JP4427287B2 - Manufacturing method of wood cement board - Google Patents

Description

  The present invention relates to a method for producing a wood cement board used for, for example, an outer wall material, a roof material and the like.

Conventionally, a wood cement board, which is a cement board reinforced with a wood reinforcing material such as a piece of wood, a wood fiber bundle, wood hair, wood powder, wood pulp, or the like, is often used as a building board such as an outer wall material or a roof material.
In the case where the building board is produced by extrusion molding or papermaking, recently, a wood cement molded body containing fine fibrous cellulose as the wood reinforcing material has been provided in consideration of extrusion moldability and papermaking properties (for example, Patent Document 1). , See Patent Document 2).
As described above, as a method for producing a wood cement board, in addition to the extrusion method and the papermaking method (wet method), the raw material mixture is spread on a formwork or a conveying plate, the mat is formed, and the mat is pressed. There are dry and semi-dry methods for curing and curing.

JP-A-10-29844 ([Claim 1]) Japanese Patent Publication No. 6-99173 (Claim 1)

The dry method and semi-dry method are very good in productivity compared with the extrusion method and papermaking method, and are desirable methods for producing a wood cement board. The dry method or semi-dry method is not applied to the production of cement board.
An object of the present invention is to ensure good productivity and sufficient strength even if the amount of wood reinforcing material used in the wood cement board is reduced.

As a means for solving the above-described conventional problems, the present invention provides a raw material mixture for front and back layers mainly composed of a hydraulic inorganic material and a wooden reinforcing material on a substrate placed on a belt conveyor as a conveying plate. Then, after adding water so that the water content becomes 30 to 50% by mass, it is spread in a mat shape, and then a core layer raw material mixture mainly composed of a hydraulic inorganic material and a wood reinforcing material is Water is added so that the water content becomes 30 to 50% by mass, and then spread in a mat shape. Further, a raw material mixture for front and back layers mainly composed of a hydraulic inorganic material and a wood reinforcing material is After adding water so that the content becomes 30 to 50% by mass, it is spread in a mat shape to form a three-layer mat, and the mat is pressed, cured, and hardened . It is a manufacturing method, and it is a raw material mixture for front and back layers 30 to 55% by mass of a hydraulic inorganic material, 12 to 14% by mass of flaky wood pieces having an opening of 4.5 mm or less as a wood reinforcing material, and wood powder having a particle size of 0.5 to 1.5 mm. It is contained in an amount of 2 to 5% by mass, and the raw material mixture for the core layer contains 30 to 55% by mass of a hydraulic inorganic material, and 2 pieces of flaky wood pieces having an opening of 4.5 to 10 mm as a wood reinforcing material. -4% by mass, wood fiber bundles are contained in an amount of 7-10% by mass, and either one of the front and back layer raw material mixture and the core layer raw material mixture has an average diameter of 0.01 to 1 μm and an average length The present invention provides a method for producing a wood cement board in which fine fibrous cellulose having a thickness of 100 to 1000 μm is contained in an amount of 5% by mass or less .
Furthermore, when the microfibrous cellulose is added to the raw material mixture, it is preferably dispersed in water and added to the raw material mixture.

[Action]
Microfibrous cellulose is very fine and thin, so it is easy to disperse uniformly in the raw material mixture, and it is easy to take in powder between fibers, and the reinforcing effect is great, so the amount of added wood reinforcing material is reduced. I can do it.
As described above, since the microfibrous cellulose is very fine and thin, the raw material mixture in which the microfibrous cellulose is mixed is easy to loosen, spread on the substrate, and form a mat with a uniform density. I can do it. In particular, when a wood reinforcing material other than the microfibrous cellulose, such as a piece of wood or a bundle of wood fibers, which is not easily entangled, is used, the workability of the raw material mixture is further improved.
Furthermore, if the microfibrous cellulose is used, the surface of the plate becomes dense and smooth. Accordingly, moisture absorption is suppressed, and crack resistance and freeze resistance are improved.

〔effect〕
In the present invention, a wood cement board having sufficient strength even if the amount of wood reinforcement added is reduced is provided. In the present invention, the wood cement board is produced by a dry method, so that the productivity is very good and it can be provided at low cost.
The present invention is described in detail below.

[Hydraulic inorganic material]
As the hydraulic inorganic material used in the present invention, cements such as Portland cement, blast furnace cement, silica cement, fly ash cement, and alumina cement are used. The cements are hardened by a hydration reaction in the presence of water.

[Wood reinforcement]
Examples of the wood reinforcing material used in the present invention include wood chips, wood powder, wood fibers, pulp, wood fiber bundles, wood wool, bamboo fibers, hemp fibers and the like.
Particularly desirable wood reinforcements are wood chips and / or wood fiber bundles. As the piece of wood, a piece of wood having a width of 0.5 to 2 mm, a length of 1 to 20 mm, and an aspect ratio (length / thickness) of 20 to 30 is used, and the wood fiber bundle usually has a main trunk diameter of about 0.1 to 0.1 mm. The actual length of the main trunk is in the range of about 2 to 35 mm, more preferably 10 to 30 mm, and the wood fiber bundle is preferably branched and / or bent and / or bent. The above-mentioned pieces of wood and wood fiber bundles are easily loosened in the raw material mixture, can be mixed uniformly, and improve the workability of spreading.

In the present invention, fine fibrous cellulose is further added. The microfibrous cellulose is produced, for example, by cutting the fibrous cellulose by shearing force by passing a suspension of fibrous cellulose through a small diameter orifice under high pressure at a high speed (Japanese Patent Publication No. 60-19921). Publication).
The fine fibrous cellulose usually has an average diameter of 0.01 to 1 μm and an average length of 100 to 1000 μm.
Since the above-mentioned microfibrous cellulose is also easily dispersed uniformly in the raw material mixture and is easily loosened, the workability for spreading is improved.

[Third component]
In addition to the above raw materials, a part of the cement is further replaced with silica-containing materials such as silica sand, silica stone powder, silica fume, blast furnace slag, fly ash, shirasu balloon, perlite, bentonite, diatomaceous earth and / or pozzolanic materials. Or, anhydrous or crystallized chloride such as calcium chloride, magnesium chloride, iron chloride, aluminum chloride, sodium chloride, potassium chloride, lithium chloride, aluminum sulfate, alum, iron sulfate, lithium sulfate, sodium sulfate, Anhydrous or crystallized sulfates such as potassium sulfate and magnesium sulfate, nitrates such as calcium nitrate and calcium nitrite, anhydrous or crystallized nitrites, formates such as calcium formate and calcium acetate, and anhydrous anhydrides of acetate Or crystallized product, sodium aluminate, water Cement accelerators or wax such lath, paraffin, water repellent agents such as silicon, a foamable thermoplastic plastic beads such as expandable polystyrene beads may be added.

[Wood cement board waste pulverized product]
In the present invention, a wood cement board waste material pulverized product may be further added. The wood cement board waste material pulverized material is a wood cement board waste material pulverized material using wood reinforcing material such as wood fragments, wood fiber bundles, wood powder, wood pulp, etc., for example, used for outer wall materials, roofing materials, etc. Waste materials generated when a building is demolished, repaired, or the like, or chips or cuts generated when the wood cement board is manufactured. These waste materials are mixed as a pulverized product with a wood cement board raw material and reused in the production of a wood cement board.
The wood cement board waste material is pulverized into a primary pulverized product having a particle size of 0.5 to 2.0 mm by a hammer mill, and the primary pulverized product can be reused as a part of the wood cement board raw material. A secondary pulverized product obtained by secondary pulverizing the primary pulverized product with a roller mill may be used as a raw material. The wood cement board waste material pulverized product used in the present invention preferably has a specific surface area of about 4000 to 8000 cm ² / g.

[Raw material preparation]
In the present invention, 30-80% by mass of the hydraulic inorganic material and usually 10-40% by mass of the wooden reinforcing material are added to the raw material mixture mainly composed of the hydraulic inorganic material and the wooden reinforcing material. . If desired, a slight amount of the third component is added to the raw material mixture, and then the raw material mixture is hydrated so that the water content is 30 to 50% by mass.
The microfibrous cellulose is usually added to the raw material mixture in an amount of 5% by mass or less, preferably 0.05% by mass or more, but the microfibrous cellulose is separate from other wood reinforcing materials, At the time of hydration, it is dispersed in water and added to the raw material mixture. As described above, the microfibrous cellulose is easy to uniformly disperse in water. Therefore, if the microfibrous cellulose is added to the raw material mixture in a state of being dispersed in water, the microfibrous cellulose is uniformly added to the raw material mixture. Can be mixed.

[Manufacture of wood cement board]
In the present invention, a dry method (semi-dry method) having a single layer or a three-layer structure is applied to the production of the wood cement board.
The single-layer wood cement board of the present invention is manufactured by spreading a raw material mixture on a substrate to form a mat, and then curing the mat by pressing and curing. The raw material mixture is usually 30 to 80% by mass of the hydraulic inorganic material, 10 to 40% by mass of the wood reinforcing material of wood pieces and / or wood fiber bundles, and the raw material mixture thus prepared further has an average diameter of 0. 0.01 to 1 μm, average fiber length of 100 to 1000 μm of microfibrous cellulose added in an amount of 5% by mass or less, added so that the amount of water is 30 to 50% by mass or less, and the cement hardening accelerator is an amount of several mass% or less. It is prepared by addition. The raw material mixture thus prepared is produced by spraying on a substrate as described above, forming a mat, and curing the mat by pressing and curing.

In the continuous manufacturing method, a large number of the substrates are placed and placed on a belt conveyor as a transport plate.
If desired, the raw material mixture spread on the substrate is slightly pressed by a roll or the like to adjust the thickness, and the surface is smoothed to form a mat, which is then pressed in step 2 in the presence of moisture. It is pre-cured and formed into a desired shape.

  The pressing conditions are usually a pressing pressure of 1 to 3 MPa, a temperature of 60 to 80 ° C., a pressing time of about 6 to 20 hours, and heating is usually performed with steam. The pressing is performed by sandwiching the mat between two substrates, but a predetermined shape, uneven pattern, or the like may be applied to the substrate surface. The precured material obtained by the pressure precuring in Step 2 is cured in an autoclave in Step 3.

The curing conditions are usually a pressure of 0.6 to 1 MPa, a temperature of 160 to 180 ° C., and a time of about 5 to 10 hours. The autoclave curing causes a calcium silicate reaction between the cement and the silicate-containing substance.
Further, in step 3, curing may be performed at room temperature of 25 ° C. for 7 days. However, in this case, it is desirable to lower the mixing ratio of the silicic acid-containing substance and increase the cement.
In this way, the single-layered wood cement board of the present invention is produced, and the specific gravity of the wood cement board is usually 0.8 to 1.2.

In the case of a three-layer structure wood cement board, the composition of the raw material mixture A for the front and back layers is usually 30 to 55% by mass of cement, 15 to 35% by mass of a silicic acid-containing substance, 5 to 20% by mass of wood reinforcing material of wood pieces, 1 to 8% by weight of wood powder, 5 to 30% by weight of pulverized wood cement board waste, 30 to 30% water added with 5% by weight or less of microfibrous cellulose having an average diameter of 0.01 to 1 μm and an average fiber length of 100 to 1000 μm It is prepared by adding 50% by mass.
The composition of the raw material mixture B for the core layer is usually 30 to 55% by mass of cement, 0 to 25% by mass of fly ash, 2 to 15% by mass of wood reinforcing material of wood pieces, and 5 to 20% by mass of wooden reinforcing material of wood fiber bundle. In addition, the polystyrene foam beads 2-3% by mass, the wood cement board waste material pulverized material 5-40% by mass, the raw material mixture thus prepared further has an average diameter of 0.01-1 μm and an average fiber length of 100-1000 μm. It is prepared by adding water so that 5% by mass or less of microfibrous cellulose is added to 30 to 50% by mass or less.
A cement hardening accelerator is usually added to the raw material mixtures A and B in an amount of several mass% or less.

  In the case of the above-mentioned raw material mixture A for the front and back layers, a wood powder having a particle size of 0.5 to 1.5 mm is usually used as a wood reinforcing material to give a flaky wood piece having a mesh size of 4.5 mm or less or a dense structure. In the case of the raw material mixture B for the core layer, a flaky wood piece having an opening of 4.5 to 10 mm or an average diameter of 1. It is desirable to use a coarse wood reinforcing material such as a wood fiber bundle of about 0 mm and a length of 20 mm.

  As a method for producing a three-layer structure wood cement board, the raw material mixture A is spread in a mat shape on a substrate, and then the raw material mixture B is spread in a mat shape thereon, and further, the raw material mixture A is further formed thereon. Is sprayed in a mat shape. When wood fragments and wood fiber bundles, especially wood fiber bundles made bulky by bending and / or bending and / or bending, are used as the wood reinforcing material, the raw material mixture becomes easy to loosen and uniformly on the template. Easy to spread.

  The three-layer mat is pressed and cured in the same manner as the single-layer mat. In the autoclave curing, the calcium silicate reaction between the cement and the silicic acid-containing substance is completely carried out as in the case of the single-layer structure mat. However, when foaming thermoplastic beads are added to the core layer, The foamable thermoplastic beads are completely foamed and the foam particles melt and then rapidly shrink to form a number of pores within the core layer. A thermoplastic coating layer is formed on the inner wall surface of the hole.

  The thickness of the front and back layers of the three-layered wood cement board thus produced is usually 10 to 30% of the total thickness, and the specific gravity is 0.8 to 1.2.

As described above, the microfibrous cellulose is easily loosened, and further, when a piece of wood and / or a wood fiber bundle is used as a wood reinforcing material, the wood piece and / or the wood fiber bundle is also easily loosened. It is easy to loosen, it can be easily spread on the substrate, and a uniform mat can be formed.
The present invention will be described more specifically below.

[Examples 1 to 5, Comparative Examples 1 and 2]
As shown in Table 1, 75% by mass of cement, 20-25% by mass or less of wood pieces as a wood reinforcing material, and 45% by mass of water to which 0.1 to 5.0% by mass of fine fibrous cellulose was added were prepared. A single-layer wood cement board sample having a board thickness of 14.0 mm was prepared according to the compositions of Comparative Examples 1 and 2 to which 1 to 5 and no microfibrous cellulose were added and 7.0% by mass was added.

  As shown in Table 1, the samples of Examples 1 to 5 in which microfibrous cellulose was added to the raw material mixture in an amount of 5% by mass or less had sufficient bending strength and cracks did not occur. On the contrary, the sample of Comparative Example 2 in which cellulose is added in an amount of 5% by mass or more (7% by mass) tends to have poor dispersibility, and cracks are generated. Moreover, even if it includes a piece of wood as a wood reinforcing material, Comparative Example 1 which does not contain fine fibrous cellulose has low bending strength.

[Examples 6 to 8, Comparative Example 3]
As shown in Table 2, raw material mixture for front and back layers to which cement, quartz sand, wood chips, wood powder, fine fibrous cellulose, rejects that are pulverized wood cement board waste materials are added, part of wood and wood Each composition of Examples 6-8 which used the raw material mixture for core layers which added the wood fiber bundle and the expanded polystyrene bead instead of powder, and the comparative example 3 which did not add microfibrous cellulose to the front and back layers and the core layer Thus, a wood cement board sample of a three-layer structure having a board thickness of 16.0 mm was prepared.

  Table 3 shows the physical properties of the wood cement board samples of Examples 6 to 8 and Comparative Example 3.

  As shown in Table 3, Comparative Example 3 containing no fine fibrous cellulose is inferior in bending strength to Examples 6, 7, and 8.

  The wood cement board of the present invention can reduce the amount of wood reinforcement added, and is useful for building materials such as outer wall materials and roof materials.

Claims (2)

A substrate mixture placed on a belt conveyor as a transport plate and juxtaposed is mixed with a raw material mixture for front and back layers mainly composed of a hydraulic inorganic material and a wood reinforcement so that the water content is 30 to 50% by mass. Then, it was spread in a mat shape, and then a core layer raw material mixture mainly composed of a hydraulic inorganic material and a wood reinforcing material was added thereto so that the water content was 30 to 50% by mass. On top of the above, it is spread in a mat shape, and further, a raw material mixture for front and back layers mainly composed of a hydraulic inorganic material and a wood reinforcing material is added thereto so that the water content becomes 30 to 50% by mass. A method for producing a three-layered wood cement board which is distributed in a mat shape to form a three-layered mat, and the mat is pressed, cured and hardened .
The raw material mixture for the front and back layers is 30 to 55% by mass of a hydraulic inorganic material, 12 to 14% by mass of flaky wood pieces having an aperture of 4.5 mm or less as a wood reinforcing material, and an aperture of 0.5 to 1.5 mm. Containing 2 to 5% by weight of wood powder of
The raw material mixture for the core layer includes 30 to 55% by mass of a hydraulic inorganic material, 2 to 4% by mass of flaky wood pieces having an opening of 4.5 to 10 mm as a wood reinforcing material, and 7 to 10% by mass of a wooden fiber bundle. % Content,
Either one of the raw material mixture for the front and back layers and the raw material mixture for the core layer contains microfibrous cellulose having an average diameter of 0.01 to 1 μm and an average length of 100 to 1000 μm in an amount of 5% by mass or less. <br/> A method for producing a wood cement board characterized by the above. The method for producing a wood cement board according to claim 1 , wherein when the fine fibrous cellulose is added to the raw material mixture, the fine fibrous cellulose is dispersed in water and added to the raw material mixture.