BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a circulation treatment system and method for a
fountain solution used in offset printing.
2. Description of the Related Art
[0002] In offset printing, control of a fountain solution is essential. A fountain solution
circulation system constantly supplies a clear fountain solution containing each ingredient
at a respective predetermined concentration to a vessel in a printing unit at a regular
flow rate and temperature, collects the fountain solution which has passed through
the vessel to restore the fountain solution to be clear, and supplies the fountain
solution to the vessel again. Most of the recent offset rotary presses employ continuous
circulation systems for fountain solutions. In order to stabilize water intake, isopropyl
alcohol (IPA) is used as an organic solvent.
[0003] The addition of IPA to a fountain solution decreases surface tension of the fountain
solution and enables nonprinting parts to be uniformly moistened with a small amount
of fountain solution. Namely, IPA improves wettability of a plate surface, thereby
maintaining printing quality. On the other hand, the use of IPA may cause some safety
and health problems for workers. Therefore, the amount of IPA used is limited to as
small an amount as possible, or a fountain solution which does not include any IPA
is used. In any case, control of a fountain solution is becoming more important.
[0004] FIG. 5 is a flow diagram showing a fountain solution circulation system 101 of a
prior art.
[0005] In FIG. 5, a raw fountain solution, water, an alcohol, etc. are mixed at precise
proportions in a fountain solution mixer 102, and the mixed fresh fountain solution
is supplied to the fountain solution circulation system 101. The fountain solution
circulation system 101 removes contaminant in the fountain solution which has returned
from a vessel 103 in a printing unit with a filtering device 104, and feeds solution
back to a tank (not shown) inside the fountain solution circulation system 101.
[0006] When the level of the fountain solution in the tank lowers, a fresh fountain solution
is added from the fountain solution mixer 102 through a float valve. The fountain
solution in the tank is kept at a predetermined temperature by a cooling device (not
shown). An alcohol concentration controller 106 controls the concentration of alcohol,
which easily evaporates. The fountain solution in the tank is continuously fed into
the alcohol concentration controller 106. The concentration of a hydrogen ion is detected
by constantly monitoring the pH of the fountain solution, and the fountain solution
is supplemented with a required amount of alcohol to keep the predetermined alcohol
concentration.
[0007] When an etching solution is used as an alternative of IPA, it is also necessary to
maintain the concentration and evaporation rate of the fountain solution by controlling
the temperature and concentration. In the case of alcohol, the concentration is controlled
using a hydrometer. On the other hand, in the case of an etching solution used as
an alternative of IPA, the concentration can be controlled by use of the fact that
the conductivity of a fountain solution is proportioned to the concentrations of an
etching solution and a concentrated alkali solution. Sometimes organic substances
generate in the fountain solution circulation system 101 and change the quality of
the fountain solution. In addition, a fountain solution contains contaminant such
as ink, paper particles and oil. Thus, it is important to keep the fountain solution
circulation system 101 clean as a whole.
[0008] Nevertheless, in the above-described fountain solution circulation system 101 of
the prior art, a porous filter material such as a sponge filter is used in the filtering
device 104, which removes the contaminant of the fountain solution returned from the
vessel 103 through a porous layer of the filter only by mechanical filtering. Accordingly,
the ability of removing impurities in the fountain solution depends on the dimension
of the pores of the filter and, normally, impurities having a diameter less than 100
µm cannot be removed.
[0009] If one tries to improve the ability of removing impurities by employing pores having
a smaller dimension, a pressure posed on the fountain solution passing through a porous
layer prevents the fountain solution from circulating at a predetermined flow rate.
If the fountain solution does not circulate at a predetermined flow rate, the fountain
solution loses normal functions, leading to deterioration of the printing quality.
Furthermore, too small pores of the filter are easily clogged with impurities, which
requires frequent maintenance of the filter.
[0010] The prior art fountain solution circulation system 101 has further disadvantages
due to the limitation of the filtering ability. Specifically, after circulating a
fountain solution in the system for a few months, the fountain solution is contaminated
and decomposed, and the quality of the fountain solution finally changes to the extent
that it cannot be used as a fountain solution. Then, the fountain solution needs to
be replaced. In many cases, a discarded fountain solution which has only been filtered
by conventional mechanical filtering cannot meet legal standards for drainage of wastewater
in terms of a biochemical oxygen demand (BOD), chemical oxygen demand (COD), n-hexane
concentration and suspended solid (SS). Thus, the discarded fountain solution is regarded
as an industrial waste, and wastewater of a fountain solution cannot be directly drained
into rivers or the like. As a result, such waste disposal is committed to specialist
companies at considerable cost.
[0011] According to the present invention, provided are a circulation treatment system and
method for a fountain solution wherein the amounts of a BOD, COD, n-hexane concentration
and SS in a fountain solution are reduced without posing any pressure on the fountain
solution, thereby recycling the fountain solution without draining off.
SUMMARY OF THE INVENTION
[0012] The circulation treatment system for a fountain solution of the present invention
is a circulation treatment system for a fountain solution for circulating and purifying
a fountain solution used in offset printing comprising a potential absorption filtering
device using an absorbing effect of a zeta potential and an activated carbon filtering
device using an absorbing effect of activated carbon, and the potential absorption
filtering device and the activated carbon filtering device are provided in the course
of a circulation passage for circulating the fountain solution.
[0013] Since fine particles of ink, paper, oil or the like generally have negative electric
potentials, a potential absorption filter in a potential absorption filtering device
is made to have a positive zeta potential. By this characteristic, it becomes possible
to absorb fine particle foreign matter, which cannot be removed by a filter comprising
a conventional porous filter material. Furthermore, by use of this potential absorption
effect, fine particle foreign matter can be reduced without posing any pressure on
a fountain solution passing through the potential absorption filter. In addition,
a fountain solution can be decolorized and deodorized when passing through the activated
carbon filter. Namely, amounts of a BOD, COD, n-hexane concentration and SS are reduced
while maintaining a predetermined flow rate, and the decolorized and deodorized fountain
solution can be used over a long period and recycled without the necessity of draining
off. As a result, no wastewater is generated, and it is not necessary to commit the
disposal of the wastewater to other companies, thereby reducing the running costs
of a fountain solution used in offset printing. Moreover, offset printing using the
thus purified fountain solution leads to improved printing quality.
[0014] Particularly, the system of the present invention may comprise a potential absorption
filtering device disposed on the upstream side of a circulation passage and an activated
carbon filtering device disposed on the downstream side of the circulation passage.
By this arrangement, fine particles of ink, paper, oil or the like contained in a
fountain solution are first removed by the potential absorption filtering device before
passing through the activated carbon filtering device, thereby significantly extending
life of an activated carbon filter in the activated carbon filtering device.
[0015] Preferably, the system of the present invention may further comprise a differential
pressure gauge for detecting a differential pressure between a pressure at an introducing
port of a circulation passage and a pressure at a discharging port of the circulation
passage and an alarm device for giving an alarm in response to a result detected by
the differential pressure gauge. A differential pressure between a pressure at an
introducing port and a pressure at a discharging port is detected to give an alarm
so that an operator is notified of the need for replacing a potential absorption filter
and an activated carbon filter. Thus, a flow rate of a fountain solution is kept at
a predetermined value, and an operator can easily control the fountain solution.
[0016] It is preferable that a differential pressure between a pressure at an introducing
port of a circulation passage and a pressure at a discharging port of the circulation
passage is 2.2kg/cm
2 or less. Then, the flow rate of a fountain solution is optimum where a purifying
effect by a potential absorption filtering device and an activated carbon filtering
device can be most efficiently used, and the printing quality can be easily maintained.
If a differential pressure is more than 2.2kg/cm
2, a potential absorption filtering device or an activated carbon filtering device
is clogged, which makes purification treatment insufficient.
[0017] A circulation treatment method for a fountain solution using a circulation treatment
system of the present invention is a circulation treatment method for a fountain solution
for circulating and purifying a fountain solution used in offset printing comprising
the steps of filtering a fountain solution using an absorbing effect of a zeta potential
and filtering the fountain solution using an absorbing effect of an activated carbon.
By this method, fine particles of ink, paper, oil or the like contained in a fountain
solution are absorbed and removed by a zeta potential, and the fountain solution is
decolorized and purified by an activated carbon, enabling the fountain solution to
be used almost indefinitely.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018]
FIG. 1 is a schematic view of a circulation treatment system for a fountain solution
according to the present invention, wherein FIG. 1A is a plan view and FIG. 1B is
a front view;
FIG. 2 is a flow diagram of the circulation treatment system for a fountain solution
shown in FIG. 1;
FIG. 3 is a partly cut out detailed view of a potential absorption cartridge enclosed
in a housing of a potential absorption filtering device shown in FIG. 1;
FIG. 4 is a longitudinal sectional detailed view of an activated carbon filtering
device shown in FIG. 1; and
FIG. 5 is a flow diagram illustrating a circulation treatment system for a fountain
solution of a prior art.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0019] FIG. 1 is a schematic view of a circulation treatment system for a fountain solution
according to the present invention, wherein FIG. 1A is a plan view and FIG. 1B is
a front view, and FIG. 2 is a flow diagram of the circulation treatment system for
a fountain solution shown in FIG. 1.
[0020] A circulation treatment system for a fountain solution 1 in the embodiment of the
present invention comprises circulation passages 9a to 9d for circulating a fountain
solution used in an offset rotary press by introducing the fountain solution from
an introducing port 8a (on the upstream side) and discharging the fountain solution
from a discharging port 8b (on the downstream side), a line pump 4 as a pumping device
for forcibly circulating the fountain solution, a potential absorption filtering device
2 using an absorbing effect of a zeta potential, and an activated carbon filtering
device 3 using an absorbing effect of activated carbon; the line pump 4, the potential
absorption filtering device 2 and the activated carbon filtering device 3 being disposed
in the course of the circulation passages 9a to 9d in this order.
[0021] The circulation treatment system for a fountain solution 1 further comprises a differential
pressure detecting transmitter 5 as a differential pressure gauge for detecting a
differential pressure between a pressure in the circulation passage 9b which is outside
the potential absorption filtering device 2 or on the side of the introducing port
8a and a pressure in the circulation passage 9d which is outside the activated carbon
filtering device 3 or on the side of the discharging port 8b to transmit a detecting
signal, a revolving light 6 as an alarm device for giving an alarm in response to
a detected level of the detecting signal, and a control panel 7 for controlling the
line pump 4, the differential pressure detecting transmitter 5 and the revolving light
6.
[0022] FIG. 3 is a partly cut out detailed view of a potential absorption cartridge enclosed
in a housing of the potential absorption filtering device shown in FIG. 1.
[0023] The potential absorption filtering device 2 encloses a potential absorption cartridge
20 as a replaceable potential absorption filter within a housing. The potential absorption
cartridge 20 is composed of a plurality of cells each of which comprises a medium
21 mainly made of resin and cellulose, a polypropylene separator 22 and an edge seal
23. The cells are layered so as to sandwich a polypropylene ring seal 24 and assembled
with a polypropylene core 25.
[0024] Generally, a potential difference is generated on an interface between different
phases. A potential caused by an electric double layer which is generated on an interface
of a particle has a portion which does not play a dynamic role (fixed bed) and a portion
which plays a dynamic role (diffusion layer). The electric phenomenon which occurs
between different phases only when there is a relative motion is called an electrokinetic
phenomenon, and the potential existing therein is called a zeta potential.
[0025] A zeta potential, as well as a Tyndall effect and a Brownian movement, is a physical
phenomenon due to a characteristic of fine particles. In general, fine particles and
microorganisms in a fluid have a negative potential. Similarly, fine particles of
ink, paper, oil or the like contained in a fountain solution have a negative potential.
To the contrary, the medium 21 in the potential absorption filtering device 2 characteristically
has a positive zeta potential, and therefore can absorb and remove these fine particles
which cannot be removed with a conventional 0.2 µm-membrane filter. Furthermore, by
using the above potential absorption effect, fine particle foreign matter can be removed
without posing any pressure on a fountain solution passing through the potential absorption
filtering device 2.
[0026] FIG. 4 is a longitudinal sectional detailed view of an activated carbon filtering
device shown in FIG. 1. An arrow in FIG. 4 indicates a flow of a fountain solution.
The activated carbon filtering device 3 encloses an activated carbon cartridge 31
as a replaceable activated carbon filter in a housing 30. The activated carbon cartridge
31 comprises activated carbon of coconut husk 33, pre filter 34 and post filter 35
contained and heat-sealed in a polypropylene nonwoven fabric 32.
[0027] The activated carbon of coconut husk 33 is hard grainy activated carbon of high quality
and capable of effectively absorbing organic substances, color, odor and impurities
from a fountain solution. The pre filter 34 and post filter 35 are made of cellulose
fibers and melamine resin. The pre filter 34 absorbs precipitates such as dirt, rust
and others, and the post filter 35 prevents the activated carbon of coconut husk 33
from flowing out. The fountain solution is filtered by the pre filter 34, and organic
substances or the like in the fountain solution are absorbed by the activated carbon
of coconut husk 33.
[0028] A dampening section 11 of an offset rotary press is provided on a plate 16 and comprises
a vessel 12 and a plurality of rollers 13, 14 and 15 arranged toward the plate 16
in this order. As shown in FIG. 2, the circulation treatment system for a fountain
solution 1 is connected to the vessel 12 in the dampening section 11 of the offset
rotary press through connection passages 10a and 10b. The connection passages 10a
and 10b are connected to the circulation treatment system for a fountain solution
1 via the introducing port 8a and the discharging port 8b, respectively. The fountain
solution in the vessel 12 circulates through the connection passage 10a, the circulation
passages 9a to 9d and the connection passage 10b in succession.
[0029] The fountain solution in the vessel 12 is forcibly fed into the circulation passage
9a by the line pump 4. The fountain solution in the vessel 12 which is introduced
into the circulation passage 9a from the connection passage 10a via the introducing
port 8a is led into the potential absorption filtering device 2 passing through the
circulation passage 9b. In the potential absorption filtering device 2, fine particles
of ink, paper and oil or the like contained in the fountain solution are absorbed
and removed by an absorbing effect of a zeta potential. By absorbing and removing
the fine particle foreign matter using the absorbing effect of the potential, the
fine particle foreign matter can be removed without posing any pressure on the fountain
solution passing through the potential absorption filtering device 2. Furthermore,
the fountain solution led to the activated carbon filtering device 3 via the circulation
passage 9c is decolorized and deodorized, and is returned into the vessel 12 through
the circulation passage 9d and the connection passage 10b.
[0030] According to the above process, the amounts of a BOD, COD, n-hexane concentration
and SS are reduced while keeping a predetermined flow rate by the potential absorption
filtering device 2 and the activated carbon filtering device 3 provided in the course
of the circulation passages 9a to 9d. Furthermore, the decolorized and deodorized
fountain solution can be used over a long period and recycled without draining off.
As a result, no wastewater of the fountain solution is generated, and thus it is not
necessary to commit the disposal of wastewater to other companies, thereby reducing
the running costs of a fountain solution used in offset printing. In addition, use
of the thus purified fountain solution in offset printing improves printing quality.
[0031] In particular, since the circulation treatment system for a fountain solution 1 of
the above-described embodiment has such a structure that the potential absorption
filtering device 2 is disposed on the upstream side of the circulation passages 9a
to 9b and the activated carbon filtering device 3 on the downstream side, fine particles
of ink, paper, oil or the like contained in a fountain solution are first removed
by the potential absorption filtering device 2 and then the fountain solution passes
through the activated carbon filtering device 3. Accordingly, life of the activated
carbon cartridge is significantly extended.
[0032] The differential pressure detecting transmitter 5 provided in the circulation treatment
system for a fountain solution 1 of the present invention detects a differential pressure
between pressures at the circulation passages 9b and 9d, and turns on the revolving
light 6 to give an alarm when the differential pressure is over 2.2kg/cm
2. The differential pressure detecting transmitter 5 detects a sharp rise in the differential
pressure in the medium 21 in the potential absorption filtering device 2 which occurs
when the absorbing ability reaches the limit, and notifies an operator of timing for
replacement of the potential absorption filtering device 2, thereby keeping a flow
rate of a fountain solution at a predetermined value. In the activated carbon filtering
device 3, the limit of the absorbing ability is detected from a rise in a differential
pressure as well.
1. A circulation treatment system for a fountain solution for circulating and purifying
a fountain solution used in offset printing comprising a potential absorption filtering
device using an absorbing effect of a zeta potential and an activated carbon filtering
device using an absorbing effect of activated carbon, said potential absorption filtering
device and said activated carbon filtering device being provided in a course of a
circulation passage for circulating said fountain solution.
2. The circulation treatment system for a fountain solution according to claim 1, wherein
said potential absorption filtering device is disposed on an upstream side of said
circulation passage and said activated carbon filtering device is disposed on a downstream
side of said circulation passage.
3. The circulation treatment system for a fountain solution according to claim 1 further
comprising a differential pressure detecting device for detecting a differential pressure
between a pressure on a side of an introducing port of said circulation passage and
a pressure on a side of a discharging port of said circulation passage and an alarming
device for giving an alarm in response to a result detected by said differential pressure
detecting device.
4. The circulation treatment system for a fountain solution according to claim 2 further
comprising a differential pressure detecting device for detecting a differential pressure
between a pressure on a side of an introducing port of said circulation passage and
a pressure on a side of a discharging port of said circulation passage and an alarming
device for giving an alarm in response to a result detected by said differential pressure
detecting device.
5. A circulation treatment method for a fountain solution for circulating and purifying
a fountain solution used in offset printing comprising the steps of:
filtering said fountain solution by an absorbing effect of a zeta potential, and
filtering said fountain solution by an absorbing effect of activated carbon.
6. The circulation treatment method for a fountain solution according to claim 5, wherein
a differential pressure between a pressure on a side of an introducing port of a circulation
passage for circulating said fountain solution and a pressure on a side of a discharging
port of the circulation passage is 2.2kg/cm2 or less.