WO1999064228A1

WO1999064228A1 - Belt constructions

Info

Publication number: WO1999064228A1
Application number: PCT/GB1999/001696
Authority: WO
Inventors: Ronald Whittaker
Original assignee: Scapa Group Ltd
Current assignee: Scapa Group Ltd
Priority date: 1998-06-06
Filing date: 1999-05-28
Publication date: 1999-12-16
Anticipated expiration: 2000-12-06
Also published as: TW408008B; AU4155399A; GB9812173D0

Abstract

A press belt for a corrugator machine comprises an endless woven fabric (20) which acts as a core or base layer, and is impregnated with and encapsulated in an elastomer material (21). The paper side of the elastomer material is provided with a coating or thin layer (22) of a contaminant-resistant (e.g. fluoropolymer) material, and the coating or the elastomer material may include an anti-static material.

Description

BELT CONSTRUCTIONS

This invention relates to a belt construction for a belt especially for

use as a press belt in a corrugator machine.

In a corrugator machine, a sheet of core paper is steam-heated to

increase its pliability and passed between a pair of meshing toothed rollers

which corrugate the core paper. Starch paste adhesive is applied to the

pleats formed in the core paper and a liner paper sheet is applied to at least

one side of the core paper, bonded together along the tips of the corrugated

paper pleats. The liner paper sheet is urged into contact with the adhesive

coated core paper pleats by a highly tensioned press belt.

Such a press belt is placed under severe operating conditions. As

heat is used to vaporise moisture, the belt must be capable of sustaining a

high temperature environment. Further, the belt is required to operate in

continued contact, under forcible pressure against the teeth of the roller to

obtain the required bonding pressure between the corrugated core paper

and the flat liner paper. The belt must also be flexible yet have longitudinal

strength and transverse rigidity sufficient to prevent wrinkling, and allow

accurate tracking of the belt, without which the belt may drift undesirably

from side to side.

EP-A-0,630,739 (Mitsuboshi) discloses a belt which is intended for

use as a press belt in laminating a liner sheet to a corrugated core paper sheet. This disclosure describes an endless belt comprising a canvas core

layer, an elastomer layer between the canvas core layer and a second,

surface, canvas layer which is extensible in the longitudinal direction of the

belt, the structure also comprising a layer or coating of a non-stick material

such as a mixture including a fluoropolymer. The non-stick material layer

is laminated as two or more panels onto the surface canvas layer, rather

than comprising an endless structure, and flex break at the joints of the

panels is the most common cause of failure.

It has been found in practice that belts made in accordance with the

above disclosure are relatively expensive to produce due to the need to

weave two canvas base cloths, from expensive high strength yarns and

because they are made by laminating the successive first canvas layer,

elastomeric layer and second canvas layer, the belts are susceptible to

delamination, which under the high pressure, temperature and shear force

conditions found in the machines they are used for, is always a considerable

problem.

It is also a problem to ensure accurate tracking of laminated belts,

since in the assembly of multi-ply belts it is difficult to ensure that the

machine direction yarns in the two canvas layers are parallel to each other,

particularly with a sheet material layer in between. A difference of just one

or two degrees can make tracking or guiding of the belt on the machine quite difficult.

It is an object of this invention to provide a belt construction which

will overcome or ameliorate some of the above problems associated with

laminated corrugator press belts.

The invention accordingly provides a corrugator press belt structure

wherein the belt comprises a single endless woven fabric which is at least

partially impregnated with an elastomer.

The endless woven fabric may be in the form of a woven base cloth

and preferably comprises aramid yarns, such as KEVLAR. Other suitable

yarn materials, either alone or blended with one or more other yarns of

different material include cotton, polyamides such as nylon 6 or nylon 6.6;

polyesters, glass, PBO, PVA, PEEK or polyketones.

The fabric is preferably fully impregnated with the elastomer.

The elastomer which at least partially impregnates the base cloth

fabric may be a natural or synthetic rubber or resin, for example a silicone

rubber, styrene butadiene rubber; ethylene propylene rubber; butyl rubber;

fluorine rubber; hydrogenated nitrile rubber or PTFE. The elastomer may be

reinforced with short fibres or with a particulate filler, such as silica powder

or ceramic nanoparticles. These will improve the wear resistance and

strength of the elastomer layer, and silicone rubber is preferred on account

of its good release properties. The elastomer typically has a Shore A hardness of at least 60.

The paper-contacting liner surface of the belt may be provided with

a coating or layer of a low adhesion material which resists bonding of

foreign material, preferably a fluoropolymer, such as PTFE etc., which may

be blended with an elastomer.

Contamination resistance may however be provided by including a

fluoropolymer in the blend of the elastomer which is used to impregnate the

base cloth.

The surface coating may be applied by building up successive layers

by lick-coating, for example by the techniques described in GB-A-2250696.

Other components, such as anti-static agents, may be incorporated

into the elastomer.

Such anti-static agents may include stainless steel powder,

polyanilines, conductive pigments, carbon fibres, or conductive

polyurethane.

A preferred embodiment of a belt construction according to the

invention will now be described by way of example, with reference to the

accompanying drawings, wherein:-

Fig. 1 is a diagram showing a belt according to the invention in use

in a corrugated board machine; and

Fig. 2 is an enlarged cross-sectional view of the belt according to the preferred embodiment of the invention.

Referring first to Fig. 1 , a corrugated board machine includes a first

ridged roller 10, and an intermeshing ridged roller 1 1 . A first sheet of core

paper 12 is fed into the nip between the toothed rollers, and is formed into

parallel ridges and troughs by the pressure acting between the rollers 10,

1 1 . The corrugated sheet is carried by roller 1 1 to engage with a second

planar sheet of liner paper 13, after application of adhesive paste to the

exposed ridges of paper 12 by a device 14.

Liner paper sheet 13 is urged by a press belt 15 under elevated

temperature conditions in an extended nip to the adhesive coated ridge

crests. The belt 15 is guided through the nip by rollers 16, 17. The thus

produced laminate is drawn off from roller 1 1 for winding up or further

processing.

A belt according to the invention is advantageously used as the press

belt 15, in the extended nip over a substantial arc of roller 1 1.

One preferred embodiment of belt fabric is shown in Fig. 2, in an

enlarged fragmentary cross-section.

The fabric comprises a core or base woven textile 20, which is fully

impregnated with and encapsulated in an elastomer material 21 which is

sufficiently thick to prevent marking of the board by the core textile layer

20. The elastomer material 21 is provided with a coating or thin layer 22 of a contaminant-resistant material.

The elastomer material may be formed as a monocoque body

encapsulating material, or by dip coting or layer application separately or

simultaneously to the woven core textile 20. The latter is a simple weave

of aramid yarns such as KEVLAR or the like, with weft and warp yarns

extending substantially in the machine and cross-machine directions. The

elastomer 21 is a styrene butadiene rubber, and the coating 22 is PTFE.

The yarns of the textile core 20 may alternatively be of or include a

blend of one or more of cotton, polyamide, polyester, glass, PBO, PVA,

PEEK or a polyketone. The yarns may be multifilament, monofilament

and/or twisted yarns.

The elastomer may be a silicone rubber, or comprise styrene

butadiene rubber; ethylene-propylene rubber; butyl rubber, fluorine rubber;

hydrogenated nitrile rubber or PTFE, or a blend of two or more thereof.

The elastomer 21 includes an anti-static agent in the form of stainless

steel powder incorporated into the elastomer. Other anti-static agents

which may be used include polyanilines, conductive pigments, carbon fibres

or conductive polyurethanes.

The coating 22 is optional, but may be of any suitable fluoropolymer

or other low adhesion material, e.g. ormocers and silicones. The low

adhesion properties may however be obtained by including a fluoropolymer in the elastomer, this may be concentrated towards the paper contacting

surface of the belt. The low adhesion coating may include an elastomer so

that the coating's elastic properties match those of the impregnating mass

21 , to avoid cracking or other disruption of the coating.

The core fabric 20 may be a canvas material, or of any desired weave

pattern, preferably one with sufficient void space to allow the elastomer to

strike through the fabric 20 and substantially completely impregnate the

fabric. In the preferred embodiment fabric 20 is endless woven in a plain

2/3 twill, semi-triplex or 2-ply (8 treadle) weave, the latter being preferred

since the relatively high thickness and permeability give good elastomer

penetration whilst typically the core fabric will contain 20-40 MD yarns per

inch and 8-25 CD yarns per inch, providing a base cloth with a thickness of

1 -2.5 mm thick.

The belt according to Fig. 2 is not subject to delamination as it does

not comprise any sheets which are adhered or laminated face to face

together. Having a single textile core also reduces the quantity of

expensive high strength yarns required, and the need to weave two or more

base cloths.

Further, the difficulties of tracking which can arise from even a small

deviation between the yarn directions of superposed fabrics of one or two

degrees are eliminated so that belt tracking is also improved. The belt is for example 1 100-3100 mm wide, 1 .2-3.5 mm thick,

possess an elongation at break of 4-1 1 %, and has elongations of 2-5 and

4% at 23 and 150°C respectively (load = 50 kgf/cm belt width). It also has

a coefficient of friction less than 0.3 relative to iron on at least one surface

and is capable of operating continuously at temperatures up to 250°C in a

steam atmosphere.

The surface coating 22 where present is relatively thin compared with

the thickness of the elastomeric coating, e.g. 0.01 -0.5 mm thick.

Claims

1. A corrugator press belt comprising a single endless woven fabric

which is at least partially impregnated with an elastomer.

2. A corrugator press belt according to claim 1 , wherein the single

endless woven fabric is in the form of a woven base cloth.

3. A corrugator press belt according to claim 2, wherein the fabric is

made from aramid yarns.

4. A corrugator press belt according to claim 2, wherein the fabric

includes yarns of any one of cotton, a polyamide, polyester, glass,

PBO, PVA, PEEK or a polyketone, alone or blended with yarns of one

or more other materials.

5. A corrugator press belt according to any preceding claim, wherein the

fabric is fully impregnated with the elastomer.

6. A corrugator press belt according to claim 1 or 5, wherein the

elastomer is a natural or synthetic rubber or resin.

7. A corrugator press belt according to claim 6, wherein the elastomer

is selected from the group comprising: a silicone rubber; a styrene

butadiene rubber; an ethylene propylene rubber; a butyl rubber; a

fluorine rubber; a hydrogenated nitrile rubber; or

polytetrafluoroethylene.

8. A corrugator press belt according to any preceding claim, wherein the elastomer is reinforced with short fibres.

9. A corrugator press belt according to any one of claims 1 to 7,

wherein the elastomer is reinforced with a particulate filler.

10. A corrugator press belt according to claim 9, wherein the particulate

filler comprises silica powder or ceramic nanoparticles.

1 1 . A corrugator press belt according to any preceding claim, wherein the

paper-contacting liner surface of the belt is provided with a coating

or layer of a low adhesion material.

12. A corrugator press belt according to claim 1 1 , wherein the low

adhesion material is blended with an elastomer.

13. A corrugator press belt according to any preceding claim, wherein a

fluoropolymer is blended with the elastomer which is used to at least

partially impregnate the fabric.

14. A corrugator press belt according to claim 1 1 , wherein the coating is

applied by building up successive layers by lick-coating.

15. A corrugator press belt according to any preceding claim, wherein the

elastomer includes an anti-static agent.

16. A corrugator press belt according to claim 15, wherein the anti-static

agent comprises any one or more selected from the group

comprising: stainless steel powder; a polyaniline; a conductive

pigment; carbon fibres; or a conductive polyurethane.