U.S. patent application number 17/377405 was filed with the patent office on 2021-11-04 for graphene dispersion.
This patent application is currently assigned to Taiwan Textile Research Institute. The applicant listed for this patent is Taiwan Textile Research Institute. Invention is credited to Ting-Yu Chang, Hsin-Chun Li, Bo-Fan Lin, Ting-Yu Wu.
Application Number | 20210340382 17/377405 |
Document ID | / |
Family ID | 1000005720473 |
Filed Date | 2021-11-04 |
United States Patent
Application |
20210340382 |
Kind Code |
A1 |
Wu; Ting-Yu ; et
al. |
November 4, 2021 |
GRAPHENE DISPERSION
Abstract
A graphene dispersion is provided. The graphene dispersion is
formed by a graphene powder and a processing solvent, wherein the
graphene in the graphene dispersion has an average diameter of 0.5
.mu.m to 1 .mu.m, 3 to 5 layers, a solid content of 5% to 50%, and
a residue oxygen content less than 1 wt %, and after being left to
stand for 12 hours, the graphene dispersion has a distribution
concentration increasing from the top section to the bottom section
of the storage container, a viscosity of 5000 cps to 8000 cps, and
a graphene concentration of 20 wt %.
Inventors: |
Wu; Ting-Yu; (New Taipei
City, TW) ; Chang; Ting-Yu; (New Taipei City, TW)
; Li; Hsin-Chun; (New Taipei City, TW) ; Lin;
Bo-Fan; (New Taipei City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Taiwan Textile Research Institute |
New Taipei City |
|
TW |
|
|
Assignee: |
Taiwan Textile Research
Institute
New Taipei City
TW
|
Family ID: |
1000005720473 |
Appl. No.: |
17/377405 |
Filed: |
July 16, 2021 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15705274 |
Sep 15, 2017 |
|
|
|
17377405 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C01P 2004/62 20130101;
C01P 2006/22 20130101; C01B 32/194 20170801; C01P 2004/61 20130101;
C01B 32/22 20170801; C01B 2204/28 20130101; C09D 7/20 20180101;
C01B 2204/04 20130101; C01B 32/19 20170801; C09D 1/00 20130101;
B01J 19/1806 20130101; C01B 32/225 20170801 |
International
Class: |
C09D 1/00 20060101
C09D001/00; B01J 19/18 20060101 B01J019/18; C01B 32/194 20060101
C01B032/194; C01B 32/19 20060101 C01B032/19; C09D 7/20 20060101
C09D007/20; C01B 32/22 20060101 C01B032/22; C01B 32/225 20060101
C01B032/225 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2016 |
TW |
105137512 |
Claims
1. A graphene dispersion formed by a graphene powder and a
processing solvent, wherein a graphene in the graphene dispersion
has an average diameter of 0.5 .mu.m to 1 .mu.m, 3 to 5 layers, a
solid content of 5% to 50%, and a residue oxygen content less than
1 wt %, and after being left to stand for 12 hours, the graphene
dispersion has a concentration distribution increasing from a top
section to a bottom section in a storage container, a viscosity of
5000 cps to 8000 cps, and a graphene concentration of 20 wt %.
2. The graphene dispersion of claim 1, wherein a concentration
difference between the top section and the bottom section in the
storage container is 0.1 wt % to 20 wt %.
3. The graphene dispersion of claim 1, wherein the graphene powder
has 5 to 10 layers.
4. The graphene dispersion of claim 1, wherein an average diameter
of the graphene powder is 3 .mu.m to 15 .mu.m.
5. The graphene dispersion of claim 1, wherein a residue oxygen
content of the graphene powder is less than 0.1 wt %.
6. The graphene dispersion of claim 1, wherein the processing
solvent comprises a hydrocarbon solvent, a halogenated hydrocarbon
solvent, an alcohol solvent, a phenol solvent, a ketone solvent, an
ester solvent, an ether solvent, an acetal solvent, an acid
solvent, an acid anhydride solvent, a nitrogen-containing compound
solvent, or a sulfur-containing compound solvent.
7. The graphene dispersion of claim 1, wherein the processing
solvent has an interfacial tension of 15 mN/m to 50 mN/m and a
Hansen solubility parameter of 5.0 MPa.sup.0.5 to 15
MPa.sup.0.5.
8. The graphene dispersion of claim 1, wherein based on a total
weight of the graphene dispersion, an amount of the graphene powder
is 0.001 wt % to 30 wt %.
9. The graphene dispersion of claim 1, wherein the processing
solvent has a polar force parameter of 0.5 MPa.sup.0.5 to 5.5
MPa.sup.0.5, a dispersing power parameter of 7.0 MPa.sup.0.5 to 9.0
MPa.sup.0.5, and a hydrogen bond force parameter of 2.0 MPa.sup.0.5
to 7.0 MPa.sup.0.5.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application of and claims
the priority benefit of U.S. application Ser. No. 15/705,274, filed
on Sep. 15, 2017, now allowed. The prior U.S. application Ser. No.
15/705,274 claims the priority benefit of Taiwan application serial
no. 105137512, filed on Nov. 16, 2016. The entirety of each of the
above-mentioned patent applications is hereby incorporated by
reference herein and made a part of this specification.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The invention relates to an air flow generating device, a
graphene dispersion, and a preparation method thereof, and more
particularly, to an air flow generating device for preparing a
graphene powder with low oxygen content, a graphene dispersion, and
a preparation method thereof.
Description of Related Art
[0003] Graphene has a two-dimensional structure formed by carbon
atoms bonded with sp.sup.2 covalent bonds, and has special
properties such as a relatively high carrier mobility, hardness,
thermal conductivity, and large surface area. Therefore, in recent
years, graphene has become a highly-valued research target in
fields such as medicine, electronics, and optoelectronic
components. At the same time, the graphene dispersion, which is
composed of graphene and a specific solvent, can be extensively
applied in the coating field, and is an important additive in
products such as conductive coatings and auxiliaries thereof,
lithium ion electrode auxiliaries, anti-corrosion coating
additives, and graphene heat spread films.
[0004] However, the known graphene dispersion preparation technique
has disadvantages for commercialization such as waste water
pollution and toxic waste exhaust issues in chemical modification
process, cost issues related to lower carbon yield for physical
method, for example, mechanical peeling, ultrasonic oscillation,
and ball milling method. These above disadvantages will strongly
increase the cost and difficulty of production management.
Moreover, current commercial products of graphene dispersion mostly
have low solid content (usually lower than 1%), wherein excess
solvent significantly causes subsequent resin properties and the
following processability problems for less controlling rheology or
viscosity, and therefore these commercial products are not suitable
for application in the coating field. Moreover, although surface
modification and excess dispersing agent (greater than 5%) could
enhance the dispersion of graphene, both may destroy intrinsic
properties of graphene coating by structure damage and
interconnection of blockage of graphene, which are respectively
generated along with chemical treatment and caused by coverage of
dispersion agent.
[0005] Based on the above, development of a graphene dispersion
that can meet both of environmental protection and
commercialization needs with high solid content, high production
yield, variation option of solvent, controllable rheology of
suspension, long stable duration of suspension, reliable quality of
products, and low manufacturing cost is still a crucial problem for
graphene industry.
SUMMARY OF THE INVENTION
[0006] The invention provides an air flow generating device for
preparing a graphene powder with low oxygen content, a graphene
dispersion, and a preparation method thereof. The graphene powder
fabricated by the air flow generating device is used to prepare the
graphene dispersion for surmounting most of obstacles of current
technical barriers in the present graphene dispersion process
effectively. As a result, a high-concentration graphene dispersion
having a specific concentration variation can be prepared to not
only meet environmental needs, but also have significantly high
solid content, good production yield, excellent suspension, and
homogenize product specifications, and to significantly reduce the
manufacturing cost of the graphene dispersion.
[0007] The graphene dispersion of the invention is formed by a
graphene powder and a processing solvent using the preparation
method of the graphene dispersion, wherein the graphene in the
graphene dispersion has an average diameter of 0.5 .mu.m to 1
.mu.m, 3 to 5 layers, a solid content of 5% to 50%, and a residue
oxygen content less than 1 wt %. The graphene dispersion of the
invention has the nature of constant viscosity of 5000 cps to 8000
cps, a graphene concentration of 20 wt %, and after being left to
stand for 12 hours, a concentration distribution of the graphene
dispersion increases from the top section to the bottom section in
a storage container.
[0008] In an embodiment of the invention, the concentration
difference between the top section and the bottom section in the
graphene dispersion is 0.1 wt % to 20 wt %.
[0009] In an embodiment of the invention, the graphene powder has 5
to 10 layers.
[0010] In an embodiment of the invention, the graphene powder has
an average diameter of 3 .mu.m to 15 .mu.m.
[0011] In an embodiment of the invention, the graphene powder has a
residue oxygen content less than 0.1 wt %.
[0012] In an embodiment of the invention, the processing solvent
includes a hydrocarbon solvent, a halogenated hydrocarbon solvent,
an alcohol solvent, a phenol solvent, a ketone solvent, an ester
solvent, an ether solvent, an acetal solvent, an acid solvent, an
acid anhydride solvent, a nitrogen-containing compound solvent, a
sulfur-containing compound solvent, a polyfunctional group solvent,
or an inorganic solvent.
[0013] In an embodiment of the invention, the processing solvent
has an interfacial tension of 15 mN/m to 50 mN/m and a Hansen
solubility parameter of 5.0 MPa.sup.0.5 to 15 MPa.sup.0.5.
[0014] In an embodiment of the invention, based on the total weight
of the graphene dispersion, the amount of the graphene powder is
0.001 wt % to 30 wt %.
[0015] In an embodiment of the invention, the processing solvent
has a polar force parameter of 0.5 MPa.sup.0.5 to 5.5 MPa.sup.0.5,
a dispersing power parameter of 7.0 MPa.sup.0.5 to 9.0 MPa.sup.0.5,
and a hydrogen bond force parameter of 2.0 MPa.sup.0.5 to 7.0
MPa.sup.0.5.
[0016] Based on the above, the air flow generating device of the
invention leads to a transformation from graphite raw materials to
a graphene powder with low oxygen content using a direct continuous
physical method, and the graphene powder has specific features of a
narrow distribution of layer number for the uniformity, a uniformed
diameter distribution for the following dispersion process with a
low energy, and well-crystalized structure for the good
compatibility with the specific solvent. At the same time, the
invention provides a high solid content graphene dispersion
utilized the graphene powder. The graphene dispersion has
advantages such as high yield for the uniformity of products and
also for the benefit of cost, high and adjustable solid content for
easy handling in the following process, and therefore the issues of
low solid content and small solvent selection of graphene
dispersion commercial products can be solved, such that
processability and the adaptability to different coating processes
can be improved to facilitate application in the coating field.
[0017] In order to make the aforementioned features and advantages
of the disclosure more comprehensible, embodiments accompanied with
figures are described in detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments of the invention and, together with the description,
serve to explain the principles of the invention.
[0019] FIG. 1 is the cross section of an air flow generating
device.
[0020] FIG. 2 is a perspective view of the rotating awl of FIG.
1.
[0021] FIG. 3A is a schematic diagram of the top surface and bottom
surface of the top of a rotating awl.
[0022] FIG. 3B is a schematic diagram of the top surface and bottom
surface of the center of the rotating awl.
[0023] FIG. 3C is a schematic diagram of the top surface and bottom
surface of the bottom of the rotating awl.
[0024] FIG. 4 is a flow schematic diagram of the manufacturing
method of a graphene powder.
DESCRIPTION OF THE EMBODIMENTS
[0025] The invention provides an air flow generating device for
preparing a graphene powder, a graphene dispersion, and a
preparation method thereof, wherein the graphene powder prepared by
the air flow generating device is used to prepare the graphene
dispersion. In the following, the details of the air flow
generating device, the graphene dispersion, and the preparation
method thereof of the invention are described.
<Air Flow Generating Device>
[0026] FIG. 1 is the cross section of an air flow generating
device, and FIG. 2 is a perspective view of the rotating awl of
FIG. 1. Referring to both FIG. 1 and FIG. 2, an air flow generating
device 100 includes an outer bushing 110 and a rotating awl 120,
wherein the outer bushing 110 has a chamber 112, an intake opening
114, and an outtake opening 116. The intake opening 114 is
connected to the chamber 112 from below and the outtake opening 116
is connected to the chamber 112 from above, and the chamber 112 has
a necked portion 112a. The rotating awl 120 and the chamber 112 are
conformally disposed in the chamber 112, and the rotating awl 120
and the inner wall of the chamber 112 have a slit spacing 108 in
between, wherein the rotating awl 120 includes a rotating body 122
and a plurality of screw threads 124, and the screw threads 124 are
distributed on the outer surface of the rotating body 122 from a
bottom 1221 of the rotating body 122 toward the top of the rotating
body 122 in a spiral manner.
[0027] In an embodiment, the quantity of the screw threads 124 can
be between 8 and 32, and the quantity of the screw threads 124 in
another embodiment can be between 12 and 18. The quantity of the
screw threads 124 is not limited by the description herein, and the
designer can change the quantity of the screw threads 124 out of
consideration of other factors based on actual need. Moreover, a
top surface 120a of the rotating awl 120 and a top surface 112b of
the necked portion 112a are level.
[0028] FIG. 3A is a schematic diagram of the top surface and bottom
surface of the top of a rotating awl, FIG. 3B is a schematic
diagram of the top surface and bottom surface of the center of the
rotating awl, and FIG. 3C is a schematic diagram of the top surface
and bottom surface of the bottom of the rotating awl. Referring to
all of FIG. 3A, FIG. 3B, and FIG. 3C, the rotating body 122 can be
divided into a bottom 1221, a top 1222, and a center 1223 located
between the bottom 1221 and the top 1222, and since the screw
threads 124 are formed on the outer surface (not shown) of the
rotating body 122, cross sections of the rotating awl 120 are taken
along the circumferential direction of the rotating awl 120, and
the cross sections of the rotating awl 120 are substantially
stellate. The depth and width of the screw threads 124 can be
designed based on actual need.
[0029] Based on the above, the diameter of the rotating body 122 is
decreased from the bottom 1221 to the top 1222. More specifically,
the diameter of a bottom surface 1221a of the bottom 1221 of the
rotating awl 120 is greater than the diameter of a top surface
1221b of the bottom 1221, the diameter of a bottom surface 1223a of
the center 1223 is equal to the diameter of the top surface 1221b
of the bottom 1221, and the diameter of the bottom surface 1223a of
the center 1223 is greater than the diameter of a top surface 1223b
of the center 1223, as shown in FIG. 3B and FIG. 3C. Moreover, the
diameter of a bottom surface 1222a of the top 1222 is equal to the
diameter of the top surface 1223b of the center 1223, and the
diameter of the bottom surface 1222a of the top 1222 is greater
than the diameter of a top surface 1222b of the top 1222, as shown
in FIG. 3A and FIG. 3B. Due to the difference among the diameters
of the bottom 1221, the center 1223, and the top 1222, the quantity
of the screw threads 124 located in each portion is also
different.
[0030] It should be mentioned that, the rotating body 122 can be
integrally formed or formed by the assembly of three columns having
different diameters. The screw threads 124 located at the top 1222
of the rotating body 122 can be disposed at the same intervals, and
an angle .theta.1 relative to the top surface 1222b or the bottom
surface 1222a of the top 1222 is fixed, and is, for instance, 15
degrees to 35 degrees; the screw threads 124 located at the center
1223 can also be disposed at the same intervals, and an angle
.theta.2 relative to the top surface 1223b or the bottom surface
1223a of the center 1223 is fixed, and is, for instance, 35 degrees
to 70 degrees; and the screw threads 124 located at the bottom 1221
can also be disposed at the same intervals, and an angle .theta.3
relative to the top surface 1221b or the bottom surface 1221a of
the bottom 1221 is fixed, and is, for instance, 70 degrees to 90
degrees. However, the angles of the screw threads 124 at the top
1222, the center 1223, and the bottom 1221 are not exactly the
same. For instance, the angle of the screw threads 124 located at
the top 1222 is 25 degrees, the angle of the screw threads 124
located at the bottom 1221 is 60 degrees, and the angle of the
screw threads 124 located at the center 1223 is about 42.5 degrees.
Moreover, the angle of the screw threads 124 at the junctions of
the top 1222, the center 1223, and the bottom 1221 can be adjusted
in response to changes in diameter, and the angle can be 35 degrees
to 85 degrees.
[0031] When the air flow generating device 100 of FIG. 1 is used,
the rotating awl 120 rotates at a rotating speed of 3000 rpm to
7000 rpm in the chamber 112. In general, when the rotating awl 120
rotates in the chamber 112, if the outer surface of the rotating
awl 120 and the surface of the inner wall of the chamber 112 are
smooth, then gas entering from the intake opening 114 is driven by
the rotation of the rotating awl 120 to produce a rotating air flow
and is dissipated from the outtake opening 116 located at the top
1222 of the outer bushing 110. Via the centrifugal force produced
by the rotation of the rotating awl 120, the rotating air flow
produces some horizontal component, but compared to the force of
the air flow escaping upward from the outtake opening 116, the
horizontal component is not significant, and is almost
negligible.
[0032] In particular, via the screw threads 124 formed on the outer
surface of the rotating body 122 in a spiral distribution, when gas
enters the chamber 112 from the intake opening 114 and is driven by
the rotating awl 120 to form a rotating air flow, the centrifugal
force guided by the screw threads 124 makes the horizontal
component of the rotating air flow significant.
[0033] Moreover, although the rotating awl 120 and the outer
bushing 110 are conformal, the slit spacing 108 between the
rotating body 122 and the inner wall of the chamber 112 changes
from the bottom surface 1221a of the bottom 1221 of the rotating
body 122 to the top surface 1222b of the top 1222 of the rotating
body 122, and is, for instance, decreased. Such design method is
based on a gas flux equation to compress the gas entering the air
flow generating device 100 when flowing upward such that air flow
is accelerated from bottom to top. Since the chamber 112 provides
one wide space S on the top surface of the top 1222 of the rotating
body 122, the air flow entering the wide space S after leaving the
rotating awl 120 is expanded, and is then dissipated from the
outtake opening 116.
[0034] In short, the air flow introduced from the intake opening
114 experiences the flow rate changes of slow, fast, and slow from
the bottom 1221 to the top 1222 of the rotating awl 120, wherein
since the air flow is immediately released to a relatively larger
space S after leaving the slit spacing 108 between the rotating awl
120 and the inner wall of the chamber 112, the volume of the gas is
continuously and rapidly expanded.
[0035] The air flow generating device 100 allows the air flow to
produce a horizontal component via the screw threads 124 and the
slit spacing 108, and after the air flow leaves the screw threads
124, the air flow produces a continuous and rapid gas volume change
in the unit space S, and therefore the production of graphene
powder requiring an intercalation process can be facilitated.
<Graphene Powder>
[0036] Via the air flow generating device, a graphene powder with
low oxygen content can be manufactured. FIG. 4 is a flow schematic
diagram of the manufacturing method of a graphene powder. In the
following, the manufacturing method of a graphene powder floc of an
embodiment of the invention is described with FIG. 4.
[0037] First, referring to FIG. 4, step S110 is performed to
perform a continuous high-speed reciprocating rolling process on a
graphite raw material to form a graphite precursor, wherein the
graphite precursor has a dislocation slippage structure. In the
present embodiment, the intercalation spacing in the graphite raw
material is, for instance, 3.354 .ANG.. The graphite precursor has
an intercalation spacing of, for instance, 3.44 .ANG. to 3.60
.ANG.; an average particle size of, for instance, 10 .mu.m to 100
.mu.m, preferably, for instance, 15 .mu.m to 35 .mu.m; an average
thickness of, for instance, 0.05 .mu.m to 1 .mu.m, preferably, for
instance, 0.3 .mu.m to 0.8 .mu.m; and a residue oxygen content of,
for instance, less than 5%, preferably, for instance, less than 1%.
Since the graphite precursor has a dislocation slippage structure,
an intercalation reaction can be facilitated in a subsequent
process. More specifically, a graphite precursor plate having a
dislocation slippage structure can be formed via the tangential
stress on the plane of a continuous high-speed reciprocating
rolling process, and then a graphite precursor powder is formed via
a dry high-speed polishing process.
[0038] Next, referring further to FIG. 4, step S120 is performed to
subject the graphite precursor to an intercalation reaction via
horizontal compressed air flow to form a graphene-gas intercalation
compound. In the present embodiment, the wind velocity of the
horizontal compressed air flow is, for instance Mach 0.3 to Mach 1,
preferably, for instance, Mach 0.5 to Mach 0.8; and the air volume
is, for instance, 186 CMM to 619 CMM, preferably, for instance, 310
CMM to 495 CMM. More specifically, the horizontal compressed air
flow can be a subcritical fluid, and since the wind velocity is,
for instance, Mach 0.3 or above, the horizontal compressed air flow
can also be referred to as subsonic compressible flow.
[0039] Next, referring further to FIG. 4, step S130 is performed to
subject the graphene-gas intercalation compound to a
swelling/exfoliation process via intercalation air pressure release
to form a graphene aggregate. Next, as shown in FIG. 4, step S140
is performed to make the graphene aggregate suspend, drift, and
collide with one another in the air flow, such that a graphene
powder is produced.
[0040] In the present embodiment, the graphene powder has the
advantages of fixed number of layers and consistent diameter
feature. More specifically, the graphene powder has, for instance,
5 to 10 layers; the thickness is, for instance, 2.5 nm to 4.5 nm;
the residue oxygen content is, for instance, less than 0.1 wt %;
and the bulk density is, for instance, 0.001 g/cm.sup.3 to 2.24
g/cm.sup.3, preferably, for instance, 0.01 g/cm.sup.3 to 0.5
g/cm.sup.3. The average diameter of the graphene powder is, for
instance, 3 .mu.m to 15 .mu.m, and more specifically, the average
diameter is, for instance, 3 .mu.m to 5 .mu.m, 5 .mu.m to 10 .mu.m,
or 10 .mu.m to 15 .mu.m, more preferably, for instance, 3 .mu.m to
5 .mu.m.
<Graphene Dispersion>
[0041] The graphene dispersion of the invention is prepared with
the graphene powder and a processing solvent, wherein based on the
total weight of the graphene dispersion, the amount of the graphene
powder is, for instance, 0.001 wt % to 30 wt %. Since the
preparation of the graphene dispersion is performed using
oligomeric graphene powder with low oxygen content having a
specific number of layers and a specific form, the graphene powder
has the feature of easy homogenization at low energy without
structural damage caused by oxidation based on the characteristics
of fixed number of layers and uniform diameter. As a result, the
resulting graphene dispersion has advantages such as high yield,
high solid content, and adjustable solid content.
[0042] More specifically, the preparation method of the graphene
dispersion of the invention includes the following steps. First, a
homogenization process is performed on the graphene powder and the
processing solvent to prepare a graphene paste. Next, a
layer-thinning process is performed on the graphene paste to
prepare a homogeneous graphene dispersion. In the following, the
details of the preparation method of the graphene dispersion of the
invention are described.
Processing Solvent
[0043] In the present embodiment, the processing solvent can
include a hydrocarbon solvent, a halogenated hydrocarbon solvent,
an alcohol solvent, a phenol solvent, a ketone solvent, an ester
solvent, an ether solvent, an acetal solvent, an acid solvent, an
acid anhydride solvent, a nitrogen-containing compound solvent, a
sulfur-containing compound solvent, a polyfunctional group solvent,
or an inorganic solvent. More specifically, the processing solvent
is, for instance, toluene, xylene (xyl), ethanol, isopropanol
(IPA), butanol, acetone, ethyl acetate, butyl acetate (BAC),
N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP),
N,N-dimethylacetamide (DMAc), or water.
[0044] However, a suitable processing solvent for the invention is
not limited to the examples provided in the above, and other
solvents having the following properties can also be used as the
processing solvent: an interfacial tension of, for instance, 15
mN/m to 50 mN/m, preferably, for instance, 20 mN/m to 40 mN/m; a
Hansen solubility parameter of, for instance, 5.0 MPa.sup.0.5 to 15
MPa.sup.0.5; a polar force parameter of, for instance, 0.5
MPa.sup.0.5 to 5.5 MPa.sup.0.5; a dispersing power parameter of,
for instance, 7.0 MPa.sup.0.5 to 9.0 MPa.sup.0.5; and a hydrogen
bond force parameter of, for instance, 2.0 MPa.sup.0.5 to 7.0
MPa.sup.0.5. More specifically, based on the total weight of the
graphene dispersion, the amount of the processing solvent is, for
instance, 70 wt % to 99.99 wt %.
Homogenization Process
[0045] In the preparation method of the graphene dispersion of the
invention, a homogenization process is performed to form a graphene
paste used as a byproduct for an intermediate process. In the
homogenization process, the average diameter of the graphene powder
is adjusted and changed by producing normal direction stress to the
graphene structure without changing the graphene thickness to
achieve the object of homogenized diameter. As a result, the
suspension of graphene in the liquid can be effectively extended,
wherein the maximum dispersion duration can achieve 150 days or
more, and also dispersant content can be limited.
[0046] In the present embodiment, two major processes of pre-mixing
and severe dispersion in homogenization are utilized, and
homogenization via equipment such as a DC mechanical mixer,
planetary mixer, mixer, ball mill mixer, three roller mixer, single
screw mixer, or double screw mixer, and therefore compared to a
known process in which graphite is used as the raw material and
graphene dispersion is obtained via dispersion, oxidation, peeling,
and centrifugal processes, the invention can solve the issues of,
for instance, low graphene content and reduced conductivity due to
structural damage from oxidation present in prior art.
Graphene Paste
[0047] In the present embodiment, the features of the graphene
paste contain: the graphene has an average diameter of, for
instance, 0.1 .mu.m to 1.5 .mu.m, preferably, for instance, 0.3
.mu.m to 0.8 .mu.m; and the graphene has a thickness of, for
instance, 2.5 nm to 4.5 nm, a residue oxygen content of, for
instance, less than 0.5%, and a solid content of, for instance, 5%
to 50%, most preferably, for instance, 15% to 30%.
Layer-Thinning Process
[0048] In the preparation method of the graphene dispersion of the
invention, a layer-thinning process is performed on the graphene
paste to form a homogeneous graphene dispersion. In the
layer-thinning process, the average thickness of the graphene
powder is changed by producing plane direction stress to the
graphene structure without changing the graphene diameter to
achieve the object of homogenized suspension. As a result,
suspension time and allowable ratio of solid content can be
increased.
[0049] In the present embodiment, the thin film process can contain
two different processes, which are respectively a mixing process
and a high-energy dispersing process. More specifically, the mixing
process can be performed via, for instance, a five-axis mixing
method, ball mill mixing method, or shear mixing method, and in the
high-energy shear process, heavy dispersion can be performed via,
for instance, high-speed homogenization or high-pressure crushing
to form a homogeneous graphene dispersion.
[0050] Via the preparation method of the graphene dispersion of the
invention, a high-concentration graphene dispersion having a
specific concentration variation can be formed without the addition
of any dispersant, and therefore the graphene structure in the
graphene dispersion is not affected by excess dispersing aid, and
good material properties are retained. More specifically, in the
graphene dispersion of the invention, the purity of the graphene is
about 100%, and the average diameter of the graphene in the
graphene dispersion is, for instance, 0.5 .mu.m to 1 .mu.m; the
number of layers is, for instance, 3 to 5; the solid content is,
for instance, 5% to 50%; the residue oxygen content of graphene is,
for instance, less than 1 wt %; and the thickness is, for instance,
0.8 nm to 4.5 nm, preferably, for instance, 1.0 nm to 2.0 nm.
[0051] Moreover, the concentration distribution of the graphene
dispersion can be increasing from the top section to the bottom
section of the storage container after being left to stand for 12
hours, the viscosity is, for instance, 5000 cps to 8000 cps, and
the graphene concentration is, for instance, 20 wt %, wherein the
concentration difference (C %) between the top section and the
bottom section of the storage container is, for instance, 0.1 wt %
to 20 wt %, preferably, for instance, 5 wt % to 15 wt %, and the
maximum stable dispersion duration can achieve 150 days or
more.
[0052] In the following, the graphene dispersion provided by the
invention is described in detail via an experimental example.
However, the following experimental example is not intended to
limit the invention.
Experimental Example
[0053] To prove that the graphene dispersion of the invention is
with higher solid content and stable dispersion, this experimental
example is provided below.
[0054] It should be mentioned that, since the preparation method of
the graphene dispersion is described in detail above, in the
following, details relating to the preparation of the graphene
dispersion are omitted for ease of explaining.
Preparation of Graphene Dispersion
[0055] Based on the preparation method of the graphene dispersion
of the invention, Table 1 provides each of the composition
conditions and process conditions for the preparation of the
graphene dispersions of example 1 to example 21. In Table 1, the
mixing ratio (G/S) represents the ratio of graphene/solvent.
TABLE-US-00001 TABLE 1 Graphene powder Homogenization process
Layer-thinning process Average Mixing Solid Processing Polishing
Mixing Solid Processing diameter Number of ratio content time bead
density Processing ratio content time Dispersing (.mu.m) layers
(G/S) (phr) (hr) (g/cm.sup.3) solvent (G/S) (phr) (hr) solvent
Example 1 10 to 15 8 to 10 1/10 10 48 5.7 NMP 1/10 10 2 NMP Example
2 5 to 10 8 to 10 1/10 10 48 5.7 NMP 1/10 10 2 NMP Example 3 3 to 5
6 to 8 1/10 10 48 5.7 NMP 1/10 10 2 NMP Example 4 3 to 5 6 to 8
1/10 10 144 5.7 NMP 1/10 10 2 NMP Example 5 3 to 5 6 to 8 1/10 10
80 5.7 NMP 1/10 10 2 NMP Example 6 3 to 5 6 to 8 1/10 10 96 5.7 NMP
1/10 10 2 NMP Example 7 3 to 5 6 to 8 1/10 10 144 5.7 NMP 1/10 10 2
NMP Example 8 3 to 5 6 to 8 1/10 10 144 5.7 NMP 1/10 10 4 NMP
Example 9 3 to 5 6 to 8 1/10 10 144 5.7 NMP 1/10 10 6 NMP Example
10 3 to 5 6 to 8 1/10 10 144 5.7 NMP 1/10 10 10 NMP Example 11 3 to
5 6 to 8 1/10 10 144 5.7 NMP 2/10 20 10 NMP Example 12 3 to 5 6 to
8 1/10 10 144 5.7 NMP 3/10 30 10 NMP Example 13 3 to 5 6 to 8 1/10
10 24 7.9 NMP 1/10 10 10 NMP Example 14 3 to 5 6 to 8 2/10 20 24
7.9 NMP 2/10 20 10 NMP Example 15 3 to 5 6 to 8 3/10 30 24 7.9 NMP
3/10 30 10 NMP Example 16 3 to 5 6 to 8 1/10 10 24 7.9 IPA 1/10 10
10 IPA Example 17 3 to 5 6 to 8 2/10 20 24 7.9 IPA 2/10 20 10 IPA
Example 18 3 to 5 6 to 8 1/10 10 24 7.9 BAC 1/10 10 10 BAC Example
19 3 to 5 6 to 8 2/10 20 24 7.9 BAC 2/10 20 10 BAC Example 20 3 to
5 6 to 8 1/10 10 24 7.9 Xyl 1/10 10 10 Xyl Example 21 3 to 5 6 to 8
2/10 20 24 7.9 Xyl 2/10 20 10 Xyl
Evaluation 1: Property Evaluation of Graphene Dispersion
[0056] The graphene dispersions formed in example 1 to example 21
were measured for graphene average diameter, number of layers, and
concentration difference (C %) between the top section and the
bottom section of the storage container after being left to stand
for 12 hours, and the evaluation results are provided in Table 2
below.
[0057] The measurement method of the concentration difference of
the dispersion includes performing solid content analysis on the
dispersion at 1/3 liquid height and 2/3 liquid height of the
storage container every 24 hours, and subtracting the concentration
C.sub.1/3% at the 1/3 location from the concentration C.sub.2/3% at
the 2/3 location to obtain the C % concentration difference,
wherein the solid content is the concentration obtained after
drying the liquid. If the concentration difference is greater than
20% (i.e., (C.sub.1/3%-C.sub.2/3%)>20%), then dispersion is
poor.
TABLE-US-00002 TABLE 2 Average Number of Concentration diameter
(.mu.m) layers difference (C %) Example 1 7 to 10 8 to 10 >50%
Example 2 3 to 5 8 to 10 >50% Example 3 1 to 3 6 to 8 >30%
Example 4 0.6 to 0.8 6 to 8 <15% Example 5 1.0 to 1.2 6 to 8
>20% Example 6 0.8 to 1.0 6 to 8 >20% Example 7 0.6 to 0.8 4
to 6 <15% Example 8 0.6 to 0.8 3 to 5 <15% Example 9 0.6 to
0.8 3 to 5 <15% Example 10 0.6 to 0.8 3 to 5 <15% Example 11
0.6 to 0.8 3 to 5 <15% Example 12 0.8 to 1.0 3 to 5 >20%
Example 13 0.6 to 0.8 3 to 5 <5% Example 14 0.6 to 0.8 3 to 5
<10% Example 15 0.6 to 0.8 4 to 6 <15% Example 16 0.6 to 0.8
3 to 5 8.89% Example 17 0.6 to 0.8 3 to 5 <5% Example 18 0.6 to
0.8 3 to 5 18.91%.sup. Example 19 0.6 to 0.8 3 to 5 <10% Example
20 0.6 to 0.8 3 to 5 3.42% Example 21 0.6 to 0.8 3 to 5 <10%
[0058] It can be known from Table 2 that, the average diameter
distribution of the graphenes of example 1 to example 21 formed
using the preparation method of the invention is homogeneous, and
therefore the issue of uneven product diameter distribution in a
known physical method such as mechanical exfoliation, ultrasonic
oscillation, or ball milling can be alleviated. Moreover, after
being left to stand for 12 hours, the concentration distribution of
the graphene dispersions of example 1 to example 21 increases from
the top section to the bottom section of the storage container.
Evaluation 2: Property Comparison of Graphene Dispersion of
Invention and Commercial Product
[0059] The graphene dispersions formed in example 1 to example 21
and the commercial products of comparative example 1 to comparative
example 6 were measured for the solid content of graphene and
maximum suspension duration, and the evaluation results are
provided in Table 3 below.
[0060] The solid content is the concentration obtained after the
liquid is dried. The definition of 150 days of suspension duration
is defined below: measurement is taken on the 150th day after the
dispersion is formed, and if the concentration difference is
<20%, then the suspension duration is at least 150 days. The
measurement method of the concentration difference is described
above and is therefore not repeated herein.
[0061] The commercial products of comparative example 1 to
comparative example 6 were formed by a known oxidation process and
stripping process without the homogenization process and
layer-thinning process provided by the invention, wherein the raw
material of comparative example 1 to comparative example 3 is
graphite, and the raw material of comparative example 4 to
comparative example 6 is graphene.
TABLE-US-00003 TABLE 3 Solid content Maximum suspension (phr)
duration (days) Example 1 10 1 Example 2 10 1 Example 3 10 1
Example 4 10 150 Example 5 10 3 Example 6 10 3 Example 7 10 150
Example 8 10 150 Example 9 10 150 Example 10 10 150 Example 11 20
150 Example 12 30 3 Example 13 10 150 Example 14 20 150 Example 15
30 30 Example 16 10 150 Example 17 20 150 Example 18 10 30 Example
19 20 150 Example 20 10 150 Example 21 20 150 Comparative 0.1 to 1
NA example 1 Comparative 0.05 NA example 2 Comparative 0.02 to 0.2
example 3 Comparative 0.2 to 5 >90 example 4 Comparative 0.0001
to 1 >7 example 5 Comparative 0.001 to 0.5 example 6
[0062] It can be known from Table 3 that, compared to comparative
example 1 to comparative example 6 using a known oxidation process
and exfoliation process, example 1 to example 21 using the
preparation method of the invention have significantly higher
graphene solid content, and therefore the preparation method of the
invention can solve the issue of low graphene solid content of
commercial products to improve processability. As a result,
application of the preparation method of the invention in the
coating field can be facilitated. Moreover, as shown in Table 3,
compared to the commercial products of comparative example 1 to
comparative example 6, the preparation method of the graphene
dispersion of the invention can effectively increase the suspension
of graphene in a liquid, such that the stable dispersion duration
can achieve 150 days.
[0063] Based on the above, in the invention, a low-oxygen contained
graphene powder with a specific number of layers is mainly formed
by an air flow generating device, and a graphene dispersion
utilizing a graphene powder with a specific number of layers and
high solid content, and therefore major issues for current
commercial graphene dispersion products such as low solid content
and limited solvent options can be solved effectively, such that
processability and adaptability in different coating processes can
be improved to facilitate application in the coating field.
Moreover, the graphene dispersion preparation method of the
invention does not require oxidation, surface modification, or
addition of a large amount of dispersing agent (>5%), and
therefore the well crystallinity of graphene structure can be
remained without structural damage during the oxidation process and
also interfacial constrain resulted by the excess dispersing agent,
and leads to a good properties thereof. Moreover, issues of
polluted water and toxic waste generated from the oxidation process
in prior art can be further solved to achieve the environmental
needs. As a result, the invention can effectively improve the most
of the current technical issues for the current graphene dispersion
process such as increasing the yield and purity, providing a
uniform distribution, and enhancing the stabilization duration of
the graphene dispersion.
[0064] Although the invention has been described with reference to
the above embodiments, it will be apparent to one of ordinary skill
in the art that modifications to the described embodiments may be
made without departing from the spirit of the invention.
Accordingly, the scope of the invention is defined by the attached
claims not by the above detailed descriptions.
* * * * *