Note: Descriptions are shown in the official language in which they were submitted.
21b9~~0
PRINTING BLANKET
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a seamless printing
blanket which is particularly suitable to use in high-speed
offset rotary printers.
Description of the Prior Art
A conventional printing blanket is in the form of
flat plate, and has been used by winding it around a blanket
I cylinder of printer.
The printing blanket has a seam portion on the
surface thereof. Hence, whenever the seam of the printing
blanket passes a nip deformed portion which is generated by
pressing the printing blanket with a plate cylinder and the
I like, the pressing pressure is varied to cause vibration and
impact load, so that the quality of printing deteriorates.
To solve the above problem, Japanese Unexamined
Patent Publication No. 5-301483 (1993) discloses a printing
blanket wherein (i) a porous and seamless compressible layer
I comprising elastomer such as rubber, (ii) a non-stretchable
layer and (iii) a seamless surface printing layer are
laminated in this order by interposing a seamless adhesive
layer between the respective layers, on an outer peripheral
surface of a cylindrical sleeve mounted on a blanket cylinder.
I The compressible layer, the surface printing layer
_ 216430
and the adhesive layer are formed by applying and drying a
coating solution including elastomer, and if used rubber,
followed by vulcanization. The compressible layer is formed
in porous state in order to render vibration absorbability and
pressure absorbability to the printing blanket. The non-
stretchable layer is formed by winding a non-stretchable wire
rod, such as thread, in helical fashion in the circumferential
direction.
The inside diameter of the sleeve corresponds to the
outside diameter of the blanket cylinder, or is slightly
smaller than that outside diameter, so that the sleeve is
strongly engaged with the blanket cylinder in the normal
condition, and when an internal pressure is applied, it has a
slight expansion in the radial direction, which permits
removal of the blanket cylinder. Thus in order to apply the
internal pressure, aeration holes that supply a pressurized
gas inside the sleeve are formed in the blanket cylinder.
Suitable sleeve include those made of pretty thin
metallic material and those made of fiber-glass reinforced
plastics. The most preferred are those made of nickel having
a thickness of about 0.125 mm in view of-the rigidity, the
strength and the elasticity.
Since the above printing blanket has not any seam in
the circumferential direction thereof, it causes neither
vibration nor impact load at the time of printing. However, a
21 b94.~0
- 3 -
plate cylinder, onto which the printing blanket is pressed,
has a seam and, when this seam passes the nip deformed
portion, vibration and impact are generated.
Some of the vibration and the impact can be absorbed
by the compressible layer and the surface printing layer
comprising elastomer as described, particularly the
compressible layer which is porous and has vibration
absorbability. Therefore, they might not cause any serious
problems for normal printing. However, when high-speed
printing of not less than 1,000 r.p.m. is carried out by a
high-speed offset rotary printer or the like, the vibration
and the impact are large, which cannot satisfactorily be
absorbed merely by the compressible layer and the surface
printing layer.
On the other hand, in the printing blanket,
irrespective of the seam of the plate cylinder, a large
expansion in the radial direction, caused by the elastic
rebound of the printing blanket which is released from the
compression after passing the nip deformed portion, and the
ordinary waves wherein the surface printing layer waves due to
the expansion, can be prevented by the non-stretchable layer
comprising non-stretchable wire rod. At the time of the high
speed printing as described, however, the ordinary waves
caused by high-speed repeated compression which is generated
when passing the nip deformed portions, expand to the
21 X9430
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compressible layer and the non-stretchable layer over the
surface printing layer, and therefore, it is impossible to
prevent these phenomena only by the non-stretchable layer.
Accordingly, the above printing blanket has the
disadvantage that printing images particularly at high-speed
printing are unclear, thereby resulting in poor printing
quality. Further at high speed printing, dynamic fatigue and
heat are generated in the respective layers due to the high-
speed repeated compression as described, so that the printing
blanket life is short. In particular, the porous compressible
layer, which has lower strength than other layers, is liable
to cause the permanent set due to the dynamic fatigue and the
heat, and then lose the elasticity, that is, a so-called
"permanent set in fatigue".
In order to obtain high printing quality, the
individual layer including the compressible layer, the non-
stretchable layer, the surface printing layer and the adhesive
layer are preferably as thin as possible. However, when each
layer is made thinner, the strength of the printing blanket in
the thickness direction is decreased. For example, when an
external impact is applied, the impact travels to the sleeve
made of pretty thin metallic material as described is liable
to have concavities or damage. This needs delicate treatment
in the transportation and the like, so that the working
ability deteriorates and the wrapping and the transportation
2169~3U
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cost rises.
Moreover, when the above printing blanket has been
used for a long period, particularly the compressible layer
causes the permanent set in fatigue as previously described.
I Thus, from the viewpoint of effective utilization of resources
and environmental protection, it is desirable that at least
the sleeve is recovered for its reuse.
In the conventional printing blanket, however, when
the compressible layer, which is formed immediately on the
I sleeve through an adhesive layer, is peeled by grinding, the
sleeve made of pretty thin metallic material is liable to be
damaged, which might often cause the damage of the sleeve,
failing to be reused.
SUMMARY OF THE INVENTION
I It is a main object of this invention to provide a
seamless printing blanket which realizes high quality printing
over a wide range from normal printing to high-speed printing,
and which has high strength to facilitate its handling.
Another object of this invention is to provide a
I printing blanket which has longer life and facilitates the
reuse of a sleeve and the like.
The printing blanket of this invention comprises:
(a) a seamless base layer comprising an elastomer;
(b) a porous seamless compressible layer comprising an
I elastomer;
2i6943~
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(c) a non-stretchable layer comprising a non-stretchable
wire rod which is wound on the compressible layer in helical
fashion along the circumferential direction; and
(d) a seamless surface printing layer comprising an
I elastomer,
all of which are laminated in this order on an outer
peripheral surface of a cylindrical sleeve mounted on a
blanket cylinder.
A seamless adhesive layer comprising elastomer is
I interposed between the respective layers.
The base layer formed immediately on the sleeve
functions to absorb vibration and impact load whenever a seam
of the plate cylinder passes a nip deformed portion.
The base layer also functions, together with the
I non-stretchable layer, to prevent the elastic rebound caused
by the printing blanket when it is released from compression
after passing the nip deformed portion, from generating a
large expansion in the radial direction and the resulting
ordinary waves.
I The base layer and other layers in this printing
blanket do not have any seam in the circumferential direction.
It is therefore possible to obtain high quality printings over
a wide range from normal printing to high-speed printing.
The base layer and the non-stretchable layer
I function to prevent a large expansion in the radial direction
CA 02169430 2000-03-22
due to the elastic rebound of the printing blanket, so that
high-speed repeated compression at high speed printing can be
depressed. Therefore, dynamic fatigue and heat can be
depressed, thus enabling to prolong the printing blanket like.
The base layer also functions to reinforce and protect
the sleeve. This allows the printing blanket to have higher
strength than conventional ones, to facilitate its handling.
Moreover, the compressible layer, which has lower strength than
other layers and is most frangible after the prolonged use of
the printing blanket, is formed on the base layer, not
immediately on the sleeve. This facilitates the removal of the
compressible layer, without causing damage to the sleeve. In
addition, since the base layer is not so fragile as the
impressible layer, it is possible to reuse the sleeve with the
base layer remained.
When preparing the printing blanket wherein the
outside diameter is slightly different from the other, the base
layer functions to adjust the thickness of the printing blanket,
thereby permitting the use of a common mandrel in producing
various blankets to offer favorable productivity.
Accordingly, in one aspect the present invention
resides in a printing blanket comprising:
(a) a seamless base layer having a thickness of 0.2 to 10
mm and comprising an elastomer;
(b) a porous seamless compressible layer having a
thickness of 0.15 to 0.6 mm and comprising an
elastomer;
CA 02169430 2000-03-22
- 7a -
(c) a non-stretchable layer comprising a non-stretchable
thread which is wound on the compressible layer in
helical fashion along the circumferential direction;
and
(d) a seamless surface printing layer having a thickness
of 0.1 to 0.4 mm and comprising an elastomer;
all of which are laminated in this order on an outer peripheral
surface of a cylindrical sleeve mounted on a blanket cylinder.
Brief Description of the Drawings
Fig. 1 is a partially cutaway view in perspective of
an embodiment of a printing blanket in this invention.
Fig. 2 is an enlarged section view showing the
- 8 - 21 b943U
multi-layer structure of the printing blanket shown in Fig. 1.
Fig. 3 is a side view showing a device for measuring
the rate of change in the peripheral length of a printing
blanket.
I Detailed Description of the Invention
This invention will be further described referring
the Drawings.
As shown in Figs. 1 and 2, the printing blanket 20
being one of the embodiments has the multi-layer structure in
I which on an outer the peripheral surface of the cylindrical
sleeve 21, the base layer 1, the porous compressible layer 2,
the non-stretchable layer 3 prepared by winding a non-
stretchable wire rod around the compressible layer 2, and the
surface printing layer 4 are laminated in this order, by
I interposing the adhesive layers 31 to 34 between the
respective layers.
As the cylindrical sleeve 21, there can be used a
variety of known sleeves including, for example, those made of
pretty thin metallic material or fiber glass reinforced
I plastics, as previously described. In particular, from the
viewpoint of the rigidity, the strength and the elasticity,
the sleeves made of nickel having a thickness of about
0.125 mm are suitable to the above printing blanket.
As the elastomer composing the base layer 1 which is
I formed on the peripheral surface of the sleeve 21 by
216~~~0
interposing the adhesive layer 31, there can be used a variety
of synthetic rubbers and thermoplastic elastomers. Preferred
are elastomers which are particularly excellent in vibration
absorbability and impact load absorbability, and have higher
damping properties to the vibration. It is more preferred
that the above elastomers have high oil resistance in view of
the resistance to printing inks and the like. Examples of
these elastomers include synthetic rubbers such as
acrylonitrile butadiene copolymer rubber (NBR), chloroprene
rubber and urethane rubber.
The thickness of the base layer 1 is preferably 0.2
to 10.0 mm, particularly 0.4 to 5.0 mm, more particularly 0.8
to 2Ø
When the thickness of the base layer 1 is less than
the above range, the base layer 1 cannot satisfactorily absorb
vibration and impact load, and therefore, the printing image
is unclear, resulting in poor printing quality. Further, in
the respective layers composing the printing blanket 20, the
dynamic fatigue and heat are generated due to high-speed
repeated compression. As a result, the compressible layer 2
having lower strength than other layers might cause the
permanent set in fatigue as described, shortening the life of
the printing blanket 20. When the thickness of the base layer
1 is more than the above range, since the rate of change in
peripheral length is increased when pressed by the plate
21 b9430
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cylinder, the printing image is, unclear, resulting in poor
printing quality.
When the base layer 1 is prepared from the synthetic
rubber such as NHR, a sheet comprising an unvulcanized
compound in which various additives are blended in an
unvulcanized rubber, is adhered on the peripheral surface of
the sleeve 21 on which the adhesive layer has been formed, and
after wrapped with a tape or the like, is vulcanized under
heating and pressurizing conditions. As a result, the seam of
the sheet is fused to give a seamless base layer 1.
Examples of the above additives include filler,
plasticizes, antioxidant, vulcanizing agent, accelerator,
activator and retarder. Each amount may be similar to that of
the conventional blankets. Specifically, to 100 parts by
weight of unvulcanized rubber, the following amounts are
preferable:
parts by weigrht
- Filler such as carbon black: 30 to 100
- Plasticizes such as stealine acid: 0.5 to 1.5
- Antioxidant: 1 to 4
- Vulcanizing agent such as sulfur: 0.5 to 3 in total
- Accelerator: 0.5 to 3
(each 0.5 to 3 when used two or more kinds)
- Activator such as zinc oxide: 3 to 5
- Retarder: 0 to 0.5
216°430
In order to form the base layer 1 having a low
thickness in the above range, the following manner, which is
the same as in the compressible layer 2 and the surface
printing layer 4 as described later, may be employed.
I Specifically, on the peripheral surface of the sleeve 21 on
which the adhesive layer 31 has been formed, a rubber cement
containing the respective additives is coated (spread) in a
predetermined thickness with the use of a doctor blade or a
doctor roll, which is then vulcanized under heating and
I pressuring conditions.
The surface of the base layer 1 thus prepared is
preferably polished by a cylindrical grinding machine or the
like to finish in a predetermined surface roughness and
thickness.
I The base layer 1 may be in a single-layer or a
multi-layer.
A base layer similar to the base layer 1 can be
provided between the non-stretchable layer 3 and the surface
printing layer 4. With this structure, the function to absorb
I the vibration and the impact load and the function to prevent
the ordinary waves are further improved, thereby increasing
the printing quality.
The compressible layer 2 which is formed on the base
layer 1 by interposing the adhesive layer 1, has a porous
I structure excellent in vibration absorbability. The porous
- 12 _ 2169430
structure is classified into an open cell structure in which
voids in a layer are connected with each other, and a closed
cell structure in which voids are independent from each other.
Both structures are applicable to this invention, but in order
to effectively give the impact absorbability, the open cell
structure is preferred.
The percent of void which indicates the proportion
of voids for the compressible layer 2 having the open cell
structure is not particularly limited, but preferably 30 to 60
~, particularly 35 to 55 $, more particularly 35 to 45 0.
When the percent of void is below 30 °s, the
compressible layer 2 could not satisfactorily absorb the
impact. When it is over 60 ~, the strength of the
compressible layer 2 might cause the permanent set in fatigue,
shortening the life of the printing blanket 20.
As elastomer composing the compressible layer 2,
those excellent in oil resistance are suited. There are, for
example, the same synthetic rubbers as described in the base
layer 1.
The thickness of the compressible layer 2 is
preferably 0.15 to 0.6 mm, particularly 0.2 to 0.5 mm, more
particularly 0.2 to 0.3 mm. When it is below 0.15 mm, the
compressible layer 2 could not satisfactorily absorb the
pressure generated by the contact-press of the plate cylinder.
Therefore, the surface of the printing blanket 20 is largely
._ 21 ~9~30
- 13 -
deformed by the press of the plate cylinder to cause a so-
called bulge, which increase the rate of change in the
peripheral length of the printing blanket 20. As a result,
the printing image is unclear, resulting in poor printing
quality.
When the thickness of the compressible layer is over
0.6 mm, the pressure of the printing blanket 20 to the plate
cylinder and a paper is decreased. Therefore, the ink
transfer ability to solid parts in the printing image (a so-
called solid applicability) is reduced to cause ink squeezeout
in the solid parts. Further, at the time of printing, the
respective layers composing the printing blanket might slip
toward downstream in the rotational direction of the printing
blanket 20, resulting in shear of ink-transfer in the
printing. In addition, the strength of the compressible layer
2 is decreased to cause the aforesaid permanent set in
fatigue, thereby shortening the life of the printing blanket
20.
When the compressible layer 2 having the open cell
structure is prepared from the aforesaid synthetic rubber, the
following leaching method is suitable to produce the layer 2.
On the surface of the base layer 1 on which the
adhesive layer 32 has been formed, a rubber cement in which
the above additives and water soluble powder such as sodium
chloride are blended in an unvulcanized rubber, is coated
2~ b'~1T30
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(spread) to a predetermined thickness with the use of the
doctor blade or the doctor roll, which is then vulcanized
under heating and pressurizing conditions, thereby forming a
vulcanized rubber layer.
The vulcanized rubber layer may be formed, like the
base layer 1, by adhering a sheet comprising an unvulcanized
compound containing the above additives, on the surface of the
base layer 1 on which the adhesive layer 32 has been formed,
followed by vulcanizing under heating and pressurizing in the
state that the surface of the base layer 1 is wrapped with a
tape or the like.
Then, the printing blanket 20 for which the
vulcanized rubber layer has been formed, is immersed in warm
water of about 60 to 100°C for about 6 to 10 hours to elute
and remove the water soluble powder, and well dried to remove
water, thereby giving a porous compressible layer 2 in which
the traces of the water soluble power have turned into open
cells.
As can be seen from the above description, the
percent of void for the compressible layer 2 changes with the
amount of the water soluble powder in the rubber cement or the
unvulcanized compound. Specifically, as the amount of the
water soluble powder compound is increased, the percent of
void is increased. Therefore, the water soluble powder should
be blended at a specific amount adjusted to form a desired
21 b~~~:St~
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percent of void into the rubber cement or the unvulcanized
compound.
On the other hand, for the formation of the
compressible layer 2 having the closed cell structure, foaming
I method is preferably employed. Specifically, an expanding
agent is added to the cement rubber or the unvulcanized
compound, and the mixture is foamed at the time of
vulcanization.
The surface of the compressible layer 2 thus
I prepared is preferably finished to have a predetermined
surface roughness and thickness, with the use of a cylindrical
grinding machine in the same manner as in the base layer 1.
The non-stretchable layer 3 which is formed on the
compressible layer 2 by interposing the adhesive layer 33, is
J formed by winding a non-stretchable wire rod on the
compressible layer 2 in circumferential direction in helical
fashion while applying tension thereto.
Examples of the wire rod include cotton string,
polyester string, and rayon string are suited, in view of the
I ease of the winding, the conformability with the adhesive
layer 33 and 34, and the non-stretching property (i.e.,
tensile strength).
The diameter of the wire rod is not particularly
limited, but preferably 0.1 to 0.5 mm, particularly 0.15 to
I 0.35 mm, more particularly 0.20 to 0.30 mm. When it is below
._ 216'; 430
- 16 -
0.1 mm, the above winding work might be difficult. When it is
over 0.5 mm, the wire rod might inhibit the compressible layer
2 from absorbing the pressure generated when the plate
cylinder is pressed thereto, and the surface of the printing
blanket 20 is liable to cause bulge, which increases the rate
of change in the peripheral length. As a result, the printing
image is unclear, resulting in poor printing quality.
In winding the wire rod in helical fashion, the
spacing between the wire rods adjacent to each other is not
particularly limited, but preferably not more than 0.05 mm.
It is more preferred to wind so as to have little spacing as
shown in Fig. 1.
When the spacing is over 0.05 mm, the non-
stretchable layer 3 could not satisfactorily prevent a large
expansion in the radical direction and the resulting ordinary
waves, which are caused by the elastic rebound of the printing
blanket when it is released from the compression after passing
the nip deformed portions.
The tensile strength in winding the wire rod (e. g.,
J cotton string) in helical fashion is preferably 100 to 800 g,
particularly 200 to 700 g, more particularly 300 to 500 g.
When it is below I00 g, the aforesaid effect of the non-
stretchable layer 3 is insufficient, thereby decreasing the
compression of the printing blanket 20 with respect to the
plate cylinder and a paper. As a result, the ink transfer
216; ~~30
ratio for solid parts in the printing image (the solid
applicability) deteriorates, resulting in ink squeezeout.
When it is over 800 g, the compressible layer 2 receives too
load at the time of the winding of the wire rod to avoid the
I Pemmanent set in fatigue.
For the elastomer composing the surface printing
layer 4 which is formed on the compressible layer 3 by
interposing the adhesive layer 3, there can be used those
excellent in vibration absorbability and impact absorbability,
I damping properties to vibration, and oil resistance. There
are, for example, the same synthetic rubbers as used in the
base layer 1. In addition, polysulfide rubber and
hydrogenated NBR are usable.
The thickness of the surface printing layer 4 is
I 0.1 to 0.4 mm, preferably 0.1 to 0.3 mm, more preferably 0.15
to 0.3 mm.
When it is below 0.1 mm, although the strength of
the surface printing layer is increased, the compression of
the printing blanket 20 to the plate cylinder and a paper is
I lowered. This might decrease the solid applicability,
resulting in the squeezeout in solid parts.
When it is over 0.3 mm, at the time of printing, the
surface printing layer 4 tends to slip downstream in the
rotational direction of the printing blanket. As the slip is
J increased, the ratio of change in peripheral length is
21b9450
increased. This might produce unclear printing image,
resulting in poor printing quality.
When the surface printing layer 4 is prepared from
the above synthetic rubber, a rubber cement containing the
I aforesaid additives and unvulcanized rubber is coated (spread)
in a predetermined thickness on the surface of the non-
stretchable layer on which the adhesive layer 34 has been
formed, with the use of the doctor blade or the doctor roll,
followed by vulcanizing under heating and pressurizing
'I conditions .
The surface printing layer 4 can also be formed, as
in the based layer 1, by adhering a sheet comprising an
unvulcanized compound containing the aforesaid additives on
the surface of the non-stretchable layer 3 on which the
I adhesive layer 34 has been formed, followed by vuicanizing
under heating and pressurizing conditions in the state that
the surface of the sheet is wrapped with a tape or the like.
The surface of the surface printing layer 4 is
preferably finished to a predetermined surface roughness and
I thickness with the use of the cylindrical grinding machine or
the like, in the same manner as in the base layer 1 and the
compressible layer 2.
The surface roughness of the surface printing layer
4 correlates closely with the printing accuracy. Therefore,
'I it is required to be strictly finished. Although the surface
Zi6~4S0
- 19 -
roughness is not particularly limited, but preferably ranges 1
to 10 ~ m, preferably 2 to Bum, more preferably 3 to 6,um,
according to ten points mean roughness (Rz).
As to the adhesive layer 31 between the sleeve 21
I and the base layer 1, when the sleeve 21 is made of metal,
suited are those comprising elastomer and having superior
adhesive properties for both the metal and the elastomer used
in the base layer 1. It is preferable to jointly use an
adhesive having superior adhesive to metal and another having
I superior adhesive to the elastomer used in the base layer 1.
Specifically, the former adhesive is coated using the doctor
blade or the doctor roll on the surface of the sleeve, and the
latter adhesive is coated thereon and dried in a similar
manner to obtain an adhesive layer having the two-layer
I structure.
The former adhesive include "Chemlock 205" available
from Load Chemical Corporation. When the base layer 1 is
prepared from the NBR, "Chemlock 252X" available from Load
Chemical Corporation, is used as the latter adhesive. These
] adhesives are unvulcanized rubbers, and act to bond between
the sleeve 21 and the base layer 1 by vulcanizing them
together with the base layer 1.
The thickness of the adhesive layer 31 is not
particularly limited. It is preferable that the thickness of
I the adhesive layer having the two-layer structure is in a
21 b9430
- 20 -
range of 0.02 to 0.25 mm. When it is below 0.02 mm,
sufficient adhesive strength could not be obtained. When it
is over 0.25 mm, the functions of other layers might be
inhibited.
The adhesive layer 32 between the base layer 1 and
the compressible layer 2; the adhesive layer 33 between the
compressible layer 2 and the non-stretchable layer 3; and the
adhesive layer 34 between the non-stretchable layer 3 and the
surface printing layer 4, are prepared from elastomer,
particularly synthetic rubbers excellent in oil resistance as
previously described.
The adhesive layer 32 is prepared by coating a
rubber cement containing the unvulcanized rubber of the
aforesaid synthetic rubber on the surface of the base layer 1,
with the use of the doctor blade or the doctor roll, and is
subjected to the vulcanization together with the compressible
layer 2 on the base layer 1.
The adhesive layer 33 is prepared by coating a
similar rubber cement on the surface of the compressible layer
2 with the use of the doctor blade or the doctor roll, on
which the wire rod composing the non-stretchable layer 3 is
wound, followed by vulcanization, by which the adhesive layer
33 and the compressible layer 2 are molten and integrally
formed around the wire rod as shown in Fig. 2.
The adhesive layer 34 is prepared by coating a
216930
- 21 -
rubber cement similar to those mentioned above on the surface
of the non-stretchable layer 3 with the use of the doctor
blade or the doctor roll, followed by the vulcanization
together with the surface printing layer 4 which is formed on
I the non-stretchable layer 3.
Alternatively, after coating the rubber cement on
the compressible layer 2, winding the wire rod, coating the
rubber cement thereon, and forming the surface printing layer
4, all of the layers may be simultaneously vulcanized to form
I the adhesive layer 33, the non-stretchable layer 3, the
adhesive layer 34 and the surface printing layer 4 at once.
The thicknesses of the adhesive layer 32, 33 or 34
is not particularly limited, and is preferably 0.01 to 0:1 mm.
When it is below 0.01 mm, sufficient adhesive could not be
I obtained. When it is over 0.1 mm, the functions of other
layers might be inhibited.
Thus, in accordance with this invention, it is
possible to obtain high quality printing in a wire range from
normal printing to high-speed printing, by the function of the
I seamless base layer, which comprises elastomer and is
laminated on the peripheral surface of the cylindrical sleeve
by interposing the adhesive layer. It is also possible to
obtain the printing blanket having no seam in the
circumferential direction, which has high strength, prolonged
I life and the ease of handling to facilitate the reuse of the
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- 22 -
sleeve and the like.
EXAMPLES
The present invention will be further illustrated by
the following nonlimiting examples.
~ Examples 1 to 7
A sleeve 21 made of nickel (the inner diameter:
169.5 mm; the length: 910 mm; the thickness: 0.125 mm,
available from Taiyo Kogyo Co., Ltd.) was mounted on a mandrel
I for vulcanization which has a similar detachable sleeve
mechanism under compressed gas, as in the aforesaid blanket
cylinder. The outer peripheral surface of the sleeve 21 was
coated and dried with the aforesaid "Chemlock 205", and then
the aforesaid "Chemlock 252X" was coated thereon and dried, to
I prepare an adhesive layer 31 having the two layer structure
(0.05 mm in thickness).
An unvulcanized compound comprising the following
ingredients was kneaded using a kneader (available from
Moriyama Seisakusho Co., Ltd.), and extruded using a 14 x 36-
I inch roll (available from KANSAI ROLL CO., LTD.) to prepare a
sheet having the thickness of 2.0 mm and the width of 900 mm.
This sheet was bonded on the surface of the adhesive layer 31.
2159430
- 23 -
.ompound fo_r h . bac _ 1 a~~r
(Ingredients) (parts by weight)
Unvulcanized NBR 100
Furnace black (filler) 60
Silica filler 40
Stearic acid (plasticizer) 1
Aromatic oil (plasticizes) 10
Amine antioxide 1.5
Powder sulfur (vulcanizing agent) 2.5
Guanidine accelerator 1
Sulfenic amide accelerator 0.5
Zinc oxide (activator) 5
Phthalic anhydride (retarder) 0.5
The surface of the sheet was wrapped with a nylon
20
band having the width of 30 mm, with the use of a wrapping
machine (available from Sumitomo Rubber Industries, Ltd.),
and was vulcanized with a vulcanizes (1000 x 2000 mm,
available from KANSAI ROLL CO., LTD.) at 140°C and 3kg/cm2 for
90 minutes, and polished with a cylindrical grinding machine
(available from Toyoda Koki Co., Ltd.), to give a base layer 1
having the thickness as shown in Table 1 (the dimensional
tolerance: within ~0.01 mm).
On the surface of the above base layer 1, a rubber
cement for adhesive layer which comprises the following
ingredients was coated with a rotational spreader employing
2169~3~
- 24 -
the doctor roll, and air-dried for 30 minutes to give an
adhesive layer 32 (0.05 mm in thickness).
Rubber cem _n . for h adh ~i v 1 ay,~r
(Ingredients) (parts by weight)
Unvulcanized NHR 90
Unvulcanized CR 10
Clay filler 70
Stearic acid (plasticizer) 1
Phenol antioxide 1
Powder sulfur (vulcanizing agent) 1
Guanidine accelerator 1
Sulfenic amide(accelerator) 1
Zinc oxide (activator)
5
Thermoset resin (adhesive) 5
Magnesium oxide 3
Toluene (solvent )
100
On the surface of the above adhesive layer 32, a
rubber cement for compressible layer which comprises the
following ingredients, was coated with the aforesaid
rotational spreading machine, and air-dried for 12 hours. The
coated surface was tightly wound with a cotton-woven sheet
(1000 mm in width), and then vulcanized with the aforesaid
vulcanizer at 140°C and 3kg/cm2 for 90 minutes.
216930
- 25 -
Rubber cement for the comn_r essible layer
(Ingredients) (parts by weight)
Unvulcanized NHR 100
Furnace black (filler) 30
Clay filler 40
Stearic acid (plasticizer) 1
Phenol antioxide 1
Powder sulfur (vulcanizing agent) 2.5
Sulfenic amide(accelerator) 1.5
Thiuram accelerator 1
Zinc oxide (activator) 5
10Sodium Chloride 50
Toluene (solvent) 100
Then, the vulcanized matter was immersed in warm
water of 70°C for 12 hours to extrude and remove the sodium
chloride, followed by hot-drying at 100°C for 60 minutes, the
surface of which is polished with the aforesaid cylindrical
grinding machine to give a porous compressible layer 2 having
the open cell (0.3 mm in thickness, within ~ 0.01 mm in
dimensional tolerance, 35 $ in the percent of void).
Preparation of the non-st_retchabl_e layer
On the surface of the above compressible layer 2,
the same rubber cement as used in the adhesive layer 32 was
coated by the aforesaid cylindrical spreading machine, and was
air-dried for 30 minutes to give an adhesive layer 33 (0.05 mm
in thickness).
2169430
- 26 -
On the adhesive layer 33, a cotton string (0.250 mm
in diameter) was wound in helical fashion while applying the
tensile strength of 380 ~ lOgf. The spacing between the
cotton strings adjacent to each other was adjusted to not more
J than 0.05 mm. The winding of the cotton string was carried
out by a cylinder-shaping machine (available from Sumitomo
Rubber Industries, Ltd.).
The surface of the wound cotton string was wrapped
up by tightly winding a cotton-woven sheet (1000 mm in width)
I in helical fashion in the circumferential direction, and was
vulcanized using the aforesaid vulcanizes at 140°C and 3kg/cm2
for 90 minutes, to prepare a non-stretchable layer 3.
On the above non-stretchable layer 3, the same
J rubber cement as used in the adhesive layer 32 was coated by
the aforesaid rotational spreading machine, and air-dried to
prepare an adhesive layer 34 having the thickness of 0.05 mm.
Then, on the above adhesive layer 34, a rubber
cement comprising the following ingredients was coated by the
~ aforesaid rotational spreading machine, and air-dried for 12
hours. The coated surface was wrapped up by tightly winding a
cotton-woven sheet (1000 mm in width) in helical fashion in
the circumferential direction, and then vulcanized with the
aforesaid vulcanizes at 140°C and 3kg/cm2 for 90 minutes.
I Rubb .r c m .n . for h . ~ ~rfa ~~_ntiy 1_a~pr
2~ _ 2 i 69~~0
(Ingredients) (parts by weight)
Unvulcanized NBR 100
Clay filler 40
Stearic acid (plasticizer) 1
Processed oil (plasticizer) 5
Powder sulfur (vulcanizing agent) 0.5
Thiuram accelerator 1
Zinc oxide (activator)
5
Thermoset resin (adhesive) 3
Quinoline compound 1
Toluene (solvent)
100
The surface of the vulcanized surface was polished
with the aforesaid cylindrical grinding machine to prepare a
surface printing layer 4 (0.2 mm in thickness, within ~0.01
mm in dimensional tolerance, 3 to 5 in ten points mean
' roughness (Rz)), thus obtaining a printing blanket.
Using the same manner as in Examples 1 to 7, except
that the base layer 1 and the adhesive layer 32 formed thereon
were omitted, a printing blanket was obtained.
Comparative Example 2
On the surface of a fabric layer (the thickness:
1.05 mm, available from Moriuchi Orimono Co., Ltd.), (i) a
porous compressible layer having the open cell structure (the
thickness: 0.3 mm, the percent of void: 35 %), which comprises
the same rubber cement for the compressible layer as used in
2169430
- 28 -
Examples 1 to 7; (ii) a reinforced layer (the thickness: 0.3
mm, available from Moriuchi Orimono Co., Ltd.); and (iii) a
surface printing layer which comprises the same rubber cement
for the surface printing layer as in Examples 1 to 7, are
51, laminated in this order, to obtain a flat printing blanket.
omt~a_rat~ ve Exampl_e 3
Out of the conventional printing blankets having no
seam in the circumferential direction thereof, which are
disclosed in Japanese Patent Unexamined Publication No. 5-
301483 (1993), a printing blanket which is provided with a
porous compressible layer having the open cell structure, was
selected and prepared.
Specifically, on the peripheral surface of a sleeve
made of nickel similar to that in Examples 1 to 7, the
"Chemlock 205" and the "Chemlock 252X" were coated and dried
in this order, to prepare an adhesive layer having the two
structure (0.05 mm in thickness). On the adhesive layer, a
cotton string (0.375 mm in diameter) was coated with the same
rubber cement for the compressible layer as in Examples 1 to
7, was wound in helical fashion and air-dried for 12 hours.
The spacing between the strings was adjusted to not more than
0.025 mm.
After repeating the above coating and air-drying
steps, the surface was wrapped up by tightly winding a cotton-
woven sheet (1000 mm in width) in the circumferential
2169450
- 29 -
direction, and then vulcanized at 140°C and 3kg/cm2 for 90
minutes, which was immersed in warm water of 70°C for 12 hours
to extrude and remove sodium chloride, and heated and dried at
100°C for 60 minutes, thus obtaining a compressible layer
J (0.15 mm in thickness, 35~ in percent of void).
On the above compressible layer, a cotton string
(0.175 mm in diameter) on which the same rubber cement as in
Examples 1 to 7, was wound in helical fashion, and air-dried
for 30 minutes, on which the same rubber cement was coated and
~ air-dried for 12 hours.
Then, the surface of the coated rubber cement was
wrapped up by tightly winding a cotton-woven sheet (1000 mm in
width) in the circumferential direction, and then vulcanized
using the aforesaid vulcanizer at 140°C and 3kg/cm2 for 90
'I minutes .
Thereafter, the vulcanized surface was polished by
the aforesaid cylindrical grinding machine to give a non-
stretchable layer (0.25 mm in thickness), and a surface
printing layer (0.45 mm in thickness, 3 to 5 in ten points
~I mean roughness (Rz)), thus obtaining a printing blanket.
Out of the conventional printing blankets having no
seam in the peripheral direction, which are disclosed in the
aforesaid publication, a printing blanket provided with a
I compressible layer in which plural micro spheres are
2169430
- 30 -
dispersed, was selected and prepared as follows.
A printing blanket was obtained in the same manner
as in Comparative Example 3, except that instead of the
compressible layer, on the surface of an adhesive layer having
5~ the two-layer structure formed on the peripheral surface of
the sleeve made of nickel, a rubber cement comprising the
following ingredients was coated and air-dried for 12 hours,
the coated surface was wrapped up by tightly winding a cotton-
woven sheet (1000 mm in width) in the circumferential
' direction, and then vulcanized using the aforesaid vulcanizer
at 140°C and 3kg/cm2 for 90 minutes to prepare a compressible
layer.
Rubbe_rcement for t he comn_ress,_'b1_e layer
(Ingredients) (parts by weight)
Unvulcanized NHR 100
Furnace black 30
Clay filler 40
Stearic acid (plasticizer) 1
Phenol antioxidant 1
Powder sulfur (vulcanizing agent) 2.5
Sulfenic amide accelerator 1.5
Thiuram accelerator 1
Zinc oxide (activator) 5
Micro spheres* 6
Toluene (solvent) 100
* Its product name: "Salanmicrosphere", available from
Matsumoto Yushi Co., Ltd.
2159430
- 31 -
The following tests were conducted for each printing
blanket prepared in Examples and Comparative Examples to
evaluate its characteristics.
5,~ The viscoelasticity (tan 6) for each printing
blanket was determined with a viscoelasticity spectrometer
(product No. DVE-V4, available from Rheology Corp.). Hased on
the fact that as the tan 8 is increased, the viscoelasticity
is improved, the vibration absorbability for each printing
~ blanket was evaluated.
To measure the tan S, a lOmm x lOmm sample
penetrating the sleeve or the base layer was taken. To this
sample, a 16 Hz sin-wave vibration having the amplitude of
0.05 mm and the initial strain of 0.1 mm was applied at
J ordinary temperature. The measuring conditions corresponded
to that when the printing blanket is used for high-speed
printing of 1000 r.p.m, the blanket receives about 17-time
repeated compressions every second.
The tan 8 for the compound composing the base layer
~ 1 of each printing blanket after vulcanization was 0.05 when
it was measured in accordance with the above measuring method.
Using the device shown in Fig. 3, the ratio of
change in peripheral length (~) for each printing blanket was
~ determined. As described above, as the ratio of change in
21 ~9~r~0
- 32 -
peripheral length is increased, the printing image is unclear
and the printing quality deteriorates. Therefore, smaller
values are preferred.
In the device of Fig. 3, the printing blanket 20 is
5', mounted on the drum 6 which has the sleeve detachable
mechanism with pressure gas, as in the aforesaid blanket
cylinder, and is fixed to the drive shift 5 that is driven
rotationally in the direction shown with an arrow in Fig. 3.
With the drum 7 corresponding to the plate cylinder for offset
rotational printings pressed against the printing blanket 20
from above with a predetermined depression, the drive shift
was rotated in a predetermined times to obtain the difference
in the rotations of drums 6 and 7, from which the ratio of
change in peripheral length (a) was determined.
' In Fig. 3, the reference numeral 8 denotes a bearing
unit that supports the drive shift 5; 9 denotes a bearing unit
that supports the shaft 71 of the drum 7 and is movable upward
and downward as shown with the white arrow; 10 denotes a
spring that supports the bearing unit 9 from below; and 11
denotes a load cell for measuring the compression of the drum
7 with respect to the printing blanket 20.
In the above device, by replacing the drum 7 with
one having different diameter, the depression of the drum 7 to
the printing blanket can be adjusted.
In measuring the change in peripheral length for the
216;'430
- 33 -
flat printing blanket in Comparative Example 2, the drum 6 is
replaced with the same drum as in the conventional blanket
cylinder around which a blanket is wound.
The measuring conditions to determine the ratio of
~ change in peripheral length with the use of the above device
were as follows:
Diameter of the drum 6
(for seamless printing blanket) ........ 169.520 mm
Diameter of the drum 6
(for flat printing blanket) ......... . 170.100 mm
Diameter of the drum 7 .................. 173.915 mm
Depression of the drum 7 to
the printing blanket 20 ............... 0.1 mm
Rotational speed of the drive shaft 5 .... 1,000 r.p.m
Revolution of the drive shaft 5 .......... 500 times
In the measuring, it was confirmed as to whether
every 100 times of revolution, the difference in revolution
between the drum 7 and the drum 6 was plus (the drum 7 had
more revolutions than the drum 6), or minus (the drum had less
revolutions than the drum 6). As a result, all the
differences in the revolutions were plus.
MeasL_rement of the permanent set ,_' n fatp..~,'?~P
Using the aforesaid device used in the measurement
of the ratio of change in peripheral length, the amount of the
permanent set in fatigue (mm) for each printing blanket was
determined. Based on the obtained results, the durability for
_ 34 _ ~ 15~~430
each printing blanket was evaluated. As the amount is
decreased, the durability is increased.
Specifically, under the conditions that the
depression of the drum 7 to the printing blanket 20 was 0.1 mm
and the rotational speed of the drive shaft 5 was 1000r.p.m,
each printing blanket was continuously rotated for 100 hours,
and the reduction of the thickness (mm) of the printing
blanket was determined as the amount of the permanent set in
fatigue. Table 1 shows the results.
Table 1
Thickness ( mm ) Entire ~~o of change Pe~ne~t
set m
Entire Base layer tan 6 i~Pe~Pher'al _ fatigue (am)
Comp.Ex.l 0.8 - 0.165 0.14 0.11
Ex. 1 1.0 0.2 0.218 0.08 0.07
Ex. 2 1.6 0.8 0.228 0.07 0.06
Ex. 3 2.2 1.4 0.251 0.06 0.05
Ex. 4 2.8 2.0 0.256 0.06 0.04
Ex. 5 5.8 5.0 0.262 0.08 0.05
Ex. 6 10.8 10.0 0.273 0.10 0.05
Ex. 7 12.8 12.0 0.273 0.12 0.05
Comp.Ex.2 - - 0.257 0.05 0.05
Comp.Ex.3 - - 0.180 0.15 0.10
Comp.Ex.4 - - 0.172 0.15 0.09
From the results in Table 1, it was confirmed that
when the thickness of the base layer was in a range of 0.2 to
10.0 mm, there could be obtained good results in the vibration
2 l 69430
- 35 -
absorbability, the ratio of change in the peripheral length
and the durability.
Using the same manner as in Example 3, except that
5I the thickness of the surface printing layer 4 was set to that
in Table 2, a printing blanket 20 was prepared.
For the printing blankets prepared in above
Examples, Example 3 and Comparative Examples 2 to 4, the above
measurement of the ratio of change in peripheral length and
10~ the following solid applicability evaluation were conducted to
evaluate each characteristics.
Each printing blanket was mounted on a high speed
offset rotational printing, and using oil based ink of
15 ~ Japanese-ink color, the solid printing was carried out on the
surface of a woodfree paper.
The standard deviation in brilliance for the solid
parts of the above printing was determined with an image
processing device (Model No. LA555, available from Piasu Co.,
20 I Ltd.). Based on the fact that as the standard deviation of
brilliance is decreased, the solid applicability is increased,
the solid applicability for each printing blanket was
evaluated. Table 2 shows the results.
216'430
= 36 -
Table 2
Thickness (mm)
Surface Ratio of change Standard
Entire printing in peripheral deviation in
layer length ($) brilliance
5'',Ex. 8 2.1 0.1 0.05 19.7
Ex. 9 2.15 0.15 0.05 18.2
Ex. 3 2.2 0.2 0.06 17.3
Ex. 10 2.25 0.25 0.06 17.2
Ex. 11 2.3 0.3 0.06 16.9
Ex. 12 2.4 0.4 0.07 17.4
Ex. 13 2.5 0.5 0.12 17.1
10Ex. 14 2.6 0.6 0.14 17.3
Comp. Ex.2 1.95 0.2 0.05 18.9
Comp. Ex.3 2.2 0.45 0.15 23.4
Comp. Ex.4 2.2 0.45 0.15 21.5
15 I From the results in Table 2, it was confirmed that
when the thickness of the surface printing layer was in a
range of 0.1 to 0.4 mm, there could be obtained good results
in the ratio of change in circumference and the solid
applicability.
20 I Examples 15 to 21
Using the same manner as in Example 3, except that
the thickness of the compressible layer 3 was set to that in
Table 3, a printing blanket 20 was prepared.
For the printing blankets of Examples, Example 3 and
25 ~ Comparative Examples 2 to 4, the measurement of the ratio of
_ 37 _ 2169430
change in circumference, the evaluation of the solid
applicability and the measurement of the permanent set in
fatigue were conducted to evaluate each characteristics.
Table 3 shows the results.
Tabla 3
Thickness (aun) Rate of change S~~.d pexm3nent
Cxnpressible ~ deviation in set in
Entire ~y~ length (~) brilh.ance fatigue (nm)
Ex. 15 2.0 0.1 0.11 16.9 0.02
10''Ex. 16 2.05 0.15 0.08 17.2 0.03
Ex. 17 2.1 0.2 0.06 17.2 0.04
Ex. 3 2.2 0.3 0.06 17.3 0.05
Ex. 18 2.3 0.4 0.05 18.4 0.05
Ex. 19 2.4 0.5 0.05 19.2 0.06
Ex. 20 2.5 0.6 0.06 19.7 0.06
' Ex. 21 2.6 0.7 0.08 22.0 0.09
,
15
Comp.Ex.2 1.95 0.3 0.05 18.9 0.05
Comp.Ex.3 2.2 1.5 0.15 23.4 0.10
Comp.Ex.4 2.2 1.5 0.15 21.5 0.09
From the results in Table 3, it was confirmed that
when the thickness of the compressible layer was in a range of
0.15 to 0.6 mm, there could be obtained good results in the
ratio of change in peripheral length, the solid applicability
and the durability.
Examples 22 to 25
216~~430
- 38 -
The procedures as in Example 3 were carried out
except that the amount of sodium chloride in the rubber cement
for the compressible layer comprising the compressible layer 2
was adjusted as follows:
amount of sodium ch1_o_r,_'de
(Example No.) (Parts by weight)
22 85
23 140
24 160
25 170
I Examples 26 to 30
Using the same manner as in Example 3, except that
the compressible layer 2 prepared by foaming in order to have
closed cell structure was used, a printing blanket 20 was
prepared.
'I Specifically, a rubber cement for the compressible
layer in which instead of the sodium chloride, an expanding
agent of dinitrosopentamethylenetetramine (DPT) and an
expanding promoting agent of urea compound were blended in the
following amounts, was coated by the aforesaid rotational
'I spreading machine, and dried for 12 hours. The coated surface
was wrapped up by tightly winding a cotton sheet (1000 mm in
width) in the circumferential direction, and then vulcanized
while foaming, at 140°C and 3kg/cm2 for 90 minutes, to prepare
a compressible layer 2 having the closed cell structure.
216'»~D
- 39 -
Amounts,(parts by weight)
Example Expanding Expanding
No. agent promoting
agent
26 5 5
27 6 6
28 8.5 8.5
29 9.5 9.5
30 10 10
For the printing blankets prepared in the above
10',I Examples, Examples 3 and Comparative Examples 2 to 4, the
aforesaid measurement of the vibration absorbability was
conducted to evaluate each characteristics. Table 4 shows the
results.
20
- 40 - ~ i b9430
Table 4
Compressible layer
Porous Percent of Entire
structure void (~) tan S
Ex. 22 Open cell 30 0.236
Ex. 3 Open cell 35 0.251
Ex. 23 Open cell 50 0.258
Ex. 24 Open cell 55 0.264
Ex. 25 Open cell 60 0.266
Ex. 26 Closed cell 30 0.198
Ex. 27 Closed cell 35 0.235
10!.Ex. 28 Closed cell 50 0.244
Ex. 29 Closed cell 55 0.248
Ex. 30 Closed cell 60 0.250
Comp.Ex.2 Open cell 35 0.257
Comp.Ex.3 Open cell 35 0.180
Comp.Ex.4 minimum spheres 35*1 0.172
*1: volume ratio of the minimum spheres
From the results in Table 4, it was confirmed that
the open cell structure was superior to the closed cell
structure in view of the vibration absorbability.
After forming the base layer 1, the compressible
layer 2 and the non-stretchable layer 3 in the same manner as
in Example 3, the same rubber cement for the adhesive layer as
in Example 3 was coated on the surface of the non-stretchable
layer 3 with the aforesaid rotational spreading machine, and
2169430
- 41 -
air-dried for 30 minutes to prepare an adhesive layer (0.05 mm
in thickness).
On the surface of this adhesive layer, a rubber
cement in which the same compound for the base layer as used
S I in Example 3 was dissolved in 100 parts by weight of toluene,
was coated in the same manner as described and air-dried for
12 hours. The coated surface was wrapped up by tightly
winding a cotton sheet (1000 mm in width) in the
circumferential direction, and was vulcanized using the
' aforesaid vulcanizer at 140°C and 3kg/cm2 for 90 minutes, and
further, the vulcanized surface was polished by the aforesaid
cylindrical grinding machine to prepare a second base layer
(0.2 mm in thickness).
On the surface of the second base layer, the
',I adhesive layer 34 and the surface printing layer 4 were formed
in the same manner as in Example 3, to prepare a printing
blanket.
For this printing blanket, the respective tests as
described were conducted to evaluate its characteristics.
~ Table 5 shows the results together with those of Example 3.
2i~~~30
- 42 -
Table 5
Entire Ratio of Standard Permanent
tan 8 change in deviation in set in
peripheral brilliance fatigue
length ( ~ ( mm )
)
Ex. 31 0.28 0.04 17.2 0.04
Ex. 3 0.251 0.06 17.3 0.05
From the results in Table 5, it was confirmed that
when the second base layer was formed between the compressible
layer 3 and surface printing layer 4, there. could be obtained
improved results in the vibration absorbability, the ratio of
change in peripheral length and the durability.
20
