KR20190017174A - A Coating Material with Crack Healing and Anti-fire for Substrates and It's Coating Method - Google Patents

Abstract

The present invention relates to a flame retardant coating agent capable of curing a crack generated in a heat-resistant base and to a coating method using the coating agent, and more particularly, to a coating agent applied to a surface of the base used under a high-temperature environment to reinforce heat resistance of the base. Disclosed is the flame retardant coating agent capable of curing the crack generated in the heat-resistant base, which is slurry dispersed in a soluble solvent for polysiloxane and a polysiloxane in a powder form. According to the present invention, by forming a coating layer having a heat absorbing function in the base (for example, a block), the heat acting on the base can be transferred more slowly when a fire occurs, so that an effect of preventing rapid propagation of the crack can be expected.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a coating agent capable of curing and refining cracks generated in a heat resistant base, and a coating method using the coating agent.

The present invention relates to a coating agent capable of curing and refining cracks generated in a heat resistant base, and a coating method using the coating agent, and more particularly, to a coating agent applied to a surface of a base used under a high temperature environment, Wherein the coating agent is a slurry in which powdery polysiloxane and silica are dispersed in a soluble solvent for polysiloxane, and a coating agent capable of curing and flaming the cracks generated in a heat resistant matrix.

Borosilicate-based porous blocks are used for lining in flue gas desulphation (FGD), a desulfurization system. In particular, the height of the target chimney is increasing based on the technological growth of the block. In recent years, It is actively applied to the FGD with a 200-meter-high chimney.

The porous block is mounted inside the chimney as described above and has two functions of protecting the support part of the chimney made of concrete material or steel material from being corroded by strongly acidic gas without being deteriorated by heat under the normal operating temperature condition of 80 ° C .

However, when an unexpected fire occurs in the FGD unit, the electric dust collecting chamber, and the temperature boiler room during the operation of such a chimney-mounted thermal power plant, the temperature rises to about 1000 ° C. At such a temperature, There is a problem that the block is damaged (see Fig. 1).

That is, when a fire occurs, the borosilicate block usually cracks due to phase transformation and thermal expansion, and the surface portion is melted by the flame, and thus the damaged borosilicate block can not perform the above two functions I can not do it.

Therefore, in order to prevent cracking in the lining block, it is preferable to fundamentally remove the occurrence of fire in the FGD system. However, it can be seen that the fire is generated substantially four times or more per year depending on the heterogeneity of the raw materials during the operation of the system, Safety measures are needed for this.

On the other hand, cracks are generated in the borosilicate block due to the fire due to the expansion of the rectangular block in the X and Y directions and the temperature gradient of the Z axis. The shape of the cracks is mainly crisscross, and in the normal working environment, as well as in the case of fire recurrence, the possibility of such cracks diffusing into the Z axis increases, and as a result, the borosilicate blocks are eventually destroyed by the growth and propagation of cracks, When the crack reaches the structure of the chimney, there is a serious problem that the structure of the chimney itself is eroded or damaged by the strong acid gas and the continuous heat.

If the borosilicate block is destroyed or cracks grow along the Z-axis of the block to the support of the chimney, the block will no longer be resistant to acid and heat by-products for the desulfurization process, The entire lining block must be replaced in advance before such severe damage. However, in this case, since it takes about 60 days to remove the existing block and rework, there was a problem of cost loss and time wasted due to shutdown of the thermal power plant during the rework.

Therefore, it is necessary to actively suppress the growth of cracks in the already constructed borosilicate block to extend the service life of the block.

Particularly, since the frequency of occurrence of block cracks is high at the upper end where the gas inlet of the lower part of the stack and the upper part of the stack are narrowest where hot combustion gas is most contacted in case of fire, Development of coating materials and coating processes is urgently required.

Korean Patent No. 10-0943713

SUMMARY OF THE INVENTION The present invention has been conceived to solve the above-mentioned problems, and it is an object of the present invention to provide a coating layer having a heat absorbing function in a base (for example, a block) so that heat A coating agent capable of curing and flame-retarding cracks generated in heat-resistant and chemical-resistant blocks for preventing rapid propagation of cracks, and a coating method using the coating agent.

It is another object of the present invention to provide a method of coating a crack in which a coating layer liquefied at a specific temperature is filled, thereby blunting cracks or inhibiting further progress and growth of cracks, A coating agent capable of curing and refining cracks generated in a heat-resistant and chemical-resistant block capable of preventing damage to a substrate, and a coating method using the coating agent.

In order to achieve the above-mentioned object, the present invention provides a coating agent which is applied to a known surface used under a high-temperature environment to reinforce the base heat resistance,

Wherein the coating agent is a slurry dispersed in a powdery polysiloxane and a soluble solvent for polysiloxane, and a coating agent capable of curing and flaming the cracks generated in a heat resistant base.

The solvent is preferably methanol or ethanol.

It is preferable that the slurry further contains silica.

It is preferable that the polysiloxane is contained in an amount of 5 to 30 parts by weight and the silica is contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of the slurry.

The coating layer applied to the matrix preferably has a thickness of 1 to 2,000 mu m.

The silica is preferably a powdery particle including at least one of fumed silica, nanoquartz, and glass bead.

Preferably, the fumed silica has a diameter of 5 to 200 nm, the nanoquartz has a diameter of 10 to 300 nm, and the glass bead has a diameter of 100 to 8000 nm.

The polysiloxane is preferably contained in an amount of 5 to 35 parts by weight based on 100 parts by weight of the slurry.

The substrate is preferably a metal, a non-metal or an organic material.

It is preferable that the slurry has fluidity so as to be applicable to the base.

As described above, according to the present invention, by forming a coating layer having a heat absorbing function in a matrix (for example, a block), the heat acting on the matrix at the time of a fire can be transmitted more slowly, .

In addition, the coating layer liquefied at a specific temperature charges the generated cracks, thereby blunting the cracks or inhibiting further progress and growth of the cracks, thereby preventing damage to the underlying base material An effect that can be expected can be expected.

Fig. 1 is a photograph showing a borosilicate block in which a crush and a melting are generated by a fire.
2 is a photograph showing (a) a reference block of a borosilicate coated with a slurry according to the present invention and (b) a borosilicate block (b) coated with the slurry according to the present invention.
FIG. 3 is a photograph of a borosilicate block coated with a slurry according to an embodiment of the present invention by heat-treating (a) and (b) measuring the temperature.
FIG. 4 is a graph illustrating a temperature change of a borosilicate block coated with a slurry according to an embodiment of the present invention.
5 is an optical image of a section after heat treatment of a slurry coated borosilicate block according to the present invention.
FIG. 6 shows XRD patterns of a borosilicate block having no slurry coating layer according to the present invention and a borosilicate block coated with slurries S1 and S2.
7 is a TGA-DTA graph for a slurry-coated block, a block with no application, and a block with S1 and S2 applied.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Embodiments in accordance with the concepts of the present invention are capable of various modifications and may take various forms, so that specific embodiments are exemplified and will be described in detail in this specification or application. It should be understood, however, that the embodiments according to the concepts of the present invention are not intended to be limited to any particular mode of disclosure, but rather all variations, equivalents, and alternatives falling within the spirit and scope of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises ", or" having ", and the like, are intended to specify the presence of stated features, integers, steps, operations, elements, , Steps, operations, components, parts, or combinations thereof, as a matter of principle.

In the case of lining blocks, the melt loss should not be large for stable use even after the fire. For example, if the block thickness is about 3 cm, the melt loss should be within about 1 cm. Experiments show that pores in a block are merged into larger pores in order to reduce the surface tension in the vitrification temperature range, rather than being melted and lost in a real fire situation. The pores of the flue gas grow to pores of about 200 mu m after the fire. As a result, the heat-resistant function of the block for protecting the support portion of the flue is rapidly deteriorated.

Therefore, the block has the same reliability before and after the fire, and it is necessary to be able to use normally after the fire, or to delay the spread of the thermal energy due to the fire inside the block in order to survive the subsequent fire again. For this reason, if the coating layer has a property of causing an endothermic reaction due to a chemical reaction, the coating layer can absorb the external heat source during the fire process, so that it is possible to prevent block deterioration by reducing the amount of heat transferred to the inside of the block.

In addition, if a coating layer capable of flame retarding by endothermic reaction is provided in a damaged portion of the block, that is, a gap between the surface melting portion and the crack, it is possible to further improve the properties of the fire resistance against the subsequent fire.

On the other hand, when a crack occurs on the surface of a block due to a fire, a preferable method for preparing a subsequent fire is to prevent the crack damage of the porous block from being limited to the surface portion and prevent spreading of cracks to the bottom portion of the block shall. Conventional methods for preventing the spread of cracks were crack blunting and cracking healing methods.

Cracking is a method of placing a spherical workpiece in the direction of crack propagation and changing the shape of the crack into a blunt form when it comes into contact with the workpiece, making it difficult to further progress the crack. However, in the case of the present invention, since the spherical porous material is used, it can be considered that the crack braining is sufficiently utilized.

Crack healing is a phenomenon in which the coating layer changes to a state capable of viscous flow when the temperature rises, and the capillary effect partially impregnates between the crack fronts or openings to fill the crack fronts or gaps, .

As a result, in the present invention, a liquid coating can be vitrified at a lower temperature than the borosilicate at the lower end of the block, or a functional coating layer for forming a liquid phase fluidized bed can be formed or a functional element can be injected into a coating layer or a functional element When the temperature is lowered due to the end of the fire and the solidified again to the solid phase, crack diffusion can be prevented positively.

In addition, if a functional coating layer is applied to the surface of the block where the fire damage has already occurred, the coating layer will absorb endothermic reaction in the subsequent fire, so that the thermal energy of the flame can be absorbed by itself and heat transfer to the lower layer can be reduced. It is possible to impart excellent flame retardancy to the block.

Of course, this method is not limited to the porous block, and the coating layer of the present invention can be simply applied to any substrate having a flat surface or having flexibility such as cloth. The solid phase coating layer remaining on the base can absorb the external heat primarily by the endothermic reaction in the event of a fire (when heating) and reduce the heat transfer to the inside of the base. The slurry coating layer is liquefied by the external heat source, It is necessary to interpret the shape and the kind of the base material to be applied as there is no limitation because it can function to prevent any further deformation by filling up Therefore, it can be applied to all types of bases such as metal, non-metal, and organic materials.

Example 1 Coating of Polysiloxane + Fumed Silica + Ethanol Slurry on the Surface of the Borosilicate Block

The slurry for base coating used in one embodiment of the present invention is composed of polysiloxane, an ethanol solvent which dissolves fumed silica and polysiloxane. The solvent is not limited to ethanol as long as it dissolves polysiloxane.

Polysiloxane is a polymer having the following structure,

Si-O basic structure and the alkyl groups R ₁ and R ₂ are H, CH ₃ , C ₂ H ₅ , C ₆ H ₅ , CH ₂ -CH, OH, and the like.

The fumed silica is a by-product of pyrolysis of SiCl ₄ , which is a powder having a large surface area due to the aggregation of nano-sized SiO _{2, and} is relatively inexpensive. However, it is also possible to use an amorphous material containing SiO ₂ such as nanoquartz, glass bead, etc. instead of fumed silica.

Preferably, the fumed silica has a diameter of 5 to 200 nm, the nanoquartz has a diameter of 10 to 300 nm, and the glass bead has a diameter of 100 to 8000 nm.

When fumed silica is coated with polysiloxane as a low-cost silica having a low thermal conductivity having a nano size, when the particle size of the silica is large, the surface roughness of the coated layer becomes large and the appearance of the coating layer is poor, (Micron size or more), silica particles and polysiloxane shrink due to heat, which increases the residual stress in the periphery of the silica particles, which is undesirable for the durability of the coating layer. That is, there is a possibility of cracking due to the residual stress after a long time.

On the other hand, when fusadicilica and polysiloxane are used together, the significance is as follows. When the polysiloxane is heated in the atmosphere or in an atmosphere containing oxygen for a long period of time at 1200 ° C. or higher, carbon in the SiOC residue, which is a pyrolysis residue of the polysiloxane, is oxidized and the SiOC is changed into an amorphous SiO ₂ phase. Therefore, nano-sized fused silica provides excellent bonding strength to allow such amorphous SiO ₂ phase to act as a sufficient bridge with the matrix in the matrix.

Although the glass beads are not fine particles of fumed silica, they are fine particles having a particle size of 8 micrometers or less. Therefore, they can be used with the same purpose as the use of fumed silica.

In the present invention, when the weight of the slurry is set to 100 parts by weight, 5 to 30 parts by weight of the polysiloxane is added, and 1 to 20 parts by weight of fumed silica is added. If only the polysiloxane is added, When the amount of polysiloxane is less than 5 parts by weight, the viscosity of the slurry is too low to obtain a sufficient viscosity suitable for coating. When the amount exceeds 35 parts by weight, the viscosity of the slurry becomes too high, . However, if it is added together with fumed silica, it should not exceed 30 parts by weight due to viscosity problems.

When fumed silica is added in an amount of less than 1 part by weight, the addition of fumed silica is hardly effected. When the amount of fumed silica is more than 20 parts by weight, the viscosity of the slurry becomes excessively high and it is difficult to apply a coating layer having a uniform thickness and various application methods Loses. Therefore, polysiloxane and fumed silica have their critical significance in the stomach content range.

- preparation of sample

A borosilicate block having a size of 100 x 100 x 35 mm was prepared as a base (coated body) of the coating agent according to the present invention. Then, two kinds of slurries having different amounts of polysiloxane added in the composition shown in Table 1 were prepared to have a total of 100 g.

Next, 250 ml of each solution was poured into a mixing container, and then 10 balls of alumina having a size of 10 mm were used to conduct a ball mill for 24 hours at a rotation speed of 250 rpm. The prepared polysiloxane-containing slurry was uniformly applied to the upper surface of the borosilicate block using a brush and then dried at a temperature of 60 ° C for 6 hours.

Figure 2 shows (a) the reference block of borosilicate not coated with the slurry according to the invention and (b) the borosilicate block (b) coated with the slurry according to the invention, respectively.

Name of sample Polysiloxane (wt%) Fumed silica (wt%) Ethanol (wt%) S1 18 10 72 S2 21.88 9.38 68.74

- Heat treatment and measurement progress

 FIG. 3 is a photograph of a borosilicate block coated with a slurry according to an embodiment of the present invention by heat-treating (a) and (b) measuring the temperature.

(a), a butane gas torch was used for heat treatment of the borosilicate block. The block was charged into the four-sided heat-resistant block and heat-treated at a temperature of 800 ° C for 5 minutes. At this time, as shown in (b), a temperature sensor capable of measuring up to 1000 ° C was placed at the lower end of the borosilicate block, and the temperature was measured for 5 minutes at intervals of 10 seconds.

FIG. 4 is a graph illustrating a temperature change of a borosilicate block coated with a slurry according to an embodiment of the present invention. In the case of the reference block (reference sample), it was confirmed that the temperature was maintained within the error range after rising to the maximum temperature value of 800 ° C. within 60 seconds.

On the other hand, in the case of the S1 sample, the temperature increased to 600 ° C in 100 seconds, which was a rapid rise pattern. However, it took about 320 seconds to reach 800 ° C because the slurry containing polysiloxane was applied to the block, This is because it shows a slower temperature rise rate than the reference sample.

The S2 sample took about 340 seconds to reach the maximum temperature value and showed a lower temperature rise rate than the S1 sample. As the polysiloxane content in the polysiloxane-containing mixed slurry contained a larger amount of polysiloxane, Suggesting that the growth rate is higher.

When a coating layer is formed on the block in accordance with the mixed slurry, the temperature gradient between the heating surface and the opposite surface is higher at the maximum temperature than in the case where the slurry is not applied due to the endothermic reaction due to the pyrolysis process of the polysiloxane Which suggests the ability of the slurry coating layer to retard the growth of the fire upon fire.

- Optical microscope analysis after heat treatment

FIG. 5 shows an optical image of a section after heat treatment of a slurry-coated borosilicate block according to the present invention.

(a) was a reference sample to which nothing had been applied on the surface, and it was confirmed that the sample was melted at a depth of 243 μm from the top after the heat treatment. The average size of the lower pores excluding the melting surface was 117 탆.

(b) shows the optical image of the section after the heat treatment on the S1 sample. As in (a), the melted portion was present from the surface to a certain depth, and the depth was 180 μm, which was about 25.9% less than the reference sample . On the other hand, the average size of the lower pores excluding the melting portion decreased to 113 탆.

(c) shows the optical image of the section after the heat treatment on the S2 sample. The depth of the upper fused portion was 91 탆, which was significantly reduced as compared with (a) and (b). In addition, the average pore size at the lower end except for the molten portion was 111 mu m. That is, the microstructure which is less influenced by the external heat source.

Therefore, when the polysiloxane is applied according to the present invention, it is confirmed that the surface melting of the block due to the heat source is remarkably reduced due to the endothermic reaction due to the pyrolysis process.

On the other hand, the molten polysiloxane coating layer densely charges the pores by the capillary force, and even when a crack occurs on the surface of the coating layer, the molten coating layer effectively fills it and solidifies, So that destruction of the block can be prevented.

In the present invention, it is preferable that the coating layer on the block has a thickness of 1 to 2,000 mu m. When the thickness of the coating layer is more than 2000 mu m, it is easily peeled off from the base after the alcohol solvent is dried When the thickness is less than 1 占 퐉, there is no effect of coating, so that there is a critical significance in the above range.

- XRD analysis after heat treatment

6 shows XRD patterns of a borosilicate block in which a slurry coating layer according to the present invention is not formed and a borosilicate block to which slurries S1 and S2 in Table 1 are applied. As a result, it was found that each sample showed an amorphous glass phase without showing a specific peak within a measurement range of 20 to 120 ° regardless of heat treatment.

These results show that the borosilicate block used in the present invention is an amorphous phase and the applied layer is composed of an amorphous phase. Kim et al. J. Kim, J. H. Eom, Y.-W. Kim, and W. S. Seo, " Electrical Conductivity of Dense, Bulk Silicon-Oxycarbide Ceramics, " J. Eur. Ceram. Soc., 35 [5] 1355-1360 (2015)] reported that amorphous SiOC is formed by pyrolysis of polysiloxane. The fumed silica used in the present invention is also composed of an amorphous phase.

Therefore, it was confirmed that the formation of the characteristic phase was not observed in the amorphous curve shown in XRD. However, it was confirmed that the high temperature reaction product of polysiloxane was amorphous and the original borosilicate block was also composed of amorphous element indirectly. This supports the fact that, at high temperatures, the viscous flow causes the coating layer to fill cracks and enable crack healing.

- TGA results

FIG. 7 shows a TGA-DTA graph for a slurry-coated block, a block with no application, and a block with S1 and S2 applied.

(a) shows the TGA results of a single polysiloxane. In the initial stage of 300 ℃, weight loss by cross linking was observed. Then, as the heat treatment progresses, the weight decreases as it is converted to ceramics at 600 ~ 800 ℃. It is considered that this is a layer which can contribute to the prevention of cracking on the surface of the borosilicate block by the SiOC + SiO ₂ amorphous composite layer.

(b) is a graph of the untreated porous borosilicate block. (a), it was found that the TGA weight change was the same within the error range. On the other hand, in the case of the DTA graph, it was confirmed that a strong endothermic peak was generated at 838.53 ° C due to the transition of the vitrification phase after the weak endothermic reaction due to evaporation of free water at about 258.57 ° C. This is the vitrification temperature at which the solid phase borosilicate block undergoes a phase change from the corresponding point to the liquid phase. Since this change is a change due to melting, it can be seen that the block itself is melted in actual fire, and therefore (b) shows the limit of the heat resistance characteristic.

(c) is a graph of the borosilicate block coated with S1. The TGA graph shows an inflection point at which the weight decreases around 170 to 180 ° C, which is attributed to the condensation reaction of functional groups such as moisture and alcohol vapor due to the crosslinking reaction of the polysiloxane [D. W. Kim, " Synthesis of Porous SiC Ceramics from a Polysiloxane, " Korea Maritime and Ocean University, M. S. Thesis, 28-30 (2007)]. In addition, the endothermic reaction of the DTA peak at around 550 ℃ shows that it is the endothermic of Polysiloxance + C -> SiOC + C due to pyrolysis of polysiloxane [YW Kim, DH Jang, JH Eom, HD Kim, " Processing of Polymer-Derived Microcellular Ceramics Containing Reactive Fillers, " Mater. Sci. Forum, 534-536 989-92 (2007)].

On the other hand, in (c), a strong endothermic peak of the borosilicate block as shown in (b) could not be confirmed, which is consistent with the above-mentioned optical microscopic results. Depending on the coating of the polysiloxane, Delayed.

(d) is a TGA-DTA graph of the S2-coated borosilicate block. As in (c), the reaction by the melting of borosilicate could not be confirmed in addition to some endothermic reaction at around 550 ° C. The decrease in TGA around 180 ° C was attributed to the condensation reaction of functional groups in the polysiloxane.

As described above, the polysiloxane-fumed silica composite coating layer formed on the block exhibits a pyrolysis of the polysiloxane when the temperature rises at a temperature of 600 ° C or higher in the event of a fire. Since pyrolysis of the polysiloxane is an endothermic reaction, And the surface temperature of the block is lowered. Ultimately, the polysiloxane is pyrolyzed and converted into an amorphous glass-like SiOC phase, and the composition of the coating layer is changed into the SiOC-SiO ₂ composite layer. Therefore, it was confirmed that when the polysiloxane is applied to the borosilicate block, the melting of the borosilicate block can be prevented more than a certain level, as in the case of the above-mentioned optical microscope and the high-temperature heat treatment. In other words, the polysiloxane layer could contribute to preventing the damage of the surface portion of the borosilicate under the assumption of fire.

In other words, the coated polysiloxane-fumed silica composite coating layer was completely adhered to the surface portion of the borosilicate block without exfoliation, and when the temperature rises during the fire, the pyrolysis of the polysiloxane proceeds when the temperature exceeds 600 ° C., Since pyrolysis is an endothermic reaction, it absorbs heat to lower the surface temperature. Ultimately, the polysiloxane is pyrolyzed and converted into an amorphous glassy SiOC phase, and the composition of the coating layer is changed to a SiOC-SiO ₂ composite layer.

The amorphous glassy SiOC is highly flowable, filling the microcracks generated in the borosilicate block by thermal shock, so it can be given a self-healing function to prevent further cracking.

It can be seen that the polysiloxane-fumed silica slurry according to the present invention can serve as a flame proofing agent for various lower substrates.

Claims (10)

As a coating agent applied to a surface of a base used under a high-temperature environment to reinforce the base heat resistance,
Wherein the coating agent is a slurry dispersed in a powdery polysiloxane and a soluble solvent for polysiloxane, wherein the coating agent is capable of healing and flaming the cracks generated in the heat resistant base. The method according to claim 1,
Wherein the solvent is methanol or ethanol. The coating agent is capable of healing and flame-retarding cracks generated in a heat-resistant base. The method according to claim 1,
Wherein the slurry further contains silica. ≪ RTI ID = 0.0 > 11. < / RTI > The method of claim 3,
Wherein the polysiloxane is contained in an amount of 5 to 30 parts by weight and the silica is contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of the slurry. The method of claim 3,
Wherein the silica is a powdery particle including at least one of fumed silica, nanoquartz and glass bead. The heat-resistant base is capable of healing and flame-retarding cracks liniment. 6. The method of claim 5,
Wherein the fumed silica is in a range of 5 to 200 nm, the nanoquartz is in a range of 10 to 300 nm, and the glass bead is in a range of 100 to 8000 nm. And a flame-retardant coating agent. The method according to claim 1,
Wherein the polysiloxane is contained in an amount of 5 to 35 parts by weight based on 100 parts by weight of the slurry. The method according to claim 1,
Wherein the coating layer applied to the matrix has a thickness of 1 to 2000 占 퐉. The method according to claim 1,
Wherein the substrate is a metal, a non-metal, or an organic material, wherein the heat-resistant base is capable of curing cracks and flame-retarding. The method according to claim 1,
Wherein the slurry has fluidity so as to be applied to a base, and wherein the slurry is capable of healing and flaming the cracks generated in the heat resistant base.

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