U.S. patent application number 16/173108 was filed with the patent office on 2019-03-07 for latex composition, production method therefor, composite material, and conductive formed product.
This patent application is currently assigned to ZEON CORPORATION. The applicant listed for this patent is ZEON CORPORATION. Invention is credited to The Ban Hoang, Masahiro Shigeta, Mitsugu Uejima.
Application Number | 20190074102 16/173108 |
Document ID | / |
Family ID | 52992549 |
Filed Date | 2019-03-07 |
United States Patent
Application |
20190074102 |
Kind Code |
A1 |
Shigeta; Masahiro ; et
al. |
March 7, 2019 |
LATEX COMPOSITION, PRODUCTION METHOD THEREFOR, COMPOSITE MATERIAL,
AND CONDUCTIVE FORMED PRODUCT
Abstract
Provided is a latex composition consists of a latex including a
polymer having a tetrahydrofuran-insoluble component content of at
least 5 mass % and no greater than 75 mass %; carbon nanotubes
having an average diameter Av and a diameter distribution 3.sigma.
satisfying a relationship 0.60>3.sigma./Av>0.20; and an
additive selected from the group consisting of a dispersant, a
cross-linking agent, a plasticizer, an antioxidant, a heat
stabilizer, a light stabilizer, an ultraviolet absorber, a pigment,
a colorant, a foaming agent, a flame retardant, a lubricant, a
softener, a tackifier, a mold release agent, a deodorant, and a
perfume. The carbon nanotubes have a specific surface area of at
least 600 m.sup.2/g, and in a Raman spectrum of the carbon
nanotubes, a ratio of G band peak intensity relative to D band peak
intensity (G/D ratio) is at least 1 and no greater than 20.
Inventors: |
Shigeta; Masahiro; (Tokyo,
JP) ; Uejima; Mitsugu; (Tokyo, JP) ; Hoang;
The Ban; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ZEON CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
ZEON CORPORATION
Tokyo
JP
|
Family ID: |
52992549 |
Appl. No.: |
16/173108 |
Filed: |
October 29, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15029727 |
Apr 15, 2016 |
10163541 |
|
|
PCT/JP2014/005390 |
Oct 23, 2014 |
|
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16173108 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08K 3/041 20170501;
C08K 2201/003 20130101; C08L 21/02 20130101; C08J 3/215 20130101;
H01B 1/24 20130101; C08K 3/041 20170501; C08K 2201/001 20130101;
C08L 9/04 20130101; B82Y 30/00 20130101; Y10S 977/932 20130101;
C08K 7/24 20130101; C08J 2309/04 20130101; C08K 2201/011 20130101;
H01B 1/04 20130101; Y10S 977/742 20130101; C08L 21/02 20130101 |
International
Class: |
H01B 1/24 20060101
H01B001/24; H01B 1/04 20060101 H01B001/04; C08J 3/215 20060101
C08J003/215; C08L 9/04 20060101 C08L009/04; C08K 7/24 20060101
C08K007/24; C08L 21/02 20060101 C08L021/02; C08K 3/04 20060101
C08K003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 24, 2013 |
JP |
2013-220719 |
Claims
1. A latex composition consisting of: a latex including a polymer
having a tetrahydrofuran-insoluble component content of at least 5
mass % and no greater than 75 mass %; carbon nanotubes having an
average diameter Av and a diameter distribution 3.sigma. satisfying
a relationship 0.60 >3.sigma./Av>0.20; and an additive
selected from the group consisting of a dispersant, a cross-linking
agent, a plasticizer, an antioxidant, a heat stabilizer, a light
stabilizer, an ultraviolet absorber, a pigment, a colorant, a
foaming agent, a flame retardant, a lubricant, a softener, a
tackifier, a mold release agent, a deodorant, and a perfume,
wherein the carbon nanotubes have a specific surface area of at
least 600 m.sup.2/g, and in a Raman spectrum of the carbon
nanotubes, a ratio of G band peak intensity relative to D band peak
intensity (G/D ratio) is at least 1 and no greater than 20.
2. The latex composition of claim 1, wherein the carbon nanotubes
constitute no greater than 10 parts by mass per 100 parts by mass
of the polymer.
3. The latex composition of claim 1, wherein the polymer is a
conjugated diene rubber.
4. A latex composition production method for producing the latex
composition of claim 1 comprising blending a dispersion liquid of
carbon nanotubes having an average diameter Av and a diameter
distribution 3.sigma. satisfying a relationship
0.60>3.sigma./Av>0.20 with a latex including a polymer having
a tetrahydrofuran-insoluble component content of at least 5 mass %
and no greater than 75 mass %, wherein the carbon nanotubes have a
specific surface area of at least 600 m.sup.2/g, and in a Raman
spectrum of the carbon nanotubes, a ratio of G band peak intensity
relative to D band peak intensity (G/D ratio) is at least 1 and no
greater than 20.
5. The latex composition production method of claim 4, further
comprising preparing the dispersion liquid of the carbon nanotubes
by dispersing carbon nanotubes having an average diameter Av and a
diameter distribution 3.sigma. satisfying a relationship
0.60>3.sigma./Av>0.20 in a solvent through dispersion
treatment that brings about a cavitation effect, wherein the carbon
nanotubes have a specific surface area of at least 600 m.sup.2/g,
and in a Raman spectrum of the carbon nanotubes, a ratio of G band
peak intensity relative to D band peak intensity (G/D ratio) is at
least 1 and no greater than 20.
6. The latex composition production method of claim 5, wherein the
dispersion treatment is one or more dispersion treatments selected
from the group consisting of dispersion treatment using ultrasound,
dispersion treatment using a jet mill, and dispersion treatment
using high-shear stirring.
7. A composite material obtainable using the latex composition of
claim 1.
8. A conductive formed product formable by forming the composite
material of claim 7.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
application Ser. No. 15/029,727 filed Apr. 15, 2016, which is a
National Stage Application of PCT/JP2014/005390 filed Oct. 23,
2014, which claims priority based on Japanese Patent Application
No. 2013-220719 filed Oct. 24, 2013. The disclosures of the prior
applications are hereby incorporated by reference herein in their
entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to a latex composition
including a latex and carbon nanotubes, a production method for the
latex composition, and a composite material and a conductive formed
product that are obtained using the latex composition.
BACKGROUND
[0003] A conventional method has been proposed in which a carbon
material, such as carbon black, is blended with a polymer, such as
a resin, in order to obtain a composite material with desired
conductivity. In recent years, there has been increased demand for
composite materials with further improved functionality in order to
meet the demand for various devices with higher performance. One
method that has been proposed for imparting superior conductivity
and mechanical properties on a composite material is a technique
that involves blending carbon nanotubes instead of a conventional
carbon material.
[0004] In one specific example, PTL 1 proposes a method in which
carbon nanotubes are blended with a latex with the objective of
improving mechanical properties and conductivity of a polymer.
[0005] On the other hand, various methods for synthesizing carbon
nanotubes have been proposed in recent years (for example, refer to
NPL 1) such as a method (hereinafter referred to as the "super
growth method") in which a catalyst activating material such as
water is brought into contact with a catalyst in accompaniment to a
feedstock gas in the synthesis of carbon nanotubes by CVD in order
to dramatically increase the activity and lifetime of the catalyst.
Carbon nanotubes with various properties are produced through these
methods.
CITATION LIST
Patent Literature
[0006] PTL 1: JP-A-2006-517996 (WO2004/072159)
Non-Patent Literature
[0007] NPL 1: Kenji Hata et al, Water-Assisted Highly Efficient
Synthesis of Impurity-Free Single-Walled Carbon Nanotubes, SCIENCE,
Nov. 19, 2004, VOL. 306, p.1362-1364
SUMMARY
Technical Problem
[0008] However, there is demand for improving properties, such as
conductivity and mechanical properties, of composite materials
having carbon nanotubes blended therein.
Solution to Problem
[0009] The present inventors conducted diligent investigation using
carbon nanotubes and polymers having various properties with the
objective of further improving properties (for example,
conductivity and mechanical properties) of a composite material.
The inventors newly discovered that conductivity of a composite
material can be increased by using carbon nanotubes having
prescribed properties and that the effect of improved composite
material conductivity achieved using the carbon nanotubes having
the prescribed properties varies significantly depending on the
properties of a polymer with which the carbon nanotubes are
combined. This discovery lead to the present disclosure.
[0010] Thus, the present disclosure provides a latex composition
including a latex that includes a polymer having a
tetrahydrofuran-insoluble component content of at least 1 mass %
and no greater than 75 mass % and carbon nanotubes that have an
average diameter (Av) and a diameter distribution (3.sigma.)
satisfying a relationship 0.60>3.sigma./Av>0.20.
[0011] In the latex composition, the carbon nanotubes preferably
constitute no greater than 10 parts by mass per 100 parts by mass
of the polymer. Moreover, the polymer is preferably a conjugated
diene rubber.
[0012] The latex composition is obtainable by blending a dispersion
liquid of carbon nanotubes having an average diameter (Av) and a
diameter distribution (3.sigma.) satisfying a relationship
0.60>3.sigma./Av>0.20 with a latex including a polymer having
a tetrahydrofuran-insoluble component content of at least 1 mass %
and no greater than 75 mass %.
[0013] The dispersion liquid of the carbon nanotubes is preferably
obtained by dispersing carbon nanotubes having an average diameter
(Av) and a diameter distribution (3.sigma.) satisfying a
relationship 0.60>3.sigma./Av>0.20 in a solvent through
dispersion treatment that brings about a cavitation effect.
Moreover, the dispersion treatment is preferably one or more
dispersion treatments selected from the group consisting of
dispersion treatment using ultrasound, dispersion treatment using a
jet mill, and dispersion treatment using high-shear stirring.
[0014] The present disclosure also provides a carbon
nanotube-containing composite material that is obtainable using the
latex composition described above.
[0015] Moreover, the present disclosure provides a conductive
formed product formable by forming the composite material.
Advantageous Effect
[0016] The present disclosure can provide a latex composition that
is applicable for forming a composite material and a conductive
formed product having superior properties, such as
conductivity.
[0017] The present disclosure can also provide a composite material
and a conductive formed product having superior properties, such as
conductivity.
DETAILED DESCRIPTION
[0018] Embodiments of the disclosure will be specifically described
below.
[0019] A presently disclosed latex composition includes a latex and
carbon nanotubes and is suited for use as a raw material for
producing a composite material and a conductive formed product
having superior conductivity.
Latex Composition
[0020] The presently disclosed latex composition includes a latex
that includes a polymer having a tetrahydrofuran-insoluble
component content of at least 1 mass % and no greater than 75 mass
% and carbon nanotubes that have an average diameter (Av) and a
diameter distribution (3.sigma.) satisfying a relationship
0.60>3.sigma./Av>0.20. As a result of the latex composition
including the combination of the polymer having the prescribed
tetrahydrofuran-insoluble component content and the carbon
nanotubes having the average diameter (Av) and the diameter
distribution (3.sigma.) satisfying the prescribed relationship, the
latex composition can be used to form a composite material and a
conductive formed product having dramatically increased
conductivity.
[0021] It should be noted that the latex composition may further
include optional additives in addition to the latex and the carbon
nanotubes.
[0022] <Latex>
[0023] The polymer included in the latex and having the
tetrahydrofuran-insoluble component content of at least 1 mass %
and no greater than 75 mass % may for example be a rubber such as a
natural rubber or a synthetic rubber and no specific limitations
are placed thereon other than the tetrahydrofuran-insoluble
component content being within the range described above. Specific
examples of rubbers that be used include natural rubber, conjugated
diene rubber, butyl rubber, and urethane rubber.
[0024] Among these rubbers, a conjugated diene rubber is preferably
used as the polymer.
[0025] The conjugated diene rubber is a homopolymer of a single
type of conjugated diene monomer, a copolymer of two or more types
of conjugated diene monomers, or a copolymer of a conjugated diene
monomer and a monomer copolymerizable therewith.
[0026] Although no specific limitations are placed on the
conjugated diene monomer, specific examples of conjugated diene
monomers that can be used include 1,3-butadiene, isoprene,
2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene,
and chloroprene. Any one of these conjugated diene monomers may be
used alone or any two or more of these conjugated diene monomers
may be used in combination. Among these conjugated diene monomers,
1,3-butadiene and isoprene are particularly preferable to be
used.
[0027] Although no specific limitations are placed on the monomer
that is copolymerizable with the conjugated diene monomer, specific
examples include aromatic vinyl monomers, ethylenically unsaturated
nitrile monomers, ethylenically unsaturated acid monomers,
ethylenically unsaturated acid derivative monomers, vinyl
heterocyclic compound monomers, carboxylic acid vinyl ester
monomers, halogenated vinyl monomers, vinyl ether monomers, and
olefin monomers. Any one of these copolymerizable monomers may be
used alone or any two or more of these copolymerizable monomers may
be used in combination. Among these copolymerizable monomers,
aromatic vinyl monomers, ethylenically unsaturated nitrile
monomers, ethylenically unsaturated acid monomers, and
ethylenically unsaturated acid derivative monomers are
suitable.
[0028] Specific examples of aromatic vinyl monomers that can be
used include styrene, .alpha.-methylstyrene, monochlorostyrene,
dichorostyrene, monomethylstyrene, dimethylstyrene,
trimethylstyrene, and hydroxymethylstyrene.
[0029] Specific examples of ethylenically unsaturated nitrile
monomers that can be used include acrylonitrile, methacrylonitrile,
fumaronitrile, .alpha.-chloroacrylonitrile, and
.alpha.-cyanoethylacrylonitrile.
[0030] Specific examples of ethylenically unsaturated acid monomers
that can be used include monovalent carboxylic acids having an
ethylenically unsaturated bond such as acrylic acid, methacrylic
acid, and crotonic acid, and polyvalent carboxylic acids having an
ethylenically unsaturated bond such as fumaric acid, maleic acid,
itaconic acid, and butene tricarboxylic acid.
[0031] Specific examples of ethylenically unsaturated acid
derivative monomers that can be used include esters, anhydrides,
and amides of ethylenically unsaturated acids.
[0032] Specific examples of ethylenically unsaturated acid ester
monomers that can be used include methyl (meth)acrylate, ethyl
(meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate,
2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, dodecyl
(meth)acrylate, 2-hydroxyethyl (meth)acrylate, and
dimethylaminoethyl (meth)acrylate.
[0033] Specific examples of ethylenically unsaturated acid
anhydride monomers that can be used include maleic anhydride and
itaconic anhydride.
[0034] Specific examples of ethylenically unsaturated acid amide
monomers that can be used include (meth)acrylamide, N-methylol
(meth)acrylamide, N,N-dimethyl (meth)acrylamide, and
(meth)acrylamido-2-methylpropane sulfonic acid and the sodium salt
thereof.
[0035] In the present description, "(meth)acryl" refers to "acryl"
and/or "methacryl."
[0036] Specific examples of vinyl heterocyclic compound monomers
that can be used include vinylpyridine and N-vinylpyrrolidone.
[0037] Specific examples of carboxylic acid vinyl ester monomers
that can be used include vinyl formate, vinyl acetate, vinyl
propionate, vinyl pivalate, isopropenyl acetate, and vinyl
versatate.
[0038] Specific examples of halogenated vinyl monomers that can be
used include vinyl chloride, vinylidene chloride, vinyl fluoride,
and vinylidene fluoride.
[0039] Specific examples of vinyl ether monomers that can be used
include methyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl
ether, n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl
ether, and dodecyl vinyl ether.
[0040] Specific examples of olefin monomers that can be used
include ethylene, propylene, 1-butene, and isobutene.
[0041] Specific examples of suitable conjugated diene rubbers
include polybutadiene rubber, polyisoprene rubber, copolymer rubber
of an aromatic vinyl monomer and butadiene, copolymer rubber of a
monomer having a carboxy group (for example, a monovalent
carboxylic acid or a polyvalent carboxylic acid), an aromatic vinyl
monomer, and butadiene, copolymer rubber of an aromatic vinyl
monomer and isoprene, copolymer rubber of a monomer having a
carboxy group, an aromatic vinyl monomer, and isoprene, copolymer
rubber of acrylonitrile and butadiene, copolymer rubber of a
monomer having a carboxy group, acrylonitrile, and butadiene,
copolymer rubber of acrylonitrile and isoprene, copolymer rubber of
a monomer having a carboxy group, acrylonitrile, and isoprene,
copolymer rubber of acrylonitrile, butadiene, and isoprene,
copolymer rubber of a monomer having a carboxy group,
acrylonitrile, butadiene, and isoprene, block copolymer rubber of
an aromatic vinyl monomer, butadiene, and an aromatic vinyl
monomer, block copolymer of an aromatic vinyl monomer, isoprene,
and an aromatic vinyl monomer, and hydrogenated products of any of
the preceding rubbers.
[0042] Among these conjugated diene rubbers, copolymer rubber of an
aromatic vinyl monomer and butadiene and copolymer rubber of
acrylonitrile and butadiene are preferable in the present
disclosure.
[0043] The weight-average molecular weight and the glass-transition
temperature of the polymer (solid component) of the latex used in
the present disclosure can be freely determined in accordance with
the intended use of the latex composition.
[0044] Although no specific limitations are placed on the
concentration of the polymer in the latex, the concentration is
preferably at least 10 mass % and no greater than 74 mass %, more
preferably at least 20 mass % and no greater than 70 mass %, and
particularly preferably at least 30 mass % and no greater than 60
mass %.
[0045] If the concentration of the polymer is too low, the
viscosity of the latex may be too low and the polymer component may
separate during storage of the latex. Conversely, if the
concentration of the polymer is too high, the polymer component may
aggregate.
[0046] Although no specific limitations are placed on the method by
which the polymer constituting the latex is produced, any of
conventional commonly known methods such as emulsion
polymerization, suspension polymerization, and solution
polymerization may be used. Among these methods, emulsion
polymerization is preferable for producing the polymer. The polymer
produced by emulsion polymerization may be used as-produced to
prepare the latex or may be used to prepare the latex after, for
example, undergoing a process in which the polymer is coagulated
and purified.
[0047] Of course, a polymer produced by solution polymerization or
suspension polymerization may be converted to a solid polymer, and
this solid polymer may be used after dissolution in a solvent or
dispersion in a solvent and conversion to an emulsion state.
[0048] A tetrahydrofuran-insoluble component content of the polymer
in the latex is required to be at least 1 mass % and no greater
than 75 mass %. Moreover, the tetrahydrofuran-insoluble component
content of the polymer is preferably at least 2 mass % and no
greater than 70 mass %, more preferably at least 2 mass % and no
greater than 65 mass %, and particularly preferably at least 5 mass
% and no greater than 60 mass %. If the tetrahydrofuran-insoluble
component content of the polymer is too small, it may be
insufficient in the improving effect of conductivity when the
polymer is used in combination with carbon nanotubes having the
prescribed properties described further below. Conversely, if the
tetrahydrofuran-insoluble component content is too large, the
dispersibility of carbon nanotubes and other additives may be
adversely affected, lowering processability of composite material
and conductive formed product.
[0049] In the present disclosure, the term
"tetrahydrofuran-insoluble component content" refers to the mass of
an insoluble component when 200 mg of the polymer is immersed in
100 mL of tetrahydrofuran (THF) for 48 hours at 25.degree. C.,
expressed as a proportion of the total polymer mass prior to
immersion in THF.
[0050] Although no specific limitations are placed on the method by
which the tetrahydrofuran-insoluble component content is adjusted,
adjustment can for example be performed by a method in which (i)
the degree of cross-linking of the polymer is adjusted through
selection of the polymerization temperature, the type(s) of
monomer(s), the amount(s) of monomer(s), and so forth, (ii) the
amount of tetrahydrofuran-insoluble component that is produced is
adjusted using a reaction inhibitor or the like, or (iii) polymers
with different tetrahydrofuran-insoluble component contents are
blended.
[0051] <Carbon Nanotubes>
[0052] The carbon nanotubes included in the presently disclosed
latex composition are required to have an average diameter (Av) and
a diameter distribution (3.sigma.) satisfying a relationship
0.60>3.sigma./Av>0.20. When carbon nanotubes for which the
ratio of the diameter distribution (3.sigma.) relative to the
average diameter (Av) is greater than 0.20 and less than 0.60 are
combined with a polymer having the tetrahydrofuran-insoluble
component content described above, a composite material and a
conductive formed product having superior conductivity can be
obtained even if only a small amount of the carbon nanotubes is
used. From a viewpoint of further improving properties of the
composite material and the conductive formed product obtained using
the latex composition, the carbon nanotubes preferably satisfy a
relationship 0.60>3.sigma./Av>0.25, and more preferably
satisfy a relationship 0.60>3.sigma./Av>0.50.
[0053] Although the reason that a composite material and a
conductive formed product having superior conductivity can be
obtained by combining the above-described carbon nanotubes with a
polymer having the above-described tetrahydrofuran-insoluble
component content is not clear, the reason is presumed to be that a
tetrahydrofuran-soluble component can favorably mix with the
above-described carbon nanotubes during production of the composite
material or the conductive formed product, whereas a
tetrahydrofuran-insoluble component cannot favorably mix with the
above-described carbon nanotubes during production of the composite
material or and the conductive formed product. In other words, it
is presumed that a composite material and a conductive formed
product demonstrating superior conductivity can be obtained through
the tetrahydrofuran-soluble component that mixes favorably with the
carbon nanotubes and the tetrahydrofuran-insoluble component that
does not mix favorably with the carbon nanotubes being finely mixed
in a prescribed ratio.
[0054] In the present disclosure, "diameter distribution
(3.sigma.)" refers to a value obtained by multiplying the standard
deviation (.sigma.) of the diameters of the carbon nanotubes by 3.
The "average diameter (Av)" and the "diameter distribution
(3.sigma.)" can each be obtained by measuring the diameters (outer
diameters) of 100 carbon nanotubes using a transmission electron
microscope.
[0055] The average diameter (Av) and the diameter distribution
(3.sigma.) may be adjusted by altering the production method or the
production conditions of the carbon nanotubes or may be adjusted by
combining a plurality of types of carbon nanotubes obtained by
different production methods.
[0056] The carbon nanotubes preferably take a normal distribution
when diameter is plotted on a horizontal axis and the probability
density of the diameter is plotted on a vertical axis, and a
Gaussian approximation is made. It is difficult to obtain a normal
distribution in a situation in which a plurality of types of carbon
nanotubes, such as carbon nanotubes obtained by different
production methods, are combined. In other words, in the present
disclosure, the carbon nanotubes are preferably a single type of
carbon nanotubes or carbon nanotubes obtained by blending a single
type of carbon nanotubes with an amount of other carbon nanotubes
that does not affect the distribution of the single type of carbon
nanotubes.
[0057] The carbon nanotubes may be single-walled carbon nanotubes
or multi-walled carbon nanotubes. However, from a viewpoint of
improving properties (for example, conductivity and mechanical
properties) of the composite material and the conductive formed
product produced using the latex composition, the carbon nanotubes
preferably have from one to five walls and more preferably have one
wall.
[0058] The carbon nanotubes preferably exhibit a radial breathing
mode (RBM) peak when evaluated by Raman spectroscopy. Note that an
RBM is not present in the Raman spectrum of a multi-walled carbon
nanotube having three or more walls.
[0059] From a viewpoint of imparting high conductivity on the
composite material and the conductive formed product, the average
diameter (Av) of the carbon nanotubes is preferably at least 0.5
nm, and more preferably at least 1 nm, and is preferably no greater
than 15 nm, more preferably no greater than 10 nm, and particularly
preferably no greater than 8 nm.
[0060] In a Raman spectrum of the carbon nanotubes, a ratio of G
band peak intensity relative to D band peak intensity (G/D ratio)
is preferably at least 1 and no greater than 20. A G/D ratio of at
least 1 and no greater than 20 enables superior conductivity to be
imparted even if the blended amount of carbon nanotubes is
small.
[0061] Furthermore, a structure of the carbon nanotubes preferably
has a length of at least 100 .mu.m and no greater than 5,000 .mu.m.
A length of at least 100 .mu.m and no greater than 5,000 .mu.m
enables superior conductivity to be imparted even if the blended
amount of carbon nanotubes is small.
[0062] The carbon nanotubes preferably have a specific surface area
of at least 600 m.sup.2/g. In a situation in which the carbon
nanotubes are mainly closed tubes, the specific surface area is
preferably at least 600 m.sup.2/g, and in a situation in which the
carbon nanotubes are mainly open tubes, the specific surface area
is more preferably at least 1,300 m.sup.2/g. A specific surface
area of at least 600 m2/g enables superior conductivity to be
imparted even if the blended amount of carbon nanotubes is
small.
[0063] The specific surface area of the carbon nanotubes can be
obtained as a nitrogen adsorption specific surface area by a BET
method.
[0064] The carbon nanotubes preferably have a weight density of at
least 0.002 g/cm.sup.3 and no greater than 0.2 g/cm.sup.3. A weight
density of no greater than 0.2 g/cm.sup.3 facilitates homogeneous
dispersion of the carbon nanotubes in the dispersion liquid and in
the latex composition due to the carbon nanotubes only being weakly
bonded to one another. In other words, a weight density of no
greater than 0.2 g/cm.sup.3 facilitates preparation of a
homogeneous dispersion liquid and a homogeneous latex composition.
A weight density of at least 0.002 g/cm.sup.3 facilitates handling
of the carbon nanotubes by improving unity of the carbon nanotubes
and inhibiting the carbon nanotubes from coming apart.
[0065] The carbon nanotubes having the properties described above
are preferably carbon nanotubes obtained through the super growth
method (hereinafter may be referred to as "SGCNTs"). The super
growth method is described, for example, in NPL 1, Japanese Patent
No. 4,621,896 (European Patent Application Publication No.
1787955), and Japanese Patent No. 4,811,712 (United States Patent
Application Publication No. 2009/297846).
[0066] The super growth method is a CVD method in which a catalyst
activating material such as water is brought into contact with a
catalyst in accompaniment to a feedstock gas in order to
dramatically increase activity and lifetime of the catalyst.
[0067] The amount of the carbon nanotubes blended into the latex
composition relative to 100 parts by mass of the polymer (solid
component) constituting the latex is normally at least 0.01 parts
by mass and no greater than 15 parts by mass, preferably at least
0.1 parts by mass, and more preferably at least 0.25 parts by mass,
and preferably no greater than 10 parts by mass, and more
preferably no greater than 7.5 parts by mass. If the amount of
carbon nanotubes is too small, conductivity cannot be ensured.
Conversely, if the amount of carbon nanotubes is too large,
fluidity of the composite material obtained using the latex
composition is reduced, leading to poorer formability.
[0068] <Additives>
[0069] A cross-linking agent may optionally be blended with the
latex composition in order to ensure formability of the composite
material and mechanical strength of the conductive formed product.
Moreover, properties of the composite material and the conductive
formed product may be improved or maintained by optionally blending
the latex composition with a plasticizer, an antioxidant, a heat
stabilizer, a light stabilizer, an ultraviolet absorber, a pigment,
a colorant, a foaming agent, a flame retardant, a lubricant, a
softener, a tackifier, a mold release agent, a deodorant, a
perfume, or the like.
[0070] It should be noted that instead of blending these additives
with the latex composition, these additives may be directly blended
with the composite material produced using the latex composition.
Furthermore, one portion of an additive may be blended with the
latex composition and a remaining portion of the additive may be
directly blended with the composite material.
[0071] No specific limitations are placed on the cross-linking
agent that is blended as necessary, other than being a
cross-linking agent that is normally used as a typical rubber
cross-linking agent. Representative examples of the cross-linking
agent include sulfuric cross-linking agents and organic peroxide
cross-linking agents, among which, a sulfuric cross-linking agent
is preferable.
[0072] Examples of sulfuric cross-linking agents that can be used
include sulfur such as powdered sulfur, flowers of sulfur,
precipitated sulfur, colloidal sulfur, surface-treated sulfur, and
insoluble sulfur; sulfur-containing compounds such as sulfur
chloride, sulfur dichloride, morpholine disulfide, alkylphenol
disulfide, dibenzothiazyl disulfide,
N,N'-dithio-bis(hexahydro-2H-azenopin-2), phosphorus-containing
polysulfides, and polymeric polysulfides; and sulfur donor
compounds such as tetramethyl thiuram disulfide, selenium dimethyl
dithiocarbamate, and 2-(4'-morpholinodithio)benzothiazole.
[0073] If a sulfuric cross-linking agent is used, a cross-linking
aid such as zinc flower or stearic acid; or a cross-linking
promotor such as those that are based on guanidine, aldehyde-amine,
aldehyde-ammonia, thiazole, sulfenamide, or thiourea may be used in
combination with the sulfuric cross-linking agent.
[0074] Examples of organic peroxide cross-linking agents that can
be used include dicumyl peroxide, cumene hydroperoxide, t-butyl
cumyl peroxide, para-menthane hydroperoxide, di-t-butyl peroxide,
1,3-bis and 1,4-bis(t-butylperoxyisopropyl)benzene,
1,1-di-t-butylperoxy-3,3-trimethylcyclohexane,
4,4-bis-(t-butyl-peroxy)-n-butylvalerate,
2,5-dimethyl-2,5-di-t-butylperoxyhexane,
2,5-dimethyl-2,5-di-t-butylperoxyhexyne-3,
1,1-di-t-butylperoxy-3,5,5-trimethylcyclohexane, p-chlorobenzoyl
peroxide, t-butylperoxyisopropyl carbonate, and t-butylperoxy
benzoate.
[0075] If an organic peroxide cross-linking agent is used, a
polyfunctional compound such as trimethylolpropane trimethacrylate,
divinyl benzene, ethylene dimethacrylate, or triallyl isocyanurate
can for example be used as a cross-linking aid in combination with
the organic peroxide cross-linking agent.
[0076] Although no specific limitations are placed on the amount of
the cross-linking agent that is used, the amount of the
cross-linking agent relative to 100 parts by mass of the polymer is
preferably at least 0.1 parts by mass and no greater than 10 parts
by mass, and more preferably at least 0.2 parts by mass and no
greater than 5 parts by mass.
[0077] Furthermore, although no specific limitations are placed on
the amount of the cross-linking aid or cross-linking promoter that
is used in combination with the sulfuric cross-linking agent, the
amount is preferably at least 0.1 parts by mass and no greater than
10 parts by mass relative to 100 parts by mass of the polymer.
[0078] Moreover, although no specific limitations are placed on the
amount of the crosslinking aid that is used in combination with the
organic peroxide crosslinking agent, the amount is preferably at
least 0.5 parts by mass and no greater than 20 parts by mass
relative to 100 parts by mass of the polymer.
[0079] The plasticizer that is blended as necessary is preferably
added to and mixed with the latex composition as an aqueous
emulsion. Blending of the plasticizer as an aqueous emulsion
enables micro-level homogenous mixing of the polymer in the latex,
the carbon nanotubes, and the plasticizer such that bleeding of the
plasticizer is less likely to occur and facilitates preparation of
a composite material having superior properties.
[0080] Although no specific limitations are placed on the method by
which the aqueous emulsion of the plasticizer is prepared, a
preparation method in which the plasticizer is added to an aqueous
medium containing a surfactant in an amount equivalent to from 0.5
mass % to 10 mass % of the plasticizer while vigorously stirring
the aqueous medium is preferable. Examples of the surfactant
include anionic surfactants such as potassium rosinate, sodium
lauryl sulfate, potassium oleate, and sodium
dodecylbenzenesulfonate; non-ionic surfactants such as
polyoxyethylene alkyl ether, polyoxyethylene alkyl ester, and
polyoxyethylene sorbitan alkyl ester; and cationic surfactants such
as didecyldimethyl ammonium chloride and stearyl trimethyl ammonium
chloride. The concentration of the plasticizer in the aqueous
emulsion is preferably from 5 mass % to 70 mass %.
[0081] (Latex Composition Production Method)
[0082] No specific limitations are placed on the method by which
the above-described latex and the above-described carbon nanotubes
are mixed to produce the latex composition. Examples of methods
that can be used to produce the latex composition include, for
example, (I) a method in which a powder of the carbon nanotubes is
added to the latex and dispersed by dispersion treatment and (II) a
method in which the latex is mixed with a carbon nanotube
dispersion liquid in which the carbon nanotubes are already
dispersed in a solvent such as water. Among these methods, method
(II) is preferable from a viewpoint of increasing dispersibility of
the carbon nanotubes.
[0083] In the above-described method (II), the carbon nanotube
dispersion liquid can be obtained by adding the above-described
carbon nanotubes to a dispersant aqueous solution in which a
dispersant is dissolved as necessary and subjecting the resultant
mixture to dispersion treatment by a dispersion method that brings
about a cavitation effect. A dispersion method that brings about a
cavitation effect can also be used for dispersion treatment in the
above-described method (I).
[0084] Examples of dispersants that can be used to disperse the
carbon nanotubes include surfactants and polysaccharides. From a
viewpoint of dispersibility of the carbon nanotubes, a surfactant
is preferable and an anionic surfactant is more preferable.
[0085] A dispersion method that brings about a cavitation effect
utilizes shock waves caused by the rupture of vacuum bubbles formed
in water when high energy is applied to the liquid. This dispersion
method enables dispersion of the carbon nanotubes in the water
without damaging the properties of the carbon nanotubes. Specific
examples of dispersion treatments utilizing a dispersion method
that brings about a cavitation effect include dispersion treatment
using ultrasound, dispersion treatment using a jet mill, and
dispersion treatment using high-shear stirring. These dispersion
treatments may be performed alone or in combination. Specifically,
an ultrasonic homogenizer, a jet mill, and a high-shear stirring
device are suited for carrying out these dispersion treatments.
Conventional commonly known devices may be used as the
aforementioned devices.
[0086] Although no specific limitations are placed on the method by
which the latex and the carbon nanotube dispersion liquid are
mixed, mixing may be performed by a stirring method that enables
homogeneous mixing of the latex and the carbon nanotube dispersion
liquid.
Composite Material
[0087] The presently disclosed composite material can be produced
using the latex composition described above. Specifically, the
composite material may for example be obtained simply by drying the
above-described latex composition or by causing the above-described
latex composition to coagulate to form crumbs and then drying the
crumbs. The composite material produced using the above-described
latex composition includes the above-described polymer and carbon
nanotubes and, as a consequence, has superior properties such as
conductivity.
[0088] Although no specific limitations are placed on the method by
which the latex composition is coagulated, examples of methods that
can be used include a method in which the latex composition is
added to a water-soluble organic solvent, a method in which an acid
is added to the latex composition, a method in which a salt is
added to the latex composition, and a method in which the latex
composition is added to an aqueous solution containing a coagulant
and is salted out. Among these methods, the method in which the
latex composition is added to an aqueous solution containing a
coagulant and is salted out is preferable. Examples coagulants that
can be used include calcium chloride, sodium chloride, calcium
hydroxide, aluminum sulfate, and aluminum hydroxide. The amount of
the coagulant that is used relative to 100 parts by mass of the
polymer (solid component) constituting the latex is preferably at
least 0.5 parts by mass and no greater than 150 parts by mass, and
more preferably at least 0.5 parts by mass and no greater than 20
parts by mass.
[0089] In a situation in which the polymer constituting the latex
includes a cationic monomeric unit such as dodecyltrimethylammonium
bromide, cetyltrimethylammonium bromide, or
distearyldimethylammonium chloride, a dilute sulfuric acid aqueous
solution or the like is preferably added in salting out of the
latex composition in order to adjust the pH of the coagulant
aqueous solution to less than or equal to the isoelectric point of
the latex composition. This adjustment of the pH of the coagulant
aqueous solution increases the zeta-potential of a functional group
of the cationic monomeric unit contained in the polymer
constituting the latex, which improves dispersibility of the carbon
nanotubes and enables crumbs of large particle diameter to be
obtained through coagulation. The particle diameter of the crumbs
has a significant influence on the degree of dehydration and the
crumb recovery rate in processing by a shaker screen or squeezer
after coagulation and washing processes, and also on dryness in a
drying process, thus the average particle diameter of the crumbs is
preferably at least 0.5 mm and no greater than 40 mm.
[0090] Washing, dehydration, and drying of the crumbs can be
carried out by the same washing, dehydration, and drying methods as
used in normal rubber production. In one specific example, the
crumbs resulting from coagulation are first separated from water
using a mesh filter, a centrifugal separator, or the like, are
subsequently washed, and are then dehydrated using a squeezer or
the like. Next, the crumbs are dried until they reach a desired
water content using a band dryer, a vertical through-dryer, a
single-screw extruder, a twin-screw extruder, or the like that is
commonly used in rubber production to obtain the composite material
containing the carbon nanotubes and the polymer. Note that the
composite material may be obtained by carrying out coagulation and
drying simultaneously in a twin-screw extruder.
[0091] Furthermore, the composite material may be produced by
further adding additives such as an anti-aging agent and a
reinforcing agent as necessary to a composite obtained by
coagulating the latex composition (optionally including additives
such as a plasticizer and a resin other than the polymer
constituting the latex) and drying the resultant crumbs, followed
by kneading with using a kneading device such as a roll kneader or
a Banbury mixer.
Conductive Formed Product
[0092] The presently disclosed conductive formed product can be
produced using the composite material described above. Although no
specific limitations are placed on the method by which the formed
product is obtained using the composite material, the formed
product can for example be obtained by a method in which forming is
carried out using a forming machine, such as an extruder, an
injection molder, a compressor, or a roller, that is suited to the
desired shape of the formed product and in which cross-linking is
carried out as necessary to fix the shape of the formed product.
The cross-linking may be performed after or during the forming. The
forming temperature is preferably from 10.degree. C. to 200.degree.
C., and more preferably from 25.degree. C. to 120.degree. C. The
cross-linking temperature is preferably from 100.degree. C. to
200.degree. C., more preferably from 130.degree. C. to 190.degree.
C., and particularly preferably from 140.degree. C. to 180.degree.
C. The cross-linking time is preferably from 1 minute to 5 hours,
and more preferably from 2 minutes to 1 hour.
[0093] Depending on the shape, dimensions, and so forth of the
formed product, secondary cross-linking may be carried out because
internal cross-linking of the formed product may be insufficient
even if cross-linking occurs at the surface of the formed
product.
[0094] The presently disclosed conductive formed product includes
the above-described polymer and carbon nanotubes and, as a
consequence, has superior properties such as conductivity.
EXAMPLES
[0095] The following provides more specific explanation of the
present disclosure through examples and comparative examples.
However, the present disclosure is not limited to the following
examples.
[0096] In the following examples and comparative examples, "parts"
and "%" refer to amounts on a mass basis unless otherwise
specified. Surface resistivity and volume conductivity were
measured in the examples and comparative examples as follows.
Surface Resistivity
[0097] After forming an applied film into a circular thin-film of
approximately 40 mm to 60 mm in diameter and 100 .mu.m to 500 .mu.m
in thickness, four square test pieces of 10 mm.times.10 mm were cut
out to be used as measurement samples.
[0098] The surface resistivity of each of the measurement samples
was measured by a method in accordance with JIS K7194 as described
below using a low resistivity meter (product name:
Loresta.RTM.-GPMCP-T610 (Loresta is a registered trademark in
Japan, other countries, or both); produced by Mitsubishi Chemical
Analytech, Co., Ltd.). A PSP probe was selected as a four-pin probe
of the low resistivity meter.
[0099] Specifically, a measurement sample was mounted on an
insulating board, the probe was pressed against a central position
of the measurement sample (position 5 mm vertically and 5 mm
laterally), and surface resistivity was measured by applying
voltage having a maximum value of 90 V. Surface resistivity was
measured at 50 random locations on the four measurement sample test
pieces and an average value was calculated.
Volume Conductivity
[0100] Vacuum press forming of 450 mg of an obtained test piece was
performed in a vacuum at a temperature of 120.degree. C. with a
pressure of 0.4 MPa for a pressing time of 5 minutes to form a
circular thin-film of approximately 40 mm to 60 mm in diameter and
100 .mu.m to 500 .mu.m in thickness. Four square test pieces of 10
mm.times.10 mm were then cut out to be used as measurement
samples.
[0101] The volume conductivity of each of the measurement samples
was measured by a method in accordance with JIS K7194 as described
below using the low resistivity meter (product name:
Loresta.RTM.-GPMCP-T610; produced by Mitsubishi Chemical Analytech,
Co., Ltd.). A PSP probe was selected as a four-pin probe of the low
resistivity meter.
[0102] Specifically, a measurement sample was mounted on an
insulating board, the probe was pressed against a central position
of the measurement sample (position 5 mm vertically and 5 mm
laterally), and conductivity was measured by applying voltage
having a maximum value of 90 V. Conductivity was measured at 50
random locations on the four measurement sample test pieces and an
average value was calculated.
Production Example 1
[0103] SGCNTs-1 were synthesized under the following conditions by
the super growth method described in Japanese Patent No.
4,621,896.
[0104] -Synthetic Conditions- [0105] Carbon compound: Ethylene
(supply rate: 50 sccm) [0106] Atmospheric gas: Mixed gas of helium
and hydrogen (supply rate: 1,000 sccm) [0107] Pressure: 1 atm
[0108] Additive amount of water vapor: 300 mass ppm [0109] Reaction
temperature: 750.degree. C. [0110] Reaction time: 10 minutes [0111]
Metal catalyst: Iron thin-film (thickness: 1 nm) [0112] Substrate:
Silicon wafer
[0113] The resultant SGCNTs-1 had a BET specific surface area of
1,050 m.sup.2/g. When the SGCNTs-1 were measured using a Raman
spectrophotometer, a radial breathing mode (RBM) spectrum was
observed in a low-wavenumber domain from 100 cm.sup.-1 to 300
cm.sup.-1, which is characteristic of single-walled carbon
nanotubes. When the diameters of 100 randomly selected tubes from
among the SGCNTs-1 were measured using a transmission electron
microscope, the average diameter (Av) was 3.3 nm, the diameter
distribution (3.sigma.) was 1.9 nm, and 3.sigma./Av was 0.58.
Production Example 2
[0114] In Production Example 2, 30 mg of the SGCNTs-1 were added to
300 mL of a 1 mass % aqueous solution of sodium lauryl sulfate
(product name: Emal.RTM. O (Emal is a registered trademark in
Japan, other countries, or both); produced by Kao Corporation) and
a jet mill (product name: JN20; produced by Jokoh Co., Ltd.) was
used to obtain an aggregate-free SGCNT-1 dispersion liquid.
Production Example 3
[0115] The same operation as in Production Example 2 was performed
with the exception that 30 mg of HiPco.RTM. (HiPco is a registered
trademark in Japan, other countries, or both) was added to 300 mL
of a 1 mass % aqueous solution of sodium lauryl sulfate (product
name: Emal.RTM. O; produced by Kao Corporation) to obtain an
aggregate-free HiPco-1 dispersion liquid. The HiPco.RTM. was
produced by Nanolntegris Inc. and had a BET specific surface area
of 700 m.sup.2/g. When the diameters of 100 randomly selected tubes
from among the HiPco.RTM. were measured using a transmission
electron microscope, the average diameter (Av) was 1.1 nm, the
diameter distribution (3.sigma.) was 0.2 nm, and 3.sigma./Av was
0.18.
Production Example 4
[0116] The same operation as in Production Example 2 was performed
with the exception that 30 mg of NC7000 was added to 300 mL of a 1
mass % aqueous solution of sodium lauryl sulfate (product name:
Emal.RTM. O; produced by Kao Corporation) to obtain an
aggregate-free NC7000-1 dispersion liquid. The NC7000 was produced
by Nanocyl and had a BET specific surface area of 290 m.sup.2/g.
When the diameters of 100 randomly selected tubes from among the
NC7000 were measured using a transmission electron microscope, the
average diameter (Av) was 9.3 nm, the diameter distribution
(3.sigma.) was 2.6 nm, and 3.sigma./Av was 0.28.
Example 1-1
[0117] In Example 1-1, 5.063 g of the SGCNT-1 dispersion liquid was
mixed with 0.5 g of an acrylonitrile-butadiene-based latex (product
name: CYATEX.RTM. NA-20 (CYATEX is a registered trademark in Japan,
other countries, or both); produced by Nippon A&L Inc.;
THF-insoluble component content of acrylonitrile-butadiene rubber
(polymer): 70%) to achieve a ratio of 2 parts of carbon nanotubes
relative to 100 parts of polymer and the mixture was stirred for 1
hour to obtain an SGCNT-1/rubber mixed solution (latex
composition). The resultant mixed solution was poured into a glass
petri dish and was held in a dry air flow environment at 50.degree.
C. for 48 hours to evaporate moisture and obtain an applied film
(composite material). A surface resistivity of 83 .OMEGA./sq. was
measured using the applied film.
Example 1-2
[0118] An applied film was obtained through the same operation as
in Example 1-1 with the exception that the latex used in Example
1-1 was changed to other acrylonitrile-butadiene-based latex
(product name: Nipol.RTM. Lx554 (Nipol is a registered trademark in
Japan, other countries, or both); produced by Zeon Corporation;
THF-insoluble component content of acrylonitrile-butadiene rubber:
60%). A surface resistivity of 117 .OMEGA./sq. was measured using
the applied film.
Example 1-3
[0119] An applied film was obtained through the same operation as
in Example 1-1 with the exception that the latex used in Example
1-1 was changed to other acrylonitrile-butadiene-based latex
(product name: Nipol.RTM. Lx553; produced by Zeon Corporation;
THF-insoluble component content of acrylonitrile-butadiene rubber:
43%). A surface resistivity of 134 .OMEGA./sq. was measured using
the applied film.
Example 1-4
[0120] An applied film was obtained through the same operation as
in Example 1-1 with the exception that the latex used in Example
1-1 was changed to other acrylonitrile-butadiene-based latex
(product name: Nipol.RTM. Lx552; produced by Zeon Corporation;
THF-insoluble component content of acrylonitrile-butadiene rubber:
27%). A surface resistivity of 176 .OMEGA./sq. was measured using
the applied film.
Comparative Example 1
[0121] An applied film was obtained through the same operation as
in Example 1-1 with the exception that the latex used in Example
1-1 was changed to other acrylonitrile-butadiene-based latex
(product name: Nipol.RTM. Lx551; produced by Zeon Corporation;
THF-insoluble component content of acrylonitrile-butadiene rubber:
0%). A surface resistivity of 504 .OMEGA./sq. was measured using
the applied film.
Example 2-1
[0122] An applied film was obtained through the same operation as
in Example 1-1 with the exception that the mixing ratio was changed
to 2.521 g of the SGCNT-1 dispersion liquid and 0.5 g of the latex
such that the amount of carbon nanotubes was 1 part relative to 100
parts of polymer. A surface resistivity of 2,117 .OMEGA./sq. was
measured using the applied film.
Example 2-2
[0123] An applied film was obtained through the same operation as
in Example 1-2 with the exception that the mixing ratio of the
SGCNT-1 dispersion liquid and the latex was changed in the same way
as in Example 2-1 such that the amount of carbon nanotubes was 1
part relative to 100 parts of polymer. A surface resistivity of
2,476 .OMEGA./sq. was measured using the applied film.
Example 2-3
[0124] An applied film was obtained through the same operation as
in Example 1-3 with the exception that the mixing ratio of the
SGCNT-1 dispersion liquid and the latex was changed in the same way
as in Example 2-1 such that the amount of carbon nanotubes was 1
part relative to 100 parts of polymer. A surface resistivity of
2,825 .OMEGA./sq. was measured using the applied film.
Example 2-4
[0125] An applied film was obtained through the same operation as
in Example 1-4 with the exception that the mixing ratio of the
SGCNT-1 dispersion liquid and the latex was changed in the same way
as in Example 2-1 such that the amount of carbon nanotubes was 1
part relative to 100 parts of polymer. A surface resistivity of
2,959 .OMEGA./sq. was measured using the applied film.
Comparative Example 2
[0126] An applied film was obtained through the same operation as
in Comparative Example 1 with the exception that the mixing ratio
of the SGCNT-1 dispersion liquid and the latex was changed in the
same way as in Example 2-1 such that the amount of carbon nanotubes
was 1 part relative to 100 parts of polymer. A surface resistivity
of 8,025 .OMEGA./sq. was measured using the applied film.
Example 3-1
[0127] In Example 3-1, 12.5 g of the NC7000-1 dispersion liquid was
mixed with 0.5 g of an acrylonitrile-butadiene-based latex (product
name: CYATEX.RTM. NA-20; produced by Nippon A&L Inc.;
THF-insoluble component content of acrylonitrile-butadiene rubber:
70%) to achieve a ratio of 5 parts of carbon nanotubes relative to
100 parts of polymer and the mixture was stirred for 1 hour to
obtain an NC7000-1/rubber mixed solution. The resultant mixed
solution was poured into a glass petri dish and was held in a dry
air flow environment at 50.degree. C. for 48 hours to evaporate
moisture and obtain an applied film. A surface resistivity of 1,136
.OMEGA./sq. was measured using the applied film.
Example 3-2
[0128] An applied film was obtained through the same operation as
in Example 3-1 with the exception that the latex used in Example
3-1 was changed to other acrylonitrile-butadiene-based latex
(product name: Nipol.RTM. Lx554; produced by Zeon Corporation;
THF-insoluble component content of acrylonitrile-butadiene rubber:
60%). A surface resistivity of 1,351 .OMEGA./sq. was measured using
the applied film.
Example 3-3
[0129] An applied film was obtained through the same operation as
in Example 3-1 with the exception that the latex used in Example
3-1 was changed to other acrylonitrile-butadiene-based latex
(product name: Nipol.RTM. Lx553; produced by Zeon Corporation;
THF-insoluble component content of acrylonitrile-butadiene rubber:
43%). A surface resistivity of 1,587 .OMEGA./sq. was measured using
the applied film.
Example 3-4
[0130] An applied film was obtained through the same operation as
in Example 3-1 with the exception that the latex used in Example
3-1 was changed to other acrylonitrile-butadiene-based latex
(product name: Nipol.RTM. Lx552; produced by Zeon Corporation;
THF-insoluble component content of acrylonitrile-butadiene rubber:
27%). A surface resistivity of 1,876 .OMEGA./sq. was measured using
the applied film.
Comparative Example 3
[0131] An applied film was obtained through the same operation as
in Example 3-1 with the exception that the latex used in Example
3-1 was changed to other acrylonitrile-butadiene-based latex
(product name: Nipol.RTM. Lx551; produced by Zeon Corporation;
THF-insoluble component content of acrylonitrile-butadiene rubber:
0%). Surface resistivity could not be measured using the applied
film (i.e., surface resistivity exceeded the measurement limit of
10.sup.7 .OMEGA./sq.).
Example 4-1
[0132] In Example 4-1, 5.063 g of the SGCNT-1 dispersion liquid was
mixed with 0.5 g of an acrylonitrile-butadiene-based latex (product
name: CYATEX.RTM. NA-20; produced by Nippon A&L Inc.;
THF-insoluble component content of acrylonitrile-butadiene rubber:
70%) to achieve a ratio of 2 parts of carbon nanotubes relative to
100 parts of polymer and the mixture was stirred for 1 hour to
obtain an SGCNT-1/rubber mixed solution. The resultant mixed
solution was poured into 2-propanol to coagulate and after 1 hour
of stirring was filtered to collect coagulated material. The
coagulated material was dried under reduced pressure at 40.degree.
C. for 12 hours to obtain a test piece. A volume conductivity of
0.51943 S/cm was measured using the test piece.
Example 4-2
[0133] A test piece was obtained through the same operation as in
Example 4-1 with the exception that the latex used in Example 4-1
was changed to other acrylonitrile-butadiene-based latex (product
name: Nipol.RTM. Lx554; produced by Zeon Corporation; THF-insoluble
component content of acrylonitrile-butadiene rubber: 60%). A volume
conductivity of 0.42786 S/cm was measured using the test piece.
Example 4-3
[0134] A test piece was obtained through the same operation as in
Example 4-1 with the exception that the latex used in Example 4-1
was changed to other acrylonitrile-butadiene-based latex (product
name: Nipol.RTM. Lx553; produced by Zeon Corporation; THF-insoluble
component content of acrylonitrile-butadiene rubber: 43%). A volume
conductivity of 0.32582 S/cm was measured using the test piece.
Example 4-4
[0135] A test piece was obtained through the same operation as in
Example 4-1 with the exception that the latex used in Example 4-1
was changed to other acrylonitrile-butadiene-based latex (product
name: Nipol.RTM. Lx552; produced by Zeon Corporation; THF-insoluble
component content of acrylonitrile-butadiene rubber: 27%). A volume
conductivity of 0.26036 S/cm was measured using the test piece.
Comparative Example 4
[0136] A test piece was obtained through the same operation as in
Example 4-1 with the exception that the latex used in Example 4-1
was changed to other acrylonitrile-butadiene-based latex (product
name: Nipol.RTM. Lx551; produced by Zeon Corporation; THF-insoluble
component content of acrylonitrile-butadiene rubber: 0%). A volume
conductivity of 0.03214 S/cm was measured using the test piece.
Example 5-1
[0137] In Example 5-1, 2.516 g of the SGCNT-1 dispersion liquid was
mixed with 0.5 g of an acrylonitrile-butadiene-based latex (product
name: CYATEX.RTM. NA-20; produced by Nippon A&L Inc.;
THF-insoluble component content of acrylonitrile-butadiene rubber:
70%) to achieve a ratio of 1 part of carbon nanotubes relative to
100 parts of polymer and the mixture was stirred for 1 hour to
obtain an SGCNT-1/rubber mixed solution. The resultant mixed
solution was poured into 2-propanol to coagulate and after 1 hour
of stirring was filtered to collect coagulated material. The
coagulated material was dried under reduced pressure at 40.degree.
C. for 12 hours to obtain a test piece. A volume conductivity of
0.052428 S/cm was measured using the test piece.
Example 5-2
[0138] A test piece was obtained through the same operation as in
Example 5-1 with the exception that the latex used in Example 5-1
was changed to other acrylonitrile-butadiene-based latex (product
name: Nipol.RTM. Lx554; produced by Zeon Corporation; THF-insoluble
component content of acrylonitrile-butadiene rubber: 60%). A volume
conductivity of 0.048729 S/cm was measured using the test
piece.
Example 5-3
[0139] A test piece was obtained through the same operation as in
Example 5-1 with the exception that the latex used in Example 5-1
was changed to other acrylonitrile-butadiene-based latex (product
name: Nipol.RTM. Lx553; produced by Zeon Corporation; THF-insoluble
component content of acrylonitrile-butadiene rubber: 43%). A volume
conductivity of 0.044414 S/cm was measured using the test
piece.
Example 5-4
[0140] A test piece was obtained through the same operation as in
Example 5-1 with the exception that the latex used in Example 5-1
was changed to other acrylonitrile-butadiene-based latex (product
name: Nipol.RTM. Lx552; produced by Zeon Corporation; THF-insoluble
component content of acrylonitrile-butadiene rubber: 27%). A volume
conductivity of 0.021484 S/cm was measured using the test
piece.
Comparative Example 5
[0141] A test piece was obtained through the same operation as in
Example 5-1 with the exception that the latex used in Example 5-1
was changed to other acrylonitrile-butadiene-based latex (product
name: Nipol.RTM. Lx551; produced by Zeon Corporation; THF-insoluble
component content of acrylonitrile-butadiene rubber: 0%). A volume
conductivity of 0.00041142 S/cm was measured using the test
piece.
Comparative Example 6-1
[0142] In Comparative Example 6-1, 5.021 g of the HiPco-1
dispersion liquid was mixed with 0.5 g of an
acrylonitrile-butadiene-based latex (product name: CYATEX.RTM.
NA-20; produced by Nippon A&L Inc.; THF-insoluble component
content of acrylonitrile-butadiene rubber: 70%) to achieve a ratio
of 2 parts of carbon nanotubes relative to 100 parts of polymer and
the mixture was stirred for 1 hour to obtain a HiPco-1/rubber mixed
solution. The resultant mixed solution was poured into a glass
petri dish and was held in a dry air flow environment at 50.degree.
C. for 48 hours to evaporate moisture and obtain an applied film.
Surface resistivity measured using the applied film exceeded the
measurement limit.
Comparative Example 6-2
[0143] An applied film was obtained through the same operation as
in Comparative Example 6-1 with the exception that the latex used
in Comparative Example 6-1 was changed to other
acrylonitrile-butadiene-based latex (product name: Nipol.RTM.
Lx554; produced by Zeon Corporation; THF-insoluble component
content of acrylonitrile-butadiene rubber: 60%). Surface
resistivity measured using the applied film exceeded the
measurement limit.
Comparative Example 6-3
[0144] An applied film was obtained through the same operation as
in Comparative Example 6-1 with the exception that the latex used
in Comparative Example 6-1 was changed to other
acrylonitrile-butadiene-based latex (product name: Nipol.RTM.
Lx553; produced by Zeon Corporation; THF-insoluble component
content of acrylonitrile-butadiene rubber: 43%). Surface
resistivity measured using the applied film exceeded the
measurement limit.
Comparative Example 6-4
[0145] An applied film was obtained through the same operation as
in Comparative Example 6-1 with the exception that the latex used
in Comparative Example 6-1 was changed to other
acrylonitrile-butadiene-based latex (product name: Nipol.RTM.
Lx552; produced by Zeon Corporation; THF-insoluble component
content of acrylonitrile-butadiene rubber: 27%). Surface
resistivity measured using the applied film exceeded the
measurement limit.
Comparative Example 6-5
[0146] An applied film was obtained through the same operation as
in Comparative Example 6-1 with the exception that the latex used
in Comparative Example 6-1 was changed to other
acrylonitrile-butadiene-based latex (product name: Nipol.RTM.
Lx551; produced by Zeon Corporation; THF-insoluble component
content of acrylonitrile-butadiene rubber: 0%). Surface resistivity
measured using the applied film exceeded the measurement limit.
[0147] These results demonstrate that a composite material and a
conductive formed product having low resistance values can be
obtained by using a dispersion liquid of carbon nanotubes that have
an average diameter (Av) and a diameter distribution (3.sigma.)
satisfying a relationship 0.60>3.sigma./Av>0.20 in
combination with a latex including a polymer that has a
tetrahydrofuran-insoluble component content of from 1 mass % to 75
mass %.
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