Continuous process and apparatus for manufacturing conductive polymer components

• US 5,849,129 A
• Filed: 10/16/1997
• Issued: 12/15/1998
• Est. Priority Date: 08/15/1995
• Status: Expired due to Fees

• Current Assignee: Bourns, Multifuse (Hong Kong), Ltd.
• Original Assignee: Bourns, Multifuse (Hong Kong), Ltd.
• Inventors: Wiryana, Sidharta, Zhang, Mengruo, Hogge, Steven Darryl
• Primary Examiner(s): Stemmer, Daniel
• Application Number:
  US08/953,017
• Time in Patent Office: 425 Days
• Field of Search: 156/324, 156/244.11, 156/244.22, 156/244.24, 156/244.27, 156/356, 156/360, 156/361, 29/611, 29/612, 338/22 R, 425/377, 425/114
• US Class Current: 156/244.27
• CPC Class Codes: B29C 2948/92019 Pressure
• CPC Class Codes: B29C 2948/92152 Thickness
• CPC Class Codes: B29C 2948/9238 Feeding, melting, plasticising or pumping zones, e.g. the melt itself
• CPC Class Codes: B29C 2948/92438 Conveying, transporting or storage of articles
• CPC Class Codes: B29C 2948/92466 Auxiliary unit, e.g. for external melt filtering, re-combining or transfer between units
• CPC Class Codes: B29C 2948/926 Flow or feed rate
• CPC Class Codes: B29C 2948/92647 Thickness
• CPC Class Codes: B29C 2948/92828 Raw material handling or dosing, e.g. active hopper or feeding device
• CPC Class Codes: B29C 2948/92952 Drive section, e.g. gearbox, motor or drive fluids
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/37 Gear pumps
• CPC Class Codes: B29C 48/387 using a screw extruder and a gear pump
• CPC Class Codes: B29C 48/40 using two or more parallel screws or at least two parallel non-intermeshing screws, e.g. twin screw extruders
• CPC Class Codes: B29C 48/92 Measuring, controlling or regulating
• CPC Class Codes: B29K 2995/0005 Conductive
• CPC Class Codes: B32B 2309/10 linear, e.g. length, distance, width
• CPC Class Codes: B32B 2309/72 For measuring or regulating, e.g. systems with feedback loops
• CPC Class Codes: B32B 37/153 at least one layer is extruded and immediately laminated while in semi-molten state
• CPC Class Codes: H01C 1/028 the resistive element being embedded in insulation with outer enclosing sheath
• CPC Class Codes: H01C 1/1406 Terminals or electrodes formed on resistive elements having positive temperature coefficient
• CPC Class Codes: H01C 7/027 : consisting of conducting or semi-conducting material dispersed in a non-conductive organic material
• CPC Class Codes: Y10T 29/49083 : Heater type
• CPC Class Codes: Y10T 29/49085 : Thermally variable

Abstract

A direct extrusion process for manufacturing conductive polymer articles of manufacture employs a twin screw compounding extruder that compounds a polymeric mixture from materials received, in predetermined proportions, from gravimetric feeders, then extrudes a compounded conductive polymeric material in the melt phase. The extrudate is then fed into a gear pump that allows the extruder to discharge the compounded material, while it is still in the melt stage, at a relatively low pressure. The gear pump produces a substantially constant volumetric output of the compounded "melt phase" material at sufficiently high pressure for delivery into a sheet die. The sheet die forms the compounded material, while still in the melt phase, into a continuous web. The formed polymeric web, while at a temperature just below the melt temperature of the polymeric material, is fed into a mechanism that laminates a continuous web of conductive metal foil onto each side of the polymeric web, the foil webs being pre-heated to a temperature slightly above the melt temperature of the polymeric material. The continuous web of laminate may then be cut into measured lengths, prior to stamping or punching out the individual components. Uniformity in the conductive polymeric extrudate may be enhanced by controlling the extruder and the feeders through a feedback system using the pump inlet pressure as the control parameter. The thickness of the laminated web may be maintained within desired tolerances by closed loop feedback control of the sheet die and/or the laminating mechanism.

Claims

1. A process for manufacturing conductive polymer electronic components, comprising the steps of:

(a) controllably feeding a polymer and a conductive filler in predetermined proportions at predetermined feed rates into a compounding extruder apparatus;

(b)(1) melting the polymer and mixing and dispersing the polymer and conductive filler in the compounding extruder apparatus, and (b)(2) discharging therefrom, at a first pressure, a compounded conductive extrudate in a melted state;

(c) pumping the discharged extrudate, while still in a melted state, at a second pressure that is higher than the first pressure, into a sheet die;

(d) forming the extrudate, while still in a melted state, into a continuous polymeric web in the sheet die;

(e) laminating the continuous polymeric web between first and second conductive foil webs to form a continuous laminated web;

(f) forming the laminated web into a plurality of conductive polymer electronic components;

(g) measuring the pressure of the extrudate after it is discharged from the compounding extruder apparatus and before the pumping step, and generating a measured pressure signal having a value representative of the measured pressure;

(h) periodically comparing the value of the measured pressure signal with a set point pressure value and generating a pressure difference signal having a value representative of the difference between the value of the measured pressure signal and the set point pressure value; and

(i) using the pressure difference signal to control the feed rates of the polymer and the filler and the extrusion rate of the compounding extruder apparatus.

2. The process of claim 1, further comprising the steps of:

measuring the thickness of the laminated web and generating a measured thickness signal having a value representative of the measured thickness of the web;

periodically comparing the value of the measured thickness signal with a set point thickness value and generating a thickness difference signal having a value representative of the difference between the value of the measured thickness signal and the set point thickness value; and

using the thickness difference signal to control the thickness of the laminated web.

3. The process of claim 2, wherein the step of using the thickness difference signal to control the thickness of the laminated web comprises the step of controlling at least one of (i) the thickness of the polymer web before the step of laminating, and (ii) the thickness of the laminated web after the step of laminating.

11. The process of claim 2, wherein the step of laminating is performed with the polymeric web at a temperature that is slightly below the melting point of the extrudate, and with the first and second foil webs slightly above the melting point of the extrudate.

14. The process of claim 2, further comprising the steps of:

(f) measuring the thickness of the laminated web and generating a measured thickness signal having a value representative of the measured thickness of the web;

periodically comparing the value of the measured thickness signal with a set point thickness value and generating a thickness difference signal having a value representative of the difference between the value of the measured thickness signal and the set point thickness value; and

using the thickness difference signal to control the thickness of the laminated web.

17. The process of claim 14, wherein the step of using the thickness difference signal to control the thickness of the laminated web comprises the step of controlling at least one of (i) the thickness of the polymer web before the step of laminating, and (ii) the thickness of the laminated web after the step of laminating.

4. A process for manufacturing conductive polymer electronic components, comprising the steps of:

(a) providing a twin screw compounding extruder apparatus;

(b) controllably feeding a polymer and a conductive filler in predetermined proportions at predetermined feed rates into the compounding extruder apparatus;

(c)(1) melting the polymer and mixing and dispersing the polymer and conductive filler in the compounding extruder apparatus and (c)(2) discharging therefrom, at a first pressure, a compounded conductive extrudate in a melted state;

(d) pumping the discharged extrudate, while still in a melted state, at a second pressure that is higher than the first pressure, into a sheet die;

(e) forming the extrudate, while still in a melted state, into a continuous polymeric web in the sheet die;

(f) laminating the continuous polymeric web between first and second conductive foil webs to form a continuous laminated web;

(g) forming the laminated web into a plurality of conductive polymer electronic components;

(h) measuring the pressure of the extrudate after it is discharged from the compounding extruder apparatus and before the pumping step, and generating a measured pressure signal having a value representative of the measured pressure;

(i) periodically comparing the value of the measured pressure signal with a set point pressure value and generating a pressure difference signal having a value representative of the difference between the value of the measured pressure signal and the set point pressure value; and

(j) using the pressure difference signal to control the feed rates of the polymer and the filler and the extrusion rate of the compounding extruder apparatus.

5. The process of claim 4, wherein the step of pumping comprises the step of pumping the extrudate into the sheet die at a substantially constant volumetric rate.

6. The process of claim 4, further comprising the steps of:

measuring the thickness of the laminated web and generating a measured thickness signal having a value representative of the measured thickness of the web;

periodically comparing the value of the measured thickness signal with a set point thickness value and generating a thickness difference signal having a value representative of the difference between the value of the measured thickness signal and the set point thickness value; and

using the thickness difference signal to control the thickness of the laminated web.

7. The process of claim 4, wherein the step of laminating is performed with the polymeric web at a temperature that is slightly below the melting point of the extrudate, and with the first and second foil webs slightly above the melting point of the extrudate.

8. The process of claim 6, wherein the step of using the thickness difference signal to control the thickness of the laminated web comprises the step of controlling at least one of (i) the thickness of the polymer web before the step of laminating, and (ii) the thickness of the laminated web after the step of laminating.

9. The process of claim 4, wherein the step of extruding comprises the step of discharging the extrudate at a discharge pressure, the process further comprising the step of maintaining the discharge pressure within a predetermined range.

10. The process of claim 9, wherein the step of maintaining the discharge pressure comprises the steps of:

measuring the discharge pressure before the pumping step, and generating a measured pressure signal having a value representative of the discharge pressure;

periodically comparing the value of the measured pressure signal with a set point pressure value and generating a pressure difference signal having a value representative of the difference between the value of the measured pressure signal and the set point pressure value; and

using the pressure difference signal to control the step of discharging so as to tend to minimize the absolute value of the pressure difference signal, whereby the discharge pressure is maintained within the predetermined range.

12. The process of claim 9, wherein the step of laminating is performed with the polymeric web at a temperature that is slightly below the melting point of the extrudate, and with the first and second foil webs slightly above the melting point of the extrudate.

13. The process of claim 10, wherein the step of laminating is performed with the polymeric web at a temperature that is slightly below the melting point of the extrudate, and with the first and second foil webs slightly above the melting point of the extrudate.

15. The process of claim 9, further comprising the steps of:

measuring the thickness of the laminated web and generating a measured thickness signal having a value representative of the measured thickness of the web;

periodically comparing the value of the measured thickness signal with a set point thickness value and generating a thickness difference signal having a value representative of the difference between the value of the measured thickness signal and the set point thickness value; and

using the thickness difference signal to control the thickness of the laminated web.

16. The process of claim 10, further comprising the steps of:

measuring the thickness of the laminated web and generating a measured thickness signal having a value representative of the measured thickness of the web;

periodically comparing the value of the measured thickness signal with a set point thickness value and generating a thickness difference signal having a value representative of the difference between the value of the measured thickness signal and the set point thickness value; and

using the thickness difference signal to control the thickness of the laminated web.

18. The process of claim 15, wherein the step of using the thickness difference signal to control the thickness of the laminated web comprises the step of controlling at least one of (i) the thickness of the polymer web before the step of laminating, and (ii) the thickness of the laminated web after the step of laminating.

19. The process of claim 16, wherein the step of using the thickness difference signal to control the thickness of the laminated web comprises the step of controlling at least one of (i) the thickness of the polymer web before the step of laminating, and (ii) the thickness of the laminated web after the step of laminating.