JP2008162860A - Methods for producing calcined gypsum and gypsum board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing calcined gypsum by which, even if raw material gypsum is calcined and is subjected to water addition treatment, setting time does not delay, and to provide a gypsum product utilizing the calcined gypsum obtained by the above method. <P>SOLUTION: When raw material gypsum is calcined and is subjected to water addition treatment and the calcined gypsum is recalcined, the calcined gypsum can be produced in which the amount of the water to be mixed is reduced and setting time does not delay. Further, even when recycle gypsum causing the increase of the amount of the water to be mixed is largely used as gypsum raw material, in the calcined gypsum produced in this way, the amount of the water to be mixed is reduced and setting time does not delay, thus an ordinary gypsum board can be produced without reducing the productivity of the gypsum board. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a calcined gypsum by firing raw material gypsum, and a method for producing a gypsum board using the calcined gypsum.

For calcined gypsum, raw gypsum such as chemical gypsum and natural gypsum are singly or mixed and calcined, and raw gypsum that is mainly dihydrate gypsum (CaSO ₄ · 2H ₂ O) is mainly hydrated gypsum (CaSO gypsum). ₍₄ · 1 / 2H ₂ O). The theoretical values of the combined water (crystal water) content based on the chemical formulas of dihydrate gypsum and hemihydrate gypsum are 20.9 wt% and 6.2 wt%, respectively. The raw material gypsum usually contains free water (adhesion water) other than compound water.

  The calcined gypsum obtained above can be used as a raw material for various gypsum products because it forms a dihydrate when it is made into a slurry by adding an appropriate amount of water, and is used suitably as a raw material for various gypsum products. Used as a raw material.

  Gypsum board is a plate-like body formed by coating a core mainly composed of dihydrate gypsum with base paper for gypsum board. During production, calcined gypsum, adhesion aid, curing accelerator, foam for weight reduction, Other additives, etc., and further admixture and water are kneaded, and the calcined gypsum slurry obtained as a result is poured between upper and lower gypsum board base paper, formed into a plate shape, and then roughened after curing. After cutting and forced drying, it is cut into product dimensions.

  The gypsum board manufactured as described above is widely used as an interior material for buildings because of fire resistance, sound insulation, workability and economy. In recent years, due to the social demand for volume reduction of industrial waste, as the rate of recycling gypsum board waste at the time of new construction and dismantling to gypsum board manufacturers has increased, the ratio of recycled gypsum to gypsum board raw material gypsum has also increased. It has improved. However, with the improvement of the recycling rate, mainly due to the fact that the gypsum crystals of recycled gypsum are fine, the amount of mixed water of calcined gypsum to give the calcined gypsum slurry proper fluidity increases, and the gypsum board In this drying process, excess water that must be dried increases, so that the necessary drying energy increases, and the productivity of gypsum board is greatly reduced.

  There are the following as prior arts for reducing the amount of mixed water of calcined gypsum used for manufacturing a gypsum board.

  For example, in Japanese Patent Publication No. 3-51665 (Patent Document 1), water is added to the blended gypsum raw material to the blender and the calcined gypsum raw material in a weight ratio of about 1% to about 10% of the raw material. Mixing and drying the surface of calcined gypsum particles with a small amount of free water for a short time to prevent the particles from becoming unnecessarily fine and water soluble, and drying the calcined gypsum subjected to the above heel treatment at high temperature Pulverizing the dried and heeled calcined gypsum to increase the surface area of the gypsum particles, thereby increasing the rate of strength increase in the gypsum board and increasing the final strength of the gypsum particles. And a method of producing calcined gypsum that can reduce the amount of mixed water by about 20% compared to calcined gypsum that is not hydrotreated.

Although this prior art disclosed herein has the processing steps shown in FIG. 1, this method is shown to evaporate the remaining free water of the heeled calcined gypsum in the drying step. In addition, it is described that it is necessary to select so that the combined water of calcined gypsum is not removed. However, this method can reduce the amount of mixed water of calcined gypsum and reduce the required drying energy, but the setting time of gypsum board has to be reduced because the setting time is delayed, or the production speed of gypsum board is reduced. In order to prevent this, a large amount of setting accelerator must be used, and there is a problem that various physical properties of the gypsum board are lowered.
Japanese Examined Patent Publication No. 3-51665

  An object of the present invention is to provide a method for producing calcined gypsum that does not delay the setting time even if raw material gypsum is calcined and hydrotreated to reduce the mixed water amount of calcined gypsum.

  Another object of the present invention is to provide a method for producing a gypsum board using part or all of the calcined gypsum obtained by the above production method.

  As a result of intensive studies, the inventors of the present invention applied water treatment to the calcined gypsum obtained by calcining the raw gypsum (primary calcining) and re-calcining (secondary calcining), thereby reducing the amount of mixed water. The inventors have found that calcined gypsum that does not delay time can be obtained, and have reached the present invention.

  That is, the method for producing calcined gypsum according to the first aspect of the present invention includes a treatment step shown in FIG. 2, a primary calcining step of calcining raw gypsum to obtain calcined gypsum, and a part of the obtained calcined gypsum Alternatively, it is characterized by comprising a hydrotreating step in which the entire amount is hydrolyzed and a secondary firing step in which the calcined gypsum obtained by the hydrotreating is further refired.

  The difference between the present invention and the prior art shown in FIG. 1 is that the calcined gypsum obtained by hydrotreating is further refired. In the prior art, the hydrolyzed gypsum does not evaporate the combined water. In contrast to what is heated in the range, the present invention is different in that it is fired so as to evaporate the combined water.

  A method for producing calcined gypsum according to a second aspect of the present invention is the method for producing calcined gypsum according to the first aspect, wherein the raw material gypsum includes recycled gypsum.

  The method for producing calcined gypsum according to the invention described in claim 3 is characterized in that, in the method for producing calcined gypsum according to claim 1 or 2, the ratio of recycled gypsum is 2 to 50 wt% of the raw gypsum.

  The method for producing calcined gypsum according to the invention described in claim 4 is the method for producing calcined gypsum according to any one of claims 1 to 3, wherein in the hydrating process, the amount of water for hydrotreating the calcined gypsum is 1 to 1 per gypsum. It is characterized by 10 wt%.

  The method for producing calcined gypsum according to the invention described in claim 5 is the method for producing calcined gypsum according to claims 1 to 4, wherein the combined water of the calcined gypsum hydrotreated in the secondary firing step is 3 to 7 wt%. It is characterized by.

  The method for producing calcined gypsum according to the invention described in claim 6 is the method for producing calcined gypsum according to any one of claims 1 to 5, wherein in the hydrating process, the water used for the hydrating treatment uses the adhering water of the raw gypsum. It is characterized by that.

  The method for producing calcined gypsum according to the invention described in claim 7 is the method for producing calcined gypsum according to any one of claims 1 to 6, wherein the firing means in the primary firing step and the secondary firing step use the same firing apparatus. It is characterized by that.

  The method for producing a gypsum board according to the invention described in claim 8 is characterized in that a part or all of the calcined gypsum obtained by the method described in claims 1 to 7 is used.

  According to the present invention, calcined gypsum can be produced by calcining raw material gypsum, hydrotreating it, and recalculating the calcined gypsum, which has a small amount of mixed water and does not delay the setting time. Moreover, even if a large amount of recycled gypsum that causes an increase in the amount of mixed water is used as a raw material for gypsum, calcined gypsum manufactured as described above has a small amount of mixed water and does not delay the setting time, thus reducing the productivity of gypsum board A normal gypsum board can be produced without causing it.

  Embodiments of the present invention will be described below.

  The calcined gypsum of the present invention is produced by subjecting the entire amount or a part of the calcined gypsum obtained by primary firing of the raw material gypsum to secondary firing.

  As the raw material gypsum of the present invention, natural gypsum, chemical gypsum such as neutralized gypsum or by-product gypsum, or a mixture of two or more types thereof can be used. Examples of main chemical gypsum include phosphate gypsum, hydrofluoric acid gypsum, titanium gypsum, and flue gas desulfurization gypsum.

  The raw gypsum (natural gypsum or chemical gypsum) contains 1 to 25 wt% of adhering water.

  The raw gypsum of the present invention may include recycled gypsum.

  The recycled gypsum may be any recycled gypsum that is recovered from waste gypsum board generated by a gypsum board manufacturer, waste gypsum board generated at the time of new construction or dismantling, and the like.

  The mixing ratio of the recycled gypsum to the normal raw material gypsum is in the range of 2 to 50 wt%, more preferably in the range of 10 to 30 wt%. If the recycle rate is low, the recovered gypsum cannot be digested, and if the recycle rate is too high, the gypsum crystal of the recycle gypsum is fine and the productivity of the gypsum board is greatly reduced.

  In the primary firing step, the raw gypsum is fired by a conventional method using a kettle, a rotary kiln or the like used by those skilled in the art to obtain calcined gypsum. The baking apparatus used is not particularly limited. The product temperature of the calcined gypsum upon completion of firing (baked) is preferably 130 to 180 ° C., more preferably 130 to 155 ° C., which allows rapid water treatment. When the product temperature of the calcined gypsum obtained is 130 ° C. to 155 ° C., the calcined gypsum is not forcedly cooled during the water treatment (the product temperature of the calcined gypsum during the water treatment is 100 ° C. to 130 ° C.). Exhibits an effect of reducing the amount of mixed water. However, when the product temperature of the calcined gypsum during the hydration treatment is about room temperature (about 10 to 50 ° C.), the amount of mixed water of the calcined gypsum is further reduced. In the case where the product temperature of the obtained calcined gypsum is 155 to 180 ° C., the calcined gypsum uses a cooling device such as a drum cooler in order to exert the effect of reducing the amount of mixed water during the hydration treatment. To 50 ° C.). In the hydration treatment step, 1 to 10 wt% of water is added to the calcined gypsum after the primary firing, and dispersed and stirred to obtain a hydrotreated calcined gypsum. Any mixing and stirring device may be used as long as it can perform dispersion stirring. If the amount of water is more than 10 wt%, dihydrate gypsum precipitates, and if it is less than 1 wt%, the effect of reducing the amount of mixed water is hardly obtained. The amount of water added is more preferably 2 to 5 wt%.

  In the hydration treatment step, the calcined gypsum after the primary firing may be mixed with the raw gypsum, and the hydrotreated calcined gypsum may be obtained using the adhering water contained in the raw gypsum. In this case, the method of mixing the calcined gypsum obtained by the primary firing and the raw gypsum is not particularly limited. For example, the calcined gypsum is circulated using a transport means such as a screw conveyor to form the raw gypsum. You may make it mix and raw material gypsum may be newly mixed with calcined gypsum after primary baking using transport means, such as a belt conveyor. In addition, it is preferable to use existing equipment as a means for mixing calcined gypsum and raw material gypsum because it does not require new equipment investment costs. Since the water adhering to the raw material gypsum is used for the hydrating treatment, it is not necessary to add water other than the adhering water, and it is not necessary to install new equipment for the hydrating treatment, so the cost can be greatly reduced.

  In the hydration process, the calcined gypsum after the primary firing is mixed with the raw material gypsum, and the hydrotreated calcined gypsum is obtained using the adhering water contained in the raw material gypsum. 5 to 150 wt% is preferable. When raw gypsum and calcined gypsum are mixed in the above ratio, calcined gypsum can be hydrotreated only with existing equipment, and the amount of mixed water is reduced by secondary calcining of the hydrotreated calcined gypsum, delaying the setting time No calcined gypsum is obtained.

  In the secondary firing step (re-firing), the calcined gypsum hydrotreated by a conventional method is calcined using a calcining apparatus such as a kettle or a rotary kiln used by those skilled in the art to obtain calcined gypsum. The combined water of the obtained calcined gypsum is preferably 3 to 7 wt%, and more preferably 3 to 5 wt% which tends to promote the setting of calcined gypsum. If the combined water is more than 7 wt%, unfired dihydrate gypsum remains, which adversely affects the setting time of the calcined gypsum and the fluidity of the calcined gypsum slurry. It is preferable to use the same firing device used in the secondary firing as the one used in the primary firing because it is not necessary to install a new firing device and the cost can be greatly reduced. It is not limited to using.

  In the present invention, the primary firing treatment step, the hydration treatment step, and the secondary firing treatment step may further include a grinding treatment step of grinding the calcined gypsum using a grinding device such as a tube mill.

  The pulverization treatment step is performed before or after the hydration treatment step or after the secondary calcination, but preferably is performed after the secondary calcination step.

  The calcined gypsum thus obtained is kneaded with an adhesion aid, a curing accelerator, foam for weight reduction, other additives and the like, and further an admixture and water. (Hereinafter referred to as “sludge”) is poured between upper and lower base papers, formed into a plate shape between upper and lower forming rolls and between upper and lower plates, and then cured on a conveyor belt, roughly cut, and forced It can be effectively used as a raw material for the production of normal gypsum board produced by cutting into product dimensions after drying.

The raw material gypsum is a mixture of 100 gm pass 90 wt% of natural gypsum 40 wt% and flue gas desulfurization gypsum 60 wt%, natural gypsum 35 wt%, flue gas desulfurization gypsum 55 wt%, and recycled gypsum 10 wt%. 100 mesh pass 90 wt%, natural gypsum 30 wt%, flue gas desulfurization gypsum 50 wt%, and recycled gypsum 20 wt mixture 100 mesh pass 90 wt%, natural gypsum 25 wt%, flue gas desulfurization gypsum 45 wt%, and Four types of a mixed product of 30 wt% recycled gypsum having a 100 mesh pass and 90 wt% were used.
[Example 1]
The processing steps are shown in FIG.

3 kg of raw material gypsum was charged into a small kettle, and the final baking was performed at a baked product temperature of 165 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was placed in a sealed container and allowed to stand for 24 hours, and then the calcined gypsum was taken out of the sealed container and pulverized using a small pot mill, and the bran specific surface area of the calcined gypsum was adjusted to about 7000 cm ² / g. These calcined gypsums were measured for product temperature, then placed in a sealed container, added with 3 wt% water per calcined gypsum, and immediately subjected to hydration by vigorously stirring for 1 minute. About 1.0 g was collected from the calcined gypsum after the hydrolysis treatment, and the combined water (compound water B) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was again charged into a small kettle and subjected to secondary firing at a baked product temperature of 165 ° C. The obtained calcined gypsum was allowed to cool to room temperature and then pulverized using a small pot mill to adjust the brain specific surface area to about 8000 cm ² / g to obtain a calcined gypsum sample.
[Example 2]
The processing steps are shown in FIG.

3 kg of raw material gypsum was charged into a small kettle, and the final baking was performed at a baked product temperature of 150 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was immediately pulverized using a small pot mill, and the bran specific surface area of the calcined gypsum was adjusted to about 7000 cm ² / g. These calcined gypsums were measured for product temperature, then placed in a sealed container, added with 3 wt% water per calcined gypsum, and immediately subjected to hydration by vigorously stirring for 1 minute. About 1.0 g was collected from the calcined gypsum after the hydrolysis treatment, and the combined water (compound water B) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was again charged into a small kettle and subjected to secondary firing at a baked product temperature of 165 ° C. The obtained calcined gypsum was allowed to cool to room temperature and then pulverized using a small pot mill to adjust the brain specific surface area to about 8000 cm ² / g to obtain a calcined gypsum sample.
[Example 3]
The processing steps are shown in FIG.

3 kg of raw material gypsum was charged into a small kettle, and the final baking was performed at a baked product temperature of 150 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was placed in a sealed container and allowed to stand for 24 hours, and then the calcined gypsum was taken out of the sealed container and pulverized using a small pot mill, and the bran specific surface area of the calcined gypsum was adjusted to about 7000 cm ² / g. These calcined gypsums were measured for product temperature, then placed in a sealed container, added with 3 wt% water per calcined gypsum, and immediately subjected to hydration by vigorously stirring for 1 minute. About 1.0 g was collected from the calcined gypsum after the hydrolysis treatment, and the combined water (compound water B) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was again charged into a small kettle and subjected to secondary firing at a baked product temperature of 165 ° C. The obtained calcined gypsum was allowed to cool to room temperature and then pulverized using a small pot mill to adjust the brain specific surface area to about 8000 cm ² / g to obtain a calcined gypsum sample.
[Example 4]
The processing steps are shown in FIG.

3 kg of raw material gypsum was charged into a small kettle, and the final baking was performed at a baked product temperature of 165 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was placed in a sealed container and allowed to stand for 24 hours, and then the calcined gypsum was taken out of the sealed container and pulverized using a small pot mill, and the bran specific surface area of the calcined gypsum was adjusted to about 7000 cm ² / g. These calcined gypsums were measured for product temperature, then placed in a sealed container, added with 3 wt% water per calcined gypsum, and immediately subjected to hydration by vigorously stirring for 1 minute. About 1.0 g was collected from the calcined gypsum after the hydrolysis treatment, and the combined water (compound water B) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was again charged into a small kettle and subjected to secondary firing at a baked product temperature of 175 ° C. The obtained calcined gypsum was allowed to cool to room temperature and then pulverized using a small pot mill to adjust the brain specific surface area to about 8000 cm ² / g to obtain a calcined gypsum sample.
[Example 5]
The processing steps are shown in FIG.

3 kg of raw material gypsum was charged into a small kettle, and the final baking was performed at a baked product temperature of 150 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. Immediately the remaining plaster of Paris, and pulverized using a small pot mill, to prepare a Blaine specific surface area of the calcined gypsum at about 7000 cm ² / g. These calcined gypsums were measured for product temperature, then placed in a sealed container, added with 3 wt% water per calcined gypsum, and immediately subjected to hydration by vigorously stirring for 1 minute. About 1.0 g was collected from the calcined gypsum after the hydrolysis treatment, and the combined water (compound water B) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was again charged into a small kettle and subjected to secondary firing at a baked product temperature of 175 ° C. The obtained calcined gypsum was allowed to cool to room temperature and then pulverized using a small pot mill to adjust the brain specific surface area to about 8000 cm ² / g to obtain a calcined gypsum sample.
[Example 6]
The processing steps are shown in FIG.

3 kg of raw material gypsum was charged into a small kettle, and the final baking was performed at a baked product temperature of 150 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was placed in a sealed container and allowed to stand for 24 hours, and then the calcined gypsum was taken out of the sealed container and pulverized using a small pot mill, and the bran specific surface area of the calcined gypsum was adjusted to about 7000 cm ² / g. These calcined gypsums were measured for product temperature, then placed in a sealed container, added with 3 wt% water per calcined gypsum, and immediately subjected to hydration by vigorously stirring for 1 minute. About 1.0 g was collected from the calcined gypsum after the hydrolysis treatment, and the combined water (compound water B) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was again charged into a small kettle and subjected to secondary firing at a baked product temperature of 175 ° C. The obtained calcined gypsum was allowed to cool to room temperature and then pulverized using a small pot mill to adjust the brain specific surface area to about 8000 cm ² / g to obtain a calcined gypsum sample.
[Example 7]
The processing steps are shown in FIG.

3 kg of raw material gypsum was charged into a small kettle, and the final baking was performed at a baked product temperature of 165 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was placed in a sealed container and allowed to stand for 24 hours, and then the calcined gypsum was taken out of the sealed container and pulverized using a small pot mill, and the bran specific surface area of the calcined gypsum was adjusted to about 7000 cm ² / g. 50 wt% of the obtained calcined gypsum was subjected to secondary firing after the water treatment, and the remaining 50 wt% calcined gypsum (calcined gypsum only for primary firing) was left as it was. The calcined gypsum to be secondarily fired after the water treatment was placed in an airtight container, added with 3 wt% water per calcined gypsum, and immediately stirred vigorously for 1 minute for water treatment. 0.5 g from the calcined gypsum after the hydrolysis treatment and 0.5 g from the calcined gypsum only subjected to the primary firing were mixed and mixed water (compound water B) was measured by a test method according to JIS R 9101. The remainder of the calcined gypsum after the hydration treatment was again charged into a small kettle and subjected to secondary firing at a baked product temperature of 165 ° C. The obtained calcined gypsum is allowed to cool to room temperature, and then pulverized using a small pot mill together with the rest of the calcined gypsum obtained only above, and the brain specific surface area is adjusted to about 8000 cm ² / g. A sample calcined gypsum was obtained.
[Example 8]
The processing steps are shown in FIG.

3 kg of raw material gypsum was charged into a small kettle, and the final baking was performed at a baked product temperature of 140 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was immediately pulverized using a small pot mill, and the bran specific surface area of the calcined gypsum was adjusted to about 7000 cm ² / g. 50 wt% of the obtained calcined gypsum was subjected to secondary firing after the water treatment, and the remaining 50 wt% calcined gypsum (calcined gypsum only for primary firing) was left as it was. The calcined gypsum to be secondarily fired after the water treatment was placed in an airtight container, added with 3 wt% water per calcined gypsum, and immediately stirred vigorously for 1 minute for water treatment. 0.5 g from the calcined gypsum after the hydrolysis treatment and 0.5 g from the calcined gypsum only subjected to the primary firing were mixed and mixed water (compound water B) was measured by a test method according to JIS R 9101. The remainder of the calcined gypsum after the hydration treatment was again charged into a small kettle and subjected to secondary firing at a baked product temperature of 165 ° C. The obtained calcined gypsum is allowed to cool to room temperature, and then pulverized using a small pot mill together with the rest of the calcined gypsum obtained only above, and the brain specific surface area is adjusted to about 8000 cm ² / g. A sample calcined gypsum was obtained.
[Example 9]
The processing steps are shown in FIG.

3 kg of raw material gypsum was charged into a small kettle, and the final baking was performed at a baked product temperature of 140 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was placed in a sealed container and allowed to stand for 24 hours, and then the calcined gypsum was taken out of the sealed container and pulverized using a small pot mill, and the bran specific surface area of the calcined gypsum was adjusted to about 7000 cm ² / g. 50 wt% of the obtained calcined gypsum was subjected to secondary firing after the water treatment, and the remaining 50 wt% calcined gypsum (calcined gypsum only for primary firing) was left as it was. The calcined gypsum to be secondarily fired after the hydration treatment was subjected to the hydration treatment by placing it in a sealed container, adding 3 wt% water per calcined gypsum, and immediately stirring vigorously for 1 minute. 0.5 g from the calcined gypsum after the hydrolysis treatment and 0.5 g from the calcined gypsum only subjected to the primary firing were mixed and mixed water (compound water B) was measured by a test method according to JIS R 9101. The remainder of the calcined gypsum after the hydration treatment was again charged into a small kettle and subjected to secondary firing at a baked product temperature of 165 ° C. The obtained calcined gypsum is allowed to cool to room temperature, and then pulverized using a small pot mill together with the rest of the calcined gypsum obtained only above, and the brain specific surface area is adjusted to about 8000 cm ² / g. A sample calcined gypsum was obtained.
[Example 10]
The processing steps are shown in FIG.

Raw material gypsum (1.5 kg) was charged into a small kettle, and the final baking was performed at a baked product temperature of 165 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was placed in an airtight container and allowed to stand for 24 hours, and then the calcined gypsum was taken out from the airtight container, the product temperature of the calcined gypsum was measured, and 1.5 kg of new raw material gypsum was mixed. In addition, 1.0g was extract | collected from the mixture here, and the compound water (compound water B) was measured with the test method by JISR9101. The remaining mixture was charged into a small kettle and subjected to secondary firing at a baked product temperature of 165 ° C. The obtained calcined gypsum was allowed to cool to room temperature and then pulverized using a small pot mill to adjust the brain specific surface area to about 8000 cm ² / g to obtain a calcined gypsum sample.
[Example 11]
The processing steps are shown in FIG.

Raw material gypsum (1.5 kg) was charged into a small kettle and subjected to primary firing at a baked product temperature of 140 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was mixed with 1.5 kg of fresh raw gypsum immediately after measuring the product temperature. In addition, 1.0g was extract | collected from the mixture here, and the compound water (compound water B) was measured with the test method by JISR9101. The remaining mixture was charged into a small kettle and subjected to secondary firing at a baked product temperature of 165 ° C. The obtained calcined gypsum was allowed to cool to room temperature and then pulverized using a small pot mill to adjust the brain specific surface area to about 8000 cm ² / g to obtain a calcined gypsum sample.
[Example 12]
The processing steps are shown in FIG.

Raw material gypsum (1.5 kg) was charged into a small kettle and subjected to primary firing at a baked product temperature of 140 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was placed in a sealed container and allowed to stand for 24 hours, and then the calcined gypsum was taken out from the sealed container, and the product temperature of the calcined gypsum was measured and then mixed with 1.5 kg of new raw material gypsum. In addition, 1.0g was extract | collected from the mixture here, and the compound water (compound water B) was measured with the test method by JISR9101. The remaining mixture was charged into a small kettle and subjected to secondary firing at a baked product temperature of 165 ° C. The obtained calcined gypsum was allowed to cool to room temperature and then pulverized using a small pot mill to adjust the brain specific surface area to about 8000 cm ² / g to obtain a calcined gypsum sample.
[Comparative Example 1]
The processing steps are shown in FIG.

3 kg of raw material gypsum was charged into a small kettle, and the final baking was performed at a baked product temperature of 165 ° C. to obtain calcined gypsum. After standing for 24 hours in a sealed vessel plaster of Paris, removed plaster of Paris from the closed vessel, after measuring the product temperature of the calcined gypsum was pulverized by using a small pot mill, about a Blaine specific surface area of the calcined gypsum 8000 cm ² / g A calcined gypsum sample was prepared.
[Comparative Example 2]
The processing steps are shown in FIG.

3 kg of raw material gypsum was charged into a small kettle, and the final baking was performed at a baked product temperature of 165 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The calcined gypsum was placed in a sealed container and allowed to stand for 24 hours, and then the calcined gypsum was taken out from the sealed container and pulverized using a small pot mill, and the bran specific surface area of the calcined gypsum was adjusted to about 7000 cm ² / g. These calcined gypsums were measured for product temperature, then placed in a sealed container, added with 3 wt% water per calcined gypsum, and immediately subjected to hydration by vigorously stirring for 1 minute. Here, about 1.0 g was collected from the calcined gypsum after the hydrotreatment, and the combined water (compound water B) was measured by a test method according to JIS R 9101. The remaining calcined gypsum is put in a drier, left at a preset temperature of 40 ° C. for 24 hours, the remaining free water of the calcined gypsum is evaporated, and then pulverized using a small pot mill to have a specific surface area of about 8000 cm ² / g. A calcined gypsum sample was prepared.
[Comparative Example 3]
The processing steps are shown in FIG.

3 kg of raw material gypsum was charged into a small kettle, and the final baking was performed at a baked product temperature of 165 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The remaining calcined gypsum was immediately pulverized using a small pot mill, and the bran specific surface area of the calcined gypsum was adjusted to about 7000 cm ² / g. These calcined gypsums were measured for product temperature, then placed in a sealed container, added with 3 wt% water per calcined gypsum, and immediately subjected to hydration by vigorously stirring for 1 minute. Here, about 1.0 g was collected from the calcined gypsum after the hydrotreatment, and the combined water (compound water B) was measured by a test method according to JIS R 9101. The remaining calcined gypsum is put in a drier, left at a preset temperature of 40 ° C. for 24 hours, the remaining free water of the calcined gypsum is evaporated, and then pulverized using a small pot mill to have a specific surface area of about 8000 cm ² / g. A calcined gypsum sample was prepared.
[Comparative Example 4]
The processing steps are shown in FIG.

3 kg of raw material gypsum was charged into a small kettle, and the final baking was performed at a baked product temperature of 165 ° C. to obtain calcined gypsum. About 1.0 g was collected from the calcined gypsum after the primary firing, and the combined water (compound water A) was measured by a test method according to JIS R 9101. The calcined gypsum was placed in a sealed container and allowed to stand for 24 hours, and the calcined gypsum was taken out from the sealed container and pulverized using a small pot mill, and the bran specific surface area of the calcined gypsum was adjusted to about 7000 cm ² / g. 50 wt% of the obtained calcined gypsum was hydrotreated, and the remaining 50 wt% calcined gypsum (calcined gypsum only for primary firing) was left as it was. The calcined gypsum to be hydrolyzed was added with water of 3 wt% per calcined gypsum after measuring the product temperature and immediately stirred vigorously for 1 min. Here, 0.5 g from the calcined gypsum after the hydrolysis treatment and 0.5 g from the calcined gypsum only subjected to the primary firing were collected and mixed, and the combined water (compound water B) was measured by a test method according to JIS R 9101. The remainder of the calcined gypsum after the hydration treatment was put into a dryer and left at a preset temperature of 40 ° C. for 24 hours to evaporate the remaining free water of the calcined gypsum. After the water treatment, the calcined gypsum from which the remaining free water was evaporated and the rest of the calcined gypsum obtained above were pulverized using a small pot mill to adjust the specific surface area of the brain to about 8000 cm ² / g. A calcined gypsum sample was obtained.

  The physical property test of the calcined gypsum of the samples obtained in Examples 1 to 12 and Comparative Examples 1 to 4 was performed.

This final calcined gypsum compound water (defined as compound water C) was in accordance with JIS R 9101. The test method for the mixed water amount and setting time of calcined gypsum was in accordance with JIS R 9112. Each test result and raw material composition are shown in Table 1 (Examples 1 to 12) and Table 2 (Comparative Examples 1 to 4).
In the calcined gypsum obtained in Examples 1 to 12 and Comparative Examples 1 to 4, the amount of mixed water increased as the blending ratio of the recycled gypsum to the raw material gypsum increased. On the other hand, the setting time due to the difference in the blending ratio of the recycled gypsum No change was seen.

  The calcined gypsum obtained in Example 1 is 20% less mixed water than the calcined gypsum obtained in Comparative Example 1, and the setting time is shorter than that of the calcined gypsum obtained in Comparative Example 2. The amount of mixed water is less than that of the calcined gypsum obtained in the above, and the setting time is short. The amount of mixed water is less than that of the calcined gypsum obtained in Comparative Example 4, and the setting time is short.

  The amount of water mixed in the calcined gypsum obtained in Example 2 is further reduced by 20% compared to the calcined gypsum obtained in Example 1.

  The amount of water mixed in the calcined gypsum obtained in Example 3 is 10% lower than that of the calcined gypsum obtained in Example 2.

  The calcined gypsum obtained in Example 4 has a shorter setting time than the calcined gypsum obtained in Example 1.

  In the calcined gypsum obtained in Example 5, the amount of mixed water is reduced by 20% compared to the calcined gypsum obtained in Example 1, and the setting time is shortened.

  The amount of water mixed in the calcined gypsum obtained in Example 6 is 10% lower than that in the calcined gypsum obtained in Example 5.

  The calcined gypsum obtained in Example 7 has a slightly larger amount of mixed water than the calcined gypsum obtained in Example 1, but is not so problematic.

  The calcined gypsum obtained in Example 8 shows a mixed water amount and setting time equivalent to the calcined gypsum obtained in Example 1.

  The calcined gypsum obtained in Example 9 is 10% less mixed water than the calcined gypsum obtained in Example 1.

  The calcined gypsum obtained in Example 10 has a slightly larger amount of mixed water than the calcined gypsum obtained in Example 1, but is not so problematic.

  The calcined gypsum obtained in Example 11 shows a mixed water amount and setting time equivalent to the calcined gypsum obtained in Example 1.

  The amount of water mixed in the calcined gypsum obtained in Example 12 is 10% lower than that in the calcined gypsum obtained in Example 1.

  That is, according to the present invention, calcined gypsum having a low amount of mixed water and a short setting time can be obtained by subjecting the raw material gypsum to primary calcination, followed by water treatment and secondary calcination.

  Furthermore, by using the water adhering to the raw gypsum for the hydration treatment, it is not necessary to provide new equipment for the hydration treatment, and the cost can be significantly reduced. Obtainable.

1 shows a processing flow for gypsum board production with prior art water treatment. The processing flow which shows the outline | summary of this invention is shown. The processing flow of the 1st thru / or 6th example of the present invention is shown. The processing flow of the 7th thru / or 9th example of the present invention is shown. The processing flow of 10th thru | or 12th Example of this invention is shown. The processing flow of the comparative example 1 is shown. The processing flow of the comparative example 2 and the comparative example 3 is shown. The processing flow of the comparative example 4 is shown.

Claims (8)

  In the method for producing calcined gypsum, a primary calcining step in which raw gypsum is calcined to obtain calcined gypsum, a hydrotreating step in which a part or all of the obtained calcined gypsum is hydrolyzed, and a calcined product obtained by hydrotreating A method for producing calcined gypsum comprising a secondary calcining step in which gypsum is further calcined.   The method for producing calcined gypsum according to claim 1, wherein the raw gypsum includes recycled gypsum.   The method for producing calcined gypsum according to claim 1 or 2, wherein the ratio of the recycled gypsum is 2 to 50 wt% of the raw gypsum.   The method for producing calcined gypsum according to any one of claims 1 to 3, wherein, in the hydrating treatment step, the amount of water to which the calcined gypsum is hydrotreated is 1 to 10 wt% per calcined gypsum.   5. The method for producing calcined gypsum according to claim 1, wherein the combined water of the hydrotreated calcined gypsum is 3 to 7 wt%.   The method for producing calcined gypsum according to claim 1, wherein in the hydration treatment step, water used for the hydration treatment uses adhering water of raw material gypsum.   The method for producing calcined gypsum according to claim 1, wherein the same calcining apparatus is used as the calcining means in the primary calcining step and the secondary calcining step.   A method for producing a gypsum board, wherein part or all of the calcined gypsum obtained by the method according to claim 1 is used.

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