U.S. patent application number 12/812543 was filed with the patent office on 2010-11-18 for carbon aerogels, process for their preparation and their use.
This patent application is currently assigned to EVONIK DEGUSSA GMBH. Invention is credited to Manfred Dannehl, Arkadi Maisels, Johann Mathias, Frank Stenger, Yves Gorat Stommel, Jutta Zimmermann.
Application Number | 20100288160 12/812543 |
Document ID | / |
Family ID | 40280856 |
Filed Date | 2010-11-18 |
United States Patent
Application |
20100288160 |
Kind Code |
A1 |
Maisels; Arkadi ; et
al. |
November 18, 2010 |
Carbon Aerogels, Process for Their Preparation and Their Use
Abstract
The invention relates to carbon aerogels with particle sizes
less than 1 .mu.m, The carbon aerogels are prepared by (A) reating
a mono- and/or polyhydroxybenzene, an aldehyde and a catalyst in a
reactor at a reaction temperature T in the range from
75-200.degree. C. at a pressure of 80-2400 kPa, (B) then spraying
the reaction mixture from process step (A) into an acid, to drying
the resulting product from process step (B) and (D) carbonizing it.
The carbon aerogels according to the invention can be used as
filler, reinforcing filler, UV stabilizer, electrode material,
sound absorbents, thermal insulating material, catalyst, catalyst
support, conductivity additive, absorbent for as and/or liquid
preparation or pigment.
Inventors: |
Maisels; Arkadi; (Hanau,
DE) ; Stommel; Yves Gorat; (Shanghai, CN) ;
Stenger; Frank; (Alzenau, DE) ; Zimmermann;
Jutta; (Alzenau, DE) ; Dannehl; Manfred; (Kahl
am Main, DE) ; Mathias; Johann; (Kahl, DE) |
Correspondence
Address: |
LAW OFFICE OF MICHAEL A. SANZO, LLC
15400 CALHOUN DR., SUITE 125
ROCKVILLE
MD
20855
US
|
Assignee: |
EVONIK DEGUSSA GMBH
Essen
DE
|
Family ID: |
40280856 |
Appl. No.: |
12/812543 |
Filed: |
January 15, 2009 |
PCT Filed: |
January 15, 2009 |
PCT NO: |
PCT/EP2009/050422 |
371 Date: |
July 12, 2010 |
Current U.S.
Class: |
106/31.13 ;
106/273.1; 106/672; 423/445R; 428/317.9; 521/82 |
Current CPC
Class: |
C01B 32/05 20170801;
Y10T 428/249986 20150401; B01J 13/0091 20130101; C01P 2004/62
20130101; C01P 2006/14 20130101; C01B 32/00 20170801 |
Class at
Publication: |
106/31.13 ;
428/317.9; 423/445.R; 106/672; 106/273.1; 521/82 |
International
Class: |
B32B 3/26 20060101
B32B003/26; C01B 31/02 20060101 C01B031/02; C09D 11/00 20060101
C09D011/00; C09D 11/02 20060101 C09D011/02; C08L 95/00 20060101
C08L095/00; C08J 9/00 20060101 C08J009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 17, 2008 |
DE |
102008005005.9 |
Oct 14, 2008 |
EP |
08166593.7 |
Claims
1-10. (canceled)
11. A carbon aerogel, comprising particles with a mean particle
size of less than 1 .mu.m.
12. The carbon aerogel of claim 11, wherein said carbon aerogel has
a carbon content of 95-100% by weight.
13. The carbon aerogel of claim 12, wherein the density of said
carbon aerogel is 0.005-2.0 g/cm.sup.3.
14. The carbon aerogel of claim 13, comprising particles with a
mean particle size of between 0.05 and 1 .mu.m as determined by
laser diffraction according to International Organization for
Standardization (ISO) procedure 13320-1 (1999).
15. The carbon aerogel of claim 13, comprising particles with a
mean particle size of between 0.5 and 0.95 .mu.m as determined by
laser diffraction according to ISO procedure 13320-1 (1999).
16. The carbon aerogel of claim 13, wherein the density of said
carbon aerogel is 0.15-1.5 g/cm.sup.3.
17. The carbon aerogel of claim 13, wherein the density of said
carbon aerogel is 0.35-1.3 g/cm.sup.3.
18. A process for producing the carbon aerogel of claim 11,
comprising: a) reacting a mono- and/or polyhydroxybenzene and an
aldehyde in the presence of a catalyst, wherein the reaction is
carried out at a temperature in the range of 75-200.degree. C. and
at a pressure of 80-2400 kPa; (b) spraying the reaction mixture
produced in step a) into an acid; (c) drying the product produced
in step (b); and (d) carbonizing the dried product produced in step
c).
19. The process of claim 18, wherein said mono- and/or
polyhydroxybenzene is selected from the group consisting of:
phenol, catechol, resorcinol, phloroglucinol, hydroquinone and
mixtures thereof.
20. The process of claim 19, wherein said aldehyde is selected from
the group consisting of: formaldehyde, glyoxal, glutaraldehyde,
furfural and mixtures thereof.
21. The process of claim 18, wherein said catalyst is an alkali
metal hydroxide or alkaline earth metal hydroxide.
22. The process of claim 18, wherein said catalyst is selected from
the group consisting of: NaOH, KOH, Na.sub.2CO.sub.3,
Li.sub.2CO.sub.3, K.sub.2CO.sub.3, and NH.sub.3.
23. The process of claim 22, wherein the concentration of mono-
and/or polyhydroxybenzene and aldehyde in the reaction mixture is
10-60% by weight, and a) said mono- and/or polyhydroxybenzene is
selected from the group consisting of: phenol, catechol,
resorcinol, phloroglucinol, hydroquinone and mixtures thereof; and
b) said aldehyde is selected from the group consisting of:
formaldehyde, glyoxal, glutaraldehyde, furfural and mixtures
thereof.
24. The process of claim 23, wherein the concentration of mono-
and/or polyhydroxybenzene and aldehyde in the reaction mixture is
20-40% by weight.
25. The process of claim 23, wherein the molar ratio of mono-
and/or polyhydroxybenzene to aldehyde is 1:1 to 1:4.
26. The process of claim 25, wherein said acid is selected from the
group consisting of hydrochloric acid, nitric acid, phosphoric
acid, sulphuric acid, acetic acid, formic acid and oxalic acid.
27. The process of claim 26, wherein the reaction of step a) is
performed in the presence of a pore former selected from the group
consisting of: ethylene glycol, polyethylene glycol, butylene
glycol, diethylene glycol, triethylene glycol, gamma-butyrolactone,
propylene carbonate, dimethylformamide, monoethanolamine,
N-methyl-2-pyrrolidinone, and mixtures of thereof.
28. A product comprising the carbon aerogel of claim 1, wherein
said product is selected from the group consisting of: a rubber,
plastic, plastic dispersion, adhesive, printing ink toner, coatin,
battery, fuel cell, ceramic, dye, paper, bitumen, and concrete.
29. The product of claim 28, wherein said product is an inkjet
ink.
30. The product of claim 28, wherein said product is a rubber or
plastic.
Description
[0001] The invention relates to carbon aerogels, to a process for
production thereof and to the use thereof.
[0002] U.S. Pat. No. 4,997,804 discloses organic aerogels produced
from resorcinol-formaldehyde, hydroquinone-resorcinol-formaldehyde,
phloroglucinol-resorcinol-formaldehyde and
catechol-resorcinol-formaldehyde. This process forms macroscopic
shaped bodies whose volume is determined by the reactor
geometry.
[0003] Moreover, U.S. Pat. No. 5,508,341 discloses a process for
producing organic aerogels, wherein an aqueous organic phase is
stirred in mineral oil until the organic phase polymerizes to a
gel. The organic aerogels thus obtained have a particle size of 1
.mu.m to 3 mm.
[0004] WO 02/12380 discloses porous resins which are carbonized to
mesoporous carbon with a particle size of 2 .mu.m to 2 mm.
[0005] WO 01/19904, U.S. Pat. No. 6,737,445 (B2), U.S. Pat. No.
6,297,293 (B1), US2002065333 (A1) disclose processes for producing
monolithic polymer or carbon structures with defined
mesoporosity.
[0006] Barral (Journal of Non-Crystalline Solids, Vol. 225, p.
46-50, 1998), Wu and Fu (Microporous and Mesoporous Materials, Vol.
96, p. 115-120, 2006) and Wu et al. (Journal of Non-Crystalline
Solids 351 (2005) 915-921) disclose that monolithic polymer or
carbon structures with defined porosity can be produced by a
two-stage process (pH shift instead of constant pH).
[0007] A disadvantage of the known carbon aerogels is the poor
dispersibility, for example in coating applications.
[0008] It is an object of the invention to provide a carbon aerogel
which, owing to its fine division, has good dispersibility.
[0009] The invention provides a carbon aerogel, which is
characterized in that the mean particle size is less than 1 .mu.m,
preferably between 0.05 and 1 .mu.m, more preferably between 0.1
and 1 .mu.m, most preferably between 0.5 and 0.95 .mu.m.
[0010] The mean particle size is determined by means of laser
diffraction to ISO 13320-1 (1999). To evaluate the diffraction
spectrum measured, the Mie theory with the assumption of spherical
particles is employed. The laser diffraction analysis instrument
used is a HORIBA LA-920. To analyse particle sizes<1 .mu.m, it
is necessary to have information about the scattering in the
sideways and backward direction. For this reason, the instrument
used utilizes 13 different detectors, 12 for measurement in the
sideways and backward direction, and also, through a Fourier lens,
an array of 75 photodiodes for measurement in the forward
direction. The light sources used are a tungsten lamp (50 W) whose
light is filtered to 405 nm, and an He--Ne laser (0.1 W) with a
wavelength of 632.8 nm.
[0011] For the measurement, the carbon aerogel is first introduced
at room temperature, with the aid of a magnetic stirrer, into
distilled water which has been adjusted with 0.1 M NaOH to a pH of
9-10. The solids concentration is 1% by weight. The dispersion is
effected in a water-cooled 30 ml snap-lid bottle by means of an
ultrasound finger (from Bandelin, 70 W, pulsation 80) for 4.5
minutes. In a further step, the dispersed suspension is introduced
dropwise into the dispersion liquid present in the wet cell in the
analysis instrument (distilled water adjusted to pH 9-10 with 0.1 M
NaOH) until laser shadowing between 5 and 10% is achieved. The
pumped circulation of the suspension now present in the analysis
instrument into the test cell is effected by means of the stirrer
incorporated into the analysis instrument.
[0012] The diffraction spectrum is evaluated by means of the Mie
theory and a relative refractive index of 1.5 and an absorption
index of 0.3. The particle size distribution is shown as the
numerical distribution Q.sub.0 by conversion from the corresponding
volume distribution. The mean particle size here refers, according
to ISO 13320-1, to the x.sub.50 of the Q.sub.0 distribution.
[0013] The inventive carbon aerogel may have a mean fractal
dimension of 1.0 to 2.7, preferably of 1.1 to 2.5, more preferably
of 1.2 to 2.3.
[0014] The mean fractal dimension of the carbon aerogel is
determined by means of image analysis of transmission electron
micrographs according to Rogak et al. (Aerosol Science and
Technology, Vol. 18, 1993, p. 25-47).
[0015] The inventive carbon aerogel may have a density of 0.005-2.0
g/cm.sup.3, preferably 0.15-1.5 g/cm.sup.3, more preferably
0.35-1.3 g/cm.sup.3.
[0016] The density of the carbon aerogel is determined by the
determination of the specific pore volume in N.sub.2 adsorption
measurements. When the specific pore volume v.sub.p is known from
the N.sub.2 adsorption measurement, the following expression is
obtained for the density .rho..sub.C-A of the carbon aerogel:
.rho..sub.C-A=1/(1/.rho..sub.C+v.sub.p). For the density of the
carbon .rho..sub.C and for the specific pore volume v.sub.p,
numerical values corresponding to dimensions g/cm.sup.3 and
cm.sup.3/g respectively are used.
[0017] The inventive carbon aerogel may be a foam.
[0018] The pH of the inventive carbon aerogel may be <7.0,
preferably <6.0, more preferably <5.0.
[0019] To determine the pH, 1 g of the carbon aerogel is admixed
with 20 ml of deionized, CO.sub.2-free water in an Erlenmeyer flask
and stirred on a magnetic stirrer for 1 min. Subsequently, the
glass electrode (Hamilton Polilyte Pro 120) of the pH analysis
instrument (Titroprocessor 686, from Metrohm) is immersed approx.
10 mm into the suspension, ensuring that the electrode touches
neither the sediment formed nor the vessel wall. As soon as a
constant value has been established, the pH is read off.
[0020] The inventive carbon aerogel may have an STSA value of
20-1300 m.sup.2/g, preferably of 30-1000 m.sup.2/g, more preferably
of 50-800 m.sup.2/g.
[0021] The STSA measurement is effected according to DIN ISO 9277
(1995).
[0022] The inventive carbon aerogel may have a BET value of 20-1500
m.sup.2/g, preferably of 100-1200 m.sup.2/g, more preferably of
400-900 m.sup.2/g.
[0023] The BET surface area is determined to DIN ISO 9277 (1995) in
a NOVA e2000 sorption analysis instrument from QUANTACHROME. The
sorption gas used is nitrogen. Before the determination, the
samples are baked at a temperature of 350.degree. C. and a pressure
of <13.3 Pa for more than 12 hours. The sorption isotherms are
evaluated to determine the BET surface area in the relative
pressure range p/p.sub.0 of 0.01 to 0.1.
[0024] The inventive carbon aerogel may have a mesopore volume of
0.005-5 cm.sup.3/g, preferably of 0.05-3 cm.sup.3/g, more
preferably of 0.2-2 cm.sup.3/g.
[0025] The inventive carbon aerogel may have a mean mesopore
diameter of 1.8-50 nm, preferably of 5-45 nm, more preferably of
10-35 nm.
[0026] The mesopore volume and the pore radius distribution are
determined to DIN 66134 (1998) by the BJH method from the
desorption data of the isotherms recorded in the relative pressure
range p/p.sub.0 of 0.99 to 0.34.
[0027] In addition, the inventive carbon aerogel may have a
micropore volume of 0.01-1.0 cm.sup.3/g, preferably of 0.05-0.5
cm.sup.3/g, more preferably of 0.1-0.35 cm.sup.3/g.
[0028] The micropore volume is determined to DIN 66135-1, 66135-2,
66135-3 (2001) by the t-plot process. The t-plot is evaluated by
the de Boer equation.
[0029] The inventive carbon aerogel may have a content of volatile
constituents of <15.0% by weight, preferably of <5.0% by
weight, more preferably of <1.5% by weight, most preferably of
<0.5% by weight.
[0030] The volatile constituents>950.degree. C. are determined
on the basis of DIN 53552 (1977). To this end, the sample is first
dried to constant weight in a drying cabinet at 105.degree. C. and
cooled in a desiccator. Subsequently, the sample, in a departure
from DIN 53552, is filled into a quartz crucible (13 ml) and
covered with a lid which has a hole of approx. 2 mm in the centre.
In a muffle furnace, it is finally heated to 950.degree. C. for 7
min. The cooling is again effected in a desiccator. The volatile
fractions are calculated from the weight loss.
[0031] The inventive carbon aerogel may have a My value of 200-400,
preferably of 250-390, more preferably of 260-380.
[0032] The My value is determined by drying the carbon aerogel to
constant weight at 105.degree. C. and then cooling it in a
desiccator.
[0033] 1.3 g of the dried carbon aerogel are weighed into a cup
with a screw lid (PTFE, volume 240 ml). 27.3 g of component A,
consisting of 77% by weight of Alkydal F3100 (60%) (from Bayer) and
23% by weight of diluent (composed of 68.2% by weight of xylene,
13.6% by weight of ethoxypropanol, 9.1% by weight of butanol, 4.6%
by weight of butylglycol and 4.5% by weight of Baysilon (10% by
weight of Baysilon OL 17 (from Bayer) and 90% by weight of
xylene)), and 12.7 g of component B (77% by weight of Maprenal MF
800 (55%) (from Ineos) and 23% by weight of diluent (composition as
in component A)) are additionally weighed in. 275 g of steel beads
(Chromanite, O=3 mm) are added and the lid is screwed on.
[0034] The mixture is shaken for 30 min in an air-cooled shaking
mixer (Skandex BAS 20K mixer (from Lau)). The mixture thus produced
is referred to as black paste. A 90 .mu.m-thick layer of the black
paste is applied with the aid of a doctor blade to a clean,
degreased glass plate (cut microscope slide, AA09013002EA0MNZ, from
Gerhard Menzel Glasbearbeitungswerk GmbH & Co KG) with a
degreased surface and, after venting, baked in a force-air oven at
130.degree. C. over 30 min.
[0035] After cooling, the colour is analysed to DIN 55 979 (1989)
through glass.
[0036] The inventive carbon aerogel may have a Gy value of 50-130,
preferably of 60-130, more preferably of 70-130.
[0037] The Gy value is determined by weighing 60 g of steel beads
(chromanite, O=3 mm), 62.9 g of white paste (GX white pigment paste
from BASF), 2.3 g of hardener (Luwipal 012 (from BASF)) and 16.0 g
of the black paste from the My determination together into a cup
with a screw lid (PTFE, volume 240 ml) and mixing partially. The
cup is closed and the mixture is shaken in an air-cooled shaking
mixer (Skandex mixer BAS 20K (from Lau)) for 30 min.
[0038] The colour paste is processed further within 10 min in order
to prevent sedimentation. To this end, a 90 .mu.m-thick coating
layer is applied with a doctor blade to a clean, degreased glass
plate (cut microscope slide, AA09013002EAOMNZ, from Gerhard Menzel
Glasbearbeitungswerk GmbH & Co KG) and, after venting, baked in
a force-air oven at 130.degree. C. within 30 min. After cooling,
the colour measurement to DIN 55 979 is effected through glass.
[0039] The inventive carbon aerogel may have a carbon content of
85-100% by weight, preferably of 95-100% by weight, more preferably
of 98-100% by weight, most preferably of 99-100% by weight.
[0040] The inventive carbon aerogel may have an electric surface
resistivity of 1 kOhm to 1 TOhm.
[0041] The electrical surface resistivity is measured on the
coating slabs for the My determination. Before the measurement, the
coating slabs are stored at 23.degree. C. and 54% relative air
humidity for 24 hours. The measurement is effected at 23.degree. C.
and 23% relative air humidity with an M 1500 P megaohmmeter (from
Sefelec). The measurement is effected at a voltage of 500 V by
means of two electrodes of application area in each case 5.times.30
mm laden with 275 g of applied weight for 60 s. Between the two
electrodes, there is thus an area of 30.times.30 mm.
[0042] The inventive carbon aerogel (first inorganic phase) may
comprise a second inorganic phase. The second inorganic phase may
be distributed within the carbon aerogel and/or on the surface. The
proportion of the second inorganic phase in the carbon aerogel
based on the total weight may vary from 0.001-0.8 part by weight,
preferably from 0.01-0.5 part by weight, more preferably from
0.03-0.4 part by weight.
[0043] The second inorganic phase may be nanostructured.
[0044] The second inorganic phase may comprise metal elements
and/or ions, for example silicon, gold, silver, platinum,
palladium, ruthenium, rhodium, iridium, nickel, cobalt, iron,
copper, zinc and mixtures of the aforementioned substances, and/or
nonmetal elements, for example carbon black, carbon aerogels,
carbon nanotubes, carbon nanorods, graphite and graphitic
structures, and mixtures of the aforementioned substances.
[0045] The invention further provides a process for producing the
inventive carbon aerogels, which is characterized in that
[0046] (A) a mono- and/or polyhydroxybenzene, an aldehyde and a
catalyst are reacted in a reactor at a reaction temperature T in
the range of 75-200.degree. C., preferably in the range of
80-150.degree. C., more preferably in the range of 95-135.degree.
C., at a pressure of 80-2400 kPa, preferably of 100-700 kPa, more
preferably of 125-500 kPa,
[0047] (B) then the reaction mixture from process step (A) is
sprayed into an acid,
[0048] (C) the resulting product from process step (B) is dried
and
[0049] (D) carbonized.
[0050] The polyhydroxybenzene used in process step (A) may be a di-
or trihydroxybenzene, for example catechol, resorcinol,
phloroglucinol, hydroquinone and mixtures thereof. Preferably, a
monohydroxybenzene (phenol) may be used.
[0051] The aldehyde used in process step (A) may be formaldehyde,
glyoxal, glutaraldehyde, furfural and mixtures thereof. The
aldehyde used in process step (A) may preferably be formaldehyde.
The aldehydes used may also be present as an aqueous solution or in
a solvent.
[0052] In addition, it is possible to use precondensates based on
mono- and/or polyhydroxybenzene and aldehyde, for example resols
and novolac.
[0053] The solvents used may be water, alcohols, ketones and
mixtures of the aforementioned substances.
[0054] Process step (A) can be performed without the addition of a
pore former.
[0055] Process step (A) can be performed with addition of a pore
former.
[0056] The pore formers used may, for example, be ethylene glycol,
polyethylene glycol, butylene glycol, diethylene glycol,
triethylene glycol, gamma-butyrolactone, propylene carbonate,
dimethylformamide, monoethanolamine or N-methyl-2-pyrrolidinone,
and mixtures of the aforementioned substances.
[0057] The catalyst used may be a base, for example an alkali metal
hydroxide or alkaline earth metal hydroxide, with a sufficient
solubility in the solvent. For this purpose, it is possible to use
NaOH, KOH, Na.sub.2CO.sub.3, Li.sub.2CO.sub.3, K.sub.2CO.sub.3,
NH.sub.3 or any other base. Preferably, NaOH may be used.
[0058] The concentration of mono- and/or polyhydroxybenzene and
aldehyde in the reaction mixture may be 10-60% by weight,
preferably 20-40% by weight, more preferably 20-30% by weight.
[0059] The molar ratio of mono- and/or polyhydroxybenzene to
aldehyde may be 1:1 to 1:4, preferably 1:2 to 1:3, in the reaction
mixture of process step (A).
[0060] The molar ratio of the mono- and/or polyhydroxybenzene used
to NaOH may be 0.1 to 100, preferably 0.5 to 50, more preferably
0.7 to 20, in the reaction mixture of process step (A).
[0061] The aldehyde which is used with preference in process step
(A) may be a solution of formaldehyde, water and stabilizers, for
example methanol.
[0062] The pH of the reaction mixture in process step (A) may vary
from 8.5 to 12, preferably from 9.0 to 9.7.
[0063] The starting compounds can be mixed in process step (A) in a
separate vessel, possibly at a temperature different from the
reaction temperature T specified.
[0064] The pressure existing in process step (A) can be applied
from the outside, or generated by increasing the temperature in a
closed system or by a combination of the two.
[0065] On attainment of the reaction temperature T, the reaction
time in process step (A) may be between 0.001 and 1000000 s,
preferably between 1 and 36000 s, more preferably between 60 and
3600 s.
[0066] The reaction in process step (A) can be effected with
stirring.
[0067] The time at which the reaction mixture from process step (A)
is sprayed into the acid in process step (B) can be determined with
light transmission measurements. The light transmission value at
the time of spraying may, at a wavelength of 475 nm, be less than
80%, preferably between 0.01% and 50%, more preferably between 0.1%
and 40%, of the starting transmission.
[0068] The light transmission can be measured in situ with the E
616 photometer (from Metrohm).
[0069] The acid used in process step (B) may be present either as a
solution or as a gas.
[0070] The acid used in process step (B) may be used either in
concentrated or dilute form.
[0071] The acid used in process step (B) may be an inorganic acid,
for example mineral acid, or organic acid. The mineral acid may be
hydrochloric acid, nitric acid, phosphoric acid or sulphuric acid.
The organic acid may be acetic acid, formic acid or oxalic
acid.
[0072] The acid used may have a pH of less than 2.0, preferably
0.5-1.5, more preferably 0.5-1.0.
[0073] The amount of acid solution used may be at least the amount,
preferably at least five times the amount, of the liquid mixture
from process step (A) introduced.
[0074] The acid solution from process step (B) may have a
temperature of 0-200.degree. C., preferably 10-90.degree. C., more
preferably of 15-50.degree. C.
[0075] The gaseous acid from process step (B) may have a
temperature of 10-300.degree. C., preferably 50-200.degree. C.,
more preferably of 70-180.degree. C.
[0076] The reaction mixture from process step (A) can be sprayed
into the acid by means of nozzles.
[0077] The nozzle orifices may be 0.01 to 3 mm, preferably 0.05 to
2 mm, more preferably 0.1 to 1.5 mm.
[0078] The nozzles used may be one-substance or multisubstance
nozzles.
[0079] The atomizer media used may be gaseous substances, for
example such as air, nitrogen, CO.sub.2, argon and/or vaporous or
gaseous acids such as HCl.
[0080] The nozzles used may be full-cone, hollow-cone, flat-jet and
smooth-jet nozzles.
[0081] The reaction mixture from process step (A) can be sprayed
into the acid through external fields.
[0082] The external fields may be electrical or acoustic fields,
for example ultrasound.
[0083] The reaction mixture from process step (A) can be sprayed
into the acid via rotary atomizers, vibratory atomizers or Venturi
nozzles.
[0084] The droplet size generated by the spraying in process step
(B) may be 50 nm to 3 mm, preferably 100 nm to 1 mm, more
preferably 200 nm to 0.5 mm.
[0085] The residence time in the acid from process step (B) may be
between 0.01 and 100000 s, preferably between 1 and 10000 s, more
preferably between 10 and 5000 s.
[0086] The resulting product of process step (B) can be thickened
and subsequently dried.
[0087] The resulting product from process step (B) can be thickened
by means of centrifugation, sedimentation, filtration, or
thermally.
[0088] The drying in process step (C) can be effected convectively,
supercritically, by means of freeze-drying, infrared radiation,
microwave drying, or as a combination of the aforementioned drying
processes.
[0089] In the case of use of gaseous acid in process step (B),
process step (C) can be carried out within process step (B).
[0090] The drying temperature in the convective drying may be
10-300.degree. C., preferably 50-200.degree. C. The drying
temperature in the freeze-drying may be -50-0.degree. C.,
preferably -20-0.degree. C.
[0091] The convective drying may be carried out as
spray-drying.
[0092] For the spray-drying, the resulting product from process
step (B) may optionally also be used without thickening. The
spray-drying can be carried out at a temperature of 80-300.degree.
C., preferably of 80-250.degree. C.
[0093] The residual moisture content of the product from process
step (C) based on the proportion by mass of the solvent in the
reaction mixture from process step (A) may be 0-90% by weight,
preferably 10-80% by weight, more preferably 65-75% by weight. The
proportion by mass of the solvent is determined
gravimetrically.
[0094] The product obtained from process step (C) may be comminuted
before further processing. A further drying step may follow.
[0095] The carbonization of process step (D) can be carried out at
a temperature of 500-1400.degree. C., preferably 600-900.degree.
C., more preferably 650-800.degree. C. The carbonization can be
effected with exclusion of oxygen, for example under protective
gas, preferably nitrogen or argon, or under reduced pressure. The
carbonization can be effected by means of infrared, microwave,
plasma, electrical or thermal heating.
[0096] The process according to the invention can be carried out
continuously or batchwise.
[0097] The carbon aerogel obtained from process step (D) can be
aftertreated, for example oxidized and/or activated, in a
subsequent step.
[0098] The aftertreatment can be effected physically and/or
chemically.
[0099] The carbon aerogel which has been obtained from process step
(D) and optionally aftertreated can be granulated for better
handling.
[0100] The granulated carbon aerogel can be wet-, dry-, oil-and/or
wax-granulated.
[0101] The granulation liquids used may be water, silanes or
hydrocarbons, for example petroleum or cyclohexane, with or without
addition of binders, for example molasses, sugars, lignosulphonates
and numerous other substances, alone or in combination with one
another.
[0102] The inventive carbon aerogels can be used, inter alia, as a
filler, reinforcing filler, UV stabilizer, electrode material,
sound absorber, thermal insulation material, catalyst, catalyst
support, conductivity additive, absorber for gas and/or liquid
formulations or pigment.
[0103] The inventive carbon aerogels can be used, inter alia, in
rubber, plastic, plastics dispersions, adhesives, printing inks
including inkjet inks, other inks, toners, coatings, batteries,
fuel cells, ceramic, dyes, paper, bitumen, concrete and other
building materials. The inventive carbon aerogels can also be used
as reducing agents in metallurgy.
[0104] The invention further provides a coating which is
characterized in that it comprises the inventive carbon
aerogel.
[0105] The inventive carbon aerogel may be present in the coating
at 0.1 to 30% by weight, preferably 0.5 to 10% by weight.
[0106] The invention further provides a plastics mixture which is
characterized in that it comprises the inventive carbon
aerogel.
[0107] The inventive carbon aerogel may be present in the plastics
mixture at 0.1 to 30% by weight, preferably 0.5 to 10% by
weight.
[0108] The invention further provides a printing ink which is
characterized in that it comprises the inventive carbon
aerogel.
[0109] The inventive carbon aerogel may be present in the printing
ink at 0.1 to 50% by weight, preferably 0.5 to 40% by weight.
[0110] The invention further provides an ink which is characterized
in that it comprises the inventive carbon aerogel.
[0111] The inventive carbon aerogel may be present in the ink at
0.1 to 50% by weight, preferably 0.5 to 40% by weight.
[0112] The invention further provides a rubber mixture which is
characterized in that it comprises the inventive carbon
aerogel.
[0113] The inventive carbon aerogel may be present in the rubber
mixture at 0.1-200 parts by weight, preferably 5-150 parts by
weight, based on the rubber in the rubber mixture.
[0114] The inventive carbon aerogels have the advantage that, owing
to the fineness, the dispersibility is improved over the carbon
aerogels known from the prior art.
[0115] The process according to the invention has the advantage
that a fine product is obtained directly in the process according
to the invention.
EXAMPLE 1
Comparative Example
Barral, Journal of Non-Crystalline Solids, Vol. 225, p. 47 (Double
Step Process), 1998
[0116] 0.68 g of phloroglucinol is dissolved in 101.6 g of water at
room temperature. 0.32 g of 37% formaldehyde solution is added to
the solution. Subsequently, 0.02 g of calcium hydroxide is added. A
closed glass vessel containing the solution is heated without
stirring in a silicone oil bath at 90.degree. C. After a 5-minute
residence time in the silicone oil bath, the still liquid solution
is cooled to room temperature. Subsequently, 0.128 g of 37% HCl
solution is added. The resulting solution is kept at a temperature
of 92.degree. C. for 72 h. The resulting organic gel is dried at
room temperature and then carbonized in a muffle furnace at
800.degree. C. under nitrogen for 1.5 hours. The resulting carbon
system has a particle size distribution with x.sub.50=1.07 .mu.m
(mean particle size) and x.sub.95=3.09 .mu.m. The carbon aerogel
has a specific surface area of 233.5 m.sup.2/g and a mesopore
volume of 0.008 cm.sup.3/g.
EXAMPLE 2
Comparative Example
WO 02/12380 A2, Examples 1-2
[0117] Examples 1-2 mentioned in the patent WO 02/12380 A2 are
reworked according to the description.
[0118] The resulting carbon system has a particle size distribution
which cannot be characterized fully by means of the analysis method
specified (x.sub.95>3.0 mm). The carbon aerogel has a specific
surface area of 535.2 m.sup.2/g and a mesopore volume of 0.459
cm.sup.3/g. The M.sub.y value of this carbon aerogel is 226.9.
EXAMPLE 3
[0119] 4.5 g of phenol are dissolved in 19.5 g of water at room
temperature. 11.77 g of 37% formaldehyde solution are added to the
solution. Subsequently, the solution is adjusted to the pH of 9.1
with 0.73 g of 25% sodium hydroxide solution. A closed glass vessel
containing the solution is heated without stirring in a silicone
oil bath at 90.degree. C. After an eight-hour residence time in the
silicone oil bath, the still liquid solution is sprayed by means of
a Schlick model 121 V, type 8 hollow-cone nozzle (bore 0.8 mm) at a
pressure of 2.5 bar into ten times the volume of the HCl solution
at pH=1.0. After 20 hours of residence time at room temperature,
the acid solution containing the organic fine particulate sediment
is dried at 160.degree. C. in a spray dryer. The dry gel is
carbonized in a muffle furnace at 800.degree. C. under nitrogen for
1.5 hours. The resulting fine particulate carbon system has a
particle size distribution with x.sub.50=316 nm (mean particle
size) and x.sub.95<512 nm. The carbon aerogel has a specific
surface area of 613.3 m.sup.2/g and a mesopore volume of 0.044
cm.sup.3/g. The M.sub.y value of this carbon aerogel is 239.0. The
M.sub.y value is higher than in example 2 (comparative example) and
thus indicates better dispersibility.
EXAMPLE 4
[0120] 1.9 g of phenol (P) are dissolved in 11.52 g of water at
room temperature. 4.97 g of 37% formaldehyde (F) solution are added
to the solution. Subsequently, the solution is adjusted to the pH
of 9.1 with 0.31 g of 25% sodium hydroxide solution. A closed
vessel containing the solution is heated without stirring in a
silicone oil bath at 85.degree. C. After a ten-hour residence time
in the silicone oil bath, the still liquid solution is sprayed by
means of a Schlick model 121 V, type 8 hollow-cone nozzle (bore 0.8
mm) at a pressure of 2.5 bar into ten times the volume of the
oxalic acid solution with pH=0.95 at a temperature of 85.degree. C.
The acid solution containing the organic fine particulate sediment
formed is stored in a likewise closed vessel at 85.degree. C. After
90 hours, the acid solution containing the fine particulate
sediment is dried in a spray dryer at 160.degree. C. The dried gel
is carbonized in a muffle furnace at 800.degree. C. under nitrogen
for 1.5 hours. The resulting fine particulate carbon system has a
particle size distribution with x.sub.50=495 nm (mean particle
size) and x.sub.95=917 nm. The carbon aerogel has a specific
surface area of 734.8 m.sup.2/g and a mesopore volume of 1.07
cm.sup.3/g. The mesopore distribution is shown in FIG. 1. The
M.sub.y value of this carbon aerogel is 285.7. The M.sub.y value is
higher than in example 2 (comparative example) and thus indicates
better dispersibility.
EXAMPLE 5
[0121] 1.9 g of phenol are dissolved in 11.52 g of water at room
temperature. 4.97 g of 37% formaldehyde solution are added to the
solution. Subsequently, the solution is adjusted to the pH of 9.1
with 0.31 g of 25% sodium hydroxide solution. A closed vessel
containing the solution is heated without stirring in a silicone
oil bath at 85.degree. C. After a ten-hour residence time in the
silicone oil bath, the still liquid solution is sprayed by means of
a Schlick model 121 V, type 8 hollow-cone nozzle (bore 0.8 mm) at a
pressure of 2.5 bar into ten times the volume of the oxalic acid
solution with pH=0.95 at a temperature of 85.degree. C. The acid
solution containing the organic fine particulate sediment formed is
stored in a likewise closed vessel at 85.degree. C. After 90 hours,
the acid solution containing the fine particulate sediment is dried
in a spray dryer at 160.degree. C. The dried gel is carbonized in a
muffle furnace at 800.degree. C. under nitrogen for 1.5 hours. The
resulting fine particulate carbon system has a particle size
distribution with x.sub.50=770 nm (mean particle size) and
x.sub.95=1916 nm. The carbon aerogel has a specific surface area of
699.9 m.sup.2/g and a mesopore volume of 0.85 cm.sup.3/g. The
mesopore distribution is shown in FIG. 2. The M.sub.y value of this
carbon aerogel is 272.7. The M.sub.y value is higher than in
example 2 (comparative example) and thus indicates better
dispersibility.
EXAMPLE 6
[0122] 1.9 g of phenol are dissolved in 11.52 g of water at room
temperature. 4.97 g of 37% formaldehyde solution are added to the
solution. Subsequently, the solution is adjusted to the pH of 9.1
with 0.31 g of 25% sodium hydroxide solution. A closed vessel
containing the solution is heated without stirring in a silicone
oil bath at 125.degree. C. The interior of the vessel is
pressurized with a pressure of 4.5 bar (absolute). After an
18-minute residence time in the silicone oil bath, the still liquid
solution is sprayed by means of a Schlick model 121 V, type 8
hollow-cone nozzle (bore 0.8 mm) at a pressure of 2.5 bar into ten
times the volume of HCl with pH=0.95 at a temperature of 25.degree.
C. The acid solution containing the organic fine particulate
sediment formed is stored in a likewise closed vessel at 25.degree.
C. After 24 hours, the acid solution containing the fine
particulate sediment is dried in a spray dryer at 200.degree. C.
The dried gel is carbonized in a muffle furnace at 800.degree. C.
under nitrogen for 1.5 hours. The resulting fine particulate carbon
system has a particle size distribution with x.sub.50=810 nm (mean
particle size) and x.sub.95=1956 nm. The carbon aerogel has a
specific surface area of 700.0 m.sup.2/g and a mesopore volume of
1.03 cm.sup.3/g. The mesopore distribution is shown in FIG. 3. The
M.sub.y value of this carbon aerogel is 276.3. The M.sub.y value is
higher than in example 2 (comparative example) and thus indicates
better dispersibility.
EXAMPLE 7
[0123] 3.8 g of phenol are dissolved in 23.00 g of water at room
temperature. 9.84 g of 37% formaldehyde solution are added to the
solution. Subsequently, the solution is adjusted to the pH of 9.1
with 0.62 g of 25% sodium hydroxide solution. A closed vessel
containing the solution is heated without stirring in a silicone
oil bath at 125.degree. C. The interior of the vessel is
pressurized with a pressure of 4.5 bar (absolute). After a
19-minute residence time in the silicone oil bath, the still liquid
solution is sprayed by means of a Schlick model 121 V, type 8
hollow-cone nozzle (bore 0.8 mm) at a pressure of 2.5 bar into ten
times the volume of HCl with pH=1.01 at a temperature of 25.degree.
C. The acid solution containing the organic fine particulate
sediment formed is stored in a likewise closed vessel at 25.degree.
C. After 24 hours, the acid solution containing the fine
particulate sediment is dried in a spray dryer at 220.degree. C.
The dried gel is carbonized in a muffle furnace at 800.degree. C.
under nitrogen for 1.5 hours. The resulting fine particulate carbon
system has a particle size distribution with x.sub.50=830 nm (mean
particle size) and x.sub.95=1990 nm. The carbon aerogel has a
specific surface area of 689.9 m.sup.2/g and a mesopore volume of
0.91 cm.sup.3/g. The mesopore distribution is shown in FIG. 4. The
M.sub.y value of this carbon aerogel is 274.2. The M.sub.y value is
higher than in example 2 (comparative example) and thus indicates
better dispersibility.
* * * * *