JP2836941B2 - Method for manufacturing gypsum sheet board - Google Patents

Description

The present invention relates to a novel method for producing a gypsum paperboard.

[Prior Art] Conventionally, a gypsum sheet is made of powdered hemihydrate gypsum (mainly β gypsum).
Hemihydrate gypsum), fibrous substance, setting regulator for hemihydrate gypsum and / or
Alternatively, water is added to the other additive materials and mixed to form a mixed slurry, and the slurry is formed into a solid by a mesh rotating drum into a film, and the obtained film is laminated and dewatered.
It is manufactured by pressing and drying.

[Problems to be Solved by the Invention] According to the above-mentioned conventional method, as a gypsum raw material, a powdery hemihydrate gypsum is used. Mold hemihydrate gypsum is not used.

When using β-type hemihydrate gypsum, the β-type hemihydrate gypsum is generally obtained by calcining in a gas phase at 120 ° C. to 170 ° C. in a kettle kiln, so gypsum dihydrate, type III or type II anhydrous gypsum can be used. Mixed,
The stability of the setting and curing speed is poor, and the strength is also negative. Therefore, in addition to the faster setting and hardening rate of β-type hemihydrate gypsum compared to α-type hemihydrate gypsum, a large amount of a curing regulator is required in the papermaking process to perform industrial continuous production in the papermaking process. And it is difficult to control the setting and hardening. As a result, the quality of the product is reduced, and the cost burden is large.

In addition, in the case of β-type hemihydrate gypsum, since its transitivity is poor, β-type hemihydrate gypsum, a fibrous material, a super-aid, a curing regulator and / or other additive materials are required to obtain a normal gypsum sheet. The slurry obtained by adding water to the mixture is made on a surface of a rotating drum to form a film of about 0.5 mm, and several sheets of the film are combined to obtain a product having a predetermined thickness. In this method, the productivity is inferior to that of a fourdrinier method in which the slurry is supplied onto a belt conveyor surface having a dewatering mechanism to obtain a product having a predetermined thickness in a single papermaking operation. Not suitable for manufacturing.

Once the α-type hemihydrate gypsum is used as a gypsum raw material in powder form, excess, dehydration,
The drying process requires a large amount of heat and electric energy, and at the same time, the quality of the gypsum sheet is reduced due to the formation of gypsum dihydrate, type III or type II anhydrous gypsum in these processes. Hateful.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the conventional method and to provide a completely new method for economically producing a high quality gypsum sheet board.

[Means for Solving the Problems] That is, the present invention provides: (a) a gelatinization step of converting gypsum dihydrate to α-type hemihydrate gypsum by a pressurized aqueous solution method to obtain an α-type hemihydrate gypsum slurry; A mixing step of preparing a mixed slurry by adding the α-type hemihydrate gypsum slurry obtained from the pregelatinization step and a fibrous material and, if desired, other admixtures; (c) forming a mixed slurry obtained from the mixing step Wherein the slurry circuit is a closed circuit, and the slurry temperature in the mixing step (b) and the papermaking step (c) is 85 ° C. or higher. The present invention relates to a method for producing a gypsum papermaking plate.

 Hereinafter, the present invention will be further described.

In the present invention, an α-type hemihydrate gypsum slurry (hereinafter referred to as a hot slurry) at about 100 ° C. obtained by a pressurized aqueous solution method of gypsum dihydrate, which is a starting material, is subjected to the next step without concentration or solid-liquid separation. And mixed with fibrous materials, other admixtures and water to form a mixed slurry, and adjusted its concentration to 85 ° C or higher to form a paper without using a curing regulator, and then pressurized. This is a method of forming and drying a gypsum sheet.

The present inventors have previously proposed an economical method for producing α-type hemihydrate gypsum for building materials in JP-A-64-61315 and JP-A-64-61316, and also for a method for producing a gypsum sheet. Although proposed in Japanese Patent Application Laid-Open No. 60-42267 and the like, the present invention has been achieved as a result of further study of these two production methods.

Specifically, by forming a closed liquid system in which the pressurized aqueous solution method, which is one form of the α-type hemihydrate gypsum production method, and the gypsum papermaking process are connected, the amount of heat in the α-formation process can be changed from the mixing process to the papermaking process. The slurry temperature up to 85 ° C. or more; under this temperature condition, succinic acid used in the pregelatinization step,
In combination with the hydration-inhibiting action of citric acid and their habit modifiers, there is almost no progress in hydration of the pregelatinized hemihydrate gypsum. In addition, these habit modifiers have only a weak hydration inhibiting effect in this temperature range, so that it is not necessary to use a curing regulator.

Fineness of the pregelatinized hemihydrate gypsum, the residence time in the reactor, the processing conditions at the time of α-type hemihydrate gypsum production such as temperature, or the brane specific surface area by wet pulverization of the generated pregelatinized hemihydrate gypsum 2500 ~ 4000cm ² / g to improve the entanglement with the fibrous material and the uniformity of pressure of the primary board to increase the strength of the product; the excess of the hot slurry is the α-type hemihydrate gypsum slurry at room temperature Alternatively, it is remarkably superior to β-type hemihydrate gypsum slurry at the same temperature, and has a good mixing property with the fibrous material, and a mixed slurry having good uniformity is obtained; Therefore, it is based on the knowledge that a gypsum sheet with a high bulk specific gravity (1.6 to 2.0) and a thick material can be easily obtained, and that efficient production can be performed by a fourdrinier method.

Table 1 shows the change over time of the slurry temperature and the compounded water of the content gypsum, and Table 2 shows the relationship between the slurry temperature and the transient property.

Test method: (1) Preparation of α-type hemihydrate gypsum slurry: flue gas desulfurization gypsum was fed into continuous reactor (27) (sodium succinate concentration = 0.01% by weight as habit modifier, slurry concentration = 35% by weight, (Reaction temperature = 142 ° C) Transformation into α-type hemihydrate gypsum to obtain a hot slurry at 95 ° C.

A predetermined amount of hot water at 61 ° C., 69 ° C., 82 ° C. and 95 ° C. was added to this hot slurry to prepare an α-type hemihydrate gypsum concentration of 10% at 62 ° C., 71 ° C., 87 ° C.
Approximately 500 g of a test slurry at 95 ° C. and 95 ° C. are obtained.

(2) Temperature maintenance and measurement of compound water: 60 ° C, 70 ° C, 85 ° C and 95 ° C while stirring this test slurry in a beaker.
, And about 20 g was withdrawn every predetermined time, and the combined water of the plaster was measured.

Compound water is measured according to JIS R 9101 “Chemical analysis method for gypsum”.

Test method: (1) Preparation of α-type hemihydrate gypsum: flue gas desulfurization gypsum in continuous reactor (27) (Sodium succinate concentration = 0.01% by weight as habit modifier, slurry concentration = 30% by weight, reaction Temperature = 14
(2 ° C.) Transferred to α-type hemihydrate gypsum, dried and pulverized to obtain α-type hemihydrate gypsum powder having a Blaine specific surface area of 3020 cm ² / g.

(2) Preparation of β-type hemihydrate gypsum: flue gas desulfurization gypsum was calcined in a batch type kettle test kettle (30) (temperature = 130 ° C., time = 60).
) And pulverized to obtain a β-type hemihydrate gypsum powder having a Blaine specific surface area of 3300 cm ² / g.

(3) 100 g of each hemihydrate gypsum powder with 200 g of warm water at 30 ° C and 90 ° C
Stir for 30 seconds to obtain a slurry.

(4) The slurry was poured into a Buchner funnel (120 mmφ), and the mixture was evacuated and vacuumed (degree of vacuum = 300 mmHg).

(5) The excess time was defined as the time (visual observation) from when the slurry was begun to when the surface of the cake that had been removed became dry.

(6) The moisture (%) attached to the cake was calculated as follows by drying the overcake at 45 ° C.

Moisture adhering to cake (%) = (weight before drying−weight after drying) × 100 / (weight after drying) The results in Tables 1 and 2 above show that the transient properties differ significantly depending on the slurry temperature, and that Hot slurries show little progress in hydration. Also, the third
The table shows the relationship between fineness and strength.

Test method: JIS R 9112 "Physical test method for gypsum for ceramic shape material"
According to. However, the kneading water amount (water / gypsum) was set to 75%.

The results in Table 3 indicate that the strength is low when the Blaine specific surface area is 2500 cm ² / g or less.

[Function] In the present invention, since the wet method is consistent from the production of hemihydrate gypsum to the papermaking process, gypsum dihydrate is not accompanied by the vaporization and evaporation of the liberated water produced by the transition to hemihydrate gypsum. Compared to the case of using β-type hemihydrate gypsum, only a low calorie is required, and in the α-formation process for producing α-type hemihydrate gypsum,
Since no excess and dehydration steps are required, the amount of capital investment and power costs in running can be halved. This lowers the cost of α-type hemihydrate gypsum and makes α-type hemihydrate gypsum substantially usable as a raw material for a gypsum sheet.

In the present invention, since the α-type hemihydrate gypsum is not once powdered as described above, there is no formation of gypsum dihydrate, type III or type II anhydrous gypsum, and therefore, the setting and curing rate in the process from mixing to papermaking is reduced. It is stable and easy to control, and there is no deterioration in product quality.

In the present invention, since the mixing and papermaking are performed at a temperature of 85 ° C. or more, a curing regulator is not required. Therefore, the quality of the product is not degraded by the curing regulator, and the production cost is small.

In the present invention, the slurry for papermaking is remarkably excellent in permeability, so that dehydration is sufficiently performed in the vacuum-passing step, so that a general gypsum-made board can be easily manufactured (1.3 to 1.6 g / cm ³ ) and has a flexural strength (100 to 100 g / cm ³ ). 200kg / cm ² ) product can be obtained without pressurizing process,
By applying a normal pressure (10 to 500 kg / cm ² ), a high density and high strength gypsum paperboard can be obtained.
Furthermore, since thick papermaking can be performed at one time, production can be performed by the fourdrinier papermaking method, and at the same time, more efficient production can be performed in the circular net papermaking method than in the conventional method. The fourdrinier method is suitable for the production of thick products, and the thickness is 15 mm.
It is possible to manufacture a gypsum-made sheet to a certain degree, and therefore it is possible to obtain a product free of delamination, which is a disadvantage of the net-type papermaking method in terms of quality.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the process chart of FIG. 1, but it should be understood that the present invention is not limited to this.

Gypsum dihydrate is supplied from the line (21), a habit modifier is supplied from the line (22), and a circulating liquid is supplied from the line (23) to the raw gypsum slurry tank (1). The raw material slurry is supplied to the reactor (2) via the line (24), and has a solid content of 20 to 160 ° C.
Pressurized hydrothermal treatment is performed under the conditions of 50% and a habit modifier concentration of 0.005 to 0.05% to obtain an α-type hemihydrate gypsum slurry (hereinafter, referred to as a hot slurry). The heating is performed by steam from the line (35).

Here, the dihydrate gypsum is a chemical gypsum such as natural gypsum or by-product gypsum from a flue gas desulfurization device. Succinic acid as a habit modifier
Citric acid or salts thereof are used, but succinic acid and salts thereof are preferred because the control of the habit crystal effect is easy.

As a method for producing α-type hemihydrate gypsum by the pressurized aqueous solution method, a batch method in which the raw material slurry is mixed under pressure in an autoclave and subjected to hydrothermal treatment, or the raw material slurry is continuously fed from one end of the autoclave and discharged from the other end Is a continuous method in which the hydrothermal treatment is performed, and the production method proposed by the present inventors (JP-A-64-61315: a continuous production method of α-type hemihydrate gypsum, JP-A-64-61316) Gazette: α-type hemihydrate gypsum and a process for producing the same are economical, and an active α-type hemihydrate gypsum slurry can be stably obtained, which is also preferable in terms of quality.

This hot slurry is led to the flash tank (3) via the line (25), decompressed to atmospheric pressure, and
Is supplied to the dynamic mill (4) and pulverized.
The pulverized hot slurry is supplied to a papermaking slurry adjusting tank (5) via a line (27). The flash steam from the flash tank (3) is returned to the raw gypsum slurry tank (1) via the line (33) and used for heating and raising the temperature of the raw material.

Here, as the fineness of the α-type hemihydrate gypsum, the Blaine specific surface area = 2500 from the pressure uniformity of the primary board, the hydration reactivity and the like.
Preferably it is 40004000 cm ² / g.

Hot slurry from line (27), waste paper pulp from line (28), fibrous material such as glass fiber and auxiliary material and other additives and replenishing water from line (29), line (30)
Is mixed in the papermaking slurry preparation tank (5).

The temperature of the papermaking slurry preparation tank (5) is controlled to a constant slurry temperature of 85 ° C. or more by a temperature controller (6). It is necessary to control this temperature to 85 ° C. or higher, including in the papermaking process, in order to prevent the progress of hydration of the gypsum slurry.

The raw material mixing ratio in the papermaking slurry preparation tank (5) is 1 to 40% by weight of a fibrous material to 100% by weight of α-type hemihydrate gypsum,
Other additives are 10% by weight or less, and solid content / moisture (weight ratio) is 0.02 to 0.2.

The prepared papermaking slurry flows from the slurry distributor (9) through a line (31) to the upper surface of an endless belt conveyor (8) having a decompression filter (10).
It is dehydrated while moving on the top, and the undelivered moisture is about 20% by weight.
Next board. At this time, the primary board is air-cooled, and the temperature rapidly drops to 30 to 60 ° C., which is an environmental temperature at which hydration (dihydration) of α-type hemihydrate gypsum proceeds.

The primary board is cut by a cutter (11) of a predetermined size through a line (34) installed on the same plane as the endless belt conveyor, transferred to a pressurizer (12), and pressurized at a pressure of 10 to 500 kg / cm ^2. To get a secondary board. The secondary board is dried by a dryer (13) to form a gypsum sheet. The liquid dehydrated by the vacuum filter (10) and the pressurizer (12) is collected in the liquid tank (7) via the line (32), and is circulated and used as water for preparing a raw gypsum slurry and a papermaking slurry.

Here, the slurry distributor (9) is 1 depending on the thickness of the product.
Set up 5 to 5 formulas. The orientation of the fibrous material is changed by adjusting the relative angle between the flow direction of the papermaking slurry discharged from the slurry distributor (9) and the moving direction of the endless belt conveyor (8) to control the length / width ratio of the product strength. Although possible, they are generally set in parallel in the same direction.

Next, an example of the production of a gypsum sheet made by the apparatus shown in FIG. 1 will be described.

First, fuming desulfurization gypsum was transferred to α-type hemihydrate gypsum in a continuous reactor (27) (sodium succinate concentration = 0.01% by weight as a habit modifier, slurry concentration = 30% by weight, reaction temperature = 142 ° C). By wet pulverization, an α-type hemihydrate gypsum slurry at 97 ° C was obtained. On the other hand, an additive slurry at 88 ° C. comprising 7, 10, 13 and 1000 parts by weight of pulp fiber, wollastonite powder, calcium carbonate powder and warm water respectively was obtained.

This α-type hemihydrate gypsum slurry 1020 g and additive slurry 412
A slurry (solid content / moisture weight ratio = 0.09) was obtained by kneading 0 g, and the slurry was poured into a vacuum filter having an excess area of 180 mmφ, and was filtered at a degree of vacuum of 300 mmHg to obtain a primary board. This primary board is press-formed with a pressing force of 30 kg / cm ² ,
After being cured at room temperature for 24 hours, it was dried in a bubble drier at 45 ° C. and subjected to a strength test. The results are shown in Table 4. In addition, the Blaine specific surface area of the α-type hemihydrate gypsum was 3120 cm ² / g.

The bending strength test is based on JIS A 5403.

The dimensional change rate test is based on JIS A 5418.

[Brief description of the drawings]

FIG. 1 is a process chart of a gypsum papermaking board according to one embodiment of the present invention. In the figure, 1 ... raw gypsum slurry tank, 2 ...
Reactor, 3 ... Flash tank, 4 ... Dynamic mill, 5 ... Papermaking slurry preparation tank, 6 ... Temperature controller, 7 ... Liquid tank, 8 ... Endless belt conveyor, 9
… Slurry distributor, 10… Decompressor, 11… Cutter, 12… Pressurizer, 13… Dryer, 21-35… Line.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shigeo Watanabe 4-13-1 Tokodai, Ishioka City, Ibaraki Prefecture (72) Inventor Noriaki Koga 4-13-2, Tokodai, Ishioka City, Ibaraki Prefecture (58) Field surveyed ( Int.Cl. ⁶ , DB name) C04B 28/14 C04B 11/032

Claims (2)

(57) [Claims] (A) an α-form half-gypsum slurry obtained by transferring gypsum dihydrate to α-form hemihydrate gypsum by a pressurized aqueous solution method; A mixing step of preparing a mixed slurry by adding a water gypsum slurry, a fibrous material and, if desired, other admixtures; (c) a sheet forming step of forming the mixed slurry obtained from the mixing step to form a gypsum sheet. Wherein the slurry circuit is a closed circuit, and the slurry temperature in the mixing step (b) and the papermaking step (c) is 85 ° C. or higher. 2. In the pregelatinization step (a), one or more selected from succinic acid, citric acid and salts thereof in a concentration of 0.005 to 0.05% of the reaction solution are used as a habit modifier. Item 4. The method for producing a gypsum sheet according to Item 1.