Method for preparing silicon dioxide aerogel under normal pressure, silicon dioxide aerogel and felt pad

Abstract

The invention discloses a method for preparing silicon dioxide aerogel under normal pressure, the silicon dioxide aerogel and a felt pad, and relates to the technical field of aerogels, the method comprises the following steps: mixing a solution containing an inorganic silicon source with acid to obtain silicic acid sol; standing the silicic acid sol to form gel, and performing aging treatment on the gel to obtain wet gel; adding a modifier into the wet gel, and carrying out surface hydrophobic modification treatment; and carrying out drying treatment on the modified wet gel to obtain the silicon dioxide aerogel. According to the technical scheme provided by the invention, the preparation period is short, the production cost is low, and the obtained silicon dioxide aerogel product has excellent performance.

Description

Technical Field

[0001] The present invention relates to the technical field of aerogels, and in particular to a method for preparing silica aerogels at normal pressure, the silica aerogels, and a felt pad. Background Art

[0002] Silica aerogel is a lightweight, nanoporous material with high porosity, large surface area, low density, and low thermal conductivity. These characteristics make it a promising material for applications in thermal engineering, acoustics, optics, microelectronics, and particle detection. Despite its excellent performance, silica aerogel's high production cost has significantly limited its widespread application.

[0003] Currently, aerogels with good performance can be prepared under normal pressure using water glass as a silicon source. However, inherent drawbacks such as a long preparation cycle (aging, solvent exchange, and surface modification steps require several days) and high organic solvent consumption (multiple solvent exchanges) remain unresolved. Therefore, providing a method for preparing silica aerogels with a short preparation cycle, low production costs, and excellent performance has become an urgent technical problem in the field. Summary of the Invention

[0004] The main purpose of the present invention is to provide a method for preparing silica aerogel at normal pressure, silica aerogel, and felt pad, so as to achieve a short preparation cycle, low production cost, and the obtained silica aerogel product has excellent performance.

[0005] To achieve the above object, the present invention provides a method for preparing silica aerogel at normal pressure, comprising the following steps:

[0006] S1, mixing a solution containing an inorganic silicon source with an acid to obtain a silicic acid sol;

[0007] S2, allowing the silicic acid sol to stand to form a gel, and then aging the gel to obtain a wet gel;

[0008] S3, adding a modifier to the wet gel to perform surface hydrophobic modification treatment;

[0009] S4, drying the modified wet gel to obtain the silica aerogel.

[0010] In one embodiment, in the step of mixing the solution containing the inorganic silicon source with an acid to obtain a silicic acid sol,

[0011] The hydrogen ion concentration in the silicate sol is 2 to 6 mol / L; and / or,

[0012] The concentration of silicon dioxide in the silicic acid sol is 0.8-2 mol / L.

[0013] In one embodiment, in the step of mixing the solution containing the inorganic silicon source with an acid to obtain a silicic acid sol,

[0014] The inorganic silicon source includes water glass, silica sol, solid silicon dioxide extracted from fly ash or crop waste, liquid silicon dioxide extracted from fly ash or crop waste; and / or,

[0015] The acid includes any one of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.

[0016] In one embodiment, in step S3, the modifier includes volatile silicone oil or a non-polar organic solvent containing volatile silicone oil; and / or,

[0017] The amount of the modifier added to the wet gel is 150-200% by volume; and / or,

[0018] The surface modification treatment time is 2-6 hours, and the surface modification treatment temperature is 40-70°C.

[0019] In one embodiment, the volatile silicone oil includes at least one of hexamethyldisiloxane, octamethyltrisiloxane, octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane; and / or,

[0020] The non-polar organic solvent includes one of n-hexane, cyclohexane or n-heptane; and / or,

[0021] In the non-polar solvent containing volatile silicone oil, the volume proportion of the volatile silicone oil is greater than or equal to 50%.

[0022] In one embodiment, the method further comprises: adding an interface agent in step S1 or step S3;

[0023] The interface agent includes a polar organic solvent or an aqueous solution of a polar organic solvent;

[0024] Wherein, the polar organic solvent includes at least one of methanol, ethanol, acetone, ethylene glycol and isopropanol; and / or,

[0025] The volume proportion of the polar organic solvent in the aqueous solution of the polar organic solvent is greater than or equal to 50%.

[0026] In one embodiment, when the interface agent is added in step S1, the volume proportion of the interface agent in the silicate sol is 20-30%.

[0027] In one embodiment, when the interfacial agent is added in step 3, the amount of the interfacial agent added is 50-100% by volume of the wet gel.

[0028] In one embodiment, in the step of drying the modified wet gel to obtain the silica aerogel,

[0029] The drying temperature of the drying process is less than 300°C.

[0030] Another aspect of the present invention provides a silica aerogel having a tap density of 0.05-0.20 g / cm 3 The thermal conductivity of the silica aerogel is 0.015-0.030 W / (m·K), and the contact angle of the silica aerogel is not less than 160°.

[0031] In another aspect, the present invention provides a silica aerogel felt pad comprising silica aerogel.

[0032] In the technical solution of the present invention, a cheap inorganic silicon source and an acid are used as precursors, and an acidic wet gel is first prepared by a sol-gel method, and then hydrophobic modification is performed with a modifier, and finally a drying treatment is performed to obtain the final product. In the method for preparing silica aerogel at normal pressure described in the present invention, corresponding devices or molds can be used to prepare silica aerogel products including powders, blocks and composite materials (such as silica aerogel felt). The preparation method provided by the present invention has a short process cycle, low solvent consumption, and low production cost; the silica aerogel product prepared by this method has a low density and good hydrophobic properties, and its thermal conductivity is also extremely low, which is very suitable for application in the field of thermal insulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0034] Figure 1 This is a flow chart of the method for preparing silica aerogel at normal pressure provided by an embodiment of the present invention.

[0035] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0038] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of such features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0039] Silica aerogel is a lightweight, nanoporous material with high porosity, large surface area, low density, and low thermal conductivity. These characteristics make it a promising material for applications in thermal engineering, acoustics, optics, microelectronics, and particle detection. Despite its excellent performance, silica aerogel's high production cost has significantly limited its widespread application.

[0040] Currently, silica aerogels are mostly prepared using supercritical drying processes. However, supercritical process equipment is complex, costly, and dangerous. Therefore, atmospheric pressure drying processes have gradually become a hot topic. As early as the 1990s, Deshpande, Douglas, and others at the University of New Mexico in the United States first successfully prepared silica aerogels at atmospheric pressure using an organosilicon source as a precursor through sol-gel, solvent exchange, and surface modification.

[0041] Although water glass can be used as a silicon source to produce aerogels with good performance under normal pressure, inherent disadvantages such as a long preparation cycle (aging, solvent exchange, surface modification, etc. require several days) and high organic solvent consumption (multiple solvent exchanges) have not been resolved. To address these difficulties, some researchers have attempted to use a one-step method of solvent exchange and surface modification to prepare silica aerogels, but the problems of high modifier consumption and large amounts of organic waste liquid have not been resolved.

[0042] Therefore, providing a method for preparing silica aerogel with a short preparation cycle, low production cost, and excellent performance of the obtained silica aerogel product has become a technical problem that needs to be solved urgently in this field.

[0043] In view of this, the present invention provides a method for preparing silica aerogel at normal pressure, see Figure 1 , including the following steps:

[0044] Step S1, mixing a solution containing an inorganic silicon source with an acid to obtain a silicic acid sol;

[0045] Step S2, allowing the silicic acid sol to stand to form a gel, and then subjecting the gel to an aging treatment to obtain a wet gel;

[0046] Step S3, adding a modifier to the wet gel to perform surface hydrophobic modification treatment;

[0047] Step S4: drying the modified wet gel to obtain the silica aerogel.

[0048] In the technical solution of the present invention, a cheap inorganic silicon source and an acid are used as precursors, and an acidic wet gel is first prepared by a sol-gel method, and then hydrophobic modification is performed with a modifier, and finally a drying treatment is performed to obtain the final product. In the method for preparing silica aerogel at normal pressure described in the present invention, corresponding devices or molds can be used to prepare silica aerogel products including powders, blocks and composite materials (such as silica aerogel felt). The preparation method provided by the present invention has a short process cycle, low solvent consumption, and low production cost; the silica aerogel product prepared by this method has a low density and good hydrophobic properties, and its thermal conductivity is also extremely low, which is very suitable for application in the field of thermal insulation.

[0049] In one embodiment, in the step of mixing the solution containing the inorganic silicon source with an acid to obtain a silicic acid sol, the hydrogen ion concentration in the silicic acid sol is 2 to 6 mol / L; and the silicon dioxide concentration in the silicic acid sol is 0.8 to 2 mol / L.

[0050] It should be noted that the aging treatment of silica gel primarily involves treatment under specific conditions (e.g., different solvents, time, and temperature). This treatment can significantly improve the mechanical properties and thermal stability of the silica gel, optimizing its pore structure and surface properties. For example, in the embodiments of the present invention, an aging treatment of 1 hour at room temperature can be employed.

[0051] In one embodiment, in the step of mixing a solution containing an inorganic silicon source with an acid to obtain a silicic acid sol, the inorganic silicon source includes water glass, silica sol, solid silicon dioxide extracted from fly ash or crop waste, or liquid silicon dioxide extracted from fly ash or crop waste; and the acid includes any one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

[0052] Silica sol includes alkaline silica sol, which is a colloidal solution of silica particles of varying sizes in water, with a pH range of 9 to 10. Alkaline silica sol is commercially available. Fly ash, an industrial byproduct of coal-fired power generation, contains a large amount of amorphous silicon and silicon products, which can be effectively extracted through various processes. Agricultural waste, such as rice husks and straw, is also rich in silicon, and valuable silicon compounds can also be extracted through proper treatment. Alkaline leaching and acid leaching are the two main processes used to extract solid silica. The alkaline leaching method involves reacting fly ash with an alkaline solution (such as NaOH) to dissolve the amorphous silicon dioxide. Solid silica is then obtained through precipitation and filtration. This method is not only suitable for extracting silica from fly ash, but can also be used to treat agricultural waste. Acid leaching is similar to alkaline leaching, but uses an acidic solution, such as sulfuric acid or hydrochloric acid. This acid leaching releases silicon from fly ash as soluble silicates, which are subsequently converted into solid silicon dioxide through a chemical reaction. Solid silicon dioxide extracted from fly ash or agricultural waste, and liquid silicon dioxide extracted from fly ash or agricultural waste, can be obtained using any of the existing methods, which will not be further described in the present embodiments.

[0053] In one embodiment, the modifier includes volatile silicone oil or a non-polar organic solvent containing volatile silicone oil; the amount of the modifier added to the wet gel is 150-200% by volume; the surface modification treatment lasts for 2-6 hours, and the temperature is 40-70°C. A suitable modifier and its addition amount can effectively modify the wet gel.

[0054] In one embodiment, the volatile silicone oil includes at least one of hexamethyldisiloxane, octamethyltrisiloxane, octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane; the non-polar organic solvent includes one of n-hexane, cyclohexane or n-heptane; and the volume proportion of the volatile silicone oil in the non-polar solvent containing the volatile silicone oil is greater than or equal to 50%.

[0055] The addition of a modifier to the wet gel modifies the groups of the wet gel from hydrophilic groups to hydrophobic groups. Wherein, volatile silicone oil is used as the modifier, and the modifier can be recycled.

[0056] In one embodiment, the method further includes: adding an interfacial agent in step S1 or step S3; the interfacial agent includes a polar organic solvent or an aqueous solution of a polar organic solvent; wherein the polar organic solvent includes at least one of methanol, ethanol, acetone, ethylene glycol and isopropanol; and the volume proportion of the polar organic solvent in the aqueous solution of the polar organic solvent is greater than or equal to 50%.

[0057] The interfacial agent can be added in step S1 or added together with the modifier in step S3. The function of the interfacial agent is to introduce the oily modifier into the aqueous gel, thereby effectively exerting the surface modification effect of the modifier.

[0058] In one embodiment, when the interface agent is added in step S1, the volume proportion of the interface agent in the silicic acid sol is 20-30%.

[0059] In one embodiment, when the interfacial agent is added in step 3, the amount of the interfacial agent added in the wet gel is 50-100% by volume.

[0060] In one embodiment, in the step of drying the modified wet gel to obtain the silica aerogel, the drying temperature of the drying treatment is less than 300°C.

[0061] Drying is a conventional technical means in the field. The present invention has no specific requirements for the drying process. It can be drying by heating at normal pressure or drying in a vacuum. At the same time, the present invention does not make specific requirements for the drying temperature and time. Those skilled in the art can select appropriate drying temperature and time according to the needs of on-site operations, but the drying temperature should not exceed 300°C.

[0062] Another aspect of the present invention provides a silica aerogel having a tap density of 0.05-0.20 g / cm 3 The thermal conductivity of the silica aerogel is 0.015-0.030 W / (m·K), and the contact angle of the silica aerogel is not less than 160°.

[0063] In another aspect, the present invention provides a silica aerogel mat, comprising silica aerogel. In the method for preparing silica aerogel at normal pressure described herein, corresponding devices or molds can be used to prepare silica aerogel products including powders, blocks, and composite materials (such as silica aerogel mats).

[0064] In summary, the technical solution of the present invention has at least the following beneficial effects:

[0065] 1) Using cheap and easily available inorganic silicon sources, the polar organic solvents (such as ethanol) used can also be their aqueous solutions, which greatly reduces the cost of raw materials and solvents;

[0066] 2) Using a one-step modification method, the entire process can be completed within 12 hours, which is significantly shorter than the conventional atmospheric pressure preparation method in this field (3-5 days);

[0067] 3) Due to the use of acidic gel and one-step modification, not only is the consumption of organic solvents greatly reduced compared to conventional atmospheric pressure preparation methods, but no additional catalyst is required during the modification, and waste liquid is also greatly reduced;

[0068] 4) Volatile silicone oil is used as a modifier, which can be recycled. Conventional atmospheric pressure preparation methods in this field often use silane coupling agents as modifiers, which have high reactivity and cannot be recycled.

[0069] 5) The technical solution of the present invention can predict the progress of aerogel surface modification. That is, before modification, the gel is hydrophilic and sinks in the lower aqueous phase. After modification, the gel becomes hydrophobic and lipophilic and floats to the upper oil phase. At this time, the modification process can be visually observed until the modification is completed.

[0070] The technical solutions of the present invention are further described in detail below in conjunction with specific embodiments and drawings. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0071] Example 1

[0072] This embodiment provides a method for preparing silica aerogel at normal pressure, which comprises the following steps:

[0073] (1) 50 mL of alkaline silica sol with a mass concentration of 30% and 100 mL of deionized water were mixed in a beaker, and then added to a mixed solution containing 50 mL of concentrated hydrochloric acid (the concentration of concentrated hydrochloric acid is 12 mol / L) and 50 mL of ethanol, and stirred for 5 minutes to obtain acidic silica sol.

[0074] (2) The acidic silica sol obtained in step (1) is allowed to stand for gelation, and after the gel is formed, the gel is aged at room temperature for 1 hour to obtain a wet gel.

[0075] (3) Take 50 mL of the aged wet gel and add it to a container with a stirring device. Add 100 mL of octamethyltrisiloxane as a modifier. After the wet gel is completely soaked, continue stirring in a 50°C water bath for 2 hours to perform surface modification until the gel is completely modified from hydrophilic to hydrophobic. Before the modification, the gel is hydrophilic and sinks in the lower aqueous phase. After the modification is completed, the gel becomes hydrophobic and oleophilic and floats to the upper oil phase.

[0076] (4) Open the stopcock at the bottom of the container to release the liquid in the container; transfer the solid part to a blast drying oven for normal pressure drying, drying at 60°C for 1 hour, drying at 120°C for 2 hours, and drying at 150°C for 3 hours to obtain a silica aerogel product.

[0077] The performance parameters of the silica aerogel product prepared in this example were measured as follows: tap density 0.083 g / mL, thermal conductivity 0.019 W / (m·K), and contact angle 169°.

[0078] The measurement of thermal conductivity refers to GB / T 10294-2008, and the testing instrument is: Xi'an Xiaxi Electronic Technology Co., Ltd.'s flat plate thermal conductivity meter TC1100.

[0079] It can be seen that the silica aerogel product prepared in Example 1 of the present invention has a low density and good hydrophobicity, and its thermal conductivity is also extremely low, and is very suitable for application in the field of thermal insulation.

[0080] Example 2

[0081] This embodiment provides a method for preparing silica aerogel at normal pressure, which comprises the following steps:

[0082] (1) 50 mL of 39-degree Baume water glass and 100 mL of deionized water were mixed in a beaker, and then added to a mixed solution containing 50 mL of dilute sulfuric acid (the concentration of dilute sulfuric acid was 50-70 wt%) and 50 mL of ethanol, and stirred for 5 minutes to obtain an acidic silica sol.

[0083] (2) The acidic silica sol obtained in step (1) is allowed to stand for gelation, and after the gel is formed, the gel is aged at room temperature for 1 hour to obtain a wet gel.

[0084] (3) Take 50 mL of the aged wet gel and add it to a container with a stirring device. Add 100 mL of hexamethyldisiloxane as a modifier. After the wet gel is completely soaked, continue stirring in a 60°C water bath for 3 hours to perform surface modification until the gel is completely modified from hydrophilic to hydrophobic. Before the modification, the gel is hydrophilic and sinks in the lower aqueous phase. After the modification is completed, the gel becomes hydrophobic and oleophilic and floats to the upper oil phase.

[0085] (4) Open the stopcock at the bottom of the container to release the liquid in the container; transfer the solid part to a blast drying oven for normal pressure drying, drying at 60°C for 1 hour, drying at 120°C for 2 hours, and drying at 150°C for 3 hours to obtain a silica aerogel product.

[0086] The performance parameters of the silica aerogel product prepared in this example were measured as follows: tap density 0.092 g / mL, thermal conductivity 0.020 W / (m·K), and contact angle 156°.

[0087] Example 3

[0088] This embodiment provides a method for preparing silica aerogel at normal pressure, which comprises the following steps:

[0089] (1) 50 mL of 39-degree Baume water glass and 100 mL of deionized water were mixed in a beaker, and then added to a mixed solution containing 50 mL of concentrated hydrochloric acid (the concentration of concentrated hydrochloric acid was 12 mol / L) and 50 mL of methanol, and stirred for 5 minutes to obtain an acidic silica sol.

[0090] (2) The acidic silica sol obtained in step (1) is allowed to stand for gelation, and after the gel is formed, the gel is aged at room temperature for 1 hour to obtain a wet gel.

[0091] (3) Take 50 mL of the aged wet gel and add it to a container with a stirring device. Add 100 mL of hexamethyldisiloxane as a modifier. After the wet gel is completely soaked, continue stirring in a 50°C water bath for 4 hours to perform surface modification until the gel is completely modified from hydrophilic to hydrophobic. Before the modification, the gel is hydrophilic and sinks in the lower aqueous phase. After the modification is completed, the gel becomes hydrophobic and oleophilic and floats to the upper oil phase.

[0092] (4) Open the stopcock at the bottom of the container to release the liquid in the container; transfer the solid part to a blast drying oven for normal pressure drying, drying at 60°C for 1 hour, drying at 120°C for 2 hours, and drying at 150°C for 3 hours to obtain a silica aerogel product.

[0093] The performance parameters of the silica aerogel product prepared in this example were measured as follows: tap density 0.074 g / mL, thermal conductivity 0.018 W / (m·K), and contact angle 167°.

[0094] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformation made by utilizing the contents of the present invention's description and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A method for preparing silica aerogel at normal pressure, characterized in that: The following steps are involved: S1, mixing a solution containing an inorganic silicon source with an acid to obtain a silicic acid sol; S2, allowing the silicic acid sol to stand to form a gel, and then aging the gel to obtain a wet gel; S3, adding a modifier to the wet gel to perform surface hydrophobic modification treatment; S4, drying the modified wet gel to obtain the silica aerogel.

2. The method according to claim 1, characterized in that In the step of mixing the solution containing the inorganic silicon source with an acid to obtain a silicic acid sol, The hydrogen ion concentration in the silicate sol is 2 to 6 mol / L; and / or, The concentration of silicon dioxide in the silicic acid sol is 0.8-2 mol / L.

3. The method according to claim 1, characterized in that In the step of mixing the solution containing the inorganic silicon source with an acid to obtain a silicic acid sol, The inorganic silicon source includes water glass, silica sol, solid silicon dioxide extracted from fly ash or crop waste, liquid silicon dioxide extracted from fly ash or crop waste; and / or, The acid includes any one of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.

4. The method according to claim 1, wherein In step S3, the modifier includes volatile silicone oil or a non-polar organic solvent containing volatile silicone oil; and / or, The amount of the modifier added to the wet gel is 150-200% by volume; and / or, The surface modification treatment time is 2-6 hours, and the surface modification treatment temperature is 40-70°C.

5. The method according to claim 4, characterized in that The volatile silicone oil includes at least one of hexamethyldisiloxane, octamethyltrisiloxane, octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane; and / or, The non-polar organic solvent includes one of n-hexane, cyclohexane or n-heptane; and / or, In the non-polar solvent containing volatile silicone oil, the volume proportion of the volatile silicone oil is greater than or equal to 50%.

6. The method according to claim 1, characterized in that The method further comprises: adding an interface agent in step S1 or step S3; The interface agent includes a polar organic solvent or an aqueous solution of a polar organic solvent; Wherein, the polar organic solvent includes at least one of methanol, ethanol, acetone, ethylene glycol and isopropanol; and / or, The volume proportion of the polar organic solvent in the aqueous solution of the polar organic solvent is greater than or equal to 50%.

7. The method according to claim 6, characterized in that When adding the interface agent in step S1, The added amount of the interface agent accounts for 20-30% by volume of the silicate sol.

8. The method according to claim 1, characterized in that When adding the interface agent in step 3, The added amount of the interface agent accounts for 50 to 100% of the volume of the wet gel.

9. A silica aerogel prepared according to any one of claims 1 to 8, characterized in that: The tap density of the silica aerogel is 0.05-0.20 g / cm 3 The thermal conductivity of the silica aerogel is 0.015-0.030 W / (m·K), and the contact angle of the silica aerogel is not less than 160°.

10. A silica aerogel felt pad, characterized in that: The silica aerogel according to claim 9 is included.

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