CA2187899A1 - Combination roll and die coating method and apparatus with improved die lip - Google Patents
Combination roll and die coating method and apparatus with improved die lipInfo
- Publication number
- CA2187899A1 CA2187899A1 CA002187899A CA2187899A CA2187899A1 CA 2187899 A1 CA2187899 A1 CA 2187899A1 CA 002187899 A CA002187899 A CA 002187899A CA 2187899 A CA2187899 A CA 2187899A CA 2187899 A1 CA2187899 A1 CA 2187899A1
- Authority
- CA
- Canada
- Prior art keywords
- coating
- die
- lip
- upstream
- downstream
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C5/00—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work
- B05C5/02—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work the liquid or other fluent material being discharged through an outlet orifice by pressure, e.g. from an outlet device in contact or almost in contact, with the work
- B05C5/0254—Coating heads with slot-shaped outlet
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C1/00—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating
- B05C1/04—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length
- B05C1/08—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line
- B05C1/0813—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line characterised by means for supplying liquid or other fluent material to the roller
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C1/00—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating
- B05C1/04—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length
- B05C1/08—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line
- B05C1/0817—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line characterised by means for removing partially liquid or other fluent material from the roller, e.g. scrapers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C9/00—Apparatus or plant for applying liquid or other fluent material to surfaces by means not covered by any preceding group, or in which the means of applying the liquid or other fluent material is not important
- B05C9/06—Apparatus or plant for applying liquid or other fluent material to surfaces by means not covered by any preceding group, or in which the means of applying the liquid or other fluent material is not important for applying two different liquids or other fluent materials, or the same liquid or other fluent material twice, to the same side of the work
Landscapes
- Coating Apparatus (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
Abstract
A die coating method and apparatus includes a die (40) having an upstream bar (64) with an upstream lip (60) and a downstream bar (66) with a downstream lip (62). The upstream lip is formed as a land (68) and the downstream lip is formed as a sharp edge (70). Coating fluid exists the die (40) from the slot to form a continuous coating bead between the upstream die lip, the downstream die lip, and the surface being coated. A metering roller (332) removes excess coating fluid from the coated web. The apparatus cam include a roller (330) on which the coating fluid is initially coated and which contacts a web. A doctor blade (338) or a metering roller removes excess coating fluid from the roller.
Description
~wos5129765 21 8~99 P.,l/~ 7 ROLL AND DIE COATINa ~T}~OD A~D AppARaTlJ6 WIT}I l~.~J . L.-J DIE 1IP
Tr r~TNTrAT FT~rn The present invention relates to coating methods. More particularly, the present invention relates to coating methods using a die.
RA~ K~ OF THE INVENTION
U.S. Patent No. 2,681,294 discloses a vacuum method for stabilizing the coating bead for direct extruslon and slide types of metered coating systems.
Such stAh; 1; z~Ation onhAnr-~c the coating cArAh; 1 i ty of these systems. However, these coating systems lack 5--ff;r;ont overall cArAh;lity to provide the thin wet layers, even at very low liquid viscosities, required for some coated products.
U.S. Patent No. 4,445,458 f~;crlrseG an extrusion type bead-coating die with a beveled draw-down surf ace to impose a b/iUllda,L y f orce on the ~ .IlLLr~am side of the coating bead and to reduce the amount of vacuum norocc:~ry to maintain the bead.
Reduction of the vacuum m;n;~i~oc chatter defects and coating streaks. To improve coating quality, the obtuse angle of the beveled surf ace with respect to the slot axis, and the position along the slot axis of the bevel toward the moving web (overhang) and away from the moving web (underhang) must be optimized.
The optimization results in the high quality needed for coating photosensitive - lci~nc~ However, the thin-layer performance rAr~hi 1 ity needed for some coated pLudu~;Ls is lacking.
Figure 1 shows a known coating die 10 with a vacuum chamber 12 as part of a metered coating system.
A coating liquid 14 is precisely sllrplied by a pump 16 to the die lO for application to a moving web 18, supported by a backup roller 20. Coating liquid is 2~ 87899 wo ss/2s76s ~"rPl~P'l through a channel 22 to a manifold 24 for distribution through a slot 26 in the die and coating onto the moving web 18. A6 shown in Figure 2, the coating liquid passes through the slot 26 and forms a 5 c--nt;n~ C coating bead 28 between the U~LL~U die lip 30 and the downstream die lip 32, and the web 18.
D~ -lrnc fl and f2, the width of the lips 30, 32 commonly range from O . 25 to O . 76 mm. The vacuum chamber 12 applies a vacuum U~_~Le-llll of the bead to 10 stAh~ the bead . While this conf iguration works adequately in many situations, there is a need for a die coating method which i ,jv~:s the performance of known methods.
15 srrMMARY OF ~rrF ~NVE N~ION
The present invention i5 a die coating apparatus for coating fluid coating onto a surface.
The ~aLc.~us inrl~ c a die having an u~a~Le:alll bar with an u~D~al~ lip and a downstream bar with a 20 d~ ~L~am lip. The u~ c.m lip is formed as a land and the ~ LLe~llu lip is formed as a sharp edge. A
y runs through the die between the U~LL~Iu and l ~IlDL~:cuu bars. The pAccA3 _y has a slot defined by the U~ L~::alU and downstream lips, and 25 coating fluid exits the die from the slot to form a rnnt~mlrnlc coating bead between the upstream die lip, tha d .I,,LL-,~m die lip, and the surface being coated.
A metering roller removes excess coating fluid. The bead does not significantly move into the space 30 between the land and the surface to be coated even as vacuum is increased.
Alternatively the apparatus can include a roller on which the coating f luid is initially coated and which contacts the web . An excess coating f luid 35 remover removes excess coating fluid from the roller.
A die coats the coating f luid onto the roller. The ~ 87~99 WO 95129765 PCrlUS95103367 remover can be a doctor blade or a metering roller and the coating liquid on the roller can be kiss trzmsferred to the web.
A method of die coating according to the 5 present invention in~ A-.~ passing coating fluid through a slot; improving coating performance by . rh~nq~ nq at least one of the relative orientationS of the land and the sharp edge; removing excess coating fluid from the surface to be coated using a metering 10 roller; s~lectinq the length of the land, the edge angle of the A~ LL~ u bar, the die attack angle between the 1 L . ~ bar 6urface of the coating slot And a tangent plane through a line on the surface to be coated parallel to, and directly opposite, the 15 sharp edge, and the coating gap distance between the ~harp edge and the surf ace to be coated in combination with each other; and selecting the slot height, the overbite, and the ~u..v~ly~:nce in combination with each other .
RRTl;~ 'K I 1-,~ . OF THE l)RAWINGS
Figure 1 is a schematic, ~:LU5'; 3ec~ional view of a. known coating die.
Figure 2 is an enlarged cross-sec~ n~ l view of the slot and lip of the die of Figure 1.
Figure 3 is a ~:LOSS s~actional view of an extrusion die of the present invention.
Figure 4 is an enlarged UL05;3 s~_Lional view of the slot and lip of the die of Figure 4.
Figure 5 is a ~;Lo6F sectional view of the slot and lip similar to that of Figure 4.
Figure 6 is a ~:Loss~ n~l view of an alternative vacuum chamber arr~r~ L.
Figure 7 is a cross-sectl~n~l view of another alternative vacuum chamber "LlC~ily~ .
wo ss/2s76s Figure 8 is a ~LO56 SP~' tt~n~l view of an alternative extrusion die of the present invention.
Figures 9a and 9b are enlarged cross-5~ tl~nAl views of the slot, face, and vacuum chamber of the die of Figure 8.
Figures lOa and lOb are schematic views of the die of Figure 8.
Figure 11 shows coating test results which compare the performance of a known extrusion die and an extrusion die of the present invention for a coating liquid of 1. 8 centipoise viscosity.
Figure 12 shows _ ~.tive test results for a coating liquid of 2 . 7 centipoise viscosity.
Figure 13 is a collection of data from coating tests.
Figure 14 is a graph of constant G/Tw lines for an extrusion coating die of the present invention for nine di~ferent coating liquids.
Figure 15 is a schematic view of a three roll reverse roll coater using the die of the present invention .
Figure 16 is schematic view of a two roll reverse roll coater using the die of the present invention .
Figure 17 is a schematic view of a gravure coater using the die of the present invention.
Figure 18 is a two roll extrusion coater using the die of the present invention.
Figures l9a, l9b, and l9c are cross-sectir~n~l views of a kiss coater using the die of the present invention.
Figures 20a, 20b, and 20c are cross-s~ctionAl views of a kiss coater using the die of the present invention.
Figure 20d is a ~.LO55 se_l.ional view of a kiss coater using the die of Figure l9c.
~WO95/29765 2 1 8 78 99 ~ 7 TT.TCn nr.~
This invention i8 a die coating method and ap~..Lus where the die in-~ t~c a charp edge and a S land which are positioned to improve and optimize perf ormance . The land is conf igured to match the shape of the surface in the immediate area of coating liquid application. The land can be curved to match a web passing around a backup roller or the land can be flat to match a free span of web between rollers.
Figure 3 shows the extrusion die 40 with a vacuum chamber 4 2 Or the present invention . Coating liquid 14 is supplied by a pump 46 to the die 40 for application to a moving web 48, supported by a backup roller 50. Coating liquid is supplied through a channel 52 to a manifold 54 for distribution through a slot 56 and coating onto the moving web 48. As shown in Figure 4, the coating liquid 14 passes through the slot 56 and forms a continuous coating bead 58 among the u~LL~calll die lip 60, the l~ LLæ~n die lip 62, ~nd the web 48. The coating liquid can be one of uus liquids or other fluids. The U~DLLe:~lU die lip 60 is part of an upstream bar 64, and the LL- am die 62 lip is part of a ~1~ LL~al~ bar 66.
The height of the slot 56 can be controlled by a U-shaped shim which can be made of brass or st:~inl-~sc steel and which can be deckled. The vacuum chamber 42 applies vacuum uyDLL~alu of the bead to stabilize the coating bead.
As shown in Figure 5, the U,u-,LL~:alu lip 60 is formed as a curved land 68 and the ~' ..,-LL-~am lip 62 is rormed as a sharp edge 70. This configuration u~s overall perforr-nre over that Or known die-type coaters. T, uied performance means permitting 35 operating at increased web speeds and increased coating gaps, operating with higher coating liquid 2l 7 9q W095/2976s 8 8 I~ll~J.., 7 viscosities, and creating thinner wet coating layer ~h;. ~
The 6harp edge 70 should be clean and free of nicks and burrs, and should be straight within 5 micron in 25 cm of length. The edge radius should be no greater than 10 microns. ~he radius of the curved land 68 should be equal to the radius of the backup roller 50 plus a minimal, and non-critical, 0.13 mm ~11. nre for coating gap and web thic-kn~cl~.
10 Alternatively, the radius of the curved land 68 can exceed that of the backup roller 50 and shims can be used to orient the land with respect to the web 48. A
given COIIveLye,l.Ce C achieved by a land with the same radiu- as the backup roller can be achieved by a land with a larger radius than the backup roller by D~-n~rlllating the land with the shims.
Figure 5 also shows dimensions of geometric operating parameters for single layer extrusion. The length Ll o~ the curved land 68 on the upstream bar 64 2 0 can range f rom 1. 6 mm to 2 5 . 4 mm . The pref erred length L1 is 12 . 7 mm. The edge angle Al of the ~ "..LL-aam bar 66 can range from 20 to 75, and is preferably 60. The edge radius of the sharp edge 70 should be from about 2 microns to about 4 microns and preferably le6s than 10 microns. The die attack angle A2 between the downstream bar 66 surface of the coating slot 56 and the tangent plane P through a line on the web 48 surface parallel to, and directly opposite, the sharp edge 70 can range from 60 to 120 and i5 prefer~bly 90-95, such as 93. The coating gap G1 is the perpendicular distance between the sharp edge 70 and the web 48. (The coating gap G1 is measured at the sharp edge but is shown in some Figures spaced from the sharp edge for drawing 3 5 clarity . Regardless of the location of Gl in the ~wogs/2s76s 2 r~
drawings - and due to the UU~ V~l~UL~ of the web the gap lncreaDes aE~ one moves away from the sharp edge - the gap i8 - :d at the sharp edge. ) Slot height H can range from 0. 076 mm to 5 3.175 mm. Overbite O is a positioning of the sharp edge 70 of the ~ ..r,LL~:~m bar 66, with respect to the ., A~ ~L.~alll edge 72 of the curved land 68 on the U~DLL~IIU bar 64, in a direction toward the web 48.
overbite also can be viewed a6 a retraction of the 10 ~ . ~IDLL-.~m edge 72 of the curved land 68 away from the web 48, with respect to the sharp edge 70, for any given coating gap Gl. Overbite can range from O mm to O . 51 mm, and the settings at opposite ends of the die slot should be within 2 . 5 microns of each other. A
15 precision mounting system for this coating system is required, for example to accomplish precise overbite uniformity. C~...vt~y~nce C is a counterclockwise, as shown in Figure 5, angular positioning of the curved land 68 away from a location parallel to (or 20 c~ .. ..l ~ lc with) the web 48, with the r' ....LLe~n edge 72 being the center of rotation. Cu..ve:Lyc:ilce can range from 0 to 2.29, and the settings at opposite ends of the die slot should be within o. 023 of each other. The slot height, overbite, and c~ ry~ ~- e, as 25 well as the fluid properties such as viscosity affect the performance of the die coating d~L~lLUS and method.
From an overall performance s~r~nrlroint~ for liquids within the viscosity range of 1,000 centipoise 30 and below, it is preferred that the slot height be 0.18 mm, the overbite be O . 076 mm, and the ;O~v-zly~ e be O . 57. Performance levels using other slot heights can be nearly the same. Performance advantages can also be found at viscosities above 1,000 centipoise.
21 878q9 Wo 95/29765 1 ~ ~
Holding c~,..v~Ly~l~ce at 0.57, some other optimum slot height and overbite combinationD are as ~ollows:
Slot Hei~ht Overbite 0.15 mm 0.071 mm 0. 20 mm 0 . 082 mm 0.31 mm 0.100 mm 0.51 mm 0.130 mm 10 In the liquid viscosity range noted above, and for any given C~...v~Lyel~ce value, the optimum overbite value Appears to be directly proportional to the square root of the slot height value. Similarly, for any given slot height value, the optimum overbite value appearD
15 to be inversely proportional to the square root of the C~ .Lyt ..~;e value.
As shown in Figure 6, the vacuum chamber 42 can be an integral part of, or clamped to, the u~D~.ec.-u bar 64 to allow precise, repeatable vacuum 20 system gas flow. The vacuum chamber 42 is formed using a vacuum bar 74 and can be cnnnDrtecl through an optional vacuum restrictor 76 and a vacuum manifold 78 to a vacuum source channel 80. A curved vacuum land 82 can be an integral part of the u~DLLealu bar 64, or 25 can be part of the vacuum bar 74, which is secured to the U~DLL~:al~ bar 64. The vacuum land 82 has the same radius of ~;ULVCI~ULe as the curved land 68. The curved land 68 and the vacuum land 82 can be f inish-ground together so they are "in line" with each other. The 30 vacuum land 82 and the curved land 68 then have the same COllVeLY~I~Cê C with respect to the web 48.
The vacuum land gap G2 is the distance between the vacuum land 82 and the web 48 at the lower edge of the vacuum land and is the sum total of the 35 coating gap Gl, the overbite 0, and the t~ plA~ --L
cauDed by ~ ~JIlv~Lyellce C of the curved land 68.
21 87~99 wo 95/29765 1~", 7 (Regardless of the location of G1 in the drawings the gap is the perp--n~9; c~ r distance between the lower edge of the vacuum land and the web. ) When the vacuum land gap G2 i8 large, an excessive inrush of ambient 5 air to the vacuum chamber 42 occurs. Even though the vacuum source may have suf f icient capacity to ~ e and maintain the specified vacuum ~L~5~UL~
level at the vacuum chamber 42, the inrush of air can degrade coating performance.
In Figure 7, the vacuum land 82 i8 part of a vacuum bar 74 which is attached to the U~DLL~IU bar 64. During fabrication, the curved land 68 i8 f inished with the C;~ v~L ~ e C "ground in . " The vacuum bar 74 i5 then attached and the vacuum land 82 15 is finish ground, using a different grind center, such that the vacuum land 82 is parallel to the web 48, and the vacuum land gap G2 is equal to the coating gap G
when the dQsired overbite value is set. The vacuum land length L2 may range from 6 . 35 mm to 25 . 4 mm. The 20 preferred length L2 is 12.7 mm. This ~mho~ L has greater overall coating performance c~r~h;l~ty in difficult coating situations than the: 'i L of Figure 6, but it is always finish ground for one specific set of operating conditions. So, as coating 25 gap G1 or overbite 0 are changed vacuum land gap G2 may move away from its optimum value.
In Figures 8 and 9 the UyDl.Le:cllU bar 64 of the die 40 is mounted on an u}JDLLedm bar positioner 84, and the vacuum bar 74 is mounted on a vacuum bar 30 positioner 86. The curved land 68 on the U~a~L~:-IIII bar 64 and the vacuum land 82 on the vacuum bar 74 are not connected directly to each other. The vacuum chamber 42 is connected to its vacuum source through the - vacuum bar 74 and the positioner 86. The mounting and 35 positioning for the vacuum bar 74 are separate from those for the U~JD~L ~alll bar 64. This; ;)~_8 _g_ ~l 87~q9 wo 95/29765 . ~ 67 perforr-nre of the die and allows precise, r~re~
vacuum system gas f low. Irhe robust conf iguration of the vacuum bar system also aids in the ~ d perf ormance as compared with known systems . Also, 5 this configuration for the vacuum bar 74 could improve performance of other known coaters, such as slot, ~xtrusion, and slide coaters. A flexible vacuum seal strip 88 seal6 between the upstream bar 64 and the vacuum bar 7 4 .
The gap G2 between the vacuum land 82 and the web 48 is not affected by coating gap Gl, overbite 0, or .;~..vcL~nC6 C changes, and may be held at its optimum value continuously, during coating. The vacuum land gap G2 may be set within the range f rom o . 076 mm to O . 508 mm. The preferrea value for the gap G2 is 0.15 mm. The preferred angular position for the vacuum land 82 is parallel to the web 48.
During coating, the vacuum level is adjusted to produce the best quality coated layer. A typical vacuum level, when coating a 2 centipoise coating liquid at 6 microns wet layer thirkn~ and 30.5 m/min web speed, is 51 mm H20. Decreasing wet layer th;rkn~C, increasing viscosity, or increasing web speed could require higher vacuum levels ~Yr--eA; ng 150 2 5 mm H20 . Dies of this invention exhibit lower satisfactory minimum vacuum levels and higher satisfactory maximum vacuum levels than known systems, and in some situations can operate with ZQro vacuum where known systems cannot.
Figures lOa and lOb show some positioning adJuL~ Ls and the vacuum chamber closurQ. Overbite ad~ translates the ~ LL aul bar 66 with respect to the upstream bar 64 such that the sharp edge 70 moves toward or away from the web 48 with respect to the ~ LLacl~u edge 72 o~ the curved land 68. Adjusting c.,.,ve Ly_l~ce rotates the upstream bar 64 wo9s/2s765 2 1 8 7 8 9 9 and the ' L- an, bar 66 together around an axis running through the ~ ..,LL~am edge 72, such that the curved land 68 moves from the position shown in Figure 10, ~way from parallel to the web 48, or back toward 5 parallel. Coating gap adju~,i L translates the U~,~LL. a~o bar 64 and the ~ LL~a~ bar 66 together to change the distance between the sharp edge 7 0 and the web 48, while the vacuum bar remains stationary on its mount 86, and the vacuum seal strip 88 flexes to 10 prevent air leakage during adjustments. Air leakage at the ends of the die into the vacuum chamber 42 is m;n;m;~od by end plates 90 attached to the ends of the vacuum bar 7 4 which overlap the ends of the u~ L, e cllU
bar 64. The vacuum bar 74 is 0.10 mm to 0.15 _m 15 longer than the upstream bar 64, so, in a centered condition, the clearance between each end plate 90 and the upstream bar 64 will range from 0 . 050 mm to 0. 075 mm.
one -~l e -~cl operating characteristic has 20 been obs~L~-d during coating. The bead does not move significantly into the space between the curved land 68 and the moving web 48, even as vacuum is increased.
This allows using higher vacuum levels than is pos$;hlP with known extrusion coaters, and provides a 25 cv~ ;n~ly higher performance level. Even where little or no vacuum is required, the invention exhibits ; vv~d perf ormance over known systems .
That the bead does not move signif icantly into the space between the curved land 68 and the web 48 also 30 means that the effect of "runout" in the backup roller 50 on ~ .LL~a-,~ coating weight does not differ from that for known extrusion coaters.
Figure 11 graphs results of coating tests which compare the perf ormance of a known extrusion die 35 with an extrusion die of this invention. In the tests, the 1.8 centipoise coating liquid containing an ~l ~7~d99 wo gsl29765 r~
organic solvent was applied to a plain polyester f ilm web. The performance criterion was minimum wet layer th~rlrn-~c~ at four different coating gap levels for each of the two coating systems, over the 6peed range 5 Or 15 to 60 m/min. Curves A, B, C, and D use the known, prior art die and were performed with coating gaps of 0.254 mm, 0.203 mm, 0.152 mm, and 0.127 mm, respectively. Curves E, F, G, and H use a die according to this invention at the same respective 10 coating gaps. The lower wet th;rl~naCc levels for this invention, ~d to the prior art die, are easily visible. Figure 12 shows _ ~ tive test results for a similar coating liquid of 2 . 7 centipoise viscosity, at the same coating gaps. Once again, the performance 15 a~v~.l,Lc-ge for this invention is clearly visible.
Figure 13 is a collection of data from coating tests where liquids at seven different viscosities, and containing different organic solvents, were applied to plain polyester film webs.
20 The results compare performance of the prior art extrusion coater (PRIOR) and this invention (NEW).
The perf ormance criteria are mixed . Perf ormance advc.l~tages ~or this invention can be f ound in web speed (Vw), wet layer thirl-n~cc (Tw), coating gap, 25 vacuum level, or a combination of these.
One measure of coater performance is the ratio of coating gap to wet layer thi rl-n~cc (G/Tw), ror n particular coating liquid and web speed. Figure 14 shows a series of cv.v-La,,L G/Tw lines and viscosity 30 values of an extrusion die of this invention, for nine different coating liquids. The liquids were coated on plain polyester film base at a web speed of 30. 5 m/min. A few viscosity values appear to be out of order, due to the effect of other coatability factors.
35 Four additional performance lines have been added after calculating the G/Tw values for 30.5 m/min web 2~ rJq Wo95l29765 p~ ", ~
~peed from Figures 11 and 12. From top to bottom, the solid performance lines are the G/Tw for liquids o~
2 . 7 centipoise and 1. 8 centipoise coated by a known extrusion die and the G/Tw for liquids of 2 . 7 5 centipoise and 1. 8 centipoise coated by an extrusion die of this invention. The lines for of this invention rt~Las~ l greater G/Tw values than the lines for o~ the prior art coating die. In addition, the lines for this invention are close to being lines of ~.. ,.,~1 ,Inl G/Tw, averaging 18 . 8 and 16 . 8, respectively.
The lines of the known coater show conQid-o~ably more G/Tw variation over their length. This invention has a much i vv_d operating characteristic for ~-;ntA~nin~ a coating bead at low wet th;~kn~ s values, over known systems.
Coating dies of this invention can be used as high performance liquid feed devices for roll and kiss coaters. Figure 15 shows a three roll reverse roll coater using an extrusion die 40 to feed coating liquid 14 to a casting roller 330. Because the surface of the casting roller 330 passes the die 40 in a ~ -~l direction, the die 40 is inverted and the vacuum chamber 42 is above the slot and the coating bead . This does not af f ect coating perf ormance . A
metering roller 332 removes excess coating liquid, leaving a precise layer on the casting roller 330. A
doctor blade 334 removes the excess coating liquid from the metering roller 332 and drops it into a liquid return pan 336 for recirculation.
M~An~hil~, a bead-splitting action transfers part of the coating liquid from the casting roller 330 to the web 48 moving around the backup roller 50.
After the bead splits, a second doctor blade 338 cleans the r~ ;n~n J coating liquid from the casting roller 330 and runs it into the recirculation pan 336.
Alternatively, the backup roller 50 can be rubber wo 95ng76s 2 1 8 7 ~ 9 9 covered 60 the castinq roller 330 can contact the web and tr~ns~er all of the coating liquid in this area to the web. The second doctor blade 338 would then clean any liquid from the casting roller 330 which i6 outside of the web width.
Figure 16 shows a two roll reverse roll coater using an extru6ion die 40 to feed coating liguid to the surface of the web 48 moving around the backup roller 14, which is a wrapped casting roller.
The metering roller 332 removes excess coating liquid from the surface of the web 48, leaving the desired, precise wet coated layer. The doctor blade 334 cleans the excess coating liquid from the metering roller 332 and runs it into the recirculation pan 336. Use of this system in one example increased the vacuum window from 5 . 08 mm to over 254 mm H20, and increased the liquid feed coating gap from 0 .10 mm to 0 . 36 mm, thereby improving stability and practically eliminating streaking.
Figure 17 shows a gravure coater using an extrusion die 40 to feed coating liquid to the surface of a knurled roller 340. The die 40 has its vacuum chamber 42 above its coating slot. A doctor blade 342 removes excess coating liquid from the knurl pattern ~o that the desired amount transfers to the web 48 moving around the rubber-~uve:~d backup roller 314.
The excess coating liquid recirculates through the pan 336. This method of feeding coating liquid to the surface of a knurled roller can also be used for other forms of gravure coating such as reverse, offset, and dif f erential .
Figure 18 shows a two roll extrusion coater using an extrusion die 40 to feed ccating liquid to the surface of the casting roller 330, with stability from the vacuum chamber 42. The layer of coating liquid is thin and precise 80 that a metering roll is 21 8789q wo 95l2976~
not required. The bead split takes place directly to the web 48 moving around the backup roller 314. A
doctor blade 338 remove6 the coating excess liquid rrom the casting roller 330 and recirculates it -~ 5 through the pan 336. Alternatively, the backup roller 50 can be rubber covered 80 the casting roller 330 can contact the web and transfer all of the coating liquid in this area to the web. The second doctor blade 338 would then clean any liquid from the casting roller 330 which is outside of the web width.
Figure l9a shows a kiss coater where an extrusion die 40 feeds coating liquid through a manifold 54 and a slot 56 to a transfer roller 344 such as a spindle having a ~;~ tQr ranging from 25.4 mm to 50.8 mm. The coating bead is st2~hili7od by the vacuum chamber 42. The coating liguid on the transfer roller 344 is kiss transferred to form the coated layer on the web 48. The small 1;: Qr transfer roller 344 has a small kiss transfer area, and ~ ~ve 8 web stability over that with a larger transfer roller by reducing web flutter and cross tension marks. The surface of the transfer roller 344 can be, for example, smooth, polished, medium grind, grit blasted, or knurled.
Figure l9b shows a ki6s coater where the extrusion die 40 with a vacuum chamber 42 feeds coating liquid to the surface of a kiss transfer roller 344. The roller 344 haB a larger rli2 - than the spindle of Figure l9a. The coating liguid is kiss transferred to form the coated layer on the web 48.
Figure l9c shows a kiss coater where a slide coating die 310 feed2-2 coating liquid to the surface of a kiss transfer roller 344. The coating liquid is kiss transferred to form the coated layer on the web 48.
2~ 87899 Wo gs/2s765 r~
Figure 20a shows a kiss coater where n dual-layer extrusion die lOo reeds two coating liquids 116, 124 through ~hAnn~ 118, 126 to the 6urface of a spindle, such as a transfer roller 344 having a 1l~ tt:L ranging from 25.4 mm to 50.8 mm. The two coating liquids on the transfer roller 344 are transferred to form two coated layers on the web 48.
~igure 20b shows a kiss coatQr where a dual-layer extrusion die 100 feeds coating liquid to a kiss transfer roller. The roller 344 has a larger rl~ ~r than the roller of Figure 20a. Two coating liquids 116, 124 are fed through two separate manifolds and two separate slots to meet at the coating bead. The two coating liquids are transferred to the web forming wet coated layers.
Figure 20c shows a kiss coater where a dual-layer extrusion die 100 feeds coating liquid to a kis6 transfer roller 344. The two coating liquids 116, 124 are fed through two manifolds, but only one slot, meeting inside the die. The two coating liquids on the surface of the transfer roller 344 are transferred to form the two coated layers on the web 48.
Figure 20d shows a kiss coater where a multiple layer coating version of the die 220 of Figure l9c feed6 four coating liquids onto the surface of the tran~fer roller 344. Four liquids 116, 124, 346, 348 are fed through the die 100, down slide surfaces 236 to form four layers on the surface of the transfer roller 344. These layers are transferred to ~o ~onn ~our ~o~t~ I l=yer- or the web ib.
Tr r~TNTrAT FT~rn The present invention relates to coating methods. More particularly, the present invention relates to coating methods using a die.
RA~ K~ OF THE INVENTION
U.S. Patent No. 2,681,294 discloses a vacuum method for stabilizing the coating bead for direct extruslon and slide types of metered coating systems.
Such stAh; 1; z~Ation onhAnr-~c the coating cArAh; 1 i ty of these systems. However, these coating systems lack 5--ff;r;ont overall cArAh;lity to provide the thin wet layers, even at very low liquid viscosities, required for some coated products.
U.S. Patent No. 4,445,458 f~;crlrseG an extrusion type bead-coating die with a beveled draw-down surf ace to impose a b/iUllda,L y f orce on the ~ .IlLLr~am side of the coating bead and to reduce the amount of vacuum norocc:~ry to maintain the bead.
Reduction of the vacuum m;n;~i~oc chatter defects and coating streaks. To improve coating quality, the obtuse angle of the beveled surf ace with respect to the slot axis, and the position along the slot axis of the bevel toward the moving web (overhang) and away from the moving web (underhang) must be optimized.
The optimization results in the high quality needed for coating photosensitive - lci~nc~ However, the thin-layer performance rAr~hi 1 ity needed for some coated pLudu~;Ls is lacking.
Figure 1 shows a known coating die 10 with a vacuum chamber 12 as part of a metered coating system.
A coating liquid 14 is precisely sllrplied by a pump 16 to the die lO for application to a moving web 18, supported by a backup roller 20. Coating liquid is 2~ 87899 wo ss/2s76s ~"rPl~P'l through a channel 22 to a manifold 24 for distribution through a slot 26 in the die and coating onto the moving web 18. A6 shown in Figure 2, the coating liquid passes through the slot 26 and forms a 5 c--nt;n~ C coating bead 28 between the U~LL~U die lip 30 and the downstream die lip 32, and the web 18.
D~ -lrnc fl and f2, the width of the lips 30, 32 commonly range from O . 25 to O . 76 mm. The vacuum chamber 12 applies a vacuum U~_~Le-llll of the bead to 10 stAh~ the bead . While this conf iguration works adequately in many situations, there is a need for a die coating method which i ,jv~:s the performance of known methods.
15 srrMMARY OF ~rrF ~NVE N~ION
The present invention i5 a die coating apparatus for coating fluid coating onto a surface.
The ~aLc.~us inrl~ c a die having an u~a~Le:alll bar with an u~D~al~ lip and a downstream bar with a 20 d~ ~L~am lip. The u~ c.m lip is formed as a land and the ~ LLe~llu lip is formed as a sharp edge. A
y runs through the die between the U~LL~Iu and l ~IlDL~:cuu bars. The pAccA3 _y has a slot defined by the U~ L~::alU and downstream lips, and 25 coating fluid exits the die from the slot to form a rnnt~mlrnlc coating bead between the upstream die lip, tha d .I,,LL-,~m die lip, and the surface being coated.
A metering roller removes excess coating fluid. The bead does not significantly move into the space 30 between the land and the surface to be coated even as vacuum is increased.
Alternatively the apparatus can include a roller on which the coating f luid is initially coated and which contacts the web . An excess coating f luid 35 remover removes excess coating fluid from the roller.
A die coats the coating f luid onto the roller. The ~ 87~99 WO 95129765 PCrlUS95103367 remover can be a doctor blade or a metering roller and the coating liquid on the roller can be kiss trzmsferred to the web.
A method of die coating according to the 5 present invention in~ A-.~ passing coating fluid through a slot; improving coating performance by . rh~nq~ nq at least one of the relative orientationS of the land and the sharp edge; removing excess coating fluid from the surface to be coated using a metering 10 roller; s~lectinq the length of the land, the edge angle of the A~ LL~ u bar, the die attack angle between the 1 L . ~ bar 6urface of the coating slot And a tangent plane through a line on the surface to be coated parallel to, and directly opposite, the 15 sharp edge, and the coating gap distance between the ~harp edge and the surf ace to be coated in combination with each other; and selecting the slot height, the overbite, and the ~u..v~ly~:nce in combination with each other .
RRTl;~ 'K I 1-,~ . OF THE l)RAWINGS
Figure 1 is a schematic, ~:LU5'; 3ec~ional view of a. known coating die.
Figure 2 is an enlarged cross-sec~ n~ l view of the slot and lip of the die of Figure 1.
Figure 3 is a ~:LOSS s~actional view of an extrusion die of the present invention.
Figure 4 is an enlarged UL05;3 s~_Lional view of the slot and lip of the die of Figure 4.
Figure 5 is a ~;Lo6F sectional view of the slot and lip similar to that of Figure 4.
Figure 6 is a ~:Loss~ n~l view of an alternative vacuum chamber arr~r~ L.
Figure 7 is a cross-sectl~n~l view of another alternative vacuum chamber "LlC~ily~ .
wo ss/2s76s Figure 8 is a ~LO56 SP~' tt~n~l view of an alternative extrusion die of the present invention.
Figures 9a and 9b are enlarged cross-5~ tl~nAl views of the slot, face, and vacuum chamber of the die of Figure 8.
Figures lOa and lOb are schematic views of the die of Figure 8.
Figure 11 shows coating test results which compare the performance of a known extrusion die and an extrusion die of the present invention for a coating liquid of 1. 8 centipoise viscosity.
Figure 12 shows _ ~.tive test results for a coating liquid of 2 . 7 centipoise viscosity.
Figure 13 is a collection of data from coating tests.
Figure 14 is a graph of constant G/Tw lines for an extrusion coating die of the present invention for nine di~ferent coating liquids.
Figure 15 is a schematic view of a three roll reverse roll coater using the die of the present invention .
Figure 16 is schematic view of a two roll reverse roll coater using the die of the present invention .
Figure 17 is a schematic view of a gravure coater using the die of the present invention.
Figure 18 is a two roll extrusion coater using the die of the present invention.
Figures l9a, l9b, and l9c are cross-sectir~n~l views of a kiss coater using the die of the present invention.
Figures 20a, 20b, and 20c are cross-s~ctionAl views of a kiss coater using the die of the present invention.
Figure 20d is a ~.LO55 se_l.ional view of a kiss coater using the die of Figure l9c.
~WO95/29765 2 1 8 78 99 ~ 7 TT.TCn nr.~
This invention i8 a die coating method and ap~..Lus where the die in-~ t~c a charp edge and a S land which are positioned to improve and optimize perf ormance . The land is conf igured to match the shape of the surface in the immediate area of coating liquid application. The land can be curved to match a web passing around a backup roller or the land can be flat to match a free span of web between rollers.
Figure 3 shows the extrusion die 40 with a vacuum chamber 4 2 Or the present invention . Coating liquid 14 is supplied by a pump 46 to the die 40 for application to a moving web 48, supported by a backup roller 50. Coating liquid is supplied through a channel 52 to a manifold 54 for distribution through a slot 56 and coating onto the moving web 48. As shown in Figure 4, the coating liquid 14 passes through the slot 56 and forms a continuous coating bead 58 among the u~LL~calll die lip 60, the l~ LLæ~n die lip 62, ~nd the web 48. The coating liquid can be one of uus liquids or other fluids. The U~DLLe:~lU die lip 60 is part of an upstream bar 64, and the LL- am die 62 lip is part of a ~1~ LL~al~ bar 66.
The height of the slot 56 can be controlled by a U-shaped shim which can be made of brass or st:~inl-~sc steel and which can be deckled. The vacuum chamber 42 applies vacuum uyDLL~alu of the bead to stabilize the coating bead.
As shown in Figure 5, the U,u-,LL~:alu lip 60 is formed as a curved land 68 and the ~' ..,-LL-~am lip 62 is rormed as a sharp edge 70. This configuration u~s overall perforr-nre over that Or known die-type coaters. T, uied performance means permitting 35 operating at increased web speeds and increased coating gaps, operating with higher coating liquid 2l 7 9q W095/2976s 8 8 I~ll~J.., 7 viscosities, and creating thinner wet coating layer ~h;. ~
The 6harp edge 70 should be clean and free of nicks and burrs, and should be straight within 5 micron in 25 cm of length. The edge radius should be no greater than 10 microns. ~he radius of the curved land 68 should be equal to the radius of the backup roller 50 plus a minimal, and non-critical, 0.13 mm ~11. nre for coating gap and web thic-kn~cl~.
10 Alternatively, the radius of the curved land 68 can exceed that of the backup roller 50 and shims can be used to orient the land with respect to the web 48. A
given COIIveLye,l.Ce C achieved by a land with the same radiu- as the backup roller can be achieved by a land with a larger radius than the backup roller by D~-n~rlllating the land with the shims.
Figure 5 also shows dimensions of geometric operating parameters for single layer extrusion. The length Ll o~ the curved land 68 on the upstream bar 64 2 0 can range f rom 1. 6 mm to 2 5 . 4 mm . The pref erred length L1 is 12 . 7 mm. The edge angle Al of the ~ "..LL-aam bar 66 can range from 20 to 75, and is preferably 60. The edge radius of the sharp edge 70 should be from about 2 microns to about 4 microns and preferably le6s than 10 microns. The die attack angle A2 between the downstream bar 66 surface of the coating slot 56 and the tangent plane P through a line on the web 48 surface parallel to, and directly opposite, the sharp edge 70 can range from 60 to 120 and i5 prefer~bly 90-95, such as 93. The coating gap G1 is the perpendicular distance between the sharp edge 70 and the web 48. (The coating gap G1 is measured at the sharp edge but is shown in some Figures spaced from the sharp edge for drawing 3 5 clarity . Regardless of the location of Gl in the ~wogs/2s76s 2 r~
drawings - and due to the UU~ V~l~UL~ of the web the gap lncreaDes aE~ one moves away from the sharp edge - the gap i8 - :d at the sharp edge. ) Slot height H can range from 0. 076 mm to 5 3.175 mm. Overbite O is a positioning of the sharp edge 70 of the ~ ..r,LL~:~m bar 66, with respect to the ., A~ ~L.~alll edge 72 of the curved land 68 on the U~DLL~IIU bar 64, in a direction toward the web 48.
overbite also can be viewed a6 a retraction of the 10 ~ . ~IDLL-.~m edge 72 of the curved land 68 away from the web 48, with respect to the sharp edge 70, for any given coating gap Gl. Overbite can range from O mm to O . 51 mm, and the settings at opposite ends of the die slot should be within 2 . 5 microns of each other. A
15 precision mounting system for this coating system is required, for example to accomplish precise overbite uniformity. C~...vt~y~nce C is a counterclockwise, as shown in Figure 5, angular positioning of the curved land 68 away from a location parallel to (or 20 c~ .. ..l ~ lc with) the web 48, with the r' ....LLe~n edge 72 being the center of rotation. Cu..ve:Lyc:ilce can range from 0 to 2.29, and the settings at opposite ends of the die slot should be within o. 023 of each other. The slot height, overbite, and c~ ry~ ~- e, as 25 well as the fluid properties such as viscosity affect the performance of the die coating d~L~lLUS and method.
From an overall performance s~r~nrlroint~ for liquids within the viscosity range of 1,000 centipoise 30 and below, it is preferred that the slot height be 0.18 mm, the overbite be O . 076 mm, and the ;O~v-zly~ e be O . 57. Performance levels using other slot heights can be nearly the same. Performance advantages can also be found at viscosities above 1,000 centipoise.
21 878q9 Wo 95/29765 1 ~ ~
Holding c~,..v~Ly~l~ce at 0.57, some other optimum slot height and overbite combinationD are as ~ollows:
Slot Hei~ht Overbite 0.15 mm 0.071 mm 0. 20 mm 0 . 082 mm 0.31 mm 0.100 mm 0.51 mm 0.130 mm 10 In the liquid viscosity range noted above, and for any given C~...v~Lyel~ce value, the optimum overbite value Appears to be directly proportional to the square root of the slot height value. Similarly, for any given slot height value, the optimum overbite value appearD
15 to be inversely proportional to the square root of the C~ .Lyt ..~;e value.
As shown in Figure 6, the vacuum chamber 42 can be an integral part of, or clamped to, the u~D~.ec.-u bar 64 to allow precise, repeatable vacuum 20 system gas flow. The vacuum chamber 42 is formed using a vacuum bar 74 and can be cnnnDrtecl through an optional vacuum restrictor 76 and a vacuum manifold 78 to a vacuum source channel 80. A curved vacuum land 82 can be an integral part of the u~DLLealu bar 64, or 25 can be part of the vacuum bar 74, which is secured to the U~DLL~:al~ bar 64. The vacuum land 82 has the same radius of ~;ULVCI~ULe as the curved land 68. The curved land 68 and the vacuum land 82 can be f inish-ground together so they are "in line" with each other. The 30 vacuum land 82 and the curved land 68 then have the same COllVeLY~I~Cê C with respect to the web 48.
The vacuum land gap G2 is the distance between the vacuum land 82 and the web 48 at the lower edge of the vacuum land and is the sum total of the 35 coating gap Gl, the overbite 0, and the t~ plA~ --L
cauDed by ~ ~JIlv~Lyellce C of the curved land 68.
21 87~99 wo 95/29765 1~", 7 (Regardless of the location of G1 in the drawings the gap is the perp--n~9; c~ r distance between the lower edge of the vacuum land and the web. ) When the vacuum land gap G2 i8 large, an excessive inrush of ambient 5 air to the vacuum chamber 42 occurs. Even though the vacuum source may have suf f icient capacity to ~ e and maintain the specified vacuum ~L~5~UL~
level at the vacuum chamber 42, the inrush of air can degrade coating performance.
In Figure 7, the vacuum land 82 i8 part of a vacuum bar 74 which is attached to the U~DLL~IU bar 64. During fabrication, the curved land 68 i8 f inished with the C;~ v~L ~ e C "ground in . " The vacuum bar 74 i5 then attached and the vacuum land 82 15 is finish ground, using a different grind center, such that the vacuum land 82 is parallel to the web 48, and the vacuum land gap G2 is equal to the coating gap G
when the dQsired overbite value is set. The vacuum land length L2 may range from 6 . 35 mm to 25 . 4 mm. The 20 preferred length L2 is 12.7 mm. This ~mho~ L has greater overall coating performance c~r~h;l~ty in difficult coating situations than the: 'i L of Figure 6, but it is always finish ground for one specific set of operating conditions. So, as coating 25 gap G1 or overbite 0 are changed vacuum land gap G2 may move away from its optimum value.
In Figures 8 and 9 the UyDl.Le:cllU bar 64 of the die 40 is mounted on an u}JDLLedm bar positioner 84, and the vacuum bar 74 is mounted on a vacuum bar 30 positioner 86. The curved land 68 on the U~a~L~:-IIII bar 64 and the vacuum land 82 on the vacuum bar 74 are not connected directly to each other. The vacuum chamber 42 is connected to its vacuum source through the - vacuum bar 74 and the positioner 86. The mounting and 35 positioning for the vacuum bar 74 are separate from those for the U~JD~L ~alll bar 64. This; ;)~_8 _g_ ~l 87~q9 wo 95/29765 . ~ 67 perforr-nre of the die and allows precise, r~re~
vacuum system gas f low. Irhe robust conf iguration of the vacuum bar system also aids in the ~ d perf ormance as compared with known systems . Also, 5 this configuration for the vacuum bar 74 could improve performance of other known coaters, such as slot, ~xtrusion, and slide coaters. A flexible vacuum seal strip 88 seal6 between the upstream bar 64 and the vacuum bar 7 4 .
The gap G2 between the vacuum land 82 and the web 48 is not affected by coating gap Gl, overbite 0, or .;~..vcL~nC6 C changes, and may be held at its optimum value continuously, during coating. The vacuum land gap G2 may be set within the range f rom o . 076 mm to O . 508 mm. The preferrea value for the gap G2 is 0.15 mm. The preferred angular position for the vacuum land 82 is parallel to the web 48.
During coating, the vacuum level is adjusted to produce the best quality coated layer. A typical vacuum level, when coating a 2 centipoise coating liquid at 6 microns wet layer thirkn~ and 30.5 m/min web speed, is 51 mm H20. Decreasing wet layer th;rkn~C, increasing viscosity, or increasing web speed could require higher vacuum levels ~Yr--eA; ng 150 2 5 mm H20 . Dies of this invention exhibit lower satisfactory minimum vacuum levels and higher satisfactory maximum vacuum levels than known systems, and in some situations can operate with ZQro vacuum where known systems cannot.
Figures lOa and lOb show some positioning adJuL~ Ls and the vacuum chamber closurQ. Overbite ad~ translates the ~ LL aul bar 66 with respect to the upstream bar 64 such that the sharp edge 70 moves toward or away from the web 48 with respect to the ~ LLacl~u edge 72 o~ the curved land 68. Adjusting c.,.,ve Ly_l~ce rotates the upstream bar 64 wo9s/2s765 2 1 8 7 8 9 9 and the ' L- an, bar 66 together around an axis running through the ~ ..,LL~am edge 72, such that the curved land 68 moves from the position shown in Figure 10, ~way from parallel to the web 48, or back toward 5 parallel. Coating gap adju~,i L translates the U~,~LL. a~o bar 64 and the ~ LL~a~ bar 66 together to change the distance between the sharp edge 7 0 and the web 48, while the vacuum bar remains stationary on its mount 86, and the vacuum seal strip 88 flexes to 10 prevent air leakage during adjustments. Air leakage at the ends of the die into the vacuum chamber 42 is m;n;m;~od by end plates 90 attached to the ends of the vacuum bar 7 4 which overlap the ends of the u~ L, e cllU
bar 64. The vacuum bar 74 is 0.10 mm to 0.15 _m 15 longer than the upstream bar 64, so, in a centered condition, the clearance between each end plate 90 and the upstream bar 64 will range from 0 . 050 mm to 0. 075 mm.
one -~l e -~cl operating characteristic has 20 been obs~L~-d during coating. The bead does not move significantly into the space between the curved land 68 and the moving web 48, even as vacuum is increased.
This allows using higher vacuum levels than is pos$;hlP with known extrusion coaters, and provides a 25 cv~ ;n~ly higher performance level. Even where little or no vacuum is required, the invention exhibits ; vv~d perf ormance over known systems .
That the bead does not move signif icantly into the space between the curved land 68 and the web 48 also 30 means that the effect of "runout" in the backup roller 50 on ~ .LL~a-,~ coating weight does not differ from that for known extrusion coaters.
Figure 11 graphs results of coating tests which compare the perf ormance of a known extrusion die 35 with an extrusion die of this invention. In the tests, the 1.8 centipoise coating liquid containing an ~l ~7~d99 wo gsl29765 r~
organic solvent was applied to a plain polyester f ilm web. The performance criterion was minimum wet layer th~rlrn-~c~ at four different coating gap levels for each of the two coating systems, over the 6peed range 5 Or 15 to 60 m/min. Curves A, B, C, and D use the known, prior art die and were performed with coating gaps of 0.254 mm, 0.203 mm, 0.152 mm, and 0.127 mm, respectively. Curves E, F, G, and H use a die according to this invention at the same respective 10 coating gaps. The lower wet th;rl~naCc levels for this invention, ~d to the prior art die, are easily visible. Figure 12 shows _ ~ tive test results for a similar coating liquid of 2 . 7 centipoise viscosity, at the same coating gaps. Once again, the performance 15 a~v~.l,Lc-ge for this invention is clearly visible.
Figure 13 is a collection of data from coating tests where liquids at seven different viscosities, and containing different organic solvents, were applied to plain polyester film webs.
20 The results compare performance of the prior art extrusion coater (PRIOR) and this invention (NEW).
The perf ormance criteria are mixed . Perf ormance advc.l~tages ~or this invention can be f ound in web speed (Vw), wet layer thirl-n~cc (Tw), coating gap, 25 vacuum level, or a combination of these.
One measure of coater performance is the ratio of coating gap to wet layer thi rl-n~cc (G/Tw), ror n particular coating liquid and web speed. Figure 14 shows a series of cv.v-La,,L G/Tw lines and viscosity 30 values of an extrusion die of this invention, for nine different coating liquids. The liquids were coated on plain polyester film base at a web speed of 30. 5 m/min. A few viscosity values appear to be out of order, due to the effect of other coatability factors.
35 Four additional performance lines have been added after calculating the G/Tw values for 30.5 m/min web 2~ rJq Wo95l29765 p~ ", ~
~peed from Figures 11 and 12. From top to bottom, the solid performance lines are the G/Tw for liquids o~
2 . 7 centipoise and 1. 8 centipoise coated by a known extrusion die and the G/Tw for liquids of 2 . 7 5 centipoise and 1. 8 centipoise coated by an extrusion die of this invention. The lines for of this invention rt~Las~ l greater G/Tw values than the lines for o~ the prior art coating die. In addition, the lines for this invention are close to being lines of ~.. ,.,~1 ,Inl G/Tw, averaging 18 . 8 and 16 . 8, respectively.
The lines of the known coater show conQid-o~ably more G/Tw variation over their length. This invention has a much i vv_d operating characteristic for ~-;ntA~nin~ a coating bead at low wet th;~kn~ s values, over known systems.
Coating dies of this invention can be used as high performance liquid feed devices for roll and kiss coaters. Figure 15 shows a three roll reverse roll coater using an extrusion die 40 to feed coating liquid 14 to a casting roller 330. Because the surface of the casting roller 330 passes the die 40 in a ~ -~l direction, the die 40 is inverted and the vacuum chamber 42 is above the slot and the coating bead . This does not af f ect coating perf ormance . A
metering roller 332 removes excess coating liquid, leaving a precise layer on the casting roller 330. A
doctor blade 334 removes the excess coating liquid from the metering roller 332 and drops it into a liquid return pan 336 for recirculation.
M~An~hil~, a bead-splitting action transfers part of the coating liquid from the casting roller 330 to the web 48 moving around the backup roller 50.
After the bead splits, a second doctor blade 338 cleans the r~ ;n~n J coating liquid from the casting roller 330 and runs it into the recirculation pan 336.
Alternatively, the backup roller 50 can be rubber wo 95ng76s 2 1 8 7 ~ 9 9 covered 60 the castinq roller 330 can contact the web and tr~ns~er all of the coating liquid in this area to the web. The second doctor blade 338 would then clean any liquid from the casting roller 330 which i6 outside of the web width.
Figure 16 shows a two roll reverse roll coater using an extru6ion die 40 to feed coating liguid to the surface of the web 48 moving around the backup roller 14, which is a wrapped casting roller.
The metering roller 332 removes excess coating liquid from the surface of the web 48, leaving the desired, precise wet coated layer. The doctor blade 334 cleans the excess coating liquid from the metering roller 332 and runs it into the recirculation pan 336. Use of this system in one example increased the vacuum window from 5 . 08 mm to over 254 mm H20, and increased the liquid feed coating gap from 0 .10 mm to 0 . 36 mm, thereby improving stability and practically eliminating streaking.
Figure 17 shows a gravure coater using an extrusion die 40 to feed coating liquid to the surface of a knurled roller 340. The die 40 has its vacuum chamber 42 above its coating slot. A doctor blade 342 removes excess coating liquid from the knurl pattern ~o that the desired amount transfers to the web 48 moving around the rubber-~uve:~d backup roller 314.
The excess coating liquid recirculates through the pan 336. This method of feeding coating liquid to the surface of a knurled roller can also be used for other forms of gravure coating such as reverse, offset, and dif f erential .
Figure 18 shows a two roll extrusion coater using an extrusion die 40 to feed ccating liquid to the surface of the casting roller 330, with stability from the vacuum chamber 42. The layer of coating liquid is thin and precise 80 that a metering roll is 21 8789q wo 95l2976~
not required. The bead split takes place directly to the web 48 moving around the backup roller 314. A
doctor blade 338 remove6 the coating excess liquid rrom the casting roller 330 and recirculates it -~ 5 through the pan 336. Alternatively, the backup roller 50 can be rubber covered 80 the casting roller 330 can contact the web and transfer all of the coating liquid in this area to the web. The second doctor blade 338 would then clean any liquid from the casting roller 330 which is outside of the web width.
Figure l9a shows a kiss coater where an extrusion die 40 feeds coating liquid through a manifold 54 and a slot 56 to a transfer roller 344 such as a spindle having a ~;~ tQr ranging from 25.4 mm to 50.8 mm. The coating bead is st2~hili7od by the vacuum chamber 42. The coating liguid on the transfer roller 344 is kiss transferred to form the coated layer on the web 48. The small 1;: Qr transfer roller 344 has a small kiss transfer area, and ~ ~ve 8 web stability over that with a larger transfer roller by reducing web flutter and cross tension marks. The surface of the transfer roller 344 can be, for example, smooth, polished, medium grind, grit blasted, or knurled.
Figure l9b shows a ki6s coater where the extrusion die 40 with a vacuum chamber 42 feeds coating liquid to the surface of a kiss transfer roller 344. The roller 344 haB a larger rli2 - than the spindle of Figure l9a. The coating liguid is kiss transferred to form the coated layer on the web 48.
Figure l9c shows a kiss coater where a slide coating die 310 feed2-2 coating liquid to the surface of a kiss transfer roller 344. The coating liquid is kiss transferred to form the coated layer on the web 48.
2~ 87899 Wo gs/2s765 r~
Figure 20a shows a kiss coater where n dual-layer extrusion die lOo reeds two coating liquids 116, 124 through ~hAnn~ 118, 126 to the 6urface of a spindle, such as a transfer roller 344 having a 1l~ tt:L ranging from 25.4 mm to 50.8 mm. The two coating liquids on the transfer roller 344 are transferred to form two coated layers on the web 48.
~igure 20b shows a kiss coatQr where a dual-layer extrusion die 100 feeds coating liquid to a kiss transfer roller. The roller 344 has a larger rl~ ~r than the roller of Figure 20a. Two coating liquids 116, 124 are fed through two separate manifolds and two separate slots to meet at the coating bead. The two coating liquids are transferred to the web forming wet coated layers.
Figure 20c shows a kiss coater where a dual-layer extrusion die 100 feeds coating liquid to a kis6 transfer roller 344. The two coating liquids 116, 124 are fed through two manifolds, but only one slot, meeting inside the die. The two coating liquids on the surface of the transfer roller 344 are transferred to form the two coated layers on the web 48.
Figure 20d shows a kiss coater where a multiple layer coating version of the die 220 of Figure l9c feed6 four coating liquids onto the surface of the tran~fer roller 344. Four liquids 116, 124, 346, 348 are fed through the die 100, down slide surfaces 236 to form four layers on the surface of the transfer roller 344. These layers are transferred to ~o ~onn ~our ~o~t~ I l=yer- or the web ib.
Claims (7)
1. A die coating apparatus for coating fluid coating onto a web moving around a backup roller comprising:
- a die (40) having an upstream bar (64) with an upstream lip (60) and a downstream bar (66) with a downstream lip (62), wherein the upstream lip (60) is formed as a land (68) having a shape cor-responding to that of the backup roller (50), and the downstream lip (62) is formed as a sharp edge (70), having an edge radius no greater than 10 microns, - a passageway (52) running through the die (40) between the upstream and downstream bars (64, 66), wherein the passageway comprises a slot (56) defined by the upstream and downstream lips (60, 62), wherein coating fluid exits the die (40) from the slot (56) to form a continuous coating bead (58) between the upstream die lip (60), the down-stream die lip (62), and a surface being coated, and - a metering roller (332) which removes excess coating fluid from the surface being coated.
- a die (40) having an upstream bar (64) with an upstream lip (60) and a downstream bar (66) with a downstream lip (62), wherein the upstream lip (60) is formed as a land (68) having a shape cor-responding to that of the backup roller (50), and the downstream lip (62) is formed as a sharp edge (70), having an edge radius no greater than 10 microns, - a passageway (52) running through the die (40) between the upstream and downstream bars (64, 66), wherein the passageway comprises a slot (56) defined by the upstream and downstream lips (60, 62), wherein coating fluid exits the die (40) from the slot (56) to form a continuous coating bead (58) between the upstream die lip (60), the down-stream die lip (62), and a surface being coated, and - a metering roller (332) which removes excess coating fluid from the surface being coated.
2. A die coating apparatus for coating fluid coating onto a web comprising:
- a roller (330) on which the coating fluid is initially coated and which subsequently transfers the coating fluid to the web (48), - means (338) for removing excess coating fluid from the roller (330) wherein the removing means (338) contacts the roller (330) to remove excess coating fluid, - a die (40) for coating the coating fluid onto the roller (330) and having an upstream bar (64) with an upstream lip (60) and a downstream bar (66) with a downstream lip (62), wherein the upstream lip (60) is formed as a land (68) having a curved shape matching the roller (330) and the downstream lip (62) is formed as a sharp edge (70) having an edge radius no greater than 10 microns, and - a passageway (52) running through the die (40) between the upstream and downstream bars (64, 66), wherein the passageway (52) comprises a slot (56) defined by the upstream and downstream lips (60, 62), wherein coating fluid exits the die (40) from the slot (56) to form a continuous coating bead (58) between the upstream die lip (60), the down-stream die lip (62), and the surface being coated.
- a roller (330) on which the coating fluid is initially coated and which subsequently transfers the coating fluid to the web (48), - means (338) for removing excess coating fluid from the roller (330) wherein the removing means (338) contacts the roller (330) to remove excess coating fluid, - a die (40) for coating the coating fluid onto the roller (330) and having an upstream bar (64) with an upstream lip (60) and a downstream bar (66) with a downstream lip (62), wherein the upstream lip (60) is formed as a land (68) having a curved shape matching the roller (330) and the downstream lip (62) is formed as a sharp edge (70) having an edge radius no greater than 10 microns, and - a passageway (52) running through the die (40) between the upstream and downstream bars (64, 66), wherein the passageway (52) comprises a slot (56) defined by the upstream and downstream lips (60, 62), wherein coating fluid exits the die (40) from the slot (56) to form a continuous coating bead (58) between the upstream die lip (60), the down-stream die lip (62), and the surface being coated.
3. The apparatus of claim 2 wherein the removing means (338) comprises a doctor blade.
4. The apparatus of claim 2 wherein the removing means comprises a metering roller (332).
5. The apparatus of claim 3 wherein the coating liquid on the roller is kiss transferred to the web (48).
6 A method of die coating a surface comprising:
passing coating fluid through a slot (56) defined by an upstream bar (64) with an upstream lip (60) and a downstream bar (66) with a downstream lip (62), wherein the upstream lip is formed as a land (68) having a shape corresponding to that of the surface to be coated and the downstream lip (62) is formed as a sharp edge (70) having an edge radius no greater than 10 microns, - improving coating performance by changing the orientation of one of the land (68) and the sharp edge (70), - removing excess coating fluid from the surface to be coated using a metering roller (332) which con-tacts the surface to be coated, - selecting a length (L) of the land (68), an edge angle (A1) of the downstream bar (66), a die attack angle (A2) between the downstream bar sur-face of the coating slot (56) and a tangent plane through a line on the surface to be coated parallel to and directly opposite the sharp edge (70), and a coating gap distance (G) between the sharp edge (70) and the surface to be coated in combination with each other, and - selecting a slot height (H), an overbite (O), and a convergence (C) in combination with each other.
passing coating fluid through a slot (56) defined by an upstream bar (64) with an upstream lip (60) and a downstream bar (66) with a downstream lip (62), wherein the upstream lip is formed as a land (68) having a shape corresponding to that of the surface to be coated and the downstream lip (62) is formed as a sharp edge (70) having an edge radius no greater than 10 microns, - improving coating performance by changing the orientation of one of the land (68) and the sharp edge (70), - removing excess coating fluid from the surface to be coated using a metering roller (332) which con-tacts the surface to be coated, - selecting a length (L) of the land (68), an edge angle (A1) of the downstream bar (66), a die attack angle (A2) between the downstream bar sur-face of the coating slot (56) and a tangent plane through a line on the surface to be coated parallel to and directly opposite the sharp edge (70), and a coating gap distance (G) between the sharp edge (70) and the surface to be coated in combination with each other, and - selecting a slot height (H), an overbite (O), and a convergence (C) in combination with each other.
7. The method of claim 6 further comprising the step of applying a vacuum upstream of a formed coating bead (58) to stabilize the bead (58), wherein the bead (58) does not significantly move into the space between the land (68) and the surface to be coated even as vacuum is increased.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US23656894A | 1994-04-29 | 1994-04-29 | |
| US08/236568 | 1994-04-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2187899A1 true CA2187899A1 (en) | 1995-11-09 |
Family
ID=22890039
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002187899A Abandoned CA2187899A1 (en) | 1994-04-29 | 1995-03-17 | Combination roll and die coating method and apparatus with improved die lip |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0757595B1 (en) |
| JP (1) | JP3777405B2 (en) |
| KR (1) | KR970702757A (en) |
| CN (1) | CN1068250C (en) |
| BR (1) | BR9507568A (en) |
| CA (1) | CA2187899A1 (en) |
| DE (1) | DE69509651T2 (en) |
| MX (1) | MX9605130A (en) |
| TW (1) | TW301955U (en) |
| WO (1) | WO1995029765A1 (en) |
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|---|---|---|---|---|
| US6168682B1 (en) | 1998-02-10 | 2001-01-02 | 3M Innovative Properties Company | Method of manufacturing an optical recording medium |
| US6531025B1 (en) | 1998-08-03 | 2003-03-11 | The Procter & Gamble Company | Gravure roll printing process for adhesive application for disposable absorbent articles |
| EP0978263A1 (en) * | 1998-08-03 | 2000-02-09 | The Procter & Gamble Company | Improved adhesive printing process for disposable absorbent articles |
| US6531027B1 (en) * | 1998-08-03 | 2003-03-11 | The Procter & Gamble Company | Adhesive printing process for disposable absorbent articles |
| JP2001310151A (en) * | 2000-05-01 | 2001-11-06 | Yokoyama Seisakusho:Kk | Slit coater |
| US7097673B2 (en) | 2001-06-07 | 2006-08-29 | 3M Innovative Properties Company | Coating edge control |
| US6813820B2 (en) | 2001-12-19 | 2004-11-09 | 3M Innovative Properties Company | Method of improving coating uniformity |
| US6720025B2 (en) | 2002-07-01 | 2004-04-13 | 3M Innovative Properties Company | Slot extrusion coating methods |
| JP2007505737A (en) | 2003-09-17 | 2007-03-15 | スリーエム イノベイティブ プロパティズ カンパニー | Method for forming a coating layer having a substantially uniform thickness, and die coater |
| DE102005004891A1 (en) | 2005-02-03 | 2006-08-10 | Man Roland Druckmaschinen Ag | Device for transporting printing paper rolls |
| DE102005006064A1 (en) * | 2005-02-10 | 2006-08-24 | Man Roland Druckmaschinen Ag | Device for applying a fluid to a printing plate |
| JP2006255660A (en) * | 2005-03-18 | 2006-09-28 | Fuji Photo Film Co Ltd | Coating method and coater |
| JP3970915B2 (en) * | 2005-09-29 | 2007-09-05 | 日東電工株式会社 | Method for producing optical functional film |
| CN100448551C (en) * | 2006-08-18 | 2009-01-07 | 青岛美露亚工艺品有限公司 | Automatic coating device of artificial pearl small ball |
| JP5540539B2 (en) * | 2009-03-25 | 2014-07-02 | Ｔｄｋ株式会社 | Liquid coating apparatus and coating method |
| CN102029237A (en) * | 2010-12-09 | 2011-04-27 | 黄文俊 | Over-spray paint recovery device |
| KR20120072201A (en) * | 2010-12-23 | 2012-07-03 | 한국전자통신연구원 | Method for fabricating polarizer |
| JP2013099708A (en) * | 2011-11-08 | 2013-05-23 | Jfe Steel Corp | Method and device for roll-coating to ribbon-like substrate |
| CN105436017A (en) * | 2015-11-24 | 2016-03-30 | 无锡普瑞腾传动机械有限公司 | Painting equipment for painting line |
| CN105436018A (en) * | 2015-11-24 | 2016-03-30 | 无锡普瑞腾传动机械有限公司 | Improved painting equipment for painting line |
| CN105665232B (en) * | 2016-04-14 | 2018-01-26 | 江苏中邦输送带有限公司 | A kind of Teflon adhesive tape glues the adjustable dip molding machine of thickness |
| EP3476495A1 (en) * | 2017-10-26 | 2019-05-01 | RAMPF Holding GmbH & Co. KG | Slot die, coating arrangement comprising such a slot die, and cleaning device for such a slot die |
| DE102019113819A1 (en) * | 2019-05-23 | 2020-11-26 | Airbus Operations Gmbh | Device for paint application |
| CN110586405A (en) * | 2019-08-01 | 2019-12-20 | 安徽辉盛机电科技股份有限公司 | Novel coating machine |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE678130A (en) * | 1965-04-08 | 1966-09-21 | ||
| GB1192515A (en) * | 1967-05-22 | 1970-05-20 | Maxime Georges Willynck | Improvements in or relating to Coating Devices |
| US4245582A (en) * | 1979-02-02 | 1981-01-20 | Beloit Corporation | Adjustable rod holder for metering rod coaters |
| JPS5617661A (en) * | 1979-07-23 | 1981-02-19 | Fuji Photo Film Co Ltd | Painting method |
| US4445458A (en) * | 1982-07-21 | 1984-05-01 | E. I. Du Pont De Nemours And Company | Beveled edge metered bead extrusion coating apparatus |
| US4912948A (en) * | 1985-03-22 | 1990-04-03 | Union Carbide Chemicals And Plastics Company Inc. | Vacuum guide used in flexible sheet material treatment |
| US4774109A (en) * | 1987-07-21 | 1988-09-27 | Nordson Corporation | Method and apparatus for applying narrow, closely spaced beads of viscous liquid to a substrate |
| US5186753A (en) * | 1990-07-10 | 1993-02-16 | Ishikawajima-Harima Jukogyo Kabushiki Kaisha | Fountain coater |
| DE69224881T2 (en) * | 1991-11-06 | 1998-08-27 | Konishiroku Photo Ind | Extrusion type coating device and coating method |
| JP2684485B2 (en) * | 1992-02-13 | 1997-12-03 | 富士写真フイルム株式会社 | Coating device |
-
1995
- 1995-03-17 BR BR9507568A patent/BR9507568A/en not_active Application Discontinuation
- 1995-03-17 DE DE69509651T patent/DE69509651T2/en not_active Expired - Fee Related
- 1995-03-17 WO PCT/US1995/003367 patent/WO1995029765A1/en active IP Right Grant
- 1995-03-17 CA CA002187899A patent/CA2187899A1/en not_active Abandoned
- 1995-03-17 EP EP95912929A patent/EP0757595B1/en not_active Expired - Lifetime
- 1995-03-17 JP JP52821095A patent/JP3777405B2/en not_active Expired - Fee Related
- 1995-03-17 MX MX9605130A patent/MX9605130A/en not_active IP Right Cessation
- 1995-03-17 CN CN95192787A patent/CN1068250C/en not_active Expired - Fee Related
- 1995-03-31 TW TW084214654U patent/TW301955U/en unknown
-
1996
- 1996-10-28 KR KR1019960706089A patent/KR970702757A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| TW301955U (en) | 1997-04-01 |
| DE69509651D1 (en) | 1999-06-17 |
| JP3777405B2 (en) | 2006-05-24 |
| CN1147216A (en) | 1997-04-09 |
| JPH10500354A (en) | 1998-01-13 |
| DE69509651T2 (en) | 2000-03-09 |
| BR9507568A (en) | 1997-08-05 |
| EP0757595B1 (en) | 1999-05-12 |
| MX9605130A (en) | 1997-08-30 |
| EP0757595A1 (en) | 1997-02-12 |
| KR970702757A (en) | 1997-06-10 |
| CN1068250C (en) | 2001-07-11 |
| WO1995029765A1 (en) | 1995-11-09 |
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