THERMOPLASTIC ELASTOMERS DERIVED FROM DE-VULCANIZED RUBBER

Abstract

A thermoplastic copolymer is made by first de-vulcanizing a sulfur-crosslinked elastomeric material to produce a liquid phase component. The liquid phase component is subsequently mixed with a compatible thermoplastic polymer at a temperature above its melting point thereof, and the resulting mixture is cooled to produce a solid product.

Claims

1. A method of making a thermoplastic elastomer, comprising: utilizing a de-vulcanized elastomeric material which as such is a liquid phase component; subsequently mixing said liquid phase component with a compatible thermoplastic polymer at a temperature above the melting point thereof; and cooling the resulting mixture to produce a solid thermoplastic elastomer.

2. A method as claimed in claim 1, comprising mixing about 25-75% de-vulcanized elastomeric polymer with about 25-75% post-consumer, post-industrial or virgin thermoplastic resin with appropriate monomeric content.

3. A method as claimed in claim 1 comprising mixing about 30-70% de-vulcanized SBR/NR derived from post-consumer tire crumb with about 30-70% virgin, post-industrial or post-consumer polystyrene resins.

4. A method as claimed in claim 1 comprising mixing about 30-70% de-vulcanized SBR/NR derived from post-consumer tire crumb with about 30-70% virgin, post-industrial or post-consumer polyolefin resins.

5. A method as claimed in claim 1 comprising mixing about 30-70% de-vulcanized NBR with about 30-70% virgin, post-industrial or post-consumer ABS polymer.

6. A method as claimed in claim 1 comprising mixing about 30-70% de-vulcanized EPDM with about 30-70% virgin, post-industrial and post-consumer polyolefin resins.

7. A method as claimed in claim 1 comprising mixing about 30-70% de-vulcanized EPDM with about 30-70% virgin, post-industrial and post-consumer ethylene vinyl acetate polymer.

8. A method as claimed in claim 1 comprising mixing about 30-70% de-vulcanized post-consumer tire derived elastomer with about 30-70% virgin, post-industrial and post-consumer polyolefin resin.

9. A method as claimed in claim 1 wherein the mixing takes place in an internal mixer such as a Banbury mixer, twin-screw extruder or Farrel Continuous Mixer.

10. A method as claimed in claim 1 wherein the thermoplastic polymer elements may vary from 10-90% of the mixture.

11. A method as claimed in claim 1 wherein the de-vulcanized elastomeric polymer elements may vary from 10-90% of the mixture.

12. A method as claimed in claim 1 wherein an additional thermoplastic polymer element may be added to produce a ter-polymer alloy.

13. A method of making a thermoplastic elastomer, comprising: utilizing a de-vulcanized elastomeric material which as such is a liquid phase component; subsequently mixing said liquid phase component with a compatible thermoplastic polymer at a temperature ideally within about 5 deg C above the melting point thereof; and cooling the resulting mixture to produce a solid thermoplastic elastomer.

14. The method of claim 13, wherein the thermoplastic is a monomer, copolymer or terpolymer.

15. The method of claim 13, wherein shear mixing is used to reduce the viscosity of the elastomer.

16. A method of making a thermoplastic elastomer using a mixer, comprising: introducing a de-vulcanized elastomer phase to the mixer, reducing the elastomer phase viscosity by applied shear using the mixer, subsequently introducing a thermoplastic phase at a process temperature minimally above the melt point of the utilized plastic; and subsequently mixing the thermoplastic phase and elastomer phase to produce a thermoplastic elastomer.

17. The method of claim 16, wherein the temperature is ideally within about 5 deg Celsius above of the melt point of the thermoplastic.

Description

BRIEF DESCRIPTION OF FIGURES

[0026] Embodiments of the invention will now be described in conjunction with the accompanying drawings, wherein:

[0027] FIG. 1: Illustrates an example using Primary Screw Configuration for Leistritz 27.5 mm Twin Screw Extruder

[0028] FIG. 2: Illustrates an example using Secondary Screw Configuration for Leistritz 27.5 mm Twin Screw Extruder

[0029] FIG. 3: Illustrates an example using Tertiary Screw Configuration of 27.5 mm Leistritz Twin Screw Extruder

[0030] This invention will now be described in detail with respect to certain specific representative embodiments thereof, the materials, apparatus and process steps being understood as examples that are intended to be illustrative only. In particular, the invention is not intended to be limited to the methods, materials, conditions, process parameters, apparatus and the like specifically recited herein.

DETAILED DESCRIPTION

[0031] Embodiments of the invention are based on the discovery that maximizing the physical properties of polymer blends is dependent upon the degree of comingling of the polymers on a molecular level. Elastomers typically require much higher shear when mixing than do thermoplastics to achieve high levels of dispersion. The differential in viscosities between the elastomer and plastic phases makes thorough blending of the materials difficult in some conventional thermoplastic or rubber mixers.

[0032] The present applicant has discovered that in order to have the elastomeric phase and thermoplastic phase homogenize, it is ideal if the mixing temperature is minimally above the glass transition temperature of the thermoplastic phase. Further escalation above this minimal temperature increment above the glass transition temperature may result in over softening of the thermoplastic phase to the extent that it will not present sufficient resistance to shear (because of insufficient viscosity) in order to fully disperse into the elastomeric phase within it. However, precise temperature control during mixing may present a technical challenge to the required dispersion of the elastomeric phase.

[0033] The applicant has further discovered that techniques to enhance dispersion of the elastomeric phase into the composite could involve delayed introduction of the thermoplastic constituent through a side feeder after initial viscosity-reduction of the elastomeric phase. The temperature profile along the barrel length should be gradually increased to the glass transition temperature of thermoplastic phase at the point of the side feeder barrel section. By narrowing the viscosity gap between the phases before mixing a more thorough homogenous mix will be achieved.

[0034] In general, a significant distinction over the prior art is that the elastomeric material is sufficiently de-vulcanized into the liquid state before blending with the plastic resin such that it is susceptible to the further shear-induced viscosity-reduction of the mixing apparatus prior to the introduction of the thermoplastic into the mixing process. In the liquid state, the material is alternatively re-vulcanizable (using curing agents) as a stand-alone rubber compound, with or without the addition of plastic resin.

[0035] The de-vulcanization of the subject elastomeric material prior to its blending in accordance with embodiments of the present invention prevents re-crosslinking unless extra sulphur is added. The pre de-vulcanized liquid phase of the elastomer allows for shear induced viscosity reduction, enhancing the resultant physical properties of the blend. As an example, it solves the problem of impact resistance and brittleness of thermoplastics given the intimate mixing between the de-vulcanized elastomer(s) and thermoplastic components deriving a material with thermoplastic elastomer properties.

[0036] Embodiments of the first step of the present invention utilizes free flowing powder (that is a super viscous liquid) that is optimally applicable to extrusion compounding equipment and processes. Free flowing powder material is easily introduced via continuous loss-in-weight feeders at the extrusion compounding stage as typical thermoplastic or TPE compounding equipment anticipates granulated or pelletized materials.

[0037] Methods in accordance with embodiments of the invention can be used with any thermoplastic resin as long as the elastomer component is compatible (common monomers) with the aforementioned thermoplastic resin. The liquid phase mixing is ideally carried out (<5 Celsius) above the melt temperature of the thermoplastic. Ideally, the elastomer is subjected to a targeted level of mechanical shear to reduce its viscosity to the targeted level and as achievable by the geometry of the screws or applied energy of the mixing apparatus.

[0038] The physical properties of these mixtures made in accordance with embodiments of the invention are dependent on the specific elastomer and thermoplastic polymers used, the thermoplastic/elastomer ratio and the process conditions utilized during the mixing process. Process conditions should be optimized for the particular materials used. Process conditions include mixing temperature, mixer elements (including rotors or screws), and applied power.

[0039] Preferably, the blending process takes place in a high shear mixer typical in the elastomer, plastic or TPE compounding industries including but not limited to twin screw extruders, Farrell Continuous Mixers (FCMs) or Banbury mixers for example, wherein the apparatus is maintained above the melt temperature of the plastic resin and induces a level of desired shear applicable to the elastomer.

[0040] The starting material can be any de-vulcanized rubber particulate derived from any cross-linked elastomer compound that has been reduced to the liquid phase by virtue of its pre-de-vulcanization. Some specific examples of such suitable materials are shown in the non-limiting table below.

[0041] The post-consumer, post-industrial or virgin thermoplastic(s) should be in the form of suitable monomers, copolymers or terpolymers that are miscible with corresponding liquid-phase de-vulcanized rubber material, which is referred to herein as de-vulcanized rubber particulate or by the acronym DRP.

[0042] Non-limiting examples of suitable copolymers and DRP combinations include: [0043] Polyolefin-EPDM DRP [0044] ABS-NBR DRP [0045] PVC-Polychloroprene DRP [0046] Polystyrene-Styrene-Butadiene DRP [0047] Polyolefin-Isobutylene DRP
where EDPM stands for ethylene propylene diene monomer, ABS stands for acrylonitrile butadiene styrene, NBR stands for acrylonitrile-butadiene rubber and PVC stands for polyvinyl chloride.

[0048] The thermoplastic (crystalline phase) material provides rigidity, melt-formability and melt flow. The elastomeric (amorphous phase) material provides ductile strength, flexibility, impact resistance, and resistance to cold temperature brittleness.

[0049] If desired, it may be advantageous to add more than one thermoplastic or elastomer to provide specific material properties such as solvent resistance, high temperature resistance or any benefit that is provided by each and any of the virgin elastomers and thermoplastics singularly or as copolymers.

[0050] Non-limiting specific examples that have been tested by the current Applicant include: [0051] Varying proportions of EPDM DRP with either virgin or regrind (i.e. either post-consumer or post-industrial) HDPE [0052] Varying proportions of EPDM DRP with either virgin or regrind LLDPE [0053] Varying proportions of EPDM DRP with virgin polypropylene homo-polymer [0054] Varying proportion of NBR DRP and ABS/PC regrind [0055] Varying proportions of SBR/NR (post-consumer tire crumb) DRP with HDPE [0056] Varying proportions of SBR/NR (post-consumer tire crumb) DRP with LLDPE
where HDPE is high-density polyethylene, NBR is acrylonitrile-butadiene rubber, LLDPE is low linear density polyethylene and ABS (from post-consumer e-waste computer cases)/PC is acrylonitrile butadiene styrene blended with polycarbonate resin.

[0057] After mixing, the resulting mixture is cooled to produce a solid product.

[0058] The physical properties of the blends of various experiments are shown in the following tables. In each case, the elastomer was first fully de-vulcanized into the liquid phase and subsequently blended using a twin screw extruder or Banbury mixer as indicated. Table 1 is a summary of examples wherein only recycled thermoplastics were blended with recycled rubber EPDM DRP and SBR/NR DRP (made from mixed passenger and truck Tire crumb). Table 2 is a summary of examples wherein only virgin thermoplastic resins were blended with EPDM DRP. The EPDM DRP was blended at increasing levels to virgin polyolefin resins (LDPE, HDPE and PP) and the virgin properties of the resin are used as a control group.

TABLE-US-00001 TABLE 1 Blends utilizing post-consumer or post-industrial thermoplastics Recycled Composites Plastic Elastomer Plastic Physical Property Measurements Mixer Resin (Rubber) Resin Rubber Tensile Elonga- Duro- Melt or Description Descritpion (%) (%) (MPa) tion (%) meter IZOD Flow Blender Molding Post- 60 30 70 8.4 2 98 4.3 8.4 Twin Injection Consumer Durometer Screw HDPE EPDM Post- 60 50 50 6.2 25 82 6.5 4.4 Twin Injection Consumer Durometer Screw HDPE EPDM Post- 60 70 30 5.9 300 75 Un- 0.6 Twin Injection Consumer Durometer break- Screw HDPE EPDM able LLDPE Film Passenger 50 50 4.7 10 75 Banbury Compres- Scrap Tire Crumb sion LLDPE Film Passenger 30 70 4.00 125 72 Un- 0.2 Banbury Compres- Scrap Tire Crumb break- sion able Post- 70 30 70 12.1 533 85 Un- 0.4 Banbury Compres- consumer Durometer break- sion HDPE EPDM able

TABLE-US-00002 TABLE 2 Blends utilizing virgin thermoplastics Melt Flow Tensile Tensile Notched MFI Formu- Resin Strength Modulus Izod (gm/10 lation (%) (MPa) (MPa) (J/m) min) Control Dowlex 100 9 237 399 25 Resin 2517 1 83070 70 9 0.7 162 16 289 7.8 LLDPE VIR60 2 85050 50 10 0.9 90 3 338 4.2 LLDPE VIR60 3 87030 30 7 0.6 66 11 242 FRAC LLDPE VIR60 Control Dow 100 25 870 55 25 Resin 25455E 4 83070 70 18 0.6 428 17 81 6.48 HDPE VIR60 5 85050 50 12 0.4 266 18 285 5.76 HDPE VIR60 6 87030 30 11 0.7 169 15 391 FRAC HDPE VIR60 Control Ineos 100 26 1340 No 25 Resin N02G-00 Break 7 83070 PP 70 15 0.9 393 12 396 10.68 VIR60 8 85050 PP 50 11 0.3 221 18 454 5.16 VIR60 9 87030 PP 30 8.0 +/_ 0.3 133 + 18 366 Frac VIR60
where 83070 means 30% EPDM and 70% of the subsequently listed thermoplastic; where 85050 means 50% EPDM and 50% of the subsequently listed thermoplastic; and where 87030 means 70% EPDM and 30% of the subsequently listed thermoplastic.

[0059] Tensile strength indicates pressure required to break sample under an applied tensile strain, tensile modulus indicates rigidity of the sample, impact resistance indicates energy required to fracture the sample when struck and melt flow indicates the materials ability to flow when heated (also an indication of material processibilty in product manufacturing).

TABLE-US-00003 TABLE 3 Blends utilizing different processing conditions Part 1: Screw Configuration and Extrusion Temperature Effects Low Intensity Screw 17030 HIPS 47030A BS 87030LLDPE 87030HDPE 87030PP Test 150.00 160.00 170.00 175.00 200.00 225.00 170.00 185.00 200.00 170.00 185.00 200.00 170.00 185.00 200.00 TEMP Tensile Mpa 4.95 5.18 5.12 5.72 6.01 6.58 5.54 5.36 5.39 6.88 7.21 7.32 12.16 12.12 11.71 Elongn 35.00 8.00 1.00 14.58 19.17 21.20 218.00 214.00 207.00 50.70 102.60 84.90 50.00 40.00 50.00 Duro 85.00 85.00 85.00 90.00 90.00 90.00 80.00 80.00 80.00 85.00 85.00 85.00 90.00 90.00 90.00 IZOD ft-lb/in 4.42 3.71 3.43 2.64 2.08 2.37 3.88 3.38 3.51 3.60 3.86 3.87 2.84 2.97 2.80 MFI g/10 min 0.40 0.42 0.47 2.56 1.25 0.79 13.28 18.68 22.12 11.35 9.02 3.49 30.72 25.99 22.88 230 C. 5 kg wt FlexMODMpa 401.00 426.00 452.00 464.00 421.00 96.00 85.30 72.70 668.00 634.00 1903.00 407.00 497.00 423.00 Medium Intensity Screw 17030 HIPS 47030A BS 87030LLDPE 87030HDPE 87030PP Test 150.00 160.00 170.00 175.00 200.00 225.00 170.00 185.00 200.00 170.00 185.00 200.00 170.00 185.00 200.00 Tensile Mpa 5.07 5.06 5.08 6.20 6.00 6.10 5.02 2.65 5.17 6.74 6.91 6.39 7.16 8.54 8.29 Elongn 53.00 71.00 73.00 22.00 212.00 20.00 190.00 214.00 175.00 57.00 57.00 61.00 49.70 76.90 70.20 Duro 85.00 85.00 85.00 90.00 90.00 90.00 80.00 80.00 80.00 85.00 85.00 85.00 90.00 90.00 90.00 IZOD ft-lb/in 4.32 5.14 4.30 3.03 2.79 2.59 4.78 4.32 4.30 4.45 4.38 4.64 3.00 8.95 3.74 MFI g/10 min 0.21 0.15 0.12 1.25 0.51 0.46 11.00 17.85 23.00 6.52 7.55 10.51 16.10 16.10 15.90 230 C. 5 kg wt FlexMODMpa 287.00 256.00 284.00 558.00 562.00 546.00 62.00 61.00 78.00 168.00 159.00 142.00 235.00 256.00 284.00 High Intensity Screw 17030 HIPS 47030A BS 87030LLDPE 87030HDPE 87030PP Test 150.00 160.00 170.00 175.00 200.00 225.00 170.00 185.00 200.00 170.00 185.00 200.00 170.00 185.00 200.00 Tensile Mpa 5.25 4.88 5.24 6.04 6.21 6.17 5.57 5.24 5.45 7.21 7.19 7.69 8.89 8.94 9.04 Elongn 68.00 72.00 64.00 23.00 22.00 22.00 235.00 200.00 187.00 52.00 45.00 47.00 54.00 58.00 57.00 Duro 85.00 85.00 85.00 90.00 90.00 90.00 80.00 80.00 80.00 85.00 85.00 85.00 90.00 90.00 90.00 IZOD ft-lb/in 4.41 4.80 4.60 3.16 2.71 1.94 4.03 4.02 4.07 4.62 4.13 3.91 3.44 4.16 3.35 MFI g/10 min 0.19 0.10 0.17 0.38 0.34 0.48 16.32 17.10 19.84 9.88 4.19 3.14 24.10 24.70 25.60 230 C. 5 kg wt FlexMODMpa 345.00 287.00 340.00 438.00 497.00 537.00 57.00 58.00 66.00 218.00 262.00 245.00 301.00 292.00 329.00 Ave Temp Effects 150.00 160.00 170.00 175.00 200.00 225.00 170.00 185.00 200.00 170.00 185.00 200.00 170.00 185.00 200.00 Tensile Mpa 5.09 5.04 5.15 5.99 6.07 6.28 5.38 4.42 5.34 6.94 7.10 7.13 9.40 9.87 9.68 Elongn 52.00 50.33 46.00 19.86 21.06 21.07 214.33 209.33 190.00 53.23 68.20 64.30 51.23 58.30 59.07 Duro 85.00 85.00 85.00 90.00 90.00 90.00 80.00 80.00 80.00 85.00 85.00 85.00 90.00 90.00 90.00 IZOD ft-lb/in 4.38 4.55 4.11 2.94 2.53 2.30 4.23 3.91 3.96 4.22 4.12 4.14 3.09 5.36 3.30 MFI g/10 min 0.27 0.22 0.25 1.40 0.70 0.58 13.53 17.88 21.65 9.25 6.92 5.71 23.64 22.26 21.46 230 C. 5 kg wt FlexMODMpa 316.00 314.67 35.00 482.67 507.67 501.33 71.67 68.43 72.07 351.33 351.67 763.33 314.67 348.33 345.33 Ave Screw Effects 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 Tensile Mpa 5.08 5.07 5.12 6.10 6.10 6.14 5.43 4.28 5.42 7.36 6.68 7.36 12.00 8.00 8.96 Elongn 14.67 65.67 68.00 18.32 21.33 22.33 213.00 193.33 207.33 48.00 58.33 48.00 46.67 65.60 56.33 Duro 85.00 85.00 85.00 90.00 90.00 90.00 80.00 80.00 80.00 85.00 85.00 85.00 90.00 90.00 90.00 IZOD ft-lb/in 3.85 4.59 4.60 2.36 2.80 2.60 3.59 4.47 4.04 4.22 4.49 4.22 2.87 5.23 3.65 MFI g/10 min 0.43 0.16 0.15 1.53 0.74 0.40 18.03 17.28 17.75 5.74 8.19 5.74 26.53 16.03 24.80 230 C. 5 kg wt FlexMODMpa 413.50 275.67 324.00 445.67 555.33 490.637 84.50 67.00 60.67 241.67 156.33 241.67 442.33 258.67 307.33

[0060] Table 3 illustrates combined results of screw geometry versus mixing temperatures for TPEs manufactured consistent with the methods of the described invention, and consisting of 70% elastomeric content and chemically compatible thermoplastic constituents. The illustrated blends include styrenic-based passenger tire crumb rubber DRP with polystyrene plastic, an Acrylonitrile elastomer DRP with ABS plastic and EPDM elastomer DRP with three polyolefin plastics. Table 3 is intended to be illustrated and not limiting.

[0061] In each the elastomeric phase was introduced to the extruder and subjected to shear kneading before mingling with the thermoplastic element of the compound. Increased shear by altering the screw geometry as well as selection of a mixing temperature just above the melt temperature of that particular thermoplastic yielded the most desired physical properties. Higher tensile strength, greater elongation and impact resistance as well as higher melt flow and lower flexural modulus were achieved under optimal processing conditions, whereby the highest degree of mixing homogeneity was achieved when the elastomer phase viscosity was reduced, and thermoplastic phase viscosity maintained at its highest level just above its melting point. The ability to manipulate the elastomer phase rheology is due to the utilization of pre de-vulcanized material prior to mixing as it is in a super viscous liquid state.

[0062] Experiments were also performed to compare the methods of the prior art with methods in accordance with embodiments of the invention. The results are shown in the following table.

TABLE-US-00004 TABLE 4 Comparison Sample of De-vulc EPDM from DRP vs methods described in U.S. Pat. No. 6,313,183 Melt Flow Tensile Tensile Notched MFI Resin Strength Modulus Izod (gm/10 Formulation % (MPa) (MPa) (J/m) min) A 50% PP with EPDM DRP (NRT- applicant-Method) 85050 PP VIR60 50 11 0.3 221 18 552 5.16 B 50% PP with EPDM (Devulcanized in situ Method as per prior art) 85050 PP VIR60 50 11 +/_ 0.2 240 +/_ 11 526 Fractional* Note: *Insufficient met flow to injection mold

[0063] Using the same formulation and starting resin, comparable samples were produced. Sample A (applicant method) used pre-devulcanized EPDM and subsequent staged blending using the method in accordance with embodiments of the invention. Sample B was obtained using the method described in U.S. Pat. No. 6,313,183, whereby the material was not pre-de-vulcanized prior to blending.

[0064] With the methods in accordance the invention the most notable differences are primarily in melt flow and secondarily in impact strength (as measured by the IZOD). The improved melt flow is of significant benefit for the processability of the material (e.g. injection molding) and is due to the sequence of the invention steps that lead to the greater degree of de-vulcanization of the EPDM in sample A prior to its blending with a plastic compound, and as such, the greater homogenization of the typically disparate materials. This liquid phase mixing also explains the difference in IZOD given the improved homogeneity of the resin and de-vulcanized rubber that can be achieved by blending in a fully liquid phase.

[0065] A slight improvement in impact strength may also be attributed to greater homogeneity of the mixture but the differences are not great enough to establish that fact on one experimental sample. Embodiments of the invention offer the advantage over the prior art in retaining a melt flow, which is suitable to effectively process the material into useable goods.

[0066] Of note also is the improvement in brittleness properties of the plastic, which correspond to the impact characteristics as represented by the IZOD numbers, which increase with the efficacy of the elastomeric content. The efficacy of the elastomeric content is dependent on its optimal de-vulcanization prior to its subsequent liquid state blending with plastic. IZOD impact testing is an ASTM standard method of determining the impact resistance of materials. Another advantage of the methods in accordance with the invention is that it is possible to employ a continuous mixing process apparatus like a twin-screw extruder of Farrel Continuous Mixer (FCM) for mixing. DRP from pre-de-vulcanization of the cured elastomer material is a free flowing powder. This presents processing advantages over virgin rubber or sheeted rubber scrap in that it is addable to twin screw mixing processes through continuous loss-in-weight feeder systems. Such systems are more commonly employed in thermoplastic compounding practice than bulk batch mixing (Banbury) employed in rubber compounding, although any suitable high shear mixer can be used.

[0067] Considering embodiments of the invention using DRP, a super viscous liquid, application of shear will bring about a reduction in viscosity. The applicant generally found maximum physical property results were achieved at the highest shear configuration. With respect to temperature best results were mostly achieved at the lower temperature of the examined temperature range. With respect to thermoplastics the highest viscosity is achieved immediately upon softening.

[0068] Therefore, the pre-devulcanization and transmutation of the elastomer to a super viscous liquid with subsequent shearing to further reduce viscosity is a core teaching of embodiments of the invention to achieving maximum physical property results. Coupled with this condition, the maintenance of temperature ideally within 5 deg Celcius of the melt point of the thermoplastic and as such whereby the thermoplastic phase is maintained at its highest viscosity, also translates into improved physical properties. Improved physical properties for mixtures occur when the most complete homogenous phase of the constituents is acquired by virtue of the minimization of the viscosity-differential between the elastomeric and thermoplastic constituents.

[0069] Below are some examples of specific method steps tested by the present applicant. Such examples are meant to be illustrative rather than limiting.

Example 1

17030HIPS

[0070] SBR DRP was introduced to a 27.5 mm Leistritz twin screw extruder at a rate of 7 Kg per hour. The apparatus was configured with screw geometry as displayed in FIG. 1-3. For each of three trials. The extruder temperature zones were set to to 150, 160, and 170 Celsius for each of three trials. The extrusion rate was 125 RPM for all successive trials. A total of nine trials were performed.

[0071] High Impact Polystyrene regrind was introduced at Zone 4 of the extruder as in FIG. 1-3 at a rate of 3 Kg/hr. Material was pelletized and injection molded at 200 C for testing purposes. Test results are displayed in Table 3: Optimal mixing conditions determined by maximal physical properties were achieved with the 3.sup.rd most aggressive screw configuration and the lowest temperature selected.

Example 2

47030ABS

[0072] NBR DRP was introduced to a 27.5 mm Leistritz twin screw extruder at a rate on 7 Kg per hour. The apparatus was configured with screw geometry as displayed in FIG. 1-3. For each of three trials. The extruder temperature zones were set to 175, 200, and 225 Celsius for each of three trials. The extrusion rate was 125 RPM for all successive trials. A total of nine trials were performed.

[0073] Acrylonitrile Butadiene Styrene thermoplastic was introduced at Zone 4 of the extruder as in FIG. 1-3 at a rate of 3 Kg/hr. Material was pelletized and injection molded at 200 C for testing purposes. Test results are displayed in Table 3:

[0074] Optimal mixing conditions determined by maximal physical properties were achieved with the 3rd most aggressive screw configuration and the lowest temperature selected.

Example 3

87030 LLDPE

[0075] EPDM DRP was introduced to a 27.5 mm Leistritz twin screw extruder at a rate on 7 Kg per hour. The apparatus was configured with screw geometry as displayed in FIG. 1-3. For each of three trials. The extruder temperature zones were set to 175, 185, and 200 Celsius for each of three trials. The extrusion rate was 125 RPM for all successive trials. A total of nine trials were performed.

[0076] Low Linear Density Polyethylene regrind thermoplastic was introduced at Zone 4 of the extruder as in FIG. 1-3 at a rate of 3 Kg/hr. Material was pelletized and injection molded at 200 C for testing purposes. Test results are displayed in Table 3: Optimal mixing conditions determined by maximal physical properties were achieved with the 3rd most aggressive screw configuration and the lowest temperature selected.

Example 4

87030 HDPE

[0077] EPDM DRP was introduced to a 27.5 mm Leistritz twin screw extruder at a rate on 7 Kg per hour. The apparatus was configured with screw geometry as displayed in FIG. 1-3. For each of three trials. The extruder temperature zones were set to 175, 185, and 200 Celsius for each of three trials. The extrusion rate was 125 RPM for all successive trials. A total of nine trials were performed.

[0078] High Density Polyethylene regrind thermoplastic was introduced at Zone 4 of the extruder as in FIG. 1-3 at a rate of 3 Kg/hr. Material was pelletized and injection molded at 200 C for testing purposes. Test results are displayed in Table 3: Optimal mixing conditions determined by maximal physical properties were achieved with the 3rd most aggressive screw configuration and the lowest temperature selected.

Example 5

87030 PP

[0079] EPDM DRP was introduced to a 27.5 mm Leistritz twin screw extruder at a rate on 7 Kg per hour. The apparatus was configured with screw geometry as displayed in FIG. 1-3. For each of three trials. The extruder temperature zones were set to 170, 185, and 200 Celsius for each of three trials. The extrusion rate was 125 RPM for all successive trials. A total of nine trials were performed.

[0080] Polypropylene homopolymer thermoplastic was introduced at Zone 4 of the extruder as in FIG. 1-3 at a rate of 3 Kg/hr. Material was pelletized and injection molded at 200 C for testing purposes. Test results are displayed in Table 3: Optimal mixing conditions determined by maximal physical properties were achieved with the 3rd most aggressive screw configuration and the medium temperature selected. It was later determined 170 C was insufficient to melt the polypropylene homopolymer, thus 185 C was the lowest temperature setting employed above the melt temperature of the thermoplastics.

[0081] The progressive increase in the average for the acquired physical properties, as shown in Table 3, with the addition of shear inducing elements to the screw geometry and regression of physical properties with increasing process temperatures indicate: [0082] 1. Additional shear decreases the viscosity of the elastomer phase [0083] 2. Increasing temperature of the process lowers the viscosity of the thermoplastic phase [0084] 3. Separation of the input of materials allows the conditioning of the elastomer phase prior to comingling with the thermoplastic phase. [0085] 4. Best physical properties attained whereby constituent viscosities are closest in value. [0086] 5. Pre-de-vulcanization of the elastomer phase allows for the greatest viscosity reduction prior to comingling with the thermoplastic phase due to its change of physical state from solid to super viscous liquid.

[0087] Numerous modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.