WO2011052048A1 - Gypsum board - Google Patents

Abstract

Provided is a gypsum board which can sufficiently suppress bending, even when produced using a starting gypsum material that contains a large amount of water-soluble salts as impurities. Further, the gypsum board is unproblematic in compressive strength, hardening time, pH, and so on. A gypsum board produced by filling a gypsum-containing slurry into a frame mold and hardening the slurry, wherein the slurry contains both calcined gypsum and 0.2 to 5.0 parts by mass of a cement per 100 parts by mass of the calcined gypsum.

Description

Plasterboard

The present invention relates to a gypsum board. More specifically, even when gypsum having a high content of water-soluble salts corresponding to impurities is used for preparing a slurry to be cured, the occurrence of bending can be sufficiently prevented. Related to gypsum board.

Conventionally, a gypsum board is generally loaded with a gypsum-containing slurry between a lower base paper that also serves as a formwork and an upper back base paper, and is continuously conveyed in this state while the slurry is cured and hardened in the meantime. Manufactured by cutting the body. The gypsum-containing slurry is prepared by mixing various admixtures, chemicals, and required amounts of water in addition to calcined gypsum (half-water gypsum) obtained by firing raw gypsum. In addition to natural gypsum, various chemical gypsum, such as phosphate gypsum, flue gas desulfurization gypsum, titanium gypsum (gypsum produced as a by-product in the production of titanium oxide), hydrofluoric acid gypsum (produced as a by-product in the production of hydrofluoric acid) Used), salt gypsum, refined gypsum and the like. However, the gypsum board produced by such a conventional production method has a problem that when it absorbs moisture and the water content becomes high, the gypsum board tends to bend, and among them, the content of water-soluble salts corresponding to impurities is high as a raw material gypsum. There is a problem that the resulting gypsum board is greatly bent.

As a gypsum board that prevents the occurrence of bending, an example in which a crystal modifier such as copper sulfate is used in combination in a slurry to be cured (for example, see Patent Document 1), and an example in which an aggregated phosphate is used in combination (for example, Patent Document) 2) is known. However, the conventional example such as Patent Document 1 has a problem that the occurrence of bending cannot be sufficiently prevented, and the conventional example such as Patent Document 2 is expensive and causes environmental pollution. There is a problem that there is also a fear of becoming.

Another example of a gypsum board imparted with fire resistance and water resistance is also known in which cement is used in combination with a slurry to be cured (for example, see Patent Document 3). A conventional example such as Patent Document 3 uses a large amount of cement, specifically about 20 to 40% cement, together with gypsum. However, this conventional example has a problem that the strength of the gypsum board obtained, for example, the compressive strength is low, the slurry takes a long time to cure, and the pH is extremely high.

International Publication No. 2007/110428 JP-T-2001-50495 JP 61-83664 A

The problem to be solved by the present invention is that even when gypsum having a high content of water-soluble salts corresponding to impurities is used as a raw material, the occurrence of bending can be sufficiently prevented, and the compressive strength can be prevented. The present invention provides a gypsum board that does not cause problems in curing time, pH, and the like.

The present invention which solves the above-mentioned problems is a gypsum board in which a mold is charged with a gypsum-containing slurry and cured, and 0.2 to 5.0 parts by mass of cement per 100 parts by mass of calcined gypsum obtained by firing gypsum. The gypsum board is obtained by curing a slurry used at a ratio of

The gypsum board according to the present invention uses 0.2 to 5.0 parts by mass of cement per 100 parts by mass of calcined gypsum (semihydrate gypsum) obtained by firing gypsum, and requires various admixtures and chemicals. The slurry is prepared by mixing them with water as appropriate, and the slurry is loaded between a form frame, for example, a front base paper also serving as a mold and a back base paper, and cured.

In the gypsum board according to the present invention, as the gypsum, in addition to natural gypsum, various chemical gypsum, such as phosphate gypsum, flue gas desulfurization gypsum, titanium gypsum, hydrofluoric gypsum, salt gypsum, refined gypsum, etc. Can do. The content (concentration) of water-soluble salts corresponding to the impurities in the gypsum used for preparing the slurry varies depending on the type and amount of chemical gypsum used and the properties at that time. In addition to various Portland cements, blast furnace cement, fly ash cement, silica cement, alumina cement, and the like can be used as the cement. Portland cement is preferable, and ordinary Portland cement is more preferable. Furthermore, pulp, glass fiber, vermiculite and the like can be appropriately used as the admixture, and curing accelerators, curing retarders, water reducing agents and the like can be appropriately used as the chemicals.

The gypsum board according to the present invention, as described above, is obtained by curing a slurry using 0.2 to 5.0 parts by mass of cement per 100 parts by mass of calcined gypsum obtained by firing gypsum, It is characterized in that the amount of cement used for calcined gypsum is significantly lower than conventional gypsum boards that use cement for the preparation of the slurry. The reason is that if the use ratio of cement is less than 0.2 parts by mass per 100 parts by mass of calcined gypsum, it will not be possible to sufficiently prevent the resulting gypsum board from being bent. Further, when the proportion of the cement used exceeds 5.0 parts by mass, the compressive strength of the resulting gypsum board decreases, the time required for curing increases, and the pH increases remarkably.

In gypsum board made by hardening slurry using cement together with calcined gypsum, the compressive strength is higher than when cement is not used, and the time required for hardening is relatively short, and the pH is also kept to a level where there is no problem. In this case, it is necessary to use a slurry to be hardened in a proportion of 0.2 to 5.0 parts by mass of cement per 100 parts by mass of calcined gypsum, preferably 0.3 to 2.0 parts by mass of cement. The cement is used at a ratio of 0.5 to 1.0 parts by mass, more preferably at a ratio of 0.5 parts by weight.

The gypsum board according to the present invention can sufficiently prevent the occurrence of bending as compared with the conventional gypsum board as described above, and does not cause problems in compressive strength, curing time, pH and the like. In addition, there is an effect that it is possible to prevent the surface base paper and the back surface base paper from being easily peeled off due to moisture absorption. The manifestation of this effect is significant when the calcined gypsum used for the preparation of the slurry is a calcined gypsum having a high content of water-soluble salts corresponding to impurities. When the content of water-soluble salts corresponding to impurities in the raw material gypsum increases mainly due to the type and amount of the chemical gypsum as described above used as the raw material gypsum and the properties at that time, A slurry is prepared using calcined gypsum baked, and the hardened gypsum board is easy to bend, especially when it is used under high humidity due to moisture absorption. Even if it exists, according to this invention which uses a predetermined amount of cement together, generation | occurrence | production of such a bending can fully be prevented.

Specifically, the expression of the effect of the present invention as described above is that calcined gypsum used for the preparation of the slurry has a total content of water-soluble potassium salt, sodium salt and magnesium salt of those oxides (K ₂ O, Na ₂ O and MgO) in terms of 500 g / kg or more of gypsum, for example 500 to 2500 mg / kg of gypsum, which is remarkable when used as a raw material, and in particular, the total content of water-soluble potassium, sodium and magnesium salts Is particularly prominent when the oxide is 600 mg / kg or more in terms of oxides, for example, 600 to 2500 mg / kg.

According to the present invention, even when gypsum having a high content of water-soluble salts corresponding to impurities is used as a raw material, it is possible to sufficiently prevent the resulting gypsum board from being bent, and There is no problem in compressive strength, curing time and pH.

In the Example etc. of this invention, the graph which illustrates the relationship between the addition amount of normal Portland cement, and the compressive strength of the hardened | cured material obtained. The graph which illustrates the relationship between the water-soluble salt content in the gypsum used as a raw material, and the bending of the test piece cut out from the gypsum board obtained in the Example of this invention.

Hereinafter, in order to clarify the configuration and effects of the present invention, examples and comparative examples will be described, but the present invention is not limited to these examples.

Test category 1
Comparative Example 1
A flue gas desulfurization gypsum having a total content of water-soluble potassium salt, sodium salt and magnesium salt in terms of oxides of 632 mg / kg (hereinafter simply referred to as water-soluble salt content 632 mg / kg) is calcined, and calcined gypsum (Hemihydrate gypsum). A slurry was prepared by mixing 200 parts by mass of this calcined gypsum with 170 parts by mass of water. This slurry was loaded into a mold and cured, then demolded and dried at 40 ° C. until a constant weight was obtained to obtain a 12.5 mm × 900 mm × 1820 mm gypsum board. A test piece of 12.5 mm x 150 mm x 650 mm was cut out from this gypsum board, and this test piece was supported at two points with a span of 600 mm under the condition of 40 ° C x 90% RH. The bending at the center of the span was measured with a measuring instrument (a Digimatic indicator, trade name, manufactured by Mitutoyo Corporation). The results are summarized in Table 1.

Comparative Examples 2-4
Instead of 170 parts by mass of water, a slurry was prepared in the same manner as in Comparative Example 1 except that 170 parts by mass of an aqueous solution in which copper sulfate pentahydrate was added in the amount shown in Table 1 was used. After obtaining the gypsum board, the test piece was cut out and the deflection was measured. The results are summarized in Table 1.

Comparative Examples 5-7
In place of 170 parts by mass of water, a slurry was prepared in the same manner as in Comparative Example 1 except that 170 parts by mass of an aqueous solution in which an amount of sodium trimetaphosphate as shown in Table 1 was added was used. After obtaining, the test piece was cut out and the deflection was measured. The results are summarized in Table 1.

Comparative Examples 8-11 and Examples 1-7
In place of 200 parts by mass of calcined gypsum, a slurry was prepared in the same manner as in Comparative Example 1 except that 200 parts by mass of calcined gypsum mixed with ordinary Portland cement in the amount shown in Table 1 was used. After obtaining the gypsum board, the test piece was cut out and the deflection was measured. The results are summarized in Table 1.

In Table 1,
Addition amount: parts by mass of additive per 100 parts by mass of calcined gypsum

As is apparent from the results in Table 1, copper sulfate pentahydrate cannot sufficiently prevent the occurrence of bending. Although sodium trimetaphosphate can sufficiently prevent the occurrence of bending, it is expensive as described above, and there is a risk of causing environmental pollution. On the other hand, in Examples and the like using 0.2 parts by mass or more, preferably 0.3 parts by mass or more of ordinary Portland cement per 100 parts by mass of calcined gypsum, as in the case of using sodium trimetaphosphate, the occurrence of bending is caused. This can be sufficiently prevented, and the problem as in the case of using sodium trimetaphosphate does not occur.

Test category 2
Comparative Example 12
A flue gas desulfurization gypsum having a water-soluble salt content of 632 mg / kg was calcined to obtain calcined gypsum (half water gypsum). A slurry was prepared by mixing 375 g of water with 500 g of this calcined gypsum. This slurry was loaded into a 50 mm × 50 mm × 50 mm mold and cured, then demolded and dried at 40 ° C. until a constant weight was obtained, to obtain a cured product. The cured body was subjected to autograph (manufactured by Shimadzu Corporation, trade name, model number AG-10TE), loaded at a load speed of 1 mm / min, and the load value when the cured body was buckled was determined as the compressive strength (N / mm ² ). The results are shown in Table 2 and FIG.

Examples 8 to 14 and Comparative Examples 13 to 15
In place of 500 g of calcined gypsum, a slurry was prepared in the same manner as in Comparative Example 12 except that 500 g of calcined gypsum mixed with ordinary Portland cement in an amount corresponding to the addition amount shown in Table 1 was used. After obtaining, the compressive strength was measured. The results are shown in Table 2 and FIG.

In Table 2,
Amount of addition: part by weight of ordinary Portland cement per 100 parts by weight of calcined gypsum

As is apparent from the results in Table 2 and FIG. 1, the case where the addition of ordinary Portland cement per 100 parts by mass of calcined gypsum is in the range of 0.20 to 5.0 and no ordinary Portland cement is added (comparative example) Compared with 12), the compressive strength is about the same or higher, but if the added mass part of ordinary Portland cement is larger than that, for example, 10.0 or more, the compressive strength does not add ordinary Portland cement. It becomes lower than the case (Comparative Example 12). Also in terms of compressive strength, the added part by mass of ordinary Portland cement per 100 parts by mass of calcined gypsum is preferably 0.3 to 2.0.

Test category 3
Comparative Example 16
A flue gas desulfurization gypsum having a water-soluble salt content of 632 mg / kg was calcined to obtain calcined gypsum (half water gypsum). A slurry was prepared using this calcined gypsum, and the curing time (the amount of completion) was measured using this slurry in accordance with JIS-R9112. Further, the pH of the obtained cured product was measured according to JIS-R9101. The results are summarized in Table 3.

Example 15 and Comparative Examples 17-19
Instead of calcined gypsum, a slurry was prepared in the same manner as in Comparative Example 16 except that a mixture of calcined gypsum mixed with ordinary Portland cement in an amount corresponding to the addition amount shown in Table 1 was used to obtain a cured product. The curing time (minute of completion) and pH were measured. The results are summarized in Table 3.

In Table 3,
Amount of addition: part by weight of ordinary Portland cement per 100 parts by weight of calcined gypsum

As is clear from the results in Table 3, when the added mass part of ordinary Portland cement per 100 parts by mass of calcined gypsum is 20-30, it is harder than when no ordinary Portland cement is added (Comparative Example 16). Time increases and pH increases significantly.

Test category 4
Comparative Example 20
A mixture of natural gypsum having a water-soluble salt content of 227 mg / kg and flue gas desulfurization gypsum was calcined to obtain calcined gypsum (half water gypsum). Using this calcined gypsum, a slurry was prepared and a gypsum board was obtained in the same manner as in Comparative Example 1 of Test Category 1 below, and then a test piece was cut out and the deflection after 48 hours was measured. The results are shown in Table 4 and FIG.

Comparative Examples 21-31
The source (kind) and mixing ratio of the flue gas desulfurization gypsum were changed, and the gypsum having the water-soluble salt content shown in Table 4 was baked to obtain calcined gypsum (half-water gypsum). Using these calcined gypsum, a slurry was prepared and a gypsum board was obtained in the same manner as in Comparative Example 20 below. Then, a test piece was cut out and the deflection after 48 hours was measured. The results are summarized in Table 4 and FIG.

Example 16
Instead of calcined gypsum, a slurry was prepared and a gypsum board was obtained in the same manner as in Comparative Example 27 except that a mixture of ordinary Portland cements in the amount shown in Table 4 was used. A piece was cut out and the deflection after 48 hours was measured. The results are shown in Table 4 and FIG.

Example 17
Instead of calcined gypsum, a slurry was prepared and a gypsum board was obtained in the same manner as in Comparative Example 30, except that a mixture of ordinary Portland cements in the amount shown in Table 4 was used. A piece was cut out and the deflection after 48 hours was measured. The results are shown in Table 4 and FIG.

Example 18
Instead of calcined gypsum, a slurry was prepared and a gypsum board was obtained in the same manner as in Comparative Example 31 except that a mixture of ordinary Portland cements in the amounts shown in Table 4 was used. A piece was cut out and the deflection after 48 hours was measured. The results are shown in Table 4 and FIG.

As is clear from the results of Table 4 and FIG. 2, when the content of soluble salts in the gypsum used as a raw material increases, the occurrence of bending increases, particularly when the content of soluble salts is 500 mg / kg or more. According to the present invention, even when such a gypsum having a high content of soluble salts is used as a raw material, the occurrence of bending can be sufficiently prevented.

Claims (4)

In a gypsum board formed by loading a gypsum-containing slurry into a mold and curing, the slurry using 0.2 to 5.0 parts by mass of cement per 100 parts by mass of calcined gypsum obtained by calcining gypsum was cured. Gypsum board characterized by comprising. The gypsum board according to claim 1, wherein the slurry is a mixture of 0.3 to 2.0 parts by mass of cement per 100 parts by mass of calcined gypsum. The gypsum board according to claim 1 or 2, wherein the gypsum has a total content of water-soluble potassium salt, sodium salt and magnesium salt of 500 mg / kg or more in terms of oxides. The gypsum board according to any one of claims 1 to 3, wherein the cement is ordinary Portland cement.

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