JPH07185435A - Die structure for slot coating - Google Patents

Abstract

PURPOSE: To provide a new and useful sutucture of a slot coating die which is desined to apply a substantially stripe-free coating of a hot melt material (for instance, hot melt vanish) on a moving substrate such as a printed label material. CONSTITUTION: The coating die 12 has an upper lip 36, a lower lip 38 and a slot 34 disposed between the upper and lower lips. The upper lip has been cut out to the lower lip. The front surface of the upper lip has (i) a break-in surface, (ii) a release surface being extended beyond the break-in surface, and being curved so as to be away from the moving substrate and (iii) a shape defining the relief surface being extended from the slot to the break-in surface. When the slot coating die 12 is operated, the hot melt material is extruded through the slot, small particles in the hot melt material are released from the slot coating die by the shape of the upper die member. Thus, the accumulation of these particles and/or the stripe formation of the coating are prevented.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates generally to slot coating dies for applying a coating of hot melt material to a moving substrate, and more particularly to substantially stripping hot melt varnish on printed label material. The present invention relates to a slot-coating die for applying the coating without causing the above.

[0002]

Prior U.S. patent application assigned to the assignee of the present invention (filed Jan. 15, 1993, application no. 08 /
005, 237, "Mechanisms and Methods for Applying a Desired Protective Finish to Printed Label Material"), discloses a method and apparatus for applying a hot melt varnish coating to a moving web of printed label material. Has been done. The preferred slot coating die disclosed in that application is the Nordson model EP-51-2 slot coating die.

The Nordson model EP-51-2 slot coating die is believed to be effective in applying hot melt varnish to moving label material for a very long period of time without substantial streaking. This slot coating die has an upper lip and a lower lip,
And a gap formed between the upper lip and the lower lip. The hot melt varnish is extruded through the gap and onto the printed side of the web of printed label material. The upper lip has an end edge that acts as a doctor blade that rubs the varnish paint in an essentially smooth and streak-free state as the web of printed label material leaves the slot coating die.

[0004]

SUMMARY OF THE INVENTION The present invention provides a coating of hot melt material (eg, hot melt varnish) on a moving substrate such as a web of printed label material in a substantially streak-free manner. Disclosed are improved structures for slot coating dies to further enhance performance. In particular, the Nordson model EP-51-2 slot coating die label coating method extrudes hot melt varnish onto a web through a slot (generally perpendicular to the web). The end edge of the upper lip has a relatively sharp (knife-like) shape to place the paint in an essentially smooth, streak-free condition (or scrape) and is placed close to the web Has been done. However, over time, small particles in the varnish may accumulate near the distal edge of the upper lip. These particles can cause coating streaks if not removed regularly. In order to remove particles, it is necessary to interrupt the coating operation, pull the slot coating die away from the substrate and clean such particles.

[0005]

SUMMARY OF THE INVENTION The present invention provides for (i) an essentially smooth, stripe-free coating of a hot melt material on a moving substrate, and (ii) coating of small particles in the hot melt material. Provided is a slot coating die designed to release from the die and moving substrate and minimize (or eliminate) the need to interrupt the coating process to prevent streaking of the coating.

The coating die of the present invention has an upper lip, a lower lip, and a slot located between the upper and lower lips. The substrate moves forward through the coating die (ie, the substrate moves through the coating die lower lip, slot, and upper lip in that order). As the substrate advances through the slot coating die, a layer of hot melt material (eg, hot melt varnish) is extruded through the slots and applied to the substrate. The upper lip is
(i) guiding the hot melt material at least partially and flowing in the direction of movement of the substrate, (ii) as the substrate advances through the coating die, the hot melt material is gently and essentially smooth. Conditioned, (iii) has a structure that releases small particles in the coating material from the slot coating die to prevent these particles from accumulating in the coating die and to prevent streaking of the coating.

In a preferred embodiment, the front surface of the upper lip of the slot coating die is (i) a leveling surface, (ii)
It has a shape that defines a relief surface extending between the slot and the leveling surface, and (iii) a release surface that extends beyond the leveling surface and curves away from the moving substrate. The relief surface and the leveling surface are shaped to at least partially guide the coating material extruded through the slot in the direction of movement of the substrate, and (ii) smooth and essentially smooth the coating. The release surface has a shape such that small particles in the hot melt material are gently released from the slot coating die.
These particles may remain as relatively innocuous fines on the coating, but they do not accumulate in the slot coating die and thus do not cause streaking of the coating.

The slot coating die of the present invention comprises:
US Patent Application No. 08/00 filed January 15, 1993
No. 5,237, "Mechanisms and Methods for Applying the Desired Protective Finish to Printed Label Material", is particularly effective for applying hot melt varnish to a web of printed label material. Hereinafter, the features of the present invention will be described in more detail with reference to the accompanying drawings.

[0009]

DETAILED DESCRIPTION OF THE INVENTION As explained above, the slot coating die of the present invention is particularly useful in a mechanism for applying hot melt varnish to printed label material. Incorporated herein by reference, assigned to the assignee of the present invention, 19
US Patent Application No. 08/00 filed January 15, 1993
5,237, "Mechanisms and Methods for Providing a Desired Protective Finish on Printed Label Material", discloses a printed label coating scheme that can effectively use the slot coating dies of the present invention.

As shown in FIG. 1, the label coating device 10 includes
It includes a slot coating die 12 designed to apply a coating of hot melt varnish to a web 14 of printed label material. The transfer roll 16 contacts the unprinted side of the printed label material web 14 and conveys the printed label material web 14 at a relatively constant rate and through the slot coating die 12. As the printed label material web 14 passes through the slot coating die 12, the hot melt varnish is extruded through the slot coating die 12 to provide a coating 15 (FIG. 4) on the printed label material web 14. Applied on the printed side. The slot coating die 12 has a shape according to the present invention and is essentially striped coating of hot melt varnish on the printed side of the web 14 transported by the transport roll 16 and passing through the slot coating die 12. Are arranged with respect to the transfer roll 16 so that

The label coating apparatus 10 is arranged in (i) a hot melt applicator tank 18 in which the varnish is substantially melted in a liquid (molten) state, (ii) a manifold of the tank 18 and is hot. It also includes a constant volume metering gear pump 20 for pumping the metered molten varnish from the melt applicator tank 18, and (iii) a flexible conduit 22 for transferring the molten varnish to the slot coating die 12. The metering gear pump 20 can be driven at an essentially constant speed to pump a metered amount of molten varnish to the slot coating die 12 at an essentially constant flow rate. The speed of the metering gear pump 20 can be selectively varied to vary the flow rate of the varnish to the slot coating die 12. To further meter the amount of molten varnish directed to the slot coating die 12, a metering device of the type well known in hot melt adhesive metering (not shown) is used to slot coat the molten varnish. Die 12
It can be placed in a flexible conduit 22 for transport to The hot melt applicator tank 18 is preferably a Nordson Model 6000 hot melt applicator tank, which is a well known type of hot melt applicator tank for hot melt adhesives.

Furthermore, in order to supply the hot melt varnish from a storage drum (not shown) to the hot melt applicator tank 18, optionally a drum melter / device having a known construction for hot melt adhesives / A combination of drum unloaders 24 can also be provided. The thickness of the coating 15 of the hot melt varnish applied to the web 14 is (i) the flow rate of the varnish from the metering gear pump 20 to the slot coating die 12, and (ii) the web 14 passing through the slot coating die 12. Speed, and
(iii) Determined by factors such as the spacing between the slot coating die 12 and the web 14. Varnish coating 1
The thickness of 5 is (i) the flow rate of the varnish from the metering gear pump 20 to the slot coating die 12, (ii) the speed of the web 14 passing through the slot coating die 12, and to a lesser degree (web porosity). Depending on the degree, but (i
ii) It can be easily adjusted by changing the distance between the slot coating die 12 and the web 14.

The coating 15 of hot melt varnish is web 1
No. 4, No. 08 / 005,237, entitled "Mechanisms and Methods for Providing a Desired Protective Finish on Printed Label Material," filed Jan. 15, 1993. Is processed by. In particular, the web 14 is wrapped substantially around the transfer roll 16 and is conveyed by the transfer roll 16 from the slot coating die 12 to the treatment zone 26 where the varnish coating is processed to a smooth, glossy finish. Then web 1
4 is sent to the finishing zone 28, where the glossy finish is fixed in the coating of varnish and the web is conditioned to be processed as finished label material. In the finished label material, the coating of the varnish (i) gives the web of printed label material a desired glossy finish, and (ii) the web of printed label material with damage or damage caused by ambient conditions. Protects against deterioration and protects the printed web of label material from scratches and abrasion. further,
When the label material is used in certain types of packaging (eg food packaging), the coating also acts as a barrier that prevents odors from passing through the packaging.

The slot coating die 12 includes an upper die member 30, a lower die member 32, and a slot 34 formed between the upper and lower die members (see FIGS. 1 and 4). The upper and lower die members consist of tool steel, preferably P-20 type tool steel. The slot coating die 12 has an upper lip 36 integrally molded with the upper die member 30 and a lower lip 36 integrally molded with the lower die member 32. Slot 34 extends between upper and lower lips 36, 38. The lower lip 38
It has a front side 40 that faces the printing side of the web 14 carried by the transfer roll 16 and is located in close proximity thereto. The upper lip 36 is a web 1 carried by the transfer roll 16.
The front side 42 facing the print side of 4 and arranged in close proximity thereto
Have.

As shown in FIGS. 1 and 4, as the transfer roll moves web 14 through slot 12.
Web 14 passes through lower lip 38, slot 34 and upper lip 36 in that order. The slot 34 is designed so that the molten hot melt varnish is extruded therethrough at a predetermined flow rate and pressure. The front faces 42, 40 of the upper and lower lips have a special shape according to the invention, which (i) at least partially redirects the varnish to flow in the direction of movement of the web 14,
(ii) forming a hot melt varnish on the web 14 into an essentially smooth, non-striped coating, and (iii) as the web passes through the slot coating die 12, removes the small particles in the varnish from the slot coating die. Release from 12.

The hot melt varnish extruded through the slot coating die 12 is preferably Swif.
t Adhesives, 3100 Woodcreek Drive, PO Box 1546,
Hot melt varnish material from Downers Grove, Illinois 60515, having product number 2H195. Hot melt varnish is (i) substantially solid at room temperature, and (ii) about 230
^It has a softening point of ^o F (110 ° C), and (iii) about 350 ^o F (1
At 77 ° C.) it melts to a substantially liquid state and can be extruded through the slot coating die 12 onto the web 14. In addition, hot melt varnishes are used in web 14 according to the principles of US patent application Ser.
Applied to a transfer roll 1 in an essentially normal atmosphere.
After being transported a predetermined distance on the web 14 by means of 6, it partially solidifies to a predetermined state.

The web 14 comprises a substantial portion of the transfer roll 16 (eg, about 220 ^° to about 27 perimeter of the transfer roll 16).
Over 0 ^o), wound in a state in which the side facing the unprinted web 14 is in contact with the transfer roll 16. The slot coating die 12 is tilted slightly downward (eg, at a tilt angle of Φ with respect to the horizontal line extending through the axis of rotation of the transfer roll 16) so that the molten varnish passes through the slot coating die 12. And is pushed out in a direction slightly downward with respect to the moving direction of the web 14 carried by the transfer roll 16. Transfer roll 16
Accurately rotates at a speed selected by a known driving means (not shown in the figure) to move the web 14 at a predetermined constant speed so that the slot coating die 1
Pass 2. In order to change the speed at which the web 14 passes through the slot coating die 12, the transfer roll 1
The rotation speed of 6 can be selectively changed.

The slot coating die 12 is connected to a support structure of known construction, such as the Nordson model "NT" support mechanism (not shown), which mechanism pre-slots the slot coating die 12 from the web 14. The web 14 can be supported and held at a predetermined inclination angle Φ at a predetermined distance. In particular, the lower die member 32 is connected to the "NT" support mechanism by connecting means well known to those skilled in the art. The upper die member 30 is
A dowel aligned with the lower die member 32 and (i) fitted into each conventional dowel hole in the die member (see, eg, the dowel hole in FIG. 5) and aligned with the die member (shown in the figure). Not), and (i
i) by a conventional fixture (not shown) that extends through holes in the die member (see, for example, holes 52 in upper die member 30 in FIGS. 3 and 5) to join the die members together. It is connected to the lower die member 32. In addition, shims (not shown, but of known construction) may be used to limit the spacing between die members to limit the width of the slots 34. In addition, the upper die member 30 has threaded holes 54 (FIGS. 2 and 5) for receiving screws of known construction and for securing the die members together.

In accordance with the present invention, the front surface 42 of the upper lip 36 is
Has a shape for forming a hot melt varnish on the web 14 into a smooth, non-striped coating and removing small particles in the varnish from the coating die 12 without causing striping of the coating. In particular, the front surface 42 of the upper lip 36
(i) a leveling surface 60, (ii) a release surface 62 curved away from the leveling surface 60 and away from the web 14, and
(iii) has a shape that defines a relief surface 64 extending from the slot 34 to the beginning of the leveling surface 60.

Relief surface 64 is preferably substantially linear and generally extends along a tangent to transfer roll 16. The break-in surface and the release surface begin at the end of the relief surface 64 and constitute a continuous area of curved surface having a predetermined radius R ₁ . The area of the curved surface that constitutes the leveling surface 60 begins at the end of the relief surface and is proximate to the web 14. The rest of the curved surface,
The portion forming the release surface 62 is curved away from the leveling surface 60 and further away from the web 14. In the preferred embodiment, the lower edge 70 of the relief surface 64 is proximate to the slot 34. The upper edge 72 of the lower lip 38 is also adjacent to the slot 34. The lower edge 70 of the relief surface 64 is the upper edge 7 of the lower lip 38.
Offset (or cut off) with respect to 2.
Relief surface 64 towards the surface 60 Shi not from the lower edge 70 extends in relief angle θ of up to about 2 ^o.
Thus, the relief surface 64, together with the moving web 14, defines a converging passage 66 towards the leveling surface. The passages will be slot 34 during the coating process.
The hot melt varnish extruded through the web 14
In the direction of movement of at least partially turning (or guiding) towards the leveling surface 60. The front surface 40 of the lower lip 38 extends downwardly from the upper edge 72. The upper edge 72 is not in contact with the web 14 but is located sufficiently close to the web 14 to prevent hot melt varnish from flowing past the lower die member 32. Front 4
The remaining portion of the zeros are offset (or cut away) and extend away from the transfer roll 16 to provide an inlet for guiding the web 14 near the coating die 12.

As shown in FIG. 4, during operation of the slot coating die 12, the hot melt varnish is removed from the slot 34.
Extruded through and formed by the coating die 12 into a smooth, streak-free coating on the moving web 14. In particular, the coating die 12 is inclined downward at a small angle Φ (towards the direction of movement of the web 14).
The lower lip 38 has its upper edge 72 not in contact with the web 14, but is positioned sufficiently close to the web 14 to prevent hot melt varnish from flowing past the lower lip 38. The upper lip 36 is shaped to redirect (or guide) towards the leveling surface 60 in the direction of the web 14 moving the hot melt varnish. The leveling surface 60 makes light contact with the hot melt varnish, gently rubbing the varnish, leaving it essentially smooth and streak-free. The release surface 62 is gently curved away from the leveling surface 60 and away from the web 14 so that the small particles in the varnish pass through the die and are released from the slot coating die 12. Thus, the particles pass through the die and become relatively harmless fines, but do not accumulate in the slot coating die, there is no need to interrupt the coating process and clean the slot coating die, and strip the varnish coating. It does not cause formation.

As mentioned above, slot coating dies constructed in accordance with the principles of the present invention are particularly effective in the mechanism of coating a web of printed label material with a layer of hot melt varnish. An example of such a mechanism has the structure: Transfer roll silicon coated steel roll-transfer roll diameter 6.0inch (15.24cm) below at an angle of hot melt varnish 220 winding of Swift Adhesives Type 2H195-01E transfer roll around the web ^o die angle Φ about 3.0 ^o Inclination shim thickness 0.010inch (0.025cm) Upper die lip shift (or cutoff) about 0.005inch (0.0127cm) Radius of rounded upper lip 0.236inch (0.599cm) Round from slot since partial linear distance L ₁ to the end 0.315inch (0.800cm) linear distance L ₂ 0.139inch to the start portion of the Shi not from the slot surface (0.353cm) coating thickness 0.001inch ~0. 0015inch (0.002cm-0.0038cm) web printed foil label material or printed paper label Ru material Extrusion temperature of varnish 350 ^° F (177 ° C) Web speed 25-300FPM Flow rate of varnish Approximately 5-80lbs / 1 hour Relief angle θ 2.0 ^°

The above example illustrates a slot coating die having a structure that is particularly effective for webs transported by a suitable hot melt varnish and a 6.0 inch (15.24 cm) radius transfer roll. (i) radius of rounded portion, (ii) linear distance L ₁ from slot to end of rounded portion, (iii) linear distance L ₂ from slot to start of leveling surface, (iv) slot Coating die tilt angle, (v) relief angle θ, and
(vi) Certain features of the slot die shape, such as the displacement (or trimming) of the upper die lip, correlate to allow small particles from the slot coating die when smoothing the coating to an essentially smooth finish. Release to. The particular relationship of these ingredients can be changed with each other, along with the size of the transfer roll, the type of hot melt varnish, and the like.

Of course, the above embodiments of the slot coating die mechanism are useful for coating printed label material, but variations are possible. For example, the transfer roll may be made of chrome. Moreover, printed label material or other types of products can be formed of materials such as polyethylene. Furthermore, although the slot coating die is generally horizontal with respect to the transfer roll at about 9 o'clock (this is the general position and orientation), the die has a different circumference of the transfer roll. It can also be placed in position. Further, the relief surface 64 of the upper lip can be slightly curved rather than straight. Furthermore, E
Other hot melt materials such as VA (ethylene vinyl acetate) or polyethylene type can also be used. Still other variations of the principles of the invention will be apparent to those skilled in the art for applying hot melt coatings to various substrates.

[Brief description of drawings]

1 is a diagrammatic view of a portion of a printed label coating apparatus with a slot coating die constructed in accordance with the principles of the present invention.

2 is a cross-sectional view of the upper die member of the present invention taken along line 2-2 of FIG.

3 is a cross-sectional view of the upper die member of the present invention taken along line 3-3 of FIG.

FIG. 4 is an area 4- of the slot coating die of FIG.
Figure 4 is a close-up view of Figure 4, schematically showing how particles are released from the slot coating die as the varnish is smoothed and striped.

5 is a bottom view of the upper die member of FIGS. 2 and 3. FIG.

Claims (10)

[Claims] 1. An apparatus comprising a slot coating die and means for moving a substrate and passing through the slot coating die, wherein the slot coating die is used when the substrate passes through the slot coating die. A substrate may be provided with a coating of hot melt material, the substrate including an upper lip, a lower lip, and a slot disposed between the upper lip and the lower lip, wherein the substrate is the slot coating die When passing through, the substrate passes through the lower lip of the slot coating die, the slot, and the upper lip in this order, and the upper lip of the slot coating die,
A slot coating characterized by smoothing the coating to an essentially smooth finish and having a shape that releases small particles in the coating material from the coating die when the coating is smoothed to an essentially smooth finish. Die structure. 2. The upper lip has a shape that defines a leveling surface for leveling the coating to an essentially smooth finish and a release surface that extends beyond the leveling surface and away from the web. 2. The slot coating of claim 1, wherein the release surface is shaped to release small particles in the coating material from the slot coating die when the coating has an essentially smooth finish. Die structure. 3. The upper lip has a shape that defines a relief surface extending between the slot and the leveling surface, the slot having a shape that pushes hot melt material toward the substrate, 3. The slot coating die structure of claim 2, wherein the relief surface has a shape that at least partially guides the hot melt material extruded from the slot toward the leveling surface. 4. The lower lip is adjacent to the slot,
Having an upper edge having a shape that prevents hot melt material from flowing through the lower lip when coated on the substrate, and wherein the relief surface has a lower edge proximate to the slot The slot coating die structure of claim 3, wherein the lower edge of the relief surface is offset from the upper edge of the lower lip by a predetermined amount. 5. The slot coating die of claim 4, wherein the relief surface converges from the lower edge of the upper lip toward the leveling surface at a predetermined relief angle. Structure. 6. The slot coating die structure of claim 5, wherein the release surface is curved with a predetermined radius of curvature away from the leveling surface and the web. 7. The radius of curvature of the release surface is (i) a linear distance L ₁ from the slot to the end of the release surface, (ii) a linear distance L ₂ from the slot to the beginning of the leveling surface, (ii
i) a predetermined deviation between the lower edge of the relief surface and the upper edge of the lower lip, and (iv) correlating to the predetermined relief angle, the coating being essentially smooth. 7. The slot coating die structure of claim 6 wherein the small particles in the coating material can be released from the coating die when smoothed. 8. The leveling surface and the release surface are:
8. The slot coating die structure of claim 7, which defines a continuous area of curved surface having a single radius of curvature. 9. The slot coating die structure according to claim 1, wherein the hot melt material includes a hot melt varnish. 10. The relief surface is about 2 ^° from the lower edge of the upper lip toward the leveling surface.
5. The die structure for slot coating according to claim 4, wherein the die structure converges at a relief angle of.