JPH0229619B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing unfired refractories. Continuous casting nozzles, sliding nozzles, immersion nozzles, etc. are used under harsh conditions and require a combination of corrosion resistance and spalling resistance. Because of this, various types of firing types have been developed, and have achieved better results in actual furnaces than conventional firing types. This material mixes a thermosetting resin binder with fireproof aggregate, press-forms this, and then heats it to harden and dry the thermosetting resin.
When the unfired refractories formed in this way are used in an actual furnace, they are brought into contact with molten metal and fired at the high temperature of the molten metal, thereby causing residual carbon in the thermosetting resin to coke. However, in the process of baking the thermosetting resin into coke, some of the carbon components and other components of the thermosetting resin are removed.
H ₂ O, CO ₂ , CO, etc. are volatilized and released from the refractory, which causes the refractory to shrink, causing horizontal cracks in the nozzle, peeling at the upper end, loosening of the set, etc., and the risk of accidents is extremely high. It was a big one. In order to reduce the shrinkage that occurs when this unfired refractory is fired with molten metal and turned into coke, the inventors first made the molten metal sufficiently shrink when it is heated to harden and dry. The present invention was conceived based on the discovery that it is very effective to reduce the components released by volatilization during firing. Therefore, in order to moisten the refractory aggregate and improve its kneading properties, as well as to improve its shapeability during press molding, the refractory aggregate is prepared by dissolving or dispersing thermosetting resin in a wetting agent such as water or a solvent. It is added to the material, but
In the present invention, the concentration of the resin component is lowered by increasing the blending amount of the wetting agent in the thermosetting resin, and by increasing the blending amount of the wetting agent in the fire-resistant aggregate, the thermosetting resin is The amount of resin blended is small, and when curing and drying by heating, the wetting agent that is blended in a large amount is evaporated, so that the refractory is sufficiently shrunk in advance. When refractories are used in an actual furnace and fired with molten metal, the amount of thermosetting resin blended is small, so the amount of volatilized components in the resin is small compared to the total amount of refractories, which reduces shrinkage of the refractories at this time. This can be reduced. That is, while the amount of wetting agent blended in the thermosetting resin was conventionally about 10 to 15% by weight, in the present invention, the blending amount of the wetting agent was increased to 20% by weight of the thermosetting resin.
The present invention is characterized by the fact that the amount is more than % by weight, and the present invention will be explained in detail below. As the thermosetting resin that serves as the binder for the composition for unfired refractories, it is possible to use general thermosetting resins, but resol type, novolac type phenolic resins, or furan resins have a large amount of residual carbon. Mainly used for points. This thermosetting resin is used as a binder in a state in which it is dissolved or dispersed in a wetting agent such as a solvent or water, and the binder is made by blending the wetting agent in an amount of 20% by weight or more with respect to the thermosetting resin. If the amount is less than 20% by weight, no effect of preventing shrinkage of the unfired refractory can be expected. Further, the upper limit of the amount of the wetting agent blended is not particularly limited, but approximately 70% by weight is suitable. If the thermosetting resin is spread further than this and the resin content is reduced, the binder effect of the resin will not be sufficiently exhibited and the strength of the unfired refractory will be significantly reduced. In addition, the amount of solvent blended has been reduced from 10 to 15
If the amount of resin is reduced by increasing the amount by weight, it tends to cause a decrease in the strength of the unfired refractory, so it is recommended to use a thermosetting resin with an average molecular weight of 300 or more to prevent the decrease in strength. Make it.
Furthermore, as a wetting agent, water, ethylene glycol, diethylene glycol, propylene glycol, furfuryl alcohol, ethanol, methanol, etc., which do not participate in the curing reaction of thermosetting resins, can be used. The remaining water, alcohol, etc. can be used as a wetting agent as is. A composition for unfired refractories is obtained by mixing a binder prepared by dissolving or dispersing a thermosetting resin in a wetting agent with a refractory aggregate, but it is generally used as a refractory aggregate. You can use whatever is available. Examples include silica (crystalline, amorphous), waxite, clay, shale, baked clay, shale, synthetic mullite, kyanite, spinel, sintered alumina, zircon, zirconia, magnesia, chromite, carbon regular carbon, crystalline phosphorous graphite), SiC, Si ₃ N ₄ ,
B ₄ C, etc. non-oxides, etc. Incidentally, in order to prevent the strength from decreasing in the intermediate temperature range of the refractory, a silane coupling agent or a low melting point metal may be further blended. The silane coupling agent is an organic functional silane monomer having two types of reactive groups. On the other hand, the reactive groups are usually chloro, alkoxy, or acetoxy groups, which are hydrolyzed to form silanol (Si(OH) ₃ ) and release water adhering to the surface of glass and metal oxides, which are fireproof aggregates. Condenses and bonds with OH group. The other reactive group is usually a vinyl group, a meta-acroxy group, an amino group, an epoxy group, etc., and reacts with the binder to bond with it. Therefore, the silane coupling agent can bind the binder and the refractory aggregate, and can prevent the strength of the refractory from decreasing in the intermediate temperature range. Examples of silane coupling agents include γ-
glycidoxypropyltrimethoxysilane γ-methacryloxypropyltrimethoxysilane

[Formula] N _{-β(aminoethyl)γ-aminopropyltrimethoxysilane (H2N-C2H4-NH-C3H6Si ( OCH3 ) 3 ) ,}
N-β(aminoethyl)γ-aminopropyltrimethyldimethoxysilane γ-Aminopropyltriethoxysilane ( _H2N
−C ₃ H ₆ −Si(OC ₂ H ₅ ) ₃ or the like can be used. In addition, metal aluminum, zinc, aluminum-magnesium alloy, etc. can be used as low-melting point metals, and these metals improve the strength of refractories in the intermediate temperature range by melting and coating the carbide surface. It also has the effect of improving the oxidation resistance of refractories. The composition for unfired refractories prepared as described above is then press-molded, and although it is a mixture of a thermosetting resin and a wetting agent, the amount of resin binder added to the refractory aggregate is the same as before. 80-90% by weight refractory aggregate to 20-2% resin binder is common. Therefore, if the wetting agent in the resin binder in the conventional resin binder is 10% by weight, and in the present invention the wetting agent in the resin binder is 20% by weight, in the present invention, the amount of the wetting agent is determined based on the total amount of the composition. will increase by 0.2-2% by weight and the amount of thermosetting resin will decrease by 0.2-2% by weight. This composition is pressed and molded, and the molded product is further heated to about 200° C. to harden the thermosetting resin and dry it. An unfired refractory is obtained which is shaped by a wetting agent during press molding and solidified by heating and drying. Here, the wetting agent contained in the composition is volatilized during this heating drying process, but since the wetting agent is contained in a large amount, the refractory undergoes a large weight loss and volume shrinkage at this point, and also volatilizes. Due to the large number of components, the porosity of the refractory increases. Next, when the refractories obtained in this way are used in an actual furnace, they are exposed to high temperatures by molten metal, and the residual carbon component of the thermosetting resin is burned and turned into coke, and the thermosetting resin The remaining carbon components, oxygen components, and hydrogen components H ₂ O, CO ₂ , CO
However, since the amount of thermosetting resin is small, the amount of volatilization is also small, and the volumetric shrinkage of the refractory when it is turned into graphite due to the high temperature of the molten metal can be suppressed. As described above, according to the present invention, a large volumetric shrinkage is caused in advance by volatilizing a large amount of wetting agent during heating and drying, and moreover, when firing with molten metal in an actual furnace, By suppressing the volumetric shrinkage caused by volatile matter by suppressing the amount of volatile matter, it is possible to reduce the volumetric shrinkage when refractories are used and prevent the occurrence of transverse cracks, upper peeling, and loosening of refractories. be. In addition to the above-mentioned nozzles, the present invention also applies to converters,
It is also useful for bricks in steelmaking furnaces such as electric furnaces, secondary refining furnaces, and ladles. The invention will now be illustrated by examples. Preparation of thermosetting resin binder () 940 g of phenol, 92% paraformaldehyde
424 g, 630 g of water, and 7.5 g of lithium hydroxide were placed in a four-loop flask and heated to 70° C. over about 90 minutes. The reaction was continued for 180 minutes, and after the reaction was completed,
The pressure was gradually reduced to 650 mmHg, and dehydration was performed under reduced pressure until the internal temperature reached 75°C. The obtained resol type phenolic resin is a brown liquid with a water content of 3% and an average molecular weight of 350.
The viscosity at °C was 130 poise. To the thus obtained resol type phenolic resin, 1% by weight of γ-glycidoxypropyltrimethoxysilane was added as a silane coupling agent,
After thorough mixing, a resin binder (-(1)) with a residual carbon content of 53% by weight was obtained. In addition, 25% by weight of ethylene glycol is mixed with this to achieve a viscosity of 20 poise and a residual carbon content.
42% by weight of resin binder (-(2)) was obtained. Furthermore, 10% by weight of water and 15% by weight of propylene glycol were mixed to achieve a viscosity of 18 poise and a residual carbon content of 42%.
A weight percent resin binder (-(3)) was obtained. Preparation of thermosetting resin binder () 940 g of phenol, 92% paraformaldehyde
Put 228 g, 340 g of water, and 7.5 g of oxalic acid into four flasks, reflux for 60 minutes, and then boil for 150 g.
The reaction was carried out for minutes. After the reaction was completed, dehydration was started at normal pressure and concentration was continued until the internal temperature reached 150°C. The obtained novolak type phenolic resin was a viscous liquid with a water content of 1.0%, an average molecular weight of 450, and a viscosity of 350 poise at 25°C. N-β (aminoethyl) was added as a silane coupling agent to the novolak type phenolic resin thus obtained.
1% by weight of γ-aminopropyltrimethoxysilane was added and mixed well. This was mixed with 15% by weight of ethylene glycol and 15% by weight of hexamethylenetetramine to obtain a resin binder (-(1)) having a residual carbon content of 57% by weight and a viscosity of 120 poise. Similarly, 30% by weight of ethylene glycol and 15% by weight of hexamethylenetetramine were mixed to give a viscosity of 80 poise and a residual carbon content of 38%.
A weight percent resin binder (-(2)) was obtained. Furthermore, 10% water by weight, 30% propylene glycol
When mixed by weight%, the viscosity is 70 poise and the amount of residual carbon is 35
A weight percent resin binder (-(3)) was obtained. Resin binder obtained as above (1),
-(2), -(3), -(1), -(2), -(3) are mixed in the proportions shown in Tables 1, 2 and 3 for use in refractories. A composition was prepared, this composition was press-molded, and then heated at 200°C for 24 hours to harden and dry to obtain an unfired refractory. The properties of the unfired refractories thus obtained were measured and are shown in Tables 1, 2 and 3.

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[Table] Looking at the residual expansion rates in Tables 1, 2, and 3 above, it can be seen that the comparative examples had large shrinkage and troubles, whereas those of each of the examples It is confirmed that there is almost no shrinkage or very small shrinkage, and no trouble occurs.

Claims (1)

[Claims] 1. A refractory composition is prepared by blending a thermosetting resin and a wetting agent into a refractory aggregate, and setting the blending amount of the wetting agent to 20% by weight or more of the thermosetting resin. , an unfired refractory characterized in that the refractory composition is molded and heat treated at the curing temperature of the thermosetting resin to evaporate the wetting agent, and then the molded product is fired with molten metal in an actual furnace. How things are manufactured. 2. The method for producing an unfired refractory according to claim 1, wherein the thermosetting resin has an average molecular weight of 300 or more.