Patent Application
20170137977
1. Field
The present subject matter relates to an oriented tape including high density polyethylene and polypropylene, woven cloths made therefrom, and end products of commercial use in packaging applications, and applications such as ground cover.
2. Description of Related Art
Flexible intermediate bulk containers (FIBCs) utilize various fabrics (such as woven polypropylene and PVC coated fabrics) and various fabric weights and sewing methods, depending on the necessary strength of the bag and its desired factor of safety. Such bags vary in size to generally hold from 5 to 120 cubic feet of material and up to about 6,000 pounds of product. They generally can be designed with various shaped tops suitable for filling, can have a solid bottom or a sewn-in discharge spout configuration, and have lifting handles. For dry or fluidized products that require a more rigid bag for stability, solid support inserts may be placed inside the bag, and between the outer bag surface and a liner (if one is used) to provide the bag's sidewalls with more rigidity.
It has been discovered that an oriented polyolefin tape, comprising a blend of 5 wt % to 35% polypropylene homopolymer (PP), with 65 wt % to 95% high density polyethylene (HDPE), with or without minor components of additives, when melt blended, such as in a single screw extruder as practiced here or in a comparable extrusion system such as a twin screw extruder, cast and machine direction (MD) oriented, produces a slit tape with mechanical properties which are superior to oriented tapes produced in the same manner from the individual HDPE or PP resins.
When woven into fabrics, the fabric properties are superior in physical properties to fabrics woven from the tapes produced either from the HDPE or from the PP resin alone. The FIBC bags produced with the woven fabric also demonstrate the superior performance of the individual tapes. It was also discovered that the weaving properties of the blended tapes are superior to those of 100% PP or PE tape.
Selection of the HDPE/PP pairs are based upon the relative melt viscosity of the resin pairs used to control the production of a desired fibrous morphology for the dispersed PP phase in the HDPE continuous phase.
The tapes of the subject matter can be further improved in weaving and physical property performance by the addition of a co-extruded layer of HDPE to the surfaces of the oriented tape of the subject matter.
It has also been discovered that the UV stability of the blended tape is significantly improved in comparison to the 100% PP tapes allowing for at least a 50% reduction in UV additive concentrations in the blend tapes and subsequent fabric. As the use of UV additives result in a loss of physical strength of the oriented tapes, this result can be used to reduce the additive concentration giving further physical property improvement at comparable levels of UV resistance performance. UV stability was measured according to norm SR EN 21898/Annex A. Successful passage of the test is that a tape retains 50% of its initial strength and elongation properties at 200 hours exposure.
The tapes of the subject matter can be woven into fabrics which can be fabricated into containers such as bags, including FIBC bags, shipping sacks and dunnage bags. Other useful products such as ground cover; geotextiles, such as those used to line waste dumps, holding ponds and settling ponds; and straps and ropes can be made from the tapes of the subject matter. This woven fabric and other products produced from the woven fabric have an improved hand and fabric softness which will be an improvement in the perception of the fabric and bags and other articles of commerce produced from the woven fabric. The woven fabrics of the present subject matter can offer efficiency improvement in the bag fabrication step, in terms of time to make the bag and safety from less rigid fabric.
The bags made from the woven fabric of the blended tapes have a broader usable temperature range for customer use than either the PP or PE only bags. In particular this will provide benefits for high temperature filling of pure PE bags and low temperature storage & usage of PP only bags.
The tapes and containers of the subject matter may also be made electrically conductive. For instance, any tape, woven cloth or fiber herein may further comprise electrically conductive filaments including conductivity increasing additives to render the product electrically conductive. The conductivity increasing additive may include at least one of carbon black, graphite, a metal such as silver, platinum, copper, aluminum, and others, an intrinsically conducting polymer (ICP) such as polyaniline, polyacetylene, polyphenylene vinylene, polythiophene, polyphenylene sulfide, and others.
Due to the superior strength observed for the blended tapes it should be possible to decrease the thickness of the tapes while matching the existing physical properties requirements of FIBC bags currently used. Alternatively, the strength of the bags may be increased allowing a producer to develop new customer end-use applications.
As will be realized, the subject matter described herein is capable of other and different embodiments and its several details are capable of modifications in various respects, all without departing from the claimed subject matter. Accordingly, the drawings and description are to be regarded as illustrative and not restrictive.
Broadly, the subject matter relates to an oriented tape comprising polypropylene homopolymer, high density polyethylene, optional compatibilizers, and optional fillers such as reinforcing fillers, UV additives, and a process of making the tape as well as woven articles made from the tape. Use of the tapes and woven articles of the subject matter is envisioned also. The subject matter includes a process of making an oriented tape. Each component, process, and use is described hereinbelow.
The oriented tape comprises polypropylene homopolymer and high density polyethylene. The polypropylene homopolymer may be isotactic or syndiotactic. The polypropylene homopolymer (PP) useful herein has a melt flow index (MFI) at 230° C./2.16 kg of 0.5-8, preferably 1-7, and successively more preferably 1.2-6; 1.5-4; 1.6-3; 1.7-2.5; and 1.8-2.2. Most preferably, the polypropylene MFI is 1.9-2.1. The Melt Flow Index (MFI), or Melt Flow Rate (MFR), (used interchangeably) is determined according to ISO 1133, or ASTM 1238-04c, “Standard Test Method for Melt Flow rates of Thermoplastics by Extrusion Plastometer,” as known in the art. When other sources of polypropylene are used, useful alternate polypropylene MFIs include 2.2-3.8 and successively more preferably: 2.4-3.6; 2.6-3.4; and 2.8-3.2. In this alternate embodiment, the most preferable polypropylene MFI is 2.9-3.1. The density of polypropylene homopolymer useful herein may be 0.890.-0.946 g/cc, preferably 0.895-0.940; successively more preferably: 0.90-0.935; 0.905-0.930; and 0.905-0.928. Most preferably, the polypropylene density is 0.905-0.915.
Polypropylenes made by Ziegler-Natta or metallocene catalysis and in combination with any co-catalyst, modifiers and/or catalyst support are suitable in the present subject matter. Any known polymerization technique may be used to produce the polypropylenes useful in the subject matter, for example bulk, gas phase and bulk/gas combination polymerization. Commercial manufacturers and/or sellers of polypropylene useful herein include from Saudi Basic Industries Corporation (Sabic); LyondellBasell Industries, Braskem, Mitsui Chemical, Inc, ExxonMobil Chemical, Borealis AG; Unipetrol Deutschland, GmbH, Reliance Industries, Ltd., and others. Suitable polypropylenes herein include those sold under the Mosten™ trademark from Unipetrol Deutschland GmbH such as Mosten™ TB002 and Reliance H030SG, available from Reliance Industries Ltd, as well as other polypropylene products commercially available.
In many embodiments and as described herein, the polypropylenes useful in the present subject matter are polypropylene homopolymers. However, it will be understood that the present subject matter may in certain versions include the use of polypropylene copolymers and/or terpolymers instead of, or in addition to, polypropylene homopolymer.
The high density polyethylene (HDPE) useful herein has a melt flow index at 190° C./2.16 kg of 0.1-3.5, more preferably 0.15-3. The HDPE MFI is successively more preferably 0.17-2.5; 0.17-2; 0.17-1.5; and 0.17-1.25. Most preferably, the HDPE MFI is 0.17-0.95. The density of high density polyethylene useful herein is 0.941-0.997 g/cc, and successively more preferably 0.943-0.985; 0.947-0.980; 0.950-0.975; and 0.953-0.970. Most preferable is HDPE with a density of at least 0.955 g/cc. High density polyethylene made by Ziegler-Natta, chromium or metallocene catalysis and in combination with any co-catalyst, modifiers and/or catalyst support are suitable in the present subject matter. Any known polymerization technique may be used to produce the polyethylene useful in the subject matter, for example gas phase, slurry and solution polymerization.
Commercial manufacturers and/or sellers of high density polyethylene useful herein include Saudi Basic Industries Corporation (Sabic); LyondellBasell Industries; Borealis AG; ExxonMobil Chemical, Chevron Phillips Chemical, INEOS Polyolefins, TVK Polska, Slovnaft and others. Specific suitable high density polyethylenes include those sold under the Sabic™, Basell™, Tipelin™ and Borealis™ trademarks from the companies of the same names above, for example, Sabic™ FO4660, and Borealis™ VS5580 as well as and other high density polyethylene products commercially available.
A summary of the properties of several selected resins and fillers appears in Table 1.
The proportions of polypropylene homopolymer (PP) and high density polyethylene (HDPE) in the melt blend can be 5-35 wt % PP and 65-95 wt % HDPE; alternately 10-30 wt % PP and 70-90 wt % HDPE; alternately 12.5-25 wt % PP and 75-87.5 wt % HDPE, alternately 15-22.5 wt % PP and 77.5-85 wt % HDPE. In certain embodiments, the melt blends used in the present subject matter tapes consist essentially of polypropylene homopolymer as described herein and high density polyethylene as described herein. In particular embodiments, the melt blends consist of polypropylene homopolymer as described herein and high density polyethylene as described herein.
Fillers and additives. A variety of fillers and additives can be used in producing the oriented tapes of the subject matter. Fillers are added to change physical properties of a thermoplastic material, such as whiteness, coefficient of friction, and stiffness. Filler materials useful in the present subject matter include hard clays, soft clays, chemically modified clays, mica, talc, calcium carbonate, dolomite, titanium dioxide, amorphous precipitated hydrated silica and mixtures thereof. Other filler materials are known in the art. CaCO3 masterbatch concentrates in a polyolefin such as polyethylene or polypropylene are suitable in the present subject matter.
Flame retardant fillers may be used. Useful flame retardant fillers include bayerite aluminum hydroxide, gibbsite aluminum hydroxide, boehmite, magnesium hydroxide, phosphorus or organophosphorus compounds, melamine cyanurate, antimony oxide; and/or halogenated organic compounds such as dipentaerithritol, tetrabromobisphenol A carbonate oligomer, brominated polystyrene, melamine cyanurate, brominated phenoxy polymers, dioctyl tetrabromo terephthalate, decabromodiphenyloxide, tetrabromobisphenol A, brominated polymeric epoxy, polydibromophenylene oxide, and others. Flame retardants may be used in an amount of up to 5 wt %, alternately 0.1-5 wt %, alternately 0.5-3 wt %, alternately 1-2.5 wt %.
Functional additives may be included in the melt blend to impart desired properties to the final extruded tape or cloth woven therefrom.
One type of additives, UV additives, also known as UV inhibitors serve to limit or eliminate the detrimental effects of high-energy ultraviolet radiation on thermoplastic compositions by absorbing the radiation. The tapes of the subject matter typically include, at the melt-blend stage, up to 3 wt % of at least one UV additive.
UV additives useful in the practice of the present subject matter include hindered amines, substituted hydroxyphenyl benzotriazoles, carbon black, benzophenone, barium metaborate monohydrate, various phenylsalicylates, nickel dibutyl dithiocarbamate, phenylformamidine, titanium dioxide, and others. The inventors herein have found that the polymer blend of the subject matter requires less UV additive to achieve similar or superior UV resistance to prior art polymer blends. The polymer blends of the subject matter can require as much as 10% less, and successively more preferably 20% less, 30% less, and 40% less UV additive than prior art blends. Most preferably, 50% less UV additive is required, as compared to a similar composition including polypropylene.
Fillers and additives can be added directly to a melt blend (neat), or as is commonly practice added in a masterbatch form that contains a polyolefin “carrier” that can be added to the melt blend. Fillers and additives may be added in the extruder. In the masterbatch, a PP or PE carrier, containing between 10-80% of the filler or additive, is used to deliver the filler or additive to the melt blend.
Accordingly, the melt blend may include 0-30 wt % of at least one filler, alternately 0-20 wt %. Other alternate or preferable ranges of filler that are useful include 0.1-20 wt %, 0-15 wt %, 0.1-15 wt %, 2-6 wt %, 1.6-4.8 wt %, 0-5 wt %, 0.1-5 wt %, 0.1-4 wt %, 2-4 wt %, 2-3 wt %, 0.5-3.5 wt %, 0.75-3.5%, and 1-3 wt %. Fillers may be added neat or as masterbatch. Useful fillers include CaCO3.
Additives, such as UV additives, additives useful herein may be delivered neat or in a masterbatch as discussed for fillers hereinabove. Tapes of the subject matter typically include, at the melt-blend stage, up to 3 wt % of at least one additive, for example 0.1 to 3 wt %. Other alternate or preferable ranges of additives include 0.1 to 2.5 wt %, 0.75-2 wt %, 0-1 wt %, 0.05-0.4 wt %, 0.05-1 wt %, 0.075-0.75 wt %, 0.1-0.5 wt %, 0.08-0.15 wt %. In another embodiment, the melt blend may contain no greater than 0.2 wt % neat of an additive such as a UV additive.
For all additives and fillers noted herein, it is envisioned, that any amount listed, whether delivered as masterbatch or neat, may be delivered in the other form to provide the same ultimate amount of active ingredient. For those ranges of fillers and additives not specified as masterbatch or neat, the presumption is that the filler is added neat.
An embodiment of the subject matter is an oriented polyolefin tape comprising an extruded and stretched melt blend comprising the components: (a) 5 to 35 wt % 0.5-8 MFI (230° C./2.16 kg) polypropylene homopolymer, (b) 65 to 95 wt % 0.3-3.5 MFI (190° C./2.16 kg) of high density polyethylene, (c) 0-30 wt % of at least one filler, (d) 0-3 wt % of at least one additive, and (e) 0-5 wt % of at least one compatibilizer. In one embodiment, the total of the components does not exceed 100 wt %. Preferably, the total of components (a)-(e) does not exceed 100 wt %.
The process of the subject matter involves several parameters. Broadly, the subject matter includes a process of making an oriented polyolefin tape comprising: (a) melt blending the components (i) 5 to 35 wt % 0.5-8 MFI (230° C./2.16 kg) polypropylene homopolymer and (ii) 65-95 wt % 0.1-35 MFI (190° C./2.16 kg) high density polyethylene to form a melt blend, (iii) 0-30 wt % of at least one filler, (iv) 0-3 wt % of at least one additive, (v) 0-5 wt % of at least one compatibilizer, (b) extruding the melt blend at 220-295° C. through a die to form an extrudate, (c) water quenching the extrudate, (d) slitting the extrudate to form at least one tape, and (e) heating and stretching the at least one tape at 50-500 m/min and 80-140° C. Preferably, the total of the components does not exceed 100 wt %; more preferably the total of the components (i)-(v) does not exceed 100 wt %.
The polypropylene homopolymer, high density polyethylene and optional additives (filler, UV additive and compatibilizer) are melt blended at a melt temperature of 200-300° C., preferably 220-295° C., more preferably 225-290° C., and successively more preferably 235-285, 240-280 and 245-275° C. Most preferably, the melt blending is undertaken at 250-275° C.
The melt blend is produced by charging the extruder with a mixture of solid pellets which are melted and blended by the extruder. The extruder may be single screw or twin screw. The extruder typically includes at least one of each of filter, melt pipe and die, such as a slot die. Melt pipes and dies are set to temperature ranges in the preceding paragraph. Useful extruders, include those commercially available from Starlinger GmbH, Vienna, Austria, Bag Solutions Worldwide, Vienna Austria, Yong Ming Machinery Manufacturing Co., Ltd, China.
Extruder screw speeds can vary, but are typically 25-250 rpm, preferably 50-200, more preferably 75-175 rpm, and yet more preferably 100-150 rpm. The slot die has a slot gap of 0.1-3 mm, preferably 0.2-1.5 mm, more preferably 0.25-1.0 mm, still more preferably 0.3-0.7 mm, yet more preferably 0.4-0.7 mm. In other embodiments, the die gap is 0.01 to 0.1 inches (0.254 to 2.54 mm). The melt blend is cast through the slot die into a water bath having a temperature of 20-60° C., preferably 25-55° C., more preferably 30-50° C., still more preferably 35-45° C. The gap between the slot die and the water bath is 10-150 mm, preferably 20-100 mm, more preferably 20-80 mm, still more preferably 20-75 mm even more preferably 30-50 mm, yet more preferably 30-40 mm, still more preferably 35-40 mm.
A cast sheet results, which has a thickness of 50-250 microns, preferably 60-240 microns, more preferably 70-230 microns, yet more preferably 80-220 microns, still more preferably 100-200 microns. The cast sheet is produced at a speed of about 30-70 m/min, preferably 35-65 m/min, more preferably 40-60 m/min, still more preferably 45-55 m/min. A cast sheet is slit with one or more knives into a plurality of tapes, such as 2-350. The tapes are then stretched through a hot air oven and stretched (or drawn) over a series of Godet rolls. The tapes may be stretched over Godet rolls both before in and after the oven, or only in or after the oven. The Godet rolls may precede or follow the oven. The hot air oven may have an air temperature of 80-150° C., preferably 90-140° C., more preferably 100-130° C., for example 115-125° C., or 120-130° C., which are lower temperatures than required for stretching pure polypropylene fibers. The stretching over the Godet rolls may be at a ratio of 2:1-10:1, preferably 3:1-9:1; more preferably 4:1-8:1, still more preferably 5:1-8:1. The tapes after stretching are wound on bobbins. The tapes are wound onto the bobbins at an angle of no greater than 8 degrees, preferably 3-8 degrees, preferably less than 6 degrees, preferably 4-5.5 degrees, more preferably 4.5-5.5 degrees. The final tapes wound onto the bobbins have a width of 0.5-5 mm, preferably 1-4.5 mm, more preferably 1.5-4 mm, yet more preferably 2-3.5 mm.
The tapes have surfaces that are flat or profiled, which results from the use of either of two types of die lips, flat or profiled. An advantage of the smooth tapes is that the denier can be adjusted more exactly. Conversely, an advantage of the profiled tapes is that the tape slips less (on the bobbin and after weaving in the fabric). Accordingly, it is envisioned that any tape in any embodiments herein may be flat or profiled.
The flat or profiled tapes have as-extruded width and thickness dimensions that are related to the final dimensions through the stretch ratio according to the relation that the final width (thickness) is the original width (thickness) divided by the square root of the stretch ratio. The stretch ratio is the ratio of the final tape speed as wound onto a bobbin divided by the cast tape speed. The tapes have a final thickness of less than 250 microns, preferably 10-250 microns, more preferably 15-200 microns, still more preferably 25-150 microns, yet more preferably 25-125 microns, and most preferably 25-75. In an alternate embodiment, the tapes have a thickness no greater than 250 microns, and successively more preferably <225, <220, <200, <175, <150, <125, <100, <75, <50, and <40 microns.
The tapes have an average weight of 700-2200 denier, preferably 800-1800, more preferably 900-1700. The tapes have a tenacity of 4-10 gm/denier, preferably 5-10 gm/denier, more preferably 6-10 gm/denier. The tapes have an elongation to break of 15-35%, preferably 20-30% more preferably 22.5-27.5%, and a residual shrinkage of less than 10%, preferably less than 5%, more preferably less than 4%, yet more preferably less than 3%, still more preferably less than 2%.
Without being bound by a particular theory, it is believed that the source of the increased physical properties of the HDPE/PP blend tapes is the production of oriented and crystallized PP fibrils within the HDPE matrix. This is demonstrated in Table 2.
Exemplary compositions formulated according to the principles of the subject matter bear out this belief, showing a high melting point of 168° C. observed for the PP component of (b) as compared to the second heat melting point of 162° C. observed for the PP by DSC (differential scanning calorimetry) in the second heat of (b). Also, this is to be compared to the DSC first heat melting point of 164° C. observed for the PP component in the cast sheet (i.e., “base sheet”) from which the drawn tapes were produced. DSC was performed per ASTM D 3418-08. Samples were heated at 10° C./min from 35° C. to 275° C., held at 275° C. for 5 minutes, cooled to 35° C. at 10° C./min, held at 35° C. for 5 minutes, then reheated to 275° C. at 10° C./min. All testing was performed in a nitrogen environment.
The increased PP first heat melting points of both the cast sheet and drawn tapes indicate a significantly increased level of molecular orientation and crystallization in the PP phase of the blend. The presence of highly oriented PP fibrils in the HDPE matrix would result in a PP fiber reinforced HDPE matrix which is believed to be the ultimate source of the superior strength of the blend tapes. It is believed that the PP domains in the blend are more highly oriented in the HDPE matrix as compared to commercial tapes due to the PP fibril orientation at the HDPE tape orientation temperatures which are significantly lower than the orientation temperatures typical of PP tape orientation and at higher effective stretch ratios which were achieved with the HDPE.
The increased first melting point of the HDPE in the matrix also indicates an increased level of orientation in the HDPE relative to the cast sheet.
The impact of the blend and the choice of HDPE resins on tape properties are seen in
Abbreviations used in Table 3 include:
Test Methods: Samples were tested using several standard methods listed below.
1. Tensile properties were measured with a separation speed of 250 mm/min and an initial jaw separation of 500 mm, according to EN ISO 13934.
2. Tenacity gm/9000 m
3. Shrinkage (Following ASTM D-4974-93 and DIN 53866)
Bag testing was conducted according to DIN EN ISO 21898
UV Weather exposure Tests: SR EN 21898/Annex A, Lamp B313.
The tensile properties of the tape are measured on a tensile tester by gripping and stretching at a fixed rate (in accordance with ISO 20629 or DIN 53834) and the force to break the tape is measured and reported as the Tenacity (equivalent to the ultimate strength) which is the strength at break for a tape of a specific size. The units of tenacity are gm/denier. The maximum load at break, in grams, is normalized to the cross sectional area of the tape using the denier as opposed to the cross sectional area of the tape. So the tensile force is reported as tenacity in gm/denier.
The total percentage of stretching at which the tape breaks in the tensile test is recorded as the percent elongation at maximum strength (Fmax) and is equivalent to the elongation at break
The tensile properties of the woven cloth are measured by both the (Strip Test according to EN ISO 13934 (DIN 53857) and the MD elongation is determined by the Grab Test according to DIN 53858.
Bag testing included burst tests and burst testing after thirty load cycles were applied to the bag. In these tests the test bags were filled with polymer pellets and suspended by its lifting straps on fixed arms in the test device. A ram was lowered into the bag and the force measured until the bag burst. The force to burst the bag was recorded as well as the type and location of failure. In the cycle testing the bag was preloaded thirty times to a fraction of the bursting load to pre-stress the bag. After the last cycle was complete, the load was increased until the bag burst.
98.2% Mosten TB002, a 2MFI (@230° C./2.16 kg) PP was blended with 0.5% PP79021/20UV (a UV concentrate) and 1% WPT1371 (a 70% CaCO3 concentrate in 3 MFI homopolymer polypropylene) and the blend charged to a single screw extruder fitted with a filter, melt pipe and slot die. The polymer blend was melted at a screw speed of 123 rpm producing approximately 54 kg/hr of melt at a melt temperature of 271° C. The melt pipe and die temperatures were set to 270° C. The melt was then extruded from a slot die with a nominal 0.5 mm slot gap, cast downwards into a water bath at approximately 38° C. with a die lip to water distance of approximately 50 mm. The resulting cast sheet was produced at approximately 52 m/min and was approximately 96 microns thick. The cast sheet was then slit into 30 tapes using knives and the edges removed. The slit tapes were transferred into a hot air oven set to 165/164° C. and stretched over a series of Godet rolls at a speed of 325.4 m/min to give a stretch ratio of approximately 6.2:1. The stretched tapes were then conditioned and relaxed approximately 7.8% over several more sets of Godet rolls to give a final tape speed of 300 m/min and a final stretch ratio of approximately 5.7:1. The tapes were wound on bobbins and set aside for testing and weaving.
Three of the thirty bobbins produced were tested. Tapes produced were 2.8 mm wide and 40 microns thick and had an average denier of 898 gm, strength of 6.75 gm/denier, an elongation to break of 20.9% and a residual shrinkage of 6.9%.
98% Sabic FO4660, a 0.7MFI (@190° C./2.16 kg) HDPE was blended with 2% WPT1371 and the blend charged to a single screw extruder fitted with a filter, melt pipe and slot die. The polymer blend was melted at a screw speed of 117 rpm producing approximately 60 kg/hr of melt at a melt temperature of 265° C. The melt pipe and die temperatures were set to 260° C. The melt was then extruded from a slot die with a nominal 0.5 mm slot gap, cast downwards into a water bath at approximately 35° C. with a die lip to water distance of approximately 40 mm. The resulting cast sheet was produced at approximately 49.5 m/min and was approximately 73.8 microns thick. The cast sheet was then slit into 30 tapes using knives and the edges removed. The slit tapes were transferred into a hot air oven set to 120/119° C. and stretched over a series of Godet rolls at a speed of 321.7 m/min to give a stretch ratio of approximately 6.4:1. The stretched tapes were then conditioned and relaxed approximately 6.7% over several more sets of Godet rolls to give a final tape speed of 300 m/min and a final stretch ratio of approximately 6:1. The tapes were wound on bobbins and set aside for testing and weaving.
Five specimens from one bobbin produced were tested. Tapes produced were 3.1 mm wide and 35 microns thick and had an average denier of 955 gm, strength of 4.76 gm/denier, an elongation to break of 44.53% and a residual shrinkage of 3.5%.
Next the blend of Comparative Example B was extruded and cast as in Comparative Example B, but then stretched at various stretch ratios to optimize the properties of the oriented tapes produced from the Sabic FO4660. An optimum the gm/denier strength and elongation properties was found at a maximum MD stretch ratio (MDX) of approximately 6.5 giving properties of 5.1 to 5.3 gm/denier with an elongation of approximately 13%.
Production Sample Tape #3. 98% INEOS ELTEX A4009MFN1325, a 0.9MFI (@190° C./2.16 kg) HDPE was blended with 2% WPT1371 and the blend charged to a single screw extruder fitted with a filter, melt pipe and slot die. The polymer blend was melted at a melt pump speed of 42 rpm (screw speed of 40.7 rpm) producing approximately 370 kg/hr of melt at a melt temperature of 264° C. The melt pipe and die temperatures were set to 265° C. The melt was then extruded from a slot die with a nominal 0.5 mm slot gap, cast downwards into a water bath at approximately 33° C. with a die lip to water distance of approximately 45 mm. The resulting cast sheet was produced at approximately 39.3 m/min and was approximately 99.82 microns thick. The cast sheet was then slit into 185 tapes using knives and the edges removed. The slit tapes were transferred into a hot air oven set to 105/105° C. and stretched over a series of Godet rolls at a speed of 300.0 m/min to give a stretch ratio of approximately 7.6:1. The stretched tapes were then conditioned and relaxed approximately 0.0% over several more sets of Godet rolls to give a final tape speed of 300 m/min and a final stretch ratio of approximately 7.6:1. The tapes were wound on bobbins and set aside for testing and weaving.
Five specimens each from eight bobbins produced were tested. Tapes produced were 2.8 mm wide and 42 microns thick and had an average denier of 1017 gm, strength of 5.64 gm/denier, an elongation to break of 33.8% and a residual shrinkage of 6.53%.
The tapes were woven into fabric which was sewn into bags for testing using DIN EN ISO 21898. The results in
All of the HDPE samples were optimized for properties by varying the MDX and the properties obtained are presented in
73% Sabic FO4660, a 0.7MFI (@190°/2.16 kg) HDPE was blended with 25% Mosten TB002, a 2MFI (@230° C.) PP and 2% WPT1371 and the blend charged to a single screw extruder fitted with a filter, melt pump, melt pipe and slot die. The polymer blend was melted at a melt pump speed of 38.5 rpm (screw speed of 50.9 rpm) producing approximately 330 kg/hr of melt at a melt temperature of 263° C. The melt pipe and die temperatures were set to 260° C. The melt was then extruded from a slot die with a nominal 0.5 mm slot gap, cast downwards into a water bath at approximately 35° C. with a die lip to water distance of approximately 40 mm. The resulting cast sheet was produced at approximately 36.2 m/min and was approximately 111.64 microns thick. The cast sheet was then slit into 165 tapes using knives and the edges removed. The slit tapes were transferred into a hot air oven set to 125/124° C. and stretched over a series of Godet rolls at a speed of 300.0 m/min to give a stretch ratio of approximately 8.2:1. The stretched tapes were then conditioned and relaxed approximately 0.0% over several more sets of Godet rolls to give a final tape speed of 330 m/min and a final stretch ratio of approximately 8.2:1. The tapes were wound on bobbins and set aside for testing and weaving.
Five specimens each from eight bobbins produced were tested. Tapes produced were 3.3 mm wide and 35 microns thick and had an average denier of 1005 gm, stretch of 7.01 gm/denier, an elongation to break of 23.6% and a residual shrinkage of 3.7%. This demonstrates the superior physical properties which can be produced from the blends as compared to 100% PP and 100% HDPE in Comparative Examples A, B, and C.
The Sample #1 blend without UV additive showed unacceptable UV aging performance (
The tapes were woven into fabric which was sewn into bags for testing using DIN EN ISO 21898. The results in
75% of Sabic FO4660, a 0.7MFI (@190° C./2.16 kg) HDPE was blended with 25% Mosten TB002, a 2MFI (@230° C.) PP, 1.0% PP79021/20UV (a 20% UV concentrate in 11 MFI homopolymer polypropylene) and 2% WPT1371 and the blend charged to a single screw extruder fitted with a filter, melt pump, melt pipe and slot die. The polymer blend was melted at a melt pump speed of 38.5 rpm (screw speed of 50.9 rpm) producing approximately 330 kg/hr of melt at a melt temperature of 263° C. The melt pipe and die temperatures were set to 260° C. The melt was then extruded from a slot die with a nominal 0.5 mm slot gap, cast downwards into a water bath at approximately 30° C. with a die lip to water distance of approximately 40 mm. The resulting cast sheet was produced at approximately 37.5 m/min and was approximately 109.57 microns thick. The cast sheet was then slit into 185 tapes using knives and the edges removed. The slit tapes were transferred into a hot air oven set to 125/124° C. and stretched over a series of Godet rolls at a speed of 300.0 m/min to give a stretch ratio of approximately 7.9:1. The stretched tapes were then conditioned and relaxed approximately 0.0% over several more sets of Godet rolls to give a final tape speed of 300 m/min and a final stretch ratio of approximately 7.9:1. The tapes were wound on bobbins and set aside for testing and weaving.
Five specimens each from nine bobbins produced were tested. Tapes produced were 3.1 mm wide and 39 microns thick and had an average denier of 992 gm, stretch of 6.41 gm/denier, an elongation to break of 24.9% and a residual shrinkage of 4.0%. This indicates that the addition of UV concentrate decreases the physical properties of the oriented tapes (well known for the 100% PP tapes). But as shown in Table 4, the UV stability of the blends with 1% UV concentrate are better than the pure PP UV stability at 1.5% UV concentrate. This demonstrates that the blends can be produced with lower percentages of UV additive which represents a material cost reduction and is an additional advantage of the blends relative to 100% PP tapes.
The Sample #2 blend with 1% UV additive showed comparable to better UV stability than the Standard PP tape with 1.5% UV additive (
The tapes were woven into fabric which was sewn into bags for testing using DIN EN ISO 21898. The results in
83.5% of Sabic FO4660, a 0.7MFI (@190° C./2.16 kg) HDPE was blended with 15% Mosten TB002, a 2MFI (@230° C.) PP, 0.5% PP79021/20UV (a UV concentrate) and 1% WPT1371 and the blend charged to a single screw extruder fitted with a filter, melt pipe and slot die. The polymer blend was melted at a screw speed of 138 rpm producing approximately 54 kg/hr of melt at a melt temperature of 272° C.
The melt pipe and die temperatures were set to 270° C. The melt was then extruded from a slot die with a nominal 0.5 mm slot gap, cast downwards into a water bath at approximately 38° C. with a die lip to water distance of approximately 40 mm. The resulting cast sheet was produced at approximately 37.5 m/min and was approximately 111.00 microns thick. The cast sheet was then slit into 30 tapes using knives and the edges removed. The slit tapes were transferred into a hot air oven set to 125/124° C. and stretched over a series of Godet rolls at a speed of 317.2 m/min to give a stretch ratio of approximately 8.5:1. The stretched tapes were the conditioned and relaxed approximately 5.38% over several more sets of Godet rolls to give a final tape speed of 300 m/min and a final stretch ratio of approximately 8.0:1. The tapes were wound on bobbins and set aside for testing and weaving.
Five specimens each from three bobbins produced were tested. Tapes produced were 3.1 mm wide and 39 microns thick and had an average denier of 922 gm, stretch of 6.51 gm/denier, an elongation to break of 25.8% and a residual shrinkage of 1.25%.
The Sample #3 tape with no UV additive showed superior UV stability relative to Sample #1 and exceeded the minimum acceptable property retention of 50% for both the tape strength and % Elongation as shown in
83.5% Borealis VS5580, a 0.95MFI (@190° C./2.16 kg) HDPE was blended with 15% Mosten TB002, a 2MFI (@230° C.) PP, 0.5% PP79021/20UV (a UV concentrate) and 1% WPT1371 and the blend charged to a single screw extruder fitted with a filer, melt pipe and slot die. The polymer blend was melted at a screw speed of 127 rpm producing approximately 54 kg/hr of melt at a melt temperature of 271° C. The melt pipe and die temperatures were set to 270° C. The melt was then extruded from a slot die with a nominal 0.5 mm slot gap, cast downwards into a water bath at approximately 38° C. with a die lip to water distance of approximately 40 mm. The resulting cast sheet was produced at approximately 37.5 m/min and was approximately 105.66 microns thick. The cast sheet was then slit into 30 tapes using knives and the edges removed. The slit tapes were transferred into a hot air oven set to 125/124 C and stretched over a series of Godet rolls at a speed of 307.3 m/min to give a stretch ratio of approximately 8.2:1. The stretched tapes were then conditioned and relaxed approximately 2.35% over several more sets of Godet rolls to give a final tape speed of 300 m/min and a final stretch ratio of approximately 8.0:1. The tapes were wound on bobbins and set aside for testing and weaving.
Five specimens each from three bobbins produced were tested. Tapes produced were 3.1 mm wide and 39 microns thick and had an average denier of 890 gm, strength of 6.54 gm/denier, an elongation to break of 26.8% and a residual shrinkage of 3.70%.
83.5% Sabic FO4660, a 0.7MFI (@190° C./2.16 kg) HDPE was blended with 15% Reliance H030SG, a 3MFI (@230° C.) PP, 0.5% PP79021/20UV (a UV concentrate) and 1% WPT1371 and the blend charged to a single screw extruder fitted with a filter, melt pipe and slot die. The polymer blend was melted at a screw speed of 128 rpm producing approximately 54 kg/hr of melt at a melt temperature of 271° C. The melt pipe and die temperatures were set to 270° C. The melt was then extruded from a slot die with a nominal 0.5 mm slot gap, cast downwards into a water bath at approximately 35° C. with a die lip to water distance of approximately 40 mm. The resulting cast sheet was produced at approximately 37.1 m/min and was approximately 106.99 microns thick. The cast sheet was then slit into 30 tapes using knives and the edges removed. The slit tapes were transferred into a hot air oven set to 125/125° C. and stretched over a series of Godet rolls at a speed of 307.3 m/min to give a stretch ratio of approximately 8.2:1. The stretched tapes were then conditioned and relaxed approximately 2.35% over several more sets of Godet rolls to give a final tape speed of 300 m/min and a final stretch ratio of approximately 8.0:1. The tapes were wound on bobbins and set aside for testing and weaving.
Five specimens each from three bobbins produced were tested. Tapes produced were 3.1 mm wide and 39 microns thick and had an average denier of 922 gm, strength of 6.43 gm/denier, an elongation to break of 27.4% and a residual shrinkage of 2.8%.
alternative HDPE continuous phase resin. 83.5 wt % Basell APC7440 F2, a 1.8MFI (190° C./5 kg) HDPE was blended with 15 wt % Mosten TB002, a 2MFI (2.16 kg/230° C.) PP, 0.5% PP79021/20UV (a UV concentrate) and 1% WPT1371 and the blend charged to a single screw extruder fitted with a filter, melt pipe and slot die. The polymer blend was melted at a screw speed of approximately 128 rpm producing approximately 54 kg/hr of melt at a melt temperature of approximately 271° C. The melt pipe and die temperatures were set to 270° C. The melt was then extruded from a slot die with a nominal 0.5 mm slot gap, cast downwards into a water bath at approximately 35° C. with a die lip to water distance of approximately 40 mm. The resulting cast sheet was produced at approximately 37.1 m/min. The cast sheet was then slit into 30 tapes using knives and the edges removed. The slit tapes were transferred into a hot air oven set to 125/125° C. and stretched over a series of Godet rolls at a stretch ratio of approximately 6.0:1. The blend ran poorly on the orienting equipment giving relatively low strengths of 6.0 gm/denier @25% elongation and continuous tape breaks. The test was stopped and no bobbins were produced for testing and weaving.
It is believed that this comparative example E indicates that the high viscosity of the APC 7440 F2 (
Having completed several runs on various pieces of commercial scale processing equipment it is clear that there is a melt processing interaction between the HDPE and PP where the resin combination determines the final physical properties of the oriented tapes and therefore woven fabric properties.
The test runs have achieved successful production of tapes with a lower HDPE MI, (viscosity) range than was previously believed. The resin experiment defines the range of acceptable combinations of HDPE and PP based on average resin viscosity (MI and MF). During the course of the program, the melt viscosity of the various HDPE and PP resins have been measured to improve understanding of the melt viscosity impact of the component resins on the blending effects.
The operational hypothesis for the blend property development is that the bulk melt phase (HDPE) viscosity disperses the dispersed phase (PP) melt into fibrils which are then cold stretched at HDPE stretching temperatures giving superior tape properties than the bulk HDPE phase would develop. It is believed that if the HDPE bulk phase viscosity is unable to produce the melt fibrils of PP then the tape properties will not be better than the HDPE tapes. This low strength HDPE/PP blend tape could occur if the HDPE viscosity is much higher than the PP melt viscosity resulting in a spherical PP dispersed phase of small diameter, or if the PP viscosity is much lower than the HDPE viscosity resulting in a large diameter spherical PP dispersed phase. The results of the experiment would support this hypothesis.
In part the suitability of the HDPE/PP resin blend is impacted by the (1) stretch ratio, (2) stretch temperature, (3) water bath to die quenching configuration and (4) the interaction between line speed and oven temperatures.
The water bath temperature also affects operability, particularly at start up. In addition, due to the low COF of HDPE to steel, the number of Godet rolls clearly affects the uniformity of the tape properties (8 rolls being insufficient for uniform stretching, and 10 rolls appearing to work quite well). There may also be an impact of the extruder barrel temperature profile on the PP domain morphology (shape) however.
Process conditions for the Resin experiment were determined with the blend of Sabic FO4660 HDPE/Tipelin FS 471-02 at a blend ratio of 82.5% HDPE/15% PP with the addition of 0.5% UV additive and 2% CaCO3 concentrate. Once optimum conditions are determined for the standard blend, the HDPE and PP resin MI and MF were varied to explore the significance of each on final tape properties. In particular the resin experiment will be a 22 design with a center point (see Table 5).
The process impact on tape properties were examined independently from the resin viscosity ranges in a separate Box-Behnken design.
Experimental: Materials:
The comparative resin viscosities are displayed in
The subject matter teaches range of 0.3 to 3.5 MI for HDPE and 0.5 to 8.0 MF for the PP. This experiment will explore the ranges of the HDPE MI and PP MF in a 22 design with a center point. Table 5 lists the treatment combinations and resins in design order. The order of runs is random.
During the run the same PP resin was used the HDPE resin was varied.
The combination of the 4 MI HDPE and 8 MF PP yielded no stretched tapes. However, for the purpose of the analysis the results for the 4 MI HDPE were substituted based on the assumption they represent the properties of the HDPE without the reinforcing effect of the dispersed PP. If the product had been successfully made one could presume that the base HDPE tape properties represented by test 2 [Treatment combination (a)] would have been obtained.
An additional test of the ExxonMobil HSY-800 (0.60 MI HDPE) with the 8 MF Hostalen GC7255, produced before the other resins were produced, yielded results where the HDPE strength was not enhanced by the PP addition indicating that the high MF PP phase was likely overdispersed to spherical domains as opposed to the desired fibrils of the patent.
At the start of the run, the Sabic FO4660 resins are blended with the Reliance H030SG PP resin and 2% CaCO3 and 0.5% UV concentrates to establish a starting point for the run and establish the center point for the designed experiment. Tape dimensions for the target fabric were determined as 900 den, tape width of 2.5 mm and the knife width set to 7.29 mm and the target sheet thickness at 0.123 mm. Warp tapes (not fibrillated) were produced. At this point the purpose was to determine the effect of resin changes.
Summary of the process conditions are as follows in Table 7.
The results obtained are presented in Table 8. The key finding is that the HDPE resin MI has a significant impact on tape properties (
Also from
Tape strength vs. HDPE MI (190° C., 2.16 kgm); in design units x=(−1, 0, 1).
Tape gm/den=−0.845x2−1.615x+6.31 Equation 1:
% Elongation=5.2525x+21.903 Equation 2:
Therefore, it becomes apparent that the HDPE as the continuous phase is controlling the morphology of the PP phase which then develops the improved blend properties. The PP, while important for the development of the tape properties, does not control the overall development of the tape properties.
Consequently, the most significant range in many applications will be the HDPE MI range, while the PP MF range can be broadened somewhat to represent its interaction with the continuous phase.
To determine the optimum HDPE MI range
Tape strength vs. HDPE MI (190° C., 2.16 kgm)
Tape gm/den=−0.9439[MI]+7.1782 Equation 3:
% Elongation=2.8903[MI]+17.175 Equation 4:
For example for minimum target tape strength of 5.5 gm/den, the HDPE MI should be:
MI=(5.5 gm/den−7.1782 gm/den)/(−0.9439 gm/den/MI)=1.78MI
This gives a tape elongation of 22% for the annealing conditions of the experiment.
Many other benefits will no doubt become apparent from future application and development of this technology.
All patents, applications, standards, and articles noted herein are hereby incorporated by reference in their entirety.
The present subject matter includes all operable combinations of features and aspects described herein. Thus, for example if one feature is described in association with an embodiment and another feature is described in association with another embodiment, it will be understood that the present subject matter includes embodiments having a combination of these features.
As described hereinabove, the present subject matter solves many problems associated with previous strategies, systems and/or devices. However, it will be appreciated that various changes in the details, materials and arrangements of components, which have been herein described and illustrated in order to explain the nature of the present subject matter, may be made by those skilled in the art without departing from the principle and scope of the claimed subject matter, as expressed in the appended claims.
This application is a continuation-in-part (CIP) application of U.S. Ser. No. 13/550,637 filed Jul. 17, 2012, which claims priority to U.S. Ser. No. 61/523,480 filed Aug. 15, 2011, and U.S. Ser. No. 61/551,481 filed Oct. 26, 2011, both of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61523480 | Aug 2011 | US | |
| 61551481 | Oct 2011 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13550637 | Jul 2012 | US |
| Child | 15257377 | US |
