JP2003137633A - Wood chip cement board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lightweight wood chip cement board which has excellent strength and water resistance. SOLUTION: The wood chip cement board consists of a cement material, wood chips, an inorganic lightweight aggregate, and water, and, at least one side of a base material layer in which the amount of the chips accounts for 5 to 10 wt.% to the total weight is stacked with a surface layer consisting of a cement material, fine wood chips finer than the above chips, an inorganic fine aggregate having a mean grain diameter of <=100 μm, and water, and in which the amount of the chips accounts for 5 to 15 wt.% to the total weight, and, a coefficient A defined by the formula (1) is >=3: A=a/bc (1) [wherein, a and b respectively denote the yield stress (MPa) and an elastic modulus (MPa) in a bend test measured in accordance with JIS A1408, and c denotes a dimensional change ratio on drying at 60 deg.C for 48 hr after the saturation of water].

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piece of wood cement board used as a building material for an outer wall or the like. 2. Description of the Related Art Conventionally, wood chip cement boards have been used mainly for the outer walls of buildings, because they can have both the fire resistance of a hardened cement body and the workability and nailing properties of a wood material. (Japanese Patent Publication No. 5-13098). However, the wood chip cement board, when increasing the amount of wood chip to increase the workability, the amount of water absorption from the cement board surface increases, the dimensional change increases, warping over time, the incidence of cracks increases, In addition to the problem that the long-term durability is reduced, there is a disadvantage that the fire resistance is reduced. In addition, when the amount of wood chips is reduced in order to improve water resistance, there is a disadvantage that the strength and cracking resistance of the wood chip cement plate are reduced, and the workability is deteriorated. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a light-weight, high-strength, water-resistant wood chip cement board. A wood chip cement board of the present invention comprises a cement material, a wood chip, an inorganic lightweight aggregate, and water, and the amount of the wood chip is 5 to 15% by weight based on the total weight. On at least one side of the base material layer occupying a cement material, fine wood pieces finer than the above wood pieces, inorganic fine aggregate having an average particle size of 100 μm or less, and water, and the amount of the above fine wood pieces is 5 to 15 with respect to the total weight. A wood chip cement board on which a surface layer occupying weight% is laminated, wherein a coefficient A defined by the equation (1) is used.
Is 3 or more. A = a / bc (1) [where a and b are JIS A1408, respectively.
Stress (MP) in the bending test measured according to
a) represents the elastic modulus (MPa), and c is 60 ° C. after water saturation.
[0005] In the wood chip cement board of the present invention, the cement material used for the base layer is not particularly limited. For example, ordinary portland cement, special portland cement (early strength) Hydraulic cements such as Portland cements such as Portland cement); air-hard inorganic substances such as lime and gypsum. Further, when a heating step such as a hot press is used in the molding step, a thermosetting component capable of shortening the curing time may be used in combination with Portland cement. [0006] Examples of the thermosetting component include alumina cement, anhydrous gypsum, gypsum hemihydrate and the like. These may be used alone or in combination of two or more. These thermosetting components, by being combined with Portland cement, ettringite when hydrated _{(3CaO · Al 2 0 3 ·} 3CaS0 4 · 32H
₂₀ ) to accelerate the curing reaction. [0007] If necessary, calcium hydroxide (hydroxide) such as slaked lime or quick lime may be added to the cement material to adjust the amount of calcium component. In the wood chip cement board of the present invention, the wood chip used for the base layer is not particularly limited, and a wood chip obtained by subdividing a wood chip made from new wood, construction waste wood, or the like can be suitably used. For example, cedar, cypress, pine,
Toga, straw, oak, nara, birch, beech, oak, lauan,
Materials made of materials such as lark, chestnut, zelkova, shii, willow and bamboo can be used. As a method for producing the above-mentioned wood piece, a known method can be used, and examples thereof include pressing, pressing with a rotating roll, cutting with a slitter and a cutter. [0010] The shape of the wood piece is appropriately selected according to the application and the desired strength.
mm and a thickness of 2 mm or less are preferable. If the amount of the above-mentioned wood chips is too small, the effect of reinforcing the base material layer becomes small, the strength becomes insufficient, the specific gravity increases, the weight of the wood chip cement plate increases, and the lightness is impaired. On the other hand, if the amount is too large, the water absorption rate increases, the dimensional stability decreases, and the fire resistance also decreases. Therefore, the amount is limited to 5 to 15% by weight based on the total weight of the base material layer. In the wood chip cement board of the present invention, the inorganic lightweight aggregate used in the base layer is not particularly limited, and examples thereof include fly ash balloons, glass beads, glass balloons, perlite, shirasu balloons, vermiculite, and the like. If the average particle size of the inorganic lightweight aggregate is too small, it is difficult to form a lightweight aggregate having a small bulk density, and if the average particle size is too large, it tends to become a defect and the strength of the base material is reduced.
It is preferably from 30 to 400 μm, more preferably from 50 to 2 μm.
00 μm. If the bulk density of the inorganic lightweight aggregate is too high, the effect of reducing the weight of the wood chip cement board is reduced.
/ Cm ³ or less. When the amount of the inorganic lightweight aggregate is too small, the effect of reducing the weight of the wood chip cement board is small, and when the amount is too large, the strength of the base material layer is reduced. 40 parts by weight are preferred. In the wood chip cement board of the present invention, if the amount of water used for the base material layer is too small, the hydration reaction of the cement material becomes insufficient and the strength is reduced. Also,
If the amount is too large, a small mass can be formed at the time of mixing and cannot be uniformly mixed, and the formed base material layer becomes inhomogeneous and low-strength. Therefore, 20 to 60 parts by weight with respect to 100 parts by weight of the cement material. Is preferred. The base layer of the wood chip cement board of the present invention comprises the above cement material, wood chip, inorganic lightweight aggregate and water, and the amount of the wood chip accounts for 5 to 15% by weight based on the total weight. is there. In the wood chip cement board of the present invention, the same cement material as that used for the base material layer can be used for the surface layer. In the wood chip cement board of the present invention, the fine wood piece used for the surface layer can be smaller in average volume than the wood piece used for the base material layer. The above-mentioned thin wood pieces are obtained by finely pulverizing the wood pieces. Examples of the method for fine pulverization include a method using a ring-type hammer mill (manufactured by Pearlman) and a disk cutter mill (“HT-300” manufactured by Horai). The shape of the thin wood piece is appropriately selected according to the application, the desired strength and the like. If the average size of the thin wood pieces is too small, the dispersibility decreases during mixing, and if the average size is too large, the surface decoration performance decreases, so the length is 0.5 to 10 m.
m, a width of 0.1 to 2 mm and a thickness of 0.05 to 1 mm are preferable, and the average volume (length × width × thickness) is 0.02 times or less of the average volume of a piece of wood used for the base material. preferable. In particular, it is preferable to use a fibrous wood piece having an average aspect ratio of 8 or more as a thin wood piece used for at least one of the surface layers (usually, when used as an outer wall, the back side when used). By doing this,
When the strength of the surface layer on this side is increased and the wood chip cement board is used as the outer wall, cracks can be prevented by wind pressure. Also, on the surface of the other layer (usually, when used as an outer wall, the side that becomes the surface when used), it is preferable to use sawdust-shaped small pieces of wood in order to form a decorative pattern. If the amount of the thin wood pieces is too small, the effect of reinforcing the surface layer is small, the strength is insufficient, the specific gravity is increased, the weight of the wood chip cement board is increased, and the lightness is impaired. Also, if too much, the water absorption rate will increase,
Since the dimensional stability is reduced and the fire resistance is also reduced, the content is limited to 5 to 15% by weight based on the total weight of the surface layer. The amount of wood chips in the base material layer and the amount of fine wood chips in the surface layer are preferably substantially the same in order to make the dimensional change rates of dry and wet changes of each layer the same. In the wood chip cement board of the present invention, the inorganic fine aggregate used for the surface layer is not limited as long as it has an average particle size of 100 μm or less. For example, silica sand, silica stone powder, silica sand, blast furnace slag, fly Ash, silica fume,
Wollastonite, mica and the like. By using a fine inorganic fine aggregate having an average particle size of 100 μm or less, when the cement material is hardened, the voids such as the interface between the fine particles of the surface layer and the cement material are filled with the inorganic fine aggregate, A cured product having high denseness and excellent strength is obtained, and has a low water absorption rate, and thus has excellent water resistance. The above-mentioned inorganic fine aggregate has an average particle size of 100 μm.
When it becomes larger, it is difficult to fill the voids such as the interface between the thin wood pieces and the cement material with the inorganic fine aggregate, and a dense cured body cannot be obtained, the strength is reduced, and the water absorption speed is increased, so that the water permeability is poor. It will be. If the amount of the above-mentioned inorganic fine aggregate is too small, it is insufficient to fill the gap between the fine wood pieces and the cement material in the hardened material, a dense hardened material cannot be obtained, the strength becomes insufficient, and the water absorption rate becomes lower. Becomes faster, the dimensional stability is reduced, if too much, the proportion of cement material as an adhesive component is reduced, and strength may be reduced, so 10 to 80 parts by weight with respect to 100 parts by weight of cement material preferable. In the wood chip cement board of the present invention, the amount of water used for the surface layer is the same as that of the base material layer, but is not necessarily equal. The thickness of the surface layer is preferably 0.5 mm or more, since if it is too thin, water resistance and reinforcing effect cannot be expected. The wood chip cement board of the present invention has the above-mentioned surface layer laminated on at least one surface of the above-mentioned substrate layer, and the coefficient A defined by the above formula (1) is 3 or more. It is characterized by. In the above formula (1), a / b corresponds to the elongation at the yield point (not always completely coincident), and the larger the ratio, the more difficult it is for the wood chip cement board to break. Also,
As for c, the smaller this is, the more difficult it is to cause breakage (dimensional change leading to yield point elongation) based on the aging dry and wet cycle. Therefore, the larger the value of a / b and the smaller the value of c, the larger the coefficient A, and the smaller the dimensional change due to drying shrinkage and shrinkage due to shrinkage due to aging and neutralization of the hardened cement over time. The yield stress a (MPa) and the elastic modulus b (M
Pa) can be calculated by a bending test measured according to JIS A1408, respectively. The dimensional change rate c can be calculated from the amount of change after measuring the size after being saturated (for example, after immersing in water for one day) and the size after drying at 60 ° C. for 48 hours. As a method for producing the wood chip cement board of the present invention, for example, a composition comprising the above cement material, fine wood pieces, inorganic fine aggregate and water is mixed by a conventionally known method such as a Henschel mixer or an omni mixer. After that, the mixture is sprayed and dropped on a mold and deposited, and on the upper surface, a composition consisting of cement material, wood chips, inorganic lightweight aggregate, and water is similarly sprayed, and further on the upper surface, In the same manner, a composition comprising a cement material, a thin wood piece, an inorganic fine aggregate, and water is sprayed in the same manner, and the composition is cured by pressurizing and heating with a hot press or the like for a predetermined time and then released. The present invention will be described below in more detail with reference to examples. (Examples 1 to 5, Comparative Example 2) Raw material and cement material A used for manufacturing wood chip cement board A early strength Portland cement (manufactured by Taiheiyo Cement) 80 parts by weight Thermosetting component Alumina cement (manufactured by Denki Kagaku) Name "DENKA No. 2") 10 parts by weight Plaster of Paris (Adra Industry Co., Ltd.) 6 parts by weight Slaked lime (Komagata Lime Industry Co., Ltd.) 4 parts by weight previously mixed. A wood chip in which wood cypress and cedar are mixed is cut or pulverized to a length of 60 mm or less, a width of 20 mm or less, and a thickness of 2 mm or less (average length 10 mm, average width 1 mm, average thickness 0.5
mm). Thin wood piece A Ring wood hammer mill (manufactured by Pearlman)
Finely pulverized, average length 1.4 mm, average width 0.3 mm,
One with an average thickness of 0.1 mm. Thin wood piece B The above wood piece is finely pulverized with a disk cutter mill (manufactured by Horai Co., model "HT-300"), and the average length is 4 mm.
The average width is 0.4 mm and the average thickness is 0.2 mm. Fly Ash Balloon manufactured by Taiheiyo Cement Co., Ltd., trade name "Pozzospheres"
(Average particle size: 130 μm) Silica sand No. 8 (Rokuriya Mining Co., Ltd., average particle size: 70 μm) Fly Ash Pacific Cement Co., Ltd., trade name “Super Flow” (average particle size: 10 μm) Manufacturing Method A kneaded product obtained by supplying a predetermined amount of cement material A, fine wood chip A, silica sand, fly ash, and water shown in Table 1 to a Henschel mixer was mixed with a metal having a joint pattern with a depth of 5 mm. It was sprayed and dropped on a mold plate made of a resin to obtain a surface layer (surface side) having a predetermined thickness. Then, a predetermined amount of cement material A,
The kneaded material obtained by supplying the wood chips, the inorganic lightweight aggregate, and the water to the Henschel mixer was scattered and dropped on the above-mentioned surface layer to be stacked and laminated to obtain a base material layer having a predetermined thickness. Further, a kneaded material obtained by supplying a predetermined amount of cement material A, fine wood piece A, fine wood piece B, silica sand, fly ash, and water to the Henschel mixer is sprayed and dropped on the above-mentioned base material layer to be deposited and laminated. Thus, a surface layer (back side) having a predetermined thickness was obtained. The laminate obtained by laminating the surface layers on both sides of the base material layer obtained as described above was subjected to a pressure of 4 MPa and a temperature of 97
Cured by hot pressing at 12 ° C for 12 minutes,
Thereafter, the mold was released from the template to obtain a wood chip cement plate having a thickness of about 15 mm in which the surface layer was laminated on the base material layer. (Comparative Example 1) In place of cement material A, ordinary Portland cement (manufactured by Taiheiyo Cement Co., hereinafter referred to as “cement material B”) was used.
A wood chip cement board was obtained in the same manner as in Example 2, except that the mixture was cured by autoclaving for 18 hours while being pressed at 1 ° C at 1 ° C. [Table 1] Calculation of Coefficient A The wood chip boards obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were subjected to the following tests. Yield stress, modulus of elasticity Wood piece cement board adjusted to one week of age is JIS A14
Bending test was performed according to the method described in No. 08, and yield stress a and elastic modulus b were calculated. Dimensional change rate The obtained wood chip cement board was cut into a 150 mm × 50 mm dumbbell shape, and the dimensions after immersion in water for 1 day and the dimensions after further drying at 60 ° C. for 48 hours were measured with a micrometer. Then, the dimensional change rate c was calculated from the equation (2). c = (dimension after immersion in water−dimension after drying) / dimension after drying (2) Durability test The wood chip cement boards obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were each 900 mm × Cut into a shape of 900 mm, fixed to a square pipe-shaped square frame made of aluminum alloy with a width of 30 mm, a height of 15 mm, and a thickness of 1 mm with an adhesive and a screw.
After hydration carbonation treatment was performed at 80 ° C., 80% RH, and 10% CO ₂ for 3 days, a dry / wet repetition test (a cycle of watering 2 h → 90 ° C. drying 9 hr) was repeated 30 times. After repeating the hydration carbonation treatment and the dry / wet repetition test alternately three times, remove from the frame and remove 150 mm x 50 m
m and subjected to the following test. Evaluation of physical properties after durability test Bending test A bending test was performed according to JIS A1408, and the yield stress and elastic modulus were calculated. Water absorption test -1) Dimensional change rate Dimension after immersion in water for 1 day, and 4% at 60 ° C.
The dimensions after drying for 8 hours are measured with a micrometer,
The dimensional change rate was calculated in the same manner as in the equation (2). -2) Flexural yield stress After immersion in water for 1 day, the flexural yield stress after further drying at 60 ° C for 48 hours was measured according to JIS A1408. The measurement was performed with 40 samples, and the ratio of those having a yield stress of 9 MPa or less is shown in Table 2. -3) Warp amount After immersion in water for one day and further drying at 60 ° C. for 48 hours, a thread was attached to both ends of the wood chip cement board, and the hollow amount (warpage amount) at the center was measured on a scale. From the above results,
The results are summarized in Table 2. [Table 2] The wood chip cement board of the present invention comprises a cement material, a wood chip, an inorganic lightweight aggregate, and water, wherein the amount of the wood chip accounts for 5 to 15% by weight based on the total weight. At least one surface of the layer is composed of a cement material, fine wood pieces finer than the above wood pieces, inorganic fine aggregate having an average particle size of 100 μm or less, and water, and the amount of the above wood pieces is 5 to 15 with respect to the total weight.
This is a wood chip cement board on which a surface layer occupying weight% is laminated, wherein the coefficient A defined by the equation (1) is 3 or more, so that it is lightweight, strong, and water-resistant. It will be excellent.

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Claims (1)

Claims: 1. A cement material, a wood chip, an inorganic lightweight aggregate, and water, wherein the amount of the wood chip is 5 to 15 with respect to the total weight.
At least one surface of the base layer occupying 5% by weight is composed of a cement material, fine wood pieces finer than the above wood pieces, inorganic fine aggregate having an average particle size of 100 μm or less, and water. A wood chip cement board on which a surface layer occupying 〜15% by weight is laminated, wherein the coefficient A defined by the formula (1) is 3 or more. A = a / bc (1) [where a and b are JIS A1408, respectively.
Stress (MP) in the bending test measured according to
a) represents the elastic modulus (MPa), and c is 60 ° C. after water saturation.
Represents the dimensional change rate when dried for 48 hours.]