JAPAN TAPPI JOURNAL Vol.61
No.7
July 2007 Abstracts
Perspective and Current Research
Trend of Pulping Research
Yuji Matsumoto
Wood Chemistry Laboratory, Department of Biomaterial Sciences, The
University of Tokyo
By a wide survey of inhomogeneity of lignin structure,
a certain tendency was found among characteristic factors of lignin
structure.
Generally, when a certain tree species has lower lignin content,
its lignin is richer in  -O-4 structure, especially of erythro type,
and, sryringyl type of aromatics. Interestingly, these characteristics
are thought to be favorable for delignification reactions during
pulping and bleaching. This result suggests the importance of the
analysis of lignin structure for the survey of suitable woods for
pulping.
The Influence of Pulp on the Printability
Yukio Tani
Research Development Div., Pulp & Paper Research Laboratory,
Oji Paper Co., Ltd.
When paper is treated as a communicative function,
it does print to the paper and the first time additional value
occurs. Then,
the paper does have a commercial value in the market. In this paper,
required properties of pulp on printing are discussed when irradiating
pulp reverse from the view point of the print and looking at it.
In the case of printability, there are print runability and print
quality. These properties aren't always compatible, and become
the request to be often disagreed with by.
On printing, the shade of the image is resolved into halftone-dots
and the image is expressed as the continuous aggregate of dots.
The principle is the same even if the different printing method
by plate is taken. Therefore, so-called "Dot-reproducibility" is
very important to perform better printability, since the print
quality is increased by how much a dot is precisely reproduced
on the substance in printing. In any printing methods, the smoothness
is indispensable for this dot-reproducibility, and pulp is also
required to produce good smoothness. In addition to smoothness,
surface strength, internal strength, tensile strength, appropriate
shrinkage and cutting property (amount of paper powder) are requested
on pulp to ensure good printability, e.g. picking, piling, blistering,
folding fracture, and print fluting and so on.
Understanding the problems of final printed products becomes an
important point when discussing the quality of the pulp as an intermediate-product.
It is considered that printability of pulp also becomes one of
the big guideposts in studies and developments of pulp in the future.
Keywords: printability, halftone-dot reproducibility, smoothness,
pulp
Effect of Pulp Quality on Printability(II)
Koji Okomori
Pulp and Paper Research Laboratory, R&D Division, Nippon Paper
Industries Co., Ltd.
Production of coated paper has been increased since it was invented.
Bitoko grade is one of the staple commodities of coated paper and
the characteristic is the paper containing mechanical pulp. Because
bitoko grade paper is mostly printed by rotary offset press with
heat-set ink, it is necessary to withstand printing problems like
heat-set roughening, blistering and so on. Heat-set roughening
is roughening at solid area of printed matter due to rising of
fibers. Paper absorbs fountain solution during printing and the
fibers are released from out-of-plane stress. Then the shape of
the fibers changes from collapsed state to tubular at drying process
of the press, and the fibers rise. Mainly, the long fibers of mechanical
pulp, especially which cell wall is thick, cause this problem.
The effect of pulp is greater than coating conditions such as pre-calendering,
coating weight and so forth. Therefore it is quite important to
control pulp quality for the better printability.
Current Trend in Mechanical Pulping
Akifumi Hatta
Metso Fiber KK
Even there is no movement of new mechanical pulp project in Japan,
capacity of mechanical pulp manufacture is still increasing in
the world. As main driving force of this movement, cost reduction
has been done by various methods; fewer and larger production units
with bigger equipment, process to get lower cost and higher quality,
low energy segment and etc.
Even in the existing plants, Metso is working to improve them.
One key equipment is mechanical steam separator to improve fiber
loss and retention time between two refiners. Adjustable gap sensor
instead of conventional TDC sensor is also available now.
The Design Concept of the Saving Energy for OCC Screening System
Junichi Hashimoto
Research & Development Dept., Voith IHI Paper Technology Co.,
Ltd.
Customers' trials of stock preparation conducted by the VIPT's
Technology Center were, except large-scale pilot equipment, mainly
performance tests and single process simulation of the single equipment
until around 1988. However, recent test mainstream, in the both
paperboard and paper fields, turn to be the test to verify the
improvement of quality deteriorated by change of raw material quality,
improvement of productivity, reduction of production cost, and
quality improvement required by end users.
Regarding quality test, customers are more concerned about detailed
areas such as adhesive-related contaminants, dirt and flake than
in the past. Therefore, highly technological systems optimizing
a single equipment performance are strongly being required by customers.
Customer requirement for high quality product being more and more
intensified and the difficulty in recycling of waste paper being
expected, we need to enhance our technology to be able to respond
to these changes of industry's situation. Additionally, in order
to develop the "Post-Recycle 60", we VIPT are willingly ready to
cooperate with this trend.
This time we would like to introduce our development concept of OCC Screening
System with the focus on achieving energy saving and quality improvement at the
same time.
Technical Tasks & Solutions for Improvement of Recycled Pulp
Rate
Kazumi Fujita
Technical & Engineering Dept., Aikawa Iron Works Co., Ltd.
The increasing target of domestic wastepaper recycling rate
to 60% by the end of 2005 had been achieved 2 years ahead by a
result of great effort of various quarters. And today, "increasing
the paper recycling rate to 62% by the end of 2010" had been
set as a new goal again. About 630,000t per year wastepaper usage
increase is a condition for this new target realization.
Because of the wastepaper recycling rate for board-paper is already
more than 90%, increasing of fine wastepaper recycling rate is
needed for the 62% target realization. But, the reality is that
there is almost no high quality fine wastepaper remain. In addition,
in the booming China the low exactly sorted US wastepaper is avoided,
the Japanese wastepaper exporting became regular and domestic wastepaper
itself is exhausting rapidly.
Innovation and reform in various fields is necessary to achieve recycling rate
62% under such strict situation. In this seminar, I will show the technical tasks
and the solutions of efficient use of low quality wastepaper in the stock preparation
process that is Aikawa's field.
Keywords: 62% Wastepaper Recycling Rate, Chinese Pulp & Paper Industry,
Japanese Wastepaper
Stock Exporting, Wastepaper Stock Exhaustion,
Efficient Use of Low Quality
Wastepaper Stock, Improvement of Recycle
Pulp
Rate
KP Kiln Dam Ring Preventive Agent
Masahiro Tsurumi
Shizuoka 1st Sec, Techno Chemical Div., Thaihokohzai Co., Ltd.
In the causticizing process, the operation for kiln often requires
continuous stability, but the operation is stopped by compulsion
due to rapid development of dam ring in some cases.
The dam ring is produced in the following manner: Low-melting alkali
impurities such as sodium are supplied together with mud as a core
from the kiln end and the low-melting substance exposed to high-temperature
gas is made viscous to loosely bind the cores. Then, loose binding
moved away from the high-temperature gas under the continuous supply
of the mud changes into hard binding in the coating due to temperature
decrease or re-carbonation. These reactions continuously work resulting
in the formation of a large dam.
Our company, long engaged in producing and selling fuel additives,
tried relatively simple countermeasures through chemical addition
against the dam ring and has proven many achievements. The details
of our actual results are explained in this book.
The Impact of Elemental Chlorine Free Bleaching on Effluent Characteristics
Hitoshi Takagi
Research Department, Japan Pulp and Paper Research Institute, Inc.
The amendment of Air Pollution Control Law that required pulp and
paper mills to reduce discharge of chloroform was promulgated in
1996. Since then, Japanese pulp and paper companies have gradually
been introducing elemental chlorine free (ECF) bleaching. In 2006,
the production of ECF pulps exceeded 80 percent of Japanese bleached
chemical pulp production.
Generations of chloroform, chlorinated phenolic compounds, and chlorinated dioxins
were decreased dramatically with ECF bleaching. The AOX level in ECF bleaching
mill effluent was less than 0.2kg per ton of bleached pulp. On the contrary,
chlorate discharges were increased with chlorine dioxide bleaching.
Whether ECF conversion decreases the adverse effects of mill effluents on aquatic
organisms is evaluating in Japan Pulp and Paper Research Institute.
It can be concluded that misgivings about the discharge of organic chlorine compounds
from Japanese pulp and paper mills were practically eliminated by ECF conversion.
Keywords: Elemental Chlorine Free Bleaching (ECF), Chloroform, Dioxin, Chlorate,
Effluent
Overview of Elementary Chlorine Free Bleaching
Shintaro Sasada
Technology Division, Oji Paper Co., Ltd.
In order to reduce environmental impact, chlorine bleaching process
has been converted to ECF bleaching, in Japan, following North
Europe and North America. Oji Paper Group, according to Environmental
Charter Action Guidelines, planned to convert kraft pulp (KP) bleaching
process to ECF bleaching. Hardwood bleaching system at Kasugai
Mill was converted in August 2000, followed by other domestic mills.
All the 8 mills of our group has been completed conversion in June
2006.
Oji Paper Group invested 1.6 billion yen for the conversion of
all the 8 mills, where bleaching towers were rebuilt, and other
equipments were renovated including the one for chemical production.
In this presentation, details of the investment are reported, taking
Kushiro LBKP bleaching process as an example.
Conversion to ECF bleaching results in the increase of manufacturing
costs, but keeps quality of bleached pulp and stabilizes operation,
without any major troubles.
Technical Problems and their Measures for ECF Bleaching
Shin-ichi Hara
Hachinohe Mill, Mitsubishi Paper Mills Limited
In Hachinohe mill of Mitsubishi Paper Mills Limited, the bleached
kraft pulp (BKP) line named "3BKP" was switched to an elementary
chlorine free (ECF) bleaching in October 2000, and "2BKP" was switched
to the ECF bleaching in August 2005.
It was found that there were some differences as to bleaching behaviors
between the ECF bleaching whose first stage was chlorine dioxide
and a conventional chlorine bleaching. For example, the ECF bleaching
was more susceptible to a brightness of oxygen-delignified pulp
than the conventional one. Emissions of adsorbable organic halogen
and of chloroform were decreased by introducing the ECF bleaching.
Thus, environmental targets were achieved. However, technical problems
as to the ECF bleaching operation and a pulp quality newly occurred.
These problems were an increased bleaching cost, calcium oxalate
scales on diffuser screen and a discoloration of pulps and so on.
Measures to hexenuronic acid which is deeply related to the problems
have to be pursued for a fundamental solution to the problems.
This paper described in regard to characteristics of the ECF bleaching,
the technical problems and their measures that became apparent
through the ECF bleaching operation.
Keywords: ECF bleaching, Chlorine bleaching, Bleaching cost, Calcium
oxalate scale,
Discoloration of pulp, Hexenuronic acid
Problems and Measures in ECF Bleaching Operation
Makoto Horiguchi
Technical Division, Kishu Paper Co., Ltd.
Kishu mill, Kishu Paper fiber line was converted to ECF bleaching
sequence in August 2004. This plant was introduced to the hot chlorine dioxide
process (DUAL-D),
and this bleaching sequence has D*(i)-EP-D.
Also D*stage tower was adopted the gravity feed system (Difeed system) with the
first installation in the world.
The scale adhesion of some places is enumerated as a problem in current ECF operation.
Continuous operation is possible now by the removal of the scale by a high-pressure
washing and the acid washing when a biannual regular repair.
The D*stage is effective as color reversion. However, temperature conditions
are changed from 90℃ planned at first because the amount of the steam use is
large to 85℃ now and the amount of the steam use has been reduced.
(i):D* notes hot chlorine dioxide stage
The Recent Activities of ECF Bleaching
Kazuo Yamasaki
Production Dept. of Technical & Engineering Div., Nippon Paper Industries
Co., Ltd.
Elementary Chlorine Free (ECF) bleaching, the bleaching method with no chlorine
gas, has now become global standard. With the raising concern over environmental
issue and to meet the demand from consumers, ECF bleaching is rapidly spreading
among Japanese paper industries as well.
In accordance with the Nippon Paper Group's Environment Charter (established
in 1993), Nippon Paper Industries has been keenly engaged in sustainable business
activities that are in harmony with nature. Conversion of all bleaching lines
to ECF is one of such activities.
When installing ECF bleaching, Nippon Paper Industries pioneered in introducing
new technologies such as ozone bleaching and hot acid treatment in Japan. In
this report details of NPI's introduction of those new technologies in ECF bleaching
are presented.
Keywords: Kraft pulp, ECF bleaching
Measurement of the Elastic Modulus of Paperboard from the Low-Frequency Vibration
Modes of Rectangular Plates
Jun Sato and Ian M. Hutchings
Institute for Manufacturing, Department of Engineering, University of Cambridge
Jim Woodhouse
Department of Engineering, University of Cambridge
Static methods (e.g. tensile testing) and ultrasonic methods have been most commonly
used in the past to measure the elastic modulus of paper and paperboard. The
static method, however, does not provide a dynamic value for modulus, and the
accurate measurement of travel-time needed for the ultrasonic method is rather
delicate and prone to error. A further problem is that the timescale (or frequency)
involved in these methods is often far removed from the actual conditions experienced
in the paper industry and in applications of these materials. A method using
low frequency vibrations to excite out-of-plane bending vibrations, which are
visualised as Chladni figures, might appear to be simple and unsophisticated,
but can readily be applied to paper and paperboards in the frequency range from
10 to 1000 Hz. Characteristic patterns are generated on rectangular or square
samples at each resonant frequency. From the assumption that machine-made paper
is generally orthotropic and that the boundaries are free, values of dynamic
Young's modulus and dynamic Poisson's ratio can be calculated by identifying
only a few low-frequency modes.
Values of dynamic Young's modulus derived by this method for various core-board
samples are lower than those obtained from ultrasonic measurements, which is
consistent with a model for viscoelastic behaviour in which elastic modulus depends
on frequency. Dynamic Poisson's ratios in the machine direction and cross direction
are also derived with high reproducibility. The vibration frequencies required
to excite the modes depend on the sample sizes, but no significant differences
in elastic moduli were seen for samples with sizes ranging from 75 x 75 to 200
x 200 mm; the main restriction of the method is that the sample should be reasonably
flat.
The sensitivity of the vibration method is demonstrated by the reduction in stiffness
of paper which can be detected when its surface is scratched or damaged; detection
of such damage by ultrasonic measurements is much more difficult. It is suggested
that the vibration method using Chladni patterns is well suited to the accurate
and reliable measurement of the dynamic elastic constants of the paper/paper
board, at frequencies appropriate to the processing and use of these materials.
The elastic constants obtained by this method may be useful within the paper
industry for product and process design.
Keywords: paper, paperboard, vibrational modes, Chladni patterns, Young's modulus,
Poisson's ratio, elastic constants, Rayleigh's principle
Relations between Elastic Bending Deformation Strength, Shape and Elastic Moduli
for Case of Anisotropic Corrugated Fiberboard Box Shape (Square Tube) under Uniform
Compression
Satoru Matsushima
Ehime University, Center for Cooperative Research and Development
Shigeo Matsushima
Professor Emeritus, Ehime University
Elastic bending deformation analysis for case of anisotropic corrugated fiberboard
box shape (square tube: width L, height h and thickness T=5.54mm) under uniform
compression (-0.10N/mm2) on upper and lower edges was performed. And characteristic
behavior of stress and deflection for its case was discussed.
Absolute maximum normal stress  bxmax* in the width direction is
at plate centers, and maximum normal stress bymax in the height direction, maximum
bending principal
stress b0max and maximum deflection wmax are at centers of side edges for side
plate (L=350, h=300mm). Absolute maximum bending shear stress  bxymax* and maximum
bending principal shear stress b0max* are plate corners. bxmax*, bymax,bxymax*
and wmax increase and decrease with L increase. And bxmax* and wmax increase
and decrease, and bymax and bxymax* increase with h increase. bxmax*, bymax,bxymax*
and wmax increase with Ex increase and decrease with Ey increase. bxmax* and
bymax increase, and bxymax* and
wmax increase and decrease with  xy increase.
Key Words: Structural Analysis, Computational Mechanics, Elastic Strength of
Corrugated
Fiberboard, Elastic Stress Analysis Structural Strength, Numerical Analysis
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