JPS62191455A - Anhydrous gypsum papered board and manufacture - 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 (Field of Industrial Application) The present invention relates to a fiber-reinforced anhydrous gypsum board (hereinafter simply referred to as gypsum board) and a method for manufacturing the same. More specifically, it relates to a sheet material and an industrial continuous manufacturing method thereof, which comprises forming a sheet from a slurry containing type hydrogypsum, short fibers, and a hardening accelerator, and press-forming this sheet. .

(Prior Art) Gypsum board is a noncombustible material with excellent bending strength, dimensional stability, fire resistance, and heat insulation properties. Furthermore, since it has similar processability to plywood in terms of sawing, nailing, and curved surface processing, it is widely used as a material for fireproof and fireproof structures.

Regarding the manufacturing method of this gypsum board,
No. 39, No. 57-49004, No. 55-36628, JP-A-60-42267 and No. 60-171261
There are inventions disclosed in Japanese Patent Publication No. 1, No. 2003-12300, and the gypsum boards of these inventions use semi-aqueous plaster as a matrix in all cases.

However, since the hydration reaction of semi-aqueous paper is rapid, there have been problems in paper forming using round or long paper making machines.

That is, the production process from kneading raw materials and water to papermaking and pressurization requires a considerable amount of time. During this period, it is necessary to delay the hydration reaction of the semi-aqueous surface, and a setting retarder is used. There are many disturbance factors to the setting retardation effect of this semi-water surface slag, which has had a serious adverse effect on process control and quality control.

The first disturbance factor is that during the papermaking process, part of the semi-aqueous slag flows into the production water through the mesh, and while passing through the circulation system, the semi-aqueous sulfur turns into dihydrate gypsum, causing the production water to be reused. In some cases, dihydrate gypsum is mixed in. Even if a small amount of this dihydrate gypsum is present, it acts as a setting accelerator for semi-hydrated gypsum, causing fluctuations in the setting time of the raw material and inhibiting the stability of the process.

The second disturbance factor is when raw sheet shreds and raw defective products are reused as raw materials, the trihydration reaction is in progress, so there are quantitative and temporal fluctuations. In other words, this changes the amount of gypsum dihydrate and affects the setting.

The third disturbance factor is a variation in the residence time of the raw material slurry due to equipment malfunction or failure, which also causes a variation in the trihydration reaction before molding, and has a significant impact on the process.

Furthermore, when the cured product is cut into predetermined dimensions, chips, damaged products, and defective products are generated. The scrap powder that is pulverized for collection and use is in the form of gypsum dihydrate.
This also results in fluctuations in the hydration reaction. However, it is also possible to calcinate the material after pulverization to make it semi-hydrated, but this requires equipment.

In this way, when paper forming is performed using a semi-aqueous matrix as a matrix, there are many problems in stabilizing coagulation.

The above-mentioned Japanese Patent Publication No. 57-49004 is an invention by the present inventors, and is an invention that improves the above-mentioned drawbacks when papermaking is performed using a semi-aqueous surface layer, and improves the contact time and residence time of the semi-aqueous surface layer with water. This is to ensure stable operation by reducing the amount of These require new paper making machines and scrap burning equipment.

Further, a method of blending dihydrate gypsum as it is without providing scrap firing equipment is partially disclosed in Japanese Patent Application Laid-open No. 171261/1983. There are the above-mentioned problems when mixing dihydrate gypsum with semi-aqueous gypsum, and even if production is possible by using a large amount of setting retarder, product properties such as bending strength and dimensional changes may be affected. New problems arise, such as a decrease in peel strength, interlayer peel strength, etc.

On the other hand, Type 1 water gypsum hardens slowly, so it is a raw material that is rarely used other than in small quantities as plaster.

(Problems to be Solved by the Invention) In the conventional method for manufacturing gypsum boards using semi-water gypsum, there are too many factors that change the setting time, making process management complicated and difficult.

In addition, in order to solve these difficulties, large amounts of setting retarders were added, but as a result, setting fluctuated over a long period of time and remained uncured for several days after production. This continued, and the properties of the product deteriorated.

On the other hand, type 2 anhydrous gypsum has a slow hydration rate, so usually a curing accelerator is added to it and curing is almost completed in four weeks or more. However, when paper-forming is performed using ■ type water gypsum as a raw material, the hydration rate fluctuates greatly even when a hardening accelerator is added, and product strength, glabella peel strength, dimensional change rate, etc. Moreover, there were also drawbacks such as generation of efflorescence and powderiness, and performance as an industrial product could not be obtained.

The objects of the present invention are (1) to obtain a gypsum board with a high hydration rate and high quality using type II anhydrous gypsum as a raw material, and (2) to solve the problems of stability and ease of production in the papermaking process.

(Means for Solving the Problems) The present inventors have completed the present invention by conducting intensive research on manufacturing and property improvement using various types of gypsum.

The gist of the present invention is: ■ Type water gypsum 98-6
Anhydrous gypsum paper board containing 0% by weight, 2 to 40% by weight of short fibers, and a gypsum hardening accelerator and having a hydration rate of 45% or more, and a slurry containing these raw materials as the main components are made into sheets. , this sheet is 1~300 kg/cnl
The present invention relates to a fiber-reinforced anhydrous gypsum paper board that is pressure-formed in a process, and a method for manufacturing the same.

Short fibers consist of asbestos or a combination of asbestos and other fibers, or of pulp or a combination of pulp and other non-asbestos fibers.

Pressure molding pressure ranges from low pressure of 1 to 10 kg/cd to 10 kg/cd.
It is carried out in a low to medium pressure range of ~300 kg/cot.

Further, 1 to 50 parts by weight of inorganic powder may be added by external cutting to 100 parts by weight of H-type water gypsum and short fibers.

The steps of the manufacturing method according to the present invention are as follows.

That is, 5 to 15 times as much water is added to the raw material to form a slurry, which is retained in a chest to homogenize the kneaded material, and this slurry is formed into a sheet using a circular wire or Fourdrinier machine. Cut the edge of this raw sheet and use a roll press or surface press to give a weight of 1 to 10 kg/cnt (roll press pressure is a value calculated from the specific gravity of the product) or a surface press to give a weight of 1 to 10 kg/cnt
Pressure molding is performed at 0 to 300 kg/cnl. This pressure is determined by the material composition, product strength, and moisture content of the raw sheet (
It is selected within the range of 10 to 90% of the raw board moisture content (referred to as raw board moisture content).

This pressurized green sheet is cured until hydrated and hardened. At this time, it is necessary to cure the edges of the board so that they do not dry out. The curing period is 2 days or more, preferably 3 days or more and about 2 to 3 weeks. After curing, it is dried if necessary and cut into standard dimensions to be manufactured into products.

If pressure molding is not performed here, the product will not have good surface smoothness and will also have low strength. Furthermore, if the pressing force exceeds 300 kg/cId, the moisture content of the raw sheet cannot be secured, and accordingly, the water necessary for hydration and the specified amount of curing accelerator cannot be secured in the sheet. Become.

Therefore, the hydration X of the product does not proceed and the properties of the product deteriorate.

In papermaking, a kneaded slurry is used to form a film mainly composed of solids in the slurry using the suction force of a rotating drum whose surface is formed with a net.A suitable number of films are laminated on a making roll to form a sheet. do. Paper making is carried out using a round netting machine or a fourdrinier machine that supplies slurry onto a belt conveyor surface with a dewatering function to form a gypsum board.

Roll press in pressure forming also includes pressurization of a circular mesh making roll.

The water temperature during papermaking needs to be 10°C or higher from the viewpoint of production efficiency, and preferably 20°C or higher. The upper limit is 3 due to the curing effect.
The temperature is about 5°C.

The material-related configuration of the present invention is as follows.

■ Type water gypsum is a natural dihydrate gypsum or a by-product of phosphoric acid or titanium production or removal, etc. A fired product of dihydrate gypsum, or a by-product during hydrofluoric acid production ■ Type water gypsum and other general-purpose products are used. It will be done. In addition, the fineness of the ■ type water gypsum is 1,000 to 9.00 in Blaine value. OO0cnl/g
That's about it. This range is selected from the viewpoints of permanence and aqueous phase reactivity. ■Model water gypsum amount is 98-60% by weight
It is. (2) The amount of type water gypsum is determined in relation to 2 to 40% by weight of short fibers. If the fiber content is less than 2%, a large amount of solid content flows out through the wire gauze during papermaking, making papermaking impossible. Moreover, when the amount of fiber exceeds 40%, it becomes no longer a gypsum board but a fibrous board. As a result, the strength of the product and the adhesion between the layers deteriorate, making it unusable as a gypsum board.

■Type: 100 parts by weight of water gypsum and short fibers, 0 to 0 inorganic powder
A formulation of 80 parts by weight is also carried out.

■■ of short fibers is 2 to 40% by weight. Asbestos or a combination of asbestos and other fibers is used as the short fiber. If asbestos is not used, pulp or a combination of pulp and other non-asbestos fibers is used.

The short fibers used are natural fibers such as asbestos and cellulose (pulp), inorganic fibers such as glass fiber, carbon fiber, glass wool, rock wool, and ceramic wool, and fibers such as polyamide, polypropylene, polyvinyl alcohol, polyester, polyethylene, and acrylic. These are general-purpose fibers such as synthetic fibers, and can be used singly or in combination depending on the paper-formability, moisture content of the raw board, product strength, etc.

Asbestos is used to improve the strength of the product and the moisture content of the green board, but due to regulations and the like, the amount of asbestos is 10% or less, preferably 5% or less.

When using non-asbestos fibers, the amount of tap x bulb is 1
% or more, preferably 2 to 10%.

If the pulp content is 1% or less in a non-asbestos type, the dispersion and yield of raw materials during papermaking will be poor, making production extremely difficult.

Moreover, if it exceeds 10%, the dispersion of the pulp will be poor during paper making, it will be difficult to obtain homogeneity of the material, and it will not be possible to obtain nonflammability as a building material.

The pipe is beaten to a predetermined degree of beating as necessary.

The freeness is Canadian standard freeness (C3F) 80.
0 to 30 ml, and the degree of beating varies depending on the blending amount and the combination of fibers. In the case of non-asbestos materials, dispersion during papermaking,
From the viewpoint of yield, product strength, delamination strength, and green board moisture content, it is preferably about 500 to 50 m1.

Beating is carried out using a general-purpose machine such as a pulper, disc refiner, or cone refiner.

■As a hardening accelerator for type water gypsum, HzSO* is used.

KzSOt, NazSOt+ (NHt)zsOa+
Mg5On, Zn5O,, Fe50*+Cu5Oa
, A 1 z(SOa)3 and their double salts such as KAi'(sot)z 42tlzO, NaAA(S
O2)z42HzO.

Ni14. Alums such as A I (son) z・1211zO, NaCe.

CaC12+ Chlorides such as MgC1z, NaHSO,
, acid hydrogen salts such as KHSO4, NaNOs, NH4NO
3. General-purpose nitrates such as KNO3 can be used alone or in combination. The amount of hardening accelerator is the amount retained in the board, and is 0.3 to 4.0% based on type water plaster;
Preferably it is 0.5 to 3.5%. This amount is 0.3%
In the following, even if curing is performed for 4 weeks or more, the hydration rate, bending strength, etc. are extremely low, and a material that can be put to practical use cannot be obtained. Addition of more than 4.0% will not have the effect of improving bending strength, etc., and will instead increase the dimensional change rate and cause efflorescence.

In addition to the above-mentioned curing agents, Cab, Ca(Off)z,
Mg(Otl)z cement, chlorine of basic slag, silica gel, etc. also have the effect of accelerating hardening, and are used in combination in some cases. In this case, since there is no fear of efflorescence, it is added up to about 10%.

Inorganic powders can be divided into three types based on their usage functions. The first is a fine powder with a fineness of about 7,000 cJ/g or more, such as bentonite, activated clay, zepiolite, attapulgite, other clay minerals, silicon dust, diatomaceous earth, and the like. This fine powder is used as an auxiliary material during papermaking to obtain homogeneity of the raw material by improving the dispersibility of the raw material and adjusting the filtration time. It is also used to improve the glabellar peel strength of board materials and the moisture content of green boards. The amount is 0-20%, preferably 3
It is about 10%. If it exceeds 20%, a large amount of raw material escapes into the waste water, making operation difficult and causing deterioration in the properties of the product. These materials are especially suitable for non-asbestos formulations.
Although it is effective in many cases, it is also used in the case of asbestos.

The second inorganic powder is a pulverized product (scrap) of the dihydrated cut product, and this scrap is reused as part of the raw material.

The amount is about 0 to 35%. Scraps of dihydrate gypsum do not affect the setting of Type ① water gypsum, so they are reused unfired. Scrap is a mixture of crushed gypsum and fine fibers and has the effect of improving the yield of raw materials.

Examples of the third inorganic powder include fillers or lightening materials such as limestone, slaked lime, silica stone, slag, fly ash, wollastonite, mica, perlite, vermiculite, and shirasu balloon.

The total amount of these inorganic powders is 0 to 50 parts by weight based on 100 parts by weight of type (1) water gypsum and short fibers.

Polymer flocculants are sometimes added to improve the quality of raw materials. It is particularly used for non-asbestos materials, but it can also be used for asbestos materials. As the polymer flocculant, general-purpose products such as anionic sodium polyacrylate and polyacrylamide, or nonionic polyacrylamide and polyethylene oxide are used alone or in combination. The amount added is about 1 to 10 ppm.

According to the method of the present invention, the possibility of progress of the setting reaction of gypsum during the papermaking process is eliminated by using type 1 water gypsum and a hardening accelerator instead of hemihydrate gypsum and a setting retardant. , continuous stable continuous operation over long periods of time has become easier. In addition, cutting waste or product scraps during the process do not affect the hydration reaction of Type Water Gypsum, so they can be reused as raw materials as they are. For this reason, there is no need for new papermaking or firing equipment, and mass production is possible because the paper is manufactured using existing equipment.

On the other hand, type 2 anhydrous gypsum has a slow curing speed, and for this reason a curing accelerator is added. However, during the papermaking process, the curing accelerator flowed out together with water and was not effectively captured in the plate.

For this reason, a large amount of fiber was blended, asbestos was used as the fiber, and beaten pulp was used when blending non-asbestos fibers, and the pressing force was set in a relatively low range of 1 to 300 kg/c+J. As a result, the moisture content of the raw board was increased, and hydration water and hardening accelerator were effectively secured in the board.

From these results, a product with a hydration rate of 45 was obtained as a gypsum board.

(Example) The following examples are presented to further explain the invention.

In the following Examples and Comparative Examples, slurries were prepared by kneading with a pulper using 5 times the weight of water relative to the total amount of raw materials. At this time, the raw materials were homogenized by adding a hardening accelerator, each fiber, fine powder such as bentonite, scrap, type 1 water gypsum, and other inorganic powder to water in this order. This slurry was passed through a chest, further diluted to a solid concentration of 1/10, formed into a paper using a circular mesh rotating drum, and wound into a sheet using a making roll to a predetermined thickness. This sheet was pressure-formed using a press to have a thickness of about 6 fins.

After pressure molding, curing was performed, and after curing, drying and cutting were performed. Note that Comparative Examples were also produced in the same manner.

The formulations, manufacturing conditions, and property test results for each example and comparative example are shown in Tables 1 to 6.

Examples 1 to 6 Tables 1 and 2 show the results obtained by changing the blending ratio of gypsum and short fibers.

Examples 7 to 14 Table 3 shows the formulations and results when the Canadian standard freeness (C3F) of short fibers and valves were changed.

Examples 15 to 21 and Comparisons 1 to 2 Table 4 shows the formulations and results obtained by changing the pressurization method and pressure.

Table 5 shows the formulations and results when potassium sulfate and sodium chloride were added as gypsum hardening accelerators.

Shi, LL! ~34 and Inside the Car 16 Table 6 shows the formulations and results when bentonite was blended as an inorganic powder.

The test methods in Tables 1 to 6 showing the results of Examples 1 to 34 and Comparative Examples 1 to 6 are as follows.

Test method Specific gravity: Based on JISA5418 asbestos cement calcium silicate plate Bending strength: Based on JrSA5418 asbestos cement calcium silicate plate (bending strength) Dimensional change rate: Based on JIS^5418 asbestos cement calcium silicate plate (length change Raw board moisture content: Based on JISA5418 asbestos cement calcium silicate board (moisture content) (drying at 60℃ for 24 hours) Peeling strength: Pull a 5 x 5 cm board in the thickness direction and measure the interlayer strength between the boards. measurement.

Permanent ratio: Dry the pulverized sample at 45°C,
Raise the temperature to 0℃ and measure the amount of dehydration of crystal water from dihydrate gypsum. The hydration rate was determined from the amount of gypsum mixed.

Efflorescence test: The lower 5 cm of a 5 cm wide x 20 cm long test piece was immersed in water, stored in a constant temperature room at 20°C and 60% humidity, and the condition was visually observed after 2 weeks.

◎ None at all ○ is almost impossible △ Occurs in some parts × Quite a lot of occurrence Surface smoothness: Determined by visual observation of a 50 x 40 cm test piece.

◎ Good O is Good △ Some unevenness × Some unevenness (Effects of the invention) (1) Type II anhydrous gypsum is used, and the gypsum board has a high hydration rate, high bending strength, and a small dimensional change rate. ,
A noncombustible building material was obtained that had high quality such as high interlayer peel strength, did not cause efflorescence, and had excellent workability such as sawing, nailing, and bending workability.

(2) Compared to the case of using conventional hemihydrate gypsum, when using type hemihydrate gypsum, manufacturing stability can be easily obtained, products with stable quality can be obtained, and industrial production We were able to make this even easier.

(3) By using type II anhydrous gypsum, when recovering materials during the manufacturing process and product scrap, the recovered materials do not affect the hydration reaction of type II aqueous gypsum, so they can be used as raw materials as they are. reused as a part.

This eliminates the need for new manufacturing or scrap firing equipment, resulting in resource and energy savings.

(4) By improving the amount of U-type water gypsum, short fiber mixture, and pressure molding pressure, hydration water and hardening accelerator could be effectively captured in the board material. These improvements have improved the hydration rate, making it possible to use type 2 hydrogypsum, which had low utility value, such as type 2 hydrogypsum, which is a by-product from the hydrofluoric acid manufacturing process, in its original form.

Claims (11)

[Claims] (1) Type II anhydrous gypsum 98-60% by weight, short fibers 2-4
0% by weight, an anhydrous gypsum paper board containing a gypsum hardening accelerator as a main component, and having a hydration rate of 45% or more. (2) The paper-made board according to claim (1), wherein the short fibers are made of asbestos or a combination of asbestos and other fibers. (3) The paper-made board according to claim (1), wherein the short fibers are composed of pulp or pulp and other non-asbestos fibers. (4) The sheet-made board according to claim (1), wherein 1 to 80 parts by weight of an inorganic powder is blended with 100 parts by weight of Type II anhydrous gypsum and short fibers. (5) Type II anhydrous gypsum 98-60% by weight, short fibers 2-4
An anhydrous gypsum paper board with a hydration rate of 45% or more, which is characterized by forming a slurry containing 0% by weight and a gypsum hardening accelerator as the main component, and then press-forming it at 1 to 300 kg/cm^2. Production method. (6) The method for manufacturing a paperboard according to claim (5), wherein the short fibers are made of asbestos or a combination of asbestos and other fibers. (7) The method for manufacturing a paperboard according to claim (5), wherein the short fibers are pulp or pulp and other non-asbestos fibers. (8) The manufacturing method according to claim (5), wherein 1 to 80 parts by weight of an inorganic powder is blended with 100 parts by weight of Type II anhydrous gypsum and short fibers. (9) The manufacturing method according to claim (5), wherein the pressure of pressure molding is 1 to 10 kg/cm^2. (10) The pressure of pressure molding is 10 to 300 kg/cm^2
The manufacturing method according to claim (5). (11) The raw board moisture content of the pressure-formed sheet is 10 to 90.
% of the manufacturing method according to claim (5).