JP2003011110A - Wood cement board and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wood cement board of a good dimensional stability and a good surface crack resistance. SOLUTION: In order to improve a surface crack resistance an aromatic polyether amide fiber and a dry fibrillated pulp are mixed in front and rear layers of the wood cement board having a three layer structure such as the front layer, the rear layer and a core layer.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A wood cement board is a mat formed by spraying a raw material mixture mainly composed of wood reinforcing materials such as wood chips, wood powder, wood fibers, pulp and cements on a substrate to form a mat. It is manufactured by performing autoclave curing after pre-curing by pressing. In order to improve the dimensional stability of such a wood cement board, conventionally, it has been generally accepted that increasing the specific gravity of the board and reducing the addition amount of the wood reinforcing material are effective means.

[0003]

However, with such means, there is a problem that the toughness of the plate is lowered and the plate surface becomes hard and brittle with age, and microcracks are likely to occur.

[0004]

[Means for Solving the Problems] As a means for solving the above-mentioned conventional problems, the present invention comprises a wood reinforcing material and cements as main raw materials, and a front and back layer having a dense structure and a core layer having a rough structure. The present invention provides a wood cement board which has a three-layer structure, and in which the front and back layers are a mixture of aromatic polyetheramide fibers and dry defibrated pulp. The front and back layers are preferably mixed with the aromatic polyetheramide fibers in an amount of 3% by weight or less and the dry defibrated pulp in an amount of 20% by weight or less, and the aromatic polyetheramide fibers have a fiber length of 4 or less. .About.8 mm, fiber diameter is 5 to 20 .mu.m, fiber length of the dry defibrated pulp is 0.5 to 6 mm, fiber diameter is 7 to 15
It is preferably in the form of cotton in μm. Furthermore, the specific gravity of the wood cement board is preferably 1.0 to 1.6. In order to produce the above-mentioned wood cement board, wood reinforcing material and cements are used as main raw materials on the substrate, and further, a raw material mixture for front and back layers in which aromatic polyetheramide fibers and dry defibrated pulp are mixed is sprinkled. The surface layer or the back layer mat is formed, and the core layer raw material mixture containing a wood reinforcing material and cement as a main material is sprinkled on the surface layer or the back layer mat to form the core layer mat, and the core layer mat is formed. A method of spraying the above-mentioned raw material mixture for the front and back layers to form the back layer or the front layer mat, and pressing the above three-layer mat to carry out autoclave curing after pre-curing is applied. Usually, the autoclave curing temperature is preferably 160 ° C. or higher.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. [Cements] The cement-based inorganic material used in the present invention includes cements such as Portland cement, blast furnace slag cement, silica cement, fly ash cement, and alumina cement. Silica powder, silica sand, silica stone powder, water glass, silica fume, shirasu balloon, perlite, diatomaceous earth, dolomite, and other silicic acid-containing substances may be mixed with the cements. When the cements and the silicic acid-containing substance are mixed, the mixing ratio (weight ratio) of the cements and the silicic acid-containing substance is 1: 2.5 to.
It is about 6: 1.

[Wood Reinforcement Material] The wood reinforcement material used in the present invention includes wood powder, wood wool, wood chips, wood fibers, wood pulp, wood fiber bundles and the like. The wood reinforcement material is bamboo fiber, hemp. A material containing lignocellulose as a main component such as fiber, bagasse, chaff, rice straw, etc. may be mixed. The preferred wood reinforcing material is a width of 0.5 to 2.0 mm, a length of 1 to 20 mm, an aspect ratio (length / thickness) of 20 to 30 wood pieces, a diameter of 0.1 to 2.0 mm, and a length of 2 to 35 mm. There are branched and / or curved and / or bent wood fiber bundles of.

In the present invention, as the above-mentioned wood reinforcing material, a material regenerated from wood scrap can be used. As the wood scrap, for example, waste wood generated when dismantling a wooden building, sawdust or mill ends generated from the sawing process,
There are veneer lace scraps generated from the plywood manufacturing process, thinnings of conifers, scraps of wood cement boards and scraps. Further, in the present invention, wood reinforcing materials other than wood such as bamboo fiber, bamboo chips, hemp fiber, coconut fiber, and sugarcane slag can be used.

[Aromatic Polyetheramide Fiber] The aromatic polyetheramide fiber is obtained by polymerizing an aromatic diamine such as paraphenylenediamine, 3,4′-diaminodiphenyl ether and chloroparaphenylenediamine with terephthalic acid chloride. It is a fiber that is manufactured, commonly called aramid fiber, which has alkali resistance,
It has excellent heat resistance and a high Young's modulus. Further, the aromatic polyetheramide fiber has a rough surface, is firmly fixed in the cement hardened material matrix of the front and back layers, serves as a cement hardened material binder, strength, dimensional stability, crack resistance. To contribute. The aromatic polyetheramide fiber used in the present invention has a fiber length of 4 to 8 mm and a fiber diameter of 5 to 20.
μm is desirable.

[Dry Defibrated Pulp] The pulp used in the present invention is a dry defibrated pulp that is defibrated by a dry method using a defibrating machine such as a disc defibrating machine and is in the form of cotton. The dry defibrated pulp has a fiber length of 0.5 to 6 mm and a fiber diameter of 7 to 15
μm is desirable.

[Third component] In the molding material of the wood cement board of the present invention, calcium chloride,
Magnesium chloride, potassium sulfate, calcium sulfate, magnesium sulfate, aluminum sulfate, sodium aluminate, potassium aluminate, calcium formate, calcium acetate, calcium acrylate, cement hardening accelerator such as water glass, vermiculite, mineral powder such as bentonite, A waterproofing agent such as wax, wax, paraffin, silicone, and a surfactant, a water repellent, a foamable thermoplastic bead, and a plastic foam may be added. Further, in the present invention, a reject which is a crushed material of a wood cement board may be used. The reject is manufactured by crushing the wood cement board waste material to an average particle size of about 50 to 150 μm with an impact crusher and / or a scraping crusher. It should be noted that these examples do not limit the present invention.

[Blending of Raw Material Mixture A for Front and Back Layers] The raw material mixture A for front and back layers of the wood cement board of the present invention is cement 30
-60 wt%, silicic acid-containing substance 30-60 wt%, and wood reinforcing material 5-25 wt%. In the present invention,
The raw material mixture A is further mixed with the aromatic polyetheramide fibers and the dry defibrated pulp. In this case, the amount of the aromatic polyetheramide fiber added is 3% by weight or less in the raw material mixture A, and the amount of the dry defibrated pulp added is 20% by weight or less, preferably 10% by weight or less.

[Compounding of Core Layer Raw Material Mixture B] The core layer raw material mixture B of the wood cement board of the present invention comprises cements 30 to 6
It is a mixture of 5% by weight, 5 to 25% by weight of wood reinforcing materials such as wood chips and / or bundles of wooden fibers, and 10 to 40% by weight of rejects. When synthetic fibers such as vinylon fibers and polypropylene fibers are added, they have a binder effect and a reinforcing effect, and when 0.5 to 5% by weight of thermoplastic foam particles are mixed, pores are formed in the core layer and It is a desirable material because it improves the corrosion resistance.

[Method for Producing Wood Cement Board] As a method for producing a wood cement board of the present invention, it is desirable to adopt a dry production method in which the steps can be easily continued and the apparatus is simple. In step 1 of the dry manufacturing method, the mixture A is spread on the substrate in a mat shape, then the mixture B is spread on the substrate in a mat shape, and the mixture A is spread on the mat in a mat shape. However, in this case, the mixture A and the mixture B each contain 30 to 45% by weight of water for the curing reaction.
Add it. When the wood fiber bundle of the mixture B is made bulky by branching and / or bending and / or bending, the mixture B is easily disentangled and easily spread evenly on the substrate. In the continuous manufacturing method, a large number of the above substrates are placed on the belt conveyor. The raw material mixture scattered on the substrate is slightly pressed by a roll or the like if desired.

The mat is then pressed and pre-cured in step 2 to form the desired shape. Clamping conditions are usually a clamping pressure of 1 to 30 MPa, a temperature of 60 to 80 ° C., and a time of 10 to 3
It is performed in about 0 hours, and heating is usually performed with steam. The pressing is performed by sandwiching the mat between the substrates, but the substrate may be provided with a predetermined shape, an uneven pattern or the like. The pre-cured product obtained by the pressure pre-curing in step 2 is cured in an autoclave in step 3. The curing conditions are usually pressure of 0.5 to 2 MPa and temperature of 160 to 18.
The temperature is 0 ° C. and the time is 5 to 12 hours.

By the autoclave curing, the calcium silicate reaction between the cement and the silicic acid-containing substance is completely carried out, and the wood cement board is improved by the aromatic polyetheramide fiber (aramid fiber) mixed in the front and back layers. Crack resistance is obtained, and the dry defibrated pulp improves the toughness of the front and back layers, and further has good surface crack resistance.

In the above autoclave curing, 16
It is desirable to apply a high temperature of 0 ° C. or higher to smoothly proceed the hardening reaction of cements and to reduce the residual amount of unreacted materials as much as possible. The residual unreacted material adversely affects the dimensional stability of the plate.

As described above, the aromatic polyetheramide fiber is excellent in alkali resistance and heat resistance, and therefore, it does not melt and does not deform even when a high temperature of 160 ° C. or higher is applied in the cement hardened material matrix. , The intensity does not change.

In order to further improve dimensional stability, the wood cement board of the present invention preferably has a high specific gravity, that is, a specific gravity of 1.0 to 1.6, more preferably 1.2 to 1.4. Is desirable.

[Examples 1 to 7] A raw material mixture for front and back layers and a core layer shown in Table 1 was prepared. First, the raw material mixture for front and back layers was sprinkled on a lower template to form a mat having a thickness of 7 mm. Sprinkle the raw material mixture for the core layer on top to make a 39 mm thick mat,
Further, the raw material mixture for the front and back layers is sprinkled thereon to form a mat having a thickness of 46 mm, and the upper mold plate is brought into contact with the mat from above, followed by press-molding to perform pre-cure for 10 hours at a pressure of 20 MPa and a temperature of 70 ° C. The obtained molded product having a three-layer structure was a plate-shaped product having a diameter of 18 mm, and the molded product was then secondarily cured in an autoclave at a pressure of 0.6 MPa and a temperature of 165 ° C. for 7 hours to obtain the cement in the molded product. The silicic acid-containing substance was cured by the calcium silicate reaction, and the aramid fibers of the front and back layers were firmly fixed in the form of fine fibers in the cured product matrix.

[Comparative Examples 1 and 2]
A raw material mixture for the front and back layers and the core layer shown in (3) was prepared, and a molded product having a three-layer structure with a thickness of 18 mm was produced under the same conditions as in the examples using the raw material mixture. The molded body was hardened by the calcium silicate reaction between the cement and the silicic acid-containing substance in the molded body.

[0021]

[Table 1]

[0022]

[Table 2]

As shown in Table 2, Example 1 of the present invention
Samples Nos. 7 to 7 show good crack resistance due to the aromatic polyetheramide fibers (aramid fibers) mixed in the front and back layers, and the dry defibrated pulp improves the toughness of the front and back layers, resulting in even better surface resistance. Has cracking properties. On the other hand, in Comparative Example 1 in which neither the aromatic polyetheramide fiber nor the dry defibrated pulp was added to the front and back layers, the crack resistance was significantly inferior to the sample of the Example, and the aramid fiber was not added to the front and back layers. Example 2 is also inferior in crack resistance.

[0024]

In the present invention, since the aromatic polyetheramide fiber and the dry defibrated pulp are added only to the front and back layers,
The amount of expensive aromatic polyetheramide fibers used can be kept to a minimum, and even in wood cement boards set to a high specific gravity to improve dimensional stability, the above-mentioned aromatic polyetheramide fibers provide crack resistance. The surface crack resistance is greatly improved due to the improved toughness of the front and back layers by the dry defibrated pulp.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C04B 40/02 C04B 40/02 // (C04B 28/02 16:02 Z 16:02 16:06 E 16 : 06 18:16 18:16) F-term (reference) 4F100 AE01A AE01B AE01C AK46A AK46C AK46J AK54A AK54C AK54J AL01A AL01C AP00A AP00B AP00C AP00 PA PA03 PA03 PA23 PA23 PA23 PA23 PA23 PA22 PA23 PA06A22A23 PA34 PE06 4G052 AB30 AB42

Claims (6)

[Claims] 1. A wood-based reinforcing material and cements as main raw materials,
A wood cement board characterized by having a three-layer structure of front and back layers having a dense structure and a core layer having a rough structure, wherein the front and back layers are a mixture of aromatic polyetheramide fibers and dry defibrated pulp. 2. The wood cement board according to claim 1, wherein the aromatic polyetheramide fibers are mixed in the front and back layers in an amount of 3% by weight or less and the dry defibrated pulp is mixed in an amount of 20% by weight or less. 3. The aromatic polyetheramide fiber has a fiber length of 4 to 8 mm and a fiber diameter of 5 to 20 .mu.m, and the dry defibrated pulp has a fiber length of 0.5 to 6 mm and a fiber diameter of 7-1.
The wood cement board according to claim 1 or 2, wherein the wood cement board has a size of 5 μm and is cotton-like. 4. The specific gravity of the wood cement board is 1.0 to 1.
6. The wood cement board according to claim 1, which is 6. 5. A surface layer or a back layer mat by spraying a raw material mixture for the front and back layers, which comprises a wood reinforcing material and cements as main raw materials, and further, aromatic polyetheramide fibers and dry defibrated pulp, on a substrate. And then forming a core layer mat by sprinkling the core layer raw material mixture mainly composed of a wood reinforcing material and cement on the surface layer or the back layer mat, and forming the core layer mat on the front layer and the back layer. The method for producing a wood cement board according to any one of claims 1 to 4, wherein the raw material mixture is sprayed to form a back layer or surface mat, and the three-layer mat is pressed to perform autoclave curing after pre-curing. 6. The method for producing a wood cement board according to claim 5, wherein the autoclave curing temperature is 160 ° C. or higher.