U.S. patent application number 12/162232 was filed with the patent office on 2009-02-12 for belt for papermaking machine.
This patent application is currently assigned to ICHIKAWA CO., LTD.. Invention is credited to Tsutomu Ishii.
Application Number | 20090038770 12/162232 |
Document ID | / |
Family ID | 38327378 |
Filed Date | 2009-02-12 |
United States Patent
Application |
20090038770 |
Kind Code |
A1 |
Ishii; Tsutomu |
February 12, 2009 |
BELT FOR PAPERMAKING MACHINE
Abstract
The present invention provides a belt for a papermaking machine
having excellent property such as crack resistance, abrasion
resistance and hair crack resistance. The belt for a papermaking
machine of the present invention is a belt for a papermaking
machine having an outer peripheral surface stacked on the felt side
of a substrate, characterized in that the outer peripheral surface
comprises an intermediate layer in contact with the substrate and
an outermost layer located on the outer periphery of the
intermediate layer, wherein the intermediate layer is made of
polyurethane cured with dimethylthiotoluenediamine, and the
outermost layer is made of cured polyurethane cured with an curing
agent other than dimethylthiotoluenediamine, or a thermosetting
resin selected from epoxy resins and unsaturated polyester resins,
and a drainage gutter is provided by cutting on the outer
peripheral surface, and so that the bottom of the drainage gutter
is cut to a position which is deeper than the boundary surface
between the intermediate layer and the outermost layer.
Inventors: |
Ishii; Tsutomu; (Tokyo,
JP) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
ICHIKAWA CO., LTD.
BUNKYO-KU
JP
|
Family ID: |
38327378 |
Appl. No.: |
12/162232 |
Filed: |
January 29, 2007 |
PCT Filed: |
January 29, 2007 |
PCT NO: |
PCT/JP2007/051362 |
371 Date: |
August 15, 2008 |
Current U.S.
Class: |
162/358.4 |
Current CPC
Class: |
D21F 3/0227
20130101 |
Class at
Publication: |
162/358.4 |
International
Class: |
D21F 3/00 20060101
D21F003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2006 |
JP |
2006-022618 |
Claims
1. A belt for a papermaking machine having an outer peripheral
surface stacked on the felt side of a substrate, characterized in
that the outer peripheral surface comprises an intermediate layer
in contact with the substrate and an outermost layer located on the
outer periphery of the intermediate layer, wherein the intermediate
layer is made of polyurethane cured with
dimethylthiotoluenediamine, and the outermost layer is made of
cured polyurethane cured with an curing agent other than
dimethylthiotoluenediamine, or a thermosetting resin selected from
epoxy resins and unsaturated polyester resins, and a drainage
gutter is provided by cutting on the outer peripheral surface, and
so that the bottom of the drainage gutter is cut to a position
which is deeper than the boundary surface between the intermediate
layer and the outermost layer.
2. The belt for a papermaking machine according to claim 1, wherein
the outermost layer is made of polyurethane cured with
methylenebisorthochloroaniline.
3. The belt for a papermaking machine according to claim 1, wherein
the thermosetting resin is a bisphenol A type epoxy resin.
Description
TECHNICAL FIELD
[0001] The present invention relates to a belt for a papermaking
machine (hereinafter, may be referred to as "belt" for short). In
more detail, it is a belt for a papermaking machine having its
outer peripheral surface composed of a multilayer and excellent
property such as crack resistance, abrasion resistance and
permanent-deformation resistance.
BACKGROUND ART
[0002] A belt for a papermaking machine composed of a substrate and
polyurethane is used in each manufacturing step in a paper factory.
In other words, a shoe press belt or a transfer belt is used in a
press part of a paper manufacturing step, whereas a soft calender
belt is used in a calender part.
[0003] Basically, these belts are composed of a substrate made of
fabrics etc. to strengthen the whole belt, and polyurethane stacked
on both sides or a single side of the substrate. In order to
manufacture such belts, the steps for coating a substrate with a
liquid polyurethane polymer, impregnating and curing with a curing
agent are applied.
[0004] Various kinds of polyurethane are used as the polyurethane
for a belt for a papermaking machine depending on a using part such
as a press part and use in a papermaking step. In any use, the
polyurethane is required to have excellent properties because the
belt rotates at a high speed around a roller and is exposed to
strong pressure between rollers or a roller and a press shoe.
Especially, high-speed operation of a paper machine and
high-pressurization of press parts, which were caused for improving
productivity of papermaking, have lately brought severer conditions
of use of the belt. The belt to be used in such a high-performance
papermaking machine is required to have performance at a higher
level. The belt for a papermaking machine is generally required to
have the properties such as abrasion resistance,
permanent-deformation resistance, crack resistance and compression
fatigue resistance.
[0005] As described above, the belt has polyurethane stacked on
both sides or a single side of the substrate. In the case of both
sides, the outer peripheral surface is brought in contact with the
felt side, whereas the inner peripheral surface is brought in
contact with a press roller and a press shoe. Because the outer
peripheral surface stacked on the felt side is exposed to severe
pressure and drainage gutters are generally provided on the outer
peripheral surface to improve hydration efficiency, cracks tend to
be generated at the bottom and edge of the drainage gutters. In
addition, there has been a problem that the surface of the
protruding portions located between adjacent drainage gutters tends
to suffer abrasion. Therefore, the polyurethane to be used as the
outer peripheral surface among the polyurethane constituting a belt
is particularly required to have improved crack resistance and
abrasion resistance.
[0006] In order to produce polyurethane, a diisocyanate having two
isocyanate groups at the terminal and a polyol having a plurality
of hydroxyl groups at the terminal are subjected to polyaddition
reaction to produce a urethane prepolymer having the isocyanate
groups at the terminal and then thus obtained liquid urethane
prepolymer, which is low molecular weight, is added with a curing
agent (chain extender) and cured under heating to obtain solid
polyurethane of high molecular weight.
[0007] Selection of a curing agent to be used in the production of
high-molecular weight polyurethane has an important effect on the
property of the polyurethane. Typical examples of the curing agent
of polyurethane for papermaking include dimethylthiotoluenediamine
(DMTDA) and methylenebisorthochloroaniline (MBOCA), both of which
are frequently used. MBOCA is excellent in abrasion resistance,
whereas DMTDA is particularly excellent in crack resistance. Crack
resistance is an important property for a belt to be used in
papermaking and DMTDA is often used for use requiring crack
resistance.
[0008] In patent literature 1, for example, DMTDA used as a curing
agent for the polyurethane of a belt for a papermaking machine
gives a belt for a papermaking machine having a good balance
between crack resistance, abrasion resistance and
permanent-deformation resistance.
[0009] As a crack being generated in a belt, however, in addition
to the usual cracks caused by strong external force, tiny hair-like
cracks, so-called hair cracks, are generated on the surface of the
protruding portions located between adjacent drainage gutters. A
material cured with DMTDA has the weak point that hair cracks tend
to be generated, although it is excellent in preventing usual
cracks. And this had a problem that the hair cracks generated
evenly over the surface of the protruding portions of a belt
increase surface roughness resulting in abrasion by friction. The
drainage gutters are generally provided on the outer peripheral
surface of a belt to be used in papermaking in order to drain
squeezed water. There is a phenomenon that the edges of the surface
of the protruding portions located between the adjacent drainage
gutters are chipped, which tends to occur more often in a material
cured with DMTDA.
[0010] On the other hand, a material cured with MBOCA has the weak
point that cracks tend to be generated, although it is excellent in
abrasion resistance. It has been known that polyurethane having
high hardness selected to improve particularly the abrasion
resistance of a belt for a papermaking machine tends to generate
more cracks even though it is a material cured with DMTDA or a
material cured with MBOCA. In other words, it has been considered
that it is generally difficult to attain both enhancing abrasion
resistance and preventing cracks at the same time which conflict
with each other.
Patent Literature 1: JP-A-2004-52204
DISCLOSURE OF INVENTION
Problem to be Solved by the Invention
[0011] After having studied a way to solve the above problem, since
cracks are often generated on the bottom and its edge of the
drainage gutter located on the polyurethane resin layer on the
polyurethane peripheral surface and because the hair crack and
abrasion on the surface of the protruding portion of the belt
should be noted, the present inventor has found that a belt
excellent in all of crack resistance, abrasion resistance and hair
crack resistance can be obtained by making a resin stacked on the
outer periphery (felt side) of a substrate to 2 or more multilayer,
stacking a material excellent in crack resistance for a layer
(hereinafter referred to as intermediate layer) to be in direct
contact with the substrate, stacking a material excellent in
abrasion resistance and hair crack resistance on the peripheral
layer thereof, and making an outermost layer (hereinafter, referred
to as outermost layer for short) located on the outer peripheral
surface, and also, when the drainage gutter is set on the outer
peripheral surface, by cutting the drainage gutter on the
peripheral surface so that its bottom is deeper than the boundary
surface between the intermediate layer and the outermost layer
resulting in forming the bottom and its edge of the drainage gutter
with the material excellent in crack resistance and in forming the
outermost layer with the material excellent in abrasion resistance
and hair crack resistance.
[0012] Specifically, polyurethane cured with DMTDA is stacked for
the intermediate layer, whereas polyurethane cured with a curing
agent other than DMTDA, for example, with MBOCA, or a thermosetting
resin selected from epoxy resins and unsaturated polyester resins
is stacked for the outermost layer.
[0013] That is, the present invention is a belt for a papermaking
machine having an outer peripheral surface stacked on the felt side
of a substrate, characterized in that the outer peripheral surface
comprises an intermediate layer in contact with the substrate and
an outermost layer located on the outer periphery of the
intermediate layer, wherein the intermediate layer is made of
polyurethane cured with dimethylthiotoluenediamine, and the
outermost layer is made of cured polyurethane cured with an curing
agent other than dimethylthiotoluenediamine, or a thermosetting
resin selected from epoxy resins and unsaturated polyester resins,
and a drainage gutter is provided by cutting on the outer
peripheral surface, and so that the bottom of the drainage gutter
is cut to a position which is deeper than the boundary surface
between the intermediate layer and the outermost layer.
ADVANTAGES OF THE INVENTION
[0014] The belt for a papermaking machine of the present invention
is excellent in abrasion resistance and hair crack resistance
because the polyurethane cured with a curing agent other than
DMTDA, for example, MBOCA, or a thermosetting resin selected from
epoxy resins and unsaturated polyester resins is set on the
outermost layer. In addition, since a drainage gutter is cut to a
position deeper than the boundary surface between the above two
layers and the polyurethane cured with DMTDA of the intermediate
layer is exposed at the bottom and its edge of the drainage gutter,
cracks is hardly generated at the bottom and its edge. On the other
hand, the surface of protruding portions located between adjacent
drainage gutters is the material of the outermost layer, therefore
the chip on the edge can be protected as well. Thus, a belt for a
papermaking machine more excellent than conventional belts in all
aspects of crack resistance, abrasion resistance and hair crack
resistance is provided.
BEST MODE FOR CARRYING OUT THE INVENTION
[0015] FIG. 1 illustrates the structure of the belt for a
papermaking machine of the present invention. FIG. 1 is a
cross-sectional view of the belt 1 and a shoe-side resin layer 3
and a felt-side resin layer 4 are stacked on the inner peripheral
surface and on the outer peripheral surface of a substrate 2
respectively.
[0016] The felt-side resin layer 4 on the outer peripheral surface
comprises an intermediate layer 5 and an outermost layer 6, wherein
the intermediate layer 5 is in contact with the substrate and the
outermost layer 6 is stacked on the outside of the intermediate
layer. A plurality of drainage gutters 7 are provided on the belt
in the direction of belt traveling. Since the drainage gutter 7 is
cut to a position deeper than the boundary surface 9 between the
intermediate layer 5 and the outermost layer 6, the exposed
intermediate layer 5 forms the bottom 8 and its edge of the
drainage gutter 7.
[0017] The outer peripheral surface of the belt obtained by such a
stacking method and installation of the drainage gutter comprises
the intermediate layer 5 and the outermost layer 6, wherein the
outermost layer 6, which is in contact with the felt side in a
papermaking machine, is made of polyurethane cured with a curing
agent other than DMTDA, for example, cured with MBOCA, or a
thermosetting resin selected from epoxy resins and unsaturated
polyester resins. Therefore, abrasion, hair cracks and chips on the
edge of the surface of protruding portions, are suppressed even in
a high speed and high pressure operation of a papermaking machine.
On the other hand, since the drainage gutter 7 is cut to a position
deeper than the boundary surface 9 between the intermediate layer 5
and the outermost layer 6, and the bottom 8 and its edge made of
the polyurethane cured with DMTDA which is excellent in crack
resistance, cracks are hardly generated.
[0018] Among the felt-side resin layer 4 of the outer periphery of
the belt of the present invention, the intermediate layer 5 is made
of polyurethane cured with DMTDA and the outermost layer 6 is
particularly required to have abrasion resistance and hair crack
resistance. Polyurethane cured with a curing agent other than DMTDA
or a thermosetting resin selected from epoxy resins and unsaturated
polyester resins is used as a material for the outermost layer
6.
[0019] In the belt for a papermaking machine, besides the felt-side
resin layer 4 constituting the outer peripheral surface of the
above substrate 2, the shoe-side resin layer 3 is also usually
stacked on the shoe side of the substrate 2. Similarly to the outer
peripheral surface, thermosetting polyurethane is used most
frequently as a material for the shoe-side resin layer 3.
[0020] As a substrate, a woven fabric is usually used, but two
overlapped fabrics without weaving, a film, a knitted material and
a spiral winding made of narrow width belt form are also used.
[0021] A polyurethane of the intermediate layer is produced by
reacting a polyol and a diisocyanate to form a urethane prepolymer,
and the prepolymer is mixed with a curing agent (chain extender)
and then applied to a substrate followed by drying and curing (or
heating) to obtain polyurethane of high molecular weight.
[0022] Examples of the polyol for producing a urethane prepolymer
include a polyether polyol such as polyethylene glycol,
polypropylene glycol and polytetramethylene glycol; and a polyester
polyol such as polycaprolactone ester, polycarbonate, polyethylene
adipate, polybutylene adipate and polyhexene adipate.
[0023] As a diisocyanate for urethane prepolymer raw material, any
usually known substance as a raw material for polyurethane, such as
tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI),
m-xylene diisocyanate and naphthalene diisocyanate can be used, but
TDI and MDI are particularly preferable. The 4,4'-isomer of MDI is
most preferable among various isomers. A mixture of TDI and MDI can
also be used. The mixing ratio of a polyol and a diisocyanate in
the reaction for producing a urethane prepolymer from them is an
equivalent ratio of isocyanate group/OH group of the range of 1.3/1
to 4/1, preferably 1.4/1 to 1.6/1.
[0024] The reaction product contains a large amount of an unreacted
diisocyanate and solvent, which are removed by distillation to
obtain the prepolymer as a distillation residue.
[0025] Dimethylthiotoluenediamine of a curing agent has various
isomers depending on the substitution location of the dimethylthio
group and the amino group. A mixture of these isomers can be used
and is commercially available as ETHACURE 300 (trade name) made by
ALBEMARLE Co. in USA.
[0026] Methylenebisorthochloroaniline of a curing agent is
commercially available as IHARA CUAMINE-MT (trade name) made by
IHARA CHEMICAL INDUSTRY CO., LTD.
[0027] A urethane prepolymer and a curing agent are preferably
mixed in such a mixing ratio that the equivalent ratio of an active
hydrogen group of the curing agent and an isocyanate group of the
urethane prepolymer is 0.9 to 1.10.
[0028] The curing reaction with a curing agent can be conducted by
a known method. The temperature of the curing reaction is usually
20 to 150.degree. C., preferably 90 to 140.degree. C. It is
preferable to continue the reaction for at least 30 minutes.
[0029] The urethane prepolymer has generally low viscosity, of
which the chain is extended with a curing agent (chain extender) to
obtain polyurethane of high molecular weight. In the production of
the belt for a papermaking machine of the present invention that is
composed of multilayered polyurethane and a substrate 2, the
substrate 2 such as a fabric is impregnated with a mixture of a
urethane prepolymer forming the intermediate layer 5 and a curing
agent, dried and cured (or may be heated) to form the intermediate
layer 5, and then a mixture of a urethane prepolymer and a curing
agent or a thermosetting resin selected from epoxy resins and
unsaturated polyester resins is applied onto the intermediate layer
5 to obtain the outermost layer 6. And, the belt shown in FIG. 1 is
obtained, wherein the inner peripheral surface of the substrate 2
is impregnated and stacked with the polyurethane layer and the
opposite side is impregnated and stacked with the outer peripheral
surface composed of the intermediate layer 5 and the outermost
layer 6.
[0030] In the case where the thermosetting polyurethane is used in
the outermost layer 6, the kind, the mixing ratio and the reaction
temperature etc. of the polyol and diisocyanate of raw material are
almost similar to in the intermediate layer 5, but a curing agent
other than dimethylthiotoluenediamine (DMTDA) is used. The curing
agent includes an aromatic diamine (methylenebisorthochloroaniline
(MBOCA), trimethylene-bis-4-aminobenzoate,
1,2-bis-(2-aminophenylthio)ethane, methylenedianiline sodium
chloride complex, trimethylene glycol-di-paraaminobenzoate); an
aliphatic polyol (1,4-butanediol, trimethylpropane); an aromatic
polyol (hydroquinonediethylol ether) and the like. MBOCA is
particularly preferable from the standpoints of abrasion
resistance, hair crack resistance and the like.
[0031] A thermosetting resin other than polyurethane such as an
epoxy resin and an unsaturated polyester resin can also be used for
the outermost layer 6. The epoxy resin is preferably a bisphenol A
type epoxy resin that is produced by condensation of bisphenol A
and epichlorohydrin and cured with a curing agent such as an
aliphatic amine, an aromatic amine and an acid anhydride. The
unsaturated polyester resin is preferably an unsaturated polyester
resin that is produced by curing a mixture of an unsaturated
polyester resin obtained from an unsaturated dicarboxylic acid and
a glycol and a polymerizable vinyl monomer such as styrene with a
radical initiator such as an organic peroxide. An epoxy resin among
the above thermosetting resins is particularly preferable for use
in the outermost layer 6 of the present invention.
[0032] The unsaturated polyester resin of a thermosetting resin, is
commercially available as ADEKA RESIN EP4100 (trade name) made by
ADEKA Corporation.
[0033] The bisphenol A type epoxy resin of another thermosetting
resin is commercially available as U-PICA 4516P (trade name) made
by Japan U-PICA Company, Ltd.
[0034] The method for stacking polyurethane resin on both sides of
a substrate 2 is carried out by the following steps as shown in,
for example, FIGS. 2 and 3.
[0035] (Step 1)
[0036] A substrate 2 is stretched between rollers 20 and 21 as
shown in FIG. 2 and a mixture of a urethane prepolymer to form a
shoe-side resin layer 3 and dimethylthiotoluenediamine (DMTDA) of a
curing agent, is applied onto the substrate 2 from a resin-coating
nozzle 22 while rotating the rollers, and the shoe-side resin layer
3 is dried and cured (or may be heated).
[0037] (Step 2)
[0038] After drying and curing of the shoe-side resin layer 3, the
front and back of the substrate 2 is inverted, as shown in FIG. 3,
a mixture of a urethane prepolymer to form an intermediate layer 5
and DMTDA of a curing agent, is applied onto the other side of the
substrate 2 stacked with the shoe-side resin layer 3, and dried and
cured (or may be heated) to form the intermediate layer 5.
Furthermore, a mixture of a urethane prepolymer to form an
outermost layer 6 (not shown in the figure) and MBOCA of a curing
agent, is similarly applied onto the intermediate layer 5 shown in
FIG. 3 and dried and cured (or may be heated) to form sequentially
a felt-side resin layer 4 composed of the intermediate layer 5 and
the outermost layer 6.
[0039] When a thermosetting resin selected from epoxy resins and
unsaturated polyester resins is used for the outermost layer 6, the
outermost layer can be formed by adding a curing agent or a radical
initiator to an uncured liquid resin, which is commercially
available, such as a condensate of bisphenol A and epichlorohydrin
and a mixture of an unsaturated polyester and a polymerizable vinyl
monomer followed by heating and curing similarly to in curing of
the urethane prepolymer.
[0040] After the felt-side resin layer 4 is thus formed as the
outer peripheral surface of the substrate 2, a drainage gutter 7 is
formed. The drainage gutter 7 is formed by cutting the belt in the
direction of belt traveling with a rotary cutter and the like. In
the present invention, since the polyurethane cured with DMTDA
forming the intermediate layer 5 is necessary to be exposed and
form the bottom and its edge of the drainage gutter 7, the drainage
gutter 7 is cut as shown in FIG. 1 so that its bottom is deeper
than the boundary surface 9 between the intermediate layer 5 and
the outermost layer 6.
[0041] The relative ratio about thickness of each layer on the
outer peripheral surface is preferably 40 to 90, particularly
preferably 50 to 80 for the intermediate layer 5, and preferably 60
to 10, particularly preferably 50 to 20 for the outermost layer 6,
relative to the total thickness 100 of the felt-side resin layer 4.
A too thick intermediate layer 5 (too thin outermost layer 6)
causes earlier exposure of the intermediate layer 5 to the belt
surface when abrasion of the outermost layer 6 proceeds in the use
of the belt. In contrast, a too thin intermediate layer 5 (too
thick outermost layer 6) causes cracks sometimes at the bottom 8
and its edge vicinity or the adjacent gutter wall, because the
boundary surface 9 between the intermediate layer 5 and the
outermost layer 6 gets closer to the bottom 8 of the drainage
gutter 7, therefore it is not favorable.
[0042] In the present invention, the depth of the drainage gutter 7
is 40 to 70, preferably 50 to 60, relative to relative ratio 100 of
the thickness of the felt-side resin layer 4. The drainage gutter 7
is cut so that the boundary surface 9 forms a part of the wall of
the drainage gutter 7. The distance from the boundary surface to
the bottom 8 is preferably 10 to 90, particularly preferably 40 to
60 relative to depth 100 of the drainage gutter 7. The deeper
drainage gutter 7 than the above depth unfavorably causes cracks
sometimes at the bottom 8 and its edge vicinity or the adjacent
gutter wall. In contrast, the shallower drainage gutter 7 than the
above depth unfavorably lowers dehydration efficiency of the
belt.
EXAMPLES
[0043] The present invention is described specifically with
reference to the following examples, however, to which the present
invention is not limited at all. In each example and comparative
example, the urethane prepolymer, the curing agent and the
thermosetting resin used as materials for the intermediate layer
and the outermost layer are as follows.
(1) Urethane prepolymer: "TAKENATE L-2395 (made by Takeda
Pharmaceutical CO., LTD.)" (2) Curing agent DMTDA: "ETHACURE 300"
made by ALBEMARLE Co. (80/20 mixture of 3,5-dimethylthio
2,4-toluenediamine/3,5-dimethylthio 2,6-toluenediamine) (3) Curing
agent MBOCA: "IHARA CUAMINE-MT" made by IHARA CHEMICAL INDUSTRY
CO., LTD. (methylenebisorthochloroaniline) (4) Thermosetting resin:
"ADEKA RESIN EP4100" (made by ADEKA Corporation): bisphenol A type
epoxy resin obtained by condensation of bisphenol A and
epichlorohydrin
Example 1
Stacking of Polyurethane on the Inner Peripheral Surface
[0044] DMTDA was prepared as a curing agent and mixed with the
urethane prepolymer so that the equivalent ratio of H/NCO was
0.97.
(Coating of Prepolymer)
[0045] A substrate 2 was stretched between rollers 20 and 21 as
shown in FIG. 2 and the mixture of the above urethane prepolymer to
form a resin layer 3 on the inner peripheral surface (shoe side)
and the curing agent was applied onto the substrate 2 from a
resin-coating nozzle 22 while rotating the rollers, and the
shoe-side resin layer 3 was then dried and cured.
(Stacking of Polyurethane of Intermediate Layer)
[0046] Subsequently, the front and back of the substrate 2 was
inverted and a mixture of the urethane prepolymer to form the
intermediate layer 5 and DMTDA of a curing agent, was applied onto
the other side of the substrate 2 as shown in FIG. 3, and dried and
cured.
(Stacking of Polyurethane of Outermost Layer)
[0047] When the intermediate layer 5 was cured and lost its
fluidity, the urethane prepolymer and MBOCA of a curing agent were
mixed so that the equivalent ratio of H/NCO was 0.97. The mixture
was applied onto the intermediate layer 5 to form the outermost
layer 6 and then dried and cured. Subsequently, the polyurethane on
the inner peripheral surface, the polyurethane of the intermediate
layer and the polyurethane of the outermost layer were completely
cured by reacting at 100.degree. C. for 3 hours with a heat source
23 installed above.
[0048] Thus, the belt having one layer on the inner peripheral
surface and two layers of the intermediate layer 5 and the
outermost layer 6 stacked on the outer peripheral surface of the
substrate 2 was obtained. The thickness of each layer on the outer
peripheral surface is 1.5 mm (75) for the intermediate layer 5 and
0.5 mm (25) for the outermost layer relative to the total thickness
2.0 mm (relative ratio: 100) of the felt-side resin layer 4.
[0049] After the polyurethane was cured, the drainage gutter 7 of a
width of 1.0 mm and a depth of 1.0 mm was formed using a rotary
cutter on the surface of the polyurethane on the outer peripheral
surface. The layer of the polyurethane cured with DMTDA, which was
the intermediate layer 5, was thus exposed to form the bottom of
the drainage gutter.
(Evaluation of Properties)
[0050] The properties of the obtained sample belt were
measured.
[0051] The method for measuring the properties is as follows.
(1) Cracks
[0052] The device shown in FIG. 4 was used for the measurement. The
both ends of the test piece 31 were sandwiched by the cramp hands
32 and 32, which were designed to interlock right and left in
reciprocating motion. The tension applied to the test piece 31 was
3 kg/cm and the speed of the reciprocating motion was 40
cm/sec.
[0053] Also, the test piece 31 was sandwiched between the rotary
roller 33 and the press shoe 34 so that the outer peripheral
surface was brought into contact with the rotary roller 33, and
pressed at 36 kg/cm.sup.2 by moving the press shoe toward the
rotary roller.
[0054] The reciprocating motion was repeated onto the test piece
using this device and the number of the reciprocating motion was
counted until cracks were generated at the bottom and its edge of
the test piece 31. Subsequently, the protruding portions located
between drainage gutters on the outer peripheral surface of the
test piece were observed for hair cracks generation.
(2) Abrasion Resistance
[0055] The device shown in FIG. 5 was used for the measurement. In
FIG. 5, the test piece 31 was set under the press board 35 and the
outer peripheral surface on the undersurface (object surface of
measurement) of the test piece 31 was brought into contact with the
rotary roller 36 and subjected to pressing. The friction block 37
was mounted on the outer periphery of the rotary roller 36. The
test piece 31 was subjected to contact friction for 20 minutes
under the conditions of a pressure of 10 kg/cm and a rotation speed
of the rotary roller of 100 m/minute and was measured for the loss
of thickness after the test.
Example 2
[0056] In Example 1, the polyurethane cured with MBOCA was replaced
by ADEKA RESIN EP4100 (bisphenol A type epoxy resin) of a
thermosetting resin, as the resin of the outermost layer, and a
belt sample was prepared similarly to in Example 1. The properties
of the obtained sample belt were measured. The results are also
shown in Table 1.
TABLE-US-00001 TABLE 1 construction of outer properties of
peripheral surface belt intermediate outermost The number hair
layer layer until crack crack abra- curing curing generation
genera- sion resin agent resin agent (.times.10.sup.4) tion (mm)
Exam. poly- DMTDA poly- MBOCA 14~16 slight 0.05 1 urethane urethane
or less Exam. poly- DMTDA bisphenol A type 14~15 slight 0.05 2
urethane epoxy resin or less C. Ex. -- -- poly- DMTDA 14~16 marked
0.2 1 urethane C. Ex. -- -- poly- MBOCA 10~12 marked 0.05 2
urethane or less Exam.: Example C. Ex.: Comparative Example
Comparative Example 1
[0057] A belt sample was prepared similarly to in Example 1 except
that a single layer of only the polyurethane cured with DMTDA used
as the intermediate layer in Example 1 was formed on the outer
peripheral surface. The properties of the obtained belt sample were
measured. The results are also shown in Table 1.
Comparative Example 2
[0058] A belt sample was prepared similarly to in Example 1 except
that a single layer of only the polyurethane cured with MBOCA used
as the outermost layer in Example 1 was formed on the outer
peripheral surface. The properties of the obtained sample belt were
measured. The results are also shown in Table 1.
[0059] As apparent from the results in Table 1, the belt of the
present invention, which the outer peripheral surface has two
layers comprising of the intermediate layer of the polyurethane
cured with DMTDA and the outermost layer of the polyurethane cured
with MBOCA, has the improved and balanced crack resistance,
abrasion resistance and hair crack resistance.
[0060] In contrast, the belt of Comparative Example 1, which the
outer peripheral surface has a single layer of the polyurethane
cured with DMTDA, has insufficient abrasion resistance and hair
crack resistance although having good crack resistance, whereas the
belt of Comparative Example 2, which the outer peripheral surface
has a single layer of the polyurethane cured with MBOCA, is
inferior in crack resistance and has insufficient hair crack
resistance although having good abrasion resistance.
INDUSTRIAL APPLICABILITY
[0061] The present invention provides a belt for a papermaking
machine superior in crack resistance, abrasion resistance, hair
crack resistance and the like to a conventional belt having
polyurethane on the outer peripheral surface constituted by a
single layer. The improved durability of the belt of the present
invention is expected to increase productivity in a papermaking
process leading to quality improvement and cost reduction of the
product.
BRIEF DESCRIPTION OF THE DRAWINGS
[0062] FIG. 1 Cross-sectional view showing the construction of the
belt for a papermaking machine of the present invention
[0063] FIG. 2 Manufacturing step of the belt for a papermaking
machine of the present invention
[0064] FIG. 3 Manufacturing step of the belt for a papermaking
machine of the present invention
[0065] FIG. 4 Test device of crack resistance
[0066] FIG. 5 Test device of abrasion resistance
DESCRIPTION OF REFERENCE NUMERALS
[0067] 1 Belt [0068] 2 Substrate [0069] 3 Shoe-side resin layer
[0070] 4 Felt-side resin layer [0071] 5 Intermediate layer [0072] 6
Outermost layer [0073] 7 Drainage gutter [0074] 8 Bottom of
drainage gutter [0075] 9 Boundary surface between intermediate
layer and outermost layer [0076] 20, 21 Roller [0077] 22
Resin-coating nozzle [0078] 23 Heat source [0079] 31 Test piece
[0080] 32 Cramp hand [0081] 33 Rotary roller [0082] 34 Press shoe
[0083] 35 Press board [0084] 36 Rotary roller [0085] 37 Friction
block
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