Source: http://www.google.com/patents/US8043696?dq=7222078
Timestamp: 2017-07-25 20:54:59
Document Index: 592537680

Matched Legal Cases: ['Application No. 60', 'Application No. 20040122196', 'Application No. 20040122196', 'Application No. 20040122196', 'Application No. 20040122196', 'Application No. 20040122196']

Patent US8043696 - Microlayer structures and methods - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsImproved microlayer structures and methods typically employing at least 4 stacked layers of polymers (e.g., including alternating layers of components A and B), such as that obtained by coextrusion. The layers each have a thickness of less than about 50 microns. One optional approach involves forming...http://www.google.com/patents/US8043696?utm_source=gb-gplus-sharePatent US8043696 - Microlayer structures and methodsAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS8043696 B2Publication typeGrantApplication numberUS 11/577,385PCT numberPCT/US2005/038103Publication dateOct 25, 2011Filing dateOct 20, 2005Priority dateOct 22, 2004Fee statusLapsedAlso published asDE602005015352D1, DE602005026220D1, EP1805001A1, EP1805007A1, EP1812634A1, EP1812634B1, EP1814704A2, EP1814704B1, EP1814716A1, EP1814716B1, US7887660, US8685514, US9227346, US20080254281, US20080257482, US20080261471, US20080265457, US20080265464, US20110114215, US20120077005, WO2006047366A1, WO2006047374A1, WO2006047375A1, WO2006047376A1, WO2006047376A9, WO2006091245A2, WO2006091245A3Publication number11577385, 577385, PCT/2005/38103, PCT/US/2005/038103, PCT/US/2005/38103, PCT/US/5/038103, PCT/US/5/38103, PCT/US2005/038103, PCT/US2005/38103, PCT/US2005038103, PCT/US200538103, PCT/US5/038103, PCT/US5/38103, PCT/US5038103, PCT/US538103, US 8043696 B2, US 8043696B2, US-B2-8043696, US8043696 B2, US8043696B2InventorsHongyu Chen, Ronald Wevers, David G. McLeodOriginal AssigneeDow Global Technologies LlcExport CitationBiBTeX, EndNote, RefManPatent Citations (131), Non-Patent Citations (49), Referenced by (9), Classifications (43), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetMicrolayer structures and methods
US 8043696 B2Abstract
Improved microlayer structures and methods typically employing at least 4 stacked layers of polymers (e.g., including alternating layers of components A and B), such as that obtained by coextrusion. The layers each have a thickness of less than about 50 microns. One optional approach involves forming an intermediate form that includes at least one elongated member made from the plurality of layers, from which a shaped composite article may be made.
4. The elongated member of claim 1, wherein the polymers of the at least two adjoining layers each have a peak melting temperature that differ by at least 5° C.
5. The elongated member of claim 1, wherein the polymer of at least one of the layers has a melting point below 125° C., and an adjoining layer has a peak melting point above 160° C.
6. The elongated member of claim 5, wherein the A component includes a propylene-ethylene copolymer that exhibits a melt flow rate at 230° C. per ASTM D1238 of 0.3 to 50 g/10 min; a density per ASTM D792 of 0.858 to 0.888 g/cc; an ethylene content of 5 to 25 wt %; a Melting Range from 50 to 135° C.; a Shore A Hardness from about 40 to about 90; and a flexural modulus per ISO 178 of 10 to 280 MPa and the B component includes a polypropylene homopolymer that exhibits a melt flow rate at 230° C. per ASTM D1238 of less than 7 g/10 min; a 1% secant flexural modulus of greater than 2000 MPa; a crystallinity of at least 70%; an isotactic pentad/triad ratio of greater than 85%; and a peak melting temperature of greater than 160° C.
17. The elongated member of claim 1, wherein at least one layer includes a propylene-ethylene copolymer that exhibits a melt flow rate at 230° C. per ASTM D1238 of 0.3 to 50 g/10 min; a density per ASTM D792 of 0.858 to 0.888 g/cc; an ethylene content of 5 to about 25 wt %; a Melting Range from 50 to 135° C.; a Shore A Hardness from 40 to 90; and a flexural modulus per ISO 178 of 10 to 280 MPa.
18. The elongated member of claim 1, wherein at least one layer includes a polypropylene homopolymer that exhibits a melt flow rate at 230° C. per ASTM D1238 of less than 7 g/10 min; a 1% secant flexural modulus of greater than 2000 MPa; a crystallinity of at least 70%; an isotactic pentad/triad ratio of greater than 85%; and a peak melting temperature of greater than 160° C.
21. An elongated member comprising at least 9 stacked and coextruded polymer layers that are continuous in profile and include at least 5 component A microlayers, and a component B microlayer interposed between each pair of adjacent component A microlayers, wherein each microlayer has a thickness less than about 50 microns, the component A microlayers and the component B microlayers have peak melting temperatures that differ by at least 5° C., the adjoining A and B microlayers differ in molecular orientation, the component A microlayers include an ethylene-based polymer or a propylene-based polymer, the component B microlayers include an ethylene-based polymer or a propylene-based polymer, the elongated member is prepared by drawing at a draw ratio of greater than 18, wherein the drawing includes a step of drawing at a temperature above the melting point of one of components A and B and below the melting point of the other component.
The present application claims priority to, and the benefit of the filing date of, U.S. Provisional Application No. 60/621,463 filed on Oct. 22, 2004; 60/717,965 filed on Sep. 16, 2005; 60/718,025 filed on Sep. 16, 2005; and 60/725,399 filed on Oct. 11, 2005, (Express Mail No. EV789808245US), all of which are incorporated by reference.
The present application is related to concurrently filed, commonly owned, copending application entitled Apparatus and Process for Manufacturing Shaped Plastic Reinforced Composite Articles Ser. No. 11/577,392; Improved Polyolefinic Materials For Plastic Composites Ser. No. 11/577,394; Plastic Composite Articles and Methods of Making Same Ser. No. 11/577,384; and Improved Composite Pipes and Method of Making Same Ser. No. 11/577,393; all of which are incorporated by reference.
The present invention pertains generally to multiple layer polymeric structures, and particularly to structures and methods employing thermoplastic microlayers.
The past several decades have seen considerable advancement in engineering materials through the development of improved composite materials. Composites allow designers to combine advantageous features of multiple component materials to arrive at a material that typically has one or more different properties than the component materials individually.
Microlayer structures that employ four or more layers have been disclosed in the art for various purposes, such as in U.S. Pat. Nos. 5,126,880 and 6,837,698, and Dooley, “Viscoelastic Flow Effects in Multilayer Polymer Co-extrusion”, Technische Universiteit Eindhoven (2002) (ISBN 90-386-2983-4), incorporated by reference all incorporated by reference. It would be attractive to employ microlayer structures in plastic composites. It would also be attractive to have improved microlayer structures, regardless of their intended application.
The present invention is directed to embodiments that feature at least 4 stacked layers that each include a polymer, each layer having a thickness less than about 50 microns (an more typically considerably thinner, e.g., possibly even thinner than about 5 microns), and each layer differing relative to its adjoining layer in at least one characteristic selected from composition, degree of crystallization, molecular orientation, molecular weight, melt rate, peak melting temperature, glass transition peak, temperature of crystallization, seal initiation temperature, softening point, molecular weight distribution or any combination thereof.
In one approach, the polymer of at least one or possibly each microlayer of the elongated member will be a propylene-based polymer (e.g., a polypropylene homopolymer, such as an isotactic polypropylene homopolymer). For example, one or more (or even all) of the microlayers may employ polypropylene. It is also possible that the polymer of at least one microlayer includes ethylene. The polymers of at least two adjoining microlayers may include ethylene (e.g., selected from a propylene-ethylene copolymer, a linear low density polyethylene, a high density polyethylene or any mixture thereof). The polymer of each adjoining microlayer may include polyethylene. Typically, the polymers of at least two adjoining microlayers each have a peak melting temperature that differ by at least about 5° C.
FIG. 1A and FIG. 1B illustrate examples of cross sections of elongated members of the present teachings, it being recognized that microlayer structures commonly will employ plural alternating A and B layers.
Though particularly useful as reinforcement materials for a composite material, the present invention is not limited to such application, as will be seen herein. However, to the extent microlayers are employed as reinforcement materials, in a first particular aspect, the processes of the present invention are directed toward making an intermediate form and include steps of a) providing at least one elongated member including a microlayer structure of a first thermoplastic material and having a surface portion capable of melting prior to the melting of an adjoining or internal portion (such as an internal oriented portion); and b) processing the elongated member into an intermediate form that may include a plurality of repeating structural units that are generally free to move relative to each other, wherein the form is capable of being processed to form a substantially smooth, ruck-free shaped finished article. In general, though not required in every instance elongated members will comprise an oriented polyolefin in at least one of the microlayers, and particularly one that can be processed according to the present teachings with substantial retention of its initial morphology.
Among the specific advancements offered by the present invention is the recognition of specific polyolefinic material combinations that have unique applicability in the composites field. In particular, one aspect of the present invention is premised upon the recognition for use in a microlayer elongated member of a propylene-based (e.g., a propylene-ethylene copolymer, a propylene-α-olefin copolymer, mixtures thereof or otherwise) copolymer that has a melting point that is below an adjoining polypropylene layer, and specifically an oriented polypropylene layer. Upon processing to form articles as taught herein, the resulting materials (especially the oriented polypropylene layer) exhibits a degree of retained morphology from its initial drawn state, heretofore not attainable using conventional materials. Accordingly, aspects of the present invention are premised upon the use of a propylene-ethylene copolymer that has an ethylene content of about 3 to 25 wt. % (e.g., 5 to 15 wt. %), a melting range of about 50 to 135° C., and a flexural modulus of about 8 to about 325 Mpa or higher (e.g., at least about 375 MPa), and a second thermoplastic material that includes a polyolefin, such as a propylene-based polymer. Such propylene-ethylene copolymer may have a Shore A Hardness of from about 40 to 90 (or higher), a molecular weight distribution of about 1.5 to about 4, and a melt flow rate of at least about 0.3 g/10 min, or any combination thereof.
One example of a propylene-based polymer that may be employed generally will be isotactic and relatively stiff. For example, it may be a polypropylene homopolymer that has a 1% secant flexural modulus of greater than about 1000 MPA, (and more specifically greater than about 2000 Mpa (e.g., about 2500 Mpa or higher)), an isotactic pentad/triad ratio of greater than about 70% (e.g., greater than about 85%) or both. Moreover, such a polypropylene typically will have a peak melting temperature of greater than about 160° C. (e.g., greater than about 165° C.), a crystallinity of at least about 30% (more specifically at least about 50% or even 70%) or both.
The intermediate form typically includes a plurality of elongated member layers, with at least one of the layers including an elongated member stretched to at least about 5× (and possibly as high as 15× or higher). The elongated members may comprise a coextruded microlayer tape and the consolidating step, particularly where a propylene-based polyolefin is employed in an elongated member, includes maintaining the intermediate form at a temperature of at least about 150° C. for at least about one minute, after the core pipe is covered with the intermediate form. A plurality of layers of windings may be employed.
If employed, the protective jacket typically includes a polymer and the jacket has a pressure rating (per ISO 9080) of greater than about PE 80. Resulting pipes will have a hoop stress performance for withstanding a pressure of 7 MPa at 80° C. for up to 250 hours. Any jacket applied, at least one of the thermoplastic materials of the intermediate form, or both may include a non-migratory process aid or surface modifier agent as taught herein. In one approach, at least one of the first thermoplastic material and the second thermoplastic material includes ethylene. In a specific aspect, the elongated member is made from (i) a first thermoplastic material that comprises a propylene-ethylene copolymer, (ii) a second thermoplastic material that comprises an isotactic polypropylene homopolymer (e.g., having a crystallinity of at least about 30%, and an isotactic pentad/triad ratio of greater than about 70%); or a combination of (i) and (ii). A plurality of microlayers may be employed for the elongated member.
Turning first to the intermediate forms of the present invention, in general, these forms will include at least one elongated member with a composition that includes at least one thermoplastic material. By “elongated member”, it is generally meant a member that has one of its dimensions (e.g., length) that is longer than at least one other dimension (e.g., width, height, thickness, or diameter), particularly, the length of an elongated member here in substantially greater (e.g., by a factor of at least about 10 or higher) than the width or height. Accordingly, elongated members herein could include, but are not necessarily limited to a member selected from fibres, rods, cords, yarns, tapes, filaments, straps or any combination thereof. As can be appreciated from the above, in a number of aspects, films may also be contemplated as within the meaning of “elongated members”. Small scale members may also be possible, such as whiskers or platelets. Though “elongated member” is regarded broadly herein, it should be recognized that particularly preferred forms of the elongated member specifically will include one or more of yarns, tapes, fibres and filaments. A highly preferred elongated member is in the form of a tape.
Indeed, among the many unique features of the present invention is the ability to make effective use of the above-referenced monolithic materials, such as the mentioned geophysical textiles. These materials currently commonly find many civil engineering applications (although the present teachings are not so continued), such as one or more of erosion control/soil retention, silt fence, landscaping, reinforcement, separation (e.g., for paving), drainage and other applications. Quite often, geophysical textiles exhibit a relatively high bi-directional strength and stiffness and comprise woven fibers that may not be consolidated and may thus exhibit some amount of permeability, permitivity or both. Properties of geophysical textiles can vary over a wide range. By way of example, it may be possible that the geophysical textiles will exhibit a grab tensile strength (per ASTM D4632) of at least about 0.3 kN, and more specifically ranging from about 0.5 to about 3 kN, and a grab tensile strength elongation (per ASTM D4632) of at least 10%, e.g., about 15%, with levels of 50% or higher also possible. The geophysical textiles will exhibit a Mullen burst strength (per ASTM D3786) of at least about 1000 kPa, and more specifically from about 2000 to 10,000 kPa (e.g., about 3000 to 7000 kPa), and a puncture strength (per ASTM D4833) of at least 0.20 kN, and more specifically ranging from about 0.25 kN to about 0.80 kN. Examples of commercially available geophysical textiles include polypropylene fabrics, such as those offered under the name Propex® (from Propex Fabrics (Georgia)), as well as geophysical textiles offered by Don & Low under the designation LOTREK, by Mirafi (Ten Cate Nicolon) under the designation GEOLON, and other vendors such as US Fabrics, Inc. and LINQ Industrial Fabrics, Inc.
The present teachings advantageously afford the ability to make elongated members such as a tape a plurality (e.g., at least 4) of adjoining layers of polymers (e.g., polymer A and polymer B—referred to herein as an A-B component structure, such as A-B, A-B-A, A-B-C, A-B-C-D, etc. or any combination thereof, such as A-B-D, A-B-C-B-D, A-C-B, or otherwise, where the C and D designations denote without limitation yet additional potential polymers, for example, as may be encountered with the microlayer teachings presented herein). When different polymers are employed within an elongated member they may each be of the same composition or a different composition. They may be from the same general family of polymers (e.g., polyolefins), or different. They may be from the same specific type of polymer within a family (e.g., polypropylene), but vary relative to each other with respect to some characteristic such as weight average molecular weight, polydispersity, morphology; melt rate or other melt characteristic, or any combination thereof. It should be appreciated that one or more of the components (e.g., A, B, C, D or some other component) need not necessarily be a polymer, but may be an additive, or other functional material.
In general, where an elongated member includes at least a component A and component B, typically, the melting points (which may occur over a range of temperatures) of the components A and B will differ, with the melting point (namely, the peak melting temperature for materials that have a melting range) of the component A being below the melting point of component B. In addition, the higher melting point material typically will be at least partially oriented (e.g., mono-axially or bi-axially). The relative melting points may differ by as small as about 5° C., but will more typically vary by at least about 10° C., more preferably at least about 20° C., and in one specific example may vary by as much as at least about 25° C. (e.g., about 30° C.) or higher. For example, without limitation, component A may have a melting point of about 130° C. and component B may have a melting point of above about 160° C. As a result of the spread of the temperatures for the melting point, what results is that a processing window is realized within which the component A is able to flow and fuse with adjoining material, for achieving consolidation upon cooling. In the meantime, by maintaining the processing temperature of the component B at below its melting point, the risk can be reduced that the component B will suffer significant degradation to its initial morphology, and compromise to its properties, such as the overall high flexural modulus of the elongated member. In turn, additional benefits can be realized by the ability upon conclusion of processing, and especially in finished articles, to realize a substantial preservation of the initial morphology within the elongated member. In addition to the ability to retain morphology, consolidating near the lower end of the temperature range has the additional benefit that the elongated component will be generally less prone to relax or shrink.
Effectively, therefore, the desired spread in relevant melt characteristic temperature of the respective components A and B (e.g., a difference of about 5, 10, 20, 25, or 30° C. or more in such melt characteristic temperature of the polymer) is selected generally so that fusion of the component A can occur without reduction to the enhanced mechanical properties that component B possesses relative to component A in their initial solid states.
In more detail, the elongated members of the present invention will be derived from a film (which film may be un-oriented, but more typically will be monoaxially oriented, biaxially oriented or otherwise). For example, it is possible that the elongated members (and particularly elongated members selected from at least one of the yarns, tapes, fibres or filaments) could be made by subjecting a molten polymer (e.g., at a melt temperature of the polymer, such as about 200 to 240° C. for various polyolefins or other thermoplastics) to a blown film process (e.g., an air quenched blown film process, such as discussed in WO2005035598, incorporated by reference), by a cast film or sheet (e.g., quenching an extruded molten polymer using a chilled roller), or by film or sheet extrusion (e.g., such as through a water-bath). Combinations of these approaches may also be employed. The film or sheet can then be slit into predetermined widths, using a suitable cutting operation such as sonic slitting, hot knife slitting, a combination thereof or otherwise. Slit films can then be processed into the desired denier (e.g., from about 1000 to about 20,000, e.g., possibly greater than about 13,500) and weight (e.g., a weight of at least about 7 g/denier and possibly at least as high as about 9 g/denier or higher, and even more specifically higher than about 10 g/denier) through a heating phase (such as by use of a hot table) or a stretching operation (optionally employing a stretching oven for elevated temperature stretching). For some embodiments, slit films may have a tex characteristic (the weight of length of about 10 km tape) of from about 60 to 300. Slit films can also be fibrillated and wound onto bobbins for later use in final products. The entire process as described typically will be a continuous process, but need not be.
By way of further particular example, another possible approach for forming an elongated member (and particularly an elongated member selected from yarn, tape, fibre or filament) may be to subject a molten polymer (e.g., at a melt temperature of 90 to 230° C.) to a step of extrusion (e.g. following which it passed through a water bath at a temperature of 20 to 40° C.) with a suitable die (optionally with a tapered opening) such as a sheet die (e.g. a Collin Teachline extruder) to form a cast sheet of up to about 10 mm thickness (more typically it is about 1 mm thick). The sheet is slit into widths of about 1 to 20 mm, more particularly about 2 to 10 mm (e.g., about 5 mm) and stretched between goddets in one or more heated ovens to a draw ratio of about 2 to 10 (e.g., about 5) or higher at about 50 to 70° C. (e.g., 60° C.). The resulting yarn, tape, fibre or filament may then be further stretched at one or more elevated temperatures (e.g., greater than about 120° C., such as at a temperature of about 140 to 200° C. (e.g., about 170° C.)) at one or more additional draw ratios of at least about 2 to 8 (e.g., about 3.5), which results in a desired thickness (e.g., about 0.3 to 2 mm, more specifically about 0.05 to 0.3 mm (particularly when the cast sheet is about 1 mm thick) or possibly larger or smaller). It may also be possible to include one or more stretching steps at a temperature below the melting point of the stretched polymer. One possible stretching operation involves stretching a material that includes a polypropylene homopolymer at a temperature of about 170° C. to a draw ratio of at least 5, more specifically at least 10, and still more specifically at least 15.
As can be gleaned from the above, as the present teachings relate to stretching, the skilled artisan will appreciate that many alternative approaches to stretching are possible. It is common in many such instances that a film or sheet is subjected to one or more stretching (e.g., uniaxial, biaxial or otherwise) steps, such as for forming a yarn, tape, fibre or filament. Stretching can be performed in a single-stage operation or a plural stage operation (e.g., a dual-stage process). Stretching typically will be done at an elevated temperature (e.g., particularly for polyolefins, greater than about 60° C., and even more typically greater than about 100° C., such as between about 100 to about 200° C., more specifically up to about 190° C. (e.g., about 120 to 180° C., and even more specifically for polypropylenes about 140 to about 190° C., such as about 150° C. to 170°), it being recognized that temperature conditions for other materials such as polyesters may be other than as set forth). Considered another way, for a system that includes higher and lower melting point components, the stretching typically will occur at a temperature that is above the melting temperature of the lower melting point component, and within about 10° C. of the peak melting temperature of the higher melting point component. The amount of film stretch per stage (as compared with its isotropic melt state) can be selected as desired, ranging for example from about 2× to about 20× or higher (e.g., about 4× to 10×, about 8× to 15× or possibly about 15× to 18×, or even about 25× to 40×). Further, the stretching can be accomplished by a single stage (so that one stretch accomplishes the entirety of the stretching), or plural stage operation (e.g., a plurality of consecutive stretches). Higher or lower stretch amounts may be possible. Further, though disclosed particularly for single stage stretches, a plurality of sequential steps may also be employed for accomplishing the desired stretch amount. During each stage the temperature of the film can be kept constant or varied over a range of temperatures. Stretching amounts herein are disclosed with reference to a comparison of the resulting elongated member with the film formed from an isotropic melt. Additional aspects of elongated member formation will be addressed more specifically in the discussion herein.
Propylene-based polymers include but are not limited to propylene homopolymer or interpolymers of propylene with at least one of C2 or C4-C20 α-olefins, and may be referred to as homopolymer polypropylene (hPP), random copolymer polypropylene (RCP), high crystalline polypropylene (HCPP), rubber-modified polypropylene (generally a hPP or RCP matrix with a disperse “rubber” phase), also referred to as impact or block copolymers (ICP), or propylene-ethylene copolymers. Propylene-based polymers may be made via various processes, including but not limited to solution, slurry, or gas phase, using various catalyst systems such as Ziegler-Natta (Z-N), metallocene, or other advanced, non-metallocene complexes. Propylene-based polymers may be isotactic, syndiotactic or atactic, but preferably are isotactic.
A preferred propylene-ethylene copolymer for use herein (whether alone or in combination with another polymer, such as a polypropylene homopolymer or random polypropylene, and whether used in an outer layer (e.g., a lower melting point layer) or an inner layer (e.g., a higher melting point layer)) preferably is a specialty propylene-ethylene copolymer and thus has a combination of two, three or more (e.g., a combination of all) of the following characteristics: a) a Molecular Weight Distribution (MWD) of about 1.5 to about 4 (e.g., 2 to 3), b) a Melt Flow Rate (at 230° C.) (MFR) (per ASTM D1238) of at least about 0.3 (e.g., about 0.5 g/10 min), and more specifically about 0.3 to about 50 g/10 min (e.g., 2 to 25 g/10 min), c) a density (per ASTM D792) of about 0.80 to about 0.95 g/cc, and more particularly about 0.85 to 0.91 (e.g. 0.858 to 0.888 g/cc); d) a comonomer content of about 3 to 25 wt % (e.g., 5 to 15 wt %); e) a Glass Transition Temperature (Tg) of about 0 to about −50° C. (e.g., −15 to −35° C.); f) a Melting Range from about 40 to about 160° C. (e.g., 50 to 135° C.); g) a Shore A Hardness from about 25 to about 100, and more particularly about 40 to about 90 (e.g., 50 to 75); and h) a flexural modulus (per ISO 178) of about 5 to 1000 MPa, or more particularly from 8 to 325 MPa (e.g., 10 to 280 MPa), or higher (e.g., in excess of 2000 MPa). By way of example, without limitation, such material may have a flexural modulus of about 8 to about 325 MPa (e.g., about 10 to 280 MPa), an ethylene content of about 3 to 25 wt %, and optionally a peak melting peak below about 135° C., a Shore A Hardness from about 25 to about 100, and more particularly about 40 to about 90 (e.g., 50 to 75); or a combination of both. A commercially available example of one such copolymer is available from the Dow Chemical Company under the name VERSIFY. In one particular example, the above characteristics are observed in the elongated member and thereafter in a resulting composite article prepared according to the teachings herein.
One particular example of an attractive polypropylene for use in the present includes or more specifically consists essentially of an isotactic polypropylene homopolymer (e.g., as prepared and analyzed in accordance with the teachings of WO 2004/033509 and US 20040122196, hereby incorporated by reference; see Appendix herein for additional teachings of materials characterizations analyses). Accordingly, for use in the component B, one example of a specific polypropylene is characterized by a combination of two, three, four, five, six or more (e.g., a combination of all) of the following characteristics: a) a molecular weight distribution (Mw/Mn) of less than about 5.5, as measured by gel-permeation chromatography according to the teachings published in WO 2004/033509 and US Patent Application No. 20040122196 (see Appendix), b) a melt flow rate (at 230° C.) (per ASTM D1238) of less than about 25 g/10 min, more preferably less than about 10 g/10 min, and more preferably less than about 7 g/10 min (e.g., less than about 5 g/10 min), c) a 1% secant flexural modulus (per ASTM D790-00) of greater than about 2000 MPa (e.g., greater than about 300,000 psi), d) less than about 2% (e.g., less than about 1%) xylene solubles, as measured according to the teachings published in WO 20041033509 and US Patent Application No. 20040122196 (see also, Appendix herein), e) a haze (per ASTM D1003) of less than about 25%, f) a crystallinity of at least about 30%, more specifically at least about 50%, and still more particularly greater than about 70%, as measured by differential scanning calorimetry according to the teachings published in WO 2004/033509 and US Patent Application No. 20040122196 (see also, Appendix herein), g) an isotactic pentad/triad ratio of greater than about 70%, more preferably greater than about 85% and still more preferably greater than about 95%, and even still more preferably greater than about 99%, using nuclear magnetic resonance (NMR) according to the teachings published in WO 2004/033509 and US Patent Application No. 20040122196 (see also, Appendix herein); and h) a crystallization temperature (e.g., as measured according to the teachings of WO2004/033509 and US Patent Application No. 20040122196 (see also, Appendix herein)) of greater than 133° C. In one illustrative example, it is possible that the pentad isotacticity is at least 96%, more preferably at least 97%, and most preferably at least 98%. Typically, the polypropylene homopolymer will exhibit a peak melting point of at least 160° C. (e.g., at least 165° C. or even 170° C.). By way of example, the polypropylene homopolymer will exhibit a peak melting point of at least 160° C. (e.g., at least 165° C. or even 170° C.), and a crystallinity of at least about 30%, more specifically at least about 50%, and still more particularly greater than about 70%, an isotactic pentad/triad ratio of greater than about 70%, more preferably greater than about 85% and still more preferably greater than about 95%, and even still more preferably greater than about 99%, or both such isotacticity and crystallinity. In a particular example, the polypropylene homopolymer further will exhibit a 1% secant flexural modulus (per ASTM D790-00) of greater than about 2000 MPa In one particular example, the above characteristics are observed in the elongated member and thereafter in a resulting composite article prepared according to the teachings herein. For example, it is possible that the material of the component B actually exhibits an increase in peak melting point in a resulting consolidated composite article (e.g., by as much as 3, 5 or even 8° C.) as compared with its peak melting point prior to consolidation.
For example, one specific polypropylene is characterized by an Mw/Mn of less than about 7, a melt flow rate of less than about 7 g/10 min, a 1% secant flexural modulus of greater than about 2000 MPa and less than 2% by weight xylene solubles. An example of such polypropylene is discussed in US2004/0122196 entitled “Highly crystalline polypropylene with low xylene solubles” and WO2004/033509 entitled “Highly crystalline polypropylene with low xylene solubles”, both incorporated by reference where techniques for determination of the above characteristics are also taught.
It is also recognized herein that additional advantageous results may be obtained (e.g., to aid in stretching) by including within the higher melting point layer such as component B (e.g., as a blend, a copolymer, or a combination thereof), an optional minor amount (relative to the component B) of a lower melting point polyolefinic copolymer, such as a propylene-ethylene copolymer (e.g., of the type described above, such as VERSIFY™ copolymer available from The Dow Chemical Company). Such co-polymer preferably has a combination of two, three or more (e.g., a combination of all) of the above-discussed characteristics for a specialty propylene-ethylene copolymer. Without intending to be bound by theory, it is believed that the inclusion within the component B of a lower melting point polyolefinic material functions to help bond the component B layer to the component A layer; it also is believed that the presence of the lower melting point polyolefinic material helps to bond individual fibrils within the component B layer to each other. Likewise it may be possible to vary the characteristics of component A, by including in the component A minor amounts of a material disclosed herein for the component B.
As mentioned, the higher melting point polymer (e.g., the component B in the illustrative embodiment including an A-B structure) is typically a major contributor to the overall mechanical properties of the elongated member. Though not required in every instance, it is frequently desired that the component B exhibit good stretching characteristics, particularly under elevated temperature (e.g., about 170° C.). Accordingly, it may be possible that the component B exhibit a draw ratio (i.e., the ratio of the initial to final thickness of the body) of at least about 8, more preferably at least about 12, and still more preferably at least about 16 or higher, without rupture or significant compromise to its overall performance. It is also recognized herein that by incorporating an amount of propylene-ethylene copolymer (such as the specialty copolymer as described above) in the component B, such relatively high stretch is possible. From this, it will also be appreciated that, even though the presence of the copolymer initially will reduce the stiffness of the component B, substantial gains in the stiffness of the final stretched material will be realized, because the enhanced stretch capabilities of the material will afford greater opportunity for stiffening to occur during the stretch.
As for examples of particular preferred materials for the higher melting point material (e.g., the material B in the illustrative A-B structure combination), use of a high stiffness, (and in one preferred approach, a highly isotactic) propylene homopolymer. Examples of such homopolymers are described above and in US2004/0122196 entitled “Highly crystalline polypropylene with low xylene solubles” and WO2004/033509 entitled “Highly crystalline polypropylene with low xylene solubles”, both incorporated by reference, will permit even higher stretch capabilities (e.g., at least about 10×, more preferably at least about 15×, and still more preferably at least about 20×) in a single step stretching process, thus reducing or even eliminating the need for additional stretching steps, annealing steps that may be employed herein or both. Of course, it will be appreciated that the employment of a highly crystalline polypropylene is desired, it is not mandatory, and good results are also obtainable using polypropylenes that are not highly crystalline (e.g., various conventional polypropylenes derived by Ziegler-Natta catalyst, mini-random polypropylene copolymer, as well as others discussed herein).
By way of illustration, one approach to the manufacture of an elongated member involves the formation of a film that is coextruded so that it results in an A-B plural layer alternating structure, wherein the component A is a random copolymer of propylene and about 3 to 15 wt. % ethylene (e.g., about 5 to 15 wt. %) (with a density of about 0.9 g/cm3), and has a melting point of about 50 to about 135° C. (e.g., 100 to 140° C.), and the component B is a polypropylene homopolymer with a peak melting point of about 150 to 170° C. (it being recognized that for some embodiments a melting point in excess of about 170° C. may be possible (e.g., from about 150 to 180° C. or higher)). Accordingly, it is possible that the difference in melting point between component A and B may be as little as about 5 to 9° C., or higher than about 75° C. The relative amounts of the A and B components range from about 1:1 to 25:2, and still more specifically about 2:15 to 1:10 (e.g., about 2:17)). The component A or B may have any suitable weight average molecular weight, such as about 50 to about 400 kg/mol, and more typically about 200 to about 300 kg/mol.
By way of summary, it is contemplated that in accordance with the present teachings a multiple layer structure may be employed that includes at least two adjoining layers, which differ by their melting point. Thus a higher melting point material (which typically will be oriented) is used in combination with a lower melting point material. The lower melting point material typically will reside on an external surface of the elongated member, so that melting can occur. It is disclosed that the materials employed may be selected from a variety of alternative materials, with one particularly preferred combination including a propylene-ethylene copolymer as a lower melting point material layer, and a higher melting point polypropylene homopolymer layer (specifically one that is oriented). The layers may incorporate other additives as disclosed herein (e.g., polydimethylsiloxane or another suitable non-migratory process aid or surface property agent). It may be possible that amounts (e.g., minor amounts) of the higher melting point polypropylene homopolymer material (e.g., is incorporated into the propylene-ethylene copolymer as taught. Alternatively, or in addition thereto, it is also possible that the amounts (e.g., minor amounts) of the lower melting point propylene-ethylene copolymer material is incorporated into the polypropylene homopolymer as taught. Examples of highly preferred combinations of materials include a lower melting point propylene-ethylene copolymer of a type having characteristics similar to VERSIFY™, available from The Dow Chemical Company, in combination with a highly isotactic polypropylene homopolymer, such as is taught above and in US2004/0122196 and WO2004/033509, both incorporated by reference.
Turning now with more specificity to aspects of microlayer teachings, by “microlayer” it is meant a layer of relatively fine thickness, e.g., smaller than about 50 microns, more preferably smaller than about 20 microns, more preferably less than about 10 microns in thickness, still more preferably less than about 7 microns in thickness, and even still more preferably less than about 5 microns in thickness. Typically, when employed, microlayers will be fabricated as an assembly of a plurality of stacked, preferably coextruded layers that each include a polymer, co-polymer or mixture thereof. For example, each microlayer may include one or both of the above materials described previously for the layers of components A and B in the illustrative A-B combination, or yet still another component. The number of individual microlayers in a typical elongated member typically will vary from one to four. More commonly, however, the microlayers will comprise at least four or more, and more specifically at least five or more layers of materials, with each layer preferably differing relative to its adjoining layer.
As discussed, one approach is to employ a structure consistent with that of FIG. 1A that includes a plurality of microlayers that alternate between differing materials of components A and B. For example, this may be expressed as ((A-B)n-A) where n is an integer of 2 or greater. Elongated members where n is 3, 4 or more, 10 or more, 20 or more, 50 or more, 100 or more, 200 or more and 300 or more (e.g., 500 to 1000 layers, or possibly even 1000 to 5000 layers or more) are also contemplated. Microlayer elongated members may be fabricated using any suitable technique, such as layer-multiplying extrusion. One approach is to coextrude a plurality of layers, such as by using a microlayer melt splitter or a hemispherical microlayer coextrusion feedblock. Optionally, extrusion may be onto a chill roll. Lamination techniques may also be used in addition to or in combination with a coextrusion step. In general, the polymers of the layers will be selected so that melt viscosities are approximated to help prevent layer instability or nonuniformity, and so that the polymers used have sufficient interfacial adhesion so that adjoining layers will not delaminate. Additional illustrative teachings are found in U.S. Pat. No. 5,568,316 (also teaching the use of coextrusion devices such as described in U.S. Pat. Nos. 3,773,882 and 3,884,606; 5,269,995; 5,094,793 and 5,094,788, all of the foregoing patents being incorporated by reference). See also, U.S. Pat. Nos. 5,540,978; 5,448,404; 5,339,198; 5,316,703; 5,217,794; 5,126,880; 6,837,698 and EP 0647183B1, all of which are incorporated by reference. See also, thesis of Dooley, “Viscoelastic Flow Effects in Multilayer Polymer Co-extrusion”, Technische Universiteit Eindhoven (2002) (ISBN 90-386-2983-4), incorporated by reference; and Rastogi, et al. “Heterogeneity in Polymer Melts from Melting of Polymer Crystals”, Nature Materials Vol. 4 (August 2005) (published online on 24 Jul. 2005) incorporated by reference; Jin, et al., “Structure of Polypropylene Crystallized in Confined Nanolayers”, PPS-20: Polymer Nanotechnology Symposium (20-24 Jun. 2000) incorporated by reference. It should be recognized, however, that aspects of the invention contemplated that the selection of the materials for use herein does not require any specific degree of reflectance within any layer or combination of layers. Accordingly, it is contemplated that resulting elongated members reflect less than 40% (or even less than 20%) of visible light incident on the body. Likewise, the materials may be free of any coloring agent for giving the body a metallic appearance. They may also be selected without regard to individual optical thicknesses of the constituent layers, or the sum of the optical thicknesses.
In addition, optionally (and having application herein for multi-layer structures apart from only microlayers), a tie-in layer or an intermediate bonding agent (e.g., adhesive, primer or otherwise) layer, may be used between adjoining layers of multi-layer elongated member materials, such as between adjoining layers of a microlayer material. In the context of polyolefinic multi-layer materials, typically the tie-in layer or an intermediate bonding agent layer typically includes a polyolefin with a functional reactive group. The use of a tie-in layer or an intermediate bonding agent layer is particularly useful where the compositions of the layers are chemically disparate. For example, when a polyolefin is used as one layer and a polyester or polyamide as the other layer, a layer that includes a polyolefin with a functional reactive group (e.g. a layer including a coupling agent such as maleic anhydride-grafted polypropylene modifiers, available under the designation Polybond® (from Crompton-Uniroyal Chemical, a polyolefin with an epoxy functionality, a polyolefin with a (meth)acrylate (e.g., glycidyl methacrylate) or (meth)acrylic acid functionality, or otherwise) may be used to increase the bonding strength between the layers. It is also possible to employ a tie-in layer or intermediate bonding agent that includes a copolymer that includes a polyethylene, a polypropylene or a mixture thereof. For example, without limitation, one possible approach might be to employ two or more microlayers that are polyolefinic homopolymers (e.g., polypropylene or polyethylene), and to bind such microlayers together with a propylene copolymer, an ethylene copolymer or a mixture thereof. Of course, it will be appreciated that the above-discussed tie-in layer or intermediate bonding agent layer may also be used in elongated members that are not microlayers.
Exemplary microlayer elongated members comprise at least about 50 wt % (of the overall microlayer structure) of a higher melting point material component B with the balance a lower melting point material component A, in accordance with the foregoing discussion of components A and B, more preferably between at least about 60 wt % of component B, and most preferably between about 70 and 96 wt % of component B with the balance component A. Preferably, component A comprises polypropylene copolymer in an amount of about 0 to 100 wt %, while propylene-ethylene copolymer (e.g. the previously discussed specialty propylene-ethylene copolymer, such as VERSIFY™ copolymer) may comprise about 5 to 100 wt % of component A. Component A may also include a non-migratory processing or surface modification (e.g., friction reduction) agent such as discussed previously (e.g., polydimethylsiloxane, a fluoropolymer such as a fluoroelastomer or the like) in an amount of about 0 to 4 wt % of the component. Component A may also include other compositions as discussed above in amounts of about 0 to 8 wt % of the component.
To illustrate the above, without limitation, microlayer elongated members having from about 100 to 525 layers or more (alternating between layers consisting essentially of component A, and layers consisting essentially of component B, and optionally including other polymer component layers) and made to include from about 5 to about 25 parts by weight of the above discussed component A, and about 95 to 75 parts by weight of the above discussed component B, which is drawn at a draw ratio of about 18 to 28 at a draw temperature in excess of 150° C. (e.g., 165° C.). More specific examples are included in the following table.
>150° C.
Resulting microlayer structures are capable of exhibiting a tensile modulus (per ASTM D-638 or ISO527) at least about 10 GPa, and more specifically at least 12 GPa (e.g., from 12 to 15 GPa). Draw ratios (for drawing at a draw temperature in excess of 150° C. (e.g., 165° C.)) in excess of 18, are possible with these materials, particularly for a lamellar polymeric body having at least 4 layers including at least a first layer that includes a first polymeric material selected from a thermoplastic polymer, a thermoplastic co-polymer, or a combination thereof, and having a thickness less than about 50 microns, and an adjoining second layer of that includes a second polymeric material selected from a thermoplastic polymer, a thermoplastic co-polymer, or a combination thereof, and having a thickness less than about 50 microns. This is particularly so when wherein the first and second polymeric materials each layer differs relative to each other in composition, degree of crystallization, molecular orientation, molecular weight, melt rate, peak melting temperature, glass transition peak, temperature of crystallization, seal initiation temperature, softening point, molecular weight distribution or any combination thereof (for example, a microlayer that includes a propylene-based polymer, and another different adjoining microlayer).
By way of example, without limitation, one possible two step stretch process is also used in microlayer elongated members that contain between about 3 and 33 layers having ratios of component B to component A of about 3:1 to about 9:1 (e.g., about 4:1). The first stretch is completed at about 65° C. (draw ratio of about 6.5) and the second stretch step is completed at about 165° C. (draw ratio of about 3). Accordingly, as with other stretch operations herein for elongated members having differing characteristics than that just described, one stretch is performed above the melting point of one layer, but below the melting point of another layer, such as the constrained layer. Of course, it will be appreciated that the stretch temperature may vary depending upon the materials selected for the microlayers. For example, without limitation, it is possible that for an elongated member that includes a polyester (e.g., PET), that the drawing temperature may range from about 120° C. to about 250° C. Moreover, it is within the teachings herein to increase the orientation of at least the higher melting point material during stretching, such as by increasing the Hermans Orientation Function, as measured according to the teachings of Zuo, et al., “In Situ Synchotron SAXS/WAXD Studies on Stretching of Isotactic Polypropylene, Poly. Mat'ls. Sci. & Eng., 93 (2005) 761.n addition, microlayer elongated members that combine polypropylene and PET (i.e. Lighter C88 from Equipolymers) are also made (such as having from about 3 to 150 alternating layers, e.g., about 5 to 129 layers). A tie-in layer such as that including maleic anhydride grafted polypropylene (e.g., POLYBOND 3002 from Crompton) may be employed. The five layer material is arranged as such: PP-polybond-PET-polybond-PP with a ratio of 7/3/80/3/7. The 129 layer material is arranged as such: (PP-Polybond-PET-Polybond)n-PP, where n is 32, with the same ratio of materials as in the five layer material. By way of summary, without limitation, the present teachings address the fabrication of microlayer structures that will typically include at least 4 stacked layers, each having a thickness less than about 50 microns, and each layer differs relative to its adjoining layer in at least one characteristic selected from composition, degree of crystallization, molecular orientation, molecular weight, melt rate, peak melting temperature, glass transition peak, temperature of crystallization, seal initiation temperature, softening point, molecular weight distribution or any combination thereof. In one approach, the polymer of at least one or possibly each layer of the elongated member will be a propylene-based polymer (e.g., a polypropylene homopolymer, such as an isotactic polypropylene homopolymer). For example, one or more (or even all) of the layers may employ polypropylene. It is also possible that the polymer of at least one layer includes ethylene. The polymers of at least two adjoining layers may include ethylene (e.g., selected from a propylene-ethylene copolymer, a linear low density polyethylene, a high density polyethylene or any mixture thereof).
A variety of other specific combinations of polyolefinic materials may be employed for microlayers. For example, without limitation, a coextruded multiple layer assembly may formed that includes a polyolefin (e.g., a polyethylene homopolymer) having a melt index below about 4, a molecular weight distribution of less than about 5 and a peak melting point of at least about 128° C., and a polyolefinic adjoining layer (e.g., a co-polyethylene) that has a peak melting point of less than 125° C. The coextruded layers may be subject to at least one stretch at a temperature between about 115 and 141° C. Another specific example includes adjoining microlayers of polypropylenes prepared by Ziegler-Natta catalysts, wherein each of the adjoining layers respectively are a homopolymer, a random copolymer, or alternating layers of homopolymer and random copolymer. Yet another possible combination contemplates the use of a polypropylene homopolymer layer adjoining a polyethylene homopolymer layer, or optionally including an intermediate layer such as a propylene-ethylene copolymer, a random polypropylene, an ethylene copolymer, or a mixture thereof. Typically, the polymers of at least two adjoining layers each have a peak melting temperature that differ by at least about 5° C.
By way of example, without limitation, a generally polyolefinic intermediate form may be consolidated by one or more steps of applying at least about 50 kN (and more specifically, greater than about 150 kN (e.g., 350 kN), while maintaining the form at one or more temperatures above the melting point of the exposed surface of the elongated members (e.g., from about 100 to about 175° C., and more specifically less than about 150° C.) for a sufficient period of time (e.g., about 1 to about 5 minutes). Longer or shorter times are also possible (e.g., consolidating at an elevated temperature for about 0.25 hour, about 0.5 hour, or even longer than about 1 hour).
It will be appreciated that in the course of preparing the intermediate forms of the present invention, the forms may be strain hardened (i.e., strengthened or hardened by plastic deformation below the recrystallization temperature range of the constituent materials). Strain hardening may occur before, during or after consolidation. If after consolidation, then it is preferred that strain elongation be kept below about 15% and more preferably below about 10%. If before or during consolidation, the strain elongation amounts can be at least about 10 to 40%. Higher or lower amounts are also possible. One particular approach to shaping of the intermediate form (whether single layer or multi-layer) involves the employment of a resilient structure that permits for displacement (e.g., slippage) of the intermediate form during deformation. Various particular approaches are disclosed, without limitation, co-pending and commonly owned U.S. Provisional Application Ser. No. 60/718,025, filed Sep. 16, 2005, entitled “Apparatus and Process for Manufacturing Shaped Plastic Reinforced Composite Articles,” (incorporated by reference). By way of example, it is contemplated that a intermediate form that includes a plurality of thermoplastic elongated members is deformed while displaceably clamping a heated intermediate form during the deforming. The intermediate form is thus clamped in a manner such that while a force is applied for deforming the intermediate form, the intermediate form is free to move without deformation within a predetermined limit. The thermoplastic elongated members of the intermediate form are at least partially consolidated for forming a three dimensional article having a predetermined orientation of the elongated members. Optionally, the intermediate form is stamped in a secondary forming operation (e.g., below the temperature of the displaceably clamping step, such as substantially at or below room temperature).
The temperature at which the second thermoplastic material is introduced into the cavity is sufficiently high that it causes at least a portion of the intermediate form to melt and resolidify in intimate bonding contact with the second thermoplastic material. In this regard, it may be possible to control the tool temperature into which the second thermoplastic material is introduced to help control the rate of solifidification. For example, one approach is to employ a fluid cooled tool, such as a liquid (e.g., water) cooled tool and to maintain the wall temperature of the tool adjacent the cavity at more than about 15° C., more specifically more than about 30° C., below the melting point of the lowest melting point of the materials in the intermediate form (e.g., the component A material in an A-B or A-B-A type material).
By more specific way of illustration, for injection molding a thermoplastic material (e.g., a polypropylene material) into a tool cavity that has an intermediate form including about 3 to 8 layers of an elongated member having at least components A and B (e.g., a tape where the component A includes a material with a melting point of about 120° C.), a water-cooled tool (e.g., made of a tool steel such as one including chromium and molybdenum (such as P20), PX5, H13, S7 or the like) is used to maintain the wall defining the tool cavity at a temperature of about 80° C. After injection molding, for a typical part that has a wall thickness of about 2 to 4 mm and an overall weight of about 0.3 to 1 kg, the molded article is kept in the tool for about 5 to 60 seconds or more prior to ejection. For example, for articles prepared according to the present invention, it is expected that the time will more typically range from about 15 to 35 seconds. An example of a suitable molding machine is a 300 metric ton Demag injection molding machine.
Though it is possible that the melting point of the bulk material that is combined with the intermediate form will be below the lowest melting point of any material in the intermediate form, it is expected that more commonly the melting point of the bulk material will be above the highest melting point of any material in the intermediate form. For example, it is possible that a difference between the melting point of the bulk material and the highest melting point of any material in the intermediate form will exceed 10° C., more specifically 30° C., and even more specifically 50° C.
In yet another aspect of the present invention, reinforced composites made according to the present invention exhibit excellent dimensional stability over a broad range of temperatures. For example, the linear coefficient of thermal expansion (−40° C. to +80° C.) may range from about 17 to 24 μm/m-° C., and more particularly is about 19 μm/m-° C.
Articles made in accordance with the present invention exhibit excellent impact resistance and other mechanical properties. It is contemplated, for example, that automotive vehicle components will meet or exceed standards for energy management in side impacts, knee bar and glove box door impact, header and rail head impacts and/or bumper performance, such as United States Federal Motor Vehicle Safety Standard (“FMVSS”) 214, FMVSS 208, FMVSS 201, and/or otherwise embodied in 49 C.F.R. 581.
The materials of the present invention are suitable for any of a number of different applications, ranging from automotive vehicle components, to construction materials, to appliances, and other applications. Examples include, without limitation, a spare tire well liner, a cargo liner, a bed-liner, a seat back, a vehicle dashboard, vehicle instrument panel, a knee bar, a glove box, vehicle interior trim, a bumper, a spoiler, an air diffuser, a hood scoop, an air dam, a fuel tank, a sun roof deflector, a vehicle stone guard, an automotive body panel, a vehicle wheel well liner, a shifter knob, a switch knob, a hand-brake brake handle, a luggage roof box, a door handle, body armor, a helmet, a boat hull, a flotation device, a shipping container, luggage, an attaché, a shin guard, an elbow pad, a knee pad, a chest protector, a face mask, a pipe, a tabletop, a pressure vessel, a protective shield, downhole drilling equipment housing, a boat hull, a safe, a lock, a fluid container, a flooring, a wall or other panel, roofing, a refrigerator housing, a washer/dryer housing, benches, seats, rails, a hand tool, a prosthesis, an orthotic, a wheelchair or component thereof, a television housing, audio equipment housing, a portable tool housing, a camera housing, a consumer electronic product housing, an air conditioner compressor housing, a beam, a girder, a fascia, a shutter, shoe soles or otherwise.
As seen in FIG. 4E-G, the elongated member 214 (having a width (w)) of the intermediate form may be wrapped or wound (e.g., helically) around a core pipe 216 in a manner suitable for making hose or pipe, and optionally consolidated. In one aspect, multiple elongated members may be braided together to cover the core pipe, which may in turn lead to increased durability and low temperature impact resistance of the pipe. Any suitable angle (α) may used for the winding(s) of the elongated members around the core pipe, with the angle being preferably about 30° to 90° relative to the perpendicular axis of the pipe. More preferably, the angle of the winding angle is greater than about 45°, and more preferably greater than 50° but less than 55° (e.g., about 45° to 54°). In one aspect, for achieving an especially attractive combination of axial and hoop stress performance, an angle of about 54.7°. However, it should be appreciated that even larger winding angles are desirable if possible, such as greater than about 60° (e.g., from 60 to 75°), or even greater than about 75°. Any suitable intermediate form may be employed, including windings, weaves or a combination. Consecutive windings may adjoin or overlap each other, or they may be spaced relative to each other such as by a pitch distance (p), which may range up to about 10, 25 or even about 50 mm or more, such as for a pipe having a diameter (d) of from about 5 to 500 mm, 1000 mm or even 2000 mm, and more specifically about 10 mm to 100 mm or larger. The number of layers of windings may vary for achieving the desired properties in the resulting pipe. For example, the number of winding layers may range from about 1 to 100, or even from about 2 to 50. Some embodiments may employ up to about 25 winding layers, and some may contain as few as about 10 or less winding layers.
In one aspect, the core pipe is covered with multiple layers of elongated members, such as two, three, four, five or more layers. The same or different materials may be used for each layer. In a preferred embodiment, at least two layers of the same materials are used to cover the core pipe. Each layer is counterwound in the opposite direction at an identical angle to the perpendicular axis enabling a balanced layer structure. It should be appreciated, of course, that as between each winding layer it is possible to vary the winding angle, to vary the composition or other characteristic of the elongated member, to vary the width or thickness of the elongated member, to apply a film layer, to apply a coating, to vary the pitch distance, or any combination thereof. The step of winding can be performed at room temperature. It may also be performed at an elevated temperature (e.g., at least about 40° C.
The pipe may be consolidated at any point, and generally thereafter will exhibit a substantial retention of morphology from its initial state in any elongated member portion. For example, the core pipe may be consolidated before being covered by the jacket. In one preferred approach, the pipe is consolidated after one or more of the layers cover the pipe core or after the protective jacket covering has been added. In addition, multiple consolidation steps may be utilized, although only one consolidation step is preferred. One advantageous approach is to apply an intermediate form over a pipe and then consolidate the intermediate form (e.g., by conducted heat, convective heat, radiant heat, or a combination thereof). Consolidation may take place at an elevated temperature (e.g., for a polyolefinic elongated member) of about 100 to about 175° C., and more specifically less than about 150° C.) for a sufficient period of time (e.g., about 1 to about 5 minutes). Longer or shorter times are also possible, e.g., up to about 0.25 hour or longer (as taught previously). In the course of consolidation, assuming the material of the elongated member of the intermediate form will at least partially melt and fuse to the pipe. Under such approach, it is possible to secure the reinforcement layers from the intermediate forms to the underlying pipe without an optional step of laser welding or other local heat treatment.
Preferably, the pipes constructed according to this invention meet or exceed the following physical parameters, such as hoop stress performance of greater than about 10 MPa at 20° C. for 50 years; slow crack growth (SCG) performance (per test method ISO 13479) of greater than at least 500 h, and more particularly greater than 1000 h at 9.2 bar at 80° C.; rapid crack growth (RCP) performance (per test method ISO 13477) of greater than 10 bar at 0° C.; or a combination of both characteristics
In one exemplary embodiment, a pipe is constructed with an inner pipe (e.g., a thermoplastic inner pipe, such as a polyethylene, a polypropylene or a combination thereof, two exterior layers of consolidated coextruded tapes, which initially are applied to the inner pipe as an unconsolidated winding or woven intermediate form. The tapes have at least an A-B component structure as described elsewhere herein, and particularly a microlayer structure having plural alternating A and B layers. In one particular example, before applying the tapes to the inner pipe, the tapes will have been drawn to a draw ratio of at least 4, more specifically at least 8, and even more specifically, at least 12 (e.g., 16). Each layer of coextruded tapes is applied by winding at least one elongated member at a winding angle of from about 50 to about 60° (e.g., 54°). The tapes are consolidated while disposed on the inner pipe by heating at above 150° C. for at least one minute (e.g., at 160° C. for four minutes), but preferably shorter than about 0.25 hour. When compared to the core pipe alone, the exemplary pipe shows at least a 20% and more preferably at least a 30% better burst strength (per test method ISO 1167, using a pressure increase of 1 bar min−1 until failure). When hoop stress performance (per test method ISO 1167) is compared (using 80° C. at 7 MPa), the core pipe alone fails in under 10 hours, while the exemplary pipe fails only after about 250 hours. An exemplary pipe made with four layers of coextruded tapes, similar to that described above exhibits no failures for at least 500 hours, and more preferably at least about 1000 hours of testing.
Performance of a consolidated sheet (1.85 mm thickness) of coextruded tape including an propylene-ethylene copolymer co-extruded with a polypropylene homopolymer as disclosed herein (designated as Sample X) (about 0.04 mm thick by 3 mm wide) is compared with the performance of materials such as that available commercially under the designation CURV™ (denoted respectively as “Sample A” and “Sample B”) in the 1.5 and 2.2 mm thicknesses shown), using a falling dart impact test (per ISO 7765-1) at room temperature and at (−)40° C. FIGS. 5A and 5B illustrate data obtainable according to a preferred embodiment of the present invention.
A spare tire bin is injection molded with a polypropylene bulk material, along with a three layer (3L) consolidated twill woven coextruded polypropylene tape (about 0.04 mm thick by 3 mm wide) intermediate form on one side of the polypropylene bulk material. The resulting article is ruck free and exhibits a 400% improvement as compared with a 40% long glass fiber composite with a 20% glass filled polypropylene matrix, when impacted at 8 MPH at −30° C. A complete ductile break is observed without shattering; i.e., no flying pieces are observed during impact.
Example 2 is repeated but the intermediate form is placed on both sides of the polypropylene bulk material, exhibiting enhanced stiffness and impact resistance relative to the Example 2 composite.
Example 3 is repeated but with a monolayer polypropylene tape in the twill weave of the intermediate form. The resulting article is ruck free and exhibits improvement as compared with a 40% long glass fiber composite with a 20% glass filled polypropylene matrix, when impacted at 8 MPH at −30° C. A complete ductile break is observed without shattering.
A sample of a spare tire bin (2.2 cm deep, 15 cm wide, 25 cm long and wall thickness of 2.25 mm) composite is fabricated from a consolidated six layer (6L) intermediate form made with woven coextruded polypropylene tape (each layer being about 0.18 mm thick consolidated). The intermediate form is positioned on the bottom of the bin. It is impact tested and compared with baseline blow molded material a 30% short glass fiber reinforced polypropylene. The test employs an actuator velocity of 8 mph, a fixture with a 5.1 cm round impactor. The test is done at room temperature and at −30° C., and involves hitting the bottom of the bin, off center, with the intermediate form positioned so that it is in tension for receiving the load. The results are shown in the graphs of FIGS. 6A and 6B.
By way of illustration of one constrained consolidation operation for a multiple layer woven intermediate form, it is possible that a compression moulding press with manual controls is heated-up to pre selected temperature (e.g., from 110 to 150° C.). A woven intermediate form in accordance with the above teachings is cut to the same size as the plates of the press (e.g., 30×30 cm, with the fabric being cut parallel with the direction of the fibers). Layers of the fabric are stacked up and placed between a protective layer (e.g., a Mylar film), and this stack is placed between a top and a bottom metal plate, which is delivered to the press. The press is immediately closed, and a force is applied (e.g., 150 kN is applied for 1 minute). Subsequently, the force is increased (e.g., to 350 kN for 3 minutes). Press heating is switched off and open water cooling of the press is performed, while the workpiece is still under pressure. The press is opened and the plates and Mylar film is removed. The resulting workpiece exhibits consolidation (e.g., with a density greater than 95% theoretical density).
By way of example of one thermoforming operation, a compression moulding press (e.g., a manually operated one equipped with a mold for square cups dimensioned as 20×20×4 cm). Extruded polypropylene sheet is laminated on both sides with a layer of a woven intermediate form (e.g., by sheet extrusion). The laminated sheet is heated in the press (5 minutes contact heat) followed by thermoforming and cooling the press under pressure before demoulding. The temperatures of different samples are varied from 180 to 165 to 150° C. It is observed that delamination near the highly stressed and sharp corners becomes lower at the reduced temperatures.
A consolidated intermediate form (30×30 cm plate surface) is thermoformed on a manual Fonteyne compression moulding press, equipped with a square cup mold. The initial forming temperature (Tmale side and female side) is 150° C. It is heated 5 minutes in the press, by contact heat. Then the press is closed and for 1 minute a force of 50 kN is applied. The resulting article exhibits an attractive surface finish.
An extruder (operated at a temperature of 165 (drop-in) to 190° C., and a die temperature of 200° C.) is used. Upper, middle, and lower roll temperatures are respectively 90, 80, and 40° C. A line speed of 0.8-0.10 m/min is used. The feed stock has a sheet width of 35 cm, a thickness of 1.0 to 1.2 mm polypropylene, and the intermediate forms are each 0.2 mm thick and 50 cc wide. The intermediate forms are fed at the first roll from above, and in a separate run, the intermediate forms are fed at the first roll from below. In yet another run, opposing layers of the intermediate form are fed from the top and the bottom at the first roll. Good adhesion is obtained, with no or insignificant amounts of warpage detected.
Reference herein to “first” and “second” are not intended as limiting to combinations that consist of only first and second items. Where so-referenced, it is possible that the subject matter of the present invention may suitably incorporate third, fourth or more items. Reference to “elongated member” is not intended to foreclose coverage of a plurality of elongated members. Further, reference to “(meth)acrylate” refers to either or both of acrylate and methacrylate. Except where stated, the use of processing steps such as “consolidating” or “shaping” or their conjugates do not require complete consolidation or shaping; a partial consolidation or shaping is also contemplated. The disclosure of an “A-B” component structure does not foreclose the presence of additional layers, or additional materials that differ from components A and B. Moreover, the disclosure of “a” or “one” element or step is not intended to foreclose additional elements or steps. Use of the term “about” or “approximately” in advance of a range denotes that both the upper and lower end and not intended as being bound by the amount recited in the range (e.g., “about 1 to 3” is intended to include “about 1 to about 3”). Unless otherwise stated, or as dictated otherwise by the context of usage, references to “mixtures” or “combinations” of polymers contemplates alloys, blends or even co-polymers of such polymers.
Unless stated otherwise, dimensions and geometries of the various embodiments depicted herein are not intended to be restrictive of the invention, and other dimensions or geometries are possible. Plural structural components step can be provided by a single integrated structure or step. Alternatively, a single integrated structure step might be divided into separate plural components or steps. However, it is also possible that the functions are integrated into a single component or step. “Comprising”, “having”, and “including” and their word forms also contemplate the more restrictive terms “consisting of” and “consisting essentially of”.
Degree of crystallinity is measured by differential scanning calorimetry (DSC) using a Q1000 TA Instrument. In this measurement a small ten milligram sample of the propylene polymer is sealed into an aluminum DSC pan. The sample is placed into a DSC cell with a 25 cubic centimeter per minute nitrogen purge and cooled to about minus 100° C. A standard thermal history is established for the sample by heating it at 10° C. per minute to 225° C. The sample is kept at 225° C. for 3 minutes to ensure complete melting. The sample then is cooled at 10° C. per minute to about −100° C. The sample is again kept isothermal at −100° C. for 3 minutes to stabilize. It is then reheated at 10° C. per minute to 225° C. The observed heat of fusion (ΔHobserved) for the second scan over a range of 80-180° C. is recorded. The observed heat of fusion is related to the degree of crystallinity in weight percent based on the weight of the sample (e.g., sample of polypropylene) by the following equation: Crystallinity %=(ΔHobserved)/(ΔHisotactic pp)×100, where the heat of fusion for isotactic polypropylene (ΔHisotactic pp) is reported in B. Wunderlich, Macromolecular Physics, Volume 3, Crystal Melting, Academic Press, New York, 1960, p 48, is 165 Joules per gram (J/g) of polymer. The peak temperature of crystallization from the melt is determined by the DSC as above with a cooling rate of 10° C./min. The melting temperature is determined by the peak of the melting transition. A similar analysis would apply for materials other than polypropylene, substituting reported ΔH values for the other materials.
Molecular weight distribution (MWD) (e.g., for the polypropylene homopolymers) is determined by gel permeation chromatography (GPC) as follows. The polymers are analyzed by gel permeation chromatography (GPC) on a Polymer Laboratories PL-GPC-220 high temperature chromatographic unit equipped with four linear mixed-bed columns, 300×7.5 mm (Polymer Laboratories PLgel Mixed A (20-micron particle size)). The oven temperature is at 160° C. with the autosampler hot zone at 160° C. and the warm zone at 145° C. The solvent is 1,2,4-trichlorobenzene containing 200 ppm 2,6-di-t-butyl-4-methylphenol. The flow rate is 1.0 milliliter/minute and the injection size is 100 microliters. A 0.2% by weight solution of the sample is prepared for injection by dissolving the sample in nitrogen purged 1,2,4-trichlorobenzene containing 200 ppm 2,6-di-t-butyl-4-methylphenol for 2.5 hrs at 160° C. with gentle mixing.
Melt flow rate is measured in accordance with ASTM D 1238-01 test method at 230° C. with a 2.16 kg weight for the propylene-based polymers. Melt index for the ethylene-based polymers is measured in accordance with ASTM D 1238-01 test method at 190° C. with a 2.16 kg weight.
Isotactic pentad percent, Isotactic triad percent and the Isotactic pentad/triad ratio are determined by one of ordinary skill in the art according to the following: 13C nuclear magnetic resonance (NMR) provides a direct measure of the tacticity of poly(propylene) homopolymers. The analysis used here neglects chain ends and inverse insertions. For the triad names (mm, mr, and rr) ‘m’ stands for meso, and ‘r’ stands for racemic. The isotactic triad percent is a measure of the mm triads. V. Busico, R. Cipullo, G. Monaco, M. Vacatello, A. L. Segre, Macromolecules 1997, 30, 6251-6263 describes methods for determining isotactic pentad and triads using NMR analysis.
The isotactic pentad/triad ratio is the ratio of the isotactic pentad percent to the isotactic triad percent. In determining the isotactic pentad and triad values, the samples are prepared by dissolving 0.5 g of the polypropylene homopolymer in a mixture of 1.75 g of tetrachloroethane-d2 (TCE-d2) and 1.75 g of 1,2-orthodichlorobenzene. Samples are homogenized in a heating block at 150° C. and heated with a heat gun to facilitate mixing. NMR experiments are performed on a Varian Unity+400 MHz, at 120° C., using a 1.32 sec acquisition time, 0.7 sec repetition delay, 4000 acquisitions and continuous proton decoupling (fm-fm modulation), with and without spinning the sample. Total scan time used is 2.25 hrs.
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Influence of dispersed rubbery phase, Polymer vol. 35, No. 14 1994 p. 2995-3004.* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS8241736Nov 7, 2011Aug 14, 2012Cryovac, Inc.Multilayer, heat-shrinkable film comprising a plurality of microlayersUS8409697Jun 28, 2012Apr 2, 2013Cryovac, Inc.Multilayer, heat-shrinkable film comprising a plurality of microlayersUS8505432 *Sep 10, 2010Aug 13, 2013Alliant Techsystems, Inc.Multilayer backing materials for composite armorUS8667879 *Jul 9, 2013Mar 11, 2014Alliant Techsystems Inc.Multilayer backing materials for composite armorUS8820133 *Sep 30, 2008Sep 2, 2014Apple Inc.Co-extruded materials and methodsUS9534153Jul 3, 2013Jan 3, 2017Intertape Polymer Corp.Carton sealing tapeUS20090197059 *Sep 30, 2008Aug 6, 2009Apple Inc.Co-extruded materials and methodsUS20120060676 *Sep 10, 2010Mar 15, 2012Alliant Techsystems Inc.Multilayer backing materials for composite armorWO2013084084A1 *Oct 22, 2012Jun 13, 2013Kimberly-Clark Worldwide, Inc.Tough multi-microlayer films* Cited by examinerClassifications U.S. Classification428/335, 428/411.1, 428/516, 428/515International ClassificationB32B7/00Cooperative ClassificationY10T428/1393, Y10T428/24975, Y10T428/139, Y10T428/1359, Y10T428/1352, Y10T428/1303, Y10T428/264, Y10T428/2495, Y10T428/13, Y10T428/31504, Y10T428/24942, Y10T428/31913, Y10T156/10, Y10T428/31909, Y10T442/2008, D10B2505/02, D10B2401/041, D10B2321/022, D10B2321/021, D03D15/0088, D03D15/00, B32B27/32, B32B1/00, B29K2023/12, B29K2023/0641, B29C2043/3631, B29C2043/3602, B29C70/04, B29C51/004, B29C43/36European ClassificationB29C43/36, B29B11/16, B29C70/04, D03D15/00, B32B1/00, B32B27/32, B29C51/00B2, D03D15/00O2Legal EventsDateCodeEventDescriptionDec 17, 2010ASAssignmentOwner name: DOW GLOBAL TECHNOLOGIES INC., MICHIGANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:THE DOW CHEMICAL COMPANY;REEL/FRAME:025519/0739Effective date: 20101202Owner name: THE DOW CHEMICAL COMPANY, MICHIGANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:DOW BENELUX B.V.;REEL/FRAME:025519/0696Effective date: 20101202Owner name: DOW BENELUX B.V., NETHERLANDSFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:WEVERS, RONALD;REEL/FRAME:025519/0673Effective date: 20101124Owner name: DOW GLOBAL TECHNOLOGIES INC., MICHIGANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:CHEN, HONGYU;MCLEOD, DAVID G.;SIGNING DATES FROM 20101124 TO 20101129;REEL/FRAME:025519/0659Mar 30, 2011ASAssignmentOwner name: DOW GLOBAL TECHNOLOGIES LLC, MICHIGANFree format text: CHANGE OF NAME;ASSIGNOR:DOW GLOBAL TECHNOLOGIES INC.;REEL/FRAME:026047/0635Effective date: 20101231Jun 5, 2015REMIMaintenance fee reminder mailedOct 25, 2015LAPSLapse for failure to pay maintenance feesDec 15, 2015FPExpired due to failure to pay maintenance feeEffective date: 20151025RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services