JP5275124B2 - Refractory composition, irregular refractory, regular refractory - Google Patents

Description

  The present invention is a refractory material such as lining of molten metal containers such as blast furnaces, kneading cars, converters, ladles, smelting reduction furnaces, nozzles provided in continuous casting equipment, immersion nozzles, long nozzles, sliding nozzles, stoppers, etc. In addition, the present invention relates to a refractory composition used for irregular shaped refractories such as tap outlets and joint materials.

  The refractory composition used for the above-mentioned regular refractories and amorphous refractories is generally prepared by blending a refractory aggregate with a phenol resin as a binder component and kneading the phenol resin. Yes, a shaped refractory can be obtained by heat treatment after molding the refractory composition, or an amorphous refractory can be obtained by heat treatment without molding (see, for example, Patent Document 1 and Patent Document 2). .

  In the above refractory composition, a novolac type phenol resin is generally used as the phenol resin of the binder component. Then, in order to cure the novolac type phenol resin in a temperature range of about 150 to 200 ° C. to make it infusible and obtain a refractory having a regular shape or an amorphous shape, it is necessary to add a curing agent. Tetramine is used. Hexamethylenetetramine can be advantageously used because it is inexpensive and can improve the fixed carbon content of the refractory.

  However, novolak-type phenolic resin and hexamethylenetetramine are likely to react even at low temperatures, and this tendency is particularly prominent when mixed in a liquid state, and the viscosity of the refractory composition is likely to increase. For this reason, when a novolak-type phenol resin and hexamethylenetetramine react to cause an increase in viscosity, the refractory composition is hardened during use due to changes over time. Also, the refractory composition may be exported and used overseas. In this case, after preparing the refractory composition, the period until it is used becomes longer, especially when transported through the equator. The reaction proceeds further by the action of temperature, and the refractory composition is often harder.

  And when the viscosity of the refractory composition is increased and hardened in this way, when the molded refractory is molded to produce a fixed refractory, the density of the molded body is reduced even if molded at a predetermined pressure, There was a problem that it was impossible to obtain a regular refractory having a density of. Also in the case of an irregular refractory, for example, when used as a tap outlet filling material that fills and closes a blast furnace outlet with a refractory composition, when the viscosity of the refractory composition is high and hard, There was a problem that it could not be filled by being fully pushed into the outlet. Thus, the refractory composition using hexamethylenetetramine as the curing agent has a problem that the viscosity increases with time and the pot life is short.

  In addition, novolac type phenolic resin and hexamethylenetetramine are highly reactive. For example, when heated to 200 ° C. or more as in the case of use as a filler, hexamethylenetetramine is added to 100 parts by mass of novolac type phenolic resin. Only by blending about 5 to 3.5 parts by mass, it can be rapidly gelled. On the contrary, this means that hexamethylenetetramine is extremely sensitive to the amount used, and hexamethylenetetramine has a problem that it is necessary to strictly control the amount used.

  On the other hand, there are solid and liquid phenol resins used as a binder. When using a solid phenol resin, it is necessary to dissolve the phenol resin in a solvent and knead it with the refractory aggregate. Even in the case of a liquid phenol resin, it is necessary to dilute the phenol resin with a solvent and knead it with the refractory aggregate in order to reduce the viscosity of the phenol resin. As this solvent, it is common to use ethylene glycol, propylene glycol, etc., but when a refractory composition is molded and then heated to produce a shaped refractory, or a refractory composition at a tap, etc. When heated as an amorphous refractory by being heated by the action of hot pig iron, the solvent in the refractory composition is evaporated and removed by this heating.

  However, the solvent contained in the refractory composition is evaporated when the heating temperature reaches the boiling point of the solvent, and is rapidly evaporated in a short time. When the solvent evaporates rapidly in this way, the structure of the regular refractory or the irregular refractory is destroyed, the porosity is increased, and a dense refractory cannot be obtained.

JP-A-8-169773 JP 2003-89571 A

  This invention is made | formed in view of said point, and aims at providing the refractory composition which can lengthen a pot life, and can obtain a more precise refractory. The object is to provide a refractory composition.

  The refractory composition according to the present invention comprises a refractory aggregate, a phenol resin as a binder component, a solvent as a phenol resin diluent, and an acetal resin as a phenol resin curing agent. It is a feature.

Acetal resin decomposes by heating at high temperature to release formaldehyde, which causes the phenol resin to gel and harden. It does not decompose at the temperature at which the refractory composition is stored, and does not cause the phenol resin to gel. The increase in viscosity due to the change can be suppressed. For this reason, the pot life of a refractory composition can be lengthened by using an acetal resin as a hardening | curing agent of a phenol resin.
Further, the present invention is characterized by containing hexamethylenetetramine in addition to the acetal resin as a curing agent for the phenol resin, and by using hexamethylenetetramine in this way, the decomposition temperature of the acetal resin or lower is used. Even at this temperature, the phenol resin can be cured, and the curability of the refractory composition can be enhanced.

  Moreover, in this invention, said solvent is a 2 or more types of mixed solvent from which a boiling point differs, It is characterized by the above-mentioned.

  Two or more kinds of solvents having different boiling points in the mixed solvent are evaporated in the order in which the heating temperature reaches the boiling point of each solvent, and it is possible to prevent the solvent from rapidly evaporating when heating the refractory composition. And a dense refractory can be obtained.

  Moreover, in this invention, content of acetal resin is 0.1-30 mass parts with respect to 100 mass parts of phenol resins, It is characterized by the above-mentioned.

  By setting the content of the acetal resin within this range, the pot life of the refractory composition can be extended without causing insufficient gelation or curing reaction.

  In addition, the present invention is characterized by containing an acetal resin decomposition accelerator.

  By containing the decomposition accelerator in this way, the decomposition of the acetal resin can be promoted by heating when using the refractory composition, and the curing of the phenol resin can be accelerated, thereby increasing the curability. It is something that can be done.

  According to the present invention, the acetal resin does not gel and react rapidly with the phenol resin, and can suppress an increase in viscosity due to a change with time. By blending as a phenol resin curing agent, The pot life of the refractory composition can be increased.

  And by using this refractory composition, a dense regular refractory and an irregular refractory can be obtained, and it can be used as a filling agent with a high filling property. .

It is a graph of TGA.

  Embodiments of the present invention will be described below.

  The refractory composition according to the present invention contains a refractory aggregate, a phenol resin as a binder component, a solvent as a phenol resin diluent, and an acetal resin as a phenol resin curing agent as main components. Prepared.

In the present invention, the above-mentioned refractory aggregate can be used without any particular problem as long as it is normally used as a raw material for refractories, and any refractory raw material from coarse to fine powders can be blended with a particle size. Can be used. For example, electrofused alumina, electrofused magnesia, etc., sintered products such as sintered magnesia, natural raw materials such as natural magnesia, bauxite, andalusite, sillimanite, super calcined alumina, silica flour, etc. Fine powder raw materials can be used. Moreover, in order to improve corrosion resistance, it is preferable to mix | blend the powder of the carbonaceous material with bad wettability with molten slag as a fireproof aggregate. The carbonaceous material may be any carbonaceous material such as natural graphite, artificial graphite, pitch, coke, carbon black, quiche graphite, mesophase carbon, and charcoal, but it should be as pure as possible. preferable. As the refractory aggregate, Al, Mg, Ca, Si, or one or more of these alloys can be blended and used. Further, various carbides, borides, nitrides such as SiC, B ₄ C, BN, Si ₃ N _{4 and the} like can be used as an antioxidant for the carbonaceous material.

  Moreover, what was prepared by making phenols and aldehydes react in presence of a reaction catalyst as said phenol resin in this invention can be used.

  Phenols mean phenol and derivatives of phenol. For example, in addition to phenol, trifunctional compounds such as m-cresol, resorcinol and 3,5-xylenol, and tetrafunctional compounds such as bisphenol A and dihydroxydiphenylmethane. Bifunctional o- or p such as o-cresol, p-cresol, p-ter-butylphenol, p-phenylphenol, p-cumylphenol, p-nonylphenol, 2,4 or 2,6-xylenol -Substituted phenols can be mentioned, and also halogenated phenols substituted with chlorine or bromine can be used. Of course, in addition to selecting and using one of these, a plurality of types can be mixed and used.

  As the aldehyde, formalin in the form of an aqueous solution is optimal, but forms such as paraformaldehyde, acetaldehyde, benzaldehyde, trioxane, and tetraoxane can also be used. It can be used by replacing with aldehyde or furfuryl alcohol.

  The blending ratio of the above phenols and aldehydes is preferably set so that the molar ratio is in the range of 1: 0.5 to 1: 3.5. As a reaction catalyst, when preparing a novolac-type phenol resin, inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid, organic acids such as oxalic acid, paratoluenesulfonic acid, benzenesulfonic acid and xylenesulfonic acid, and acetic acid Zinc or the like can be used. When preparing a resol-type phenolic resin, an alkaline earth metal oxide or hydroxide can be used, and an aliphatic group such as dimethylamine, triethylamine, butylamine, dibutylamine, tributylamine, diethylenetriamine, or dicyandiamide. Primary, secondary, tertiary amine, aliphatic amines having aromatic rings such as N, N-dimethylbenzylamine, aromatic amines such as aniline and 1,5-naphthalenediamine, ammonia, hexamethylenetetramine, etc. Other divalent metal naphthenic acids and divalent metal hydroxides can also be used.

  In the present invention, a novolac type phenol resin is mainly used as the phenol resin, but a novolac type phenol resin and a resol type phenol resin may be used in combination. Various modified phenolic resins such as silicon modified, rubber modified, boron modified, etc. can be used. However, it does not matter whether the storage stability is stable or the refractory aggregate is acidic (for example, silica) or basic (for example, MgO). Considering the points that can be used, novolak type phenol resin is most preferable.

  In order to improve the adhesion between the refractory aggregate and the phenol resin, a coupling agent such as γ-aminopropyltriethoxysilane, γ- (aminoethyl) aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, etc. Can also be used.

  In the present invention, the solvent may be anything as long as it dissolves the phenol resin, but a solvent having a relatively high boiling point of 150 to 450 ° C. is preferable. Although not particularly limited, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene recall, tetraethylene glycol, furfural, glycerin, polyglycerin, diglycerin, n-decanol, 2-undecyl alcohol, secondary tetradecyl alcohol, secondary heptadecyl alcohol, butylene glycol, 2-methyl-2,4-pentadiol, hexanediol-2,5, heptanediol-2,4, dipropylene glycol, dibutyl Examples thereof include phthalate, di-2-ethylhexyl phthalate, diethyl phthalate, diheptyl phthalate, and propylene carbonate.

  These solvents can be used alone, but can also be used as a mixed solvent in which a plurality of solvents are mixed. When using a mixed solvent, it is preferable to use a combination of a plurality of solvents having different boiling points.

The acetal resin used as a phenol resin curing agent in the present invention is a resin having a unit structure of oxymethylene (—CH ₂ O—) and is a polymer of formaldehyde. Examples of the acetal resin include homopolymers in which 1000 or more oxymethylenes are linearly linked and have no side chain, and copolymers containing oxyethylene (—CH ₂ CH ₂ O—) in the polyoxymethylene main chain. Either can be used. As this acetal resin, those commercially available from Polyplastics, Asahi Kasei, Mitsubishi Engineering Plastics, DuPont, BASF Japan, Toray, and the like can be used.

  A decomposition accelerator that accelerates the decomposition of the acetal resin may be used in combination with the acetal resin. As the decomposition accelerator, zinc chloride, benzylmethyl-P-hydroxyphenylsulfonium-hexafluoroantimonate, hexafluoroantimonate, or the like, an organic acid such as xylene sulfonic acid, or an inorganic acid such as phosphoric acid can be used.

  Then, the refractory composition of the present invention is prepared by blending the above refractory aggregate with other materials such as a phenol resin, a solvent, an acetal resin, and a decomposition accelerator if necessary, and kneading them. It is something that can be done. Here, the kneading procedure is not particularly limited. For example, a phenol resin solution in which a phenol resin is preliminarily dissolved in a solvent is blended with a refractory aggregate, and further an acetal resin or the like is blended at room temperature or A refractory composition can be prepared by kneading under heating.

  Although the compounding quantity of each component of a refractory composition is not specifically limited, It is preferable to set a phenol resin to the range of 1-30 mass parts with respect to 100 mass parts of refractory aggregates. Moreover, the range of 1-80 mass parts is preferable with respect to 100 mass parts of phenol resins for the compounding quantity of a solvent.

  Furthermore, the compounding quantity of acetal resin has the preferable range of 0.1-30 mass parts with respect to 100 mass parts of phenol resins. When the blending amount of the acetal resin is less than 1 part by mass with respect to 100 parts by mass of the phenol resin, it is difficult to sufficiently cure the phenol resin by the acetal resin. Conversely, if the blending amount of the acetal resin exceeds 30 parts by weight with respect to 100 parts by weight of the phenol resin, the pot life of the refractory composition does not change, but the blending amount becomes excessive and the amount of fixed carbon decreases. Moreover, the compounding quantity of a decomposition accelerator has the preferable range of 1-40 mass parts with respect to 100 mass parts of acetal resin.

  The refractory composition of the present invention prepared as described above is characterized in that an acetal resin is blended as a curing agent for a phenol resin. When the acetal resin is heated to 100 ° C. or higher, depolymerization occurs and formaldehyde (HCHO) begins to be released. When further heated, thermal decomposition occurs at 270 ° C., and the main chain is cleaved to supply a large amount of formaldehyde. Is done. And this formaldehyde makes it gelatinize by carrying out the crosslinking reaction of a phenol resin, and can harden a phenol resin.

  As described above, the acetal resin is decomposed by the action at a high temperature of 100 ° C. or more to release formaldehyde, and the phenol resin is gelled by the action of formaldehyde, and the room temperature at which the refractory composition is stored or slightly higher than room temperature. At this temperature, the acetal resin does not release formaldehyde and does not gel the phenol resin. Therefore, by blending and using an acetal resin as a phenol resin curing agent in a refractory composition, the phenol resin in the refractory composition does not become polymerized in a normal storage state, and changes with time. The increase in viscosity can be suppressed, and the pot life of the refractory composition can be increased.

  For this reason, even after the refractory composition is allowed to stand for about 1 month, the refractory composition has a very small increase in viscosity and does not become hard and has high fluidity. Therefore, when producing a refractory composition by molding a refractory composition such as a brick or a nozzle, a molded article having a high density can be obtained by molding at a predetermined pressure. A high-density shaped refractory can be produced. Also in the case of an irregular refractory, for example, when used as a tap outlet filling material filled with a refractory composition at the outlet of a blast furnace, the viscosity of the refractory composition is low and the fluidity is high. It can be fully pushed into the outlet and filled.

  At this time, by adding a decomposition accelerator for the acetal resin as described above, when the acetal resin is heated at a temperature of 100 ° C. or higher, an ether bond (− C—O—C—) can be easily cut, and the curing action of the phenol resin by the acetal resin when preparing the regular refractory or the irregular refractory can be promoted. In addition, since the decomposition accelerator does not decompose the acetal resin at the temperature at which the refractory composition is stored, there is little adverse effect on the effect of extending the pot life of the refractory composition.

  When the phenol resin is to be gelled and cured by heating at a temperature equal to or lower than the decomposition temperature of the acetal resin, hexamethylenetetramine may be used in combination as a curing agent and blended in the refractory composition. When hexamethylenetetramine is used in combination with the acetal resin, the blending ratio of the acetal resin and hexamethylenetetramine is preferably set in the range of 1 to 200 parts by mass of hexamethylenetetramine with respect to 100 parts by mass of the acetal resin.

  Moreover, the solvent is contained in the refractory composition as described above, and the solvent evaporates by heating when preparing the amorphous refractory or the regular refractory. And as mentioned above, when the temperature of the heating reaches the boiling point of the solvent, if the solvent rapidly evaporates in a short time, the structure of the regular refractory and the irregular refractory is destroyed, the porosity becomes high, and the dense Refractories cannot be obtained.

  Therefore, in this case, it is preferable to use a mixed solvent in which a plurality of solvents having different boiling points are combined. When a mixed solvent composed of a plurality of solvents having different boiling points is used as described above, when heating to prepare an amorphous refractory or a fixed refractory, the solvent evaporates in order from the solvent with the lower boiling point as the heating temperature rises. The solvent can be prevented from evaporating rapidly in a short time. For this reason, when the solvent evaporates, the structure of the regular refractory or the irregular refractory is not destroyed, and a dense refractory can be obtained.

  Next, the present invention will be specifically described with reference to examples.

(Production Example 1 of Novolac Type Phenolic Resin)
A reaction vessel was charged with 940 parts by weight of a phenol resin, 568 parts by weight of 37% by weight formalin, and 3.76 parts by weight of oxalic acid, and refluxed for about 1 hour with stirring, and reacted at the reflux temperature for 3 hours. Next, heating was performed while dehydrating until the internal temperature reached 170 ° C. Furthermore, after depressurizing at 40 hPa (30 Torr) while reducing the pressure until the internal temperature reached 200 ° C., the contents of the reaction vessel were discharged onto a stainless steel vat. The softening point of the novolak type phenol resin thus obtained was 78 ° C.

(Test Example 1)
To 70 parts by mass of the novolak-type phenol resin obtained in Production Example 1 above, ethylene glycol (boiling point 197.6 ° C.), diethylene glycol (boiling point 244.3 ° C.), and triethylene glycol (boiling point 287.4 ° C.) are equivalent. 30 parts by mass of the mixed solvent was added and mixed well to obtain a phenol resin solution. The viscosity (25 ° C.) of this phenol resin solution was 49 Pa · s.

  Next, 4 parts by mass of an acetal resin (“F30-01F” manufactured by Mitsubishi Engineering Plastics Co., Ltd.) having a particle size of 840 μm or less is added to 100 parts by mass of this phenol resin solution, and the mixture is mixed well. Got.

  And about this test composition, Shimadzu Corporation differential thermal / thermogravimetric simultaneous measurement apparatus “DTG-60 / 60H” was used, and the measurement atmosphere was set in air flow and the heating rate was set to 10 ° C./min. Then, thermogravimetric analysis (TGA) measurement was performed from room temperature to 400 ° C. The results are shown in FIG.

(Comparative Test Example 1)
A comparative test composition was obtained in the same manner as in Test Example 1 except that hexamethylenetetramine was used in place of the acetal resin in Test Example 1 described above. The comparative test composition was subjected to thermogravimetric analysis in the same manner as described above. The results are shown by a thick solid line in FIG.

(Test Example 2)
30 parts by mass of ethylene glycol (boiling point: 197.6 ° C.) was added to 70 parts by mass of the novolak type phenol resin obtained in Production Example 1 and mixed well to obtain a phenol resin solution. The viscosity (25 ° C.) of this phenol resin solution was 8.5 Pa · s.

  Next, 4 parts by mass of the acetal resin powder used in Test Example 1 was added to 100 parts by mass of this phenol resin solution and mixed well to obtain a test composition.

  The test composition was subjected to thermogravimetric analysis in the same manner as described above. The results are shown in FIG.

(Comparative Test Example 2)
A comparative test composition was obtained in the same manner as in Test Example 2 except that hexamethylenetetramine was used in place of the acetal resin in Test Example 2 above. The comparative test composition was subjected to thermogravimetric analysis in the same manner as described above. The result is shown by a thin solid line in FIG.

  As seen in the comparison between Test Example 1 and Comparative Test Example 1 in FIG. 1 and Test Example 2 and Comparative Test Example 2, Test Example 1 and Test Example 2 using an acetal resin as a curing agent are hexamethylene as a curing agent. The weight reduction is larger than those of Comparative Test Example 1 and Comparative Test Example 2 using tetramine. That is, by using acetal resin as a curing agent, since the progress of curing is slow, the weight loss by heating increases, which means that the pot life is increased by using acetal resin as a curing agent. Means.

  Further, as seen in the comparison between Test Example 1 and Test Example 2 and Comparative Test Example 1 and Comparative Test Example 2 in FIG. 1, Test Example 1 using three kinds of mixed solvents having different boiling points as solvents is a single solvent. The weight reduction is smaller than that of Test Example 2 using the same, and the weight loss of Comparative Test Example 1 is similarly smaller than that of Comparative Test Example 2. This means that the solvent can be prevented from abruptly evaporating in a short time by using a mixed solvent having different boiling points.

(Test Examples 3 to 6)
The test composition was obtained by adding the acetal resin powder used in Test Example 1 to 100 parts by mass of the phenol resin solution obtained in Test Example 1 in the amount shown in Table 1 and mixing well.

  About this test composition, the gelation time in 300 degreeC and the fixed carbon content in 800 degreeC were measured. The results are shown in Table 1.

  Here, about 5 g of the test composition is weighed and put into a test tube, and this test tube is put into a blower dryer set in advance at 300 ° C. and heated, and the test composition flows even if the test tube is tilted 90 °. The time when it disappeared was defined as the gel time. The measurement of the amount of fixed carbon was performed according to JIS K6910.

(Comparative Test Examples 3 to 7)
A comparative test composition was obtained by adding hexamethylenetetramine in the blending amount shown in Table 1 to 100 parts by mass of the phenol resin solution obtained in Test Example 1 and mixing well. For this comparative test composition, the gelation time at 300 ° C. and the amount of fixed carbon at 800 ° C. were measured, and the results are shown in Table 1.

  As seen in Table 1, in Test Examples 3 to 6 using an acetal resin as a curing agent, the gelation time is increased by increasing the amount of the curing agent used from 3.4 parts by mass to 4.5 parts by mass. From 190 minutes to 70 minutes, that is, with an increase of 1.1 parts by mass of the curing agent, the gelation time is shortened by 120 minutes. On the other hand, in Comparative Test Examples 3 to 7 using hexamethylenetetramine as a curing agent, the gelation time is increased from 235 minutes by increasing the amount of the curing agent used from 1.6 parts by mass to 2.5 parts by mass. 15 minutes, that is, an increase of 0.9 parts by mass of the curing agent shortens the gelation time by 220 minutes. As described above, the gelation time changes sensitively with respect to the increase or decrease in the amount of hexamethylenetetramine, and it is necessary to strictly control the amount of hexamethylenetetramine used, but the acetal resin increases or decreases the amount of the compound. On the other hand, the change in gelation time is insensitive, and it is confirmed that the acetal resin does not need to strictly control the blending amount as compared with hexamethylenetetramine. In addition, in Test Examples 3 to 6 using an acetal resin as a curing agent and Comparative Test Examples 3 to 7 using hexamethylenetetramine, the amount of fixed carbon increased in the same manner as the blending amount increased.

(Test Example 7)
To the test composition obtained in Test Example 4, 1% by mass of zinc chloride as an acetal resin decomposition accelerator was added to the total amount to obtain a test composition.

(Test Example 8)
To the test composition obtained in Test Example 4, 1% by mass of xylene sulfonic acid as an acetal resin decomposition accelerator was added to the total amount to obtain a test composition.

  For the test compositions obtained in Test Examples 7 to 8, the gelation time at 300 ° C and the amount of fixed carbon at 800 ° C were measured, and the results are shown in Table 2.

  As apparent from comparison with Test Example 4 in Table 1, the addition of the decomposition accelerator shortens the gel time and confirms that the curing time can be shortened.

( Reference Example 1 )
Ethylene glycol, diethylene glycol, and triethylene glycol were added to and mixed with the novolac type phenol resin obtained in “Preparation Example 1 of novolak type phenol resin” in the same manner as in Test Example 1 to obtain a phenol resin solution A. .

  Then, 70 parts by mass of fused alumina as a refractory aggregate and 30 parts by mass of natural graphite having a purity of 98% are put into a mixer, and further 8 parts by mass of the phenol resin solution A and 0.6% of an acetal resin as a curing agent. A refractory composition in a wet state was obtained by adding part by mass and kneading for 20 minutes.

(Example 1 )
A wet refractory composition was obtained in the same manner as in Reference Example 1 except that 0.3 parts by mass of acetal resin and 0.3 parts by mass of hexamethylenetetramine were used as the curing agent.

( Reference Example 2 )
Ethylene glycol was added to and mixed with the novolac type phenol resin obtained in the above “Novolak type phenol resin production example 1” in the same manner as in Test Example 2 to obtain a phenol resin solution B.

  Then, 70 parts by mass of fused alumina and 30 parts by mass of natural graphite having a purity of 98% were used as the refractory aggregate, and these were put into a mixer. Further, 8 parts by mass of the phenol resin solution B and 0.6 mass of the acetal resin as the curing agent were used. A refractory composition in a wet state was obtained by adding part by mass and kneading for 20 minutes.

(Example 2 )
A wet refractory composition was obtained in the same manner as in Reference Example 2 except that 0.3 part by mass of acetal resin and 0.3 part by mass of hexamethylenetetramine were used as the curing agent.

( Reference Example 3 )
In Reference Example 1 , a wet refractory composition was obtained in the same manner as Reference Example 1 except that 0.2 parts by mass of zinc chloride was further added as a decomposition accelerator.

(Comparative Example 1)
A wet refractory composition was obtained in the same manner as in Reference Example 1 except that 0.6 parts by mass of hexamethylenetetramine was used as the curing agent.

(Comparative Example 2)
A wet refractory composition was obtained in the same manner as in Reference Example 2 except that 0.6 parts by mass of hexamethylenetetramine was used as the curing agent.

As described above, 250 g of the refractory compositions obtained in Examples 1 and 2, Reference Examples 1 to 3 and Comparative Examples 1 and 2 are placed in a mold having an inner diameter of 45 mm, and molded at a pressure of 98 MPa using a hydraulic press. Thus, a molded product was obtained. Next, this molded product was put into a hot air circulating dryer heated to 250 ° C. and heat-treated for 10 hours to obtain a molded refractory in which the phenol resin of the molded product was cured.

  The molded refractories thus obtained were measured for bulk specific gravity, volatile content, compressive strength, and appearance. The bulk specific gravity was measured according to JIS R2001, and the compressive strength was measured according to JIS R2206.

  The volatile matter was obtained from the following equation by measuring the mass before heat treatment and after heat treatment.

[100- (mass after heat treatment (g) / mass before heat treatment (g)) × 100] (%)
Appearance is measured by visual observation. If there are no blisters or cracks, `` ◎ '', there are several blisters, but `` ○ '' if there are no cracks, countless blisters, and those with cracks. It was determined as “x”.

  On the other hand, the molded product obtained as described above was placed in a heat-resistant box, which was then covered with coke and set in an electric furnace (“Silicnit Electric Furnace Model BSH-1530” manufactured by Siliconit Co., Ltd.). And it heated up to 600 degreeC with the temperature increase rate of 10 degreeC / min, and also baked the refractory by carrying out baking processing on the conditions to temperature-fall after hold | maintaining at this temperature for 3 hours.

  The calcined refractory thus obtained was also measured for bulk specific gravity, volatile content, compressive strength, and appearance.

  As can be seen in Table 3, each of the examples has a high bulk specific gravity, a low volatile content, suppressed occurrence of swelling and cracks, a high compressive strength, and a dense refractory. It was obtained.

(Examples 3-4, Reference Examples 4-5 , Comparative Examples 3-4)
In 100 parts by mass of refractory aggregate having a composition of 44 parts by mass of fused alumina, 12 parts by mass of coke, 19 parts by mass of silicon carbide, and 25 parts by mass of silicon nitride, phenol resin solutions A and B, cured, in the amounts shown in Table 4 A wet refractory composition was obtained by adding an agent (acetal resin, hexamethylenetetramine) and kneading with a Simpson mixer for 30 minutes.

  In order to evaluate the performance of the refractory composition as a filler such as a tap outlet filler, a pipe having one inner diameter of 75 mm and a length of 300 mm closed is filled with the refractory composition, and this is heated to 600 ° C. And heat-treated for 30 minutes. And after taking out and cooling this heat-processed baked refractory, it cut | disconnected in the longitudinal direction and divided into 2 and observed the structure | tissue of the baked refractory visually.

  In addition, the same heat treatment was performed at a furnace temperature of 1200 ° C., and the structure of the fired refractory was similarly visually observed.

  Further, test pieces each having a length of 30 mm and a height of 50 mm were cut out from the refractories fired by heat treatment as described above, and the compressive strength and the porosity were measured.

Moreover, in order to investigate the time-dependent change of a refractory composition, the refractory compositions of Examples 3 to 4, Reference Examples 4 to 5 and Comparative Examples 3 to 4 having almost the same compressive strength in a wet state are placed in a plastic bag. Then, it was placed in a dryer at 80 ° C., and heat-cured as it was for 24 hours, and the compressive strength was measured.

  As can be seen from Table 4, each of the examples has no cracks in the heat-treated fired refractory, the structure is good, the compressive strength is high, the porosity is small, and the dense A refractory was obtained. As can be seen from the results of change over time, in each of the examples, the progress of curing was not rapid, and the pot life could be increased.

Claims (7)

It contains a refractory aggregate, a phenolic resin as a binder component, a solvent as a phenolic resin diluent, and an acetal resin as a phenolic resin curing agent. A refractory composition comprising methylenetetramine in an amount of 1 to 200 parts by mass with respect to 100 parts by mass of an acetal resin .   The refractory composition according to claim 1, wherein the solvent is a mixed solvent of two or more kinds having different boiling points.   The refractory composition according to claim 1 or 2, wherein the content of the acetal resin is 0.1 to 30 parts by mass with respect to 100 parts by mass of the phenol resin.   The refractory composition according to any one of claims 1 to 3, further comprising an acetal resin decomposition accelerator. An amorphous refractory comprising the refractory composition according to any one of claims 1 to 4 . 6. The amorphous refractory according to claim 5 , wherein the refractory is used as a tap outlet filler. A regular refractory comprising the refractory composition according to any one of claims 1 to 4 .

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