Patent Application
20090163663
This application relates to a method of preparing an elastomeric thermoplastic polyurethane (TPU) blend, in particular, by extruding a mixture of a thermoplastic polyurethane, a polyolefin copolymer blend and an amine-modified polypropylene compatibilizer. The application further includes uses of this material, in particular, in escalator handrails.
Elastomeric materials are used in the escalator handrail industry. It has been estimated that over 80% of the cost of making an escalator handrail is attributed to the cost of the raw materials used in the construction of the handrail. The largest component when constructing handrails, in terms of both construction and cost, are thermoplastic polyurethane resins. Currently, the cost of thermoplastic polyurethane resins account for 80% of the raw material cost of making escalator handrails.
In accordance with the present disclosure, a method of preparing an elastomeric TPU blend is disclosed. In particular, the application discloses a method of preparing a TPU blend comprising reactively extruding a mixture of a TPU, a polyolefin copolymer blend and an amine-modified polypropylene compatibilizer, wherein the polyolefin copolymer blend is a blend of a polyolefin and an elastomeric olefin. The method of the present disclosure results in an elastomeric TPU blend material which significantly reduces the amount of TPU used in its construction, but retains the elastomeric and mechanical properties, such as tensile strength and modulus, of a TPU material.
The present disclosure therefore includes a method of preparing an TPU blend comprising reactively extruding a mixture comprising:
In particular, the present disclosure relates to a method of preparing a TPU blend comprising reactively extruding a mixture comprising:
In an embodiment of the disclosure, the TPU is selected from a polyester-based TPU or a polyether-based TPU. In another embodiment, the TPU is a polyester-based TPU.
In an embodiment of the disclosure, the polyolefin is selected from polyethylene or polypropylene. In another embodiment of the disclosure, the polyolefin is polypropylene.
In an embodiment of the disclosure, the elastomeric olefin is a polypropylene elastomeric olefin. In a subsequent embodiment of the disclosure, the polypropylene elastomeric olefin is able to co-crystallize with polypropylene.
In an embodiment of the present disclosure, the amine-modified compatibilizer is prepared by accurately metering molten diamine into an extruder during reactive extrusion of the maleated polypropylene. In an embodiment of this disclosure, the diamine is an alkylene diamine. In another embodiment, the diamine is a C4-12alkylene diamine. In a subsequent embodiment, the diamine is selected from hexamethylenediamine or dodecamethylenediamine.
The present disclosure also includes a TPU blend composition comprising a blend or reaction product of a TPU, a polyolefin copolymer blend and an amine-modified polypropylene compatibilizer, wherein the polyolfin colpoymer blend is a blend or reaction product of a polyolefin and an elastomeric olefin.
The disclosure also includes uses of the elastomeric material composition described herein, for example, for the production of parts for escalator handrails and rollers for use on escalators and elevators; as well as for motor vehicles such as bumpers, spoilers, fenders, as well as tools, appliances, sporting goods, footwear and tube connectors.
Other features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples while indicating preferred embodiments of the invention are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description
The invention will now be described in relation to the drawings in which:
This application relates generally to a method of preparing a TPU blend comprising reactively extruding a mixture of a TPU, a polyolefin copolymer blend and an amine-modified polypropylene compatibilizer, wherein the polyolefin copolymer blend is a blend of a polyolefin and an elastomeric olefin.
In embodiments of the disclosure, the method of preparing the TPU blend comprises reactively extruding a mixture comprising:
In an embodiment of the disclosure, the components of the TPU blend are first dry-blended.
In an embodiment of the disclosure, the TPU comprises from about 40% to about 70% by weight of the TPU blend. In another embodiment, the TPU comprises from about 50% to about 60% by weight of the TPU blend. In a subsequent embodiment, the TPU comprises about 55% by weight of the TPU blend. In an embodiment of the disclosure, the TPU is selected from a polyester-based TPU or a polyether-based TPU. In another embodiment, the thermoplastic TPU is a polyester-based TPU.
The polyolefin copolymer blend component of the mixture comprises from about 20% to about 50% by weight of the TPU blend. In an embodiment, the polyolefin copolymer blend comprises from about 30% to about 40% by weight of the TPU blend. In another embodiment, the polyolefin copolymer blend comprises about 35% by weight of the TPU blend.
The polyolefin copolymer blend is comprised of a polyolefin and an elastomeric olefin. In an embodiment of the disclosure, the polyolefin comprises from about 30% to about 70% by weight of the polyolefin copolymer blend. In another embodiment, the polyolefin comprises about 50% by weight of the polyolefin copolymer blend. In an embodiment, the polyolefin is selected from polyethylene or polypropylene. In another embodiment, the polyolefin is polypropylene.
In an embodiment of the disclosure, the elastomeric olefin comprises from about 30% to about 70% by weight of the polyolefin copolymer blend. In another embodiment, the elastomeric olefin comprises about 50% by weight of the polyolefin copolymer blend. In an embodiment, the elastomeric olefin can be any elastomeric olefin which is able to co-crystallize with the polyolefin. The ability of the polyolefin and the elastomeric olefin to co-crystallize results in polyolefin copolymer blends having desirable service temperatures. In an embodiment, the elastomeric olefin is a propylene elastomer containing isotactic propylene crystallinity. In an embodiment of the disclosure, the elastomeric olefin is a propylene-rich elastomer.
In another embodiment the components of the TPU blend are reactively extruded using a twin screw extruder using methods known in the art. The components of the TPU blend may be melt blended in the extruder and extruded into fine strands, for example, through a two-hole die. The strands of the TPU blend of the present disclosure are then cut into pellets, which can then be shaped and molded for practical use.
The amine-modified polypropylene compatibilizer of the present disclosure comprises from about 1% to about 15% by weight of the TPU blend. In an embodiment, the amine-modified polypropylene compatibilizer comprises from about 5% to about 10% by weight of the TPU blend.
In the method of the present disclosure, the amine-modified polypropylene compatibilizer is prepared by accurately metering molten diamine into an extruder during reactive extrusion of the maleated polypropylene as shown in
Included within the scope of this disclosure is the operation of two twin-screw extruders wherein the amine-modified polypropylene compatibilizer is produced in one extruder and fed directly into another extruder, which reactively combines the TPU and the polyolefin copolymer blend for production of the elastomeric material. A schematic of this continuous process arrangement is shown in
In an embodiment of the disclosure, the amine can be any suitable alkylene diamine, and in a subsequent embodiment, the diamine is a C4-12alkylene diamine, wherein alkylene includes both straight-chain and branched alkylene groups. In another embodiment, the diamine is selected from hexamethylenediamine or dodecamethylenediamine. In an embodiment, the diamine is hexamethylenediamine.
The method of the present disclosure, results in an elastomeric material which possesses desirable mechanical properties such as tensile strength and elongation at break. It possesses good elastomeric properties as determined by various analytical methods such as using a Dynamic Mechanical Analyzer (DMA) and a rheometer. The blend of the present disclosure also showed desirable elastomeric properties in an accelerated handrail durability test where a handrail made by replacing at least 50% of the TPU with a blend of the present disclosure was tested on a test rig with an escalator drive system. This handrail was able to run at 7 times the normal escalator speed for an acceptable length of time.
The present disclosure also includes an elastomeric material composition comprising a blend or reaction product of a thermoplastic polyurethane, a polyolefin copolymer blend and an amine-modified polypropylene compatibilizer, wherein the polyolfin colpoymer blend is a blend or reaction product of a polyolefin and an elastomeric olefin. In an embodiment of the disclosure, the composition comprises of a blend or reaction product of:
In understanding the scope of the present disclosure, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Finally, terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies. The terms “a” and “an” are understood to mean herein “one” or “one or more”.
The following non-limiting examples are illustrative of the present invention:
The commercial maleated polypropylenes used in this work were provided by Chemtura Corporation (Middlebury Conn.) and were POLYBOND® 3150 and 3200. These contain 0.5 and 1 wt % maleic anhydride (MAH), respectively. Two aliphatic diamines from Sigma-Aldrich Ltd. (Oakville, Ontario) were selected for the amination reaction. These were hexamethyleneldiamine (HMDA) and dodecamethylenediamine (DMDA). Amination experiments were carried out in a 34 mm Leistritz co-rotating twin-screw extruder (TSE). The maleated polypropylene and amine materials were metered separately. The amines were pre-melted using a hot bath and metered at a constant volumetric flow rate through an ISCO 250D syringe pump. The bath temperatures for HMDA and DMDA were set to 60 and 95° C. respectively. All the tubes in and out of the syringe pump were wrapped and heated by electrical heater bands. The controller for the band heater was set to 2 and 5.5, for HMDA and DMDA respectively. The syringe pump was calibrated using a volumetric flask (the pump was running at a set value of 10 ml/min for 30 s, the measured volume of diamine 5.2 ml). The HMDA density at 60° C. is 0.8 g/ml. The DMDA density was estimated experimentally to be 8.1 g/ml.
The factors that were studied included polymer flow rate, screw speed and amine:maleated polypropylene molar ratio. Experiments were conducted according to a statistical design. The diamine:maleated polypropylene molar ratio was varied from 0.5:1 to 3:1.
Polybond® 3200 extrudates could not be stretched steadily into a continuous filament for pelletization. After addition of diamines, the melt strength became larger, and strands could be readily stretched into a uniform filament for pelletization. However, at high diamine:maleated polypropylene molar ratio, the extrudates at a low screw speed (50 rpm) were foamy, and bubbly, so stretching of the strands became unsteady. This difference was especially obvious for the DMDA. At a diamine:maleated polypropylene molar ratio of 3, the reactive extrudates for both diamines were foamy and the stretching flow was unsteady. In the case of Polybond® 3150, the strands could be stretched steadily without the addition of the diamines and the previous effects were less pronounced. For both Polybond® materials, the extrudates appeared to be very hard when the diamine:maleated polypropylene ratio was set to 0.5, and the strand stretching was not uniform, leading to frequent breaking of the strands.
The conversion of maleated polypropylene to aminated polypropylene was characterized by titration and FTIR. Titration and FTIR data clearly follow the maleated polypropylene conversion through reaction with amine groups. Characterization results from FTIR measurements are shown in
The reactive blending of various combinations of two different thermoplastic polyurethanes, TPU1: Pearlthane® 12K85A and TPU2: Pearithane® D12F75 (both from Merquinsa of Barcelona, Spain), three different elastomeric polypropylene blends PP1: 50% Profax® 8523+50% Adflex® V109F, PP2: 50% Profax® 8523+50% Vistamaxx® 3000, and PP3: 50% Profax® 8523+50% Softell® TKS203D (Profax®, Adflex® and Softell® were obtained from Basell Polyolefins, Wilmington, Del. and Vistamaxx® 3000 was obtained from Exxon Mobil Chemical Corp. Houston, Tex.) and three different amine-containing compatibilizers (Comp. 1, Comp. 2 and Comp. 3 from Table 3) was carried out using the same twin-screw extruder and screw configuration that was used for the amination reactions. Both thermoplastic polyurethanes were dried prior to blending using a desiccant dryer supplied by Escalator Handrail Company. After drying, the moisture content was checked and found to be very low (between 0.005 and 0.02%). The dried thermoplastic polyurethane was dry-blended with the polypropylene phase (blend of polypropylene and elastomeric olefin) and the amine-containing compatibilizer and the mixture was fed to the extruder through a loss-in-weight K-Tron feeder. The compositions of the final blends are listed in Table 2 along with their mechanical properties. Mechanical properties were measured using specimens cut from molded plaques.
The glass transition temperature of samples 5, 15, 21 and TPU1 and TPU2 were measured by dynamic mechanical thermal analysis (DMTA) as shown in
Based on these mechanical results, samples 15 and 21 were selected for morphological characterization by scanning electron microscopy (SEM) due to their high tensile strength and elongation at break. Blends 15 and 21 were made using PP2 and thermoplastic polyurethane TPU1 and TPU2 respectively. In addition, sample 5 was selected randomly from the blends made using PP1.
Linear viscoelastic measurements were carried out at 190° C. using a TAI AR200 parallel plate rheometer. Storage and loss moduli data as well as viscosity data are shown in
A handrail was prepared by replacing 50% of the TPU with a TPU blend of the present disclosure. The handrail was placed on a test rig which uses the drive system from an actual escalator but is run at 210 meters/minute or 7 times the speed of a normal escalator. This test was run continuously for 8 weeks, at the end of which the handrail dimensions were measured and appearance noted. The handrail prepared using a blend of the present disclosure showed acceptable performance in this test.
While the present disclosure has been described with reference to what are presently considered to be the preferred examples, it is to be understood that the disclosure is not limited to the disclosed examples. To the contrary, the disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
All publications, patents and patent applications are herein incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety. Where a term in the present application is found to be defined differently in a document incorporated herein by reference, the definition provided herein is to serve as the definition for the term.
This application claims the benefit of U.S. Provisional Application No. 61/014,831 filed Dec. 19, 2007, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61014831 | Dec 2007 | US |
