JP2000044302A - High density ligneous cement plate, high density multilayer cement plate, and their production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce cement plate excellent in flexural strength and impact resistance at high productivity by curing a mixture including minute ligneous fibers, wood chips and cement and adjusting the specific gravity. SOLUTION: This cement plate consists of a cured product obtained by curing a mixture containing (A) (pref. <=10 wt.%) minute ligneous fibers (pref. pulp powder having <=5 mm major axis, <=0.5 mm minor axis and <=0.1 mm thickness), (B) (pref. <=10 wt.%) wood chips (pref. having 1.0-35 mm major axis, 0.5-8.0 mm minor axis and 0.05-2.0 mm thickness) and (C) cement, and by making the specific gravity of the whole of the cured product become >=1.4 g/cm3. The cement plate is produced by spreading a raw material mixture containing minute ligneous fibers, wood chips and cement onto a base plate to form a mat and by curing the mat in a pressed state in the presence of moist. A multilayered ligneous cement plate is produced by forming an outer layer consisting of a cured product of a mixture containing minute ligneous fibers and cement on the surface (or underside) of the above cement plate as a base layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high specific gravity wood cement board and a multi-layer high specific gravity wood cement board used as a roofing material, for example, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, there has been provided a fiber reinforced cement board using pulp fiber as a reinforcing material instead of asbestos which causes environmental pollution (Japanese Patent Application Laid-Open No. Hei 4-369555).
In order to manufacture the fiber-reinforced cement board, a raw material mixture containing cement and pulp fiber is supplied in a layered form on a forming belt, pressed over water and formed into a plate shape, and the formed article is formed into a predetermined shape. A dry method of cutting out and curing and curing is applied.

[0003]

In the above prior art, the use of pulp fibers results in a low-density raw material mixture. Therefore, in order to obtain a product having a high specific gravity, it is necessary to increase the amount of the raw material mixture supplied in layers on the forming belt, and the raw material mixture layer becomes thick and bulky. For this reason, there was a problem that the raw material mixture layer easily collapsed, the compression ratio at the time of pressing was increased, and the vertical stroke of the pressing device was increased, thereby lowering productivity. When pulp fibers are used, agglomeration of the raw material mixture is liable to occur, which may cause unevenness in the product and cracks.

[0004]

Means for Solving the Problems As a means for solving the above-mentioned conventional problems, the present invention comprises a cured product of a mixture containing fine wood fibers, wood chips and cement, and has a specific gravity of 1.4 g / g as a whole. there is provided a high-density wood cement board which is cm ³ or more, the fine Hosoki quality fiber diameter 5mm or less,
It is a powder pulp having a minor axis of 0.5 mm or less and a thickness of 0.1 mm or less, and the wood piece has a major axis of 1.0 to 35 mm and a minor axis of 0.5 to 8.0.
mm and a thickness of 0.05 to 2.0 mm. Further, in the present invention, a multi-layer high-density wood cement board comprising the above-described high-density wood cement board as a base layer, and a surface layer made of a cured product of a mixture containing fine wood fibers and cement provided on the front and / or back surface of the base layer Is provided.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. [Fine Wood Fiber] The fine wood fiber used in the present invention is mainly obtained from conifers and usually has a major axis of 5 mm or less, a minor axis of 0.5 mm or less, and a thickness of 0.1 mm or less. When the major axis of the fine wood fiber exceeds 5 mm and / or when the minor axis exceeds 0.5 mm and / or when the thickness exceeds 0.1 mm, the denseness of the surface layer decreases,
There is a possibility that the water-absorbing property and the moisture-absorbing property are increased and the freeze-thaw resistance is reduced. Further, when the major diameter of the fine wood fiber exceeds 5 mm, the fiber becomes thread-like or the fibers are easily entangled with each other, and it becomes difficult to stir and uniformly mix the raw material mixture. Agglomeration is likely to occur in
Further, in the production by a dry method to be described later, when the raw material mixture is sprayed on the substrate to form the mat, the mat is not easily loosened, which may hinder the spraying and may make it impossible to form a uniform mat. As a desirable fine wood fiber, a so-called powder pulp obtained by pulverizing a sheet-like pulp agglomerate by a turbo mill or the like is desirable. The use of the powder pulp facilitates uniform mixing of the raw material mixture, so that no agglomeration occurs in the raw material mixture,
It is also very easy to spray. Furthermore, in powder pulp such as bleached kraft pulp of conifers (NBKP), most of the cement hardening inhibitors such as carbohydrates contained in wood are removed. Hard to get up.

[Wood chips] Wood chips used in the present invention are mainly obtained from conifers and usually have a major axis of 1.0 to 35 mm, preferably 5 to 20 mm, a minor axis of 0.5 to 8.0 mm, and preferably 0.5 to 8.0 mm. 5 mm, thickness 0.05 to 2.0 mm, preferably 0.
Those having a size of about 1 to 0.5 mm are used. If the major axis of the wood piece is less than 1.0 mm, if the minor axis is less than 0.5 mm, or if the thickness is less than 0.05 mm, the cement matrix connecting effect is not remarkable and the reinforcing effect is reduced, and If the major axis of the wood piece exceeds 35 mm, the minor axis exceeds 8 mm, or the thickness exceeds 2 mm, the raw material mixture mat becomes too bulky and the specific gravity is 1.
It is difficult to obtain a high-density product of 4 g / cm ³ or more.

[Cement] Examples of the cement used in the present invention include portland cement, blast furnace cement, silica cement, fly ash cement, alumina cement and other cements.

[Silicate-Containing Substance] In the present invention, it is desirable to use a silicic acid-containing substance in combination with the above cement. As the silicic acid-containing substance, for example, sand, gravel,
Examples thereof include crushed stone, silica sand, silica stone powder, silica fume, blast furnace slag, fly ash, shirasu balloon, silicate-containing substances such as pearlite, and the like.

[Other raw materials] In addition to the above raw materials, in the present invention, active lime-containing substances such as gypsum dihydrate, hemihydrate gypsum, anhydrous gypsum, slaked lime, quick lime, etc., for example, wollastonite, sepiolite, glass fiber, rock wool Such as inorganic fibers,
For example, polyethylene fiber, polypropylene fiber, polyester fiber, organic fiber such as polyamide fiber, water glass,
A curing accelerator consisting of one or a mixture of two or more of magnesium sulfate, aluminum sulfate, sodium carbonate, etc.
Alternatively, an additive such as alumina cement showing a cement hardening accelerating action by addition of a very small amount, polyvinyl alcohol, an aqueous paste such as carboxymethyl cellulose,
Styrene-butadiene latex, synthetic resin emulsion reinforcing agents such as acrylic resin emulsion, wax,
Water repellents such as paraffin, silicon, and metal salts of higher fatty acids may be mixed.

[Preparation of Raw Material Mixture] In the present invention, the mixing ratio of fine wood fiber as a wood reinforcing material and wood chips is usually 90:10 to 10:90 by weight, more preferably 6 to 10:90.
The weight ratio is 0:40 to 40:60. If the wood chips are less than the above mixing ratio, the mat of the raw material mixture becomes bulky and easily collapses, and if the wood chips exceed the above mixing ratio, it becomes difficult to obtain a high-density product, and the wood chips existing on the product surface due to aging deteriorate. The peeling phenomenon is likely to occur, and the surface is roughened to easily absorb water or moisture, and the freeze-thaw resistance may be deteriorated. Furthermore, the amount of the cement hardening inhibitor eluted from the wood chips may increase, which may cause cement hardening inhibition.

The wood reinforcing material mixed with the fine wood fibers and the wood chips is contained in the raw material mixture in an amount of 2 to 10% by weight, preferably 3 to 10% by weight.
8% by weight, more preferably about 4 to 6% by weight. If the added amount of the mixed wood reinforcing material is less than 2% by weight, the reinforcing effect is not sufficient, and if it exceeds 10% by weight, it becomes difficult to obtain a high-density product, and water and moisture resistance, dimensional stability, The freeze-thaw resistance, the incombustibility, and the like are adversely affected, and the setting of the cement may be inhibited by the cement setting inhibitor eluted from the wood chips in the mixed wood reinforcement.

When a cement and a silicic acid-containing substance are used in combination, the mixing ratio of the cement and the silicic acid-containing substance is usually from 40:60 to 50% when performing autoclave curing.
60:40 weight ratio, usually 7 for natural curing
The weight ratio is 0:30 to 90:10. Other raw materials such as a curing accelerator and a water repellent are usually added to the raw material mixture in an amount of about several percent by weight or 1 percent by weight or less.

Usually, 15 to 5 water is added to the raw material mixture.
0 parts by weight are added and mixed. The above-mentioned water is desirably performed by spraying water while stirring the added mixture. According to such an addition method, lumps are not easily formed in the mixture.

[Preparation of Raw Material Mixture for Surface Layer] In the present invention, when a surface layer is further provided on the base layer, fine wood fibers are usually contained in the raw material mixture in an amount of 1 to 10% by weight, preferably 4% by weight.
About 6% by weight is added. If the amount of the fine wood fiber is less than 1% by weight, the surface is brittle and cracks are easily formed, the layer thickness is not sufficient, and the compression ratio is not increased, so that it is difficult to obtain a dense and smooth surface. Become. Also 10
If the content is more than 10% by weight, water and moisture resistance, dimensional stability, nonflammability and the like are adversely affected. The fine wood fiber-cement mixture is mixed with water and, if desired, other raw materials in the same manner as the base layer raw material mixture to prepare a surface layer raw material mixture.

[Manufacture of Wood Cement Board] In order to manufacture the wood cement board of the present invention, a dry method is applied. In the dry method, first, when forming a multi-layer consisting of a surface layer and a base layer, the raw material mixture for the surface layer is sprayed on a carrier plate or a substrate such as a template to form a surface mat, and the base layer is further formed thereon. The base material mat is formed by spraying the raw material mixture. In the mat forming step, the ratio of the amount of the surface material mixture to the amount of the base material mixture to be sprayed is usually 1: 1 to 1: 6 by weight, preferably 1: 1.
１ ： 1: 2.5 weight ratio is set.

The raw material mixture for a surface layer may be further sprayed on the base layer mat to form the surface layer mat. The amount of application in this case is the same as in the case of the lowermost surface mat. In this case, the surface mat below (the lowermost layer of) the base mat is the front side, and the surface mat above the base mat is the back side. An embossed pattern may be provided on the surface of the substrate.

When a single layer consisting of only the base layer is formed, the above-mentioned raw material mixture for the base layer is directly sprayed on a substrate to form a mat.

The single-layer mat or the multi-layer (two-layer or three-layer) mat is usually pressed at a high pressure of about 25 to 200 kg / cm ² and pre-cured at room temperature for 24 hours or less.
Pre-cured by heating at 80 ° C for 5 to 10 hours. After compression curing, the pre-cured product is autoclaved, cured at high temperature,
Alternatively, it is cured by natural curing, and further dried by heating or natural drying. Thereafter, if desired, the obtained wood cement board may be subjected to painting, water repellent treatment and the like. The wood cement board of the present invention thus obtained usually has a density of 1.4 g / cm ³ or more, preferably 1.6 g / cm ^3.
m ³ or more, more preferably 1.8 to 2.0 g / cm ³ , the surface layer or the surface layer and the base layer are dense, and have high strength and durability, water and moisture resistance and dimensional stability. . If the density is 1.4 g / cm ³ or less, the product will have an increased water-absorbing / absorbing property, resulting in poor dimensional stability, freeze-thaw resistance, and eventually poor weatherability and durability.

[0019]

According to the present invention, wood chips are added to fine wood fiber as a wood reinforcing material of wood cement board, so that agglomeration is hardly formed in the raw material mixture and the density of the raw material mixture is increased. Therefore, the mat to be formed does not become bulky, the shape of the mat is prevented from being deformed, and the compression ratio by a press for obtaining a high specific gravity product does not increase, thereby improving the productivity. The wood piece improves the toughness of the product, improves the brittleness, and gives the product excellent in bending strength and impact resistance. In the case of a multilayer structure of the surface layer and the base layer, a product with a more dense surface can be obtained, and since the raw material composition of the surface layer and the base layer is similar, the interlayer adhesion is improved and the two layers are integrated. I do. Therefore, both layers follow the change of the plate integrally, and the dimensional stability is improved.

[Examples 1 to 4, Comparative Examples 1 and 2] (Single-layer cement plate) A raw material mixture having the composition shown in Table 1 was sprayed on a substrate at a rate of 17 kg / m ² to form a mat.

[0021]

[Table 1]

Each of the above mats is pressed at a pressure of 50 kg / cm ² , heated to 50 ° C. and left for 8 hours to be pre-cured, then removed from the mold and left at room temperature for 4 days for curing. Was. A sample almost completely cured by the natural curing is used as a sample. Table 2 shows the measurement results of the physical properties of the sample.
Shown in

[0023]

[Table 2]

According to Table 2, all of the samples of Examples 1 to 4 did not have a bulky mat, did not lose their shape, and had high specific gravity and high strength, and were excellent in water and moisture resistance, dimensional stability and freeze-thaw resistance. However, in Comparative Example 1 in which no wood chips were added, the mat thickness was increased and the mat became bulky, the shape of the mat was lost at both ends, and the Young's modulus was high and the brittleness was observed. In the case of Comparative Example 2 in which only a piece of wood was used as a wood reinforcing material, a peeling phenomenon of the piece of wood was observed on the surface of the sample.

[Examples 5 to 9] (Multilayer cement plate) A surface material mixture having the composition shown in Table 3 was placed on a substrate at 5.4 kg / kg.
m ² to form a surface mat (surface), and further form a base material mixture having a composition shown in Table 3 at a rate of 17 kg / m ^{2 on} the surface mat to form the base mat. The same surface layer raw material mixture was sprayed in the same amount on the base layer mat to form the surface layer mat (back surface).

[0026]

[Table 3]

Each of the three-layer mats is pressed at a pressure of 50 kg / cm ² , heated to 50 ° C. and left for 8 hours to be pre-cured, then removed from the mold and left at room temperature for one week for curing. Was. A sample completely cured by this natural curing is used as a sample. Table 4 shows the measurement results of the physical properties of the sample.

[0028]

[Table 4]

According to Table 4, the samples of Examples 5 to 9 all have high density and high strength, and show good toughness (low Young's modulus) and dimensional stability.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) E04C 2/26 E04C 2/26 PSF term (Reference) 2B260 AA12 BA01 BA02 BA13 BA19 CA02 CB01 CD05 CD22 EA01 EA05 EB02 EB06 EB21 EB42 2E162 CA06 FA01 FA02 FA03 FA05 FA09 FA12 FA14 FC01 FC03 FD06 4G012 PA15 PA34 PE03 PE05

Claims (7)

[Claims] 1. A cured product of a mixture containing fine wood fibers, wood chips and cement, having a total specific gravity of 1.4 g / cm.
High specific gravity wood cement board characterized by being ³ or more 2. The fine wood fiber has a major axis of 5 mm or less and a minor axis of 0.1 mm.
2. A powder pulp having a length of 1.0 to 35 mm, a short diameter of 0.5 to 8.0 mm, and a thickness of 0.05 to 2.0 mm. High specific gravity wood cement board described in 3. The high-density wood cement board according to claim 1, wherein the wood chips and the fine wood fibers are contained in the mixture in an amount of 10% by weight or less. 4. A high-density wood cement board according to claim 1 or 2 as a base layer, and a surface layer made of a cured product of a mixture containing fine wood fibers and cement is provided on the surface and / or back surface of the base layer. Multi-layer high specific gravity wood cement board characterized by 5. The method according to claim 1, wherein a raw material mixture containing fine wood fibers, wood chips and cement is sprayed on a substrate to form a mat, and the mat is cured by pressing in the presence of moisture. High specific gravity wood cement board described in 6. A raw material mixture containing fine wood fibers and cement is sprayed on a substrate to form a surface mat, and a raw material mixture containing fine wood fibers, wood chips and cement is sprayed on the surface mat. The method for producing a multi-layered high-density wood cement board according to claim 4, wherein the multi-layered mat is cured by pressing in the presence of moisture. 7. A method for producing a multi-layer high specific gravity wood cement board according to claim 6, wherein a raw material mixture containing fine wood fibers and cement is further sprayed on said base mat to form a surface mat.