Method for producing prehydrolyzed polysilicates

Abstract

The present invention relates to a method for preparing a prehydrolyzed polysilicate, in which polysilicate is used as a reactant in the synthesis of the prehydrolyzed polysilicate, and the polysilicate is hydrated in the presence of an alcohol-based compound produced by hydration of a compound represented by Chemical Formula 1 without the addition of a separate alcohol-based solvent.

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0074291 filed on June 8, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a method for producing a prehydrolyzed polysilicate that does not require a separate reaction solvent during the reaction. [Background technology]

[0003] Aerogel is a super-porous, high-specific surface area (≧500m2) material with a porosity of 90-99.9% and pore sizes in the range of 1-100 nm. 2 / g) and has excellent properties such as being ultra-lightweight, ultra-insulating, and ultra-low dielectric. Therefore, in addition to research and development of aerogel materials, research into its applications as environmentally friendly high-temperature insulating materials, extremely low dielectric thin films for highly integrated devices, catalysts and catalyst carriers, electrodes for supercapacitors, and electrode materials for seawater desalination is also being actively conducted.

[0004] The biggest advantage of aerogel is that it has super-insulation properties, exhibiting a thermal conductivity of less than 0.300 W / m K, which is lower than that of conventional organic insulation materials such as polystyrene, and that it can solve the fatal weaknesses of organic insulation materials, namely, vulnerability to fire and the generation of harmful gases during fire.

[0005] Aerogel is usually produced by producing a wet gel from silica precursors such as water glass and alkoxysilane series (TEOS, TMOS, MTMS, etc.), and then removing the liquid components inside the wet gel without destroying the microstructure. Representative silica aerogel forms are classified into three types: powder, granule, and monolith, and are generally produced in powder form.

[0006] In particular, among the silica precursors, tetraethyl orthosilicate (TEOS) is a material that is widely used in industrial fields such as coating agents, insulating agents, and the manufacture of porous ceramics, and various products such as pure TEOS, condensed TEOS, and prehydrolyzed TEOS (HTEOS) are available on the market.

[0007] Among them, HTEOS is an ethyl polysilicate oligomer material with a wide molecular weight distribution. When it is synthesized in the form of an oligomer from a TEOS monomer, the physical properties such as gelation time can be adjusted, so it can be easily applied according to the user's reaction conditions. In addition, it has the advantage of producing reproducible physical properties of the final product.

[0008] The HTEOS is generally synthesized by performing partial hydration and condensation reactions on an alkoxysilane monomer compound such as TEOS under acidic conditions. In this case, the condensation reaction proceeds by refluxing under acidic conditions, and since the condensation rate is very slow, the condensation reaction must be performed for a long period of time to achieve a desired level of condensation, which results in high energy costs and reduced process efficiency, and the raw material cost of the alkoxysilane monomer compound such as TEOS used as a reactant is high, which increases the production cost. On the other hand, a condensation catalyst may be used to increase the condensation rate, but in this case, it is difficult to control the molecular weight of the reaction product, and since a catalyst purchase cost is incurred and a catalyst separation process must be added in the synthesis stage, the process becomes more complicated and the production cost increases.

[0009] Therefore, a method for synthesizing prehydrolyzed polysilicate has been proposed that uses polysilicate as a reactant instead of an alkoxysilane monomer compound such as TEOS, which can omit the condensation reaction compared to the existing manufacturing method using TEOS, and therefore has a simple process and can significantly reduce manufacturing costs.

[0010] In the method using polysilicate as the reactant, a method was used in which polysilicate was reacted with an acidic aqueous solution using ethanol as a solvent. The use of an amphiphilic (amphiphilic) solvent such as ethanol is essential because phase separation occurs when an acidic aqueous solution is added to polysilicate.

[0011] Such reactions are carried out by using an amphiphilic solvent such as ethanol to react the polysilicate with water, so that the final product is obtained in the form of a hydrated polysilicate diluted in ethanol. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Special Publication No. 2014-501320 [Patent Document 2] Korean Patent Publication No. 2020-0062506 Summary of the Invention [Problem to be solved by the invention]

[0013] The problem to be solved by the present invention is to provide a method for producing a prehydrolyzed polysilicate by using polysilicate as a reactant for synthesizing the prehydrolyzed polysilicate and not requiring a separate reaction solvent during the reaction. [Means for solving the problem]

[0014] In order to solve the above problems, the present invention provides a method for producing a prehydrolyzed polysilicate. (1) The present invention provides a method for preparing a prehydrolyzed polysilicate, the method including: introducing polysilicate and a compound represented by the following Chemical Formula 1 into a reactor (Step 1); further introducing an acidic aqueous solution into the reactor to prepare a reaction mixture (Step 2); and stirring the reaction mixture to carry out a hydration reaction (Step 3).

[0015] [ka]

[0016] R1 is alkyl having 1 to 20 carbon atoms, cycloalkyl having 3 to 20 carbon atoms, or vinyl having 1 to 20 carbon atoms, and each R2 is independently alkyl having 1 to 20 carbon atoms.

[0017] (2) The present invention provides a method for producing a prehydrolyzed polysilicate in the above (1), in which the compound represented by Chemical Formula 1 is hydrated to form an alcohol compound represented by Chemical Formula 2 and a silanol compound represented by Chemical Formula 3:

[0018] [ka]

[0019] [ka]

[0020] R1 is alkyl having 1 to 20 carbon atoms, cycloalkyl having 3 to 20 carbon atoms, or vinyl having 1 to 20 carbon atoms, and R2 is alkyl having 1 to 20 carbon atoms.

[0021] (3) The present invention provides a method for producing a prehydrolyzed polysilicate according to the above (1) or (2), wherein the hydration of the polysilicate in step 3 is carried out in the presence of an alcohol compound represented by Chemical Formula 2 formed by hydration of a compound represented by Chemical Formula 1:

[0022] [ka]

[0023] R2 is an alkyl group having 1 to 20 carbon atoms.

[0024] (4) The present invention provides a method for producing a prehydrolyzed polysilicate according to any one of the above (1) to (3), wherein R1 and R2 are each independently an alkyl group having 1 to 6 carbon atoms.

[0025] (5) The present invention provides a method for producing a prehydrolyzed polysilicate according to any one of (1) to (4), wherein the compound of Chemical Formula 1 is an alkyltrialkoxysilane.

[0026] (6) The present invention provides a method for producing a prehydrolyzed polysilicate according to any one of (1) to (5), wherein the polysilicate and the compound of Chemical Formula 1 have a Si molar ratio of 6:1 to 15:1.

[0027] (7) The present invention provides the method for producing a prehydrolyzed polysilicate according to any one of the above (1) to (6), wherein the acidic aqueous solution contains 0.005 to 0.20 parts by weight of an acid catalyst relative to 100 parts by weight of the polysilicate.

[0028] (8) The present invention provides a method for producing a prehydrolyzed polysilicate according to any one of the above (1) to (7), wherein the polysilicate has an average degree of polymerization of 3 to 30.

[0029] (9) The present invention provides the method for producing a prehydrolyzed polysilicate according to any one of (1) to (8), wherein step 3 is carried out at 15 to 25° C. for 30 minutes to 2 hours.

[0030] (10) The present invention provides a method for producing a prehydrolyzed polysilicate according to any one of (1) to (9), wherein no additional alcohol-based solvent is added to the reactor other than the polysilicate and the compound of Chemical Formula 1.

[0031] (11) The present invention provides a method for producing a prehydrolyzed polysilicate according to any one of the above (1) to (10), wherein the polysilicate includes one or more selected from the group consisting of methyl polysilicate, ethyl polysilicate, propyl polysilicate, isopropyl polysilicate, butyl polysilicate, secondary butyl polysilicate, tertiary butyl polysilicate, hexyl polysilicate, cyclohexyl polysilicate, and dodecyl polysilicate.

[0032] (12) The present invention provides a method for producing a prehydrolyzed polysilicate according to any one of (1) to (11), wherein the compound of Chemical Formula 1 includes at least one selected from the group consisting of alkyltriethoxysilane and alkyltrimethoxysilane.

[0033] (13) The present invention provides a method for producing a prehydrolyzed polysilicate according to any one of (1) to (12), wherein the compound of Chemical Formula 1 is methyltriethoxysilane.

[0034] (14) The present invention provides a method for producing a prehydrolyzed polysilicate according to any one of (1) to (13), wherein the compound of Chemical Formula 1 is alkyltriethoxysilane, the alkyltriethoxysilane is hydrated to form alkylsilanol and ethanol, and the hydration of the polysilicate in step 3 is carried out in the presence of the ethanol formed by hydration of the alkyltriethoxysilane. Effect of the Invention

[0035] The method for producing prehydrolyzed polysilicate according to the present invention uses polysilicate as a reactant for synthesizing prehydrolyzed polysilicate, and therefore, unlike a production method using an alkoxysilane-based monomer compound as a reactant, a condensation reaction can be omitted, so that the synthesis time can be significantly shortened. Also, since a separate reaction solvent is not required during the reaction, it can be usefully used when the reaction must be carried out under conditions where the use of a solvent is not desired or when a high-concentration prehydrolyzed polysilicate is to be obtained. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] The present invention will be described in more detail below to facilitate understanding of the present invention. In this regard, the terms and words used in the specification and claims should not be interpreted as being limited to their ordinary and dictionary meanings, but should be interpreted as having meanings and concepts that are consistent with the technical ideas of the present invention, in accordance with the principle that the inventors themselves may appropriately define the concepts of terms in order to best describe the invention.

[0037] A method for preparing a prehydrolyzed polysilicate according to an embodiment of the present invention includes the steps of: introducing polysilicate and a compound represented by the following Formula 1 into a reactor (Step 1); further introducing an acidic aqueous solution into the reactor to prepare a reaction mixture (Step 2); and stirring the reaction mixture to perform a hydration reaction (Step 3).

[0038] [ka]

[0039] R1 is alkyl having 1 to 20 carbon atoms, cycloalkyl having 3 to 20 carbon atoms, or vinyl having 1 to 20 carbon atoms, and each R2 is independently alkyl having 1 to 20 carbon atoms.

[0040] In general, when a monomer compound such as prehydrolyzed TEOS is used as a silica precursor for manufacturing silica aerogel or silica aerogel blanket, it is difficult to control the molecular weight or gelation reaction time of the final product, and the stability is reduced, so a prehydrolyzed polysilicate oligomer having a molecular weight of about 1000 is prepared and used. This is because, when an oligomer-type substance is used, unlike a monomer such as TEOS, stability can be ensured even when the degree of hydration is increased to control the gelation reaction time. However, in the conventional process for synthesizing the prehydrolyzed polysilicate, an alkoxysilane monomer compound such as TEOS monomer was used as a reactant, so a condensation reaction after partial hydration was necessarily involved. In this case, the condensation reaction proceeds by reflux reaction under acidic conditions, and since the condensation rate is very slow, in order to achieve a desired level of condensation, the condensation reaction must be carried out for a long period of time, which results in high energy costs and reduced process efficiency, and the cost of raw materials for alkoxysilane monomer compounds such as TEOS used as reactants is high, which results in an increase in production cost. On the other hand, a condensation catalyst may be used to increase the condensation rate, but in this case, it is difficult to control the molecular weight of the reaction product, and since a catalyst purchase cost is incurred and a catalyst separation process must be added in the synthesis stage, the process becomes more complicated and the production cost increases.

[0041] However, the method for producing the prehydrolyzed polysilicate of the present invention does not use an alkoxysilane monomer compound such as TEOS as a reactant, but uses polysilicate and includes only a step of partial hydration, and omits a condensation reaction, thereby improving the efficiency of the synthesis process, and the raw material unit price is relatively inexpensive, so that an economic effect can be obtained in terms of the production unit price, and a prehydrolyzed polysilicate with excellent storage stability can be synthesized by using a method in which the gelation reaction time and the weight average molecular weight can be easily controlled by adjusting the content and pH of the acid catalyst. In addition, the method for producing the prehydrolyzed polysilicate of the present invention does not require a separate reaction solvent during the reaction, so it can be usefully used when the reaction must be carried out under conditions where the use of a solvent is not desired or when a high-concentration prehydrolyzed polysilicate is to be obtained.

[0042] Hereinafter, each step of the method for producing a prehydrolyzed polysilicate according to one embodiment of the present invention will be described in detail.

[0043] Stage 1) Step 1) of the present invention is a step of feeding reactants, polysilicate and the compound represented by Chemical Formula 1, into a reactor.

[0044] [ka]

[0045] R1 is alkyl having 1 to 20 carbon atoms, cycloalkyl having 3 to 20 carbon atoms, or vinyl having 1 to 20 carbon atoms, and each R2 is independently alkyl having 1 to 20 carbon atoms.

[0046] In one example of the present invention, specifically, R1 may be alkyl having 1 to 12 carbon atoms, cycloalkyl having 3 to 12 carbon atoms, or vinyl having 1 to 12 carbon atoms, more specifically, alkyl having 1 to 6 carbon atoms, or alkyl having 1 to 4 carbon atoms, and specifically, R2 may each independently be alkyl having 1 to 12 carbon atoms, more specifically, alkyl having 1 to 6 carbon atoms, or alkyl having 1 to 5 carbon atoms.

[0047] In one example of the present invention, the R1 may be alkyl having 1 to 4 carbon atoms, and the R2 may be ethyl.

[0048] By using polysilicate as a reactant, the present invention can omit the condensation reaction in the prehydrolyzed polysilicate synthesis process, and can show a better silica production yield per unit content than when an alkoxysilane-based monomer compound is used as a reactant.

[0049] The polysilicate according to an embodiment of the present invention may have a silica (SiO2) production yield of 30% by weight or more, specifically, 30 to 45% by weight. Here, the silica (SiO2) production yield is a value that indicates the content of silica that can be produced from 100% by weight of polysilicate as a percentage, and the higher the silica production yield of a material, the more silica can be produced with the same content. If the silica production yield is high, a relatively small amount of raw material can be used to obtain a silica precursor containing a desired level of silica content, which has the effect of reducing the raw material cost.

[0050] The polysilicate usable in the present invention is not limited as long as it is a polysilicate that can form a prehydrolyzed polysilicate that can be used as a silica precursor for silica aerogel or aerogel blanket by partial hydration reaction. Specifically, an alkyl polysilicate may be used, and more specifically, it may include one or more selected from the group consisting of methyl polysilicate, ethyl polysilicate, propyl polysilicate, isopropyl polysilicate, butyl polysilicate, secondary butyl polysilicate, tertiary butyl polysilicate, hexyl polysilicate, cyclohexyl polysilicate, and dodecyl polysilicate.

[0051] According to one embodiment of the present invention, the polysilicate may have an average degree of polymerization of 3 to 30, specifically 5 to 15, more specifically 5 to 12, and specifically the polysilicate may be an oligomer having the above degree of polymerization. When the polysilicate satisfies the above average degree of polymerization, storage stability and fluidity are ensured, and ease of use is excellent. In this case, the average degree of polymerization was measured using GPC (Gel Permeation Chromatography, Waters 2489 UV-vis Detector).

[0052] The compound of Formula 1 can be hydrated with water from an acidic aqueous solution introduced into the reactor in step 2) described below to form an alcohol compound represented by Formula 2 and a silanol compound represented by Formula 3 below, and the alcohol compound represented by Formula 2 acts as an amphiphilic solvent used for hydration of polysilicate in step 3 described below.

[0053] [ka]

[0054] [ka]

[0055] R1 is alkyl having 1 to 6 carbon atoms, cycloalkyl having 3 to 6 carbon atoms, or vinyl having 1 to 6 carbon atoms, and R2 is alkyl having 1 to 6 carbon atoms. Specific examples of R1 and R2 are as defined in Chemical Formula 1.

[0056] According to one embodiment of the present invention, the amount of the compound of Chemical Formula 1 in step 1) may be changed, and the amount of the compound of Chemical Formula 1 may be determined depending on the amount of alcohol solvent required for the reaction and the content of silica (SiO2) contained in the final prehydrolyzed polysilicate.

[0057] The polysilicate and the compound of Chemical Formula 1 may have a Si molar ratio of 5:1 to 15:1, and may be used at a molar ratio of 6:1 to 15:1, taking into consideration the concentration of the hydrated polysilicate obtained as the final product and the content of silica (SiO2) contained in the prehydrolyzed polysilicate finally produced. In addition, the polysilicate and the compound of Chemical Formula 1 may have a Si molar ratio of 7:1 to 14:1, 8:1 to 13:1, and more specifically, 8:1 to 12:1. The Si molar ratio refers to the ratio of the number of moles of Si contained in the polysilicate to the number of moles of Si contained in the compound of Chemical Formula 1. If the Si content of the compound of Formula 1 is too low relative to the Si content of the polysilicate, the amount of alcohol formed by hydration of the compound of Formula 1 is small, so the amount of alcohol may be insufficient for proper hydration of the polysilicate, and if the Si content of the compound of Formula 1 is too high relative to the Si content of the polysilicate, the amount of alcohol formed by hydration of the compound of Formula 1 is too high, so the concentration of the hydrated polysilicate obtained as the final product may be low. In addition, when the polysilicate and the compound of Formula 1 satisfy the above-mentioned Si molar ratio range, the hydration degree of the synthesized prehydrolyzed polysilicate may have an appropriate range.

[0058] The alcohol compound of Chemical Formula 1 produced is not limited to a specific type as long as it is an alcohol known to be usable in producing a prehydrolyzed polysilicate, and may be, specifically, an alcohol having 1 to 20 carbon atoms, more specifically, an alcohol having 1 to 12 carbon atoms, an alcohol having 1 to 6 carbon atoms, or an alcohol having 1 to 5 carbon atoms.

[0059] Stage 2) Step 2) according to one embodiment of the present invention is a step of preparing a reaction mixture for partial hydration, in which an acidic aqueous solution is further added to a reactor containing the reactants and stirred to prepare a reaction mixture.

[0060] In addition, the reaction mixture prepared in step 2) may contain 2 to 42 parts by weight, specifically 3 to 30 parts by weight, and more specifically 3 to 20 parts by weight of water, based on 100 parts by weight of polysilicate.

[0061] Here, the acidic aqueous solution is a mixture containing an acid catalyst and water, and the water contained in the acidic aqueous solution preferentially hydrates the compound of Formula 1 introduced in step 1 to form an alcohol compound represented by Formula 2 and a silanol compound represented by Formula 3 as described above, and the formed alcohol compound represented by Formula 2 serves as an amphiphilic solvent to further hydrate the polysilicate.

[0062] The amount of water and acid catalyst contained in the acidic aqueous solution and the pH of the acidic aqueous solution can be adjusted to control the degree of hydration of the polysilicate, and the gelation time and pH of the final prehydrolyzed polysilicate can be adjusted by controlling the degree of hydration of the polysilicate.

[0063] The acidic aqueous solution may contain 0.005 to 0.200 parts by weight of the acid catalyst relative to 100 parts by weight of the polysilicate reactant, specifically 0.008 to 0.100 parts by weight, more specifically 0.010 to 0.090 parts by weight of the acid catalyst.

[0064] In the present invention, the acid catalyst content contained in the acidic aqueous solution is the same as the acid catalyst content in the entire reaction mixture. By satisfying the acid catalyst content, the hydration rate during the hydration reaction described below can be improved, thereby further improving the efficiency of the hydration reaction, and therefore the gelling reactivity of the synthesized prehydrolyzed polysilicate can be improved, and the polycondensation reaction of the prehydrolyzed polysilicate itself can be suppressed to ensure excellent storage stability, and the problem of corrosiveness due to an excessive amount of acid catalyst can be prevented.

[0065] The acid catalyst according to one example of the present invention is not particularly limited and may be, for example, one or more selected from the group consisting of hydrochloric acid, nitric acid, acetic acid, sulfuric acid, and hydrofluoric acid, and may be preferably hydrochloric acid.

[0066] In addition, the acidic aqueous solution according to one embodiment of the present invention may be an acidic aqueous solution having a pH of 0.5 to 2.5, from the viewpoint of synthesizing a prehydrolyzed polysilicate having an optimal hydration degree and gelation reactivity, and the pH range can be 1.0 to 2.5, and a prehydrolyzed polysilicate having an optimal pH and gelation time can be produced.

[0067] In addition, the reaction mixture prepared in step 2) may contain 2 to 42 parts by weight, specifically 3 to 30 parts by weight, more specifically 3 to 20 parts by weight of water, based on 100 parts by weight of the polysilicate. If the amount of water is too small, the water is contained in a very small amount relative to the amount of polysilicate, so that the desired degree of hydration cannot be achieved during the hydration reaction, and when the prehydrolyzed polysilicate with a low degree of hydration is used as a silica precursor in an aerogel manufacturing process, the proportion of hydroxyl groups (-OH) that induce gelation is low, so that the gelation reaction may not proceed smoothly. In addition, if the amount of water is too large, the degree of hydration of the final prehydrolyzed polysilicate becomes very high, and most of the alkoxy functional groups of the silica precursor are replaced with hydroxyl groups, so that gelation reaction may occur during storage and preservation, and the viscosity may easily increase, which may reduce storage stability and processability.

[0068] In addition, in step 2), the content of water and acid catalyst in the reaction mixture and the pH of the acidic aqueous solution can be adjusted to control the degree of hydration, so that undesired gelation reaction does not occur during storage and preservation, thereby ensuring excellent storage stability. The gelation time of the prehydrolyzed polysilicate can also be adjusted according to the above variables, so that when a gelation reaction is induced, a desired gelation time can be achieved.

[0069] Stage 3) Step 3) according to one embodiment of the present invention is a step of stirring the prepared reaction mixture to carry out a hydration reaction to form a prehydrolyzed polysilicate in a partially hydrated state.

[0070] Specifically, in step 3) of the present invention, the hydration reaction can be carried out by stirring the reaction mixture. The hydration of the polysilicate in step 3) is carried out in the presence of the alcohol compound represented by Chemical Formula 2 formed by hydration of the compound represented by Chemical Formula 1 as described above, and therefore, in step 3) according to one example of the present invention, hydration with the compound represented by Chemical Formula 1 is preferentially carried out in the presence of the acid catalyst of the acid aqueous solution.

[0071] [ka]

[0072] When only the acidic aqueous solution is added to the polysilicate, phase separation occurs between the polysilicate and the acidic aqueous solution, and there is no reactivity between them. In order for the reaction to occur between the polysilicate and the acidic aqueous solution, the presence of an amphiphilic solvent such as alcohol is essential. The amphiphilic solvent such as alcohol remains in the final product, so that the final product, the prehydrolyzed polysilicate, is obtained in a form diluted in the amphiphilic solvent.

[0073] In step 3) according to an embodiment of the present invention, the reaction mixture is stirred to preferentially hydrate the compound of Chemical Formula 1, thereby forming an alcohol compound represented by Chemical Formula 2, which acts as an amphiphilic solvent between the polysilicate and the aqueous acid solution to hydrate the polysilicate. In addition, for example, as shown in the following reaction formula 2, the hydration of the polysilicate can be more easily promoted by the alcohol generated by the hydration of the polysilicate. Therefore, the present invention does not require the introduction of a separate amphiphilic solvent, for example, an alcohol-based solvent, for the hydration of the polysilicate, other than the compound of Chemical Formula 1. Therefore, the present invention does not require a separate alcohol-based solvent for the hydration of the polysilicate, and thus a high-concentration prehydrolyzed polysilicate can be obtained as a final product.

[0074] [ka]

[0075] In one embodiment of the present invention, the compound of Chemical Formula 1 may include at least one selected from the group consisting of alkyltriethoxysilane and alkyltrimethoxysilane, specifically alkyltriethoxysilane, and more specifically, the compound of Chemical Formula 1 may be methyltriethoxysilane.

[0076] In one embodiment of the present invention, when the compound of Formula 1 is alkyltriethoxysilane, the alkyltriethoxysilane is hydrated with the aqueous acid solution introduced in step 2 to form alkylsilanol and ethanol, and the hydration of the polysilicate in step 3 may be performed in the presence of the ethanol formed by hydration of the alkyltriethoxysilane.

[0077] In step 3) according to one embodiment of the present invention, partial hydration can be carried out by stirring at room temperature, specifically at 15 to 25° C., for 30 minutes to 2 hours. The present invention uses polysilicate as a reactant, and can synthesize prehydrolyzed polysilicate only by carrying out the hydration reaction in step 3). Since the present invention does not require a condensation reaction, which is essential when synthesizing prehydrolyzed polysilicate using a conventional alkoxysilane monomer compound as a reactant, the synthesis process is simple and requires relatively low energy costs.

[0078] The present invention provides a prehydrolyzed polysilicate that is synthesized by the above-mentioned method and has excellent viscosity characteristics, storage stability, and processability. The prehydrolyzed polysilicate may be a prehydrolyzed alkyl polysilicate, and more preferably, a prehydrolyzed ethyl polysilicate (HTEOS), which is most useful as a silica precursor in the preparation of silica aerogel or silica aerogel blanket.

[0079] In the present invention, the prehydrolyzed polysilicate may mean a polysilicate that has been partially hydrated, specifically, a polysilicate in which some of the alkoxy functional groups of the polysilicate have been replaced with hydroxyl groups.

[0080] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to exemplary embodiments thereof, so that those skilled in the art can easily practice the present invention. However, the present invention may be embodied in many different forms and is not limited to the exemplary embodiments set forth herein.

[0081] Example 1 10.000g of ethyl polysilicate (TEOS40, ethyl polysilicate with SiO2 content of 40%) and 0.882g of methyltriethoxysilane (MTES) as a compound of chemical formula 1 were added to the reactor (Si molar ratio of polysilicate to MTES is 9:1). Then, 0.378g of HCl aqueous solution (HCl: 0.002g) with pH 1.8 was added to the reactor to prepare a reaction mixture. At this time, the reaction mixture prepared contains a total of 0.376g of water. The mixture was stirred at room temperature (20±5°C) for 1 hour. At the beginning of the reaction, the reaction product was opaque, but became transparent due to the generation of ethanol due to the hydration of MTES, and the partial hydration of ethyl polysilicate continued. Prehydrolyzed ethyl polysilicate (HTEOS) oligomer in ethanol was obtained as the final product.

[0082] Examples 2 to 6 A prehydrolyzed ethyl polysilicate (HTEOS) oligomer in ethanol was obtained as a final product in the same manner as in Example 1, except that the amount of the HCl aqueous solution having a pH of 1.8 was adjusted to the values ​​shown in Table 1 below.

[0083] Examples 7 to 12 A prehydrolyzed ethyl polysilicate (HTEOS) oligomer in ethanol was obtained as a final product in the same manner as in Example 1, except that the amount of methyltriethoxysilane (MTES) as the compound of Chemical Formula 1 in Example 1 was adjusted to the values ​​shown in Table 1 below.

[0084] Example 13 A prehydrolyzed ethyl polysilicate (HTEOS) oligomer in ethanol was obtained as a final product in the same manner as in Example 1, except that triethoxy(propyl)silane was added in the amounts shown in Table 1 below instead of methyltriethoxysilane (MTES) as the compound of Chemical Formula 1 in Example 1.

[0085] Comparative Example 1 10.000g of ethyl polysilicate (TEOS40) and 1.209g of ethanol were added to the reactor. Then, 0.243g of an aqueous HCl solution with a pH of 1.8 (HCl: 0.001g) was added to the reactor to prepare a reaction mixture. The amount of ethanol was determined to be the minimum amount that would allow the ethyl polysilicate and the aqueous HCl solution to be mixed transparently. At this time, the reaction mixture prepared contained a total of 0.242g of water. After stirring at room temperature (20±5°C) for 1 hour, prehydrolyzed ethyl polysilicate (HTEOS) oligomer in ethanol was obtained as the final product.

[0086] Comparative Examples 2 to 6 A prehydrolyzed ethyl polysilicate (HTEOS) oligomer in ethanol was obtained as a final product in the same manner as in Comparative Example 1, except that the amount of the HCl aqueous solution having a pH of 1.8 and the minimum amount of ethanol required for the aqueous solution were changed.

[0087] Reference example 1 A prehydrolyzed ethyl polysilicate (HTEOS) oligomer in ethanol was obtained as a final product in the same manner as in Example 1, except that the amount of methyltriethoxysilane (MTES) as the compound of Chemical Formula 1 in Example 1 was adjusted to the values ​​shown in Table 1 below.

[0088] Experimental Example 1) Ethanol produced (g) The amount of ethanol produced was calculated using the number of moles of water added for the hydration of the polysilicate.

[0089] 2) EtOH content (wt%) In Examples 1 to 13, the content (wt%) of EtOH produced was calculated by dividing the mass of ethanol produced by the total amount of reactants.

[0090] In addition, in Comparative Examples 1 to 6, the content (wt%) of EtOH produced was calculated by dividing the total mass of the input ethanol and the produced ethanol by the total mass of the reactants.

[0091] 3) SIO2 content (wt%) 10 g of the final products obtained from Examples 1 to 13 and Comparative Examples 1 to 6 were taken, and 1 g of ammonia water was added thereto, followed by gelation and calcination at 400°C for 2 hours to obtain pure SiO2. The mass of the obtained SiO2 was measured, and the SiO2 content (wt%) in the obtained final products was calculated.

[0092] [Table 1]

[0093] As can be seen from Table 1, in Examples 1 to 13, ethanol was effectively produced by the hydration of methyltriethoxysilane (MTES) or triethoxy(propyl)silane, which is a compound represented by Chemical Formula 1, without the need for a separate ethanol solvent, and the hydration of ethylpolysilicate was thereby carried out. Examples 1 to 6 are examples in which the amount of acidic aqueous solution (HCl) was gradually increased, and the degree of hydration of the polysilicate produced can be controlled by adjusting the amount of water and acid catalyst contained in the acidic aqueous solution.

[0094] Comparative Example 1 is an example in which the minimum amount of ethanol was added to eliminate layer separation between the polysilicate and the acidic aqueous solution when the polysilicate was reacted with the acidic aqueous solution, and ethyl polysilicate and the acidic aqueous solution were mixed transparently. Comparative Examples 2 to 6 are examples in which the amount of the acidic aqueous solution added was increased, and the amount of ethanol added was increased accordingly. Unlike the Examples, these are examples in which the ethanol solvent for the reaction of the polysilicate with the acidic aqueous solution was added separately.

[0095] When Examples 1 to 6 and Comparative Examples 1 to 6 are compared with each other in which the same molar ratio of water and polysilicate (TEOS40) is added, it was confirmed that Examples 1 to 6 can produce prehydrolyzed polysilicate having a higher SiO2 content using the same ratio of water and polysilicate compared to Comparative Examples 1 to 6. Examples 1 to 6 according to one embodiment of the present invention show the effect that can be achieved by using an alcohol compound generated by decomposing a compound represented by Chemical Formula 1 into an alcohol compound and a silanol compound as an amphiphilic solvent, and this effect is differentiated from the conventional method for producing prehydrolyzed polysilicate in which a separate alcohol compound is used as an amphiphilic solvent even though the alcohol compound generated during the reaction remains in the final product, and a prehydrolyzed polysilicate having a low SiO2 content is produced.

[0096] Meanwhile, referring to Examples 7 to 11, it was confirmed that the SiO2 content changes depending on the molar ratio of Si between polysilicate and methyltriethoxysilane (MTES), a compound represented by Chemical Formula 1, and it was confirmed that the SiO2 content in the final product can be controlled by adjusting the molar ratio of Si between polysilicate and methyltriethoxysilane (MTES), a compound represented by Chemical Formula 1, within an appropriate range. By increasing the number of moles of Si contained in polysilicate compared to the number of moles of Si in the compound represented by Chemical Formula 1, the SiO2 content in the final product tended to increase.

[0097] In Reference Example 1, the amount of the compound represented by Formula 1 added was small compared to the polysilicate, so that the hydration reaction of step 3 of the present invention was not performed. When the moles of Si contained in the polysilicate are excessively increased beyond a certain range compared to the moles of Si in the compound represented by Formula 1 as in Reference Example 1, the interface between the produced polysilicate and the acid aqueous solution may be separated, and the reactants may not be mixed, and the reaction may not proceed, or the amount of alcohol may be insufficient, and the reaction may not proceed smoothly, so the effect of shortening the synthesis time of the prehydrolyzed polysilicate of the present invention and the effect of synthesizing the prehydrolyzed polysilicate without using a separate solvent may not be achieved.

[0098] As described above, in the case of Examples 1 to 13, it is possible and effective to reduce the total amount of reactants used to hydrate the polysilicate without using a separate ethanol solvent, compared to the case of using a conventional ethanol solvent, and the hydration of the polysilicate is effectively performed.

[0099] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical concept or essential features of the present invention. Therefore, the above-described embodiments should be understood as illustrative in all respects and not restrictive.

Claims

1. Step 1: adding polysilicate and a compound represented by the following Formula 1 to a reactor; adding an acidic aqueous solution to the reactor to prepare a reaction mixture (step 2); and agitating the reaction mixture to carry out the hydration reaction (step 3). The acidic aqueous solution contains 0.005 to 0.20 parts by weight of an acid catalyst based on 100 parts by weight of the polysilicate, The polysilicate and the compound represented by Formula 1 are prepared by the following method: 【Chemistry 1】 R １ is an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or a vinyl group having 1 to 20 carbon atoms; R ２ are each independently alkyl having 1 to 20 carbon atoms.

2. The compound represented by Formula 1 is hydrated to form an alcohol compound represented by Formula 2 and a silanol compound represented by Formula 3: 【Chemistry 2】 【Chemistry 3】 R １ is an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or a vinyl group having 1 to 20 carbon atoms; R ２ is alkyl having 1 to 20 carbon atoms.

3. 3. The method for producing a prehydrolyzed polysilicate according to claim 2, wherein the hydration of the polysilicate in step 3 is carried out in the presence of the alcohol compound represented by Chemical Formula 2 formed by hydrating the compound represented by Chemical Formula 1.

4. The R １ and R ２ The method for producing a prehydrolyzed polysilicate according to claim 1, wherein each of the groups is independently an alkyl group having 1 to 6 carbon atoms.

5. 2. The method for preparing a prehydrolyzed polysilicate according to claim 1, wherein the compound represented by Formula 1 is an alkyltrialkoxysilane.

6. 2. The method for producing a prehydrolyzed polysilicate according to claim 1, wherein the polysilicate has an average degree of polymerization of 3 to 30.

7. 2. The method for preparing a prehydrolyzed polysilicate according to claim 1, wherein the step 3 is carried out at 15 to 25° C. for 30 minutes to 2 hours.

8. 2. The method for preparing a prehydrolyzed polysilicate according to claim 1, wherein no additional alcohol-based solvent is added to the reactor other than the polysilicate and the compound represented by Formula 1.

9. 2. The method for producing a prehydrolyzed polysilicate according to claim 1, wherein the polysilicate comprises one or more selected from the group consisting of methyl polysilicate, ethyl polysilicate, propyl polysilicate, isopropyl polysilicate, butyl polysilicate, secondary butyl polysilicate, tertiary butyl polysilicate, hexyl polysilicate, cyclohexyl polysilicate, and dodecyl polysilicate.

10. 2. The method for producing a prehydrolyzed polysilicate according to claim 1, wherein the compound represented by Chemical Formula 1 comprises at least one selected from the group consisting of alkyltriethoxysilane and alkyltrimethoxysilane.

11. 2. The method for preparing a prehydrolyzed polysilicate according to claim 1, wherein the compound represented by Chemical Formula 1 is methyltriethoxysilane.

12. The compound represented by the formula 1 is an alkyltriethoxysilane, and the alkyltriethoxysilane is hydrated to form an alkylsilanol and ethanol; 2. The method of claim 1, wherein the hydration of the polysilicate in step 3 is carried out in the presence of the ethanol formed by hydrating the alkyltriethoxysilane.

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