Agitating – Rubber or heavy plastic working – Rotating and reciprocating stirrer
Reexamination Certificate
1999-06-15
2001-04-03
Cooley, Charles E. (Department: 1723)
Agitating
Rubber or heavy plastic working
Rotating and reciprocating stirrer
C366S080000, C366S081000, C366S091000, C366S097000, C366S288000, C366S289000, C366S305000, C366S317000
Reexamination Certificate
active
06210030
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates in general to molding with polymers, and in particular to a new and useful apparatus for controlling the viscosity of polymeric materials by disentanglement. The invention also pertains to methods of using such an apparatus.
Following is a list of references which is material to the present invention:
[1] J. P. Ibar, ACS Polym. Prep., 21(1), 215 (1980), “Vibro-Molding: A New Process to Mold Polymeric Materials.”
[2] J. P. Ibar, Polym—Plast. Technol. Eng., 17(1), 11 (1981)., “Rheomolding: A New Process to Mold Polymeric Materials.”
[3] J. Lemelson, U.S. Pat. No. 4,288,398 (1981).
[4] J. W. Pendleton, U.S. Pat. No. 3,298,065 (1965).
[5] P. S. Allen and M. Bevis, U.S. Pat. No. 4,925,161 (1985). Also R. A. Malloy in “Plastic Part Design for Injection Molding”, Hanser/Gardner Publications (1993), pp.59, 60.
[6] P. S. Allan et al.,
Composites Manufacturing,
The Wolfson Center of Materials Processing, Brunel, The University of West London, Uxbridge, Middlesex, pp. 80-84 (June 1990).
[7a] J. P. Ibar, U.S. Pat. No. 4,469,649 (1984), “Method and Apparatus For Transforming The Physical Characteristics of Material By Controlling The Influence of Rheological Parameters.”
[7b] J. P. Ibar, EP Patent 0273830 B1 (1991), “Method and Plant For Fabricating A Product By Injecting Material Into A Mold With Treatment of Injected Material.”
[7c] J. P. Ibar, U.S. Pat. No. 4,919,870 (1988), “Process Of and Apparatus For Treating A Shaped Product.”
[7d] J. P. Ibar, U.S. patent application Ser. No. 07/880,926 (1993) now U.S. Pat. No. 5,306,129, “Molding Deformable Materials With Use of Vibrating Wall Surfaces.”
[7e] J. P. Ibar, abandoned U.S. patent application Ser. No. 08/124,147 (1993), “Molding Apparatus and a Method of Using the Same.”
[7f] J. P. Ibar, U.S. patent application Ser. No. 08/138,673 (1993), abandoned “Improved Injection Molding Process and Apparatus.”
[7g] J. P. Ibar, Canadian Patent CA 1,313,840 (1993) “Process and Device for Producing an Article by Injection of Material Into a Mold.”
[7h] J. P. Ibar, EP Patent No. 0 274 317 (1993), “Process and Device for Extruding a Product in the Form of a Film, Plate, Tube, Bar or Thread.”
[8] J. P. Ibar, Modern Plastics, vol. 25 No. 1, 85 (1995).
[9] A. Kikuchi and R. F. Callahan, “Quality improvements Resulting from Rheomolding”, SPE ANTEC 1996 Conference Proceedings (CD-ROM), Injection Molding, H4-New Technologies and Developments, Part I.
[10] G. L. Slonimskii, et Al,
Vysokomol.
Soyed; A16, 1, 2342 (1974).
[11] S. N. Nurmukhametov, et Al,
Mekhanika Polimerov;
No. 4, 579 (1976).
[12] J. Casulli, J. R. Clermont, A. Vonziegler and B. Mena, “The Oscillating Die:
A Useful Concept in Polymer Extrusion
” Polym. Eng. Sci.; 30 (23), 1551 (1990).
[13] C. M. Wong, C. H. Chen and A. I. Isayev, “Flow of Thermoplastics in an
Annular Die under Parallel Oscillations
”, Polym. Eng. Sci.; 30 (24), 1574 (1990).
[14] B. Mena, O. Manero and D. M. Binding, “
Complex Flow of Visco
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elastic Fluids through Oscillating Pipes: Interesting Effects and Applications
”, J. of Non-Newtonian Fluids Mechanics; 5, 427 (1979).
[15] B. Mena, O. Manero and D. M. Binding, Rheol. Acta; 16, 573 (1977).
[16] B. Mena, O. Manero and D. M. Binding, Rheol. Acta; 17, 693 (1978).
[17] L. R. Shmidt and J. L. Maxam, “Injection Molding Polycarbonate Compact Disks: Relationship between Process Conditions, Birefringence and Block Error Rate”, SPE ANTEC 1988 Technical Papers, 34, 334 (1998).
[18] L. R. Shmidt and J. L. Maxam, “Injection Molding of Polycarbonate Optical Disks Using an Oscillatory Boundary Condition”, SPE ANTEC 1992 Technical Papers, 38, 447 (1992).
[19] H. A. Hengesbach, K. W. Schramm, D. Woben, R. Sarholz, “Ausrustung von Spritzgiessmaschinen (Equipping of Injection Molding Machines), Report II-1 from IKV, at the Rhineland-Westphalian Technical University (RWTH) in Aachen (1976).
[20] K. W. Schramm, “Injection Molding of Structural Parts Consisting of Plastic Molding Materials Utilizing Forced Oscillating Flow Processes”, Doctor-Engineer Thesis, Rhenish-Westphalian College of Technology (1976).
[21] Lee, U.S. Pat. No. 4,793,954.
[22] J. P. Ibar, “Melt Viscosity Reduction of Plastics by Vibration during Filling in Injection Molding.”, ANTEC 1997, Toronto, SPE Reprints (1997).
[23] J. P. Ibar, “Smart Processing of Plastics Through Vibration Controlled Shear Thinning and Orientation”, 1997 ASME International Mechanical Engineering Congress and Exposition. Reprint MD-Vol. 79, pp 223-348, 1997.
[24] J. P. Ibar, U.S. Pat. No. 5,885,495.
[25] J. P. Ibar, “Control of Viscosity of Polymer Melts Prior to Molding by Disentanglement Methods”, ANTEC 99 Conference Proceedings, Volume II, 1900 (1999).
[26] L. A. Utracki, NATO/ASI Advanced Study Institute,
Development in Processing for Polymer Property Enhancement
, Caminha, Portugal, May 17-28 1999.
[27] J. D. Ferry, “Viscoelastic Properties of Polymers”, Appendix C, page 640, Second Edition, John Wiley & Sons, NY. Library of Congress Catalog Card#: 76-93301.
BACKGROUND OF THE INVENTION
It is well known to those skilled in molding polymeric materials that the processing parameters (e.g. temperatures, pressures, flow rates, flow length etc.) are a direct consequence of the viscosity of the melt which is governed by the state of entanglements of the macromolecules. The resin “melt index” usually characterizes the fluidity of the melt and can be used to specify a certain resin grade suitable for a given molding application. The melt index is a function of the molecular weight of the macromolecular chains and their degree of entanglement. A high melt index corresponds to a high flow resin. The mechanical performance of a molded product is also a strong function of its molecular weight characteristics, the longer the macromolecular chains the stronger and stiffer the final article. Unfortunately the high strength required of plastics during their usage often results in a lack of fluidity during the molding operation, with as a result, high operational molding costs and molding defects (weld lines, sink marks etc.). One accepted practice which is designed to compensate for this lack of control of melt fluidity includes decreasing the molecular weight of the macromolecules being molded. Although this decreases the viscosity, improving the flow length significantly, it often results in a reduction of the mechanical properties, in particular strength and stiffness. Moreover, this practice cannot be used in those instances wherein the final molded product has to be very small and/or thin, such as in thin-wall injection molding applications.
In summary, the resin suppliers have succeeded in providing the plastic industry with means to lower the viscosity to ease up processing or increase melt elasticity by blending grades of different molecular weights. The problem with that solution is that the mechanical performance of the lower molecular weight polymers is also severely reduced, a compromise for better processability which processors have to pay.
The industry would welcome a process which allows the decrease of viscosity of plastic melts without the need to change the molecular weight of the resins, with the added advantage of a reduction of the number of grades a resin manufacturer has to offer.
Shear thinning of plastic materials is well known and is used practically to lower the viscosity of melts during the filling stage of injection molding by increasing the speed of the injecting piston. This is particularly useful in the case of thin wall injection molding where considerable forces are required to fill the mold when the viscosity of the melt remains quasi-Newtonian.
It is also well known that shear thinning can be obtained, at a giv
Cooley Charles E.
Notaro & Michalos P.C.
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