JPS589066B2 - fire resistant composition - Google Patents

Description

Detailed Description of the Invention The present invention relates to monolithic refractories (castable refractories) mainly used for pouring construction, spraying construction, pressure-feeding construction,
The present invention relates to a fireproof composite that can be applied by troweling, ramming, vibrating, etc., and can also be applied to press cast products and unfired brick tiles.

Castable refractories commonly used in the past include those made by blending alumina cement with refractory aggregate, but these castable refractories have drawbacks due to the alumina cement used as a binder.

In order to improve this point, research has already been carried out on the use of ρ-alumina, a type of transition alumina, as a binder, and it has also been found that dispersants or vaporized silica are effective as bonding aids.

As vaporized silica, high-purity silica obtained by hydrolyzing silicon tetrachloride in an oxyhydrogen flame and low-purity silica dust obtained as a by-product when manufacturing metal silicon alloys can be used. Those with a high value are extremely expensive;
Silica dust varies in quality, and since it is a by-product, there may be problems in supply.

In order to solve these problems, the present invention uses glass powder as a bonding aid that can replace vaporized silica, uses a dispersant as a bonding aid, and uses electrolyte or organic glue to improve workability in this case. It is added with an agent.

Next, the composition of the present invention will be explained in detail.

(1) Aggregate As aggregate, any material other than those that react with alumina and significantly lower the melting point can be used, and all refractory materials that are generally used as shaped refractories can be used.

Acidic aggregate; silica, zircon, zirconia.

From the point of view of heat resistance, siliceous aggregate has a eutectic point (1595°C) with alumina, but if used at a temperature lower than this, it is possible to create castable refractories with stable strength. be.

In particular, when fused silica is used as an aggregate, a material with high spalling resistance can be obtained, and when foamed silica is used, lightweight refractories can be produced.

Neutral aggregate: chromia, alumina, mullite, sillimanite, silica-alumina refractories, silicon carbide, carbon, cordierite, spinel, chromite group refractories, nitrides, borides.

There is no decrease in heat resistance when blended with ρ-alumina.

It is the most common aggregate. Basic aggregate; magnesia, magnesia chromia-based refractory material.

Sintering is promoted and stabilized by reacting with alumina at high temperatures to form spinel.

Insulating aggregate; foamed alumina, foamed silica, foamed zirconia, chamotte, ceramic fiber, perlite, vermiculite, sawdust, styrofoam with rice moth.

Combustible materials can also be used as aggregates, including sawdust, rice hulls, styrofoam, and KHP of around 90 parts (weight).
-2 (ρ-alumina made by Sumitomo Aluminum Smelting Co., Ltd.)
Can be used as a heat insulating refractory material.

It is also effective to use an AE agent and a foaming agent in combination with the heat insulating aggregate.

The particle size composition of aggregate is important, and the particle size composition is determined from the workability aspect that matches the purpose of use, such as pouring construction, troweling construction, spraying construction, etc., or from the physical property standpoint, such as high strength and volume stability. .

These are basically the same concepts as general caster pull refractories.

Also, since castable refractories are unfired bodies, the use of sillimanite group raw materials such as kyanite and andalusite is effective in improving firing shrinkage due to heating and cooling, as is the case with general castable refractories.

Furthermore, as with general castable refractories, clay and ultrafine powder, especially aggregate powder of 2μ or less, are effective for finely adjusting workability.

(2) ρ-Alumina ρ-Alumina is gypsite (α-A1203.3H2
0), is an intermediate alumina produced by dehydrating pierite (β-Al203.3H20) in vacuum at low temperature.

The intermediate aluminas confirmed so far are ρ, χ, η,
There are seven types of γ, δ, θ, and κ, and among intermediate aluminas, ρ−
Only alumina has condensing properties and then exhibits a hardening phenomenon.

ρ-Alumina is hardened by the following reaction.

ρ-alumina + water → bayerite, boehmite gel Commercially available ρ-alumina is manufactured by Sumitomo Aluminum Smelting Co., Ltd. (KHP-2J), and this is composed of ρ-alumina, boehmite dehydrate, γ-alumina, χ- It is a mixture of alumina and contains about 60 parts (by weight) of ρ-alumina.

A comparison of its chemical composition with alumina cement is shown in Table 1.

The amount of ρ-alumina mixed in the aggregate as a castable refractory is 0.6 or more in terms of weight ratio (1φ for KHP-2).
(above), when glass powder or dispersant is blended as a bonding aid, the weight ratio should be 0.3 or more (0.5 or more for KHP-2), and if it is less than that, room temperature curability will decrease. .

(3) Glass Powder Frit is the best glass powder that is easily available.

Frit is a glass powder obtained by melting one or a mixture of two or more of silicate, borate, or phosphate, etc., and rapidly cooling and pulverizing it. have

Usually, the softening temperature is in the range of 300 to 1000°C, and it is also used in enamel, cloisonné, ceramic glazes, and sealants for electronic parts.

Common ones are borosilicate type or soda lime silicate type.

The smaller the particle size of the frit, the greater the effect, but time and energy are spent on grinding.

Those having an average particle size of about 10 μm to 150 μm are relatively easily available and convenient to use.

The amount of additive is 0.2% (weight) to 8% (weight)% [O-5%
(weight) to 7o (f amount) is good; if it is less than 0.2% (weight), the sintering effect will not be obtained, and if it is more than 8% (weight), problems will occur in heat resistance.

Table 2 shows the results of comparing various sintering aids with glass powder.

Samples 1 to 16 are various calcined materials in a basic composition of 88% (weight) of mullite aggregate, 4% (weight) of calcined alumina, and 8% (weight) of KHP-2 (ρ-alumina manufactured by Sumitomo Aluminum Smelting Co., Ltd.). They were baked at 1100°C with the addition of a setting aid, and the strength of each was measured.

From Table 2, beer bottle glass powder and frit are found to be effective as sintering aids, and the effect of frit is particularly remarkable.

It is presumed that Si, Fe-Si, SiC, SiN4, etc. do not exhibit their bonding effect unless the temperature is higher.

The borates, phosphates, and silicates that are normally used as binders for refractories are water-soluble, and when added in large amounts, the dissolved components inhibit the hardening of the ρ-alumina, resulting in no binding effect. it is conceivable that.

Also, as seen in beer bottle glass powder, the fineness of the additives also has a large effect.

As for frit, even one with a fairly coarse particle size has shown great effects with a small amount.

That is, a glass powder that is insoluble in water, has a high degree of fineness, and has a low softening temperature is considered to be effective.

Next, an experiment was conducted to confirm the effect using a general commercially available frit, and the results are shown in Table 3.

The composition of the samples of Examples 1 to 5 was SK chamotte, calcined alumina powder, sericite clay powder, KHP-12 (ρ-alumina made by Sumitomo Aluminum Smelting Co., Ltd.), polyol dispersant, borosilicate frit (average A composition having a particle size of 30μ and a softening temperature of 570Q) is shown, and a comparative example shows a composition in which no frit is added.

From Table 3, it can be seen that the frit does not have an adverse effect on the dry strength at 105°C, but increases the firing strength at 1100°C.

Furthermore, the hot strength at 1400°C has been improved.

(4) Dispersant ρ - Using a dispersant as a bonding aid in castable refractories using alumina as a binder is effective in improving workability, reducing the amount of added water, and increasing strength after curing. Alkali silicate, alkali phosphate, organic dispersant for cement concrete (lignin sulfonic acid type, oxycarboxylic acid type, alkylaryl sulfonic acid type)
is valid.

If the dispersant is added in an amount of 20 parts (by weight) or more to the total amount of fine powder of 74 μm or less in the castable refractory composition, deterioration in workability and bleeding become noticeable.

It is said that in normal concrete, the water/cement ratio decreases due to the water reduction effect and the strength increases.
In ρ-alumina bonding, ρ-alumina is uniformly dispersed by a dispersant, and the effect as a binder is enhanced, so that the strength can be sufficiently increased even without necessarily having a water-reducing effect.

However, in general, when a dispersant is used, the amount of added water is reduced and fluidity is improved.

At this time, a separation phenomenon occurs in which the aggregate sinks, especially the lower part solidifies.

This is hardly a problem as long as the material is used continuously for kneading and construction, but if the kneaded material is temporarily left in a tray box or the like, the lower part may become tight and reuse may be difficult.

This can be improved to some extent by adjusting the particle size, but small amounts of one or more of Honbushi clay, sericite, bentonite, white carbon, or vaporized silica powder may also be used.

A particularly effective means is to add an electrolyte or an organic sizing agent.

Electrolytes are substances that dissolve in water and produce ions.
Salts produced from acids and alkalis are effective here, particularly alkali metal salts or alkaline earth metal salts.

Organic thickening agents are water-soluble polymers that have a large thickening effect, such as starch, natural rubber, and cellulose.
Especially xanthan gum, gum arabic, methyl cellulose,
Carboxymethyl cellulose, calcined starch, etc. are effective.

The amount of electrolyte or organic sizing agent added is 0.01% (weight) to 1
% (weight) or less, especially 0.01% (weight) to 0.5% (weight) is best, and 1% (weight) or more should not be used except for special purposes.

Next, Examples 6 to 12 and Comparative Example 2, in which a dispersant was used as a binding aid and an electrolyte or an organic sizing agent was added thereto, were compared to the fourth example.
Shown in the table.

The composition of each sample was as follows: synthetic mullite, calcined alumina, KHP-2 (ρ-
alumina), a polyalkylaryl sulfonate dispersant, sodium hexametaphosphate, an electrolyte, or an organic sizing agent.Comparative examples have the same composition but do not contain an electrolyte or an organic agent.

The pot life was measured at 20°C.

It can be seen from Table 4 above that the addition of an electrolyte and an organic sizing agent reduces the separation phenomenon without causing a decrease in strength, and also extends the usable time and improves workability.

Next, Table 5 shows Examples 13 to 15 in which the amounts of frit, dispersant, and electrolyte added were varied, and Comparative Example 3 in which vaporized silica was used without adding these.

The composition of each sample is calcined bauxite, kyanite, calcined alumina powder, white carbon powder, Honbushi clay powder, soda lime frit (average particle size 70μ, softening temperature 600℃), high silicate frit (average particle size 50μ, softening temperature 970°C), β-naphthalene sulfonic acid formalin condensate dispersant (1), isobutylene maleic anhydride polymer dispersant (2), KHP-2 (manufactured by Sumitomo Aluminum Smelting Co., Ltd.) ρ-alumina) and common salt as an electrolyte, and the comparative example was made by adding vaporized silica to the same aggregate, KHP-2.

The pot life was measured at 20°C.

From Table 5, the binding aid effect of frit is the sintering effect at around A1100℃ and the increase in hot strength at 1400℃, and the effect on heat resistance is small compared to the binding effect, and is equivalent to the addition of vaporized silica. It can be seen that the physical property values of

According to the present invention, since glass powder is added as a bonding aid to a fireproof composition using ρ-alumina as a binder, it is cheaper and has a certain quality compared to the previously developed vaporized silica as a bonding aid. It can provide a constant supply of silica, and its binding effect is in no way inferior to vaporized silica.

When using a dispersant as a bonding aid, by adding an electrolyte or an organic sizing agent to it, the dispersant can homogeneously disperse ρ-alumina in the composition and have the same bonding effect as when vaporized silica is added. At the same time, the separation phenomenon caused by the addition of a dispersant can be prevented by adding an electrolyte or an organic sizing agent.
As a result, the workable time can be improved.

Claims (1)

[Scope of Claims] 1. A fire-resistant composition characterized by using ρ-alumina as a binder and adding glass powder as a bonding aid. 2. A fire-resistant composition comprising ρ-alumina as a binder, a dispersant as a binding aid, and an electrolyte as a separation preventive agent. 3. A fire-resistant composition comprising ρ-alumina as a binder, a dispersant as a binding aid, and an organic sizing agent as a separation preventing agent.