JPH0598771A - Moisture-proof gypsum board and its manufacture - Google Patents

Abstract

PURPOSE:To raise the moisture-proofing effect of a gypsum board by a method in which the surface of a gypsum board is covered uniformly with a resin film only by a regulated amount per unit area to form a moisture-impermeable layer. CONSTITUTION:While supplying a gypsum board 1 of a Stoeckigt size of 340sec. or more continuously at a rate of 100-180 m/min, a synthetic resin emulsion 2a containing 50-60wt% vinylidene chloride copolymer particles of an average grain size of 1-13pm, consisting of 85-95 pts.wt. vinylidene chloride and 5-15 pts.wt. (meth)acrylate, is applied to the gypsum board l to coat it with a thickness of 0.1-0.5mm of film from a curtain flow coater 7. The emulsion 2a coat on the board 1 is dried at 120-200 deg.C for 1.5-2.0min to form the resin film of 60-70g/m2 on the board 1. The board 1 is placed on pallets and cooled to form a moisture-proof gypsum board 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moisture-proof gypsum board which is used for moisture-proof measures such as ceilings and walls, has a low moisture permeability, is inexpensive, and is resistant to blocking. Further, the present invention relates to a method for producing a moisture-proof gypsum hode having low moisture permeability and less likely to cause blocking, at low cost.

[0002]

2. Description of the Related Art As an interior material and / or an exterior material constituting a ceiling, a wall, etc. of a building such as a house, an inorganic board is used in consideration of fire resistance. The ceiling or wall thus configured has a problem that moisture such as water vapor generated in the room permeates through the ceiling material or the wall material to cause dew condensation in the attic or in the wall.

Therefore, a moisture-proof inorganic board having a resin film formed on the surface thereof, which is unlikely to allow moisture to permeate (moisture-permeate) into an attic or a wall, has been considered. The resin film is a synthetic resin with film-forming properties and low moisture permeability applied to an inorganic board,
It is made by drying. Considering the convenience of use, the moisture-proof inorganic board is required to pass water and moisture as little as possible and to be provided at a low cost. Therefore, the resin film needs to be formed as thin as possible as long as it has moisture resistance. If the thickness of the resin film is unnecessarily large, it takes time to dry when forming the film, resulting in low manufacturing efficiency, or the amount of resin used increases the manufacturing cost, or the resin film is formed by heating and drying. When several tens to several hundreds of formed products are stacked and cooled, blocking (adhesion between boards) may occur.

As a moisture-proof inorganic board that solves these problems, a moisture-proof gypsum board is proposed in which a vinylidene chloride resin film having a low moisture permeability and an excellent blocking resistance is formed on the surface of the gypsum board. The gypsum board is used as the inorganic board for the following reasons. The gypsum board is a thick gypsum layer as a core material with both front and back surfaces and side surfaces in the length direction covered with board base paper, and has no unevenness like other inorganic boards have on the surface. Since it does not have it, it is possible to form an extremely thin resin film and prevent the occurrence of blocking. The vinylidene chloride-based resin has a drawback that the adhesive strength is weak, but when the surface of the plate material is paper, the adhesiveness of the vinylidene chloride-based resin film is improved.

Considering mass productivity, such a resin film is formed by applying a resin to the surface of the gypsum board while feeding the gypsum board with the surface thereof facing up and down and heating and drying. Is good. The resin coating method applicable to the production line for flow work includes a roll coater method, a spray method, and a curtain flow coater method. However, near the edge of the surface of the gypsum board, the seams of the board base paper run linearly along the length direction, and minute steps corresponding to the thickness of the paper are created linearly. When an extremely thin resin is applied by the method, a film breakage occurs at this portion, and the moisture permeation preventing function is impaired. Further, even when an extremely thin resin is applied by a spray method, film breakage occurs at this portion, and coating leakage also occurs at other portions, and the moisture permeation preventing function is significantly impaired. Therefore, the inventors
It was decided to apply the resin by the curtain flow coater method. This is because the curtain flow coater method does not cause such a problem at all.

In the case of coating by the curtain flow coater method, the product is usually sent at a speed of 100 to 180 m / min. Therefore, if the surface to be coated has irregularities such as the plaster cement board, the downstream side of the convex portion. There are air pockets on the surface, which can cause uneven coating, but if the board is gypsum board,
Since there is no unevenness on the surface, such coating unevenness is unlikely to occur.

To apply the vinylidene chloride resin, an aqueous emulsion in which vinylidene chloride resin particles are emulsified in an aqueous medium is used. This is because the water-based synthetic resin emulsion uses water as a medium, and therefore has higher safety than a synthetic resin solution using an organic solvent as a medium. Based on the above findings, the inventors applied a water-based synthetic resin emulsion of vinylidene chloride-based resin on a surface of a gypsum board using a curtain flow coater and heat-dried it to obtain an extremely thin moisture-proof film. A layer is provided.

[0008]

However, when the water-based synthetic resin emulsion is applied to a gypsum board, it impregnates the inside of the base paper on the surface of the gypsum board, and a very thin resin film is evenly formed on the surface of the gypsum board. The problem of not being formed arises. When the coating amount is increased, a resin film is formed, but the thickness becomes thicker, which causes blocking and an increase in manufacturing cost.

Therefore, it has been considered to make the base paper on the surface of the gypsum board highly water repellent so that the emulsion is not impregnated. However, if the water repellency of the base paper is high,
Even if the above-mentioned water-based synthetic resin emulsion is applied to the base paper, it is repelled, so that there arises a problem that it cannot be applied very thinly and uniformly. This invention provides a damp-proof gypsum board in which a very thin resin film for moisture protection is uniformly formed on the surface of the gypsum board, and the resin film is sufficiently strongly adhered to the surface of the gypsum board, and which is hard to cause blocking. The first object is to provide a method for producing a practical moisture-proof gypsum hode capable of efficiently forming a very thin resin film for moisture prevention on the surface of the gypsum board that is hard to cause blocking and is the first object. There are two issues.

[0010]

In order to solve the above-mentioned first problem, the present invention provides a moisture-proof gypsum board having a moisture-proof coating of a vinylidene chloride copolymer having a coating amount of 60 to 70 g / m ^2. Therefore, the gypsum board base paper has a Steckigt sizing degree of 340 seconds or more, and the vinylidene chloride copolymer is a copolymer of 85 to 95 parts by weight of vinylidene chloride and 5 to 15 parts by weight of (meth) acrylate. A moisture-proof gypsum board is provided.

In order to solve the above-mentioned second problem, the present invention is a gypsum board having a base paper having a Steckigt sizing degree of 340 seconds or more on the surface thereof, and the front and back surfaces thereof are oriented up and down to 100 to 180 m / min. Provided is a method for producing a moisture-proof gypsum board in which the following coating step (a) and drying step (b) are sequentially performed while continuously supplying at a rate of minutes. (A) Vinylidene chloride and (meth) acrylate are 8
Curtain of water-based synthetic resin emulsion containing 50-60% by weight of vinylidene chloride-based copolymer particles having an average particle diameter of 1-3 μm, which are copolymerized at a weight ratio of 5: 15-95: 5, as a film forming component 0.1 to 0. by flow coating.
Applying the synthetic resin emulsion to the base paper of the gypsum board by flowing it down to the gypsum board with a curtain thickness of 5 mm.

(B) The synthetic resin emulsion applied to the base paper of gypsum board at a temperature of 120 to 200 ° C.
A step of forming a moisture-proof film made of a vinylidene chloride-based copolymer by drying for 5 to 2.0 minutes. The moisture-proof gypsum board of the present invention has a resin coating for moisture protection having a coating amount of 60 to 70 g / m ² formed on the surface. Coating amount is 60g
If it is less than / m ^2, it will not be a uniform resin film that is not affected by the fine irregularities of the base paper, causing moisture or water to permeate,
Moreover, there is a problem that the curtain is cut off.
If it exceeds g / m ² , there is a problem that it takes a long time to form the resin film or blocking occurs, which causes a high cost.

In the gypsum board used in the present invention, the base paper on the surface of the gypsum board must have a Steckigt sizing degree of 340 seconds or more. If the base paper has two or more layers,
It is necessary that at least the front layer base paper has such a Steckigt sizing degree. When the Steckigt sizing degree of the base paper is less than 340 seconds, the amount of coating on the base paper is 6
There is a problem that the resin film of 0 to 70 g / m ² is not uniformly formed and the moisture-proof property is low, or the moisture-proof property is sufficient but an extremely thin resin film is not formed, resulting in high cost. The base paper on the surface of the gypsum board preferably has a Steckigt sizing degree of 1000 seconds or less. If the Steckigt sizing degree is too high, for example,
Paper coated with an emulsion resin by a roll coater on the surface such as calendar-coated paper has too little water permeation, which may cause insufficient drying and curling of the gypsum during the production of gypsum board. Not suitable for gypsum board base paper. The material of the base paper is not particularly limited.

The resin film formed on the surface of the gypsum board is made of vinylidene chloride copolymer, and this resin film functions as a moisture-proof film. The vinylidene chloride copolymer used in the present invention is obtained by copolymerizing vinylidene chloride and (meth) acrylate in a weight ratio of 85:15 to 95: 5. Here, as the (meth) acrylate, a methacrylate such as methyl methacrylate, an acrylate such as methyl acrylate, a (meth) acrylic acid such as acrylic acid or methacrylic acid, etc. may be used alone or in combination of two or more kinds. It will be done. When the ratio of vinylidene chloride is more than the above range, the film forming property of the copolymer is deteriorated and the moisture-proof film is not formed, and (meth)
When the ratio of acrylate is more than the above range, the copolymer is likely to block.

The moisture-proof gypsum board of the present invention can be obtained by forming a resin film made of a vinylidene chloride copolymer on the gypsum board. The method of forming the resin film can be appropriately performed, but the following method is preferable because it can be produced at low cost, with less paint loss, with good productivity, and without causing blocking. That is, the gypsum board is 100 to 180 m /
This is a method in which the coating step (a) and the drying step (b) are sequentially performed while continuously supplying at a speed of a minute. Here, the moving speed of the gypsum board is set within the above range, because there is a problem that the coating amount increases below the above range and blocking occurs, and above that there is a problem that curtain breakage occurs. Is.

In the coating step (a), the average particle size is 1 to 3 μm.
50 vinylidene chloride-based copolymer particles as a film forming component
A water-based synthetic resin emulsion containing -60% by weight is applied. Such an aqueous synthetic resin emulsion has, for example, a viscosity of 50 to 1000 cP at 25 ° C., is hard to impregnate when applied to the base paper, and is uniformly applied. The vinylidene chloride-based copolymer particles are obtained by copolymerizing vinylidene chloride and (meth) acrylate as described above. If the average particle size of the copolymer particles is out of the above range, there is a problem that curtain breakage occurs.

The coating method of the water-based synthetic resin emulsion is as follows.
Curtain flow coating is used for the above reasons. The reason why the flow-down condition at that time is set as above is that there is a problem that the curtain thickness is below the above range, and that the curtain thickness is above the above range, there is a problem that the coating amount increases and pinholes occur. is there. After applying the water-based synthetic resin emulsion in this manner, the drying step (b)
Is applied. This drying needs to be performed at a temperature of 120 to 200 ° C. for 1.5 to 2.0 minutes. If it is performed at a temperature lower than 120 ° C, there is a problem of poor drying (blocking occurs), and if it is performed at a temperature higher than 200 ° C, the coating film is decomposed or vinylidene chloride is decomposed (yellowing), or the board base paper is used. There is a problem that the applied fungicide decomposes and becomes ineffective. If the time is shorter than 1.5 minutes, there is a problem of poor drying (blocking occurs), and if the time is longer than 2.0 minutes, there is a problem of extension of drying equipment or increase of drying cost.

In this way, on the base paper of gypsum board,
Coating amount of vinylidene chloride resin 60-70g / m ²
The resin film of is formed.

[0019]

[Function] On a base paper with a Steckigt size of 340 seconds or more
Moisture-proof coating made of vinylidene chloride-based copolymer is 60-7
By forming a coating amount of 0 g / m ² , it becomes difficult for water and moisture to permeate this coating. Moreover, the vinylidene chloride copolymer is 85 to 95% by weight of vinylidene chloride,
15 to 5% by weight of (meth) acrylate (total of both is 1
(00% by weight),
It has a good film-forming property, so it is easy to form a thin film with good moisture resistance without pinholes. Moreover, since the generated film does not cause blocking even at high temperatures, the boards will not stick even if they are stacked immediately after drying.

The coating step (a) and the drying step (b) while continuously supplying the gypsum board having the above-mentioned base paper on the surface.
By sequentially performing the above steps, the gypsum board as described above can be obtained efficiently and stably.

[0021]

The present invention will be described in detail below with reference to its embodiments. As shown in FIG. 1, the moisture-proof gypsum board according to the present invention uses the gypsum board 1 as a plate material for interior, and its surface (this is usually only one side, but in some cases, double-sided). May be.)
Has a resin film 2 made of vinylidene chloride based resin for preventing moisture permeation. The gypsum board 1 has a plate-shaped gypsum body covered with a board base paper. This base paper has a Steckigt size degree of 340 seconds or more. The resin film 2 is a resin film having a film amount of 60 to 70 g / m ^{2 made} of a copolymer of 85 to 95 parts by weight of vinylidene chloride and 5 to 15 parts by weight of (meth) acrylate, and is uniformly formed. As shown in FIG. 2, this resin film 2
It is formed by applying the synthetic resin emulsion 2a of the copolymer using a curtain flow coater 7 and then heating and drying. This synthetic resin emulsion 2a is an aqueous emulsion containing 50 to 60% by weight of particles of the copolymer having an average particle size of 1 to 3 μm. As described above, since the synthetic resin emulsion 2a is applied using the curtain flow coater 7, as shown in FIG. 2, near the surface edge of the gypsum board 1, along the length direction of the board, The seam 1a of the base paper runs linearly, and minute steps corresponding to the thickness of the paper are linearly generated, but the linear stepped portion can be applied without interruption. This forming method will be specifically described below.
In FIG. 2, the synthetic resin emulsion 2a is drawn in a thin streak shape, but this is for convenience of illustration, and it is actually preferable to apply it as a uniform curtain.

First, as shown in FIG. 3, the gypsum board 1
Is conveyed by the conveyor 3 in a state where its surface is oriented in the up-down direction to pass through the drying furnace 4 to be pre-dried. This preparation step is performed as needed. Gypsum board 1
The transportation speed of is within the range of 100 to 180 m / min.
Then, this gypsum board 1 is applied to the curtain flow coater 7
And a vinylidene chloride-based synthetic resin emulsion 2a is applied to the upper surface of the gypsum board 1 by the curtain flow coater 7. At this time, the emulsion 2a
Is made to flow so that the curtain 13 has a film thickness of 0.1 to 0.5 mm.

When the synthetic resin emulsion is applied by the curtain flow coater 7, the curtain 13 is used.
It is preferable to make the film thickness of the gypsum board uniform in the width direction so that the coating amount can be made uniform on the entire surface of the gypsum board. Therefore, as shown in FIG. Of. The gypsum board 1 coated with the synthetic resin emulsion is heated and dried in a drying oven 8, stacked on a pallet 9 or the like, cooled, and shipped.

As described above, the gypsum board 1 on which the resin film 2 made of a vinylidene chloride-based synthetic resin emulsion for preventing moisture permeation is formed on the surface of the gypsum board 1 is used as a ceiling material or a wall material. It is used by directly attaching it to the ceiling or wall foundation by facing it or facing the opposite side. Then, moisture such as water vapor in the room is blocked by the resin film 2 and does not enter the attic or the wall. Therefore, it is possible to effectively prevent the occurrence of dew condensation.

The vinylidene chloride resin coating can surely prevent the permeation of moisture as described above, is also excellent in water resistance and oil resistance, and can give the surface of the gypsum board 1 gloss. it can. Since the vinylidene chloride-based synthetic resin emulsion can be formed into a film even by drying at a low temperature of about 40 to 50 ° C., a large facility capacity is not required, which is advantageous in saving energy. Since the vinylidene chloride-based resin film has excellent blocking resistance as described above, even if the moisture-proof gypsum boards 10, 10 ... Immediately after coating and drying the synthetic resin emulsion are stacked in layers, the moisture-proof gypsum board 10 There is no possibility that 10 ...

By the way, in order to prevent moisture from permeating into the back of a hut or the inside of a wall to form dew condensation, a plywood laminated with a polyethylene film (moisture-proof plywood) is attached to a ceiling substrate or a wall substrate. It has been attempted to put a ceiling material such as a gypsum board or a wall material on it, but this would require time and effort for construction, and the cost would increase. Since it has a moisture-proof property by itself, it is not necessary to use the above-mentioned moisture-proof plywood and can be directly attached to a ceiling base or a wall base for use. When the resin film 2 (moisture-proof film) is subjected to cloth tensioning, for example, the concentration of starch paste is increased (for example, 80 parts diluted, that is, 20 parts water to 80 parts paste). it can.

Specific examples and comparative examples of the present invention will be shown below, but the present invention is not limited to the following examples. -Example 1-The gypsum board 1 is a gypsum board conforming to JIS A6901, and the board base paper has a Steckigt size degree of 3.
A material having a basis weight of 230 g / m ² in 80 seconds was used. The dimensions were 900 mm × 2400 mm × thickness 12 mm.

As the synthetic resin emulsion 2a, 55% by weight of vinylidene chloride-based copolymer particles having an average particle size of 1.5 μm obtained by copolymerizing vinylidene chloride and methyl methacrylate at a weight ratio of 95: 5. An emulsion containing and having a viscosity at 25 ° C. of 900 cP was used. The moisture-proof gypsum board 1 is performed as follows in the procedure shown in FIGS.
I made 0. The gypsum board 1 is pre-dried while being sent at a speed of 172 m / min, and then passed under a natural flow-type curtain flow coater 7, and the synthetic resin emulsion 2a is applied to the upper surface of the moisture-proof gypsum board 1 by the curtain flow coater 7. Was applied with a film thickness of 0.3 mm.
The gypsum board 1 coated with the synthetic resin emulsion 2a is heated and dried at a temperature of 170 ° C. for 1.5 minutes in a drying oven 8, stacked on a pallet 9 and cooled to obtain a moisture-proof gypsum board 10. ..

-Examples 2 to 10-A moisture-proof gypsum board 10 was obtained in the same manner as in Example 1 except that the changes shown in Table 1 were made. -Comparative Example 1-Example 1 except that the base paper of the gypsum board 1 having a Steckigt sizing degree of 280 seconds was used.
A moisture-proof gypsum board was obtained in the same manner as in.

Comparative Example 2 The same as Example 1 except that the vinylidene chloride-based copolymer used in Example 1 had a vinylidene chloride weight ratio of 78 and a methyl methacrylate weight ratio of 22. A moisture-proof gypsum board was obtained. Comparative Example 3 Moisture proofing in the same manner as in Example 1 except that a vinylidene chloride copolymer having a vinylidene chloride weight ratio of 98 and a methyl methacrylate weight ratio of 2 was used as in Example 1. A gypsum board was obtained.

-Comparative Example 4-A moisture-proof gypsum board was obtained in the same manner as in Example 1 except that the amount of the resin film was 54 g / m ² . -Comparative Example 5-A moisture-proof gypsum board was obtained in the same manner as in Example 1 except that the amount of the resin film was 85 g / m < ² >.

Comparative Example 6 A moisture-proof gypsum board was obtained in the same manner as in Example 1 except that the synthetic resin emulsion having a copolymer particle content of 40% by weight was used. -Comparative Example 7-A moisture-proof gypsum board was obtained in the same manner as in Example 1 except that the synthetic resin emulsion having a copolymer particle content of 70% by weight was used.

The amount of the resin film on the surface of the moisture-proof gypsum board obtained in the above Examples and Comparative Examples, the adhesive strength of the resin film with the base paper, the uniformity of the resin film (film forming property), the blocking resistance, and the transparency. The humidity was examined and the results are shown in Tables 2 and 3. The amount of the resin film was determined by measuring the applied weight. The adhesive strength between the resin film and the base paper is the standard condition of JIS A1612 (adhesive strength of ceiling board adhesives and adhesive strength test method of the adhesive construction method), or JIS A1613 (wall board adhesives The adhesive strength and the adhesive strength test method of the bonding method) are shown as the measured values when pulled under standard conditions.

The uniformity of the resin film was shown by observing the curtain when the synthetic resin emulsion was applied by a curtain flow coater and showing whether the curtain was formed (○) or cut without forming the curtain (×). Blocking resistance is such that 100 sheets of moisture-proof gypsum board with dimensions of 900 mm × 2400 mm × thickness of 12 mm are stacked as one unit on a pallet, and 100 units as one unit are stacked in three stages and after 12 hours, the resin films stick to each other. It was indicated by whether (x) or not sticking (○).

The moisture permeability was measured by the moisture permeability test method (cup method) of the moisture-proof packaging material of JIS Z0208. The Steckigt sizing degree of the base paper was measured by the paper Steckigt sizing degree test method of JIS P8122.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

As shown in Tables 1 to 3, the moisture-proof gypsum board of the examples has excellent blocking resistance on the gypsum board surface,
It has a resin film with high adhesive strength to the base paper and low moisture permeability. On the other hand, in Comparative Example 1, since the Steckigt sizing degree of the base paper is less than 340 seconds, the vinylidene chloride copolymer coating material is impregnated into the board base paper layer to form a uniform moisture-proof coating layer. However, the moisture permeability did not fall below the standard value of 30 [g / m ² · 24 hours]. In Comparative Example 2, blocking occurred because the proportion of vinylidene chloride in the copolymer was less than 85% by weight. In Comparative Example 3, since the proportion of vinylidene chloride in the copolymer was more than 95% by weight, the film forming property of the copolymer was deteriorated and it was difficult to form the moisture-proof coating. In Comparative Example 4, since the amount of the resin film was less than 60 g / m ² , curtain breakage was likely to occur and a uniform moisture-proof film layer could not be formed. In Comparative Example 4, even if the moisture-proof coating layer could be formed, the thickness of the moisture-proof coating layer could not be ensured, so that the moisture vapor transmission performance was the standard value 30.
It does not fall below [g / m ² · 24 hours]. In Comparative Example 5, the amount of the resin film was more than 70 g / m ² , and therefore the drying was insufficient and blocking occurred. In Comparative Example 6, since the content of the vinylidene chloride copolymer particles in the synthetic resin emulsion is 40% by weight, the uniformity of the resin film is lacking and the moisture permeability is 30 [g / m] which is the standard value. ² · 2
4 hours] It did not fall below. In Comparative Example 7, blocking occurred because the content of the vinylidene chloride copolymer particles in the synthetic resin emulsion was 70% by weight.

[0040]

EFFECTS OF THE INVENTION The moisture-proof gypsum board of the present invention can effectively prevent the permeation of moisture, is less likely to cause blocking, and can be manufactured at a low cost. According to the method for producing a moisture-proof gypsum board of the present invention, such an excellent moisture-proof gypsum board can be easily manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a perspective view showing one embodiment of a moisture-proof gypsum board of the present invention.

FIG. 2 is a perspective view showing a main part of one embodiment of the method for producing a moisture-proof gypsum board of the present invention.

FIG. 3 is a schematic view showing steps of a method for producing a moisture-proof gypsum board according to the present invention.

[Explanation of symbols]

 1 Gypsum board 2 Resin film layer for preventing moisture permeation 2a Vinylidene chloride-based synthetic resin emulsion 7 Curtain flow coater 10 Moisture-proof gypsum board 13 Curtain of synthetic resin emulsion

Claims (2)

[Claims] 1. A vinylidene chloride-based copolymer 60
A moisture-proof gypsum board having a moisture-proof coating with a coating amount of up to 70 g / m ² , wherein the gypsum board base paper has a Steckigt size degree of 3
A moisture-proof gypsum board for 40 seconds or more, wherein the vinylidene chloride-based copolymer is a copolymer of 85 to 95 parts by weight of vinylidene chloride and 5 to 15 parts by weight of (meth) acrylate. 2. A gypsum board having a Steckigt sizing degree of 340 seconds or more on its surface is continuously fed at a speed of 100 to 180 m / min while the front and back surfaces of the gypsum board are oriented vertically. Application step (a) and drying step (b)
A method for manufacturing a moisture-proof gypsum board that sequentially performs (A) Vinylidene chloride and (meth) acrylate are 8
Curtain of water-based synthetic resin emulsion containing 50-60% by weight of vinylidene chloride-based copolymer particles having an average particle diameter of 1-3 μm, which are copolymerized at a weight ratio of 5: 15-95: 5, as a film forming component 0.1 to 0. by flow coating.
Applying the synthetic resin emulsion to the base paper of the gypsum board by flowing it down to the gypsum board with a curtain thickness of 5 mm. (B) A step of forming a moisture-proof coating made of a vinylidene chloride-based copolymer by drying the synthetic resin emulsion applied to the base paper of gypsum board at a temperature of 120 to 200 ° C. for 1.5 to 2.0 minutes.