U.S. patent application number 17/636278 was filed with the patent office on 2022-09-15 for complex fibers of cellulose fibers with inorganic particles and processes for preparing them.
The applicant listed for this patent is NIPPON PAPER INDUSTRIES CO., LTD.. Invention is credited to Moe Fuchise, Ayaka Hasegawa.
Application Number | 20220290373 17/636278 |
Document ID | / |
Family ID | 1000006430927 |
Filed Date | 2022-09-15 |
United States Patent
Application |
20220290373 |
Kind Code |
A1 |
Hasegawa; Ayaka ; et
al. |
September 15, 2022 |
COMPLEX FIBERS OF CELLULOSE FIBERS WITH INORGANIC PARTICLES AND
PROCESSES FOR PREPARING THEM
Abstract
The present invention aims to provide complex fibers comprising
a cellulose fiber strongly covered by a lot of inorganic particles
on its surface. In the present invention, an excellent complex
fiber of a cellulose fiber with inorganic particles can be prepared
on the basis of the value of (D50-D10)/D50 calculated from the
particle size distribution of (a) or (b) below: (a) the filtrate
obtained by filtering an aqueous suspension of the complex fiber at
a solids content of 0.1% through a 60-mesh sieve (having an opening
of 250 .mu.m); or (b) the fraction corresponding to an effluent
volume (L) of 18.51 to 19.50 and an efflux time (sec) of 37.4 to
48.0 when an aqueous suspension of the complex fiber at a solids
content of 0.3% is classified using a fiber classification analyzer
under the conditions of a flow rate of 5.7 L/min, a water
temperature of 25.+-.1.degree. C., and a total effluent volume of
22 L.
Inventors: |
Hasegawa; Ayaka; (Tokyo,
JP) ; Fuchise; Moe; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NIPPON PAPER INDUSTRIES CO., LTD. |
Tokyo |
|
JP |
|
|
Family ID: |
1000006430927 |
Appl. No.: |
17/636278 |
Filed: |
September 4, 2020 |
PCT Filed: |
September 4, 2020 |
PCT NO: |
PCT/JP2020/033627 |
371 Date: |
February 17, 2022 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D21H 15/12 20130101;
D21H 17/66 20130101; D21H 17/70 20130101 |
International
Class: |
D21H 15/12 20060101
D21H015/12; D21H 17/66 20060101 D21H017/66; D21H 17/70 20060101
D21H017/70 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 6, 2019 |
JP |
2019-163073 |
Claims
1. A process for preparing a complex fiber of a cellulose fiber
with inorganic particles, comprising the steps of: synthesizing
inorganic particles in a solution containing a cellulose fiber to
give a complex fiber; and determining the particle size
distribution of (a) or (b) below: (a) the filtrate obtained by
filtering an aqueous suspension of the complex fiber at a solids
content of 0.1% through a 60-mesh sieve (having an opening of 250
.mu.m); or (b) the fraction corresponding to an effluent volume (L)
of 18.51 to 19.50 and an efflux time (sec) of 37.4 to 48.0 when an
aqueous suspension of the complex fiber at a solids content of 0.3%
is classified using a fiber classification analyzer under the
conditions of a flow rate of 5.7 L/min, a water temperature of
25.+-.1.degree. C., and a total effluent volume of 22 L, thereby
calculating (D50-D10)/D50.
2. The process of claim 1, wherein the aqueous suspension of the
complex fiber is prepared in such a manner that (D50-D10)/D50 is
0.85 or less.
3. The process of claim 1, wherein the complex fiber has an average
fiber diameter of 500 nm or more.
4. The process of claim 1, wherein the inorganic particles comprise
a metal salt of calcium, magnesium, barium or aluminum, or metal
particles containing titanium, copper or zinc, or a silicate.
5. A process for preparing a complex fiber sheet, comprising the
step of forming a sheet from a complex fiber obtained by the
process of claim 1.
6. A complex fiber of a cellulose fiber with inorganic particles,
wherein the value of (D50-D10)/D50 calculated from the particle
size distribution of (a) or (b) below is 0.85 or less: (a) the
filtrate obtained by filtering an aqueous suspension of the complex
fiber at a solids content of 0.1% through a 60-mesh sieve (having
an opening of 250 .mu.m); or (b) the fraction corresponding to an
effluent volume (L) of 18.51 to 19.50 and an efflux time (sec) of
37.4 to 48.0 when an aqueous suspension of the complex fiber at a
solids content of 0.3% is classified using a fiber classification
analyzer under the conditions of a flow rate of 5.7 L/min, a water
temperature of 25.+-.1.degree. C., and a total effluent volume of
22 L.
7. A complex fiber of a cellulose fiber with inorganic particles,
passing through a 60-mesh sieve (having an opening of 250 .mu.m)
when an aqueous suspension of the complex fiber at a solids content
of 0.1% is processed through the sieve, wherein the value of
(D50-D10)/D50 calculated from the particle size distribution of the
filtrate having passed through the sieve is 0.85 or less.
8. A complex fiber of a cellulose fiber with inorganic particles,
derived from the fraction corresponding to an effluent volume (L)
of 18.51 to 19.50 and an efflux time (sec) of 37.4 to 48.0 when an
aqueous suspension of the complex fiber at a solids content of 0.3%
is classified using a fiber classification analyzer under the
conditions of a flow rate of 5.7 L/min, a water temperature of
25.+-.1.degree. C., and a total effluent volume of 22 L, wherein
the value of (D50-D10)/D50 calculated from the particle size
distribution of the fraction is 0.85 or less.
9. A method for analyzing a complex fiber of a cellulose fiber with
inorganic particles, comprising the step of: determining the
particle size distribution of (a) or (b) below: (a) the filtrate
obtained by filtering an aqueous suspension of the complex fiber at
a solids content of 0.1% through a 60-mesh sieve (having an opening
of 250 .mu.m); or (b) the fraction corresponding to an effluent
volume (L) of 18.51 to 19.50 and an efflux time (sec) of 37.4 to
48.0 when an aqueous suspension of the complex fiber at a solids
content of 0.3% is classified using a fiber classification analyzer
under the conditions of a flow rate of 5.7 L/min, a water
temperature of 25.+-.1.degree. C., and a total effluent volume of
22 L, thereby calculating (D50-D10)/D50.
10. The process of claim 2, wherein the complex fiber has an
average fiber diameter of 500 nm or more.
11. The process of claim 2, wherein the inorganic particles
comprise a metal salt of calcium, magnesium, barium or aluminum, or
metal particles containing titanium, copper or zinc, or a
silicate.
12. The process of claim 10, wherein the inorganic particles
comprise a metal salt of calcium, magnesium, barium or aluminum, or
metal particles containing titanium, copper or zinc, or a
silicate.
13. A process for preparing a complex fiber sheet, comprising the
step of forming a sheet from a complex fiber obtained by the
process of claim 2.
14. A process for preparing a complex fiber sheet, comprising the
step of forming a sheet from a complex fiber obtained by the
process of claim 3.
15. A process for preparing a complex fiber sheet, comprising the
step of forming a sheet from a complex fiber obtained by the
process of claim 4.
16. A process for preparing a complex fiber sheet, comprising the
step of forming a sheet from a complex fiber obtained by the
process of claim 10.
17. A process for preparing a complex fiber sheet, comprising the
step of forming a sheet from a complex fiber obtained by the
process of claim 11.
18. A process for preparing a complex fiber sheet, comprising the
step of forming a sheet from a complex fiber obtained by the
process of claim 12.
Description
TECHNICAL FIELD
[0001] The present invention relates to complex fibers of a
cellulose fiber with inorganic particles and processes for
preparing them.
BACKGROUND ART
[0002] Fibers such as woody fibers exhibit various characteristics
based on the functional groups or the like on their surface, but
sometimes require surface modification depending on the purposes,
and therefore, techniques for modifying the surface of the fibers
have already been developed.
[0003] For example, a technique for precipitating inorganic
particles on a fiber such as a cellulose fiber is disclosed in PTL
1, which describes a complex comprising crystalline calcium
carbonate mechanically bonded onto a fiber. Further, PTL 2
describes a technique for preparing a complex of a pulp with
calcium carbonate by precipitating calcium carbonate in a
suspension of the pulp by the carbonation process.
CITATION LIST
Patent Literature
[0004] PTL 1: JPA 1994-158585 [0005] PTL 2: U.S. Pat. No.
5,679,220
SUMMARY OF INVENTION
Technical Problem
[0006] In conventional complex fibers comprising a cellulose fiber
covered by inorganic particles on its surface, the cellulose fiber
and the inorganic particles did not bind together with sufficient
strength, so that the cellulose fiber was covered by only small
amounts of the inorganic particles or the inorganic particles
sometimes dropped from the cellulose fiber. Under such
circumstances, the present invention aims to provide complex fibers
comprising a cellulose fiber strongly covered by a lot of inorganic
particles on its surface.
Solution to Problem
[0007] The present invention includes, but not limited to, the
following:
[1] A process for preparing a complex fiber of a cellulose fiber
with inorganic particles, comprising the steps of: synthesizing
inorganic particles in a solution containing a cellulose fiber to
give a complex fiber; and determining the particle size
distribution of (a) or (b) below: (a) the filtrate obtained by
filtering an aqueous suspension of the complex fiber at a solids
content of 0.1% through a 60-mesh sieve (having an opening of 250
.mu.m); or (b) the fraction corresponding to an effluent volume (L)
of 18.51 to 19.50 and an efflux time (sec) of 37.4 to 48.0 when an
aqueous suspension of the complex fiber at a solids content of 0.3%
is classified using a fiber classification analyzer under the
conditions of a flow rate of 5.7 L/min, a water temperature of
25.+-.1.degree. C., and a total effluent volume of 22 L, thereby
calculating (D50-D10)/D50. [2] The process of [1], wherein the
aqueous suspension of the complex fiber is prepared in such a
manner that (D50-D10)/D50 is 0.85 or less. [3] The process of [1]
or [2], wherein the complex fiber has an average fiber diameter of
500 nm or more. [4] The process of any one of [1] to [3], wherein
the inorganic particles comprise a metal salt of calcium,
magnesium, barium or aluminum, or metal particles containing
titanium, copper or zinc, or a silicate. [5] A process for
preparing a complex fiber sheet, comprising the step of forming a
sheet from a complex fiber obtained by the process of any one of
[1] to [4]. [6] A complex fiber of a cellulose fiber with inorganic
particles, wherein the value of (D50-D10)/D50 calculated from the
particle size distribution of (a) or (b) below is 0.85 or less: (a)
the filtrate obtained by filtering an aqueous suspension of the
complex fiber at a solids content of 0.1% through a 60-mesh sieve
(having an opening of 250 .mu.m); or (b) the fraction corresponding
to an effluent volume (L) of 18.51 to 19.50 and an efflux time
(sec) of 37.4 to 48.0 when an aqueous suspension of the complex
fiber at a solids content of 0.3% is classified using a fiber
classification analyzer under the conditions of a flow rate of 5.7
L/min, a water temperature of 25.+-.1.degree. C., and a total
effluent volume of 22 L. [7] A complex fiber of a cellulose fiber
with inorganic particles, passing through a 60-mesh sieve (having
an opening of 250 .mu.m) when an aqueous suspension of the complex
fiber at a solids content of 0.1% is processed through the sieve,
wherein the value of (D50-D10)/D50 calculated from the particle
size distribution of the filtrate having passed through the sieve
is 0.85 or less. [8] A complex fiber of a cellulose fiber with
inorganic particles, derived from the fraction corresponding to an
effluent volume (L) of 18.51 to 19.50 and an efflux time (sec) of
37.4 to 48.0 when an aqueous suspension of the complex fiber at a
solids content of 0.3% is classified using a fiber classification
analyzer under the conditions of a flow rate of 5.7 L/min, a water
temperature of 25.+-.1.degree. C., and a total effluent volume of
22 L, wherein the value of (D50-D10)/D50 calculated from the
particle size distribution of the fraction is 0.85 or less. [9] A
method for analyzing a complex fiber of a cellulose fiber with
inorganic particles, comprising the step of: determining the
particle size distribution of (a) or (b) below: (a) the filtrate
obtained by filtering an aqueous suspension of the complex fiber at
a solids content of 0.1% through a 60-mesh sieve (having an opening
of 250 .mu.m); or (b) the fraction corresponding to an effluent
volume (L) of 18.51 to 19.50 and an efflux time (sec) of 37.4 to
48.0 when an aqueous suspension of the complex fiber at a solids
content of 0.3% is classified using a fiber classification analyzer
under the conditions of a flow rate of 5.7 L/min, a water
temperature of 25.+-.1.degree. C., and a total effluent volume of
22 L, thereby calculating (D50-D10)/D50.
Advantageous Effects of Invention
[0008] According to the present invention, complex fibers
comprising a cellulose fiber strongly covered by a lot of inorganic
particles on its surface, which allow for improved production
efficiency during post-processes such as dehydration and
sheet-forming, can be obtained.
[0009] The inorganic particles and the cellulose fiber bind
together more strongly than in conventional complex fibers, so that
the inorganic particles rarely drop during dehydration and
sheet-forming (i.e., the inorganic particles are efficiently
retained in post-processes) and drainage is also improved because
free small size particles decrease. The improved dewaterability or
drainage leads to improved productivity of various products (i.e.,
increased dehydration speed and sheet-forming speed) as a matter of
course, but also leads to improved functionality of products made
from the complex fibers of the present invention or the like
because the functional inorganic particles rarely drop.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 shows an electron micrograph of Sample 1
(magnification: 3000.times.).
[0011] FIG. 2 shows an electron micrograph of Sample 2
(magnification: 3000.times.).
[0012] FIG. 3 shows an electron micrograph of Sample 3
(magnification: 3000.times.).
[0013] FIG. 4 shows an electron micrograph of Sample 4
(magnification: 3000.times.).
[0014] FIG. 5 shows an electron micrograph of Sample 5
(magnification: 3000.times.).
[0015] FIG. 6 shows an electron micrograph of Sample 6
(magnification: 3000.times.).
[0016] FIG. 7 shows an electron micrograph of Sample 7
(magnification: 3000.times.).
[0017] FIG. 8 shows an electron micrograph of Sample 8
(magnification: 3000.times.).
[0018] FIG. 9 shows an electron micrograph of Sample 9
(magnification: 3000.times.).
[0019] FIG. 10 shows electron micrographs of Sample 10
(magnification: left 3000.times.; right 10000.times.).
[0020] FIG. 11 shows electron micrographs of Sample 11
(magnification: left 3000.times.; right 10000.times.).
[0021] FIG. 12 shows electron micrographs of Sample 12
(magnification: left 3000.times.; right 10000.times.).
[0022] FIG. 13 shows an electron micrograph of Sample A
(magnification: 3000.times.).
[0023] FIG. 14 shows an electron micrograph of Sample B
(magnification: 3000.times.).
[0024] FIG. 15 shows an electron micrograph of Sample C1
(magnification: 3000.times.).
[0025] FIG. 16 shows an electron micrograph of Sample C2
(magnification: 3000.times.).
[0026] FIG. 17 shows an electron micrograph of Sample D1
(magnification: 3000.times.).
[0027] FIG. 18 shows an electron micrograph of Sample D2
(magnification: 3000.times.).
DESCRIPTION OF EMBODIMENTS
[0028] The present invention relates to complex fibers (complexes)
comprising a cellulose fiber strongly covered by inorganic
particles on its surface. In preferred embodiments of the complex
fibers of the present invention, 15% or more of the fiber surface
is covered by the inorganic particles.
[0029] In the complex fibers of the present invention, the
inorganic particles rarely drop from the fiber because the fiber
and the inorganic particles bind together via hydrogen bonds or the
like rather than simply being mixed. Typically, the binding
strength between a fiber and inorganic particles in a complex can
be evaluated by, for example, a value such as ash retention (%,
i.e., [(the ash content in a sheet)/(the ash content in the complex
before disintegration)].times.100). Specifically, a complex is
dispersed in water to a solids content of 0.2% and disintegrated in
a standard disintegrator as defined in JIS P 8220-1: 2012 for 5
minutes, and then formed into a sheet using a 150-mesh wire
according to JIS P 8222: 1998, and the ash retention in the
resulting sheet can be used for the evaluation. In the present
invention, however, even complex fibers that could not be
sufficiently evaluated for their binding strength by conventional
methods can be evaluated by classifying them to identify better
complex fibers having high binding strength.
[0030] In the present invention, composite particles can be
suitably evaluated in a complex fiber of a cellulose fiber with
inorganic particles by analyzing the particle size distribution of
(a) or (b) below:
(a) the filtrate obtained by filtering an aqueous suspension of the
complex fiber at a solids content of 0.1% through a 60-mesh sieve
(having an opening of 250 .mu.m); or (b) the fraction corresponding
to an effluent volume (L) of 18.51 to 19.50 and an efflux time
(sec) of 37.4 to 48.0 when an aqueous suspension of the complex
fiber at a solids content of 0.3% is classified using a fiber
classification analyzer under the conditions of a flow rate of 5.7
L/min, a water temperature of 25.+-.1.degree. C., and a total
effluent volume of 22 L.
[0031] Specifically, the value of (D50-D10)/D50 calculated from the
volume-based particle size distribution of (a) or (b) can be used
as the basis for evaluation. Here, D10 and D50 each represent the
particle size determined from the volume-based particle size
distribution, wherein D10 is the 10th percentile particle size and
D50 is the 50th percentile particle size. If the value of
(D50-D10)/D50 is lower, it means that the sample has a narrower
particle size distribution, indicating that inorganic materials
firmly adhere to the fiber surface. In preferred embodiments, the
value of (D50-D10)/D50 is 0.85 or less.
[0032] Synthesis of Complex Fibers
[0033] In the present invention, complex fibers can be synthesized
by synthesizing inorganic particles in a solution containing a
fiber such as a cellulose fiber. This is because the surface of the
fiber provides a suitable site where the inorganic particles are
precipitated, thus facilitating the synthesis of complex fibers.
Processes for synthesizing the complex fibers may comprise
stirring/mixing a solution containing a fiber and precursors of
inorganic particles in an open reaction vessel to synthesize a
complex or injecting an aqueous suspension containing a fiber and
precursors of inorganic particles into a reaction vessel to
synthesize a complex. As described below, inorganic particles may
be synthesized in the presence of cavitation bubbles generated
during the injection of an aqueous suspension of a precursor of an
inorganic material into a reaction vessel. Inorganic particles can
be synthesized on the cellulose fiber by a known reaction in either
case.
[0034] Generally, inorganic particles are known to be produced
through the process of: clustering (repeated association and
dissociation of a small number of atoms or molecules), nucleation
(transition from a cluster to a stable aggregate in which
associated atoms or molecules no longer dissociate when the cluster
exceeds a critical size), and growth (capturing of additional atoms
or molecules by a nucleus to form a larger particle), and it is
said that nucleation is more likely to occur when the concentration
of the raw material or the reaction temperature is higher. The
complex fibers of the present invention comprising a cellulose
fiber strongly covered by inorganic particles on its surface can be
obtained primarily by controlling the concentrations of the raw
materials, the beating degree (specific surface area) of pulp, the
viscosity of the solution containing the fiber, the concentrations
and feed rates of chemicals added, the reaction temperature, and
the stirring speed so that nuclei are efficiently bound onto the
fiber and that particle growth is promoted.
[0035] In the present invention, a liquid may be injected under
conditions where cavitation bubbles are generated in a reaction
vessel or a liquid may be injected under conditions where
cavitation bubbles are not generated. The reaction vessel is
preferably a pressure vessel in either case. As used herein, the
term "pressure vessel" refers to a vessel that can withstand a
pressure of 0.005 MPa or more. Under conditions where cavitation
bubbles are not generated, the pressure in the pressure vessel is
preferably 0.005 MPa or more and 0.9 MPa or less expressed in
static pressure.
[0036] (Cavitation Bubbles)
[0037] For synthesizing the complex fibers of the present
invention, inorganic particles can be precipitated in the presence
of cavitation bubbles. As used herein, the term "cavitation" refers
to a physical phenomenon in which bubbles are generated and
disappear in the flow of a fluid in a short time due to a pressure
difference. The bubbles generated by cavitation (cavitation
bubbles) develop from very small "bubble nuclei" of 100 .mu.m or
less present in a liquid when the pressure drops below the
saturated vapor pressure in the fluid only for a very short
time.
[0038] In the present invention, cavitation bubbles can be
generated in a reaction vessel by a known method. For example, it
is possible to generate cavitation bubbles by injecting a fluid
under high pressure, or by stirring at high speed in a fluid, or by
causing an explosion in a fluid, or by using an ultrasonic vibrator
(vibratory cavitation) or the like.
[0039] In the present invention, the reaction solution of raw
materials or the like can be directly used as a jet liquid to
generate cavitation, or some fluid can be injected into the
reaction vessel to generate cavitation bubbles. The fluid forming a
liquid jet may be any of a liquid, a gas, or a solid such as a
powder or pulp or a mixture thereof so far as it is in a flowing
state. Moreover, another fluid such as carbonic acid gas can be
added as an additional fluid to the fluid described above, if
desired. The fluid described above and the additional fluid may be
injected as a homogeneous mixture or may be injected
separately.
[0040] The liquid jet refers to a jet of a liquid or a fluid
containing solid particles or a gas dispersed or mixed in a liquid,
such as a liquid jet containing a pulp or a raw material slurry of
inorganic particles or bubbles. The gas referred to here may
contain bubbles generated by cavitation.
[0041] The flow rate and pressure are especially important for
cavitation because it occurs when a liquid is accelerated and a
local pressure drops below the vapor pressure of the liquid.
Therefore, the cavitation number a, which is a fundamental
dimensionless number representing a cavitation state, is desirably
0.001 or more and 0.5 or less, preferably 0.003 or more and 0.2 or
less, especially preferably 0.01 or more and 0.1 or less. If the
cavitation number .sigma. is less than 0.001, little benefit is
obtained because the pressure difference from the surroundings is
small when cavitation bubbles collapse, but if it is greater than
0.5, the pressure difference in the flow is too small to generate
cavitation.
[0042] When cavitation is generated by emitting a jetting liquid
through a nozzle or an orifice tube, the pressure of the jetting
liquid (upstream pressure) is desirably 0.01 MPa or more and 30 MPa
or less, preferably 0.7 MPa or more and 20 MPa or less, more
preferably 2 MPa or more and 15 MPa or less. If the upstream
pressure is less than 0.01 MPa, little benefit is obtained because
a pressure difference is less likely to occur from the downstream
pressure. If the upstream pressure is higher than 30 MPa, a special
pump and pressure vessel are required and energy consumption
increases, leading to cost disadvantages. On the other hand, the
pressure in the vessel (downstream pressure) is preferably 0.005
MPa or more and 0.9 MPa or less expressed in static pressure.
Further, the ratio between the pressure in the vessel and the
pressure of the jetting liquid is preferably in the range of 0.001
to 0.5.
[0043] In the present invention, inorganic particles can also be
synthesized by injecting a jetting liquid under conditions where
cavitation bubbles are not generated. Specifically, the pressure of
the jetting liquid (upstream pressure) is controlled at 2 MPa or
less, preferably 1 MPa or less, while the pressure of the jetting
liquid (downstream pressure) is released, more preferably 0.05 MPa
or less.
[0044] The jet flow rate of the jetting liquid is desirably in the
range of 1 m/sec or more and 200 m/sec or less, preferably in the
range of 20 m/sec or more and 100 m/sec or less. If the jet flow
rate is less than 1 m/sec, little benefit is obtained because the
pressure drop is too small to generate cavitation. If it is greater
than 200 m/sec, however, special equipment is required to generate
high pressure, leading to cost disadvantages.
[0045] In the present invention, cavitation may be generated in the
reaction vessel where inorganic particles are synthesized. The
process can be run in one-pass mode, or can be run through a
necessary number of cycles. Further, the process can be run in
parallel or in series using multiple generating means.
[0046] Liquid injection for generating cavitation may take place in
a vessel open to the atmosphere, but preferably takes place within
a pressure vessel to control the cavitation.
[0047] When cavitation is generated by liquid injection, the solids
content of the reaction solution is preferably 30% by weight or
less, more preferably 20% by weight or less. This is because
cavitation bubbles are more likely to homogeneously act on the
reaction system at such levels. On the other hand, the solids
content of the aqueous suspension of slaked lime forming the
reaction solution is preferably 0.1% by weight or more to improve
the reaction efficiency.
[0048] When a complex of calcium carbonate with a cellulose fiber
is synthesized in the present invention, for examples, the pH of
the reaction solution is basic at the start of the reaction, but
changes to neutral as the carbonation reaction proceeds. Thus, the
reaction can be controlled by monitoring the pH of the reaction
solution.
[0049] In the present invention, stronger cavitation can be
generated by increasing the jetting pressure of the liquid because
the flow rate of the jetting liquid increases and accordingly the
pressure decreases. Moreover, the impact force can be stronger by
increasing the pressure in the reaction vessel because the pressure
in the region where cavitation bubbles collapse increases and the
pressure difference between the bubbles and the surroundings
increases so that the bubbles vigorously collapse. This also helps
to promote the dissolution and dispersion of carbonic acid gas
introduced. The reaction temperature is preferably 0.degree. C. or
more and 90.degree. C. or less, especially preferably 10.degree. C.
or more and 60.degree. C. or less. Given that the impact force is
generally thought to be maximal at the midpoint between the melting
point and the boiling point, the temperature is suitably around
50.degree. C. in cases of aqueous solutions, though significant
effects can be obtained even at a lower temperature so far as it is
within the ranges defined above because there is no influence of
vapor pressure.
[0050] For preparing the complex fibers of the present invention,
various known auxiliaries can also be added. For example, chelating
agents can be added, specifically including polyhydroxycarboxylic
acids such as citric acid, malic acid, and tartaric acid;
dicarboxylic acids such as oxalic acid; sugar acids such as
gluconic acid; aminopolycarboxylic acids such as iminodiacetic acid
and ethylenediaminetetraacetic acid and alkali metal salts thereof;
alkali metal salts of polyphosphoric acids such as
hexametaphosphoric acid and tripolyphosphoric acid; amino acids
such as glutamic acid and aspartic acid and alkali metal salts
thereof; ketones such as acetylacetone, methyl acetoacetate and
allyl acetoacetate; sugars such as sucrose; and polyols such as
sorbitol. Surface-treating agents can also be added, including
saturated fatty acids such as palmitic acid and stearic acid;
unsaturated fatty acids such as oleic acid and linoleic acid;
alicyclic carboxylic acids; resin acids such as abietic acid; as
well as salts, esters and ethers thereof; alcoholic activators,
sorbitan fatty acid esters, amide- or amine-based surfactants,
polyoxyalkylene alkyl ethers, polyoxyethylene nonyl phenyl ether,
sodium alpha-olefin sulfonate, long-chain alkylamino acids, amine
oxides, alkylamines, quaternary ammonium salts, aminocarboxylic
acids, phosphonic acids, polycarboxylic acids, condensed phosphoric
acids and the like. Further, dispersants can also be used, if
desired. Such dispersants include, for example, sodium
polyacrylate, sucrose fatty acid esters, glycerin fatty acid
esters, ammonium salts of acrylic acid-maleic acid copolymers,
methacrylic acid-naphthoxypolyethylene glycol acrylate copolymers,
ammonium salts of methacrylic acid-polyethylene glycol
monomethacrylate copolymers, polyethylene glycol monoacrylate and
the like. These can be used alone or in combination. They may be
added before or after the synthesis reaction. Such additives can be
added preferably in an amount of 0.001 to 20%, more preferably 0.1
to 10% of inorganic particles.
[0051] Further in the present invention, the reaction can be a
batch reaction or a continuous reaction. Typically, the reaction is
preferably performed by a batch reaction process because of the
convenience in removing residues after the reaction. The scale of
the reaction is not specifically limited, and can be 100 L or less,
or more than 100 L. The volume of the reaction vessel can be, for
example, in the order of 10 L to 100 L, or may be in the order of
100 L to 1000 L.
[0052] Furthermore, the reaction can be controlled by the
electrical conductivity of the reaction solution or the reaction
period, and specifically it can be controlled by adjusting the
period during which the reactants stay in the reaction vessel. In
the present invention, the reaction can also be controlled by
stirring the reaction solution in the reaction vessel or performing
the reaction as a multistage reaction.
[0053] In the present invention, the reaction product complex fiber
is obtained as a suspension so that it can be stored in a storage
tank or subjected to further processes such as concentration,
dehydration, grinding, classification, aging, or dispersion, as
appropriate. These can be accomplished by known processes, which
may be appropriately selected taking into account the purpose,
energy efficiency and the like. For example, the
concentration/dehydration process is performed by using a
centrifugal dehydrator, thickener or the like. Examples of such
centrifugal dehydrators include decanters, screw decanters and the
like. If a filter or dehydrator is used, the type of it is not
specifically limited either, and those commonly used can be used,
including, for example, pressure dehydrators such as filter
presses, drum filters, belt presses and tube presses; or vacuum
drum filters such as Oliver filters or the like, which can be
conveniently used to give a calcium carbonate cake. Grinding means
include ball mills, sand grinder mills, impact mills, high pressure
homogenizers, low pressure homogenizers, Dyno mills, ultrasonic
mills, Kanda grinders, attritors, millstone type mills, vibration
mills, cutter mills, jet mills, breakers, beaters, single screw
extruders, twin screw extruders, ultrasonic stirrers,
juicers/mixers for home use, etc. Classification means include
sieves such as meshes, outward or inward flow slotted or round-hole
screens, vibrating screens, heavyweight contaminant cleaners,
lightweight contaminant cleaners, reverse cleaners, screening
testers and the like. Dispersion means include high speed
dispersers, low speed kneaders and the like.
[0054] The complex fibers in the present invention can be
compounded into fillers or pigments as a suspension without being
completely dehydrated, or can be dried into powder. The dryer used
in the latter case is not specifically limited either, and air-flow
dryers, band dryers, spray dryers and the like can be conveniently
used, for example.
[0055] The complex fibers of the present invention can be modified
by known methods. In one embodiment, for example, they can be
hydrophobized on their surface to enhance the miscibility with
resins or the like.
[0056] In the present invention, water is used for preparing
suspensions or for other purposes, in which case not only common
tap water, industrial water, groundwater, well water and the like
can be used, but also ion-exchanged water, distilled water,
ultrapure water, industrial waste water, and the water obtained
during the separation/dehydration of the reaction solution can be
conveniently used.
[0057] Further in the present invention, the reaction solution in
the reaction vessel can be used in circulation. Thus, the reaction
efficiency increases and a desired complex of inorganic particles
with a fiber can be readily obtained by circulating the reaction
solution to promote stirring of the solution.
[0058] Inorganic Particles
[0059] In the present invention, the inorganic particles to be
complexed with a fiber are not specifically limited, but preferably
insoluble or slightly soluble in water. The inorganic particles are
preferably insoluble or slightly soluble in water because the
inorganic particles are sometimes synthesized in an aqueous system
or the fiber complexes are sometimes used in an aqueous system.
[0060] As used herein, the term "inorganic particles" refers to a
compound of a metal element or a non-metal element. Further, the
compound of a metal element refers to the so-called inorganic salt
formed by an ionic bond between a metal cation (e.g., Na.sup.+,
Ca.sup.2+, Mg.sup.2+, Al.sup.3+, Ba.sup.2+ or the like) and an
anion (e.g., O.sup.2-, OH.sup.-, CO.sub.3.sup.2-, PO.sub.4.sup.3-,
SO.sub.4.sup.2-, NO.sub.3.sup.-, Si.sub.2O.sub.3.sup.2-,
SiO.sub.3.sup.2-, Cl.sup.-, F.sup.-, S.sup.2- or the like). The
compound of a non-metal element includes, for example, a silicate
(SiO.sub.2) or the like. In the present invention, the inorganic
particles are preferably at least partially a metal salt of
calcium, magnesium or barium, or the inorganic particles are
preferably at least partially a silicate, or a metal salt of
aluminum, or metal particles containing titanium, copper, silver,
iron, manganese, cerium or zinc.
[0061] These inorganic particles can be synthesized by a known
method, which may be either a gas-liquid or liquid-liquid method.
An example of gas-liquid methods is the carbonation process,
according to which magnesium carbonate can be synthesized by
reacting magnesium hydroxide and carbonic acid gas, for example.
Examples of liquid-liquid methods include the reaction between an
acid (e.g., hydrochloric acid, sulfuric acid or the like) and a
base (e.g., sodium hydroxide, potassium hydroxide or the like) by
neutralization; the reaction between an inorganic salt and an acid
or a base; and the reaction between inorganic salts. For example,
barium sulfate can be obtained by reacting barium hydroxide and
sulfuric acid, or aluminum hydroxide can be obtained by reacting
aluminum sulfate and sodium hydroxide, or composite inorganic
particles of calcium and aluminum can be obtained by reacting
calcium carbonate and aluminum sulfate. Such syntheses of inorganic
particles can be performed in the presence of any metal or
non-metal compound in the reaction solution, in which case the
metal or non-metal compound is efficiently incorporated into the
inorganic particles so that it can form a composite with them. For
example, composite particles of calcium phosphate and titanium can
be obtained by adding phosphoric acid to calcium carbonate to
synthesize calcium phosphate in the presence of titanium dioxide in
the reaction solution.
[0062] (Calcium Carbonate)
[0063] Calcium carbonate can be synthesized by, for example, the
carbonation process, the soluble salt reaction process, the
lime-soda process, the soda process or the like, and in preferred
embodiments, calcium carbonate is synthesized by the carbonation
process.
[0064] Typically, the preparation of calcium carbonate by the
carbonation process involves using lime as a calcium source to
synthesize calcium carbonate via a slaking step in which water is
added to quick lime CaO to give slaked lime Ca(OH).sub.2 and a
carbonation step in which carbonic acid gas CO.sub.2 is injected
into the slaked lime to give calcium carbonate CaCO.sub.3. During
then, the suspension of slaked lime prepared by adding water to
quick lime may be passed through a screen to remove less soluble
lime particles contained in the suspension. Alternatively, slaked
lime may be used directly as a calcium source. In cases where
calcium carbonate is synthesized by the carbonation process in the
present invention, the carbonation reaction may be performed in the
presence of cavitation bubbles.
[0065] In cases where calcium carbonate is synthesized by the
carbonation process, the aqueous suspension of slaked lime
preferably has a solids content in the order of 0.1 to 40% by
weight, more preferably 0.5 to 30% by weight, still more preferably
1 to 20% by weight. If the solids content is low, the reaction
efficiency decreases and the production cost increases, but if the
solids content is too high, the flowability decreases and the
reaction efficiency decreases. In the present invention, calcium
carbonate is synthesized in the presence of cavitation bubbles,
whereby the reaction solution and carbonic acid gas can be well
mixed even if a suspension (slurry) having a high solids content is
used.
[0066] Aqueous suspensions containing slaked lime that can be used
include those commonly used for the synthesis of calcium carbonate,
and can be prepared by, for example, mixing slaked lime with water
or by slaking (digesting) quick lime (calcium oxide) with water.
The slaking conditions include, but not specifically limited to, a
CaO concentration of 0.05% by weight or more, preferably 1% by
weight or more, and a temperature of 20 to 100.degree. C.,
preferably 30 to 100.degree. C., for example. Further, the average
residence time in the slaking reactor (slaker) is not specifically
limited either, but can be, for example, 5 minutes to 5 hours, and
preferably within 2 hours. It should be understood that the slaker
may be batch or continuous. It should be noted that, in the present
invention, the carbonation reactor (carbonator) and the slaking
reactor (slaker) may be provided separately, or one reactor may
serve as both carbonation reactor and slaking reactor.
[0067] In the synthesis of calcium carbonate, the nucleation
reaction proceeds more readily when the concentrations of the raw
materials (Ca ions, CO.sub.3 ions) in the reaction solution are
higher and the temperature is higher, but nuclei are less likely to
adhere to cellulose fibers and free inorganic particles are more
likely to be synthesized in the suspension under such conditions
when complex fibers are prepared. Thus, the nucleation reaction
must be suitably controlled if one desires to prepare a complex
fiber in which calcium carbonate has been strongly bound.
Specifically, this can be accomplished by optimizing the
concentration of Ca ions and the pulp consistency and reducing the
feed rate of CO.sub.2 per unit time. For example, the concentration
of Ca ions in the reaction vessel is preferably 0.01 mol/L or more
and less than 0.20 mol/L. If it is less than 0.01 mol/L, the
reaction does not readily proceed, but if it is 0.20 mol/L or more,
free inorganic particles are more likely to be synthesized in the
suspension. The pulp consistency is preferably 0.5% or more and
less than 4.0%. If it is less than 0.5%, the reaction does not
readily proceed because the frequency with which the raw materials
collide with fibers decreases, but if it is 4.0% or more,
homogeneous complexes cannot be obtained due to insufficient
stirring. The feed rate of CO.sub.2 per unit time is desirably
0.001 mol/min or more and less than 0.060 mol/min per liter of the
reaction solution. If it is less than 0.001 mol/min, the reaction
does not readily proceed, but if it is 0.060 mol/min or more, free
inorganic particles are more likely to be synthesized in the
suspension.
[0068] (Magnesium Carbonate)
[0069] Magnesium carbonate can be synthesized by a known method.
For example, basic magnesium carbonate can be synthesized via
normal magnesium carbonate from magnesium bicarbonate, which is
synthesized from magnesium hydroxide and carbonic acid gas.
Magnesium carbonate can be obtained in various forms such as
magnesium bicarbonate, normal magnesium carbonate, basic magnesium
carbonate and the like depending on the synthesis method, among
which basic magnesium carbonate is especially preferred as
magnesium carbonate forming part of the fiber complexes of the
present invention. This is because magnesium bicarbonate is
relatively unstable, while normal magnesium carbonate consists of
columnar (needle-like) crystals that may be less likely to adhere
to fibers. However, a fiber complex of magnesium carbonate with a
fiber in which the surface of the fiber is covered in a fish
scale-like pattern can be obtained if the chemical reaction is
allowed to proceed in the presence of the fiber until basic
magnesium carbonate is formed.
[0070] Further in the present invention, the reaction solution in
the reaction vessel can be used in circulation. Thus, the reaction
efficiency increases and desired inorganic particles can be readily
obtained by circulating the reaction solution to increase contacts
between the reaction solution and carbonic acid gas.
[0071] In the present invention, a gas such as carbon dioxide
(carbonic acid gas) is injected into the reaction vessel where it
can be mixed with the reaction solution. According to the present
invention, the reaction can be performed with good efficiency
because carbonic acid gas can be supplied to the reaction solution
without using any gas feeder such as a fan, blower or the like and
the carbonic acid gas is finely dispersed by cavitation
bubbles.
[0072] In the present invention, the concentration of carbon
dioxide in the gas containing carbon dioxide is not specifically
limited, but the concentration of carbon dioxide is preferably
higher. Further, the amount of carbonic acid gas introduced into
the injector is not limited and can be selected as appropriate.
[0073] The gas containing carbon dioxide of the present invention
may be substantially pure carbon dioxide gas or a mixture with
another gas. For example, a gas containing an inert gas such as air
or nitrogen in addition to carbon dioxide gas can be used as the
gas containing carbon dioxide. Gases containing carbon dioxide
other than carbon dioxide gas (carbonic acid gas) that can be
conveniently used include exhaust gases discharged from
incinerators, coal-fired boilers, heavy oil-fired boilers and the
like in papermaking factories. Alternatively, the carbonation
reaction can also be performed using carbon dioxide emitted from
the lime calcination process.
[0074] In the synthesis of magnesium carbonate, the nucleation
reaction proceeds more readily when the concentrations of the raw
materials (Mg ions, CO.sub.3 ions) in the reaction solution are
higher and the temperature is higher, but nuclei are less likely to
adhere to cellulose fibers and free inorganic particles are more
likely to be synthesized in the suspension under such conditions
when complex fibers are prepared. Thus, the nucleation reaction
must be suitably controlled if one desires to prepare a complex
fiber in which magnesium carbonate has been strongly bound.
Specifically, this can be accomplished by optimizing the
concentration of Mg ions and the pulp consistency and reducing the
feed rate of CO.sub.2 per unit time. For example, the concentration
of Mg ions in the reaction vessel is preferably 0.0001 mol/L or
more and less than 0.20 mol/L. If it is less than 0.0001 mol/L, the
reaction does not readily proceed, but if it is 0.20 mol/L or more,
free inorganic particles are more likely to be synthesized in the
suspension. The pulp consistency is preferably 0.5% or more and
less than 4.0%. If it is less than 0.5%, the reaction does not
readily proceed because the frequency with which the raw materials
collide with fibers decreases, but if it is 4.0% or more,
homogeneous complexes cannot be obtained due to insufficient
stirring. The feed rate of CO.sub.2 per unit time is desirably
0.001 mol/min or more and less than 0.060 mol/min per liter of the
reaction solution. If it is less than 0.001 mol/min, the reaction
does not readily proceed, but if it is 0.060 mol/min or more, free
inorganic particles are more likely to be synthesized in the
suspension.
[0075] (Barium Sulfate)
[0076] Barium sulfate is a crystalline ionic compound represented
by the formula BaSO.sub.4 and composed of barium ions and sulfate
ions, and often assumes a plate-like or columnar form and is poorly
soluble in water. Pure barium sulfate occurs as colorless crystals,
but turns yellowish brown or black gray and translucent when it
contains impurities such as iron, manganese, strontium, calcium or
the like. It occurs as a natural mineral or can be synthesized by
chemical reaction. Especially, synthetic products obtained by
chemical reaction are not only used for medical purposes (as
radiocontrast agents) but also widely used for paints, plastics,
storage batteries and the like by taking advantage of their
chemical stability.
[0077] In the present invention, complexes of barium sulfate with a
fiber can be prepared by synthesizing barium sulfate in a solution
in the presence of the fiber. For example, possible methods include
the reaction between an acid (e.g., sulfuric acid or the like) and
a base by neutralization; the reaction between an inorganic salt
and an acid or a base; and the reaction between inorganic salts.
For example, barium sulfate can be obtained by reacting barium
hydroxide and sulfuric acid or aluminum sulfate, or barium sulfate
can be precipitated by adding barium chloride into an aqueous
solution containing a sulfate.
[0078] In the synthesis of barium sulfate, the nucleation reaction
proceeds more readily when the concentrations of the raw materials
(Ba ions, SO.sub.4 ions) in the solution are higher and the
temperature is higher, but nuclei are less likely to adhere to
cellulose fibers and free inorganic particles are more likely to be
synthesized in the suspension under such conditions when complex
fibers are prepared. Thus, the nucleation reaction must be suitably
controlled if one desires to prepare a complex fiber in which
barium sulfate has been strongly bound. Specifically, this can be
accomplished by optimizing the concentration of Ba ions and the
pulp consistency and reducing the feed rate of SO.sub.4 ions per
unit time. For example, the concentration of Ba ions in the
reaction vessel is preferably 0.01 mol/L or more and less than 0.20
mol/L. If it is less than 0.01 mol/L, the reaction does not readily
proceed, but if it is 0.20 mol/L or more, free inorganic particles
are more likely to be synthesized in the suspension. The pulp
consistency is preferably 0.5% or more and less than 4.0%. If it is
less than 0.5%, the reaction does not readily proceed because the
frequency with which the raw materials collide with fibers
decreases, but if it is 4.0% or more, homogeneous complexes cannot
be obtained due to insufficient stirring. The feed rate of SO.sub.4
ions per unit time is desirably 0.005 mol/min or more and less than
0.080 mol/min per liter of the reaction solution. If it is less
than 0.001 mol/min, the reaction does not readily proceed, but if
it is 0.080 mol/min or more, free inorganic particles are more
likely to be synthesized in the suspension
[0079] (Hydrotalcite)
[0080] Hydrotalcite can be synthesized by a known method. For
example, hydrotalcite is synthesized via a co-precipitation
reaction at controlled temperature, pH and the like by immersing a
fiber in an aqueous carbonate solution containing carbonate ions
forming interlayers and an alkaline solution (sodium hydroxide or
the like) in a reaction vessel, and then adding an acid solution
(an aqueous metal salt solution containing divalent metal ions and
trivalent metal ions forming host layers). Alternatively,
hydrotalcite can also be synthesized via a co-precipitation
reaction at controlled temperature, pH and the like by immersing a
fiber in an acid solution (an aqueous metal salt solution
containing divalent metal ions and trivalent metal ions forming
host layers) in a reaction vessel, and then adding dropwise an
aqueous carbonate solution containing carbonate ions forming
interlayers and an alkaline solution (sodium hydroxide or the
like). The reaction typically takes place at ordinary pressure,
though a process involving a hydrothermal reaction using an
autoclave or the like has also been proposed (JPA 1985-6619).
[0081] In the present invention, chlorides, sulfides, nitrates and
sulfates of magnesium, zinc, barium, calcium, iron, copper, cobalt,
nickel, and manganese can be used as sources of divalent metal ions
forming host layers. On the other hand, chlorides, sulfides,
nitrates and sulfates of aluminum, iron, chromium and gallium can
be used as sources of trivalent metal ions forming host layers.
[0082] In the present invention, carbonate ions, nitrate ions,
chloride ions, sulfate ions, phosphate ions and the like can be
used as interlayer anions. Sodium carbonate is used as a source of
carbonate ions, when they are used as interlayer anions. However,
sodium carbonate can be replaced by a gas containing carbon dioxide
(carbonic acid gas) such as substantially pure carbon dioxide gas
or a mixture with another gas. For example, gases containing carbon
dioxide that can be conveniently used include exhaust gases
discharged from incinerators, coal-fired boilers, heavy oil-fired
boilers and the like in papermaking factories. Alternatively, the
carbonation reaction can also be performed using carbon dioxide
emitted from the lime calcination process.
[0083] In the synthesis of hydrotalcite, the nucleation reaction
proceeds more readily when the concentrations of the raw materials
(metal ions forming host layers, CO.sub.3 ions and the like) in the
solution are higher and the temperature is higher, but nuclei are
less likely to adhere to cellulose fibers and free inorganic
particles are more likely to be synthesized in the suspension under
such conditions when complex fibers are prepared. Thus, the
nucleation reaction must be suitably controlled if one desires to
prepare a complex fiber in which hydrotalcite has been strongly
bound. Specifically, this can be accomplished by optimizing the
concentration of CO.sub.3 ions and the pulp consistency and
reducing the feed rate of metal ions per unit time. For example,
the concentration of CO.sub.3 ions in the reaction vessel is
preferably 0.01 mol/L or more and less than 0.80 mol/L. If it is
less than 0.01 mol/L, the reaction does not readily proceed, but if
it is 0.80 mol/L or more, free inorganic particles are more likely
to be synthesized in the suspension. The pulp consistency is
preferably 0.5% or more and less than 4.0%. If it is less than
0.5%, the reaction does not readily proceed because the frequency
with which the raw materials collide with fibers decreases, but if
it is 4.0% or more, homogeneous complexes cannot be obtained due to
insufficient stirring. The feed rate of metal ions per unit time is
desirably 0.001 mol/min or more and less than 0.010 mol/min, more
desirably 0.001 mol/min or more and less than 0.005 mol/min per
liter of the reaction solution in the case of Mg ions, for example,
though it depends on the type of metal. If it is less than 0.001
mol/min, the reaction does not readily proceed, but if it is 0.010
mol/min or more, free inorganic particles are more likely to be
synthesized in the suspension.
[0084] (Alumina/Silica)
[0085] Alumina and/or silica can be synthesized by a known method.
When any one or more of an inorganic acid or an aluminum salt is
used as a starting material of the reaction, the synthesis is
accomplished by adding an alkali silicate. The synthesis can also
be accomplished by using an alkali silicate as a starting material
and adding any one or more of an inorganic acid or an aluminum
salt, but the product adheres better to fibers when an inorganic
acid and/or aluminum salt is used as a starting material. Inorganic
acids that can be used include, but not specifically limited to,
sulfuric acid, hydrochloric acid, nitric acid or the like, for
example. Among them, sulfuric acid is especially preferred in terms
of cost and handling. Aluminum salts include aluminum sulfate,
aluminum chloride, aluminum polychloride, alum, potassium alum and
the like, among which aluminum sulfate can be conveniently used.
Alkali silicates include sodium silicate or potassium silicate or
the like, among which sodium silicate is preferred because of easy
availability. The molar ratio between silicate and alkali is not
limited, but commercial products having an approximate molar ratio
of SiO.sub.2:Na.sub.2O=3 to 3.4:1 commonly distributed as sodium
silicate J3 can be conveniently used.
[0086] In the present invention, complex fibers comprising silica
and/or alumina deposited on the surface of a fiber are prepared
preferably by synthesizing silica and/or alumina on the fiber while
maintaining the pH of the reaction solution containing the fiber at
4.6 or less. The reason why this results in complex fibers covered
well on the fiber surface is not known in complete detail, but it
is believed that complex fibers with high coverage ratio and
adhesion ratio can be obtained because trivalent aluminum ions are
formed at a high degree of ionization by maintaining a low pH.
[0087] In the synthesis of silica and/or alumina, the nucleation
reaction proceeds more readily when the concentrations of the raw
materials (silicate ions, aluminum ions) in the reaction solution
are higher and the temperature is higher, but nuclei are less
likely to adhere to cellulose fibers and free inorganic particles
are more likely to be synthesized in the suspension under such
conditions when complex fibers are prepared. Thus, the nucleation
reaction must be suitably controlled if one desires to prepare a
complex fiber in which silica and/or alumina has been strongly
bound. Specifically, this can be accomplished by optimizing the
pulp consistency and reducing the feed rate of silicate ions and
aluminum ions added per unit time. For example, the pulp
consistency is preferably 0.5% or more and less than 4.0%. If it is
less than 0.5%, the reaction does not readily proceed because the
frequency with which the raw materials collide with fibers
decreases, but if it is 4.0% or more, homogeneous complexes cannot
be obtained due to insufficient stirring. The feed rate of silicate
ions and aluminum ions added per unit time is desirably 0.001
mol/min or more, more desirably 0.01 mol/min or more per liter of
the reaction solution, and it is desirably less than 0.5 mol/min,
more desirably less than 0.050 mol/min in the case of aluminum
ions, for example. If it is less than 0.001 mol/min, the reaction
does not readily proceed, but if it is 0.050 mol/min or more, free
inorganic particles are more likely to be synthesized in the
suspension.
[0088] In one preferred embodiment, the average primary particle
size of the inorganic particles in the complex fibers of the
present invention can be, for example, 1.5 .mu.m or less, or the
average primary particle size can be 1200 nm or less, or 900 nm or
less, or the average primary particle size can be even 200 nm or
less, or 150 nm or less. On the other hand, the average primary
particle size of the inorganic particles can be 10 nm or more. It
should be noted that the average primary particle size can be
determined from electron micrographs.
[0089] (Aluminum Hydroxide)
[0090] Aluminum hydroxide is a crystalline ionic compound
represented by the formula Al(OH).sub.3 and composed of aluminum
ions and hydroxide ions, and often assumes a particulate form and
is poorly soluble in water. Synthetic products obtained by chemical
reaction are not only used for pharmaceuticals and adsorbents but
also used for flame retardants or fire retardants by taking
advantage of their property of releasing water when heated.
[0091] In the present invention, complexes of aluminum hydroxide
with a fiber can be prepared by synthesizing aluminum hydroxide in
a solution in the presence of the fiber. For example, possible
methods include the reaction between an acid (e.g., sulfuric acid
or the like) and a base by neutralization; the reaction between an
inorganic salt and an acid or a base; and the reaction between
inorganic salts. For example, aluminum hydroxide can be obtained by
reacting sodium hydroxide and aluminum sulfate, or aluminum
hydroxide can be precipitated by adding aluminum chloride into an
aqueous solution containing an alkali salt.
[0092] In the synthesis of aluminum hydroxide, the nucleation
reaction proceeds more readily when the concentrations of the raw
materials (Ak ions, OH ions) in the solution are higher and the
temperature is higher, but nuclei are less likely to adhere to
cellulose fibers and free inorganic particles are more likely to be
synthesized in the suspension under such conditions when complex
fibers are prepared. Thus, the nucleation reaction must be suitably
controlled if one desires to prepare a complex fiber in which
aluminum hydroxide has been strongly bound. Specifically, this can
be accomplished by optimizing the concentration of OH ions and the
pulp consistency and reducing the feed rate of Al ions added per
unit time. For example, the concentration of OH ions in the
reaction vessel is preferably 0.01 mol/L or more and less than 0.50
mol/L. If it is less than 0.01 mol/L, the reaction does not readily
proceed, but if it is 0.50 mol/L or more, free inorganic particles
are more likely to be synthesized in the suspension. The pulp
consistency is preferably 0.5% or more and less than 4.0%. If it is
less than 0.5%, the reaction does not readily proceed because the
frequency with which the raw materials collide with fibers
decreases, but if it is 4.0% or more, homogeneous complexes cannot
be obtained due to insufficient stirring. The feed rate of Al ions
added per unit time is desirably 0.001 mol/min or more and less
than 0.050 mol/min per liter of the reaction solution. If it is
less than 0.001 mol/min, the reaction does not readily proceed, but
if it is 0.050 mol/min or more, free inorganic particles are more
likely to be synthesized in the suspension.
[0093] Cellulose Fibers
[0094] The complex fibers used in the present invention comprise a
cellulose fiber complexed with inorganic particles. Examples of
cellulose fibers forming part of the complexes that can be used
include, without limitation, not only natural cellulose fibers but
also regenerated fibers (semisynthetic fibers) such as rayon and
lyocell and synthetic fibers and the like. Examples of raw
materials of cellulose fibers include pulp fibers (wood pulps and
non-wood pulps), cellulose nanofibers, bacterial celluloses,
animal-derived celluloses such as Ascidiacea, algae, etc., among
which wood pulps may be prepared by pulping wood raw materials.
Examples of wood raw materials include softwoods such as Pinus
densiflora, Pinus thunbergii, Abies sachalinensis, Picea jezoensis,
Pinus koraiensis, Larix kaempferi, Abies firma, Tsuga sieboldii,
Cryptomeria japonica, Chamaecyparis obtusa, Larix kaempferi, Abies
veitchii, Picea jezoensis var. hondoensis, Thujopsis dolabrata,
Douglas fir (Pseudotsuga menziesii), hemlock (Conium maculatum),
white fir (Abies concolor), spruces, balsam fir (Abies balsamea),
cedars, pines, Pinus merkusii, Pinus radiata, and mixed materials
thereof; and hardwoods such as Fagus crenata, birches, Alnus
japonica, oaks, Machilus thunbergii, Castanopsis, Betula
platyphylla, Populus nigra var. italica, poplars, Fraxinus, Populus
maximowiczii, Eucalyptus, mangroves, Meranti, Acacia and mixed
materials thereof.
[0095] The technique for pulping the wood raw materials (woody raw
materials) is not specifically limited, and examples include
pulping processes commonly used in the papermaking industry. Wood
pulps can be classified by the pulping process and include, for
example, chemical pulps obtained by digestion via the kraft
process, sulfite process, soda process, polysulfide process or the
like; mechanical pulps obtained by pulping with a mechanical force
such as a refiner, grinder or the like; semichemical pulps obtained
by pulping with a mechanical force after a chemical pretreatment;
waste paper pulps; deinked pulps and the like. The wood pulps may
have been unbleached (before bleaching) or bleached (after
bleaching).
[0096] Examples of non-wood pulps include cotton, hemp, sisal
(Agave sisalana), abaca (Musa textilis), flax, straw, bamboo,
bagas, kenaf, sugar cane, corn, rice straw, Broussonetia
kazinoki.times.B. papyrifera, Edgeworthia chrysantha and the
like.
[0097] The pulp fibers may be unbeaten or beaten, and may be chosen
depending on the desired properties of complex sheets to be formed
therefrom, but they are preferably beaten. This can be expected to
improve the sheet strength and to promote the adhesion of inorganic
particles.
[0098] Moreover, these cellulosic raw materials can be further
treated, whereby they can also be used as powdered celluloses,
chemically modified celluloses such as oxidized celluloses, and
cellulose nanofibers (CNFs) (microfibrillated celluloses (MFCs),
TEMPO-oxidized CNFs, phosphate esters of CNFs, carboxymethylated
CNFs, mechanically ground CNFs and the like). Powdered celluloses
used in the present invention may be, for example, rod-like
crystalline cellulose powders having a defined particle size
distribution prepared by purifying/drying and grinding/sieving the
undecomposed residue obtained after acid hydrolysis of an accepted
pulp fraction, or may be commercially available as KC FLOCK (from
Nippon Paper Industries Co., Ltd.), CEOLUS (from Asahi Kasei
Chemicals Corp.), AVICEL (from FMC Corporation) and the like. The
degree of polymerization of celluloses in the powdered celluloses
is preferably in the order of 100 to 1500, and the powdered
celluloses preferably have a crystallinity of 70 to 90% as
determined by X-ray diffraction and also preferably have a volume
average particle size of 500 nm or more and 100 .mu.m or less as
determined by a laser diffraction particle size distribution
analyzer.
[0099] Oxidized celluloses used in the present invention can be
obtained by oxidation with an oxidizing agent in water in the
presence of an N-oxyl compound and a compound selected from the
group consisting of a bromide, an iodide or a mixture thereof, for
example. Cellulose nanofibers can be obtained by disintegrating the
cellulosic raw materials described above. Disintegration methods
that can be used include, for example, mechanically grinding or
beating an aqueous suspension or the like of a cellulose or a
chemically modified cellulose such as an oxidized cellulose using a
refiner, high pressure homogenizer, grinder, single screw or
multi-screw kneader, bead mill or the like. Cellulose nanofibers
may be prepared by using one or a combination of the methods
described above. The fiber diameter of the cellulose nanofibers
prepared can be determined by electron microscopic observation or
the like and preferably falls within the range of, for example, 5
nm to 300 nm. During the preparation of the cellulose nanofibers, a
given compound can be further added before and/or after the
celluloses are disintegrated and/or micronized, whereby it reacts
with the cellulose nanofibers to functionalize their hydroxyl
groups. Functional groups used for the functionalization include
acyl groups such as acetyl, ester, ether, ketone, formyl, benzoyl,
acetal, hemiacetal, oxime, isonitrile, allene, thiol, urea, cyano,
nitro, azo, aryl, aralkyl, amino, amide, imide, acryloyl,
methacryloyl, propionyl, propioloyl, butyryl, 2-butyryl, pentanoyl,
hexanoyl, heptanoyl, octanoyl, nonanoyl, decanoyl, undecanoyl,
dodecanoyl, myristoyl, palmitoyl, stearoyl, pivaloyl, benzoyl,
naphthoyl, nicotinoyl, isonicotinoyl, furoyl and cinnamoyl;
isocyanate groups such as 2-methacryloyloxyethyl isocyanate; alkyl
groups such as methyl, ethyl, propyl, 2-propyl, butyl, 2-butyl,
tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl,
dodecyl, myristyl, palmityl, and stearyl; oxirane, oxetane, oxyl,
thiirane, thietane and the like. Hydrogens in these substituents
may be substituted by a functional group such as hydroxyl or
carboxyl. Further, the alkyl groups may partially contain an
unsaturated bond. Compounds used for introducing these functional
groups are not specifically limited and include, for example,
compounds containing phosphate-derived groups, compounds containing
carboxylate-derived groups, compounds containing sulfate-derived
groups, compounds containing sulfonate-derived groups, compounds
containing alkyl groups, compounds containing amine-derived groups
and the like. Phosphate-containing compounds include, but not
specifically limited to, phosphoric acid and lithium salts of
phosphoric acid such as lithium dihydrogen phosphate, dilithium
hydrogen phosphate, trilithium phosphate, lithium pyrophosphate,
and lithium polyphosphate. Other examples include sodium salts of
phosphoric acid such as sodium dihydrogen phosphate, disodium
hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, and
sodium polyphosphate. Further examples include potassium salts of
phosphoric acid such as potassium dihydrogen phosphate, dipotassium
hydrogen phosphate, tripotassium phosphate, potassium
pyrophosphate, and potassium polyphosphate. Still further examples
include ammonium salts of phosphoric acid such as ammonium
dihydrogen phosphate, diammonium hydrogen phosphate, triammonium
phosphate, ammonium pyrophosphate, ammonium polyphosphate and the
like. Among them, preferred ones include, but not specifically
limited to, phosphoric acid, sodium salts of phosphoric acid,
potassium salts of phosphoric acid, and ammonium salts of
phosphoric acid, and more preferred are sodium dihydrogen phosphate
and disodium hydrogen phosphate because they allow phosphate groups
to be introduced with high efficiency so that they are convenient
for industrial applications. Carboxyl-containing compounds include,
but not specifically limited to, dicarboxylic compounds such as
maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric
acid, adipic acid, and itaconic acid; and tricarboxylic compounds
such as citric acid, and aconitic acid. Acid anhydrides of
carboxyl-containing compounds include, but not specifically limited
to, acid anhydrides of dicarboxylic compounds such as maleic
anhydride, succinic anhydride, phthalic anhydride, glutaric
anhydride, adipic anhydride, and itaconic anhydride. Derivatives of
carboxyl-containing compounds include, but not specifically limited
to, imides of acid anhydrides of carboxyl-containing compounds, and
derivatives of acid anhydrides of carboxyl-containing compounds.
Imides of acid anhydrides of carboxyl-containing compounds include,
but not specifically limited to, imides of dicarboxylic compounds
such as maleimides, succinimides, and phthalimides. Derivatives of
acid anhydrides of carboxyl-containing compounds are not
specifically limited. For example, they include acid anhydrides of
carboxyl-containing compounds in which hydrogen atoms are at least
partially substituted by a substituent (e.g., alkyl, phenyl or the
like) such as dimethylmaleic anhydride, diethylmaleic anhydride,
and diphenylmaleic anhydride. Among the compounds containing
carboxylate-derived groups listed above, preferred ones include,
but not specifically limited to, maleic anhydride, succinic
anhydride and phthalic anhydride because they are convenient for
industrial applications and can be readily gasified. Further, the
cellulose nanofibers may be functionalized by a compound physically
adsorbed rather than chemically bonded to the cellulose nanofibers.
Compounds to be physically adsorbed include surfactants and the
like, which may be anionic, cationic, or nonionic. When the
celluloses are functionalized as described above before they are
disintegrated and/or ground, these functional groups can be
removed, giving back the original hydroxyl groups after they are
disintegrated and/or ground. The functionalization as described
above can promote disintegration into cellulose nanofibers or help
cellulose nanofibers to be mixed with various materials during
their use.
[0100] The fibers shown above may be used alone or as a mixture of
two or more of them. For example, fibrous materials collected from
waste water of a papermaking factory may be supplied to the
carbonation reaction of the present invention. Various composite
particles including those of various shapes such as fibrous
particles can be synthesized by supplying such materials to the
reaction vessel.
[0101] In the present invention, materials that are incorporated
into the product inorganic particles to form composite particles
can be used in addition to a fiber. In the present invention,
composite particles incorporating inorganic particles, organic
particles, polymers or the like can be prepared by synthesizing
inorganic particles in a solution containing these materials in
addition to a fiber such as a pulp fiber.
[0102] The fiber length of the fiber to be complexed is not
specifically limited, and the average fiber length can be, for
example, in the order of 0.1 .mu.m to 15 mm, or may be 1 .mu.m to
12 mm, 100 .mu.m to 10 mm, 400 .mu.m to 8 mm or the like.
Especially in the present invention, the average fiber length is
preferably 400 .mu.m or more (0.4 mm or more).
[0103] The average fiber diameter of the fiber to be complexed is
not specifically limited, and the average fiber diameter can be,
for example, in the order of 1 nm to 100 .mu.m, or may be 500 nm to
100 .mu.m, 1 .mu.m to 90 .mu.m, 3 .mu.m to 50 .mu.m, 5 .mu.m to 30
.mu.m or the like. Especially in the present invention, the average
fiber diameter is preferably 500 nm or more because the production
efficiency during post-processes can be improved.
[0104] The average fiber length and the average fiber diameter of
the fiber can be determined by a fiber length analyzer. The fiber
length analyzer includes, for example, Valmet Fractionator (from
Valmet K.K.)
[0105] The fiber to be complexed is preferably used in such an
amount that 15% or more of the surface of the fiber is covered by
inorganic particles, and the weight ratio between the fiber and the
inorganic particles can be, for example, 5/95 to 95/5, or may be
10/90 to 90/10, 20/80 to 80/20, 30/70 to 70/30, or 40/60 to
60/40.
[0106] In the complex fibers of the present invention, 15% or more
of the surface of the fiber is covered by inorganic particles in
preferred embodiments, and when the surface of the cellulose fiber
is covered at such an area ratio, characteristics attributed to the
inorganic particles predominate while characteristics attributed to
the fiber surface diminish.
[0107] The complex fibers of the present invention can be used in
various shapes including, for example, powders, pellets, moldings,
aqueous suspensions, pastes, sheets, boards, blocks, and other
shapes. Further, the complex fibers can be used as main components
with other materials to form molded products such as moldings,
particles or pellets. The dryer used to dry them into powder is not
specifically limited either, and air-flow dryers, band dryers,
spray dryers and the like can be conveniently used, for
example.
[0108] The complex fibers of the present invention can be used for
various applications and they can be widely used for any
applications including, for example, papers, fibers, cellulosic
composite materials, filter materials, paints, plastics and other
resins, rubbers, elastomers, ceramics, glasses, tires, building
materials (asphalt, asbestos, cement, boards, concrete, bricks,
tiles, plywoods, fiber boards, ceiling materials, wall materials,
floor materials, roof materials and the like), furniture, various
carriers (catalyst carriers, drug carriers, agrochemical carriers,
microbial carriers and the like), adsorbents (decontaminants,
deodorizers, dehumidifying agents and the like), antimicrobial
materials, antiviral agents, anti-wrinkle agents, clay, abrasives,
friction materials, modifiers, repairing materials, thermal
insulation materials, thermal resistant materials, heat dissipating
materials, damp proofing materials, water repellent materials,
waterproofing materials, light shielding materials, sealants,
shielding materials, insect repellents, adhesives, medical
materials, paste materials, discoloration inhibitors,
electromagnetic wave absorbers, insulating materials, acoustic
insulation materials, interior materials, vibration damping
materials, semiconductor sealing materials, radiation shielding
materials, flame retardant materials and the like. They also can be
used for various fillers, coating agents and the like in the
applications mentioned above. Among them, they are preferably
applied for adsorbents, antimicrobial materials, antiviral agents,
friction materials, radiation shielding materials, flame retardant
materials, building materials, and thermal insulation
materials.
[0109] The complex fibers of the present invention may also be
applied for papermaking purposes including, for example, printing
papers, newsprint papers, inkjet printing papers, PPC papers, kraft
papers, woodfree papers, coated papers, coated fine papers,
wrapping papers, thin papers, colored woodfree papers, cast-coated
papers, carbonless copy papers, label papers, heat-sensitive
papers, various fancy papers, water-soluble papers, release papers,
process papers, hanging base papers, flame retardant papers
(incombustible papers), base papers for laminated boards, printed
electronics papers, battery separators, cushion papers, tracing
papers, impregnated papers, papers for ODP, building papers, papers
for decorative building materials, envelope papers, papers for
tapes, heat exchange papers, chemical fiber papers, aseptic papers,
water resistant papers, oil resistant papers, heat resistant
papers, photocatalytic papers, cosmetic papers (facial blotting
papers and the like), various sanitary papers (toilet papers,
facial tissues, wipers, diapers, menstrual products and the like),
cigarette rolling papers, paperboards (liners, corrugating media,
white paperboards and the like), base papers for paper plates, cup
papers, baking papers, abrasive papers, synthetic papers and the
like. Thus, the present invention makes it possible to provide
complexes of a fiber with inorganic particles having a small
primary particle size and a narrow particle size distribution so
that they can exhibit different characteristics from those of
conventional inorganic fillers having a particle size of more than
2 Further, the complexes of a fiber with inorganic particles can be
formed into sheets in which the inorganic particles are not only
more readily retained but also uniformly dispersed rather than
being aggregated in contrast to those in which inorganic particles
are simply mixed with a fiber. In preferred embodiments, the
inorganic particles in the present invention are not only adhered
to the outer surface and the inside of the lumen of the fiber but
also produced within microfibrils, as proved by the results of
electron microscopic observation.
[0110] Further, the complex fibers of the present invention can be
used typically in combination with particles known as inorganic
fillers and organic fillers or various fibers. For example,
inorganic fillers include calcium carbonate (precipitated calcium
carbonate, ground calcium carbonate), magnesium carbonate, barium
carbonate, aluminum hydroxide, calcium hydroxide, magnesium
hydroxide, zinc hydroxide, clay (kaolin, calcined kaolin,
delaminated kaolin), talc, zinc oxide, zinc stearate, titanium
dioxide, silica products prepared from sodium silicate and a
mineral acid (white carbon black, silica/calcium carbonate
complexes, silica/titanium dioxide complexes), terra alba,
bentonite, diatomaceous earth, calcium sulfate, zeolite, inorganic
fillers consisting of the ash produced and recycled from the
deinking process and inorganic fillers consisting of complexes of
the ash with silica or calcium carbonate formed during recycling,
etc. Calcium carbonate-silica complexes include not only calcium
carbonate and/or precipitated calcium carbonate-silica complexes
but also those complexes using amorphous silica such as white
carbon black. Organic fillers include urea-formaldehyde resins,
polystyrene resins, phenol resins, hollow microparticles,
acrylamide complexes, wood-derived materials (microfibers,
microfibrillar fibers, kenaf powders), modified/insolubilized
starches, ungelatinized starches and the like. Fibers that can be
used include, without limitation, not only natural fibers such as
celluloses but also synthetic fibers artificially synthesized from
raw materials such as petroleum, regenerated fibers (semisynthetic
fibers) such as rayon and lyocell, and even inorganic fibers and
the like. In addition to the examples mentioned above, natural
fibers include protein fibers such as wool and silk yarns and
collagen fibers; complex carbohydrate fibers such as
chitin-chitosan fibers and alginate fibers and the like. Examples
of cellulosic raw materials include pulp fibers (wood pulps and
non-wood pulps), bacterial celluloses, animal-derived celluloses
such as Ascidiacea, algae, etc., among which wood pulps may be
prepared by pulping wood raw materials. Examples of wood raw
materials include softwoods such as Pinus densiflora, Pinus
thunbergii, Abies sachalinensis, Picea jezoensis, Pinus koraiensis,
Larix kaempferi, Abies firma, Tsuga sieboldii, Cryptomeria
japonica, Chamaecyparis obtusa, Larix kaempferi, Abies veitchii,
Picea jezoensis var. hondoensis, Thujopsis dolabrata, Douglas fir
(Pseudotsuga menziesii), hemlock (Conium maculatum), white fir
(Abies concolor), spruces, balsam fir (Abies balsamea), cedars,
pines, Pinus merkusii, Pinus radiata, and mixed materials thereof;
and hardwoods such as Fagus crenata, birches, Alnus japonica, oaks,
Machilus thunbergii, Castanopsis, Betula platyphylla, Populus nigra
var. italica, poplars, Fraxinus, Populus maximowiczii, Eucalyptus,
mangroves, Meranti, Acacia and mixed materials thereof. The
technique for pulping the wood raw materials is not specifically
limited, and examples include pulping processes commonly used in
the papermaking industry. Wood pulps can be classified by the
pulping process and include, for example, chemical pulps obtained
by digestion via the kraft process, sulfite process, soda process,
polysulfide process or the like; mechanical pulps obtained by
pulping with a mechanical force such as a refiner, grinder or the
like; semichemical pulps obtained by pulping with a mechanical
force after a chemical pretreatment; waste paper pulps; deinked
pulps and the like. The wood pulps may have been unbleached (before
bleaching) or bleached (after bleaching). Examples of non-wood
pulps include cotton, hemp, sisal (Agave sisalana), abaca (Musa
textilis), flax, straw, bamboo, bagas, kenaf, sugar cane, corn,
rice straw, Broussonetia kazinoki.times.B. papyrifera, Edgeworthia
chrysantha and the like. The wood pulps and non-wood pulps may be
unbeaten or beaten. Moreover, these cellulosic raw materials can be
further treated so that they can also be used as powdered
celluloses, chemically modified celluloses such as oxidized
celluloses, and cellulose nanofibers (CNFs) (microfibrillated
celluloses (MFCs), TEMPO-oxidized CNFs, phosphate esters of CNFs,
carboxymethylated CNFs, mechanically ground CNFs). Synthetic fibers
include polyesters, polyamides, polyolefins, and acrylic fibers;
semisynthetic fibers include rayon, acetate and the like; and
inorganic fibers include glass fiber, carbon fiber, various metal
fibers and the like. All these may be used alone or as a
combination of two or more of them.
[0111] The average particle size or shape or the like of the
inorganic particles forming part of the complex fibers of the
present invention can be identified by electron microscopic
observation. Further, inorganic particles having various sizes or
shapes can be complexed with a fiber by controlling the conditions
under which the inorganic particles are synthesized.
[0112] Forms of the Complex Fibers
[0113] In the present invention, the complex fibers described above
can be formed into various molded products (articles). For example,
the complex fibers of the present invention can be readily formed
into sheets having a high ash content. Further, the resulting
sheets can be laminated to form multilayer sheets.
[0114] Paper machines (sheet-forming machines) used for preparing
sheets include, for example, Fourdrinier machines, cylinder
machines, gap formers, hybrid formers, Rotoformers, multilayer
paper machines, known sheet-forming machines combining the
papermaking methods of these machines and the like. The linear
pressure in the press section of the paper machines and the linear
calendering pressure in a subsequent optional calendering process
can be both selected within a range convenient for the runnability
and the performance of the complex fiber sheets. Further, the
sheets thus formed may be impregnated or coated with starches,
various polymers, pigments and mixtures thereof.
[0115] During sheet forming, wet and/or dry strength additives
(paper strength additives) can be added. This allows the strength
of the complex fiber sheets to be improved. Strength additives
include, for example, resins such as urea-formaldehyde resins,
melamine-formaldehyde resins, polyamides, polyamines,
epichlorohydrin resins, vegetable gums, latexes, polyethylene
imines, glyoxal, gums, mannogalactan polyethylene imines,
polyacrylamide resins, polyvinylamines, and polyvinyl alcohols;
composite polymers or copolymers composed of two or more members
selected from the resins listed above; starches and processed
starches; carboxymethyl cellulose, guar gum, urea resins and the
like. The amount of the strength additives to be added is not
specifically limited.
[0116] Further, high molecular weight polymers or inorganic
materials can also be added to promote the adhesion of fillers to
fibers or to improve the retention of fillers or fibers. For
example, coagulants can be added, including cationic polymers such
as polyethylene imines and modified polyethylene imines containing
a tertiary and/or quaternary ammonium group, polyalkylene imines,
dicyandiamide polymers, polyamines, polyamine/epichlorohydrin
polymers, polymers of dialkyldiallyl quaternary ammonium monomers,
dialkylaminoalkyl acrylates, dialkylaminoalkyl methacrylates,
dialkylaminoalkyl acrylamides and dialkylaminoalkyl methacrylamides
with acrylamides, monoamine/epihalohydrin polymers, polyvinylamines
and polymers containing a vinylamine moiety as well as mixtures
thereof; cation-rich zwitterionic polymers containing an anionic
group such as a carboxyl or sulfone group copolymerized in the
molecules of the polymers listed above; mixtures of a cationic
polymer and an anionic or zwitterionic polymer and the like.
Further, retention aids such as cationic or anionic or zwitterionic
polyacrylamide-based materials can be used. These may be applied as
retention systems called dual polymers in combination with at least
one or more cationic or anionic polymers or may be applied as
multicomponent retention systems in combination with at least one
or more anionic inorganic microparticles such as bentonite,
colloidal silica, polysilicic acid, microgels of polysilicic acid
or polysilicic acid salts and aluminum-modified products thereof or
one or more organic microparticles having a particle size of 100
.mu.m or less called micropolymers composed of
crosslinked/polymerized acrylamides. Especially when the
polyacrylamide-based materials used alone or in combination with
other materials have a weight-average molecular weight of 2,000,000
Da or more, preferably 5,000,000 Da or more as determined by
intrinsic viscosity measurement, good retention can be achieved,
and when the acrylamide-based materials have a molecular weight of
10,000,000 Da or more and less than 30,000,000 Da, very high
retention can be achieved. The polyacrylamide-based materials may
be in the form of an emulsion or a solution. Specific compositions
of such materials are not specifically limited so far as they
contain an acrylamide monomer unit as a structural unit therein,
but include, for example, copolymers of a quaternary ammonium salt
of an acrylic acid ester and an acrylamide, or ammonium salts
obtained by copolymerizing an acrylamide and an acrylic acid ester,
followed by quaternization. The cationic charge density of the
cationic polyacrylamide-based materials is not specifically
limited.
[0117] Other additives include drainage aids, internal sizing
agents, pH modifiers, antifoaming agents, pitch control agents,
slime control agents, bulking agents, inorganic particles (the
so-called fillers) such as calcium carbonate, kaolin, talc and
silica and the like depending on the purposes. The amount of these
additives to be used is not specifically limited.
[0118] The basic weight (i.e., basis weight: the weight per square
meter) of the sheets can be appropriately controlled depending on
the purposes, and it is advantageously 60 to 1200 g/m.sup.2 for use
as, for example, building materials because of high strength and
low drying load during preparation. Alternatively, the basis weight
of the sheets can be 1200 g/m.sup.2 or more, e.g., 2000 to 110000
g/m.sup.2.
[0119] Molding techniques other than sheet forming may also be
used, and molded products having various shapes can be obtained by
the so-called pulp molding process involving casting a raw material
into a mold and then dehydrating/drying it under vacuum or the
process involving spreading a raw material over the surface of a
molded product of a resin or metal or the like and drying it, and
then releasing the dried material from the substrate or other
processes. Further, the complexes can be molded like plastics by
mixing them with a resin or can be used as reinforcing materials by
mixing them in cement or rubber. Alternatively, the complexes can
be formed into boards by compression molding under pressure and
heat as typically used for preparing boards of inorganic materials
such as cement or gypsum, or can be formed into blocks. The
complexes can be not only formed into sheets that can typically be
bent or rolled up, but also formed into boards if more strength is
needed. They can also be formed into thick masses, i.e., blocks in
the form of a rectangular cuboid or a cube, for example.
[0120] In the compounding/drying/molding processes shown above,
only one complex can be used, or a mixture of two or more complexes
can be used. Two or more complexes can be used as a premix of them
or can be mixed after they have been individually compounded, dried
and molded.
[0121] Further, various organic materials such as polymers or
various inorganic materials such as pigments may be added to the
molded products of the complexes afterwards.
[0122] The molded products prepared from the complexes of the
present invention can be printed on. The method for printing is not
specifically limited, and known methods can be used including, for
example, offset printing, silkscreen printing, screen printing,
gravure printing, microgravure printing, flexographic printing,
letterpress printing, sticker printing, business form printing, on
demand printing, furnisher roll printing, inkjet printing and the
like. Among them, inkjet printing is preferred in that a
comprehensive layout need not be prepared in contrast to offset
printing and it can be performed even on large sheets because large
size inkjet printers are relatively easily available. On the other
hand, flexographic printing can be conveniently used even for
molded products having such a shape as a board, molding or block
because it can be successfully performed even on molded products
having a relatively uneven surface.
[0123] Further, the printed image formed by printing may have any
type of pattern as desired including, but not specifically limited
to, wood texture patterns, stone texture patterns, fabric texture
patterns, objective patterns, geometric patterns, letters, symbols,
or a combination thereof, or may be filled with a solid color.
EXAMPLES
[0124] The present invention will be explained more in detail with
reference to specific experimental examples, but the present
invention is not limited to the specific examples below. Unless
otherwise specified, the concentrations, parts and the like as used
herein are based on weight, and the numerical ranges are described
to include their endpoints.
[0125] Experiment 1. Synthesis of Complexes
1-1. Complex Fibers of Ba Sulfate with a Cellulose Fiber
[0126] (Sample 1, FIG. 1)
[0127] After 436 g of a 1% pulp slurry (LBKP, CSF=450 mL, average
fiber length: about 0.7 mm, average fiber diameter: about 19 .mu.m)
and 18.8 g of barium hydroxide octahydrate (NIPPON CHEMICAL
INDUSTRIAL CO., LTD.) were mixed using a Three-One Motor agitator
(500 rpm), aluminum sulfate (alum stock solution, 25.8 g) was added
dropwise at a rate of 0.4 g/min. After completion of the dropwise
addition, stirring was continued for 30 minutes to give Sample
1.
[0128] (Sample 2, FIG. 2)
[0129] After 533 g of a 1.7% pulp slurry (LBKP, CSF=450 mL, average
fiber length: about 0.7 mm, average fiber diameter: about 19 .mu.m)
and 12.4 g of barium hydroxide octahydrate (NIPPON CHEMICAL
INDUSTRIAL CO., LTD.) were mixed using a Three-One Motor agitator
(667 rpm), aluminum sulfate (67.2 g of a 4-fold dilution of alum
stock solution in water) was added dropwise at a rate of 1.1 g/min.
After completion of the dropwise addition, stirring was continued
for 30 minutes to give Sample 2.
[0130] (Sample 3, FIG. 3)
[0131] After 437 g of a 1% pulp slurry (NBKP, CSF=425 mL, average
fiber length: about 1.7 mm, average fiber diameter: about 26 .mu.m)
and 18.8 g of barium hydroxide octahydrate (NIPPON CHEMICAL
INDUSTRIAL CO., LTD.) were mixed using a Three-One Motor agitator
(500 rpm), aluminum sulfate (alum stock solution, 26.1 g) was added
dropwise at a rate of 0.4 g/min. After completion of the dropwise
addition, stirring was continued for 30 minutes to give Sample
3.
[0132] (Sample 4, FIG. 4)
[0133] After 436 g of a 1% pulp slurry (LBKP, CSF=450 mL, average
fiber length: about 0.7 mm, average fiber diameter: about 19 .mu.m)
and 18.8 g of barium hydroxide octahydrate (NIPPON CHEMICAL
INDUSTRIAL CO., LTD.) were mixed using a Three-One Motor agitator
(500 rpm), aluminum sulfate (alum stock solution, 25.8 g) was added
dropwise at a rate of 1.0 g/min. After completion of the dropwise
addition, stirring was continued for 30 minutes to give a complex
slurry.
[0134] (Sample 5, FIG. 5, Inorganic Particles Alone)
[0135] In a 2-L vessel, 437 g of water and barium hydroxide
octahydrate (NIPPON CHEMICAL INDUSTRIAL CO., LTD., 18.8 g) were
mixed using a Three-One Motor agitator (500 rpm), and then aluminum
sulfate (alum stock solution, 25.8 g) was added dropwise at a rate
of 1.0 g/min. After completion of the dropwise addition, stirring
was continued for 30 minutes to give a sample of barium sulfate
particles.
[0136] (Sample 6, FIG. 6, a Mixture of Inorganic Particles and a
Cellulose Fiber)
[0137] A mixture of 120 g of a 1% pulp slurry (LBKP, CSF=450 mL,
average fiber length: about 0.7 mm, average fiber diameter: about
19 .mu.m) and 121 g of the slurry of barium sulfate particles of
Sample 6 (concentration 3.0%) was stirred with water to give a
mixed slurry of barium sulfate and a cellulose fiber.
[0138] (Sample 7, FIG. 7)
[0139] After 500 g of a 1% pulp slurry (LBKP/NBKP=8/2, average
fiber length: about 1.2 mm, average fiber diameter: about 14 .mu.m)
and 5.82 g of barium hydroxide octahydrate (FUJIFILM Wako Pure
Chemical Corporation) were mixed using a Three-One Motor agitator
(1000 rpm), sulfuric acid (FUJIFILM Wako Pure Chemical Corporation,
2.1 g) was added dropwise at a rate of 0.8 g/min. After completion
of the dropwise addition, stirring was continued for 30 minutes to
give a sample of a complex slurry.
[0140] (Sample 8, FIG. 8)
[0141] After 500 g of a 1% pulp slurry (LBKP/NBKP=8/2, average
fiber length: about 1.2 mm, average fiber diameter: about 14 .mu.m)
and 5.82 g of barium hydroxide octahydrate (FUJIFILM Wako Pure
Chemical Corporation) were mixed using a Three-One Motor agitator
(1000 rpm), sulfuric acid (FUJIFILM Wako Pure Chemical Corporation,
2.1 g) was added dropwise at a rate of 63.0 g/min. After completion
of the dropwise addition, stirring was continued for 30 minutes to
give a sample of a complex slurry.
[0142] (Sample 9, FIG. 9)
[0143] After 500 g of a 1% pulp slurry (LBKP/NBKP=8/2, average
fiber length: about 1.2 mm, average fiber diameter: about 14 .mu.m)
and 5.82 g of barium hydroxide octahydrate (FUJIFILM Wako Pure
Chemical Corporation) were mixed using a Three-One Motor agitator
(1000 rpm), sulfuric acid (FUJIFILM Wako Pure Chemical Corporation,
88 g of a 2% aqueous solution) was added dropwise at a rate of 8.0
g/min. After completion of the dropwise addition, stirring was
continued for 30 minutes to give a sample of a complex slurry.
[0144] (Sample 10, FIG. 10)
[0145] After a 1% pulp slurry (LBKP/NBKP=8/2, Canadian Standard
Freeness CSF=about 80 mL, average fiber length: 1.21 mm, 500 g) and
barium hydroxide octahydrate (FUJIFILM Wako Pure Chemical
Corporation, 5.82 g) were mixed while stirring using a Three-One
Motor agitator (1000 rpm), sulfuric acid (FUJIFILM Wako Pure
Chemical Corporation, 88 g of a 2% aqueous solution) was added
dropwise at a rate of 8.0 g/min using a peristaltic pump. After
completion of the dropwise addition, stirring was continued for 30
minutes to give a sample. Observation by electron microscopy showed
that plate-like barium sulfate spontaneously adhered to the fiber
surface and covered it (the primary particle size of barium sulfate
particles: 200 to 1500 nm, the average primary particle size of
barium sulfate particles: 500 nm).
[0146] (Sample 11, FIG. 11)
[0147] After a 1% pulp slurry (LBKP, CSF=500 mL, average fiber
length: about 0.7 mm, 1300 g) and barium hydroxide octahydrate
(FUJIFILM Wako Pure Chemical Corporation, 57 g) were mixed while
stirring using a Three-One Motor agitator (800 rpm), aluminum
sulfate (alum stock solution, 77 g) was added dropwise at a rate of
2 g/min using a peristaltic pump. After completion of the dropwise
addition, stirring was continued for 30 minutes to give a sample.
Observation by electron microscopy showed that plate-like barium
sulfate spontaneously adhered to the fiber surface and covered it
(the primary particle size of barium sulfate particles: 20 to 800
nm, the average primary particle size of barium sulfate particles:
100 nm).
[0148] (Sample 12, FIG. 12)
[0149] In a vessel (a machine chest having an internal volume of 4
m.sup.3), a 2% pulp slurry (LBKP/NBKP=8/2, CSF=390 mL, average
fiber length: about 1.3 mm, solids content 25 kg) and barium
hydroxide octahydrate (NIPPON CHEMICAL INDUSTRIAL CO., LTD., 75 kg)
were mixed, and then aluminum sulfate (alum, 98 kg) was added
dropwise at a rate of about 500 g/min using a peristaltic pump.
After completion of the dropwise addition, stirring was continued
for 30 minutes to give a sample. Observation by electron microscopy
showed that plate-like barium sulfate spontaneously adhered to the
fiber surface and covered it (the primary particle size of barium
sulfate particles: 50 to 1000 nm, the average primary particle size
of barium sulfate particles: 80 nm).
[0150] 1-2. A Complex Fiber of Al Hydroxide with a Cellulose
Fiber
[0151] (Sample A, FIG. 13)
[0152] After 437 g of a 1% pulp slurry (LBKP, CSF=450 mL, average
fiber length: about 0.7 mm, average fiber diameter: about 19 .mu.m)
and 4.8 g of sodium hydroxide (FUJIFILM Wako Pure Chemical
Corporation) were mixed using a Three-One Motor agitator (500 rpm),
aluminum sulfate (alum stock solution, 25.8 g) was added dropwise
at a rate of 0.8 g/min. After completion of the dropwise addition,
the reaction solution was stirred for 30 minutes, and washed with
about 3 volumes of water to remove the salt, thereby giving Sample
A.
[0153] 1-3. A Complex Fiber of Silica/Alumina with a Cellulose
Fiber
[0154] (Sample B, FIG. 14)
[0155] In a 2-L resin vessel, 910 g of a 0.5% pulp slurry (NBKP,
CSF: 360 mL, average fiber length: about 1.7 mm, average fiber
diameter: about 18 .mu.m) was stirred using a laboratory mixer (600
rpm). To this aqueous suspension was added dropwise aluminum
sulfate (alum stock solution) for about 4 minutes until the pH
reached 3.8, and then aluminum sulfate (alum, 156 g) and an aqueous
sodium silicate solution (FUJIFILM Wako Pure Chemical Corporation,
concentration 8%, 265 g) were added dropwise at the same time for
about 60 minutes to maintain the pH at 4. A peristaltic pump was
used for the dropwise addition, and the reaction temperature was
about 25.degree. C. Then, an aqueous sodium silicate solution
(FUJIFILM Wako Pure Chemical Corporation, concentration 8%, 200 g)
alone was added dropwise for about 80 minutes to adjust the pH to
7.3, thereby giving a sample of a complex slurry.
[0156] 1-4. Complex Fibers of Hydrotalcite with a Cellulose
Fiber
[0157] (Sample C1, FIG. 15)
[0158] A mixed aqueous solution (acid solution) of MgSO.sub.4
(FUJIFILM Wako Pure Chemical Corporation) and
Al.sub.2(SO.sub.4).sub.3 (FUJIFILM Wako Pure Chemical Corporation)
was prepared as a solution for synthesizing hydrotalcite (HT). The
concentration of MgSO.sub.4 was 0.6 M, while the concentration of
Al.sub.2(SO.sub.4).sub.3 was 0.1 M.
[0159] After 2250 g of a 2.0% pulp slurry (NBKP, CSF=270 mL,
average fiber length: about 1.8 mm, average fiber diameter: about
19 .mu.m) was mixed with 88.6 g of sodium hydroxide (FUJIFILM Wako
Pure Chemical Corporation) and 14.8 g of sodium carbonate (FUJIFILM
Wako Pure Chemical Corporation) using a Three-One Motor agitator
(650 rpm), 1362 g of the acid solution was added dropwise at a rate
of 4.7 g/min while keeping the temperature at 50.degree. C. After
completion of the dropwise addition, the reaction solution was
stirred for 30 minutes, and washed with about 3 volumes of water to
remove the salt, thereby giving a sample.
[0160] (Sample C2, FIG. 16)
[0161] After 2281 g of a 1.6% pulp slurry (NBKP, CSF=690 mL,
average fiber length: about 1.9 mm, average fiber diameter: about
19 .mu.m) was mixed with 88.6 g of sodium hydroxide (FUJIFILM Wako
Pure Chemical Corporation) and 14.8 g of sodium carbonate (FUJIFILM
Wako Pure Chemical Corporation) using a Three-One Motor agitator
(650 rpm), 1322 g of the acid solution was added dropwise at a rate
of 4.6 g/min while keeping the temperature at 50.degree. C. After
completion of the dropwise addition, the reaction solution was
stirred for 30 minutes, and washed with about 3 volumes of water to
remove the salt, and further filtered by suction through a filter
paper to give a sample (solids content: about 35%).
[0162] 1-5. Complex Fibers of Calcium Carbonate with a Cellulose
Fiber
[0163] (Sample D1, FIG. 17)
[0164] An aqueous suspension in an amount of 10 L containing
calcium hydroxide (slaked lime Ca(OH).sub.2, 100 g, FUJIFILM Wako
Pure Chemical Corporation) and a powdered cellulose (KC FLOCK.TM.
W-06MG from Nippon Paper Industries Co., Ltd., average particle
size: 6 .mu.m, 100 g) was provided. A 40-L closed system was
charged with this aqueous suspension and cavitation was generated
by injecting carbonic acid gas into the reaction vessel to
synthesize a complex fiber of calcium carbonate microparticles with
a fiber by the carbonation process. The reaction temperature was
about 15.degree. C., the carbonic acid gas source was a
commercially available liquefied gas, the injection flow rate of
the carbonic acid gas was 3 L/min, and the reaction was stopped
when the pH of the reaction solution reached about 7 (from the pH
of about 12.8 before the reaction).
[0165] During the synthesis of the complex fiber, cavitation
bubbles were generated in the reaction vessel by injecting the
reaction solution into the reaction vessel while circulating it.
Specifically, cavitation bubbles were generated by injecting the
reaction solution through a nozzle (nozzle diameter: 1.5 mm) under
high pressure. The jet flow rate was about 70 m/s, the inlet
pressure (upstream pressure) was 7 MPa and the outlet pressure
(downstream pressure) was 0.3 MPa.
[0166] (Sample D2, FIG. 18)
[0167] A complex fiber was synthesized in the same manner as
described for Sample D1 except that the powdered cellulose used was
W-100G (from Nippon Paper Industries Co., Ltd., average particle
size: 37 .mu.m) and that the injection flow rate of the carbonic
acid gas was 20 L/min.
TABLE-US-00001 TABLE 1 Synthesis conditions of the complex fiber
Feed rate of Ion precursors of concentration inorganic particles
Fiber in the per liter of the Chemical Inorganic Concentration
chemicals reaction solution application Application Temperature
particles Type (%) added (M) (mol/L/min) rate time (min) (.degree.
C.) Sample 1 Ba sulfate LBKP 1.0 2.3 0.03 0.4 68 23 (a complex
fiber) [SO.sub.4 ions] g/min Sample 2 Ba sulfate LBKP 1.7 0.6 0.01
1.1 61 23 (a complex fiber) [SO.sub.4 ions] g/min Sample 3 Ba
sulfate NBKP 1.0 2.3 0.04 0.4 61 22 (a complex fiber) [SO.sub.4
ions] g/min Sample 4 Ba sulfate LBKP 1.0 2.3 0.09 1.0 25 22 (a
complex fiber) [SO.sub.4 ions] g/min Sample 5 Ba sulfate -- -- 2.3
0.10 1.0 23 22 (inorganic [SO.sub.4 ions] g/min particles alone)
Sample 6 Ba sulfate LBKP 1.0 -- -- -- -- -- (a mixture) Sample 7 Ba
sulfate L/N = 8/2 1.0 18.3 13.6 0.8 2.7 21 (a complex fiber) [SO4
ions] g/min Sample 8 Ba sulfate L/N = 8/2 1.0 18.3 1220 63 0.03 21
(a complex fiber) [SO4 ions] g/min Sample 9 Ba sulfate L/N = 8/2
1.0 0.2 0.04 8.0 11 21 (a complex fiber) [SO4 ions] g/min Sample 10
Ba sulfate L/N = 8/2 1.0 0.037 0.038 8 -- -- (a complex fiber) [SO4
ions] g/min Sample 11 Ba sulfate LBKP 1.0 0.139 0.004 2 -- -- (a
complex fiber) [SO4 ions] g/min Sample 12 Ba sulfate L/N = 8/2 2.0
0.190 0.001 500 -- -- (a complex fiber) [SO4 ions] g/min Sample A
Al hydroxide LBKP 1.0 0.3 0.004 0.8 31 22 (a complex fiber) [OH
ions] g/min Sample B Silica/alumina NBKP 0.5 2 .1 0.03 2.6 60 25 (a
complex fiber) [Al ions] g/min Sample C1 Hydrotalcite NBKP 2.0 0.6
0.001 4.7 292 51 (a complex fiber) [Mg ions] g/min Sample C2
Hydrotalcite NBKP 1.6 0.6 0.001 4.6 287 50 (a complex fiber) [Mg
ions] g/min Sample D1 Ca Carbonate Powdered 1.0 0.135 0.010 3 13 15
(a complex fiber) cellulose [Ca ions] L/min Sample D2 Ca Carbonate
Powdered 1.0 0.135 0.09 20 5 15 (a complex fiber) cellulose [Ca
ions] L/min
[0168] Experiment 2. Evaluation of the Complex Samples
[0169] 2-1. Evaluation of Coverage Ratio and Others
[0170] Each complex sample obtained was washed with ethanol, and
then observed with an electron microscope. The results showed that
the inorganic material covered the fiber surface and spontaneously
adhered to it in each sample. The coverage ratio of each complex
sample is shown in the table below, demonstrating that the coverage
ratio was 15% or more in each sample.
[0171] Further, the slurry of each complex fiber obtained (3 g on a
solids basis) was filtered by suction through a filter paper, and
then the residue was dried in an oven (105.degree. C., 2 hours) and
the mass fraction of the inorganic particles in the complex fiber
was assessed by determining the ash content.
[0172] The average fiber length and the average fiber diameter of
the fiber were reported on the basis of the fiber length determined
by Valmet Fractionator. The fiber length was determined under the
conditions that the solids content of the slurry was adjusted to
0.1 to 0.3% and that the water temperature in the system was
adjusted to 25.degree. C..+-.1.degree. C.
[0173] 2-2. Evaluation by Screening/Automatic Classification
<Screening of the Complex Samples>
[0174] The synthesized slurries were filtered through a mesh filter
to remove coarse particles in the slurries. Each complex sample
obtained (1 g on a solids basis) was diluted with water to a solids
content of 0.1%, and 0.2 liters of the suspension was completely
filtered through a 60-mesh sieve (having an opening of 250 .mu.m),
and washed with 0.6 liters of water. Then, the filtrate obtained
after filtration was analyzed for the particle size distribution by
a wet process (Mastersizer 3000 from Malvern).
[0175] <Automatic Classification of the Complex Samples>
[0176] In addition to screening, each sample was automatically
classified into multiple fractions under predetermined conditions
using a fiber classification analyzer (Valmet Fractionator). This
is a system that enables a pulp slurry to be automatically
classified into five fractions (FRs 1 to 3: long to short fibers;
FRs 4 to 5: fine fibers/fillers) according to the efflux time after
it has been passed through a tube having a length of about 100 m at
a constant temperature and a constant rate and separated into
streams containing long fibers to fine fibers/fillers on the basis
of the hydrodynamic size.
[0177] Specifically, each complex sample (3 g on a solids basis)
was diluted with water to a solids content of 0.3%, and about 250 g
of the diluted sample was passed in triplicate through the fiber
classification analyzer (at a water temperature of 25.+-.1.degree.
C. during classification), and the fractions separated under the
effluent conditions shown below were collected.
TABLE-US-00002 TABLE 2 FR Effluent volume (L) Efflux time (sec) 1
16.00 to 17.55 10.6 to 27.2 2 17.56 to 18.05 27.3 to 32.5 3 18.06
to 18.50 32.6 to 37.3 4 18.51 to 19.50 37.4 to 48.0 5 19.51 to
20.50 48.1 to 59.0
[0178] FR4 collected was allowed to stand in a bucket for several
hours until fibrous materials settled, and after the supernatant
was discarded, the particle size distribution was determined by a
wet process (Mastersizer 3000 from Malvern).
[0179] <Particle Size Distribution>
[0180] The value of "(D50-D10)/D50" was calculated from D10 (the
10th percentile particle size) and D50 (the 50th percentile
particle size) in the volume-based particle size distribution
determined as described above. If this value is lower, it means
that the sample has a narrower particle size distribution,
indicating that the inorganic material firmly adheres to the fiber
surface.
[0181] 2-3. Evaluation of the Retention in Sheet Forming
[0182] Each of the complex samples obtained (Samples 1 to 12 and
Sample A) was prepared into a handsheet having a basis weight of
100 g/m.sup.2 using a 150-mesh wire according to JIS P 8222: 2015,
and the retention of paper stock components was calculated from the
basis weight of the resulting sheet.
.largecircle.: 70% or more .DELTA.: 50% or more and less than 70%
x: less than 50%
[0183] 2-4. Evaluation of Drainage
[0184] Each of the complex samples obtained (Samples 1 to 12 and
Sample A) was diluted with water to a solids content of 0.1% to
prepare a slurry containing 0.15 g of inorganic solids in total
solids, and the resulting slurry was passed through a membrane
filter (0.8 .mu.m) under a reduced pressure of 20 mmHg and the flow
through time was determined.
.circleincircle.: less than 2 minutes .largecircle.: 2 minutes or
more and less than 4 minutes .DELTA.: 4 minutes or more and less
than 6 minutes x: 6 minutes or more
TABLE-US-00003 TABLE 3 Mass fraction Filtrate after FR4 in
automatic Fiber of filtration classification Average Average
Coverage inorganic (D50 - (D50 - Retention Inorganic fiber fiber
ratio particles D50 D10 D10)/ D50 D10 D10)/ in sheet particles Type
length diameter (%) (%) (.mu.m) (.mu.m) D50 (.mu.m) (.mu.m) D50
forming Drainage Sample 1 Ba sulfate LBKP 0.7 mm 19 .mu.m 97 76 32
11.2 0.65 34 11.3 0.67 .smallcircle. .smallcircle. (a complex
fiber) Sample 2 Ba sulfate LBKP 0.7 mm 19 .mu.m 90 53 35 11.9 0.66
37 12.0 0.68 .smallcircle. .circleincircle. (a complex fiber)
Sample 3 Ba sulfate NBKP 1.7 mm 26 .mu.m 90 74 41 13.6 0.67 43 13.8
0.68 .smallcircle. .smallcircle. (a complex fiber) Sample 4 Ba
sulfate LBKP 0.7 mm 19 .mu.m 98 72 22 2.6 0.88 23 2.7 0.88 .DELTA.
x (a complex fiber) Sample 5 Ba sulfate -- -- -- 0 99 28 11.2 0.59
29 11.3 0.61 x x (inorganic particles alone) Sample 6 Ba sulfate
LBKP 0.7 mm 19 .mu.m 8 76 28 10.7 0.62 29 10.8 0.63 .DELTA. .DELTA.
(a mixture) Sample 7 Ba sulfate L/N = 8/2 1.2 mm 14 .mu.m 85 45 24
1.9 0.92 25 1.9 0.92 .DELTA. .DELTA. (a complex fiber) Sample 8 Ba
sulfate L/N = 8/2 1.2 mm 14 .mu.m 60 45 24 2.1 0.91 25 2.1 0.91
.DELTA. .DELTA. (a complex fiber) Sample 9 Ba sulfate L/N = 8/2 1.2
mm 14 .mu.m 95 45 28 5.1 0.82 30 5.2 0.82 .smallcircle.
.smallcircle. (a complex fiber) Sample Ba sulfate L/N = 8/2 1.2 mm
14 .mu.m 49 44 29 4.2 0.86 28 4.0 0.86 .DELTA. .DELTA. 10 (a
complex fiber) Sample Ba sulfate LBKP 0.7 mm 13 .mu.m 98 38 25 3.0
0.88 25 3.1 0.88 .DELTA. .DELTA. 11 (a complex fiber) Sample Ba
sulfate L/N = 8/2 1.3 mm 14 .mu.m 51 73 24 1.8 0.92 23 2.0 0.92
.DELTA. x 12 (a complex fiber) Sample Al LBKP 0.7 mm 19 .mu.m 95 34
32 9.8 0.69 33 9.9 0.70 .smallcircle. .smallcircle. A (a hydroxide
complex fiber) Sample Silica/ NBKP 1.7 mm 18 .mu.m 80 76 43 9.5
0.78 46 9.6 0.79 -- -- B (a alumina complex fiber) Sample Hydro-
NBKP 1.8 mm 19 .mu.m 95 69 23 5.1 0.78 25 5.1 0.79 -- C1 (a talcite
-- complex fiber) Sample Hydro- NBKP 1.9 mm 19 .mu.m 95 69 26 6.0
0.76 28 6.5 0.77 -- -- C2 (a talcite complex fiber) Sample Ca
Powdered 1.0 mm 6 .mu.m 75 53 45 8.6 0.81 -- -- -- -- -- D1 (a
Carbonate cellulose complex fiber) Sample Ca Powdered 1.0 mm 37
.mu.m 90 54 7 0.9 0.86 -- -- -- -- -- D2 (a Carbonate cellulose
complex fiber)
[0185] The table shows that Samples 1 to 3 and 9 of complex fibers
having a relatively high D50 value in the filtrate after
classification exhibited higher retention in sheet forming as
compared with Samples 4 to 8. This indicates that high proportions
of functional inorganic particles can be incorporated into sheets,
which means not only high production efficiency but also high
functional quality of the sheets.
[0186] Further, an evaluation of drainage showed that Samples 1 to
3 and 9 of complex fibers were dehydrated faster than Samples 4, 7,
8, 10 to 12 of complex fibers, Sample 5 of inorganic particles
alone and Sample 6 of a mixture when they were supposed to be
formed into sheets containing equivalent amounts of inorganic
particles. This may be attributed to the fact that Samples 1 to 3
and 9 of complex fibers contain relatively low amounts of fine
particles influencing the drainage. If the drainage is better, the
drying process can be shortened/reduced, leading to improved
productivity (reduced web break frequency and increased
sheet-forming speed) during the preparation of sheets or the like,
which means great benefits especially when preparing thick
sheets.
* * * * *