Patent Application
20250074675
The present invention relates to polyester straps, methods of their manufacture, systems and uses thereof, particularly as may be used in bundling applications of discrete articles into bundles.
Plastic straps (or “straps”, as well as “strapping”) formed primarily of synthetic polymers are widely used in known-art apparatus which provide tensile bundling of loads, particularly bundling of discrete article into bundles. Primarily such polymers are based on polyolefins or polyesters. Such discrete articles bundled with such plastic straps include, without limitation, generally planar, generally two-dimensional articles such as sheet like articles as well as folded articles such as cardboard boxes, as well as three-dimensional articles, including without limitation, packaged articles, boxes, cartons, and the like. Prior to bundling the articles are typically stacked or layered in register to provide an assembly which is then formed into a bundle utilizing one or more straps which are first drawn around the assembly to form a continuous loop, then the strap is tensioned and thereafter the loop is sealed or otherwise bonded or affixed to retain the tension within the strap of the continuous loop. One common technique includes bonding overlapping parts of the strap to form a loop, such as by heating. Bundles may include one or more such tensioned loops in order to retain the bundled articles within the assembly. However many such apparatus and straps used in bundling do exhibit various technical problems and shortcomings. Some of these have been addressed previously, and the prior art includes documents which address strapping devices and straps themselves which provide certain benefits. The following are a non-limiting list of such documents: U.S. Pat. Nos. 8,859,682, 9,315,700; 10,669,085; US Published Application 2011/0319565A1, US Published Application 2019/0255761A1, US Published Application 2019/0270231A1, WO 2015/042631A1, WO 2015/042632A2, and EP3052690A1.
JP 2005-001679 discloses a thermoplastic synthetic band useful in a packaging machine, the thermoplastic necessarily used is limited to a polyolefin and in particular polypropylene which is not a crystalline or semi-crystalline polymer which may be oriented on a microscopic scale.
U.S. patent Ser. No. 10/669,085 discloses a tape-like packaging element which may be formed of a polyester. The tape-like packaging element is limited to having cavities having no angles or apicies, and are preferably elliptical or circular as is depicted in its drawing figures. Friction welding is taught as the means for bonding faces of the tape-like packaging element. With attention to
Although straps and strapping devices of the prior art may provide certain benefits, there remains a real and continuing need in the art to provide further solutions and advantages in this technical field, particularly wherein narrower width straps are contemplated.
One shortcoming in the relevant art relates to overcoming technical challenges relating to the use of polyester strapping. Such polyester strapping is primarily offered in widths ranging from about 9 mm and higher, and while narrower polyester strapping is known, such do not typically have widths less than 6 mm. This is due to both manufacturing challenges as well as the ability to produce a satisfactory weld joint relative to the material's tensile strength. Using both heat seal and friction welding machines on polyester strapping, particularly low width (i.e., not exceeding about 9 mm) crystallizes the molecular chains creating an unstable brittle weld joint. The heat produced also emits toxic vapors when welding polyester. In low load applications requiring strapping having widths in the 5 mm-6 mm range, polypropylene (“PP”) is therefore the primary polymer used. However, there are superior benefits specific to polyester in these applications such as polymer sustainability, low fibrillation, better molecular relaxation, and lower creep under constant load. Thus, and with particular attention to polyester strapping having widths not in excess of 5 mm, and preferably less than 5 mm, there is specific need in the art to provide further solutions and advantages with such narrower strapping.
In a first aspect the present invention relates to a plastic strap (or, “strapping tape”), having a plurality of voids or cavities extending therein from one or both major faces of the plastic strap, which plastic strap is narrow, and which is particularly useful in producing tensioned, continuous, welded loop about the bundled articles. Preferably the weld is formed by ultrasonic welding, and in desired embodiments is necessarily formed by ultrasonic welding. In a preferred embodiment of this first aspect the plastic strap is formed of an at least partially crystalline thermoplastic material which is ultrasonically welded, the plastic strap having a length, a width and a thickness, two substantially parallel major faces having a width and a length separated by the thickness, at least one of the major faces having a plurality of voids extending into the thickness from the major face, each of the voids having straight boundary lines at their periphery wherein they intersect a major face of the plastic strap, each of the voids present in the interior of the plastic strap and having a depth, a void surface area and a void volume measurable from the major face of the plastic strap, wherein per unit length of the plastic strap the cumulative void surface area is from 20% to 90%, preferably from 30% to 50%, and the cumulative void volume is from 5% to 65%, preferably from 10% to 60%, especially preferably from 25% to 30%, in the region of the plastic strap which is subsequently ultrasonically welded and at least partially melted forming a bond therebetween.
In a second aspect the present invention relates to provide processes for tensile bundling of loads which utilize the aforementioned plastic strap.
In a third aspect the present invention relates to improvements in apparatus, apparatus operation and/or bundled articles relating to the use of the aforementioned plastic strap.
These and further aspects will become apparent from a consideration of the following specification and drawings relating to the present invention.
The plastic straps (which may also be referred to as ‘strapping tape’) of the present invention may comprise all extendable/stretchable partially crystalline plastic materials or mixtures/blends of these plastic materials as thermoplastic material. A thermoplastic material within the meaning of the present description is a meltable/weldable, polymeric organic solid, which may be produced synthetically or semi-synthetically from monomeric organic molecules and/or biopolymers. A partially crystalline thermoplastic material may for example be selected from the group of polyolefins, polyesters or polyamides, or mixtures of these polymers. Moreover, fillers or additives may be admixed to the provided plastic material. Advantageously the thermoplastic material is a polyester, especially preferably one or more polyalkylene terepthalates. Preferably the plastic strap is formed of a polyalkylene terephalate polymer, i.e, polybutylene terephalate but preferably polyethylene terephthalate, or copolymers comprising at least 50%, preferably at least 75% of one or more polyalkylene terephthalate monomers. A particular preferred embodiment of the plastic strap is when the plastic strap is substantially or exclusively a polybutylene terephthalate (“PBT”), but especially preferably a polyethylene terephthalate polymer (“PET”), or copolymer thereof. Advantageously, where a copolymer is utilized, it comprises at least 50% polyalkylene terephthalate, preferably at least 75% polyalkylene terephthalate with the remaining balance up being one or more copolymers, or additives which are not necessarily copolymerizable but which may provide further technical benefits to the result in plastic straps.
The plastic straps of the present invention may also include or more conventional additives, such as colorants, fillers (organic or inorganic), splicing inhibitors based on styrene based polymers and copolymers thereof (such as, or consisting of: polystyrene, styrene-butadiene copolymer, acrylonitrile-butadine-styrene copolymer, methylmethacrylate-acrylonitrile-butadiene-styrene copolymer, styrene-acrylonitrile copolymer, acrylonitrile-styrene-acrylate copolymer, styrene-maleic acid-anhydride copolymer, acrylonitrile-ethylene-styrene copolymer, acrylonitrile-chlorinated polyethylene styrene copolymer, methylmethacrylate-butadiene-styrene copolymer, styrene-alpha methyl styrene copolymer), splicing inhibitors selected from, or consisting of: olefin-acrylate copolymers, thermoplastic polymers, low density polyethylene, linear low density polyethylene, polyethylene, polypropylene, butadiene rubber, and mixtures thereof. Such conventional additives if present, cumulatively do not exceed more than about 15% wt., more preferably (and in order of increasing preference) not more than 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1.5%, 1%, 0.5%, and 0.25% wt. of the total mass (weight) of the ultimate plastic strap.
Preferably the plastic straps of the invention contain not more than 5% wt., polyolefins, more preferably not more than 2% wt. polyolefins, especially not more than 0.75% wt. polyolefins. In certain particularly preferred embodiments, the plastic straps (strapping tapes) of the invention do not contain any polyolefins, even those as may be present as splicing inhibitors.
The plastic straps of the invention include a plurality of voids (which may be also referred to as recesses or cavities) on one or both major faces thereof, and extending inwardly into the body of the plastic strap from the flat faces transverse to the longitudinal length of the plastic straps. Preferably the plurality of voids is patterned. The voids are based on non-circular or non-elliptical cavities, viz., cavities having straight boundary lines at their periphery wherein they intersect a major face of the plastic strap. Such plastic straps have as their longest dimension a length—and perpendicular to their length with two parallel major faces separated by a thickness of the plastic strap, the thickness being the smallest relative dimension, and the length being the longest dimension. The dimensions of the thickness of the plastic straps, prior to a treatment which provides the voids is advantageously between about 0.15 millimeters (“mm”) and about 0.35 millimeters, preferably are between about 0.20 mm and 0.30 mm, and especially preferably are between about and 0.20 and 0.28 mm. Concurrently, the width of the straps, that is to say the dimension of the flat faces transverse to the longitudinal length is advantageously between 1 and 5.5 mm, preferably between about 3.0 and 5.5 mm, and more preferably between about 4.40 and 5.10 mm. In certain embodiments the preferred width does not exceed about 5 mm. Preferably the respective ratio of width/thickness is in the range of about 10 to about 16. In certain preferred embodiments, the width of the plastic straps is not in excess of about 5.10 mm, and preferably is in the range (inclusive) of 4.6-5.0 mm, or 4.5-4.9 mm. With regard now to the length, this is at least 10 times that of the width, more preferably at least 100 times that of the width, and still more preferably at least 1000 times that of the width. With regard to the length, will be appreciated that this is the major dimension, and in practical application plastic strap is wound upon a supply spool, in a ribbon-like configuration and thus it is understandable that when provided to an apparatus in such a wound spool, its length is substantially longer than either the thickness or the width, with its length decreasing as the contents of the wound spool are utilized in a bundling operation.
The plastic strap exhibits very good mechanical properties, in particular a high tensile strength. This is particularly surprising as in the preferred embodiments wherein the plastic straps are not more than 5.10 mm in width, and have a thickness not exceeding 0.45 mm, the tensile strength of the plastic strap is technically satisfactory for providing and retaining bundled articles, even after the utilization of ultrasonic welding in order to form a continuous, welded loop about the bundled articles. This region of the weld at overlapped major faces of a plastic strap together, form a bond therebetween by at least partially melting the plastic strap, viz. at the two ends of the plastic strap to thereby form a loop. In preferred embodiments, the width of the strap is not in excess of 5.0 mm, and in order of increasing preference, not in excess of: 4.9 mm, 4.8 mm, 4.7 mm, 4.6 mm, 4.5 mm, 4.4 mm, 4.3 mm, 4.25 mm, 4.2 mm, 4.1 mm, 4.0 mm, 3.9 mm, 3.8 mm, 3.75 mm, 3.7 mm, 3.6 mm, 3.5 mm, 3.5 mm, 3.4 mm, 3.3 mm, 3.25 mm, 3.2 mm, 3.1 mm, 3 mm, 2.9 mm, 2.8 mm, 2.75 mm, 2.7 mm, 2.6 mm, 2.5 mm, 2.4 mm, 2.3 mm, 2.25 mm, 2.2 mm, 2.1 mm and 2 mm. The preferred minimum width of the strap may also be found, in order of increasing preference in the reverse order of recitation of dimensions of the immediately preceding sentence. The use of ultrasonic welding, which is distinguishable from thermal welding, and uses high-frequency energy in order to provide the welded joint between overlapped major faces. This result is surprising due to the reduced dimensions as compared to the prior art, and also wherein when the plastic strap is formed substantially of or of a polyalkylene terephthalate, in particular a stretched, semi-crystalline polyalkylene terephthalate such as polyethylene terephthalate, the reduced physical dimensions, still provide good strength and interfacial welding, and particularly in the immediate regions outside of the ultrasonic welding region the semicrystalline structure of the polyalkylene terephthalate plastic tape is not unduly weakened or compromised resulting from the ultrasonic welding operation.
Wherein the plastic strap is formed substantially from a polyethylene terephthalate, the preferred molecular weight of the polyethylene terephthalate polymer (or which may be substantially polyethylene terephthalate, with up to 10% copolymers or non-copolymerizable additives) is in the range of about 0.72 to about 0.86 intrinsic viscosity. Wherein the plastic strap is formed substantially from a polyethylene terephthalate, following extrusion it has been stretched along its length to an extent of at least about 350%, preferably at least about 400%, more preferably at least about 450%, and preferably at least about 490% as compared to its pre-stretched length. As is known in the art, such stretching provides a degree of orientation of the polymer chains and improves the tensile strength in the direction of stretching,
At least one major face of the plastic strap is provided with a plurality of voids extending into the interior of the plastic strap, preferably via embossing, in particular with a continuous embossing, by means of an embossing device comprising at least one embossing roller. In certain embodiments only one major face of the plastic strap is provided with said plurality of voids. The at least one embossing roller comprises on its roller surface projections for generating voids on/into the at least one major face of the strap. The at least one embossing roller comprises projections which extend outwardly and radially from the surface of the embossing roller (also referred to as the “nominal surface”) with uppermost points of the individual projections as measured from the axis of the embossing roller is equidistant therefrom, or may vary by up to about 25% from the average dimension of the individual projections from the axis. The individual projections have an uppermost point, which may be a peak, or may be a flat, concave, or convex geometrical surface, which uppermost point extends most outwardly from the axis of the embossing roller. Extending inwardly from the uppermost point, each of the projections extend inwardly towards the axis, and advantageously terminate at a base which is coincident with a radius of the embossing roller. The geometry of the base of the individual projections may have any of the following geometries: square, trapezoidal, rectangular, staggered rectangular, herringboned rectangular, hexagonal, triangular, ovular, and diamond. At the region of the major face wherein the individual projections intersect, the voids exhibit substantially straight boundary lines. In preferred embodiments, non-circular or non-elliptical cavities, are excluded. Of these geometries is most desirable that the longest individual direction or length of the individual projects are oriented to be coincident with the longitudinal length of the plastic strap. Of these geometries is most desirable that the geometry of at least the base of the individual projections include one or more angles, or at least one apex in the voids, which distinguishes them from circular and elliptical geometries which would have no such angles or apices. A nominal base radius of the embossing roller thus may be used to define a face which limits the penetration of the individual projections into the body of the plastic strips when pressed against at least one, or both of the major faces of the plastic strap in order to deform the same, and to provide a patterned surface to one or both of the major faces. The patterned surface with its plurality of individual projections of the embossing roller imprints a reverse ‘image’ of these individual projections when urged against at least one major face, and deforms the major face (viz., surface) when the individual projections extend into the interior of the plastic strap. Thus, after treatment with the embossing roller, or embossing rollers, at least one of the normally planar major face of the plastic strap is provided with a surface texture, with voids being formed as a result of the impingement of the individual projections, the voids being into the interior of the plastic strap and having a depth, a base area and a void volume measurable from the major face of the plastic strap.
In particularly preferred embodiments, as compared in a unit length of the plastic strap prior to the provision of the plurality of voids extending into the interior of the plastic strap, the cumulative void surface area is from 20% to 90% preferably 22% to 70% at the surface area of a major face. In certain preferred embodiments the cumulative void surface areas is at least 22% at the surface area of a major face, and in order of increasing preference is at least 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 30%, 39%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 40%, 49%, 50%, 51%, 50%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, and 65%. Conversely, certain preferred embodiments the cumulative void surface areas not in excess of 65% at the surface area of a major face, and in order of increasing preference is not more than 64%, 63%, 60%, 61%, 60%, 50%, 50%, 57%, 56%, 55%, 54%, 53%, 52%, 51%, 50%, 49%, 48%, 47%, 46%, 45%, 44%, 43%, 42%, 41%, 40%, 39%, 38%, 37%, 36%, 35%, 34%, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, and 24%. Preferred embodiments may have a range within any of the aforesaid percentages. In some particularly preferred embodiments, the cumulative void surface area percentage of is in the range of from 30% to 50%, more preferably 32% to 45%, yet more preferably 34% to 42%.
Certain particularly preferred embodiments are disclosed with reference to one or more of the examples described herein. Such is measured as compared to the non-embossed plastic strap, per a unit length thereof.
In particularly preferred embodiments, as compared in a unit length of the plastic strap prior to the provision of the plurality of voids extending into the interior of the plastic strap, the cumulative void volume of the individual voids present at one or both of the major faces is from 5% to 65%. In certain preferred embodiments, the cumulative void volume of the individual voids is at least 5%, 7%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 30%, 39%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 40%, 49%, 50%, 51%, 50%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, and 65%. Conversely, in certain preferred embodiments, the cumulative void volume of the individual voids present at one or both of the major faces is not in excess of: 64%, 63%, 60%, 61%, 60%, 50%, 50%, 57%, 56%, 55%, 54%, 53%, 52%, 51%, 50%, 49%, 48%, 47%, 46%, 45%, 44%, 43%, 42%, 41%, 40%, 39%, 38%, 37%, 36%, 35%, 34%, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6% and 5%. Preferred embodiments may have a range within any of the aforesaid percentages. Especially preferably, the cumulative void volume of the individual voids present at one of the major faces (i.e, where the opposite major faces is not embossed), or at both major faces is preferably from 10% to 60%, more preferably 20-50%, and especially preferably of 25-30% of the total volume of the same unit length of the plastic strap. Again the cumulative void volume may be controlled by the depth of embossment.
The aforesaid voidages and cumulative void volume are especially desirably present in the regions where two parts of a plastic strap overlap and are ultrasonically welded, particularly in the region of the ultrasonic welded overlapped major faces of the plastic strap which are at least partially melted and form a bond therebetween.
In certain particularly preferred embodiments, only one of the major faces of the of the plastic strap is provided with the plurality of voids extending into the interior of the plastic strap, while the opposite and substantially parallel major face of the plastic strap includes non-patterned plurality of voids, viz., a randomized arrangement of voids, or alternately has no voids. In a further preferred embodiment, both of the opposite and substantially major faces of the plastic strap are provided with the plurality of voids extending into the interior of the plastic strap. In certain embodiments the pattern of the plurality of voids extending into the interior of the plastic strap, is the same on both major faces. In certain embodiments, a first pattern of the plurality of voids extending into the interior of the plastic strap from one of its major faces is different than a second pattern of the plurality of voids extending into the interior of the plastic strap from the other of its major faces.
The applicant notes that while the foregoing discussion is in relation to a generally cylindrical, and embossing roller, the same principles concerning the use of the embossing roller may be transposing utilized with a non-cylindrical roller. That is to say, the provision of patterned voids on one or both of the major faces of the plastic straps may be also provided by the use of any other apparatus, such as for example one or more plates, being flat or arcuate, or ultimately the provision of reciprocating die having formed surface projections which may be urged against one or both of the major faces of the plastic straps.
The plastic straps of the invention having the plurality of voids extending into the interior of the plastic strap as described herein may provide further technical advantages. While not wishing to be bound by the following hypothesis, the plurality of voids may provide an improved clamping surface which useful during the formation of strapping, as a transmission of force from a clamping or closing apparatus to the plastic strap that is as uniform as possible may take place. This is particularly the case wherein the plurality of voids formed is patterned in a uniform arrangement or array and also particularly advantageously wherein the void volume of the individual voids is substantially equal to each other, or varies by not more than approximately 25%, more preferably not more than 10%, and predict preferably not more than 5%. Moreover, in the course of an ultrasonic welding process, a reduced timespan required for the formation of a strapping loop formed of the plastic straps taught herein may be feasible which also may improve the tensile strength at the point of the ultrasonic weld formed as lower exposure to the ultrasonic head may reduce temperature buildup at the point of the weld and reduce disruption of the orientation of the polymer, particularly when a polyalkylene terephthalate is used, especially wherein the plastic is polyethylene terephthalate. Also, while not wishing to be bound by the following further hypothesis, the provision of a first major face of the strap having a plurality of voids layered in register and in contact with a second major face of the strap prior to, and during the ultrasonic welding step is suspected to allow for creeping of melted polymer fluidized during the brief ultrasonic welding step to engage with interior voids and when quickly cooled provides for physical engagement and with the increased surface area provided by the voids present per unit length of the plastic strap as compared to a like plastic strap (as per the prior art, without interior voids but only flat surfaces) provides more adhesion due to the increased surface area, as well as entry of a part of the polymer initially present on the second major face to creep or interlock within the voids of the first major face, forming a three-dimensional engagement region between the now ultrasonically welded parts of the plastic strap. Such is believed to contribute favorably to the ultimate tensile strength of the welded loop of the plastic strap, particularly in the weld region and permits for a reduced width. Such an effect is believed to arise particularly wherein prior to ultrasonic welding, both the first major face and the second major face comprise a plurality of voids, which are ultrasonically welded. In such an embodiment, creeping of melted polymer fluidized from the first major face, and simultaneous creeping of melted polymer fluidized from the second major face during the ultrasonic welding process may form physical entanglements upon cooling which may improve the weld strength of the loop formed of the plastic strap particularly within the weld region.
The accompanying figures forming an integral part of this application illustrate various features of the invention, and include the depiction of certain currently preferred embodiments. It is to be understood that the figures are provided for informational purposes, and the depicted embodiments are not to be construed as necessarily limiting as to the scope of the invention. Furthermore, like numerals, letters and other labels are used amongst the various drawing figures to illustrate elements relative to the invention and the various drawing figures.
As is seen in
Between adjacent projections 35 are present formed hollows 40 which extend between the peak radius 38 and the nominal radius surface 34. The hollows are bounded by sides 37A which converge to a base 37B, and opposite thereto by a span 37C which is the open space between adjacent peaks 37. When the embossing roller 30 is urged against one or both major faces of a plastic strap, the projections 35 extend beyond the major face(es), and into the interior 17 and thereby deforms the plastic strap 10 to imprint one or more of the major faces (c.f.
It is to be understood that the degree of penetration by the projections 35 and their respective peaks 37 beyond the peak radius 38 and passing through the major face of the plastic strap 10 can be varied, and different degrees of penetration can be achieved. Reference is made to
From the configuration of this ‘small’ pattern and a corresponding degree of penetration, various dimensions of a plastic strap 10 according to this embodiment of the present invention may be determined. The following is based on a sample segment of plastic strap 10 which prior to embossing had a length of 25 mm, a width of 4.8 mm, a thickness of 0.35 mm, a mass of 0.0428 g, and a volume of 42 mm3. The surface area of each of the two major faces 12, 14 was 120 mm2. Based on this sample segment were calculated at the differing degrees of embossment the cumulative area of the voids 20 at each of the embossed major face(s) and the cumulative volume of the voids 20 for the sample segment.
For the ‘maximum’ embossment (0.17 mm penetration per side, 33.4%) the cumulative void surface area (c.f.,
The above determinations were used to calculate the following for a 1 meter length of a plastic strap 10 conforming to the preferred embossment (0.11 mm penetration per side, 20%). The total area of the plastic strap 10 pre-embossing was 3400 mm2, following embossing, the total area of the voids at the major surface is 1802 mm2 providing a cumulative void surface area percentage of 38% per side of the plastic strap 10.
Using this ‘large’ diamond pattern preferably the minimum embossment is 1.9% at 0.01 mm penetration per side, the maximum embossment is 39% at 0.17 mm penetration per side, with a preferred embossment is 20% at 0.10 mm penetration per side. However, as before, the preferred range for embossment is in the range of 25-30% which may be achieved by suitably controlling the actual extent of penetration of the projections 35 into the interior of the plastic strap 10.
From the configuration of this ‘large’ diamond pattern and a corresponding degree of penetration, various dimensions of a plastic strap 10 according to this embodiment of the present invention may be determined.
For the ‘maximum’ embossment (0.17 mm penetration per side, 39%) the cumulative void surface area (c.f.,
The above determinations were used to calculate the following for a 1 meter length of a plastic strap 10 conforming to the preferred embossment (0.11 mm penetration per side, 20%) of
As to the ultimate shapes of preferred embodiments of plastic straps 10 relevant to the present invention, these are discussed in more detail in
The plan view of
In this preferred embodiment, at least one of the sidewalls 20A is angled with respect to the one or more of the longitudinal apex orientation lines G1, G2 and G3 and is angled, i.e, by angle “a” with respect thereto. This angle is preferably in the range of about 25 to about 35 degrees, more preferably in the range of about 28 to 30 degrees. A particularly preferred angle is discussed and disclosed with reference to
With reference now to
Exemplary, albeit nonlimiting, dimensions of a preferred pattern of projections 35 are disclosed with reference to
A plastic strap was formed substantially from a polyethylene terephthalate, having a composition of 99.9% wt. PET, exhibiting an intrinsic viscosity of 0.78. The plastic strap was formed by extrusion, having a width in the range of between 4.5 to 5.1 mm, having a thickness in the range of between 0.30 mm to 0.45 mm by passing a melt of the PET through an extruder die, shaped with a rectangular orifice having dimensions 25 mm×1.56 mm and is simultaneously drawn and quenched by a factor of 2 to 2.2—which essentially reduced the cross-sectional dimension of the strap from the orifice's dimensions to about 11.5 mm×0.8 mm. The plastic strap was reheated and stretched again by a factor of 2.5 to 3.2 along its length. The resultant strap had a mass of 1.55 to 1.75 grams per meter of length, a tensile strength of >40 kgF, and a degree (extent) of embossment of from 15% to 30%. Thereafter the strap was embossed with the to provide a pattern of voids as depicted in
Two of the foregoing embossed straps were layered in register, and at an overlap region were welded using an ultrasonic welding apparatus, SONIXS (ex. EAM-Mosca Corp.) at the following protocol: Weld time between 80-120 ms (preferably 100 ms), Cool time between 100-500 ms (preferably 100 ms) and strap tension between 260N and 350 N (Preferably 310N). The resultant ultrasonically welded and now joined straps were evaluated for weld strength and weld efficiency. It was determined that the weld strength was approximately 33 kgF, and the weld efficiency (weld strength/tensile strength) was approximately 71%.
A plastic strap formed substantially from a polypropylene polymer having a composition of 99% wt. polypropylene (“PP”), and a Melt Flow Index of 1.2. The plastic strap was formed by extrusion, having a width in the range of between 4.40 mm-5.10 mm, having a thickness in the range of between 0.40 mm to 0.55 mm by passing a melt of the PP through an extruder die, and quenching the extruded plastic strap. The resultant strap had a mass of 1.45 to 1.60 grams per meter of length, a tensile strength of 54 kgF, and a degree (extent) of embossment of from 15% to 35%. The resultant pattern was as depicted in
Two of the foregoing polypropylene straps were layered in register, and at an overlap region were welded using an ultrasonic welding apparatus, SONIXS (ex. EAM-Mosca Corp.) at the following protocol: Weld time between 80-120 ms, cool time between 100-500 ms, and strap tension between 325N and 580 N. The resultant ultrasonically welded and now joined straps were evaluated for weld strength and weld efficiency. It was determined that the world strength was approximately 35 kgF, and the weld efficiency (weld strength/tensile strength) was approximately 65%.
A plastic strap formed substantially from a polypropylene polymer having a composition of 99% wt. polypropylene (“PP”), and a Melt Flow Index of 1.2. The plastic strap was formed by extrusion, having a width having a nominal width of 5 mm, a nominal thickness of 0.5 mm (actual dimensions are given in the following Table C2) by passing a melt of the PP through an extruder die, and quenching the extruded plastic strap. The resultant strap had a mass of 1.45 to 1.60 grams per meter of length, a tensile strength of 54 kgF, and a degree (extent) of embossment of from 15% to 35%. The resultant pattern was as depicted in
Sample lengths of two of the foregoing polypropylene straps were layered in register, and at an overlap region were welded using an ultrasonic welding apparatus, SONIXS (ex. EAM-Mosca Corp.) at the following protocol: Weld time between 80-120 ms, cool time between 100-500 ms, and strap tension between 325N and 580 N. The resultant ultrasonically welded and now joined straps were evaluated for weld strength and weld efficiency; the results are reported on the following Table C2. It was determined that the weld strength was approximately 35 kgF, and the weld efficiency (weld strength/tensile strength) was approximately 65%.
As can be appreciated from the reported results of the foregoing table, each of the four samples of embossed PP strapping, two of which had an emboss/void percentage of 18.66%, and two of which had an emboss/void percentage of 29.17% were tested for weld strength. Notably the former two samples exhibited a 66.65% weld strength, the latter two sample exhibited a 62.99% weld strength which were considered to be very similar. Notably the differences in the emboss/void percentage appeared to have little effect on the weld efficiencies of the PP strap.
A plastic strap was formed substantially from a polyethylene terephthalate, having a composition of 99.9% wt. PET, exhibiting an intrinsic viscosity of 0.78. The plastic strap was formed by extrusion, having a nominal width of 9 mm, having a thickness in the range of between 0.50 mm to 0.65 mm by passing a melt of the PET through an extruder die, shaped with a rectangular orifice having dimensions 64 mm by 4 mm and is simultaneously drawn and quenched by a factor of about 4.25—which essentially reduced the cross-sectional dimension of the strap from the orifice's dimensions to about 8.7 mm×0.62 mm. The plastic strap was reheated and stretched again by a factor of 1.1 to 1.2 along its length. The resultant strap had a mass of 6.15 to 6.35 grams per meter of length, a tensile strength of >90 kgF. Samples of the resultant strap were subjected to two different degrees of embossment, approx. 15% and approximately 25% (actual extent of embossment is reported on the following table) utilizing an embossing roller 30 as depicted in the drawing figures. The patterned embossment was as in
For purposes of testing ultrasonic weld strength, two of the foregoing embossed straps were layered in register, and at an overlap region were welded using an ultrasonic welding apparatus, SONIXS (ex. EAM-Mosca Corp.) at the following protocol: Weld time between 80-120 ms (preferably 100 ms), Cool time between 100-500 ms (preferably 100 ms) and strap tension between 260N and 350 N (preferably 310N). The resultant ultrasonically welded and now joined straps were evaluated for weld strength and weld efficiency.
The results from three samples of each of the two embossed straps are reported in the following Table E2.
Notably the PET strap exhibited very satisfactory weld efficiencies, particularly with higher percentages of embossment/void %. It was surprisingly observed that for the same nominal width and thickness of the PET strap, there was a 41.7% increase in weld efficiency notwithstanding the 64.4% increase in the embossment/void %.
This result was considered to be surprising in view of the fact that the ‘deeper’ embossments did not detract from the weld strengths as might have otherwise been expected, as the deeper embossments would have reduced the cross-sectional thickness of the strap in the region of the embossments. While not wishing to be bound by the following, it is believed that the semi-crystalline nature of the polymer used in forming the strap played a role in the weld efficiencies realized.
A plastic strap formed substantially from a polypropylene polymer having a composition of 99% wt. polypropylene (“PP”), and a Melt Flow Index of 1.2. The plastic strap was formed by extrusion, having a width having a nominal width of 9 mm, a nominal thickness of 0.5 mm (actual dimensions are given in the following Table C3) by passing a melt of the PP through an extruder die, and quenching the extruded plastic strap. The resultant strap had a mass of 2.85 grams to 2.95 grams per meter of length, a tensile strength of >70 kgF, and a degree (extent) of embossment of from 25% to 45%.
Sample lengths of two of the foregoing polypropylene straps were layered in register, and at an overlap region were welded using an ultrasonic welding apparatus, SONIXS (ex. EAM-Mosca Corp.) at the following protocol: Weld time between 80-120 ms, cool time between 100-500 ms, and strap tension between 325N and 580 N. The resultant ultrasonically welded and now joined straps were evaluated for weld strength and weld efficiency; the results are reported on the following Table C3.
It is again observed that the nominal 9 mm PP straps, that the differences in the emboss/void percentage appeared to have little effect on the weld efficiencies of the PP strap.
A plastic strap was formed substantially from a polyethylene terephthalate, having a composition of 99.9% wt. PET, exhibiting an intrinsic viscosity of 0.78. The plastic strap was formed by extrusion, having a width in the range of between 4.5 to 5.1 mm, having a thickness in the range of between 0.30 mm to 0.45 mm by passing a melt of the PET through an extruder die, shaped with a rectangular orifice having dimensions 25 mm×1.56 mm and is simultaneously drawn and quenched by a factor of 2 to 2.2—which essentially reduced the cross-sectional dimension of the strap from the orifice's dimensions to about 11.5 mm×0.8 mm. The plastic strap was reheated and stretched again by a factor of 2.5 to 3.2 along its length. The resultant strap had a mass of 1.55 to 1.75 grams per meter of length, a tensile strength of >40 kgF, and a degree (extent) of embossment of from 15% to 30%. Thereafter the strap was embossed with a patterned roller to provide a pattern of voids as depicted on
Samples of the of the foregoing embossed straps were layered in register, and at an overlap region were welded using an ultrasonic welding apparatus, SONIXS (ex. EAM-Mosca Corp.) at the following protocol: Weld time between 80-120 ms (preferably 100 ms), Cool time between 100-500 ms (preferably 100 ms) and strap tension between 260N and 350 N (Preferably 310N). The resultant ultrasonically welded and now joined straps were evaluated for weld strength and weld efficiency. The results of this test are indicated in the following table:
As is visible from the above results, the greater void % of 37.08% of the latter three samples did not detract from the weld efficiency, but was rather improved as compared to the former three samples having a void % of 15.14%. All of the straps exhibited satisfactory tensile strength.
Consistent with the above testing protocols, in particular the use of an ultrasonic welder for providing the weld joining together of the respective straps (which of course, may be representative of the two ends of a continuous loop of a particular strap, used in bundling an array or plurality of discrete articles and keeping them bundled, due to the tension within the continuous loop formed as consequence of the ultrasonic welding step of these two ends) is believed due to the enhancement in the narrowed strap of E1, viz., the embossed PET strap having a preferred embossment pattern on at least one of the major faces of the PET strap, the mechanical properties of the embossed PET strap the PET being partially crystalline in nature, and the combination of the ultrasonic welding step used, now make possible the use of narrower PET straps than those previously thought in bundling applications of discrete articles. This is in part also made possible by the use of ultrasonic welding in forming a continuous loop of the embossed PET strap, and the nature of energy transfer of ultrasonic welding, which induces frequency/oscillation in the region of the weld joint formed from overlapping straps, which contrasts with thermal and/or frictional welding which, on the relatively small mass of PET strap within the weld joint would induce molecular crystallization in the regions immediately adjacent to the weld joint, possibly within the region of the weld joint itself. Such would induce strap embrittlement along the weld, and cause the thermal and/or frictional welded joint to fail, particularly under the tensile condition to which the continuous loop of PET strap would be subjected in a conventional bundling operation. Surprisingly the present inventors have overcome such a shortcoming, and provide an unexpected but technically satisfactory solution wherein a narrow, embossed PET strap may be used. Such is unexpected from the prior art, which suggests only wider PET straps in such applications, and in particular wherein the continuous loop of PET strap formed from such wider PET straps were also welded utilizing a thermal and/or frictional welding step.
Again, the examples and embodiments disclosed herein and in the drawing figures (and photographs) are by way of illustration and not by way of limitation. Further embodiments of plastic strap, and processes for their production and use are also feasible in full within the present inventive scope.
This application claims priority to U.S. Provisional patent application Ser. No. 63/580,077, filed 1 Sep. 2023, and by this reference thereto incorporates its entire disclosure herein.
| Number | Date | Country | |
|---|---|---|---|
| 63580077 | Sep 2023 | US |
