JP2007302483A - Hollow spherical type ii anhydrous gypsum particle, method for producing hollow spherical type ii anhydrous gypsum particle, and porous lightweight hardened gypsum product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide hollow spherical type II anhydrous gypsum particles which can retain their shapes within a gypsum product prepared by hardening a hydraulic gypsum slurry to which they are added and to provide a porous lightweight hardened gypsum product obtained by using them. <P>SOLUTION: The hollow spherical type II anhydrous gypsum particles of the present invention are produced by the step of preparing an aqueous solution prepared by adding a crystal habitat modifier to an aqueous gypsum solution of a specified concentration, the step of subjecting the prepared aqueous solution to spray drying at a gypsum recovery temperature of 150 to 250°C under specified conditions of a drying temperature, a compressor pressure, and a blower pressure to obtain β type I gypsum hemihydrate hollow spherical particles, and the step of burning the β type I gypsum hemihydrate hollow spherical particles at 350 to 550°C. And the lightweight and high-strength porous lightweight hardened gypsum product can be obtained by hardening a hydraulic gypsum composition prepared by adding 5 to 20 wt.% above type II anhydrous hollow spherical gypsum particles to calcined plaster by adding water thereto. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel type II anhydrous gypsum hollow spherical particle, a production method thereof, and a porous lightweight gypsum hardened body containing the type II anhydrous gypsum hollow spherical particle.

  In recent years, the trend toward healthy homes that ensure energy saving, safety, comfort, and mental and physical health has been increasing. Gypsum board is relatively inexpensive and has excellent heat insulation properties, so it is used for building interior materials. However, the addition of required performance such as safety and comfort is one of the future issues. . In recent years, many high-rise condominiums and buildings have been built, but in order to reduce the weight of the building, lightweight and high-strength interior materials are required. In order to approach this required performance, making the gypsum hardened body porous is one effective means, and if it is a porous body, the added value such as humidity control ability, environmental hormone and VOC adsorption capacity etc. Can be granted.

  However, in general, a method of increasing the amount of mixed water is used to make the gypsum hardened body porous. However, this method has a problem that the strength is significantly reduced by making the porous material porous. In addition, a method of adding a polymer hollow spherical particle to make it porous is also conceivable, but since the nonflammability of the gypsum hardened body may be reduced, or cracks may occur through the surface of the hollow spherical particle, It is desirable to produce particles. Patent Document 1 discloses hollow columnar calcium carbonate. Since the hollow columnar calcium carbonate of Patent Document 1 has a low specific gravity, when added to a gypsum slurry and cured, it contributes to making the gypsum hardened body porous, but because it is a different material, the nonflammability of the hardened body is reduced. Alternatively, cracks may occur through the surface of the hollow spherical particles.

Non-Patent Document 1 describes that β-type semi-water I gypsum hollow spherical particles can be produced by spray drying a gypsum aqueous solution. Hollow spherical particles can be produced with the same material by this method, but when β-type semi-water I gypsum hollow spherical particles are added to the gypsum slurry and cured, the shape of the hollow spherical particles is not maintained in the gypsum cured body, It did not contribute to making it porous.
Japanese Patent Laid-Open No. 2005-200222 Abstracts of the 111th Academic Lecture Meeting of the Inorganic Materials Society (33)

  The present invention provides a type II anhydrous gypsum hollow spherical particle that maintains its shape in a gypsum cured body after being added to a hydraulic gypsum slurry and cured, and a porous lightweight gypsum cured product thus obtained. For the purpose.

  The type II anhydrous gypsum hollow spherical particles of the present invention are characterized by having a hollow structure inside.

  The type II anhydrous gypsum hollow spherical particles of the present invention include a step of preparing an aqueous solution in which a predetermined concentration of a gypsum aqueous solution and a crystallite is blended, and the aqueous solution is subjected to gypsum under a predetermined drying temperature, compressor pressure, and blower pressure. A production method comprising spray drying at a recovery temperature of 150 to 250 ° C. to obtain β-type semi-water I gypsum hollow spherical particles and firing the β-type semi-water I gypsum hollow spherical particles at 350 to 550 ° C. It is produced by.

  Since it is produced by the production method, uniform spherical particles can be obtained. Moreover, the particle size control of the type II anhydrous gypsum hollow spherical particles is easy.

  Furthermore, the production method can be continuously operated, and the type II anhydrous gypsum hollow spherical particles of the present invention can be efficiently produced.

  Since the type II anhydrous gypsum hollow spherical particles of the present invention have a hollow structure inside, when added to a gypsum hardened body, it contributes to making it porous. Furthermore, since it is formed of the same material as the gypsum hardened body, the strength of the gypsum hardened body can be maintained.

  According to the method for producing type II anhydrous gypsum hollow spherical particles of the present invention, type II anhydrous gypsum hollow spherical particles can be formed of uniform spherical particles. Moreover, the particle size control of the type II anhydrous gypsum hollow spherical particles becomes easy. Furthermore, according to the method for producing type II anhydrous gypsum hollow spherical particles of the present invention, continuous operation is possible, and the type II anhydrous gypsum hollow spherical particles of the present invention can be efficiently produced.

  Since the porous lightweight gypsum cured product of the present invention contains the type II anhydrous gypsum hollow spherical particles of the present invention, a lightweight gypsum cured product can be provided while maintaining strength.

  Moreover, when the porous lightweight gypsum hardened body of the present invention is blended in a hydraulic gypsum slurry, the setting is accelerated.

  Embodiments of the present invention will be described.

  The type II anhydrous gypsum hollow spherical particles of this embodiment have a hollow body structure inside.

  The type II anhydrous gypsum hollow spherical particles of the present embodiment include a step of preparing an aqueous solution in which a gypsum aqueous solution having a predetermined concentration and a crystal clearing agent are mixed, and the aqueous solution is subjected to a predetermined drying temperature, a compressor pressure, and a blower pressure. Production comprising a step of spray drying at a gypsum recovery temperature of 150 to 250 ° C. to obtain β-type semi-water I gypsum hollow spherical particles and a step of firing the β-type semi-water I gypsum hollow spherical particles at 350 to 550 ° C. Produced by the method.

The concentration of the gypsum aqueous solution is (1.1) to (18.4) mmol · dm ⁻³ . As the gypsum, α-type or β-type hemihydrate gypsum is used, but dihydrate gypsum may be used.

  Examples of the crystallizing agent include citric acid, (α-amylase), (d-glutamic acid) and the like. Of these, citric acid can be preferably used.

  The addition amount of the crystallizing agent is (0.1) to (1.0) wt%.

  The drying temperature is (180) to (450) ° C.

  The gypsum recovery temperature is (180) to (220) ° C.

  The compressor pressure is (40) to (120) kPa.

The blower pressure is (-50) hPa. → Effects only on recovery amount The firing temperature in the firing step is (300) to (1000) ° C., preferably 350 to 550 ° C.

  The firing time in the firing step is (0.5) to (2) hours, preferably (1) to (2) hours.

  The particle size of the type II anhydrous gypsum hollow spherical particles of this embodiment is 4 μm to 50 μm, and preferably 10 μm to 20 μm.

  The porous lightweight gypsum hardened body of the present embodiment is characterized in that water is added to a hydraulic gypsum composition in which 5 to 20 wt% of type II anhydrous gypsum hollow spherical particles are added to calcined gypsum and cured.

The porous lightweight gypsum hardened body of this embodiment is characterized in that the type II anhydrous gypsum hollow spherical particles of this embodiment are dispersed in a needle-like crystal matrix of dihydrate gypsum.
Examples Hereinafter, preferred examples of the present invention will be described.
A method for producing type II anhydrous gypsum hollow spherical particles and a cured porous lightweight gypsum according to the present invention will be described with reference to FIG.
(Preparation of type II anhydrous gypsum hollow spherical particles)
Hemihydrate gypsum was dissolved in pure water to prepare a dihydrate gypsum solution having a concentration of 18.8 mmol · dm ⁻³ (S101). A spray solution was prepared by adding 0.1 wt% of citric acid to the dihydrate gypsum solution (S102). The spray solution is introduced into the spray dryer at a flow rate of 0.30 cm ³ · s ⁻¹ and spray-dried under the conditions of a drying temperature of 400 ° C., a compressor pressure of 60 kPa, a blower pressure of -50 hPa, and a sample recovery temperature of 200 ° C. (S103) Thus, β-type semi-water I gypsum hollow spherical particles having a particle size of about 20 μm were obtained (S104).

The obtained β-type semi-water I gypsum hollow spherical particles were calcined at 500 ° C. for 1 hour to form II-type anhydrous gypsum hollow spherical particles (S106 to S107).
(Preparation of porous lightweight gypsum hardened body)
Next, a method for producing a porous lightweight gypsum hardened body using type II anhydrous gypsum hollow spherical particles obtained by the above method will be described.

  First, reagent calcined gypsum is prepared (S108), and the type II anhydrous gypsum hollow spherical particles obtained in the above production process are added thereto (S109).

  Hollow spherical particles were added to the reagent calcined gypsum so as to be 5 to 20 wt%, and water was added to the reagent calcined gypsum at a mixed water amount of 70 wt% (S110) and cured (S111) to produce a cured product. (S112).

  The type II anhydrous gypsum hollow spherical particles were identified with a scanning electron microscope. Further, the compressive strength was measured as an index representing the strength of the cured product.

  FIG. 2 shows a scanning electron micrograph of type II anhydrous gypsum hollow spherical particles obtained by spray drying. As shown in FIG. 2a, the product is a spherical secondary particle having a particle size of about 20 μm composed of fine needle-like primary particles, and it is confirmed that it is type II anhydrous gypsum by X-ray diffraction pattern and thermal analysis. It was.

  FIG. 2b shows a fracture surface of the obtained type II anhydrous gypsum hollow spherical particles included in an epoxy resin and cut with a microtome. FIG. 2c shows an enlarged view of type II anhydrous gypsum hollow spherical particles, and 2 (d) shows the internal structure of the hollow particles.

  As shown in FIGS. 2b to 2d, the internal structure of the spherical particles was a hollow body. Next, the porosity of the gypsum hardened body is expressed by the porosity.

  The porosity was determined by the following formula from the density of the gypsum hardened body.

Porosity (%) = (1− (measured bulk density ÷ (two water gypsum theoretical density × (1−hollow spherical particle addition rate / 100) + type II anhydrous gypsum theoretical density × hollow spherical particle addition rate / 100))) × 100
When the effect of the addition of hollow spherical particles on the porosity of the hardened gypsum was examined, the porosity was 56% without the addition of hollow spherical particles, but the porosity tends to increase with the addition of hollow spherical particles. It was seen.

  FIG. 3 shows the relationship between the compressive strength and the porosity of a cured porous lightweight gypsum obtained by changing the amount of hollow spherical particles added and the amount of mixed water. The conventional porous cured products obtained by changing the amount of mixed water show a tendency for the compressive strength to decrease linearly as the porosity increases, and when the porosity is 61%, the compressive strength is 50%. Decreased to. On the other hand, when the amount of hollow spherical particles added is changed, the compressive strength also decreases under the condition where the added amount is small, but with the addition of 5 wt% or more, there is almost no decrease in compressive strength even when the porosity is increased. At the same porosity of 61%, the decrease in compressive strength was about 20%.

Further, when the hardened fracture surface to which the hollow spherical particles were added was observed with a scanning electron microscope, it was confirmed that the hollow spherical particles had a structure uniformly dispersed in the entanglement of the needle-shaped crystals of dihydrate gypsum. . The photographs are shown in FIGS. 5 (a) and 5 (b).
In addition, the formation of needle-like crystals of dihydrate gypsum was partially confirmed on the surface of the hollow spherical particles, and this entanglement is considered to be the main cause of increasing the strength.

  FIG. 4 shows the amount of type II anhydrous gypsum hollow spherical particles added to the setting time of the cured product. The setting time of the cured product tended to be shortened by adding hollow spherical particles, and when it was added at 20 wt%, the initial setting was 14 minutes and the final setting was 17 minutes.

  The type II anhydrous gypsum hollow spherical particles of the present invention can be used to produce a gypsum hardened body that is lightweight and has high strength.

The manufacturing method of the type II anhydrous gypsum hollow spherical particle and the porous lightweight gypsum hardened body by the Example of this invention is shown. It is a figure which shows the electron micrograph showing the shape of the type II anhydrous gypsum hollow spherical particle by the Example of this invention. FIG. 2 shows a fracture surface of a type II anhydrous gypsum hollow spherical particle included in an epoxy resin in an example of the present invention and cut by a microtome. FIG. 4 is an enlarged view of type II anhydrous gypsum hollow spherical particles. It is a figure which shows the internal structure of a hollow particle. The graph showing the relationship between the compressive strength of the porous lightweight gypsum hardened | cured material obtained by changing the addition amount of the type II anhydrous gypsum hollow spherical particle and the amount of mixed water of this invention, and a porosity. A graph showing the amount of type II anhydrous gypsum hollow spherical particles added to the setting time of the gypsum hardened body. It is a figure which shows the electron micrograph of the gypsum hardened body which added the type II anhydrous gypsum hollow spherical particle of this invention. It is a figure which shows the enlarged electron micrograph of the gypsum hardened body which added the type II anhydrous gypsum hollow spherical particle of this invention.

Claims (5)

Type II anhydrous gypsum hollow spherical particles characterized by having a hollow structure inside. The type II anhydrous gypsum hollow spherical particle according to claim 1, having a particle diameter of 4 to 20 µm. A step of preparing an aqueous solution in which a predetermined concentration of gypsum aqueous solution and a crystal clearing agent are mixed;
Spray drying the aqueous solution under a predetermined drying temperature, compressor pressure and blower pressure at a gypsum recovery temperature of 150 to 250 ° C. to obtain β-type semi-water I gypsum hollow spherical particles;
Firing the β-type semi-water I gypsum hollow spherical particles at 350 to 550 ° C.,
A method for producing type II anhydrous gypsum hollow spherical particles, comprising: A porous lightweight gypsum cured product obtained by adding water to a hydraulic gypsum composition in which 5 to 20 wt% of type II anhydrous gypsum hollow spherical particles are added to calcined gypsum and curing. The cured porous lightweight gypsum according to claim 4, wherein the type II anhydrous gypsum hollow spherical particles are dispersed in an acicular crystal matrix of dihydrate gypsum.