GB2292369A - Paper core for rolled thin film - Google Patents

Abstract

A method for forming a tube for the core of a roll of film, foil or the like is provided. A meltable material 20 is extruded onto to a paper sheet. The paper sheet is then cut into ribbons 18. A plurality of uncoated paper ribbons are wound to form the inner plies 12 of a tube. The coated ribbons 18 are then wound about the plies formed by the uncoated ribbons to form the outer plies and surface of the tube. The entire tube is heat treated to melt the coating 20. The film is affixed on the paperboard tube preferably by first statically charging the coating and wound thereabout so that the tube forms the core of the roll. The coating may be polypropylene, polyethelyne or EVA. <IMAGE>

Description

A PAPER CORE FOR ROLLED 1!EIIN FILMS AND METHOD FOR FORMING THEREOF BACKGROUND OF THE INVENTION This invention is directed to a method for forming a core about which thin film is rolled, and in particular about forming a core as a paperboard tube.

It is known in the prior art to use heavy duty paper ply sheets wound together to form a paperboard tube providing the core of a roll of film such as plastic wrap, foil or the like. However, as the film is wound, any discontinuities on the surface of the tube make an impression in the film which is amplified as each layer of film is wound about the tube, because each layer of film merely builds on the discontinuity. Accordingly, it is desirable to have as smooth an outer surface as possible.

It is known in the prior art to form ply multi-ply spiral tubes by winding ribbons of paper around a mandrel. The ribbon plies are layered over each other. One source of discontinuity in the surface of the tube core is where two ribbon edges abut each other forming a seam in each layer of the paperboard tube. It is known in the prior art to remove discontinuities at the seam by skiving. Skiving is the beveling of the abutting edges of the top most ribbon layers to remove any such discontinuities. Further improvements in smoothness are made by saturating the outside ply with a heat-setable resin. The saturated tube is pushed through a heat die, reducing the outer diameter of the tube and allowing the resin to set. The most common resin is a phenolic resin which hardens about the tube forming a hard outer surface. Even greater smoothness is made by wet sanding the outer surface.

To make the tube readily usable by a manufacturer, a layer of tape is sometimes laid on the tube to attach the film to the tube as a start point for rolling the film about the tube, the tube forming the core for the entire roll.

This prior art process has been satisfactory. However, it suffers from the deficiency that it is a very complex process which is sensitive to many variables such as the heat of the die, the presence of moisture during the formation and application of the resin, and the dimensions of the product because the outer diameter changes during the process because of the hardening of the resin and the use of heat. Secondly, the process is capital intensive requiring many materials such as resins, chemicals, and heaters and dies. Furthermore, resins and the chemical must be mixed with a great degree of skill. This difficulty makes for an expensive process. Lastly, the tape on the tube creates a discontinuity in the tube surface, the one thing the entire process must avoid.

Accordingly, it is desirable to form a paperboard tabe core about which a thin film may be attached which simplifies the process while removing discontinuities.

SUMMARY OF THE INVENTION Uncoated chipboard is cut into a plurality of ribbons. A paper web is coated with a material capable of extrusion, melting and maintaining a static charge and is cut into a plurality of ribbons. The uncoated chipboard ribbons are wound about a mandrel to form the inner plies of a tube wall. The coated paper ribbons are then wound about the inner plies to form the outer surface of a paperboard tube. The tube as a whole is treated to soften the coating of the outer plies to join the plies at the seams formed by the abutting edges of the adjacent plies. The treatment is one of a variety of non-contact methods for altering the surface of a polymeric coating. Examples include corona discharge on polyethylene or polypropylene, or flame treatment on ethylene vinylacetate hot melt coating.The coated layer is then statically charged and a film is directly applied to the tube by static electric attraction to the tube. This film is then rolled about the tube.

Accordingly, it is an object of the invention to provide an improved method for forming a roll of film or foil about a paperboard tube core.

Yet another object of the invention is to provide a simpler method for forming a paperboard core tube which may be utilized as a core.

Yet another object of the invention is to provide a paperboard core which further removes discontinuities in the surface without the need for chemical sanding or skiving.

Still another object of the invention is to provide a paperboard core capable of supporting a film roll without the need of tape or other adhesive.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the article possessing the features, properties, and the relation of elements, which are exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which: FIG. 1 is a perspective view of a paperboard tube core and roll of film formed in accordance with the invention; and FIG. 2 is a sectional view of a fragment of the paperboard core.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Reference is made to FIGS. 1 and 2 in which a roll of film formed about a paperboard core is generally indicated as 10.

Uncoated paper is cut into a plurality of ribbons which are wound about a mandrel. The ribbons are wound to form two to forty plies 12 which form the inner plies of a wall 14 of a paperboard tube 10.

Seams 16 are formed at abutting edges of plies 12.

A second group of ribbons is formed by coating a sheet of paper with polypropylene or polyethylene by extrusion or some other process. These sheets are then split into narrow ribbons which are then wound by a mandrel about plies 12 to form outer plies 18 of tube 10 having coating 20 on its outer surface. The seams 16 formed between abutting edges of 18 may also be skived or sanded to remove any discontinuities. To further remove discontinuities in the outer layer, paperboard tube 10 is treated so that the outer coating 20 softens and attaches eliminating any discontinuity formed by seams 16.

In a preferred embodiment, plies 12 and 18 have a thickness within a range of 0.009 inches to 0.040 inches. Wall 14 has an overall thickness between 0.02 inches and 1 inch. The inner diameter of wall 14 ranges from .50 inches to 12 inches dependent upon the size and use of the roll although these ranges are by way of example and in no way limiting.

Coating 20, if made of polypropylene or polyethylene is capable of receiving and holding a static charge. Accordingly, in an embodiment in which a roll of plastic film is supported by tube 10 the outer layer of tube 20 is statically charged. A film 22 is affixed to paperboard tube 10 by the attraction from the static charge and is then wound about the paperboard tube 10, tube 10 forming the core for the entire roll of film.

By forming the outer layers of a paperboard tube of paper ribbons coated with an extrudable meltable material it is possible to remove discontinuities formed at the seams in the paperboard tube by heat treating the entire paperboard tube to join the edges of the seams by melting the outer layer and smoothing out the layer to fill any discontinuities at the seams. By utilizing an outer layer capable of holding a static charge, the plastic film may be directly applied to the tube through static electric attraction without the need for tape removing a further source of discontinuities. The above explanation was in connection with a roll of film. However, the method for forming the tube itself, with the exception of static charging the tube is equally applicable for foils or other types of rolls.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above method and in the article set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter language might be said to fall therebetween.

Claims (7)

CLAIMS WHAT IS CLAIMED IS:

1. A paperboard tube for supporting a roll of film comprising a wall said wall formed as a plurality of paperboard plies; at least the outer layer of paperboard plies being coated, said coated paperboard plies being coated with an extrudable or meltable material.

2. The paperboard tube as claimed in claim 1, wherein said coating is one of polypropylene and polyethylene.

3. The paperboard tube as claimed in claim 1, wherein said coating is capable of being statically charged.

4. The paperboard tube of claim 1, wherein said paperboard plies are formed as inner plies and outer plies, said inner plies being uncoated and said outer plies being disposed about said inner plies, said outer plies being coated.

5. A method for forming a roll of film about a paperboard tube comprising the steps of extruding a meltable coating on to a sheet of paper; cutting the coated sheet of paper into a plurality of ribbons; winding ribbons of uncoated chipboard to form the inner plies of said paperboard tube; winding said ribbons of coated paper about said uncoated plies to form an outer layer of said paperboard tube; heat treating the entire tube to melt the coating; and affixing a film to the paperboard tube.

6. The method of claim 4, further comprising the step of statically charging the coating to affix the film to the paperboard tube.

7. The method of claim 5, wherein said coating is formed of one of polypropylene, polyethylene and EVA hot melt.