Shoe press belt
A shoe press belt, and a method for manufacturing and using it. The press belt comprises a base formed of heat-resistant elastomer, inside which base there is a support structure comprising a plurality of support yarns. At least some of the support yarns are heat-resistant polymer yarns, the polymer structure of the material of which comprises a naphthalene group.
1. A shoe press belt which is an independent piece with a shape of an endless loop, runnable in a shoe press through a long nip between at least one roll and a press shoe, the shoe press belt comprising:
a base which is of an elastomeric heat-resistant material;
a plurality of polymeric support yarns arranged in at least one yarn layer inside the base; and
a first surface on the side of the press shoe, and a second surface on the side of a fibre web,
wherein at least some of the support yarns are heat-resistant polymer yarns, the polymer structure of the material of which comprises a naphthalene group,
wherein the structure of said heat-resistant polymer yarn comprises completely aromatic liquid crystalline polymer, the completely aromatic liquid crystalline polymer being poly(4-hydroxybenzoic acid-co-6-hydroxy-2-naphthoic acid) and the glass transition temperature Tg of said polymer material is at least 110° C.,
wherein the shoe press belt is impermeable, and
wherein the force required for a 2-% stretch of said heat-resistant polymer yarn is at least 10 cN/tex, 20° C.
2. The shoe press belt as claimed in claim 1 , wherein the force required for a 2-% stretch of the yarn being at least 100 cN/tex.
3. The shoe press belt as claimed in claim 1 , wherein
at least the support yarns of the yarn layer closest to the first surface on the side of the press shoe are heat-resistant yarns.
4. The shoe press belt as claimed in claim 1 , wherein
the press belt comprises at least one machine-direction yarn layer and at least one cross-machine-direction yarn layer; and
at least the support yarns of the machine-direction yarn layer closest to the first surface on the side of the press shoe are disclosed heat-resistant yarns.
5. The shoe press belt as claimed in claim 1 , wherein
the base comprises heat-resistant polyurethane polymer.
6. The shoe press belt as claimed in claim 1 , wherein
the base comprises heat-resistant polyurethane polymer, and
the polyurethane polymer is made of urethane prepolymer containing isocyanate groups and of a chain extender mixture, whereby 1,4-phenylene diisocyanate is used for making the urethane prepolymer, and the chain extender mixture comprises over 25% by weight methyl-bis(3-chloro-2,6-diethylaniline).