U.S. patent application number 16/883191 was filed with the patent office on 2020-12-24 for nanocellulose/surfactant composite.
This patent application is currently assigned to SUMITOMO RUBBER INDUSTRIES, LTD.. The applicant listed for this patent is SUMITOMO RUBBER INDUSTRIES, LTD.. Invention is credited to Sumiko MIYAZAKI, Daisuke SATO.
Application Number | 20200399444 16/883191 |
Document ID | / |
Family ID | 1000004888367 |
Filed Date | 2020-12-24 |
United States Patent
Application |
20200399444 |
Kind Code |
A1 |
MIYAZAKI; Sumiko ; et
al. |
December 24, 2020 |
NANOCELLULOSE/SURFACTANT COMPOSITE
Abstract
The present invention provides nanocellulose/surfactant
composites having excellent redispersibility in water and related
compositions and methods, including methods for producing the
composites. Included is a nanocellulose/surfactant composite
containing a nanocellulose and a surfactant, the
nanocellulose/surfactant composite having a moisture content of
lower than 10%, the surfactant including an ionic surfactant having
a weight average molecular weight of 3000 or more.
Inventors: |
MIYAZAKI; Sumiko; (Kobe-shi,
JP) ; SATO; Daisuke; (Kobe-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUMITOMO RUBBER INDUSTRIES, LTD. |
Kobe-shi |
|
JP |
|
|
Assignee: |
SUMITOMO RUBBER INDUSTRIES,
LTD.
Kobe-shi
JP
|
Family ID: |
1000004888367 |
Appl. No.: |
16/883191 |
Filed: |
May 26, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L 1/02 20130101 |
International
Class: |
C08L 1/02 20060101
C08L001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 24, 2019 |
JP |
2019-116499 |
Claims
1. A nanocellulose/surfactant composite, comprising a nanocellulose
and a surfactant, the nanocellulose/surfactant composite having a
moisture content of lower than 10%, the surfactant comprising an
ionic surfactant having a weight average molecular weight of 3000
or more.
2. The nanocellulose/surfactant composite according to claim 1,
wherein the nanocellulose comprises at least one of a
microfibrillated cellulose or a cellulose nanocrystal.
3. The nanocellulose/surfactant composite according to claim 2,
wherein the microfibrillated cellulose has an average fiber
diameter of 2 to 50 nm, an average fiber length of 10 .mu.m or
less, and a degree of crystallinity of 60 to 90%.
4. The nanocellulose/surfactant composite according to claim 2,
wherein the cellulose nanocrystal has an average fiber diameter of
2 to 50 nm, an average fiber length of 500 nm or less, and a degree
of crystallinity of 70% or more.
5. A method for producing the nanocellulose/surfactant composite
according to claim 1, the method comprising steps of: mixing the
ionic surfactant with a dispersion of the nanocellulose to prepare
a liquid mixture, and drying the liquid mixture.
6. A rubber composition, comprising the nanocellulose/surfactant
composite according to claim 1.
Description
TECHNICAL FIELD
[0001] The present invention relates to nanocellulose/surfactant
composites and production methods and rubber compositions
thereof.
BACKGROUND ART
[0002] Nanocelluloses such as cellulose nanofibers (CNF) and
cellulose nanocrystals (CNC) can impart excellent properties
including high strength with lightweight. Thus, composite materials
including such nanocelluloses have been proposed.
[0003] For example, some nanocelluloses are provided in the form of
dried products prepared by drying dispersions in which
nanocelluloses are dispersed in aqueous media. In many cases, the
dried products are redispersed in aqueous media, and the
redispersions are combined with other materials such as rubbers or
resins to produce composite materials.
[0004] Upon redispersion, however, nanocelluloses are sometimes not
well dispersed. Disadvantageously, such redispersions, when
combined with other materials, cannot provide composite materials
in which the nanocelluloses are sufficiently dispersed. Therefore,
there is a need for nanocellulose materials (dried products) having
excellent redispersibility in water.
SUMMARY OF INVENTION
Technical Problem
[0005] The present invention aims to solve the problem and provide
nanocellulose/surfactant composites having excellent
redispersibility in water and related compositions and methods,
including methods for producing the composites.
Solution to Problem
[0006] The present invention relates to a nanocellulose/surfactant
composite, containing a nanocellulose and a surfactant, the
nanocellulose/surfactant composite having a moisture content of
lower than 10%, the surfactant including an ionic surfactant having
a weight average molecular weight of 3000 or more.
[0007] Preferably, the nanocellulose includes at least one of a
microfibrillated cellulose or a cellulose nanocrystal.
[0008] Preferably, the microfibrillated cellulose has an average
fiber diameter of 2 to 50 nm, an average fiber length of 10 .mu.m
or less, and a degree of crystallinity of 60 to 90%.
[0009] Preferably, the cellulose nanocrystal has an average fiber
diameter of 2 to 50 nm, an average fiber length of 500 nm or less,
and a degree of crystallinity of 70% or more.
[0010] The present invention also relates to a method for producing
the nanocellulose/surfactant composite, including steps of: mixing
the ionic surfactant with a dispersion of the nanocellulose to
prepare a liquid mixture, and drying the liquid mixture.
[0011] The present invention also relates to a rubber composition,
containing the nanocellulose/surfactant composite.
Advantageous Effects of Invention
[0012] The nanocellulose/surfactant composite of the present
invention contains a nanocellulose and a surfactant and has a
moisture content of lower than 10%. Further, the surfactant
includes an ionic surfactant having a weight average molecular
weight of 3000 or more. Such a composite has excellent
redispersibility in water. Thus, the nanocellulose/surfactant
composite can be used to provide well-dispersed nanocellulose
composite materials.
DESCRIPTION OF EMBODIMENTS
[Nanocellulose/Surfactant Composite]
[0013] The nanocellulose/surfactant composite of the present
invention contains a nanocellulose and an ionic surfactant having a
weight average molecular weight of 3000 or more, and has a moisture
content of lower than 10% by mass. The composite has excellent
redispersibility in water and can be used to provide well-dispersed
nanocellulose composite materials (e.g., rubber compositions
containing rubber and nanocellulose).
[0014] The mechanism of this effect is not clear, but may be
explained as follows.
[0015] In the case of low moisture content nanocellulose products
(e.g., dried products) prepared by drying dispersions of
nanocelluloses in water, when redispersed in water they tend not to
reconstruct dispersions in which the nanocelluloses are
sufficiently dispersed. Presumably, this is because the
nanocelluloses in the dried products or the like strongly aggregate
to each other, and this strong aggregation force inhibits the
nanocelluloses from redispersing in water. In contrast, low
moisture content nanocellulose products prepared by drying
dispersions of nanocelluloses and ionic surfactants having a
predetermined molecular weight in water can be redispersed to
reconstruct excellently dispersed nanocellulose dispersions.
[0016] Presumably, this is because the specific surfactants inhibit
the aggregation of the nanocelluloses in the dried products or the
like, thereby enabling reconstruction of dispersions in which the
nanocelluloses are sufficiently dispersed upon redispersion. Thus,
a composite containing a nanocellulose and a specific surfactant
and having a moisture content adjusted to lower than 10% by mass is
considered to have excellent redispersibility in water. It is also
considered that a nanocellulose redispersion prepared from the
composite can be used to provide excellently dispersed
nanocellulose composite materials.
[0017] The nanocellulose/surfactant composite has a moisture
content (proportion of the contained water) of lower than 10% by
mass based on 100% by mass of the composite. The moisture content
of the composite may be 7% by mass or lower, 5% by mass or lower,
or 3% by mass or lower. The composite even with such a low moisture
content can be redispersed in water to provide a well-dispersed
nanocellulose dispersion.
[0018] The moisture content is measured in accordance with JIS A
1476:2006 "Measuring method for moisture content of building
materials by drying at elevated temperature".
(Nanocellulose)
[0019] The nanocellulose in the nanocellulose/surfactant composite
is a cellulose fiber having a nano-sized fiber size (diameter) and
may be prepared by disintegrating (fibrillating) cellulose
fiber-containing materials (e.g., wood pulp) into nano-sized
fibers. In the nanocellulose, cellulose molecules are aggregated
together into nano-sized diameter fibers, and such cellulose
molecules are linked by hydrogen bonding. In plant cell walls, the
smallest units are cellulose microfibrils each having a width of
about 4 nm (single cellulose nanofibers) and form basic structural
materials of plants. The nanocellulose is a nano-sized cellulose
formed of a cellulose microfibril or an aggregate of cellulose
microfibrils.
[0020] Suitable examples of the nanocellulose include
microfibrillated celluloses (cellulose nanofibers (CNF)) and
cellulose nanocrystals (CNC). One type or a combination of two or
more types of nanocelluloses may be used.
[0021] The CNF fiber can be prepared by treating cellulose fibers
via, for example, mechanical fibrillation. A method for preparing
the CNF may be performed by fibrillating a cellulose
fiber-containing material such as pulp, e.g., by mechanically
grinding or beating a water suspension or slurry of the cellulose
fiber-containing material using a refiner, a high-pressure
homogenizer, a grinder, a single or multi-screw kneader (preferably
twin screw kneader), a bead mill, or other devices.
[0022] From the standpoints of dispersibility in a matrix and other
properties, the CNF preferably has an average fiber diameter of 10
.mu.m or less. The average fiber diameter is more preferably 500 nm
or less, still more preferably 100 nm or less, particularly
preferably 50 nm or less. The lower limit of the average fiber
diameter is not limited, but is preferably 1 nm or more, more
preferably 2 nm or more, still more preferably 3 nm or more.
[0023] The CNF preferably has an average fiber length of 100 nm or
more, more preferably 300 nm or more, still more preferably 500 nm
or more. The upper limit is also preferably 50 .mu.m or less, more
preferably 10 .mu.m or less. Moreover, the CNF preferably has an
aspect ratio (average fiber length/average fiber diameter) of 10 or
more.
[0024] The CNC crystal can be prepared by chemically treating
cellulose fibers via, for example, acid hydrolysis. A method for
preparing the CNC may be performed by known methods, such as a
chemical technique which includes treating a water suspension or
slurry of the aforementioned cellulose fiber-containing material
via, for example, acid hydrolysis with an acid such as sulfuric
acid, hydrochloric acid, or hydrobromic acid.
[0025] From the standpoints of dispersibility in a matrix and other
properties, the CNC preferably has an average fiber diameter of 10
.mu.m or less. The average fiber diameter is more preferably 500 nm
or less, still more preferably 100 nm or less, particularly
preferably 50 nm or less. The lower limit of the average fiber
diameter is not limited, but is preferably 1 nm or more, more
preferably 2 nm or more, still more preferably 3 nm or more.
[0026] The CNC preferably has an average fiber length of 50 nm or
more, more preferably 80 nm or more, still more preferably 100 nm
or more. The upper limit is preferably 800 nm or less, more
preferably 500 nm or less, still more preferably 300 nm or
less.
[0027] Herein, the average fiber diameter and average fiber length
of the nanocellulose may be measured by image analysis using
scanning electron micrographs, image analysis using transmission
electron micrographs, image analysis using atomic force
micrographs, X-ray scattering data analysis, the aperture impedance
method (Coulter principle), or other methods. As used herein, the
average fiber diameter and average fiber length of the
nanocellulose (cellulose fiber) typically refer to the average
fiber diameter and average fiber length, respectively, of the
aggregates of cellulose fibrils formed by aggregation of cellulose
molecules.
[0028] The CNF usually has a degree of crystallinity of 90% or
less, and the degree of crystallinity may be 80% or less or 70% or
less. From the standpoints of dispersibility in a rubber matrix and
other properties, the lower limit of the degree of crystallinity is
preferably 30% or more, more preferably 50% or more, still more
preferably 60% or more.
[0029] The CNC preferably has a degree of crystallinity of 70% or
more, more preferably 75% or more, still more preferably 80% or
more, from the standpoints of dispersibility in a rubber matrix and
other properties. The upper limit of the degree of crystallinity is
not limited and may be 100%.
[0030] Herein, the degree of crystallinity of the nanocellulose
refers to the degree of cellulose I crystallinity calculated from
diffraction intensity data obtained by X-ray diffraction in
accordance with the Segal's method and is defined by the following
equation: Degree of cellulose I crystallinity (%)
[(I22.6-I18.5)/I22.6].times.100
wherein 122.6 denotes the diffraction intensity of the lattice
plane (002) (diffraction angle 2.theta.=22.6.degree.), and 118.5
denotes the diffraction intensity of the amorphous portion
(diffraction angle 2.theta.=18.5.degree.) in X-ray diffraction.
[0031] Examples of the raw material (cellulose) of the
nanocellulose include plant-derived celluloses such as softwood
kraft pulp, hardwood kraft pulp, Manila hemp pulp, sisal hemp pulp,
bamboo pulp, esparto pulp, and cotton pulp; regenerated celluloses
such as regenerated celluloses (polynosic rayons) with a high
degree of polymerization produced by spinning in a low acid bath,
and solvent-spun rayons produced using amine-oxide organic
solvents; bacterial celluloses; animal-derived celluloses such as
sea squirt-derived cellulose; and nanocelluloses produced by
electrospinning.
[0032] The nanocellulose may be produced from a plant-derived
cellulose by a physical or chemical method. Examples of the
physical (fibrillation) method include a high-pressure homogenizer
method, a microfluidizer method, a ball mill method, and a grinding
mill method. Examples of the chemical method include a TEMPO
oxidation method.
[0033] The nanocellulose may also be, for example, one in which
some lignin or hemicellulose remains or one which has a chemically
modified surface (modified pulp). For example, the modified pulp
may be one in which the hydroxyl groups of cellulose fibers are
modified by at least one method selected from esterification or
etherification. Moreover, the cross sectional shape of the
nanocellulose may be either anisotropic (e.g., flat) or isotropic
(e.g., perfect circle or regular polygon).
(Ionic Surfactant)
[0034] The ionic surfactant has a weight average molecular weight
(Mw) of 3000 or more. A Mw in this range tends to provide good
redispersibility in water. The Mw is more preferably 4000 or more,
still more preferably 5000 or more. The upper limit is not limited,
but is preferably 50000 or less, more preferably 30000 or less,
still more preferably 25000 or less. Herein, the Mw can be
determined by gel permeation chromatography (GPC) (GPC-8000 series
available from Tosoh Corporation, detector: differential
refractometer, column: TSKGEL SUPERMULTIPORE HZ-M available from
Tosoh Corporation) calibrated with polystyrene standards.
[0035] Examples of the ionic surfactant in the
nanocellulose/surfactant composite include anionic surfactants and
cationic surfactants. From the standpoint of redispersibility in
water, anionic surfactants are preferred among these. One type or a
combination of two or more types of ionic surfactants may be
used.
[0036] An anionic surfactant has a hydrophobic group and a
hydrophilic group. The hydrophobic group may be any functional
group with hydrophobicity but is preferably a hydrocarbon group.
The hydrocarbon group may be a linear, branched, or cyclic.
Examples include aliphatic, alicyclic, and aromatic hydrocarbon
groups. Preferred among these are aliphatic or aromatic hydrocarbon
groups. The hydrocarbon group preferably has a carbon number of 4
to 20, more preferably 4 to 15, still more preferably 4 to 12.
[0037] Preferred among the aliphatic hydrocarbon groups are C1-C20,
more preferably C1-C10, still more preferably C1-C6 aliphatic
hydrocarbon groups. Preferred examples include alkyl groups having
the above-mentioned number of carbon atoms. Specific examples
include methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl,
sec-butyl, tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, octyl,
nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl,
and octadecyl groups. Other examples include alkenyl or alkynyl
groups having the above-mentioned number of carbon atoms, for
example, alkenyl groups such as vinyl, allyl, 1-propenyl,
1-methylethenyl, and isobutylene groups, and alkynyl groups such as
ethynyl and propargyl groups. Among these, an isobutylene group is
preferred.
[0038] Preferred among the alicyclic hydrocarbon groups are C3-C8
alicyclic hydrocarbon groups. Specific examples include
cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,
cyclooctyl, cyclopropenyl, cyclobutenyl, cyclopentenyl,
cyclohexenyl, cycloheptenyl, and cyclooctenyl groups.
[0039] Preferred among the aromatic hydrocarbon groups are C6-C12
aromatic hydrocarbon groups. Specific examples include phenyl,
benzyl, phenethyl, tolyl, xylyl, and naphthyl groups, among which
phenyl, benzyl, and phenethyl groups are preferred, with a phenyl
or benzyl group being more preferred, with a phenyl group being
particularly preferred. The tolyl or xylyl group may have a methyl
substituent(s) at any of the ortho, meta, and para positions on the
benzene ring.
[0040] The hydrophilic group is preferably at least one selected
from the group consisting of carboxyl, sulfonate, sulfate, and
phosphate groups, among which a carboxyl or sulfonate group is more
preferred, with a carboxyl group being particularly preferred.
[0041] In a preferable embodiment, the anionic surfactant has any
of the above-mentioned functional groups. Specifically, it may be
classified as, for example, a carboxylate surfactant, a sulfonate
surfactant, a sulfate surfactant, or a phosphate surfactant.
[0042] Examples of the carboxylate surfactant include C6-C30 fatty
acid salts, polycarboxylic acid salts, rosin acid salts, dimer acid
salts, polymer acid salts, tall oil fatty acid salts, and
polycarboxylate polymeric surfactants, among which C10-C20
carboxylic acid salts, polycarboxylic acid salts, and
polycarboxylate polymeric surfactants are preferred. Examples of
the sulfonate surfactant include alkylbenzene sulfonates,
alkylsulfonates, alkylnaphthalene sulfonates, naphthalene
sulfonates, and diphenyl ether sulfonates. Examples of the sulfate
surfactant include alkylsulfates, polyoxyalkylene alkylsulfates,
polyoxyalkylene alkylphenyl ether sulfates, tristyrenated phenol
sulfates, distyrenated phenol sulfates, .alpha.-olefin sulfates,
alkylsuccinic acid sulfates, polyoxyalkylene tristyrenated phenol
sulfates, and polyoxyalkylene distyrenated phenol sulfates.
Examples of the phosphate surfactant include alkylphosphates and
polyoxyalkylene phosphates. Examples of these compound salts
include metal salts (e.g., Na, K, Ca, Mg, and Zn), ammonium salts,
and amine salts (e.g., triethanolamine salts).
[0043] Examples of the alkyl groups of these surfactants include
C4-C30 alkyl groups. Examples of the polyoxyalkylene groups thereof
include those having C2-C4 alkylene groups, such as ones in which
the number of moles of ethylene oxide added is about 1 to 50.
[0044] Likewise, a cationic surfactant has a hydrophobic group and
a hydrophilic group. Examples of the cationic surfactant include
quaternary ammonium salt surfactants. Specifically, suitable are
surfactants having a quaternary ammonium group and a hydrocarbon
group as represented by the following formula:
[R.sup.11R.sup.12R.sup.13R.sup.14N].sup.+X.sup.-
wherein R.sup.11 and R.sup.12 are the same as or different from
each other and each represent a C1-C22 alkyl or alkenyl group, and
at least one of R.sup.11 and R.sup.12 has 4 or more carbon atoms;
R.sup.13 and R.sup.14 each represent a C1-C3 alkyl group; and X
represents a monovalent anion.
[0045] In the formula, preferably, one of R.sup.11 and R.sup.12 is
a methyl group and the other is a C6-C18 alkyl group. R.sup.13 and
R.sup.14 are each preferably a methyl group. Examples of X include
halogen ions such as chloride or bromide ions.
[0046] Specific examples of the cationic surfactants of the above
formula include alkyltrimethylammonium salts such as
hexyltrimethylammonium chloride, octyltrimethylammonium chloride,
decyltrimethylammonium chloride, dodecyltrimethylammonium chloride,
tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium
chloride, and stearyltrimethylammonium chloride, and their
corresponding bromides. Hexadecyltrimethylammonium bromide is
preferred among these as it can enhance dispersibility of the
nanocellulose.
[0047] The surfactant may be a commercial product available from,
for example, Elementis PLC, Kao Corporation, Dai-Ichi Kogyo Seiyaku
Co., Ltd., or Sanyo Chemical Industries, Ltd.
[0048] From the standpoint of redispersibility in water, the
nanocellulose/surfactant composite preferably contains the ionic
surfactant in an amount of 5 to 50 parts by mass relative to 100
parts by mass of the nanocellulose (solids content). The amount is
more preferably 9 parts by mass or more, still more preferably 10
parts by mass or more. The upper limit is more preferably 25 parts
by mass or less, still more preferably 20 parts by mass or
less.
[0049] The nanocellulose/surfactant composite containing a
nanocellulose and a surfactant may be produced, for example, by a
method including: a step (step (1)) of mixing the ionic surfactant
with a dispersion of the nanocellulose to prepare a liquid mixture;
and a step (step (2)) of drying the liquid mixture. In addition to
the above-mentioned steps, the production method may further
include other steps. Moreover, each step may be performed either
once or repeatedly.
(Step (1))
[0050] Step (1) includes mixing the ionic surfactant with a
dispersion of the nanocellulose to prepare a liquid mixture.
[0051] The method of mixing the ionic surfactant with a dispersion
of the nanocellulose to prepare a liquid mixture in step (1) may be
carried out, for example, by mixing the ionic surfactant with a
dispersion of the nanocellulose using a known agitator such as a
high-speed homogenizer, an ultrasonic homogenizer, a colloid mill,
or a blender mill. The temperature and duration for preparing the
liquid mixture may be appropriately selected so that the ionic
surfactant and a dispersion of the nanocellulose are sufficiently
mixed; for example, preferably at a temperature of 10 to 40.degree.
C. for 3 to 120 minutes, more preferably at a temperature of 15 to
30.degree. C. for 5 to 90 minutes.
[0052] The dispersion of the nanocellulose may be prepared by known
methods. For example, it may be prepared by dispersing the
nanocellulose in water using a mixer such as a high-pressure
homogenizer, an ultrasonic homogenizer, or a colloid mill. The
temperature and duration for the preparation may be appropriately
selected in view of the dispersion state. The amount (solids
content) of the nanocellulose in the dispersion of the
nanocellulose is not limited, but from the standpoint of uniform
dispersibility, it is 0.1 to 20% by mass, preferably 0.2 to 10% by
mass, more preferably 0.3 to 5% by mass of the dispersion (100% by
mass).
(Step (2))
[0053] Step 2 includes drying the liquid mixture obtained in step
1.
[0054] The drying method is not limited and known drying methods
that can evaporate the aqueous medium in the liquid mixture may be
appropriately used.
[0055] The drying temperature in step 2 may be appropriately
selected. For example, from the standpoints of drying efficiency
and other properties, the drying temperature is preferably
100.degree. C. or higher, more preferably 105.degree. C. or higher,
still more preferably 110.degree. C. or higher. The upper limit is
not limited, but is preferably 200.degree. C. or lower, more
preferably 190.degree. C. or lower, still more preferably
180.degree. C. or lower.
[0056] The drying duration in step 2 may be appropriately selected
depending on the drying temperature. The duration may be selected
such that the desired amount of water can be removed. The drying
duration may be one minute to 12 hours, for example. In view of
drying efficiency and other properties, it may be, for example, 10
minutes to 10 hours or may be 30 minutes to five hours. The drying
step allows the resulting nanocellulose/surfactant composite to
have a moisture content of lower than 10% by mass.
[Nanocellulose/Rubber Composite]
[0057] A nanocellulose/rubber composite can be produced from the
liquid mixture containing the ionic surfactant and the
nanocellulose obtained in step 1. However, since the
nanocellulose/surfactant composite has excellent redispersibility
in water, as described earlier, a well-dispersed
nanocellulose/rubber composite can also be produced from a
redispersion prepared by redispersing in water the
nanocellulose/surfactant composite obtained by step 2 (drying).
[0058] Specifically, an excellently dispersed nanocellulose/rubber
composite can be produced by a method including: a step (step 3) of
mixing a redispersion of the nanocellulose/surfactant composite
with a rubber latex to prepare a compounded latex; and a step (step
4) of coagulating the compounded latex. In addition to the
above-mentioned steps, the production method may further include
other steps. Moreover, each step may be performed either once or
repeatedly.
(Step 3)
[0059] Step 3 includes mixing a redispersion of the
nanocellulose/surfactant composite with a rubber latex to prepare a
compounded latex.
[0060] The redispersion of the nanocellulose/surfactant composite
may be prepared by mixing the nanocellulose/surfactant composite
with water. The preparation of the redispersion may be carried out
by known methods, such as by dispersing the
nanocellulose-containing composite in water using a mixer such as a
high-pressure homogenizer, an ultrasonic homogenizer, or a colloid
mill. The temperature and duration for the preparation may be
appropriately selected in view of the dispersion state. The amount
(solids content) of the nanocellulose in the redispersion is not
limited, but from the standpoint of uniform dispersibility, it is
0.1 to 20% by mass, preferably 0.2 to 10% by mass, more preferably
0.3 to 5% by mass of the redispersion (100% by mass).
[0061] Suitable examples of the rubber latex include diene rubber
latexes such as natural rubber latex and synthetic diene rubber
latexes (e.g., latexes of polybutadiene rubber (BR),
styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber
(SIBR), polyisoprene rubber, acrylonitrile butadiene rubber,
ethylene vinyl acetate rubber, chloroprene rubber, vinylpyridine
rubber, or butyl rubber). These rubber latexes may be used alone or
in combinations of two or more. Natural rubber latex, SBR latex, BR
latex, and polyisoprene rubber latex are more preferred among
these, with natural rubber latex being further preferred.
[0062] The pH of the rubber latex is preferably 8.5 or higher, more
preferably 9.5 or higher. A rubber latex having a pH lower than 8.5
tends to be unstable and easily coagulate. The pH of the rubber
latex is preferably 12 or lower, more preferably 11 or lower. A
rubber latex having a pH higher than 12 may be degraded.
[0063] The rubber latex may be prepared by conventionally known
methods. Alternatively, it may be any commercial product. The
rubber latex preferably has a rubber solids content of 10 to 80% by
mass, more preferably 20 to 60% by mass.
[0064] During the mixing in step 3, the redispersion of the
nanocellulose/surfactant composite and the rubber latex may be
mixed and sufficiently stirred until they form a uniform dispersion
to prepare a compounded latex. The mixing may be carried out, for
example: by dropwise adding the redispersion of the
nanocellulose/surfactant composite to the rubber latex placed in a
known agitator such as a blender mill with stirring; or by dropwise
adding the rubber latex to the redispersion of the
nanocellulose/surfactant composite while stirring.
[0065] The pH of the compounded latex is preferably 9.0 or higher,
more preferably 9.5 or higher. A compounded latex having a pH lower
than 9.0 tends to be unstable. The pH of the compounded latex is
preferably 12 or lower, more preferably 11.5 or lower. A compounded
latex having a pH higher than 12 may be degraded.
[0066] In step 3, from the standpoint of dispersibility of the
nanocellulose, the redispersion is preferably mixed with the rubber
latex such that the amount of the nanocellulose is 1 to 150 parts
by mass relative to 100 parts by mass of the rubber solids in the
rubber latex. The amount of the nanocellulose is more preferably 5
parts by mass or more, but is more preferably 100 parts by mass or
less, still more preferably 70 parts by mass or less, particularly
preferably 30 parts by mass or less.
[0067] The mixing temperature and duration in step 3 are preferably
at 10 to 40.degree. C. for 3 to 120 minutes, more preferably at 15
to 30.degree. C. for 5 to 90 minutes, in order to prepare a uniform
compounded latex.
(Step 4)
[0068] Step 4 includes coagulating the resulting compounded latex.
The coagulation may be accomplished, for example, by adjusting the
pH of the compounded latex obtained in step 3 to 3 to 5, preferably
3 to 4. The coagulation of the compounded latex by pH adjustment
may usually be carried out by adding an acid to the compounded
latex. Examples of the acid for coagulation include sulfuric acid,
hydrochloric acid, formic acid, and acetic acid. The coagulation
step is preferably performed at 10 to 40.degree. C.
[0069] A flocculant may also be added to control the coagulation
(the size of the coagulated particle aggregates). Examples of the
flocculant include cationic polymers.
[0070] The resulting coagula (aggregates containing the coagulated
rubber and nanocellulose) may be filtrated, dried, further dried,
and subjected to rubber kneading using a kneading machine such as a
two-roll mill or a Banbury mixer by known methods to obtain a
nanocellulose/rubber composite in which the nanocellulose is
uniformly dispersed in the rubber matrix. The nanocellulose/rubber
composite may contain other components as long as the effect is not
inhibited.
[Rubber Composition]
[0071] The nanocellulose/rubber composite may be used in the form
of a masterbatch. For example, a rubber composition containing the
nanocellulose/rubber composite can be used in a variety of
applications. In the nanocellulose/rubber composite, the
nanocellulose is sufficiently dispersed in the rubber. Thus, a
rubber composition obtained by mixing the nanocellulose/rubber
composite with other components can also achieve sufficient
dispersion of the nanocellulose. This provides effective
reinforcement and a balanced improvement of rubber physical
properties including durability (tensile strength at break) and
fuel economy.
[0072] The rubber composition contains a rubber component. The
rubber component preferably includes the rubber component derived
from the rubber latex such as natural rubber latex, SBR latex, BR
latex, or polyisoprene rubber latex (the rubber component contained
in the nanocellulose/rubber composite) in an amount of 50% by mass
or more, more preferably 75% by mass or more, still more preferably
85% by mass or more. The amount may be 100% by mass.
[0073] In particular, the rubber component preferably includes a
natural rubber derived from a natural rubber latex (a natural
rubber contained in a composite produced from a nanocellulose and a
natural rubber latex) in an amount of 50% by mass or more, more
preferably 75% by mass or more, still more preferably 85% by mass
or more, based on 100% by mass of the rubber component. The amount
may be 100% by mass.
[0074] The rubber component of the rubber composition may include
an additional rubber component other than the rubber (rubber
component) contained in the nanocellulose/rubber composite.
Examples of the additional rubber component include diene rubbers
such as isoprene-based rubbers, polybutadiene rubber (BR),
styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber
(SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber
(CR), and acrylonitrile butadiene rubber (NBR). Other examples
include butyl rubbers and fluororubbers. These rubbers may be used
alone or in combinations of two or more. From the standpoints of
tire physical properties, SBR, BR, and isoprene-based rubbers are
preferred as the rubber component.
[0075] The additional rubber component may include an unmodified
diene rubber or a modified diene rubber.
[0076] The modified diene rubber may be any diene rubber having a
functional group interactive with a filler such as silica. For
example, it may be a chain end-modified diene rubber obtained by
modifying at least one chain end of a diene rubber with a compound
(modifier) having the functional group (chain end-modified diene
rubber terminated with the functional group); a backbone-modified
diene rubber having the functional group in the backbone; a
backbone- and chain end-modified diene rubber having the functional
group in both the backbone and chain end (e.g., a backbone- and
chain end-modified diene rubber in which the backbone has the
functional group and at least one chain end is modified with the
modifier); or a chain end-modified diene rubber that has been
modified (coupled) with a polyfunctional compound having two or
more epoxy groups in the molecule so that a hydroxyl or epoxy group
is introduced.
[0077] Examples of the functional group include amino, amide,
silyl, alkoxysilyl, isocyanate, imino, imidazole, urea, ether,
carbonyl, oxycarbonyl, mercapto, sulfide, disulfide, sulfonyl,
sulfinyl, thiocarbonyl, ammonium, imide, hydrazo, azo, diazo,
carboxyl, nitrile, pyridyl, alkoxy, hydroxyl, oxy, and epoxy
groups. These functional groups may be substituted. Amino
(preferably amino whose hydrogen atom is replaced with a C1-C6
alkyl group), alkoxy (preferably C1-C6 alkoxy), and alkoxysilyl
(preferably C1-C6 alkoxysilyl) groups are preferred among
these.
[0078] Non-limiting examples of the SBR include
emulsion-polymerized styrene-butadiene rubber (E-SBR) and
solution-polymerized styrene-butadiene rubber (S-SBR). These types
of SBR may be used alone or in combinations of two or more.
[0079] From the standpoints of tire physical properties, the SBR
preferably has a styrene content of 5% by mass or higher, more
preferably 10% by mass or higher, still more preferably 15% by mass
or higher. The styrene content is also preferably 60% by mass or
lower, more preferably 40% by mass or lower, still more preferably
30% by mass or lower.
[0080] Herein, the styrene content of the SBR is determined by
.sup.1H-NMR.
[0081] The SBR may be a commercial product manufactured or sold by,
for example, Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi
Kasei Corporation, or Zeon Corporation.
[0082] The SBR may be an unmodified SBR or a modified SBR. Examples
of the modified SBR include those into which functional groups as
listed for the modified diene rubber are introduced.
[0083] From the standpoints of wet grip performance and other
properties, the amount of the SBR, if present, based on 100% by
mass of the rubber component is preferably 10 to 90% by mass, more
preferably 20 to 80% by mass.
[0084] Non-limiting examples of the BR include high cis BR having
high cis content, BR containing syndiotactic polybutadiene
crystals, and BR synthesized using rare earth catalysts (rare
earth-catalyzed BR). These types of BR may be used alone or in
combinations of two or more. In particular, the BR is preferably a
high cis BR having a cis content of 90% by mass or higher to
improve abrasion resistance.
[0085] The BR may be an unmodified BR or a modified BR. Examples of
the modified BR include those into which functional groups as
listed for the modified diene rubber are introduced.
[0086] From the standpoints of abrasion resistance and other
properties, the amount of the BR, if present, based on 100% by mass
of the rubber component is preferably 10 to 90% by mass, more
preferably 20 to 80% by mass.
[0087] The BR may be a commercial product of, for example, Ube
Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, or Zeon
Corporation.
[0088] Examples of the isoprene-based rubbers include natural
rubber (NR), polyisoprene rubber (IR), refined NR, modified NR, and
modified IR. The NR may be one commonly used in the rubber industry
such as SIR20, RSS #3, or TSR20. Non-limiting examples of the IR
include those commonly used in the rubber industry such as IR2200.
Examples of the refined NR include deproteinized natural rubber
(DPNR) and highly purified natural rubber (UPNR). Examples of the
modified NR include epoxidized natural rubber (ENR), hydrogenated
natural rubber (HNR), and grafted natural rubber. Examples of the
modified IR include epoxidized polyisoprene rubber, hydrogenated
polyisoprene rubber, and grafted polyisoprene rubber. These
isoprene-based rubbers may be used alone or in combinations of two
or more.
[0089] From the standpoints of fuel economy and other properties,
the amount of the isoprene-based rubber, if present, based on 100%
by mass of the rubber component is preferably 10 to 90% by mass,
more preferably 20 to 80% by mass.
[0090] From the standpoints of rubber physical properties, the
amount of the nanocellulose per 100 parts by mass of the rubber
component in the rubber composition is preferably 2 parts by mass
or more, more preferably 5 parts by mass or more, still more
preferably 7 parts by mass or more. From the standpoints of
dispersibility of the nanocellulose and other properties, the
amount is also preferably 100 parts by mass or less, more
preferably 50 parts by mass or less, still more preferably 30 parts
by mass or less.
[0091] The rubber composition may contain additional fillers other
than the nanocellulose. Examples of the additional fillers include
carbon black, silica, calcium carbonate, talc, alumina, clay,
aluminum hydroxide, aluminum oxide, and mica. From the standpoints
of tire physical properties, carbon black or silica is preferred
among these.
[0092] Non-limiting examples of the carbon black include N134,
N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.
Examples of commercial products include those available from Asahi
Carbon Co., Ltd., Cabot Japan K.K., Tokai Carbon Co., Ltd.,
Mitsubishi Chemical Corporation, Lion Corporation, NSCC Carbon Co.,
Ltd, and Columbia Carbon. These may be used alone or in
combinations of two or more.
[0093] The amount of the carbon black per 100 parts by mass of the
rubber component is preferably 5 parts by mass or more, more
preferably 15 parts by mass or more. When the amount is not less
than the lower limit, good properties such as abrasion resistance
and grip performance tend to be obtained. The amount is also
preferably 100 parts by mass or less, more preferably 50 parts by
mass or less. When the amount is not more than the upper limit, the
rubber composition tends to obtain good processability.
[0094] The carbon black preferably has a nitrogen adsorption
specific surface area (N.sub.2SA) of 50 m.sup.2/g or more, more
preferably 80 m.sup.2/g or more, still more preferably 100
m.sup.2/g or more. When the N.sub.2SA is not less than the lower
limit, good abrasion resistance and good grip performance tend to
be obtained. The N.sub.2SA is also preferably 200 m.sup.2/g or
less, more preferably 150 m.sup.2/g or less, still more preferably
130 m.sup.2/g or less. Carbon black having a N.sub.2SA of not more
than the upper limit tends to exhibit good dispersibility.
[0095] The nitrogen adsorption specific surface area of the carbon
black can be determined in accordance with JIS K6217-2:2001.
[0096] Examples of the silica include dry silica (anhydrous silica)
and wet silica (hydrous silica). Wet silica is preferred among
these because it contains a large number of silanol groups.
Examples of usable commercial products include those available from
Degussa, Rhodia, Tosoh Silica Corporation, Solvay Japan, and
Tokuyama Corporation. These may be used alone or in combinations of
two or more.
[0097] The amount of the silica per 100 parts by mass of the rubber
component is preferably 25 parts by mass or more, more preferably
30 parts by mass or more, still more preferably 50 parts by mass or
more. When the amount is not less than the lower limit, good wet
grip performance and good handling stability tend to be obtained.
The upper limit of the amount is not limited but is preferably 300
parts by mass or less, more preferably 200 parts by mass or less,
still more preferably 170 parts by mass or less, particularly
preferably 100 parts by mass or less, most preferably 80 parts by
mass or less. When the amount is not more than the upper limit,
good dispersibility tends to be obtained.
[0098] The silica preferably has a nitrogen adsorption specific
surface area (N.sub.2SA) of 70 m.sup.2/g or more, more preferably
140 m.sup.2/g or more, still more preferably 160 m.sup.2/g or more.
When the N.sub.2SA is not less than the lower limit, good wet grip
performance and good tensile strength at break tend to be obtained.
The upper limit of the N.sub.2SA of the silica is not limited but
is preferably 500 m.sup.2/g or less, more preferably 300 m.sup.2/g
or less, still more preferably 250 m.sup.2/g or less. When the
N.sub.2SA is not more than the upper limit, good dispersibility
tends to be obtained.
[0099] The N.sub.2SA of the silica is measured by the BET method in
accordance with ASTM D3037-93.
[0100] The rubber composition containing silica preferably further
contains a silane coupling agent.
[0101] Non-limiting examples of the silane coupling agent include
sulfide silane coupling agents such as bis(3-triethoxysilylpropyl)
tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide,
bis(4-triethoxysilylbutyl)tetrasulfide,
bis(3-trimethoxysilylpropyl)tetrasulfide,
bis(2-trimethoxysilylethyl)tetrasulfide,
bis(2-triethoxysilylethyl)trisulfide,
bis(4-trimethoxysilylbutyl)trisulfide,
bis(3-triethoxysilylpropyl)disulfide,
bis(2-triethoxysilylethyl)disulfide,
bis(4-triethoxysilylbutyl)disulfide,
bis(3-trimethoxysilylpropyl)disulfide,
bis(2-trimethoxysilylethyl)disulfide,
bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,
N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,
N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl
methacrylate monosulfide; mercapto silane coupling agents such as
3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane,
and NXT and NXT-Z both available from Momentive; vinyl silane
coupling agents such as vinyltriethoxysilane and
vinyltrimethoxysilane; amino silane coupling agents such as
3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane;
glycidoxy silane coupling agents such as
y-glycidoxypropyltriethoxysilane and
y-glycidoxypropyltrimethoxysilane; nitro silane coupling agents
such as 3-nitropropyltrimethoxysilane and
3-nitropropyltriethoxysilane; and chloro silane coupling agents
such as 3-chloropropyltrimethoxysilane and
3-chloropropyltriethoxysilane. Examples of commercial products
include those available from Degussa, Momentive, Shin-Etsu
Silicone, Tokyo Chemical Industry Co., Ltd., AZmax. Co., and Dow
Corning Toray Co., Ltd. These silane coupling agents may be used
alone or in combinations of two or more.
[0102] The amount of the silane coupling agent per 100 parts by
mass of the silica is preferably 3 parts by mass or more, more
preferably 6 parts by mass or more. When the amount is 3 parts by
mass or more, good properties such as tensile strength at break
tend to be obtained. The amount is also preferably 20 parts by mass
or less, more preferably 15 parts by mass or less. The silane
coupling agent in an amount of 20 parts by mass or less will
produce an effect commensurate with the amount.
[0103] The rubber composition may contain a plasticizer.
[0104] From the standpoints of processability and other properties,
the amount of the plasticizer per 100 parts by mass of the rubber
component is preferably 2 parts by mass or more, more preferably 5
parts by mass or more, still more preferably 7 parts by mass or
more. From the standpoints of tensile strength at break and other
properties, the amount is also preferably 50 parts by mass or less,
more preferably 30 parts by mass or less, still more preferably 20
parts by mass or less.
[0105] Non-limiting examples of the plasticizer include plastic
materials which are liquid at 25.degree. C., such as oils and
liquid resins. One type or a combination of two or more types of
these plasticizers may be used.
[0106] Non-limiting examples of the oils include conventionally
known oils, for example: process oils such as paraffinic process
oils, aromatic process oils, and naphthenic process oils; low PCA
(polycyclic aromatic) process oils such as TDAE and MES; vegetable
fats and oils; and mixtures thereof. From the standpoints of
abrasion resistance and tensile properties, aromatic process oils
are preferred among these. Specific examples of the aromatic
process oils include Diana Process Oil AH series available from
Idemitsu Kosan Co., Ltd.
[0107] Non-limiting examples of the liquid resins include liquid
aromatic vinyl polymers, coumarone-indene resins, indene resins,
terpene resins, rosin resins, and hydrogenated products of the
foregoing.
[0108] Liquid aromatic vinyl polymers refer to resins produced by
polymerizing a-methylstyrene and/or styrene. Examples include
liquid resins such as styrene homopolymers, a-methylstyrene
homopolymers, and copolymers of a-methylstyrene and styrene.
[0109] Liquid coumarone-indene resins refer to resins that contain
coumarone and indene as main monomer components forming the
skeleton (backbone) of the resins. Examples of monomer components
which may be contained in the skeleton other than coumarone and
indene include styrene, a-methylstyrene, methylindene, and
vinyltoluene.
[0110] Liquid indene resins refer to liquid resins that contain
indene as a monomer component forming the skeleton (backbone) of
the resins.
[0111] Liquid terpene resins refer to liquid terpene-based resins
typified by resins produced by polymerization of terpene compounds
such as .alpha.-pinene, .beta.-pinene, camphene or dipentene, and
terpenephenol resins produced from terpene compounds and phenolic
compounds.
[0112] Liquid rosin resins refer to liquid rosin-based resins
typified by natural rosins, polymerized rosins, modified rosins,
and ester compounds thereof, or hydrogenated products thereof.
[0113] The rubber composition may contain a solid resin (a polymer
that is solid at room temperature (25.degree. C.)).
[0114] The amount of the solid resin, if present, per 100 parts by
mass of the rubber component is preferably 1 part by mass or more,
more preferably 3 parts by mass or more, still more preferably 5
parts by mass or more. The amount is also preferably 50 parts by
mass or less, more preferably 30 parts by mass or less, still more
preferably 20 parts by mass or less. When the amount is within the
range indicated above, good wet grip performance tends to be
obtained.
[0115] Non-limiting examples of the solid resin include solid
styrene resins, coumarone-indene resins, terpene resins,
p-t-butylphenol acetylene resins, acrylic resins, dicyclopentadiene
resins (DCPD resins), C5 petroleum resins, C9 petroleum resins, and
05/C9 petroleum resins. These may be used alone or in combinations
of two or more.
[0116] Solid styrene resins refer to solid polymers produced from
styrenic monomers as structural monomers, and examples include
polymers produced by polymerizing a styrenic monomer as a main
component (50% by mass or more). Specific examples include
homopolymers produced by polymerizing a styrenic monomer (e.g.,
styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene,
a-methylstyrene, p-methoxystyrene, p-tert-butylstyrene,
p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene)
alone, copolymers produced by copolymerizing two or more styrenic
monomers, and copolymers of styrenic monomers and additional
monomers copolymerizable therewith.
[0117] Examples of the additional monomers include acrylonitriles
such as acrylonitrile and methacrylonitrile; unsaturated carboxylic
acids such as acrylic acid and methacrylic acid; unsaturated
carboxylic acid esters such as methyl acrylate and methyl
methacrylate; dienes such as chloroprene, butadiene, and isoprene;
olefins such as 1-butene and 1-pentene; and
.alpha.,.beta.-unsaturated carboxylic acids and acid anhydrides
thereof such as maleic anhydride.
[0118] In particular, solid a-methylstyrene resins (e.g.,
a-methylstyrene homopolymers, copolymers of a-methylstyrene and
styrene) are preferred.
[0119] Examples of the solid coumarone-indene resins include solid
resins having structural units as described for the liquid
coumarone-indene resins.
[0120] Examples of the solid terpene resins include polyterpene,
terpene phenol, and aromatic modified terpene resins.
[0121] Polyterpene resins refer to resins produced by
polymerization of terpene compounds, or hydrogenated products of
the resins. The term "terpene compound" refers to a hydrocarbon
having a composition represented by (C.sub.5H.sub.8).sub.n or an
oxygen-containing derivative thereof, each of which has a terpene
backbone and is classified as, for example, a monoterpene
(C.sub.10H.sub.16), sesquiterpene (C.sub.15H.sub.24), or diterpene
(C.sub.20H.sub.32). Examples of such terpene compounds include
.alpha.-pinene, .beta.-pinene, dipentene, limonene, myrcene,
alloocimene, ocimene, .alpha.-phellandrene, .alpha.-terpinene,
.gamma.-terpinene, terpinolene, 1,8-cineole, 1,4-cineole,
.alpha.-terpineol, .beta.-terpineol, and .gamma.-terpineol.
[0122] Examples of the solid polyterpene resins include solid
terpene resins made from the aforementioned terpene compounds, such
as .alpha.-pinene resins, .beta.-pinene resins, limonene resins,
dipentene resins, and .beta.-pinene-limonene resins, and solid
hydrogenated terpene resins produced by hydrogenation of these
terpene resins.
[0123] Examples of the solid terpenephenol resins include solid
resins produced by copolymerization of the aforementioned terpene
compounds and phenolic compounds, and solid resins produced by
hydrogenation of these resins. Specific examples include solid
resins produced by condensation of the aforementioned terpene
compounds, phenolic compounds, and formaldehyde. The phenolic
compounds include, for example, phenol, bisphenol A, cresol, and
xylenol.
[0124] Examples of the solid aromatic modified terpene resins
include solid resins obtained by modification of terpene resins
with aromatic compounds, and solid resins produced by hydrogenation
of these resins. The aromatic compounds may be any compound having
an aromatic ring, including, for example: phenol compounds such as
phenol, alkylphenols, alkoxyphenols, and unsaturated hydrocarbon
group-containing phenols; naphthol compounds such as naphthol,
alkylnaphthols, alkoxynaphthols, and unsaturated hydrocarbon
group-containing naphthols; styrene and styrene derivatives, such
as alkylstyrenes, alkoxystyrenes, and unsaturated hydrocarbon
group-containing styrenes; coumarone; and indene.
[0125] Examples of the solid p-t-butylphenol acetylene resins
include solid resins produced by condensation of p-t-butylphenol
and acetylene.
[0126] The solid acrylic resins are not limited, but solvent-free
solid acrylic resins are suitable because they contain little
impurities and have a sharp molecular weight distribution.
[0127] Examples of the solvent-free solid acrylic resins include
(meth)acrylic resins (polymers) synthesized by high temperature
continuous polymerization (high temperature continuous bulk
polymerization as described in, for example, U.S. Pat. No.
4,414,370, JP S59-6207 A, JP H5-58005 B, JP H1-313522 A, U.S. Pat.
No. 5,010,166, and annual research report TREND 2000 issued by
Toagosei Co., Ltd., vol. 3, pp. 42-45, all of which are hereby
incorporated by reference in their entirety) using no or minimal
amounts of auxiliary raw materials such as polymerization
initiators, chain transfer agents, and organic solvents. Herein,
the term "(meth)acrylic" means methacrylic and acrylic.
[0128] Preferred are solid acrylic resins that are substantially
free of auxiliary raw materials such as polymerization initiators,
chain transfer agents, and organic solvents. Also preferred are
such acrylic resins having a relatively narrow compositional
distribution or molecular weight distribution, produced by
continuous polymerization.
[0129] As described above, solid acrylic resins which are
substantially free of auxiliary raw materials such as
polymerization initiators, chain transfer agents, and organic
solvents, namely which are of high purity, are preferred. The
purity of the solid acrylic resins (the resin content of the
resins) is preferably 95% by mass or more, more preferably 97% by
mass or more.
[0130] Examples of the monomer components of the solid acrylic
resins include (meth)acrylic acids and (meth)acrylic acid
derivatives such as (meth)acrylic acid esters (e.g., alkyl esters,
aryl esters, aralkyl esters), (meth)acrylamides, and (meth)
acrylamide derivatives.
[0131] In addition to the (meth)acrylic acids or (meth)acrylic acid
derivatives, aromatic vinyls, such as styrene, a-methylstyrene,
vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, or
divinylnaphthalene, may also be used as monomer components of the
solid acrylic resins.
[0132] The solid acrylic resins may be formed only of the
(meth)acrylic components or may further contain constituent
components other than the (meth)acrylic components. Moreover, the
solid acrylic resins may contain a hydroxyl group, a carboxyl
group, a silanol group, or other groups.
[0133] The plasticizer and the solid resin may each be a commercial
product of, for example, Maruzen Petrochemical Co., Ltd., Sumitomo
Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation,
Rutgers Chemicals, BASF, Arizona Chemical, Nitto Chemical Co.,
Ltd., Nippon Shokubai Co., Ltd., JXTG Nippon Oil & Energy
Corporation, Arakawa Chemical Industries, Ltd., or Taoka Chemical
Co., Ltd.
[0134] From the standpoints of crack resistance, ozone resistance,
and other properties, the rubber composition preferably contains an
antioxidant.
[0135] Non-limiting examples of the antioxidant include:
naphthylamine antioxidants such as phenyl-.alpha.-naphthylamine;
diphenylamine antioxidants such as octylated diphenylamine and
4,4'-bis(.alpha.,.alpha.'-dimethylbenzyl)diphenylamine;
p-phenylenediamine antioxidants such as
N-isopropyl-N'-phenyl-p-phenylenediamine,
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and
N,N'-di-2-naphthyl-p-phenylenediamine; quinoline antioxidants such
as 2,2,4-trimethyl-1,2-dihydroquinoline polymer; monophenolic
antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated
phenol; and bis-, tris-, or polyphenolic antioxidants such as
tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)
propionate]methane. Among these, p-phenylenediamine or quinoline
antioxidants are preferred, with
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine or
2,2,4-trimethyl-1,2-dihydroquinoline polymer being more preferred.
Examples of commercial products include those available from Seiko
Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko
Chemical Industrial Co., Ltd., and Flexsys.
[0136] The amount of the antioxidant per 100 parts by mass of the
rubber component is preferably 0.2 parts by mass or more, more
preferably 0.5 parts by mass or more. When the amount is not less
than the lower limit, sufficient ozone resistance tends to be
obtained. The amount is also preferably 7.0 parts by mass or less,
more preferably 4.0 parts by mass or less. When the amount is not
more than the upper limit, good appearance tends to be
obtained.
[0137] The rubber composition preferably contains stearic acid.
From the standpoint of the balance between the above-mentioned
properties, the amount of the stearic acid per 100 parts by mass of
the rubber component is preferably 0.5 to 10 parts by mass, more
preferably 0.5 to 5 parts by mass.
[0138] The stearic acid may be conventionally known one, such as a
commercial product of, for example, NOF Corporation, Kao
Corporation, FUJIFILM Wako Pure Chemical Corporation, or Chiba
Fatty Acid Co., Ltd.
[0139] The rubber composition preferably contains zinc oxide. From
the standpoint of the balance between the above-mentioned
properties, the amount of the zinc oxide per 100 parts by mass of
the rubber component is preferably 0.5 to 10 parts by mass, more
preferably 1 to 5 parts by mass.
[0140] The zinc oxide may be conventionally known one, such as a
commercial product of, for example, Mitsui Mining & Smelting
Co., Ltd., Toho Zinc Co., Ltd., HakusuiTech Co., Ltd., Seido
Chemical Industry Co., Ltd., or Sakai Chemical Industry Co.,
Ltd.
[0141] The rubber composition may contain a wax. Non-limiting
examples of the wax include petroleum waxes, natural waxes, and
synthetic waxes produced by purifying or chemically treating a
plurality of waxes. These waxes may be used alone or in
combinations of two or more.
[0142] Examples of the petroleum waxes include paraffin waxes and
microcrystalline waxes. The natural waxes may be any wax derived
from non-petroleum resources, and examples include plant waxes such
as candelilla wax, carnauba wax, Japan wax, rice wax, and jojoba
wax; animal waxes such as beeswax, lanolin, and spermaceti; mineral
waxes such as ozokerite, ceresin, and petrolatum; and purified
products of the foregoing waxes. Examples of usable commercial
products include those available from Ouchi Shinko Chemical
Industrial Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical
Co., Ltd. The amount of the wax may be selected appropriately in
view of ozone resistance and cost.
[0143] The rubber composition preferably contains sulfur in order
to form moderate crosslinks between polymer chains and achieve a
good balance between the above-mentioned properties.
[0144] The amount of the sulfur per 100 parts by mass of the rubber
component is preferably 0.1 parts by mass or more, more preferably
0.5 parts by mass or more, still more preferably 0.7 parts by mass
or more, but is preferably 6.0 parts by mass or less, more
preferably 4.0 parts by mass or less, still more preferably 3.0
parts by mass or less. When the amount is within the range
indicated above, a good balance between the above-mentioned
properties tends to be achieved.
[0145] Examples of the sulfur include those commonly used in the
rubber industry, such as powdered sulfur, precipitated sulfur,
colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and
soluble sulfur. Examples of usable commercial products include
those available from Tsurumi Chemical Industry Co., Ltd., Karuizawa
Sulfur Co., Ltd., Shikoku Chemicals Corporation, Flexsys, Nippon
Kanryu Industry Co., Ltd., and Hosoi Chemical Industry Co., Ltd.
These may be used alone or in combinations of two or more.
[0146] The rubber composition preferably contains a vulcanization
accelerator.
[0147] The amount of the vulcanization accelerator is not limited
and may be arbitrarily selected according to the desired cure rate
and crosslink density. Yet, the amount is usually 0.3 to 10 parts
by mass, preferably 0.5 to 7 parts by mass per 100 parts by mass of
the rubber component.
[0148] Any type of vulcanization accelerator may be used including
usually used ones. Examples of the vulcanization accelerator
include thiazole vulcanization accelerators such as
2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and
N-cyclohexyl-2-benzothiazylsulfenamide; thiuram vulcanization
accelerators such as tetramethylthiuram disulfide (TMTD),
tetrabenzylthiuram disulfide (TBzTD), and
tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide
vulcanization accelerators such as N-cyclohexyl-2-benzothiazole
sulfenamide, N-t-butyl-2-benzothiazolyl sulfenamide,
N-oxyethylene-2-benzothiazole sulfenamide, and
N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine
vulcanization accelerators such as diphenylguanidine,
diorthotolylguanidine, and orthotolylbiguanidine. These may be used
alone or in combinations of two or more. From the standpoint of the
balance between the above-mentioned properties, sulfenamide or
guanidine vulcanization accelerators are preferred.
[0149] In addition to the above-mentioned components, the rubber
composition may appropriately contain usual additives used in
applied fields, such as release agents or pigments.
[0150] The rubber composition can be prepared by known methods,
such as by kneading components including the filler/rubber
composite in a rubber kneading machine such as an open roll mill or
a Banbury mixer, and vulcanizing the kneaded mixture.
[0151] The kneading conditions are as follows. In a base kneading
step that includes kneading additives other than vulcanizing agents
and vulcanization accelerators, the kneading temperature is usually
50 to 200.degree. C., preferably 80 to 190.degree. C., and the
kneading duration is usually 30 seconds to 30 minutes, preferably
one minute to 30 minutes. In a final kneading step that includes
kneading the vulcanizing agents and vulcanization accelerators, the
kneading temperature is usually 100.degree. C. or lower, preferably
from room temperature to 80.degree. C. The composition obtained
after kneading the vulcanizing agents and vulcanization
accelerators is usually vulcanized by, for example, press
vulcanization. The vulcanization temperature is usually 120 to
200.degree. C., preferably 140 to 180.degree. C.
[0152] The rubber composition may be used in, for example, tires,
rubber footwear soles, rubber floor materials, vibration proof
rubbers, seismic isolators, flame butyl rubbers, belts, tubes,
packing materials, medical stoppers, and other industrial rubber
products. In particular, the rubber composition can preferably be
used as a rubber composition for tires owing to its ability to
improve durability (tensile strength at break), handling stability,
fuel economy, and other properties.
[0153] The rubber composition may suitably be used in pneumatic
tires. Such pneumatic tires can be produced using the rubber
composition by usual methods. Specifically, an unvulcanized rubber
composition into which materials are compounded as needed may be
extruded into the shape of a tire component and then assembled with
other tire components in a tire building machine in a usual manner
to build an unvulcanized tire, which may then be heated and
pressurized in a vulcanizer to produce a tire.
EXAMPLES
[0154] The present invention will be described in greater detail
with reference to, but not limited to, examples.
[Evaluation Method]
[0155] CNC/surfactant composites and CNF/surfactant composites were
evaluated as described below.
(Moisture Content)
[0156] The moisture content (%) of each CNC/surfactant or
CNF/surfactant composite was measured in accordance with JIS A
1476:2006 "Measuring method for moisture content of building
materials by drying at elevated temperature".
(Recovery Ratio)
[0157] To 10 g of each CNC/surfactant or CNF/surfactant composite
was added 500 g of pure water, and they were stirred and
ultrasonicated for 10 minutes to effect redispersion.
CNC/surfactant or CNF/surfactant redispersions were thus
prepared.
[0158] The recovery ratio (%) of the CNC/surfactant or
CNF/surfactant redispersions was determined by the following
equation. A higher recovery ratio indicates better
redispersibility.
[Recovery ratio (%)]=[Viscosity (mPas) of CNC/surfactant or
CNF/surfactant redispersion]/[Viscosity (mPas) of CNC slurry (CNC
aqueous dispersion) or CNF slurry (CNF aqueous
dispersion)].times.100
[0159] The viscosity (mPas) was measured at 23.degree. C. using a
tuning-fork vibration viscometer.
[0160] The chemicals used in the preparation of the CNC/surfactant
composites and the like are listed below.
[0161] CNC: cellulose nanocrystal (average fiber length: 100 to 300
nm, average fiber diameter: 5 to 50 nm, degree of crystallinity:
80%, solids content: 2% by mass) available from Inno Tech
Alberta
[0162] Surfactant A: NUOSPERSE FX 605 (anionic surfactant, sodium
polycarboxylate (hydrophobic group: hydrocarbon group, hydrophilic
group: COO.sup.- (carboxyl group), counter ion: Na.sup.+), Mw:
6000) available from Elementis PLC
[0163] Surfactant B: DEMOL EP (anionic surfactant, sodium
polycarboxylate (hydrophobic group: isobutylene group, hydrophilic
group: COO.sup.- (carboxyl group), counter ion: Na.sup.+), Mw:
20000) available from Kao Corporation
[0164] Surfactant C: DEMOL NL (anionic surfactant (hydrophobic
group: hydrocarbon group, hydrophilic group: SO.sub.3.sup.-
(sulfonate group), counter ion: Na.sup.+), Mw: 20000) available
from Kao Corporation
[0165] Surfactant D: NUOSPERSE FX 600 (anionic surfactant, amine
polycarboxylate (hydrophobic group: phenyl group, hydrophilic
group: COO.sup.- (carboxyl group), counter ion: NH.sub.4.sup.+),
Mw: 2000) available from Elementis PLC
[0166] Surfactant E: TERIC 16A29 (nonionic surfactant,
CH.sub.3(CH.sub.2).sub.15(OC.sub.2H.sub.4).sub.29--OH)) available
from Huntsman Corporation
(Preparation of CNC/Surfactant Composite)
[0167] To a 1% by mass CNC aqueous dispersion prepared from CNC and
pure water was added the surfactant in the predetermined amount
shown in the formulation in Table 1, and they were stirred using a
high-speed homogenizer at room temperature (20 to 30.degree. C.)
for five minutes to give a mixture (liquid mixture) containing CNC
and the surfactant. Then, the liquid mixture was filtrated and
dried (170.degree. C., 60 minutes) to obtain a CNC/surfactant
composite.
TABLE-US-00001 TABLE 1 CNC/surfaotant composite A B C D E X
Surfactant Surfactant A Surfactant B Surfactant C Surfactant D
Surfactant E -- (anionic, (anionic, (anionic, (anionic, (nonionic)
Mw: 6,000) Mw: 20,000) Mw: 20,000) Mw: 2,000) Amount (parts by
mass) of 10 10 10 10 10 -- surfactant relative to 100 parts by mass
(solids content) of CNC Moisture content 7 8 6 7 8 8 (% by mass)
Recovery ratio (%) of 100 80 80 50 50 50 redispersion
[0168] The chemicals used in the preparation of the CNF/surfactant
composites and the like are listed below.
[0169] Microfibrillated plant fiber: biomass nanofiber (trade name
"BiNFi-s cellulose", solids content: 2% by mass, moisture content:
98% by mass, average fiber diameter: 20 to 50 nm, average fiber
length: 500 to 1000 nm, degree of crystallinity: 70%) available
from Sugino Machine Limited
[0170] TEMPO: 2,2,6,6-tetramethylpiperidine-1-oxyl
[0171] Sodium bromide: a product available from FUJIFILM Wako Pure
Chemical Corporation
[0172] Sodium hypochlorite: a product available from Tokyo Chemical
Industry Co., Ltd.
[0173] NaOH: NaOH available from FUJIFILM Wako Pure Chemical
Corporation
[0174] Surfactant A: NUOSPERSE FX 605 (anionic surfactant, sodium
polycarboxylate (hydrophobic group: hydrocarbon group, hydrophilic
group: COO.sup.- (carboxyl group), counter ion: Na.sup.+), Mw:
6000) available from Elementis PLC
[0175] Surfactant B: DEMOL EP (anionic surfactant, sodium
polycarboxylate (hydrophobic group: isobutylene group, hydrophilic
group: COO.sup.- (carboxyl group), counter ion: Na.sup.t), Mw:
20000) available from Kao Corporation Surfactant F: polyethylene
oxide (Mw: 150000)
(Preparation of Microfibrillated Plant Fiber Dispersion (CNF
Aqueous Dispersion))
[0176] An amount of 10 g of the microfibrillated plant fiber, 150
mg of TEMPO, and 1000 mg of sodium bromide were dispersed in 1000
mL of water. To the dispersion was added a 15% by mass sodium
hypochlorite aqueous solution such that the amount of sodium
hypochlorite was 5 mmol per gram (absolute dry weight) of the
microfibrillated plant fiber, followed by starting a reaction. The
pH during the reaction was maintained at 10.0 by dropwise adding a
3M aqueous NaOH solution. The reaction was considered to be
completed when the pH no longer changed. The reaction product was
filtered through a glass filter and then subjected to five cycles
of washing with plenty of water and filtration, thereby obtaining a
water-impregnated, reacted fiber with a solids content of 15% by
mass.
[0177] The fiber was diluted to form a 1% by mass CNF aqueous
dispersion.
(Preparation of CNF/Surfactant Composite)
[0178] To the 1% by mass CNF aqueous dispersion was added the
surfactant in the predetermined amount shown in the formulation in
Table 2, and they were stirred using a high-speed homogenizer at
room temperature (20 to 30.degree. C.) for five minutes to give a
mixture (liquid mixture) containing CNF and the surfactant. Then,
the liquid mixture was filtrated and dried (170.degree. C., 60
minutes) to obtain a CNF/surfactant composite.
TABLE-US-00002 TABLE 2 CNF/surfactant composite A B F Y Surfactant
Surfactant A Surfactant B Surfactant F -- (anionic, (anionic, (PEO,
Mw: 6,000) Mw: 20,000) Mw150,000) Amount (parts by mass) of 20 20
20 -- surfactant relative to 100 parts by mass (solids content) of
CNF Moisture content (% by mass) 7 5 7 8 Recovery ratio (%) of
redispersion 100 80 50 50
[0179] The chemicals used in the preparation of rubber compositions
are listed below.
[0180] Natural rubber latex: field latex obtained from Muhibbah
LATEKS
[0181] CNC/surfactant redispersions: prepared as described in the
recovery ratio evaluation
[0182] CNF/surfactant redispersions: prepared as described in the
recovery ratio evaluation
[0183] Carbon black: SHOBLACK N220 (N.sub.2SA: 111 m.sup.2/g)
available from Cabot Japan K.K.
[0184] Oil: process X140 available from Japan Energy
Corporation
[0185] Antioxidant: OZONONE 6C
(N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) available from
Seiko Chemical Co., Ltd.
[0186] Zinc oxide: zinc oxide #1 available from Mitsui Mining &
Smelting Co., Ltd.
[0187] Stearic acid: stearic acid "TSUBAKI" available from NOF
Corporation
[0188] Sulfur: powdered sulfur available from Tsurumi Chemical
Industry Co., Ltd.
[0189] Vulcanization accelerator: NOCCELER NS
(N-tert-butyl-2-benzothiazolylsulfenamide) available from Ouchi
Shinko Chemical Industrial Co., Ltd.
(Preparation of CNC/Natural Rubber Composite or CNF/Natural Rubber
Composite)
[0190] The CNC/surfactant redispersion A, B, C, D, or E, or the
CNF/surfactant redispersion A, B, or F was mixed with the natural
rubber latex at a ratio of 10 parts by mass of CNC or CNF (solids
content) relative to 100 parts by mass of the rubber solids, and
they were stirred using a high-speed homogenizer at room
temperature for five minutes to prepare a compounded latex having a
pH of 10.2. To the compounded latex was added a 2% by mass formic
acid aqueous solution at room temperature to adjust the pH to 3 to
4 to form coagula. The coagula were filtered and dried. CNC/natural
rubber composites A, B, C, D, and E, and CNF/natural rubber
composites A, B, and F were thus prepared.
[0191] Moreover, a CNC/natural rubber composite X and a CNF/natural
rubber composite Y were prepared as described above, except that
the CNC aqueous dispersion (no surfactant) and the CNF aqueous
dispersion (no surfactant) were used instead of the CNC/surfactant
redispersion and the CNF/surfactant redispersion, respectively.
<Preparation of Rubber Composition>
[0192] The materials other than the sulfur and vulcanization
accelerator shown in the formulation in Table 3 or 4 were kneaded
using a 1.7-L Banbury mixer at 150.degree. C. for four minutes.
Then, the sulfur and vulcanization accelerator were added to, the
kneaded mixture and they were kneaded using an open roll mill at
80.degree. C. for four minutes to give an unvulcanized rubber
composition. The unvulcanized rubber composition was
press-vulcanized at 170.degree. C. for 12 minutes using a 2
mm-thick mold to obtain a vulcanized rubber composition.
[0193] The vulcanized rubber compositions prepared as above were
evaluated as described below. It should be noted that Comparative
Examples 1-3 and 2-2 are used as standards of comparison in Tables
3 and 4, respectively.
[Evaluation Method]
(CNC or CNF Dispersibility)
[0194] The vulcanized rubber compositions were observed with an
electron microscope to evaluate dispersibility of CNC or CNF in the
rubber matrix. The CNC or CNF dispersibility of each formulation
example is expressed as an index relative to the standard
comparative example taken as 100. A higher index indicates better
dispersibility of CNC or CNF.
(Tensile Strength at Break)
[0195] A tensile test was performed on No. 3 dumbbell-shaped rubber
specimens prepared from the vulcanized rubber compositions in
accordance with JIS K 6251 "Rubber, vulcanized or
thermoplastic--Determination of tensile stress-strain properties"
to measure the tensile strength at break (TB). The TB of each
formulation example is expressed as an index relative to the rubber
specimen of the standard comparative example (standard specimen)
(=100) using the equation below. A higher TB index indicates a
higher tensile strength at break and better reinforcement and
durability.
(TB index)=(TB of each formulation example)/(TB of standard
comparative example).times.100
(Fuel Economy)
[0196] The loss tangent (tan .delta.) and complex modulus E* (MPa)
of each formulation example (vulcanized rubber composition) were
measured using a viscoelastic spectrometer VES (Iwamoto Seisakusho
Co., Ltd.) at a temperature of 70.degree. C., an initial strain of
10%, a dynamic strain of 1%, and a frequency of 10 Hz. Tan .delta.
and E* indexes of each formulation example were calculated using
the tan .delta. and E* of the standard comparative example each
taken as 100. A higher tan .delta. index indicates a lower rolling
resistance and better fuel economy. A higher E* index indicates
better modulus. In addition, a balance index calculated as "E*
index x tan .delta. index/100" was determined. A higher balance
index indicates a better balance between modulus and fuel
economy.
TABLE-US-00003 TABLE 3 Example Comparative Example 1-1 1-2 1-3 1-1
1-2 1-3 Formulation CNC/natural rubber 110 (10) (parts by mass)
composite A (amount of CNC) CNC/natural rubber 110 (10) composite B
(amount of CNC) CNC/natural rubber 110 (10) composite C (amount of
CNC) CNC/natural rubber 110 (10) composite D (amount of CNC)
CNC/natural rubber 110 (10) composite E (amount of CNC) CNC/natural
rubber 110 (10) composite X (amount of CNC) Carbon black 30 30 30
30 30 30 Oil 10 10 10 10 10 10 Antioxidant 3 3 3 3 3 3 Zinc oxide 3
3 3 3 3 3 Stearic acid 2 2 2 2 2 2 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5
Vulcanization 1 1 1 1 1 1 accelerator Evaluation CNC dispersibility
130 120 120 100 100 100 Tensile strength 110 105 108 85 80 100 at
break (TB index) Fuel economy 110 105 105 90 80 100 (tan .delta.
index) Complex modulus 120 110 110 105 105 100 (E* index) Balance
132 116 116 95 84 100 (= E* .times. tan .delta./100) CNC/natural
rubber composite X: No surfactant
TABLE-US-00004 TABLE 4 Comparative Example Example 2-1 2-2 2-1 2-2
Formulation CNF/natural rubber composite A 110 (10) (parts by mass)
(amount of CNF) CNF/natural rubber composite B 110 (10) (amount of
CNF) CNF/natural rubber composite F 110 (10) (amount of CNF)
CNF/natural rubber composite Y 110 (10) (amount of CNF) Carbon
black 30 30 30 30 Oil 10 10 10 10 Antioxidant 3 3 3 3 Zinc oxide 3
3 3 3 Stearic acid 2 2 2 2 Sulfur 1.5 1.5 1.5 1.5 Vulcanization
accelerator 1 1 1 1 Evaluation CNF dispersibility 120 115 80 100
Tensile strength at break (TB index) 110 105 90 100 Fuel economy
(tan .delta. index) 110 105 90 100 Complex modulus (E* index) 130
110 95 100 Balance (=E* .times. tan .delta./100) 143 116 86 100
CNF/natural rubber composite Y: No surfactant
[0197] As shown in Tables 3 and 4, composites containing an ionic
surfactant having a weight average molecular weight of 3000 or more
and a nanocellulose exhibited excellent redispersibility in water,
despite their moisture content of lower than 10% by mass. Moreover,
rubber compositions containing the composites exhibited good
dispersibility of the nanocellulose (good CNC or CNF
dispersibility) and also had excellent tensile strength at break
and fuel economy as well as an excellent balance between modulus
and fuel economy.
* * * * *