KR20210131602A - Gypsum board - Google Patents

Abstract

As a gypsum board containing a composition comprising 100 parts by weight of calcined gypsum and 0.1-0.4 parts by weight of gelatinized starch, the present invention relates to the gypsum board wherein the gelatinized starch has a solubility of 5-12%, and the gypsum board has a hardness of 90 N or more measured according to ASTM C 473 and a nail pulling resistance of 220 N or more. Therefore, an objective of the present invention is to provide the gypsum board having excellent mechanical strength and adhesive strength to a base paper.

Description

Gypsum Board{GYPSUM BOARD}

The present invention relates to a gypsum board having excellent mechanical strength and adhesion to base paper.

In general, gypsum products include solidified gypsum in which calcined gypsum is hydrated by water to form a crystalline hydrated gypsum matrix (calcium sulfate dihydrate), and such gypsum products have high structural strength and are widely applied to buildings. In particular, gypsum products are used in structural parts of buildings where fire resistance and heat insulation properties are required, and a typical commercial product of gypsum products is gypsum board. Various types of gypsum boards, such as general gypsum boards, fireproof gypsum boards, waterproof gypsum boards, sound insulation gypsum boards, and antibacterial gypsum boards, are being applied as interior materials for buildings.

In addition, the gypsum board is generally manufactured through a process of mixing calcined gypsum and water, and various additives are added to manufacture the gypsum board having various functions. In this case, the calcined gypsum typically includes a hydrate or hemihydrate of calcium sulfate, or anhydrous calcium sulfate. The additives include, for example, potassium sulfate as a curing accelerator, fine gypsum dihydrate powder, and starch, fibers or admixtures as an adhesion aid. In addition, multifunctional gypsum boards are manufactured by adding ingredients suitable for the purpose of gypsum boards, such as vermiculite and glass fiber.

Specifically, Korean Patent Registration No. 1,334,105 (Patent Document 1) discloses a lightweight gypsum board comprising a hardened gypsum composition formed with water, stucco, pregelatinized starch and a naphthalenesulfonate dispersant and placed between two cover sheets. , wherein the pregelatinized starch comprises 0.5% to 10% by weight based on the weight of stucco, a lightweight gypsum board is disclosed. However, the lightweight gypsum board of Patent Document 1 uses high-viscosity starch, which increases the amount of mixed water (70% or more), decreases strength, and causes problems such as process drift due to aggregation of gypsum and starch at the gypsum slurry outlet. In particular, when the amount of mixed water of the gypsum board increases, the drying cost for drying in the dryer increases by the increased amount of water mixture, and as the drying cost and drying time increase, the productivity of the gypsum board decreases, which may cause an increase in manufacturing cost. have.

Therefore, there is a need for research and development on a gypsum board having excellent mechanical strength and adhesion to the base paper.

Korean Patent Registration No. 1,334,105 (published on: May 20, 2008)

An object of the present invention is to provide a gypsum board having excellent mechanical strength and adhesion to base paper.

The present invention relates to a gypsum board comprising 100 parts by weight of calcined gypsum and 0.1 to 0.4 parts by weight of a composition comprising gelatinized starch,

The gelatinized starch has a solubility of 5 to 12%,

The gypsum board provides a gypsum board having a hardness of 90N or more, and a nail pulling resistance of 220N or more, measured according to ASTM C 473.

The gypsum board according to the present invention has excellent mechanical strength such as hardness, flexural fracture load and nail pulling resistance, and has excellent adhesion to base paper, so that it can be usefully used as an interior material in various fields.

Hereinafter, the present invention will be described in detail.

Gypsum board

The gypsum board according to the present invention contains a composition comprising 100 parts by weight of calcined gypsum and 0.1 to 0.4 parts by weight of gelatinized starch.

plaster of plaster

Calcined gypsum may be hemihydrate gypsum (CaSO ₄ ·1/2H ₂ O) as the main material of the gypsum board. Specifically, the calcined gypsum may be hemihydrate gypsum that has lost _{3/2H 2} O in crystallized water by drying and calcining _{dihydrate gypsum (CaSO 4} ·2H ₂ O) having two molecules of water of crystallization (WC, Water of Crystallization). . At this time, when water is added to the hemihydrate gypsum, a hydration reaction occurs, and the gypsum board is hardened by returning to dihydrate gypsum. can do.

The average particle size of the regular calcined gypsum may be 18 to 45 μm, or 25 to 45 μm. When the average particle size of the calcined gypsum is less than 18 μm, the specific surface area of the calcined gypsum increases and the curing time of the composition is shortened and a problem of poor fluidity of the composition occurs. The time delay may cause a problem of using an excessive amount of curing agent.

luxury starch

The pregelatinized starch serves to improve the strength of the gypsum board and improve adhesion to the base paper.

The gelatinized starch may be obtained by gelatinizing natural starch in water at room temperature and adding water solubility to the properties of natural starch. At this time, since the natural starch reacts directly with water at room temperature to form a high-viscosity starch solution, the amount of mixed water of the gypsum board can be increased.

When the gypsum board contains natural starch, high viscosity starch is used compared to the pregelatinized starch, so the amount of mixed water required to form the composition for the board increases during manufacturing of the gypsum board, and the probability of gypsum sticking at the outlet is very high. . In addition, due to the increase in the amount of coma, a lot of moisture is contained in the core of the gypsum, and when it is dried, large pores are formed at the place where the moisture escapes, and there is a concern that the strength of the gypsum board is reduced.

On the other hand, when the gypsum board contains gelatinized starch, a large amount of mixed water is not required as in the case of using high-viscosity natural starch, and the process can be operated while maintaining the same amount of mixed water as before the starch is added. In addition, the gypsum board containing the gelatinized starch can improve hardness and nail pulling resistance, compared to the gypsum board containing the natural starch.

In addition, when the gypsum board contains oxidized starch, when the gypsum board is dried at a high temperature in a dryer, migration is performed from the gypsum core to the gypsum board base paper, so that the base paper and the gypsum board can be adhered. However, due to the characteristics of oxidized starch, high viscosity cannot be formed, so depending on drying conditions, adhesion between the gypsum core and the base paper cannot be formed, and a problem of evaporation together with moisture may occur.

On the other hand, since the gelatinized starch remains in the core of the gypsum by forming a high viscosity, there is little variation depending on the drying conditions, and a part of the input amount remains in the core of the gypsum to improve the strength of the manufactured gypsum board, and a part moves to the surface Thus, the adhesion between the base paper and the gypsum core can be improved.

In addition, the gelatinized starch has a solubility of 5 to 12%. For example, the gelatinized starch may have a solubility of 8 to 12%. When the solubility of the gelatinized starch is more than 12%, the viscosity of the starch is too high, so that it is not kneaded in the composition for gypsum board, so that it is impossible to develop a high-strength product. In addition, even when the solubility of the gelatinized starch is less than 5%, the gelatinized starch in the composition for gypsum board is not sufficiently dissolved, so it is difficult to obtain the effect of improving the hardness and nail pulling resistance of the gypsum board. In addition, when the solubility of the gelatinized starch is within the above range, there is an effect of improving the strength of the prepared gypsum board and improving the adhesion between the gypsum core and the base paper. In this case, the solubility of the gelatinized starch is the solubility in water at 25°C.

The gelatinized starch may have a viscosity of 100 to 400 cps at 25°C, and a gelatinization temperature of 20 to 60°C. For example, the gelatinized starch may have a viscosity of 200 to 300 cps at 25°C, and a gelatinization temperature of 25 to 60°C.

The gelatinized starch may contain moisture of 10 wt% or less, or 5 wt% or less based on the total weight of the starch. When the moisture content of the gelatinized starch is within the above range, there is no change in appearance, such as aggregation of the gelatinized starch due to moisture, and the processability of a composition including the same is improved. In addition, when the water content of the gelatinized starch is within the above range, it is effective in improving the strength of the prepared gypsum board by forming a composition of high viscosity upon reaction with calcined gypsum. On the other hand, when the moisture content in the gelatinized starch is more than 10% by weight, the amount of mixed water of the composition for gypsum board is increased, and agglomeration occurs in appearance, making it impossible to quantitatively inject.

In addition, the gelatinized starch may be included in the composition in an amount of 0.1 to 0.4 parts by weight, or 0.10 to 0.25 parts by weight, based on 100 parts by weight of calcined gypsum. When the content of the gelatinized starch is within the above range, the strength improvement effect of the prepared gypsum board is excellent compared to the amount of the gelatinized starch, which is economical. When the content of the gelatinized starch is less than 0.1 parts by weight, the strength improvement effect of the prepared gypsum board is insufficient, and when it exceeds 0.4 parts by weight, the fluidity of the composition for gypsum board is reduced and the gelatinized starch is attached to the slurry outlet, so fairness is not guaranteed. There may be problems with degradation.

additive

The composition for gypsum board may further include at least one additive selected from the group consisting of a water reducing agent, a curing agent, a weight reducing agent, and a sequestering agent.

In this case, the additive may be included in the composition in an amount of 0.5 to 5.0 parts by weight, or 0.8 to 2.0 parts by weight based on 100 parts by weight of calcined gypsum.

The water reducing agent serves to impart fluidity to the composition for gypsum board, and is not particularly limited as long as it is added as a water reducing agent for gypsum board. In addition, the water reducing agent may be included in the composition in an amount of 0.5 to 2.0 parts by weight or 0.6 to 1.0 parts by weight based on 100 parts by weight of calcined gypsum.

The curing agent serves to accelerate the curing of the composition for gypsum board by accelerating the hydration reaction during the hydration process by contact with the gypsum and water. At this time, the curing agent is not particularly limited as long as it is usually added as a curing agent for gypsum board, and for example, it may be at least one selected from the group consisting of _{potassium sulfate and dihydrate gypsum (CaSO 4} ·2H _{2 O) powder.} In addition, the curing agent may be included in the composition in an amount of 0.1 to 1 parts by weight or 0.2 to 0.6 parts by weight based on 100 parts by weight of calcined gypsum.

The weight reducing agent serves to reduce the weight of the gypsum board by controlling the density of the manufactured gypsum board, and is not particularly limited as long as it is added as a foaming agent or a weight reducing agent for the gypsum board. In addition, the weight reducing agent may be included in the composition in an amount of 0.01 to 0.1 parts by weight, or 0.04 to 0.08 parts by weight based on 100 parts by weight of calcined gypsum.

The sequestering agent serves to prevent discoloration of the gypsum board due to metal ions, and is not particularly limited as long as it is added as an agent for preventing discoloration of the gypsum board. In addition, the sequestering agent may be included in the composition in an amount of 0.01 to 0.1 parts by weight, or 0.02 to 0.06 parts by weight based on 100 parts by weight of calcined gypsum.

The composition for gypsum board may have a viscosity of 250 to 300 cps at 25° C., and a coma of 65 to 80%.

The gypsum board may have a hardness of 90N or more, measured according to ASTM C 473, and a nail pull-out resistance of 220N or more. For example, the gypsum board may have a hardness of 95N or more, measured according to ASTM C 473, and a nail pull-out resistance of 235N or more.

In addition, the gypsum board may have a bending fracture load of 365N or more in the longitudinal direction measured according to KS F 3504, and a bending fracture load of 160N or more in the width direction. For example, the gypsum board may have a bending fracture load of 370N or more in the longitudinal direction measured according to KS F 3504, and a bending fracture load of 165N or more in the width direction.

The composition has an inner diameter of 7 cm at the bottom, 6 cm in diameter at the top, and a height of 4 cm. The composition flows out when the composition is filled in a slump cone with a height of 4 cm and lifted to a height of 10 cm after 5 seconds. , or 100 to 130 mm.

As described above, the gypsum board according to the present invention has excellent mechanical strength such as hardness, bending fracture load and nail pulling resistance, and has excellent adhesion to base paper, so that it can be usefully used as an interior material in various fields.

Hereinafter, the present invention will be described in more detail through examples. However, these examples are only for helping the understanding of the present invention, and the scope of the present invention is not limited to these examples in any sense.

[Example]

Examples 1 to 4 and Comparative Examples 1 to 7. Composition for gypsum board and preparation of gypsum board

A composition for gypsum board was prepared by mixing the components with the content shown in Tables 1 and 2. After that, the composition for gypsum board was placed between base papers, and the composition was molded and dried in a dryer to prepare a gypsum board having a width of 150 mm, a length of 150 mm, and an average thickness of 9.5 mm.

Ingredients (parts by weight) Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 plaster of plaster 100 100 100 100 100 100 100 Luxurious Starch-1 0.1 0.15 0.2 0.4 0.05 0.5 One water reducing agent 0.6 0.6 0.6 0.6 0.6 0.6 0.6 BMA 0.2 0.2 0.2 0.2 0.2 0.2 0.2 potassium sulfate 0.2 0.2 0.2 0.2 0.2 0.2 0.2 lightweight agent 0.06 0.06 0.06 0.06 0.06 0.06 0.06 sequestering agent 0.045 0.045 0.045 0.045 0.045 0.045 0.045

Ingredients (parts by weight) Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 plaster of plaster 100 100 100 100 oxidized starch 0.15 - - - Pregelatinized starch-2 (solubility 3%) - 0.15 - - Pregelatinized starch-3 (solubility 13%) - - 0.15 - Gelatinized starch-4 (moisture content: 15% by weight) - - - 0.15 water reducing agent 0.6 0.6 0.6 0.6 BMA 0.2 0.2 0.2 0.2 potassium sulfate 0.2 0.2 0.2 0.2 lightweight agent 0.06 0.06 0.06 0.06 sequestering agent 0.045 0.045 0.045 0.045

At this time, in the composition for gypsum board of Comparative Example 7, agglomeration of starch occurred, including gelatinized starch-4 having a high water content, so that it was impossible to manufacture gypsum board.

Hereinafter, information related to each component used in Comparative Examples and Examples is shown in Table 3.

Configuration ingredient note plaster of plaster Hemihydrate gypsum (CaSO ₄ 1/2H ₂ O) Average particle size: 37±7㎛ Luxurious Starch-1 - Solubility at 25°C: 8%, viscosity at 25°C: 260cps, gelatinization temperature: 25°C, moisture content: 5% by weight Luxurious Starch-2 - Solubility at 25°C: 3%, viscosity at 25°C: 50cps, gelatinization temperature: 25°C, moisture content: 5% by weight Luxurious Starch-3 - Solubility at 25°C: 13%, Viscosity at 25°C: 10,000cps, Gelatinization Temperature: 25°C, Water Content: 5% by weight Luxurious Starch-4 - Solubility at 25°C: 15%, viscosity at 25°C: 10,000cps, gelatinization temperature: 25°C, moisture content: 15% by weight oxidized starch - Viscosity at 70°C: 120cps, gelatinization temperature: 70°C, moisture content: 13% by weight water reducing agent 2-amino-1,5-naphthalenedisulfonic acid sodium salt (3CaO·3Al ₂ O ₃ ·CaSO ₄ ) - BMA Unmilled dihydrate gypsum (CaSO ₄ ·2H ₂ O) Average particle size: 15㎛ lightweight agent R ₁ O(CH ₂ CH ₂ O)SO ₃ NH ₄ ,
R ₁ : CH ₃ (CH ₂ ) _n , n=9.7 - sequestering agent Sulphite (K ₄ Fe(CN) ₆ 3H ₂ O) -

Test Example 1. Characteristic evaluation of gypsum board

The physical properties of the gypsum boards prepared in Examples and Comparative Examples were measured as follows, and the results are shown in Table 4 below.

(1) Liquidity

Fluidity was measured as the average diameter of the ejection formed when the composition flowed out when the composition was filled in a slump cone with an inner diameter of 7 cm at the bottom, 6 cm in inner diameter and 4 cm in height, and lifted to a height of 10 cm after 5 seconds. Since the composition for gypsum board becomes comatose and hardening begins immediately, measurement of the fluidity of the composition for gypsum board should be carried out as soon as possible.

(2) curing time

The curing time was measured as inflow time, initial setting time, and outgrowth time. At this time, if the curing time is excessively long, the gypsum crystals change from needle to plate shape, and the bonding force with the base paper is reduced, thereby reducing the adhesive force between the base paper and the core material. Mechanical properties may decrease.

The inflow time was measured according to KS L 9002, and specifically, the time until the time until the mark of the reagent spoon appeared faintly and disappeared soon while the composition for gypsum board was put into a SUS beaker and stirred with a reagent spoon. Thus, it was set as the inflow time.

In addition, the initial setting time was measured according to KS L 9002, and specifically, the composition for gypsum board, whose inflow time was measured as described above, was poured into a rubber mold, and the composition was prepared with a vicart needle having a diameter of 2 mm and a weight of 300 ± 1 g. As the composition hardens when pressed, the insertion depth of the needle gradually becomes shorter, and the time taken until the needle entry depth does not reach the bottom of the rubber mold was defined as the initial setting time.

The surface bell time was measured according to KS L 9002, and specifically, the composition for gypsum board, whose inflow time was measured as described above, was poured into a rubber mold, and the composition was pressed with a vicart needle having a diameter of 2 mm and a weight of 300 ± 1 g. was cured. At this time, as in the initial setting time, the time when the depth of needle entry became 1 mm from the surface was set as the time of the seeding.

(3) coma

The coma rate is the weight of water input relative to the weight of calcined gypsum.

(4) Adhesion

The adhesive strength between the base paper and the gypsum board was measured by measuring the dry adhesive strength by whether or not peeling occurred between the base paper and the gypsum board after leaving the manufactured gypsum board at a temperature of 25 to 30 ° C and a relative humidity of 50 to 60% for 24 hours. . In addition, after leaving the prepared gypsum board at a temperature of 40±2° C. and a relative humidity of 85 to 90% for 48 hours, the wet-adhesive adhesion was evaluated by whether or not peeling occurred between the base paper and the gypsum board. At this time, when peeling occurred between the base paper and the gypsum board, it was evaluated as poor adhesion.

(5) hardness

The gypsum board was measured for hardness according to ASTM C 473.

Specifically, a gypsum board of 305 mmX76 mm (width X length) was used as the test piece, and the edge portion of the test piece was fixed to the edge hardness measuring device so that it was facing upward, and after measuring three times, the average value was used as the hardness.

(6) Flexural failure load

The flexural fracture loads in the longitudinal and width directions were measured using the KS F 3504 flexural fracture load measurement method.

(7) nail pull resistance

Nail pulling resistance was measured according to ASTM C 473.

Specifically, a gypsum board of 152mmX152mm (widthXlength) was used as the test piece, and the test piece was fixed to the auxiliary plate, and a jig (nail shank Dia. 2.515±0.076mm, Nail head Dia. 6.350±0.127mm) was used. The jig was lowered until the nail head part came into contact with the surface of the test piece. After that, the zero point was set and the maximum load value was measured while the nail shank broke the specimen, and it was used as the nail pull-out resistance.

As shown in Table 4, the compositions for gypsum boards of Examples 1 to 4 had adequate fluidity, excellent workability, and adequate curing time, so that the prepared gypsum boards had excellent adhesion. In addition, the gypsum board of Example was excellent in hardness, flexural fracture load and nail pulling resistance.

On the other hand, the gypsum board of Comparative Example 1 containing a small amount of gelatinized starch lacked hardness, adhesive strength and flexural fracture load. In addition, the compositions for gypsum boards of Comparative Examples 2 and 3 containing an excess of pregelatinized starch had low fluidity and insufficient workability, and the gypsum boards of Comparative Example 3 having a high coma had low drying efficiency and lacked adhesion. In addition, the gypsum board of Comparative Example 4 containing oxidized starch had problems with low hardness and low nail pulling resistance. In addition, the composition of Comparative Example 5, including gelatinized starch-2 having low solubility, had an excessively long curing time, and thus the adhesive strength of the prepared gypsum board was insufficient. In addition, the gypsum board of Comparative Example 6 containing gelatinized starch-3, which had too high solubility, lacked adhesion.

Claims (6)

A gypsum board comprising a composition comprising 100 parts by weight of calcined gypsum and 0.1 to 0.4 parts by weight of gelatinized starch,
The gelatinized starch has a solubility of 5 to 12%,
The gypsum board has a hardness of 90N or more, measured according to ASTM C 473, and a nail pull-out resistance of 220N or more, a gypsum board. The method according to claim 1,
The gelatinized starch has a viscosity at 25° C. of 100 to 400 cps, a gelatinization temperature of 20 to 60° C., and contains 10% by weight or less of moisture based on the total weight of the starch, gypsum board. The method according to claim 1,
The calcined gypsum has an average particle size of 18 to 45 μm, gypsum board. The method according to claim 1,
The composition has a viscosity at 25° C. of 250 to 300 cps, and a lethality of 65 to 80%, gypsum board. The method according to claim 1,
The composition has an inner diameter of 7 cm on the bottom, 6 cm on the inner diameter of the top, and an average diameter of 95 to 150 mm of ejection formed when the composition is filled in a slump cone with a height of 4 cm and lifted to a height of 10 cm after 5 seconds. phosphorus, gypsum board. The method according to claim 1,
The gypsum board has a bending fracture load of 365N or more in the longitudinal direction measured in accordance with KS F 3504, and a bending fracture load of 160N or more in the width direction, gypsum board.