AU8317375A - A method and apparatus for applying a coating material to a substrate - Google Patents

Description

I-

1.6

MICROCOPY RESOLUTION TEST CHART NATIONAL SURE AU01 STAND IRDS-156

SJ" 'FORM 4 REGULATION 11(1)

COMMONWEALTH OF AUSTRALIA

THE PATENTS ACT 1952-1969

CONVENTION APPLICATION FOR A PATENT

XXXWe, BOWATER PACNAGING LIMITED

of Bowater House, Knightsbridge, London SW1X 7LR, England

hereby apply for the grant of a Patent for an invention

entitled: "IMPROVEMENTS IN OR RELATING TO A METHOD AND APPARATUS FOR APPLYING A COATING MATERIAL'TO A SUBSTRATE"

which is described in the accompanying complete specification. r S This application is a Convention application and is based on the

application(s) numbered: 32498/74

S for a patent or similar protection made in GREAT BRITAIN.,

on 23rd July, 1974 trc, ji 6i" r "T ulr IS

g/Our address for service is care of GRIFFITH, HASSEL FRAZER,

Patent Attorneys, of 323 Castlereagh Street, Sydney 2000, in the

State of New South Wales, Commonwealth of Australia.

DATED this 17th day of July 1975.

B SBOWATER PACKAGING LIMITED By their Patent Attorneys:

A f 1-------GIFFITH DLLA ASSEL FRAZER------ Y, X .T Fi W O GRIFFITH HASSEL FRAZER

.ONE B--GOMM.ISSj.QN PATENTS I, I llf\ r11 -1T T 1

P.46 XCIAlON FOR.M l-OR COMPANY APPLICATIONS, AUSTRALIA

Form 7, 8. Regulations 12(1 and 12(2) COMMONWFALTH OF AUSTRALIA PATENTS ACT 1952 69

DECLARATION IN SUPPORT OF AN APPLICATION FOR A PATENT

In support of tlte Applicatior- ade by Bowater Packaging Limited

for a patent for an invention entitled: "Improvements in or relating to a method and apparatus for applying a coating material to a substrate" (FullI.I N rIC Ijd6 4 i (ctr 'Hat/)(nI of the Applicant's

address, (to solemnly and sincerely declare as follows:

1. 1 am autho'rized by the applicant for the patent to make this Declaration on its behalf.

(I till Naiie 2. Michael Joseph Curran of Ilmcntor)

of 19 cicod Ride, Petts Wood, Kent, England

is/arc the actual inventor(s) of the invention and the facts upon which tlse applicant is entitled to make tile application are as follows:- The applicanit Company is the assignee of the said invention from the actual inventor and is aloo the basic applicant in rrspect of the right to make the application under ;ection 141 3. The basic application(s) as defined by Section 141 of the Act, was/were made in

IonsryVa Great Britain on the twenty-third di tc)

(Na r,)c f day of July 1974, by Bowater xpackaging Limited Applicantl for Btasic Applicatior,)

4. The basic application(s) referred to in paragraph 3 of this Declaration was/were first ap- plication(s) made in a Convention country in respect of the invention, the subject of the application.

((try and Country) Declared at Londlon, Bngrrlancl this (ii-1

day of J i ,y, 1975.

ignatt2r

To: The Commissioner of Patents, CANBIE-RRA.

NOTE: Initial all Deletions and Alteratitons. No-.vittrssinf; or legalisatrotr required., For a Nort.Convcnition application darlete paragtispts 3 and 4 cnd initial tile deletion. F.or MIul tiple- l'rioritit.-s hicutpurate details of Al btsic aprplica tiottq tt paragrraph 3. I-or application :'or a I'atrt of Addition ad~d "otf Addition" after te word "patent" wherever the word occtirs, and 1ni ti' etch sttwt Inrtiront.

GRHIIl 11,HASSE3L S&FRAM~R, B~ox 2133, SI)E201ASTAi SYDNEY 2001. AUSTRALIA

DOCUMENTS LODGED WITH THIS APPLICATION ARE UNSUITABLE FOR REPRODUCTION AND MAY BE INSPECTED AT THE PATENT OFFICE A.C.T.

V) 1. 1QF A U1 CO10LIr.0O:AF L.I A

PA~f-rt~s ACT 1052-FS

I U 0 1NAL.)

FOR OFFICE USE-

i.p~t :jj~Number ?31/3 26t Lodged /g7 z-) CoinrItto Specification L-odged 91 Accepted: APED S4 Published 1' F-r~ority: 7 P l

IeI4I-d Art "oC 2 c 4/

TO SE COMIPLETEID BY APPLICANT Nziw .f Appilicant. BOWATER 'PACKAGING LTMTTET)

A6J~t of Ap.';icire Bowater House, Xnightshridge, London SWIX 7LR, England

At -I ivettor: Michael Joseph Currani

rEjrvct 3 13 ce~hv-j!1 St,.,

';~rA~icotV~i ~*rtile I inv~ticn w-Ifficd:

"TIPROVEMENTS IN OR RELATING TO A YTETHOD A-11) APPARMTS FOR APPLYING A COATING MATERIkTj TO AtSUBSTnRATE"

i Oil N) 0) d".:111VIV I', I.

1Z 0 M~A Irs

This invention relates to a method and apparatus for

applying a coating material, especially an adhesion-reducing

cotiiig material, to a substrate and especially to a method

and apparatus for manufacturing release papers.

Release papers, commonly used as a protective backing for pressure-sensitive adhesive-coated labels, are very often

foxned from a paper substrate on to which is applied a release

coating. The release coating reduces the adhesion of the

surface of the paper and thus ensures that the release paper

can easily be detached from the label paper without rupture of the release paper or of the adhesive coating on the label.

Release papers are also widely used for packaging, to prevent

adhesion of the packaging paper to the product.

The most commonly used release-coating materials are

l 1e organopolysiloxanes, which are effective in very low surface concentrations; for example with papers having a highly calendered finish coating weights as low as 0.6 to 0.8 grams

per square metre give satisfactory performance whilst with

a polythene-coated paper coating weights as low as 0.4 to 0.6

grains per square metre are sufficient. Copolymers of

organosiloxanes with carbon-based polymers, for example,

alkyd resins, are also used. These polymers are believed to reduce adhesion because of their high degree of orientation. Some other highly

orientated polymers, for example, polymers with long-chain

alkyl branching, are also effective; for examiple, polyvinyl

esters of fatcy acids with 16 or more carbon atoms and and copolymers of such polyesters. have been used to prepare release coatings. Other, non-polymeric, release materials have also been used; however organopolysiloxanes remain the most popular products used in this fieldo

Normally these polymers are supplied as a dispersion or solution, having a concentration of about 30% by weight

based on the dispersion or solution in toluene or *lene,

having a viscosity of between 10,000 25,000 centistokes

at 2500. Before use these dispersions may be mixed with

one or more cross-linking catalysts and are further diluted with toluene or xylene to a concentration of about 4 to

8 by weight, depending on the method of coating and the

weight required.

More recently, .water-dilutable emulsions have- been

introduced in order to overcome environmental problems

associated with solvents and to reduce costs. These are

supplied at around 4.0 by weight concentration and are diluted,

after adding a catalyst if necessary (for example, a catalyst

produced by Dow-Corning under their product identification

"0 code No. X2-7016), to about 6 to 10% by weight,

The latest addition to this range is a silicone polymer

which is supplied as a. mobile, substantially solvent-free, 0 liquid which has a viscosity of 380 centipoises at 77 F. Such

a polymr is produced by Dow-Corning under their product

identification code No. X2-7018. However, its use for the

manufacture of release papers is uneconomic because with known

coating methods it is impossible to apply coating weights sufficiently low to make the release papers so produced economically competitive with those made by conventional methods.

The present invention provides a method of applying a

coating to a substrate, which comprises applying the coating

material to a carrier made of resilient material, stretching

the carrier to increase its area, and effecting contact between

the coated surface of the stretched carrier and a substrate

to transfer the coating material from the stretched carrier

to the substrate,

The method according to the invention has the advantage that it enables a coating having a low weight per unit area to

be obtained. Furthermore, the only step that involves spreading a

coating material over a surface can be carried out by

conventional means because the coating resulting from that

stop can have a relatively high weight per unit area. The

desired coating having a relatively low weight per unit area

is obtained in the first instance on the carrier simply by

Sstretching the carrier and the resulting coating is transferred

to the substrate by bringing the stretched carrier and the

.0 substrate into contact with one another, Further, the coating composition may be more highly

concentrated than coating compositions previously used, thus

reducing the amounts of solvent required, which is beneficial

as regards both cost and the environment. Where the coating

i mr.aterial is itself a liquid, Ps is the case with many

organopolysiloxanes, the solvent can be dispensed with entirely.

This obviates the need for a solvent or water carrier and the necessary drying equipment for its removal before curing can take place.

The coating material may comprise an agent,preferably

an or-anopolysiloxanefor reducing the adhesion of the

substrate surface. The coating material may be in the form

of a solution, dispersion or emulsion in an. aqueous or organi.c solvent; alteimatively, if the active ingredient is

itself a liquid, it may be used without any solvent or diluent,

any additives or catalysts being dissolved or dispersed in the

active ingredient itself. Coating materials comprising an adhesion-reducing agent

havc special application where the substrate,which may, for

example, be in the form of separate sheets or a continuous

web, is daper. In this case a solvent-free silicone polymer,

15 uch as that referred to above, can be satisfactorily applied in a rcltively thin coating to the paper substrate.

Although in some cases it may be of advantage to have *0 a non-uniform coating applied to the substrate which can be

20 achioved, for example, by non-uniform stretching of the carrier it is usually preferred if coating is uniformly distributed over the carrier when the carrier is in its stretched condition. Prcferably, this is achieved by applying the coating material uniformly to the carrier and then stretching the carrier

uniformly in all directions. It is of advantage, when the carrier is in the form of a band or web,if the uniform stretching

of the carrier is effected by stretching the carrier, in two directions at right angles to each other and in the plane of

.ts band.

The invention further provides apparatus for applying

a coating materi1 to a substrate, the apparatus comprising

a carrier made of resilient material, means for coating a

surfa:ce of the carrier with the coating material, means for stretching the carrier after it has received the coating

material to increase 'he area of the coated surface of the

carrier and means for effecting contact between the substrate

and the coated surface of the stretched carrier to transfer the coating from the stretched carrier to the substrate.

The carrier may be made from any suitable resilient

material. For example the band can be of an elastomeric material, profercbly, natural or synthetic rubber, which has the necessary 3 resilience and is resistant to attack by .the.coating material. For exnmple, pure gum vulcanioed latex may be used which can

have a strengtheiAM filler of, for example, carbon black,

Although the carrier may be in the form of a flat sheet

it is of advantage if the carrier is in the form of a web or

band which is movable longitudinally in its own plane.

Preferably, the carrier is in the form of an endless band

mounted on rollers.

In this case there may be provided means for engaging

the edge portion of the bard, and means for so guiding the engPr:Png means that the band is stretched transversely as it

moves from the coating means to the transfer means. Further,

mean may be provided for so moving the engaging means that the band is stretched longitudinally.

It is of advantage if the guiding means is so arranged

that the width of the band, immediately upstream and downstream

(with reapect to the direction of movement of the band) of the

position where the band contacts the substrate, is the same, and the means for moving the engaging means is so arranged that

imincdiately upstream and downstream of the said position the

speed of the band is the same.

If, as will generally be the case, it is desired to

ensure that the band is uniformly stretched at the said position, the guiding moans and the means for moving the engaging means

must be so arranged that the total longitudinal stretching of

the band is equal to the total transverse stretching of the band

immediat.ely upstream of the said position.

-5 It is of advantage if the eng:aging means comprises a

I. plurality of engaging elements fastened to each edge of the band

and the guiding means comprises continuous guide tracks, one for each edge of the band, the engaging elements along each edge of the band being so engagedwith, and movable along, its respective

Track that the edge of the band is determined by the contour of the trcck. In this case the means for moving the engaging elements arranged along each edge of the band may, with advantage,

comprise a pair of rotatable elongate, for example, cylindrical,

members (such as screw conveyors) one arranged upstream and the

:'235 otier downstream of the said position, each member having a

pcripheral groove, extending spirally around its axis and along

its. length, for receiving the engaging elements (or a peripheral thead for engaging the engagin elements) so that on rotation thread for engaging the engaging elements) so that on rotation

,of the member the engaging elements are moved along their associated track. To effect transverse stretching of the band the tracks along each edge of the band are arranged to

diverge from each other upstream of the position where the

band contacts the substrate. To effect longitudinal stretching, the pitch of the groove in, or thread on each member is arranged to increase from one end of the member to the other, the pitch of the groove or thread of the upstream member of a pair of members increasing in the direction of movement of the engaging elements, and the pitch of the groove or thread of the downstream member of the pair decreasing in the direction of movement of the engaging elements, the total pitch v;ariation of the two members being the same, If the carrier is in the form of an endless band mounted on rollers it is of advantage if the means for applying the 'coatingmaterial to the carrier is arranged adjacent to a first o 'he rollers and the means for effecting contact between the

a .ustrate and the carrier is arranged adjacent to a second of

o0 the rollers. In this case, the means for effecting contact between the carrier and the substrate may comprise a further roller arranged next to the second roller so that as the substrate passes over

the further roller it is in contact with and applies pressure to

2.5 the carrier as it passes over the second roller. Since the second roller and the further roller act as

'nip-rolls' they assist in keeping the band stretched to the

required degree, as the coating material is applied to the

substrate.

Again, in this case, the means for applying the coating

material to the carrier may comprise a further roller which

contacts the band as it passes over the first roller. In this the first roller acts to press the band against the further roller. It is of advantage if the means for applying the coating

material to the bcnd comprises a bath of the coating material, a roller arran.ged to be immersed in the material and upon rotation to pick up material from the bath, which roller is in di:rect contact with the band, and constitutes the said further roller or which is in contact with a secondary roller means comprising one or more secondary rollers the or one of the

secondary rollers being in contact with the band and constituting

the said further roller. Because the band is in its stretched condition when it

applies the coating material to the substrate it will be appreciated that the surface area of the substrate being coted per unit time, say will be greater than. the surface area of the band being coated per unit time by the coating applying means. In other words, the rate at which the coating material is applied to the band and hence the spt. of rotation of the

roller(s) comprising the coating applying means will be less than that which would be necessary for achieving the same rate of coating of the substrate with the unstretched band. This is of advantage because lowering the said speed of rotation of

the roller(a) comprising the coating applying means will tend to reduce ag-i.ation of the coating material which might otherwise produce undesirable splashing and foaming effects,

Clearly means other than a roller coater may be provided

for applying the coating to the carrier and, for example, air

knif,, meyer rod, reverse roll, gravure, trailing blade or

hair brush coaters may be used.

The invention further provides a release paper fonncd

S by applying a release coating to a paper substrate using the method or the apparatus in accordance with the invention.

A coating apparatus constructed in accordance with th:'

invention and a method of coating performed in accordance with

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

reference to the accompanying drawings, in which:

Fig. 1 is a purely diaC'armuatic side elevation of part

of the coating apparatus;

Fig. 2 is. a plan view from above of the apparatus;

Fig. F. 3 is a side elevation of a part of the apparatus

on a larger scale than Figs. 1 and 2; and Fig. 4 shows, partly in section, a part of the

apparatus on a larger scale than Fig. 3. SRe:ferring to the accompanying drawings, the coating apparatus

comprises a coating bath 1 containing a coating liouid, for

example, a silicone polymer, and applicator rollers 2, 3 and 4,

the rollers 2 and 3 being immersed in the liquid,

An endless web or band 5 made of resilient material is

mounted on rollers 6 and 7. The roller 7 is arranged adjacent

to the applicator roller 4 while the roller 6 is arranged

Ksgat adjacent to a roller 8 round which can be fed a

substrate 9, of, for example, paper.

The substrate 9 may be in the form of a continuous strip which is fed to the roller 8 from a reel (not shown) or it may be fed to the roller 8 in the form of separate sheets which sheets may, for example, be formed by starting with a ree of material which is cut into sheet form prior to being, fed to the roller 8. iA plurality of engaging elements 10 are situated along the length of, and are attached to, each edge of the band The engaging elements on each side of the band are in engagement. witIIh, and aro slidably movable along, a respective continuous

iuide track 11 disposed in a vertical plane. The guide tracks 3.1 have upper parts which engage the engaging elemen'y fastened to the upper run X of the band, the upper parts diverging towards each other in the direction of movement of the band 5 (that is to say in the direction of the arrow A in Fig. 2), -ne guide tracks 11 also have lower parts which engage the engaging elements 10 fastened to the lower run Y of the band the lower parts converging towards each other in the direction of movement of the band. The engaging elements 10 on each side of the band are o moved by two pairs of rotatable screw conveyors 12, one pair for eoach edge of the band, the axes of the conveyors being horizontel' Each screw conveyor 12 is rotated by a drive means 13, for exr'-ple, a motor, and is in the form of an elongate cylinder, mounted in bearings 14, which has a groove 15 in its periphery

-5 extending spirally around its axis and along its length.

Alternatively, the groove can be replaced by a thread or rib, The screw conveyore in each pair are arranged one above the other, one engaging the engaging elements running along the upper run, X, of the band and the other along the lower run, Y, of the band. The pitch of each. screw conveyor varies along its length, the pitch variation of each conveyor being the same. The pitch of each upper conveyor increases in the direction of movement of the band while the pitch of each lower conveyor decruc:res in the direction of movement of the band macxm xm)a

The diverging and converging parts of the guide tracks 11 are ea:.ch straight and the screw conveyors 12 are each arranged with their axes parallel to the diverging or converging part of the guide track to which they are adjacent. Further, the lengths of these parts and their angles of divergence or convergence are the sa me and the upper and lower parts on each side of the bands :.re situated verticl.ly beneath one another. Thus, in a lateral direction, the stretchinG that takes place in the upper run X of

the band 5 corresponds exactly in form to the contraction that t~a:cs nlace in the lower run Y of the band. The use of similar scro' conveyors '12 above and below ensures the same correspondence in the betwceen ctretching and contraction of the band direction when the conveyors are rotated at the seime speed. The engaging elements 10 are shown in more detail in 'ig. 4, As sho.wn each element comprises a plate of 'L'-shaped cron:-sec'tion, one limb of the being fastened (permanently,

for example, by riveting, as shown or releasably) to an eyelet 16 provided close to the edge of the band 5. Clearly the way in which the elements 10 are attached to the edge of the band can b)e vari ed. For e-xVaple, each element 1.0 could be formed as a hook p)E szin- through, and :fastened to (permanently or eThy)an re eyelet 1.6 or as a clip -to grip, permanently or rc1r-. cbly, *Uhe edge portion of the band by engaging it's upper lovrr surfaces. Tlho other I.:Lm-.b of the IV0 of the ple2te extends between and iF '-'ACId by two guide roils 17 which contitute the guide track 11., )Jchclement 1L0 is; provided with support wheels 18 which rin on tie raidls 17 and Drovide smooth running movement of the elements :1D 0~~O To *revertt discn3, fement of the wheels 1L8 from the rails 1.6 the said other limb of the plate has a transverse pin 19 which cnC,,,ires the side of t1he rails 17 remote fromi the wheels 3-8. It ir"; s~be as an alternative, to replace the pin 2.9 by further cMuPiort wiheels &mirilarto the wheels 17. As shown in Fig. 4 each gaide element is provided with a, L'iV -nest 20 which enguges the groove 15 in, a corresponding screw conveyor 12. Ift each conveyor formed with a spi-*ral thread or rib then each Fuide element could, as an alternative, be iqrovided with a suitable rgu.id~e or shoe to slide on the thread. The band mey be mride any suitable resilient material, ThrisI the band can be ru)bber, for example, pure gum vulcanised lu-tex which can hatve a strengthening filler of, for example, c,,-hbo;i black. The cd. ,e portions of the banid can, if required, *be rcinforeed by r. s-brenPgthening, fabric. *~)InI Oor"attion, the rollers 2, 3 and 4 are rotated at such mpecds and in nas as to apply a predeterm~ined thickness such of corating mterial to the roller 4 and hence to the belt

A,3 the belt 5 Passes in the direction Of arrow A it is n~tr ,-Lc rd tr;,nsvcrsely by virtue of' the enga-gin e1lements Sin tho Eguide tracko 11 and l~ongitudinally by viteof

c i'iyr~ ler~lents ongaging with the screw conveyor 12. ITe Jloncitudinal stretching of the band 5 will depend on i~cV;*wint of pitoh Of, screw conveyors 12 and the transverso on the divergcnoo of the guidlo tracks 11. The v.-i i tt .on in pitch of the conveors 1-2 is chosen iin- relation to ~i t~i ergnce of the trackvs IL2 so that the totLal] stre-tchingr of LJL 1""d is onual In both ti ccc dire ction s by the time it.+ comes in'to oontnc with th rol., 6. Therefore, $~he band is stret-ched niif:onnnly in all. directi1ons at that stage. As exoluincd above, after passingi over the roller 6, t[he

opur-tion is revoxxcd so thot stretching of t.he band 5 is :c-2mv&L reduced as :tapproachcs the coatcing unit. As the band n~osover 'he roller 6 it contacts the

reussing over the roll er. Cori oequently since the h~iI si~rilystrotchcot it app. os a uniform coating to the cuh~tm. o. urther th±e wein-ht 1,er.x uit area of the costing 'lodto the sub,,trate will of course be less than. the weitght pe'r wit area initially applied -to the band 5 e-t the coating Ini~t tho io of these I weigfhtsl being depenident on the do, roe ~o~bchthe belt is strotched. **Fo r ex wi Ie 1f a woi ght o1r 2.0()rrpr por souee (11 iir x tn bard ilws)ot~oli 1 befl vw,'.ed :fromn roller 4 wic/,that is to say thie ratio of the ~urcenr~t f heband which receives coating iat-oe -the rellor 4. to the area of the coatoct c.,v-face of the bonad at the roll or 8) has been f ixed at 1 5 then the weight of coating frOM thO SUrfa-ce, Of the band deposited on the substrate will bo 0..4 grams per square metre. The fact that the coating is applied first 'to the lx-ni aind then transferred from the band to the substrate has a fur Lhrcr adirantage whien the coating material is applied in con jutition with a solvent and when the substrate is absorbent i;ith r(es1pect -to the solvernt. It in pointed out hereinbofore -that the invention ena:bles a. low coating weighat to be achieved I C) wsi Lii the use of 3-c-s so:lvont, but it mnay nevrertheless be desir- able t'Uo reduce still fur'ther the quanitity of solvent that is :ilicd 'to the subntrato in order -to reduce the absorption of 5 olvec, b th sub, ta. The -use of 'the band /achieves thi~i ruJtbec-%use solvent evaporates .from -the coating.r on tho band ~5bu.Corce t-ie oaigis transferrecd -to the substrate. If an.

Ueven greatter rate of evaporation is required, the band be red to 1,v-so tbarough a drying unit, f or exampe an oven, after the cottting has been applied to it and before the coating in tranoferred to the substrate. As an alternative to the arrangement described above the carrier is in the form of a flat sheet, and the means for -ipplying, the, coating material to -the unstretched carrier -oni- pritnes a flat plate or roller tool and means, for example, a flat pl~ate, for supporting the carrier wh,!*jt the coating material is applied to it by the tool. In this case, also. the Lieans for effectin3 contact between, the carrier and the substrate of Lscs means for bringing, the substrate into face-to-face rc._U1 aoishi) With the stretched sheet and means, for ex.:amtplo, a fl.a.,t pla-6e or roller )r pressing the substrate and stretc hed sheet agarinst oach otha2.

I

The 0FAms defining the invention are as foll~ows:-

I. A method of applying a coating -to a substrateo comprising el~j Jyink the coati~ng miatericJ.. to a carrier made of resilient r~icr~lst-re 'unL, -the carrier to increase its area, and

(:fc~otfLnj~ conta'ct betw-,een the coated swurface of the stretched c..rrLci ajnd a substrate to transfer the coating material from LHiic Ft'trc ld carrier to the subsWtrat 00 A method as claimed in claim 1 i which the coating r.Atcrial is uniformly applied toe the corrier and the coated surfa-.ce of -the carrie:r is thjenl un.iformlyr strctched in all. directions. 3. A method asl cluiri~ed in claim 2, in which the carrier is th2forni of a band or web and the uniiform stretching of the

:0 cr,-rier is effected by stretchin, the carrier in two direct Lons at riadht ,.np'Ics to each other and in the plane of the band. 4. A miethod n- claimed in any one of claimni 1 to 3, in which the ub2;kr,.to is, in the form of separate s-heetu or a continuous wieb. 5. A method as claimed in any ond of claiims 1 to 4, in which the subtrato is paper. A method u,3 cla imn-ed in any one of claims 1 to 5, in which the coating7 mterL'cial comaprises an arCe'.t for reducing the adzicsion of the oubstrate surface. A irethod asclaiimed in claim 6, in which the couting natcanal comlor:LOCS r'n 0r:nplslx~e *o 8. A mthod accLinain cl.,im 6 or claim- 7, in which the

couting., ri,,terial is subostanitially roolvent free.

n~ho, ofaplynC a coating to a substrate,~ the method by nc~b:tcvtillyas heroinibefore described with reference 't-o .cei2.'nyiL:draing.

for applying a coating material to a, subatrate, -r~t o ixlig a carrie Lr made of resilient riatorial, 7:c- ccI:ing, surface of the carriLer with the coating ma~iafor stretching the cornier after it has reccived cctli g thc teri al to increase the area of the coated surface L .Yf rcrr, 011d iierns for effectinfg contct bet-ween the sub- y,iid the coated surface of tLhe otrobhed carrier -to tranisfer t'~co-icjing., fron 'the stretched carrie-r to the substrate.

11. i'.pplt&rX.us as claimed in claim 10, in which -the carrier is i n 1,h c form of a web or baeind which is movable longitudinally t (1vql rualJ.O1

12. imp' '-_tus as claimed in claim 10 or claim 11 in which :Ljr:cr 1 i.7~ in the form of an endle~js band moLunited on rollers. i.Appo.ru Lts Fs claimedI in claimi 12, ina which mieanu's are

i1rovi( cQ for engagingv the edge portions of the band, and mIeans Cc'io i igthe engraging meana: that the band is stretched tv.'r.'(:c:Lyr~sit m~oves from the coating means to the transfer

1 1krIppratus as claimed iLn claim 13, in iwhich means are far so mov:Lilg the eain .eaxs that the band isstec-

150ratus as cla-imed ina claim 14, in which the guidilng 7 0Lo :T9~tc th2,t thc- w~idth of the banidircdctyu'- doi~ie~r', 'th resQpect -to the direction of movc-,,ent iof the Vic d of' the Iosition w'here the bond contacts the substrate, thr:imr:e and the means for noving the engrgina means is so nyrnA th~at immediately upstreama and downstreara of the said yor;iTion tho speed of tha band is the same. 16,. atus as claimed in any one of claims 13~ to 1 5, in wi:ch thec engmi~ing mocans comprises a plurality of engaging elements

?N.NIDJ to eauh edge of the band and the guiding means Comprises PoL ,~nua [guide tracks one for each edge of the band, the -nnnige lcmc.,iets _Jonv each edge of thr band being so engaged ?with, rnQ :20\.ble along~ its respective track that the edg'e of the

banid is determinod by the contour of the track. 17. Appuratus as c:laimed in clain 1 6, in vhich the means for m~oving Wie enroging elements arranged along each edge of the band cv1J1'cCs a pai~r of rotatabl~e elono-ate memmbero one arvranged uip.-

nrithe- othc'r downastream of the said position, each member 11:.im n~ peripheral groove or a peripheral thread, extend3inag .ii ALy arou-nd its axis and along its length for engaging the (1p' elizrjjbsso that on rotation of the member about itbe axis tim c ;'W±gelements are moved along their associated track, the trae:xu Plcng each edge of the band being awrangad to diverge from ::*ervch cthfcr upstrazz ofth position whxere the bsnd cnat h nubi;trmto, the pitch of the groove in, or thread on, ec.ch elogte bc; bcr acrnnrrsnged to increase from one end of the mnem.ber to t tlol -nd the pitch of the g~roove or Ghread of the u.Jstram' P of a pa~ir of' meifbers :Lcrevsiag in the direction of movewcO-. 'leg- elrnts, anid the pitch of the g~roove or thread a.-trcnm meomber of: the pair decreasing in Wh divactiori OIL I ovnmcnt of the engaging~ elements, the total pitch var~Ation of tin t;:o r' ?hrs being the name.

Claims (1)

18 'pparatus as claimed in any one of claims 12 to 17, in which the means for applying UKe coating material to the car'rier is arra,,jjrj. z.djacent to a first of' the rollers and the means for oKiactiit contbact between the substrate and the carrier is~ nrrri,;cc "djacent to a second of the rollers. 19t ipp~ratus as claimed in claim 18, in which the moans :br brLioii tho substrate into contact with the carrier comprises aflanther roller arra~nged next to the said second roller so that athe vabotrate passes over the further roller it is in contact With, ond arplieo pressure to, the carrie~r as it passes over the ruid second roller., Apparatus as claimed in.claim 18 or claim.1 9 in which the rons for applyinG the coating material to the carrier comprises a further roller which contacts the baud as it passes ovcr the first roller. 21Apporatu.,c as claimed in claim 20, in which the moans for

j~ithe, coatin3 material to the band comprises a bpth for- conavining the coatin,' matrial, a roller arranged to be imrmrsed in thu Lu.torial and upon rotation to piLck up material from the S bath, which rollor in in direct contact with the band =6d cwnzbftutes the said :urthor roller or which is in corW_ with a s;econoctry roller means, the secondary means couvrising one or, rcrc. socondary rollers, one of which occondary rollers is in ounrut with the band and constitutes the said fuc'th~r roller, 22 ApparaWtov claimed in any one of' claiws 10 to 21, in WIr.ti thoccrricv iA m~ade from eiaSomeric tytcrial. Ap2%,rratus as clolmed in claim 22, in which the matuvial V. L0ral or Pynthctic rubber.

24, Apparntus as claimed in claim 23, in which the materia1 j 1)1)'0 CAW V01c.Mni~Sed latex. r -vaaus as claimied in claim 24, i hc h ae a

nl ntrmv thcming{ fil~ler. 6" zrau for applying a corting matervial to a substrate, th'e Ppp itIus being substant ially as hereinbefore described with :Luj u:cvnce to and, as shown i~n the accompanying dravings.

A method of applying a coating to a substrate, which cbri~c applying coating ma~terial to the carrier of apparatus as c..iimcc in any one of claims 10 to 26 and transferring the coatiLng rai. from the stretched carrier to the substrate. 23 k release pap.er fonne~d by applying a release coating to c "o subutrate using tho method as claimcd i~n Eay one of claims 1 to A'Arelease paer which hus bceen form~ed by applying a release CO t ppc r sub~trate using the apparatus as claimed in any

(Bn& of cloims 10 to 26.

Datez this 17th day of July, 1975

BOWATER PACKAGING LIMITED By their Patent Attorneys GRIFFIGH, HASSEL FRAZER

FIGS

FIG4 a a. a a a a a. a.

z D/3- AOt 01 el

x

FIG.Z

9. 999 9 9 9 9 9 9 9 9 99 *9 9. 9 9 99 9 9 9 9. 9 9 9 9 99