Patent Application
20060116474
This invention relates to compatibilized thermoplastic vulcanizate blends and the use of atomic force microscopy to study the morphology of such thermoplastic vulcanizates.
In the past several decades, the use of polymers has transformed the world. Polymer science has rapidly evolved to make thousands of different thermoplastic and thermosetting products. This rapid progress in polymer science and engineering, and the growing impact of polymer technologies on industry, require optimized structure-property relationships in polymer blends.
In recent years, atomic force microscopy (AFM) has proven to be an invaluable tool for visualization of immiscible and miscible blends, as well as differentiation between partially miscible and highly compatible immiscible blends. Studies of such activities have been reported by Maier et al., J. Polym. Sci., Part B: Polym. Phys. 35, 1135, (1997); Galushka et al, Surf. Interface Anal. 25, 418, (1997), and Cabral, Macromolecules, 35, 1941, (2002).
The use of thermoplastic vulcanizates (TPV) is wide spread, as reported in Thermoplastic Elastomers, edited by Holden et al. (1996). A TPV has many of the properties of elastomers due to high elastomeric volume concentration. Because of a thermoplastic matrix, they are readily processable as a thermoplastic. See, e.g., O'Connor et al., Rubber World, December 1981-January 1982.
The effect of particle size on the mechanical properties has been clearly demonstrated, with smaller particles resulting in more ductile blends, as reported in Coran et al., Rubber Chem. Technol., 43, 141, (1980)
In general, polyolefins such as polypropylene (PP) and elastomers such as ethyl ene-propylene-diene rubber (EPDM) are compatible polymers and require no additional surface-active materials to achieve good blend properties. However, there is always room for increasing the dispersion and adhesion of two-phase systems to increase the mechanical properties.
What the art needs are better blends of thermoplastic vulcanizates that can reduce production time and energy consumption to blend such thermoplastic vulcanizates, while also providing comparable or improved physical properties of such blends.
The art also needs a means of prediction of final chemical and physical properties of thermoplastic vulcanizate blends.
“Thermoplastic vulcanizate” or “TPV” means a blend, where a thermoplastic material represents a matrix and a rubber formed of fine dispersed particles. The rubber particles have been cross-linked to provide elasticity by the process of dynamic vulcanization during its melt mixing with a molten thermoplastic.
The present invention solves that problem by introducing compatibilizers into TPV blends, even for such blends that are otherwise generally have compatible thermoplastic and rubber materials. It is unexpected that a generally compatible TPV would require compatibilizer. However, the present invention provides reduced production time and energy consumption during manufacturing as a result of the addition of a minor amount of compatibilizer to a generally compatible system, such as PP/EPDM blends.
The present invention also solves the problem by investigating the efficiency of compatibilizer using Atomic Force Microscopy (AFM). AFM can elucidate the morphology development of the PP/EPDM blends with and without compatibilizer, can develop structure/processing/property relationships of such blends, and can demonstrate the usefulness of AFM as a prediction tool in developing structure/property/processing relationships of such compatibilized blends. While some studies have employed AFM to study a TPV blend, none has investigated the effect of a compatibilizer on a generally compatible TPV blend.
One aspect of the present invention is a thermoplastic vulcanizate compound, comprising a blend of (a) a polyolefin; (b) an olefinic rubber; and (c) a minor amount of a compatibilizer selected from the group consisting of styrenic block copolymers, alpha-olefin copolymers, a copolymer comprising olefin monomeric units and aromatic monomeric units, and combinations thereof.
“Generally compatible” means that the crosslinked rubber phase of the TPV has a good adhesion and finely dispersed in a continuous olefinic phase. The average rubber particle size can range from as small as physically possible to about 10 μm in diameter. Desirably, the particle size of the rubber particles can range from about 0.1 μm to about 5 μm in diameter, and preferably from about 0.3 μm to about 2 μm in diameter.
“Minor amount” means a minor weight percentage of copolymer, relative to the olefinic rubber. Desirably, the minor weight percentage ranges from about 0.5 to about 10, and preferably from about 1 to about 5.0. Expressed alternatively in parts per hundred parts of rubber (“phr”), the minor amount of copolymer ranges from about 0.5 to about 50 phr, and preferably from about 2.5 to about 25 phr, depending on the olefinic rubber selected.
The minor amount of the copolymer serves as a compatibilizer for the otherwise compatible TPV. Desirably, the copolymer is selected from the group consisting of olefinic and styrenic copolymers, such as ethylene styrene copolymers, ethylene alpha olefin copolymers, styrenic block copolymers, such styrene ethylene butylene styrene, ethylene acrylate copolymers, and ethylene vinyl acetate copolymers. The copolymers can be random, pseudorandom, or block in structure.
Another aspect of the present invention is a method of using AFM to determine morphology of compatibilized TPV blends and to predict physical properties therefrom, comprising the steps of: (a) preparing small scale batch blends of the TPV; (b) sampling the material as a function of time; (c) elucidating the morphology as a function of time; and (d) developing structure-property relationships from the elucidated structures.
A feature of the present invention is the thermoplastic compatibilizer diffuses in the molten state into the olefinic rubber domains in the blend, with subsequent crystallization upon cooling such that the compatibilizer links domains of crosslinked olefinic rubber particles dispersed in the polyolefin matrix.
Another feature of the present invention is that the particle size of crosslinked olefinic rubber particles in an otherwise generally compatible TPV blend is reduced even further by the presence of the compatibilizer chosen. When the TPV is a blend of PP and EPDM, the high compatibility of PP and EPDM would lead one skilled in the art to expect that no compatibilizer would be needed nor would the compatibilized PP/EPDM be any more efficient than such blends without any compatibilizer.
Another feature of the present invention is the use of nano-scale resolution of AFM to identify compatibilizer linkages between olefinic crosslinked rubber domains.
An advantage of the present invention is a reduction in hardness of the compatibilized blend compared with a non-compatibilized blend, along with equivalent or improved mechanical properties of Ultimate Tensile Strength and Elongation at Break. Also, such compatibilized blends of the present invention have improved Compression Set at 100° C. and 22 hours of testing. Moreover, one skilled in the art can achieve Shore A hardness levels with TPV blends of the present invention that permit usage in very “soft touch” elastomeric products, such as hand grips, gaskets, and weather seals or other products where the Shore A hardness of the TPV is as low as about 40.
Another advantage of the present invention is using AFM to provide a visualization of the morphology development during mixing at regular intervals to allow a prediction of mechanical and impact properties as well as the optimization of the process parameters.
Another advantage of the present invention with the use of compatibilizers in PP/EPDM blends is faster residence time before introduction of curatives, increasing manufacturing efficiency and reducing energy consumption. Less complicated equipment or shorter reaction processors become possible. The overall throughput of the blend with a reduction in energy consumption more than make up for the increased cost of the otherwise generally compatible blend because of the addition of the minor amount of the compatibilizing copolymer, the “compatibilizer” described herein. Other features and advantages will become apparent when describing embodiments of the invention with respect to the following drawings.
Polyolefin
Polyolefin is a fundamental building block in polymer science and engineering because of the low cost, high volume production based on petrochemical production
Non-limiting examples of polyolefins useful in TPV blends include homopolymers and copolymers of polyethylene, polybutylene, and polypropylene (PP), the homopolymer of the last of which is preferred.
Polypropylene has thermoplastic properties best explained by a recitation of the following mechanical and physical properties: a rigid semicrystalline polymer of with a modulus of 1 GPa, a yield stress of 35 MPa, an elongation to ranging from 10 to 1000%.
Selection of a polyolefin from commercial producers uses Melt Flow Index properties. The Melt Flow Index can range from about 0.05 to about 1400, and preferably from about 0.5 to about 70 g/10 min at 230° C. under a 2.16 kg load. For PP, that Melt Flow Index should be from about 0.5 to about 70 and preferably from about 1 to about 35 g/10 min at 230° C. under a 2.16 kg load.
Non-limiting examples of PP useful for the present invention are those commercially available from multinational suppliers such as Dow Chemical, Basell Polyolefins, and BP Amoco.
Olefinic Rubber
Nonlimiting examples of olefinic rubbers are identified above. They are especially useful in TPV because their reasonable cost for properties desired. Of these rubbers, EPDM is preferred because it is a fundamental building block in polymer science and engineering due to its low cost, high volume, commodity synthetic rubber also based on petrochemical production.
The thermosetting properties of EPDM are best explained by the following mechanical and physical properties: low compression set, the ability to be oil extended to a broad range of hardness, and good thermal stability.
Selection of an olefinic rubber from commercial producers uses Mooney Viscosity properties. The Mooney Viscosity for olefinic rubbers can range from about 10 to about 200, and preferably from about 20 to about 100 ML 1+4 @100° C. For EPDM, that Mooney Viscosity should be from about 20 to about 100, and preferably from about 40 when the rubber is oil extended.
Non-limiting examples of EPDM useful for the present invention are those commercially available from multinational companies such as Bayer, Dupont Dow Elastomers, Uniroyal Chemical, ExxonMobil, and others.
A vulcanizing agent needs to be added to a well-mixed blend of EPDM rubber and thermoplastic PP during mixing. Dynamic vulcanization of olefinic rubber occurs while mixing continues. Curatives such as brominated phenolics and non brominated phenolics in the presence of a catalyst (commercially available from Schenectady International, Inc. of Schenectady, N.Y.) are included in the blend after mixing in an amount ranging from about 1 to about 8, and preferably from about 2 to about 5 phr. Alternative crosslinking agents can be organic peroxides, such as dicumyl peroxide or amyl peroxide commercially available from Atofina Chemicals and Akzo Nobel.
TPV Blends of PP and EPDM
Bringing together the attributes of PP as a thermoplastic and EPDM as an olefinic rubber is very desirable in the art because of the excellent elastomeric properties of crosslinked EPDM rubber domains dispersed in semicrystalline PP, which itself has good mechanical and chemical resistance. As such, there are many commercial blends of PP/EPDM TPV blends where the amount of EPDM is adjusted to provide hardness and elastomeric control to the blend. However, in these commercial blends, a compatibilizer is not needed to enhance the compatibility of PP and EPDM. The present invention has found the value of including a compatibilizing copolymer unexpectedly changes the morphology of the TPV for production and performance benefits.
Because commercial uses of PP/EPDM TPV blends are determined by end use properties desired, an expression of relative participation of these constituents in the blends should not be viewed as limiting to one skilled in the art. Without undue experimentation, one skilled in the art can vary the constituent concentrations of blends of the present invention to achieve a desire Shore A hardness or a level of elastomeric control (such as compression set) not previously possible, because of the unique morphology generated by the addition of a compatibilizer copolymer to an otherwise generally compatible TPV blend.
For the preferred TPV blend, concentration of the constituents of the blend can range in a ratio of PP:EPDM from about 1:4 to about 2:1, and preferably from about 1:3 to about 1:1. In stating these ranges, the amount of optional oil (to be discussed later) has not been considered.
Compatibilizer
A thermoplastic compatibilizer for the rubber phase in a TPV is useful in the present invention because of the decreased time for dispersion of the rubber as well as the decrease in particle size of the EPDM domains, all while maintaining equivalent or better mechanical properties at a lower Shore A hardness.
Non-limiting examples of compatibilizers include styrenic block copolymers, such as styrene-butadiene-styrene and styrene-ethylene-butylene-styrene, copolymers of alpha-olefins, such as ethylene-octene, ethylene-butene, ethylene-propylene, and copolymers comprising olefin monomeric units and aromatic units (e.g., alpha-olefins with styrenics such as ethylene-styrene copolymers), and combinations thereof. The compatiblizers can be block copolymers, random copolymers, or pseudorandom copolymers.
Concentration of compatibilizer in the PP/EPDM blend has been identified above in the definition of minor amount.
Optional Oil
Oil extended olefinic rubbers are also useful in the present invention. Oil extension is well known in the art. Oil can be a separate ingredient in the blend or can be a part of the olefinic rubber, depending on commercial source of supply. In TPV blends, it is often desirable to include an oil to extend the rubber portion of the blend. This oil extension provides the properties of lower hardness and better compression set while reducing cost of the rubber to achieve the same volume.
Non-limiting examples of oils suitable for optional use in the present invention include paraffinic mineral oil and napthathenic mineral oils.
Concentration of oil in the PP/Compatibilizer/EPDM blend can range from about 0 to about 200 phr, and preferably from about 0 to about 100 phr.
Preparation of Blends
Blends can be made on a batch basis or a continuous basis. Economies of scale for production seek a continuous mixing and blending process.
For batch production, the TPV samples can be made on a mixing head, typically a Brabender-type mixing head. All resins can be charged into the mixing head at a temperature ranging from about 170 to about 210° C., and preferably from about 175 to about 185° C. Mixing proceeds at a pace ranging from about 10 to about 100 rpm (revolutions per minute), and preferably from about 75 to about 85 rpm for a duration ranging from about 1 to about 5 minutes, and preferably from about 2 to about 4 minutes. Thereafter, a suitable amount of curative is added, ranging from about 1 to about 8 phr, and preferably from about 2 to about 5 phr. The mixture is then allowed to mix for an additional period of time, ranging from about 1 to about 10, and preferably from about 6 to about 8 minutes to permit dynamic vulcanization of the olefinic rubber domains. For kinetic analysis, small samples can be]then removed from the mixture at intervals ranging from about 30 to about 60 seconds, and preferably from about 25 to about 35 seconds. Plugs of the cured blend were then removed and compression molded into a 7.6×15.2×0.31 cm (3×6×0.125 inch) plaque mold at a temperature ranging from about 170° C. to about 210° C., and preferably from about 175 to about 185° C. The plug material is held under no pressure for 30 seconds and then the pressure was increased to 1100 kN force over a period of about 3 minutes. Pressure of 1100 kN force was applied for 4 minutes, and then the samples were cooled while maintaining pressure.
Continuous production of TPV blends is preferred and can use any of the equipment and processes known to those skilled in the art. The addition of the minor amount of the compatibilizing copolymer according to the present invention should not alter the preferred means of malting the TPV blend into which the compatibilizing copolymer is to be added.
A wide variety of reactive extrusion equipment can be employed. Preferred is a twin screw corotating extruder with an L/D ratio ranging from about 38 to about 60, and preferably from about 40 to about 52.
The profile for the preferred PP/EPDM reactive extrusion can be a flat 190° C. profile and 500 rpm. The material can be fed at 27 kg/hr (60 lbs/hr) on a 25 mm twin screw extruder.
To obtain samples for kinetic analysis, after the extruder reached steady state conditions, the barrels can be set to 60° C. and water cooling can be used to cool the barrel down to 105° C. Then the water cooling can be turned off. The barrels can be then subsequently set at 180° C. and the screws can be pulled out when the barrels reached 150° C.
Once compatibilized and evaluated with AFM according the methods of the present invention, TPV blends, especially of PP and EPDM, have great utility in polymer science. Such compatibilized blends exhibit increased mechanical properties at lower hardness values. In commercial usage, such properties can translate into softer compounds having equivalent mechanical properties to harder compounds, which is unexpected because, in general, decreasing the hardness of a TPV also reduces its mechanical properties.
PolyOne Corporation (www.polyone.com) sells TPV blends into the automotive, consumer and industrial markets. Customers of PolyOne Corporation use TPV blends for a wider variety of products, including without limitation, handgrips, seals, gaskets, gearshift boots, housing and “soft touch” applications. Commercial usage requires production molding such as injection molding techniques, extrusion molding techniques, and blow molding techniques known to those skilled in the art of polymer science and engineering.
Further embodiments of the invention are described in the following Examples.
Materials
All TPVs were made with a constant weight fraction of paraffinic mineral oil included to target a specific hardness and EPDM, both 37.5 wt %. The level of PP was either 25 wt % for the non-compatibilized system, or 20 wt % PP for the compatibilized system and 5 wt % of a thermoplastic compatibilizer. No molecular variables of the EPDM, oil, or PP were introduced; the only change in parameters was the addition of a minor amount of a compatibilizing copolymer according to the present invention. The chosen ingredients were pariffinic mineral oil; polypropylene homopolymer having a Melt Flow Index of 12 from Basell; EPDM being Buna KA 8537 from Bayer, and compatibilizing copolymer: ethylene styrene interpolymer DE201 from Dow Chemical.
In an effort to determine the suitability of the compatibilizer with the EPDM and the PP, blends were first prepared at a 20/80 ratio, EPDM/compatibilizer, or PP/compatibilizer respectively. Each blend was charged to a Brabender mixing head at 80 RPM, 180° C. and mixed for 5 minutes. The plug was then removed and allowed to air cool. An additional 20/80 EPDM/compatibilizer with 20 phr additional oil blend was prepared under the same conditions to determine the effect of oil on compatibility.
The TPV samples were also made on the Brabender mixing head. All resins were again charged at 180° C., 80 rpm and mixed for 3 minutes. After 3 minutes, a suitable amount of brominated phenolic curative was added and the mixture was allowed to mix for an addition 7 minutes. Small samples were removed from the mixture at 30 second intervals. The remaining plugs were then removed and compression molded at 180° C. The material was held under no pressure for 30 seconds and then the pressure was increased to 1100 kN force over a period of 3 minutes. Pressure of 1100 kN force was applied for 4 minutes, and then the samples were cooled while maintaining pressure.
Techniques
Atomic Force Microscopy (AFM).—To study the morphology of the blends, the cross-sections were microtomed perpendicular to the surface of the plaques and observed directly. The AFM images were obtained in air with a commercial scanning probe microscope Nanoscope IIIa (Digital Instruments, Santa Barbara, Calif.) operating in the tapping mode. Measurements were performed at ambient conditions using rectangular type Si probes with a spring constant of 50 N/m−1 and resonance frequencies in the 284-362 kHz range. The tip radius was 10 nm. The AFM topographic (height) and the elastic (phase) images were simultaneously obtained under normal and hard tapping conditions on the microtomed surface of blends. Phase images revealed hard regions in bright (thermoplastic phase) and soft regions in dark (rubber phase), except for
Differential Scanning Calorimetry (DSC).—A TA Instruments model DSC 2920 was used to measure the melting behavior of the compatibilizer relative to the PP. The temperature was scanned from −120° to 260° C. at heating/cooling rates of 10° C./minute. A nitrogen gas purge of 50 mil/minute was used. Second heats are reported.
Pliysicalproperties.—Specimens were die cut from the compression molded plaques and subsequently tested for room temperature compression set (22 hrs), tensile properties, and hardness. ASTM D3954-00, D638-00-Type 4, D2240-00 were followed, respectively.
To confirm that the compatibilizer had a very strong affinity for EPDM materials, blends were made solely of virgin EPDM and compatibilizer. Atomic Force Microscopy (AFM) was used to determine the interaction, if any, between the materials. The image in
In addition, the rough phase boundaries observed on the rubber particles and small lamella protruding into rubber phase indicated diffusion of compatibilizer into the rubber phase. This can be seen in the image of
Suitable plasticizers can be added to TPV systems and may act as both processing aid in the melt and also as a softener at the low temperature of use. The effect of mineral oil on the systems was also investigated. The AFM image in
The image in
Macroscopic Morphology Development.—The addition of small amounts of compatibilizer was seen to have several effects on the production of TPVs. First, as indicated by DSC data (
Consequently, a curing agent can be added earlier in the process validating the use of a compatibilizer. This is an unexpected advantage of the invention, reducing production time and saving energy.
Microscopic pre-cure morphology.—FIGS. 5(a) and 5(b) compare the microscopic pre-cure morphology of both non-compatibilized and compatibilized blends, respectively. Three minutes of mixing time was chosen for comparison, just prior to curative addition. In the non-compatibilized system, as seen in
Micro post-cure morphology.—The dispersion of the EPDM is shown in FIGS. 6(a) and 6(b) after curative addition without and with the compatibilizer, respectively. Six minutes of mixing time is depicted, 3 minutes after curative addition.
Nano-morphology.—The appearance of EPDM domains larger than 2 μm was disconcerting, and higher magnifications were used to discern the true EPDM dispersed morphology. Unexpectedly as a result of the use of AFM, what appeared to be large scale rubber domains was in fact aggregates of several EPDM domains separated by thin nano-ligaments of compatibilizer. This result was revealed most clearly in a three-dimensional topological AFM image, as seen in
It became apparent that the EPDM domains were in reality much smaller in the compatibilized system. However, determining the difference is only possible at high magnification, due to the size scale of the separating ligaments, about 50 nm. The resolution of the images should have revealed these ligaments on the micro scale, if the ligaments were completely composed of hard PP domains. However, as shown previously, the compatibilizer has a strong affinity for EPDM, with a large degree of interpenetrating chains. The blurring of the EPDM interface was caused by the compatibilizer phase interpenetrating different rubber particles. The diffusion of the compatibilizer into the EPDM results in an aggregate of EPDM domains that are physically networked by the compatibilizer. Only the use of AFM was able to determine the true morphology of the TPV blend.
The evidence of the compatibilizer location is shown in a comparison of
Without being limited to a particular theory, it is proposed that the presence and location of the compatibilizer should have several strong effects on the properties of the materials. First, one would expect better bonding of the EPDM to the PP phase, resulting in higher tensile strength. Second, due to the crystalline nature of the compatibilizer, one would expect greater connectivity of the EPDM phases. This is accomplished via a physical network structure of the compatibilizer phase spanning the EPDM particles, with crystallite domains in each. Greater connectivity should result in a more networked structure, and therefore higher elastic response. The presence of the greater adhesion should also manifest in lower compression set values with more “snap back” of the PP phase after deformation, which should translate to lower compression set values. In addition, the presence of smaller EPDM domains will result in greater elongation to break, as discussed previously. Lastly, the intermediate hardness of the compatibilizer relative to the PP and EPDM should lower the hardness of the sample. The reduction in PP concentration to accommodate the addition of the compatibilizer (while maintaining the overall level of thermoplastic) will also lower hardness.
Physical Properties.—In order to test the proposition of the theory articulated above concerning the interaction of the processing/structure/property relationships of blends of the present invention, each of the typical physical attributes were tested for conventional, non-compatibilized blends and compatibilized blends of the present invention. The same materials at the same concentrations of mixing as used in the above examples (Comparative Example D and Example 1) were tested. First, the hardness of the samples was determined to yield a baseline for comparison, as one would expect several property trends by changing the hardness alone, without the introduction of a compatibilizer. The addition of the compatibilizer does significantly affect the hardness, lowering the Shore A value (15 sec relaxation) from 72 to 64, a considerable drop in value. This translates into a difference of two property grades in the commercial marketplace, a significance for users of TPV blends.
Physical properties are listed in Table I.
One skilled in the art would expect a decrease in compression set due to the lower hardness of the sample alone. However, to maximize the differences between the samples, compression set was measured at 100° C., well above the melting point of the compatibilizer. Compression values were lower by 9 percent because of the introduction of the compatibilizer, namely from 31 to 22%. It is difficult to distinguish the relative contributions of the compatibilizer and the lower hardness. However, even a 22 percent reduction unexpectedly provides a large improvement in compression set values when the samples only differ in hardness by 8 Shore points.
The compatibilizer showed little or no effect on Ultimate tensile strength (UTS). However, when one considers that the hardness is 8 Shore A points lower with compatibilizer, maintaining equal tensile strength at significantly lower hardness is strong evidence of the anchoring and bonding effects of the compatibilizer, in addition to the generation of a smaller particle size. Also, it can be seen that the addition of compatibilizer increases the elongation by about 30 percent. While not a relatively large change, it still is a notable increase.
This combination of properties in addition to unexpected shorter process times result in easier production of TPV's with enhanced properties.
Thus, AFM is an excellent tool for examining the morphological structure of TPVs from the macro to the micro scale. Structure/property/processing relationships have been illustrated to explain the effect of compatibilizer on producing TPVs with equivalent or improved mechanical properties at lower hardness, utilizing shorter mixing times. Thus, introduction of compatibilizers into blends of the present invention not only improves blend properties but also improves manufacturing efficiency and energy consumption.
Continuous Processing—Comparative Example E and Example 2 To validate the small scale batch process Examples above, a continuous process was used to prepare TPV blends. The blends were made on a 25 mm Werner and Pfleiderer twin screw corotating extruder with an L/D ratio of 44. The blends were fed to the extruder and processed using the following conditions: a flat 190° C. profile and 500 rpm. The material was fed at 27 kg/hr. After the extruder reached steady state conditions, the barrels were set to 60° C. and water cooling was used to cool the barrel down to 105° C. Then the water cooling was turned off. The barrels were then subsequently set at 180° C. and the screws were pulled out when the barrels reached 150° C. Samples of materials at the third barrel section (12 L/D) were then analyzed by AFM morphology to determine if a difference dispersion rate occurred for the compatibilized system relative to the uncompatibilized system. These micrographs are shown in
Clearly, the compatibilized system seen in
Other compatibilizers were studied. These Examples were prepared using Buna KA 8902 (Bayer) as the EPDM and were run on a Brabender conical twin screw extruder, which was set up with a temperature profile of 170-185-200-200° C. and 150° C. at the die. Ice water was used in the water bath to cool the strands before pelletizing. The screw speed and feed rate were adjusted to get 30 sec. residence time. At least 2.2 kg. of material for each example was collected after reaching steady state (about 2.5 min.). The dispersion was checked using Atomic Force Microscopy. Table 2 shows the formulations and results.
The morphology exhibited in AFM photomicrographs clearly showed that Examples 3-7 have improved dispersion with smaller average particles compared to Comparative Example F which does not.
The next Examples were run with Royalene 4594 from Uniroyal as the EPDM on a Brabender conical twin screw extruder under the same conditions as for Examples 3-7. Table 3 shows the formulations and results.
The morphology exhibited by AFM photomicrographs showed improvement in particle size for Examples 8-10 and even better improvement for Examples 11-12.
The next Examples were run with three Nordel MG grades, which differ only in terms of Mooney viscosity, as the EPDM on a Brabender conical twin screw extruder under the same conditions as for Examples 3-7. Table 4 shows the formulations and results.
In each instance, the Examples had a smaller largest particle size than the comparable Comparative Example.
Additional Examples were prepared in a co-rotating intermeshing twin screw extruder. A Werner & Pfleiderer ZSK-30 twin screw extruder with a 36 L/D was used, fitted with a Gala underwater pelletizer with the water maintained at or below 50° C. The temperature settings used were 148-162-177-190-199-182-177° C. and 160° C. at the die. The screw speed and feed rate were adjusted to get 30 sec. and 40 sec. residence time. At least 2.2 kg (5 lb) of material were collected after reaching steady state (2.5 min.). The dispersion was checked using Atomic Force Microscopy. Table 5 shows the compositions and results.
These results showed excellent improvement of dispersion as shown by largest size of particle—an order of magnitude difference for Examples 19-23 compared with Comparative Example K. Moreover, melt flow rate was halved.
The invention is not limited to the above embodiments. The claims follow.
This application claims priority from U.S. Provisional Patent Application Ser. No. 60/416,658 bearing Attorney Docket Number 1200211 and filed on Oct. 7, 2002.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US03/31764 | 10/2/2003 | WO | 4/4/2005 |
| Number | Date | Country | |
|---|---|---|---|
| 60416658 | Oct 2002 | US |
