JPH0476943B2 - - Google Patents

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 set retarder, and the required water is molded into powdered gypsum consisting of 50 to 95 parts by weight of hydratable gypsum and 5 to 50 parts by weight of dihydrate, a total of 100 parts by weight. , relates to a method for producing high quality said boards by curing and drying. 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 gypsum board manufacturing technology is to add water to calcined gypsum, which is made by heating and dehydrating dihydrate gypsum, and then forming and hardening it to obtain a plate-like product of a predetermined shape. Therefore, dihydrate gypsum, which does not have hardening properties as plaster, cannot be used in principle, and if even a few percent of dihydrate gypsum is mixed in calcined gypsum, the strength of the molded product will not only decrease significantly, but also In the case of paper-covered gypsum board, the adhesion to the paper is also lost. others,
Since gypsum dihydrate promotes the setting of gypsum, the mixed use of calcined gypsum and gypsum dihydrate was denied, as the amount of setting retardant added was increased to alleviate this effect.
(Special Publication No. 57-49004). Therefore, if a powdered gypsum equivalent to a known gypsum board could be produced by replacing a considerable proportion of the calcined gypsum with gypsum, it would require a huge amount of heat to produce gypsum from the gypsum dihydrate. It becomes possible to save energy. On the other hand, there are several proposals regarding gypsum boards and methods for manufacturing the same, which do not use calcined gypsum but instead use dihydrate gypsum and are molded and hardened. However, even though these methods require extremely high pressure, such as 300 Kg/cm ² or more, the bending strength of the resulting gypsum board is only about 10 to 35 Kg/cm ² (Special Publications Publication No. 49 of the Showa era).
-31012) or relatively low 10-250Kg/
Although it can be press-formed at a pressure of ^1.2 cm2, the bending strength of the resulting product is extremely low, at around 5 to 30 kg/ ^cm2 (Special Publication No. 55-349), and can only be used as a practical building material. 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 dihydrate gypsum in the production of gypsum boards, eased the manufacturing conditions for products using dihydrate, and We conducted extensive research on improving strength. As a result, it was surprisingly found that 5 to 50% of the powdered gypsum used for fiber-filled gypsum board
When using 1 part by weight of gypsum dihydrate and 95 to 50 parts by weight of calcined gypsum, the practical strength of the gypsum board is equal to that of 100% calcined gypsum, and the manufacturing process is It was discovered that the present invention could be carried out more smoothly and efficiently, and the present invention was completed based on this knowledge. As is clear from the above description, an object of the present invention is to provide a new method for manufacturing a gypsum board. More specifically, it is possible to use calcined gypsum and dihydrate gypsum together as raw material gypsum powder, and the manufacturing method The object of the present invention is to provide a manufacturing method that is smooth, efficient, and has a strength that can be used for practical purposes. The present invention has the following main configurations. For 100 parts by weight of powdered gypsum consisting of 50 to 95 parts by weight of hydrated gypsum and 5 to 50 parts by weight of dihydrate, 0.5 to 30 parts by weight of fibers, and 0.1 to 2.0 parts by weight of setting retardation to the hydrated gypsum. 1. A method for producing a non-combustible gypsum board, which comprises forming a mixture of an agent and water before the hydrated gypsum is hydrated, and then hardening and drying the mixture. The structure and curing 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 dihydrate gypsum are substantially used together. The hydrated gypsum used is any one of α-type hemihydrate gypsum, β-type hemihydrate gypsum, or soluble anhydrite obtained by heat-treating dihydrate gypsum by a known method, or a mixture of two or more types. The fineness of the wettable gypsum used is preferably 5000 in Blaine specific surface area value.
cm ² /g or less. 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, it is preferable that the particle size is 500 μm or less in maximum particle size and the Blaine specific surface area value is 1000 cm ² /g or more. In addition, when a papermaking method is adopted as the molding method according to the present invention, the specific surface area value is
It is preferably 5000 cm ² /g or less. This is because it becomes possible to minimize the loss of the used hydrated gypsum powder into the filtrate. On the other hand, as long as the particle size of gypsum dihydrate is 500μ or less, its source or manufacturing method does not matter. As is well known, gypsum dihydrate is used as an industrial raw material.
In addition to natural products, there are many types of chemical industry (by-product) products. These are, for example, flue gas desulphurization gypsum, phosphate gypsum, salt gypsum, titanium gypsum and fluoric 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, if the dihydrate gypsum has an excessively fine powder, it significantly accelerates the setting of coexisting hydrated gypsum (hemihydrate gypsum 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. Therefore,
The fineness of the dihydrate gypsum is expressed by the Blaine specific surface area value.
It is preferably 5000 cm ² /g or less. When using gypsum dihydrate, it is preferable to mix and disperse it during disintegration of the fibers. The proportions of the above-mentioned hydrated gypsum and dihydrate gypsum 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 of 50 parts by weight or more, 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 gypsum dihydrate and the strength of the gypsum board.

[Table] The fibers used in the present invention include one or more types of inorganic fibers such as asbestos or glass fibers, or natural or synthetic organic fibers such as cellulose fibers, vinylon fibers, polypropylene fibers, or polyamide fibers. Can be used in combination. Among these, asbestos fibers and cellulose fibers have particularly strong adhesion to plaster (hardened material), so it is preferable to use either one or a mixture of these fibers in the fibers to be used. Incorporating the above-mentioned fibers into the mixture for producing gypsum board according to the present invention improves the brittleness of the resulting hardened gypsum body, and also improves impact strength and bending strength, and improves flexibility. make it good 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. If it is less than 0.5 part by weight, the above-mentioned effects are insufficiently expressed,
Even if it is blended in an amount exceeding 30 parts by weight, the effect does not improve.
Not economical. On the other hand, some physical properties may deteriorate. The amount of water used in the aforementioned mixture according to the invention is:
It is not limited and varies depending on the molding method. However, for the amount of said mixture other than water,
By mixing 2500% by weight, a mixture that is easy to mold can be obtained. The minimum amount of water required is the amount of water required for the hydratable gypsum to be completely hydrated. As the gypsum setting retarder used in the present invention, any of known substances such as glycerin, alcohol, phosphate, carboxylic acid, oxycarboxylic acid or their salts, and amino acid derivatives can be used. However, when a large amount of dihydrate gypsum, such as 5 to 50 parts by weight, is actively blended into 100 parts by weight of powdered gypsum as in the present invention, the setting retarding effect can be obtained even with a small addition. It is necessary to satisfy the condition that the strength of the hardened gypsum product is large and the strength of the obtained gypsum hardened body is not reduced. In view of the above, the best retardant that the inventors have found is tartaric acid or a metal salt thereof, or more preferably a combination of one or more thereof and an amino acid derivative. The metal for the metal salt is preferably an alkali metal. The amount of setting retarder used varies depending on the method of forming the gypsum board that is the object of the method of the present invention, but it is typically 0.1 to 100 parts by weight of the hydrated gypsum used.
Requires 2 parts by weight. If it is less than 0.1 part by weight, delayed setting and hardening cannot 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 the above raw materials is preferably 7.
Adjust as above. The preparation method may include using a small amount of a basic substance such as cement, slaked lime, etc. as an additive in the mixture. Such PH adjustment not only enhances the curing of the curing retarder and prevents the formation of rust or scale on the gypsum board manufacturing equipment according to the present invention, but also prevents the production of nails from driving into manufactured gypsum boards during use. It has effects such as rust prevention. As a molding method for manufacturing a gypsum board using the mixture according to the present invention 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 employed, 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 pressurization process is included as part of the shaping process, the process must be completed before the hydrated gypsum in the raw material mixture is hydrated. The pressure during pressurization is 10 to 500Kg/
Must be carried out in cm ² . In particular, gypsum boards compression-molded at a pressure of 50 kg/cm ² or higher with the above-mentioned mixture according to the present invention are obtained by using only hydrated gypsum as powdered gypsum, regardless of the inclusion of dihydrate gypsum. It is possible to obtain a product that is almost as strong as the previous one. After the molded gypsum board is hydrated, it is allowed to dry. Drying may be carried out by a known method under appropriate conditions. As described above, the gypsum board according to the present invention is obtained, but the effluent mixture generated during the manufacturing process is
It can be recycled and used as is. Further, recovered products such as morphologically defective products of the gypsum board or cut ends during molding according to the method of the present invention can be re-pulverized and reused as the raw material dihydrate gypsum and part of the fibers. The reason why these recycled or recovered materials can be used is that even if the hydrated gypsum in these reused raw materials hydrates and turns into dihydrate gypsum, they can be treated as raw material dihydrate gypsum and used in the present invention. This is because the blending ratio of such raw materials can be adjusted, and this can be said to be an effect that cannot be predicted from conventional methods that use only hydrated gypsum as powdered gypsum. However, even in the case of reuse as described above, it goes without saying that the proportion of dihydrate gypsum in the total raw materials must not exceed 50% by weight of the powdered gypsum. According to the method of the present invention, by stacking a plurality of molded raw boards and press-forming them,
Integrated thick gypsum boards of any thickness can be manufactured. In the method of the present invention, various known additives can be used to improve various physical properties of the target gypsum board. These are, for example, wollastonite, mica, vermiculite, diatomaceous earth or permalite. Addition of needle-shaped or scale-shaped additives such as wollastonite and mica has been shown to improve bending strength, reduce dimensional change rate, and improve heat resistance.On the other hand, vermiculite and diatomaceous earth Alternatively, the addition of lightweight additives such as pearlite has effects such as a reduction in bulk specific gravity and a reduction in dimensional change rate. Note that the type of additive is not limited to these, of course. It is desirable that the amount of these minerals added be determined within the framework of the amount of fibrous material used in the raw material mixture according to the present invention. That is, good results are obtained when the total amount of the fiber and the mineral is within the range of 0.5 to 30 parts by weight based on 100 parts by weight of powdered gypsum. 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 dihydrate 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, since the filterability of the slurry is improved, the papermaking properties are improved, and it is not necessary to use asbestos and pulp together as the fibers used. This is based on the mixed use of dihydrate gypsum as powdered gypsum. Furthermore, for stable continuous operation when white water and running gypsum are recycled, there is no need to increase the amount of setting retardant (compared to the case where dihydrate gypsum is not mixed). Furthermore, when tartaric acid or its metal salt and an amino acid derivative (for example, commercially available product name Pufftard) are combined as the retardant, the amount of retardant added is smaller than when tartaric acid or its metal salt is used alone. By pressure forming after papermaking according to the method of the present invention, most of the amino acid derivatives contained before forming move into the filtration water, so the hydration effect of the paper product is promoted, and a high-strength gypsum board can be formed in a short time. is obtained. In addition, the gypsum board processed by the method of the present invention is only a few percent
The strength of conventional gypsum boards manufactured with dihydrate gypsum mixed in was significantly lower than that without dihydrate gypsum, but even if dihydrate gypsum was used for half of the gypsum raw material, It has the advantage that 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 its fire resistance and water resistance, but also its physical properties as an interior material, such as bending strength, impact resistance, dimensional stability, and flexibility. ,
It also has better workability and nail retention properties. Examples and comparative examples using papermaking methods and other manufacturing methods are shown below. The following methods were adopted as testing methods for these. Bending strength: JISA 5418 (asbestos cement calcium silicate board) Impact strength: JISC 2210 (asbestos cement board for electrical insulation) Dimensional change rate: JISA 5418 (asbestos cement calcium silicate board) Heating shrinkage rate: JISA 9510 (calcium silicate board) Insulating material). However, the heating condition was 850°C for 2 hours. Non-flammable: Ministry of Construction Notification No. 1828 Examples 1 to 9, Comparative Examples 1 to 6 The following raw materials were mixed in the proportions shown in Table 1 below. Exhaust gypsum: Dihydrate gypsum produced by flue gas desulfurization method (particle size: 0.59m/m sieve, Blaine 1200cm ² /
g) Phosphate gypsum: Phosphate dihydrate (particle size is 0.59m/
(Through m-mesh sieve, Blaine 900cm ² /g) β-type hemihydrate gypsum: Calcined gypsum commercially available α-type hemihydrate gypsum: α-gypsum for molding material commercially available Asbestos: Amoysite asbestos broken up with a pan-shaped grinder Waste paper: Waste newspaper Pulp glass fiber: E glass cut product, length, 1/2 inch Slaked lime: Commercial product Tartaric acid: Commercial product Amino acid derivative: Pufftard S-02 [manufactured by Ajinomoto Co., Inc.] The mixing method of the above raw materials is a setting retarder. Only tartaric acid and amino acid derivatives are used in the external weight percent of β-type hemihydrate gypsum or α-type hemihydrate gypsum, which is hydrated gypsum, and the other parts are used in the internal weight percent (note: weight percent).
The same). The mixing order is as follows: a slurry of a predetermined amount of asbestos, waste paper or glass fiber fibers, slaked lime, dihydrate gypsum, tartaric acid, and an amino acid derivative mixed with water;
A predetermined amount of β-type hemihydrate gypsum or α-type hemihydrate gypsum is added and mixed until the total solid concentration is 10% in the slurry.
The amount of water was adjusted to % by weight. The slurry thus obtained was scooped up using a rotary circular mesh cylinder and placed on an endless felt to form a thin film.
Dehydrated using a dehydrator with suction power of ~10 mmHg,
The material was placed on a making roll and laminated to the target thickness of 6 mm, which was then cut with a cutter to obtain a green sheet. The raw sheet thus obtained is pressurized and dehydrated at a predetermined pressure before the calcined gypsum contained therein is hydrated, and the pressurized and dehydrated product is effectively dried to perform the method of the present invention. A gypsum board according to or a comparative example was obtained. In addition, as a comparative example, the same procedure was carried out except that gypsum dihydrate was not added or 50% by weight or more of gypsum was used. Various performance tests were conducted on the product gypsum board obtained as described above, and the results are shown in Table 2.

【table】

[Table] Note. * Kg/cm ²

[Table] Examples 10 to 18, Comparative Examples 7 to 12 The same raw materials as those used in Examples 1 to 9 were mixed in the proportions shown in Table 3 below, and 10% by weight of the mixture, that is, the solid content, was used. Add twice the amount of water to make a slurry, pour the slurry onto a slip paper, spread it to a uniform thickness, dehydrate it by suction, then press-form it at the pressure shown in the same table, and continue to harden and dry to obtain a gypsum board. Its bulk specific gravity and bending strength were measured. The results are shown in the same table.

【table】

[Table] Note: * Kg/cm ² , ** Kg/cm ²
Example 19 (Filterability of mixtures related to the present invention) Wood pulp (softwood) was filtered using a disc-type rear liner with Canadian Standard Freeness (CSF) values of 50, 200, and 400.
and 700c.c. 5g each of these four samples and 45g of calcined gypsum or calcined gypsum
Water was added to a mixture of 22.5 g of flue gas desulfurization gypsum and 22.5 g of flue gas desulfurization gypsum to adjust the total amount to 1, and the mixture was stirred to form a slurry. These slurries were measured individually at 45m of the CSF measuring device.
The water was poured onto the esh net, and the filtrate was collected for 30 seconds from the time it was poured. The volume of this filtered water was measured and shown in Table 5 below. Subsequently, the dry weight of the powder solid content in each filtrate was measured and shown in Table 6 as the amount of powder loss.

[Table] As is clear from Table 5, for the same CSF value, the amount of water filtered by the slurry mixed with dihydrate gypsum is significantly larger than that of the slurry mixed with calcined gypsum alone.

[Table] As is clear from Table 6, for the same CSF value, the amount of powder loss in the filtration water of the slurry mixed with gypsum dihydrate is significantly smaller than that of the slurry mixed with gypsum dihydrate.

Claims (1)

[Claims] 1. 50 to 95 parts by weight of hydrated gypsum and a fineness of 5000 cm ² /g
Powdered gypsum consisting of 5 to 50 parts by weight of the following dihydrate gypsum:
A mixture consisting of 0.5 to 30 parts by weight of fibers per 100 parts by weight, 0.1 to 2.0% by weight of a setting retarder to the hydrated gypsum, and water, in which the dihydrate gypsum is dissolved during disintegration of the fibers. A method for producing a noncombustible gypsum board by a paper-making method, characterized in that the mixture is molded and hardened and dried before the hydrated gypsum is hydrated. 2. The method according to claim 1, which uses asbestos fibers, cellulose fibers, or a combination thereof. 3. The method according to claim 1, wherein tartaric acid or a metal salt thereof is used as the setting retarder. 4. The method according to claim 1, wherein the pH of the mixture consisting of hydrated gypsum, dihydrate gypsum, fibers, setting retarder, and water is adjusted to 7 or higher. 5. The method according to claim 1, wherein the mixture being molded is pressure molded at a pressure of 10 to 500 kg/cm ² . 6. The method according to claim 1, wherein the raw sheet after papermaking is pressure-formed at a pressure of 10 to 500 kg/cm ² .