CA1222683A

CA1222683A - Floatable sheet material and method of making

Info

Publication number: CA1222683A
Application number: CA000494317A
Authority: CA
Inventors: Stanley Lazar
Original assignee: Cantar Corp
Current assignee: Cantar Corp
Priority date: 1985-10-31
Filing date: 1985-10-31
Publication date: 1987-06-09

Abstract

ABSTRACT OF THE DISCLOSURE

A floatable on water, translucent laminated plastic sheet material having a plastic embossed film with a plurality of embossments dispersed thereon except at the longitudinal edges thereof. The emboss-ments are spaced apart and separated by land areas and a plastic backing film is laminated to the embossed film at the said longitudinal edges and at the land areas. Thus air containing buoyant cells are formed by the embossments of the embossed film and the backing film. The improvement comprise a fibrous material laminated to the sheet material at least at the longi-tudinal edges thereof, whereby the edges are reinforced by the fibrous material and the edges may be attached to correspondingly reinforced edges of another of the sheet material without substantially weakening the attached sheets of material at the attachments thereof.

Description

îz~26~33 , FLOATABLE SHEET MATERIAL AND METHOD OF M~KING
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The present invention relates to a floatable sheet material and to a method of making that float-able sheet material. More particularly, the inventionrelates to such floatable sheet material which may be assembled into covers for swimming pools.

BACKGROUND OF THE INVENTION
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Floatable sheet material has been used in the art for covering swimming pools so that during the cooler part of the swimming season, the floatable sheet material will retain the heat in the swimming pool water and, additionally, allow the water to be heated by sunlight. These covers are normally made of a kransluce~t plastic which has been rendered buoyant so that the covers float on the swimming pool water but will allow the sun's rays to pass through the covers and heat the water in the pool. During cooler periods, these covers prevent loss of heat from the water in the swimming pools. The covers are not normally secured to the sides of the pool, but are I originally manufactured, or cut, to substantlally cover the water in the pool. When the pool is to be used, the covers are removed, often by rolling onto a reel system near the pool, and are again replaced on the pool when the pool is not in use.

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` 3LZZ21683 The pool covers experience substantial stress when being removed from the pool or replaced thereon. Not only are the covers often of considerable size, and hence weight, e.g. ZO ft. x 40 ft., but especially when remo~ing the covers from the pool, the covers will be wet and will entrain some water, there-by increasing the weight. Thus, the covers can be quite heavy, and correspondingly substantial strain is placed on the covers when removing from or placing on the pool. In addition, strong winds can mave the covers about the pool, since they are free floating on the water, and that wind action can place additional stress on the covers.
As can be therefore appreciated, the covers must be strong and be able to withstand considerable stress, or otherwise the covers will deter;orate with use and begin to tear. Once the covers tear, they are, of course, more dif~icult to remove and replace on the pool and the stress during such removal and replace~
ment increases the likelihood of causing greater tears.
Such pool covers may be made by a variety of methods, but by far most of the pool covers are made by attaching sections of floatable on water (buoyant), translucent laminated plastic sheet material. 'rhis sheet material is produced by laminating an embossed film with a plurality of embossments dispersed thereon to a backing film whereby air containing buoyant cells are formed by the embossments of the embossed film and the backing film. The laminated sheet material is 3 usually made in widths of about 4 or 6 feet, and in ~ ~'r~ ~

~222tii33 continuous running lengths. The edges of the contin-uous running lengths (the longitudinal edges) are not embossed and do not, therefore, contain the buoyant cells. The running lengths of the sheet material are cut to appropriate lengths for a particular pool length and the width of the pool cover is achieved by attaching, one to the other, the appropriately cut running lengths. For example, for a 20 ft. wide and 40 ft. long pool cover, ~ feet wide running lengths are cut to sections of approximately 40 feet in length, and five of these 4 feet wide sections are attached, edge to edge, in order to provide the required 20 foot width of the pool cover.
The edges are attached, one to the other, by a variety of methods, but unfortunately all of these methods weaken the edges at the points of attachment.
For example, when the edges are attached, one to the other, by heat sealing, that heat sealing weakens the attached edges. In addition heat sealing distorts the films and the pool co~er will not lie flat on the water, resulting in an unsightly appearance. Similar-ly, when the edges are attached by adhesives or the iike, the adhesives w-111 likewise weaken and distort those attached edges, since an adhesive, in order to be effective, must in part dissolve the plastic of the sheet material. The strongest means of attachment of the edges are by sewing, but here again, the needle punctures of the edges during the sewing operation weakens the attached edges.

i ~22;~6~33 Thus, generally speaking, the weakest points of the pool cover are along the attachments of the edges of the sheet material. With continued use of the pool cover, as explained above, thesa weakest points begin to give way and the pool cover will tear and become unserviceable.
It would therefore be of substantial advan-tage to the art to provide such sheet material, where sections of the sheet material can be attached, edge to edge, without substantially weakening the attached sheets of materials at the attachments thereof. Corre-spondingly, it would be of decided advantage to the art to provide pool covers where the attachments of the sheet material do not substantially weaken the sheet material at the attachments thereof. Finally, it would also be a substantial advantage to the art to provide methods for producing such improved sheet materials and pool covers.

BRIEF DESCRIPTION OF THE INVENTION
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The present invention is based on three primary discoveries, and several subsidiary discover-ies. First, it was discovered that the conventional method of manufacture of the buoyant sheet material is amenable to modification such that during manufacture ' of the sheet material longitudinal edges of t,he contin-uous running lengths of sheet material can be easily and inexpensively reinforced. In this regard, it was discovered ,that the introduction of a reinforcement, ,.. ,~ :

~ . 12~Zt;;i~3 at least along the longitudinal edges, neither substan-tially complicates the conventional process or substan-tially increases the cost of production of the sheet material. Further, and surprisingly, it was discovered that the introduction of such reinforcement, at least along the longitudinal edges of the sheet material, did not interfere with the conventional lamination of the embossed film to the backing film in order to provide the buoyant cells.
Second, it was discovered that such rein-forcement, at least along the longitudinal edges, substantially avoided the problem of tearing of attached sections of sheet material (in the form of a pool cover) even with continued use, and even when the attachments were accomplished by the convenient conven-tional manners such as heat sealing and sewing.
These two primary discoveries, therefore, allowed the production of much improved sheet material without substantially increasinx the steps of operat-ing the conventional process for making the sheetmaterial or substantially increasing the expense of producing the sheet material. This is a considerable advantage of the present invention. It will be appreciated in this regard, that the pool cover market is a highly competitive market, and any substantial increases in the cost of either opera~ing the conven-tional process or producing ~he conven~ional pool covers would be a decided disadvantage in the market-place.

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~ hird, it was most unexpectedly found that the amount of reinforcing required at the longitudinal edges to avoid tearing along the points of attachment is quite small. In this regard, it will be appreciated that the sheet material is made of plastic films having very low tear strengths, and once a small tear occurs at the points of the attachment of the sections of sheet material, that tear will relatively rapidly further develop in the plastic films. However, with even a small amount of reinforcement at longitudinal edges, the low tear strength of the plastic films is overcome and small tears at the points of attachment will not propagate into large tears which make the pool cover unserviceable.
As a subsidiary discovery to the above, it was found that the most efficient reinforcement is that of a fibrous material, since during lamination of the embossed ~ilm to the backing film, the fibrous material can be laminated to the resulting sheet material so as to provide tear resistance in essential-ly all directions. This, of course, is opposed to a non-fibrous material, such as a more tear resistant plastic film or foam. As a further subsidiary discovery in this regard, lt was found that the fibrous material may be either woven or non-woven fibrous material and, as noted above, only small amounts thereof need be used. Indeed, the fibrous material may be in the form of only a scrim which is, as is well known in the art, an exceptionally thin and 3o ~22683 lightweight fibrous material. This is the pref'erred embodiment for the reasons explained below.
Finally, it was discovered that in the case of lightwei.ght woven or non-woven fibrous materials, e.g. scrims and fabrics, the backing fi]m for the sheet material may be constituted by a coatlng or lamination on the fibrous material and thus the fibrous material may be essentially co-extensive with the entire sheet material. This not only provides the desired reinforcement at the edges, but also rein-forces the entire pool cover, especially against abra-sion of the pool cover when removing the pool cover from the pool and when replacing the pool cover thereon.
Accordingly, briefly stated, the present invention is an improvement in a floatable on water, translucent laminated plastic sheet material. The sheet material has ~ plastic embossed film with a, plurality of embossments dispersed thereon except at the longitudinal edges thereof. The embossments are spaced apart and separated by land areas between the embossments. A plastic backing film is laminated to the embossed film at the longitudinal edges and at the land areas. Thus, this lamination provides air contain-ing buoyant cells which are formed by the embossmentsof the embossed film and the backing film. This is a conventional sheet material for producing pool covers, and the present improvement comprises a fibrous material laminated to the sheet ma-terial at least at the longitudinal edges thereof, ~Ihereby the edges are 12;~2~83 reinforced by the fibrous material and the edges may be attached to correspondin~ly reinforced edges of another section of sheet material without substantial-ly weakening the attached ~heets of material a-t the attachments thereof.
Similarly, there is provided an improvement in the process for producing a floatable on water, translucent plactic sheet material. In the process, the above-identified embossed film is laminated to the above-identified backing film at the edges and land areas to form the buoyant cells, as identified above, and the improved process is laminating fibrous material to the sheet material at least at the longitu-dinal edges thereof, whereby the edges are reinforced by the fibrous material and the edges may be attached to correspondingly reinforced edges of another section of sheet material without substantially weakening the attached sheets of material at the attachments -thereof.

BRIEF DESCRIPTION OF THE DRAWING

Figure 1 is a diagrammatic illustration of the conventional process and apparatus for producing the present sheet material, but is modified to carry out the present process and produce the present improved sheet materlal.
Figure 2 is a top view of the improved sheet material produced by the improved process.
Figure 3 is a cross~section of the sheet material of Figure 2, taken along lines A-A and show-ing reinforcement only at the edges of the sheet material.

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Flgure 4 shows another embodiment wherein the reinforcing material is co-extensive with the width and length of the sheet rnaterial.
Figure 5 shows an enlarged view of the embodime~t of Figure 4, in connection with -the backing film thereof.
Figure 6 shows a partial top view of two attached sections of the sheet material.

DETAILED DESCRIPTION OF THE INVENTION
_ As no-ted above, the present improved sheet material may be produced with only a slight, and there-fore, advantageous, modification of the conventional process for making such sheet material. For sake of conciseness, the details of the conventional process for making the sheet material will not be discussed herein in detail, since those details are well known to the art. Thus, details of such conventional process-es are disclosed in U.S. Patents 3,026,231; 3,142,559;
3,20~,~93; 3,294,3~7; and 3,416,9~4. The latter patent represents the more usual form of this conventional process and is specifically incorporated herein by reference for those details.
Howe~er, the con~entional process can be understood by reference to Figure 1. In that process, a plastic film 1 is pre-heated on a heat~ng drum 2.
Similarly, plastic film 3 may be pre-heated (pre-heat-ing is not required), on a heating drum 4. Drum 2 and, if desired, drum 4 contain hot water, oil, steam or Z~33 the like. The plastic f;lm 1, the film to be embossed, is referred to in the ar~ as the embossed film, even prior to its embossment, and that terminology will be used hereinafter. Likewise, the other film 3 is referred to as the backing film, since it backs the embossments of the embossed film and that terminology will be used herelnafter.
The embossed film 1 and the backing film 3 are passed through a nip formed between an embossing roll 5 and a backing roll 6. The embossing roll 5 has a plurality of cavities in its surface, which cavities are connected to a vacuum source so that when the embossed film is contac-ted by the embossing roll (the film bein~ in a pre-heated condition) the film is sucked into the cavities and embossed. At the same time, the backing film 3 is pressed against the embossed film and laminated thereto. The backing roll 6 is normally covered with an elastorner, e.g. silicone rubber, since it is pressed against the embossing roll at considerable pressures, e.g. 20 to ~0 lbs. per linear inch or more. The laminateA embossed film and backing film form the present sheet material 7. The outer edges of embossing roll 5 have no cavities therein so that the outer longitudinal edges of the laminated sheet material 7 have no embossments, and hence no buoyant cells. These edges are used for attaching sections of the sheet material together for forming a pool cover.
3o ~ZZ2683 The embossments ~ on sheet material 7 can be of a variety of sizes and shapes and the particular size and shape is not critical, so long as the buoyant cells produced thereby provide sufficient flotation for the sheet material so that the sheet material will float on water. However, generally speaking, the em-bossments (and hence the cavities i.n the embossing roll 5) will be essentially hemispherical or partly hemispherical in shape, and will have diameters as little as 1/~th inch to as much as 1-1/2 inches, but more usually the diameters will be from 1/L~ inch to 3/4 inch. Nevertheless, instead of hemispherical shape, the embossments may be cyli.ndrical, rectangular, triangular or any other desired shape, and the partlcular shape is not substantially important so long as sufficient buoyancy of the sheet material is provided. But more usually, the emboss-ments will be either hemispherical or partly hemispher-ical, e.g. 1/~ to 1/2 of a sphere.
Again, depending upon the particular size and shape of the embossments, the percentage of the area of the sheet material covered by the embossments in order to ~rovide suffici.ent flotation will vary.
Nevertheless, ~enerally speaking, the embossments will comprise at least 20% of the area of the embossed film (20% of the area of the sheet material) but more usually will comprise at least L~0% and up to 60 - 70%
of the area of the embossed film (the area of the sheet material). The arrangement of the embossments may also vary, as will be easily appreciated, but more usually the embossments are relatively uniformly dispersed on the embossed film (on the sheet material).

22f~83 It wlll be appreci.ated that in order to emboss -the embossed fllm and to laminate the back:ing film thereto, those films must be heated, prior -to passing through the ni.p 9 formed between the embossing roll 5 and the backing roll 6, to an elevated tempera-ture sufficient that the embossed film is laminated thereto. This temperature is referred to in the art as the embossi.ng temperature, or alternately, the laminating temperature, or alternately the sealing temperature, and these temperatures are well known in the art for various plastic films and the details thereof need not be discussed herein for sake of conciseness. However, as an example, the embossing temperature of ordi.nary polyethylene film is approxi-mately 220F. ~owever, to insure good lamination ofthe two films, i.t is the usual practice to heat at least one of the films, and preferably both of the ~ilms, to a temperature above the embossing tempera-ture, i.e. at or near the fusion temperature of the films (that temperature where the films began to lose their tensile properties, but at which temperature the films are very easy to laminate into a permanent lamina-tion). Here again, the fusion temperatures for the vari.ous plastic fi.lms are well known in the art, but, for example, the fusion temperature of ordinary polyethylene is approximately 270F. Thus, the heating of the films is such that the embossed film is at least above its embossing temperature but at or below its fusion temperature and likewise, the backing film is at a temperature such that the combination of ~2Z2~l~3 temperatures of the embossed film and the backing film are ~sufficient to permanently laminate the embossed film and the backing film.
In order to insure the above noted tempera-S tures and to better control the temperatures of thefilms, it is a practice in the art to provide addi-tional heat to the films prior to being passed to the nip 9 of embossing roll 5 and backing roll 6. This heat is often applied in the form of radiant heat sup-plied by radiant heaters 10 and 11. ~adiant heaterscan be fine tuned for precise temperature control by varying the power thereto.
As noted above, the embossed film will have a plurality of embossments dispersed thereon except at the longitudinal edges thereof. These embossments are spaced apart and separated from each other by unem-bossed portions of the film referred to in the art as land areas. During the laminating step the backing film is laminated to the embossed film at the longitud-inal edges and at those land areas. By such lamina-tion, air containing buoyant cells are formed by the embossments of the embossed film and the backing film.
The foregoing is the conventional process for producing -the sheet material of which the present ~5 invention provides an improvement. That conventional process, as noted above, is well known in ~he art and need not be further d:iscussed for sake of conciseness.
The modification to that conventional process to provide the present improved process will be discussed , .1$,;
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~ 2~ 3 hereinafter, but for sake of clari.-ty, the improved sheet material will first be discussed.
As can be appreciated from the above discuss-ion of the conventional process, the plastic films used in the process to produce the sheet material are normally thermoplastic, and indeed the preferred embod-iment of the present invention is where the plastic films are thermoplas-tic. The particular thermoplastic may vary widely but usually the thermoplastic is either polyvinyl chloride or polyvinylidene chloride or an olefin polymer or nylon. It is preferred to use an olefin polymer and polyethylene or polypropylene olefin polymers are most preferred. The plastic films used for the sheet material may or may not have a coating thereon for improving the laminating proper-ties of the films. Such coatings are well known in the art and need not be described herein.
In order to attach sections of the sheet material for producing pool covers, the continuous running lengths of the sheet material made by the conventional process have unembossed longitudinal edges 13, as shown in Figure 2. The width 14 of the longitudinal edges 13 can vary considerably, but generally the width of the longitudinal edges are up to about three inches, but rnore usually the width is from about 0.5 to 2 inches e.g. 1 inch or sa.
As will be appreciated from the above des-cription of the conventional process, the sheet material could be produced by means other than heat laminating. For example, the embossed ~ilm and the ' 1~2Z683 backing film could be laminated by adhesive lamination rather than heat lamination. This is achievable simply by providing that earlier the embossed film or the backing film have a pressure sensitive adhesive there-on, or even a heat activated adhesive thereon. How-ever, it is preferred that the lamination of the backing film to the embossed film be by heat lamina-tion where the films are themo~lastic films and the films are heat laminated together. This is preferred in the present process by reason of the reinforcement introduced into the process and into the product, as briefly described above.
The reinforcement is a fibrous material which is laminated to the sheet material at least at the longitudinal edges thereof. The fibers of the fibrous material may be either natural or synthetic fibers, but synthetic fibers are preferred, especially synthetic fibers which are thermoplastic fibers. When the thermoplastic fibers are made of a thermoplastic similar to the thermoplastic of the films, this allows lamination of the fibrous material to the sheet material with only a very slight modification of the conventional process for making the sheet material.
For example, when the thermoplastic fibers are made of an olefin polymer, e.g. polyethylene or polypropylene, and the films are made of a similar olefin polymer, the laminating temperatures of the fibrous material will be close to the laminating temperatures of the films. By thus provlding such a combination of films 3o læ~26~

and fibrous material, the fibrous materlal rnay be laminated to the sheet material by feedi.ng the fibrous material into the convent:ional process. However, it will be appreciated tha~ while the polymer of the fîbrous material may be similar -to the polymer of the fi.lms, preferably the polymer of the fibrous material will not have the same embossing or fusion tempera-tures of that of the fllm. If these temperatures were the same for both of the fibrous material and the films, then the chances of melting the fibrous material while embossing and laminating the films would be considerably increased. It is possible, however, to use fibrous materials made of the same material as the films and having the same emhossing and fusion temperatures, since the fibrous material will not normally be pre-heated to the extent of pre-heating the films. However, this requires much more careful control of the process and is therefore not the preferred embodimen-t of the invention.
. To avoid the above problem, when the fibrous material is of a polymer similar to the polymer of the films, the fibrous material should have embossin~ and fusion temperatures at least slightly above those temp-~ratures of the films. For example, the films may be of low density polyethylene ~nd the fibrous materials may be of high density polyethylene. The embossin~ and fusion temperatures of high densi-ty polyethylene are slightly higher than the embossing and fusion tempera-tures of low density polyethylene. These slight di.ffer-ences i.n temperature make the process easier to ..,,. /,,, 12226~3~

operate and will ensure that the .fibrous material remains in the laminated sheet material as distinct fibers and not melted residues thereof. This will be more clear from a description of the process includi.ng the present improvements where the fibrous material is feed into the process.
In this latter regard, referring again to Figure 1, the fibrous material 15 may simply be fed to the nip 9 between embossed film 1 and backing film 3 and along the outer edges of embossing roll 5 where there are no embossing cavities and the longitudinal edges of the sheet ma~erial are formed. I~ one.embodi-ment, the fibrous material 15 is of a material con-siderably different from the polymers of films 1 and 3, i.e. is either not a thermoplastic or has embossing and fusion kemperatures considerably above those temp-eratures of the plastic films 1 and 3. In this case, the pre-heating of films 1 and 3 may be to higher temperatures by drums 2 and ~ and radiant heaters 11 and 10, than ~hat necessary to laminate the films, these higher temperatures being sufficient to compen-sate for the lower temperature of reinforcing material 15. These high temperatures need not be substantially greater than the temperatures practiced in. the ordi-nary process without the fibrous material, since the amount of fibrous material used for reinforcing pur-poses, as noted above, can be quite small. Thus, in this case~ when lamination actually occurs between rolls 5 and 6, the temperature of all of the embossed film, backing film and fibrous material will be essen-tially the same by virtue of close contact therebetween in entering the nip 9 between rolls 5 and 6 and during passing through the nip 9 of rolls 5 and 6. Since in this case the temperatures of all of the ernbossed film, backing film and fibrous material will be essentially the same, the fibrous material rnay be laminated to the sheet material with no substantial change to the conventional process other than feeding the fibrous material thereto. This is a very important advantage of the present. invention, since this embodi-ment requires very little modification of the conven-tional process and very little additional equipment.
In another embodiment, the fibrous material may be heated to about the lamination temperature of the films. Since also as noted above, very small amounts of such fibrous material are required for ade-qua~e reinforcing, the fibrous material may be very conveniently heated to about that lamination tempera-ture by very inexpensive and simple means. Thus, for example, a bank of radiant heaters 16 disposed next thereto ~See Figure 1) may be used. These heaters may be disposed on only one side o~ the fibrous material, as shown in Figure 1, or on both sides. Further, since rolls 5 and 6 may also be heated, and indeed roll 5 is usually heated in the conven~ional process, additional heat to achieve lamination o:F all of film 1, film 3 and fibrous material 15 may be supplied thereby.
Optionally, of course, combinations of heating drums and radiant heaters, as explained above, rnay be used.
The purpose of heating the fibrous material to about the lamination temperature of the films is simply for convenience in controlling the temperatures of lamina-tion. Thus, rather than heating the films 1 and 3 . ., _ 1 ~_ , ........................... .
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lZ~Z6~3 hl~her than necessary for lamination thereof in order to accommodate the cooler unheated fibrous material, by heating the fibrous material to near the lamination temperatures, films 1 and 3 can be processed in the manner normally practiced in the art and without any changes in the temperatures of that normally practiced process. Thus, the temperature to which the fibrous material is heated is decidedly not criticial, and can be from, indeed, unheated fibrous material up to the embossing or fusing temperatures of the films to be laminated, but more generally will be somewhere near the lamination temperatures of those film.
The fibrous material may be laminated to the sheet material in positions other than that described above. For example, the fibrous material may be laminated to the sheet material by feeding the fibrous makerial between embossed film 1 and embossing roll 5 as shown by dotted line 17 indicating fibrous materia:L. Likewise, the fibrous material may be fed between backing film 3 and backing roll ~, as shown by dotted line 1~. Of course, in both of these latter embodiments, heaters, such as radiant heaters 16, may be, and preferably are, provided for the same reasons explained above. Nevertheless, it is preferred that 2S the reinforcing be laminated between embossed film 1 and backing film 3 as shown in Figure 1. Figure 3 shows this preferred embodiment where the embossed film 1 with embossments ~ separated by land areas 20 are laminated to backing film 3 with the fibrous . .

~261~33 reinforcing material 15 laminated therein between at longitudinal edges 13. It will be noted that in this embodiment that the fibrous material is substantially co-extensive with the longitudinal edges, i.e. essen-tially the entire area of the edges have fi.brousmaterial laminated thereto. The preferred embodiment 9 as noted above, is where this co-extensive lamination of fibrous material is laminated into the sheet material, i.e. between the embossed film 1 and the backing film 3.
However, the reinforcing material need not be onl~ at the longitudinal edges o~ the sheet material. Thus, when a fibrous material is in a batt, scrim or fabric form, of essentially the same width as the ~idth of the embossed film, the backing film may actually ta~e the form of a coating on the fibrous material or a lamination of the backing film on the fibrous material. In this embodiment, therefore, the fibrous material is substantially co extensive with the embossed film, i.e. the width of the embossed film is essentially the same as the width of the fibrous material. This embodiment not only provides the above described reinforcements at the longitudinal edges of the sheet material, but in addition reinforces the entire sheet material This is a particular advantage in that it will provide additional strength to a pool co~er made from the sheet material so that the pool cover can withstand greater stress, and particularly greater abrasion, in rèmoving the pool cover from the pool and replacing the pool cover thereon. In this regard, the fibrous material can simpl~ be in batt (non-consolidated) form but for added strength, it is preferred that the fibrous material be in scrim or , 122~6~33 , fabric form, i.e. a woven or non-woven scrim or fabric. This allows the coating or lamination on the scrim or fabric to provide the backing film by means of conventional fabric coaters and laminators.
F'igure 4 illustrates this embodiment where the fibrous material 15 is in the form of a woven or non-woven scrim fabric and the backing film 3 is in the form of a coating or lamination on the fabric to form a coated or laminated scrim or fabric. Of course, if desired, the positions of the scrim or fabric 15 and coating or lamination 3 could be reversed such that the fibrous material 15 is on the bottom side of backing film 3 ( in the form of a coating or lamina-tion), as opposed to that actually shown in Figure 4.
In either case, however, the coated or laminated scrim or fabric is essentially co-extensive with the emboss-ed film (as shown in Figure 4).
Again, as described above, in this lattsr embodiment the coating or laminat;on film is prefer-ably a heat sealable coating or lamina-tion film, preferably of the same material as the ~lastic films, e.g. an olefin polymer such as polyethylene or polypro-pylene.
Fi~ure 5 shows such a resulting sheet material in expanded detail. In that figure ~he fibrous material 25 is a woven scrim and has a lamina-tion film 26 thereon. Optionally, the scrim may have a lamination film on both sides and the second lamina-tion fil~ 27 (shown only partially in Figure 5) may be disposed on the opposite side of scrim 25 from lamina-tion film 26.

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~ i :ILZ~26i83 As noted above, it was surprisingly found that the fibrous material need not be disposed on the sheet material in any great amount from a weight point of view, and this is an important advantage of the in~ention. Indeed, adequate reinforcement is provided merely by a woven or non-woven scrim. A scrim is a very lightweight fabric having weights of between about 1 and ~-1/2 ounces per square yard, especially about 3-~ ounces per square yard. For example a woven scrim of high density polyethylene having warp and weft yarn counts of as little as 4 per inch may be used, although at least 5 per inch is preferred. When very lightweight scrims are used, such as those immed-iately described above, another important advantage of the invention may be realized. Thus, the very light-weight scrim may be laminated to the backing film in a separate operation from that shown in Figure 1, and the resulting lamination of the very lightweight scrim and backing film can be substituted in the process shown in Figure 1 for backing film 3 and no separate feeding of fibrous material 15 is required. Such light-~eight scrims, also, do not substantially effect the lamination of embossed film 1 to backing film 3, and thus the conventional process may be operated without any substantial change at all, other than substituting ,for backing film 3 the previously laminated light-weight scrim and backing film. The lamination ~f the lightweight scrim to the backing film, in a separate operation, can be done on conventional laminators, the 3 operation o~ which is well known to the ar~. Alterna-tively, combinations of certain polymeric lightweight 1~

~ Z2Z~;~33 j ~,.. .
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scrims and polymeric films are commercially avai]able from the DuPont Company. For example, the DuPont Company has commercially available a lightweight scrim, of the nature described above, made from high density polyethylene which is laminated to a film of low density polyethylene. This commercially available product is quite acceptable for the present process.
While this commercially available lamination does not I give maximum reinforcement~ in the nature described j 10 above, the reinforcemen~ provided is, nevertheless, I quite adequate for many uses of the sheet material in ! producing pool GOVers. This is because -the reinforcing ¦ stops tears, primarily induced by stitching for attach-ment of the sheet materials, as explained above, from developing into longer tears. The fibrous reinforce-ment, therefore, serves as a tear stop and even light-¦ weight scrims, of the nature described above, are ePfective in this regard. This will be better under-I stood from the explanation, below, in re~ard to attach-¦ 20 ment of the sheet materials to form a pool cover.
Essentially the same process as described above in connection with a lamination of a lightweight scrim onto a film as a separate step of the process i may also be cond~cted in reinforcing only the longitu-, 25 dinal edges of the sheet material. Thus, the same ~ype '~ of lamination of a lightweight scrim and a film may be u~ed in addition to the films as shown in Figure 1, i.e. embossed film 1 and backing film 3. However, in this embodiment, the lamination of the lightweight scrim and film will be fed into -the process in the lZZZ6~33 same manner shown in Figure 1~ but in ~his case the lightweight scri.m and fllm lami.nation will be substi-tuted for fibrous material 15 in Figure 1. ~or example, rolls of lamination of li~htwei.ght scri.m and film having the requi.red width for the longitudinal edge desi.red, are simply disposed a-t each longitudinal edge of film 1 and film 3 and fed into nip 9 in the manner shown in Figure 1. This will d:i.spose that lamination at the longitudinal edges of the films and will be heat sealed be-tween films 1 and 3, as shown by 15 in Figure 3.
This latter embodiment of the process has a further advantage. The lamination of the lightwe;.ght scrim and film make the fibrous materlal much easier to handle, especi.ally when the f:ibrous material is in a very lightweight form, such as ~he ligh~weight scrim described above, or in the form of an unconsolidated material, e.g. a batt or lightly consolidated felt. In addition, this embodiment of the lnvention has yet another further important advantage. Since the light-weight scrim, for example, is already lami.nated to a film, this allows the lamination of scrim and fi.lm to be further coated, preferably on both sides, with a coating which allows an easier heat seal of embossed film 1 and backing film 3. For example, where the lightweight scrim is made of a high density polyethy-lene and the film laminated thereto is made of a low density polyethylene, si.milar to the low density poly-ethylene normally used for films 1 and 3, i.t will be 3o 122Z~

necessary to bring the temperature of the laminated scrim up to or close to the cmbossing temperature or above, e.g. near the fusion temperature, to ensure that a good heat seal occurs bekween fllms 1 and 3 and the lam:inated scrlm. However, the necessity to bring the laminated scrlm to those higher temperatures can be avoided by simply coating the laminated scrim with coating materials which will fuse at lower tempera-tures. Thus, for example, a lamination of a high density polyethylene scrim with a low density polyethy-lene film can be coated with yet a lower density polyethylene coating, preferably on both sldes, and that yet lower density polye-thylene coating will fuse to both films 1 and 3 at a much lower temperatures and give a good heat seal between all of films 1 and 3 and the laminated scrim. Lower density polyethylene coatings can be adequately heated to such fusion temperatures by lesser amounts of heat than required by, for example, infrared heaters 16, as shown in Figure 1, and can be quite adequately heated to fusion temperatures by more simple means, such as an air gun 20, as shown in Figure 1.
Indeed, the same types of coatings, as explained in the foregoing paragraph, may be used when a lamination of the fibrous materials and the film is used in lieu of backing film 3, as explained above. In this case, however, after laminating the fibrous material, e.g. a lightweight scrim, to the backing film, -that lamination is then coated, preferably on both sldes, with an appropriate coating ma-terial ~7~

~2Z683 .

having lower fusion temperatllres. Tt~is will i.nsure that the lami.nation of the fibrous material and fi.lm, used in lieu of backing ~ilm 3, can be processed in the same manner as the conventional process which uses ordinary homogeneous films as embossing film 1 and backing film 3. It will be appreciated i.n this regard, that the presence of the fibrous material, which will be of a higher melting point than the film to which it is laminated can cause some minor distrubances i.n the conventional process and may require some higher temperatures for adequate heat sealing. However, with the coatings on the lamination of fibrous material and backing film, no substantial adjustment of tempera-tures or other operating parameters are required, and the process can be practiced in a very conventional manner and merely by substituting the lamination of , the fibrous material and the backing film for the backing film 3 of Figure 1. This makes operation of the process exceedingly simple and inexpensive, and for this reason is the preferred embodiment of the inventi.on.
Instead of providing a further coating on a laminated scrim, as described above, the lightweight scrim may be coated d:irectly wi.th a coating having a

2~ lower fusion temperature tno prior lamination of -the lightweight scrim and a film). Such coated scrim may be used i.n the same manner as described abo~e, i~e.
either only at the longitudinal edges or over the entire width of the sheet material or in lieu of the backing film 3.

, . ~

~Z2Z~83 The sheet material is attached to at least one other corresponding reinforced sheet material, i.e. having at least reinforcement lr. the longitudinal edges thereof, for forming a swimming pool cover. A
partial section of such cover is shown in Figure 6.
Thus, the longitudinal edge 13 of one section 30 overlaps the underlying longitudinal edge 31 (shown as dotted lines) of another section 32 of sheet material and these two sections are attached at attachment points 33, shown in the drawing as double stitches.
; The threads used for the stitching may be any threads, but again are preferably syntheti.c threads, e.g.
fibrous polyethylene or polypropylene threads.
However, instead of stitching, as shown in Figure 6, the attachment may be by heat sealing, which is another ~eans of attachment commonly used in the art, although this is not preferred for thç reasons explained above. The required number of sheet material to form the desired width for the pool cover are similarly attached. Of course, prior to attaching sections of the sheet material, the continuous running lengths of sheet material are cut to appropriate lengths ~or the size of the pool covered.
As will be appreciated from the foregoing description of the process and the product, i.e. the sheet material, a major feature of the invention is in providing an inexpensive and easy to operate process for producing a much improved sheet material, especial-ly from a tear resistant point of view, and con-comitantly a much improved product with little or no :~2~Z6~33 additional cost in the product itself. The improved tear resistance is a result of a disposition of the - fibrous material. It can be easily appreciated that when a tear begins to develop in a homogeneous material, such as plastic films, the tear propagation in tha~ m~terial will go exceedingly rapidly. However, that propagation of the tear is either eliminated or substantially reduced by the present reinforcement. As the tear propagates, it will encounter the laminated reinforcements and at that point of the reinforcement, i.e. the fibrous material, tear resistance consider-ably lncreases. Stated another way, tear propagation is considerably reduced and if the tear exceeds the first encounter of the fiber of the fibrous material, it wil] encounter subsequent fibers of the fibrous material and again tear propagation will be substan-tially reduced. It can therefore be seen, that the arnount of fibrous material required for substantial reinforcement is very small indeed and this is an important discovery of the invention. While the light-weight scrims, as described above, are quite adequate, the reinforcement may be of a much more substantial nature, if desired. That reinforcement can be to the - extent of a tightly woven relatively heavy fabric, 2~ e.g. up to 10 to 12 ounces per square yard, but reinforce~ent o~ this magnitude is really not neces-s~ry, and only serves to increase the cost of the sheet materials produced. Heavier reinforcements of this nature, however, are of advantage when disposed across the entire sheet materlal, since the heavier 12226~33 reinforcement will provlde greater abrasion reslstance in removlng and replacing the pool covers on the pool, as explained above. Similarly, instead of heavy woven fabrics, heavy non-woven fabric may be used, with a like result.
The invention will now be illustrated in connection with the following example. It should be understood, however, that the invention is not restricted to this example, but extends to the breadth of the foregoing disclosure and following claims. The example, however, does goes to the preferred embodi-ment of the invention, especially in regard to produc-ing the improved product at a minimum cost.

EXAMPL~

A conventional "bubble" laminating machine, manufactured by the Canadian Tarpoly Company, as dia~rammatically shown in Figure 1, was threaded with low density polyethylene film. The embossed film was mils thick and the backing film 3 was 3 mils thick.
Each film was 53 inches wide. Hot water at temperature between 120 and 130 F was circulated through embossing roll 5. Backing roll 6 had a non-stitch elastomeric covering thereon (silicone rubber). The pressure between rolls 2 and 4 was about 40 to 50 pounds per linear inch. Ten radiant heaters ~I.R.
heaters) 11 and ten radiant heaters 10, powered at about 5500 wa-tts each, preheated, respectively films 1 3o ~ZZ26~3 and 3. Each bank of heaters, 10 and 11 were laterally movable, away from and towards, each film and the film temperatures were adjusted by such movement so that each film in a steady state of processing were heated to the laminating temperature (determined by when films 1 and 3 permanently laminate together).
Coated scrim 15 was fed at each longitudinal edge of the films 1 and 3 and between each of the films. The coated scrim had a weight of about 3 oz.
per square yard and was made of high density polyethy-lene woven fabric (about 5 warp and weft threads per inch) with a low density polyethylene coating on both sides thereof (made by the DuPont Company). Each scrim was preheated with a hot air gun 20, operated at about 2000 wat-ts. Under steady state conditions the film speeds (and product speed~ was about 45 feet per minute.
The resulting embossed laminate was selvaged to about a ~ feet width and cut to 40 feet long sections. Four such sections were double stitched along the edges thereof ~through the scrim laminated between the embossed and backin~ films) with fibrous polypropylene thread using a 300 ~ double stitch headed Singer sewing machine and chain stitching. The resulting pool cover was strong and durable.
As can be seen from the above, the process of the present invention is an ine~pensive and easy to operate modification of the conventional process for making shee-t materials of the present nature. 1'hus, 3o -3n-. , .

:12~ 3 the i.ncreased costs of processing is minimal. Addi-t;.on-ally, since the reinforci.ng material can be qui.te small in relationshlp to the weight of the plastic f'ilms, the additional cost for the reinforcing material can be quite small. Under these c.ircum-stances, the invention provides a very much improv~d sheet material, and hence pool cover, with only very small i.ncreases in costs thereof. This is a sub-stantial advantage to the ar-t.

. .

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a floatable on water, translucent heat laminated swimming pool cover being composed of a plurality of sec-tions of plastic sheet material having a plastic embossed film with a plurality of embossments dispersed thereon except at the longitudinal edges thereof, said embossments being spaced apart and separated by land areas between said embossments, and a plastic backing film heat laminated to said embossed film at the said longitudinal edges and at said land areas, whereby air containing buoyant cells are formed by the embossments of the embossed film and the backing film, the improvement comprising fibrous material heat laminated to said sections of sheet material between the embossed film and the backing film at least at the longitudinal seam edges of each section, whereby said longitudinal seam edges are reinforced by the fibrous material and said reinforced longitudinal seam edges are attached by sewing to correspondingly reinforced longitud-inal seam edges of another section of said sheet material and whereby substantially weakening of the attached sewed sections of sheet material at the seam edges thereof is avoided.

2. The swimming pool cover of claim 1 wherein the plastic films are made of a thermoplastic.

3. The swimming pool cover of claim 2 wherein the thermoplastic is polyethylene or polypropylene.

4. The swimming pool cover of claim 3 wherein the fibrous material is in the form of thermoplastic fibers.

5. The swimming pool cover of claim 4 wherein the fibers are made of polyethylene or polypropylene.

6. The swimming pool cover of claim 4 wherein the fibrous material is in batt, scrim or fabric form.

7. The swimming pool cover of claim 6 wherein the fibrous material is in the form of a scrim.

8. The swimming pool cover of claim 1 wherein the backing film is in the form of a coextensive lamination of the backing film and the fibrous material.

9. The swimming pool cover of claim 8 wherein the said lamination of said fibrous material and backing film is coated on at least one side with a heat sealable coating.

10. The swimming pool cover of claim 1 wherein the fibrous material is in the form of a separate lamination of lightweight scrim and a plastic lamination film.

11. The swimming pool cover of claim 9 where said separate lamination has a plastic coating on at least one side thereof.

12. The swimming pool cover of claim 10 where there is a coating on both sides of the separate lamination and the coatings have a lower laminating temperature than the laminating temperature of the embossed film, backing film, scrim or lamination film.

13. The swimming pool cover of claim 12 wherein said coated separate lamination is laminated to said embossed film in lieu of said backing film and the said scrim is coextensive with said separate lamination.