System and method for producing an aerogel composite material, and aerogel composite material

Abstract

A system and method for producing an aerogel composite material includes a reaction vessel having a movable carrier basket for receiving a plurality of fiber mats, and a plurality of plates to space the fiber mats apart from one another. Once the plates have been removed, there are gaps between the aerogel insulating boards, through which hot drying air can be blown during a drying process. The method has the advantage that the quantities of solvents and reagents to be disposed of are minimal, and in addition thereto, no complex work-up processes are necessary.

Claims

1. A system for industrial production of a fiber-reinforced aerogel plate, comprising: a first reservoir for a solvent, a second reservoir for an organosilane compound, a third reservoir for a hydrophobizing agent, a fourth reservoir for an acid, a fifth reservoir for a base, a reaction vessel for receiving a plurality of fiber mats, a cover for the reaction vessel, a plurality of connecting lines between the first, second, third, fourth and fifth reservoirs and the reaction vessel, a removable basket for receiving the plurality of fiber mats in the reaction vessel, and a plurality of plates to space the plurality of fiber mats apart from each other.

2. The system according to claim 1, further comprising a first heat exchanger device on the reaction vessel to heat or cool the reaction vessel or contents of the reaction vessel to a specific temperature.

3. The system according to claim 1, further comprising a connection on the reaction vessel for blowing a drying gas, a supply line connected to a port for the drying gas, the supply connected to a heating device, a discharge line for the drying gas, in communication with a second heat exchanger on the reaction vessel, and a blower or a pump for introducing the drying gas into or drawing it from the reaction vessel.

4. The system according claim 1, further comprising a removable carrier basket in the reaction vessel, in which the plurality of fiber mats are arranged.

5. The system according to claim 1, further comprising a mixer/settler with a stirrer, the mixer/settler in communication with the reaction vessel with a first line and in communication with the first reservoir with a second line.

6. The system according to claim 5, wherein the second line is in communication with a distillation device.

7. The system according to claim 5, wherein the mixer/settler is connected via the first line line to the third reservoir.

8. The system according to claim 3, wherein the second heat exchanger is in communication with the reaction vessel with a recirculation line.

9. The system according to claim 1, further comprising a separate heating/cooling circuit to heat the reaction vessel.

10. A system for the industrial production of a fiber-reinforced aerogel plate, comprising: a plurality of reservoirs comprising: a first reservoir for a solvent, a second reservoir for an organosilane compound, a third reservoir for a hydrophobizing agent, a fourth reservoir for an acid, and a fifth reservoir for a base, a reaction vessel for receiving a plurality of fiber mats, a plurality of connecting lines between said plurality of reservoirs and the reaction vessel, wherein the reaction vessel is in communication directly or indirectly with the first reservoir and the third reservoir teach via a recirculation line.

11. The system according to claim 10, further comprising, a first heat exchanger on the reaction vessel to heat or cool the reaction vessel or contents of the reaction vessel to a specific temperature.

12. A method for producing a fiber-reinforced aerogel plate, comprising: preparing a silicatic sol, hydrophobizing the gel with a hydrophobizing agent in the presence of an acid as catalyst, arranging initially a plurality of fiber mats and a corresponding plurality of intermediate plates alternately in a reaction vessel, so that two fiber mats of the plurality of fiber mats are separated from each other by a respective intermediate plate of the plurality of intermediate plates, adding the silicate sol to the reaction vessel until gelling is started, and draining a reaction solution from the reaction vessel after gelling of the gel, removing the intermediate plates and drying the formed, fiber-reinforced aerogel plates at a temperature >100° C.

13. The method according to claim 12, further comprising spacing adjacent fiber mats from each other by at least 10 mm.

14. The method according to claim 12, further comprising arranging the fiber mats on a carrier basket, which fits into the reaction vessel.

15. The method according to claim 12, wherein the drying of the fiber-reinforced aerogel plates takes place within the reaction vessel.

16. The method according to 15, wherein the drying takes place by blowing a hot drying gas through the reaction vessel.

17. The method according to claim 15, further comprising circulating the drying gas and condensing out volatiles absorbed in the drying gas.

18. The method according to any one of claim 12, wherein the drying takes place at temperatures >120° C.

19. The method according to claim 12, wherein the gelling, hydrophobizing and drying are carried out in the reaction vessel.

20. The method according to claim 12, further comprising using hexamethyldisiloxane (HDMSO) as the hydrophobizing agent.

21. The method according to claim 12, wherein in the hydrophobizing a ratio of solvent and water is at least 4%.

22. The method according to any one of claim 12, wherein a proportion by weight of the hydrophobizing agent in a liquid hydrophobizing solution is at least 50%.

23. The method according to claim 12, further comprising using nitric acid as the acid.

24. The method according to claim 12, wherein the silicate sol is prepared by hydrolysis of alkoxysilanes or hydroxyalkoxysilanes.

25. The method according to to claim 12, wherein the preparation of the sol is carried out in alcohol or an alcohol-containing solvent mixture.

26. The method according to claim 12, further comprising adjusting a pH in the hydrophobizing to a value between 0.2 and 6.

27. The method according to claim 12, further comprising preparing the sol by hydrolysis of tetraethoxysilane (TEOS) with a mass fraction of between 5 and 30 percent by weight of SiO.sub.2.

28. The method according to claim 12, wherein the gelling occurs in a temperature range between 30° C. and 80° C.

29. The method according to claim 12, further comprising mixing the sol with mineral fibers.

30. The method according to claim 29, further comprising using rockwool fibers as the mineral fibers.

31. The method according to claim 12, wherein the hydrophobization is carried out in situ without prior solvent exchange.

32. The method according to claim 12, further comprising adding a silylating agent when preparing the silicatic sol.

33. The method according to claim 12, further comprising forming a composite material of an aerogel and mineral fibers havinq a thermal conductivity between 8 and 25 mW/m K.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

(1) The invention will be explained in more detail with reference to the following examples. In particular,

(2) FIG. 1 schematically shows an industrial system with a reaction vessel, various reservoirs for receiving the necessary agents and solvents for the production of fiber-reinforced aerogel plates;

(3) FIG. 2 shows an embodiment of a reaction vessel consisting of a double-walled trough, a cover for closing the trough; and a plurality of carrier baskets accommodated in the vessel for simultaneously receiving and transporting a plurality of fiber mats;

(4) FIG. 3 shows a single, empty carrier basket according to FIG. 2;

(5) FIG. 4 shows a carrier basket loaded with a plurality of fiber mats and intermediate plates;

(6) FIG. 5 shows the inner trough of the reactor vessel of FIG. 2; and

(7) FIG. 6 shows the outer shell of the trough of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

(8) FIG. 1 schematically shows an industrial system for the production of aerogel plates with a reaction vessel 11, various reservoirs 13, 15, 17, 19, 21, 23 and 25 for receiving the reactants and solvents for carrying out the reaction, as well as vessels 27, 29 and 31 for the preparation of the reaction mixtures and intermediate storage of the partially spent reaction solutions. The storage, reaction and mixing vessels are connected to each other via lines 37 to 63, so that the necessary reaction mixtures can be produced. Specifically, the following vessels and lines are defined:

(9) reaction vessel 11,

(10) reservoir 13 for an organosilane compound (TEOS)

(11) reservoir 15 for solvent (EtOH)

(12) reservoir 17 for water

(13) reservoir 19 for sulfuric acid (H2S04)

(14) reservoir 21 for aqueous ammonia solution (NH.sub.4OH),

(15) reservoir 23 for hydrophobizing agent (HMDSO),

(16) reservoir 25 for nitric acid (HNO3),

(17) mixing vessel 27 for producing an alcoholic TEOS solution,

(18) mixing vessel 29 for producing a diluted mixture of EtOH and H2SO4,

(19) mixing vessel 31 for preparing a diluted ammonia solution,

(20) reaction vessel 33 for producing a sol,

(21) connecting line 34 between the reaction vessel 33 and the mixing vessel 27

(22) connecting line 35 between the reaction vessel 33 and the mixing vessel 29

(23) vessel 36 for the intermediate storage of the partially spent reaction mixture,

(24) line 37 for connecting the reservoir 13 with the mixing vessel 27

(25) line 39 for connecting the reservoir 15 with the mixing vessel 27

(26) line 41 for connecting the reservoir 15 with the mixing vessel 31

(27) line 43 for connecting the reservoir 15 with the mixing vessel 29

(28) line 45 for connecting the reservoir 17 with the reaction vessel 33

(29) line 47 for connecting the reservoir 19 with the mixing vessel 29

(30) line 49 for connecting the reservoir 21 with the reactor 11

(31) line 51 for connecting the reservoir 23 with the reactor 11

(32) line 53 for connecting the reservoir 25 with the mixing vessel 31

(33) line 55 for connecting the reaction vessel 33 with the reactor 11

(34) line 57 for connecting the mixing vessel 31 with the reactor 11

(35) line 59 for connecting the reactor 11 with the intermediate vessel 35

(36) line 61 for connecting the intermediate vessel 35 with the reservoir 15

(37) line 63 for connecting the intermediate vessel 35 with the reservoir 23

(38) 65 discharge line for residues

(39) 67 pump

(40) 69 heat exchangers

(41) 71 supply line for the drying gas

(42) 73 heating source in the supply line 71

(43) 75 discharge line

(44) 77 pump

(45) 79 distillation column

(46) The core of the schematically illustrated production system according to FIG. 1 is the reaction vessel 11. This can be heated by means of the heating/cooling circuit 67, 68, 69 to a certain temperature, usually 60 to 80° C., and maintained at this temperature. A supply line 71 leads into the reaction vessel, through which a drying gas, such as air, can be blown into the reaction vessel 11. In the supply line 71, a heating source 73 is integrated, which allows the gas or the air to be heated to a temperature of up to about 200° C., or about 150° C. For discharging the air, a discharge line 75 is provided. This is in connection with a pump 77 for drawing the drying gas. In the discharge line 75, a heat exchanger 79 is provided, by means of which a large part of the solvent entrained in the drying gas is condensed. The remainder of the solvent contained in the drying gas is separated in the pump 77, such as a cyclone separator. Subsequently, the dried drying gas can be returned to the supply line 71 again.

(47) The reaction vessel 11 communicates via the connecting line 55 with the reaction vessel 33. The reaction vessel 33 serves to produce a sol and is in turn connected via the connecting lines 34, 35 to the mixing vessel 27 on the one hand and to the mixing vessel 29 on the other hand. The connecting line 37, which is in communication with the TEOS reservoir 13, and on the other hand, the connecting line 39, which communicates with the solvent reservoir 15, enter the mixing vessel 27. The mixing vessel 29 is also connected via the connecting line 43 with the solvent reservoir 17 and, on the other hand, via the connecting line 47 with the sulfuric acid reservoir 19. Through this arrangement of vessels and connecting lines, a sol can be prepared and transferred to the reaction vessel 11.

(48) The reaction vessel 11 is also connected via the connecting line 57 with the mixing vessel 31. The mixing vessel 31 is used to prepare a diluted, alcoholic nitric acid solution and is connected for this purpose via the connecting lines 41, 53 on the one hand to the solvent reservoir 15 and on the other hand to the nitric acid reservoir 25. With the nitric acid solution in the manufacturing process, the existing gel is acidified for the subsequent hydrophobizing with HMDSO.

(49) The supply of HMDSO in the reaction vessel 11 occurs via the connecting line 51, which connects the vessel 11 with the HMDSO reservoir 23.

(50) Last but not least, the reaction vessel 11 is also connected to the ammonia reservoir 21 via the connecting line 49. The ammonia solution is needed in the manufacturing process to initiate gelling. Optionally, a vessel 50 may be provided to prepare a diluted ammonia solution.

(51) The reaction solutions present in the reaction vessel 11 can be discharged via line 59 into the vessel 36, which serves as a settler and for intermediate storage. Depending on the process step, the contents of the vessel 36 are conducted either via the line 63 into the HMDSO vessel or via the line 61 into the solvent reservoir 15. Via the line 65, the contents can also be supplied for disposal. For working up the solvent, a distillation column 79 is provided in the connecting line 61, by means of which the solvent used for the main purpose can be separated from other reaction components.

(52) The exemplary embodiment of a reaction vessel 11 shown in FIGS. 2 to 6 serves to receive a plurality of fiber boards and is designed for the industrial production of aerogel composite thermal insulation boards. The reaction vessel 11 comprises a trough 81, a cover 83 for closing the vessel and a plurality of carrier baskets 85, which can be arranged in the trough 81. The reaction vessel 11 is therefore a trough 81 in this embodiment.

(53) A single carrier basket 85 is shown in FIG. 3. It consists of one rectangular platform 87, to which walls 89a, 89b connect at two opposite sides. The walls 89a, 89b are connected to each other by upper struts 91 in order to provide the carrier basket 85 with the necessary stability. At the upper end above the two struts, eyelets 93 are formed in the walls 89a, 89b, by means of which the carrier baskets 85 can be lifted by a crane.

(54) FIG. 4 shows a loaded carrier basket 85. Between the walls 89a, 89b, fiber mats 95 and intermediate plates 97 are alternately arranged, i.e. between two adjacent fiber mats 93, an intermediate plate 95 is respectively provided. After the gelling and hydrophobizing process and the removal of the intermediate plate, a gap is thereby formed between the fiber mats 95. Through this gap, hot drying gas, such as air, can be passed through for the purpose of drying the aerogel plates. This makes it possible to dry the aerogel plates directly in the reaction vessel 11.

(55) The trough 81 according to FIGS. 5 and 6 is double-walled and consists of an inner trough 99 and an outer shell 101. On the inner side of the outer shell, circumferential baffles 103 are provided, which, when the inner trough 99 is inserted, form a spiral channel, which leads from the inlet 105 to the outlet 107.

(56) In order for the solvent and air to flow through the reaction vessel as unhindered as possible, the platform 87 of the carrier basket 85 has a plurality of perforations 109. It is conceivable that at the bottom of the reaction vessel also baffles or channels are provided in order to direct the air in the spaces between the fiber insulation boards.

(57) The manufacturing process of a fiber-reinforced composite thermal insulation board is as follows: First, a sol is prepared starting from an organic organosilane compound. The organosilane compound used is tetraethoxysilane (TEOS for short), which can be obtained inexpensively in large quantities. A desired amount of TEOS is transferred to the mixing vessel 27 and diluted with a certain amount of alcohol to allow the TEOS to reach the desired concentration. Alcohol is introduced into the mixing vessel 29 and a defined amount of sulfuric acid is dissolved. The alcoholic TEOS solution and the alcoholic sulfuric acid solution are then transferred to the reaction vessel 33 and stirred vigorously by means of the stirrer. To start the hydrolysis of the TEOS, a small amount of water is supplied via the line 45. At 40° C. to 60° C., it takes between 1 and 6 hours, until the TEOS hydrolyzes and the sol is formed. The sol thus prepared is then transferred to the reactor 11, in which a plurality of fiber insulation boards were previously arranged alternately with intermediate plates. The fiber mats and intermediate plates are arranged in the carrier basket 91 and thus can all be transferred into the reactor all at once. In the reactor 11, then, such an amount of the sol is admitted until the insulating fiber boards are covered with the sol. Then the reaction mixture is heated to about 50° C. to 70° C. and basified by adding an appropriate amount of ammonia solution. Once the reaction mixture is basified, gelling begins immediately. Normally gelling will take 5 to 15 minutes. Thereafter, the gel is aged at the same temperature for 72 hours. After that time the gelation is almost completed.

(58) Thereafter, the solvent mixture is discharged into the vessel 35 and subsequently purified by distillation. Since the mixture consists predominantly of ethanol, the majority of the ethanol used for the gel formation can be recovered and returned to the reservoir 15.

(59) After draining the solvent mixture, the reactor 11 is filled with HMDSO from the reservoir 23 until the insulating fiber boards are covered with the solution. Then, nitric acid dissolved in ethanol is added in the mixture and the pH is adjusted to between 1 and 3. At the same time the temperature of the reactor is raised to about 60° C. to 78° C. Under these conditions, the free OH groups react with the multiple excess of HMDSO and are thereby passivated.

(60) Depending on the chosen temperature, the hydrophobizing lasts between about 1 and 5 hours (24 h at 75° C.). At 75° C., the hydrophobizing takes between 1 and 2 hours. After the hydrophobization is completed, the reaction mixture is discharged and transferred to the vessel 35. Thereafter, a small amount of water is added to the reaction mixture and allowed to rest between 10 and 24 hours until a lower water phase and an upper organic phase are formed. The water phase containing salts and partially reacted HMDSO is drained and disposed of. The rest, which is prevalently HMDSO, is then returned via line 63 into the reservoir 23 and used for the hydrophobization of a subsequent charge. It has been shown that the hydrophobization can also proceed satisfactorily with solutions in which the proportion by weight of HMDSO is only 70%. If the hydrophobizing reaction is no longer satisfactory, then the mixture can be distilled and practically pure HMDSO can be recovered. According to practical experiments in a hydrophobization reaction, only between 3% and 6% of the HMDSO are used. This means that only between 3% and 6% of the HMDSO used must be replaced again so that the original amount of HMDSO is restored. Overall, the manufacturing process is highly process-optimized, since only a few waste products are produced. The solvent EtOH can mostly be reused. The acids HNO3 and H2SO4 are used only in catalytic amounts, and the other organic reagents HMDSO and TEOS are mostly converted in the hydrolysis or hydrophobization or can be reused in a subsequent reaction.

(61) Precursor P75E20:

(62) Pre-product Production Batch:

(63) At room temperature (RT), provide TEOS 77.3 L (72.7 kg), add 16.6 L (13.1 kg) of ethanol (=MIX A) at 600 rpm,

(64) Place 16.6 L (13.1 kg) of ethanol in a small feed vessel, add H2SO4 95-98% m/m, 32.9 mL (60.5 g) (=MIX B), exothermal reaction (˜30-35° C.)

(65) Add MIX B to MIX A in 1 h @ RT @ 600 rpm

(66) Add 9.4 L (9.4 kg) H20 in 2 h @ RT @ 600 rpm

(67) Load precursor and store, total pre-product 119.93 L

(68) Sol Production:

(69) Add 47.1 L (42.9 kg) P75E20 or precursor or pre-product, add 113.8 L (89.8 kg) ethanol with stirring at RT @ 600 rpm, increase stirring to 900 rpm and condition sol to 45° C.

(70) Sol Act. Gelling:

(71) At Tmax. switch off heating and add base solution (activation, initiator, pH adjustment, adjust H2SO4 (Precursor)

(72) Base Solution:

(73) 5.1 L H2O+0.4 L NH.sub.4OH 28-30% m/m: Total 55 L base solution (0.54 M)

(74) Production of the Aerogel Fiber Composite Material

(75) 47.1 L of a prehydrolyzed sol (75% prehydrolyzed, 20% (m/m) SiO.sub.2 content) in EtOH (abs.) is diluted with a little more than twice the amount of ethanol (113.8 L) and homogenized with stirring (900 rpm). At the same time, the mixture is heated to approximately 45° C. Once the temperature has settled and the mixture is homogenized, an aqueous NH.sub.4OH aqueous solution (0.4 L aqueous base+5.1 L H2O (ca. 5 L, 0.55 M) is added to the sol, briefly homogenized and then transferred to the reactor 11 provided with a temperature sensor, in which already a plurality of mineral fiber mats with a specific weight between 40 kg/m3 and 70 kg/m3 is introduced. Thereafter, the contents of the vessel are heated to about 65° C., and the mixture is left to age. Aging of the gel occurs between 6 and 96 hours, between 24 and 84 hours, or for about 48-72 hours. After gelling, the solvent is released, transferred to the vessel 35 and worked up by distillation.

(76) The reactor 11 is then filled with such an amount of HMDSO that the fiber mats are covered, and heated to about 75° C. Gel in the same vessel is hydrophobized by adding an excess of HMDSO (presently about 70 L of a 60% to 98% (m/m) HMDSO (+HNO3 in EtOH solution) and about 5 L of a substantially alcoholic HNO3 solution (approx. 4 to 9% m/m) for 24 h at 75° C. dynamically, i.e. by circulation of the liquid phase.

(77) After cooling, the partially used hydrophobizing solution is transferred to the mixer/settler 35 and diluted with a little water (about 10% of the volume of solvent present). Two phases then form, an aqueous, lower phase which can be disposed of, and an organic upper phase which contains the HMDOS and which can be reused in a next batch.

(78) Once the partially spent HMDSO solution is drained, the intermediate plates 97 are removed and immediately hot air, heated to about 150° C., is blown through the line 77 into the reaction vessel 11. Via the line 75 connected to the vessel cover 83, the air saturated with solvent and HMDSO leaves the reactor 11. In the cyclone separator 77 then the solvent, HMDSO and water are condensed after the air passing through the heat exchanger 79 was previously slightly cooled. To the surprise of the inventors, the fiber mats can be dried immediately with hot air at a temperature of between 100 and 150° C., desireably about 150° C., without them becoming brittle, collapsing or substantially shrinking. The air is reheated after the condensing of the volatile components (solvent and HMDSO) and then re-circulated to the reactor.

(79) In the mixer/settler 36, about 10% by volume of water is added to the hydrophobizing solution used and the mixture is stirred vigorously for 10 to 30 minutes. Thereafter, the mixture is allowed to stand overnight with an aqueous phase settling to the bottom. The aqueous phase is separated and discarded. The reclaimed hydrophobizing solution may then be reused in a next batch, optionally after being concentrated with HMDSO.

(80) The present invention relates to a system and a method for producing an aerogel composite material. The system is characterized by having a reaction vessel with a removable carrier basket for receiving a plurality of fiber mats and a plurality of plates to space the fiber mats apart. After the removal of the plates between the aerogel insulating plates, gaps are provided, through which hot drying air can be blown during drying. The method has the advantage that the amounts of solvents and reagents to be disposed of are minimal and that no elaborate work-up processes are necessary.