JPS5812220B2 - Manufacturing method of waterproof lightweight gypsum board - Google Patents

Description

[Detailed description of the invention] The present invention involves kneading methylolated melamine resin with gypsum,
The present invention relates to a method of kneading a suitable formaldehyde scavenger in the presence of a suitable formaldehyde scavenger in order to capture traces or small amounts of formaldehyde generated during the production of water-resistant gypsum boards.

It has long been known that when water is added to hemihydrate gypsum and kneaded, a water-use reaction occurs and condensation occurs. A lightweight gypsum hardened body can be manufactured by incorporating the above.

The above method is a known method, as it has been attempted in the production of gypsum boards, but if the main body is made of lightweight gypsum board with a specific gravity of about 0.4 to 0.7, physical strength, fire resistance, etc. Decrease.

Therefore, the desired physical properties can be maintained or improved by containing an appropriate polymer compound or reinforcing fiber, and by making the board thickness 30 to 100 mm, which is thicker than commercially available gypsum boards.

On the other hand, as gypsum is said to be sensitive to water, the water saturation strength of commercially available gypsum boards or boards with a thickness of 30 to 100 mm is extremely low. limited to etc.

However, if the water saturation strength is maintained at about 50 modulus or higher, such as with calcium silicate plates or ALC (lightweight concrete), the applications can be expected to expand dramatically.

Furthermore, regarding product storage, packaging, and water exposure during construction,
It has the advantage that it does not require much attention compared to the conventional method.

Various methods have been tried to date to make gypsum waterproof, and the usual method for making waterproof gypsum boards is to knead an emulsion of asphalt and paraffin wax as waterproofing agents.

In addition, many methods have been attempted to improve the water resistance of gypsum by adding water resistance agents such as urethane resin, urea resin, melamine resin, silicone compounds, inorganic cement, lime, and calcium silicate. There is.

Asphalt-based emulsions and paraffin-based emulsions are very cheap and have excellent economical aspects, but in order to achieve the desired water resistance, the amount added to 100 parts of gypsum is usually 10 to 20 parts by weight. Since it requires a large amount of 100 ml, there are problems with its non-combustibility and fire resistance as a building material.

On the other hand, melamine resin has the desired effect even when added in a small amount, and is a water resistance imparting agent that is economically comparable to asphalt emulsions and paraffin wax emulsions.
From this point of view, many methods have been proposed for making plaster waterproof using melamine resin.

For example, a method of increasing the water saturation strength of a cured product by using a melamine resin and a metal compound in combination (JP-A-49-21420, JP-A-49-71017, JP-A-51-3)
0587), application to a coating agent using a large amount of thermosetting resin such as 10 to 20 parts of melamine resin (Japanese Unexamined Patent Publication No. 130432/1982), heating with a reduced amount of melamine resin added to sewage. Pressure molding method (Takekosho 49-
98851), conversely, the amount of water added is large, gypsum/water =
1.00/1.31 to 5.00, a method for producing a lightweight gypsum hardened body by adding 0 to 10 parts by weight of melamine resin (Japanese Unexamined Patent Publication No. 52-107023), thermosetting resin such as melamine resin A method of using a combination of melamine resin and a thermoplastic resin (Japanese Patent Publication No. 44-14236), a method of using a melamine resin and a furan resin together (Japanese Patent Publication No. 48-73426), polyvinyl resin under the conditions of gypsum/water = 100/50 to 400. Architectural board using 5 to 10 parts by weight of alcohol and 3 to 40 parts by weight of melamine resin or other resin and fibrous reinforcing material to polyvinyl alcohol
Many examples have been attempted, such as (No. 094 Publication).

However, there are many types of melamine resin, ranging from molding materials to adhesives, and commercially available melamine resins in particular have been modified for each purpose, such as by adding urea resin. In reality, it is difficult to select a melamine resin that is water resistant and suitable for manufacturing gypsum-based products.

In the present invention, when manufacturing lightweight gypsum board, we have integrated the effects of water saturation strength of the product, the stability of gypsum slurry such as setting time during manufacturing, the stability of melamine resin, and the continuous manufacturing method using melamine resin mixed wire. Taking this into consideration, it was found that the most suitable melamine resin is an aqueous solution of methylolated melamine resin.

However, when using methylolated melamine resin, formaldehyde is generated during the production of lightweight gypsum boards, so the present invention aims to solve this problem and eliminates formaldehyde without impairing the above-mentioned characteristics during production. The main idea is to find a suitable scavenger that suppresses the generation of water, and to further improve the effect of imparting water resistance to methylolated melamine resin.

That is, the present invention provides a powder based on hemihydrate gypsum, 10
0 parts by weight of water and methylolized melamine resin 0.1
~10 parts by weight, mixed with 0.01 to 10 parts by weight of a compound selected from at least one of melamine, thiourea, and ethylene urea as a formaldehyde scavenger, and stirred to incorporate air bubbles to form a lightweight gypsum board. The present invention provides a method for manufacturing a waterproof, lightweight gypsum board comprising:

Embodiments of the invention will be described below.

A slurry containing hemihydrate gypsum, water, methylolated melamine resin, formaldehyde scavenger, and additives such as a foaming agent is kneaded using a high-speed stirrer, then poured into a mold and cured in air until the water content is less than 2%. Dry until

For industrial production, the steps from pouring the slurry to drying are carried out continuously.

That is, the raw materials are fed into a high-speed kneading machine such as a pin mixer and poured onto a moving forming belt.

The gypsum slurry hardens on the forming belt and is automatically cut and loaded onto a trolley.

The board on the trolley is moved inside the dryer, and the moisture content of the board is adjusted to 2% or less when it leaves the dryer.

In the above manufacturing process, if there is no formaldehyde scavenger, formaldehyde in an amount of 0.1 to 10% by weight will be generated based on the methylolated melamine resin in the dryer, but in the presence of a formaldehyde scavenger, the amount of formaldehyde added will vary. Although it depends, it can be suppressed to 0 to 3 weight units.

In continuous manufacturing, the properties of the slurry are as important as the speed of the forming belt or the surface material such as nonwoven fabric or paper.
Generally, the slurry has an apparent setting time (AST) of 2 to 2
0 minutes, the fluidity of the slurry is 100 to 300 mm according to the flow value specified in JLSR-5201, and the slurry pH is 5.
It is desirable to set it to ~9.

The appropriate specific gravity of the lightweight gypsum board is 0.5 to 0.8, and it is molded to a thickness of 30 to 100 mm in consideration of fire resistance and noncombustibility.

Therefore, enough air bubbles to obtain the above-mentioned specific gravity are mixed into the slurry, and a foaming agent and a polymeric substance are added to stabilize the air bubbles.

Each component in the raw materials will be explained below.

The hemihydrate gypsum used in the present invention is flue gas desulfurization gypsum, phosphate gypsum, titanium gypsum, peroxylate gypsum, etc. α-type hemihydrate gypsum or β-type hemihydrate gypsum (calcined gypsum is used as a mixture of both).

The water used to harden hemihydrate gypsum is usually 100% hemihydrate gypsum.
30 to 100 parts by weight, preferably 50 to 9 parts by weight
0 parts by weight is suitable.

The methylolated melamine resin is suitably used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 4 parts by weight, per 100 parts by weight of powder (solid content) containing gypsum, and is in the form of an aqueous solution or aqueous dispersion. used.

Melamine has three amino groups, and common melamine resins are methylolated versions thereof.

The methylolated melamines applied in the present invention are monomethylolated melamines to hexamethylolated melamines, mixtures thereof including their prepolymers.

Furthermore, in order to improve their water solubility and storage stability, alcohols such as methanol and butanol may be added, or they may be partially etherified.

Formaldehyde scavenger is a powder (solid substance) containing gypsum
A suitable amount is 0.01 to 10 parts by weight, preferably 0.3 to 2 parts by weight, per 100 parts by weight.

As a scavenger, compounds that reduce the amount of formaldehyde generated without significantly impairing the properties of the slurry and the physical properties of the product, such as urea-based compounds (urea, thiourea, ethylene urea, etc.), sulfites, (sodium sulfite, Calcium sulfite, potassium sulfite, etc.), ammonium salts (
ammonium chloride, ammonium sulfate, ammonium thiocyanate, etc.), amine compounds (hydroxylamine hydrochloride, hexamethylenediamine, m-phenylenediamine, melamine, dicyanamide, etc.) and metal sulfates (ferrous sulfate, ferric sulfate, (cupric sulfate, aluminum sulfate, etc.), but those that give the most remarkable effect are melamine, thiourea, and ethylene urea, and remarkable effects appear when they are used alone or in combination.

Additives such as gypsum hardening accelerators include potassium sulfate, potassium alum, silicate, ammonium chloride,
There are hydrochloric acid, sulfuric acid, quicklime, etc., and AST of gypsum slurry
In order to adjust the AST to 3 to 20 minutes, preferably 3 to 12 minutes, the amount added is preferably 0 to 2 parts by weight, particularly 0.5 to 1.5 parts by weight, based on 100 parts by weight of gypsum.

As reinforcing fibers, inorganic fibers such as glass fibers, carbon fibers, and asbestos fibers, or organic fibers such as pulp, cotton, hemp, and synthetic fibers are suitable, and the amount added is O to 10 parts by weight per 100 parts by weight of plaster. parts, especially 0.5 to 3 parts by weight are preferred.

Examples of polymer compounds include water-soluble polymer substances such as polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxyl methyl cellulose, hydroxyethyl cellulose, and polyethylene oxide, or mixtures thereof, and the amount added is 0 to 10 parts by weight per 100 parts by weight of gypsum. , particularly preferably 0.5 to 3 parts by weight.

These are effective in increasing the viscosity of the slurry, improving foaming stability, and improving the strength of the cured product.

Next, a normal surfactant is used as a foaming agent, and the amount added is preferably 0 to 2 parts by weight, particularly 0.05 to 0.5 parts by weight, per 100 parts by weight of gypsum.

In addition, for hemihydrate gypsum that hardens quickly, add 0 to 2 parts by weight of a gypsum hardening retarder such as an amino acid type, and if the foaming effect is very good, use an antifoaming agent such as a silicone type or alcohol. It is also possible to add 2 parts by weight.

Of course, the above additives can be used alone or in combination.

In the above composition, fire resistance such as heat shrinkage rate, bending strength,
In order to improve physical properties such as compressive strength, or to reduce weight, 0 to 100% tensile agent is added per 100 weight of gypsum.
It is also effective to add 30 parts by weight, especially 5 to 25 parts by weight.

As a stimulant, whitebait of various particle sizes, whitebait balloons, slag, perlite, vermiculite, calcium silicate powder,
Examples include water glass foam, inorganic or organic lightweight aggregates such as expanded polystyrene, or waste sand.

By the way, methylolated melamine is mainly cured by heating in a dryer and exerts the desired water resistance on plaster, but accelerating the curing of methylolated melamine before drying the plasterboard has a better effect on water resistance. It may be large.

In such cases, the methylolated melamine cure rate depends on the pH
Therefore, it is preferable to maintain the gypsum slurry in an acidic or neutral range of pH 4 to 8.

Therefore, in principle, any acid may be used as the methylolated melamine curing accelerator, and acids such as sulfuric acid and hydrochloric acid may be used as the methylolated melamine curing accelerator.
It is effective to add to the extent that H can be maintained.

Furthermore, latent curing agents, i.e. compounds that generate acids when exposed to heat, etc. For example, ammonium salts such as ammonium chloride, ammonium sulfate, ammonium phosphate, and ammonium acetate can also be used.

As mentioned above, in addition to the auxiliary materials that can be added to the gypsum slurry, in order to make the lightweight gypsum board a material with excellent fire resistance, physical and mechanical strength, impact resistance, and surface finish. It is also effective to place woven or non-woven fabric or paper on the board surface.

Woven or non-woven fabrics consist of natural or artificial fibers, stable or continuous filaments bonded by physical (e.g. melting), chemical (e.g. adhesives) or mechanical (e.g. knitting) methods; There are organic fibers such as polyester, polyamide, polypropylene, polyethylene, cellulose acedate, polyvinyl chloride, acrylic resin, and silk, and inorganic fibers such as glass fiber, asbestos fiber, and carbon fiber.

Further, as the paper, base board paper used for ordinary gypsum board or base paper made waterproof is suitable.

The lightweight gypsum board manufactured using the above-mentioned raw materials generates very little formaldehyde during manufacturing, and is a water-resistant gypsum material with improved strength when saturated with water.

Examples will be described below along with comparative examples.

Comparative Example 1 155 g of water was added to a 500 ml beaker, and commercially available methylolated melamine resin 5I (added as a 2-fold diluted aqueous solution) was added.
While adding 202 g of α-hemihydrate gypsum, 50 g of whitebait, and 5 g of polyvinyl alcohol, stir and mix for 1 minute.

This slurry was poured into a mold of 20 x 20 x 70 mm, and the mold was removed after one plating period.

The above test piece was placed in a glass tube of an electric furnace and heated to 160°C.
While heating to 0°C and flowing nitrogen at 1 to 2 ml/see,
Gases such as water vapor were absorbed into the water trap.

Formaldehyde in the aqueous solution in the trap was determined at regular intervals by the sodium sulfite method, and the mixture was heated until formaldehyde could no longer be detected (Experiment No. 1).

Additionally, calcium sulfite, ammonium chloride, copper sulfate, urea, diacetylurea, and trimethylurea were added as formaldehyde scavengers to the above gypsum slurry, and the amount of formaldehyde generated was measured in the same manner (Experiments Nos. 2 to 7).
).

Example 1 Adding melamine, thiourea or ethylene urea as a formaldehyde scavenger to the gypsum slurry of Comparative Example 1,
The amount of formaldehyde generated was measured.

The results are shown in Table 1 and the attached drawings together with Comparative Example 1 (
Experiment numbers 8-12).

In the figure, curve 1 shows the case when thiourea is added, curve 2 shows the case when ethylene urea is added, and curve 3 shows the case when melamine is added.

The amount of formaldehyde scavenger is by weight relative to the methylolated melamine.

However, no formaldehyde was observed to be generated over the heating time shown in the table above.

Formaldehyde generation rate is 1 for blank (no scavenger)
It was set as oo%.

Comparative Example 2 A 2.01 container K was charged with 6.4 kg of water, 0.2 kg of polyvinyl alcohol, and 0.015 kg of a commercially available surfactant, and foamed to a predetermined amount while stirring.

Next, 8 kg of α-hemihydrate gypsum, 2 k9 whitebait, 0.2 k9 glass fiber cut into 1/2 inch pieces, and 0.25 kg of commercially available methylolated melamine resin were added, and after stirring for 1 minute,
It was poured into a mold of 50 x 250 x 65 mm and removed from the mold after 1 hour.

Drying was performed at 100 to 150° C. for 6 hours and at 80° C. or lower for 24 hours, and it was confirmed that the moisture content was 1 factor or less.

Example 2 Thiourea or melamine was added as a formaldehyde scavenger to the system of Comparative Example 2, and a lightweight gypsum board was obtained in the same manner as in Comparative Example 2.

The physical property test results are shown in Table 2 together with Comparative Example 2.

Example 3 Put 200 g of water in a 500 ml beaker, add 5 g of commercially available methylolated melamine (added as a 2-fold diluted aqueous solution), α-1 hemihydrate gypsum, β-2 hemihydrate gypsum mixture (α/β = 20/8
0) 200g, whitebait 50g, polyvinyl alcohol 5
Add g and stir and mix for 1 minute starting from the orange.

This slurry was poured into a 20x20x70 mm mold and demolded after 1 hour.

The above test piece was placed in a glass tube in an electric furnace according to Comparative Example 1, and the amount of formaldehyde generated was measured (Experiment No. 1) Example 3 Melamine was added as a formaldehyde scavenger to the gypsum slurry of Comparative Example 3, and formaldehyde was The amount generated was measured (experiment numbers 2-3).

Example 4 and Comparative Example 4 Comparative Example 30 Melamine and methylolated melamine were added as formaldehyde scavengers and a 10-dihydrochloric acid aqueous solution was added as a hardening accelerator to a gypsum slurry, and the amount of formaldehyde generated was measured.

The results are shown in Table 3 together with Comparative Example 3 and Example 3 (experiment numbers 4 to 6).

However, no formaldehyde was observed to be generated over the heating time shown in the table above.

The formaldehyde generation rate was set as 100% in Comparative Example 3.

Comparative example 5 20/8 kg of water, 0.2 kg of polyvinyl alcohol in a container
g and 0.015 kg of a commercially available surfactant were added, stirred, and foamed to a predetermined amount.

Next, 1.6 kg of α-1 hemihydrate gypsum and 6.4 kg of β-1 hemihydrate gypsum.
kl9, whitebait 2kg, glass fiber cut into inch pieces 0.2k9, commercially available methylolated melamine resin 0.25k
After stirring for 1 minute, pour into a mold of 750 x 250 x 65 mm. The mold was demolded after 1 hour.

Drying was performed at 100 to 150° C. for 6 hours and at 80° C. or lower for 24 hours, and it was confirmed that the moisture content was 1% or more.

The results of the bending strength test of the plates are shown in Table 4 along with the plates with compositions in which no methylolated melamine resin was present.

Example 5 and Comparative Example 6 Comparative Example. In the gypsum slurry of Step 5, 0.125 kg of 10-dihydrochloric acid aqueous solution was added as a methylolated melamine resin hardening agent, and 0.1 kg of ethylene urea was added as a formaldehyde scavenger.
A lightweight gypsum board was obtained in the same manner as in Comparative Example 5 except that K9 was added.

The results of the bending strength test of the plate are shown in Table 4 together with Comparative Example 5.

[Brief explanation of the drawing]

The accompanying drawing is a graph showing the relationship between the amount of formaldehyde scavenger added and the formaldehyde generation rate in the production of lightweight gypsum board according to the present invention.

Claims (1)

[Claims] 1 100 parts by weight of powder based on hemihydrate gypsum, water and 0.1 to 10 parts by weight of methylolated melamine resin, and as a formaldehyde scavenger selected from melamine, thiourea, and ethylene urea, at least 1 or more. Compound 0
．． 1. A method for producing a lightweight gypsum board, which comprises mixing with 1 to 10 parts by weight of 0.01 to 10 parts by weight, incorporating air bubbles by appropriate stirring, and forming a lightweight gypsum board.