CA2179172A1

CA2179172A1 - Papermachine clothing

Info

Publication number: CA2179172A1
Application number: CA 2179172
Authority: CA
Inventors: Craig Valentine; Ian Christison Sayers
Original assignee: Individual
Current assignee: Voith Fabrics Heidenheim GmbH and Co KG
Priority date: 1993-12-15
Filing date: 1994-12-14
Publication date: 1995-06-22
Also published as: FI962458A0; GB2284772A; EP0734471A1; FI962458A; GB2284772B; GB9325608D0; JPH09507534A; WO1995016820A1; AU1215995A

Abstract

A method of making a shoe press belt comprises the step of feeding a base cloth (13) over a rotating drum (11) and applying a polymer coating to the base cloth (13), as the base cloth (13) is fed over the rotating drum (11). The polymer coating is impregnated with a fused silica or aramid thixotrope.

Description

2t7~72 pAPERM~CHINE Cl.C~ G
The present lnvention relates to paper~s~chine clothing and particularly but not ~xclu5ively to 6hoe press }~elts One forin o~ papermachine clothing comprises a wov~n or non woven base cloth to which a coating of polymer is applied.
In one method of ~anufacture ~ endless ba3e cloth is ~ed around a serie~ of rollers and around a part o~ a hori~ontally mounted rotatable drum. As thu belt passes around the drum heat-so_tened poly~er is apE~lied into the nip between the belt and the drur-.
rn tnis proces~; there i8 a tendency for the heat softened poly~er to slu~p ns it ~ppro~chea the ~ase of the dru~. This iB undesirAble in that th~ pol~eric lnyer ~pplied to the belt is of non uni~orm th~r~ P~
Th~ pressr~t i~vention has ~een made from a c~rLsLderation of this probl~
Accor~ing to a first nsp~ct of the pres~3nt invention th~r~ i3 providad a nLethod of making pArPI~--Ah; nt~ clothing co~prising the ~t~p of feeding a bn~ cloth over a rotating body and applying a pol~mer co~tin~ layer to the base cloth a~ th~ basQ c}oth i8 fed over the rotating body, wh~reln the polymQr coating i8 il~lpre~nnted with a thi~otrope prior to coatLrlg the }~asecloth. 'rh~ thixotrope acts to increaSe the vi~sco:lity of thl~ "fluid" polym~r once Applied to the base cloth .
Surprisingly the toughne85, modulus and a~ra8ion resist~nc~ of t~e pap-3rmachine clothing is ci~nifjt~tly AMENDED S~

K~ ~ . i u 1 U~ I ~v~ w ~ JU ~ ~nw r L ~ I u ~ ~AJ _ ~ v ~ ~u I ~J CU . . ~ . i_l . --1. ~ L
improved by incorporation of the thixotrope into the polymer coating.
hccording to a -econd aspect o~ the present invention there is provided papern~ac~ine clothing comprising a laminAte structu~e comprising a b~se cloth having a layer of polymer coating thereon, wherein the polymer i8 impregnated with a thixotrope .
Aramid fibre~ snch as RIZVLAR ~RI~I~ tpara-phenylene terephth~llamide~ are pre~erred. The fibres are preferably ch~pped into l~ngths in the range from 0 . 8mm to ~ . OOmm and pref~rably have a diameter 1~ the order of 12,u~ 13VLAR (Rl~
is p~rticul~r~y preferred in that the rAndom orientation and physical et~t~nglem~t of the fibres ~nd fibri~s thereof ~lign in th~ direction oi applied ~h-~r thu~ increasing the viscoslty of th~ polymer. Alt~rnatively fused silica may ~e u8ed 25 a thilcotrope.
The polym~r i8 preferably t~ -31~ olyur~than~ is pref ~rr~d.
In order that the pre~ent inventLon ~ay ~ more readily under8tood ~ spec~tc P~hoAi ~, thereof will now be r~ r~h~
by way of exa~ple only with referQnc~ to the sinyle a- -nying drawing which shows one apparatus for m~king pAr~ ~h; ne clothiAg in ~ccord~mce with the present inventinn.
R~forring to the drawing an app~ratu3 lO for ~MEI~IDED Sl~,f:~T

WO 95/16820 lr ~ I, . ¦ ~73 l 2~79172 making par~ hin~ clothing such as a shoe press belt comprises a horizontally mounted rotatable drum 11 and a plurality of rollers 12 which define a path over which an endless base cloth 13 travels. A series of infra-red heaters 14 are provided adjacent the drum 11 on the side of the base cloth 13 which is remote from the drum 11 A polyurethane coating may be applied to the base cloth 13 by utilising a feed nozzle to project the heat softened polymer into the nip 15 between the base cloth 13 and the top of the drum 11. The polyurethane coating is impregnated with chopped aramid fibres in order to prevent sagging of the polymer on the drum and to improve the abrasion resistance of the belt.
- In order to impregnate ~the polyurethane coating with the chopped aramid fibres the fLbres are added in substantially equal amounts to the ~h~ et precursor material. The aramid containing precursors (e.g. polyol and isocyanate) are mixea inmediatelY prior to applying the impregnated coating to the base cloth. The amount of aramid fibre added is preferably less than 396 by weight .
The strength of a prior art polyurethane coated belt "A" was tested. Similarly the strength of a belt incorporating 0.17% REVI/AR (RTM) was tested. The results are set out below.

WO95116820 2 ~ ~ ~ 3 ~ 2 i~l . , I

Average Strength (Kg/2. 5cm) 'A' Polyurethane (Prior Art) 91.3 ' B ' Polyurethane 9 4 . 5 + O.1796 Revlar It can be seen that the incorporation of very small amounts of REVLAR fibres significantly increases the strength o~ the press belt.
It is to be understood that the above descrlbed embodiment is by way of illustration only. Many r~,tions _nd ~ rl~tlons are poss~b1e.

Claims

1. A method of making papermachine clothing comprising the step of feeding a base cloth over a rotating body and applying a polymer coating layer to the base cloth as the base cloth is fed over the rotating body, wherein the polymer coating is impregnated with a thixotrope prior to coating the base cloth.

2. A method of making papermachine clothing as claimed in claim 1, wherein the thixotrope comprises an aramid.

3. A method of making papermachine clothing as claimed in claim 1 or claim 2, wherein the thixotrope comprises aramid fibres.

4. A method of making papermachine clothing as claimed in claim 3, wherein the length of the fibres is in the range from 0.8mm to 4.0mm.

5. A method of making papermachine clothing as claimed in claim 3 or claim 4, wherein the fibres have a diameter of substantially 12µm.

6. A method of making papermachine clothing as claimed in claim 1, wherein the thixotrope comprises fused silica.

7. A method of making papermachine clothing as claimed in any preceding claim, wherein the polymer is a thermosetting polymer.

8. A method as claimed in any preceding claim, wherein the polymer comprises polyurethane.

9. A method of making a shoe press belt using the method of any of claims 1 to 8.

10. Papermachine clothing comprising a laminate structure comprising a base cloth having a layer of polymer coating thereon, wherein the polymer is impregnated with a thixotrope.

11. Papermachine as claimed in claim 10, wherein the thixotrope comprises an aramid.

12. Papermachine clothing as claimed in claim 10 or claim 11, wherein the thixotrope comprises aramid fibres.

13. Papermachine clothing as claimed in claim 12, wherein the length of the fibres is in the range from 0.08mm to 4.0mm.

14. Papermachine clothing as claimed in claim 12 or claim 13, wherein the fibres have a diameter of substantially 12µm.

15. Papermachine clothing as claimed in claim 10, wherein the thixotrope comprises fused silica.

16. Papermachine clothing as claimed in any of claims 10 to 15, wherein the polymer is thermoset,

17. Papermachine clothing as claimed in any of claims 10 to 15, wherein the polymer comprises polyurethane.

18. The use of the papermachin clothinf of any of claims 10 to 17 as a shoe press belt.