Slipsheet, divider sheet and method for making the same
The present disclosure provides a slipsheet and/or divider sheet and method for making the same, and method for moving and storing containers with use of the slipsheets or divider sheets. The sheets have an imprint or an embossing that provides a raised planar surface. The raised planar surface preferably comprises a plurality of ridges, crowns or crests, which are preferably arranged in a pattern throughout an upper surface of the sheet. To make the sheet, a die can be etched to have protuberances or bumps, and the die is preferably pressed into a sheet of pliable thermoplastic material. The sheet thus made has a plurality of indentations formed by the protuberances or bumps on the die, and the sheet has a planar outer surface comprising a plurality of ridges, crowns and crests between the indentations.
1. A method for making a slipsheet, comprising the steps of:
extruding a first sheet comprising high density polyethylene;
extruding a second sheet comprising linear low density polyethylene; and
passing the first and second sheets through a plurality of rollers, thereby forming a single unitary sheet having a top surface and a bottom surface,
wherein one of the plurality of rollers comprises an indented surface having a plurality of indentations, and the indented surface of the roller is adapted to impart a raised surface on the top surface of the single unitary sheet, and
wherein the indentations have a size adapted to provide a desired coefficient of friction of the raised surface that is less than a coefficient of friction of the bottom surface of the single unitary sheet.
2. The method of claim 1 , wherein the step of extruding the first sheet and the step of extruding the second sheet are performed by co-extrusion.
3. The method of claim 2 , wherein each of the rollers within the plurality of rollers are arranged vertically relative to the other rollers.
4. The method of claim 2 , wherein each of the rollers within the plurality of rollers are arranged horizontally relative to the other rollers.
5. The method of claim 2 , wherein a first sheet extrusion die and a second extrusion die are placed one above the other with linear low density polyethylene extruded and fed to an upper die and high density polyethylene fed to a lower die.
6. The method of claim 2 , wherein the plurality of rollers comprises a first roller which has a smooth surface, a second roller which has a surface comprising a plurality of protuberances and a plurality of recesses, and a third roller which has a smooth surface, and wherein the second roller is located between the first roller and the third roller.
7. The method of claim 6 , wherein the plurality of rollers press the first and second sheets together and form a single unitary sheet, the plurality of recesses on the surface of the second roller form raised surfaces on the top surface of the single unitary sheet, and the plurality of protuberances on the surface of the second roller form recessed surfaces on the top surface of the single unitary sheet.
8. The method of claim 2 , wherein the linear low density polyethylene sheet is fed to a co-extrusion box in a line between a HDPE extruder and a single sheet extrusion die.
9. The method of claim 2 , wherein the linear low density polyethylene sheet is fed immediately upstream of a single sheet extrusion die, which also receives a high density polyethylene sheet that has been extruded.
10. The method of claim 6 , wherein the plurality of rollers are arranged vertically with the second roller below the first roller and the third roller below the second roller.
11. The method of claim 6 , wherein the plurality of rollers are arranged horizontally with the second roller below the first roller and the third roller below the second roller.
12. The method of claim 7 , wherein the bottom surface comprises a recessed surface and a grid of ridges, wherein the recessed surface comprises a plurality of indentations arranged in a pattern.
13. The method of claim 12 , wherein the raised surface is relatively smooth in comparison to the bottom surface.
14. A method for making a slipsheet, comprising:
co-extruding a unitary sheet of plastic comprising a first sheet comprising high density polyethylene and a second sheet comprising low density polyethylene, wherein the unitary sheet has a top surface and an opposing bottom surface; and
passing the unitary sheet of plastic through a plurality of rollers, wherein the plurality of rollers press the first sheet and the second sheet together, wherein at least one of the plurality of rollers comprises an indented surface adapted to impart a raised surface on the top surface of the unitary sheet and further wherein the indented surface is adapted to provide a desired coefficient of friction value of the raised surface that is less than a coefficient of friction of the bottom surface the unitary sheet.
15. The method according to claim 14 further comprising the step of providing a plurality of extrusion dies arranged vertically with respect to each other with low density polyethylene fed to an upper one of the plurality of extrusion dies and high density polyethylene fed to a lower one of the plurality of extrusion dies.
16. The method according to claim 14 wherein the plurality of rollers comprises a first roller having a smooth surface, a second roller having a plurality of protuberances and a plurality of recesses, and a third roller having a smooth surface.
17. The method according to claim 16 wherein the second roller is located between the first roller and the third roller.
18. The method according to claim 14 wherein the recessed surface is smoother than the bottom surface.
19. The method according to claim 18 wherein the bottom surface comprises a plurality of ridges and a plurality of indentations.
20. A slipsheet made according to the method of claim 1 .
21. A slipsheet made according to the method of claim 14 .