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AssigneeGeneral Electric Company
InventorsRay Clarence Lever, Edward Vincent Wilkus
Estimating the term…
A method of compounding thermoplastic polymeric material and fillers, including additives and agents, and unique compounded products. The compounding method comprises mixing the thermoplastic polymeric material in particulate form with particulate filler, and in progressive sequence melting the surface portion of the thermoplastic particles, blending the filler with said molten surface portion of the thermoplastic particles and removing the resultant blended melt and filler from the surface of the thermoplastic particles. The mixing and melting, and the blending and removing, are continued until the filler is substantially assimilated into the polymeric material and the thermoplastic particles become substantially diminished by melting and blending, or the method can be carried further if desired. The compounded product thus prepared is characterized by a distinctive stratified consistency.
The method of manufacturing an electrically insulated conductor having an insulation of a compound comprising thermoplastic polymeric material and filler, comprising the steps of:
The method of manufacturing an electrically insulated conductor having an insulation of a compound of thermoplastic polyolefin polymeric material and filler, comprising the steps of:
The method of manufacturing an electrically insulated conductor having an insulation of a compound comprising thermoplastic polymeric material and filler, comprising the steps of:
The method of manufacturing an electrically insulated conductor having an insulation of a compound comprising thermoplastic ethylene-containing polymeric material and filler, comprising the steps of:
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
Compounding polymers with additives, e.g. colouring: solid polymers with solid and/or liquid additives
Systems, i.e. flow charts or diagrams; Plants: for mixing rubber
Adding charges , i.e. additives: fillers or reinforcements , e.g. fibres
Making granules: by dividing preformed material
Term ended 6 Sep 1994 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
Typically the compounding of thermoplastic polymeric materials, or admixing of the composition ingredients, is carried out with very costly and massive apparatus, such as a Banbury or similar large volume internal mixer, or an open roll mill. The means and procedures therefore are not unlike those applied in compounding elastomers or rubber generally. In such conventional compounding procedures, large masses of the polymeric or elastomeric material, for example, 300 to 500 pound chunks, are heat fluxed and masticated to reduce the tenacious characteristic of the material to a workable plastic consistency whereupon the other compound ingredients are added and worked through the resulting plastic body with intensive kneading type mixing action.
However, when working with these large batches in typical production apparatus of this type, the overall operation and its control becomes so unwieldy that many commercial manufacturing operations require a combination of two or more types of mixers, such as a Banbury operating in sequence with an open roll mill and followed by a pelletizer, whereby the compounding is carried out in a series of separate means and steps.
Also, the complexity of performing common compounding operations with such apparatus of limited flexibility, creates high manpower requirements as well as rather exacting demands upon the performance of operating personnel. For instance, the intractable consistency of a typical polymeric material, and in turn, its receptivity to blending with the other ingredients is largely dependent upon the internal temperatures and heat control throughout its mass. Moreover, its receptivity to blending may also be influenced to varying degrees by the type and amount of added ingredients, among other possible variable factors. Thus, when handling such large masses of polymeric material as in most commercial operations, internal temperatures throughout a voluminous mass and the dispersion of the added ingredients therethrough without incurring adverse effects, requires a deft balancing of the compound processing conditions. Overmixing tends to degrade polymeric compositions due to excessive mechanical action disruption and/or shearing of the molecular structure of the polymer, and/or over heating of the polymeric material or ingredients contained therewith resulting from the additional heat generated internally from the continued mixing action. Thus, the compounding operation should be gauged so as to terminate the mixing as soon as an adequate degree of dispersion of components through the polymeric mass has been attained.
FIG. 1 comprises a schematic diagram illustrating the sequence and stages of the ingredients progressing through the compounding method of this invention;
FIGS. 2 and 3 are photomicrographs of a transverse section of the same compounded ingredients at 800 .times. magnification, with FIG. 2 illustrating the continuous homogeneous phase type of product of the prior art, and FIG. 3 illustrating the stratified system of the preferred products of this invention; and,
FIG. 4 is a perspective view of a section of metal conductor insulated with a compounded product of the method of this invention.
The method of compounding thermoplastic material and filler of this invention primarily comprises effecting the mixing of particles of thermoplastic polymeric material with particulate filler, and while so mixing, effecting the progressive melting of the surface portion of the thermoplastic particles, whereby the mixing action causes the particulate filler to adhere and blend with the viscid molten surface portions of the thermoplastic particles and also causes the resultant blended polymeric melt and filler to be removed from the polymer particle substructure.
Substantially any type of mixing device providing a sufficient degree of agitation to maintain an extensive intermingling action between the particles of the thermoplastic polymeric material and filler will suffice. However to expedite the carrying out of the overall compounding method, and for reasons which will be made clear hereinafter, it is highly preferred that the mixing be performed in a high energy and high velocity impeller type mixer, such as exemplified by the Henschel mixing apparatus of U.S. Pat. No. 2,945,634, which is adapted for producing a very vigorous intermingling of particles. This type of mixing apparatus generally operates with impeller speeds within the approximate range of about 1000 to 2000 R. P. M.
The heat to effect a melting of the thermoplastic polymeric material particles, can be derived for substantially any source, or combination of sources. It can be either internally generated by the friction of colliding particles or supplied from an external origin, or both, and can also include appropriate preheating of the ingredients through any of such means to accelerate the rate of completing the method. The preferred manner of parcticing the method of this invention comprises the internal generation of at least part of the heat energy required through the intensive attrition of the particles of polymeric material and the action of the filler mixing and colliding together at high energies and velocities. Effective internal heating through particle attrition alone and adequate to produce the required melting for most thermoplastic polymeric materials can be attained with the Henschel type of mixer having a high speed impeller action.