JPS5919060B2 - Gypsum composition for casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cast river gypsum composition particularly suitable for molding large plate-like objects.

In order to manufacture plate-like products using gypsum as the main material,
The gypsum composition is poured into a vertical or horizontal mold and molded and hardened, but if the product is large, such as 3 x 8 shaku or 4 x 8 shaku, and has mold patterns on both the front and back, it is necessary to set the mold. It is necessary to use a vertical type, taking into consideration the area required for this, as well as equal degassing from both the front and back surfaces during manufacturing.

In this case, if water floating, material separation, foaming, etc. occur during casting of the gypsum composition, the product will not be homogeneous, but commercially available cast gypsum compositions have fluidity and antifoaming properties. , and there is no one that does not have water floating or material separation.

Therefore, even when making large plate-shaped objects, the reality is that the mold is placed horizontally and raw materials are poured into the mold.

Therefore, it is impossible to manufacture a product with a mold pattern on the upper surface because of poor gas release.

Furthermore, if the hardening material in the composition is gypsum alone, the expansion during hardening is large and cracks are likely to occur during curing.

Therefore, it has been considered to add hydraulic cement for the purpose of improving plasticity and strength, and one example is the one described in JP-A-51-4216, which is particularly relevant to extrusion molding compositions. It is.

In extrusion molding, it is impossible to mold a panel having a deep uneven pattern such as a relief pattern on both the front and back sides.

In addition, in pressure molding, it is difficult to mold a panel with uneven patterns on both sides, especially when considering degassing in the patterned portion of the lower surface, and even if it is possible, the equipment cost will increase.

The present invention was made in view of the above points, and by providing a gypsum composition with good fluidity and no water floating, even large plate-like objects with mold patterns on both the front and back sides can be easily poured into vertical molds. It is a method that makes it possible to easily manufacture everything from small-scale, high-mix products to mass-produced products without requiring large equipment costs like pressure molding, etc., and has a specific surface area of 4.0.
00~10.000cTL/g α-type soil water gypsum 70~
95 parts by weight, 5 to 30 parts by weight of cement, 0.5 to 30 parts by weight of water reducing agent
This is a cast river gypsum composition characterized by mainly containing 2.0 parts by weight.

And as needed, water floating prevention agent hardening regulator,
Antifoaming agents may also be added.

There are α-type and β-type hemihydrate gypsum, and the α-type hemihydrate used in the present invention is particularly strong.

This makes it possible to manufacture large wall materials, etc.

The particle size of this α-type clay water gypsum is 4.000 to 10.
,009c11! Use L/g.

If the particle size is less than 4,000 ayt/11, water will float, making it unsuitable for pour molding using a vertical mold, and if it exceeds 10,000 cTL/g, it will harden rapidly.
The pot life (time until viscosity increases and fluidity decreases after mixing) is less than 5 minutes, making it impractical.

*The present invention In the present invention, such α-type earth water gypsum is used together with cement.

As the cement, Portland cement, pozzolan cement, blast furnace cement, etc. are used.

Such cement is added to adjust the expandability of α-type earth water gypsum when it hardens, and also to increase its strength.

A test was conducted on the mixing ratio of α-type soil water gypsum and cement, and the results shown in Table 1 were obtained.

α-type soil water gypsum has a specific surface area of 6.550 crl/,
! i' was used, and Portland cement was used as the cement.

In addition, water reducing agent (melamine formalin resin sulfonate [
1.0 parts by weight of Melment (trade name: manufactured by Showa Denko), 0.04 parts by weight of an antifoaming agent (silicone resin type), and 25 parts by weight of kneading water were used.

As is clear from Table 1, if the amount of cement is less than 5 parts by weight, the flow value will be poor, the starting time will be long, and the setting expansion will be large, so that it cannot be used as a casting material, which is the object of the present invention.

Furthermore, if the amount of cement exceeds 30 parts by weight, drying shrinkage will be greater than solidification expansion, and cracks will occur during curing when large plate-shaped products are made.

Therefore, for 70 to 95 parts by weight of α-type soil water gypsum,
The optimal blending range is 5 to 30 parts by weight of cement.

If only α-type soil water gypsum and cement are used, the fluidity may be insufficient and a water floating phenomenon may occur, so in the present invention, 01
It is essential to blend 5 to 260 parts by weight of a water reducing agent.

Examples of water reducing agents include melamine formalin resin sulfonate (trade name: Nimerment, manufactured by Showa Denko), alkylaryl sulfonate (trade name: Mighty 100, manufactured by Kao Atlas ■), and product name: High Flute, Monohon. (made of oil and fat) etc. are used.

If these are less than 0.5 parts by weight, their effects will be small; 2.
If it exceeds 0 parts by weight, the water floating phenomenon cannot be prevented, which is not preferable.

In the present invention, in addition to the above, water floating preventive agents, hardening regulators, and antifoaming agents that are often used in gypsum thread compositions can be used. Examples of water floating preventive agents include methyl cellulose, polyvinyl alcohol, etc. is effective, and the amount is preferably up to 0.05 parts by weight.

Effective curing modifiers include generally known protein-based retarders, potassium sulfate, aluminum sulfate, sodium oxalate, and the like, and the amount thereof is preferably up to 1 part by weight.

As an antifoaming agent, silicone resin type (product name: X5O-
418K (manufactured by Shin-Etsu Chemical ■), polyoxyethylene (trade name: Nopco, manufactured by San Nopco ■), etc. are effective, and the amount thereof is preferably up to 0.5 part by weight.

The optimal amount of kneading water is 25±3 parts by weight.

Next, examples and comparative examples will be described.

Example 1 A cast river gypsum composition of the present invention having the following formulation was obtained using α-type earth water gypsum produced as a by-product during the production of phosphoric acid with a specific surface area of 5.620 crttl &.

α-type soil water gypsum 80 parts by weight Portland cement 20 Water reducing agent (product name: Melment [mentioned above]) 1. OS antifoaming agent (trade name: X5O-418K [listed above:]) 0.04 # 25 parts by weight of water was added to the composition of the present invention and thoroughly kneaded.

The starting time was 30 minutes and the flow was 203 m/m.

This composition is 900WX2,400LX40tm/
In order to produce a plate-shaped body of size m, the material was poured into a vertical mold in which an uneven pattern with a depth of 2 m and 1 m was to be formed on both the front and back sides.

A 26m/m thick cardboard was placed inside the mold as a core material.
The mold was arranged so that 7 m/m thick material was deposited on both sides.

The mold was released 2 hours after curing and left to dry for 2 weeks indoors.

This product plate-like product had no surface stains or air bubbles due to water floating on the gypsum, and did not develop any cracks even after curing, and a beautiful mold pattern was obtained on both the front and back surfaces.

The bending strength of the cured gypsum after 7 days was 132 kg/c.
It was TL.

Example 2 A cast river gypsum composition of the present invention having the following formulation was obtained using α-type earth water gypsum produced as a by-product during the production of phosphoric acid and having a specific surface area of 6.550 cffl/g.

α-type soil water gypsum 80 parts by weight Portland cement 20 Water reducing agent (product name: Melment [mentioned above]) 1.2 TTT adjustment agent (sodium oxalate) 0.5# antifoaming agent (product name: X-50- 418K [supra]) 0.04 g 25 parts by weight of water was added to this composition of the present invention and thoroughly kneaded.

The starting time was 32 minutes and the flow was 186 m/m.

This composition was cast into a plate in the same manner as in Example 1.

The product had no surface stains or air bubbles due to floating plaster, and no cracks occurred after curing.

The bending strength of the cured gypsum after 7 days was 1281y/f.
It was fl.

Example 3 In Example 2, 900 yen was produced without using corrugated core material.
A plate-shaped body of Wx2,400Lx14 tm/m was produced, and the product had no surface stains or air bubbles due to water floating, and no cracks were formed even after curing.

In addition, the bending strength of the gypsum hard compound after 7 days was 136k.
It was y/i.

Comparative Example 1 A cast river gypsum composition of the present invention having the following formulation was obtained using α-type earth water gypsum produced as a by-product during the production of phosphoric acid and having a specific surface area of 3.790 CrIL/g.

α-type soil water gypsum 80 parts by weight Portland cement 20 Water reducing agent (product name: Melment [mentioned above]) 1. Ott water anti-flotation agent (trade name: Nimetolose [mentioned above]) O-03tt 1 Curing regulator (sodium oxalate) 0.5
ttt foaming agent (trade name: X-50-418K [listed above]) O-04tt 25 parts by weight of water was added to this composition and thoroughly kneaded.

The starting time was 32 minutes, and the float was 186 ml.

This composition was cast into a plate in the same manner as in Example 1.

This plate-like body had many air bubbles due to floating water, and the strength of the upper part (at the time of manufacture) was insufficient.

; Comparative Example 2 Specific surface area 6. , 550 cr7 L/g of α-type earth water gypsum produced as a by-product during the production of phosphoric acid, a cast river gypsum composition of the present invention having the following formulation was obtained.

α-type soil water gypsum 60 parts by weight Portland cement 40 Water reducing agent (product name: Melment [mentioned above)] 1.2 TTT adjustment agent (sodium oxalate) o, 5 TTT foaming agent (product name: X-50-418K) [Supra]) o, o4tt □ 25 parts by weight of water was added to this composition and thoroughly kneaded.

The starting time was 29 minutes and the flow was 203 mA.

This composition was cast into a plate in the same manner as in Example 1.

Although this plate-like body had no surface stains due to water floating, cracks occurred due to shrinkage during curing.

Even when the composition of the present invention is cast and molded in a vertical mold as described above, a homogeneous and strong plate-like body can be obtained, and a mold pattern can be formed on both the front and back sides. It is useful when applied to building materials such as doors, partitions, etc.

Claims (1)

[Claims] 1. Specific surface area 4,000 to 10,000 cr? L/!
j α type earth water gypsum 70-95 parts by weight, cement 5-3
1. A cast river gypsum composition, characterized in that it mainly contains 0 parts by weight and 0.5 to 20 parts by weight of a water reducing agent. 2. A cast river gypsum composition according to claim 1, which contains a water floating preventer, a hardening regulator, and an antifoaming agent.