JP2017137208A - Manufacturing method of fiber contaminated gypsum board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a fiber contaminated gypsum board having good properties by using a recycled anhydrous gypsum derived from gypsum board waste as a raw material.SOLUTION: There is provided a manufacturing method of a fiber contaminated gypsum board by using a recycled anhydrous gypsum with pH of 9.5 or more and less than 12, obtained by burning gypsum dihydrate by pulverizing gypsum board waste at 600°C to 1200°C as a main raw material, adding water to a blended article containing an inorganic filler, a reinforced fiber and a curing promoter and mixing the same, making the same a sheet form by a papermaking method and then pressure molding and curing the same, wherein the inorganic filler is contained at 30 to 150 pts.mass based on 100 pts.mass of the recycled anhydrous gypsum, the reinforced fiber is contained at 5 to 15 pts.mass based on total 100 pts.mass of the powder raw material and the curing promoter is contained at 2 to 12 pts.mass based on 100 pts.mass of the amount of added water.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a fiber-reinforced gypsum board.

  Gypsum board is a building material that has been widely used in the interior of buildings. Gypsum board is made of hemihydrate gypsum, which is highly reactive and fast-setting, and is made by pouring a mixture of other admixtures and water and kneading them between the base paper for gypsum board. It is manufactured by a method of continuously forming a plate shape through an apparatus. Such a gypsum board has a configuration in which a hardened gypsum body, which is a core material, is reinforced with paper pasted on both sides, and thus has high rigidity, but lacks toughness and has a defect that is not suitable for construction on a curved surface. On the other hand, a fiber-mixed gypsum board with a large amount of reinforcing fibers added therein is useful as an incombustible building material capable of curved construction, and is used everywhere as an interior material for buildings with high design. Such a fiber-containing gypsum board is formed by a papermaking method in which reinforcing fibers, gypsum and other admixtures are dispersed in a large amount of water. Is too fast to control reaction and is not suitable for papermaking. For this reason, the fiber-mixed gypsum plate is manufactured by using type II anhydrous gypsum having low reactivity as the main raw material, blending reinforcing fibers and a curing accelerator therein, and curing and curing after papermaking (Patent Documents 1 to 3). 4).

JP 63-60146 A JP-A 64-24061 Japanese Unexamined Patent Publication No. 64-51357 Japanese Unexamined Patent Publication No. 64-51358

So-called hydrofluoric acid gypsum produced during the production of hydrofluoric acid, which has been relatively inexpensive and easily available, has been used as type II gypsum, which is the main raw material for fiber-mixed gypsum board. Hydrofluoric acid gypsum is produced in the process of producing hydrofluoric acid by allowing concentrated sulfuric acid to act on fluorite. However, since the reaction proceeds under the condition of using concentrated sulfuric acid and the reaction temperature is high, it is produced as type II anhydrous gypsum. For this reason, compared to firing dihydrate gypsum such as flue gas desulfurization gypsum, the production cost of type II anhydrous gypsum is low, and since it is a by-product, there is an advantage that the transaction price is low. However, in recent years, with the change in the industrial production method of hydrofluoric acid, type II anhydrous gypsum obtained at the time of hydrofluoric acid production has become difficult to obtain, and a new source of type II anhydrous gypsum is required. . Therefore, the present inventor conducted research on various types of type II anhydrous gypsum sources, and as a result, reclaimed anhydrous gypsum obtained by pulverizing and firing the waste material of gypsum board generated in large quantities in the dismantling of buildings, etc. It came to the judgment that it was the most promising. However, when we tried to use regenerated anhydrous gypsum derived from this gypsum board waste as the source of type II anhydrous gypsum for fiber-mixed gypsum board, the characteristics were significantly different from fluoric acid gypsum, so it was good under the same conditions as before. It has been found that it is impossible to obtain a stable fiber-containing gypsum board stably and efficiently.
Accordingly, an object of the present invention is to provide a production method for stably and efficiently obtaining a fiber-mixed gypsum board having good characteristics using recycled anhydrite derived from gypsum board waste.

  Therefore, the present inventor baked dihydrate gypsum derived from gypsum board waste material to obtain a regenerated anhydrous gypsum having a specific pH, which was mixed with a specific amount of an inorganic filler, reinforcing fibers, and a curing accelerator to prepare a slurry. The present invention was completed by finding that a fiber-containing gypsum board having good curved surface workability can be obtained stably and efficiently by paper-making and curing and curing.

  That is, the present invention provides the following [1] to [4].

[1] Regenerated anhydrous gypsum having a pH of 9.5 or more and less than 12 obtained by baking dihydrate gypsum powder obtained by pulverizing gypsum board waste material at 600 ° C. to 1200 ° C., containing inorganic fillers, reinforcing fibers, and curing accelerators A method for producing a fiber-mixed gypsum board that is mixed by adding water to a composition containing, made into a sheet by a papermaking method, press-molded, and cured and cured,
The inorganic filler is included in an amount of 30 to 150 parts by mass with respect to 100 parts by mass of regenerated anhydrous gypsum, the reinforcing fiber is included in an amount of 5 to 15 parts by mass with respect to a total of 100 parts by mass of the powder raw material, and the curing accelerator is added. The manufacturing method of the fiber mixing gypsum board characterized by including 2-12 mass parts with respect to 100 mass parts of quantity of water.
[2] The method for producing a fiber-mixed gypsum board according to [1], wherein refiner-treated softwood pulp is used as part or all of the reinforcing fibers.
[3] The method for producing a fiber-containing gypsum board according to [1] or [2], wherein one or more selected from alkali metal sulfates and alkali metal hydrogen sulfates are used as the curing accelerator.
[4] The fiber-containing gypsum according to any one of [1] to [3], wherein the regenerated anhydrous gypsum is a regenerated anhydrous gypsum having a Blaine specific surface area of 3000 to 6000 cm ² / g, containing 60% by mass or more of type II anhydrous gypsum. A manufacturing method of a board.
[5] The method for producing a fiber-mixed gypsum plate according to any one of [1] to [4], wherein the low-temperature curing is performed for 2 days to 10 days under conditions of 5 to 20 ° C. and a relative humidity of 80 to 95% after pressure molding. .

  According to the manufacturing method of the present invention, a fiber-mixed gypsum plate having good curved surface workability can be stably and efficiently obtained by using recycled anhydrous gypsum obtained from readily available gypsum board waste.

It is a graph which shows the heating weight loss rate measurement result of dihydrate gypsum. It is a graph which shows the pH measurement result at the time of baking dihydrate gypsum (all measure 10g of samples after 1 hour heat processing at each heating temperature).

  In the present invention, regenerated anhydrous gypsum having a pH of 9.5 or more and less than 12 obtained by baking dihydrate gypsum powder (hereinafter, gypsum board pulverized powder) obtained by pulverizing gypsum board waste is used as a main raw material. Generally, it is said that anhydrous gypsum is produced when dihydrate gypsum is heated to 300 ° C. or higher in air. Therefore, the present inventor conducted various studies on useful firing conditions for obtaining regenerated anhydrous gypsum suitable for the purpose of the present invention. As a result, in the measurement of the heat loss rate, as shown in FIG. 1, no significant difference was observed between the reagent dihydrate gypsum and the gypsum board pulverized powder, but when each pH was measured, there was a difference as shown in FIG. When regenerated anhydrous gypsum in the range where the pH value of the gypsum board pulverized powder is rapidly increased is used for the fiber-mixed gypsum plate, it was found that the hydration reaction proceeds rapidly and the strength development is improved.

  The gypsum board waste material includes not only gypsum board waste material already used as building materials, but also gypsum board scraps generated during construction such as new construction and renovation, and waste materials during gypsum board production. Since the gypsum board waste is usually in the form of a board or a fragment thereof, the gypsum board whose main component is dihydrate gypsum by separating the paper of the surface material and the hardened gypsum of the core material and crushing the core material Get ground powder. Here, the degree of pulverization is preferably performed so that the average particle diameter is 50 μm or less, considering the ease of firing.

The dihydrate gypsum powder is calcined at 600 to 1200 ° C. to make anhydrous gypsum. Here, it is important in order to stabilize the pH of the raw material slurry at the time of production in an appropriate range, so that the regenerated anhydrous gypsum obtained has a pH of 9.5 or more and less than 12. A gypsum board can be obtained stably. A more preferred pH is 10.5 to 11.5. More preferable firing conditions are 800 to 1000 ° C. × 30 minutes or more. If the pH of the regenerated anhydrous gypsum is too high or too low, the raw material slurry at the time of papermaking will not be in the preferred pH range, and as a result, the hydration reaction in the curing process will be difficult to proceed, so good quality fiber mixing A gypsum board cannot be obtained stably.
Here, the pH of the regenerated anhydrous gypsum is the pH when 5 g of regenerated anhydrous gypsum is dispersed in 50 ml of water.

The obtained regenerated anhydrous gypsum preferably contains 60% by mass or more of type II anhydrous gypsum, more preferably 70% by mass or more, and more preferably 80% by mass or more from the viewpoint of obtaining a good fiber-mixed gypsum plate. Preferably, 90% by mass or more is more preferable.
In addition, the value of the specific surface area of the reclaimed anhydrous gypsum is preferably 2000 to 9000 cm ² / g, preferably 3000 to 6000 cm ² / g, from the viewpoint of obtaining sufficient strength and reducing the raw material loss during papermaking. More preferably.

  In producing a fiber-mixed gypsum board, in the present invention, an inorganic filler, reinforcing fibers, and a curing accelerator are further used as raw materials. Examples of the inorganic filler include one or more selected from calcium carbonate, diatomaceous earth, silica, wollastonite, and perlite. In addition, some of the inorganic fillers may be used effectively as scrap raw material, which is produced by crushing cutting waste generated in the cutting process and polishing powder generated in the polishing process when manufacturing the fiber-containing gypsum board. Shall be included. Since the inorganic filler does not contribute to the curing reaction in the low temperature curing, it inhibits the strong bonding between the binders and has the effect of giving flexibility to the plate after curing. For this reason, it can be said that it has the role which improves curved surface workability. The inorganic filler is preferably a powder that does not greatly affect the pH of the raw slurry. The amount of the inorganic filler used is preferably 30 to 150 parts by mass, more preferably 50 to 100 parts by mass with respect to 100 parts by mass of the regenerated anhydrous gypsum. If the added amount of the inorganic filler is less than 30 parts by mass, it is difficult to obtain the required flexibility, and if it exceeds 150 parts by mass, the effect of strength reduction becomes large.

  Examples of reinforcing fibers include natural fibers such as pulp, inorganic fibers such as glass fibers, carbon fibers, and ceramic fibers, and synthetic fibers such as polyamide, polypropylene, polyvinyl alcohol, polyethylene, and acrylic. Use more than seeds as appropriate. Of these, softener pulp refined is effective as a process fiber at the time of papermaking and is also preferable because of its high reinforcing effect. Although the usage-amount of a reinforcing fiber is 5-15 mass parts with respect to a total of 100 mass parts of a powder raw material from the point which acquires curved surface workability, 5-10 mass parts is more preferable. If the amount of the reinforcing fiber used is less than 5 parts by mass, a sufficient reinforcing effect cannot be obtained, and if it exceeds 15 parts by mass, it causes poor dispersion and a decrease in nonflammability.

The curing accelerator is not particularly limited as long as it has an accelerating effect on the hydration reaction of anhydrous gypsum, and neutral to weakly basic sulfates and their double salts, oxyhydrogen salts, and the like. Can be mentioned. Among them, alkali metal sulfates (for example, sodium sulfate (Na ₂ SO ₄ ), potassium sulfate (K ₂ SO ₄ ), etc.) and alkali metal hydrogen sulfates (for example, sodium hydrogen sulfate (NaHSO ₄ ), potassium hydrogen sulfate (KHSO ₄ )) Etc.), and one or more of them can be used. In addition, in the case of the hydrofluoric acid anhydrous gypsum conventionally used, the slaked lime for processing an excess sulfate radical was added after the main reaction in the formation reaction process. For this reason, hydrofluoric anhydride gypsum has a pH of around 12 due to the effect of slaked lime, and it is effective to lower the pH slightly by adding aluminum sulfate or the like as a hardening accelerator when manufacturing a fiber-containing gypsum board. (Patent Document 4). However, in the present invention, since the pH is adjusted under the firing conditions when producing regenerated anhydrous gypsum, it is not necessary to add an acid-based curing accelerator. The amount of the curing accelerator used is preferably 2 to 12 parts by mass with respect to 100 parts by mass of water to be added, from the viewpoint of obtaining a fiber-mixed gypsum board having sufficient strength and good curved surface workability. More preferably, it is 10 parts by mass. If it is less than 2 parts by mass, the necessary promotion effect cannot be obtained, and even if it is added in excess of 12 parts by mass, the improvement of the promotion effect is not recognized. The curing accelerator can be used after being dissolved in water in advance.

Water is added to the raw material and mixed to form a raw material slurry. Here, the amount of water used is preferably 5 to 25 times, more preferably 10 to 20 times the mass of the entire raw material solids (excluding the curing accelerator), from the viewpoint of ensuring good dispersibility and papermaking. preferable. In order to form a slurry, it is preferable to mix and stir with a stirrer such as a pulper.
At this time, the temperature of the raw material slurry is preferably 15 to 38 ° C, more preferably 20 to 35 ° C from the viewpoint of papermaking efficiency. Moreover, the pH of the raw material slurry is preferably in the range of pH 10 to 12 and more preferably in the range of pH 10.5 to 11.5 in order to efficiently promote the hydration reaction in low temperature curing and to obtain good strength expression.

The raw slurry can be made using, for example, a round net making machine. The raw material slurry stored in the bat is made up with a cylinder and laminated to a desired thickness with a making roll to form a sheet.
The obtained sheet is pressure-formed at 2 to 10 MPa so as to have a desired thickness.

  As the curing method, low temperature curing is preferable, and curing is preferably performed for 2 to 10 days under conditions of 5 to 20 ° C. and a relative humidity of 80 to 95%.

  According to the method of the present invention, despite using recycled anhydrous gypsum derived from gypsum board waste, it has sufficient bending strength and curved surface workability as a building material, good dimensional stability, sound insulation, processing It is possible to stably obtain a fiber-mixed gypsum board having properties and the like.

EXAMPLES Next, an Example is given and this invention is demonstrated still in detail.
The raw materials used in the examples and comparative examples are as follows.

Regenerated anhydrous gypsum:
(1) Baking temperature of about 800 ° C., pH of 11, brane value of about 5000 cm ² / g
(2) Firing temperature of about 1000 ° C., pH of 10, brain value of about 5000 cm ² / g
(3) Baking temperature of about 500 ° C., pH of 8.2, Blaine value of about 5000 cm ² / g
Calcium carbonate: Brain value about 5500cm ² / g
Perlite: Foamed and pulverized pearlite Particle size: 0.3 mm or less Scrap: Grinded cutting waste generated in the cutting process during production of fiber-mixed gypsum board and abrasive powder generated in the polishing process Pulp: Softwood bleached pulp Canadian standard freeness approx. 320 mL
(Brain value is according to JIS R 5201, Canadian standard freeness according to JIS P 8121-2)

  A raw material blend was obtained at the blending ratio shown in Table 1 below, 1000 parts by weight of water was added to 100 parts by weight of the solid content of the raw material blend, and mixed and stirred to obtain a raw material slurry. Next, the raw material slurry was formed into a sheet by a table test simulating a papermaking method, and further dehydrated and pressed at a press pressure of 6 MPa to obtain a green plate having a width of 40 mm and a length of 160 mm. The obtained green plate was put into a thermostatic chamber set at a temperature of 10 ° C. and a humidity of 80% and subjected to low temperature curing for 7 days to obtain a fiber mixed gypsum plate having a thickness of about 10 mm. Various characteristics of the obtained fiber-mixed gypsum board are also shown in Table 1.

The test methods for various characteristics are as follows.
Bulk density: According to JIS A 5430: 9.5.
Hydration rate of gypsum: Immediately after curing, a test piece of about 40 mm square is cut out and dried at 40 ° C. for 24 hours, and the mass (W ₁ ) is measured. Next, after heating at 180 ± 5 ° C. for 30 minutes and cooling to room temperature, the mass (W ₂ ) was measured and obtained from Equation 1.
The molecular weight of gypsum was dihydrate gypsum (172.1), anhydrous gypsum (136.1), and crystal water (36.0), and the amount of dihydrate gypsum in scrap was 50%.
Formula 1 A: Anhydrous gypsum compounding ratio (%)
B: Scrap content (%)
C: Mass reduction rate (%) = (W ₁ −W ₂ ) / W ₁ × 100
X: Crystal water of dihydrate gypsum hydrated with anhydrous gypsum (%)
= (C−Y) / (100−C) × 100
Y: Crystal water of dihydrate gypsum in scrap (%)
= (B x 0.5) x (36.0 / 172.1)
Z: Hydration rate (%) = X / A × 136.1 / 36.0 × 100
Bending strength: JIS A 5430: 9.3: JIS A 5430: 9.3 after measuring a test piece of 40 mm × 160 mm size at 40 ° C. for 24 hours and measuring the maximum load by a three-point bending test method with a bending span of 100 mm and a crosshead speed of 1 mm / min Obtained from .2.

  From the various characteristics shown in Table 1, Examples 1 to 7 have sufficient bending strength and are good fiber-mixed gypsum plates. On the other hand, Comparative Examples 1 to 4 generally resulted in small values of bending strength. In Comparative Example 1, since the pH of the regenerated anhydrous gypsum is low, the reactivity is poor and the hydration of the gypsum is insufficient. Since Comparative Examples 2 and 3 lack the addition of a curing accelerator, the hydration of gypsum is still insufficient. In Comparative Example 4, since the reinforcing fibers are insufficient, the hydration of the gypsum is sufficiently advanced and the bending strength is increased. However, since it is hard and brittle, curved surface workability cannot be ensured.

  Next, using the formulation of Example 2, trial production of a fiber-mixed gypsum board using an actual factory machine was performed. The press conditions and curing conditions were the same as in the table test except that a round net paper making machine was used and the thickness was 6 mm. Table 2 shows the physical properties of the actual prototype. The bulk density, flexural strength, and length change rate due to water absorption were measured according to JIS A 5430. However, the water-containing state at the time of the test was left to stand at 40 ° C. for 24 hours or more and dried until a constant weight was obtained.

From the evaluation results shown in Table 2, it can be seen that a high-quality fiber-mixed gypsum board was obtained with a high bending strength and a small dimensional change rate due to water absorption.
In addition, as a result of conducting a curved surface construction test to be screwed to the trunk base of the radius of curvature R = 800 mm for the standard test specimen (910 mm × 1820 mm) of the actual machine prototype, the occurrence of breakage, cracks, etc. was not recognized, It had good curved surface workability.

  As mentioned above, according to the manufacturing method of this invention, the fiber mixed gypsum board with favorable curved construction property can be stably obtained using the reproduction | regeneration anhydrous gypsum obtained from the easily available gypsum board waste material.

Claims (5)

Recycled anhydrous gypsum with a pH of 9.5 or more and less than 12 obtained by baking dihydrate gypsum powder pulverized from gypsum board waste material at 600 ° C to 1200 ° C, containing inorganic filler, reinforcing fiber and curing accelerator It is a method for producing a fiber-mixed gypsum board that is mixed by adding water to a product, formed into a sheet by a papermaking method, press-molded, and cured and cured.
The inorganic filler is included in an amount of 30 to 150 parts by mass with respect to 100 parts by mass of regenerated anhydrous gypsum, the reinforcing fiber is included in an amount of 5 to 15 parts by mass with respect to a total of 100 parts by mass of the powder raw material, and the curing accelerator is added. The manufacturing method of the fiber mixing gypsum board characterized by including 2-12 mass parts with respect to 100 mass parts of quantity of water.   The method for producing a fiber-mixed gypsum board according to claim 1, wherein refiner-treated softwood pulp is used as a part or all of the reinforcing fibers.   The manufacturing method of the fiber mixed gypsum board of Claim 1 or 2 using 1 type, or 2 or more types selected from an alkali metal sulfate and an alkali metal hydrogen sulfate as the said hardening accelerator. The fiber-containing gypsum board according to any one of claims 1 to 3, wherein the regenerated anhydrous gypsum is a regenerated anhydrous gypsum having a Blaine specific surface area of 3000 to 6000 cm ² / g and containing 60% by mass or more of type II anhydrous gypsum. Production method.   The method for producing a fiber-mixed gypsum plate according to any one of claims 1 to 4, wherein after the pressure molding, low-temperature curing is performed for 2 to 10 days under conditions of 5 to 20 ° C and a relative humidity of 80 to 95%.

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