Refractory material for thermal insulation patching

Abstract

To provide a refractory material for thermal insulation patching, which exhibits superior adhesion, anti-cracking effect, ease of trowel release, and storage stability, while having high thermal insulation performance.SOLUTION: A refractory material for thermal insulation patching comprises a thermally insulating refractory aggregate, a refractory clay, and cellulose fibers. The content of the cellulose fibers is 0.3 to 40 wt.% externally calculated, with the sum of the thermally insulating refractory aggregate and the refractory clay being 100 wt.% (where the upper limit is 20 wt.% when the average fiber length of the cellulose fibers is 800 μm or more to 2000 μm or less).SELECTED DRAWING: Figure 4(a)

Description

Technical Field

[0001] The present invention mainly relates to a refractory for heat-insulating patching used for repairing refractories, and particularly relates to a refractory for heat-insulating patching having good adhesiveness, crack prevention effect, peeling resistance and storability, and high heat-insulating property.

Background Art

[0002] Refractories are worn out during use, but their scale and form vary depending on the equipment and conditions in which the refractories are used. Therefore, various monolithic refractories are used for repairing refractories depending on the application and scale.

[0003] Generally, monolithic refractories for repair are usually prepared by putting materials such as refractory aggregates into a mixer, adding water and kneading, and then constructed by methods such as pouring or spraying. Therefore, they are suitable for large-scale construction, but they are time-consuming and laborious to prepare. Therefore, in the case of minor repairs, refractory patching materials are often used.

[0004] Refractory patching materials are kneaded earth-like refractories in which refractory aggregates, refractory clay, binders, etc. are kneaded with water in advance. They are packed with vinyl etc. to prevent evaporation of water and stored in small portions. Since refractory patching materials can be constructed manually, it is not necessary to prepare or carry in repair equipment, and repairs can be performed in a short time, so there are also advantages in terms of the operation surface. On the other hand, since the operation efficiency of the equipment using refractories varies greatly depending on the frequency and time required for repair, in the case of small-scale damage, the repair itself may be postponed until disassembly, but there are also many cases where troubles occur due to inability to repair.

[0005] Since the amount required for repair varies depending on the degree of damage to the repair location, it is important that the refractory for patching can be stored in small portions for a long time. The repair interval varies depending on the equipment and operating conditions, but it is often on a monthly basis. Also, in equipment operating at high temperatures, it is often difficult to know the wear status of the refractory until just before repair, so it is difficult to predict the required amount of the repair material. Therefore, it is necessary to prepare the repair material with a margin, and the unused repair material is stored for several months until the next repair. However, if the storage property is poor, the unused repair material will be discarded.

[0006] In such refractory for patching, in addition to refractory aggregate and refractory clay, phosphate solution has been mainly used as a binder conventionally. Since the phosphate solution has high viscosity, the refractory for patching added with the phosphate solution has appropriate adhesiveness and plasticity along with high refractoriness and high temperature strength.

[0007] In order to improve the storage property of the refractory for patching using phosphate, various methods have been proposed. For example, Patent Document 1 describes that by suppressing the reaction of phosphate by using an organic acid in combination and reducing the change over time of the phosphate-bonded amorphous refractory, the storage property of the refractory for patching is improved. Thus, many of the conventional refractories for patching have added a substance for improving the storage property while using phosphate as a binder. Also, Patent Document 2 describes that phosphate is used as an inorganic binder when importance is attached to the strength after construction of the patching refractory.

[0008] In recent years, heat-insulating refractory aggregate has been increasingly used in heat-insulating refractory castables, and the demand for heat-insulating refractory for patching has also been increasing. The heat-insulating refractory for patching contains heat-insulating refractory aggregate, and the heat-insulating refractory aggregate often contains a large amount of alkali metals (such as Na and K) and alkaline earth metals (such as Ca and Mg), such as fine porous CA6 (CaO·6Al 2 O 3 ).

[0009] However, it has been found that since phosphate reacts with alkali metals and alkaline earth metals in the heat-insulating refractory aggregate and hardens, it gradually loses its plasticity and the workability required for patching construction (the storage stability deteriorates significantly). There is also a method of separately storing the phosphate solution and mixing it with the aggregate and kneading it before construction, but there are problems such as unstable quality, complexity, and time-consuming. In addition, in the equipment in the steel field (for example, heating furnaces) where the cycle of refractory construction, temperature rise, several months of sealing, temperature drop, several days of repair, and several months of sealing is repeated, in order to maintain the operation efficiency, the repair period has to be shortened, and there is a need to carry out small-scale repairs in a simple way. However, refractory materials for heat-insulating patching that meet such needs have not been put into practical use. Therefore, a refractory material for patching with high heat insulation, appropriate adhesiveness, and plasticity without adding phosphate is desired.

[0010] In addition to heat insulation, refractory materials for heat-insulating patching need to meet many conditions. One of them is the hardness (softness) that affects workability. There is no standard for the hardness of refractory materials for heat-insulating patching, but it can be evaluated by, for example, consistency. The refractory material for patching is hard when the consistency is low and soft when the consistency is high. The consistency can be measured by the penetration depth of a cone using a consistometer. Generally, the hardness of refractory materials for heat-insulating patching depends on the amount of added water. If the amount of added water is insufficient, the refractory material for heat-insulating patching is too hard (the consistency is too low), but if the amount of added water is increased too much, the shape retention of the refractory material for heat-insulating patching deteriorates, and sagging and falling occur when it is applied to the wall surface or ceiling surface.

[0011] Also, even with the same amount of added water, differences in the physical properties of refractory materials for heat-insulating patching occur due to seasonal factors and variations in materials. Therefore, when manufacturing refractory materials for heat-insulating patching, the amount of added water is determined based on the consistency. Therefore, in this specification, various physical properties of refractory materials for heat-insulating patching will be evaluated with the consistency being constant during manufacturing.

[0012] The refractory for heat-insulating patching should also have a good crack prevention effect. The refractory for heat-insulating patching may be extended by hand or the like during construction, but it may crack at that time. Whether or not cracks occur depends not only on the hardness of the refractory for heat-insulating patching, but also on the shape retention property. In addition, cracks may occur in the refractory for heat-insulating patching from before construction after long-term storage. Therefore, prevention of cracking is also important for the refractory for heat-insulating patching.

[0013] The refractory for heat-insulating patching should further have good release from the trowel. The release from the trowel can be evaluated by whether or not the refractory for heat-insulating patching remains on the hand after construction. The quality of the release from the trowel depends on the adhesiveness and the shape retention property. If the adhesiveness is too high or the shape retention property is poor, the release from the trowel will be poor. Also, even if the adhesiveness is the same level, if the structure is easily separated, the refractory for heat-insulating patching will remain on the hand (the release from the trowel becomes poor).

[0014] Since the consistency of the refractory for heat-insulating patching tends to gradually decrease with the passage of time during storage, storage stability is also important in order to maintain good physical properties for a long time. The storage stability can be evaluated by the amount of decrease in consistency after the passage of time. As described above, since phosphates have high reactivity with heat-insulating refractory aggregates such as fine porous CA6 that lose plasticity the next day, it is better not to contain phosphates in order to ensure good storage stability.

[0015] In this way, the refractory for heat-insulating patching needs to have not only heat-insulating properties but also good adhesiveness, crack prevention effect, release from the trowel, and storage stability. However, since phosphates have high reactivity with heat-insulating refractory aggregates, they cannot be used. Therefore, a refractory for heat-insulating patching having a good combination of the above physical properties has not been obtained until now.

Prior Art Documents

Patent Documents

[0016]

Patent Document 1

Patent Document 2

[0017] Accordingly, an object of the present invention is to provide a refractory for heat-insulating patching that has good adhesiveness, a crack prevention effect, release from a trowel, and storage stability, and also has high heat insulation properties. [Means for Solving the Problems]

[0018] As a result of intensive studies in view of the above object, the present inventors have found that for a refractory for heat-insulating patching that is not suitable for using a phosphate binder because it contains a heat-insulating refractory aggregate having high reactivity with phosphates, cellulose fibers are promising as an additive that can impart good adhesiveness, a crack prevention effect, release from a trowel, and storage stability while maintaining high heat insulation properties.

[0019] Plant fibers contained in wood chips, cardboard, waste paper, etc. are composed of three main components: cellulose, hemicellulose, and lignin, and among them, cellulose accounts for about 50% of the main components. The plant fibers are firmly adhered by lignin to form a plant fiber aggregate. Cellulose fibers are obtained by separating the plant fiber aggregate by mechanical or chemical action.

[0020] Cellulose fibers, which are plant fibers, not only have high water absorption and water retention properties due to their structure, but also have an expected crack prevention effect by cross-linking. Therefore, it is also conceivable to add cellulose nanofibers (CNF), which are cellulose fibers loosened to the nanolevel, to refractory materials for heat-insulating patching. For example, Patent Document 3 describes that when reinforcing fibers such as cellulose nanofibers (CNF) obtained by further finely loosening cellulose fibers to the nanolevel are added to cement paste or cement mortar, a water retention effect and a crack prevention effect during curing can be obtained. However, CNF has a problem that it is difficult to control the concentration and dispersibility. There is also a method of adding CNF after premixing and dispersing it with water in advance to enhance dispersibility, but since the amount of water added during production needs to be adjusted for refractory materials for heat-insulating patching due to seasonal factors and the like, there is a problem that the CNF dispersion solution also needs to be adjusted at the same time. Therefore, CNF is not suitable as an additive for refractory materials for heat-insulating patching.

[0021] In addition, there is a product commercially available as "pulp fiber" among plant fibers. "Pulp fiber" not only has a long average fiber length but also tends to have a large variation in fiber length. However, since there is no clear definitional difference between pulp fiber and cellulose fiber, in this specification, both will be collectively referred to as cellulose fiber.

[0022] When a commercially available product as "pulp fiber" is added to a refractory material for heat-insulating patching, although an improvement in crack prevention effect and storage stability is observed, it has been found that the adhesiveness and spatula separation are insufficient. As a result of intensive research on the cause, in order to impart good adhesiveness, crack prevention effect, spatula separation, and storage stability to the refractory material for heat-insulating patching, it is not only necessary to optimize the average fiber length of the cellulose fiber to be added, but also to adjust the addition amount of the cellulose fiber according to the average fiber length of the cellulose fiber. This led to the idea of the present invention.

[0023] That is, the refractory for heat-insulating patching of the present invention contains a heat-insulating refractory aggregate, a refractory clay, and cellulose fiber, and the content of the cellulose fiber is 0.3 to 40% by weight on an external basis with the total of the heat-insulating refractory aggregate and the refractory clay being 100% by weight (however, when the average fiber length of the cellulose fiber is 800 μm or more and 2000 μm or less, the upper limit is 20% by weight). This is the characteristic.

[0024] When the refractory for heat-insulating patching of the present invention does not contain a refractory aggregate, with the total of the heat-insulating refractory aggregate and the refractory clay being 100% by weight, it is preferable that the heat-insulating refractory aggregate is 60 to 99% by weight and the refractory clay is 1 to 40% by weight.

[0025] Since the heat-insulating refractory aggregate has lower strength than the refractory aggregate, it is preferable that the refractory for heat-insulating patching of the present invention further contains a refractory aggregate. When containing a refractory aggregate, with the total of the heat-insulating refractory aggregate, the refractory aggregate, and the refractory clay being 100% by weight, it is preferable that the total of the heat-insulating refractory aggregate and the refractory aggregate is 60 to 99% by weight and the refractory clay is 1 to 40% by weight. The weight ratio of the heat-insulating refractory aggregate to the refractory aggregate can be appropriately set according to the required levels of heat insulation and strength.

[0026] It is preferable that the heat-insulating refractory aggregate contains an alkali metal or an alkaline earth metal. The heat-insulating refractory aggregate is particularly preferably a fine porous CA6 aggregate or a fine porous alkaline refractory aggregate.

[0027] It is preferable that the cellulose fiber has an average fiber diameter of 10 to 100 μm.

[0028] The cellulose fiber may be composed of two or more types of cellulose fiber groups having different average fiber lengths. In this case, it is preferable to adjust the fiber length and the addition amount of each cellulose fiber group so that the average fiber length of the entire added cellulose fiber falls within the range of 150 to 2000 μm.

[0029] When the refractory for heat-insulating patching of the present invention further contains cellulose powder, it is preferable that the total of the heat-insulating refractory aggregate (when the refractory aggregate is contained, the heat-insulating refractory aggregate + the refractory aggregate) and the refractory clay is 100% by weight, and the cellulose powder is externally added in an amount of 0.5 to 10% by weight.

[0030] The refractory for heat-insulating patching of the present invention preferably does not contain phosphates.

Advantages of the Invention

[0031] The refractory for heat-insulating patching of the present invention contains a heat-insulating refractory aggregate, a refractory clay, and cellulose fibers, and the content of the cellulose fibers is externally added in an amount of 0.3 to 40% by weight based on the total of the heat-insulating refractory aggregate and the refractory clay being 100% by weight (however, when the average fiber length of the cellulose fibers is 800 μm or more and 2000 μm or less, the upper limit is 20% by weight). Therefore, it has good adhesiveness, crack prevention effect, spatula separation, and storage stability, and has high heat insulation. Therefore, the refractory for heat-insulating patching of the present invention can be suitably used for repairing refractories that require high heat insulation.

Brief Description of the Drawings

[0032]

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Embodiments for Carrying Out the Invention

[0033] Embodiments of the present invention will be described in detail below, but the present invention is not limited thereto, and various modifications can be made within the scope of the technical idea of the present invention.

[0034] [1] Composition of Refractory for Heat Insulating Patching The refractory for heat insulating patching of the present invention contains heat insulating refractory aggregate (or heat insulating refractory aggregate + refractory aggregate), refractory clay, and cellulose fiber. Each component will be described in detail below.

[0035] (1) Heat Insulating Refractory Aggregate The heat-insulating refractory aggregate has no particular limitation as long as it has sufficient strength together with high heat insulation, and various porous and lightweight refractory aggregates (for example, fine porous CA6 aggregate containing a large amount of CaO, fine porous aggregate containing FeO, etc.) can be selected according to the application. When a porous heat-insulating refractory aggregate is used in the patching refractory, since the water absorption is high, the amount of added water increases, and the amount of added water is significantly larger than that of the patching refractory without using the heat-insulating refractory aggregate. Therefore, the adjustment range of various physical properties of the patching refractory becomes important. Heat-insulating refractory aggregates containing no alkali metal or alkaline earth metal (for example, hollow alumina aggregate, etc.) can also be used, but since they can be used in combination with a phosphate binder, the effect of the present invention is relatively low.

[0036] Among the heat-insulating refractory aggregates, those containing an alkali metal or an alkaline earth metal are preferable because they have high heat insulation. The heat-insulating refractory aggregates containing an alkali metal or an alkaline earth metal are fine porous CA6 aggregate, fine porous alkaline refractory aggregate, etc. The fine porous CA6 aggregate has a composition of CaO·6Al 2 O 3 and has fine pores. The heat resistance of the fine porous CA6 aggregate is about 1830°C, the bulk specific gravity is about 0.7 g / cm 3 and the porosity is about 75%. In order to have sufficient heat resistance, the apparent porosity of the heat-insulating refractory aggregate is preferably 30% or more.

[0037] The maximum particle size of the heat-insulating refractory aggregate is preferably 1 to 7 mm, more preferably 2 to 3 mm, similar to that of a general patching refractory. However, if the maximum particle size of the refractory aggregate is smaller than 1 mm, it will be close to a liquid like mortar and it will be difficult to construct by hand. Although hollow aggregates can also be used, since the heat-insulating patching refractory may be stretched or crushed by hand, large-sized hollow aggregates are not suitable.

[0038] (2) Refractory aggregate Refractory aggregates with lower heat insulation than the heat-insulating refractory aggregates can also be used in combination. Refractory aggregates generally have a refractoriness of 1000 °C or higher. The refractory aggregates are not particularly limited as long as they do not impair plasticity and workability, and various types can be selected according to the application. For example, fused alumina, sintered alumina, bauxite, kyanite, andalusite, mullite, chamotte, grog, silica, alumina magnesia spinel, zircon, zirconia, silicon carbide, etc. can be used alone or in combination. Note that when using cellulose fibers, the amount of added water increases and the shrinkage at particularly high temperatures becomes large. Therefore, a material that expands at high temperatures may be used as the refractory aggregate.

[0039] The maximum particle size of the refractory aggregate is preferably 1 to 7 mm, more preferably 2 to 3 mm. Generally, when the maximum particle size is large, the strength of the refractory for heat-insulating patching improves, and when the maximum particle size is small, the workability of the refractory for heat-insulating patching improves. However, if the maximum particle size of the refractory aggregate is less than 1 mm, it becomes close to a liquid like mortar and it becomes difficult to construct by hand.

[0040] (3) Refractory clay The refractory clay that imparts plasticity and adhesiveness to the refractory for heat-insulating patching is not particularly limited as long as it has a refractoriness of 1000 °C or higher. The main mineral components of the refractory clay are kaolinite, bentonite, montmorillonite, sepiolite, quartz, etc. In addition to refractory clay, there are refractory binders such as alumina cement and silica sol that can obtain strength, but binders that hydrate and harden like cement due to long-term storage are not suitable. If necessary, binders other than refractory clay may be used in combination, but even in that case, refractory clay is essential. Since cellulose fibers burn out at less than about 500 °C, the high-temperature strength is ensured by the refractory clay.

[0041] The average particle size of the refractory clay is preferably 30 μm or less, more preferably 20 μm or less. If the average particle size of the refractory clay exceeds 30 μm, sufficient plasticity and adhesiveness cannot be imparted to the refractory for heat-insulating patching.

[0042] (4) Content (a) When not containing refractory aggregate When the mineral composition of the refractory for heat-insulating patching does not contain refractory aggregate, with the total of heat-insulating refractory aggregate and refractory clay being 100% by weight, the heat-insulating refractory aggregate is preferably 60 - 99% by weight, and the refractory clay is preferably 1 - 40% by weight. If the refractory clay is less than 1% by weight, the clay in the matrix is insufficient and the structure does not hold together. On the other hand, if the refractory clay is 40% by weight or more, the added water amount increases too much and the strength decreases. The content of the refractory clay is more preferably 3 - 20% by weight. Therefore, the content of the refractory aggregate is more preferably 80 - 97% by weight.

[0043] (b) When containing refractory aggregate When the refractory for heat-insulating patching contains refractory aggregate, with the total of heat-insulating refractory aggregate, refractory aggregate and refractory clay being 100% by weight, heat-insulating refractory aggregate + refractory aggregate is preferably 60 - 99% by weight, and more preferably 80 - 97% by weight. Therefore, the refractory clay is preferably 1 - 40% by weight, and more preferably 3 - 20% by weight. The weight ratio of the heat-insulating refractory aggregate to the refractory aggregate can be appropriately set according to the required levels of heat insulation and strength. However, in order to obtain sufficient heat insulation, the content of the heat-insulating refractory aggregate is preferably 20% by weight or more, and more preferably 30% by weight or more.

[0044] (4) Cellulose fiber The starting material of the cellulose fiber is not particularly limited as long as it is plant-derived. The cellulose fiber can be produced, for example, by mechanically or chemically crushing and defibrating wood, waste paper, cardboard, etc. In the case of cellulose fiber produced from waste paper, it is preferably one from which ink, etc. has been removed.

[0045] The cellulose fibers used in the present invention do not necessarily need to be completely defibrated into bundles of plant fibers, and a plurality of plant fibers may be in a state bound by hemicellulose and lignin. Therefore, as long as the cellulose fibers have a desired average fiber length, they may contain remaining hemicellulose and lignin. Note that the degree of defibration of plant fibers can be determined by the average fiber diameter, and it can be said that sufficient defibration has been achieved when the average fiber diameter is 100 μm or less.

[0046] (a) Average fiber length and addition amount There is a close correlation between the average fiber length and addition amount of cellulose fibers and the adhesiveness, crack prevention effect, spatula separation, and storage stability of refractory materials for heat insulation patching. Generally, as the addition amount of cellulose fibers increases, the amount of added water increases, and at the same addition amount, the amount of added water increases as the average fiber length increases. In addition, the consistency increases in proportion to the amount of added water, and the rate of decrease in consistency during storage decreases. This is considered to be because the water retention capacity of cellulose fibers increases when the amount of added water is large. Also, when the average fiber length increases, voids are formed between the fibers, and since there is also a water retention effect in these voids, it is considered that the amount of added water increases as the average fiber length increases.

[0047] The crack prevention effect is higher as the average fiber length is longer. This is considered to be because as the average fiber length is longer, the structure is more likely to be united by the cross-linking effect. However, as will be described later, if the addition amount of cellulose fibers becomes too large even when the average fiber length is sufficiently long, the cracks will deteriorate. In particular, when a large amount of long-fiber cellulose fibers are added, the feel of the refractory material for heat insulation patching becomes close to that of paper, the consistency is high, but the structure becomes loose before construction.

[0048] Adhesion and sagging resistance are related to both the adhesiveness to the construction surface and the shape retention property that prevents sagging and peeling after adhesion. Generally, adding long cellulose fibers has an effective cross-linking effect similar to the crack prevention effect described above, so the shape retention property is good, but adding short cellulose fibers results in better adhesiveness. Therefore, it is necessary to adjust the average fiber length of the cellulose fibers to satisfy both adhesiveness and shape retention property.

[0049] As described above, since the adhesiveness, crack prevention effect, sagging resistance, and storage stability of the refractory for heat-insulating patching change depending on the average fiber length and addition amount of the cellulose fibers, it is necessary to optimize the average fiber length and addition amount of the cellulose fibers. As a result of intensive research, it was found that cellulose fibers having an average fiber length of 150 to 2000 μm should be added externally in an amount of 0.3 to 40% by weight based on the total of the heat-insulating refractory aggregate (when containing a refractory aggregate, heat-insulating refractory aggregate + refractory aggregate) and refractory clay being 100% by weight (however, when the average fiber length of the cellulose fibers is 800 μm or more and 2000 μm or less, the upper limit is 20% by weight).

[0050] When the average fiber length exceeds 2000 μm, the dispersibility of the cellulose fibers deteriorates, and the adhesiveness of the refractory for heat-insulating patching decreases. On the other hand, when the average fiber length is less than 150 μm, the aspect ratio (average fiber length / average fiber diameter) is too low, and the crack prevention effect and sagging resistance of the refractory for heat-insulating patching decrease.

[0051] Since the addition effect of the cellulose fibers depends on their average fiber length, it is necessary to change the addition amount according to the average fiber length. As a result of intensive research, it was found that (a) when the average fiber length is 150 μm or more and less than 800 μm, the addition amount of the cellulose fibers may be in the range of 0.3 to 40% by weight, and (b) when the average fiber length is 800 μm or more and 2000 μm or less, it is necessary to set the upper limit of the addition amount of the cellulose fibers to 20% by weight.

[0052] (a) When the average fiber length is 150 μm or more and less than 800 μm When adding cellulose fibers with an average fiber length of 150 μm or more and less than 800 μm, which are short, to heat-resistant refractory aggregates and refractory clay (optionally + refractory aggregates), the balance of adhesiveness, crack prevention, and peeling is good. Therefore, the addition amount range can be 0.3 to 40% by weight. If the addition amount of cellulose fibers is less than 0.3% by weight, a sufficient addition effect cannot be obtained. Also, if the addition amount exceeds 40% by weight, the adhesiveness will instead decrease. The addition amount of cellulose fibers with an average fiber length of 150 μm or more and less than 800 μm is preferably 0.3 to 30% by weight, more preferably 0.5 to 30% by weight, and most preferably 0.5 to 20% by weight.

[0053] (b) When the average fiber length is 800 μm or more and 2000 μm or less When adding cellulose fibers with an average fiber length of 1800 μm or more and 2000 μm or less, which are long, to heat-resistant refractory aggregates and refractory clay (optionally + refractory aggregates), good adhesiveness, crack prevention effect, and peeling can be obtained. However, it has been found that if there is too much, the crack prevention effect and adhesiveness will instead decrease. Therefore, it is necessary to lower the upper limit of the addition amount of cellulose fibers with an average fiber length of 800 μm or more and 2000 μm or less to 20% by weight. That is, the addition amount of cellulose fibers with an average fiber length of 800 μm or more and 2000 μm or less needs to be 0.3 to 20% by weight. The addition amount of this cellulose fiber is preferably 0.5 to 20% by weight, more preferably 0.5 to 10% by weight, and most preferably 0.5 to 8% by weight.

[0054] To obtain a good combination of adhesiveness, crack prevention effect, peeling, and storage stability, the average fiber length of the cellulose fiber is preferably 250 to 1800 μm, more preferably 400 to 1500 μm, and most preferably 400 to 1000 μm.

[0055] As described above, a longer fiber length is better for shape retention, while a shorter fiber length is better for adhesion. Therefore, two or more types of cellulose fibers with different fiber lengths may be added to satisfy both adhesion and shape retention. Also, for example, when only short cellulose fibers are added in a small amount, the adhesion is too high, and the aggregation of the tissue is poor, resulting in poor spatula release. The ease of tissue aggregation is improved by the cross-linking effect of cellulose fibers, but if the addition amount of cellulose fibers is too large, the balance with the fine refractory clay in the matrix deteriorates, and the tissue becomes fragmented. For this reason, it has been found that it is good to adjust by adding a small amount of cellulose fibers that are somewhat long.

[0056] For example, when adding two types of cellulose fibers with different fiber lengths, the first cellulose fiber preferably has an average fiber length of 150 to 600 μm, and the second cellulose fiber preferably has an average fiber length of 900 to 2000 μm. Of course, even when adding two or more types of cellulose fibers with different fiber lengths, the cellulose fibers as a whole need to have an average fiber length of 150 to 2000 μm.

[0057] Since the refractory clay affects the adhesiveness and consistency of the refractory for heat-insulating patching, it is preferable to adjust the adhesiveness and consistency with the addition amount of cellulose fibers after determining the addition amount of the refractory clay.

[0058] (b) Average fiber diameter As described above, the fibrillation degree of cellulose fibers can be evaluated by the average fiber diameter, and the average fiber diameter is preferably 100 μm or less, more preferably 10 to 70 μm. When the average fiber diameter exceeds 100 μm, the dispersibility and water retention of the cellulose fibers deteriorate, and the adhesiveness and storage stability of the refractory for patching decrease.

[0059] (c) Measurement method The average fiber length and average fiber diameter of cellulose fibers can be measured by an optical automatic analysis method. As the measuring device, for example, a fiber tester (manufactured by L&W) is used.

[0060] (5) Cellulose powder If the cellulose fiber is continuously pulverized, it will become cellulose powder with a fiber length comparable to the fiber diameter. The aspect ratio of the cellulose powder is about 0.6 to 1.8. Since the cellulose powder has no cross-linking effect, it does not have a crack prevention effect. However, when used in combination with cellulose fibers having a long fiber length, it can impart good adhesion and storage properties to the refractory for heat-insulating patching. Therefore, with the total of the heat-insulating refractory aggregate (when containing a refractory aggregate, heat-insulating refractory aggregate + refractory aggregate) and the refractory clay being 100% by weight, 0.5 to 10% by weight of cellulose powder may be added externally to the refractory for heat-insulating patching.

[0061] (6) Other additives Regarding phosphates, it is better not to add them to the refractory for heat-insulating patching to ensure sufficient storage properties. However, with the total of the heat-insulating refractory aggregate (when containing a refractory aggregate, heat-insulating refractory aggregate + refractory aggregate) and the refractory clay being 100% by weight, if it is a small amount of 0.1% by weight or less (based on solid content) externally, it may be added.

[0062] [2] Physical properties of the refractory for heat-insulating patching The refractory for heat-insulating patching may be applied manually. In that case, since the consistency and spatula release are evaluated by the user's feeling, the wider the adjustment range of them, the more preferable. Similarly, since the usage conditions are different when covering the ceiling surface, wall surface, horizontal surface, studs, etc., the preferable consistency and adhesiveness are wide, and again, the wider the adjustment range, the more preferable. The various physical properties of the refractory for heat-insulating patching of the present invention can be adjusted by the selection of the average fiber length of the cellulose fiber and the addition amount, and it has high versatility. Specifically, by selecting an appropriate average fiber length, addition amount, and added water amount so as to satisfy the physical properties required for the usage conditions, various physical properties such as adhesiveness, crack prevention effect, spatula release, and storage properties can be adjusted. Also, by using cellulose fibers with different fiber lengths in combination, various physical properties can be adjusted.

Examples

[0063] The present invention will be described in more detail by the following examples, but the present invention is not limited to these examples. The addition amounts shown in the examples and comparative examples are in weight % unless otherwise specified.

[0064] Examples 1 to 5 and Comparative Example 1 With respect to a total of 100% by weight of 60% by weight of a heat-insulating refractory aggregate (fine porous CA6), 30% by weight of a refractory aggregate, and 10% by weight of a refractory clay, water in the amounts (weight %) shown in Table 1 was added externally and kneaded to produce a refractory for heat-insulating patching of Comparative Example 1. Further, with respect to a total of 100% by weight of 60% by weight of a heat-insulating refractory aggregate (fine porous CA6 aggregate), 30% by weight of a refractory aggregate, and 10% by weight of a refractory clay, cellulose fibers having an average fiber length of 150 μm were added externally at a ratio of 0.5 to 30% by weight, and water in the amounts (weight %) shown in Table 1 was added and kneaded to produce refractories for heat-insulating patching of Examples 1 to 5. The amount of added water is expressed as the external weight % when the total of the heat-insulating refractory aggregate, refractory aggregate, refractory clay, and cellulose fibers is 100% by weight. The amount of added water was adjusted so that the consistency after kneading was the same for all samples.

[0065] For the samples of each example and comparative example, the consistency, crack prevention effect, adhesiveness, spatula separation, and storage stability were evaluated as follows. The evaluation results are shown in Table 1.

[0066] (1) Consistency and its storage stability The consistency was measured at room temperature using a consistency meter according to the following procedure. First, each sample was filled to the brim in a cylindrical container (inner diameter: 100 mm, depth: 75 mm), a 200 g weight was placed on the cone of the consistency meter, and the height was adjusted so that the tip of the cone contacted the surface of the sample. Then, the support of the cone was released and left for 5 seconds, and the depth to which the cone penetrated into the sample by its own weight was measured. The consistency was measured within 10 minutes after kneading on the day of kneading. Also, each sample was put into a plastic bag and sealed, stored at a constant temperature of 30°C, and the consistency after 1 day, 14 days, and 30 days was measured. The storage stability of the consistency was evaluated by the ratio of the consistency after each number of days to the consistency within 10 minutes after kneading (set as 100).

[0067] (2) Crack prevention effect and its storage stability Five testers each picked up 200 g of each sample and formed it into a sphere so that no cracks would occur on the surface. As shown in FIGS. 1(a) and 1(b), the spherical sample 1 was placed on the iron plate 2, and as shown in FIGS. 2(a) and 2(b), after manually pressing it until the height reached 7 mm, each person visually observed the degree of cracking on the side surface 1a of the sample 1', and the degree of cracking was evaluated in three levels according to the following criteria. The average of the evaluation results of the five people was taken as the final evaluation result. The above evaluation was carried out within 2 hours after kneading each sample. Also, the same test was carried out after storing each sample for 30 days to evaluate the storage stability of crack prevention. ◎ No cracks occurred even after pressing. 〇 Cracks with a maximum width of less than 1 cm occurred when pressed, but the cracks could be erased by gently rubbing with a finger. × (a) Cracking was severe from the beginning and a spherical sample without cracks could not be created, or (b) Even if a spherical sample without cracks could be created, cracks with a maximum width of 1 cm or more occurred after pressing.

[0068] (3) Adhesiveness and its storage stability Each sample, 100 g, molded into a spherical shape was placed on an iron plate and pressed by hand until the maximum diameter was 90 cm, as shown in Figures 3(a) and 3(b), and then the iron plate 2 was turned upside down and placed on a horizontal base (not shown). Next, as shown in Figures 4(a) and 4(b), a plastic hammer 3 was dropped 10 times from a height of 2 cm onto the upper surface of the iron plate 2, and it was observed whether or not the sample 1' had fallen. If it had fallen, the adhesiveness was recorded as 0 g. If it did not fall, the weight of each sample 1' was increased in 100 g increments to 200 g, 300 g, and so on, and the same test as above was repeated until the sample 1' fell, and the maximum weight that did not fall was recorded as the adhesiveness of each sample. For example, if it did not fall at 200 g but fell at 300 g, the adhesiveness was 200 g. The above evaluation was performed within 2 hours after kneading each sample. In addition, the same test was performed on each sample after storage for 30 days to evaluate the shelf life of the adhesiveness.

[0069] (4) Soldering ability and preservability Each sample 1 was molded into a cylindrical shape with a diameter of 100 mm and a height of 100 mm, and was sandwiched between a pair of upper and lower nitrile rubber plates 4a and 4b as shown in Fig. 5(a) and Fig. 5(b). After pressing the upper rubber plate 4a until the load reached 2.5 kN using an Amsler testing machine, the upper rubber plate 4a was removed [Fig. 5(c)], and the weight W 1 of the upper rubber plate 4a with sample 1" attached thereto was measured, and the weight W 1 of the upper rubber plate 4a itself was subtracted from the weight W 0 to obtain the amount of adhesion W of sample 1". The iron releasability of sample 1" was evaluated based on the adhesion amount W according to the following criteria. The above evaluation was performed within 2 hours after mixing of each sample. The same test was also performed on each sample after 30 days of storage to evaluate the iron releasability. ◎ The adhesion amount of the sample was less than 5 g. 〇 The adhesion amount of the sample was 5 g or more but less than 10 g. × The adhesion amount of the sample was 10 g or more.

[0070]

Table 1

[0071] As is clear from Table 1, in Comparative Example 1 without the addition of cellulose fiber, the preservability of the crack prevention effect was poor. On the other hand, the refractory for heat-insulating patching of Examples 1 to 4 to which 0.5 to 10% by weight of cellulose fiber having an average fiber length of 150 μm was added had good adhesiveness, crack prevention effect, spatula separation, and their preservability. In addition, the refractory for heat-insulating patching of Example 5 to which 30% by weight of cellulose fiber having an average fiber length of 150 μm was added had relatively low adhesiveness and its preservability, but had good crack prevention effect and its preservability, and spatula separation and its preservability. Therefore, it can be seen that the upper limit of the addition amount of cellulose fiber having an average fiber length of 150 μm is preferably 30% by weight, and more preferably 20% by weight.

[0072] Examples 6 to 10 For a total of 60% by weight of heat-insulating refractory aggregate (fine porous CA6), 30% by weight of refractory aggregate, and 10% by weight of refractory clay, a refractory for heat-insulating patching was produced in the same manner as in Examples 1 to 5 except that cellulose fiber having an average fiber length of 400 μm was added at a ratio of 0.5 to 30% by weight externally. The average fiber diameter of the cellulose fiber was about 40 μm in all cases. The consistency, adhesiveness, crack prevention effect, spatula separation, and preservability were evaluated in the same manner as in Examples 1 to 5. The results are shown in Table 2.

[0073]

Table 2

[0074] As is clear from Table 2, the refractory materials for heat-insulating patching in Examples 6-9, to which 0.5-10 wt% of cellulose fiber having an average fiber length of 400 μm was added, were good in both crack prevention effect and its storage stability, adhesiveness and its storage stability, and spatula separation and its storage stability. Further, the refractory material for heat-insulating patching in Example 10, to which 30 wt% of cellulose fiber having an average fiber length of 400 μm was added, was relatively low in adhesiveness and its storage stability, but was good in crack prevention effect and its storage stability, and spatula separation and its storage stability. Therefore, it can be seen that the upper limit of the addition amount of cellulose fiber having an average fiber length of 400 μm is preferably 30 wt%, more preferably 20 wt%.

[0075] Examples 11-14 and Comparative Example 2 Refractory materials for heat-insulating patching were produced in the same manner as in Examples 1-5, except that cellulose fibers having an average fiber length of 1000 μm were added at an external addition ratio of 0.5-30 wt% with respect to the total of 60 wt% of heat-insulating refractory aggregate (fine porous CA6), 30 wt% of refractory aggregate, and 10 wt% of refractory clay. The average fiber diameter of the cellulose fibers was about 40 μm in all cases. The consistency, adhesiveness, crack prevention effect, spatula separation, and storage stability were evaluated in the same manner as in Examples 1-5. The results are shown in Table 3.

[0076]

Table 3

[0077] As is clear from Table 3, all of the refractory materials for heat-insulating patching in Examples 11 to 14 to which 0.5 to 10% by weight of cellulose fibers having an average fiber length of 1000 μm were added had good crack prevention effects and their storability, adhesiveness and its storability, and spatula separation and its storability. On the other hand, the refractory material for heat-insulating patching in Comparative Example 2 in which the addition amount of cellulose fibers was 30% by weight had low storability of the crack prevention effect, adhesiveness and its storability. Therefore, it can be seen that the upper limit of the addition amount of cellulose fibers having an average fiber length of 1000 μm is 20% by weight, preferably 10% by weight.

[0078] Examples 15 to 18 and Comparative Example 3 Refractory materials for heat-insulating patching were produced in the same manner as in Examples 1 to 5, except that cellulose fibers having an average fiber length of 2000 μm were added at a ratio of 0.5 to 30% by weight externally to a total of 60% by weight of heat-insulating refractory aggregates (fine porous CA6), 30% by weight of refractory aggregates and 10% by weight of refractory clay. The average fiber diameter of the cellulose fibers was about 40 μm in all cases. The consistency, adhesiveness, crack prevention effect, spatula separation and storability were evaluated in the same manner as in Examples 1 to 5. The results are shown in Table 4.

[0079]

Table 4

[0080] As is clear from Table 4, all of the refractory materials for heat-insulating patching in Examples 15 to 18, to which cellulose fibers with an average fiber length of 2000 μm were added at a ratio of 0.5 to 10% by weight, had good crack prevention effects and their storage properties, adhesiveness and its storage properties, and spatula separation and its storage properties. On the other hand, the refractory material for heat-insulating patching in Comparative Example 3, to which cellulose fibers with an average fiber length of 2000 μm were added at a ratio of 30% by weight, had low storage properties of the crack prevention effect, and adhesiveness and its storage properties. Therefore, it can be seen that the upper limit of the addition amount of cellulose fibers with an average fiber length of 2000 μm is 20% by weight, preferably 10% by weight, and more preferably 8% by weight.

[0081] Comparative Examples 4 to 8 Except that cellulose powder with an average particle size of 40 μm was added at an external coating ratio of 0.5 to 30% with respect to the total of 60% by weight of heat-insulating refractory aggregate (fine porous CA6), 30% by weight of refractory aggregate, and 10% by weight of refractory clay, refractory materials for heat-insulating patching were produced in the same manner as in Examples 1 to 5, and the consistency, adhesiveness, crack prevention effect, spatula separation, and storage properties were evaluated. The results are shown in Table 5.

[0082]

Table 5

[0083] As is clear from Table 5, all of the refractory materials for heat-insulating patching to which cellulose powder was added had extremely poor storage properties of the crack prevention effect. In addition, the refractory material for heat-insulating patching in Comparative Example 8, to which the addition amount of cellulose powder was 30% by weight, also had low adhesiveness and its storage properties.

[0084] Comparative Examples 9 to 13 For the total of 60 wt% of heat-insulating refractory aggregate (fine porous CA6), 30 wt% of refractory aggregate, and 10 wt% of refractory clay, refractory materials for heat-insulating patching were produced in the same manner as in Examples 1 to 5, except that cellulose fibers with an average fiber length of 2300 μm were added at a ratio of 0.5 to 30 wt% externally. The average fiber diameter of the cellulose fibers was about 40 μm in each case. The consistency, adhesiveness, crack prevention effect, spatula separation, and storage stability were evaluated in the same manner as in Examples 1 to 5. The results are shown in Table 6.

[0085]

Table 6

[0086] As is clear from Table 6, for the refractory materials for heat-insulating patching in Comparative Examples 9 and 10, to which 0.5 to 1 wt% of cellulose fibers with an average fiber length of 2300 μm were added, both the adhesiveness and its storage stability were poor. Also, for the refractory materials for heat-insulating patching in Comparative Examples 11 to 13, to which 5 to 30 wt% of cellulose fibers with an average fiber length of 2300 μm were added respectively, the storage stability of the crack prevention effect was extremely poor, and the adhesiveness and its storage stability were also low.

[0087] Based on the experimental results shown in Tables 1 to 6, the correlation between the average fiber length and addition amount of cellulose fiber and the adhesiveness, crack prevention effect, spatula detachment, and storage stability of the refractory for heat-insulating patching obtained was analyzed. As a result, with the total of the heat-insulating refractory aggregate (when containing a refractory aggregate, heat-insulating refractory aggregate + refractory aggregate) and refractory clay being 100% by weight, the addition amount of cellulose fiber was set to 0.3 to 40% by weight externally, and when the average fiber length was 150 μm or more and less than 800 μm, it was set to 0.3 to 40% by weight, and when it was 800 μm or more and 2000 μm or less, it was set to 0.3 to 20% by weight. It was confirmed that good adhesiveness, crack prevention effect, spatula detachment, and storage stability could be obtained.

Explanation of symbols

[0088] 1 ··· Spherical sample 1’ ··· Pressed sample 1a ··· Side surface of the pressed sample 1” ··· Sample attached to the rubber plate 2 ··· Iron plate 3 ··· Hammer 4a, 4b ··· Rubber plate

Claims

1. A refractory material for insulating patching, comprising: insulating refractory aggregate, refractory clay, and cellulose fiber having an average fiber length of 150 to 2000 μm, the content of the cellulose fiber being 0.3 to 40% by weight in outer percent, with the total of the insulating refractory aggregate and the refractory clay being 100% by weight (however, when the average fiber length of the cellulose fiber is 800 μm or more and 2000 μm or less, the upper limit is 20% by weight).

2. The insulating refractory aggregate and the refractory clay are 60 to 99% by weight, and the refractory clay is 1 to 40% by weight, with the total of the insulating refractory aggregate and the refractory clay being 100% by weight. Refractory material for insulating patching according to claim 1.

3. 2. The refractory material for insulating patching according to claim 1, further comprising a refractory aggregate.

4. The insulating refractory aggregate, the refractory aggregate and the refractory clay are 100% by weight, and the insulating refractory aggregate and the refractory clay are 100% by weight. The insulating patching refractory material according to claim 3, characterized in that the total of the insulating refractory aggregate and the refractory aggregate is 60 to 99% by weight, and the refractory clay is 1 to 40% by weight.

5. 2. The refractory material for insulating patching according to claim 1, characterized in that the insulating refractory aggregate contains an alkali metal or an alkaline earth metal.

6. 2. The refractory material for insulating patching according to claim 1, characterized in that the insulating refractory aggregate is a microporous CA6 aggregate or a microporous alkaline refractory aggregate.

7. The refractory material for insulation patching according to claim 1, characterized in that the cellulose fibers have an average fiber diameter of 10 to 100 μm.

8. 2. The refractory material for insulation patching according to claim 1, characterized in that the cellulose fibers consist of two or more types of cellulose fibers having different average fiber lengths.

9. The refractory material for insulating patching according to claim 8, characterized in that the fiber length and amount of each cellulose fiber group added are adjusted so that the average fiber diameter of the entire added cellulose fiber is in the range of 150 to 2000 μm.

10. The refractory material for insulating patching according to claim 1, further comprising cellulose powder.

11. The refractory material for insulating patching according to claim 10, characterized in that the cellulose powder is 0.5 to 10% by weight in terms of outer percentage, with the total of the insulating refractory aggregate and the refractory clay being 100% by weight.

12. 12. The refractory material for insulating patching according to any one of claims 1 to 11, characterized in that it does not contain phosphate.

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