JPH1112019A - Gypsum board for interior wall and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject board with improved surface accuracy and moisture absorbing/releasing characteristics by including gypsum, cement, inorganic powder, a fibrous material and moisture absorbing/releasing material. SOLUTION: This board comprises gypsum, cement, inorganic powder, a fibrous material and moisture absorbing/releasing material. The gypsum may be natural or synthetic one or the like, preferably α-hemihydrate gypsum produced as the by-product by the wet process that produces phosphoric acid from phosphorus ore and sulfuric acid, more preferably α-hemihydrate gypsum dried and incorporated with an inorganic alkali. The cement may be various types of Portland cement, Portland blast-furnace cement, fly ash cement or the like, used preferably at 30 to 0 pts.wt. per 70 to 100 pts.wt. of the gypsum. The inorganic powder is a light aggregate or the like, e.g. fly ashes, sirasu balloons or pearlite, its grain size being 20 to 500 μm. The fibrous material may be natural or synthetic, e.g. fibers from pulp of a vegetable, needle-leaved tree or the like, or glass fibers. The moisture absorbing/releasing material includes inorganic one, e.g. zeolite or attapulgite, or organic one, e.g. poval, CMC or thermosetting resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gypsum board for an interior wall comprising gypsum and cement as main components, an inorganic powder, pulp fiber, and a moisture absorbing / releasing substance, and a method for producing the same. It has improved accuracy and moisture absorption / release properties.

[0002]

2. Description of the Related Art As a gypsum board generally used as a building interior material, for example, a gypsum board mixed with paper, a fiber composite gypsum board mixed with glass fiber, pulp, waste paper, wood flake, and the like are known. However, the effect as moisture absorption / release performance is extremely small. Further, as an interior material having a moisture absorbing and releasing performance, there is a gypsum board mainly used as an interior base material in an art museum, a museum, an exhibition room, a general house and the like. In addition to gypsum-based boards, air-conditioning equipment is used to ensure the preservation of precious artworks and materials, especially in museums, museums, and exhibition rooms, so that there is no fluctuation in humidity, especially in the room. Needless to say, wood-based interior materials exhibiting excellent characteristics of absorbing and releasing moisture are used.

Of these, composite gypsum board mainly composed of waste paper and gypsum is GPB (Gypsum Pulp Bo).
ard). To show an example of the method of manufacturing this conventional gypsum board, mainly β-type hemihydrate gypsum,
This is obtained by dry-pulverizing waste paper such as old newspapers and old magazines into a pulp form, adding water to make a slurry form, and mixing and forming by a wet method to form a plate form. The resulting composite gypsum board can use nails, screws, etc., and can be cut using a saw,
Also in terms of strength, there is no difference in strength depending on the direction, the bending strength is high, and the performance is excellent, as compared with a so-called gypsum board made of gypsum as a core material and sandwiched with board paper.

[0004]

However, the conventional β
In a composite gypsum board (GPB) obtained by a wet method using a mold hemihydrate gypsum, aggregates called so-called lumps formed by aggregation of pulp are mixed in the obtained molded body. Since the distribution of the raw materials becomes more uneven as the generation rate of the aggregates increases, there is a problem that the board bending strength is reduced and the surface accuracy of the product is poor. As a solution to this problem, Japanese Patent Application Laid-Open No. Hei 4-300232 has been proposed, but at present it is impossible to obtain a satisfactory solution. On the other hand, there is no moisture absorption / desorption performance, which is equivalent to none at present.

[0005]

According to the present invention, it has been found that the surface accuracy and the moisture absorption / release properties are improved by using gypsum and cement as main components and using inorganic powders, fibers and moisture absorbing / releasing substances. That is, the present invention provides a gypsum board for an interior wall composed of gypsum, cement, inorganic powder, fiber, and a hygroscopic substance, and adding and mixing water to gypsum, cement, inorganic powder, fiber, and a hygroscopic substance, and forming a mold. The present invention relates to a method for producing a gypsum board for an interior wall, wherein the method is performed by pouring or forming, followed by press molding and curing.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The gypsum used in the present invention is not particularly limited, and any of natural gypsum and chemical gypsum can be used.
It is preferable to use gypsum of α-hemihydrate, which is a by-product when phosphoric acid is produced by a wet phosphoric acid production method using a phosphate rock and sulfuric acid. Further, α-hemihydrate gypsum to which an inorganic alkali is added after drying the α-hemihydrate gypsum is more preferable.

As the cement, various cements such as Portland cement, blast furnace cement, fly ash cement, silica cement and alumina cement can be used. Gypsum and cement are plaster 7
It is preferable to use 0 to 100 parts by weight of cement and 30 to 0 parts by weight of cement. Less than 70 parts by weight of gypsum or more than 30 parts by weight of cement is not preferred because cracking due to insufficient curing, drying and shrinkage occurs due to insufficient curing.
In addition, it takes a long time for curing and curing after molding, resulting in a production facility with extremely low productivity, which causes a problem in economy.

As the inorganic powder used in the present invention, for example, lightweight aggregates such as fly ash, shirasu balloon, perlite, vermiculite and the like are used. When this is used, the aggregation of the fibers can be reduced, and the weight of the board can be reduced. These are non-hydratable, do not hinder the hydration of α-type hemihydrate gypsum, and mean those which do not cause a decrease in the strength of the gypsum board. Above all, a shirasu balloon is suitable for a lightweight and high-strength board because it is spherical and lightweight and has high breaking strength. The fineness of the inorganic powder is 20
It is preferable to use those having a fineness of from 500 to 500 μm, preferably from 100 to 300 μm. If the fineness is less than 20 μm, the pulverization cost increases and the yield decreases, which is not preferable. On the other hand, if it exceeds 500 μm, the dispersibility decreases, and the adhesion of fibers and the effect of preventing coagulation decrease. The amount of the inorganic powder to be added is 1 to 30 parts by weight, preferably 3 to 1 part by weight, based on 100 parts by weight of the total of gypsum and cement.
0 parts, more preferably 3 to 7 parts by weight.
If the addition amount is less than 1 part by weight, the dispersibility of the fiber is poor, and the quality of the fiber is deteriorated such as poor surface properties and reduced strength. On the other hand, if the amount exceeds 30 parts by weight, the fluidity of the slurry is extremely reduced and molding becomes impossible, which is not preferable.

The fibers used in the present invention may be either natural fibers or synthetic fibers. For example, plant fibers, spruce, fir, pine, larch, which are obtained by dry-pulverizing waste paper, hemp, cotton stalk, straw, etc. , Pulp made of softwood (N
P), plant fibers of hardwood pulp (PL) made of poplar, hippopotamus, beech, eucalyptus and the like, and inorganic fibers such as glass fiber and rock wool. Preferably, plant fibers of softwood pulp and hardwood pulp are good, and the shape thereof is 20 to 100 μm in diameter, 50 to 7000 μm in length,
Preferably, a material having a thickness of 100 to 6000 μm is used. The purpose of using the fiber is to improve the workability of the board, reduce the weight, and improve the impact resistance. The amount of fiber to be added is based on a total of 100 parts by weight of gypsum and cement.
It is 0.05 to 5 parts by weight, preferably 1 to 2 parts. If the addition amount is less than 0.05 part by weight, it is not preferable because effects on the intended impact resistance reduction, workability and weight reduction cannot be obtained. On the other hand, if the added amount exceeds 5 parts by weight, the kneading operation is hindered, fibers are formed, the fluidity of the obtained slurry is low, and the step of pouring the slurry into the mold is particularly seriously hindered. This causes a reduction in efficiency, a deterioration in surface properties, and a reduction in quality such as a reduction in strength.

The hygroscopic substance used in the present invention is an inorganic substance composed of one or more clay minerals selected from sepiolite, attapulgite, montmorillonite, diatomaceous earth, zonolite, silica gel, activated clay, and the like.
Poval, CMC, polyethylene oxide, starch, water-soluble polymer material composed of sodium polyacrylate, thermosetting resin, thermoplastic resin, or water-absorbing polymer material obtained by modifying a synthetic rubber-based resin with the water-soluble polymer For example, an organic moisture-absorbing / desorbing additive composed of at least one organic substance selected from natural fibers, regenerated fibers, semi-synthetic fibers, and hygroscopic synthetic fibers is used.

The moisture-absorbing / desorbing substance may be used in any manner such as one or more inorganic substances, one or more organic substances, and a mixture of inorganic and organic substances. The amount of the hygroscopic substance added is 0.5 to 5 per 100 parts by weight of gypsum and cement.
Parts by weight, more preferably 1 to 3 parts by weight. The method of addition may be preliminarily mixed with gypsum and cement, or may be added when mixing with water. If the amount is less than 0.5 part by weight, sufficient moisture absorption / release performance of the board cannot be obtained, which is not preferable. If it exceeds 5 parts by weight, the hardness of the gypsum board becomes insufficient, which is not preferable.

Other fluidizers can be used if necessary, and the type thereof is not particularly limited.
The following can be used: For example, an oxycarboxylic acid type and / or a polycarboxylic acid type imparts good fluidity to a cement, and the amount of addition thereof is gypsum and cement 100%.
The amount is preferably 0.05 to 5 parts by weight, more preferably 0.1 to 2 parts by weight with respect to parts by weight. 0.05
If the amount is less than 100 parts by weight, the flow rate is 100 m
m or more is not preferable since a water-soluble slurry having a flowability of m or more cannot be obtained, which causes trouble in casting into a mold. On the other hand, if it exceeds 5 parts by weight, remarkable setting retardation is caused, which adversely affects the development of strength. Other, β
A salt of a naphthalenesulfonic acid formaldehyde polycondensate, a salt of a melaminesulfonic acid formaldehyde condensate,
A salt of an aminosulfonic acid condensate and a lignin-based fluidizing agent are used. Of these, an oxycarboxylic acid-based compound having high fluidity and having a setting retarding effect is particularly preferable.
Or a polycarboxylic acid type is preferable.

[0013] With only the components of gypsum, cement and a fluidizing agent, even if high fluidity can be imparted to the hydraulic composition, the fluidity is greatly reduced with time, so it cannot reach every corner of the mold. The liquidity is lost at a later time, which is practically inconvenient. Therefore, in the present invention, if necessary, in order to reduce the deterioration with time of high fluidity, hydroxycarboxylic acid and / or salts thereof (hereinafter, referred to as hydroxycarboxylic acids) as a retarder, and alkali metal as a promoter Further, an acid salt and / or an alkali metal bicarbonate (hereinafter, referred to as an alkali metal carbonate or the like) is further used in combination.

The amount of hydroxycarboxylic acid added as a retarder is 0.1 to 100 parts by weight of gypsum and cement.
The suitable amount is from 01 to 5 parts by weight, preferably from 0.05 to 3.0 parts by weight. If the added amount is less than 0.01 part by weight, a practical effect of preventing a decrease in fluidity cannot be obtained, which is not preferable. On the other hand, if it exceeds 5 parts by weight, the setting time becomes extremely long, and the strength development becomes poor, which is not preferable.

Examples of hydroxycarboxylic acids include malic acid, sodium malate, potassium malate, lithium malate, tartaric acid, sodium tartrate, potassium tartrate, lithium tartrate, citric acid, sodium citrate, thulium citrate, citric acid Lithium and the like can be mentioned. Of these, citric acid and its salts are particularly preferred.

The amount of the alkali metal carbonate or the like used as an accelerator is based on 100 parts by weight of gypsum and cement.
0.01 to 5 parts by weight, preferably 0.1 to 3 parts by weight is suitable. If the amount is less than 0.01 part by weight, the effect of accelerating the curing is small, and if it exceeds 5 parts by weight, the curing speed is too high, the workability is deteriorated, and the water resistance is also adversely affected. The role of the alkali metal carbonate or the like promotes the effect of preventing the fluidity from deteriorating with time and increases the rise in strength from the start of curing. not enough. Examples of the alkali metal of carbonate or bicarbonate include lithium, sodium, potassium and the like.

The alkali to be added to the α-hemihydrate gypsum obtained by the wet phosphoric acid production method is not particularly limited as long as it shows both organic and inorganic alkalinity. NaOH, KOH, Ca (OH) which are preferably inorganic compounds
₂ such as hydroxides, carbonates such as CaCO ₃ and K ₂ CO _3, and Na ₂ O, CaO, and M that form hydroxides in an aqueous solution.
Examples include basic oxides such as gO, and ammonia gas / solution, and two or more kinds may be mixed. The amount of addition is 0.1-5 parts by weight, preferably 0.3-0.5 parts by weight, per 100 parts by weight of α-hemihydrate gypsum. As a matter of course,
As the inorganic alkali, a hardening inorganic material exhibiting alkalinity such as cement may be added and mixed.

The amount of water to be added to gypsum, cement, inorganic powder, fiber and hygroscopic substance is 20 to 150 parts by weight based on 100 parts by weight of gypsum and cement. The amount of water is a factor that greatly affects the fluidity of the mixed slurry and the strength of the board, and varies depending on the type of gypsum used and the production method.

For example, when α-hemihydrate gypsum is poured into a mold, 50 to 50 parts by weight of water is added to 100 parts by weight of gypsum and cement.
The amount is preferably 100 parts by weight, more preferably 60 to 100 parts by weight.
80 parts by weight. If the amount is less than 50% by weight, the fluidity of the slurry suitable for pouring into a mold cannot be obtained. If the amount exceeds 100% by weight, a large decrease in strength is caused, and the curing time is significantly long. And the production efficiency becomes extremely low.

Similarly, when press-molding using α-hemihydrate gypsum, 20 parts of water is added to 100 parts by weight of gypsum and cement.
To 50 parts by weight, more preferably 25 to 50 parts by weight.
40 parts by weight. This is a state in which the hydration reaction of α-hemihydrate gypsum is not completed when the amount of water is less than 20 parts by weight.
If the amount exceeds 0 parts by weight, a slurry is formed, and the workability of subsequent forming and press molding becomes difficult. As a matter of course, the strength is greatly reduced, and the curing and curing time is significantly increased, resulting in an extremely low production efficiency. When pouring into a mold using β hemihydrate gypsum, for 100 parts by weight of gypsum,
The water content is preferably 60 to 150 parts by weight, more preferably 80 to 120 parts by weight.

Similarly, in the case of press molding using β-hemihydrate gypsum, water is preferably used in an amount of 20 to 60 parts by weight, more preferably 25 to 50 parts by weight, based on 100 parts by weight of gypsum.

According to the casting method of the present invention, a mixture of gypsum, cement, inorganic powder, fiber, and a moisture-absorbing / desorbing substance, if necessary, with a fluidizing agent, a retarder, and an accelerator is mixed and stirred with water. Pour the obtained slurry into the mold,
Demold at the end of setting time. The setting time referred to here is the apparent hardening of the gypsum, and the measuring method complies with JIS. Cure the gypsum board for the interior wall after demolding (room temperature to 45
° C) and drying (70 ° C to 90 ° C) to obtain a board. The curing time is 1 hour to 3 hours, and the drying time is 2 hours to 10 hours. The gypsum board for an interior wall obtained in this way is an excellent gypsum board having a uniform and good surface accuracy and having a moisture absorbing / releasing performance, without generating agglomerates of fibers and inorganic powder.

The production method of the present invention characterized by forming and then press molding is a method of adding gypsum, cement, inorganic powder, fiber and moisture-absorbing and / or moisture-absorbing substance, if necessary, with a fluidizing agent, a retarder and an accelerator. The mixture obtained by adding water to the mixture is fed to a former, and the height and width are determined on a belt conveyor while being measured, and the mixture is formed into a mat. The formed product is immediately sent to a press and pressed. After pressurizing for a certain period of time, the gypsum board for the interior wall taken out of the press machine is cured (room temperature) and dried (40 ° C to 80 ° C) to obtain a board. The curing time is 2 hours to 5 hours, and the drying time is 2 hours to 8 hours. The gypsum board for the interior wall thus obtained does not generate aggregates of the fibers and the inorganic powder,
It is a homogeneous material with good surface accuracy, high bending strength, and excellent moisture absorption / desorption performance.

[0024]

The present invention will be described in more detail with reference to the following examples. Parts are parts by weight unless otherwise specified. Example 1 α-hemihydrate gypsum (hereinafter referred to as α) in which 0.4 part of alkali (slaked lime) is added to 100 parts of α-hemihydrate gypsum by-produced when phosphoric acid is produced by wet phosphoric acid production using phosphate rock and sulfuric acid. 80 parts of hemihydrate gypsum), 20 parts of ordinary Portland cement, 5 parts of pearlite as an inorganic powder, and pulp fibers as fibers.
5 parts, 2 parts of silica gel as moisture-absorbing and desorbing substance, trade name "Mariarim AKM60F" made by Takemoto Yushi Co., Ltd. containing polycarboxylic acid (maleic anhydride) as a fluidizing agent as a main component.
0.5 part, 2 parts of potassium sulfate as a curing accelerator were uniformly mixed, and 70 parts of water were stirred and mixed for about 3 minutes. The obtained slurry was poured into a mold (die), removed from the mold 2 hours later, cured for 1 hour (room temperature), and then dried (40 ° C to 80 ° C) for 3 hours. Physical properties of the gypsum board thus obtained were evaluated. The composition is shown in Table 1, and the evaluation results of physical properties are shown in Table 2.

The evaluation of each physical property was measured as follows. (1) Surface property: The lump state of the pulp fiber and the smoothness of the entire surface of the board were visually determined. (2) Moisture absorption / desorption property: The back surface of the sample and the kiguchi were masked, and (a) 72 ° C. in a thermostat at 20 ° C. and 50% RH.
After curing for 2 hours, the sample was transferred to a thermo-hygrostat at 50 ° C. and 80% RH, and the weight change of the sample after 72 hours was measured (hygroscopicity). The sample is transferred into a humidity chamber, and the change in sample weight after 72 hours is measured (humidity release). The operations of (b) and (c) were defined as one cycle, and the weight change per surface area of each of (b) and (c) after three cycles was obtained (g / m ² ). (3) Flexural strength: Performed in accordance with JIS R 9112. A test piece (30 × 40 × 1 cm) was heated at a temperature of 2
Cured in a room at 0 ° C. and a relative humidity of 60% for 14 days, placed on a support (35 cm in width) of a bending strength tester (Marubishi Scientific Machinery Co., Ltd. GBL-500), and set a suspension at the center of the specimen. Then, the suspension is pressurized at 250 N / min. The force at which the specimen cracks is defined as the bending strength. (4) Impact resistance test: The test was carried out under the following conditions with reference to JIS A 1421 (building board), and the diameter of the dent was measured and the degree of cracks on the back surface was visually judged. Specimen size: 250 x 250 x 13 (mm) Method of supporting the specimen: whole surface support on sand Type of weight: steel ball Weight: 510 g Diameter: 50 mm Drop height: 50 cm Criterion for determining cracks on the back surface ○: No cracks at all Δ: Cracks are slightly recognized X: Cracks are significantly recognized (5) Weather resistance: JIS A 1415 Specimen size: 150 × 75 × 13 (mm) Testing machine: Sunshine Super Life Weather Meter (WEL-) (SUN-HC type gas tester Co., Ltd.) Carbon for light source: Sunshine carbon arc lamp Cycle time: arc lamp → 120 minutes Rainfall → 18 minutes Test time: 100 hours Weather resistance judgment criteria ○: Surface erosion (unevenness) Slightly observed Δ: Surface erosion (unevenness) is observed ×: Surface erosion (unevenness) is significantly observed

Example 2 The same procedure as in Example 1 was carried out except that 5 parts of pearlite was changed to 10 parts as the inorganic powder. The composition is shown in Table 1, and the evaluation results of physical properties are shown in Table 2.

Example 3 The procedure of Example 1 was repeated, except that the pulp fiber was changed from 1.5 parts to 2.5 parts. The composition is shown in Table 1, and the evaluation results of physical properties are shown in Table 2.

Example 4 The procedure of Example 1 was repeated, except that 2 parts of silica gel was changed to 3 parts as a moisture absorbing / releasing substance. The composition is shown in Table 1, and the evaluation results of physical properties are shown in Table 2.

Example 5 The procedure of Example 1 was repeated, except that 80 parts of α-hemihydrate gypsum was changed to 75 parts and 20 parts of cement was changed to 25 parts. The composition is shown in Table 1, and the evaluation of physical properties is shown in Table 2.

Example 6 Same as Example 1 except that 80 parts of α-hemihydrate gypsum was changed to 80 parts of β-hemihydrate gypsum, 2 parts of accelerator were changed to 0 parts, and 3 parts of sodium citrate was added as a retarder. I went to. The composition is shown in Table 1.
Table 2 shows the evaluation of the physical properties.

Example 7 The same formulation as in Example 1 was used except that 70 parts of water was changed to 35 parts, 2 parts of the accelerator was changed to 1 part, and 3 parts of sodium citrate was added as a retarder. The casting method was changed to a manufacturing method of forming and then press forming. That is, the mixture of the above-mentioned composition was weighed into a previously prepared forming box, formed into a mat shape by hand, and immediately pressed with a press machine at a pressure of 30 kg / cm ² for 30 minutes.
After pressurizing for 1 minute, the board taken out of the press was cured (room temperature) for 2 hours and dried (40 ° C. to 80 ° C.) for 1 hour to obtain a gypsum board for interior wall. The composition is shown in Table 1, and the evaluation of physical properties is shown in Table 2.

[0032]

[Table 1]

[0033]

[Table 2]

Comparative Example 1 The procedure of Example 1 was repeated except that the amount of α-hemihydrate gypsum was changed to 100 parts and the amount of ordinary Portland cement was changed to 0 parts. The formulation is shown in Table 3 and the evaluation of physical properties is shown in Table 4.

Comparative Example 2 The procedure of Example 1 was repeated, except that the α-hemihydrate gypsum of Example 1 was changed to 0 parts and the ordinary Portland cement was changed to 20 parts to 100 parts. The formulation is shown in Table 3 and the evaluation of physical properties is shown in Table 4.

The procedure was the same as in Example 1, except that 5 parts of the inorganic powder of Example 1 was changed to 0 part. The formulation is shown in Table 3 and the evaluation of physical properties is shown in Table 4.

Comparative Example 4 The procedure of Example 1 was repeated, except that 1.5 parts of the fiber of Example 1 was changed to 0 part. The formulation is shown in Table 3 and the evaluation of physical properties is shown in Table 4.

Comparative Example 5 The procedure of Example 1 was repeated except that the amount of the hygroscopic substance was changed from 2 parts to 0 part. The formulation is shown in Table 3 and the evaluation of physical properties is shown in Table 4.

Comparative Example 6 80 parts of α-hemihydrate gypsum of Example 1, 100 parts of β-hemihydrate gypsum, 20 parts of cement, 0 parts, 2 parts of accelerator, 0 parts, and 3 parts of retarder, 0 parts In the same manner as in Example 1, except that 70 parts of water was changed to 110 parts. The formulation is shown in Table 3 and the evaluation of physical properties is shown in Table 4.

Comparative Example 7 80 parts of the α-hemihydrate gypsum of Example 7 was added to 100 parts of cement 2
Example 7 was carried out in the same manner as in Example 7, except that 0 part was changed to 0 part.
The formulation is shown in Table 3 and the evaluation of physical properties is shown in Table 4.

[0041]

[Table 3]

[0042]

[Table 4]

[0043]

According to the present invention, the use of gypsum, cement, inorganic powder, fibers, and a moisture-absorbing / absorbing substance makes it possible for coagulation of pulp and coagulation called lumps to coexist in a molded product. In addition, since the distribution of raw materials is uniform, the gypsum board with good surface accuracy can be obtained without lowering the bending strength of the gypsum board. As a result, a gypsum board for an interior wall having moisture absorption / release performance and providing a comfortable space can be obtained.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C04B 111: 40 (72) Inventor Koichi Maeda 7-1-1, Hikoshimasako-cho, Shimonoseki-shi, Yamaguchi Pref.

Claims (10)

[Claims] 1. A gypsum board for an interior wall comprising gypsum, cement, an inorganic powder, fibers and a moisture absorbing / releasing substance. 2. The gypsum board according to claim 1, wherein the gypsum is α-hemihydrate gypsum by-produced when phosphoric acid is produced by wet phosphoric acid production using phosphate rock and sulfuric acid. 3. Gypsum is α-hemihydrate gypsum by-produced when phosphoric acid is produced by wet phosphoric acid production using phosphate rock and sulfuric acid.
2. The gypsum board according to claim 1, wherein the gypsum board is alpha hemihydrate gypsum to which 0.1 to 5 parts by weight of alkali is added per 100 parts by weight. 4. The gypsum board according to claim 1, wherein the gypsum is β-hemihydrate gypsum. 5. Cement 3 with 70-100 parts by weight of gypsum
The gypsum board according to claim 1, comprising 0 to 0 parts by weight. 6. The gypsum board according to claim 1, wherein 1 to 30 parts by weight of the inorganic powder is used based on 100 parts by weight of the gypsum and the cement. 7. The gypsum board according to claim 1, wherein the fiber is used in an amount of 0.05 to 5 parts by weight based on 100 parts by weight of gypsum and cement. 8. The gypsum board according to claim 1, wherein 0.5 to 5 parts by weight of the hygroscopic substance is used for 100 parts by weight of gypsum and cement. 9. Water is added to gypsum, cement, inorganic powder, fiber and hygroscopic substance, mixed and poured into a mold.
A method for producing a gypsum board for an interior wall, comprising curing and curing. 10. Gypsum, cement, inorganic powder, fiber and hygroscopic substance are mixed by adding water, forming,
A method for producing a gypsum board for an interior wall, which is followed by press molding and curing.