binding. The amount of water can be 5 parts by mass or more and 10 parts by mass or less per 10 parts by mass of the ground hardened cement product, but is not limited thereto.

[0020] In this embodiment, in addition to the pulverized cement hardened product, carboxylic acid, and water, a water-soluble resin can be further used. This allows the inorganic molded product to be reinforced by the water-soluble resin, making it easier to maintain a desired shape. The water-soluble resin preferably contains one or both of polyvinyl alcohol (PVA) and polyvinyl acetate (PVAc). This makes it easier to uniformly disperse the water-soluble resin in water, making it easier to produce a homogeneous inorganic molded product.

[0021] The method for producing an inorganic molded product according to this embodiment is carried out as follows. First, a mixture of pulverized hardened cement product, carboxylic acid, and water is obtained. If a water-soluble resin is used, a mixture containing the water-soluble resin is obtained. This mixture is in the form of a paste, and is obtained by blending and mixing the pulverized hardened cement product, carboxylic acid, water, and water-soluble resin in predetermined amounts.

[0022] The mixture can be obtained by blending and mixing the pulverized hardened cement product, the carboxylic acid, water, and the water-soluble resin in order. The mixture can be obtained by mixing the carboxylic acid and water to prepare an aqueous carboxylic acid solution, and then blending and mixing the aqueous carboxylic acid solution, the pulverized hardened cement product, and the water-soluble resin in order. This can improve the dispersibility of the carboxylic acid in the mixture. The concentration of the aqueous carboxylic acid solution (the mass ratio of the carboxylic acid to the total of the carboxylic acid and water blended in the mixture) is preferably 25% by mass or more and 60% by mass or less. This makes it easy to adjust the amount of the carboxylic acid to the amount of the pulverized hardened cement product to an appropriate range, and makes it easy to obtain an inorganic molded product with a specific gravity of 0.7 to 1.0.

[0023] The mixture can be obtained by mixing a carboxylic acid, a water-soluble resin, and water to prepare an aqueous solution containing the carboxylic acid and the water-soluble resin, and then blending and mixing this aqueous solution with pulverized hardened cement, thereby improving the dispersibility of the carboxylic acid and the water-soluble resin in the mixture.

[0024] After preparing the paste-like mixture as described above, the mixture is dried (dehydrated). This causes the hydroxyl groups of calcium hydroxide in the pulverized cement hardened product to react with the carboxyl groups of the carboxylic acid, and the calcium carboxylate produced by the reaction is thought to bond the pulverized products together, thereby producing an inorganic molded product. When drying the mixture, it can be left to dry naturally (air-dried at room temperature). In order to hasten the drying, the mixture can be heated slightly to dry quickly. In addition, the paste-like mixture before drying can be placed in a mold (frame) to form an inorganic molded product of a desired shape.

[0025] In this embodiment, the mixture of the pulverized hardened cement product, the carboxylic acid, and water is dehydrated and molded, so that an inorganic molded product can be obtained without or with little pressure and heat, thereby saving energy.

[0026] (summary) As described above, in the method for producing an inorganic molded article according to the first embodiment, a mixture of pulverized hardened cement, a carboxylic acid, and water is dehydrated and molded.

[0027] According to this embodiment, the hydroxyl groups of calcium hydroxide in the pulverized cement hardened product react with the carboxyl groups of the carboxylic acid to bond the pulverized products together, and the solid contents in the mixture are integrated, so that an inorganic molded product can be obtained without or with very little pressure and heat application, thereby saving energy.

[0028] A second aspect is the method for producing an inorganic molded article according to the first aspect, wherein the carboxylic acid includes citric acid.

[0029] According to this embodiment, the use of fossil resources can be reduced.

[0030] A third aspect is a method for producing an inorganic molded product according to the first or second aspect, in which the carboxylic acid is mixed in a ratio of 1 part by mass to 5 parts by mass to 10 parts by mass of the pulverized hardened cement product.

[0031] According to this embodiment, the amount of the carboxylic acid relative to the amount of the pulverized hardened cement product can be easily adjusted to an appropriate range, making it easy to obtain an inorganic molded product with a relatively high specific gravity.

[0032] A fourth aspect is a method for producing an inorganic molded product according to the first or second aspect, in which an aqueous carboxylic acid solution in which the carboxylic acid is dissolved in the water is mixed with a pulverized product of the hardened cement.

[0033] According to this embodiment, the carboxylic acid can be easily dispersed uniformly in the mixture, and a homogeneous inorganic molded product can be easily produced.

[0034] A fifth aspect is the method for producing an inorganic molded article according to the fourth aspect, wherein the concentration of the carboxylic acid aqueous solution is 25% by mass or more and 60% by mass or less.

[0035] According to this embodiment, the amount of the carboxylic acid relative to the amount of the pulverized hardened cement product can be easily adjusted to an appropriate range, making it easy to obtain an inorganic molded product with a relatively high specific gravity.

[0036] A sixth aspect is a method for producing an inorganic molded article according to the first or second aspect, wherein the hardened cement product includes a wood reinforcing material.

[0037] According to this embodiment, the inorganic molded article can be reinforced with the wood reinforcing material, and the strength of the inorganic molded article can be improved.

[0038] A seventh aspect is the method for producing an inorganic molded article according to the first or second aspect, wherein the mixture further contains a water-soluble resin.

[0039] According to this embodiment, the inorganic molded article can be reinforced with the water-soluble resin, and the shape of the inorganic molded article can be easily maintained.

[0040] An eighth aspect is the method for producing an inorganic molded article according to the seventh aspect, wherein the water-soluble resin contains at least one of polyvinyl alcohol and polyvinyl acetate.

[0041] According to this embodiment, the water-soluble resin can be easily dispersed uniformly in the mixture, and a homogeneous inorganic molded product can be easily produced. EXAMPLES

[0042] The method for producing an inorganic molded article according to the present disclosure will be described in further detail with reference to examples. The method for producing an inorganic molded article according to the present disclosure is not limited to the following method.

[0043] Example 1 The hardened cement product was a waste building material containing pulp, which was pulverized to obtain a pulverized product with an average particle size of 1 mm. Water and citric acid were mixed to prepare an aqueous citric acid solution with a concentration of 30% by mass. The pulverized hardened cement product and the aqueous citric acid solution were then poured into a plastic mold and mixed to obtain a paste-like mixture. The mixture was left in the plastic mold and allowed to air dry at room temperature to harden, obtaining an inorganic molded product.

[0044] Example 2 An inorganic molded article was obtained in the same manner as in Example 1, except that an aqueous citric acid solution having a concentration of 42% by mass was used instead of the aqueous citric acid solution having a concentration of 30% by mass.

[0045] Example 3 In Example 1, instead of the citric acid aqueous solution with a concentration of 30% by mass, a citric acid PVA aqueous solution in which PVA and citric acid were dissolved was used. In this case, the citric acid PVA aqueous solution was prepared by mixing citric acid with a PVA aqueous solution with a concentration of 10% by mass. Otherwise, an inorganic molded product was obtained in the same manner as in Example 1.

[0046] (Comparative Example) The same procedure was carried out as in Example 1, except that water not containing citric acid was used instead of the 30% by mass aqueous citric acid solution.

[0047] The above examples and comparative examples were evaluated as follows.

[0048] (Curing reaction) The inorganic molded products were evaluated by touching with the fingers. If the hardened cement product was bonded and integrated, it was rated as "good", and if it could be easily disassembled, it was rated as "bad".

[0049] (specific gravity) The inorganic molded product was cut into a predetermined shape, and the mass and volume were measured to determine the mass.

[0050] (water resistance) When an inorganic molded product was immersed in water at room temperature for 24 hours and then taken out and touched with the fingers, if it partially disintegrated, it was marked as "△", and if it did not disintegrate, it was marked as "O".

[0051] Table 1 shows the mixing ratio and evaluation of each component.

[0052] [Table 1]

Claims

1. A mixture of pulverized hardened cement, carboxylic acid, and water is dehydrated and molded. Manufacturing method for inorganic molded products.

2. The carboxylic acid includes citric acid. A method for producing the inorganic molded product according to claim 1.

3. The carboxylic acid is mixed in a ratio of 1 part by mass or more and 5 parts by mass or less with respect to 10 parts by mass of the pulverized product of the hardened cement product. A method for producing the inorganic molded article according to claim 1 or 2.

4. The carboxylic acid is dissolved in the water to obtain an aqueous carboxylic acid solution, which is mixed with the pulverized hardened cement product. A method for producing the inorganic molded article according to claim 1 or 2.

5. The concentration of the carboxylic acid aqueous solution is 25% by mass or more and 60% by mass or less. A method for producing the inorganic molded product according to claim 4.

6. The hardened cement material contains a wood reinforcing material. A method for producing the inorganic molded article according to claim 1 or 2.

7. The mixture further comprises a water-soluble resin. A method for producing the inorganic molded article according to claim 1 or 2.

8. The water-soluble resin contains at least one of polyvinyl alcohol and polyvinyl acetate. A method for producing the inorganic molded product according to claim 7.

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