US3511693A - Hot melt coating - Google Patents

Description

May 12, 1970 I D. M. DAVIDSON HOT MELT COATING 5 Sheets-Sheet 1 Filed May 1, 1967 lA/VE/VTOR DAVID M. DAVIDSON A TTORNEY May 12, 1970 D. M. DAVIDSON HOT MELT COATING 5 Sheets-Sheet 2 Filed May 1, 1967 v: mm

. B m uE May 12, 1970 D. M. DAVIDSON 3,511,693

HOT MELT comma Filed May 1, 1967 I 3 Sheets-Sheet s United States Patent US. Cl. 117102 9 Claims ABSTRACT OF THE DISCLOSURE This invention relates to apparatus and methods of applying coating material to a Web such as paper or the like, in which the coating material is one which solidifies at a temperature somewhat above normal room temperature and thus must be heated to a fiuid state for application thereof to a web. Such a coating material is referred to as a hot melt coating.

The invention relates still more particularly to the application of such a hot melt coating material by methods known as trailing blade methods.

BACKGROUND OF THE INVENTION In the past, hot melt materials have been applied to a web by various methods.

However, as far as is known, prior to this invention, a hot melt coating has not been applied to a web by a trailing blade method.

A trailing blade method of application of a coating material to a web has certain advantages which are usually not obtainable in other methods of coating. For example, better coating weight uniformity and better pattern-free coatings may be obtained by a trailing blade method of coating. Also, a trailing blade method of coating is usually capable of higher speed operation than is possible by other methods of coating. Furthermore, by the use of a trailing blade method a wider range of viscosities of coating material is possible. Also, a trailing blade method of hot melt coating has been found to reduce the amount or degree of penetration of the coating material into or through the web. This is particularly advantageous in carbon coating of a tissue web.

SUMMARY OF THE INVENTION In this invention apparatus and methods are provided for applying a hot melt coating to a web. In this invention apparatus is provided which heats a quantity of coating material at a source of supply thereof. Coating material is transmitted from the source of supply thereof to a container from which a portion of the material moves to a web. The material in the container has heat applied thereto. Means are provided for causing a relatively large volume of fiow of coating material through the container and through the source of supply thereof. Thus, the coating material is constantly applied to the web at an optimum temperature. Therefore, the viscosity of the coating material is optimum as it is applied to the web.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective diagrammatic view of coating apparatus of this invention.

FIG. 2 is an exploded perspective view drawn on a larger scale than FIG. 1, of a portion of the apparatus of FIG. 1.

3,511,693 Patented May 12, 1970 FIG. 3 is a sectional view, drawn on a larger scale than FIGS. 1 and 2, of a portion of the coating apparatus.

FIG. 4 is a diagrammatic side view, drawn on a smaller scale than the other figures with parts shown in section, showing a modification in a portion of the coating apparatus of this invention.

FIG. 5 is a diagrammatic perspective view of other apparatus of this invention.

FIG. 6 is a diagrammatic side view, drawn on a smaller scale than FIG. 5, of the apparatus of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus of this invention is adapted for use in applying a coating material to a continuous web in which the coating material comprises any coating material which solidifies at a temperature above normal room temperature. The coating material is thus a material known as a hot melt material. Such a coating material may, for example, comprise waxes, resins, certain oils, and may include pigments and the like.

FIG. 1 shows a continuous web 16 which extends-under a rotatable drum or roll 18 and over a rotatable drum or roll 20. The web 16 also extends under the roll 20 and therefrom, to the right, as shown in FIG. 1.

An elongate blade 24 is positioned adjacent the roll 20 and in engagement with the web 16, as shown in FIG. 3. The blade 24 extends substantially the length of the roll 20. The blade 24 is preferably thin and somewhat flexible. Directly below the blade 24 at a portion thereof spaced from the roll 20 is an elongate strip 26 which extends substantially the length of the blade 24. Below the strip 26 is an elongate block 28 which is also substantially the same length as the blade 24. The block 28 has a plurality of spaced-apart openings 30 therein along the length thereof. Studs 32 are used to attach the block 28 to a holder 36 as a stud 32 is positioned within each opening 30 and threadedly extends into the holder 36. The holder 36 is preferably constructed of material which has good thermal conductivity.

The block 28 has a plurality of upwardly extending pins 38 on the upper surface thereof. Each of the pins 38 extends through the strip 26 and through the blade 24 and into a cover member 40. The cover member 40 has aligned holes 42 therethrough, through which bolts 44 extend into the block 28. The cover member 40, thus, is in firm engagement with the upper surface of the blade 24, as the cover member 40 secures the blade 24 and the strip 26 to the holder 36 along the length thereof.

The holder 36 has a pair of passages 51 therein which extend the length thereof. At each end of the holder 36 is a cover plate 48 which is attached to the holder 36 by means of screws 50. The passages 51 are thus closed at the ends thereof by the plates 48.

Each plate 48 has a stem 52 secured thereto and extending therefrom. Each stem 52 extends through a slot or opening 56 in an end wall 58 for support of the holder 36. Each cover plate 48 is thus adjacent one of the end walls 58.

Each end wall 58 has an arcuate edge 60 which is in juxtaposition with the roll 20. Ordinarily, the web 16 is disposed between the end walls 58, as the web '16 engages the roll 20. A support frame member or outer wall 66 is adjacent each end wall 58. A plurality of spacer members 62 is disposed between and secured to each end wall 3 58 and its adjacent support frame member or outer wall 66. The spacer members 62 may be adjustable in length to permit lateral movement of the end walls 58 with respect to the roll 20. However, other means may be provided for support and for lateral adjustment of the end walls 58. By such lateral adjustment, the end walls 5 8 may be positioned so that the web 16 may extend under one or both of the end walls '58. The web 16 may extend laterally outside one or both of the end walls 58 so that only a portion of the web 16 may be coated, if desired.

The blade 24, the strip 26, the block 28, and the cover 40 have the ends thereof in engagement with the end walls 5 8. Thus, the blade 24, the cover member 40, the holder member 36, the end .walls 58, and a portion of the roll 20 form a container herein referred to as a con.- tainer 69. The web 16 extends through the container 69 as the web 16 engages the roll 20. The container 69 retains hot melt material 70, shown in FIG. 3, for application to the web 16.

Each end wall 58 is provided with an opening 68 therethrough adjacent the blade 24.

The hot melt coating material 70 is supplied to the container 69 through a fluid conduit 72, shown in FIG. 1. The conduit 72 has an end portion 74 provided with a plurality of spaced-apart openings 76 which are, preferably, slightly above the level of the coating material 70 within the container 69, as shown in FIG. 3.

The conduit 72 is connected to a fluid pump 78 which is also joined to a fluid conduit 80 which extends from the lower portion of a fluid tank or reservoir 82, as shown in FIG. 1.

A motor 84 is supported upon the upper part of the tank or reservoir 82 and has a rotatable shaft 86 extending downwardly therefrom Within the tank 8 2. A paddle wheel 90 or the like within the tank 82 is attached to the shaft 86 for rotation therewith.

A conduit 92 is in communication with the upper portion of the tank 82 and extends therefrom to a pump 94. A conduit 96 is also joined to the pump 94 and extends therefrom to the bottom portion of a collector 100* which is disposed below the holder 36 and the end walls 58.

A portion of a fluid conductor 102 is shown in FIG. 1 above the collector 100 and below the holder 36. The conductor 102 is joined to a suitable source of heating fluid. The conductor 102 has joined thereto a pair of inlet conductors 104. Each of the inlet conductors 104 is in communication with one of the passages 51 within the holder 36 at one end portion thereof. The opposite end portion of each of the passages 51 is in communication with an outlet conductor 108, which is joined to a return conductor 110* which extends to the source of heating fluid. The conductors 102, 104, 108, and 110 are covered with thermal insulation material 114.

A jacket 116 encompasses and surrounds the tank or reservoir 82 and has an inlet conductor 118 and an outlet conductor 120 joined thereto for flow of fluid into the jacket 116- and from the jacket 116. The inlet conductor 118 is joined to a source of heating fluid for flow of fluid therefrom, and the outlet conductor 120' is, preferably, joined to the source of heating fluid for flow of fluid thereto, for re-heating thereof.

A jacket 124 encloses the conduits 92 and 96. A jacket 126 covers the exterior surface of the collector 100'. An inlet conductor 130 is joined to the jackets 124 and 126 adjacent the collector 100 and extends from a source of heating fluid for flow of heating fluid to the jackets 124 and 126.

An outlet conductor 132 is joined to the jacket 124 adjacent the tank 82 and extends to the source of heating fluid for return of heating fluid thereto. An outlet conductor 133 is joined to the jacket 126 and extends to the source of heating fluid for return of fluid thereto.

A jacket 136 encloses the conduits 80' and 72, A conductor 138 is joined to the jacket 136 adjacent the openings 76 and extends from a source of heating fluid for 4 flow of fluid therefrom into the jacket 136. A conductor 140 is joined to the jacket 136 adjacent the tank 82 and extends to the source of heating fluid for return of heating fluid thereto.

A fluid conductor is joined to the roll 20 at one end thereof, at the axis of rotation thereof, for flow of heating fluid into the roll 20 from a source of heating fluid. A fluid conductor 152 is joined to the roll 20 at the opposite end thereof and at the axis of rotation thereof for flow of fluid from the roll 20 to the source of heating fluid.

A fluid conductor 154 is joined to the roll 18 at one end thereof, at the axis of rotation thereof, for flow of heating fluid into the roll 18 from a source of heating fluid. A fluid conductor 156 is joined to the roll 18 at the opposite end thereof, at the axis of rotation thereof, for flow of fluid from the roll 18 to the source of heating fluid. The heating fluid which flows through the rolls 18 and 20 and through any of the conductors and jackets discussed above, may be any suitable fluid, such as steam or the like or other fluid, which has a temperature appreciably higher than the melting point of the hot melt coating material 70. Preferably, the heating fluid returns to the source of the heating fluid for re-heating. However, such return is not necessary.

OPERATION As the rolls 18 and 20 rotate, the continuous web 16 moves under the roll 18 and over the roll 20 and then around a portion of the roll 20 and moves from the roll 20 at the lower portion thereof, as illustrated in FIG. 1.

In the coating of some types of webs and/or in the use of some types of hot melt coating materials, it is necessary or desirable to heat the web 16 prior to movement thereof to the roll 20. In such event, a heating fluid is forced through the roll 18, the heating fluid entering the roll 18 through the conductor 154 and leaving the roll 18 through the conductor 156.

Heating fluid flows through the conductor 150 into the roll 20 and from the roll 20 through the fluid conductor .152. Therefore, the continuous web 16 has heat added thereto by the roll 20 as the web 16 moves over and around a portion of the roll 20, with rotative movement of the roll 20.

As the web 16 moves around the portion of the roll 20 above the blade 24, the web 16 comes into engagement with the coating material 70 which is Within the container 69. Thus, a portion of the coating material 70 within the container 69 becomes positioned upon the surface of the web 16. A part of the coating material 70 which becomes positioned upon the web 16 in the container 69 is carried by the web 16 past the blade 24, as the roll 20 rotates.

The coating material 70 which is carried by the web 16 past the blade 24 soon solidifies and becomes a coating upon the web 16. Certain characteristics of the coating applied to the web 16 are determined by the relationship of the blade 24 with respect to the roll 20. The angular relationship of the blade 24 with respect to the roll 20 may be adjusted by pivotal movement of the holder 36 about the axis of the stems 52. Thus, there is movement of the blade 24 with respect to the end walls 58. Due to the fact that the openings 68 in the end walls 58 are elongate and arcuate, the blade 24 remains adjacent the openings 68, even though the blade 24 is moved upwardly, or downwardly about the axis of the stems 52. Also, the stems 52 may be moved transversely within the slots 56 in the end walls 58. Thus, the pressure of the blade 24 upon the web 16 may be adjusted.

In order to provide a proper coating to the continuous web 16, the temperature of the coating material 70 which engages the web 16 must be a proper value. As discussed above, the coating material 70 is heated in the tank or reservoir 82 prior to flow of the coating material 70 into the container 69. However, in order to maintain a desirable temperature in the portion of the coating material 70, which engages the web 16, the coating material 70 within the container 69 has heat applied thereto. Heating fluid from a source thereof is forced into the passages 51 of the holder 36 through the conductors 104. Heating fluid flows through the passages 51 of the holder 36, then from the passages 51 into the conductors 108 for return to the source of heating fluid. Heat from the fluid within the passages 51 within the holder 36 is transmitted to the blade 24, through the cover member 40, the block 28, and the strip 26. Thus, the coating material 70 which is in engagement with the holder 36, the block 28, the strip 26, and the blade 24 receives heat therefrom.

Coating material 70 flows from the openings 76 in the end portion 74 of the conduit 72, as illustrated by arrows 166 in FIGS. 1 and 3. The coating material 70 falls into the body thereof in the container 69 from positions above the level of the material 70 in the container 69. Thus, a certain degree of turbulence or agitation is caused in the coating material 70 within the container 69, providing a mixing effect thereto.

The volume of flow of the coating material 70 into the container 69 considerably exceeds the volume of the coating material 70 which engages the web 16 and moves from the container 69. Therefore, a considerable volume of the coating material 70 flows from the container 69 through the opening 68 in each end wall 58, directly above the blade 24, as illustrated by arrows 170 in FIGS. 1 and 3. Such volume of flow of the coating material 70 through the container 69 from the tank 82 is a major factor in maintaining a constant desired temperature of the coating material 70 within the container 69. During any given period of time, the volume of fluid flow of material 70 from the container 69 is five to fifty times the Volume of material 70 applied to the web 16. Thus, it is understood that the amount of coating material 70 applied to the web 16 is considerably less than the volume of fluid flow of the material 70 through the container 69.

The coating material 70 which flows from the container 69 through the openings 68, as illustrated by the arrows 170 falls into the collector 100, as shown in FIG- URE 1. The material 70 then flows to the tank 82 through the conduits 96 and 92, as illustrated by arrows 174 in FIG. 1, as the coating material 70 is pumped by the pump 94. As the material 70 flows within the conduits 96 and 92, heat is applied thereto by heating fluid carried in the jacket 124.

The coating material 70 within the tank 82 is kept in motion, as illustrated by arrows 178, by the paddle wheel 90 which is rotatively moved by the shaft 86. The material 70 within the tank 82 is heated by heating fluid which moves within the jacket 116.

Coating material 70 flows from the tank 82 and is pumped through the conduits 80 and 72 by the pump 78. Coating material 70 which flows through the conduits 80 and 72 has heat applied thereto from heating material which flows within the jacket 136.

Thus, the material 70 which enters the container 69 through the openings 76 has a desired temperature. Furthermore, for the reasons discussed above, the portion of the material 70 which is applied to the web 16 adjacent the blade 24 has the proper temperature. Thus, the web 16 which moves from the roll 20 carries an excellent coating of the hot melt coating material 70*. Ordinarily, means are provided for quickly chilling the web 16 after movement thereof from the roll 20 to quickly set the coating carried thereby.

In the application of a carbon hot melt coating to paper webs, commonly referred to as carbonizing grades of paper, by apparatus of this invention, certain parameters have been found preferable in regard to the blade 24 in obtaining uniform, pattern-free coatings. The blade 24 has a preferable thickness in the range of between .005 inch and .015 inch. The strip 26 extends to a position sufliciently close to the roll 20 and is of suflicient rigidity so that application of suitable pressures between the blade 24 and the roll 20 does not affect the deflection of the blade 24 and does not change the area of contact of the blade 24 with the web 16. Preferably, the pressure of the blade 24 with respect to the roll 20, with the web 16 therebetween, is in the range of between 60 and pounds per square inch. Equivalent results may be obtained by the use of a blade 24 having a greater thickness if correspondingly greater pressures are applied between the blade 24 and the roll 20.

FIG. 4

FIG. 4 shows a continuous web 200' which moves over rolls 202 and 204. From the. roll 204 the web 200* moves between heater elements 206. Each heater element 206 has a fluid inlet conductor 208 and a fluid outlet conductor 210 for flow of heating fluid through the heater element 206. However, the heater elements 206 may be. heated in any other suitable manner, such as by electrical means or the like. 7

Thus, the web 200 is pre-heated prior to movement thereof to a roll 212 for application of coating material 214 thereto. The coating material 214 is partially contained by a blade 216 and a blade holder 218. The blade 216 and the blade holder 218 may be heated by any suitable means, if desired. The coating material 214 may be heated at a location spaced from the blade holder 2 18 and the blade 216 and may flow to and from the position adjacent the blade holder 218 in a manner discussed above with respect to the coating material 70. The web 200 travels from. the roll 212 to rolls 220 and 222.

FIGS. 5 and 6 FIGS. 5 and 6 show a continuous web 230 which moves over a roll 232. The roll 232 may, if desired, be heated by fluid which enters the roll 232 through a conductor 234 and which leaves the roll 232 through a conductor 236, as illustrated by arrows 238 in FIG. 5. The web 230 moves from the roll 232 to a roll 240. The roll 240 is heated by fluid which flows therethrough, entering through a conductor 253, and which leaves through a conductor 255. The web 230 then moves between the roll 2-40 and a roll 242. The roll 242 is partially disposed within a body of hot melt coating material 246 carried by a container 250. The container 250 has a jacket 249 through which heating fluid flows. The roll 242 is heated by fluid which enters through a conductor 251 and which leaves through a conductor 252, as illustrated by arrows 247 in FIG. 5.

Coating material 246 is supplied to the container 250 through a conduit 254, as illustrated by arrows 245. The conduit 254 is connected to a feed tube 256 or the like, which is disposed above the container 250 and extends substantially the length thereof. The conduit 254 has a jacket 257 through which heating fluid flows. The feed tube 256 has a plurality of openings 258 therein along the length thereof from which the coating material 246 flows to maintain a supply of the material within the container 250. A portion of the material 246 is carried by the roll 2 42 toward the roll 240 as the rolls 242 and 240 rotate. The coating material 246 carried by the roll 242 is brought into engagement with the surface of the web 230 adjacent the roll 240 for coating of the web 2 30.

The web 230 moves between the roll 240 and a blade 259 which extends the length of the roll 240 for maintaining a desired thickness and density in the coating applied to the web 230 by the roll 242. The blade 259 is supported by a holder 260. Preferably, the blade 259 is heated. Any suitable heating means, not shown, are carried by the holder 260, for heating of the blade 259. The heating means may be a fluid or electrical means or any other suitable means.

The portion of the coating material 246 which is not applied to the web 230 flows from the container 250 through conduits 270 which are in spaced-apart relationship at the lower portion of the container 250. The conduits 270 are joined to a return conduit 271. The conduits 270 and 271 are covered with a jacket 273 through which heating fluid flows. The volume of fluid coating material 246 entering the container 250 through the tube 256 and leaving the container 250 through the conduits 270 may be considerable. The material 246 flowing from the container 250 within the conduits 270 returns to a supply thereof which is heated by any suitable means.

SUMMARY Thus, it is understood that by means of the apparatus and methods of this invention excellent coatings of hot melt material may be provided to a continuous Web.

The invention having thus been described, the following is claimed:

1. Apparatus for applying a hot melt coating material to a continuous web comprising:

a rotatable roll for support of a web and for movement thereof,

an elongate blade in juxtaposition with the roll,

there being a web in engagement with the roll and disposed intermediate the roll and the blade, the Web being in engagement With the roll and the blade,

an elongate holder attached to the blade in supporting relationship thereto, end wall members in engagement with the holder and the blade at opposite ends thereof so that the. holder and the blade and the end walls form a part of a container for support of a fluid coating material, the fluid coatings material being in engagement with the portion of the web which is adjacent the blade,

the end Wall members being provided with openings therethrough adjacent the blade,

a receptacle below the ends walls for receiving fluid Which flows through the openings in the end walls,

a reservoir for retaining coating material in the fluid state, conduit means for transmitting fluid from the receptacle to the reservoir, conduit means for transmitting fluid from the reservoir to a position adjacent the part of the container formed by the holder and the blade, and the end walls, heater means for the holder, heater means for the conduits, heater means for the reservoir, heater means for the receptacle, and heater means for the roll,

rotation of the roll causing the Webto move between the blade and the roll, the Web carrying therewith a portion of the coating material,

means for causing flow of fluid through the conduit means so that fluid continuously flows out of the openings in the end walls and falls into the receptacle as the fluid is transmitted to and from the reservoir.

2. Apparatus for coating a continuous web with hot melt coating material which solidifies at a temperature above normal room temperature comprising: i

rotative roll means for movement of a portion of a web which is in engagement therewith,

blade means in juxtaposition with the roll means, the

web extending between the blade means and the roll means, the web being in engagement with the blade means and the roll means,

blade holder means in supporting relationship to the blade means,

the blade means and the blade holder means serving as container means for hot melt coating material, the blade holder means including conduit means for flow of heated fluid therethrough to heat the blade means and hot melt coating material contained by the blade means and the blade holder means,

supply means for supplying hot melt coating material to the conduit means,

a part of the hot melt coating material engaging the web and being carried by the web between the blade means and the roll means with rotative movement of the roll means.

3. Apparatus for applying coating material to a web, the coating material solidifying at a temperature above normal room temperature, comprising:

container means for containing coating material in a fluid state, means for positioning a web adjacent the coating material contained by the container means for relative movement between a portion of the coating material and a portion of the web for engagement between a portion of the web and a portion of the coating material so that coating material is applied to the Web,

means for maintaining a quantity of heated coating material within the container means,

the means for maintaining a quantity of heated coating material within the container means including reservoir means spaced from the container means, means for causing flow of coating material from the reservoir means to the container means and from the container means to the reservoir means, means for heating the container means, means for applying heat to the coating material within the reservoir means and to the coating material as the coating material flows from the reservoir means to the container means and from the container means to the reservoir means.

4. The apparatus of claim 3 which includes roll means and blade means in juxtaposition one with respect to the other, the web moving between the roll means and the blade means, means for flow of coating material in adjacent relationship to the blade means.

5. The apparatus of claim 4 in which the pressure applied by the blade means and the roll means upon the web is in the range of between 60 and pounds per square inch.

6. The apparatus of claim 4 in which the thickness of the blade means is in the range of between .005 inch and .015 inch.

7. The apparatus of claim 4 in which the pressure applied by the blade means and the roll means upon the web is in the range of between 60 and 175 pounds per square inch and the thickness of the blade means is in the range of between .005 inch and .015 inch.

8. The apparatus of claim 3 in which the means for causing flow of coating material is such that the volume of the flow of coating material from the reservoir means to the container means and from the container means to the reservoir means is within the range of between five to fifty times the volume of the coating material applied to the web.

9. The method of applying hot melt coating material to a web which is moved by a rotatable roll which is engaged by the web comprising:

containing a quantity of coating material in a fluid state at a position adjacent the web,

applying heat to the coating material while the coating material is contained at a position adjacent the web, causing flow of heated coating material while the coating material is contained,

causing relative movement between the web and the coating material so that a part of the coating material and the web come into engagement one with the other,

metering the coating material by means of a flexible blade which is in juxtaposition with the web so that a portion of the coating material remains with the web,

9 10 the fiow of coating material including recirculation 2,159,152 5/ 1939 Hershberger 117-102 thereof at a rate at which the volume of coating ma- 2,328,183 8/1943 Barrett terial recirculated is within the range of from five to fifty times the volume of coating material which re- 2729193 1/1956 Scho1 l 117 111 X mains with the Web, and heating said coating ma- 5 3,179,536 4/1965 Martmek 118 119 X terial during recirculation thereof for maintenance 3, 10/1967 Nellbauef thereof above the melting temperature thereof.

RALPH S. KENDALL, Primary Examiner References Cited UNITED STATES PATENTS 10 -R.

2,111,761 3/1938 Eckert 118602 1l7--111;118413, 602 2,117,200 5/1938 Miller.

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