US2490946A

US2490946A - Stretching and laminating thermoplastic sheet material with other sheet material

Info

Publication number: US2490946A
Application number: US739054A
Authority: US
Inventors: William S Cloud
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-04-03
Filing date: 1947-04-03
Publication date: 1949-12-13
Anticipated expiration: 1966-12-13

Description

Dec. 13, 1949 2,490,946

w. s. cLou STRE ING AND LAMINATING THE OPL IC SHEET TERIAL -TH OTHER SHEET MAT AL ed April 3, 1947 Y HEATING DRUM Fl LM Patented Dec. 13, 1949 STRETCHING AND LAMINATING THERMO- PLASTIC SHEET MATERIAL WITH OTHER SHEET MATERIAL William S. Cloud, Wilmette, Ill. Application April 3, 1947, Serial No. 739,054 Claims. (Cl. 154-124) In the wrapping of standard items, such as v candy bars, which are wrapped by the millions,

very small savings in the cost of wrapping become important. Accordingly, a great deal of effort already has been spent in reducing wrapping costs. Closely associated with this effort to reduce costs has been the effort to obtain a wrapper which will adequately protect the articles to be wrapped. Candy bars, for example, may become soggy or stale with changes in humidity; if their containers are not hermetically sealed, they may become infested with insects or contaminated by dirt; other dangers are readily apparent.

Many materials, including those hereinafter set forth, and numerous methods of utilizing them have been tried over a period of years in the continued effort to obtain a wrapper satisfactory both from a cost and from a protection viewpoint. None of these appears entirely satisfactory.

Certain of the materials, such as cellophane, tin, lead and aluminum foil, and waxed, glassine and other types of paper, are not heat scalable. This precludes this most effective and widely used approach to the problem of obtaining a hermetically sealed package unless such materials are especially treated with a thermoplastic. Again, certain of the materials, such as cellophane and paper, do not provide moisture protection unless they are specially treated. Some material, such as cellophane present both problems and a solution is combined, a coating which is heat sealable being provided to allow that characteristic and also to provide moisture protection.

The coatings or lining commonly used are subject to a variety of objections. For example, they, and the step of applying them,- are relatively costly, thus in effect prohibiting the use of several desirable materials for given uses. They are frequently not sufliciently resistant to the penetration of fats and oils, so that an otherwise desirable material cannot be coated or lined and thus used for given purposes. Certain admixtures of microcrystalline or amorphous waxes with synthetic resins may possess every desirable quality needed for the body of a container which is designed to hold grease or shortening, but at'the same time such mixture may not be suitable for a coating on a material designed for candy. and other food wrappers, because the material itself is inherently tacky, or because it has qualities which prevent it from being handled readily in automatic machinery.

- Certain other materials sometimes used in packaging are too costly to permit wide use, or are subject to other objections. Foil is expensive and is relatively difficult to handle on a production line. The rubber hydrochloride sheet material sold by the Goodyear Tire & Rubber Company, of Akron, vOhio, under the trade name Pliofilm" has good general characteristics in moisture protection and ease of sealing, but its cost, especially when it is printed, is high.

Known methods of laminating sheet materials have not provided a solution of these problems. For example, the lamination of sheets of Pliofilm, which had been stretched lengthwise to make it go further and thus reduce its cost, to sheets of paper has been proposed. This would produce a laminated sheet or web the paper side of which could easily be printed and the Pliofilmside of which would be heat-scalable and resistant to acids and oils. These laminated sheets would be flexible, sanitary and provide moisture protection. However, difficulties in handling the sheets, waste incurred in trimming the edges thereof and other anticipated factors, so raised the necessary price that wide demand has not been forthcoming for these sheets. These sheets would also be subject to the limitations of Pliofilm which has been stretched in only one direction. Such a stretch is relatively uneven and therefore the sheet will tear or break if the stretching operation is continued long enough. This tearing or breaking may occur before the sheet is reduced to the desired thinness and, if not, an undesirable variation in thickness will result. This one directional stretch rearranges the molecules in the Pliofilm so that it can be torn far easier in the direction of the stretch than it can be in a direction perpendicular thereto, so that a sheet of varying strength results.

I have invented or discovered a novel method whereby a sheet of organic plastic material, such as Pliofilm, may be stretched in two directions while so controlled that approximately uniform thickness and strength result, thus allowing an unusual amount of stretching, and may be lami- 4 nated to another sheet, of paper, foil, or whatever material is desired. The result of this stretching in two directions is that the molecules of elongate shape are disposed mainly parallel to the surface of the sheet and within this plane are either distributed promiscously or predominantly disposed at rightangles to each other, thus resulting in resistance to tear in more than one direction.

The novel method produces a wrapping material which combines low cost with adequate pro- 3 tection for the articles to be wrapped. It may be utilized on standard wrapping machinery.

Other objects and advantages of my invention will be apparent from the following description and from the drawing, in which:

Fig. 1 is a diagrammatic view of one form of apparatus chosen for illustration of my invention, shown in side elevation, some details being omitted for clarity. A

Although the law requires a full and exact description of at least one form of the invention, such as that which follows, it is, of course, the purpose of a patent to cover each new inventive concept therein no matter how it may later be disguised by variations in form or additions of further improvements; and the appended claims are intended to accomplish this purpose by particularly pointing out the parts, improvements, or combinations in which the inventive concepts are found.

In order to illustrate how my method of stretching and laminating thermoplastic sheet material with other sheet material is performed, attention is directed to Figure 1, wherein a web I of unprinted, stretchable sheet material is fed or unwound from roll 2.

Certain of the web materials which will be used in connection with my invention are normally non-stretchable at room temperature. Some. such as Pliofilm, must be heated to render them soft and stretchable. The term stretchable" is, of course, relative since any film will stretch minutely. In Figure l, I have illustrated heating of the web material by having idler rolls 3 and 3' guide it around heated drum 4. However, it is to be understood both that this is not the only method of heating the web material and that, in the case of a web material which must be chemically treated to render it stretchable, this heating would be omitted and the appropriate chemical treatment substituted. I then stretch the web progressively.

In Figure l, I have illustrated an apparatus for progressively stretching successive portions of the web both laterally and longitudinally and for holding the stretched web against contraction. Such apparatus is especially desirable for use in connection with web material such as Pliofilm which, when heated and stretched, becomes very elastic.

From roll 3, the web is guided by idler roll 5 to a position where its edges are gripped at spaced intervals by holding means on the tips of arms 8, pivotally mounted on sprocket chains 1. Arms 6 are constructed and operate in substantially the same manner as arms l0 described in my copending application, Serial No. 692,323, filed August 22, 1946, wherein substantially similar stretching apparatus is fully described, said description being incorporated herein by reference. For the purpose of this application it is sufficient to indicate that sprocket chains I may be driven at the same rate as is web I. Mounted on chains I at fixed intervals are arms 6, the tips of which bear holding means. These arms are pivotally mounted so that, from the position extending horizontally inwardly toward each other at which they grip web I, they may be forced by guide bars 8 to a vertical position, to force the opposed rows of the web-holding tips away from each other and thereby stretch the web laterally. Upon completion of the lateral stretch of web I, the web-holding tips arrive at the top of the sprocket Ill. As they are carried from this position around the sprocket, the distance between the web-holding tips of arms 8, in each of the rows carried on chains I, is increased longitudinally, thereby stretching web I lengthwise.

It is to be understood that web I may be stretched by other means than those which I have illustrated. For example, it may be stretched lengthwise by driving idler roll 3' and all subsequently operating parts of the apparatus at a faster rate than heating drum 4; or it may be stretched laterally by the use of tentering means after it has been rendered stretchable, in which case provision would have to be made for holding it against contraction until after the lamination; or a combination of these may be used.

In timed relationship with the movement of web I, a second web l l of paper. foil, or whatever other suitable material is desired to be laminated with web 1, is feed or unwound from roll II. If this material is one to which web 1 will not seal under pressure, it may be guided by idler rolls i3 into a position where a suitable binder, such as glue, is applied to it.

The two webs i and Ii are brought together and passed between pressure rolls I4 and W to laminate them.

Web H is preferably narrower than stretched web I, to an extent sufficient to allow it to avoid contacting the web-holding tips of arms 6 and to be laminated to web i across the complete width of web ll. This is ensured by the disclosed apparatus wherein the web-holding tips of arms 6 extend beyond the sides of pressure roll H. The portion of web I which is to be laminated is preferably guided to pressure roll H by guide roll 9, which may be driven by any desired means.

As the two webs are being laminated, the excess edge of web I passes between cutting rolls l6 and drum I4 which trims off the unlaminated edges of web I, this excess being carried away by the web-holding tips. When web I is Plioillm, I prefer to substitute hot wires for cutting rolls l6. At this time the laminated web can also be divided into strips of any desired width by passing it between suitably placed cutting rolls.

As web I of the laminated web is in a stretched condition, and may be in an elastic condition, depending on the material used, Pliofilm, for example, being elastic when heated and stretched, it may be necessary to hold the laminated web to avoid its being distorted by the shrinking or contracting of web I. This may be done by winding it on pressure roll H which may be flexibly mounted to allow this dual use. The laminated web may be left on roll l4 until web I has set so as to lose its elastic quality. When web I is made of certain materials it may be set by other means, as by blowing cool air on it, so that it may not be necessary to roll up the laminated web and allow it to set.

It is to be noted that the difliculty and expense of slip-sheeting, heretofore necessary when winding or rolling up certain softened and stretched materials, such as Pliofilm, because of the tendency of such materials to adhere to whatever they contact, is eliminated, web ll of the laminated web serving as a "slip sheet.

I claim:

1. Web treating apparatus including spaced rows of traveling holding means having web engaging portions for holding the longitudinal edges of the web at spaced points, means for progressively feeding the web to said holding means in generally outstretched condition, and means for progressively separating the rows laterally and progressively longitudinally separating from one another the web engaging portions of each row while the webis held thereby, to stretchthe web, and means for applying to said stretched web a second web and rolling up the webs jointly, while the stretched web is thus held stretched, to maintain it against contraction until it sets.

2. Web treating apparatus including spaced rows of traveling holding means having web engaging portions for holding the longitudinal edges of the web at spaced points, means for progressively feeding the web to said holding means in generally outstretched condition, and means for progressively separating the rows laterally and progressively longitudinally separating from one another the web engaging portions of each row while the web is held thereby, to stretch the web, means for applying to said stretched web a second web and rolling up the webs jointly, while the stretched web is thus held stretched, to maintain it against contraction until it sets, and means to apply a binder to one of said webs before they are brought together.

3. Web treating apparatus including spaced rows of traveling holding means having web engaging portions for, holding the longitudinal edges of the web at spaced points, means for progressively feeding the web to said holding means in generally outstretched condition, and means for progressively separating the rows laterally and progressively longitudinally separating from one another the web engaging portions of each row while the web is held thereby, to stretch the web, and means for applying to said stretched web a second web and rolling up the webs jointly, while the stretched web is thus held stretched, to maintain it against contraction until it'set's, and means effective as the webs are rolled up for trimming from said stretched web the edges engaged by the holding means, said holding means at the time of rolling up lying beyond the ends of the roll.

4. The method of treating a web of plastic material which comprises continuously advancing a web of said material, progressively holding the web at spaced points along the longitudinal edges thereof, progressively moving the opposed points laterally away from one another to stretch the web transversely, and progressively longitudinally stretching the portion of the web between said points while said portions of the web are being held against lateral contraction, applying a second web to the stretched web and rolling up said webs jointly, while the stretched web is held stretched in both directions, to maintain the stretched web against contraction until it has set.

5. The method of treating a web of rubber hydrochloride which comprises continuously advancing a web of said material, progressively holding the web at spaced points along the longitudinal edges thereof, progressively moving the opposed points laterally away from one another to stretch the web transversely, and progressively longitudinally stretching the portion of the web between said points while said portions of the web are being held against lateral contraction, applying a narrower second web to the stretched web and rolling up said webs jointly, while the stretched web is held stretched in both directions, to maintain the stretched web against contraction until it has set.

6. The method of treating a web of rubber hydrochloride which comprises continuously advancing a web of said material, progressively heating the web to facilitate the stretching thereof,

progressively holding the web at spaced points. along the longitudinal edges thereof, progressively moving the opposed points laterally away from one another to stretch the web transversely, and progressively longitudinally stretching the portion of the web between said points while said portions of .theweb are being held against lateral contraction, applying a second web to the stretched web and rolling up said webs jointly, while the stretched web is held stretched in both directions, to maintain the stretched web against contraction until it has set.

7. The method of treating a web of plastic material which comprises continuously advancing a web of said material, progressively holding the web at spaced points along the longitudinal edges thereof, progressively moving the opposed points laterally away from one another to stretch the web transversely, and progressively longitudinally stretching the portion of the web between said points while said portions of the web are bein held against lateral contraction, applying a narrower web to the stretched web and rolling up said webs jointly, while the stretched web is held stretched in both directions, to maintain the stretched web against contraction until it has set, and trimming the stretched web to the width of the narrower web as they are rolled up.

8. The method of treating a web of rubber hydrochloride which comprises advancing a web of said material, heating the web to facilitate stretching it, progressively holding the web along the longitudinal edges thereof, progressively moving the longitudinal edges laterally away from one another to stretch the web transversely, and progressively longitudinally stretching the web between points held along the edges while said portions of the web are being held at said points against lateral contraction, applying a second web to the stretched web and rolling up said webs jointly, while the stretched web is held stretched in both directions, to maintain the stretched web against contraction until it has set.

9. The method of treating a web of rubber hydrochloride which comprises advancing a web of said material, heating the web to facilitate stretching it, progressively holding the web alon the longitudinal edges thereof, progressively moving the longitudinal edges laterally away from one another to stretch the web transversely, and progressively longitudinally stretching the web, applying a second web to the stretched web and rolling up said webs jointly, while the stretched web is held stretched in both directions by holding the stretched web along its longitudinal edges adjacent the point at which the stretched web and said second web meet and are rolled together, to maintain the stretched web against contraction until it has set.

10. Laminating apparatus including means for moving and softening a web of rubber hydrochloride, comprising a driven heated drum, opposed rows of gripping elements adapted to grip opposite edges of said web as it is passed from said drum, such elements being carried on arms pivotally mounted at spaced intervals on sprocket chains, guide bars adapted to swing the arms to increase the lateral distance between oppositelydisposed gripping elements as they travel to stretch said web laterally, sprockets over which said sprocket chains pass with the said arms generally in a plane perpendicular to the axis of said sprockets to swing said arms on each of said chains apart angularly to separate said gripping elements, to stretch said web longitudinally,

means for moving a web of paper comprising a driven drum, a roller rotating in contact'with severing the strips of said first web being held by 8 said gripping elements from the balance or said web as it is being laminated with said second web.

WILLIAM S. CLOUD.

mm ENCES cnm The following references are of record in the iile of this patent:

UNITED STATES PATENTS 10 Number Name Date 1,211,706 Hoerbelt Jan. 9. 1917 2,201,416 Wagner May 21, 1940 $439,177 Young Oct. 14, 1947