JP2002144312A - Method for manufacturing woody cement plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a woody cement plate having a desired initial strength in a smaller ettringite amount in manufacturing a thermosetting cement plate and small dimensional change due to heat or with time. SOLUTION: A method for manufacturing the woody cement plate comprises a step of hot pressing a non-flowable cement mixture containing the thermosetting cement, wood chip and water, and a drying step of molding and curing the mixture. The hot pressing step is executed under the conditions of a pressure is 4 to 10 MPa, a temperature of 90 to 100 deg.C and a time of 8 to 15 min. The drying step is executed under the conditions of a temperature of 90 deg.C, and a time of 1 to 2 hours.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a wood cement board suitable for a building material such as an outer wall.

[0002]

2. Description of the Related Art Conventionally, building materials, for example, wood cement boards are mainly used for the outer walls of buildings because of their excellent fire resistance and water resistance. This wood cement board is prepared by mixing a thermosetting cement composition mainly composed of Portland cement, wood flakes and water, and then supplying the mixture to a molding die and hot pressing (heating and pressing). It is manufactured by shaping into a predetermined shape and curing. This manufacturing method is described in, for example, Japanese Patent Publication No. 56-14005.
No. 9 discloses this.

[0003]

However, such a wood cement board has 3CaO.Al ₂ O ₃ .3C.
needles ettringite represented by aSO ₄ · 30~32H ₂ 0 was largely contaminated. This ettringite can be produced in a short period of time and provides the desired initial strength to the substrate by hot pressing, but is easily decomposed by heat and aging. For this reason, a wood cement board containing a large amount of ettringite has a high initial strength, but lacks dimensional stability over time and heat. The present invention has been made in view of the above problems, and provides a wood cement board that exhibits sufficient initial strength under relatively low temperature, low pressure, and short press conditions, and has little dimensional change even under heat or aging. Is what you do.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a wood cement board, in which a non-flowable cement mixture comprising thermosetting cement, wood chips and water is molded and hardened through a hot pressing step and a drying step. In addition, the hot pressing process includes a pressure of 4 to 10 MPa and a temperature of 90 to 100 ° C.
And the drying step is performed at a temperature of 90 ° C. for 1 to 2 hours.

As the thermosetting cement used in the present invention, Portland cement, blast furnace slag cement, silica cement, fly ash cement and the like are used as main components.
Examples thereof include those to which anhydrous gypsum, slaked lime and the like are added. When heat is applied to the thermosetting cement, Al ₂ O ₃ , CaO, and CaSO ₄ in the cement component rapidly undergo a hydration reaction with water, and 3CaO.Al ₂ O ₃ .3CaSO ₄ .30
~32H generates the ₂ O of ettringite crystals. This causes the cement composition to harden rapidly.

[0006] The above-mentioned ettringite is a thermally unstable crystal and is decomposed by heat or aging. Therefore, the wood cement board in which a large amount of ettringite is present is excellent in productivity because a desired initial strength can be obtained in a short time,
The dimensions tend to change due to heat and aging. Also, if a large amount of unreacted thermosetting cement is present, it reacts with moisture in the air and changes its dimensions.

[0007] Pine, cypress, cedar and the like are preferably exemplified as the wood chips used in the present invention from the viewpoint of cost. Also, the shape of the wood is not particularly limited,
When smoothness or denseness is required, it is preferably a sawdust made of a sieve having an opening of 1.0 mm, more preferably a sieve having an opening of 0.5 mm.
On the other hand, when lightness and strength are required, those having a length of 60 mm or less, a width of 20 mm or less, and a thickness of 2 mm or less are preferable, and contain 70% by weight or more of the passing amount classified with a sieve having an opening of 1.68 mm or less. Are particularly preferred. The amount of wood chips added is preferably from 10 to 30 parts by weight based on 100 parts by weight of the thermosetting cement from the viewpoint of dimensional stability. Further, a part of the wood piece may be replaced with an organic fiber.

The water used in the present invention is preferably 30 to 50 parts by weight based on 100 parts by weight of the thermosetting cement. In order to perform hot pressing, it is necessary to make the cement mixture non-fluid, and if it exceeds 50 parts by weight, it becomes difficult to secure the non-fluidity. On the other hand, if the amount is too small, the uniformity of the cement mixture before hardening is reduced, and the performance of the cement board is hardly exhibited. Further, an organic carboxylate may be dissolved in the water as a curing retarder.

From the viewpoint of improving the dimensional stability, a part of the wood piece may be replaced with an inorganic aggregate. In this case, examples of the inorganic aggregate include silica sand, silica stone powder, silica fume, and fly ash.

The method of mixing the raw materials (the above cement mixture) in the present invention is not particularly limited, but it is necessary to obtain a non-fluid mixture in which the wood chips are uniformly dispersed. First, water is added while stirring the wood chips. Thereafter, a method of adding the thermosetting cement while stirring is preferable in that the raw materials can be uniformly mixed.

The method of spreading the cement mixture is not particularly limited, but is preferably a method of dropping and spraying on a template because it is non-flowable.

According to the present invention, a wood cement board is obtained by subjecting the cement mixture to a hot-pressing step and a drying step to form and harden.

The hot pressing step is performed under a pressure of 4 to 10M.
It is performed under the conditions of Pa and a temperature of 90 to 100 ° C. for 8 to 15 minutes.

The pressing pressure is set at 4 to 10 MPa. By setting the pressure to 4 MPa or more, there is an effect of increasing the contact area between the thermosetting cement composition and water and increasing the reaction rate. Further, even if the pressing pressure is increased to exceed 10 MPa, the effect of further increasing the reaction rate cannot be obtained any more, resulting in inefficiency. If it is less than 4 MPa, the reaction rate is sharply reduced, the density of the wood cement board is reduced, and the strength of the base material is significantly reduced.

[0015] The pressing temperature is in the range of 90 to 100 ° C. If the temperature is lower than 90 ° C., the ettringite formation reaction rate will be low, resulting in inefficiency. or,
When the temperature exceeds 100 ° C., the decomposition of ettringite crystals becomes dominant, and the reaction rate decreases. On the other hand, when the temperature exceeds 100 ° C., a large amount of water vapor is emitted, and the water vapor accumulates in the base material.

The pressing time is 8 to 15 minutes. If the time during which the temperature of the central portion of the mixed material at the time of pressing is 90 ° C. or higher is less than 8 minutes, the reaction rate of the thermosetting cement composition decreases and the pressing time becomes inefficient. Further, even if it exceeds 15 minutes, there is almost no further effect, and conversely, the productivity is reduced.

For the above reasons, the conditions of the pressing process are as follows:
A molding method that maximizes the amount of ettringite crystal formation even with a small amount of thermosetting cement composition.
a, a wood cement board having sufficient initial strength and excellent dimensional stability can be obtained by using the conditions of a temperature of 90 to 100 ° C. and a time of 8 to 15 minutes.

The drying step following the pressing step is performed by drying at 90 ° C. for 1 to 2 hours. A large amount of unreacted water is present in the compact immediately after the pressing step, and the required strength has not yet been developed. By drying under the above conditions, excess water is released, the water distribution in the cement molding becomes uniform, and a wood cement board having a uniform strength distribution can be obtained.

In this drying step, the moisture content of the substrate is
It becomes equilibrium moisture content with water vapor in the atmosphere, and it becomes possible to reduce dimensional change due to moisture absorption and desorption. If the drying is further performed to lower the water content below the equilibrium moisture content of the base material, a phenomenon occurs in which the woody material absorbs moisture in the air, and the base material expands, which is not preferable.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to embodiments, but the present invention is not limited thereto. (Example 1) 83 parts by weight of Portland cement (manufactured by Taiheiyo Cement), alumina cement (manufactured by Denki Kagaku) 9
17 parts by weight of a cypress piece with an average particle size of 10 mm or less based on 100 parts by weight of thermosetting cement consisting of 5 parts by weight, calcined gypsum (Adra Kogyo Co., Ltd.) and 5 parts by weight slaked lime (Komagata Lime Mining Co., Ltd.) , 42 parts by weight of water and 1 part by weight of sodium citrate were weighed. To mix the above raw materials, add water in which sodium citrate is dissolved and mix for 60 seconds while stirring the hinoki pieces with a Henschel mixer (manufactured by Mitsui Mining), and then add the thermosetting cement while stirring. And mixed for 60 seconds to produce a non-flowable cementitious mixture.

The above mixture is sized 300 mm × 400 m
m, and sprayed and dropped uniformly on a mold plate having a depth of 10 mm so that the thickness of the cement plate after molding became 16 mm. SUS with 12 mesh size for the purpose of diffusing water vapor generated during hot pressing after raw material development
The wire mesh was laid on the raw material and inserted into a hot press (Oji Service Co., Ltd., hydraulic molding machine).

The above-mentioned raw material was obtained at a surface pressure of 4 MPa and a temperature of 90 ° C.
Hot pressed for 0 minutes and cured. Thereafter, the wire mesh was detached, removed from the mold, and dried at 90 ° C. for 1 hour to obtain a wood cement board.

After natural curing of the wood cement board for one week, the wood cement board has a predetermined size (50 mm × 150 mm, thickness 16 m).
m) to prepare a sample for measuring density, bending strength, and dimensional change rate.

The density of the above-mentioned wood cement board was measured by measuring the sample size, followed by drying in a dryer at 105 ° C. for 24 hours, and measuring the dry weight. Using these values, the density was calculated from the following equation. Density (g / cm ³ ) = dry weight (g)
/ Sample volume (cm ³ )

The flexural strength was measured according to JIS after measuring the sample size.
A three-point bending test was performed using an autograph in accordance with R5201 (physical test method for cement).

The dimensional change was determined by immersing the sample in water at a water temperature of 25 ° C. for 24 hours, measuring the sample size using a micrometer, and then drying the sample at 105 ° C. for 24 hours using a drier.
The sample size after drying was measured. Using these numerical values, the dimensional change rate was calculated from the following equation. Dimensional change rate (%)
= [Length after immersion (mm)-length after drying (mm) / length after drying (mm)] x 100

(Embodiment 2) The contact pressure at the time of press pressure was 10M
Except having changed to Pa, it carried out similarly to Example 1.

Example 3 Example 3 was carried out in the same manner as in Example 1 except that the temperature at the time of pressing was 97 ° C.

(Example 4) The same operation as in Example 1 was performed except that the pressing time during pressing was set to 15 minutes.

(Example 5) The surface pressure at the time of press pressure was 10 M
Except that Pa, the temperature was 97 ° C., and the pressurization time was 15 minutes, the same procedure as in Example 1 was performed.

(Comparative Example 1) Portland cement (manufactured by Taiheiyo Cement) 79 parts by weight, alumina cement (manufactured by Denki Kagaku) 11 parts by weight, calcined gypsum (manufactured by Adra Industries) 6 parts by weight, slaked lime (Komagata lime mining company) Example 1 was repeated except that a cement composition consisting of 4 parts by weight was used. (Comparative Example 2) The same operation as in Example 1 was performed except that the surface pressure during pressing was 3 MPa.

(Comparative Example 3) The surface pressure during pressing was 15 MPa
The procedure was performed in the same manner as in Example 1, except for the following.

(Comparative Example 4) The same operation as in Example 1 was performed except that the temperature at the time of pressing was 60 ° C.

(Comparative Example 5) The same procedure as in Example 1 was carried out except that the pressing time during pressing was set to 5 minutes.

(Comparative Example 6) The same operation as in Example 1 was performed except that the pressing time during pressing was set to 20 minutes.

Table 1 shows the above production conditions and the results of evaluation of the physical properties of the cement boards obtained therefrom.

[0037]

[Table 1]

In Table 1, Example 2 is a sample adjusted by increasing the press pressure. Example 3 is a sample adjusted by increasing the pressing temperature. Example 4 is a sample adjusted by increasing the pressurizing time. Example 5 is a sample in which pressing conditions were optimized. Comparative Example 1 is a sample charged with a large amount of ettringite-forming material. Comparative Example 2 is a sample adjusted by lowering the pressing pressure. Comparative Example 3
Is a sample adjusted with very high press pressure. Comparative Example 4 is a sample adjusted by lowering the press temperature. Comparative Example 5 is a sample adjusted by shortening the pressurizing time. Comparative Example 6 is a sample adjusted by increasing the pressurizing time.

As shown in Table 1, the sample of the present invention is excellent in strength and dimensional stability, and in particular, Example 5 is extremely excellent in strength and dimensional stability. Comparative Example 1, in which a large amount of the ettringite-forming material was charged, was excellent in strength but decreased in dimensional stability. In Comparative Example 2 in which the surface pressure was set to 3 MPa, the density was reduced,
Strength and dimensional stability decrease. In addition, the surface pressure is 15 MPa
Comparative Example 3 is almost the same as Example 2 in both strength and dimensional stability. In Comparative Example 4 in which the pressing temperature was lowered and in Comparative Example 5 in which the pressing time was shortened, both the density and the strength decreased.
Dimensional stability decreases. Comparative Example 6 with longer press time
Is almost the same as in the fourth embodiment.

[0040]

As described above, according to the method for producing a wood cement board of the present invention, a desired initial strength can be obtained even with a small amount of ettringite by performing a hot pressing step and a subsequent drying step under specific conditions. In addition, it becomes possible to manufacture a wood cement board with little dimensional change even under heat or aging.

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Claims (2)

[Claims] 1. A method for producing a wood cement board, comprising: forming a non-flowable cement mixture composed of thermosetting cement, wood chips, and water through a hot pressing step and a drying step, and hardening the mixture. Pressure 4-10MPa, temperature 90
A method for producing a wood cement board, characterized in that the drying is performed at a temperature of 90 ° C. for 1 to 2 hours at a temperature of 90 ° C. for 8 to 15 minutes. 2. The method for producing a wood cement board according to claim 1, wherein the non-flowable cement mixture comprises 100 parts by weight of thermosetting cement, 10 to 30 parts by weight of wood chips, and 30 to 50 parts by weight of water.