JPS6241747A - Manufacture of incombustible gypsum board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing noncombustible gypsum board.

More specifically, a mixture consisting of a predetermined amount of fibers, a specific set retarder, and the required amount of water is molded into powdered gypsum consisting of 50 to 95 parts by weight of hydrated gypsum and 50 parts by weight of industrial gypsum, hardened, and dried. This invention relates to a method for manufacturing high quality chain plates.

Among inorganic noncombustible building materials, gypsum board is widely used as an interior material because it is economically usable and has excellent fire resistance, sound insulation, heat insulation, dimensional stability, and workability. The basic technology for manufacturing gypsum boards is to add water to calcined gypsum, which is made by heating and dehydrating industrial gypsum, and then forming and hardening it to obtain a board-like product in a predetermined shape. Therefore, as a general rule, industrial water gypsum, which does not have hardening properties as plaster, cannot be used, and if even a few percent of the calcined gypsum is mixed with Mimoku gypsum, the strength of the molded product will not only decrease significantly, but also be used for paper-covered gypsum boards. In this case, adhesion to paper is also lost. In addition, since gypsum trihydrate promotes the setting of gypsum, the mixing of calcined gypsum and gypsum trihydrate was denied, such as by increasing the amount of setting retardant to alleviate this effect (Special Publication Publication No. 57-49004). Therefore, if a powdered gypsum equivalent to a known gypsum board could be manufactured by replacing a considerable proportion of the calcined gypsum with gypsum trihydrate, it would take an enormous amount of heat to manufacture calcined gypsum from gypsum trihydrate. It becomes possible to save energy.

On the other hand, there are several proposals regarding gypsum boards and their manufacturing methods that do not use calcined gypsum but instead use trihydrate gypsum to form and harden. However, they are 1, for example, ■300k
Even though extremely high pressures such as g/crrf or more are required, the bending strength of the resulting gypsum board is 10 to 35 k.
g/cm" could not be obtained.
No. 12) or ■ relatively low 10 to 250 kg/c
However, the bending strength of the resulting product is extremely low, at around 5 to 30 kg/am'(#Publication No. 55-349), and none of these products can be used practically as building materials. Not obtained.

The present inventors have solved the problems associated with the above-mentioned known technologies, namely, achieved energy savings in terms of raw materials by using trihydrate gypsum in the production of gypsum boards, eased the manufacturing conditions for products using trihydrate, and We conducted extensive research on improving strength. As a result, it was surprisingly found that trihydrate gypsum was used for 5 to 50 parts by weight of the powdered gypsum used for the m-component gypsum board, and the remaining 85 parts by weight
We have found that when using ~50 parts by weight of calcined gypsum, the practical strength of the gypsum board is as good as that using 100% calcined gypsum, and the manufacturing process can be carried out more smoothly and efficiently. Based on this knowledge, first, 100 parts by weight of powdered gypsum consisting of the above-mentioned parts by weight of calcined gypsum and gypsum trihydrate, a predetermined amount of fibers, and coagulation 'I! He invented a method for manufacturing non-combustible gypsum board, which consists of molding, curing and drying a mixture consisting of a spreading agent and water.
025587).

The invention related to this earlier application is that trihydrate gypsum, which had conventionally been considered impossible to be used in combination with calcined gypsum as a raw material gypsum powder for gypsum boards, has been made possible through the mixed use of fibers and a setting retarder. The results of various studies on setting retardants were also disclosed.

As a result of further detailed studies on setting retarders, the present inventors have found that when specific setting retarders are used in combination, it is possible to manufacture gypsum boards containing trihydrate gypsum even more smoothly and efficiently. This was confirmed through detailed study results, and the present invention was completed.

As is clear from the following description, the purpose of the present invention is to provide a method for manufacturing a gypsum board that uses trihydrate gypsum as a part of the raw material. It is an object of the present invention to provide a manufacturing method which enables the combined use of gypsum trihydrate, which is smoother and more efficient, and which provides a product with a strength that is practical.

The present invention has the following main configurations.

100 parts by weight of powdered gypsum consisting of 50 to 85 parts by weight of water-use gypsum and 5 to 50 parts by weight of industrial water gypsum;
It consists of 30 parts by weight of fiber, tartaric acid or its metal salt, and an amino acid derivative, and has a content of 0.1 to 2.0 parts by weight relative to the above hydrated gypsum.
1. A method for producing a non-combustible gypsum board, characterized in that a mixture consisting of a weight percent set retarder and water is molded and hardened and dried before the hydrated gypsum is hydrated.

The configuration and effects of the present invention will be explained in detail below.

The raw material characteristic of the method of the present invention is that hydrated gypsum and trihydrate gypsum are substantially used together. The hydrated gypsum used is α, which is obtained by heat-treating trihydrate gypsum using a known method.
It is any one of type hemihydrate gypsum, β type hemihydrate gypsum, and soluble anhydrite, or a mixture of two or more types. The fineness of the water-use gypsum used is preferably 500Qcrn''7g or less in Blaine specific surface area value.

A fineness of fineness which significantly exceeds this value tends to disadvantageously shorten the curing time of molded articles from the above-mentioned mixtures according to the invention, and in order to rectify this the addition of set retarder may be necessary. Increased and undesirable.

On the other hand, if the fineness is too coarse, the strength of the resulting cured product, that is, the gypsum board, will decrease. Therefore, the fineness is preferably 500 g or less as the maximum particle size, and the Blaine specific surface area value is preferably 11000 crrf1 or more. In addition, when a paper-making method is adopted as the molding method according to the present invention, the specific surface area value is preferably 5000 em / g or less, because the loss of the used hydrated gypsum powder into the filtrate is prevented. This is because it is possible to minimize the amount.

On the other hand, as for water gypsum, as long as its particle size is 500 μm or more and 1.5 μm, it does not matter where it comes from or how it is manufactured. As is well known, industrial water gypsum, which is used as an industrial raw material, has a large calorific value as well as many types of chemical gypsum (by-product gypsum). Examples of these materials include flue gas desulfurization gypsum, phosphate gypsum, salt production gypsum, salt gypsum, and hydrofluoric acid gypsum. Bulky products such as natural gypsum must be ground to the above-mentioned particle size, and other chemical gypsums are easier to use in this respect. On the other hand, when the gypsum powder becomes too fine, it significantly accelerates the setting of coexisting hydrated gypsum (gypsum hemihydrate and/or soluble anhydrite). The disadvantage is that in order to prevent this, the amount of set retarder to be added to the mixture for producing gypsum board must be increased. did.

Preferably, the fineness of the water gypsum is 5000 cm'/g or less in Blaine specific surface area value.

Before use, it is preferable that the gypsum be mixed and dispersed during disintegration of the fibers.

The proportions of the above-mentioned hydratable gypsum and water gypsum used are 50 to 95 parts by weight and 5 to 50 parts by weight of the former and 5 to 50 parts by weight, per 100 parts by weight of both. If the former is less than 50 parts by weight, the strength of the molded product will be insufficient, and if it exceeds 95 parts by weight, it will go against the purpose of the present invention, which is to save hydrated gypsum. On the other hand, if the latter is added in an amount exceeding 50 parts by weight, the strength of the molded product will be significantly reduced, and the practicality of the final gypsum board will be lost. The table below shows an example of the relationship between the mixing ratio of industrial gypsum and the strength of gypsum board.

Table: Water gypsum mixing ratio and gypsum board strength (kg
/ cm'') The fibers used in the present invention may be inorganic fibers such as asbestos or glass fibers, or natural or synthetic fibers such as cellulose 1aivl, vinylon fibers, polypropylene fibers or polyamide fibers. One type or a combination of two or more of these can be used. Among these, asbestos fibers and cellulose fibers are particularly useful for gypsum (
It is preferable to use one of these or a mixture of these in the fiber to be used, since it has a strong adhesive force with the cured product).

Adding the above-mentioned fibers to the mixture for producing gypsum board according to the present invention greatly improves the quality of the resulting hardened gypsum body. In addition, it improves hot water resistance, bending strength and flexibility. The amount of fiber used in the mixture is preferably 0.5 to 30 parts by weight per 100 parts by weight of powdered gypsum.
Parts by weight. If it is less than 0.5 parts by weight, the above-mentioned effects are insufficiently expressed, and even if it exceeds 30 parts by weight, the effects will not improve and it is not economical. On the other hand, some physical properties may deteriorate.

The amount of water used in the above-mentioned mixture according to the invention is not limited and varies depending on the forming method. However, by mixing 15 to 2.500% by weight based on the amount of the mixture other than water, the mixture can be easily molded. The minimum amount of water required is the amount of water required for the hydratable gypsum to be completely hydrated.

The gypsum setting retarder used in the present invention comprises tartaric acid or a metal salt thereof and an amino acid derivative. Generally known gypsum setting retarders include glycerin, alcohols, phosphates, carboxylic acids, oxycarboxylic acids or their salts, animal protein hydrolysates, and the like. Among these, citric acid and sodium citrate are preferably used for gypsum boards, and animal protein hydrolysates are preferably used for gypsum plasters. However, in the case of the present invention, a large amount of industrial water gypsum is actively blended so that it accounts for up to 50 parts by weight in 100 parts by weight of powdered gypsum, so in such cases, especially (1) The strength of the resulting hardened gypsum body should not be reduced. It is necessary to be satisfied that it acts effectively on both the sheet and the filtrate.From this standpoint, the best setting retarder found by the present inventors is a combination of tartaric acid or a metal salt thereof and an amino acid derivative. For example, it is preferable to use a formaldehyde condensate of an amino acid obtained by hydrolyzing a protein (the 4th component is glutamic acid and aspartic acid).

Next, the experiments that formed the basis for selecting the above-mentioned setting retarder will be described in detail.

First, 5 parts by weight of waste paper pulp, 9 parts by weight of asbestos, and 500 parts by weight of water were added and mixed to 80 parts by weight of powdered gypsum consisting of 65 parts by weight of monohydrate gypsum and 25 parts by weight of engineered water gypsum. When predetermined amounts of various setting retarders were added to an aqueous slurry consisting of 100 parts by weight of solids and 500 parts by weight of water, tartaric acid or its metal salts and amino acid derivatives (trade name: "Puftat", manufactured by Ajinomoto Co., Inc.) It has been found that a small amount is effective in extending the hydration of the hydratable gypsum in the aqueous slurry, and furthermore, when both are used in combination,
Even more condensation! We found that it has a prolonging effect.

Next, after adding various concentrations of various setting retarders to the aqueous slurry as described above, it was immediately filtered by suction, and the solid content of the filter paper was press-molded at a pressure of 50 kg/cryf. A gypsum board (green board) with a thickness of approximately 5 m was obtained. After putting this raw board in a plastic bag and leaving it in a sealed state for 5 days to allow the plaster to completely set, G.

The plate was dried in a dryer at 0.9°C until the moisture content was 0.5% by weight or less, and the resulting stone/g plate was subjected to a bending strength test. As a result, when tartaric acid or tartaric acid metal salts are used as a setting retarder, the bending strength of the gypsum board is almost negligible when the amount added is in the range of 0.1 to 2.0% (based on hydrated gypsum). It did not decline. In addition, when an amino acid derivative is used as a setting retarder, the amount of the amino acid derivative added is 0.1 to 0.
．． The bending strength of the gypsum board did not decrease in the range of 5 folds ψ86, but when the amount of amino S1 derivative added was 0.6% by weight, the bending strength of the gypsum board decreased somewhat as the amount of addition ♀ increased.

However, when using a combination of tartaric acid or tartaric acid metal salts and amino acid derivatives, the amount added is 0.
．． In the range of 1 to 2.0% by weight, the bending strength of the gypsum board hardly decreased. On the other hand, when setting retarders other than those mentioned above were used, the bending strength of the gypsum board decreased somewhat as the amount added increased.

From the results of the setting I spreading test and the gypsum plate bending strength test of I-H, various setting 17! Among the spreading agents, the most desirable one is one that does not cause a drop in water content even when a large amount of water gypsum coexists due to the addition of a small amount of it, and is the most desirable one that is a combination of tartaric acid or tartaric acid metal salts and amino acid derivatives. (hereinafter sometimes referred to as M1 combined setting retarder). This combination of setting retarders is effective as shown in L when the combination ratio of both is 2:8 to 8:2 in heavy weight ratio.

The amount of the combined setting retarder to be used varies depending on the method of forming the gypsum board that is the object of the method of the present invention, but the standard amount is 0.1 to 2 parts by weight per 100 parts by weight of the hydrated stone* used. use. If it is less than 0.1 part by weight, no setting retardation effect can be achieved, and if it exceeds 2 parts by weight, the strength of the hardened gypsum product is reduced.

In the present invention, the pH of the mixture or slurry obtained by mixing one or more raw materials is preferably adjusted to 7 or higher. The preparation method may be a method of using a small amount of a basic substance such as cement slaked lime as an additive in the mixture.

Such adjustment of P)l not only enhances the effect of the hardening retardant, but also improves the effect of the hardening retardant, and
av profit I, / t+ -2h
Ilz M n /f= fy correction + I
It not only has the effect of preventing rust from nails driven into the product gypsum board during use.

As a molding method for manufacturing a gypsum board using the mixture manufactured as described above, any known molding method such as pouring, dehydration, pressure compression, or paper forming can be used. However, whichever molding method is used, the molding must be performed before the hydrated gypsum in the mixture is hydrated.

If molding is performed after the hydrated gypsum in the mixture has been hydrated, the strength of the resulting hardened gypsum product will be drastically reduced, making it impossible to obtain a gypsum board that maintains practical strength. For the same reason, if a pressure compression process is included as part of the molding process, the process must be completed before the hydrated gypsum in the raw material mixture is hydrated. The pressure is 10-5
It is necessary to carry out at 00Kg/ern'. In particular, the gypsum board made by compression molding the above-mentioned mixture according to the present invention at a pressure of 50 Kg/cm' or less uses only hydrated gypsum as powdered gypsum, regardless of whether it contains industrial gypsum. It is possible to obtain a product that is almost as strong as the product obtained by using this method. The formed gypsum board is allowed to dry after hydration is complete. Drying may be carried out by a known method under appropriate conditions.

The present invention exhibits further effects as described below, particularly when gypsum boards are manufactured by the cylinder-type papermaking method. That is, in the cylinder papermaking method, raw materials to be blended are mixed with water to prepare an aqueous slurry, which is temporarily stored in a chest and then sent to a papermaking machine. At this point, it is cut into a thin sheet, but at this time, most of the tartaric acid or its metal salt mixed in the aqueous slurry remains in the sheet, and most of the amino acid derivatives are transferred to the filtered water. In this case, if only an amino acid derivative is used as a setting retarder, only a small amount remains in the sheet after papermaking, so the sheet after papermaking immediately begins to set and harden. As a result of insufficient adhesion between the sheets in the process of adjusting and cutting the sheet or the process of pressure molding, the resulting product is likely to cause delamination. On the other hand, 11, most of the amino m derivatives migrate to the filtrate, which delays the hydration of the hydratable gypsum leaking from the papermaking net when it is recycled and used. Furthermore, if tartaric acid or its metal salt is used as a setting retarder, the setting retarding effect is very large in the slurry as described above, and the setting retarding effect becomes even greater in the paper-formed sheet.

However, since most of the gypsum remains in the paper-formed sheet, it has little effect on delaying the water utilization of the water-compatible gypsum leaking from the paper-forming net. In the present invention, tartrate is used as a setting retarder in combination with its metal salt and an amino acid derivative, so even if industrial gypsum is used as a part of the raw material, a relatively small amount of addition can provide sufficient setting retarding effect. Not only is this obtained, but one part of the setting retarder constituting the combination setting retarder remains in the sheet being cut, preventing rapid setting of the sheet. The other one transfers into the filtrate and delays the hydration of the hydratable gypsum that leaks from the paper mesh, and in this way, using engineered water gypsum as a part of the raw material, gypsum is produced using the circular mesh method. In the case where the present invention is carried out by the method of making circular nets and paper sheets, it is possible to make the manufacturing of the board smooth and to remove the hydratable gypsum in the filtrate. The mixing ratio of tartaric acid or its metal salt and the amino acid derivative is preferably in the range of 2=8 to 8:2 by weight.

As described above, a gypsum board is obtained according to the present invention, and the effluent mixture generated during the manufacturing process can be recycled and used as is.

In addition, morphologically defective products of gypsum boards or products recovered from cut ends during shaping, which are seen in the method of the present invention, can be re-pulverized and reused as the four raw materials, industrial water gypsum and part of fibers. .

The reason why these recycled or recovered materials are possible is that even if the hydratable gypsum in these reused raw materials hydrates and turns into industrial gypsum, it cannot be treated as raw material industrial gypsum and used in the present invention. This is because the mixing ratio of such raw materials can be adjusted, and this can be said to be an effect that cannot be predicted from the conventional method in which only hydrated gypsum is used as powdered gypsum. However, even in the case of reuse as described above, it goes without saying that the proportion of industrial water gypsum in the total raw materials must not exceed 50% by weight of powdered gypsum. According to the method of the present invention, an integrated thick gypsum board of any thickness can be manufactured by folding together a plurality of molded raw boards and press-molding them.

In the method of the present invention, various known additives can be used to improve various physical properties of the target gypsum board. These include, for example, orastonite, mica, vermiculite, diaphragm or perlite, but are of course not limited to these. The amount of these minerals added is
It is desirable to determine this within the framework of the amount of fibrous material used in the raw material mixture according to the invention. That is, the total value of the fibrous material and the mineral material is 0.5 to 100 parts by weight of powdered gypsum.
Use within the range of 30 tons gives good results.
.

The method of the present invention is economical because it is not necessary to use only expensive hydrated gypsum as the raw material powdered gypsum, and up to half of the amount of inexpensive industrial water gypsum can be used in combination. Further, the method of the present invention can be advantageously implemented particularly when applied to a papermaking method for the following reasons. That is, (1) the transient properties of the slurry are improved, so the paper-making properties are improved, and it is not necessary to use asbestos and valve together as the fibers used;
This is based on the mixed use of industrial water gypsum as powdered gypsum. In addition, there is no need to increase the setting retardant (compared to when no industrial water gypsum is added), which is blended for stable continuous operation when circulating white water and running water gypsum. Agents include tartaric acid or its metal salts and amino acid derivatives (e.g.

By combining the commercially available product name Pufftate), a sufficient setting retardation effect can be obtained with a small amount of addition, and at the same time, when manufacturing gypsum board by the papermaking method, most of the tartaric acid or the seven metal salts are added to the sheet. On the other hand, most of the amino acid derivatives are transferred to the filtrate and can delay the hydration of the circulating hydratable gypsum.

In addition, the strength of the gypsum board produced by the method of the present invention was significantly lower than that of the conventional gypsum board manufactured with only a few percent of industrial water gypsum mixed in, compared to the case where the gypsum board was not mixed. , there is an advantage that even if industrial water gypsum is used for half of the gypsum raw material, the strength decreases only slightly. Furthermore, when compared with conventional products, the gypsum board produced by the method of the present invention has not only fire resistance and water resistance, but also various physical properties as an interior material, such as bending strength, impact resistance, dimensional stability, flexibility, It also has better workability and nail retention.

Below, we will show experimental examples, examples using papermaking methods, and comparative examples showing the magnitude of the effects of various setting retarders.

Experimental example 2 Disintegrated waste paper valve log in a plastic container, water 99
When 9 mJ1 and 0.5 g of Ca(OH)z were mixed and stirred, the pH of this mixed solution was 9.5. To this mixed solution, 0.3 g (solid shadow content) of various gypsum setting retarders shown in Table 1, either alone or in combination, was added and completely dissolved. A gypsum slurry was prepared by adding 30 g of desulfurized gypsum (dried product) and stirring. Immediately after preparation, the viscosity of this gypsum slurry is measured using a B-type viscometer, and the viscosity reaches 1,000 cps, which is the point at which the state of the gypsum in the slurry changes to a floc-like agglomerated state (change point). The results of calculating the required time are shown in Table 1. Among the setting retarders, Baftat (trade name, manufactured by Ajinomoto) was used as an amino acid derivative.

Table-1 From Table-1, the effect of delaying the setting of gypsum slurry is as follows:
It can be seen that tartaric acid or a metal salt thereof and an amino acid derivative have a much greater effect on retarding set than other set retarders, and in particular, when the two are combined, the set retarding effect increases synergistically.

Examples 1-2. Comparative examples 1-2 The following raw materials were used and blended in the proportions shown in Table 2 below.

Industrial gypsum: Two gypsum produced as a by-product of the flue gas desulfurization method, powder level is 0
．． 59ra gift sieve complete, Blaine specific surface area value 1450
cm'/g.

Gypsum hemihydrate 2. The industrial water gypsum produced by the above flue gas desulfurization method was calcined in a kettle at 180°C for 80 minutes, and then ground in an impact grinder to a Blaine specific surface area of 4300 crn'/g.

Asbestos: A mixture of equal weights of amoisite asbestos and chrysotile asbestos, which is decomposed using a pulverizer.

Waste paper bulbs: Newspaper bulb glass M fiber: E glass cut into 1/2 inch length.

Slaked lime: Commercially available Sake Sake Niichi Amino acid derivative: Pufftard [Product name, manufactured by Ajinomoto Co., Inc.] Table 2 shows the blending ratio of each example and comparative example of the above raw materials. The numerical values of the blending ratios are expressed as outer weight % for only tartaric acid and amino acid derivatives relative to hemihydrate gypsum, which is hydrated gypsum, and inner weight % for other raw materials. In addition, all raw materials are shown in solid equivalent values.

Table 2 Blending ratio (wt%) A gypsum slurry was made according to the above-mentioned mixing ratio, a green sheet was obtained using a cylinder paper machine, and this was pressure-formed to produce a gypsum board. The specific steps are as follows.

■Pour water into a bulb disintegrator, add asbestos, waste paper bulbs, glass fibers, and industrial gypsum in predetermined amounts while stirring to obtain slurry A.

■Transfer slurry A to the raw material mixer, and while stirring, first add slaked lime, then set retardant (i.e., tartaric acid, amino acid derivatives, or a combination thereof according to Table 2), and finally gypsum hemihydrate and stir thoroughly. to obtain slurry B.

(2) Transfer slurry B to a chest, and add industrial water to the slurry while stirring so that the solid content concentration of the slurry is approximately 0% by weight to obtain slurry C.

■Slurry 〇 is sent to a paper-making machine, is drawn up by a rotating circular mesh cylinder, is taken up on an endless felt equipped with a suction dewatering device, and formed into a thin film, and this film is passed on a making roll until it reaches a predetermined thickness. After stacking, cut with a cutter. Further, the gypsum board of predetermined dimensions is roughly cut into slightly thicker pieces depending on the width and length to obtain a green sheet. 0.
The entire amount of filtrate containing about 5 to 2% by weight of solids is returned to the surge tank and used for circulation.

■The obtained raw sheets are stacked up between plates such as iron plates, either singly or in a stack of multiple sheets to a predetermined thickness as required, and then pressure-formed at a pressure of 100 kg/cm'. do.

The time required for step 1 of the above production is approximately 30 to 90 minutes. The pressure-molded product obtained as described above is
After the molded body was cured until the gypsum hemihydrate was completely hydrated, it was dried in a dryer and precisely cut according to a predetermined method to obtain a final product.

In this way, the time required from the preparation of the gypsum slurry of the subsequent batch to the end of gypsum hydration after the drainage water reached equilibrium and the longitudinal bending strength of the obtained gypsum board product were measured. The bending strength was determined by JLSA 5418 (asbestos cement calcium silicate board).

The results are shown in Table-3.

Table 3 As can be seen from Table 3, in Comparative Example 2 in which an amino acid derivative alone was used as a setting retarder, most of the setting retarder escaped into the filtrate, so the hydration requirement for the gypsum that was extracted was Not only does it take a short time, but its bending strength is also low. In addition, in Comparative Example 1, in which tartaric acid alone was used as a setting retarder, most of the setting retarder remained in the shavings, so the time required for hydration of the gypsum was sufficiently long, but the bending strength was low. In Examples 1 and 2, in which a combination of tartaric acid and an amino acid derivative was used as a setting retarder, the bending strength was very high, and the time required for hydration of the gypsum was longer than at least a practically acceptable time.

Procedural amendment (method) % formula % 2. Name of the invention Method for manufacturing non-combustible gypsum board 3. Relationship to Nagisa/K case to be amended Patent applicant Oaza Ono, Onoda City, Yamaguchi Prefecture [TI6276 (024)]
Onoda Cement Co., Ltd. (and 1 other person) 4. Agent 5. Date of amendment order 6. Statement of subject matter of amendment 7. Statement of contents of amendment will be amended as follows.

Between the 5th and 6th lines of page 2, “3. Detailed description of the invention J
Insert.

8. Person who makes amendments other than the above. Relationship to the case Patent applicant 7-10-6 Ginza, Chuo-ku, Tokyo Asahi Asbestos Industry Co., Ltd. that's all

Claims (6)

[Claims] (1) 50 to 95 parts by weight of hydrated gypsum and 5 to 50 parts by weight of dihydrate gypsum
100 parts by weight of powdered gypsum consisting of 0.5 parts by weight
A mixture consisting of ~30 parts by weight of fibers, a set retarder of 0.1 to 2.0% by weight based on the hydrated gypsum, which is made of tartaric acid or a metal salt thereof, and an amino acid, and water is added to the hydrated gypsum. A method for producing a non-combustible gypsum board, characterized in that the non-combustible gypsum board is molded and hardened and dried before it is hydrated. (2) The method according to claim (1), wherein the ratio of the metal salt of tartaric acid to the amino acid derivative is in the range of 2:8 to 8:2 by weight. (3) The method according to claim (1), wherein the pH of the mixture consisting of hydrated gypsum, dihydrate gypsum, fiber, setting retarder, and water is adjusted to 7 or higher. (4) The method according to claim (1), wherein the mixture is pressure-molded at a pressure of 10 to 50 kg/cm^2. (5) The method according to claim (1), wherein the method is formed using a cylinder-type paper making machine. (6) 10 to 500 kg/cm^2 of raw sheet after papermaking
The method according to claim (5), in which pressure molding is performed at a pressure of .