US 3690297 A
Apparatus for supplying molten coating through a narrow extruding gap in a distributor head to a pond confined between a supported web and a metering blade carried by the head downstream of the gap. The metering blade extends from the lower surface of the gap and supports the pond. A heat shield is mounted to the upper gap defining member and extends over the pond to prevent heat loss from the coating material.
Description (OCR text may contain errors)
United States Patent Dentch et al.
[ Sept. 12, 1972  NON-AQUEOUS COATING OF WEBS  Inventors: Milton P. Dentch, Northboro, Mass; Robert M. Jodrey, Lake Oswego, Oreg.; Samuel L. Guastella, Westminster, Mass; Jerry J. Larrivee,
 Assignee: Blandin Paper Company, Grand Rapids, Mich.
 Filed: July 22, 1969  Appl. No.: 843,677
 U.S. Cl ..118/410, 118/429  Int. Cl ..B05c 5/02  FieldofSearch ..118/407,410,4l1,412,413,
 References Cited 7 UNITED STATES PATENTS 2,439,802 4/ 1948 Francis ..118/407 X 2,474,691 6/1949 Roehm ..1 18/410 3,070,066 12/1962 Faeber ..1 18/413 3,074,374 l/l963 Burkle ..1 18/300.6 3,348,526 10/1967 Neubauer ..118/410 3,518,964 7/1970 Nagler ..118/410 X Primary Examiner-John P. McIntosh Attorney-W. R. l-lulbert  ABSTRACT Apparatus for supplying molten coating through a narrow extruding gap in a distributor head to a pond confined between a supported web and a metering blade carried by the head downstream of the gap. The metering blade extends from the lower surface of the gap and supports the pond. A heat shield is mounted to the upper gap defining member and extends over the pond to prevent heat loss from the coating material.
16 Claims, 3 Drawing Figures PATENTED 12 3.690 297 SHEEI 1 [IF 2 FIG.
sum 2 or. 2
NON-AQUEOUS COATING WEBS This invention relates to non-aqueous coating of webs.
Objects of the invention are'to provide thin, uniform, smooth coating on webs, efficiently (e.g., at high web speeds); even with highly viscous, quick setting, printing grade coating material having low necking strength and'applied to publication paper; with inexpensive, reliable, easily maintained equipment.
The invention features. supplying molten coating through a narrow extruding gap in a distributor head, to a pond confined between the web and a metering blade carried by the head directly downstream of the gap. In preferred embodiments the pond is no greater than one-fourth inch deep; an adjustable spreader defines a surface adjacent'the gap and is integral with the head through a flexible neck, adjustment bolts being provided to raise or lower the spreader, flexing the .neck, for gap control; the blade extends forward of the gap only'a short-distance, so that as coating curls upwardly uponleaving the gap it contacts the web just beyond the top of the curl; the head is heated to maintain the molten condition of the coating; the head provides a chamber with an inlet portion tapering to an extruding portion including the gap; a shield above the pond retains heatand breaks up anyair film on the moving web; the blade is rigid enough to exert great pressure on the web and backup roll (e.g., up to 50 pounds per inch of bladewidth); web speed is in excess of 1,000 ft./min.; and the'coating sets almost immediately upon passing the blade, and is applied as thinly as under 3.5 pounds per 3,300 ftf. e 7
Other objects, features, and advantages will appear form the following description of a preferred embodiment of the invention, taken together with the attached drawings thereof, in which:
FIG. 1 is a semi-schematic elevation of a coating head connected to a screw extruder;
FIG. 2 is a cross-section of the head in operating position against the backup roll; and
FIG. 3 is a sectional view of-the head taken along 3 3 of FIG. '2.
Hopper is mounted at the inlet of a conventional heated screw ,extruder 12, the outlet of which is connected through feed pipe 14 to central inlet at the back of distributor head 22.
Inlet 20 communicates with head chamber 24, rear walls 26 and 28 (HO. 3) of which slant from the inlet to the sides of the head, respectively, so that the forward portion 30 of chamber 24 extends across the full width of the head. Top and bottom walls 32 and 34 slant towards each other, diminishing the height of chamber 24 to a narrow gap at portion 30. Top wall 36 of portion 30 is provided by spreader 38 integral with the rest of head 22 through somewhat flexible neck 40. Adjustment bolts 42 (one shown in FIG. 2) extend across recess 44 above neck 40, and enable spreader 38 to be raised or lowered, with accompanying flexure of neck 40, to control the gap in portion 30.
Metering blade 50 (0.025 inch thick, preferred range 0.0250.l inch, with a taper to a sharp point) is bolted to head 22 at the bottom of chamber portion 30, and protrudes forward of the head by three-eights inch (preferred range Vi-l .Sinch).
Teflon end deckles 54 and 56 are mounted at opposite sides of the head above blade 50. Heat shield 59 is provided one-quarter inch above blade 50. Heating pads 60, and heating element 62 are respectively provided on the surface of the head and inside spreader 38.
Head 22 is mounted on shaft 70 (FIG. 1) pivoted at opposite ends in bearings 72. Blade loading cylinders 74 are mounted to rotate shaft 70 through arms 76. Cylinders 74 are pivoted to frames 80.
The head is mounted adjacent rubber 60 P. & J. hardness, with a preferred range of 0-200 P. & J.) covered backing roll 82. Associatedconventional web handling mechanism (not shown) is provided.
In operation, web 90, of highly finished publication paper (0.0019 inch caliper), is threaded to pass over roll 82 at 2,500 ft./min. (preferred range exceeds 1,000
ft./min.). Pellets of thermoplastic printing grade coating material (greater than 50 percent pigment content) are loaded in hopper 10" and convertedto a viscous (viscosity substantially greater than 10,000 centipoise) liquid which enters chamber'24. Head 22 is kept hot to prevent the coating from setting. Cylinders 74 are actuated to position the head at an angle of 50". to the vertical (preferred range 4070) adjacent the web, and to load the tip of blade 50 against the web and roll 82 at 30 p.l.i. (pounds per inch of blade width, with a preferred range of 20-50 p.l.i.). With the blade so loaded, end deckles 54 and 56 will barely contact the web, and shield 59 will be spaced about one thirtysecond inch from the web. Chamber portion 30 is set to a 0.030 inch gap (preferred range 0.020-0.090 inch).
The molten coating will spread across the full width of the blade between the end deckles as it is forced through portion 30, and will curl away from blade 50 upon leaving the head, as shown in FIG. 2. As the mass of coating bends back over toward the blade it hits and adheres to the moving web. As the web passes by the blade all but a thin film of coating material (3.5 lbs/3,300 ftF, preferred range 0.5-15 lbs/3,300 ft?) is retained in a small pond 96 above the blade, providing an extended area over which the web isexposed to molten coating. The fact that the coating mass is traveling generally parallel to the web at initial contact, and the provision of the pond, with its extended wetting area, and the metering blade, all result in a well adhered, uniform, smooth film. The coating sets almost immediately upon passing the blade. Shield 59 conserves heat in the pond, and breaks up the air film adjacent the fast moving web.
Other embodiments will occur to those skilled in the art and are within the following claims:
What is claimed is:
1. Apparatus for applying a hot melt coating material to a moving web, comprising:
a. a backup roll mounted to rotate and support said web,
b. a source of non-aqueous melt of said material,
0. a distributor head having top and bottom members, said distributor head being connected to said source and further having 1. an extruding gap defined by said top and bottom members, said top member forming a top wall for said gap and said bottom member forming a bottom wall for said gap,
2. a hot rigid metering blade mounted to said bottom wall of said gap and having an upper surface in contact with'said material, said blade extending from said gap to provide a metering edge directly downstream of said gap, and
3. means including said top wall forming an adjustable spreader for determining the size of said p d. means for heating said distributor head to maintain the molten condition of said material,
e. means mounting said heat to have an operating position with said metering edge in contact with said web and pressed against said roll, to thereby confine with said blade and web a pond of said molten material,
f. said pond providing a web wetting zone, and
g. a shield mounted to the top member of said distributor and extending therefrom above said pond to a point adjacent said web to conserve heat to said pond and to break up any air film on said moving web.
2. The apparatus of claim 1 wherein said head provides a chamber having an inlet portion and an extruding portion of reduced height, said spreader providing a surface of said extruding portion and being movable to determine said height.
3. The apparatus of claim 2 wherein said spreader is integral with the rest of said head through a flexible neck, and an adjusting bolt is provided to raise or lower said spreader by flexing said neck.
4. The apparatus of claim 1 wherein said blade extends downstream of said gap a limited distance, controlled so that said material issuing from said gap and initially curling away from said blade will contact said web near the top of the curl.
5. The apparatus of claim 1 wherein the pressure of said blade against said roll is at least 20 pounds per inch of blade width.
6. The apparatus of claim 5 wherein said pressure is about 30 pounds per inch of blade width.
7. The apparatus of claim 1 wherein said blade is between 0.025 and 0.l25 inch thick and extends downstream of said gap by between one-quarter inch and 1.5 inch.
8. The apparatus of claim 7 wherein said blade extends downstream of said gap by three'eights inch.
9. The apparatus of claim 1 wherein said material is thermoplastic printing grade coating material and said web is highly finished publication paper.
10. The apparatus of claim 9 wherein the viscosity of said molten material is at least 10,000 centipoise.
11. The apparatus of claim 1 wherein said gap is between 0.020 and 0.090 inch high.
12. The apparatus of claim 1 wherein said gap is no greater than 0.030 inch high.
13. The apparatus of claim 1 wherein the weight of coating applied is between 0.5 and 15 lbs/3,300 ft.
14. The apparatus of claim 13 wherein said weight is no greater than 3.5 lbs/3,300 ft.
15. A distributor head for applying a hot melt coating material to a moving web on a backup roll, comprising:
a. said head having top and bottom members, and further having a chamber for receiving a molten su l of said material; b. a re ri ow extrusion gap leading from said chamber to an outside surface of said head, said extrusion gap being defined by said top and bottom mem? bers, said top member forming a top wall for said gap and said bottom member forming a bottom wall for said gap;
c. a rigid metering blade mounted in said gap, forming a portion of a bottom wall thereof, and extending therefrom with a metering edge directly downstream of said gap;
d. means for heating said head and blade to maintain material in said chamber and gap in a molten condition;
e. means for adjusting the size of said gap; and
f. a heat shield mounted to the top member of said distributor and extending from said head above said gap and blade to conserve heat in material being discharged from the gap on said blade.
16. The apparatus of claim 15 wherein said means for adjusting the size of the gap comprises a spreader integrally formed with said head through a flexible neck, said spreader forming an upper wall of said gap, and means for moving said spreader by flexing said neck.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,690,297 Dated September 12, 1972 Inventor(s) Milton P. Dentch et. al.
It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
On the cover sheet  v "Mich." should read Minn. Column 1, line 36, "form" should read from Column 3, line 11, "heat" should read head lines 1 l9 and 20, "heat to said pond" should read heat in said pond vSigned and sealed this 20th day of March 1973.
EDWARD M. FLETCHER,JR. v
ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-IOSO (10-69) USCOMM-DC 60376-P69 9 [L5, GOVERNMENT PRINTING OFFICE: I969 0-366-335.