MXPA96002229A - Method and apparatus for producing a high polyester sheet orient - Google Patents

Abstract

A method and apparatus for producing a highly oriented polyester sheet consisting of a two-stage traction process. The first traction stage is executed within a set of "zero-gap" rolling and stretching rollers, which consists of a pair of opposed rollers defining an opening therebetween, and in which the rollers are rotated in opposite directions at different speeds of linear surface in such a way that between them a predetermined proportion of traction is defined. The amorphous polyester sheet is conducted through the pass opening of the opposed rollers, and as a result of the simultaneous rolling and stretching of the polyester sheet the amorphous polyester is transformed into crystalline polyester as a result of orientation-induced crystallization. The crystalline polyester sheet is heated to a level above the glass transition temperature (Tg) immediately downstream of the opening defined between the pair of opposed rolls, and a set of output flanges is disposed downstream of the pair of rolls. the opposite rollers. The rollers of the flange assembly rotate at linear surface velocities that are greater than the linear surface velocity of the specimen downstream of the pair of opposed rollers in such a way that a second tensile ratio is defined with respect to said exemplary downstream of the pair of opposite rollers. The heating of the crystalline polyester sheet facilitates its additional stretching within the second stage of traction of the apparatus, the general traction ratio being of the order of 6: 1. Thus, a highly oriented polyester having tensile strength values of the order of 7,000 is achieved. kgs / cm2 as well as module values in the order of 210,000 to 350,000 kgs / c

Description

METHOD AND APPARATUS FOR PRODUCING A HIGHLY ORIENTED POLYESTER SHEET Inventors: Donald Van Erden Nationality: North American Address: 33456 La evie Court Wildwood, Illinois, E.U.A. Manuel C. Enríauez Nationality: North American Address: 7207 Wilson Terrace, Norton Grove, Illinois, E.U.A. Owner: ILLINOIS TOOL WOKS INC. Nationality: Of the State of Dela are, E.U.A. Address: 3600 West Lake Avenue, Glenview, Illinois, E.U.A. REFERENCE TO RELATED PATENT APPLICATIONS: This application is a Partial Continuation ("CIP") of the US Patent Application Serial Number 09 / 352,721, filed on December 12, 1994 by Donald L. Van Erden et al., And bearing by title METHOD AND APPARATUS FOR PRODUCING AN ORIENTED PLASTIC STRAND, AND THE TRACTOR SO PRODUCED, which in turn is a Partial Continuation Patent Application ("CIP") of US Patent Application Serial No. 07 / 958,803 filed on September 9. October 1992 by Donald L. Van Erden et al., and entitled "METHOD AND APPARATUS FOR PRODUCING AN ORIENTED PLASTIC STRAND", which is currently US Pat. No. 5,387,388. FIELD OF THE INVENTION: The present invention relates in general terms to a method and apparatus for producing a oriented plastic sheet and more particularly to a method and apparatus for producing a highly oriented polyester sheet exhibiting improved tensile strength and improved characteristics. , parameters or module values. BACKGROUND OF THE INVENTION: According to a typical stretching procedure of the prior art as for example, the so-called SIGNO DE process, firstly a sheet emptied of thermoplastic material, such as polypropylene, is reduced in size, ie with its reduced thickness , by rolling the sheet through a pair of closely spaced laminating rollers or cylinders rotating in opposite directions. Once the thickness of the sheet is reduced, the sheet is passed to stretch from the rolling rolls by means of a series of orienting rollers, or some set of flanges to achieve its final desired size or definitive thickness. Another process or method corresponding to the prior art which is commonly used in connection with the manufacture of stretched sheet materials is a known process or referred to as the "short hole" method which generally consists of the inlet flange, a stretcher assembly and an exit flange. According to this process, a set of heated flanges, moving at low speed, advances a sheet emptied of material, usually a film, into a stretching assembly comprising a pair of rollers or cylinders that are located with a certain distance between them. . The first roller rotates at the same speed as the input flange while the second roller rotates at a speed that is greater than that of the first roller and that is equal to the rotational speed of the output flange. Thus, when the film passes through the whole, it is stretched to its desired final size or final thickness dimension. These methods or processes corresponding to the prior art have presented several drawbacks. For example, it can be said that the properties of the straps produced through these methods or processes provide or exhibit limited increases in their strength without losses and significant in other desired properties. In addition, substantial bending of the sheets occurs when the sheets are stretched over the distance or the space defined between the rollers. U.S. Patent Application Serial No. 07 / 958,803, now US Patent 5,387,388, discloses a novel process and apparatus for achieving simultaneous lamination and stretching of such sheets in which the problems noted above could be minimized without However, other operational problems have been discovered in such processes and apparatuses that likewise needed some rectification in order to obtain simultaneously laminated and stretched sheets of thermoplastic material exhibiting other convenient properties. For example, an operational problem or deficiency that was discovered in relation to the manufacture of simultaneously laminated and stretched sheets of thermoplastic material according to the so-called "zero-gap" process and corresponding apparatus disclosed and described with US Pat. No. 5,387,388 is that when the sheet of thermoplastic material to be worked is ready, that is, to be laminated and stretched simultaneously by its passage through the opening defined between the rotating rollers in the opposite direction of the set called "zero-gap" it was found that the opposite faces of the thermoplastic sheet exhibited different values in terms of surface temperature. The reason for this is that when the thermoplastic sheet is channeled around the first roll, that is, roller upstream of the zero-gap roller assembly, the inner face of the thermoplastic sheet, ie the face of the sheet that is arranged in direct contact with the first roller, upstream, of the roller assembly, it will be heated by the first roller, upstream, or having at least its surface effectively impeded in cooling by the ambient air, since such surface it is arranged in direct contact with the first roller, upstream, and is not directly exposed to ambient air. In contrast, the outer face of the thermoplastic sheet, ie, the surface of the sheet that is not arranged in direct contact with the first roll, upstream, is effectively cooled as a result of being exposed to ambient air. Such temperature difference between the faces mentioned above of the thermoplastic sheet leads to density differentials throughout the thermoplastic sheet adversely affecting the different properties of the processed sheet, for example, its tensile strength, weldability and associated properties, as well as in Regarding the division resistance. Another problem or deficiency that was discovered in relation to the apparatus mentioned above within the zero-gap process, the simultaneous rolling and stretching, and in the corresponding method, was that due to the transformation of the thermoplastic sheet, the portions were thickened of the opposite edges of the sheet or, in other words, that the sheet did not exhibit a uniform profile in thickness or flat state over its entire width. Accordingly, when the processed sheet was then subjected to some treatment to form a thermoplastic material tie, the thickened marginal portions could not be used to make such tie rods, unless another transformation was carried out on the sheet to effectively reduce the dimensions in thickness of the marginal portions of the sheet to desired dimensions in characteristic thickness of the usual tie rods. Accordingly, the invention embodied and disclosed in US Patent Application Serial No. 08 / 352,721 was directed to an apparatus and method for producing a oriented thermoplastic stringer that was simultaneously laminated and stretched as a result of an operation in which a work piece in the form of a thermoplastic sheet was passed through an aperture defined between the rollers of opposite rotation of the "zero-gap" assembly, and in which, moreover, in order to overcome the deficiencies indicated above the apparatus and method of simultaneous rolling and stretching in the "zero-gap" process with respect to the density differentials and thickened edge portions of the rolled and stretched sheet, different heating techniques were used related to the laminated and drawn sheet, such and as has been disclosed more particularly in the Patent Application mentioned above Number 08 / 352,721, text that is incorporated in the present application as a reference material, and thanks to whose measures the deficiencies mentioned above were overcome. Certain studies and additional analysis of the existing "zero-gap" technology, as indicated above, and as disclosed and described both in U.S. Patent 5,387,388 and U.S. Patent Serial No. 08 / 352,721, on the other hand, have disclosed that when it is applied or used technology in relation to the manufacture or manufacture of sheets or straps of polyester, especially in relation to the manufacture or manufacture of such sheets or straps of polyethylene terephthalate, the resulting sheets or straps do not exhibit high characteristics, parameters or values in terms of strength tensile or module. Therefore, there is a need to develop an apparatus, with its corresponding method, to produce highly oriented polyester webs or straps, in which the apparatus and the concomitant method use special or unique techniques in orientation, stretching or rolling, in combination with certain special or unique heating techniques, therefore, the sheets or polyester struts thus produced or manufactured exhibited better values, characteristics or parameters in terms of tensile strength and modulus.

OBJECTS OF THE INVENTION Accordingly, it is an object of the present invention to provide a new and improved method, with the corresponding apparatus, for producing highly oriented sheets or straps of polyester. Another object of the present invention is to provide a new and improved method and the corresponding apparatus for producing highly oriented polyester struts or sheets that overcome the different deficiencies, drawbacks, disadvantages and problems of the processes and apparatuses corresponding to the prior art. Still another object of the present invention is to provide a new and improved method, and the corresponding apparatus, to produce highly oriented polyester webs or struts, which will be capable of producing such struts or sheets by rolling and simultaneous stretching of parts. of work in the form of a sheet to form such braces or sheets that will have a certain thickness dimension, thanks to the operation in which the work pieces in the form of a sheet are conducted in a single pass through an opening defined between a pair of "zero-gap" rollers. Still another object of the present invention is to provide a new and improved method and apparatus for producing highly oriented sheets or straps, of polyester, in which the sheets or struts thus produced exhibit clearly greater values in tensile strength and modulus when compared with the straps. or sheets produced through previously known methods and apparatus. Another object of the present invention is to provide a new and improved method with the corresponding apparatus for producing highly oriented polyester webs or struts, in which improved characteristics of uniform flatness and thickness are imparted to the stringer or laminated and stretched sheet, definitive , as differences of various heating, rolling and extrusion techniques that are imparted to the work piece or original sheet material. SUMMARY OF THE INVENTION In brief terms, the above and other additional objects are achieved in accordance with the present invention by providing a method and apparatus for producing highly oriented polyester webs or struts, which will have a certain thickness suitable for use in the strapping of packages and the like, in which the strap having the indicated convenient thickness is rolled and stretched simultaneously as a result of the operation in which a work piece in the form of a polyester sheet passes through the opening defined between a pair of rollers or cylinders that are closely spaced between them. The opening pass has a spatial dimension that is virtually less than the original thickness dimension of the sheet-shaped workpiece, and the rollers are rotated in opposite directions and with virtually different linear surface speeds. In order to improve the different properties of the tie simultaneously laminated and stretched, that is to say, for example, the tensile strength and the modulus or stiffness of the fabricated oriented sheets or struts, the sheet or the solid struts, according to the teachings of the present invention is subjected to a single orientation sequence and a single heating sequence. In particular, the orientation sequence is actually a two-stage pass sequence, in which the first pass operation is effectively carried out within the set of "zero-gap" rollers, while the second rolling operation is carried out. carried out by means of a set of output flanges in cooperation with the roller downstream of the set of "zero-gap" rollers. Concomitant therewith, the heating sequence comprises a particular mode of heating, in which, for example, the upstream and downstream rollers of the zero-hollow roller assembly, indirectly heat the solid polyester sheet or strut, and heat directly also the tie rod or the polyester sheet at a specific point with respect to the roller upstream of the set of zero-gap rollers to thus control in a precise and consistent way, and determine the orientation of the polyester sheet or stringer. In addition, the mechanical work imparted to, or printed on, the sheet or the polyester stringer when it passes through the pass between the rollers of the zero-gap roller assembly, also contributes to an additional heating of the strut or sheet for thus facilitate the stretching of the blade or shoulder and its resulting orientation. In order to improve the flat state of the resulting polyester sheet, simultaneously treated and stretched to thereby produce an increasing volume of webs from such sheets, portions of thinner edges can be initially imparted to the sheet-shaped workpiece of polyester, either upstream or anterior, with respect to the entry of the sheet-shaped workpiece in the defined course between the zero-hollow laminating rollers, or within the defined course between the zero-laminating rolls -hole. In view of the tendency of the portions of the edges of the workpiece to thicken as a result of the simultaneous operation of rolling and stretching of the sheet-shaped workpiece within the set of the zero-gap rolls, the Resulting edge portions, according to the transformation techniques of the present invention, will exhibit dimensions of thickness that will be commensurate with the thickness dimension of the central portion of the sheet-shaped workpiece, as viewed transversely by the width of the work piece of the sheet, when this piece of work is laminated and stretched simultaneously. The production of the thinner edge portions of the sheet-shaped workpiece can be carried out, for example, by rolling rollers which will have special contours and which will be used within the set of "zero-gap" rollers, which the workpiece is displaced in the form of a leaf in a mandatory manner, in which the rolling rollers with zero-gap effectively define a pass between them and which has a trapezoidal configuration in cross section. In a similar manner, although as an alternative, and according to a second means or mode for producing such thinner edge portions in the resulting workpiece, extrusion dies and draining rolls, with special contours, can be used in order to similarly providing the extruded and emptied workpiece, in sheet form, with a virtually trapezoidal configuration, so that the marginal portions, that is, the edges of the sheet-shaped workpiece, will have a conical shape. As a result of the simultaneous rolling and stretching of the sheet-shaped workpiece, its conical portions will experience greater thickening, whereby the dimensions of the thickness of the edge portions will be similar to the thickness dimension of the central portion of the sheet. the piece of work in the form of a leaf. BRIEF DESCRIPTION OF THE DRAWINGS Several other objects, features and corresponding advantages of the present invention will be presented more clearly if one takes note of the following detailed description to be considered together with the attached drawings, in which similar reference numbers identify equal parts. or corresponding in the different views and in that: Figure 1 is a fragmentary and front view of the apparatus, constructed according to the present invention, to produce a strap, that is, a plastic strap, oriented, according to the "zero-gap" manufacturing process, that is, the techniques explained in the present invention. Figure 2 is an enlarged, simplified, fragmentary, front view of the rolling and drawing rollers defining or comprising the zero-gap roller assembly of Figure 1. Figure 3 is an enlarged, partial, cross-sectional view of the rolling and stretching rollers that define the set of zero-gap rollers of Figure 1, as considered by line 3-3 of Figure 1. Figure 4 is a simplified and fragmentary cross-sectional view, on a reduced scale, of the rolling and drawing rollers defining the set of zero-gap rollers of Figure 1, as taken by the line or the direction parallel to line 3-3 of Figure 1. Figure 5 is a schematic view, similar to that of Figure 1, in which the rolling and stretching apparatus is indicated , that is, the system constructed in accordance with the principles and teachings of the present invention to produce highly oriented polyester sheets or webs. Figure 6 is a schematic view, similar to that of Figure 5, which teaches or illustrates the particular and unique heating scheme, ie, the sequence developed in accordance with the principles or teachings of the present invention, and as uses or incorporates within the entirety of the flange assemblies, zero-gap rolling mills and rollers with output flanges according to the present invention, in order to facilitate the production of highly oriented polyester sheets or material in the form of strap or strap, corresponding. Figures 7A and 7B are front views of two different embodiments of rolling rolls that can be used within the zero-gap assembly, either of Figure 5 or Figure 6, to produce polyester sheet or stringer, laminate and stretched, having portions of thinner edges, in such a way that the amount of usable sheet or stringer exhibits the convenient degree of flatness, as observed in the transverse direction by the width of the sheet or stringer, all of which with improved features. Figures 8A and 8B are cross-sectional, schematic views of extrusion dies that can be used to produce a sheet-shaped workpiece having thinner edge portions, such that the amount of sheet is improved or usable strut exhibiting the desired degree of flatness, as contemplated in the transverse direction by the width of the sheet or strut when the sheet or stringer material has already been laminated and stretched. Figure 9 is a front view of the draining rollers which are used in combination with the extrusion dies of Figures 8A and 8B to further empty and shape the sheet-shaped workpiece, extruded from the extrusion dies of Figures 8A and 8B, in such a way that the sheet-shaped workpiece can be driven downstream to the zero-gap laminator and extruder assembly. DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS Referring now to the drawings, and more particularly to Figure 1, a set of zero-gap rolls, indicated generally by reference numeral 20, is schematically illustrated for simultaneously laminating and stretching or lengthening a work piece in the form of sheet 22 to obtain a material constituted by a thin strut. The present invention is treated and illustrated only with an exclusive workpiece 22, which as a sheet is driven through the assembly 20, however, it should be understood that it is also possible to pass more than a single sheet or workpiece 22 simultaneously to It should be understood, furthermore, that the term "zero-gap" as it is being used throughout the text of this application, refers to the concept of virtually eliminating any gap between the step of rolling the work piece and the step of stretching or lengthening it. Considered in alternative form, the steps of laminating and stretching or lengthening the work piece in sheet form are achieved virtually simultaneously. Furthermore, it is noted, as indicated in Figure 1, that the zero-gap assembly 20 is located between a sheet or work piece feeder assembly 24, and a set of exit flanges 26 that are or are mounted on a frame or support 28. The feeder assembly 24 can assume any of different shapes, and as shown in Figure 1, comprises an extruder 30 for extruding a sheet or work piece 22 of transformation material, as well as a set of input flanges 32. The extruder 30 produces a workpiece in the form of sheet 22, from a suitable material, such as polypropylene, a polyester, such as for example polyethylene terephthalate (PET), or the like, and the sheet-shaped workpiece 22 is conducted, up to the assembly of inlet flanges 32, which in turn feeds the sheet-shaped workpiece into the zero-gap roller assembly 20. The sheet-shaped workpiece 22 can be heated during its passage through the assembly Inlet flanges 32 for effective preheating when entering the zero-gap roller assembly 20 to improve the operating properties, stretching or elongation, as well as the orientation properties and the resultant characteristics of the It is useful for the sheet-shaped workpiece 22, this heating technique being discussed in greater detail in relation to the manufacture of highly oriented sheets or polyester webbing, when the system or the apparatus according to FIGS. 5 and 6 is subsequently processed. It is noted that the set of input flanges 32 consists of a plurality of rollers or cylinders 34, 36, 38 and 40 that are mounted by means of suitable auxiliaries, such as, for example, arrows, not shown, on the frame or support 28. The rollers 34, 36, 38 and 40 can be solid or hollow, and in the preferred embodiment, as illustrated in Figure 1, the rollers 34, 36, 38 and 40 are essentially used only for delivering or feeding The blade-shaped workpiece 22 is correctly positioned to the zero-gap assembly 20, and virtually does not contribute to any stretching or rolling of the sheet-shaped workpiece 22. A good number of rolls other than that can be used. l indicated in Figure 1, and it can be seen that the rollers 34, 36, 38 and 40 are arranged within two rows spaced vertically, in which the rollers corresponding to the lower row 36 and 40 are located between the rollers of the row superior 34 and 38, or they are displaced in relation to the latter. The rollers 34 and 38 are also mounted to rotate clockwise, while the rollers 36 and 40 are mounted to rotate counterclockwise, and when the sheet-shaped workpiece 22 is rolled up, or channeled through , the entire set of inlet flanges 32, travels through the rollers 34, 36, 38 and 40 in the correct manner or in the proper direction with respect to the directions of rotation of the rollers 34, 36, 38 and 40. Each one of the rollers 34, 36, 38 and 40 rotate with uniform speed by suitable means, not shown, such as for example a motor and arrow transmitter assembly and all the rollers 34, 36, 38 and 40 rotate at virtually the same speed or linear surface velocity, like the upper roller 42 of the zero-hollow assembly 20, which will be discussed later in greater detail. Continuing, once the sheet-shaped workpiece 22 passes through the feeder assembly 24, it advances towards the zero-gap assembly 20 to simultaneously laminate and stretch the material to form the finished sheet 22 having a desired thickness, predetermined. The zero-gap assembly 20 comprises a pair of rollers or cylinders 42 and 44 that are rotatably mounted in opposite relation. The pass 46, that is, the distance defined between the rollers 42 and 44, can be varied basically according to the desired terminal thickness of the finished sheet 22. The zero-gap rollers 42 and 44 can be solid or hollow, and can be heated by any well-known means, not shown, such as for example a system of circulating a fluid heated through the rollers 42 and 44, in order to improve the stretching properties of the sheet material. The zero-gap rollers 42 and 44 can also be flat, as shown in Figures 1 to 4, or may have contours, as will be illustrated and will be described more specifically in later paragraphs, in order to change the shape of the work piece 22, when this sheet passes through the rollers. 42 and 44 of the zero-gap assembly 20, and provide the product of the finished workpiece with its predetermined characteristics as to its thickness profile. As best shown in Figure 2, the upper roller 42 of the zero-gap roller assembly 20 is driven clockwise, as shown by its associated arrow, while the bottom roller, or either, the lower roller 44 of the assembly 20 is driven counterclockwise, as is also shown or identified by means of its associated arrow. Thus, the sheet-shaped workpiece 22 is firstly channeled around a larger circumferential portion of the upper rolling roll 42, and then this workpiece 22 is driven through the passage 46 defined between the rolling rolls 42 and 44. It then passes around a larger circumferential portion of the lower or lower roller 44. More particularly it should be appreciated that the sheet-shaped workpiece 22 is disposed in surface contact with each of the rollers 42 and 44 of the set of zero -It is on a circumferential section that is greater than half of each of the circumferential extensions of each of the rollers 42 and 44, and further it is noted that as a result of this particular channeling of the sheet-shaped workpiece 22 through the passage 46 defined between the zero-gap laminating rollers 42 and 44 and around the outer circumferential or peripheral faces of the rollers 42 and 44, each roller 42 and 44 is disposed in contact with an opposite face or side of the sheet-shaped workpiece 22. In accordance with the illustrated embodiment of the zero-gap roller assembly according to the present invention , as shown in Figures 1 to 4, and as described in detail in combination with the figures of such drawing, the rolling and stretching rollers 42 and 44 of the zero-gap roller assembly 20 are arranged in an arrangement of upper / lower part, that is, an arrangement of upper / lower rollers in interrelation, however, it is to be noted that rollers 42 and 44, as an alternative, may be arranged in a juxtaposed arrangement, in which case the upper roller 42 will be located to the left of the lower roller 44, in such a way that the roller 42 will be the first roller, upstream, with which the workpiece in the form of sheet 22 comes into contact, while the lower roller 44, which now, in fact, it is the right roller, it will be the second roller, that is, the roller downstream, with which the work piece comes into contact in the form of a sheet 22. As best seen in Figure 2, the rollers 42 and 44 are respectively mounted on rotating shafts or arrows 52 and 54. With particular reference to FIG. 4, it is noted that the transmission system for the rollers 42 and 44 is disclosed in these figures, and it can be seen that the axes or arrows 52 and 54 of rollers 42 and 44 are operatively connected, via bearings 69 and 68, to driven arrows 48 and 50. Suitable transmission elements 56 and 58, such as for example electric motors, are mounted on the support 28 for driving the rollers 42 and 44, respectively, through the driving arrows 60 and 62, which are connected to the arrows 48 and 50 by means of suitable couplings 64 and 66, of which the coupling 66 preferably comprises a universal coupling for reasons that will be pointed out in a short time. The lower roller 44 is connected to the support 28 by means of the bearings 68 and 70, and the coupling 66, as well as the bearings 68 and 70 allow the lower roller 44 to move with respect to the support 28 by means of the actuators 72 and 74. In this way the lower roller 44 is able to move forward or away from the stationary upper roller 42 to thereby conveniently change the size of the passage 46 defined between the rollers 42 and 44. From each of the driven arrows 48 and 50 is independently driven by its separate transmission element 56 and 58, and the lower roller 44 is driven with a higher speed than that of the upper roller 42. Specifically, according to the teachings of the present invention, the lower roller 44 is driven in such a way that its linear surface velocity is preferably within the range seven to twelve (7-12) times greater than the linear surface speed of the upper roller 42 when the sheet-shaped workpiece 22 under process consists, for example, of polypropylene. However, as will be explained and explained in more detail below, when the workpiece in the form of sheet 22 which is in process is made of polyester, as for example, and preferably polyethylene terephthalate (PET) ), the linear surface velocity, that is, the stretching ratio of the lower roller 44 is within the range of four to five (4-5) times greater than the linear surface speed of the upper roller 42. In view of the above, will note that when the sheet-shaped workpiece 22 passes through the passage opening 46 defined between the upper and lower roller 42 and 44 of the zero-gap roller assembly 20, the upper roller 44 effectively operates as a brake, and the reducing operation, as such, can also effectively operate as a brake that is exerted on the underside of the sheet-shaped workpiece 22, i.e., the surface disposed in contact with the upper roller. 42, while the lower roller 44 pulls and accelerates the sheet-shaped workpiece 22, with which the roller 44 effectively operates on the upper face of the sheet-shaped workpiece 22, i.e. its surface that is in contact with the roller 44. When the sheet-shaped workpiece accelerates through the passage 46 defined between the rollers 42 and 44, it is rolled and stretched simultaneously to its final determined thickness, which The fact can be less than the spatial dimension of the pass 46, as defined between the rollers 42 and 44. Specifically, the thickness of the finished sheet 22 depends on the differential in surface and linear velocity or traction ratio that is defined between the roller 42 and the lower roller 44, that is, the faster the lower roller 44 rotates relative to the upper roller 42, the thinner the finished sheet 22 will be. It should also be noted that some stretching may occur in a slight degree before or shortly after the pass 46 defined between the pair of rollers 42 and 44, again depending on the differential in surface speed defined between the rollers 42 and 44. Thus, as indicated above, there is essentially a space of zero-gap, or else, a zero time frame between the rolling and stretching functions that are executed in relation to the sheet-shaped workpiece 22 and its transformation into the finished or finished sheet 22. As a result of such simultaneous processing of rolling and stretching, it has been noted that there is a substantially less phenomenon of folding in the width of the sheet compared to the parameters of the sheets that underwent a transformation of stretch or pull according to the procedures or techniques of past times when the sheet was stretched only after the lamination step had been carried out. After the finished sheet 22 leaves the zero-gap roller assembly 20, it is led through the output flange assembly 26. The output flange assembly 26 can assume any of several different shapes, and as shown in FIG. Figure 1, this assembly preferably comprises a plurality of rollers or cylinders 76, 78, 80, 82, 84 and 86, which are assembled with suitable auxiliaries, such as arrows or shafts, not shown, on the support 28. assembly 26, and in particular rolls 76-86, are used to pull the finished sheet 22 and remove it from the zero-gap assembly 20. The rolls 76, 78, 80, 82, 84 and 86 can be solid or hollow, and more or fewer rollers than the number indicated here can be used. The rollers 76, 78, 80, 82, 84 and 86 in this embodiment do not contribute virtually to any stretching of the finished sheet 22, however, as will subsequently be apparent, when the system of Figure 1 is modified to manufacture sheets of highly oriented polyester, the rollers of the output flange assembly of such apparatus or modified system will perform a critically important function of stretching, elongation or traction in relation to the manufacture of such polyester sheets to achieve polyester sheets which will exhibit the convenient parameters high tensile strength and modulus. Referring again to the embodiment of Figure 1, it is seen that the rollers 76, 78, 80, 82, 84 and 86 are arranged in two rows spaced vertically with the rollers of the lower row 78, 82 and 86 also spaced between the rollers of the upper row 76, 80 and 84, as considered in the transverse direction. The upper rollers 76, 80 and 84 all rotate clockwise, while the lower rollers 78, 82 and 86 all rotate counterclockwise, so that the finished sheet 22 can be properly driven through the flange assembly of the rollers. 22. The rollers 76, 78, 80, 82, 84 and 86 rotate with a uniform speed regime by means of suitable driving aids, such as for example a motor and arrow assembly, and the speed of the rollers 76, 78, 80, 82, 84 and 86 is such that, according to this embodiment of the invention, their linear surface velocities are essentially the same as those of the lower roller 44 of the zero-gap roller assembly 20 It should be noted that according to further teachings of the present invention, another method of stretching, and apparatus for instrumentation, such as for example an apparatus, system or set of stretching with short gap, can be applied, either before, or after the assembly of zero-gap 20 to modify or improve in this way in addition the characteristics of the finished sheet 22, and as has been hinted previously, this additional apparatus or system, and its concomitant stretching techniques, will be explained in greater detail in later paragraphs in relation to the special transformation or manufacture of highly oriented polyester sheets. Having now revealed the specific data of the apparatus constituting the first embodiment of the present invention, the method to be practiced by such an apparatus, and in accordance with the present invention, is described below. More particularly, the sheet-like workpiece 22 is fed from the extruder 30 to the input flange assembly 32 and wound around the rollers of the input flange assembly 34, 36, 38 and 40, so as to In turn, the sheet-shaped workpiece 22 is then fed around the upper roller 42 of the zero-gap assembly 20, this upper roller 42 being driven. of the roller assembly 20, with the same linear surface velocity as that of the rollers of the input flanges 34, 36, 38 and 40. When the sheet-shaped workpiece 22 enters the zero-gap assembly 20 , it travels around the outer peripheral face of the upper roller 42 until it reaches the passage 46 defined between the upper roller 42 and the lower roller 44. As previously noted, the faster lower rotating roller 44 pulls the workpiece. work in sheet form 22 through the passage 46, while the upper roller of slower rotation 42, like the reduction procedure as such, effectively acts as a brake on the underside of the workpiece in the form of sheet 22, that is, that surface of the workpiece 22 which is placed in contact with the upper roller 42. Thus, the sheet-shaped workpiece 22 is accelerating through the passage 46 defined between the rollers 42 and 44, and laminates and stretches simultaneously to its predetermined, definite thickness dimension as it passes through pass 46. The output flange assembly 26 then pulls the finished sheet 22 away from the lower roller 44 of the zero-gap assembly 20. and, therefore, it is noted that according to the method of the present invention, it will thus be possible to obtain the production of a flat, thin, oriented sheet 22 which is ready to be treated on its surface and / or thermally, as desired, to be slit into thin straps, as required or convenient to be used in the cinching of packages and the like according to well-known procedures. It is repeated once again that the apparatus and method described above produce a stringer of a notably better quality than those previously manufactured according to the apparatuses and methods of the prior art, as exemplified and illustrated equally by the different data noted in The following table: TABLE I As can be seen from the previous table, the zero-gap method produces straps that exhibit a higher tensile strength and a solder in greater percentage, that is, stronger. In addition, the cracking of the strap has been essentially eliminated, achieving a high tensile strength anyway, while according to the techniques and manufacturing procedure corresponding to earlier times, when the tensile strength is increased, a greater degree of cracked and decreases the percentage of the welding force. Additionally, in view of the fact that the tensile strength of the web produced according to the zero-gap process is approximately 1.47 times the tensile strength of the conventionally produced webbing, and in view of the elongation of such a strap or webbing according to With the present invention is about half that of the conventional girth, better draining performance is achieved. These results have several marketing advantages in relation to the polyethylene terephthalate (PET) polypropylene or polyether straps. More specifically, when the resistance to break of the girth is a control factor in relation to the application or specific use of the girth, then the greater tensile strength of the material will allow the use or replacement of a girdle consisting only of approximately seventy percent (70%) of the material or webbing currently used. Similarly, when the stiffness or stiffness is a control factor, or some characteristic or attribute, then the web produced according to the present is of such character, that it can be fed without problem to a cinching machine, since it is pushed around a guide weir of the webbing machine. Additionally, when the welding force of the webbing is a controlling factor or feature of importance, then the webbing consisting of less than half of the raw material currently or conventionally used will produce the equivalent joint force.

The different properties resulting from the process according to the invention give the cinch a considerable design flexibility, which can then be used in relation to a variety of applications. It is believed, for example, that the strap or strap produced by means of the system of the present invention exhibits a greater binding strength for the grain, while still being relatively easy to tear the strap through the grain. In addition, the strut produced by the zero-gap method of the present invention does not exhibit a structural delamination, as is often a characteristic factor of most of the straps corresponding to the prior art. In view of the fact that the strut of the present invention does not exhibit a structural delamination, a higher welding force is also obtained. As noted above, if a pre-stretching step is carried out between the input flange assembly and the zero-gap assembly, or when a subsequent stretching step is executed between the zero-gap assembly and the set of output flanges, the same overall characteristics are achieved, such as those achieved in accordance with the embodiment of the present invention, as described in relation to the system and the method according to Figures 4 and 4. However, it should be noted that when a pre-stretching process step is carried out on the sheet-shaped workpiece 22, a higher tensile modulus can be achieved, whereas when a post-stretch processing step is carried out on the finished sheet 22, the material from which the sheet is made has a somewhat greater tendency towards fibrillation. Referring again to the apparatus or system of Figure 1, it has been found that when the sheet-shaped workpiece 22 is driven through the input flange assembly 32, and especially when the workpiece 22 approaches the roll upper rolling mill and extruder 42 of the zero-gap set 22, the upper or outer face of the sheet-shaped workpiece 22, ie, its surface which is not placed in contact with the peripheral surface of the upper roller 42 of the zero-gap assembly 20, will tend to cool down with a rate faster than the lower or inner face of the sheet-shaped workpiece 22, which is arranged in contact with the peripheral face of the upper roller 42 of the zero-gap assembly 20, in view of the fact that the upper face or outside of the workpiece in the form of sheet 22 is exposed directly to the ambient air. As a result of such uneven or irregular cooling on the faces of the workpiece, or as a result of the development of such a temperature differential between the marked surfaces of the sheet-shaped workpiece 22, this workpiece 22 exhibits differentials. of density throughout its thickness, whereby such density differentials adversely affect some properties or characteristics of the work piece. Accordingly, in order to rectify how to solve or eliminate such a problem, an improved preheating system or apparatus has been developed, as more specifically pointed out in the pending Patent Application, cited above, Serial No. 08 / 352,721. In view of the fact that such an improved system or apparatus does not comprise the subject of this specific patent application, a detailed description of such a system or apparatus is not presented here, but rather that such text is incorporated herein as a reference material. . Continuing the explanation, it is also known that during the treatment of the workpiece in the form of a sheet 22, that is, by its rolling and stretching indicated above, the marginal portions, that is, the portions of the side edges of the work piece. Work in the form of sheet 22 will have a tendency to be thicker than the more centrally located portions of the workpiece 22. The reasons for this phenomenon are explained in the currently pending US Patent Application, Series, which was filed on the same date as the present patent application, and which is entitled METHOD AND APPARATUS FOR PRODUCING AN ORIENTED PLASTIC STRAND, AND THE STRAPPER PRODUCED THEREFORE, and the solution to this problem has been the supply of heaters of edges by the marginal portions of the sheet-shaped workpiece 22 at points immediately upstream of the passage 46 defined between the pair of laminating rollers 42 and 44. Furthermore, despite the use of such edge heaters, it was determined in addition, although certain concavities and transient bulging regions are present within the profile of the sheet, and in accordance with other teachings of the currently pending patent application, indicated above, Serial Number, additional strip heaters are also used in combination with the edge heaters mentioned above. Again, in view of the fact that such apparatus and the techniques for warming the edges of the sheet do not comprise the subject matter of the present specific patent application, a detailed description of such an apparatus and such techniques is omitted, and said material is incorporated in the present specification as a reference material. Also, it is pointed out that according to the particular teachings of the present invention, additional structural, non-heater, and associated techniques will be disclosed below to reduce the thickened marginal portions of the manufactured sheet. Continuing with the theme, it is pointed out that while the zero-gap lamination and stretching system according to Figures 1 to 4 has been, of course, extremely satisfactory and commercially successful in relation to the commercial manufacture of sheets and suspenders of polypropylene and polyester, particularly with the modifications achieved with the different improvements disclosed in the Patent Application, Serial No. 08 / 352,721, filed on December 12, 1994, and the Patent Application, Serial Number, filed on the same date as the present patent application, supplementary studies executed in relation to the sheets or the straps made of polyester, particularly polyethylene terephthalate (PET), have shown that the Apparatus or the system of Figures 1 to 4, as such, and operated according to the method and manner noted above, is not capable of producing highly oriented sheets or polyester struts, ie, sheets or webbing that exhibit , for example, a value of its tensile strength of 7,000 kg / cm2, and a value of the module that will be within the range of 7.5 million to 12.5 million kg / cm2. Accordingly, the apparatus and an operating mode, similar to those of Figures 1 to 4, but correspondingly modified according to the particular teachings of the present invention, will now be described in connection with the manufacture of such highly oriented polyester struts or struts that will exhibit a tensile strength value of 7,000 kg / cm2, and a modulus value of 7,500,000 to 12,500,000 kg / cm2. Polyester exists in two different states, that is, as a solid which can be an amorphous polyester or a crystalline polyester. The present invention is directed towards the manufacture of a sheet or a commercial type stringer consisting of crystalline polyester, as it is derived from amorphous polyester. The amorphous polyester can be changed into crystalline polyester, that is, it can be crystallized by a heat-induced crystallization, or an orientation-induced crystallization. The thermally induced crystallization of the polyester is disclosed, for example, in US Pat. No. 4,022,863, issued to Thomas J. Karass et al., On May 10, 1977, however, the tie made of polyester has a milky white color. to its appearance, and does not exhibit satisfactory crack resistance properties. Therefore, the present invention is directed to the manufacture of crystalline polyester sheets by means of an orientation-induced crystallization of amorphous polyester using a laminator system and zero-gap extruder., modified. More particularly, and now referring to FIGS. 5 and 6, a set of modified polyester rollers or changed apparatus system is generally indicated, with reference numeral 100, and as noted, comprises the set of zero rollers. hollow 120, consisting of upper and lower rollers 142 and 144, an array of inlet flanges or systems 132 consisting of rollers 134, 136, 138 and 140, as well as an arrangement or flange system 126 which is integrated by the rollers 178, 180, 182 and 184. An inactive or free-running roller 141 is sandwiched between the roller 140 of the input flange system 132, and the upper roller 142 of the zero-gap roller assembly 120, and similarly a free-running roller or idle roller 177 is sandwiched between the lower roller 144 of the zero-gap roller assembly 120, and the roller 178 of the output flange arrangement or system 126. In order to prevent induced crystallization thermally from the polyester sheet 122, led through the array of inlet flanges 132 and into the zero-gap laminator and extruder assembly 120, until then crystallization has been induced as a result of the orientation of the sheet 122 by means of the operation of the passage of the sheet 122 through the opening 146 defined between the laminating rolls 142 and 144. The temperature of the sheet 122 must be maintained below the glass transition temperature (T_) of about 80 °. C for any substantial period of time. If the polyester sheet 122 is heated to a temperature level above the glass transition temperature (Tg), for any substantial period of time, the sheet 122 will crystallize, become a sticky mass and the sheet 122 and it can not be driven correctly by its travel path through the input flange assembly 132 and the zero-gap roller assembly 120. Accordingly, in accordance with the teachings of the present invention, all the rollers of the flange assembly Inlet 134, 136, 138 and 140, like the idler roller 141 and the upper roller 142 of the zero-gap roller assembly 120, are heated and maintained to a temperature level of 75 ° C. In order to correctly transform the polyester sheet 122, that is, in order to obtain consistently oriented polyester sheets which at the same time consistently exhibit the desired tensile strength, modulus, drift resistance, crack resistance and other characteristics , it is necessary to facilitate the beginning of the orientation of the workpiece in the form of a leaf 122, at a precise point by its trajectory of movement through the system. In view of the molecular orientation and hence the crystallization, of the polyester sheet occurs within the pass opening 146 defined between the upper roller 142 and the lower roller 144 of the zero-gap assembly 120, the most advantageous point where can be started and controlled the orientation is at a site that is immediately before the passage opening 146 defined between the rollers 142, 144. From the operational point of view, and referring to Figure 5. If the terminal view is considered of the upper roller 142 on the dial of a watch, then the orientation of the sheet 122 would conveniently start within the lower right quadrant of such dial, or in other words, anywhere within the range of the two hour position until the position of six hours. It may be difficult to achieve such an orientation start in the corresponding position at 6 o'clock, since such a position comprises the site of the passage opening 146 defined between the rollers 142, 144 and therefore it is preferred to start the orientation at a site that is effectively as close to the six-hour position as possible. Therefore, according to the present invention, the infrared heaters 143 are disposed to the outside of the upper roller 142 to heat the sheet-shaped workpiece 122. Such heating changes the tensile strength of the work force in sheet form 122 in such site, and the elongation of the sheet-shaped workpiece 122 becomes easier in said place. Accordingly, the orientation of the sheet-shaped workpiece 122 is controlled or forced to begin at such a site. As illustrated in Figures 5 and 6, the infrared heaters 143 are in fact arranged at the corresponding clock position at 5 hours and 30 minutes (5:30), although it is also possible to place them at any point within the aforementioned range. from two hours to 5 hours and 30 minutes. In addition, the heaters 143 may have a length extending continuously from the position of two hours to 5 hours and 30 minutes to extend the heater region of the workpiece 122 depending on the speed of the workpiece 122 that passes through the assembly 120. While the infrared heaters 143 will raise the temperature of the workpiece 122 at such a point to a temperature value that is higher than the glass transition temperature (T_), due to the closeness of the such point to the passage opening 146 defined between the upper and lower roller 142 and 144, between which the orientation induced crystallization of the polyester sheet occurs, the thermally induced crystallization is minimized. Due to the rise in temperature of the sheet-shaped workpiece 122 to a temperature level that may be higher than the glass transition temperature (T_), the sheet-shaped workpiece 122 may exhibit a certain tendency to stick to the upper roller of the zero-gap system 142. Accordingly, in order to avoid such sticking of the sheet 122 to the upper roller 142, a water-based, water-soluble emulsion is applied as a spray, consisting of water, air and from 1% to 2% by weight of oil, coming from a spray device 145 so that it impinges on the underside of the sheet-shaped workpiece 122 in a transport position which is disposed upstream, by example, of the idler roller 141 of the input flanges. As can be seen in Figures 5 and 6, the lower face of the sheet-shaped workpiece 122 becomes the inner face with respect to the upper roller 142 of the zero-gap assembly 120 and consequently, such an emulsion will prevent any sticking that could occur between the sheet-shaped workpiece 122 and the upper roller 142 of the zero-gap assembly 120. The gluing of the oriented sheet 122 onto the lower roller 144 of the zero-gap assembly 120 is not a problem , since once the polyester sheet 122 undergoes its orientation within the pass opening 146 defined between the rollers 142 and 144 of the zero-gap assembly 120, the amorphous polyester is converted to crystalline polyester which does not exhibit adhesion properties or of stickiness. In order to correctly orient the leaf-shaped workpiece 122 within the passage opening 146 defined between the upper and lower roller 142 and 144 of the zero-gap assembly 120, the lower roller of the zero-gap system 144 rotates with a rotary speed such that the linear surface velocity of such roller 144 is virtually greater than the rotational speed and the effective linear surface velocity of the upper roller of the zero-gap system 142. Specifically, according to the present invention, it is placed the linear surface velocity of the bottom zero-hollow roll 144 as to be approximately 4 to 5 times the value of the linear surface velocity of the upper roll of the zero-gap system 142 such that the rate of traction applied to the sheet-shaped workpiece is similarly within the range of 4-5: 1. In a similar way, the rollers of the output flange assembly 178, 180, 182 and 184 rotate with a rotational speed that is greater than that of the lower roller of the zero-gap system 144 such that the linear surface velocity, and consequently the tensile ratio, the rollers of the output flange assembly 178, 180, 182 and 184 are a multiple of the linear surface velocity of the bottom zero-hollow roller 144. Specifically, according to the present invention, the speed of linear surface of the rollers of the output flanges 178, 180, 182 and 184 is placed as an approximate value of 1.1 to 1.5 times the value of the linear surface velocity of the bottom zero-gap roller 144 so that the Traction rate applied to the sheet-shaped workpiece will similarly fall within the range of 1.1-1.5: 1. Accordingly, as can be noted, the present invention comprises a two-step lamination process within a tensile ratio of approximately 6: 1 which is applied to the sheet-shaped workpiece 122. For example, when the lower roller 144, corresponding to the zero-gap system, with a rotational speed such that its linear surface velocity is 4.5 times the linear surface velocity of the zero-gap upper roller 142, and the output flange rollers 178 , 180, 182 and 184 rotate with a rotational speed such that their linear surface velocities are 1.34 times the linear surface velocity of the bottom zero-hollow roll 144, then a general or resultant ratio of 6.03 would be achieved, value that it would be applied to the sheet-shaped workpiece 122. As an alternative, the differential in the speed of the linear surface, for example, that is, the ratio of traction, between the roller bottom of the zero-gap system 144 and the upper zero-gap roller 142 could be 5.0 or 5: 1, respectively, while the differential in linear surface velocity, that is the ratio of traction defined between rollers corresponding to the set of output flanges, 178-184 and the lower roller corresponding to the zero-gap system 144 could be 1.2 or 1.2: 1, respectively, therefore, of new accounts, the general proportion of the traction would be 6: 1. In order to facilitate the secondary stretch, that is, the stretch corresponding to the second stage, and the orientation of the sheet-shaped workpiece 122, as developed between the bottom zero-gap roller 144 and the rolls of the assembly of output flanges 178-184, the bottom roll of the zero-gap system 144 is heated to a temperature level of 150 ° C while the rolls of the output flange assembly 178-184 can be maintained at room temperature (Rt. ). After experiencing the secondary stretch, ie the stretching of the second stage and the corresponding orientation, the resulting polyester sheet shows tensile strength values of 7000 kgs / cm2 and module values between 210,000 and 350,000 kgs / cm2. As noted above, during the manufacture of the workpieces in the form of an oriented sheet within the zero-gap apparatus or system, characteristic of the present invention, the workpieces manufactured in the form of a sheet have a tendency to exhibit portions thereof. or marginal regions thickened or thickened. Accordingly, it has been further noted in the above, that the supply of efficiently detailed strip heaters and strip heaters, as fully disclosed in the pending US patent application, Serial Number, rectifies or substantially eliminates such a problem to the extent that an increased volume of useful or taut sheet suitable for the final manufacture of packaging webs can be produced. The increased flat state, that is, increased quantities of finished sheets uniformly flat in their width dimensions, can also be obtained according to other non-heating manufacturing techniques, based on structure. For example, referring to Figures 7A and 7B, there are indeed profiles in front view of two rolling rollers of different contours that can be incorporated within the zero-gap assembly 120 of the system of Figures 5 and 6 in combination with the manufacture of highly oriented polyester sheets. As can be noted, of the contoured laminating rollers, 204 and 206 of FIGS. 7a and 7b, respectively, the central portions of the rolls 204 and 206 are effectively concave as seen at 208 and 209, respectively, while the portions of the rolls 204 and 206 are effectively concave. of the side edges 211 and 213 have straight or horizontal contours or configurations. In this way, when the leaf-shaped workpiece 122 is laminated and stretched within the passage opening 146, the edge portions of the sheet-shaped workpiece 122 will be worked to a greater extent than the center portions. of the workpiece 122 whereby the marginal portions of said sheet-shaped workpiece 122 will become thinner. Upon transformation within the section 146, the edge portions of the sheet-shaped workpiece 122 will also experience thickening to a certain extent, as described above, whereby the finished edge regions of the workpiece 122 , ie the finished sheet 122, will have the desired degree of thinness and uniformity of flat state, as can be similarly achieved by means of the above-mentioned techniques of edge heating and strips. As can be further noted, from Figures 7A and 7B, the primary difference between the contours or configurations of the rolling rolls 204 and 206 lies in the fact that in the case of the roll 204 of Figure 7A its central portion has a cylindrical contour as in 215 while its adjacent axial portions have tapered configurations, that is, conical, as in 217. Finally, the extreme outer end portions, that is, the portions of the edges are cylindrical as in 219, but on the other hand the section diametric of the cylindrical portions 219 is larger than a diametrical section of the central cylindrical portion 215. Similarly, in the case of the roll 206 of Figure 7B, the central portion 209 has a concave arcuate configuration while the outer end portions 221 are cylindrical and have diametrical sections that are greater than those sections of the central portion 209. Finally referring to Figures 8 A, 8B and 9, another manufacturing technique that can be applied to achieve an increased flat state or increased amounts of uniformly flat finished sheets by the dimensions of their years involves the extrusion of the sheet-shaped workpiece 122 from extrusion dies 223 and 225, specifically configured, which are respectively shown in Figures 8A and 8B. As can be noted from these Figures, each of these dies 223 and 225 in fact has a die mouth 227 and 229, with its trapezoidal configuration which, consequently, produces polyester workpieces 122 that similarly have trapezoidal configurations in cross section , or in other words, the portions of the edges 231 and 233 will be virtually thinner than the central portions of the sheet-shaped workpieces 122. In this way, when these trapezoidal configuration workpieces are laminated and stretched 122 , their portions of the edges will have thickness dimensions that are virtually equal to those of the central portion of the sheet-shaped workpiece 122 so that a virtually uniform thickness dimension is achieved over the entire width of the piece of work in sheet form 122, except, of course, in those regions of the extreme outer edges, as noted above. Furthermore, it is noted that the only important difference between the dies 223 and 225 is that the die 223 produces a sheet-shaped work piece 122 having a thickness dimension greater than a similar work piece 122 that can be produced by means of the die 225. In Figure 9, a set of casting or pouring rolls 235, 237 and 239 is disclosed, in a condition arranged in a vertical arrangement. The upper roller and the lower roller 235 and 239 each have configurations that are somewhat similar to that of the rolling rolls 204 and 206, while the central emptying roller 237 has a cylindrical configuration. Accordingly, one may note that the spaces 241 and 243 defined respectively between the drain rolls 235 and 237, and 237 and 239, have in effect trapezoidal configurations in such a way that when the workpiece in the form of sheet 122 is extruded the mouths of the dies 227 or 229, the work piece 122 is channeled initially around the emptying rolls to be inserted into the space 241, then wrapped around the roll 237 and removed from the space 243. Accordingly, it is seen that the configuration trapezoidal space 243 is actually upside down with respect to the trapezoidal configuration of the space 241. As an alternative means of creating or defining the trapezoidal spaces 241 and 243, the rollers 235 and 239 can be cylindrical while the roll 237 has a configuration similar to that of roller 204 or 206. After passing through such spaces 241 and 243, the workpiece can be transported in sheet 122 further to the zero-gap assembly 120 for transformation in accordance with the techniques of the present invention, as described above. Thus it can be seen that according to the foregoing, and specifically according to the manufacturing techniques and the apparatus developed in accordance with the principles of the present invention, a laminated and stretched sheet, already finished, consisting of highly oriented polyester is achieved and that exhibits improved characteristics in terms of tensile strength and modulus. In addition, the sheets also exhibit improved grades, that is, a greater uniformity in their flat state, whereby greater volumes of polyester straps or straps can be produced or derived therefrom. Obviously, many modifications and variants of the present invention are possible, in light of the teachings presented. Therefore, it should be understood that, within the scope of the appended claims, the present invention may also be practiced in other ways as that which has been specifically described and explained herein.

Claims (22)

1. CLAIMS: 1. An apparatus for producing a highly oriented polyester sheet comprising: a pair of opposed rollers defining a passage opening therebetween through which a work piece passes in the form of solid polyester sheet to be laminated and stretched simultaneously as this work piece passes through the opening in a single pass and in a predetermined travel direction; an element for driving the pair of opposed rollers in opposite directions and with sufficiently different linear surface speeds to simultaneously laminate and stretch the sheet-shaped workpiece within the opening defined between the pair of opposed rollers in accordance with a first proportion of predetermined traction, defined between the pair of opposed rollers by the linear surface velocities different from the pair of opposed rollers; at least one additional roller disposed downstream from one of the opposite roller pairs as observed in the predetermined travel direction to remove the workpiece in the form of a rolled sheet and drawn from the pair of opposed rolls; and an element for driving at least one of the additional rollers at a linear surface velocity sufficiently different with respect to that linear surface speed of the specimen located downstream from the pair of opposed rollers to further stretch the workpiece in the form of laminated and stretched sheet according to a second predetermined traction ratio. The apparatus as defined in claim 1, wherein the workpiece in the form of a polyester sheet is made from polyethylene terephthalate. 3. The apparatus as defined in the claim 1, in which: the indicated additional roller comprises a set of rollers forming a set of output flanges for the workpiece rolled and stretched with respect to the pair of opposed rollers. 4. The apparatus as defined in claim 1, wherein: the first tension ratio is within the range of 4-5: 1; and the second tensile ratio is in the range of 1.1-1.5: 1, whereby the proportion of general traction applied to the work piece in the form of polyester sheet is about 6: 1, and the polyester sheet is highly oriented exhibits tensile strength values of approximately 7,000 kgs / cm2 and module values in the range of approximately 210,000 to 350,000 kgs / cm2. 5. The apparatus as defined in claim 1, further comprising the following: the work piece in the form of a polyester sheet consists of amorphous polyester before said work piece passes through the opening defined between the pair of opposite rollers after which the sheet-shaped workpiece passes through the opening defined between the pair of opposite rollers, the workpiece undergoes an orientation-induced crystallization to consist of crystalline polyester; an element for heating an example, upstream, of the pair of rollers to in turn preheat the workpiece in sheet form, to a temperature level that is below the glass transition temperature (Tg) of the sheet-shaped workpiece to prevent this amorphous polyester work piece from sticking to the copy upstream of the pair of rolls, and an element to heat the copy downstream of the pair of rolls to a temperature level which is virtually above the glass transition temperature (Tg) of the sheet-shaped workpiece to facilitate further stretching of the workpiece in the form of a sheet consisting of crystalline polyester. The apparatus as defined in claim 5, further comprising: an element for heating the workpiece in the form of a sheet, at a site immediately upstream of the opening defined between the pair of opposed rolls, at a level of temperature that is higher than the glass transition temperature (T_) of the polyester sheet to predetermine control of the orientation of the polyester sheet by means of rolling and stretching the polyester sheet within the defined opening of the pass between the opposite roller pair; and an element for supplying a lubricant to a surface of the polyester sheet in a position upstream of the opening defined between the pair of opposed rollers to prevent any adhesion of the polyester sheet to the copy upstream of the pair of opposite rollers, when said work piece in the form of polyester sheet is heated to the temperature level higher than the glass transition temperature "(Tg) 7. The apparatus as defined in claim 1, wherein: the pair of opposed rollers each has a configuration comprising a concave central portion and cylindrical end portions to provide the sheet-shaped workpiece with edge portions thinner than the central portion when the sheet-shaped workpiece is driven to through the pass opening defined between the pair of opposite rollers so that a greater degree of plane state of the pi is achieved The sheet-shaped workpiece is simultaneously laminated and stretched by the width direction of said sheet-shaped workpiece simultaneously laminated and stretched after this sheet-like workpiece simultaneously laminated and stretched passed through the opening defined between the pair of opposite rollers. The apparatus as defined in claim 7, wherein the central portions of the pair of opposed rollers have an arcuate configuration. The apparatus as defined in claim 7, wherein the central portions of the pair of opposed rollers have a trapezoidal configuration. The apparatus as defined in claim 1, further comprising: die elements for extruding the sheet-shaped workpiece, elements each having a predetermined cross-sectional configuration such that the extruded workpiece it has portions of edges thinner than the central portions, in such a way that a greater degree of flatness of the work piece is achieved in the form of sheet simultaneously laminated and stretched by the width direction of said work piece after it is Workpiece in sheet form simultaneously laminated and stretched passed through the opening defined between the pair of opposite rollers. The apparatus as defined in claim 10, wherein the predetermined cross-sectional configuration of the die element is a trapezoid. 12. The apparatus as defined in claim 11, further comprising a plurality of emptying rollers disposed within a vertical arrangement to define spaces therebetween which have a trapezoidal configuration for accommodating workpieces in the form of trapezoidal configuration sheets by means of cited die elements. A method for producing a highly oriented polyester sheet comprising the steps of: supplying a pair of opposed rollers defining between them a through opening through which passes a work piece in the form of solid polyester sheet for rolling and stretching simultaneously when this sheet-shaped work piece passes through the opening in a single pass and in a predetermined transport direction; driving the pair of opposed rollers in opposite directions and at sufficiently different speeds in the linear direction to simultaneously laminate and stretch the workpiece within the opening defined between the pair of opposed rollers according to a predetermined first predetermined tension ratio between the pair of opposed rollers by the linear surface speeds different from the pair of opposite rollers; providing at least one additional rollers downstream of a specimen downstream of the pair of opposed rollers as contemplated by the predetermined conveying direction, to remove the workpiece in the form of a laminated sheet and drawn away from the pair of rollers opposites; and driving the above-mentioned additional roll copy, with at least one linear surface velocity sufficiently different from that linear surface speed of the copy downstream of the pair of opposed rolls to further stretch the workpiece in the form of a laminated sheet and stretched according to a certain second proportion of traction. The method as defined in claim 13, wherein the work piece in the form of a polyester sheet is made from polyethylene terephthalate. 15. The method as defined in claim 13, wherein: said additional roller has at least an amount of one, comprises a set of rollers defining a set of output flanges for the workpiece laminated and stretched with with respect to the pair of opposite rollers; and all the rollers of said assembly that define the set of output flanges are driven with a rotary speed to define with the specimen downstream of the pair of opposed rollers, the second tension ratio. 16. The method as defined in claim 13, wherein: the first traction alloy is within the range of 4-5: 1; and the second tensile ratio is within the range of 1.1-1.5: 1, whereby the proportion of general traction applied to the work piece in the form of a polyester sheet is approximately 6: 1 and the highly oriented polyester sheet exhibits tensile strength values of about 7000 kgs / cm2 and modulus values within the range of about 210,000 to 350,000 kgs / cm2. The method as defined in claim 13, further comprising the steps of: the work piece in the form of a polyester sheet consists of amorphous polyester before passing this work piece through the opening defined between the pair of opposite rollers, after which passage of the workpiece through the opening defined between the pair of opposite rollers undergoes a crystallization induced by orientation to thus consist of crystalline polyester; heating a specimen upstream of the pair of rollers, in order to preheat the leaf-shaped workpiece to a temperature level that is below the glass transition temperature (Tg) of the workpiece in the form of sheet to prevent the work piece in the form of an amorphous polyester sheet from sticking to the specimen upstream of the pair of rollers; and heating the downstream copy of the pair of rollers to a temperature level that is virtually above the glass transition temperature (Tg) of the sheet-shaped workpiece to facilitate further stretching of the workpiece. Work in the form of a crystalline polyester sheet. The method as defined in claim 17, further comprising the steps of: heating the sheet-shaped workpiece at a point immediately upstream of the opening defined between the pair of rollers opposite a temperature level that is greater than the glass transition temperature (Tg) of the polyester sheet in order to predetermine control of the orientation of the polyester sheet by rolling and stretching the polyester sheet within the opening defined between the pair of opposite rollers; and supplying a lubricant to a surface of the polyester sheet to be disposed in contact with the specimen upstream of the pair of opposed rollers and in a position upstream of the opening defined between the pair of opposed rollers to prevent any sticking of the polyester sheet to the specimen upstream of the pair of opposed rollers, when the work piece in the form of polyester sheet is heated to the mentioned temperature level which is higher than in the glass transition temperature (Tg). 19. The method as defined in claim 13, further comprising the step of: supplying the pair of opposed rollers with a configuration comprising a central concave portion and cylindrical end portions to provide the sheet-shaped workpiece with edge portions thinner than the central portion when the part The sheet-shaped workpiece is guided through the opening defined between the pair of opposite rollers, in such a way that a greater degree of flatness of the workpiece is achieved in the form of a leaf simultaneously laminated and stretched, in the direction width of the sheet-shaped workpiece simultaneously laminated and stretched after such a workpiece passed through the defined through opening between the pair of opposed rolls. The method as defined in claim 13, further comprising the step of: providing die elements for extruding the sheet-shaped workpiece wherein said die element has a predetermined cross-sectional configuration in such a way that the work piece in the form of an extruded sheet has portions of edges that are thinner than the central portions, in such a way that a greater degree of flatness of the work piece is achieved in the form of a leaf simultaneously laminated and stretched in the width direction of said workpiece, after this workpiece in sheet form simultaneously laminated and stretched passed through the opening defined between the pair of opposite rollers. The method as defined in claim 20, wherein the predetermined cross-sectional configuration of the die element comprises a trapezoid. The method as defined in claim 21, further comprising the step of: providing a plurality of emptying rolls disposed within a vertical array to define spaces therebetween that have a trapezoidal configuration for accommodating workpieces in the form of a trapezoidal configuration sheet, produced by the aforementioned die elements. SUMMARY OF THE INVENTION: A method and apparatus for producing a highly oriented polyester sheet consisting of a two-stage traction procedure. The first traction stage is executed within a set of "zero-gap" rolling and stretching rollers, which consists of a pair of opposed rollers defining an opening therebetween, and in which the rollers are rotated in opposite directions at different speeds of linear surface in such a way that between them a predetermined proportion of traction is defined. The amorphous polyester sheet is conducted through the pass opening of the opposed rollers, and as a result of the simultaneous rolling and stretching of the polyester sheet the amorphous polyester is transformed into crystalline polyester as a result of orientation-induced crystallization. The crystalline polyester sheet is heated to a level above the glass transition temperature (Tg) immediately downstream of the opening defined between the pair of opposed rolls, and a set of output flanges is disposed downstream of the pair of the opposite rollers. The rollers of the flange assembly rotate at linear surface velocities that are greater than the linear surface velocity of the specimen downstream of the pair of opposed rollers in such a way that a second tensile ratio is defined with respect to said exemplary downstream of the pair of opposite rollers. The heating of the crystalline polyester sheet facilitates its further stretching within the second traction stage of the apparatus, the general traction ratio being of the order of 6: 1. A highly oriented polyester having tensile strength values of the order of 7,000 kgs / cm2 as well as module values in the order of 210,000 to 350,000 kgs / cm2.