JPH0223507B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing an inorganic plate-like sound absorbing material. Conventional technology A wide variety of sound absorbing materials have been used in the past, but calcium silicate-based or cement materials are molded into plate shapes and are nonflammable and are easy to use in buildings such as houses and building kegs. A typical example is concrete. Perforated calcium silicate fireproofing boards have been used since the beginning of calcium silicate fireproofing.
This sound-absorbing material is made by forming a large number of through holes in a calcium silicate fireproof board to give it sound-absorbing properties, but its sound-absorbing properties are not very good, and when it is installed on buildings, it cannot be used with other fibrous sound-absorbing materials. It is necessary to strengthen the sound absorption performance by combining it with other materials or by providing an air layer. On the other hand, a cement concrete board with fine interconnected holes has been proposed as a sound absorbing material that exhibits better sound absorbing performance than perforated calcium silicate fireproof board-based sound absorbing materials (Japanese Patent Laid-Open No. 52-32016,
JP-A No. 53-26419, etc.). However, to manufacture this type of sound absorbing material, a cement slurry mixed with air bubbles using a foaming agent must be poured into a mold, hardened, and then placed in an autoclave and cured under high temperature and pressure. In the case of sound absorbing materials for buildings, which not only take time to manufacture, but also require mass production in the form of large panels, the cost of thermal energy is enormous and pressure curing equipment is expensive. The disadvantage is that the product becomes extremely expensive. Problems to be Solved by the Invention In view of the fact that the conventional sound absorbing board with continuous holes had the above-mentioned drawbacks despite its good sound absorbing performance, the present invention proposes a method for curing under high temperature and pressure. The aim is to make it possible to manufacture this by a method that does not require it. Means for Solving the Problems First, we will give an overview of the manufacturing method of the present invention.
The manufacturing method of the present invention involves subjecting water in which a foaming agent has been dissolved to a foaming treatment to prepare a foam liquid, which can form α-hemihydrate gypsum, β-hemihydrate gypsum, and a water-resistant cured product. A synthetic resin emulsion and reinforcing fibers are mixed and stirred to form a slurry containing the amount of closed cells necessary to finally form a porous cured material with a bulk specific gravity of 0.30 to 0.45. Injecting the cell-containing slurry into a mold, allowing the formation of open cells by coalescence of closed cells in the mold, and flowing the slurry until most of the closed cells grow into open cells in the mold. The method is characterized in that a curing retarder is added in the raw material slurry preparation process in an amount that can adjust the curing characteristics of the slurry so that the slurry maintains its properties and then rapidly hardens. Hereinafter, the manufacturing method of the present invention will be explained in order of steps. The main raw material, α-hemihydrate gypsum or β-hemihydrate gypsum (hereinafter sometimes simply referred to as gypsum), can be of the same quality as that normally used in the manufacture of gypsum board, or special I don't need anything. As the foaming agent, most foaming surfactants can be used, including but not limited to anionic surfactants that easily generate continuous foaming, especially alkyl phenyls. Ether sulfate ester salts, rosin acid salts, and the like are preferred. Examples of synthetic resin emulsions include acrylic resin emulsion, styrene-acrylic resin emulsion, vinyl acetate resin emulsion, and ethylene-acrylic resin emulsion.
Use a material that can form a water-resistant and strong cured product by heating and drying, such as vinyl acetate resin emulsion. As reinforcing fibers, inorganic fibers such as glass fibers, rock wool, and stainless steel fibers are preferred, but organic fibers such as wood pulp, rayon cloth, and various synthetic fibers may also be used. If the fibers are too long, they will become entangled and will not be uniformly dispersed in the raw material slurry, while if they are too short, the reinforcing effect will be low. The preferred length varies depending on the type of fiber, but is approximately 6 to 12 mm. Gypsum hardening rate regulators include those that have the effect of slowing down the hardening rate of gypsum and those that have the effect of accelerating the hardening of gypsum. In the present invention, the former is essential, but the latter is used as necessary. Examples of curing retarders that can be used include Pufftard P
-02 (trade name; protein decomposition product; product of Ajinomoto Co., Inc.), sodium citrate, etc. Examples of hardening accelerators include aluminum sulfate and potassium sulfate. From the above raw materials and water, as described above, a slurry mixture containing closed cells is prepared in an amount necessary to finally form a porous cured body with a bulk specific gravity of 0.30 to 0.45. To do this, first prepare water in an amount of approximately 0.6 to 0.8 times the weight of the gypsum, and dissolve a foaming agent in the amount of approximately 0.2 to 1.0% based on the weight of the gypsum to create foam. If the amount of water is less than this, the fluidity of the slurry will be poor and it will be difficult to mix the powder raw materials and bubbles uniformly and adjust the bubbles, and if the amount of water is too large, the fluidity of the slurry will become excessive. Separation occurs between the solid raw material and the bubble liquid during molding (however,
If the gypsum is slurried in advance and then mixed with the bubble solution, a portion of the above amount of water is used as slurry water). Note that a dispersant may be dissolved in this water. In order to foam the water in which the foaming agent is dissolved, it is sufficient to vigorously stir the water using an appropriate stirring device so as to entrain air, but a device for blowing fine bubbles may also be used. Foaming treatment makes the bubbles sufficiently fine and uniform,
It is desirable to carry out the process until the volume of the foamed water becomes about 4 to 6 times the volume of the original water. Gypsum, synthetic resin emulsion, and hardening retardant are added to the resulting foam liquid and mixed. It is preferable to mix these raw materials with water prepared separately, as this will prevent bubbles from breaking when mixed with the bubble liquid. After this, stir well to make a slurry with air bubbles evenly distributed, and finally prepare a slurry containing the amount of air bubbles necessary to form a porous cured body with a bulk specific gravity of 0.30 to 0.45 (this air bubble amount is This is also necessary in order to cause the bubbles to communicate quickly after the slurry is cast.) If the amount of bubbles is insufficient, more bubbles are introduced at this stage. In addition,
The reinforcing fibers are mixed at any stage of the above process. A closed-cell liquid-containing slurry is prepared as described above, and the resulting slurry is immediately molded. Molding can be carried out by any method, such as pouring the slurry into a suitable mold, or forming the slurry into a continuous plate shape using a continuous molding device and cutting it after curing. When the slurry is allowed to stand still due to casting, the air bubbles in the slurry gradually coalesce and become larger, and then become open-circuited. If more time passes without the slurry losing its fluidity, the bubbles will burst and the volume of the bubble-containing slurry will decrease. Therefore, the amount of set retarder added when preparing the aerated slurry is determined by the amount of set retarder added to retard the setting of the plaster, which normally hardens within minutes, and to reduce the amount of time required for foam control (typically 20 minutes or more) and injections, as described above. The amount must be sufficient to allow the time necessary for post-mold open cell formation (usually 60 to 120 minutes), but it is undesirable for the slurry to not harden even after the open cells are formed. Therefore, it is best to delay the curing of the slurry by using a curing retarder to end when the air bubbles reach a favorable state of communication, but it is difficult to adjust the curing timing by adjusting the amount of the curing retarder added. In such cases, a curing accelerator may be mixed into the slurry immediately before casting. When the slurry in which the communicating holes are formed is sufficiently cured, the cured product is removed from the mold, and a sound absorbing material having good sound absorbing properties can be obtained. Effects of the Invention According to the present invention as described above, an inorganic plate-like sound absorbing material that exhibits excellent sound absorbing performance by having communicating holes can be cured in a simpler manner than before without requiring autoclave curing. It can be manufactured using the same equipment and with high productivity. Note that hardened gypsum has lower strength than cement concrete, so if it simply contains a large number of communicating holes, it will become brittle, but in the production method of the present invention, reinforcing fibers are added using water-resistant resin. Perhaps because it adheres well to hardened gypsum, the reinforcing effect of the fibers is large, and it has sufficient strength for practical use. Therefore, in combination with the fact that gypsum, the main raw material, is inexpensive, the present invention makes it possible to produce a sound absorbing material with almost the same performance as conventional cement-concrete materials at a much lower cost than before. becomes. Examples and Comparative Examples By adding 0.4 parts by weight of a foaming agent (alkyl phenyl ether sulfate sodium salt) to 75 parts by weight of water and stirring vigorously with a mixer, the volume was increased to 5.3 times that of the original water. A bubble solution was prepared. Next, 100 parts by weight of β-hemihydrate gypsum, 0.25 parts by weight of a curing retardant (Pufftard P-02), and acrylic resin emulsion Acronal YJ- were added to this bubble liquid.
5 parts by weight of 3032D (resin concentration 40%; manufactured by Yuka Verdice Co., Ltd.) were added and stirred for 10 minutes, and then 0.5 parts by weight of B glass fiber chop strands were added and further stirred for 1 minute. After this, hardening accelerator (10% aqueous solution of sulfuric acid)
0.10 parts by weight was added, stirred for 1 minute, and immediately poured into a mold for curing at room temperature and heating drying at 60° C. (Example). For comparison, we also conducted an experiment in which the raw material composition was partially changed. Table 1 shows the curing time of the bubble-containing slurry in the above example (time after casting; determined by finger touch) and the properties of the obtained sound absorbing material. In addition, the sound absorbing properties of the sound absorbing material of Example and the sound absorbing material of Comparative Example 3 were
As shown in the figure (measurement conditions: sound absorbing material thickness 35 mm; no air space behind).

【table】

[Table] ** Cured before casting

[Brief explanation of drawings]

FIG. 1 is a graph showing the sound absorbing properties of the sound absorbing materials obtained in Example and Comparative Example 3.

Claims (1)

[Claims] 1. A foaming solution is prepared by performing foaming treatment on water in which a foaming agent is dissolved, and α-hemihydrate gypsum or β-hemihydrate gypsum is added to the foaming solution.
- The amount necessary to mix and stir gypsum hemihydrate, a synthetic resin emulsion capable of forming a water-resistant cured product, and reinforcing fibers, and finally form a porous cured product with a bulk specific gravity of 0.30 to 0.45. forming a slurry containing closed cells, injecting the obtained cell-containing slurry into a mold, and proceeding with the formation of open cells by coalescence of the closed cells in the mold; In the step of preparing the raw material slurry, a curing retarder is added in an amount that can adjust the curing characteristics of the slurry so that the slurry maintains fluidity until most of the cells grow into open cells and then hardens rapidly. A manufacturing method for a distinctive inorganic plate-like sound absorbing material.