JP7633543B2 - Unshaped refractories - Google Patents

Description

This disclosure relates to a castable refractory material that contains a basic aggregate and phosphoric acid as a binder.

Various types of binders are known for monolithic refractories, including cement bonds such as alumina cement, chemical bonds such as phosphoric acid, phosphates, and silicates, resin bonds, pitch bonds, and clay bonds. Of these, monolithic refractories containing phosphoric acid or phosphates show little loss of strength in the medium to low temperature range. In particular, phosphoric acid has a greater effect than phosphates.

Japanese Patent Application Publication No. 118677/1983 Japanese Unexamined Patent Publication No. 57-067070

However, castable refractories containing basic aggregates such as magnesia raw materials may harden quickly if they contain phosphoric acid as a binder (Patent Document 1). For this reason, unshaped refractories containing phosphoric acid as a binder are limited to those that mainly contain alumina raw materials as aggregates (Patent Document 2).

This disclosure has been made in consideration of the above-mentioned circumstances, and its purpose is to provide an unshaped refractory material that can suppress rapid setting, ensure a usable time, and has little loss of strength in the medium and low temperature ranges.

One aspect of the present disclosure is
The composition includes a basic aggregate, phosphoric acid as a binder, and polyacrylic acid and citric acid as additives.
The additive may include calcined alumina and/or basic aluminum lactate,
The present invention relates to a monolithic refractory material, characterized in that the contents of the phosphoric acid, the polyacrylic acid and the citric acid relative to a total content of 100 parts by mass of the basic aggregate, the calcined alumina and the basic aluminum lactate are 3.0 to 11.0 parts by mass, 0.1 to 1.0 parts by mass and 0.5 to 2.0 parts by mass, respectively.

As a result, even if the molded refractory material containing basic aggregate such as magnesia raw material contains phosphoric acid as a binder, rapid setting is suppressed, the usable time can be secured, and the phosphoric acid has the effect of minimizing the decrease in strength in the medium and low temperature range. The reason for this is not entirely clear, but it is thought that polyacrylic acid and citric acid have a pH buffering effect.

In one aspect of the present disclosure,
The additive further comprises boric acid,
The content of the boric acid is preferably 2.0 parts by mass or less (excluding 0 part by mass) relative to 100 parts by mass of the total content. This makes it possible to extend the pot life.

A preferred embodiment of the present disclosure will be described in detail below. Note that the present embodiment described below does not unduly limit the content of the present disclosure described in the claims, and not all of the configurations described in the present embodiment are necessarily essential as a solution to the present disclosure.

The amorphous refractory of this embodiment contains basic aggregate, phosphoric acid as a binder, polyacrylic acid and citric acid as additives, and may contain calcined alumina and/or basic aluminum lactate as additives, and the contents of phosphoric acid, polyacrylic acid and citric acid per 100 parts by mass of the total content of the basic aggregate, calcined alumina and basic aluminum lactate are 3.0 to 11.0 parts by mass, 0.1 to 1.0 parts by mass and 0.5 to 2.0 parts by mass, respectively. As a result, even if an amorphous refractory containing a basic aggregate such as magnesia raw material contains phosphoric acid as a binder, rapid setting is suppressed, a usable time can be ensured, and the effect of phosphoric acid in reducing the decrease in strength in the medium and low temperature range can be exhibited.

<Basic aggregate>
The monolithic refractory of this embodiment includes a basic aggregate. The basic aggregate is not particularly limited as long as it is generally used in monolithic refractories, and examples thereof include magnesia raw material, spinel raw material, calcia raw material, and dolomite raw material. In this specification, typical magnesia raw material and spinel raw material are used as basic aggregate. The magnesia raw material is not particularly limited as long as it is generally used in monolithic refractories, and examples thereof include electrofused magnesia, seawater magnesia, natural magnesia, electrofused magnesia chrome, and sintered magnesia chrome. The spinel raw material is not particularly limited as long as it is generally used in monolithic refractories, and examples thereof include electrofused spinel and sintered spinel. The grain size of the basic aggregate can be appropriately adjusted depending on the application.

<Binder>
The monolithic refractory material of this embodiment contains phosphoric acid as a binder. For example, a 75% by mass phosphoric acid solution may be used as the phosphoric acid, or the phosphoric acid concentration may be appropriately changed. The content of phosphoric acid relative to the total content of the basic aggregate, calcined alumina, and basic aluminum lactate of 100 parts by mass is preferably 3.0 to 11.0 parts by mass, more preferably 4.0 to 6.5 parts by mass. If it is less than 3.0 parts by mass, the strength decreases, and if it exceeds 11.0 parts by mass, the viscosity of the kneaded product increases, which is not preferable. In this specification, the content of phosphoric acid is calculated using the mass including components other than phosphoric acid (in the case of a 75% by mass phosphoric acid solution, the mass of the entire phosphoric acid solution including 25% by mass of components other than phosphoric acid) (the same applies to other raw materials).

<Polyacrylic acid>
The monolithic refractory material of the present embodiment contains polyacrylic acid as an additive. The content of polyacrylic acid is preferably 0.1 to 1.0 parts by mass, more preferably 0.25 to 0.5 parts by mass, based on 100 parts by mass of the total content of the basic aggregate, the calcined alumina, and the basic aluminum lactate.

<Citric acid>
The monolithic refractory of this embodiment contains citric acid as an additive. The content of citric acid is preferably 0.5 to 2.0 parts by mass, more preferably 1.0 to 1.5 parts by mass, based on 100 parts by mass of the total content of the basic aggregate, the calcined alumina, and the basic aluminum lactate . In this specification, there is no distinction between anhydrous citric acid and monohydrate citric acid.

By keeping the polyacrylic acid and citric acid within the above ranges, rapid setting is suppressed even when the castable refractory material containing basic aggregate contains phosphoric acid as a binder, and the pot life can be secured, and the phosphoric acid has the effect of minimizing the decrease in strength in the medium and low temperature range. The reason for this is not entirely clear, but it is thought that polyacrylic acid and citric acid have a pH buffering effect.

<Boric Acid>
The monolithic refractory of this embodiment may further contain boric acid as an additive. The content of boric acid is preferably 2.0 parts by mass or less (excluding 0 part by mass), more preferably 0.5 to 1.5 parts by mass, relative to 100 parts by mass of the total content of the basic aggregate, the calcined alumina, and the basic aluminum lactate. This promotes the effect of extending the pot life.

<Fine powder raw material>
The monolithic refractory of this embodiment may further contain a fine powder raw material as an additive. The fine powder raw material is not particularly limited as long as it is generally used for monolithic refractories, and examples thereof include silica fume, calcined alumina, magnesia fine powder, spinel fine powder, etc. Examples of the calcined alumina include alumina fine powder having an average particle size of 10 μm or less, and the content thereof relative to the total content of the basic aggregate, the calcined alumina, and the basic aluminum lactate of 100 parts by mass is preferably 10.0 parts by mass or less, more preferably 3 to 8 parts by mass. This makes the viscosity of the kneaded product appropriate and has excellent fluidity, thereby improving the freedom of the shape of the monolithic refractory.

<Other additives>
The monolithic refractory of this embodiment may further contain basic aluminum lactate as another additive. The content of basic aluminum lactate is preferably 0.2 to 5 parts by mass, more preferably 2 to 4 parts by mass, based on 100 parts by mass of the total content of the basic aggregate, calcined alumina, and basic aluminum lactate. This makes it possible to suppress digestion of the basic aggregate (disintegration due to hydration). The monolithic refractory of this embodiment may further contain a known dispersant, organic fiber, metal fiber, etc., depending on the purpose.

The following describes in detail the embodiments of this disclosure.

<Sample preparation>
The following raw materials were used in the examples of the present disclosure. That is, as the basic aggregate, a magnesia raw material, electrically fused magnesia containing 98% by mass of MgO, and a spinel raw material, electrically fused spinel containing 25% by mass of MgO and 75% by mass of Al ₂ O _{3 ,} were used. As the phosphate binder, a 75% by mass phosphoric acid solution was used, and as a comparative binder, a solution of aluminum phosphate I was used. As the polyacrylic acid, a commercially available industrial chemical was used, and as the citric acid and boric acid, commercially available reagents were used. As the calcined alumina, alumina fine powder with an average particle size of 10 μm or less was used. As the basic aluminum lactate, 35% by mass of Al ₂ O ₃ and 48% by mass of lactic acid were used.

The composition of the monolithic refractory raw materials is shown in Table 1. The content of each raw material was calculated using the mass of the entire raw material including impurities (for example, in the case of a 75% by mass phosphoric acid solution, the mass of the entire phosphoric acid solution including 25% by mass of components other than phosphoric acid).

The amount of water shown in Table 1 was added to the unshaped refractory raw materials and kneaded to obtain a kneaded product. The resulting kneaded product was evaluated for fluidity and bending strength as follows.

<Liquidity>
The flow test method of JIS R 2521 was applied, and the mixture filled in the flow cone was placed on a vibration table, the flow cone was removed, and the mixture was vibrated at a vibration acceleration of 1.3 G for 60 seconds to measure the vibration flow value. The flowability of the mixture was evaluated as follows: (1) workability: whether the properties of the mixture are good and suitable for work, (2) pot life: whether the pot life required for pouring can be secured, and (3) fluidity. When all three items were excellent, they were rated as excellent (◎), when they were slightly inferior to excellent (◎) but good, when they were slightly inferior to good (○) but usable, they were rated as acceptable (△), and when there was a problem with even one item and it was unusable, they were rated as unacceptable (×). When it was not possible to measure due to aggregation or hardening (rapid setting), it was rated as "N/A".

<Flexural strength>
The kneaded material was poured into a 40 mm x 40 mm x 160 mm mold, cured at 50 ° C for 24 hours, and heated at 200 ° C for 24 hours to obtain a monolithic refractory. The bending strength of the monolithic refractory was measured according to JIS R2553. Those that could not be poured into the mold due to aggregation or hardening (rapid setting) were marked as "N / A".

<Evaluation Results>
The evaluation results are shown in Table 1.

All of the examples showed excellent fluidity and bending strength. Although the fluidity of examples 3 and 5 was rated fair (△), it was not problematic for use. On the other hand, all of the comparative examples showed problems with fluidity and bending strength.

The content of phosphoric acid per 100 parts by mass of the total content of basic aggregate, calcined alumina, and basic aluminum lactate is preferably 3.0 to 11.0 parts by mass, and more preferably 4.0 to 6.5 parts by mass. This improves bending strength and provides an appropriate viscosity for the kneaded mixture, resulting in a moldable refractory with excellent fluidity.

The content of polyacrylic acid relative to 100 parts by mass of the total content of basic aggregate, calcined alumina, and basic aluminum lactate was preferably 0.1 to 1.0 parts by mass, and more preferably 0.25 to 0.5 parts by mass. The content of citric acid relative to 100 parts by mass of the total content of basic aggregate, calcined alumina, and basic aluminum lactate was preferably 0.5 to 2.0 parts by mass, and more preferably 1.0 to 1.5 parts by mass. As a result, even if the moldable refractory material containing basic aggregate contains phosphoric acid as a binder, rapid setting is suppressed, the usable time can be secured, and the phosphoric acid has the effect of minimizing the decrease in strength in the medium and low temperature range. The reason for this is not necessarily clear, but it is thought that polyacrylic acid and citric acid have a pH buffering effect.

The content of boric acid relative to 100 parts by mass of the total content of the basic aggregate, calcined alumina, and basic aluminum lactate was preferably 2.0 parts by mass or less (excluding 0 parts by mass), and more preferably 0.5 to 1.5 parts by mass. This promoted the effect of extending the pot life. The content of calcined alumina relative to 100 parts by mass of the total content of the basic aggregate, calcined alumina, and basic aluminum lactate was preferably 10.0 parts by mass or less, and more preferably 3 to 8 parts by mass. This made it possible to obtain an amorphous refractory material with appropriate viscosity and excellent fluidity. The content of basic aluminum lactate relative to 100 parts by mass of the total content of the basic aggregate, calcined alumina, and basic aluminum lactate was preferably 0.2 to 5 parts by mass, and more preferably 2 to 4 parts by mass. This made it possible to suppress the digestion (disintegration due to hydration) of the basic aggregate.

Although the present embodiment has been described in detail above, it will be readily apparent to those skilled in the art that many modifications are possible that do not substantially deviate from the novel matters and effects of the present disclosure. Therefore, all such modifications are included in the scope of the present disclosure. For example, a term described at least once in the specification together with a different term having a broader or similar meaning may be replaced with that different term anywhere in the specification. Furthermore, the configuration and operation of the manufacturing apparatus, etc. of the present embodiment are not limited to those described in the present embodiment, and various modifications are possible.

Claims (2)

The composition includes a basic aggregate, phosphoric acid as a binder, and polyacrylic acid and citric acid as additives.
The additive may include calcined alumina and/or basic aluminum lactate,
The content of the phosphoric acid, the polyacrylic acid and the citric acid relative to a total content of the basic aggregate, the calcined alumina and the basic aluminum lactate is 2.25 to 8.25 parts by mass, 0.1 to 1.0 parts by mass and 0.5 to 2.0 parts by mass, respectively. The monolithic refractory material according to claim 1,
The additive further comprises boric acid,
An amorphous refractory material characterized in that the content of boric acid per 100 parts by mass of the total content is 2.0 parts by mass or less (excluding 0 parts by mass).