JPH0920574A - Production of porous sound-absorbing material - Google Patents

Abstract

PURPOSE: To obtain a lightweight sound-absorbing material excellent in mechanical strength and sound-absorbing characteristics, by agitating under heating a slurry comprising cement particles, a foaming agent and water followed by conducting a wet curing and then autoclave curing. CONSTITUTION: A mixture of (A) cement particles to which calcium oxide, calcium hydroxide, gypsum, etc., are added such as conventional Portland cement or high-early-strength Portland cement, (B) <=3wt.%, on a solid basis, of a foaming agent consisting of e.g. an alkyl allyl ether and stable in foaming performance at >=40 deg.C, (C) 20-80wt.%, based on the component A, of a siliceous aggregate, and the rest of water, is agitated at 300-1500rpm and then heated to nearly the wet curing temperature of 40-80 deg.C and further agitated for 5-10min at the temperature. In this case, <=2wt.%, based on the whole solid component, of a foam stabilizer such as PVA or methyl cellulose is incorporated in the system. Subsequently, the resultant system is subjected to autoclave curing to obtain the objective lightweight tobermorite-based porous sound-absorbing material having continuous cells in which each cell has >=0.1mm of diameter, its compressed part has a diameter of >=10μm and also each cell has more than one openings.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous sound absorbing material containing tobermorite.

[0002]

2. Description of the Related Art Recently, various sound absorbing plates have been developed in response to a demand for noise, and the needs thereof are increasing year by year. For example, there is a sound absorbing material made of ceramics. Although this is excellent in terms of high strength, it also has problems of low porosity, insufficient sound absorption characteristics, and large specific gravity. Further, the sound absorbing material made of cement concrete is generally light-weight cellular concrete cured by autoclave, and although the sound absorbing property is better than that of the ceramic sound absorbing material, it is not sufficiently satisfactory. In addition, the strength was not satisfactory. This is considered to be due to the following reasons. Cement-concrete sound-absorbing materials usually take a long time to solidify because they are wet-cured at room temperature,
Sedimentation of the particles was likely to occur, and thus the pore distribution of the solidified product was likely to be non-uniform. Therefore, a method of performing the wet curing at a high temperature can be considered, but when the curing is performed at a high temperature, the bubbles are likely to be crushed, which causes a problem that the pore distribution of the solidified product becomes uneven. Therefore, in either case, the strength and the sound absorption coefficient could not be obtained with a large variation in the strength and the sound absorption coefficient.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems of the prior art and to provide a method of manufacturing a sound absorbing material which is lightweight and has excellent strength and sound absorbing characteristics.

[0004]

In order to solve the above problems, a method for producing a porous sound absorbing material according to the present invention is a lightweight solidified product containing tobermorite, which has continuous ventilation holes, cement particles, and foaming. A slurry consisting of an agent and water is agitated in a state of being heated to a substantially moist curing temperature, and moist curing, and then,
And a step of curing the autoclave. And, the wet curing temperature is 40 to 80 ° C.
That is, a preferable embodiment is that the content of the siliceous aggregate is 20 to 80% by weight of the cement particles.

The pores observed in the polished cross section of the solidified product are spherical pores having a diameter of 0.1 mm or more (hereinafter referred to as first pores) and pores having a diameter of less than 0.1 mm (measured by the BET method). Fine pores) (hereinafter referred to as second pores). The continuous vent means pores having a diameter of 0.1 mm or more in a communicating state, the constricted portion has a diameter of 10 μm or more, and at least one of the pores is an open pore. The constricted portion of the communicating vents refers to a void in a portion where the pores communicate with each other (also referred to as communicating holes). The determination of the continuous air holes, the measurement of the average pore diameter of the continuous air holes, and the measurement of the average diameter of the constricted portion of the continuous air holes are performed on the polished cross section of the solidified product. The diameter of the constricted portion of the continuous vent is measured by a scanning electron micrograph (magnification: 100 to 2000). Tobermorite is (5CaO ・ 6SiO ₂・ 5H
₂ O) refers to a calcium silicate hydrate.
Cement particles refer to Portland cement, mixed cement and alumina cement. Here, the term "warming up to approximately the moisture curing temperature" means that the moisture curing temperature is within ± 10 ° C.

[0006]

[Action]

According to the manufacturing method of the present invention, the slurry composed of cement particles, the foaming agent and water is stirred while being heated up to a substantially wet curing temperature, and wet cured, so that the bubbles are solidified without being crushed. And form continuous ventilation holes. The reason for this is not clear, but it is considered that the rapid temperature change at the time of wet curing was alleviated by heating the sludge, and the internal pressure expansion of the bubbles was suppressed. The wet curing is performed at a temperature higher than room temperature, preferably 40 to 80 ° C, more preferably 50 to 70 ° C. This high temperature curing accelerates the solidification, so that the sedimentation of the sludge is prevented and the increase of the bubble diameter due to the coalescence of bubbles is also suppressed. 40
If the temperature is below ℃, sedimentation of sludge is likely to occur,
If the temperature exceeds ℃, air bubbles will collapse and it will be difficult to form continuous vents. The wet curing time is preferably 2 hours or more from the viewpoint of improving the strength of the sound absorbing material. By subjecting the sludge heated to about the wet curing temperature to the wet curing at a high temperature, the pore distribution of each part becomes uniform, and a raw material of a porous sound absorbing material having good strength and sound absorbing characteristics can be obtained. The cement particles are preferably Portland cement particles such as ordinary Portland cement, early strength Portland cement, and super early strength Portland cement in terms of strength. In terms of cost and workability, particles of ordinary Portland cement and early-strength Portland cement are more preferable. In addition, in order to promote the reaction, calcium oxide, calcium hydroxide, gypsum or the like may be added.

As the foaming agent, detergents (sodium lauryl sulfate, sodium dodecylbenzenesulfonate, etc., alkyl allyl sulfonates, alkylnaphthalene sulfonates, nonylphenoxydiethoxyethyl sulfate, alkyl allyl ether salts, Anionic surfactant such as higher alcohol sulfate, alkyl allyl sulfonic acid, naphthalene alkyl sulfonate, polyoxyethylene alkyl ether, polyoxyethylene lauryl ether, fatty acid diethanolamide, polyoxyethylene lanolin alcohol ether, polyoxy Nonionic surfactants such as ethylene lanolin fatty acid ester), vegetable or animal colloids, saponins, modified colloidal butyl sulfonate naphthalene, sodium isopropyl sulfonate, sodium chloride Siumu, other surfactants (polyoxyethylene alkyl amine ether), etc. derivatives of proteins such as gelatin casein. Of these, alkylallyl ether salts and higher alcohol sulfates, which have particularly stable foaming performance even at temperatures of 40 ° C. or higher, are more preferable. The amount of the foaming agent added is preferably 3% by weight or less based on the solid content in terms of strength characteristics and sound absorption characteristics.

The silica-based aggregate is preferably mixed in the weight ratio of 20 to 80% with respect to the cement particles in terms of strength, and more preferably in the range of 40 to 60%. Within this range, the siliceous aggregate remains after the autoclave is cured, and therefore the siliceous aggregate is considered to function as the aggregate and improve the strength. Examples of the siliceous aggregate include silica sand, silica stone powder, slag powder, volcanic ash, and diatomaceous earth.

As for stirring in a heated state, the cement particles, the foaming agent and the water are stirred at a high speed of preferably 300 to 1500 rpm, preferably 5 to 10 minutes, by a stirrer equipped with a heating device. . At this time, if a bubble stabilizer is added, collapse of bubbles and coalescence of bubbles are less likely to occur even in wet curing at 40 ° C. or higher. Therefore, the bubble stabilizer is preferably added in an amount of 2% by weight or less based on the solid content. Examples of the bubble stabilizer include PVA and methyl cellulose. Here, it is possible to perform degassing under reduced pressure during stirring. From the viewpoint of sound absorption characteristics and strength improvement, water is preferably 30 to 50% by weight based on the solid content.
The water content is lower than that of the conventional sound absorbing material. The thus obtained sludge is poured into a mold and cured in a wet state at a temperature of 40 to 80 ° C. It is also possible to add a foaming agent such as metal aluminum powder together with the foaming agent at the time of stirring when forming the continuous ventilation holes. This is because the addition of a foaming agent causes gas (hydrogen in the case of metallic aluminum powder) to be generated during wet curing, which increases the pore size and porosity of the solidified product.
Lighter weight is achieved.

The average pore diameter of the continuous ventilation holes is 10 in the polishing cross section.
It is preferably 0 to 2000 μm. In this range, the sound absorption coefficient in a wide frequency range becomes good. Further, the average diameter of the constricted portion of the continuous ventilation hole is preferably 30 to 500 μm. Within this range, the sound absorption coefficient becomes good. Here, the constricted portion of the communicating air holes refers to a void in a portion where the air holes communicate with each other (also referred to as a communicating hole). The diameter of the continuous ventilation hole and the constricted portion of the continuous ventilation hole is an alkyl allyl ether salt,
Using a foaming agent such as a higher alcohol sulfate, it can be controlled by the number of revolutions of high-speed stirring, the stirring time, the amount of the foaming agent, the kind of the stabilizer and the amount thereof.

Here, it is considered that the changes in the pore state and structure of the porous sound absorbing agent are as follows. Immediately after pouring, a slurry consisting of cement particles, a foaming agent and water is agitated in a state where it is heated to a substantially humid curing temperature, and after it is made to contain bubbles, it is poured into a form (preferably heated). In the air bubbles entrained by the foaming agent, the air bubbles do not coalesce with each other, and the air bubbles and the cement particles are uniformly dispersed in the slurry without defoaming. Wet this sludge 4
When cured at a temperature of 0 to 80 ° C, water and cement particles react with each other to form a CSH gel. With this cure,
The trapped air bubbles serve as continuous ventilation holes. In addition, when the siliceous aggregate is added, water, cement particles, and the siliceous aggregate react with each other to form a C—S—H gel, and the excess siliceous aggregate remains as the siliceous aggregate. Therefore, after the wet curing, it becomes a porous body in which the entrained air bubbles in the communicating state are dispersed and becomes a soft structure containing water.

After that, by subjecting to autoclave curing, the C--S--H gel was changed to crystalline tobermorite,
Strengthened. From the viewpoint of strength improvement, autoclave curing is preferably performed at 120 to 250 ° C. for 3 hours or longer.
The conditions of 150 to 200 ° C. and 5 hours or more are more preferable.
Note that autoclave curing in a state of being immersed in water is not preferable. X-ray diffraction and thermogravimetric analysis (TG)
From this, it was confirmed that the amount ratio of tobermorite and C-S-H gel of this porous sound absorbing material was 60% or more in weight ratio when Portland cement was used as the cement particles. Incidentally, zonotolite is not recognized in the sound absorbing material of the present invention.

The porous sound-absorbing material containing tobermorite thus obtained has a large number of continuous ventilation holes therein, and has a light weight of, for example, an absolute dry specific gravity of 1.0 or less, and has good strength characteristics and sound absorption characteristics. Become. Further, the thickness of the porous sound absorbing material is preferably 30 to 100 mm. Further, depending on the pore distribution, a material having a small water absorption rate can be used, and therefore, a material having good dimensional stability against water can be obtained and can be used in a wet state. Further, the solidified product of the present invention is fire resistant,
Durability is also good.

[0015]

EXAMPLES Next, the present invention will be explained based on examples using silica sand as the silica aggregate. When agitating cement particles, siliceous aggregate, metallic aluminum powder, foaming agent and water with an agitator, an admixture such as a binder, a water reducing agent, a water retention agent, a waterproofing agent, a fluidizing agent and a shrinkage reducing agent is used. Perlite, ALC scraps, glass fiber (preferably alkali resistant glass fiber), synthetic fiber (vinylon, nylon) may be added, and for improving the strength of the solidified product, adjusting the specific gravity, and reducing the cost. , Pulp, etc. can also be added. Examples of the water reducing agent include naphthalene sulfonic acid formalin condensate salt, alkylallyl sulfonic acid, alkyl allyl sulfonate, and diethyl naphthalene formalin condensate. In addition, the foaming agent is a preform method (fine bubbles are previously created by the foaming agent,
It may be used in a method in which it is mixed with heated sludge).
The raw material prepared in this manner is used to form a predetermined shape by a casting method or the like. Further, it is also possible to perform molding in a state where a reinforcing material such as a reinforcing bar is put in the mold.

(Examples 1 to 7) Various Portland cements and alumina cements were used as cement particles,
The weight ratio of these cements and silica sand is 100: 10 to 1
It was set to 00:80, and 30 to 50% by weight of water relative to the solid content and a foaming agent were added, and the mixture was stirred with a stirrer to prepare various kinds of sludge containing bubbles. Here, a mixer with a heating device was used as a stirrer, and high-speed stirring was performed for 5 to 10 minutes at a rotation speed of 300 to 1500 rpm to prepare various kinds of sludge that were heated to a wet curing temperature of ± 10 ° C or less. Here, as the foaming agent, an alkyl allyl ether salt (trade name: Hitenol manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and a higher alcohol sulfate (trade name: Emal manufactured by Kao) are used, each containing 3% by weight or less based on the solid content. Was added. These different types of heated sludge can be
0 × 150 mm), 40 to 80 ° C., 2 to 4
Curing for 8 hours in wet condition (relative humidity 80% or more),
A solidified solid body (90 × 50 × 150 mm) having a rectangular parallelepiped shape was obtained. In addition, 2% by weight or less of PVA was added to the solid content together with the foaming agent.

The solidified material base thus obtained is
Autoclaving was carried out at 250 ° C. for 3 to 48 hours.
The compression strength and sound absorption coefficient of the solidified product thus obtained were measured, and the results are shown in Table 1.

Further, in order to observe the state of pores in the obtained solidified product, the polished sample was observed with a reflection microscope. The result is shown in FIG. Forming continuous vents,
The average diameter of the continuous air holes is 100 to 2000 μm, and the size of the constricted portion of the continuous air holes is 30 to 500 μm on average. In the observation of the polished surface, 60% or more of the pores with a diameter of 0.1 mm or more, and 8 with the pores of 1 mm or more in diameter
0% or more are continuous ventilation holes. Also, X of the solidified product obtained
Line diffraction analysis was performed. The chart is shown in FIG. In addition to tobermorite, α-quartz peak of silica sand is observed.

Regarding the measurement of compressive strength, JIS
According to A 1108. That is, a metal plate having a diameter of 50 mm is placed on the upper and lower surfaces of the sample, and pressure is applied to this plate by using an autograph. And Sound absorption coefficient is in accordance with JIS A 1405, thickness 5c
Normal incidence sound absorption coefficient was measured at m, no air layer and a frequency of 500 Hz. The average of the five samples was taken as the sound absorption coefficient, and its standard deviation was taken as the variation. Although the example using silica sand has been described above as the siliceous aggregate, the present invention is not limited to this, and blast furnace slag powder, silicate clay, volcanic ash, diatomaceous earth, etc. may be used. .

(Comparative Examples 1 to 5) In Comparative Example 1, wet curing was performed at 70 ° C. without heating sludge. In Comparative Example 2, the slurry was prepared at room temperature (25 ° C.), and the room temperature (25
℃) was cured. In Comparative Example 3, the sludge was heated and wet-cured at 70 ° C. No autoclave curing was done.
Comparative Examples 1 to 3 were performed in the same manner as in the Example except for the above.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

As is apparent from the above description, the porous sound absorbing material according to the present invention can reduce variations in strength and sound absorption coefficient and have good strength and sound absorbing characteristics as compared with conventional sound absorbing materials made of cement concrete. Is. Therefore, in order to obtain the same strength and the same sound absorbing characteristics as the conventional cement concrete sound absorbing material, the thickness of the porous sound absorbing material according to the present invention can be reduced, and the weight can be further reduced.

[Brief description of drawings]

FIG. 1 is a reflection micrograph (× 20) of a polished sample of a solidified product according to the present invention.

FIG. 2 is an X-ray diffraction chart of a solidified product according to the present invention.

Claims (3)

[Claims] 1. A method for producing a light-weight solidified product having continuous air holes and containing tobermorite, which comprises stirring a slurry of cement particles, a foaming agent and water while heating to a substantially wet curing temperature, A method for producing a porous sound absorbing material, which comprises wet curing and autoclave curing. 2. The method for producing a porous sound absorbing material according to claim 1, wherein the wet curing temperature is 40 to 80 ° C. 3. The method for producing a porous sound absorbing material according to claim 1, wherein the content of the silica-based aggregate is 20 to 80% by weight of the cement particles.