EP0077772A1

EP0077772A1 - Method and apparatus for forming an integral closure for a thermoplastic container

Info

Publication number: EP0077772A1
Application number: EP81901627A
Authority: EP
Inventors: Thomas Albert Sutrina; Raymond Douglas Behr
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1981-04-20
Filing date: 1981-04-20
Publication date: 1983-05-04
Also published as: AU7324281A; WO1982003597A1

Abstract

Procede ameliore de moulage a haute vitesse pour le fusionnement de dispositifs de fixation, avec des bandes de film a leur base, pour extruder separement du materiau brut en film ou en feuille pour la fabrication de conteneurs avec des moyens de fermeture solidaires. Le procede permet d'obtenir une multitude d'ensembles d'elements males et femelles de fixation, avec un espacement variable, dans une operation d'extrusion simple. L'appareil (10) est concu pour que l'adhesion entre les elements de fixation (48) et le film (46) ou la feuille se produise tres pres des levres de la matrice (62) avant qu'un refroidissement important du produit d'extrusion ne se produise. Des conteneurs avec des profils ameliores sont obtenus parce que la base permet aux profils de rester relativement rigides pendant la fermeture et l'ouverture.Improved high-speed molding process for fusing fastening devices, with film strips at their base, for separately extruding raw material into film or sheet for the manufacture of containers with integral closure means. The method provides a multitude of sets of male and female fasteners, with varying spacing, in a single extrusion operation. The apparatus (10) is designed so that adhesion between the fasteners (48) and the film (46) or sheet occurs very close to the lips of the die (62) before significant cooling of the product extrusion does not occur. Containers with improved profiles are obtained because the base allows the profiles to remain relatively rigid during closing and opening.

Description

METHOD AND APPARATUS FOR FORMING AN INTEGRAL CLOSURE FOR A THERMOPLASTIC CONTAINER

This invention relates to a high speed cast process and apparatus for making an improved film or sheet product with integral fastening elements.

More particularly, this invention relates to a method and apparatus of in-line forming of integral fastening elements with film or sheet stock to be made into bags or other containers which are closable by the fastening elements.

For a considerable period of time, bags with integral fastening elements have been made by the blown film process similar to that taught in U.S. Patent No. 3,340,116, for example. Here the fastening elements are extruded from the same polymer melt streams through an annular die containing extrusion orifices. Another technique for manufacturing integral fastening elements is taught, for example, in U.S. Patent No. 3,462,332. That patent discloses a cast film process wherein the fastening elements are extruded separately from the film and are thereafter joined with the film by being brought together against a rotating cooling roll while

the film and fastening elements are still in a fusible state.

While both the prior art blown film and cast film processes have produced commercial products, those made by the relatively faster cast film process have lacked certain advantages. The ability of fastening elements to resist rotation to obtain better inter¬ locking remained a desired end. The ability to readily and controllably make thickened bases for the fastening elements yet maintain high production speeds, with the ability to make multiple and variable sized bags out of ' a single cast film, all remained a need until the present invention. While U.S. Patent Nos. 3,198,228 and 3,338,284 show thickened bases, these are not found in a cast process. Also to be desired was to have cast die lips of sufficient thickness. so as not to be suscep¬ tible to damage. The reliable high speed process for producing superior integral fastening elements taught by this invention meets the needs left unanswered by the prior art.

The invention leads to flexibility and hardware and product improvements heretofore unknown to the art. The present invention permits forming of a thickened base for the fastening elements in order to permit more erect elements which do not bend or rotate out of alignment when it is desired to interlock or disengage the same. In effect, extra base strips are extruded together with the fastening elements and are joined to a separately extruded film or sheet close to their die exits. Alternatively, the base strips and fastening elements are joined to a separately extruded film or sheet within the sheeting or film die and before the base strips, fastening elements and film or sheet exit from the die slot. Thus, the fastening elements with their integral bases are joined to the film or sheet stock externally of or within the sheeting die to 5 permit ready fusing of the thickened bases to the film or sheet stock which is, in turn, formed into bags or containers. By this invention, the location and width of the base strips on the fastening elements can be changed without affecting the film or sheet extrusion.

10 The thickness of the base strips extruded with the fastening elements are independent of the film or sheet stock thickness. The present invention also permits the production of two or more bags or containers of varying size from the same film extrusion since the

15 thickened base strips can be a base for a plurality of fastening elements varyingly spaced apart. The sheet or film die lips can remain wide and therefore less susceptible to damage and still not interfere with adhesion between the fastening elements and the film or

20 sheet stock.

The invention resides in a method for forming an integral thermoplastic fastening element on a thermo¬ plastic film or sheet extruded from a film die comprising the steps of extruding at least one fastening element

25 in an angularly disposed relationship towards said film, joining said fastening element and film, cooling said film and fastening element upon a chill roll after said joining, and joining said fastening element to said film at a location closer to the film die than to

30 the chill roll.

The invention further resides in an apparatus for forming an integral thermoplastic fastening element on a thermoplastic film or sheet, including a forming die for extruding the film through a forming slot in said die, a die plate positioned adjacent to the forming for extruding said fastening element at a predetermined angle with respect to the extruded film for joining said fastening element to the film, a chill roll for cooling the combined film and fastening element, said chill roll being positioned with respect to the forming die to provide a predetermined distance (h) between a horizontal line extending tangentially of an outer circumferential surface of the chill roll and a die lip on the forming die and a predetermined distance (d). between a vertical line extending from the die lip to said outer circumferential and tangential surface of the chill roll.

The invention further resides in an apparatus for forming an integral thermoplastic fastening element on a thermoplastic film or sheet, said apparatus com¬ prising an extrusion die having a film forming slot ending, in an extrusion die lip, said die having an angularly disposed surface extending toward said film forming slot and die lip, a die plate positioned adjacent to said die slot and forming an extrusion channel for the fastening element which is arranged in an angular relationship with respect to the film forming slot to increase the acuteness of the angle of the extrudate issuing from the die plate channel with respect to the extrudate issuing from said film forming slot, and cooling means located below said extrusion die and die plate.

The invention further resides in a cast, relatively unoriented film or sheet having integral relatively stiff male and female fastening members, each of said fastening members having a base strip secured to said film or sheet over at least 90 percent of the width of each base whereby said base provides sufficient rigidity for the fastening members during each opening and closing of the fastening members for said relatively unoriented cast film.

Figure 1 is a schematic elevational view showing an extrusion apparatus for integrally forming fastening elements on film or sheet;

Figure 2 is an enlarged schematic elevational view of a sheeting die and fastening element, die block and plate as illustrated as part of the extrusion apparatus of Figure 1;

Figure 2A is a frontal view of the die block of Figure 2 showing a mechanism for adjusting the die block location;

Figure 3 is an enlarged schematic bottom view looking in the direction of line 3-3 of Figure 2 showing a plurality of die blocks and plates as associated with the film or sheeting die and particularly illustrating the fastening element die slots and the sheeting die orifice;

Figure 4 is an enlarged cross-sectional view of the film or sheeting die and fastening element die plate taken along section 4-4 of Figure 3 illustrating the extrusion of the film or sheeting stock as it is combined with a fastening element and its base, a modified arrangement of a die plate being shown in dotted lines; Figure 5 is a view like Figure 4 showing the die plate spaced from the film or sheet die by an intervening shim;

Figures 6 and 7 are similar to Figure 5 with the location of the die plate changed; and

Figures 4P, 5P, 6P and 7P are enlarged schematic cross-sectional views of representative female profiles formed by positioning the dies as illustrated in Figures 4, 5, 6 and 7, respectively.

Figure 8 is an enlarged cross-sectional view of an alternative embodiment of a film or sheeting die and die plate, similar to the die illustrated in Figure 4.

Figure 9 is a planar view of the die plate or profile plate taken along section line 9-9 of Figure 8.

Apparatus 10 illustrated in Figure 1 comprises a conventional screw extruder 12. Extending outwardly from extruder 12 is an extruder pipeline 14 for feeding a synthetic resin to a main sheeting or film die 16. For convenience, die 16 will hereinafter be called film die even though it is capable of extruding either a film or a sheet usable in this invention. Feeding from extruder pipeline 14 is a second extruder pipeline 18 which, through pump 20, supplies resin to a plurality of die blocks 22. Each die block 22 and an associated die plate 52 provide an extrusion path for extruding fastening elements which combine with the film leaving the film die 16. This apparatus permits the extrusion and fusion of fastening elements with strips of film at their base to a sheet or film extruded from the film

B ---.⁴G -' die 16. The fastening elements, base and film are represented by reference characters 48, 50, 46, respec¬ tively, as illustrated in Figures 1, 2 and 4P. These elements combine extremely close to the extrusion die lips, the joining locations illustrated in Figures 1 and 2 being exaggerated only to show that they extrude as separate components. The apparatus is capable of making cast film with multiple sets of generally U-shaped and generally arrow-shaped fastening elements, shaped like those shown in U.S. Patent No. 3,340,116, for example, integrated with the thickened base strips of film later described in detail.

An air jet 24 and/or air knife 26 can be used to assure good contact of the film and fastening elements with a chill roll 28 while screens or shields (not shown) can optionally block air flow in front of each fastening element to prevent distortion of the malleable extrusion. The air jets above the air knives pin the edges of the drawn film extrusion to the chill roll to reduce_^ narrowing of the film and thickening of the film edge. Below air knife 26 preferably are located water jets 30 which are aligned with each of the fastening elements to cool the same. It may be desirable to add second water jets 32 located on the side of the chill roll opposite from the air knife to be certain that the fastening elements are fully cooled before the same are wound.

Preferably, the combined film/fastening elements are taken off the chill roll and passed across a grooved roll 34, which can contain water suction means, and are then passed over a second take-off roll 36 which can contain a vacuum assist to hold the film closer thereto. Immediately adjacent the roll 36 is an air jet mechanism 38 to remove any excess water remaining on the extruded film fastening elements after they leave roll 36. The lower end of the air jet mechanism contains a flange or tongue 39 extending below the vertical tangent point of roll 36. The air jet (see arrows) makes tangential contact with the extruded film/fastening element combination. The air jet velocity between the tongue and roll atomizes the water which separates from the film along the path of the tongue.

From the roll 36, the film/fastening element combination is taken to a wind-up roll (not shown) or to a mechanism (not shown) for actually forming containers from the film/fas ening element combination.

Figures 2 to 4 show more detailed views of the sheeting die 16 and fastening element die block 22 illustrated in Figure 1. Polymer entering channel 40 from pipeline 14 extrudes outwardly from film forming slot 56 past corners 42 of die lip 62 adjacent the lower end of the sheeting die 16. Die block 22 is secured to the side of the film die 16 with bolts 25 extending through slot 23. The die plate 52 is bolted to the bottom surface of die block 22. A plurality of die bolt holes 27 allow for varying placement of the die blocks, and the slot 23 in each die block allows for adjustment of the die block with respect to each bolt. Each die block 22 is placed so that a lower or leading edge 74 of the die plate 52 is below the die lip 62 of film die 16. Resin from pipeline 18 passes through a channel 44 which is disposed angularly within the die block 22 and is extruded through profile orifices 68 and 70 in die plate 52 and meets with the film 46 immediately adjacent the lowermost extent of die lip 62 of the film die thereby joining the fastening elements 48 and base 50 to form the film/fastening element combination 46, 48 and 50. The angular disposition of the exit of the channel 44 increases the acuteness of 5 the angularity of the extrudate issuing therefrom so as to increase the closeness of the joining of the film/- fastening element combination.

Die block 22 carries female die plates 52 and 52', having left and right hand female profile orifices

10 70, and male die plate 54 having left and right hand male profile orifices 72. These are seen in Figure 3 which is a view looking at the face of fastener die blocks 22 as secured to film die 16. Male and female profiles 48 exit from orifices 70 and 72 and film

15 strips forming base 50 exit from orifices 68, 68' and 68" together with profiles 48. The film from film die 16 exits from film slot 56 and is joined with the profiles and their base 50 immediately adjacent die lip 62.

20 Figures 4 and 5 are enlarged detailed drawings of the arrangement of the film die 16 and die plate 52 schematically showing how closely it is believed the film/fastening element unites adjacent to the die lip 62. If film die 16 and die plate 52 are properly

25 arranged with respect to one another, they will produce a satisfactory film/fastening element combination typified by Figure 4P. If not, an unsatisfactory film/fastening element combination as typified by Figure 5P can result.

30 A fundamental problem in extruding a fastening element on cast film is to obtain satisfactory adhesion of the element to the film. It has been discovered that the closer the fastening element can be joined to the film as the latter issues from the film die, the better the chances are that satisfactory adhesion will occur, particularly at high speed extrusion rates.

Figure 4 illustrates a particular arrangement which has been found to permit high speed extrusions, in excess of 200 feet per minute, while obtaining satisfactory film/fastening element adherence as typified by Figure 4P.

To bring the extrusion of the base 50 of the fastening element (through channel 44 so that it joins film 46 issuing from channel 56) closely adjacent to the die lip 62, it is desirable to make the distance "T" of the die lip as short as practical and to have the base 50 angularly disposed towards film 46. The distance T should not be so short, however, that the die lip 62 forms a knife edge, which is easily subject to damage. For a working embodiment, a relatively wide distance T of from about 0.0508 cm (0.020 inch) to 0.0762 cm (0.030 inch) has been found practical because of the angularity of extrusion built into the apparatus by this invention.

The extrusion of film 46 can also be angled towards the extrusion of the base 50 by the relative location of the extrusion channel, as the film exits at end corners 42, with respect to the chill roll 28. For example, by locating the extrusion channel back a dis¬ tance "d" from a vertical tangent point of the chill roll 28, and a distance "h" from a horizontal tangent point of the chill roll 28 (Figure 1), the angle θ of the film extrudate 46 with respect to the vertical can be varied. 31

Likewise, by providing an angular face 80 on the film die 16, along which a matching surface 78 on the die plate 52, the die plate can slide up and down on the angular face 80 before being clamped in position, as shown in Figures 2 and 2A. Thus, the lower or leading edge 74 of die plate 52 can be located at a desired position with respect to an adjacent film surface 76. This, therefore, determines not only the angular disposition of the base 50 with respect to the film 46, but also the closeness of the two when they engage. The distance between the film surface 76, (shown extended by a dotted line in Figure 4) and die plate leading edge 74 is designated as distance "y". The gap distance between the face 80 of the film die 16, at an edge 73 of die lip 62 from an inner face 84 of the channel 44 is designated ^■*x^** . The bevel or angle a is the angular relationship between faces 80 and 84.

Several runs were made using the die arrangement shown in Figure 4 to test the variables as they may affect adhesion. In some cases the resin was varied, in others the die lip distance T was varied, the angle θ varied by changing distances d and h, the bevel angle or was varied, and the gap distance x was varied. The resins used were low density polyethylene resins. The successful runs are shown in Table I.

C'.PΓ

TABLE I

"x" Min.

Resin "T" Width gap for

Dow Melt Density Of Die d h Bevel Adhesion

Run Designation Index (g/cc) Lip (in. ) (in.) (in.) <α<°) (in-)

1 PE 747 6 .922 .026 1.9 4.4 30 .013

2 6 .922 .026 3.3 3.0 30 .013

3 6 .922 .030 2.5 4.2 20 .013

4 6 .922 .030 2.5 4.2 30 .014

5 6 .922 .030 2 4.5 20 .013

6 6 .922 .030 2 4.5 30 .015 t

7 6 .922 .026 1.9 4.5 30 .013

8 6 .922 .026 0.0 6.5 30 .013

9 PE 641 2 .922 .026 1.9 4.5 30 .012

10 PE 647 6 .923 .026 1.9 4.5 30 .013

11 PE 747 6 .922 .026 1.9 4.5 45 .013

12 II 6 .922 .020 2.0 4.5 30 .014

These runs produced fastener female profiles 48 and integrated bases 50 which adhered well to the film 46 typified by those shown in Figure 4P. While female profiles are shown for convenience, it should be appreciated that male profiles would be similarly formed. When the gap x was reduced below that indicated in Table I unsatisfactory adhesion occurred, such as illustrated in Figures 5P or 6P, for example. In these runs it was found that gap x always had to exceed 0.028 cm (.011 inch) to provide a possibility f satisfactory adhesion even though other factors were varied. In all the runs shown in Table I, the leading edge 74 of the die plate 52 was located below the bottom of the die lip 62 of the film die. Without this disposition, satisfactory adhesion was not obtained. For example, a run was made under the same conditions as Run 7 of Table 1 except that the gap dimension x was set at 0.0508 cm (0.020 inch), to provide the best chance for adhesion, but with the leading edge 74 of the die plate being flush with the die lip 62 of the film die.

Unsatisfactory adhesion resulted. It does not appear to matter whether bottom surface 81 of the die plate is angularly or horizontally disposed from edge 74.

Additional runs were made to determine the possible effect of the distance ^■*y" between the leading edge 74 of the die plate 52 and the (dotted line) film surface 76 of the film 46 based on a fixed angle θ even though the leading edge 74 might cause interference with the (dotted line) film surface. This is shown in Figure 4 where the dotted^' line of leading edge 74 extends past the projected dotted line of surface 76 of the film 46 and is pushed back to the film position shown in dotted lines by projected (dotted line) surface 76'. Actually, the dotted line film position would be

bUKEAc c■^{■ •}.?, pushed back even further by base 50 passing between leading edge 74 and film surface 76. A similar situation would also occur in Figure 7 where the distance "y" provides an insufficient clearance for the base 50.

In these additional runs, the resin used was the same; the width of channel 56 was 0.051 cm (0.020 inch); the distance T was 0-066 cm (0.026 inch); the angle o: was kept at 20°; angle θ was kept at 19°, with d = 4.826 (1.9 inches) and h = 11.43 cm (4.5 inches); the film take-away speed was 3840 meters/hour (210 ft/min), and the chill roll diameter was 61 cm (24 inches).

The other conditions were varied, however, as illustrated in Figures 5, 6 and 7. In each of these cases, a shim 84 was inserted to permit greater variation in the gap x and the location of the leading edge 74, i.e., dimension y. The variables are listed in Table II, the width of shim 84 being the distance between face 86 and face 80 as shown in Figure 5.

TABLE II Width of

Run Shim Inches Gap x Distance y

Figure 5 0.015 0.020 0.016

Figure 6 0.010 0.016 0.012

Figure 7 0.010 0.020 0.002

The profile achieved with the run of Figure 5 is represented by Figure 5P, Figure 6 by Figure 6P and Figure 7 by Figure 7P. The adhesion of base 50' to film 46 as shown in Figure 5P leaves large holes or unadhered sections and results in a clearly unsatisfactory profile. The adhesion shown between base 50" and film 46 shown in Figure 6P is improved, at least on one side, but the profile still remains unacceptable because of the poor adhesion on the other side. Note that distance y is decreased in the Figure 6 run as compared to the Figure 5 run. As distance y is decreased even further, as in the Figure 7 run, adhesion between base 50''' and film 46 becomes greatly improved. The profile is satisfactory for commercial purposes as adhesion occurs over at least 90 percent of the base width. Additional runs where distance y was reduced further, even to a negative dimension, i.e., as shown in phantom in Figure 4, with all other conditions being the same as run Figure 7, found adequate adhesion and produced satisfactory profiles.

Also viewing Figures 4 and 7 and 4P and 7P, it is observed that in these particular arrangements the leading edge 74 of the die plate not only is below but is located laterally inwardly toward film surface 76 with respect to edge 73 of the film die for satisfactory adhesion to occur. Where leading edge 74 is located outwardly of edge 73, as shown in Figure 5, or even directly below edge 73, as shown in Figure 6, unsat¬ isfactory adhesion occured (as illustrated in Figures 5P and 6P, respectively). Where the leading edge 74 is located both below and inwardly of edge 73, the polymer stream through channel 44 is urged towards the die lip 62 and the film 46 to achieve early joining.

From the various runs illustrated in Tables I and II, it can be seen that a satisfactory fastening element is extruded onto a film at high speeds, even with a relatively wide die lip if the bottom of the die plate is located below the bottom of the film die, and where the gap x is sufficiently large, and the distance y is not too great so that combining of the fastening element with the film can occur closely adjacent the die lip. In fact, the combining occurs so- closely that it is not detectable by the naked eye. It is not known what actually occurs in area 75 between base 50 and film 46 or of what dimension the area is. Under the above conditions, the base 50 has excellent adhesion to the film surface 76. These runs had profiles (male or female) of about 52 mils in height. Equally good results were obtained with profiles of 62 mils in height.

Once a satisfactory fastening element has been formed with the film, the film can be cut and sealed to form containers in the conventional manner. The arrangement of Figure 3 makes it possible to form two containers or bags because the film is provided with two sets of male and female fastening elements. Other combinations of fastening elements and spacing on a single film can be achieved with the apparatus of ^• this invention.

Similar excellent results are obtained with the alternate embodiment illustrated in Figures 8 and 9. In this embodiment, the sheeting or film die 16a is provided with a film forming slot 56a for extrusion of the film or sheet. The die is provided with a die lip 62a adjacent the terminal end of the slot 56a to form a die lip similar to the lip 62 illustrated in Figure 4. At this point, the die of Figure 8 differs from the die of Figure 4 in that the die 16a is provided with an integral feed channel (44a) within the die body for feeding thermoplastic meterial through the internal channel 44a to a die plate or profile plate 52a posi¬ tioned within a terminal cut out portion (90) provided in the die lip (62a). The plate 52a is illustrated in plan view in Figure 9 and shows an extrusion slot portion 92 for forming the male profile of a fastening element. A base portion of the fastening element is integrally formed with the male profile when extruding the thermoplastic material through an open sided slot portion 94, which is cut into an inner edge surface 96 in the plate 52a. The outer surface of the die plate 52a forms an extension of the die lip (62a). The channel (44a) is positioned at an acute angle with respect to the film slot 56a such that the fastening element is formed by and extruded through the die plate at an acute angle with respect to the adjacent surface of the film extruded through the slot (56a). The advantage of this modified die construction is that the base forming extrusion through slot portion 94 joins the main melt stream for the film within the die (16a) with the result that improved adhesion between the base of the fastening element and film are obtained. This is a particular advantage where the overall thickened layer of the film and base decrease in thickness adjacent the extremities of the base. A further advantage in the die construction of Figure 8 is that the combining of the (adhering) thermoplastic streams of the film and fastening element takes place within the die and before the streams pass the die lip (62a).

Additional advantages of the present invention are that it makes possible the forming of fastening elements on cast film at higher speeds than heretofore possible. It permits forming of a base for the fastening element in a cast process so as to present a more rigid, relatively non-rotatable element which greatly facilitates interlocking between the male and female elements. It permits the use of a relatively wide die lip so that the die lips are less subject to damage (than if they were of a knife edge or narrow configura¬ tion) without sacrificing adhesion between the fastening element and the film. The invention allows for variations in the base and male and female pro iles. These may be formed from separate polymer sources, making it possible to form the fastening elements of different materials than the film itself. It is also possible to produce two or more containers from the same film extrusion since the thickened base can form the base for two fastening elements each of which is strong enough to be pulled on when disengaging the fastening elements. It is also possible to vary the locations and numbers of male and female profiles on a given film extrudate.

While certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes in applications can be made therein without departing from the spirit and scope of the invention. For example, the film or sheet stock and/or fastening elements can be made of various other synthetic resinous materials, the size, color and shape of the components can be varied, the number of fastening elements extruded onto a film or sheet can vary, the actual design and configuration of the container can vary, from flexible bags to rigid containers, and equivalent hardware can be substituted.

ι «- ^r- *- - { "

Claims

1. A method for forming an integral thermo¬ plastic fastening element on a thermoplastic film or sheet extruded from a film die comprising the steps of extruding at least one fastening element in an angularly disposed relationship towards said film, joining said fastening element and film, cooling said film and fastening element upon a chill roll after said joining, and joining said fastening element to said film at a location closer to the film die than to the chill roll.

2. The method of Claim 1, wherein the joining of said fastening element and film is directed to occur immediately adjacent a die lip of the film die, said fastening element comprising a base which is coextruded with a male or female profile, extruding said base and profile at an angular disposition towards the film, and joining said base to the film.

3. The method of Claim 3, wherein said fastening element is extruded through a die plate, locating said die plate below said film die and towards the film to provide joining immediately adjacent the die lips of the film die.

4. The method of Claim 2 or 3, wherein the base has a cross-sectional thickness in excess of 0.028 cm (0.011 in. )

5. The method of Claim 2, 3 or 4, wherein the base is extruded at a distance of less than 0.030 cm (0.012 in) from said film.

6. The method of Claim 1, wherein the joining of said fastening element to the film is directed to occur within the film die and prior to extrusion of the film and fastening element past the die lip.

7. The method of Claim 1 including the step of simultaneously extruding a pair of fastening elements through a die plate, each fastening element having a base which is adapted to be joined to the film, one fastening element base having integrally formed there¬ with a male profile, and another fastening element base having integrally formed therewith a female profile.

8. The method of Claim 1 including the step of simultaneously extruding a plurality of pairs of fastening elements through a die plate, each fastening element having a base which is adapted tb be joined to the film, one fastening element base of a pair of elements having integrally formed therewith a male profile, and another fastening element base of said pair of elements having integrally formed therewith a female profile.

9. An apparatus for forming an integral thermoplastic fastening element on a thermoplastic film or sheet, including a forming die for extruding the film through a forming slot in said die, a die plate positioned adjacent to the forming for extruding said fastening element at a predetermined angle with respect to the extruded film for joining said fastening element to the film, a chill roll for cooling the combined film and fastening element, said chill roll being positioned with respect to the forming die to provide a predetermined distance (h) between a horizontal line extending tangen- tially of an outer circumferential surface of the chill roll and a die lip on the forming die and a predetermined

^'BL cΛi

_0"PI_ distance (d) between a vertical line extending from the die lip to said outer circumferential and tangential surface of the chill roll.

10. The apparatus of Claim 9, wherein said die plate has a leading edge, and adjusting means for positioned said die plate on the film forming die with the leading edge extending below a surface of the die lip having a predetermined width (T).

11. The apparatus of Claim 9 or 10, wherein said die block is provided with at least one pair of die plates, a first die plate having an orifice for extruding a combined base and male profile therefrom and a second die plate having an orifice for extruding a combined base and female profile therefrom, each said combined base and profile forming a complimentary fastening element for sealing of an edge of a bag or container.

12. The apparatus of Claim 10 or 11, wherein the width (T) of the die lip is from 0.05 cm (0.020 in.) to 0.076 cm (0.030 in.).

13. The apparatus of any one of Claims 9 to 12, wherein the fastening element is extruded through a channel in the die block having a gap (x), said gap being greater than 0.028 cm (0.011 in.) in depth.

14. The apparatus according to Claim 9, wherein said die is provided with an extrusion slot for the film and an integral extrusion channel for the -thermoplastic material forming the fastening element, said extrusion channel being positioned at an acute angle with respect to the film slot, and a die plate for forming the fastening element positioned within a cut out portion in the die for joining the base portion of the fastening element to the film prior to extrusion of the film and fastening element from the die.

15. An apparatus for forming an integral thermoplastic fastening element on a thermoplastic film or sheet, said apparatus comprising an extrusion die having a film forming slot ending in an extrusion die lip, said die having an angularly disposed surface extending toward said film forming slot and die lip, a die plate positioned adjacent to said die slot and forming an extrusion channel for the fastening element which is arranged in an angular relationship with respect to the film forming slot to increase the acute- ness of the angle of the extrudate issuing from the die plate channel with respect to the extrudate issuing from said film forming slot, and cooling means located below said extrusion die and die plate.

16. The apparatus of Claim 15 wherein said die block is adjustably mounted with respect to the angular face of said extrusion die, the bottom edge of the die plate facing towards the extrusion die lips and being located below the bottom of the extruder die lips.

17. The apparatus of Claim 16 wherein the bottom edge of said die plate is located laterally inwardly toward the extrudate of the extrusion die as respects the edge of the die lips adjacent the die plate.

EϋKtA

18. The apparatus of Claim 16 or 17 wherein the die plate at its bottom includes fastener-shaped orifices and base-shaped orifices in open communication with each other and the die block extrusion channel, said base-shaped orifices allowing forming of thermo¬ plastic strips at the bottom of the fastener members.

19. The apparatus of Claim 16, 17 or 18 wherein said cooling means includes a chill roll, said chill roll located such that its uppermost extent is above the die lips and one of its lateral extents extends below and to the die plate side of said die lips thereby angularly disposing the extrudate from the die lips toward the extrudate issuing from the die plate.

20. The apparatus of any one of Claims 16 to 19 wherein the lower edge of said die plate facing said extrusion die extends directly under a land area of said extruder die located to the side of the die lips adjacent the die plate.

21. The apparatus of Claim 20 wherein the distance y between said lower edge of said die plate is less than 0.030 cm (0.0012 inch) from the surface of a film or sheet issuing from the die lips.

22. The apparatus according to any one of Claims 16 to 21, including liquid cooling means for cooling said joined fastening means and said film and sheet combination, means for passing said combination around said roller, an air jet apparatus located adjacent a side of the roller over which the combination passes, said air jet apparatus including a tongue extending tangentially beyond the circumference of said roller, whereby the air jet velocity is increased to remove excess water from the surface of said combination.

23. The apparatus according to Claim 15, wherein said die is provided with an extrusion slot for the film and an integral extrusion channel for the thermoplastic material forming the fastening element, said extrusion channel being positioned at an acute angle with respect to the film slot, and a die plate for forming the fastening element positioned within a cut out portion in the die for joining the base portion of the fastening element to the film prior to extrusion of the film and fastening element from the die.

24. A cast relatively unoriented film or sheet having integral relatively stiff male and female fastening members, each of said fastening members having base strip secured to said film or sheet over at least 90 percent of the widt of each base whereby said base provides sufficient rigidity for the fastening members during each opening and closing of the fastening members for said relatively unoriented cast film.

25. The film or sheet of Claim 24 wherein said fastening members and said film or sheet are of materials differing in composition or color.