JP2004051454A - Fiber cement plate and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fiber cement plate formed in such a manner that water absorptivity is kept low without adding a large amount of chemical additives, such as water repellents, and without impeding hydration reaction, and that physical properties, such as strength, carbonation resistance, and freeze damage resistance, can be assured. <P>SOLUTION: The composition of solid raw materials for the fiber cement plate is composed, by 100 pts. wt., of 70 to 92wt% in the total amount of portland cement (A) and fine siliceous powder (B), 3 to 10wt% organic fibers (C), and the balance extenders (D), such as weight reduction materials, and further, 0.1 to 5.0wt% in total of additives of ≥2 kinds among a fatty acid ester compound (a), silicone-based compound (b), and fine reactive siliceous powder (c) are added to the raw materials, with respect to the total amount 100 of the solid raw materials. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fiber cement board and its manufacture, and more particularly to a fiber cement board used as an interior wall material and an exterior wall material of a building, and a method of manufacturing the same.
[0002]
[Prior art]
This type of fiber cement board is manufactured by mixing cement, a siliceous raw material, a fiber material, an extender, and the like at a predetermined ratio, and adding water to these materials to form a raw material. The molding method includes extrusion molding, papermaking press molding, and dehydration press molding, and the molded fiber cement board becomes a product through processes such as dehydration, curing, drying, and cutting.
[0003]
Important physical properties required of the fiber cement board include strength, dimensional stability, resistance to carbonation, and resistance to frost damage. Among them, the carbonation resistance and the frost damage resistance of the fiber cement board are greatly affected by the water absorption properties of the base material.
[0004]
In a fiber cement board with high water absorption, the amount of water that enters the base material increases, and as a side effect, expansion and contraction during absorption and release of water and carbon dioxide gas in the atmosphere and pores in the base material occur. Cement-derived calcium dissolved in the existing water reacts, there is a carbonation shrinkage due to the release of water by the heat, and there is a freeze-thaw action that repeatedly freezes and melts pore water under a low temperature environment, These effects greatly reduce durability.
[0005]
Conventional measures to suppress water absorption include: (1) Prevention of water intrusion by painting on the front and back surfaces of fiber cement boards, and (2) Relaxation of expansion and contraction caused by moisture by mixing aggregate. is there.
[0006]
In the countermeasure by coating, it is often impossible to prevent water from entering due to uneven coating of the paint or deterioration of the coating over time, and the expansion and contraction often recurs.
[0007]
In addition, measures taken by mixing the aggregate have a large adverse effect on other physical properties, such as a decrease in strength and a decrease in adhesion strength of the coating film, while improving dimensional stability.
[0008]
In recent years, a method has been proposed in which a chemical additive such as a water repellent is dispersed in a base material to form a cured product, thereby reducing the amount of water absorption. As a conventional technique of this kind, for example, a method disclosed in JP-A-2002-1715 can be mentioned. This conventional technique involves adding a fatty acid-based powder water repellent containing a fatty acid metal salt or a fatty acid ester as a main component, a silicone-based powder water-repellent, and a silane-based powder water-repellent to a hydraulic material. It is.
[0009]
[Problems to be solved by the invention]
However, when a chemical additive is added, it is necessary to add a large amount of the chemical additive in order to improve the water absorption so as to improve the dimensional stability, carbonation resistance, and frost damage resistance. Thus, there is a problem that the hydration reaction is inhibited, and the strength cannot be secured.
[0010]
Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to reduce the water absorption without inhibiting the hydration reaction without adding a large amount of a chemical additive such as a water repellent, and to improve the strength. Another object of the present invention is to provide a fiber cement board capable of ensuring physical properties such as resistance to carbonation and frost damage, and a method for producing the same.
[0011]
[Means for Solving the Problems]
To achieve the above object, the present invention provides:
The composition of the solid raw material is 100 parts by weight,
The total amount of Portland cement (A) and siliceous fine powder (B) is 70 to 92% by weight,
Organic fiber (C) is 3 to 10% by weight,
The remainder consists of fillers (D) such as lightweight materials,
Further, two or more additives of fatty acid ester compound (a), silicone compound (b), and reactive siliceous ultrafine powder (c) are added to the total amount of the solid raw materials of 100, At 0.1 to 5.0% by weight.
[0012]
The purpose of addition of each component and the reason for limiting the composition are as follows.
[0013]
Portland cement and fine silica powder, which are main raw materials, are substances that play a role of a binder directly involved in the calcium silicate reaction, and therefore, their proportions are important. When the total amount of Portland cement and the fine silica powder is 70% by weight or less, the matrix does not become dense during the hydration process with water, and the structure becomes easy to absorb water. On the other hand, if the combined amount of Portland cement and siliceous fine powder is 92% by weight or more, there is no room for other fillers or organic fibers to enter the matrix, and the composition of the material is not balanced and product quality other than water absorption is not achieved. Decreases. Therefore, the total amount of the portland cement and the siliceous fine powder is preferably 70 to 92% by weight, and the range is determined in consideration of the balance with other materials.
[0014]
The ratio of calcareous and siliceous included in Portland cement and siliceous fine powder mixture as CaO / SiO ₂ in molar ratio terms, 0.3 to 0.95, more preferably 0.45 to 0. 7
[0015]
Low heat cement is used for Portland cement. Here, the low heat cement according to the present invention includes belite as a component compound in a larger amount than ordinary cement, and has a low heat cement specified in JIS R 5210 or a water content equivalent to the low heat cement having a belite and aluminate phase content. Refers to a hard material, other cement is simply distinguished as ordinary cement. The low heat cement generates a large amount of reaction heat during water contact among the pores, and has a small amount of an aluminate phase, which is said to affect chemical resistance and dimensional stability. % Or less.
[0016]
The siliceous fine powder is subjected to a calcium silicate reaction together with cement, and the siliceous matter is 50% by weight or more in terms of SiO ₂ in 100 parts by weight. Here, “fine powder” refers to a powder having a Blaine specific surface area of 6000 cm ² / g.
[0017]
Further, a raw material in which 6 to 30% by weight of 100 parts by weight of silica fine powder is replaced with silica fume is used. If the amount is less than 6% by weight, the effect of the compounding is not observed. At 30% by weight or more, no change is observed in the effect of suppressing water absorption, and in addition, productivity is deteriorated depending on a molding method such as a dehydration press. More preferably, it is 10 to 15% by weight.
[0018]
When the Blaine specific surface area exceeds 7000 cm ² / g, the calcium silicate reaction with the cement is promoted, so that the matrix becomes dense and the strength characteristics and the water absorption characteristics are improved. If the Blaine specific surface area is 14000 cm ² / g or more, further improvement in quality cannot be expected due to the problem of aggregation and dispersion of particles, and the cost of pulverization is undesirably increased.
[0019]
In the fiber cement board according to the present invention, two or more of a fatty acid ester compound, a silicone-based compound and a siliceous reactive ultrafine powder are added as additives to improve the water absorption properties of the cured product.
[0020]
The effect of each additive on water absorption and water repellency is as follows.
[0021]
The fatty acid ester compound imparts water repellency to the raw material composition and improves the water absorption properties of the fiber cement board. That is, a part of the fatty acid ester compound is chemically bonded to the raw material composition based on the cement by the hydrolysis with the alkali derived from the cement and the formation of the fatty acid calcium salt by the reaction with the calcium component. At this time, it is considered that the hydrophobic alkyl group of the fatty acid ester compound is arranged on the surface of the pores of the base material to exhibit water repellency.
[0022]
The fatty acid ester compound is preferably an ester of a fatty acid having about 6 to 22 carbon atoms and an alcohol having about 1 to 22 carbon atoms.
[0023]
Next, the silicone compound is firmly bonded to Si contained in the raw material composition based on cement by bonding the Si with itself to the Si.
[0024]
This silicone compound includes an inert silicone oil having high thermal and chemical stability. Specifically, dimethyl silicone oil or long-chain alkyl group-containing silicone oil can be used.
[0025]
In addition, in the case of a silicone compound in which a part of the terminal group in the silicone compound is substituted with a highly hydrophobic alkyl group or aryl group, the hydrophobic alkyl group is arranged on the surface of the pores of the base material similarly to the fatty acid ester compound. Is considered to exhibit a water repellent action.
[0026]
In particular, in the case of a silicone compound whose terminal is modified with an alkyl group or an aryl group to a branched organopolysiloxane obtained by hydrolyzing an organosilane or a cyclic organopolysiloxane which is a condensate of an organosilane, a small amount of addition is required. However, it is preferable because it has a large water repellency and is economically advantageous.
[0027]
The reactive ultrafine siliceous powder is present in the interconnected pores formed on the base material composed of the calcium silicate reaction product of the cement and the siliceous fine powder, and causes a pozzolanic reaction to connect the pores. It is thought that the waterproof effect is imparted by dividing the properties and reducing the capillary action.
[0028]
This reactive siliceous ultrafine powder refers to a substance having more reactive siliceous matter than mere siliceous fine powder and having finer particles than silica fume.
[0029]
The particle size of the reactive siliceous ultrafine powder is about half the size of silica fume particles of 0.3 to 0.6 μm in microscopic observation.
[0030]
The presence or absence of the “reaction activity” here is determined by the following test.
[0031]
{Circle around (1)} Preparation of a standard sample: Cement and commercially available silica powder (Brain specific surface area: 3000 to 4000 cm ² / g) are mixed at a ratio of 6: 4 by weight. This is kneaded with water to form a mortar, and a molded body is formed into a mortar. After demolding the next day, the molded body is subjected to steam curing (60 ° C., 24 hours) to be used as a standard sample.
[0032]
{Circle around (2)} Preparation of test sample: Cement, commercially available silica powder and the siliceous fine powder are mixed in a ratio of 6: 3.5: 0.5 by weight, respectively. This is kneaded with the same ratio of water used in the preparation of the above standard sample to form a mortar, and a molded body is formed in a mold. The molded body is removed from the mold the next day, and then subjected to steam curing (60 ° C., 24 hours) to be used as a test sample.
[0033]
{Circle around (3)} Judgment of the reaction activity; crush each of the samples {circle around (1)} and {circle around (2)} and confirm the peak intensity of portlandite (2θ ≒ 18 °) originating from cement hydration by X-ray diffraction. . Standard sample, the peak intensity of each test sample, and I ₀ and I _S. Judgment is made that the reaction is active in the following cases. I _S / I ₀ ≦ 0.9
As the reactive siliceous ultrafine powder according to the present invention, for example, there is a polishing powder of glass for optical fiber.
[0034]
As described above, fatty acid ester compounds, silicone-based compounds, and reactive siliceous ultrafine powders have different mechanisms of action for suppressing water absorption and adding water repellency. Thereby, a synergistic effect can be obtained, and the water absorption characteristics of the fiber cement board can be significantly improved.
[0035]
In these additives, when the total amount of the two or more additives is 0.1% by weight or less based on the total amount of the solid raw materials, sufficient improvement in water absorption is not achieved. If it exceeds, the hydration itself of the cement is hindered, and the strength is reduced. Therefore, the added amount is preferably 0.1 to 5.0% by weight.
[0036]
When the combination of additives is a fatty acid ester and a silicone-based compound, both are liquids having high fluidity, and by preparing them as a mixed liquid in advance, the step of the adjustment step can be omitted, and the cost of the silicone compound can be reduced. It is more advantageous than a single unit, and the price / performance ratio is greatly improved.
[0037]
When the combination of additives is a silicone compound and a reactive siliceous ultrafine powder, after selecting a silicone compound having a high water-repellent effect and a reactive siliceous ultrafine powder having a completely different action, a liquid silicone It is preferable to use a slurry-like additive in which a reactive siliceous ultrafine powder is dispersed in a compound. The dispersibility of the reactive siliceous ultrafine powder is improved, and efficient compounding becomes possible.
[0038]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a method for manufacturing a fiber cement board according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a process diagram illustrating a flow of a manufacturing process of the fiber cement board according to the present embodiment.
[0039]
In the raw material mixing step 10, water is mixed with a solid raw material in which the total amount of Portland cement and the fine silica powder is 70 to 92% by weight, the organic fiber is 3 to 10% by weight, and the balance is filler. The mixture is kneaded for a minute to prepare a raw material slurry having a solid concentration of 28%.
[0040]
Next, two or more kinds of additives 11 among the fatty acid ester compound, the silicone compound, and the reactive siliceous ultrafine powder were added to the raw material slurry in a total amount of 0.1 with respect to the total amount 100 of the solid raw materials. ５5.0% by weight.
[0041]
The adjusted raw material slurry is sent to a dewatering press machine by a pump, and is supplied to a dewatering press step 12. The conditions of the dehydration press are as follows: the ultimate pressure is 5.0 MPa, and the holding time is 18 seconds.
The molded product formed into a plate shape by the dehydration press in this manner is first placed in a wet-air tank at a normal temperature and normal pressure for 5 hours in a pre-curing step 14, and then put in a wet-air tank in a steam curing step 16. Curing is performed for 6 to 10 hours while maintaining the temperature at 60 to 80 ° C. Next, in the autoclave curing step 18, curing is performed in an autoclave at 160 to 180 ° C. and 6 to 9.9 atm for 6 to 10 hours.
[0042]
Thereafter, the cured molded article is subjected to a drying step 20, a cutting step 22 for processing into a board of a predetermined size, a coating step 24, and a drying step 26 for drying the paint, thereby obtaining a fiber cement board product.
[0043]
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 2 shows the composition and the results of performance tests of examples of the fiber cement board according to the present invention. For comparison of performance, Comparative Examples 1 to 9 are given.
[0044]
The raw materials used as raw materials are as follows.
・ Low heat cement; Low heat portland cement ・ Normal cement; Normal portland cement ・ Siliceous fine powder; Silica powder silica fume (EFACO)
・ Organic fiber; Pulp (LBKP), synthetic fiber (PP)
・ Extending material; lightweight aggregate ・ Additives; fatty acid ester compound; EX-105
Silicone compound; ADEKA SUPERGUARD HS
Reactive siliceous ultrafine powder: Various items of the optical fiber polishing powder physical property test are performed under the following conditions.
・ Specific gravity; conforms to JIS A 5430 “Bulk specific gravity test (1)” ・ Water absorption rate: conforms to JIS A 5422 “Water content test” ・ Bending strength: Complies with JIS A 5430 “Bending strength test (2)” ・ Length Change rate: Based on JIS A 5430 "Length change rate test by water absorption".
-Freezing and thawing test: Complies with JIS A 5422 "Freezing and thawing resistance test". However, the observation was made 350 cycles after adding 150 cycles to the normal 200 cycles as the endurance cycle.
[0045]
-Freeze-thaw test after carbonation (1) Carbonation treatment: After adjusting the water content of the sample to 10 ± 2%, the sample was exposed to a constant temperature and humidity chamber at 25 ° C, 65% RH, and 5% CO2 for 240 hours.
(2) Freezing and thawing test: Based on JIS A 5422 "Freezing and thawing resistance test".
[0046]
Hereinafter, the effect of the embodiment will be described while comparing the embodiment with the comparative example.
Example 1, Example 2
In Examples 1 and 2, low-heat cement was 45% by weight and siliceous fine powder was 45% by weight. The total amount of these was 90% by weight of the whole raw material, and the organic fiber and the filler were 5% each. % Is common. The difference between Example 1 and Example 2 is the type of additive. In Example 1, a total of 0.3% by weight of the fatty acid ester compound and the silicone compound was added to the raw material 100. In Example 2, a silicone compound and reactive silica ultrafine powder were added in a total amount of 2.0% by weight.
[0047]
Example 3 and Example 4
Example 3 and Example 4 differ from Example 1 and Example 2 in the composition of the low heat cement and the siliceous fine powder. The total amount of these materials is 75% by weight of the raw material, and the amount of the filler is 20% by weight. % In common. As for the additives, Example 3 was a total of 1.0% by weight of the fatty acid ester compound and the silicone compound added to the raw material 100, whereas Example 4 was a mixture of the fatty acid ester compound and the reactive silica. Fine powder was added in a total amount of 3.0% by weight.
[0048]
Comparative Example 8 and Comparative Example 9 with Conventional Fiber Cement Boards are fiber cement boards made of a conventional standard ceramic siding material using ordinary cement, silica sand, organic fibers, and extenders as raw materials. In Comparative Example 8, 3.0% by weight of the fatty acid ester compound and the reactive ultrafine powder were added.
[0049]
Comparative Example 8 had a high water absorption of 27.1% despite the use of the additive, and Comparative Example 9 had a water absorption of 35.0%. Is a maximum of 23.8% and an average of 14.2%. In general, the water absorption is well suppressed.
[0050]
Regarding the flexural strength, Examples 1 to 4 show better values than Comparative Examples 8 and 9, and Comparative Examples 8 and 9 show the results in the freeze-thaw test and the freeze-thaw test after carbonation. In all cases, abnormalities were observed, while Examples 1 to 4 did not have abnormalities.
[0051]
As described above, in comparison with the conventional standard fiber cement board, Examples 1 to 4 have good performance such as strength, dimensional stability, carbonation resistance, and frost damage resistance while suppressing water absorption. It can be seen that it can be secured.
[0052]
Utility of low heat cement and additives Example 1 and Comparative Example 1 have the same composition except that the former cement is a low heat cement whereas the latter is a normal cement. It can be seen that the water absorption of Comparative Example 1 was as high as 31.4%, whereas the water absorption of Example 1 was significantly improved at 23.8%. Along with this difference in water absorption, in Comparative Example 1 of ordinary cement, abnormalities were observed in both the freeze-thaw test and the freeze-thaw test after carbonation.
[0053]
Comparative Example 2 is the same as Example 1 and Example 2 in the composition of the raw materials, except that no additive was added. Comparative Example 2 showed a high water absorption of 34.0%, and abnormalities were observed in the freeze-thaw test and the freeze-thaw test after carbonation.
[0054]
From the above, it can be seen that one of the low-heat cement and the additive alone has no effect in suppressing the water absorption to a low level, and that the effect is achieved only when both are combined.
[0055]
The difference between the effect of the combination of additives and Comparative Example 3 and Example 1 is that the former compounded the fatty acid ester compound alone, while the latter compounded the fatty acid ester compound and the silicone compound. , And other compositions are exactly the same. This difference is largely reflected in the water absorption, and it can be seen that the water absorption in Example 1 is significantly lower than that in Comparative Example 3.
[0056]
Comparative Example 3 is an example in which the fatty acid ester compound alone was added in the same amount as the additive in Example 1, whereas Comparative Example 4 was an example in which the fatty acid ester compound was added alone in a large amount. .
[0057]
In Comparative Example 4, although the water absorption was slightly improved as compared with Comparative Example 3, abnormalities were observed in the freeze-thaw test and the freeze-thaw test after carbonation, and the additive alone was used in a large amount. It can be seen that the water absorption does not decrease.
[0058]
Comparative example 5 of the utility of the siliceous fine powder has a composition in which the amount of the siliceous fine powder is smaller than that of the composition of Example 3, and the amount of the decrease is substituted by the filler. Similarly, Comparative Example 6 has a composition in which a small amount of fine silica powder is added to the composition of Example 3 and the reduced amount is replaced with silica sand. The silica sand used in Comparative Example 6 has a larger particle size than the silica stone powder used as the siliceous fine powder.
[0059]
Comparing Example 3 with Comparative Examples 5 and 6, it can be seen that in Example 3, the water absorption was significantly reduced and improved, with only the difference between the siliceous fine powder and the silica sand.
[0060]
The difference between Example 3 and Comparative Example 7 is that the former contains 29% by weight of silica fume of the siliceous fine powder, whereas the latter contains only 3% by weight, and the other compositions are the same. is there.
[0061]
Comparing Example 3 with Comparative Example 7, it can be seen that silica fume greatly contributes to the improvement in water absorption.
[0062]
【The invention's effect】
As is clear from the above description, according to the present invention, the water absorption is kept low without adding a large amount of a chemical additive such as a water repellent, and the strength and carbonic acid resistance are maintained without inhibiting the hydration of the cement. A fiber cement board capable of securing physical properties such as chemical resistance and frost damage resistance can be obtained.
[Brief description of the drawings]
FIG. 1 is a process chart showing a manufacturing process of a fiber cement board according to the present invention.
FIG. 2 is a table showing compositions and physical properties of Examples and Comparative Examples of the present invention.

Claims (5)

The composition of the solid raw material is 100 parts by weight,
The total amount of Portland cement (A) and siliceous fine powder (B) is 70 to 92% by weight,
Organic fiber (C) is 3 to 10% by weight,
The remainder is made up of an expanding material (D) such as a lightweight material,
Further, two or more additives of fatty acid ester compound (a), silicone compound (b), and reactive siliceous ultrafine powder (c) are added to the total amount of the solid raw materials of 100, A fiber cement board, wherein 0.1 to 5.0% by weight is added. The fiber cement board according to claim 1, wherein the Portland cement (A) is a low heat cement. The fiber cement board according to claim 1, wherein the siliceous fine powder (B) contains 6 to 30% by weight of silica fame in 100 parts by weight. The siliceous fine powder (B), the fiber cement board according to claim 1, characterized in that it consists of silica stone powder 7000~14000cm ² / g in Blaine specific surface area. A raw material mixing step of mixing water with the raw material of the fiber cement board having the composition according to any one of claims 1 to 4, and adjusting a raw material slurry,
A dehydration press step of forming the raw material slurry into a plate shape by a dehydration press,
A curing process for curing the dehydrated molded article;
A method for producing a fiber cement board, comprising:

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