KR102025607B1 - Manufacturing method of hydrophobic spherical silver nano silica aerogel granules - Google Patents

Abstract

The present invention relates to a method for preparing hydrophobic spherical silver nano silica aerogel granules. More specifically, the method comprises: a hydrophobic silica sol preparation step for hydrolyzing a hydrophobic silane to prepare a silica sol; a wet gel preparation step for mixing a base, an organic solvent, and a surfactant with the hydrophobic silica sol prepared through the hydrophobic silica sol preparation step, to prepare a hydrophobic silica wet gel; an aerogel polymerization step for mixing a silver precursor and a reducing agent with the hydrophobic silica wet gel prepared through the wet gel preparation step, to polymerize an aerogel; and a drying step for drying the aerogel prepared through the aerogel polymerization step. The method of preparing hydrophobic spherical silver nano silica aerogel granules can easily control the particle size in the range of 0.5 mm to 3 mm through a simple process, and provide hydrophobic spherical silver nano silica aerogel granules that can be used at high temperature of 300°C due to excellent heat resistance.

Description

Method for preparing hydrophobic spherical silver nano silica airgel granules {MANUFACTURING METHOD OF HYDROPHOBIC SPHERICAL SILVER NANO SILICA AEROGEL GRANULES}

The present invention relates to a method for preparing hydrophobic spherical silver nano silica airgel granules, and more particularly, in a simple process, it is easy to control the particle size in the range of 0.5 mm to 3 mm, and can be used even at a high temperature of 300 ° C. due to its excellent heat resistance. A method for producing a hydrophobic spherical silver nano silica airgel granule is provided.

In general, an airgel is a porous body having mesopores having a pore size in the range of 5 to 50 nm and filled with air in a space in which nanostructures are coarsely woven like a nonwoven fabric and occupy 98% of the total volume. Aerogels have a low density of less than 0.1 g / cm 3, a high specific surface area of 700 m 2 / g and a low thermal conductivity of 100 mW / m · k due to the porous structure, resulting in ultra-light insulating materials, catalytic materials, optical and acoustic materials, It has high application potential in the fields of ultra low dielectric materials and high energy physics.

In addition, it is possible to solve the fire vulnerability and the generation of harmful gases during the fire, which is a fatal weakness of the organic insulation.

In general, aerogels are prepared by preparing wet gels from silica precursors such as water glass and TEOS, and removing liquid components inside the wet gels without destroying microstructures. Representative silica airgel forms can be divided into three types: powder, granule, and monolith, and are generally prepared in the form of powder.

In the case of powder, it can be commercialized in the form of airgel blanket or airgel sheet by complexing with fiber, and in the case of blanket or sheet, it is flexible and can be bent or folded to any size or shape. Can cut Accordingly, the present invention can be applied not only to industrial applications such as insulation panels of LNG carriers, industrial insulation and space suits, insulation for transportation and vehicle power production, but also to household goods such as jackets and sneakers. In addition, the use of silica aerogels in fire doors, as well as roofs and foils in houses such as apartments, has a great effect on fire protection.

However, silica airgel powder is scattered due to high porosity, very low tap density, and small particle size, making it difficult to handle, and it is also difficult to fill.

In addition, the monolith has a high transparency in the visible light region, but the size that can be manufactured is limited, it is difficult to mold in a variety of forms, there is a disadvantage that easily broken.

In order to solve the disadvantages of the silica airgel powder and the monolithic form as described above, attempts have been made to increase the ease of handling and shape correspondence by preparing silica airgel oversizes of 0.5 mm or more. For example, a method of preparing a reaction solution obtained by hydrolyzing an alkoxysilane as a filler, followed by gelation by polycondensation reaction with a catalyst, hydrophobization treatment with a hydrophobic agent, and supercritical drying to obtain hydrophobic silica airgel granules; And a method of producing silica airgel granules by supplying airgel particles impregnated with additives, additives, and binders to a molding apparatus and compressing the same.

However, the above methods use additives such as an additional granulation device and a binder, which not only requires technically complicated processes and long processing time but also requires mass production of silica airgel as described above. Complicated processing procedures and high investment costs, as a result, require a lot of time and expensive chemicals, resulting in increased production costs, as well as the resulting particle size of the silica airgel is not uniform or too high. It has a big disadvantage.

In addition, when the silica airgel is used for high temperature, it transmits in the wavelength range of 2 ~ 8㎛, so that the thermal conductivity due to infrared radiation also increases rapidly. In order to lower the radiation thermal conductivity, a method of adding an opaque agent capable of absorbing infrared rays in the wavelength range of 8 μm or less into a silica airgel has been mainly studied. Carbon black, titania powder, iron oxide powder, aluminum oxide powder, etc. Mineral powder is widely known as an effective opacifier, but the use of carbon black as an opacifier has the advantage that it is easy to manufacture. However, it is oxidized at 500 ° C or higher. Therefore, the mineral powder is suitable as an opacifying agent for silica airgel when used as a high temperature insulating material of more than 300 ℃. However, there was a limit to high temperature products due to the increase in porosity and thermal conductivity when the opaque agent is added.

Korean Patent Registration No. 10-0868989 (2008.11.10) Korea Patent Registration No. 10-1717833 (2017.03.13)

An object of the present invention is a hydrophobic spherical silver nano silica airgel granule which provides a hydrophobic spherical silver nano silica airgel granule which can be easily controlled in a range of 0.5mm to 3mm in a simple process and has excellent heat resistance and can be used even at a high temperature of 300 ° C. It is to provide a manufacturing method.

An object of the present invention is to prepare a hydrophobic silica sol by hydrolyzing a hydrophobic silane, a hydrophobic silica wet gel by mixing a base, an organic solvent and a surfactant with a hydrophobic silica sol prepared through the hydrophobic silica sol manufacturing step Wet gel manufacturing step of preparing a, a hydrogel to prepare a hydrogel by mixing a precursor and a reducing agent in a hydrophobic silica wet gel prepared by the wet gel manufacturing step of airgel polymerization step and drying the airgel prepared by the airgel polymerization step It is achieved by providing a method for producing a hydrophobic spherical silver nano silica airgel granules, characterized in that it comprises a step.

According to a preferred feature of the present invention, the hydrophobic silica sol production step is made by mixing 75 to 85 parts by weight of hydrophobic silane and 2 to 2.5 parts by weight of inorganic acid to 100 parts by weight of purified water and hydrolyzed for 60 to 120 minutes.

According to a further preferred feature of the present invention, the hydrophobic silane is made of methyltriethoxysilane or methyltrimethoxysilane.

According to a more preferred feature of the invention, the inorganic acid is to be made of one or more selected from the group consisting of nitric acid, hydrochloric acid, acetic acid, sulfuric acid and hydrofluoric acid.

According to a further preferred feature of the present invention, the wet gel manufacturing step is based on 100 parts by weight of hydrophobic silica sol prepared by the hydrophobic silica sol step 4 to 6 parts by weight of the base, 1500 to 2500 parts by weight of an organic solvent and a surfactant It is assumed that 0.1 to 3 parts by weight are mixed.

According to a further preferred feature of the invention, the base is made of ammonia water.

According to a further preferred feature of the invention, the organic solvent is to be made of one or more selected from the group consisting of hexane, heptane, toluene and xylene.

According to an even more preferred feature of the invention, the surfactant is composed of at least one selected from the group consisting of lanolin, sorbitan monooleate, sorbitan monostearate, sorbitan monopalmitate and sorbitan monolaurate do.

According to a further preferred feature of the present invention, the airgel polymerization step is to be made by mixing 20 to 50 parts by weight of the silver precursor and 2 to 5 parts by weight of the reducing agent to 100 parts by weight of the hydrophobic silica wet gel prepared by the wet gel manufacturing step do.

According to a still further preferred feature of the present invention, the silver precursor is AgNO ₃ , AgBF ₄ , AgPF ₃ , Ag ₂ O, CH ₃ COOAg, AgCF ₃ SO ₃ , AgCl, Ag ₂ SO ₄ and CH ₃ COCH-COCH ₃ Ag It shall consist of one selected from the group which consists of these.

According to a further preferred feature of the invention, the reducing agent is to consist of sodium borohydride or hydrazine.

According to an even more preferred feature of the present invention, the drying step is to be carried out for 50 to 70 minutes at a temperature of 140 to 160 ℃ after 50 to 70 minutes at atmospheric pressure and 65 to 75 ℃ temperature.

The method for preparing hydrophobic spherical silver nano silica airgel granules according to the present invention is a simple process, which is easy to control the particle size in the range of 0.5mm to 3mm, has excellent heat resistance and can be used even at high temperatures of 300 ° C. It gives an excellent effect.

Figure 1 is a flow chart showing a method for producing a hydrophobic spherical silver nano silica airgel granules according to the present invention.
Figure 2 is a photograph taken by a scanning electron microscope (SEM) of the hydrophobic spherical silver nano silica airgel granules prepared in Example 1 of the present invention.

In the following, preferred embodiments of the present invention and the physical properties of each component will be described in detail, which is intended to explain in detail enough to be able to easily carry out the invention by one of ordinary skill in the art, This does not mean that the technical spirit and scope of the present invention is limited.

Generally, silica wet gel prepared by using water glass, tetraethyl orthosilicate, and tetramethyl orthosilicate takes the form of water filled with pupils of the solvent, and when the solvent is simply dried and removed, the liquid solvent vaporizes in gaseous / liquid phase. Due to the high surface tension of water at the interface, pore structure shrinkage and cracking tend to occur, resulting in surface area reduction and pore structure change.

In addition, the silica airgel dried in the above state is condensation reaction with each other due to the hydrophilicity of the silanol group (Si-OH) on the silica surface during the drying process, and secondly absorb the water in the air to collapse the pore structure There is a disadvantage that the thermal conductivity is increased.

Therefore, in order to maintain the pore structure, water needs to be replaced with an organic solvent, and in order to maintain low thermal conductivity, it is necessary to modify the surface of the silica airgel hydrophobicly.

However, at high temperatures, it transmits in the 2 ~ 8 ㎛ wavelength band, so the thermal conductivity due to infrared radiation also rises sharply, reducing the intrinsic thermal insulation effect of silica airgel.

Accordingly, the method for preparing hydrophobic spherical silver nano silica airgel granules according to the present invention is to prepare easy to handle airgel granules having low scattering properties having fine and uniform particle size while maintaining pore structure and low thermal conductivity even at high temperature. Not only hydrophobic silica compound, inorganic acid, organic solvent and gelation proceeded simultaneously, but also surfactant was added to the reaction to form stabilized spherical airgel granules.

In the method for preparing hydrophobic spherical silver nano silica airgel granules according to the present invention, a hydrophobic silica sol manufacturing step (S101) of preparing hydrophobic silica sol to produce a silica sol, and a hydrophobic silica sol prepared through the hydrophobic silica sol manufacturing step (S101) Mixing a base, an organic solvent, and a surfactant to produce a hydrophobic silica wet gel (S103), by mixing a silver precursor and a reducing agent with the hydrophobic silica wet gel prepared through the wet gel manufacturing step (S103). It consists of an airgel polymerization step (S105) for polymerizing airgel and a drying step (S107) for drying the airgel produced through the airgel polymerization step (S105).

The hydrophobic silica sol manufacturing step (S101) is a step of preparing a silica sol by hydrolyzing hydrophobic silane, and mixed 75 to 85 parts by weight of hydrophobic silane and 2 to 2.5 parts by weight of inorganic acid in 100 parts by weight of purified water and 60 to 120 minutes By hydrolysis.

The hydrophobic silane is preferably made of methyl triethoxy silane (METS, Methyltriethoxysilane) or methyl trimethoxy silane (MEMS, Methyltriemethoxysilane).

If the hydrophobic silica sol manufacturing step (S101) does not add purified water and inorganic acid, hydrolysis does not occur and silica sol is not generated. If the content of hydrophobic silane is less than 75 parts by weight with respect to 100 parts by weight of the purified water, the hydrolysis effect is insignificant. When the content of the hydrophobic silane is more than 85 parts by weight based on 100 parts by weight of the purified water, hydrolysis does not proceed properly, making it difficult to control the particle size of the aerogel.

At this time, the inorganic acid is preferably made of one or more selected from the group consisting of nitric acid, hydrochloric acid, acetic acid, sulfuric acid and hydrofluoric acid.

The wet gel manufacturing step (S103) is a step of preparing a hydrophobic silica wet gel by mixing a base, an organic solvent and a surfactant with a hydrophobic silica sol prepared through the hydrophobic silica sol manufacturing step (S101), the hydrophobic silica sol 100 parts by weight of the hydrophobic silica sol prepared through the preparation step (S101) is made by mixing 4 to 6 parts by weight of a base, 1500 to 2500 parts by weight of an organic solvent, and 0.1 to 3 parts by weight of a surfactant.

At this time, the base, the organic solvent and the dispersant may be sequentially added to the hydrophobic silica sol, or may be added simultaneously. Preferably, after adding and mixing a base to the silica sol, the nonpolar organic solvent and the dispersant are sequentially It may be added as.

The mixing may be performed by stirring, the stirring is preferably performed for 10 to 60 minutes at a speed of 400 to 800 rpm, but is not limited thereto.

In addition, the surfactant stabilizes the hydrophobic silica sol in the organic solvent to form a wet gel having a uniform size as well as to control the size of the wet gel. More specifically, the surfactant (surfactant) ) Is usually divided into 'head' part having polarity (hydrophilic) and 'tall' part having nonpolarity (hydrophobic), so that it is possible to form micelles (micelles) or reverse micelles, ie, spherical particles depending on the solvent. Play a role.

For example, when added in a polar solvent (hydrophilic), each molecule of the surfactant in the solvent gathers together to form a micelle by trying to contact the polar head with the solvent and the non-polar tail with the solvent. It will be.

By the characteristics of the surfactant as described above, the hydrophobic silica wet gel according to an embodiment of the present invention is in the non-polar organic solvent is mixed with the hydrophobic silica sol and a base material to form in the form of a reverse micelle to form a micelle Can be. At this time, the hydrophobic silica sol and the base material may be in the form of coexistence without reacting, as mentioned above.

In addition, the surfactant may form a hydrophobic wet gel of uniform size in the nonpolar solvent, stabilize the hydrophobic wet gel, and adjust the size of the wet gel generated according to the amount of the surfactant added. For example, as the amount of the surfactant added increases, the size of the hydrophobic wet gel produced may decrease.

When the amount of the surfactant is less than 0.1 part by weight, the amount of the surfactant may be too small to form a hydrophobic wet gel having a uniform size. On the other hand, when the amount of the surfactant is added in excess of 3 parts by weight. Excessive addition of surfactant may cause cohesion between the wet gels.

At this time, the surfactant is a nonionic surfactant and is not particularly limited and can be used in any one, but consisting of lanolin, sorbitan monooleate, sorbitan monostearate, sorbitan monopalmitate and sorbitan monolaurate It is preferably made of one or more selected from the group.

In addition, the base is preferably made of ammonia water, the solvent is preferably nonpolar, more preferably at least one selected from the group consisting of hexane, heptane, toluene and xylene.

The airgel polymerization step (S105) is a step of polymerizing an airgel by mixing a silver precursor and a reducing agent with a hydrophobic silica wet gel prepared through the wet gel manufacturing step (S103), the wet gel manufacturing step (S103) 20 to 50 parts by weight of the silver precursor and 2 to 5 parts by weight of the reducing agent are mixed with 100 parts by weight of the hydrophobic silica wet gel.

If the content of the silver precursor is less than 20 parts by weight, the performance of the airgel at high temperature may be lowered. If the content of the silver precursor exceeds 50 parts by weight, the airgel pores are lowered to increase the thermal conductivity and increase the manufacturing cost. .

In addition, when the content of the reducing agent is less than 2 parts by weight, the efficiency of the process of converting the silver precursor into silver nano is reduced, and when the content of the reducing agent exceeds 5 parts by weight, the amount of silver precursor is converted to all the silver remaining It is not preferred to add.

In this case, the silver precursor is preferably made of one selected from the group consisting of AgNO ₃ , AgBF ₄ , AgPF3, Ag ₂ O, CH ₃ COOAg, AgCF ₃ SO ₃ , AgCl, Ag ₂ SO ₄ and CH ₃ COCH-COCH ₃ Ag The reducing agent is preferably made of sodium borohydride or hydrazine.

The drying step (S107) is a step of drying the airgel produced through the airgel polymerization step (S105), after 50 to 70 minutes at atmospheric pressure and 65 to 75 ℃ temperature, at a temperature of 140 to 160 ℃ It is preferably made for 50 to 70 minutes.

The drying step (S107) may be made for 1 to 4 hours at a temperature of 20 to 190 ℃ under atmospheric pressure, as described above dried for 50 to 70 minutes at a temperature of 65 to 75 ℃ and 50 at a temperature of 140 to 160 ℃ Further drying for about 70 minutes may prevent cracking or cracking that may occur during drying.

In the wet gel manufacturing step (S103), since the silica structure contracts while being volatilized at a rapid speed for a short time, internal cracks may be generated or cracked and broken. Can be prevented.

Hereinafter, the physical properties of the hydrophobic spherical silver nano silica airgel granules prepared according to the present invention and the hydrophobic spherical silver nano silica airgel granules prepared through the preparation method will be described with reference to Examples.

<Example 1>

14.4 g of water and 0.004 g of hydrochloric acid were added to 17.8 g of MTES (methyltriethoxysilane; Sigma-Aldrich) to hydrolyze for 1.5 hours to prepare a silica sol, and 20 ml of the prepared silica sol was used as a drop size using a burette in hexane as an organic solvent. It was dropped in 400 ml, and a hydrophobic wet gel having a particle size of 3 to 4 mm was added to the hexane by adding a surfactant (Lanolin 0.4g) and 1 ml of ammonia water having a mass concentration of 28%, and then stirring the mixture at 700 rpm for 3 minutes. And hydrophobic silica airgel was prepared by injecting 0.16 g of AgNO ₃ and 0.016 g of sodium borohydride in a drop size while stirring the prepared hydrophobic wet gel for 20 minutes at a speed of 100 rpm or less, and preparing the hydrophobic silica airgel. And hydrophobic spherical silver nano silica airgel granules were prepared by drying at 70 ° C. for 1 hour under atmospheric pressure and further drying at 150 ° C. for 1 hour. Was done.

<Example 2>

Proceed in the same manner as in Example 1, using a surfactant (Lanolin 0.1g) to prepare a hydrophobic spherical silver nano silica airgel granules.

<Example 3>

Proceed in the same manner as in Example 1, using a surfactant (Lanolin 0.2g) to prepare a hydrophobic spherical silver nano silica airgel granules.

<Example 4>

Proceed in the same manner as in Example 1, using a surfactant (Lanolin 0.3g) to prepare a hydrophobic spherical silver nano silica airgel granules.

Example 5

Proceed in the same manner as in Example 1, using a surfactant (Lanolin 0.5g) to prepare a hydrophobic spherical silver nano silica airgel granules.

Comparative Example 1

Proceed in the same manner as in Example 1, to prepare a hydrophobic spherical silver nano silica airgel granules without using a surfactant.

Hydrophobic spherical silver nano silica airgel granules prepared in Example 1 were photographed with a scanning electron microscope (SEM) and are shown in FIG. 2 below.

As shown in FIG. 2 below, the hydrophobic spherical silver nano silica airgel granules prepared in Example 1 can be seen that the silver nanoparticles are well formed in the hydrophobic silica airgel.

In addition, the average particle size, pore size, thermal conductivity and the presence of hydrophobicity of the hydrophobic spherical silver nano silica airgel granules prepared through Examples 1 to 5 and Comparative Example 1 were measured and shown in Table 1 below.

{However, the pore size was confirmed by the BET measuring instrument (ASAP2010), the average pore size and pore volume were measured by the BHJ method, and the thermal conductivity was measured by the Heat Flow Meter (Netsch, HFM-436 / 3/1 Lambdal) method. Hydrophobicity was measured by an infrared spectroscopy (IR) analyzer.}

TABLE 1

As shown in Table 1, when 0.4 g of a surfactant (Lanolin) was added to 20 ml of silica sol as in Example 1 of the present invention, the hydrophobic spherical silver nano silica airgel granules had a particle size of 2 to 3 mm, The pore size is 20.5 nm, the thermal conductivity is 0.018 W / mk, it can be seen that the hydrophobicity is very excellent.

In addition, when 0.3 g of a surfactant (Lanolin) is added to 20 ml of hydrophobic silica sol as in Example 4 of the present invention, the pore size was decreased and thermal conductivity was slightly increased, but it was similar to that of the aerogel prepared in Example 1. It can be seen that the physical properties of the level are maintained.

However, when the surfactant (Lanolin) is added to less than 0.3g compared to 20ml of hydrophobic silica sol as in Examples 2 to 3 of the present invention, it can be seen that the pore size is reduced, and the thermal conductivity is significantly increased.

In addition, when the content of the surfactant (Lanolin) to more than 0.4g compared to 20ml of hydrophobic silica sol as in Example 5 of the present invention, the pore size and thermal conductivity was found to be the same level as in Example 1, hydrophobic silica sol It can be seen that the optimal content of the surfactant (Lanolin) compared to 20ml is 0.4g.

Accordingly, the method for preparing hydrophobic spherical silver nano silica airgel granules according to the present invention is a simple process, which is easy to control the particle size in the range of 0.5 mm to 3 mm, and has excellent heat resistance and can be used even at high temperatures of 300 ° C. Airgel granules can be provided.

S101; Hydrophobic silica sol manufacturing step
S103; Wet Gel Manufacturing Step
S105; Airgel polymerization step
S107; Drying stage

Claims (12)

Hydrophobic silica sol manufacturing step of hydrolyzing hydrophobic silane to prepare a silica sol;
A wet gel manufacturing step of preparing a hydrophobic silica wet gel by mixing a base, an organic solvent, and a surfactant with a hydrophobic silica sol prepared through the hydrophobic silica sol preparation step;
An airgel polymerization step of polymerizing an airgel by mixing a silver precursor and a reducing agent with the hydrophobic silica wet gel prepared through the wet gel manufacturing step; And
Consists of a drying step of drying the airgel produced through the airgel polymerization step,
The hydrophobic silica sol manufacturing step is made by mixing 75 to 85 parts by weight of hydrophobic silane and 2 to 2.5 parts by weight of inorganic acid to 100 parts by weight of purified water and hydrolyzed for 60 to 120 minutes,
The hydrophobic silane consists of methyltriethoxysilane,
The inorganic acid is a method for producing a hydrophobic spherical silver nano silica airgel granules, characterized in that made of one or more selected from the group consisting of nitric acid, acetic acid, sulfuric acid and hydrofluoric acid.
delete delete delete The method according to claim 1,
The wet gel production step is a mixture of 4 to 6 parts by weight of the base, 1500 to 2500 parts by weight of the organic solvent and 0.1 to 3 parts by weight of the surfactant to 100 parts by weight of the hydrophobic silica sol prepared by the hydrophobic silica sol manufacturing step. A method for producing hydrophobic spherical silver nano silica airgel granules.
The method according to claim 1 or 5,
The base is a method for producing a hydrophobic spherical silver nano silica airgel granules, characterized in that consisting of ammonia water.
The method according to claim 1 or 5,
The organic solvent is a method for producing a hydrophobic spherical silver nano silica airgel granules, characterized in that consisting of one or more selected from the group consisting of hexane, heptane, toluene and xylene.
The method according to claim 1 or 5,
The surfactant is a hydrophobic spherical silver nano silica airgel granules, characterized in that consisting of at least one selected from the group consisting of lanolin, sorbitan monooleate, sorbitan monostearate, sorbitan monopalmitate and sorbitan monolaurate. Manufacturing method.
The method according to claim 1,
The aerogel polymerization step of the hydrophobic spherical silver nano silica airgel granules, characterized in that by mixing 20 to 50 parts by weight of the silver precursor and 2 to 5 parts by weight of the reducing agent to 100 parts by weight of the hydrophobic silica wet gel prepared by the wet gel manufacturing step Manufacturing method.
The method according to claim 1 or 9,
The silver precursor is composed of one selected from the group consisting of AgNO ₃ , AgBF ₄ , AgPF ₃ , Ag ₂ O, CH ₃ COOAg, AgCF ₃ SO ₃ , AgCl, Ag ₂ SO ₄ and CH ₃ COCH-COCH ₃ Ag Method for producing hydrophobic spherical silver nano silica airgel granules.
The method according to claim 1 or 9,
The reducing agent is a method for producing a hydrophobic spherical silver nano silica airgel granules, characterized in that consisting of sodium borohydride or hydrazine.
The method according to claim 1,
The drying step is a hydrophobic spherical silver nano silica airgel granules manufacturing method characterized in that after the 50 to 70 minutes at a temperature of 65 to 75 ℃ temperature and conditions of atmospheric pressure, it is made for 50 to 70 minutes.

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