Press arrangement and method for pressing a fibrous web
Abstract
A press arrangement and method for pressing a fibrous web include a main press with extended press nip having a length of at least 150 mm. The main press is configured such that, when operated with a line load LL of at least 1,200 kN/m, a line-load ratio LLR of at least 0.69 and at most 1.52 is obtained. The line-load ratio LLR is defined as the quotient of a weighted line load WLL to the line load LL, the weighted line load WLL being the result of integration of the squared local pressure p(x) 2 , weighted with a weighting factor A, over the nip length x, the weighting factor A being one divided by ten megapascal. The line load LL is the result of integration of the local pressure p(x) over the nip length x, such that the following formula for the line-load ratio LLR applies: LLR = WLL LL = ∫ A * p ( x ) 2 dx ∫ p ( x ) dx = ∫ 1 10 MPa * p ( x ) 2 d x ∫ p ( x ) d x
Claims
exact text as granted — not AI-modified1 . A press arrangement for pressing a fibrous web or a packaging paper web, the press arrangement comprising:
a main press having an extended press nip, said press nip having a length of at least 150 mm; said main press configured to obtain a line-load ratio LLR of at least 0.69 and at most 1.52 when operated with a line load LL of at least 1,200 kN/m; said line-load ratio LLR being a quotient of a weighted line load WLL to said line load LL; said weighted line load WLL being a result of an integration of a squared local pressure p(x) 2 , weighted with a weighting factor A over said nip length x, and said weighting factor A being one divided by ten megapascal; said line load LL being a result of an integration of a local pressure p(x) over said nip length x; and a formula being applied for said line-load ratio LLR as follows:
LLR
=
WLL
LL
=
∫
A
*
p
(
x
)
2
dx
∫
p
(
x
)
dx
=
∫
1
10
MPa
*
p
(
x
)
2
d
x
∫
p
(
x
)
d
x
with x being expressed in mm and p being expressed in MPa, and with a pressure in said press nip being constant in a cross-machine direction.
2 . The press arrangement according to claim 1 , wherein said press nip has a length of at least 190 mm.
3 . The press arrangement according to claim 1 , wherein said line-load ratio LLR is at least 0.71 and at most 1.35.
4 . The press arrangement according to claim 1 , wherein said line-load ratio LLR is at least 0.73 and at most 1.14.
5 . The press arrangement according to claim 1 , which further comprises a pre-press located upstream of said main press in a running direction of the fibrous web.
6 . The press arrangement according to claim 5 , wherein said pre-press is located directly upstream of said main press in said running direction of the fibrous web.
7 . The press arrangement according to claim 5 , wherein said pre-press has an extended press nip and is configured to obtain a line-load ratio LLR of said pre-press of less than 0.69.
8 . The press arrangement according to claim 1 , wherein said main press is configured to be operated with a line load LL of at least 1,300 kN/m.
9 . The press arrangement according to claim 1 , wherein said main press is a shoe press including a press shoe with a substantially concave surface and a press jacket or press belt rotatably supported about said press shoe.
10 . The press arrangement according to claim 9 , wherein said press jacket is formed at least partially of polyurethane formed by a reaction of a prepolymer and a crosslinker component, said prepolymer is a reaction product of 1,4-phenylene diisocyanate (PPDI) and a polyol component including at least one of at least one polyether polyol or at least one polycarbonate polyol, and said crosslinker component includes a C2-14 diol.
11 . The press arrangement according to claim 10 , wherein said polyol component of said prepolymer includes polytetramethylene ether glycol (PTMEG) and at least one polycarbonate polyol.
12 . The press arrangement according to claim 10 , wherein said crosslinker component includes at least one of polytetramethylene ether glycol (PTMEG) or at least one polycarbonate polyol.
13 . A machine for producing a fibrous web or a packaging testliner, the machine comprising a press arrangement according to claim 1 .
14 . A method for pressing a fibrous web or a packaging paper web or a packaging testliner, the method comprising:
guiding the fibrous web through a main press having an extended press nip of at least 150 mm in length; operating the main press with a line load LL of at least 1,200 kN/m, the main press configured to obtain a line-load ratio LLR of at least 0.69 and at most 1.52; providing the line-load ratio LLR as a quotient of a weighted line load WLL to the line load LL; the weighted line load WLL being a result of an integration of a squared local pressure p(x) 2 , weighted with a weighting factor A, over the nip length x, and the weighting factor A being one divided by ten megapascal; the line load LL being a result of an integration of a local pressure p(x) over the nip length x; and applying a formula as follows for the line-load ratio LLR:
LLR
=
WLL
LL
=
∫
A
*
p
(
x
)
2
dx
∫
p
(
x
)
dx
=
∫
1
10
MPa
*
p
(
x
)
2
d
x
∫
p
(
x
)
d
x
with x being expressed in mm and p being expressed in MPa, and with a pressure in the press nip being constant in a cross-machine direction.
15 . The method according to claim 14 , which further comprises providing the length of the press nip as at least 190 mm, and operating the main press with the line load LL being at least 1,300 kN/m.
16 . The method according to claim 14 , which further comprises providing the line-load ratio LLR as at least 0.71 and at most 1.35.
17 . The method according to claim 14 , which further comprises providing the line-load ratio LLR as at least 0.73 and at most 1.14.
18 . The method according to claim 14 , which further comprises further guiding the fibrous web through a pre-press located upstream or directly upstream of the main press in a running direction of the fibrous web.
19 . The method according to claim 14 , which further comprises carrying out the method at a speed of at least 1,000 m/min.
20 . The method according to claim 14 , which further comprises carrying out the method at a speed of at least 1,200 m/min.
21 . The method according to claim 14 , which further comprises carrying out the method at a speed of more than 1,400 m/min.
22 . The method according to claim 14 , which further comprises forming the fibrous web of at least 20 wt. % of OCC fibers.
23 . The method according to claim 14 , which further comprises forming the fibrous web of at least 50 wt. % of OCC fibers.Join the waitlist — get patent alerts
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