Highly dispersed fumed silica and method for producing the same

Abstract

The present invention relates to highly dispersed fumed silica and a method for producing the same, and more particularly to a highly functional fumed silica and a method for producing the same, which has a particle size and particle size uniformity that allows for high dispersibility when mixed with an adhesive composition, and which can also impart a thickening effect and thixotropy.

Description

[Technical Field]

[0001] The present invention relates to highly dispersed fumed silica and a method for producing the same, and more particularly to a highly functional fumed silica and a method for producing the same that, when mixed with an adhesive composition, has a particle size that exhibits high dispersibility and particle size uniformity, and can also impart a thickening effect and thixotropy. [Background technology]

[0002] Conventional sealants and adhesives require high viscosity to prevent them from running down during application. While high viscosity adhesives are advantageous for maintaining their original shape after application, they also suffer from reduced applicability due to their excessively high viscosity. On the other hand, adhesives with too low a viscosity tend to run down after application, making it difficult to apply them to the desired area and shape. Special adhesives used in shipbuilding, electrical systems, and other structures require not only excellent adhesive strength but also high viscosity and good applicability.

[0003] Therefore, since it is necessary to maintain low viscosity when applying the adhesive composition and high viscosity after application to maintain the desired shape, attempts have been made to mix various additives into the adhesive composition to impart thixotropy. In the case of fumed silica, it is known that the above properties can be imparted when mixed into the adhesive composition through hydrogen bonding with oxide aggregates and van der Waals forces.

[0004] However, when fumed silica is mixed as a thixotrope to impart thixotropy to an adhesive composition, there is still a limitation: the hydrophilic surface properties of fumed silica result in low dispersibility within adhesive resins, which generally exhibit hydrophobicity.

[0005] One known technique for improving dispersibility within adhesive compositions is to hydrophobically treat the surface of fumed silica. Generally, PDMS and other hydrophobic surface treatment agents used have surface adhesive properties that cause adhesion between adjacent silica aggregates, leading to problems such as uneven particle size distribution of fumed silica. This increase in particle size due to aggregation reduces dispersion stability, decreases the thixotropy of the adhesive composition, and consequently degrades the properties of adhesives and other products.

[0006] Furthermore, if the particle size of fumed silica is adjusted to be excessively small, the interaction between fumed silica particles decreases rapidly, which can result in a reduction of thixotropy in adhesive compositions and the like.

[0007] Therefore, there is still a need to develop technologies for fumed silica and its manufacturing methods that can improve particle size uniformity while enhancing dispersibility within the adhesive composition, and ensuring excellent thickening and thixotropic effects. [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention aims to provide fumed silica and a method for efficiently producing it, which exhibits high dispersibility and dispersion stability within adhesive compositions, controlled particle size, excellent uniformity, and also ensures excellent viscosity-enhancing and thixotropic effects in adhesive compositions.

[0009] Furthermore, the present invention aims to provide fumed silica and a method for producing the same, which can maintain almost the same particle size level before and after compression of the volume of the produced fumed silica, and which has excellent transportability (mobility) and storage properties.

[0010] The objectives of the present invention are not limited to those mentioned above. Other objectives and advantages of the present invention not mentioned can be understood from the following description and more clearly from the embodiments of the present invention. Furthermore, it is readily apparent that the objectives and advantages of the present invention can be achieved by the means and combinations thereof described in the claims. [Means for solving the problem]

[0011] To achieve the above objective, according to one aspect of the present invention, fumed silica, wherein the particle size D of the fumed silica in the volume-based particle size distribution obtained by a laser diffraction particle size distribution analyzer 90 We can provide fumed silica with a diameter of 10-160 μm, exhibiting a unimodal pattern, a bulk density of 10-150 g / L, and a surface treated with a hydrophobic surface treatment agent.

[0012] The surface treatment agent may contain one or more of the following: silicone oil and silane coupling agent.

[0013] The surface treatment agent may contain one or more of the following: PDMS (Polydimethylsiloxane), DDS (Dimethyldichlorosilane), D4 (Octamethylcyclotetrasiloxane), and HMDZ (Hexamethyldisilazane).

[0014] The surface may be treated using 3 to 30 parts by weight of the surface treatment agent, based on 100 parts by weight of the fumed silica.

[0015] The specific surface area (BET) of the fumed silica is 90-450 m². 2 / g is also acceptable.

[0016] According to another aspect of the present invention, there is provided a method for producing fumed silica, comprising: (a) performing a surface treatment reaction of fumed silica by spraying a surface treatment agent in a liquid or gaseous state while stirring under an inert gas atmosphere at a temperature of 100 to 400 °C for 1 hour or more; and (b) charging the fumed silica surface-treated in step (a) into a pulverizer and pulverizing it. The produced fumed silica can satisfy the characteristics of the fumed silica according to one aspect of the present invention.

[0017] The surface treatment reaction in step (a) may be carried out in a continuous or batch manner.

[0018] The inert gas may contain any one or more of nitrogen gas, neon gas, helium gas, and argon gas.

[0019] As still another aspect of the present invention, there is provided an adhesive composition comprising fumed silica according to one aspect of the present invention and an adhesive resin.

[0020] Based on 100 parts by weight of the adhesive resin, the fumed silica may be contained in an amount of 5 to 20 parts by weight.

[0021] The viscosity of the adhesive composition measured in a state where the fumed silica is dispersed in the adhesive composition may be 100,000 to 8,000,000 cPs.

[0022] The adhesive resin may contain an epoxy resin.

Advantages of the Invention

[0023] The fumed silica according to the present invention has the advantages of high dispersibility in the adhesive composition, controlled particle size, and excellent uniformity.

[0024] [[ID=3�]]The fumed silica according to the present invention is excellent in the thickening effect in the adhesive composition and can impart excellent thixotropy.

[0025] The fumed silica according to the present invention has the advantage of excellent transportability (mobility) and storage properties, as the particle size remains at almost the same level before and after compression of its volume after production.

[0026] The method for producing fumed silica according to the present invention can efficiently produce fumed silica that satisfies the above-mentioned characteristics.

[0027] The effects described above, as well as the specific effects of the present invention, will be explained and described below in conjunction with the descriptions of embodiments for carrying out the invention. [Brief explanation of the drawing]

[0028] [Figure 1] This figure shows a graph comparing the viscosity measurements of Example 1, Comparative Example 1, and Comparative Example 2. [Figure 2] This figure shows a graph (horizontal axis: particle diameter (μm), vertical axis: volume (volume, %)) measured to confirm the volume-based cumulative 90% particle size (D90) of the fumed silica of Example 1 by particle size distribution measurement. [Figure 3] This figure shows a graph (horizontal axis: particle diameter (μm), vertical axis: volume (volume, %)) measured to confirm the volume-based cumulative 90% particle size (D90) of the fumed silica of Example 2 by particle size distribution measurement. [Figure 4] This figure shows a graph (horizontal axis: particle diameter (μm), vertical axis: volume (volume, %)) measured to confirm the volume-based cumulative 90% particle size (D90) of the fumed silica in Comparative Example 3, based on particle size distribution measurement. [Figure 5] This figure shows a graph (horizontal axis: particle diameter (μm), vertical axis: volume (volume, %)) measured to confirm the volume-based cumulative 90% particle size (D90) of the fumed silica of Comparative Example 4, based on particle size distribution measurement. [Figure 6] This figure shows a graph comparing the bulk densities of Example 3-1 and Example 3-2. [Figure 7]This figure shows a graph comparing the particle size (D90) of Example 3-1 and Example 3-2. [Modes for carrying out the invention]

[0029] The aforementioned objectives, features, and advantages will be described in detail below with reference to the attached drawings, so that a person with ordinary skill in the art to which the present invention pertains can easily implement the technical concept of the present invention. In describing the present invention, if a specific description of known technology according to the present invention is deemed to obscure the gist of the present invention, then such detailed description will be omitted. Hereafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. The same reference numerals in the drawings are used to indicate the same or similar components.

[0030] In describing this specification, if it is determined that a specific description of a related known technology would obscure the gist of this specification, such detailed description will be omitted.

[0031] In this specification, when "contains," "has," "becomes," "arranges," or "equips" a component, other parts may be added unless "only" is used. When a component is expressed singularly, it includes cases where it contains multiple components unless otherwise explicitly stated.

[0032] In interpreting the components of this specification, even if not explicitly stated otherwise, they shall be interpreted as including a margin of error.

[0033] In this specification, bulk density (unit: g / L) is measured by filling a 100 mL mass cylinder with fumed silica up to the 100 mL mark and weighing it.

[0034] In this specification, particle size analysis (particle size distribution analysis) is performed using a laser diffraction particle size analyzer (equipment name: Beckman Coulter, LASER DIFFRACTION PARTICLE SIZE ANALYZER LS13 320). A dispersion of ethanol diluted with 1% by weight of fumed silica is introduced into the analyzer and measured, with the average value after a total of six measurements being used as the reference.

[0035] In this specification, viscosity is measured using a Brookfield viscometer (equipment name: Brookfield viscometer DV-II+Pro) after placing 200 mL of the sample in a 250 mL beaker and waiting for the viscosity value to stabilize at 2 RPM using a SPINDLE LV4(64). The value measured at 25°C is used as the reference value.

[0036] In this specification, the specific surface area (BET) is based on the value obtained by the BET method according to DIN 66131 under a nitrogen atmosphere using the BELSORP model.

[0037] The present invention will be described in more detail below.

[0038] <Fumed Silica> In order to achieve the above objective, the present invention provides fumed silica, wherein the particle size D of the fumed silica in the volume-based particle size distribution obtained by a laser diffraction particle size distribution analyzer. 90 The particle size can be 10 to 150 μm, and the particle size is controlled to exhibit a unimodal pattern, while the bulk density is 10 to 150 g / L, and the surface is treated with a hydrophobic surface treatment agent.

[0039] If the particle size of fumed silica is adjusted to be excessively small, the interaction between fumed silica particles decreases sharply, which can result in a reduction of thixotropy in adhesive compositions. On the other hand, if the particle size of fumed silica is adjusted to be excessively large, the dispersion stability of the fumed silica particles decreases, leading to precipitation or layer separation in the adhesive composition, and also resulting in a reduction of thixotropy. From this perspective, the particle size D of the fumed silica of the present invention 90 For example, it may be 10 to 160 μm, for example, 50 to 150 μm, or for example, 60 to 150 μm.

[0040] In this invention, the particle size can be controlled to exhibit a unimodal pattern in fumed silica. When the particle size distribution curve is observed using a laser diffraction particle size analyzer, the presence of only a single peak within the measurement range can be interpreted as a unimodal pattern.

[0041] For example, in the case of fumed silica having a bimodal or multimodal pattern, there are two or more types of particles with relatively small particle sizes and relatively large particle sizes. However, the relatively small particles cannot contribute to imparting thixotropy or thickening effects, and the relatively large particles have poor dispersibility and are susceptible to changes over time. When mixed into an adhesive composition, this leads to problems such as layer separation or decreased viscosity due to heat, resulting in reduced physical stability. Consequently, a large amount of fumed silica must be added to achieve the desired degree of physical properties, which reduces the economic efficiency and workability of the process.

[0042] In this invention, analysis of fumed silica particles confirmed that a single-bar pattern can improve upon the problems of the bimodal pattern fumed silica described above. Specifically, it is possible to provide fumed silica with only the optimal particle size that can achieve the desired effect, by reducing useless fumed silica that cannot be realized due to particle sizes being too small or too large in the particle size distribution.

[0043] Thus, since the particle size of the fumed silica of the present invention is controlled and exhibits a single-bar pattern, and particle size uniformity is also controlled, the desired physical properties can be achieved even with the addition of only a small amount of fumed silica, without mixing an excessive amount into the adhesive composition. Furthermore, it may also have the advantage of improving process workability and process efficiency in the subsequent mixing process into the adhesive composition.

[0044] The bulk density of the fumed silica of the present invention is not particularly limited, but may be, for example, 10 to 150 g / L, 15 to 100 g / L, 20 to 80 g / L, or 30 to 50 g / L. It tends to decrease slightly in bulk density upon pulverization and increase in bulk density upon compression. As long as it satisfies the above range, it can be used as the fumed silica intended for the present invention and can be adjusted as appropriate.

[0045] Fumed silica is required to be well dispersed within the adhesive composition and to have excellent dispersibility. Furthermore, it is required that the excellent dispersibility be stably maintained over time and with temperature changes during the process after initial dispersion. From this viewpoint, the fumed silica of the present invention can be hydrophobically treated on its surface to improve dispersion stability and workability within the adhesive composition and to provide an appropriate viscosity-enhancing effect. Generally, epoxy resins used as adhesive resins in special adhesives can exhibit hydrophilicity. In the present invention, the surface treatment is performed to hydrophobicize the hydrophilic groups (e.g., hydroxyl groups (-OH)) present on the surface of the fumed silica. The method for hydrophobic surface treatment is not particularly limited, but the surface can be hydrophobicized and silylated using silicone oil or silane coupling agents such as PDMS, DDS, D4, and HMDZ. As a result, the density of -OH groups on the surface of the fumed silica decreases, the density of -CH3 groups increases, and the number of hydrogen bonds generated by the -OH groups can be reduced. The degree of hydrophobicity in the present invention is not particularly limited and can be adjusted depending on the product and application in which the fumed silica is ultimately used.

[0046] The degree of hydrophobicity in this invention can be measured by detecting and quantifying CO2 generated by burning a sample at 1000°C or higher in an O2 gas stream using a Thermo Scientific FlashEA 1112 Elemental Analyzer. The degree of hydrophobicity of the fumed silica surface-treated in this invention may be when the carbon content is, for example, 0.5 to 10%, 3 to 7%, or 4 to 6%.

[0047] According to one embodiment of the present invention, based on 100 parts by weight of the fumed silica, for example, 3 to 30 parts by weight of the surface treatment agent can be used, for example, 5 to 25 parts by weight of the surface treatment agent can be used, for example, 10 to 20 parts by weight of the surface treatment agent can be used, but is not limited to these amounts and can be adjusted depending on the type of surface treatment agent used.

[0048] In the present invention, when the specific surface area of the fumed silica is too small, a large amount of fumed silica needs to be added to achieve a thickening effect. When the specific surface area is too large, the dispersibility in the adhesive composition tends to decrease. From such a perspective, according to one embodiment of the present invention, the specific surface area (BET) of the fumed silica is, for example, 90 to 450 m 2 / g, and may be, for example, 150 to 250 m 2 / g. <000,0195> In the present invention, the specific surface area of the fumed silica after the hydrogenated surface treatment decreases compared to before the hydrogenated surface treatment, and may be, for example, 50 to 350 m 2 / g, and may be, for example, 60 to 250 m 2 / g, and may be, for example, 80 to 150 m 2 / g.

[0050] <Method for Producing Fumed Silica> To produce the fumed silica according to the present invention, (a) while stirring in an inert gas atmosphere, spraying a surface treatment agent in a liquid or gaseous state, and maintaining at a temperature of 100 to 400 °C for 1 hour or more to perform a surface treatment reaction of the fumed silica; and (b) feeding the fumed silica surface-treated in step (a) into a pulverizer and pulverizing it; a method for producing fumed silica including these steps can be provided.

[0051] (a) step is a surface treatment step of fumed silica, and while stirring in an inert gas atmosphere, a surface treatment reaction can be performed at a specific temperature and for a specific time while spraying a surface treatment agent in a liquid or gaseous state. <000020,4>

[0052] The temperature for performing the above step (a) may vary depending on the type of the surface treatment agent selected. For example, it may be a temperature of 100 to 400 °C. For example, in the case of PDMS, it is preferable to select a temperature of 330 °C or lower.

[0053] The time required for step (a) above is the surface treatment reaction time, which means the time required to maintain the above temperature range. This may be, for example, 1 to 5 hours, or for example, 2 to 4 hours, but is not necessarily limited to these, and can be adjusted depending on the amount of fumed silica to be surface treated.

[0054] The method of the surface treatment reaction in step (a) above is not particularly limited and can be carried out, for example, by continuous manufacturing or batch manufacturing. In a specific example, if batch manufacturing is chosen, a fluidized reactor, a mechanical fluidized reactor, etc., can be used as the batch reactor.

[0055] The inert gas in step (a) above may contain one or more of nitrogen gas, neon gas, helium gas, and argon gas, and nitrogen gas is preferred.

[0056] Step (b) above can be performed after step (a). The fumed silica introduced into the grinding apparatus in step (b) above is fumed silica with uncontrolled particle size, and particle size D 90 Generally, the particle size exceeds 150 μm, and when the particle size is analyzed, it shows various patterns such as unimodal, bimodal, and multimodal, indicating that the particle size distribution is not uniform and exists in a state that is not specifically controlled. Therefore, in this invention, the particle size of fumed silica is controlled by a grinding process, and specifically the particle size D of the fumed silica in the volume-based particle size distribution obtained by a laser diffraction particle size distribution analyzer. 90 The particle size is controlled to be between 10 and 160 μm and to exhibit a single-bar pattern, and the bulk density may be in the range of 10 to 150 g / L.

[0057] The grinding apparatus in step (b) above is not particularly limited as long as it can grind the material into the fumed silica targeted in this invention, and is capable of precisely adjusting the particle size with the equipment of the art. For example, a pin mill, disc mill, bead mill, blade mill, air mill, jet mill, rod mill, roller mill, wheeler mill, hammer mill, etc., can be used, and the grinding apparatuses listed above can be used in combination.

[0058] <Adhesive composition> The present invention can provide an adhesive composition comprising the fumed silica and adhesive resin of the present invention.

[0059] According to one embodiment of the present invention, the fumed silica may be contained in an amount of, for example, 5 to 20 parts by weight, or 5 to 15 parts by weight, based on 100 parts by weight of the adhesive resin. If the fumed silica is included in an excessively small amount, the thickening effect and the effect of imparting thixotropy will decrease, and if the fumed silica is included in an excessively large amount, problems such as clumping between silica particles may occur. On the other hand, if the fumed silica is included in an excessively large amount, the dispersion state of the silica particles will be poor, and the desired physical properties will not be generated, or the physical properties will change significantly over time, reducing the stability over time and potentially seriously hindering workability.

[0060] The adhesive resin may include an epoxy resin that has excellent adhesive strength in special-purpose adhesives.

[0061] The viscosity of the adhesive composition, measured with the fumed silica dispersed in it, may be, for example, 100,000 to 8,000,000 cPs, and may be adjusted depending on the final application of the adhesive. For example, when used as a marine adhesive, it may have a relatively high viscosity of 2,000,000 to 3,000,000 cPs, while when applied to relatively light objects such as automobiles, home appliances, or solar panels, it may have a relatively low viscosity of 100,000 to 150,000 cPs. However, it is not necessarily limited to these values ​​and can be adjusted depending on the specific application. The fumed silica of the present invention has the advantage of being easy to use to achieve high viscosity in adhesives.

[0062] In adhesive compositions, it is possible to select epoxy resins with high viscosity, but selecting epoxy resins with excessively high viscosity leads to a limit in workability and productivity. Since epoxy resins themselves do not exhibit thixotropy, fumed silica can generally be included in adhesive compositions as an inorganic filler that can function as both a thickener and a thixotrope.

[0063] The present invention will be described in more detail below with reference to examples and experimental examples. However, the following examples and experimental examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0064] <Experiment SET1> Example 1 Specific surface area 200m 2 10g of fumed silica (product name: KONASIL K-200) with a particle size of / g was mixed with 21g of PDMS to hydrophobize it. 10g of the hydrophobized fumed silica was then ground using an air-jet mill to obtain a particle size D. 90Fumed silica was manufactured so that the particle size was 83 μm, and a single-bar pattern was observed during particle size analysis. The volume density of the manufactured fumed silica was 40 g / L. Subsequently, 10 g of the surface-treated and pulverized fumed silica was mixed with 100 g of epoxy resin (product name: EPIKOTE828) to produce 110 g of the sample for Example 1.

[0065] Comparative Example 1 Unlike Example 1, the sample for Comparative Example 1 was prepared without adding fumed silica to the epoxy resin.

[0066] Comparative Example 2 Similar to Example 1, but with different particle sizes D of fumed silica. 90 The difference lies in the fact that the particle size was set to 8 μm. The volume density of the fumed silica produced in Comparative Example 2 was 12 g / L. The fumed silica of Comparative Example 2 was mixed with epoxy resin in the same manner as in Example 1 to prepare the sample for Comparative Example 2.

[0067] The viscosity of each sample from Example 1, Comparative Example 1, and Comparative Example 2 was measured and is shown in Figure 1. The particle size (D) of fumed silica. 90 The volume density (g / L) and the measured viscosity (cPs) are shown in Table 1 below.

[0068] [Table 1]

[0069] Referring to Figure 1 and Table 1, it was confirmed that fumed silica with the same particle size as in Example 1 clearly increased viscosity when added to epoxy resin, but the viscosity-increasing effect of fumed silica in Comparative Example 2, which was ground too finely and had a smaller particle size, was low.

[0070] <Experiment SET2> Similar to Example 1, but the particle size D of the fumed silica in Example 2, Comparative Example 3, and Comparative Example 4 is the same. 90The fumed silica used in Example 2, Comparative Example 3, and Comparative Example 4 was adjusted to differ from that described in Table 2 below, and its volume density also differed as described in Table 2 below. Fumed silica was used in Example 2, Comparative Example 3, and Comparative Example 4, respectively, and was mixed with epoxy resin in the same manner as in Example 1 to prepare samples for Example 2, Comparative Example 3, and Comparative Example 4. The viscosity of the prepared samples was measured and is shown in Table 2 below. Furthermore, the particle size of the fumed silica in Example 1, Example 2, Comparative Example 3, and Comparative Example 4 was analyzed, and the results are shown in graphs in Figures 2 to 5, respectively.

[0071] [Table 2]

[0072] Referring to Table 2 above, as shown in Examples 1 and 2, fumed silica that satisfies the particle size and volume density of the present invention clearly increases viscosity when added to epoxy resin. However, it was confirmed that the viscosity-increasing effect of fumed silica in Comparative Examples 3 and 4, which do not satisfy the particle size and volume density of the present invention, is low.

[0073] <Experiment SET3> Example 3-1 Similar to Example 1, but with different particle sizes D of fumed silica. 90 Fumed silica with a particle size of 25.3 μm and a volume density of 26.2 g / L was prepared as Example 3-1.

[0074] Example 3-2 The fumed silica from Example 3-1 was compressed using compression equipment to achieve a volume density of 70.9 g / L. The particle size D of the compressed fumed silica was then determined. 90 We measured it.

[0075] Particle size (D) of Examples 3-1 and 3-2 90 Graphs comparing the volume density and volume density are shown in Figures 6 and 7, and the numerical values ​​are shown in Table 3 below.

[0076] [Table 3]

[0077] Referring to Table 3 above, it was confirmed that hydrophobic fumed silica produced using a grinding technology in which dimethylsilyl groups are formed on the surface does not change significantly in particle size from the silica before compression, even after the compression process.

[0078] Since fumed silica exists in particulate form, it is often supplied in a compressed state. However, even under the harsh conditions of compression, deformation of properties such as particle size must be minimal. If properties such as particle size are maintained during compression, it may mean that the silica has excellent long-term storage properties and stability.

[0079] The embodiments of this specification have been described in more detail above with reference to the attached drawings, but this specification is not necessarily limited to these embodiments, and various modifications are possible without departing from the technical concept of this specification. Therefore, the embodiments disclosed herein are for illustrative purposes only, not to limit the technical concept of this specification, and these embodiments do not limit the scope of the technical concept of this specification. Accordingly, the embodiments described above should be understood to be illustrative and not limiting in all respects. The scope of protection of this specification should be interpreted as per the claims, and any technical concept within an equivalent scope should be interpreted as being included in the scope of rights of this specification.

Claims

1. Fumed silica, Particle size D of the fumed silica in the volume-based particle size distribution obtained by a laser diffraction particle size distribution analyzer. ９０ The diameter is 10-160 μm, and it exhibits a unimodal pattern. The volume density is 10 to 150 g / L. The surface is treated with a hydrophobic surface treatment agent. Fumed silica.

2. The surface treatment agent comprises one or more of silicone oil and silane coupling agents. The fumed silica according to claim 1.

3. The surface treatment agent comprises one or more of the following: PDMS (Polydimethylsiloxane), DDS (Dimethylchlorosilane), D4 (Octamethylcyclotetrasiloxane), and HMDZ (Hexamethyldisilazane). The fumed silica according to claim 2.

4. The surface is treated using 3 to 30 parts by weight of the surface treatment agent, based on 100 parts by weight of the fumed silica. The fumed silica according to claim 1.

5. The specific surface area (BET) of the fumed silica is 90 to 450 m². ２ / g is The fumed silica according to claim 1.

6. (a) A step of carrying out a surface treatment reaction of fumed silica by spraying a surface treatment agent in liquid or gaseous form while stirring under an inert gas atmosphere, and maintaining a temperature of 100 to 400°C for 1 hour or more. (b) A step of putting the fumed silica that has been surface-treated in step (a) into a pulverizer and pulverizing it, including, A method for producing fumed silica.

7. The fumed silica has a volume-based particle size distribution measured by a laser diffraction particle size distribution analyzer, and its particle size D ９０ The diameter is 10–160 μm, it exhibits a single-bar pattern, and the bulk density is 10–150 g / L. A method for producing fumed silica according to claim 6.

8. The surface treatment agent comprises one or more of silicone oil and silane coupling agents. A method for producing fumed silica according to claim 6.

9. The surface treatment agent comprises one or more of the following: PDMS (Polydimethylsiloxane), DDS (Dimethylchlorosilane), D4 (Octamethylcyclotetrasiloxane), and HMDZ (Hexamethyldisilazane). A method for producing fumed silica according to claim 8.

10. Using 100 parts by weight of the fumed silica as a reference, 3 to 30 parts by weight of the surface treatment agent are used. A method for producing fumed silica according to claim 6.

11. The surface treatment reaction in step (a) above is carried out in a continuous or batch manner. A method for producing fumed silica according to claim 6.

12. The inert gas includes one or more of nitrogen gas, neon gas, helium gas, and argon gas. A method for producing fumed silica according to claim 6.

13. Fumed silica according to any one of claims 1 to 5, Adhesive resin and including, Adhesive composition.

14. The adhesive resin is based on 100 parts by weight, and contains 5 to 20 parts by weight of the fumed silica. The adhesive composition according to claim 13.

15. The viscosity of the adhesive composition, measured with the fumed silica dispersed in it, is 100,000 to 8,000,000 cPs. The adhesive composition according to claim 13.

16. The adhesive resin includes an epoxy resin. The adhesive composition according to claim 13.

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