U.S. patent application number 13/541907 was filed with the patent office on 2013-08-01 for paper making shoe press belt.
This patent application is currently assigned to ICHIKAWA CO., LTD.. The applicant listed for this patent is Yuya TAKAMORI, Shintaro YAMAZAKI, Takao YAZAKI. Invention is credited to Yuya TAKAMORI, Shintaro YAMAZAKI, Takao YAZAKI.
Application Number | 20130192787 13/541907 |
Document ID | / |
Family ID | 47715822 |
Filed Date | 2013-08-01 |
United States Patent
Application |
20130192787 |
Kind Code |
A1 |
YAZAKI; Takao ; et
al. |
August 1, 2013 |
PAPER MAKING SHOE PRESS BELT
Abstract
A paper making shoe press belt includes a reinforcing fiber
substrate and a polyurethane laminate. The reinforcing fiber
substrate is embedded in at least one layer of the polyurethane
laminate. At least one layer of the polyurethane laminate includes
a polyurethane obtained by heat-curing a urethane prepolymer
together with a mixed curing agent. The urethane prepolymer
includes a terminal isocyanate group and is obtained by reacting a
diisocyanate compound and a long-chain polyol. The diisocyanate
compound includes at least one of toluene-diisocyanate,
diphenylmethane-diisocyanate, and paraphenylene-diisocyanate. The
mixed curing agent includes 70-99.5 mol % of
dimethylthiotoluenediamine and 0.5-30 mol % of a curing agent. The
curing agent includes at least one of
4,4'-methylenebis(2,6-diethyl-3-chloroaniline),
4,4'-methylenedianiline, and 1,4-butanediol. An equivalent ratio of
active hydrogen groups of the mixed curing agent to isocyanate
groups of the urethane prepolymer is from 1.02 to 1.15.
Inventors: |
YAZAKI; Takao; (Tokyo-to,
JP) ; YAMAZAKI; Shintaro; (Tokyo-to, JP) ;
TAKAMORI; Yuya; (Tokyo-to, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
YAZAKI; Takao
YAMAZAKI; Shintaro
TAKAMORI; Yuya |
Tokyo-to
Tokyo-to
Tokyo-to |
|
JP
JP
JP |
|
|
Assignee: |
ICHIKAWA CO., LTD.
Tokyo-to
JP
|
Family ID: |
47715822 |
Appl. No.: |
13/541907 |
Filed: |
July 5, 2012 |
Current U.S.
Class: |
162/358.4 |
Current CPC
Class: |
D21F 3/0227
20130101 |
Class at
Publication: |
162/358.4 |
International
Class: |
D21F 1/00 20060101
D21F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 1, 2012 |
JP |
2012-020045 |
Claims
1. A paper making shoe press belt, comprising: a reinforcing fiber
substrate; and a polyurethane laminate; wherein: the reinforcing
fiber substrate is embedded in at least one layer of the
polyurethane laminate; at least one layer of the polyurethane
laminate comprises a polyurethane obtained by heat-curing a
urethane prepolymer (A) together with a mixed curing agent (B); the
urethane prepolymer (A) comprises a terminal isocyanate group; the
urethane prepolymer (A) is obtained by reacting a diisocyanate
compound (a) and a long-chain polyol (b); the diisocyanate compound
(a) comprises at least one member selected from the group
consisting of toluene-diisocyanate (TDI),
diphenylmethane-diisocyanate (MDI), and paraphenylene-diisocyanate
(PPDI); the mixed curing agent (B) comprises 70-99.5 mol % of
dimethylthiotoluenediamine (c) and 0.5-30 mol % of a curing agent
(d); the curing agent (d) comprises at least one member selected
from the group consisting of
4,4'-methylenebis(2,6-diethyl-3-chloroaniline),
4,4'-methylenedianiline, and 1,4-butanediol; and an equivalent
ratio of active hydrogen groups of the mixed curing agent (B) to
isocyanate groups of the urethane prepolymer (A) ((--H)/(--NCO)) is
from 1.02 to 1.15.
2. The paper making shoe press belt of claim 1, wherein the
polyurethane laminate comprises an inner peripheral polyurethane
layer and an outer peripheral polyurethane layer.
3. The paper making shoe press belt of claim 2, wherein the inner
peripheral polyurethane layer comprises the polyurethane obtained
by heat-curing the urethane prepolymer (A) together with the mixed
curing agent (B).
4. The paper making shoe press belt of claim 3, wherein the outer
peripheral polyurethane layer has a surface comprising grooves.
5. The paper making shoe press belt of claim 3, wherein both the
inner peripheral polyurethane layer and the outer peripheral
polyurethane layer comprise the polyurethane obtained by
heat-curing the urethane prepolymer (A) together with the mixed
curing agent (B).
6. The paper making shoe press belt of claim 5, wherein the outer
peripheral polyurethane layer has a surface comprising grooves.
7. The paper making shoe press belt of claim 2, wherein the outer
peripheral polyurethane layer comprises the polyurethane obtained
by heat-curing the urethane prepolymer (A) together with the mixed
curing agent (B).
8. The paper making shoe press belt of claim 7, wherein the outer
peripheral polyurethane layer has a surface comprising grooves.
9. The paper making shoe press belt of claim 2, wherein the
reinforcing fiber substrate is embedded in both the inner
peripheral polyurethane layer and the outer peripheral polyurethane
layer.
10. The paper making shoe press belt of claim 2, further comprising
an intermediate polyurethane layer between the inner peripheral
polyurethane layer and the outer peripheral polyurethane layer.
11. The paper making shoe press belt of claim 10, wherein the
reinforcing fiber substrate is embedded in the intermediate
polyurethane layer.
12. The paper making shoe press belt of claim 1, wherein the
diisocyanate compound (a) comprises toluene-diisocyanate (TDI).
13. The paper making shoe press belt of claim 1, wherein the
diisocyanate compound (a) comprises diphenylmethane-diisocyanate
(MDI).
14. The paper making shoe press belt of claim 1, wherein the
diisocyanate compound (a) comprises paraphenylene-diisocyanate
(PPDI).
15. The paper making shoe press belt of claim 1, wherein the curing
agent (d) comprises
4,4'-methylenebis(2,6-diethyl-3-chloroaniline).
16. The paper making shoe press belt of claim 1, wherein the curing
agent (d) comprises 4,4'-methylenedianiline.
17. The paper making shoe press belt of claim 1, wherein the curing
agent (d) comprises 1,4-butanediol.
18. The paper making shoe press belt of claim 1, wherein an
equivalent ratio of active hydrogen groups of the mixed curing
agent (B) to isocyanate groups of the urethane prepolymer (A) is
from 1.05 to 1.12.
19. The paper making shoe press belt of claim 1, wherein an
equivalent ratio of active hydrogen groups of the mixed curing
agent (B) to isocyanate groups of the urethane prepolymer (A) is
from 1.02 to 1.10.
20. The paper making shoe press belt of claim 1, wherein an
equivalent ratio of active hydrogen groups of the mixed curing
agent (B) to isocyanate groups of the urethane prepolymer (A) is
from 1.10 to 1.15.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Japanese Patent
Application No. 2012-020045, filed Feb. 1, 2012, the disclosure of
which is incorporated herein by reference in its entirety.
BACKGROUND
[0002] In a paper making shoe press device, dehydration is
performed by passing a transportation felt 3 and a wet web 4
through a press section formed of a press roll 1 and a shoe 5 using
a shoe press mechanism in which a loop-like shoe press belt 2 is
provided between the press roll 1 and the shoe 5, as shown, for
example, in FIG. 3.
[0003] As shown, for example, in FIG. 1, the shoe press belt 2
includes a outer peripheral polyurethane layer 21 and a inner
peripheral polyurethane layer 22 provided on both surfaces of a
reinforcing fiber substrate 6, which is integrated into the
polyurethane layers. A large number of concave grooves 24 are
formed in the press roll side surface of the outer peripheral
polyurethane layer 21. Water squeezed from a wet web 4 during
pressing is held in the concave grooves 24, and the held water is
further transferred to the outside of the press section by the
rotation of the belt. Therefore, it is desired that the concave
grooves 24 formed in the press roll side surface of the outer
peripheral polyurethane layer 21 should have improved shape
retention properties when pressurized by a press roll 1 and the
shoe 5. It is further desired that a convex part 25 of the press
roll side surface of the outer peripheral polyurethane layer 21 be
improved in mechanical properties such as cracking resistance,
resistance to fatigue from flexing, and wear resistance against
vertical pressing force by the press roll 1, the friction of the
shoe press belt in a shoe press region, and fatigue from
flexing.
[0004] Polyurethanes that exhibit excellent cracking resistance and
wear resistance are widely used as resin materials to form the
outer peripheral polyurethane layer 21 of the shoe press belt
2.
[0005] For example, JP-A-11-247086 discloses a shoe press belt
including an outer peripheral polyurethane layer and an inner
peripheral polyurethane layer provided on both surfaces of a
reinforcing fiber substrate, which is integrated into the
polyurethane layers. The polyurethane of the outer peripheral layer
and inner peripheral layer is obtained by heat-curing a urethane
prepolymer having a terminal isocyanate group (TAKENATE L2395
manufactured by Takeda Pharmaceutical Company Limited), obtained by
reacting toluene-diisocyanate (TDI) with polytetramethylene glycol
(PTMG), and 3,3'-dichloro-4,4'-diaminodiphenylmethane (which is a
compound commercially available as MBOCA and MOCA and also known as
4,4'-methylene bis-orthochloroaniline or 4,4'-methylene
bis-(2-chloroaniline)) as a curing agent (chain extender).
[0006] JP-B-3698984, U.S. Pat. No. 7,374,641, EP 0 855 414,
JP-B-3803106, and U.S. Pat. No. 7,090,747 disclose a shoe press
belt including an outer peripheral polyurethane layer and an inner
peripheral polyurethane layer provided on both surfaces of a
reinforcing fiber substrate, which is integrated into the
polyurethane layers. The polyurethane of the outer peripheral layer
is obtained by heat-curing a urethane prepolymer having a terminal
isocyanate group (HIPREN L manufactured by Mitsui Chemicals, Inc.),
obtained by reacting toluene-diisocyanate (TDI) with
polytetramethylene glycol (PTMG), and dimethylthiotoluenediamine
(ETHACURE 300).
[0007] Dimethylthiotoluenediamine is used instead of
3,3'-dichloro-4,4'-diaminodiphenylmethane as a curing agent in
JP-B-3698984, U.S. Pat. No. 7,374,641, EP 0 855 414, JP-B-3803106,
and U.S. Pat. No. 7,090,747 because: (i) JP-A-7-292237 points out
the toxicity of 4,4'-methylenebis-(2-chloroaniline) and recommends
use of diethyltolylenediamine as a curing agent (see paragraph
[0006]), (ii) the journal "Polyfile," January 1999, pp. 37-38,
"ETHACURE 300: New Curing Agent as Substitute for MOCA" describes
that ETHACURE 300 has excellent low-temperature curability
equivalent to that of MOCA and lower toxicity than MOCA, and thus
is used as a substitute for MOCA; and (iii) the journal "POLYMER,"
vol. 36, 1995, pp. 767-774, "The effect of curative on the fracture
toughness of PTMEG/TDI polyurethane elastomers" recommends ETHACURE
300 as a substitute for MOCA as a curing agent for a TDI/PTMG-based
urethane prepolymer because a polyurethane cured with ETHACURE 300
is superior in low-temperature curability and crack growth
inhibiting effect to a polyurethane cured with MOCA (see FIG. 7 and
column "Conclusion").
[0008] JP-A-10-212333 describes both
4,4'-methylenebis-(2-chloroaniline) and dimethylthiotoluenediamine
as curing agents for a polyurethane constituting a belt.
[0009] "POLYMER," vol. 36, 1995, pp. 767-774, "The effect of
curative on the fracture toughness of PTMEG/TDI polyurethane
elastomers" indicates, in the results of the crack occurrence
resistance test shown in FIG. 7, that "a polyurethane using MOCA
has a higher initial tear strength energy than that of a
polyurethane using Ethacure 300 but ruptures at this strength
whereas the polyurethane using Ethacure 300 has a lower initial
crack occurrence tear strength energy than that of the polyurethane
using MOCA but does not lead to rupture although experiencing
increased occurrence of small cracks for a short time as understood
from the results of a subsequent repeated crack test." Results
similar to those described above would be expected for a crack
occurrence resistance test performed on a shoe press belt having
grooves on a surface as shown in the drawings of JP-A-11-247086. In
a crack occurrence resistance test performed on a shoe press belt
that does not have grooves, a polyurethane prepared using ETHACURE
300 would be expected to have a lower crack occurrence strength
energy than that of a polyurethane prepared using MOCA.
SUMMARY
[0010] In embodiments, the present invention is directed to a paper
making shoe press belt (also referred to as a shoe press belt) used
in a paper making shoe press device. In particular embodiments, the
present invention is directed to a shoe press belt used in a closed
type shoe press. Exemplary shoe press belts according to the
present invention are excellent in cracking resistance. Exemplary
shoe press belts according to the present invention include a
reinforcing fiber substrate embedded in one or more adjacent
polyurethane layers formed from a urethane prepolymer having
specific composition that is heat-cured with a mixed chain
extender.
[0011] Exemplary shoe press belts according to the present
invention exhibit excellent results in a crack occurrence
resistance test whether the belts include or do not include grooves
in an outermost surface. Exemplary shoe press belts according to
the present invention may be prepared using both ETHACURE 300 as a
main component and another curing agent having excellent
low-temperature curability as a subcomponent, as curing agents
employed to completely cure a urethane prepolymer.
[0012] In exemplary embodiments of the present invention a paper
making shoe press belt includes a reinforcing fiber substrate and a
polyurethane laminate. In a preferred embodiment, the polyurethane
laminate is integrally constituted. The reinforcing fiber substrate
is embedded in at least one layer of the polyurethane laminate. At
least one layer of the polyurethane laminate includes a
polyurethane obtained by heat-curing a urethane prepolymer (A)
together with a mixed curing agent (B). The urethane prepolymer (A)
includes a terminal isocyanate group. The urethane prepolymer (A)
is obtained by reacting a diisocyanate compound (a) and a
long-chain polyol (b). The diisocyanate compound (a) includes at
least one of toluene-diisocyanate (TDI),
diphenylmethane-diisocyanate (MDI), and paraphenylene-diisocyanate
(PPDI). The mixed curing agent (B) includes 70-99.5 mol % of
dimethylthiotoluenediamine (c) and 0.5-30 mol % of a curing agent
(d). The curing agent (d) includes at least one of
4,4'-methylenebis(2,6-diethyl-3-chloroaniline),
4,4'-methylenedianiline, and 1,4-butanediol. An equivalent ratio of
active hydrogen groups of the mixed curing agent (B) to isocyanate
groups of the urethane prepolymer (A) ((--H)/(--NCO)) is from 1.02
to 1.15.
[0013] In one embodiment of the present invention, a paper making
shoe press belt is formed of a polyurethane, wherein a reinforcing
fiber substrate is integrated with polyurethane layers and the
reinforcing fiber substrate is buried in the polyurethane, wherein
the polyurethane is obtained by heat-curing
[0014] a urethane prepolymer (A) having a terminal isocyanate group
obtained by reacting [0015] a diisocyanate compound (a) selected
from toluene-diisocyanate (TDI), [0016]
diphenylmethane-diisocyanate (MDI), and paraphenylene-diisocyanate
(PPDI) with [0017] a long-chain polyol (b), and
[0018] a mixed curing agent (B) comprising [0019] 70-99.5 mol % of
dimethylthiotoluenediamine (c) and [0020] 0.5-30 mol % of a curing
agent (d) selected from
4,4'-methylenebis(2,6-diethyl-3-chloroaniline),
4,4'-methylenedianiline, and 1,4-butanediol, and
[0021] wherein the equivalent ratio (--H/--NCO) of an active
hydrogen group (--H) of the mixed curing agent to the isocyanate
group (--NCO) of the urethane prepolymer (A) is 1.02-1.15.
[0022] In embodiments of the shoe press belt according to the
present invention, because an outer peripheral polyurethane layer
of the shoe press belt facing a wet web side is formed from a
polyurethane that is completely cured with a mixed curing agent,
the shoe press belt exhibits improved results in a crack occurrence
resistance test.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] A more complete appreciation of the invention and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings, wherein:
[0024] FIG. 1 is a cross-sectional view of an exemplary shoe press
belt;
[0025] FIG. 2 is a cross-sectional view of an exemplary shoe press
belt;
[0026] FIG. 3 is a cross-sectional view of an exemplary shoe press
device;
[0027] FIG. 4 is a schematic depiction of a test for crack
propagation properties using a De Mattia flex tester; and
[0028] FIG. 5 is a schematic depiction of a test for measuring
crack occurrence in a shoe press belt.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0029] Referring now to the drawings, wherein like reference
numerals designate identical or corresponding parts throughout the
several views, exemplary embodiments of the present invention will
be described in more detail. The present invention is not limited
to the exemplary embodiments shown in the drawings.
[0030] FIG. 1 is a cross-sectional view of an exemplary shoe press
belt 1 according to the present invention, in which a reinforcing
fiber substrate 6 is integrated with a polyurethane in an outer
peripheral layer 21 and an inner peripheral layer 22. The
reinforcing fiber substrate 6 is embedded in the polyurethane, and
grooves 24 are formed in the outer peripheral polyurethane layer
21.
[0031] FIG. 2 illustrates an alternative exemplary embodiment of
the present invention, in which grooves 24 are not formed in an
outer peripheral polyurethane layer. FIG. 2(a) shows a
configuration in which a reinforcing fiber substrate 6 is embedded
at the interface of an outer peripheral polyurethane layer 2a and
an inner peripheral polyurethane layer 2b, the layers being of like
composition. FIG. 2(b) shows a configuration in which a reinforcing
fiber substrate 6 is embedded at the interface of an outer
peripheral polyurethane layer 2a and an inner peripheral
polyurethane layer 2b, the layers being of different composition.
FIG. 2(c) shows a configuration in which a reinforcing fiber
substrate 6 is embedded in an intermediate polyurethane layer 2c
provided between an outer peripheral polyurethane layer 2a and an
inner peripheral polyurethane layer 2b.
[0032] FIG. 3 is a simplified diagram of a shoe press mechanism in
a paper making machine. In the figure, reference numeral 2 denotes
a shoe press belt, reference numeral 4 denotes a wet web, reference
numeral 3 denotes a paper-making felt, reference numeral 1 denotes
a press roll, and reference numeral 5 denotes a shoe.
[0033] FIG. 4 is an explanatory drawing showing conduct of a test
for crack propagation properties of a polyurethane test piece 61
using a De Mattia flex tester.
[0034] FIG. 5 is an explanatory drawing of a tester 42 for
measuring crack occurrence in a shoe press belt 41.
[0035] In various exemplary embodiments, the reinforcing fiber
substrate 6 may be a woven fabric as described in JP-A-11-247086,
U.S. Pat. No. 7,374,641, or EP 0 855 414, or alternative
reinforcing fiber substrates described in other documents. For
example, the reinforcing fiber substrate 6 may be a grid-like
material in which 5000 dtex multifilament twisted yarns of
polyethylene terephthalate (PET) fibers are used as warp and weft,
the warp is sandwiched in the weft, and the intersections between
the weft and the warp are bonded by polyurethane adhesion. As fiber
materials, polyamide fibers such as fibers of aramid, nylon 6,6,
nylon 6,10, and nylon 6 may be used instead of polyethylene
terephthalate fibers. Further, fibers made of different materials
may be used for the warp and the weft, or warp and weft having
different thicknesses like 5000 dtex and 7000 dtex may be used.
[0036] In various exemplary embodiments, the polyurethane that
forms the outer peripheral polyurethane layer 21 of the shoe press
belt is a polyurethane with a JIS-A hardness of 90 to 99,
preferably 94 to 97, obtained by heat-curing a urethane prepolymer
(A) having a terminal isocyanate group, obtained by reacting (a) a
diisocyanate compound selected from toluene-diisocyanate (TDI),
diphenylmethane-diisocyanate (MDI), and paraphenylene-diisocyanate
(PPDI) with (b) a long-chain polyol, and a mixed curing agent (B)
comprising (c) 70-99.5 mol % of dimethylthiotoluenediamine and (d)
0.5-30 mol % of a curing agent selected from
4,4'-methylenebis(2,6-diethyl-3-chloroaniline),
4,4'-methylenedianiline, and 1,4-butanediol, wherein the equivalent
ratio (--H/--NCO) of active hydrogen groups (--H) of the mixed
curing agent to isocyanate groups (--NCO) of the urethane
prepolymer (A) is 1.02-1.15.
[0037] In various exemplary embodiments, the polyurethane that
forms the inner peripheral polyurethane layer 22 of the shoe press
belt may be identical to the polyurethane that forms the outer
peripheral polyurethane layer 21 or may be a polyurethane having
different composition.
[0038] In various exemplary embodiments, the long-chain polyol
which is the raw material of the urethane prepolymer (A), may
include one or two or more polyol compounds selected from polyether
polyols, polyester polyols, polycaprolactone polyols, and
polycarbonate polyols. In some such embodiments, polytetramethylene
glycol (PTMG), polyethylene glycol (PEG), an addition product of
ethylene oxide with propylene oxide, propylene glycol (PPG), and/or
the like may be used.
[0039] In various exemplary embodiments, the shoe press belt is
manufactured by a method in which a mandrel surface coated with a
mold release agent is coated and impregnated with a mixture of a
urethane prepolymer and a mixed curing agent for forming an inner
peripheral polyurethane layer while rotating the mandrel so that
the inner peripheral polyurethane layer is formed to a thickness of
0.8-3.5 mm on a mandrel surface. The resulting layer is pre-cured
at 85-125.degree. C. for 0.5-1 hour. A reinforcing fiber substrate
is wound therearound and a mixture of a urethane prepolymer and a
curing agent for forming an intermediate layer is then coated to a
thickness of 0.5-2 mm. The reinforcing fiber substrate is
impregnated with the mixture which also adheres to the inner
peripheral polyurethane layer, and the resulting layer is pre-cured
at 50-120.degree. C. for 0.5-1 hour. Thereafter, the surface of the
reinforcing fiber substrate is coated and impregnated with a
mixture of a urethane prepolymer and a curing agent for forming an
outer peripheral polyurethane layer while rotating the mandrel so
that the outer peripheral polyurethane layer is formed to a
thickness of 1.5-4 mm. The resulting structure is cured at
100-130.degree. C. for 2-20 hours. Thereafter, grooves as
illustrated in FIG. 1 are carved into the outer peripheral
polyurethane layer. The grooves may be carved into the outer
peripheral polyurethane layer by bringing a heated emboss roll
having a surface with protrusions having heights of groove depths
into pressure contact with the outer peripheral polyurethane layer
during curing of the outer peripheral polyurethane layer. The
mandrel includes a heating apparatus.
[0040] In alternative embodiments, the shoe press belt is
manufactured by a method in which a mandrel surface coated with a
mold release agent is coated with a mixture of a urethane
prepolymer and a mixed curing agent for forming an inner peripheral
polyurethane layer so that the inner peripheral polyurethane layer
is formed to a thickness of 0.8-3 mm. The resulting layer is
pre-cured at 70-130.degree. C. for 0.5-2 hours. A reinforcing fiber
substrate is then wound around the external surface of the inner
peripheral polyurethane layer and a mixture of a urethane
prepolymer and a curing agent for forming an intermediate layer is
coated to a thickness of 0.5-2 mm. The reinforcing fiber substrate
is impregnated with the mixture, which also adheres to the inner
peripheral polyurethane layer. The resulting layer is pre-cured at
50-120.degree. C. for 0.5-1 hour. A mixture of a urethane
prepolymer and a mixed curing agent for forming an outer peripheral
polyurethane layer is coated so that the outer peripheral
polyurethane layer has a thickness of 2-4 mm. The resulting
structure is cured at 70-130.degree. C. for 12-20 hours. Grooves
are cut and processed in the outer peripheral polyurethane layer
with a cutting tool, and the outer peripheral polyurethane layer is
polished with sandpaper or a polyurethane abrasive cloth.
[0041] In alternative embodiments, the shoe press belt is
manufactured by a method in which a mandrel surface coated with a
mold release agent is coated with a mixture of a urethane
prepolymer and a curing agent for forming an inner peripheral
polyurethane layer so that the inner peripheral polyurethane layer
is formed to a thickness of 0.8-3 mm. The resulting layer is
pre-cured at 50-140.degree. C. for 0.5-2 hours. An intermediate
polyurethane layer having a thickness of 1-2 mm in which a
reinforcing fiber substrate is embedded (produced beforehand) is
wound around the outer surface of the inner peripheral polyurethane
layer. The intermediate layer is pressed by a nip roll heated to
50-140.degree. C. A mixture of a urethane prepolymer and a mixed
curing agent for forming an outer peripheral polyurethane layer is
further coated so that the outer peripheral polyurethane layer is
formed to a thickness of 2-4 mm. The resulting structure is cured
at 70-140.degree. C. for 2-20 hours. The outer peripheral
polyurethane layer is polished with sandpaper or a polyurethane
abrasive cloth. Grooves are cut and processed in the polished outer
peripheral polyurethane layer with a cutting tool.
[0042] In alternative embodiments, the shoe press belt is
manufactured by a method using two rolls instead of a mandrel. For
example, an endless reinforcing fiber substrate is extended between
two rolls. The surface of the reinforcing fiber substrate is coated
with a mixture of a urethane prepolymer and a curing agent. The
reinforcing fiber substrate is impregnated with the mixture and the
resulting structure is pre-cured at 50-120.degree. C. for 0.5-2
hours. A mixture of a urethane prepolymer and a mixed curing agent
for forming an inner peripheral polyurethane layer is coated onto
the reinforcing fiber substrate so that the inner peripheral
polyurethane layer is formed to a thickness of 0.5-3 mm. The
resulting structure is pre-cured at 70-140.degree. C. for 2-12
hours. A surface of the inner peripheral polyurethane layer is
polished with sandpaper or an abrasive cloth. The semifinished
product is reversed, hung on the two rolls, and extended. The
surface of the extended semifinished product is coated with a
mixture of a urethane prepolymer and a mixed curing agent for
forming an outer peripheral polyurethane layer to impregnate the
reinforcing fiber substrate. The surface of the extended
semifinished product is further coated with the mixture so that the
outer peripheral polyurethane layer is formed to a thickness of
1.5-4 mm. The resulting structure is cured at 70-140.degree. C. for
2-20 hours. After curing, the outer peripheral polyurethane layer
is polished to a predetermined thickness, and grooves are cut and
processed in the outer peripheral polyurethane layer with a cutting
tool.
EXAMPLES
[0043] In the following examples, and throughout this
specification, all parts and percentages are by weight, and all
temperatures are in degrees Celsius, unless expressly stated to be
otherwise. Where the solids content of a dispersion or solution is
reported, it expresses the weight of solids based on the total
weight of the dispersion or solution, respectively. Where a
molecular weight is specified, it is the molecular weight range
ascribed to the product by the commercial supplier, which is
identified. Generally this is believed to be weight average
molecular weight.
[0044] In order to evaluate the physical properties of polyurethane
that forms a shoe press belt, polyurethane test pieces were
produced as described below.
Reference Example 1
Example 1
[0045] A urethane prepolymer (percentage of NCO: 6.02%, viscosity
at 80.degree. C.: 400 cps, preheat temperature: 66.degree. C.)
obtained by reacting toluene-diisocyanate (TDI) with
polytetramethylene glycol (PTMG) and a mixed curing agent
consisting of 90 mol % of dimethylthiotoluenediamine (ETHACURE 300)
and 10 mol % of 1,4-butanediol (H/NCO ratio of the mixed curing
agent to the urethane prepolymer would be 1.05) were poured into a
preheated die, heated to 100.degree. C., precured at 100.degree. C.
for 0.5 hour, then removed from the die, and post-cured at
100.degree. C. for 16 hours to obtain a polyurethane sheet. A test
piece (thickness of 3.5 mm) was produced from the sheet.
Reference Example 8
Comparative Example 1
[0046] A urethane prepolymer (percentage of NCO: 6.02%, viscosity
at 80.degree. C.: 400 cps, preheat temperature: 66.degree. C.)
obtained by reacting toluene-diisocyanate (TDI) with
polytetramethylene glycol (PTMG) and a curing agent composed of
dimethylthiotoluenediamine (ETHACURE 300) (H/NCO ratio of the mixed
curing agent to the urethane prepolymer would be 0.95) were poured
into a preheated die, heated to 100.degree. C., precured at
100.degree. C. for 0.5 hour, then removed from the die, and
post-cured at 100.degree. C. for 16 hours to obtain a polyurethane
sheet. A test piece (thickness of 3.5 mm) was produced from the
sheet.
Reference Examples 2-7 (Examples 2-7) and Reference Examples 9-13
(Comparative Examples 2-6)
[0047] Polyurethane sheets were obtained in the same manner as in
Reference Example 1 except that urethane prepolymers listed in
TABLE 1 and TABLE 2 as urethane prepolymers and curing agents
listed in TABLE 1 and TABLE 2 as curing agents were used at H/NCO
ratios listed in the tables and under preheating and curing
conditions listed in the tables. Test pieces (thicknesses of 3.5
mm) were produced from the sheets.
[0048] The curing agents listed in TABLE 1 and TABLE 2 are
dimethylthiotoluenediamine (ETHACURE 300),
4,4'-methylenebis(2,6-diethyl-3-chloroaniline) (LONZACURE MCDEA),
4,4'-methylenedianiline (CAYTUR 31DA), 1,4-butanediol (1,4-BD), and
4,4'-methylenebis-(2-chloroaniline) (MOCA). CAYTUR 31DA is a
complex of 4,4'-methylenedianiline and sodium chloride dispersed in
dioctyl adipate (DOA).
[0049] The polyurethane sheet test pieces obtained in Examples 1-13
were subjected to a De Mattia flex test. In the flex test, a test
for crack propagation properties was conducted using a tester,
illustrated in FIG. 4, similar to that in the De Mattia flex test
defined in JIS-K-6260 (2005) under an atmosphere at 20.degree. C.
and a relative humidity of 52% under the following conditions. The
test piece 61 had a width of 25 mm, a length of 185 mm (including
one side of tong hold of 20 mm), a length of 150 mm between
grippers 62, a thickness of 3.4 mm, and a semicircular dimple 61a
having a radius of 1.5 mm in a center. In reciprocating motion, the
maximum distance between the grippers was 100 mm, the minimum
distance was 35 mm, a motion distance was 65 mm, and a
reciprocation speed was 360 reciprocations/min. A slit having a
length of about 2 mm was notched in the center of the test piece in
a width direction. The right and left grippers were set to be at
angles of 45.degree. with respect to a reciprocation direction,
respectively. Flexing was repeated under the foregoing conditions
and crack length was measured after predetermined increments of
strokes. The number of strokes as used herein was a value obtained
by multiplying test time by reciprocation speed. The test was
finished when the crack length exceeded 15 mm from a measurement
value of an early notch length (about 2 mm), an approximate curve
of the number of strokes and the crack length was drawn, the number
of strokes was read when the crack length was 15 mm, and a value
obtained by dividing a growing crack length (15 mm in crack
length-measurement value of early notch length) by the number of
strokes at this time was regarded as a crack propagation property.
The obtained physical properties are summarized in TABLE 1 and
TABLE 2.
TABLE-US-00001 TABLE 1 Reference Reference Reference Reference
Reference Reference Reference Example 1 Example 2 Example 3 Example
4 Example 5 Example 6 Example 7 Example 1 Example 2 Example 3
Example 4 Example 5 Example 6 Example 7 Urethane prepolymer
Isocyanate TDI TDI MDI PPDI/MDI PPDI/TDI TDI/MDI TDI/PPDI 9/1 9/1
5/5 5/5 Polyol PTMG PTMG PTMG PTMG PTMG PTMG PTMG NCO (%) 6.02 6.02
8.85 5.84 5.56 7.44 5.77 Viscosity (cps) 400 400 400 1800 1700 600
500 (@80.degree. C.) (@80.degree. C.) (@100.degree. C.)
(@55.degree. C.) (@55.degree. C.) (@80.degree. C.) (@80.degree. C.)
Preheat temperature (.degree. C.) 66 66 80 80 66 80 66 Curing agent
ETHACURE ETHACURE ETHACURE ETHACURE ETHACURE ETHACURE ETHACURE
(compound name) 300 300 300 300 300 300 300 Equivalent value 107.15
107.15 107.15 107.15 107.15 107.15 107.15 Active hydrogen (mol %)
90 70 85 99.5 70 70 85 Preheat temperature (.degree. C.) 24 24 24
24 24 24 24 Curing agent (compound 1.4-BD CAYTUR31 1.4-BD CAYTUR31
1.4-BD CAYTUR31 MCDEA name) DA DA DA Equivalent value 45.06 250
45.06 250 45.06 250 189.69 Active hydrogen (mol %) 10 30 15 0.5 30
30 15 Preheat temperature (.degree. C.) 24 24 24 24 24 24 100
Equivalent value of 100.94 150.01 97.84 107.86 88.52 150.01 119.53
curing agent Equivalent ratio 1.05 1.15 1.10 1.02 1.12 1.10 1.10
(H/NCO ratio) Blending of curing agent 15.2 24.7 22.7 15.3 13.1
29.2 18.0 (parts) Precuring condition 100/0.5 100/0.5 115/1 127/0.5
127/0.5 115/1 127/0.5 (.degree. C./hr) Post-curing condition 100/16
100/16 115/16 127/16 127/16 115/16 127/16 (.degree. C./hr) Crack
propagation 1.10 0.46 1.10 0.60 0.40 0.63 0.53 property
(.mu.m/time)
TABLE-US-00002 TABLE 2 Reference Reference Reference Reference
Reference Reference Example 8 Example 9 Example 10 Example 11
Example 12 Example 13 Comparative Comparative Comparative
Comparative Comparative Comparative Example 1 Example 2 Example 3
Example 4 Example 5 Example 6 Urethane prepolymer Isocyanate TDI
TDI TDI TDI MDI TDI/MDI 5/5 Polyol PTMG PTMG PTMG PTMG PTMG PTMG
NCO (%) 6.02 6.02 6.02 6.02 8.85 7.44 Viscosity (cps) 400 400 400
400 400 600 (@80.degree. C.) (@80.degree. C.) (@80.degree. C.)
(@80.degree. C.) (@100.degree. C.) (@80.degree. C.) Preheat
temperature (.degree. C.) 66 66 66 66 80 80 Curing agent ETHACURE
ETHACURE MOCA MOCA ETHACURE ETHACURE (compound name) 300 300 300
300 Equivalent value 107.15 107.15 133.6 133.6 107.15 107.15 Active
hydrogen (mol %) 100 100 100 100 100 100 Preheat temperature
(.degree. C.) 24 24 116 116 24 24 Curing agent (compound name)
Equivalent value Active hydrogen (mol %) Preheat temperature
(.degree. C.) Equivalent value of curing agent 107.15 107.15 133.60
133.60 107.15 107.15 Equivalent ratio 0.95 1.05 0.95 1.05 1.00 0.95
(H/NCO ratio) Blending of curing agent (parts) 14.6 16.1 18.2 20.1
22.6 18.0 Precuring condition 100/0.5 100/0.5 100/0.5 100/0.5 100/1
115/1 (.degree. C./hr) Post-curing condition 100/16 100/16 100/16
100/16 100/14 115/16 (.degree. C./hr) Crack propagation property
6.09 1.53 8.10 2.15 1.41 5.06 (.mu.m/time)
[0050] From TABLE 1 and TABLE 2, it is apparent that the
polyurethanes of the Examples exhibit better crack propagation
resistance than the polyurethanes of the Comparative Examples.
[0051] Shoe press belts were prepared using the polyurethane
compositions described above in the manner described below.
Example 1
[0052] Step 1: A release agent (KS-61: manufactured by Shin-Etsu
Chemical Co., Ltd.) was coated on the surface of a mandrel having a
diameter of 1500 mm and that was rotatable by driving means. Then,
a composition prepared by mixing the urethane prepolymer
(TDI/PTMG-based prepolymer) and the mixed curing agent as specified
in Reference Example 1 was spirally coated onto the rotating
mandrel to a thickness of 1.4 mm using an injection molding nozzle
movable in parallel to the rotation axis of the mandrel, and a
urethane resin layer was formed. The layer was left to stand at
room temperature for 40 minutes while rotating the mandrel, and the
resin was further heated at 115.degree. C. for 0.5 hour by a
heating apparatus attached to the mandrel and precured to produce a
shoe side inner peripheral polyurethane layer.
[0053] Step 2: A grid-like material was prepared using a 5000 dtex
multifilament twisted yarn of polyethylene terephthalate fibers as
weft and a 550 dtex multifilament yarn of polyethylene
terephthalate fibers as warp. The warp was sandwiched in the weft,
and the intersections between the weft and the warp were bonded by
urethane-based resin adhesion (warp density of 1 strand/cm; and
weft density of 4 strands/cm). One layer of the grid-like material
having a plurality of pieces was placed on the outer periphery of
the shoe side layer without any gap so that the weft was along the
axial direction of the mandrel. 6700 dtex multifilament yarn of
polyethylene terephthalate fibers was helically wound around the
outer periphery of the grid-like material at a pitch of 30
strands/5 cm to form a spool layer. Then, the polyurethane
composition was coated to a thickness of about 1.6 mm and
integrated as an intermediate layer to fill the gap between the
grid-like material and the spool layer, and a reinforcing fiber
substrate polyurethane intermediate layer was formed.
[0054] Step 3: A composition prepared by mixing the urethane
prepolymer and the curing agent as specified in Reference Example 1
was impregnated and coated to a thickness of about 2.5 mm on the
intermediate layer by spiral coating, heated at 115.degree. C. for
16 hours, and post-cured to produce an outer peripheral layer. The
surface of the outer peripheral layer was polished to have an
overall thickness of 5.2 mm, and a shoe press belt was obtained by
forming a large number of concave grooves (of 1.0 mm in groove
width, 1.0 mm in depth, and 3.18 mm in pitch width) in the machine
direction of the belt by a rotary blade.
Comparative Example 1
[0055] A shoe press belt was obtained in the same manner as in
Example 1 except that the polyurethane composition used in
Reference Example 6 was used instead of the polyurethane
composition in Reference Example 1 and the curing conditions of
precuring and post-curing were changed to 100.degree. C. for 0.5
hour and 100.degree. C. for 16 hours, respectively.
[Example 2] to [Example 5], [Comparative Example 2] to [Comparative
Example 6]
[0056] Shoe press belts were obtained in the same manner as in
Example 1 except that the urethane prepolymers listed in TABLE 1
and TABLE 2 as urethane prepolymers and the curing agents listed in
TABLE 1 and TABLE 2 as curing agents were used under the preheating
and curing conditions listed in the tables.
[0057] A flexing fatigue test was conducted for the obtained shoe
press belts. The flexing fatigue test was conducted by evaluating
the grooved belt samples. As the flexing fatigue test, a crack
occurrence test was conducted under an atmosphere of 20.degree. C.
and a relative humidity of 52% using the device illustrated in FIG.
5. The test piece 71 had a width of 60 mm and a length between
grippers of 70 mm. By subjecting a lower gripper 42a to
circular-arc reciprocating motion, an upper gripper 42b and the
test piece also reciprocated along a circular-arc path so that the
test piece was flexed to cause fatigue on the top of the lower
gripper. A distance between the center of the circular arc and the
top of the lower gripper was 168 mm, the migration length of the
lower gripper was 161 mm, and a reciprocation speed was 162
reciprocations/min. The weight of the upper gripper was 400 g.
Flexing was repeated under the conditions specified, and the number
of flexings until a crack occurred was measured. All the shoe press
belts according to Examples exhibited the results in which 1
million flexings could be born. The results are listed in TABLE 3
and TABLE 4.
TABLE-US-00003 TABLE 3 Example 1 Example 2 Example 3 Example 4
Example 5 Example 6 Example 7 Number of 100 (not cracked) 100 (not
cracked) 100 (not cracked) 100 (not cracked) 100 (not cracked) 100
(not cracked) 100 (not cracked) flexings (ten thousand times)
TABLE-US-00004 TABLE 4 Comparative Comparative Comparative
Comparative Comparative Comparative Example 1 Example 2 Example 3
Example 4 Example 5 Example 6 Number of flexings 20 80 15 56 50 35
(ten thousand times)
[0058] As is evident from the foregoing results, shoe press belts
according to embodiments of the present invention (e.g., as in the
Examples) are excellent in low-temperature curing properties,
exhibit improved crack occurrence inhibiting effect, and have
excellent practical values in comparison with known shoe press
belts (e.g., as in the Comparative Examples).
[0059] Where a numerical limit or range is stated herein, the
endpoints are included. Also, all values and subranges within a
numerical limit or range are specifically included as if explicitly
written out.
[0060] Obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings. It
is therefore to be understood that, within the scope of the
appended claims, the invention may be practiced otherwise than as
specifically described herein.
[0061] All patents and other references mentioned above are
incorporated in full herein by this reference, the same as if set
forth at length.
* * * * *