JP2001158650A - Cement hardening promoter and method for promoting cement hardening - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement hardening promoter enabling cement to be quickly hardened even in the presence of a cement hardening inhibitor subject to leaching from a woody reinforcing material, and to provide a method for promoting cement hardening using the above promoter. SOLUTION: This cement hardening promoter comprises a reaction product of cement slurry and formic acid. Cement is hardened by using the promoter; wherein the above reaction product which contains various complex salts exhibits uniform hardening-promotive effect irrespective of the kind of additives to be added to cement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for accelerating the hardening of cement.

[0002]

BACKGROUND OF THE INVENTION As a hardening accelerator for cement, metal chlorides such as calcium chloride and magnesium chloride have been conventionally used. The metal chlorides as the above-mentioned conventional hardening accelerators are corrosive to metals such as iron, and there is a risk of generating dioxins if waste of cement products using the hardening accelerators is incinerated. Could be adversely affected. In addition, cement boards mixed with wood reinforcement (wood cement boards) as fire-resistant or flame-retardant building boards in recent years
Is often used. However, since the wood reinforcement contains a considerable amount of saccharides as a cement hardening inhibitor, it is usual to add the cement hardening accelerator in order to promote hardening of the cement.

[0003] The above-mentioned saccharides react with calcium precipitated from cement to form insolubles, and the cement particles are coated with the insolubles to inhibit the hardening of the cement. The insoluble matter covering the particles is dissolved to expose the cement particles and accelerate the hardening. However, depending on the combination of the type of the hardening accelerator, the type of insoluble matter coating the cement particles, and the state of coating, these conventional cement hardening accelerators may have a lower dissolving power for the insoluble material coating the cement particles. In such a case, it is difficult to expose the entire cement particles, and therefore the effect of promoting cement hardening may not be large. Therefore, it is conceivable to use various types of curing accelerators in combination. However, the use of a plurality of types of curing accelerators has a drawback that the steps and equipment become complicated and the cost increases.

[0004]

2. Description of the Related Art Recently, the use of calcium formate as a hardening accelerator for cement has been increasing. Calcium formate, unlike metal chloride, does not contain chlorine and has a large effect of promoting hardening of cement. For example, JP-A-10-338
No. 561 discloses a method in which calcium formate is premixed with cement and the cement is used as a raw material for a wood cement board.

[0005]

In the above-mentioned conventional use of calcium formate, since the calcium formate easily deliquesces, the hardening of the cement is already started before the wood cement board is manufactured by moisture deliquescent in the cement. There is a risk of using it, and since it is expensive, use of a large amount leads to an increase in the cost of the product. Further, calcium formate is produced, for example, by a neutralization reaction of formic acid and slaked lime, but if slaked lime is excessive, it becomes a highly alkaline state, and when applied to a wood cement board, the cement contained in the wood reinforcing material is used. There is a possibility that the dissolution of the hardening inhibitor may be promoted, and if the formic acid is excessive, there is a problem that the cement dissolves and a predetermined product strength cannot be obtained.

[0006]

According to the present invention, as a means for solving the above-mentioned conventional problems, a cement hardening accelerator in which formic acid is added to a cement slurry and reacted to adjust the pH to a range of 6 to 9, And a method for accelerating hardening of cement by adding the cement hardening accelerator to cement to accelerate hardening of the cement. The cement hardening acceleration method is particularly useful when a wood reinforcing material is added to cement, for example, when manufacturing a wood cement board. The present invention will be described in detail below.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION [Cement] The cement used in the present invention is a mixed cement such as Portland cement including medium heat cement, high strength cement, etc., blast furnace cement, silica cement, fly ash cement, expansive cement and the like. It is a cement that can be dissolved in acids such as acid-resistant cement, special cement such as ultra-high strength cement, and dental cement.

[Cement Hardening Accelerator] The cement hardening accelerator of the present invention comprises a reaction product of a cement slurry and formic acid. To produce the cement hardening accelerator, formic acid is added to a slurry in which cement is dispersed in water. Is added directly or as an aqueous solution. Alternatively, cement is directly added to a low concentration aqueous solution of formic acid dissolved in water, or a slurry in which cement is dispersed in water is added.
The cement slurry usually has a cement concentration of 5 to 15% by weight, and the aqueous solution of formic acid usually has a concentration of 4 to 12% by weight. The addition ratio of the above-mentioned cement slurry and formic acid is adjusted so that the pH of the reaction solution is usually 6 to 9, preferably 7 to 8. If the pH of the reactant solution is less than 6, unreacted formic acid may remain and the strength of the product may be reduced by dissolving the cement. The promotion effect may be reduced.

[Cement Hardening] A cement hardening accelerator, which is a reaction product solution of the above cement slurry and formic acid, contains a salt of calcium and formic acid, a salt of aluminum and formic acid,
Various complex salts such as a salt of sodium and formic acid, and a salt of potassium and formic acid have been produced, and the cement promotes hardening almost uniformly irrespective of other additives. The amount of the hardening accelerator added to the cement is usually 0.5 to 5 weight ratio with respect to 100 weight parts of the cement, assuming the weight of the hardening accelerator as the sum of the weight of the cement and the weight of formic acid.

[0010] The hardening accelerator of the present invention is particularly useful for producing a wood cement board in which a wood reinforcing material is added to cement. Wood reinforcements are larch, lauan, yellow lauan,
It is obtained from various tree species such as cedar, pine and hemlock, and contains various sugars in various amounts depending on the tree species. However, the hardening accelerator of the present invention contains various complex salts as described above, and a substantially constant cement hardening accelerating effect can be obtained without being affected by the type and amount of sugars contained in such a wood reinforcing material. Can be

That is, since the curing accelerator of the present invention contains a plurality of types of salts, it decomposes insolubles derived from saccharides covering the cement particles in a short time irrespective of the type and amount of the saccharides. Therefore, cement promotes hardening uniformly regardless of the type of wood reinforcement. The method for producing a wood cement board using the curing accelerator of the present invention will be described in detail below.

[Wood reinforcement] Wood reinforcement, wood wool, wood chips, wood fiber, wood pulp, wood fiber bundle, etc. are used as wood reinforcement in the present invention.
Materials containing lignocellulose as a main component, such as hemp fiber, bacas, fir and rice straw, may be mixed. Preferred wood reinforcements are 0.5 to 2.0 mm in width and 1 to 20 m in length.
m, a piece of wood with an aspect ratio (length / thickness) of 20-30,
A branch having a diameter of 0.1 to 2.0 mm and a length of 2 to 35 mm and / or
Or there are curved and / or bent bundles of wood fibers.
The wood reinforcing material is usually mixed in an amount of about 5 to 40% by weight based on the cement-based inorganic powder in terms of the absolutely dry state.

[Aggregate] In addition to the cement-based inorganic powder and the wood reinforcing material, an aggregate, particularly a lightweight aggregate, may be mixed in the present invention. Examples of the aggregate include quartz sand,
Silica powder and the like are used, and as the lightweight aggregate, pearlite, shirasu balloon, expanded shale, expanded clay, calcined diatomaceous earth, fly ash, coal ash and the like are used. The aggregate is usually mixed in an amount of about 5 to 40% by weight based on the total solid content of the mixture.

[Third component] If desired, the mixture may further contain a hardening accelerator such as aluminum sulfate, magnesium sulfate, aluminates, water glass, or a waterproofing agent such as wax, wax, paraffin, surfactant, or silicone. Or a water repellent may be mixed.

[Manufacture of Wood Cement Board] In the present invention, a wood cement board is manufactured by a semi-dry method, a dry method, or a wet papermaking method. In the case of the semi-dry method, first, the above cement and wood reinforcement, and optionally, aggregate,
The curing accelerator solution of the present invention is added to and mixed with the mixture containing the third component, and the obtained molding material is sprayed on a substrate to form a mat. Water is preferably added so that the moisture content of the mat is 15 to 65% by weight.

In the case of the dry method, first, the curing accelerator solution of the present invention is added to a mixture containing the cement, the wood reinforcing material, and, if desired, the aggregate and the third component, and mixed. The mat is formed by spraying on the substrate, and water is further added to the mat. Further, it is preferable to add water so that the moisture content of the mat is 15 to 65% by weight.

After the mat has been formed as described above, the mat is pressed together with the substrate and primary cured under heating. The temperature applied in the primary curing is usually 50-100 ° C, and the pressing pressure is usually 2-5MP.
a. After the above primary curing, the obtained primary cured product is removed from the mold and cured at room temperature or in an autoclave. The room temperature curing is usually performed at room temperature for 4 to 10 days, and the autoclave curing is performed at a temperature of 140 to 180 ° C. for 10 to 18 hours. After curing at room temperature or after curing in an autoclave, the surface is coated through a drying process to obtain the final product.

When an uneven pattern is formed on the surface of the wood cement board, an uneven pattern corresponding to the uneven pattern may be formed on the mold surface of the substrate. In the case of producing a smooth wood cement board having no uneven pattern on the surface, a transport board may be directly used as a substrate.

According to the method of the present invention described above, a two-layer or three-layer wood cement board can also be manufactured. In the case of a two-layer structure, first, a molding material mixed with a fine-grained wood reinforcing material is sprayed on a substrate, and then a molding material mixed with a large-grained wood reinforcing material is sprayed thereon to form a two-layer structure. Forming a mat having a structure, pressing and heating the mat, forming a surface layer portion of a dense structure with a molding material obtained by mixing the wood reinforcing material having a fine particle diameter, and mixing the wood reinforcing material having a large particle diameter. A back layer having a rough structure is formed by a molding material.

In the case of a three-layer structure, a mat having a three-layered structure is further dispersed by spraying a molding material further mixed with a wood reinforcing material having a smaller particle diameter on the above-mentioned molding material mixed with a wood reinforcing material having a larger particle diameter. Forming, pressing and heating the mat to form a core layer composed of a mixture of the above-mentioned wood reinforcing material having a large particle diameter as a core layer portion, and forming a layer of the wood reinforcing material having a fine particle diameter above and below the core. These layers are referred to as front and back layers. Alternatively, two mats having the above-described two-layer structure may be laminated and pressed and heated so that layers made of a molding material mixed with a wood reinforcing material having a large particle diameter are in contact with each other.

In the case of wet papermaking, the above cement and wood reinforcing material, and if desired, the aggregate and the third component are dispersed in water to form a slurry having a solid content of usually 2 to 15% by weight. The mat is formed by dewatering with a paper machine such as a round-mesh machine, a hatcheck machine, or the like, and the mat is usually wound up with a making roll.
１５15 layers are laminated, the laminated mat is pressed, a semi-dry method,
Like the mat by the dry method, primary curing, curing at room temperature or curing in an autoclave, and drying and surface coating are performed to obtain the final product.

[Preparation Example 1] (Preparation of Hardening Accelerator A) A 10% by weight Portland cement slurry was prepared.
A curing accelerator A having a pH of 7.4 was prepared by adding and dissolving a 10% by weight aqueous solution of formic acid.

[Preparation Example 2] (Preparation of hardening accelerator B) 10% by weight of formic acid was added to and dissolved in an aqueous dispersion of 10% by weight of fly ash cement to obtain a pH of 7.2.
Was prepared.

Examples 1 and 2 and Comparative Example 1 Water was added to a mixture having the composition shown in Table 1 so that the water content was 45% by weight, and the mixture was stirred to make it uniform. The obtained molding material was sprayed on a carrier plate to form a mat, the mat was pressed together with the carrier plate, and primary cured at 50 ° C. for 12 hours. Thereafter, the pressed state was released, and natural curing was performed at room temperature for 4 days, and finally, drying was performed at 80 ° C. for 5 hours to obtain a wood cement board product having a thickness of 12 mm. In addition, Portland cement was used as cement in Table 1, and cypress sapwood was used as wood flake.

[0025]

[Table 1]

Test pieces (length 7 cm × width 20 cm × thickness 1.2 cm) were cut out from the cured product after the primary curing and the obtained wood cement board product, and the bending strength was measured with a span of 15 cm. Table 2 shows the results.

[0027]

[Table 2]

As shown in Table 2, the wood cement boards of Examples 1 and 2 produced using the hardening accelerator of the present invention were compared with the wood cement boards of Comparative Example 1 produced using calcium chloride. Thus, both the primary cured product and the product exhibit very high bending strength.

Examples 3, 4 and Comparative Example 2 A mixture having a composition shown in Table 3 was dispersed in water to prepare a slurry having a solid content of 6% by weight.

[0030]

[Table 3]

The slurry is formed by a fourdrinier machine to form a mat, and ten mats are laminated to form a laminated mat. The mat was pressed on a mold plate, primary cured at 50 ° C. for 12 hours, then autoclaved at 170 ° C. for 15 hours, and then dried at 85 ° C. for 5 hours to obtain a 12 mm thick wood cement plate. Got the product.

Test pieces (length 7 cm × width 20 cm × thickness 1.2 cm) were cut out from the laminate after the primary curing and the obtained wood cement board product, and the bending strength was measured with a span of 15 cm. Table 4 shows the results.

[0033]

[Table 4]

As shown in Table 4, the wood cement boards of Examples 3 and 4 produced by using the hardening accelerator of the present invention were the same as those of Comparative Example 2 produced by using water glass (No. 2). Compared to cement boards, after primary curing and both the products show very high flexural strength.

[0035]

According to the cement hardening accelerator of the present invention,
Even when a wood reinforcing material composed of a tree species containing a large amount of a cement hardening inhibitor is used, the cement can be quickly hardened, so that a wood cement board having high strength can be efficiently manufactured. Further, in the present invention, since formic acid and cement are reacted, in a wood cement board manufacturing plant, cement to be reacted with formic acid may be supplied from a cement tank used as a main material, so that the manufacturing equipment can be simplified. When formic acid is reacted with slaked lime to produce calcium formate, when formic acid is reacted with sodium hydroxide to produce sodium formate, or when formic acid is reacted with potassium hydroxide to produce potassium formate. Requires separate tanks such as slaked lime.

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Claims (3)

[Claims] 1. A cement hardening accelerator characterized in that formic acid is added to a cement slurry and reacted to adjust the pH to a range of 6 to 9. 2. A method for accelerating cement hardening, comprising adding the cement hardening accelerator of claim 1 to cement to accelerate hardening of the cement. 3. The method for accelerating hardening of cement according to claim 2, wherein a wood reinforcing material is added to said cement.