JPH0825784B2 - Method for producing anhydrous gypsum papermaking board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to a method for producing a fiber-reinforced anhydrous gypsum papermaking plate (hereinafter referred to as gypsum board), and particularly to type II anhydrous gypsum,
The present invention relates to a method for producing an anhydrous gypsum papermaking board, characterized in that a slurry containing staple fibers and a gypsum hardening accelerator as main components is formed by papermaking and cooled and cured within 48 hours immediately after boardmaking.

b. Conventional Technology Conventionally, as a raw material for gypsum boards manufactured by a papermaking method, for example, Japanese Patent Publication No. 25-25339 and Japanese Patent Publication No. 57-49004.
Hemihydrate gypsum was used as disclosed in Japanese Patent Publication No. 55-36628, Japanese Patent Publication No. 60-42267, Japanese Patent Publication No. 60-17126, and the like. The hydration rate of this hemihydrate gypsum is rapid, and when no set retarder is used,
The hydration hardening is almost completed in about 30 minutes.

In the papermaking process, the raw material hemihydrate gypsum partially flows out and circulates during the process, and the recovered raw materials such as raw boards, product cutting silos, and defective products are converted into dihydrate gypsum over time and become raw materials. Mixed in. Gypsum acts as a quick-setting agent for hemihydrate gypsum, and increases in a self-propagating manner even with the addition of a set retarder. Thus, it was difficult to determine the amount of setting retarder and to control the setting time due to the indeterminate amount of gypsum dihydrate entering sequentially from the circulation system and the recovery system.

Some improvements have been made to these drawbacks,
All of them were not sufficient and the process control was difficult, and as a result, the quality was adversely affected.

In the past, there were almost no examples in which anhydrous gypsum was industrially paper-made and mass-produced.

c. Problems to be solved by the invention Anhydrous gypsum has a slow hydration rate, which is contrary to hemihydrate gypsum,
Even if the curing accelerator is added, the desired strength cannot be obtained until about 3 to 4 weeks have passed, and by adding a large amount of the curing accelerator, the hydration rate can be increased to some extent. The filterability of the product becomes worse, and new adverse effects such as an increase in the rate of length change in the product and the appearance of a white flower phenomenon occur.

Further, the properties of the anhydrous gypsum cured product varied greatly, and it was difficult to obtain a product of constant quality.

Therefore, the present inventors have examined the following problems in the method of manufacturing a gypsum board.

(1) When type II anhydrous gypsum is used, the product varies greatly by day, month and season. What should be done to obtain a certain quality?

(2) Type II anhydrous gypsum had a slow hydration rate and required long-term curing. What should be done to develop strength early and improve productivity as an industrial product?

(3) A hardening accelerator is used for improving the hydration rate of type II anhydrous gypsum, but on the contrary, it causes deterioration of filterability and deterioration of quality such as length change rate and white sinter. Therefore, is it possible to reduce the amount of curing accelerator added?

(4) Type II anhydrous gypsum has low bending strength, peeling strength, etc., but what should be done to improve overall quality?

d. Means for solving the problems In view of the above problems, the present inventor has conducted diligent research on improvement of production and quality, and as a result, type II anhydrous gypsum was used as a matrix, which was reinforced with short fibers to produce paper. However, the present invention has been completed based on the finding that a new gypsum plate that has never existed can be obtained by performing cooling curing immediately after the plate making from the initial stage.

That is, the present invention is a type II anhydrous gypsum 98-60% by weight, short fibers 2-40% by weight, and a slurry containing the gypsum hardening accelerator as the main component is paper-formed, and the temperature is 0 to 0 within 48 hours immediately after plate making. The present invention provides a method for producing an anhydrous gypsum papermaking board which is cooled and cured at 27 ° C and a humidity of 50 to 100%.

In the gypsum board of the present invention, the gypsum hardening accelerator is added to the type II anhydrous gypsum in an amount of 0.1 to 2.5% by weight, and II
The inorganic powder can be added in an amount of 1 to 100 parts by weight based on 100 parts by weight of the total amount of the anhydrous gypsum and short fibers.

 The manufacturing process in the present invention is as follows.

Water is added to the raw material in an amount of 3 to 15 times and stirred with a pulper to form a slurry, and the stirred product is homogenized in a chest, and the slurry is formed into a sheet by a cylinder or Fourdrinier machine. After partly cutting the end portion of this sheet and performing pressure molding, cooling curing is performed within 48 hours immediately after plate making to hydrate and cure. After curing, the sheet is dried if necessary, and cut into standard dimensions to obtain a product.

In the present invention, the cooling curing is performed by shortening the time from the plate-making to the start of cooling curing. This cooling cure has a temperature of 0
〜27 ℃, relative humidity 50〜100% immediately after plate making within 48 hours, and then continue under the same cooling and curing conditions for a total of 1 to 15 days. . Therefore, the term “promptly from the initial stage” or “promptly from the initial stage” described below means “within 48 hours immediately after plate making” in the present specification.

By cooling and curing the gypsum board within 48 hours immediately after the plate making, it becomes possible to obtain a high quality gypsum that has a high hydration rate and does not fluctuate depending on the production period.

Here, the cooling temperature was set to 0 to 27 ° C immediately after the plate making.
This is because if free sheet water freezes due to cooling within 48 hours, hydration is hindered and it does not harden, so it is necessary to maintain a temperature of 0 ° C or higher to prevent freezing of the water, and 27 ° C. When the temperature exceeds 40 hours or more,
Since the hydration of the gypsum plate progresses extremely slowly, the tissue of the hardened body is composed loosely, and even if cooling curing is performed thereafter, the hydration will proceed, but with the expansion of the hardened body, the tissue loosens and the strength is improved. This is because we cannot expect it. Therefore, it is necessary to carry out cooling curing at a temperature of 0 to 27 ° C. within 48 hours immediately after plate making to enhance the hydration rate and to form the skeleton of the tissue in the initial stage. Note that hydration of gypsum is accompanied by an exothermic reaction, so it is necessary to actively remove heat.

The relative humidity is in the range of 50 to 100%. This is 50
%, The thickness of the plate material is as thin as 4 to 15 mm.
This is because drying progresses on the surface or at the ends of the four circumferences, and an uncured dry-out state occurs, making it impossible to obtain a homogeneous material.

The cooling curing conditions (temperature and humidity) following the cooling curing performed immediately after plate making within 48 hours are the same as the cooling curing conditions performed within 48 hours immediately after plate production. The total number of cooling days is selected in relation to the cooling temperature. If the temperature is low, the curing will be completed in a short period of time, but if the curing days are less than 1 day, the required properties cannot be obtained. When the temperature is steel to some extent, hydration proceeds if it is aged for a long time, but the rate of improvement in strength is small. From the viewpoint of product properties and industrial production, the total curing period is about 15 days. In the range of cooling curing temperature, the rate of quality improvement is small even after curing for 15 days or more (it may be cured or stocked for 15 days or more).

The water temperature of the kneading water at the time of papermaking is about 15 to 38 ° C, preferably 20 to 35 ° C from the viewpoint of production efficiency. When the water temperature is 15 ° C or lower, the production efficiency decreases. Further, when the temperature is 38 ° C. or higher, the effect of improving the manufacturing efficiency is small, and the effect of cooling curing performed within 48 hours immediately after the plate making in the subsequent step is deteriorated. The pH of water is 7
That is all.

Papermaking is made by a plurality of rotating drums formed by a net, and a cylinder papermaking machine that stacks it to a predetermined thickness with a making roll, or a Fourdrinier papermaking machine that is made up on an endless belt having a dehydration mechanism. Done by

The green sheet after papermaking is pressure-molded. The pressure of the pressure molding is selected in the range of 7 to 90% in terms of raw material composition and product strength design and the water content of the green sheet (referred to as the water content of the green plate). The molding pressure is 1 to 400 kg / cm ² .

Pressurization is performed by a rope press or a surface press. The pressurizing means also includes pressurizing with a making roll at the time of stacking the sheets in the cylinder manufacturing.

 Details of the raw materials in the present invention are as follows.

Type II anhydrous gypsum is natural dihydrate gypsum, or phosphoric acid,
A general-purpose material such as a calcined product of dihydrate gypsum, which is a by-product of titanium, exhaustion, etc., or a type II anhydrous gypsum, which is a by-product of hydrofluoric acid production, is used. The type II anhydrous gypsum has a Blaine value of about 2000 to 9000 cm ² / g. This is a range selected from the aspects of filterability and hydration reactivity during papermaking.

The amount of type II anhydrous gypsum is 98-60% by weight. This amount is defined in relation to 2 to 40% by weight of short fibers. Fiber amount 2%
In the following, the solid content will flow out through the wire mesh during papermaking, and papermaking will be impossible. Further, if the fiber amount exceeds 40%, a fibrous plate is formed, and the product strength and the adhesion between layers are deteriorated, and it cannot be used as a gypsum plate.

As the amount of short fibers, pulp (cellulose), natural fibers such as asbestos, glass fibers, carbon fibers, inorganic fibers such as glass wool, rock wool and ceramic wool, and polyamide, polypropylene, polyvinyl alcohol (vinylon), polyester, polyethylene , Synthetic fibers such as acrylic, etc. are used, and can be arbitrarily selected from the aspects of paper-making property, water content of green board and product properties.

In the above short fibers, the amount of pulp is 1% by weight or more, preferably 2 to 10% by weight. If the pulp content is 1% by weight or less,
The dispersion and yield of raw materials during papermaking are poor, making manufacturing extremely difficult. On the other hand, if it exceeds 10% by weight, the pulp is not well dispersed at the time of papermaking and it is difficult to obtain the homogeneity of the material, and the nonflammability as a building material cannot be obtained.

The pulp is beaten if necessary. The beating degree is 800 to 30 ml according to Canadian standard freeness (CSF), and it varies depending on the blending amount and the combination of fibers. Beater is pulper,
Use a general-purpose machine such as a disc refiner or cone type refiner.

As a hardening accelerator for type II anhydrous gypsum, H ₂ SO ₄ , K ₂ SO ₄ ,
(NH ₄ ) ₂ SO ₄ , Na ₂ SO ₄ , MgSO ₄ , ZnSO ₄ , FeSO ₄ , CuSO ₄ , Al ₂ (SO
₄ ) Sulfates and double salts such as ₃ , eg KAl (SO ₄ ) ₂・ 12H
Alums such as ₂ O, NaAl (SO ₄ ) ₂・ 12H ₂ O, NH ₄ Al (SO ₄ ) ₂・ 12H ₂ O, chlorides such as NaCl, CaCl ₂ , MgCl ₂ , NaHSO ₄ , K
Commonly used oxyhydrogen salts such as HSO ₄ and nitrates such as NaNO ₃ , NH ₄ NO ₃ , and KNO ₃ are used alone or in combination.

The amount of the curing accelerator is the amount retained in the plate material, and is 0.1 to 2.5% by weight based on the type II anhydrous gypsum. This amount is .1
If it is less than 4%, the hydration rate does not reach a predetermined level even after cooling and curing for 4 weeks or more, and properties such as bending strength are extremely low, and a plate material for practical use cannot be obtained. Even if added in excess of 2.5%, the effect of quality improvement is small, the filterability is poor at the time of papermaking, the rate of change in length of the plate material increases, and the whitening phenomenon due to the free curing accelerator occurs. The surface becomes powdery and spoils the aesthetics.

In addition to the above-mentioned curing accelerator, CaO, Ca (OH) ₂ , Mg (OH) ₂ ,
Cement, basic slag bases, silica gel and the like also have an effect of promoting hardening, and depending on the case, up to about 10% by weight can be added.

The inorganic powder is classified into three types according to its use function.

The first is a fine powder having a fineness of about 7,000 cm ² / g or more, and examples thereof include bentonite, activated clay, sepiolite, attapulgite, other clay minerals, silicon dust, and diatomaceous earth. This fine powder is used as an auxiliary material at the time of papermaking in order to improve the dispersibility of the raw material and adjust the filtration time to obtain the homogeneity of the raw material. It is also used to improve the delamination strength of the plate material and the water content of the green plate. The amount is 1 to 20% by weight, preferably about 3 to 10% by weight.

As the second inorganic powder, there is a crushed product (referred to as scrap) of the dihydrate gypsum cut product, which is reused as a part of the raw material. The amount is 1-35
It is about% by weight. Scrap is a mixture of crushed gypsum and fine fibers, and is effective in improving the yield of raw material solids.

The third inorganic powder is a filler or a weight-reducing material, and powders such as limestone, slaked lime, silica stone, slag, fly ash, dihydrate gypsum, hemihydrate gypsum, mica and wollastonite, and pearlite, vermiculite, silasbalun. Etc.

The total amount of these inorganic powders is 1 to 100 parts by weight based on the total amount based on 100 parts by weight of type II anhydrous gypsum and short fibers.

A polymer coagulant may be added in order to improve the raw material retention. In particular, it is used in the case of non-asbestos type, but is also used in the case of asbestos type. As the polymer flocculant, general-purpose products such as anionic polyacrylic acid soda, polyacrylamide, nonionic polyacrylamide, polyethylene oxide, etc. may be used alone or in combination. The addition amount is about 1 to 10 ppm.

e. Action By using type II anhydrous gypsum as a raw material, there is no condensation reaction like hemihydrate gypsum during production, and continuous production for a long time can be stably performed. In addition, the factor of fluctuation was eliminated during the process, and the process control became extremely easy.

On the other hand, Type II anhydrous gypsum had a slow hydration rate, required a long time to harden, and had large fluctuations during the day, month, and season at the time of manufacture, and it was difficult to obtain a certain quality.

This is because the curing accelerator flows out together with the circulating water during the papermaking process. Therefore, by improving the raw materials, the fiber composition, the pressure forming pressure, and the like, the water content of the raw plate was increased, and the water necessary for hydration and the hardening accelerator were secured in the plate material.

By rapidly cooling and curing from the initial stage after plate making, the hydration rate of anhydrous gypsum is improved, the skeleton of the texture of the plate material is formed in the initial stage, and the hydration reaction progresses with the passage of time thereafter. The structure became more compact, the effect of promoting hydration appeared, the specific gravity and strength increased, and the necessary properties were obtained in a short period of time, improving productivity. If the curing period was the same, the hydration rate was remarkably improved compared to the conventional one. In addition, because the rate of hydration of gypsum was improved, at the same hydration rate, when cooling curing was performed within 48 hours immediately after plate making, compared to the case where it was not,
The properties such as specific gravity, bending strength, peeling strength, and rate of change in length were significantly improved.

By rapidly cooling and curing from the three, the hydration rate was improved, the hardening accelerator of gypsum could be reduced, and the press molding pressure could be increased. Reduction of the curing accelerator has made it possible to obtain a product in which the rate of change in length is reduced and the whitening phenomenon does not occur under more severe conditions.

By rapidly cooling and curing from the beginning to four, the factors that affect the quality during the manufacturing days, months, and seasons are eliminated, and a certain level of high-quality industrial products can be obtained throughout the year. became.

f. Examples Hereinafter, examples of the present invention will be described in detail.

The raw material composition of the example is type II anhydrous gypsum 90.0, pulp 8.
0, glass fiber 2.0% by weight, and their total 100% by weight
, Outer diatomaceous earth 5.0, limestone powder 20.0, scrap 20.0
Part by weight and 1.5% by weight of potassium alum are added to the type II anhydrous gypsum as a gypsum hardening accelerator.

About 3 times the weight of the total amount of the raw materials is used to stir with a pulper to form a slurry. As a raw material, a curing accelerator, each fiber, type II anhydrous gypsum, and other inorganic powders were sequentially added to water and dispersed. This slurry was passed through a chest, further diluted to a solid content concentration of about 1/10, made into a paper by a cylinder paper making machine, and laminated with a making roll to a predetermined thickness to form a sheet. This sheet is 50kg / cm ²
And pressure molding was performed to a thickness of about 6 mm.

About 50 sheets of plate material after pressure molding were stacked, and curing was performed under a predetermined cooling curing start condition and a predetermined cooling curing condition, and then dried and cut to perform a test.

The comparative example was also manufactured by the same method and tested.

Formulation, production, curing conditions,
Table 1 shows the results of the property test. The water temperature during papermaking is
The temperature is about 33 ± 3 ° C, and the humidity during curing is in the range of 80 to 95%.

Examples 1 to 3 and Comparative Examples 1 to 2 Show the conditions and results when the cooling and curing conditions (preliminary time until start of curing, plate temperature) from the initial stage are changed.

Examples 4 to 9 and Comparative Examples 3 to 4 Show the curing start conditions of cooling curing from the initial stage, and the conditions and results when the cooling curing temperature and period are changed.

 The raw materials used and the test method are as follows.

Raw material type II anhydrous gypsum: Drainage dehydrated gypsum 600 ℃ baked product, fineness 5
630cm ² / g Pulp: Bleached pulp CSF 350ml Glass fiber: Nippon Electric Insulator Chopped Strand 6mm Kali Alum: Reagent Class 1 Diatomaceous earth: Isolite Industrial Limestone: Okutama Industrial Testing method Specific gravity: JIS A5418 "Asbestos cement calcium silicate board" Compliance (abbreviated as bulk specific gravity in JIS) Bending strength: Complies with JIS A5418 "Asbestos cement calcium silicate board" Length change rate: Complies with JIS A5418 "Asbestos cement calcium silicate board" Peel strength: 5 x 5 cm Is pulled in the thickness direction and the strength between the layers in the plate is measured.

Hydration rate: The crushed sample was dried at 45 ° C, calcined at 200 ° C, and the hydration rate for the gypsum composition was measured from the weight loss.

Raw plate water content: JIS A 5418 "Asbestos cement calcium silicate board" (Based on JIS water content measurement, but dry at 60 ℃, 24 hours) g. Effect of the Invention According to the method of the present invention, a type II gypsum, short fiber, a slurry containing gypsum hardening accelerator as a main raw material is formed into a paper, and the gypsum is rapidly cooled and cured from the beginning after plate making. The hydration rate of the plate was accelerated, productivity was improved, and higher quality performance was obtained. That is, (1) By rapidly cooling and curing from the initial stage, the hydration rate of type II anhydrous gypsum was improved, and when the hydration rate was the same, the quality was higher than in the past.

(2) Since the rate of hydration of gypsum was improved, it was possible to reduce the curing accelerator, which led to an improvement in production efficiency, a reduction in the rate of change in length, and a reduction in the white flower phenomenon.

(3) By rapidly cooling and curing from the initial stage, the hydration rate of type II anhydrous gypsum was improved, the accelerated hardening of hydration became remarkable, and the necessary properties were obtained in a short period of time, improving productivity.

(4) By rapidly cooling and curing from the initial stage, variations in the hydration rate of type II anhydrous gypsum due to the time of manufacture were removed, and industrial products of a certain quality were obtained throughout the year.

(5) By using type II anhydrous gypsum, the factor of fluctuation in setting during papermaking was eliminated, and stable operation for a long time and process control became extremely easy. This has also resulted in good product stability.

(6) As a gypsum board using type II anhydrous gypsum, it has excellent bending strength, peeling strength, and rate of change in length, and it is free from the phenomenon of white sinter, and has workability such as sawing, nailing, and bending workability. Also excellent non-combustible material was obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location C04B 14:38 Z 16:06 24:26) E (72) Inventor Yasuji Asada Moji Kitakyushu, Fukuoka Prefecture 1-10-10 Yanagi-cho, Ku (72) Inventor Tsutomu Shinozaki 1-3-57 Nishioodori, Yonezawa City, Yamagata Prefecture Misao Corp. 303 (56) References JP-A-60-42267 (JP, A) JP-A-60- 171261 (JP, A) JP 53-25339 (JP, B2) JP 57-49004 (JP, B2) JP 55-36628 (JP, B2)

Claims (3)

[Claims] 1. Type II anhydrous gypsum 98-60% by weight, short fibers 2
40% by weight and a slurry containing gypsum hardening accelerator as the main component are formed into paper, then temperature 0-27 ° C, humidity 50-100%
A method for producing an anhydrous gypsum papermaking board, which comprises cooling and curing within 48 hours immediately after boardmaking. 2. A method for producing an anhydrous gypsum papermaking board according to claim 1, wherein the gypsum hardening accelerator is used in an amount of 0.1 to 2.5% by weight based on the type II anhydrous gypsum. 3. Anhydrous gypsum papermaking according to claim 1 or 2, wherein 1 to 100 parts by weight of inorganic powder is mixed with 100 parts by weight of type II anhydrous gypsum and short fibers in total. Method of manufacturing a plate.