JPS5830257B2 - Water-resistant gypsum composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to water-resistant gypsum compositions particularly useful as building materials.

Although gypsum molded products are commonly used as building materials, because gypsum is water-soluble, it is not used in indoor bathrooms or other water areas or outdoors.

Therefore, various proposals have been made to impart water resistance to gypsum molded products.

For example, JP-A-4952823 describes adding alumina cement or Portland cement to calcined gypsum, and JP-A-4952823 discloses that alumina cement or Portland cement is added to calcined gypsum.
The publication also describes the addition of potassium silicate.

JP-A-52-37927 describes a mixture of type A hemihydrate gypsum, which has been calcined with the addition of an alkaline substance such as calcium hydroxide or barium hydroxide, and portland cement.

JP-A-54-7423 describes a composition containing oxalic acid, phosphorus oxyacid, hexafluorosilicic acid, and their sodium and potassium salts.

Various other proposals have been made, and there are many types of additives, but none of these gypsum-cement-based products satisfy all of the properties of fluidity, strength, hardening speed, and water resistance. It hasn't appeared yet.

Gypsum resin-based products are known as described in JP-A-53-144934, "New Resources - Ceracola and Its Utilization" (Published by Soft Science Co., Ltd., P403 - Setsukou Floor Materials), etc. The strength decreases significantly due to blending, and a large amount of resin must be added to improve water resistance, so this increases the strength unique to gypsum.
Impractical as it impairs fire resistance.

As a result of various studies regarding the above points, the present inventors found that
By combining the gypsum-cement-resin system, it was possible to obtain a composition that satisfies all the properties of fluidity, strength, curing speed, and water resistance.

That is, in the present invention, when kneading a mixture mainly consisting of A-type hemihydrate gypsum and cement with water, at least one of alkaline acrylic and vinyl acetate resin emulsions is used as the resin solid content. The gist of the invention is a water-resistant gypsum composition characterized in that 1.5 to 10% of the composition is added by weight.

Since hemihydrate gypsum has high strength, type A is used.

As cement, portland cement, pozzolan cement, blast furnace cement, moderate heat cement, sulfate-resistant cement, etc. are used.

A suitable ratio of gypsum and cement is 7:3 to 5:5.

In addition, to improve fluidity, melamine formalin resin sulfonate (product name: Melment, manufactured by Showa Denko ■), alkylaryl sulfonate (product name: Mighty 100, manufactured by Kao Atlas ■, product name: High Flute, folded book) Add 0.5 to 2.0 weight of a water reducing agent such as oil (manufactured by ①).

Furthermore, if necessary, water floating prevention agents such as methyl cellulose and polyvinyl alcohol, protein-based retarders, hardening modifiers such as potassium sulfate, aluminum sulfate, and sodium oxalate, silicone resins (product name: X-50-418K), etc.
- Additives such as antifoaming agents such as Shin-Etsu Chemical Co., Ltd.) and polyoxyethylene (trade name: Nopco, San Nopco Co., Ltd.) may be added as appropriate depending on the purpose.

Examples of emulsions of alkaline lJ acrylic resins include Golex BTM (product name: manufactured by Kanebo Synthetic Chemical Co., Ltd.) and Brimar MC-4530 (product name: pH 8.6 to 10).
．． 1. Nippon Acrylic Co., Ltd.) etc. are used.

Further, as an emulsion of alkaline vinyl acetate resin, Tribase M3 (trade name: pH 8.5) is used.

(Manufactured by Taihohe Corporation) etc. are used.

These are used alone or in a mixture, and the amount is 1.5 to 1.5 to
A range of 10 weight φ is appropriate.

In a test using only the gypsum-cement system, the bending strength was sufficient at 130 kg/i, but the water resistance was insufficient, and the dry-wet repeated test (the gypsum composition was mixed with water, poured into a formwork, and the next day after hardening) After demolding and curing indoors for 2 weeks, the molds were placed in still water for 24 hours and then placed in a hot air dryer at 45° C. for 24 hours, each of which was considered one cycle, and experiments were conducted up to 40 cycles in each case.

) Most hair cracks occurred before the 15th cycle.

In addition, with only one gypsum resin system, the strength decreases as the amount of resin is added, and even when 2.5 weight percent is added, the bending strength is 10
At about 0 kg/i, the water resistance was insufficient and hair cracks occurred before the 15th cycle.

According to the present invention, the water resistance is sufficient, there is no cracking after 40 cycles, and the bending strength is about 120 to 140 kg/i, which is the same as the initial strength, but the amount of cement is If the amount is 300 parts by weight less,
Even if a resin component is added, sufficient water resistance cannot be obtained, and the bending strength after 40 cycles is less than 100 kg/ffl, which poses a problem of stability during long-term use.

Moreover, if the amount of cement exceeds 500 parts by weight, it is not preferable because it causes adverse effects such as cracks in the product.

If the resin content is less than 1.5 parts by weight, no improvement in the water resistance of the product will be obtained, and if it exceeds 100 parts by weight, the initial strength will be 100 kg/CI? L or less, the strength is greatly reduced, and there are many problems in terms of fire resistance and cost.

In the present invention, especially when used for casting, a water reducing agent is added as described above, but if it is less than 0.5 weight φ, its effect will be small.2. If the weight exceeds O, water-floating development cannot be prevented and it is not preferred as a casting composition.

As described above, the present invention employs a combination of gypsum-cement-resin system, thereby obtaining a composition that satisfies all required properties such as strength and water resistance, as well as fluidity and hardening speed.

Furthermore, the composition of the present invention may be used in the form of a mortar by adding sand or the like as needed, or the surface of the cured product may be coated to improve its design.

Next, the present invention will be further explained with reference to Examples and Comparative Examples.

Example 1 40 parts by weight of Portland cement, 1.0 parts by weight of Melment (mentioned above) as a water-reducing agent, and 0 parts of Metrose (mentioned above) as a water-floating prevention agent were added to 60 parts by weight of a-grade water gypsum produced as a by-product during the production of phosphoric acid. Golex BTM (mentioned above, resin content 50 parts by weight) was mixed well.
20 parts by weight of kneading water (100 parts by weight, pH 8.4) was added, thoroughly kneaded, poured into a mold, removed from the mold, and left to cure indoors for 2 weeks to obtain a product.

The bending strength of this item was measured and was 136 kg/c.
It was rit.

Further, when the bending strength was measured at the end of 40 cycles of the dry-wet repeated test, it was 127 kg/i, and no hair cracks were observed on the surface.

Example 2 50 parts by weight of a-grade water gypsum produced as a by-product during the production of phosphoric acid, 50 parts by weight of Portland cement, 1.0 parts by weight of Melment (mentioned above) as a water reducing agent, and 0 part of Metrose (mentioned above) as a water floating prevention agent. To a well-mixed mixture of 0.005 parts by weight, Tribase M3 (as mentioned above, resin content 50 parts soil)
100 parts by weight (pH 8.5) were mixed with 20 parts by weight of water, and after thorough kneading, the mixture was poured into a mold, removed from the mold, and cured indoors for 2 weeks to form a product.

The bending strength of this item was measured and was 132 kg/c.
It was rit.

Further, when the bending strength was measured at the end of 40 cycles of the wet and dry repeated test, it was found to be 130 kg/i, and no hair cranks were observed on the surface.

Example 3 50 parts by weight of a-grade water gypsum produced as a by-product during the production of phosphoric acid, 50 parts by weight of Portland cement, 1.0 parts by weight of Melment (mentioned above) as a water reducing agent, and 0 part of Metrose (mentioned above) as a water floating prevention agent. 005 parts by weight was added, 5 parts by weight of Colex BTM (as mentioned above, resin content 50%, pH 8,4) and 23 parts by weight of kneading water were added, and after thorough kneading, the same process as in Example 1 was carried out. When this product was tested in the same manner as in Example 1, the initial bending strength was 127 kg/
The bending strength after 40 cycles of dry/wet test with i is 135k.
g/i, and no hair cracks were generated on the surface.

Comparative Example 1 The same procedure as in Example 3 was performed except that the acrylic resin emulsion was removed from the composition of Example 3 and 255 parts by weight of kneading water was used. The initial bending strength was 115 kg/i, and at the end of 40 cycles of the dry-wet test The bending strength was 64 kg/ci, and hair cracks had already appeared at the 15th cycle.

Claims (1)

[Claims] 1 When kneading a mixture mainly consisting of type A hemihydrate gypsum and cement with water, at least one of alkaline acrylic and vinyl acetate resin emulsions is added as a resin solid content of 1.5 to 10% by weight. A water-resistant gypsum composition characterized by comprising the following: