CA1196181A

CA1196181A - Film applicator system

Info

Publication number: CA1196181A
Application number: CA000404018A
Authority: CA
Inventors: Robert J. Alheid; Robert W. Carlson; Gerald R. Garde
Original assignee: Beloit Corp
Current assignee: Valmet Technologies Oy; Mitsubishi Heavy Industries Ltd
Priority date: 1981-08-06
Filing date: 1982-05-28
Publication date: 1985-11-05
Also published as: ES8307538A1; ES514269A0; MX158731A; GB2103115A; KR860001633B1; JPS5830365A; PH23200A; IT8222744A0; GB2103115B; PH23768A; KR840001291A; IT1152329B; IN159200B

Abstract

ABSTRACT OF THE DISCLOSURE
Starch solution is applied to the surface of a paper sheet web by means of a two roll press and a coating apparatus for each roll. The web is passed between the two rolls beginning at an entry nip where starch film coated on each roll surface is pressed against both sides of the web for penetration thereinto. The coating apparatus comprises a starch applicator for supplying a large excess of starch to the outer surface of the roll and an adjustable doctor blade means for metering a starch film on the roll surface for passage to the nip. The starch applicator may take the form of a fountain or applicator roll arrangement. This system permits coating at high web speeds of 3,000 to 4,000 feet per minute and permits a treatment starch solution to be of low-solids and low-viscosity as is desirable.

Description

BACKGE~OUND OF l~HE lNV~;NllO~

1. Field bf ~he Irl~ention The in~en~ioI~ re~ ates to coating ~reatmenc for a eontinuolls paper web arld, more particularly, ~co a 8y8tem for ~uch treatment which a~70ids ~he for~a~ion of large eoatirl~s ponds and i~ capable of handling coating having ~ low ~olids ar~d vi~cosity content a~c high running 8peeds.

2. The Prit)r ~rt In paper manuacture~ it is w~ll known ~o apply s~arch solutlons to a contmuou~ paper web in order to provide adequate body ~trength for the resulting paper sheets. Durir~g thi6 process, the paper i~ coated with the ~tarch on both side~ for a proper pene~cration into ~he webA
Starch treatment assemblie~ h ve conventionally c~lled for maintenance of a 3tarch pond or puddle in a nip ~e~ween two rolls before applic~tion to the web. Vne conventional device is a two roll press wherein the ~eb is pas~ed between ~wo smooth rolls ~upporting a starch por~d in ~ recelving nip beltwe~n ~he ro:lls. The web pa6se~ generally centrally through ~che pond such that bo~h sides of the web are simultaneously peneltrated by the ~arch. The problem which arises in this technique i3 that, during high speed paper flow in exce~s of 2000 fee~ per minute, ~curbuler~ce is generated i~ the 8tarch puddle which tends ~o ~hrow c:oating away from the nip and resul in uneven application. There are no means in the two roll pre~ ~o control turbulence in the s~rch pond and Imeven coating c&n result in bre.qkin~ of ttle ~hee~ ~eb.

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Another ~c~n ~AiT~g a ~tars:h pond 18 a gate roll pre~ which has a ~erle~ of con~ciE;uGus smooth rolls ln relative rotation. Two ~relatively la~ge cen~er applis~a~cor roll~ define a ~ip ~hrough w~ich a oon~inuous ~hee~ web pa~ses. T.e~d~n~ to each large applicator roll is a pair of relatiYely ~malle~ meterin~
or ga~e roll~ which deine a nip away from the applica~or roll ~upporting a starch pond. From the ps)nd, starch film i~ carried along the rolls and applied ~o both sides c,f ~he ~eb ~B it paS8eS
through the nip betwPen the large rolls. A gate- roll press will allow operating speeds up to 4,000 feet per minute; however, i~c typically requires starch having higher visoosity levels to provide starch film streng~h through ~he gate roll nips. Due to the higher solids con~ent required for vi~cosity, starch penetration in a gate roll press is ~nin~m~l. Optimum starch penetration requires low-solids and low-viscosi~y solutions. High ~olids starche6 lead to high concentrations of starch on ~he outer surfaces of the web w~ich may produce unde~ired web qualities such as sheet tackiness and bondingO Furt~er, since starch penetratlon is limited, the internal bond strength of sheets treated ln z ~ate roll press 1B generally not improved a~ are sheet~ treated in a two roll press.
The present invention is dirDcted to a film applica~or 8y8tem which eliminates the need for starch pond formation and i~ able to ~pply penetran~ ~tarch ~reatment of web~ at high ~pee~3.

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SU~R~ OF l~HE lNV~llOM
A cont:inuous paper web pa ses ~chrough a nip be~ween ~wo appllca~or rol~. Co~ing apparatus 3~rves to preme~er a uniform ilm of starch Ql~l e~c~i press roll ups~re~m o~ the nip.
l'he film is approximately equal to the maximum ~mouT~t that can be absorbed by the web a~ tE~e nip, 80 tha~ ~che~e is no ~arch puddle ~ormation. The coating apparatus for each press rol 1 compri5es a starch applica~c~r, such ~s a fountain or applica~cor roll means, or supplying an excess of starch to the face of the pres~ roll and an adjuRtable doctor blade means for meterin~ a starch film on the roll sur~ace. Each press roll then passes ~he uniform starch film from the blade means to the nip reeeiving the paper web, w~ereby the starch film contacts the web ~ust prior to the roll nip. The excess o starch originally deposi~ed on~o the pre3s roll surface maybe 15 to 40 t:imes the volume of the s~arch metered onto the applica~cor roll. The coatin~ appara~us enables the web to pass through the applicator nip at high speeds with uniform coating. In addition, the inventive system works with low-solids and low-viscosicy ~arches for relia~le, effec~ive Etarch penetration into the web.
BRIEF DESCRIPTION O~ THE :D~WINGS
Figure l ~ s a schem~tic side elevational view illus~rating a known two roll press arrangement whereln a paper web ~s pa~sed through a s~arch polld.
Figure 2 i~ 8 schematic ~ide elevatiorlal view of a kn~wn gate roll preBS a~erang~ment in which a starch pond held by gate rolls pas3e a8 film onts twt~ press ~olls for application on the ~urface of a paper web passing be~een the press rolls.

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Figure 3 i~ a sh~matie side ele~a~ional v~ew of a ilm applica~r gys~em according ~o ~he presen~ in~en~ion, w~ere spplic~to~ ~oLl means are u~ed ~o deposit 6~arch on~o press rolls for me~rin~.
Figure 4 is a diagr~mmatical side ele~a~ional view vf another ~mbodiment of a film applieator ~ystem acco~dîng to the present invention, using fountain mean~ or depositing starch onto the press rolls for me~ering.
Figure 5 is a fragmentary, schematic side elev~tlonal view illustrating the blade ~ip surface aligNment with a respective press roll for u~e with the embodime~t of Figures 3 and 4.
Figure 6 is a fragmentary, schematie side elevational view of another embodimen~ of a film applicator sy tem according to the present invention where an ela~tically deformable blade is used or metering.
Figure 7 is a fragmentary, schema~i~ side elevati.onal view illustrating deæirable blade tip alignment with a re8pective press roll ~or use with the embodiment o~ Figure 6.
DESC~IPTIQN OF THE P~EFERRED EMBODIMEMT
The invention is here described ~or use in the stareh ~reatment o~ paper web; however~ the inventive apparatus wlll hav~ applica~ion generally to coating o~ paper ~heet~ or sheet web.

Figure 1 illu~tr~es a two roll gize pre~ ~rran~emen~ 10 ~or treating a con~nuoll~ paper w b 11 ~7~t~ gt~rch frc7m a large ~tarch po~d 12 ~ a ~n~n~r ~10~ ira ~he art. The pond 12 i8 ~uppc~rted in ~he nip be~ween ~ , rol~z ~3 and 14 ~hrough whlch ~he web i~ pa~d. Thi~ arrang~ment ~as be~n found to ha~e limi~a~îon~
a~ web 6peeds in exoess of a~c)u~ 2000 fee~ per minu~e due to the creation of pond ~urbulence, The ~curbulence ~c nds to ~hxow ~alch coating away from lthe nip and can result ln brez~kln~ of lt:he sheet web. Turbulence ~ reduced ~y using lower 6~arch vi~cosit1e~, bu~
higher water evaporation :L8 then required in the web dryin~ processO
Additiona1ïy, amount~ s:)f lower visro~ity ~carc~ onto a web cannot be effect1ve1y contro11ed by rlip pressure and tho~e ~nounts of coating on a web ~end to increa~e with mach~ne ~peed. There~ore, the approaeh to contro11~ng the amoun~c vf ~arch ooa~ing on a web in a two roll ~ize press has been to use a low ~o:lids con~ent (4-6 pereent~ ~tarch pond so1u~.on~
In Flgure 2, a cor~rentlona1 gate ro11 pre s ~y tem 20 ~or starch treatment 1s shown. The paper web 11 pas~e~ between two press roll~ 21 and ~2, each o wh1Oh has bee.n coa~ed with s~arch by means of a ~ate roll arrangement. Both gate ro11 arrangemen~s ~re ident1ca1 such that only one need be described . Two ad~ a~ent gat~ or metering roll~ 23 and 24 suppor~ a sta~ch pond 25 in their nip. The metering ro11s and pre~s roll~ are ~n oontiguou~ series re1ation or he passa~e of ~tarch therebe~ween ~nd ro~:ate rela~c ve to ~ne another. In order ~o apply a ~tar h ooatirlg ~o in~ermedia~e gate roll 23 or pa~age onto the press rol1 22, the outer ~ate roll 24 ro~ates at approxima~ly 40 percen~ o ~hee~ web ~pPed, wh-lle ~h~ m~ddle ro11 23 ro~ate~ at approxima~cely 60 percent ~hee~
speed. l~e ~arch ilm formed on ~he pre~s ro11 2~ paæ~es ~co a nip 26 ~ be~cween th~ ~pre~ rolls p ~ere ~arch depos~ts on one ~ur~ace of t~e paper web. The gate roll pIess a:rrangement ~5--enables ~tarch treatment at paper ~eb ~peeds up ~co 4,000 eet per minu~e; h~w~verl suraG~ coating o~ly results duP to ~he high v~scou~ st~rch soluti~ns comlllonly used in gate roll pres3es~
It ~ diff~cult to 6uppor~c ~che starch pond ln ~e gate rolls when the viscos~2:y becomes too lo~; 80 conventional gate roll pr 8!~
starch ~olutions have generally not had les~ than 10 percent ~olids c~ntent, In~uficien~ ~arch penetra~ion causes the thus produced sheets to be of lower ~n~ernal bond ~trength than sheets prodllced wi~ a ~wo roll ~ize press.
In accordall~e with the present inven~ion, a two roll pres~ i~ provided in which a contirLuous paper web 11 (Figll~es 3 and 4~ pa~ses between two smooch applicator or press rolls 31 and 32 which form a nip 33 at the pc~int of entry o ~he web therebetween.
Ad~acent to each roll i8 a re~pet~tive doc~cor blade assembly 34 and 35 having blade holder hou~ing~ 36 and 37 for ad~u~ably cot7Ltaining blade element~ 38 and 39 extendin~ obliquely ~oward ~he outer surace of the roll6. The do~or blade assemblies 34 and 35 utilize s~raight, bevelled blades 3~, 39 (Figure 5) which are pivot~bly ad~ustable to necessary a~gle~ relative to the ~pplica~or rolls ~o meter a :eilm thicknes~ F over ~he roll~ downstream of ~he blades 38 a~d 39. The blad~s 38 a~d 39 may be of met~1 ~uch a5 steel. Howe~er t;he blades should be made of a material, ~uch a6 Teflon, which 13 softer than the correeponding applicator rO118 31 and 32~ which are preferably a~ade of, or covered by, hard rubber (0-50 P and 3~. The relat~rely fiofter blades m~ Y.e wear on ~he roll~. Althollgh ~he blades w~ll wear more guiclcly, thelr replaceme2lt is s~mple nd easy.
The straight blades 38 and 39 SFigl3o 3 and 4) are preferably ad~u~ted by flexi~le bladder means 40 and 41 which expand and contract u~der ~ r pre~ure for ~elec~civ~ posi~iorling o the doc~or blades, Such air ~u~e loaded doc~or blades are gener~lly known in the art. 5~me typ~cal example~ are ~e~ forth ïn UOSo Pa~en~ ~oO

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3 ~ 529, 315 and U. S . Pa~en~ No . 3, 778, 861.
Each pre~s roll 31 ~nd 32 1~ coa~2d with a 6tarch solu~isn r~la a corre~pond~g starch applicator means b~2 and 43 upstre~m of ~he film metering blades. The ~arc~ deposi~ced each press roll is approximate~y 1~ ~o 4~ tisle~ ~e volulme of starch film be~ng pa~sed to ~che web en~cry nip 33 ~y ~che mete~ed fi}m. A build-up or pool of solution accordingly de~elops upstream of the blade tips. Preferably~ the tre~tment fllm ~hickness F on each applicator roll i~ ~e~ ~o as to be sligh~ly les~ ~han t~e ~ m amount that can be absorbod by tha~ respec~ive side of the web 11. Thus, there i5 substantially no starch puddle formation a~ ~he nlp 33. Since no starch pond is requir~d in the inventive arra~gement~ ~he web 11 may pas~ upwardly or down-w~rdly between the roll~ 31 and 32.
In Fi~ure 3, the ~tarch applicator m~a~s i5 in the form of an npplicator roll arrangement, wherein applica~or rolls 44 and 45. extend betweea the corresponding large press roll~ 31 and 32 and a supply of s~arch solu~ion 5 contained in re~pective ba~ins 46 and 47 . The applicator roll s serve ~o coat the outer sur~ce of the large ro~ls 31 and 32 wi~h the supply o~ star~:h.
Alterna~l-rely, a~ illu~ra~ced in Figùre 4, a ~upply o starch i8 d2posi~ed on ~he respec~ive large pre6s rolls 31 and 32 by means of fountairls which deliver llquid ~3oLu~ion under pre~sure ~hrough d~livery nozzle me~ns 48 ~nd 49. S~:arc~ ~olu~i~sn i.8 pu~nped into a re pecti~re four~ta~rl del~ver~ li~e through condui~ me~ns by a pump P, ~uch as a v~riable ~peed posi~clve displacement pump. The pun~p means dellv~rs tarch solu~ion ~rom reservoir or ~tank means ~1 and 52, ~espec~i~rely, w~lch hol~ a ~olution suppïyO

Alternatlvely ~o ~he ~raight blade arrangemeT~ts ~hown ln the e~bodimen~ of Figures 3-5, 'che ~ ven~lve film applicator ~ystem may uti~z ~n el~stîcally de:formable doctor blade device 50 a~ shown in Figure 6 to meter ~he ilm F ~o ~he nip 33. Such a de~ormable me~ering blade sys~cem is the sub~ ec~ o the co~only assigned abandoned IJ. S . paterlt a~plic:atiorl Serial Number 4~2, 302, filed June 24, 1974, and also descr~bed in Bri~i~h Patent No. 1~24,150.
For purposes of ill~ls~ratic>n, ~n applicator roll 45 mec:hanism as discussed above serves to coat ~ respec~ive press roll 32, although a ountain means could be used ins~cead. The film metering criterion remains the same as above.
The elastically deformable blad device 50 is disposed downstream of ~he applica~or roll k5. T~is device comprises a blade holder frame 51 for supporting a deformable, s~ceel doc~or blade 52.
One end of the blade 52 is fixably Pmbedded in a lower end 53 of the frame. The other end of the blade extends freely ou~ward of the frame. The frame 51 i8 pivotable about a pivo~ shaft 54 by suitable operating means, ~uch as indicated b~r a hydraulic cylinder 55 wh~ch extends a link pin ~ connected to ~he lower end of the rame 53.
The bllde 52 ig ini~ially di~posed in an undeformed, ~t:raigh~ e fa~h~n as ~hown in the righ~mo~t phantom line posie.ior o th~ frame 51 in Figulre 6. Outward extension of the link 56 pivots ~he holder rame 51 into working pO~itiOZlS. The blade's fre~ end res~s at the point P and the blade 52 l~ concavely arced or ben~ by ~he in~ennedi~te e~ga~gement 'cherealong wi~h a platform ver~e~c 5~. It iB deslrable to 3et: the blade 52 and hoïder fr~me pivot ~hat 54 so that the bl~de tip ~urface 57 faces ~he press ~oll 32 ~ubs~an~ially _~.

'- ` I i tangentially at polnt P s 8hOWn ln Figure 7. Sueh positisrling as6ures that the laetered f~ i8 uni~o~ and ~ccurate de~pi~e ch~ages i~ the blade b~nding load as indica~ed by ~che blade mc~vements between ~he phantom and ~olid line po~t~on~ in Figures ~-7 .
Film F ~mo~hne~ and unio~ity ~s m2in~alned ~y keeping ~che fla~c blade tip 6urface 57 ~n ~angential engagemen'c with ~he press roll 32. Fîl~ F ~chickn~s i con~Lrolled by adju~tmen~L of the blade load or de~ree OI blade deformation produced by the pi~rotal rotation of the holder frame 51.
Proper ~arch pene~ratisn is necessary ~o improve in~ernal ~heet strength~ A major fac~or in con~rolling starch p~netration iB ~he solid~ level and ViE~C051ty of ~he ~tarch. Both low solid~ and low vi~co~ity are required to get optisllum ~tarch penetration in~co a web. In ~he conventional puddle arrangemen~s, ~he starche~ typically have low ~ol~ ds contents ~i . e,, about 6%) with high viscosi~y. The preci6e metering of the present invention system enables low solids (le~ than 10% and preferably about 5%) -low visc08ity 81~arCheS to be used in the ~creatmen~ of a sheet web running at speeds ranging from approximately 1000 to 50ûO feet per mirlute.
The above disclosed embodimen~s ~epict Syfi~ mX which preferably treat both 6ides of a web 6i~ aneou~1y bu~ s~aggPred ~urface kreatmen~s are also wi~hin the COnt:~lllpl8tiOZl oi~ ~e pre~ent in~er~cion.
Although various ~m~n~r modificatiorl~ may be ~ugges~ed by those versed in ~he art, i~c should be unders~ood ~cha~ we wish to embody with$n the ecope of ~he pa~n~ warranted hes~eoTl all sut~h modif~c~tlon~ a~ reasonably ~d properly come ~i~hln ~h~ scope of our con~cribu~ion ts ~he ar~c.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Apparatus for applying starch uniformly to a paper sheet web in the form of a low-solids and low-viscosity liquid solution enabling optimum starch penetration into the web comprising: a two roll press defined by two smooth rolls receiving the web therebetween, a nip between said rolls where the web enters for passage through said two roll press, starch applicator means for applying the starch solution onto a respective roll surface of at least one roll, and an adjustable doctor blade means cooperating with said at least one roll for selectively metering the starch volume on the respective roll surface for supplying a generally uniform starch volume to said nip for effecting complete starch penetration into said web and simultaneously eliminating puddle formation at said nip.

2. The apparatus of claim 1, wherein said starch applicator means comprises a fountain having a delivery line and a pump for passing a flow of starch solution under pressure through said delivery line.

3. The apparatus of claim 1, wherein said starch applicator means comprises an applicator roll arrangement for said at least one roll, said applicator roll arrangement comprising an applicator roll between its respective roll and a basin of starch solution whereby said applicator roll picks up solution from said basin and deposits it onto the surface of said at least one roll.

4. The apparatus of claim 1, wherein said doctor blade means comprises adjustable blade mounting means and a straight blade made of material softer than the outer surface material of said respective roll.

5. The apparatus of claim 4, wherein said blade mounting means includes air pressure tube means for relative adjustment of the pressure between said blade and said respective roll surface.

6. The apparatus of claim 1, wherein said doctor blade means comprises an elastically deformable blade, one end of which abuts against said respective roll surface and the other end of which is fixed in a blade holder frame, means for pivoting said frame about an axis, and a surface portion on said frame for concavely bending said blade according to the amount of pivotal movement of said frame to adjust thickness for said starch film.

7. The apparatus of claim 6, wherein said blade has a flat tip surface that is always substantially tangential with said respective roll surface for metering said starch film.

8. The apparatus of claim 4, wherein said straight blade has a bevelled tip surface which is always substantially tangential with said respective roll surface for metering said starch film.

9. The apparatus of claim 1, wherein the starch solution has a solids content of less than 10%.

10. The apparatus of claim 9, further comprising means for passing said web through said two press rolls at speeds between 1000 and 5000 feet per minute.

11. The apparatus of claim 1, further comprising another starch applicator means and another doctor blade means associated with the other roll, whereby starch film contacts said web on both sides at said nip.

12. The apparatus of claim 1, wherein said doctor blade means meters said starch film to slightly less than the maximum amount said web can absorb at said nip.

13. Apparatus for high speed coating of a paper web with a liquid solution having a solids content of less than 10%
comprising: a two roll press defined by two smooth rolls receiving said web therebetween, a nip between said rolls where said web enters for passage through said two roll press, an applicator means for applying coating onto a respective roll surface of at least one roll, a doctor blade means cooperating with said at least one roll for metering said coating on the respective roll surface into a generally uniform film, and means for passing said web through said two roll press at speeds over 3,000 feet per minute.

14. The apparatus of claim 13, wherein said applicator means applies 10 to 40 times the volume of metered coating film.

15. The apparatus of claim 13, further comprising another applicator means and another doctor blade means associated with the other roll, whereby film contacts said web on both sides at said nip.

16. The apparatus of claim 13, wherein said doctor blade means comprises a straight blade having a bevelled tip surface which is always substantially tangential with said respective roll surface for metering said coating film.

17. The apparatus of claim 13, wherein said doctor blade means comprises an elastically deformable blade, one end of which abuts against said respective roll surface and the other end of which is fixed in a blade holder frame, means for pivoting said frame about an axis, and a surface portion on said frame for concavely bending said blade according to the amount of pivotal movement of said frame to adjust thickness for said coating film.

18. The apparatus of claim 17, wherein said blade has a flat surface that is always substantially tangential with said respective roll surface for metering said coating film.

19. A method for high speed coating of a continuous paper web, comprising: passing said web at speeds over 3,000 feet per minute through a nip between two rolls, supplying a coating of a liquid solution having a solids content of less than 10% onto the surface of at least one of said rolls, metering said coating on said respective roll surface into a generally uniform film slightly less than the maximum amount said web can absorb at said nip, and conducting said film and said respective roll surface into contact with said web at said nip.

20. The method of claim 19, further comprising: supplying said coating on said respective roll surface at 10 to 40 times the volume of said coating transmitted to said nip.

21. The apparatus of claim 1, wherein said starch applicator means applies starch solution 10 to 40 times the volume of starch film being passed to said nip by said at least one roll.

22. The apparatus of claim 1, wherein said two roll press is a high-speed press and transports said web at speeds over 1000 feet per minute.