JPS581065B2 - Method for producing inorganic cured body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an inorganic cured product containing calcium aluminate trisulfate hydrate as a main component.

Calcium aluminate trisulfate hydrate (3CaO-Al203・3CaSO4・nH20,n
An inorganic cured body containing TSH as a main component (hereinafter abbreviated as TSH), which has a value of approximately 31 to 32, has been produced in the following manner.

That is, calcium aluminate monosulfate hydrate (3CaO:Al2O3・CaSO4・nH
20, n takes a value of approximately 12, hereinafter referred to as MSH
), gypsum, water, and a reinforcing material such as pulp are mixed to create a slurry, which is then made into paper, cured, and hardened by reacting MSH and gypsum to form TSH. It was produced dry.

However, although the inorganic cured product obtained in this manner has high strength under normal conditions, the strength decreases significantly when water is absorbed because of its high water absorption rate.

In order to prevent this, it has been considered to add a paraffin-based or fatty acid-based water repellent to the slurry to improve the water absorption rate and reduce the decrease in strength when water is absorbed.

However, even when various water repellents were added to the slurry in this way, the water absorption rate did not improve much.

The same results were obtained even when the amount and timing of addition of the water repellent agent was changed.

By the way, the water absorption rate [(water absorption weight - dry weight) / (dry weight) x 100) of an inorganic cured body with a specific gravity of 0.9 manufactured using a slurry to which no water repellent is added is 47%, The water absorption rate of an inorganic cured body with a specific gravity of 0.9 produced using a slurry in which a water repellent was added to be 0.5 to 1.5% by weight of the total solid content was 35 to 40%. .

As a result of intensive research to solve these problems, the inventors found that the main raw materials such as MSH, gypsum, and reinforcing materials in the slurry are negatively charged, and various water repellents are also negatively charged. It was discovered that the main raw material and the water repellent repel each other, so the fixation rate of the water repellent to the main raw material is poor, and the water repellent is washed away along with perspiration during papermaking.

As a result of further research, we found that T
When only the SH is positively charged and this TSH is mixed into the main raw material, the water repellent is attracted to the TSH and firmly fixed to the main raw material, preventing the water repellent from being washed away. This invention was completed after discovering that the fixing rate was significantly improved.

That is, the present invention is a method for producing an inorganic hardened material by forming a slurry containing calcium aluminate monosulfate hydrate, gypsum, and water as main components and containing a water repellent, and then curing and hardening the slurry. The gist thereof is to further contain calcium aluminate trisulfate hydrate in the slurry.

Next, this invention will be explained in detail.

The MSH used in this invention can be obtained by conventional methods such as CaO
The material obtained by blending the component raw materials, the Al203 component raw materials, and the CaSO4 component raw materials in a predetermined ratio and hydrothermally synthesizing them is used.

Such MSH and gypsum are blended in a theoretical molar ratio for TSH production.

In this case, the gypsum used may be dihydrate gypsum, hemihydrate gypsum, or anhydrous gypsum.

Water is then added to this MSH and gypsum blend and kneaded to form a slurry.

This slurry contains a paraffin-based, fatty acid-based water repellent that can be dispersed in the slurry, and TSH for fixing the water repellent.

In order to contain a water repellent agent and TSH for fixing the water repellent agent in the slurry, TSH and the water repellent agent are mixed in advance, this mixture is mixed with main raw materials such as MSH and gypsum, and this is used. The water repellent agent and TSH may be contained in the slurry by preparing a slurry, or by mixing a mixture of TSH and water repellent with a mixture of MSH and gypsum and using this to form a slurry. You may let them.

Alternatively, the mixture of TSH and water repellent may be added directly to the slurry, or one of the TSH or water repellent may be mixed into the main raw material or the MSH and gypsum formulation and the other mixed into the slurry. It may also be included.

In this case, positively charged TSH in the slurry
is mixed into the main raw material such as negatively charged MSH and gypsum, and the negatively charged water repellent is attracted to the positively charged TSH, thereby firmly fixing the water repellent to the main raw material. do.

Therefore, by uniformly dispersing and mixing TSH into the main raw material, the water repellent can be fixed to the main raw material in a uniform state.

The amount of water repellent used is 0.0% of the total solid content of the slurry.
It is preferable to select the amount from 5 to 5.0%, more preferably from 0.5 to 1.5%.

Preferably, the amount of TSH used is four times or more the amount of the water repellent.

If the amount of TSH used is below this range, the effect will be reduced.

Next, the slurry containing the water repellent and TSH is formed into a plate shape by papermaking.

In this case, the TSH mixed in the main raw material and the water repellent agent are electrically attracted to each other, and the water repellent agent is firmly fixed to the main raw material. It will not flow out together with the water discharged from papermaking felt, etc., and its retention rate will be significantly improved.

For reference, Table 1 shows the interfacial potentials of the main raw materials, water repellent (fatty acid type), and TSH in white water at pH 10.5.

Next, the plate-shaped excipient is cured, and MSH and gypsum are reacted to form TSH, thereby being hardened and dried.

In this case, the plate-shaped excipient contains TSH for fixing the water repellent, but this TSH does not adversely affect the TSH conversion reaction between MSH and gypsum in the plate-shaped excipient.

Further, the composition of the obtained TSH cured product remains unchanged, and there is no adverse effect of TSH for fixing the water repellent agent.

In this way, it is possible to obtain an inorganic cured product that contains a sufficient amount of water repellent in a uniform state, has a low water absorption rate, and exhibits a small decrease in strength upon water absorption.

Next, examples will be described together with comparative examples.

Examples 1 to 5, Comparative Examples 1 to 3 A main raw material composition consisting of 120 parts by weight (hereinafter abbreviated as parts) of MSH slurry with a solid content concentration of 45%, 30 parts of gypsum, 8 parts of pulp, and 1.5 parts of glass fiber was used. The slurry was poured into 1000 parts of white water and mixed for 1 minute using a mixer to form a mixed slurry, which was then formed into a paper sheet with a solid content of 60%.

Next, this paper-made plate was left to stand for a day and night, and then dried at 60° C. for 4 hours to obtain a plate-shaped inorganic cured product.

When producing this inorganic cured product, a fatty acid-based water repellent (trade name: Cellosol PC, manufactured by Chukyo Yushi Co., Ltd.) is added in the amount shown in Table 2 at the end of the table, and at the time shown in the same table. TSH for fixing the water repellent shown in the table was added at the time shown in the same table.

The specific gravity and water absorption rate of the obtained inorganic cured product are shown in the same table.

As is clear from Table 2, it can be seen that the inorganic cured bodies obtained in the examples have a significantly low water absorption rate, and therefore a decrease in strength upon water absorption is extremely small.

Claims (1)

[Scope of Claims] 1. A method for producing an inorganic hardened product by forming a slurry containing calcium aluminate monosulfate hydrate, gypsum and water as main components and containing a water repellent, and then curing and hardening the slurry. A method for producing an inorganic cured body, comprising further containing calcium aluminate trisulfate hydrate in the slurry. 2. The method for producing an inorganic cured body according to claim 1, wherein the content of calcium aluminate trisulfate hydrate is set to be four times or more the content of the water repellent on a weight basis.