Abstract:
Methods are disclosed for a novel and useful single pass extrusion process for the reactive extrusion and compounding of polymers. Traditional extruders utilized in reactive processes are of length to diameter ratios ranging from 30 to 1 to as high as 56 to 1. The process disclosed uses a series of sequential, very closely-coupled, independently driven screw extruders having a total effective length to diameter ratio much greater than 70 to 1 and as high as 132 to 1 or greater, and providing greatly extended reaction times, separate and multiple introductions of reactive and non-reactive agents and mechanical connections allowing for convenient screw changes and differential thermal expansion. The assembly is employed to economically produce grafted polyolefins, produce ionomers without employing the use of strong caustic agents, remove large volumes of unwanted polymer processing solvents and produce other reacted polymer species in one continuous pass.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS:  
       [0001]     This application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Patent Application Ser. No. 60/617,548 filed Oct. 11, 2004, and entitled: “Method and Apparatus for Reactive Extrusion Using a Dual Extruder Assembly of High Effective Length-to-Diameter Ratio” the disclosure of which is hereby incorporated by reference in its entirety. This application is also related to a PCT application filed of even date herewith and entitled “Continuous Extrusion Process for Producing Grafted Polymers” by J. Nicholas Fowler, et al. The disclosure of this PCT application is also hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a method and apparatus for continuously producing complex polymer compounds and reactively modified polymers in a melt phase. Compounding and reactive extrusion of polymers is a well known method for producing a wide variety of modified plastic materials including grafted polymers, ionomers, polyesters, thermoplastic elastomers, and polyurethanes. Typically, reactive extruders are comprised of single or double screw shaft assemblies rotated within an externally heated and cooled barrel and configured with various screw flight designs for feeding, melting, conveying, shearing, mixing and de-volatizing a viscous polymer fluid. Base polymers are introduced in a solid state into the feed zone of the melt extruder and subjected to shear stresses and conductive heating to produce a melt or fluid polymer. Required heating to produce a fluid or melt state differs with each polymer, but typically ranges between 130 degrees Celsius for waxes and soft polyolefins to greater than 250 degrees Celsius for some engineered thermoplastics. Reactive agents are then introduced and mixed into the molten polymer, and the polymer and agent are conveyed and stirred through a portion of the extruder to allow for the temperature and time dependent reactions to proceed. Volatiles, including un-reacted agents, agents originally contained in the base polymer and/or un-desired by-products of the reactions can then be stripped from the post reaction polymer melt. The newly reacted polymer then exits the extruder and is converted to a cooled state in a manner suitable for storage and shipping. The new, post-reaction polymer can then be additionally compounded discontinuously in a separate extrusion compounding step to add various non-reactive agents or fillers to impart cost advantages, reactive agent dilution, or modified polymer physical properties.  
         [0004]     2. Description of Related Art  
         [0005]     Prior art details the use of the numerous plastic extruders as devices for the reactive processing of polymers. The prior art includes the use of both individual single-screw extruders and individual co-rotating and counter-rotating twin-screw extruders with non-intermeshing, partially-intermeshing and fully intermeshing screw assemblies. Such individual extruder assemblies are widely employed for the reactive grafting of maleic anhydride and other di-carboxylic acid anhydrides to polyolefins, grafting silanes to polyolefins, adding and reacting various cross-linking chemicals to thermo-plastics, neutralization of acid co-polymers using metallic bases, grafting acrylic acid to polyolefins, esterification of acid copolymers, de-volatilization of polymers and various other reactive processes.  
         [0006]     The configuration and total length of the reactive extruder is determined by the nature and number of reaction steps required and the time required for each reactive or non-reactive step performed. As individual or cumulative reaction times increase, the extruder can be lengthened allowing for longer residence time in the extruder, the extruder can be rotated more slowly also allowing for longer residence time in the extruder, and/or the extruder temperatures can be increased to hasten the reaction.  
         [0007]     Lengthening the extruder longitudinally to increase residence time or to fit more reactions into an extruder must be accomplished without a proportional increase in screw diameter. The lengthening of the screw shaft(s) and maintaining a constant length to diameter ratio, L/D, does not increase residence time or longitudinal space for multiple reactive events. However, increasing shaft length and maintaining a constant shaft diameter produce increased instability of the free shaft ends and creates a potential over-torque condition of the driven shaft end.  
         [0008]     Free end shaft instability requires screw designs that incorporate support of the shaft end(s) that in turn can interfere with the process design, often developing excessive shear in the polymer during the final stages of the reaction processes. Not incorporating screw designs that account for the flexibility of the free shaft ends increases shaft wear, increases extruder barrel wear and can ultimately cause catastrophic extruder failure from torsional shaft buckling or resultant shaft torsion failure.  
         [0009]     The residence time in a reactive extruder can be increased by reducing the rpm&#39;s of the extruder shaft(s). However, if the rpm&#39;s of the extruder are slowed to increase residence time and the feed rate is held constant, the extruder shaft torque increases. All extruder shafts have a torque limit based on shaft diameter, and torque is a direct function of shaft length, feed rate and shaft rpm. The feed rate can be decreased to lower torque, but this leads to a proportional decrease in extruder productivity.  
         [0010]     Reducing the extruder shaft revolutions per minute also reduces the efficiency of the dispersive and distributive mixing between the polymer and the reactive agents. With polymer melt systems consisting of high viscosity fluids, uniform reactive conversion of the base polymer during the reaction phase requires thorough and consistent mixing of both the polymer phase and the reactive agents throughout the extruder. As the screw shaft angular velocity decreases, more mixing elements are required on the screw design to maintain the equivalent mixing effect of higher screw speeds. Therefore, reducing the extruder shaft revolutions per minute reduces mixing and mass transfer in reactive and non-reactive zones, and requires the use of additional mixing zones and thus longer extruders to achieve equivalent performance of higher rpm operations.  
         [0011]     Reactive extrusion, like all chemical reactions, is a temperature and time dependent conversion. The reactions require sufficient time and energy to melt the polymer and to mix the reactive agents into the highly viscous polymer melt. Sufficient time and energy is required for the desired reactions to proceed toward completion and to remove any un-desired by-products or un-reacted materials. The required energy input into the polymer is achieved by applying controlled electric, hot oil or steam heating to the barrels of the extruder and by frictional forces created within the polymer. These frictional forces are produced in specifically designed stirring and shearing zones of the extruder. The energy for shear heating is in turn controlled by screw design and extruder shaft torque supplied by a suitably geared electric motor coupled to the extruder shafts. If necessary, cooling of the polymer is achieved by cooling appropriate portions of the extruder barrel with air or tempered water systems incorporated into the extruder barrel.  
         [0012]     It is well understood that chemical reaction rates are directly affected by temperature, as heating accelerates the reaction. Increasing the heat in the reactive extruder decreases reaction time and increases productive output of the extruder assembly. However, it is likewise well understood that heating of polymers and reactive agents also leads to many undesirable and concurrent side reactions. These include degradation of the base polymer; degradation of the reactive agents, side reactions of degraded reactive agents and degradation of the newly reacted polymer species. The longer the polymers and reactive agents are maintained at elevated temperatures, the greater the occurrence of these un-desirable side reactions. Increasing the reaction temperatures to accelerate the reaction and thus overcome insufficient extruder length, thus results in increased polymer degradation and side reactions that reduce final product quality. Reducing the temperatures in the extruder to reduce the un-desirable side reactions and polymer degradation also reduces the rate of the preferred reactions and requires the reaction time to necessarily be extended.  
         [0013]     Extruder temperature also creates thermal expansion of the extruder barrel and screw shaft(s). Extruder temperatures can range from ambient of 10° C. to greater than 400° C. The axial expansion of the extruder shaft and barrel can exceed 0.0000124 m/m-° K. in a steel extruder. This is an expansion of 20 mm over the length of a 4,048 mm extruder for a temperature change of 390° C. Failure to allow for this linear barrel expansion can create stresses beyond the failure point of the machine parts.  
         [0014]     Multiple or slow reactions can be accommodated in reactive extrusion through the use of multiple, independent extruders that feed one another in daisy chain or serial fashion. The current art allows for several multiple extruder assembly configurations.  
         [0015]     Two extruders can be coupled together if the two extruders each are rigidly attached to independent bases and if the first extruder base is allowed to ride on wheels or bearings. The barrels of the extruders are rigidly attached, connecting the output of the first extruder barrel to the input of the second extruder barrel. The liner expansion of the first extruder barrel pushes the entire first machine base and extruder away from the point of attachment of the two extruder barrels. This is practical only if the movement of the first machine can always be kept free. This becomes increasingly difficult for extruders of large size and machines that undergo expansion and contraction on a frequent basis.  
         [0016]     Extruders can be coupled in serial fashion through flexible piping or hoses. However, this design creates a polymer flow region that is unstirred by the extruder screw flights. The polymer adjacent to the heated pipe or hose surface is subject to increased degradation and subsequent formation of gels or large cross-linked bodies within the polymer melt. Continued heating of sensitive polymers may eventually produce char or completely degraded polymer and thus contaminate the polymer stream.  
         [0017]     U.S. Pat. No. 3,536,680 describes the reactive polymerization in a single pass extrusion of styrene and other co-monomers that are liquid at room temperature. The reaction is conducted in an extrusion device consisting of three twin-screw extruders of differing inner diameters and rigidly connected to one another at right angles. No allowance is made for expansion of the connected extruders, and it is impossible by this method to accommodate long or heavy extruder devices. It is also impossible by this method to quickly remove the screw assemblies from the extruder barrels, as vertical disassembly of the extruder barrels along the horizontal axis is required.  
         [0018]     U.S. Pat. No. 4,134,714 teaches a method for connecting a multi-stage extruder apparatus utilizing a rigid side connection of the two extruders, but without mixing in the connection zone.  
         [0019]     U.S. Pat. No. 4,212,543 describes a series of cascading twin-screw extruders connected atop one another and coupled via a rigid, un-stirred connection port. No accommodation is made for differential expansion between the extruder barrels and the rigid connection, nor is allowance made for the differential expansion of the various extruder barrels and the drive assemblies.  
         [0020]     U.S. Pat. No. 4,863,653 describes a non-reactive, multiple extruder assembly wherein the two extruders are serially connected via a pipe. The polymer flow in this pipe is conveyed in plug fashion and without the benefit of stirring or mixing.  
         [0021]     U.S. Pat. No. 5,165,941 teaches a non-reactive multiple extruder apparatus for compounding non-reactive materials with polymer and utilizing two extruders to effect different shear rates in each machine. The disclosed process however includes regions of polymer flow that are un-stirred.  
         [0022]     U.S. Pat. No. 5,424,367 describes a continuous, single pass, reactive extrusion process for multiple reactions on a single extruder of length to diameter ratio of up to 66 to 1. The key feature of the disclosed process is the removal of impurities from one reaction zone before a subsequent reaction is initiated in the extruder. The process disclosed is physically limited by the number of sequential reactions and stripping operations that can be performed on a single extruder apparatus. The process also describes utilizing a multiple extruder configuration, wherein the first extruder is not physically attached to the second extruder. The polymer output from the first extruder passes as a ribbon of molten material through the space between the two discontinuous machines.  
         [0023]     Therefore it is desired to construct a multiple extruder assembly to provide for numerous reaction steps or reactions requiring extended time without concerns for shaft torque capacity or having to resort to lowered rpm&#39;s, lower feed rates or increased operating temperatures. It is further desired to connect multiple extruders sequentially so as to always maintain the polymer melt in a totally contained, controlled and stirred state and provide for the thermal expansion of the individual extruder barrels and shafts for machines of any size. It is also desired to construct such an extruder assembly that allows for independent rpm ranges in each extruder and eliminates any gaps between machine polymer flow streams.  
         [0024]     It is thus the principle object of this invention to provide a multiple extruder assembly that creates a very high length to diameter ratio, is continuous in flow pattern with no unstirred and no un-contained regions, allows for independent drive of each machine, is easily modified and cleaned and allows for thermal expansion of each machine barrel and shaft assembly. Another object of this invention is to provide an economical and practical means of preparing graft functionalized polymers with low gel formation and tailored levels of polymer molecular weight reduction. Another object of this invention is to economically produce graft functionalized polymers with modified polymer molecular weight and with amine modification. Another object of this invention is to provide a means of preparing low gel content neutralized acid co-polymers without the use of strong caustics or exotic metal alloys as materials of construction. Another object of this invention is to provide a means to remove large quantities of volatiles from polymer melt streams. Another object of this invention is to provide a multiple extruder assembly with sufficient length to perform more than one of these processes sequentially or repeatedly and in one continuous pass.  
       SUMMARY OF THE INVENTION  
       [0025]     The invention relates to a unique assembly of extrusion equipment and the use of said assembly in the continuous production of various reacted and compounded polymers in a multiple stage extrusion reactor. It comprises a series of directly connected polymer extruders serially attached and constructed such that the discharge of each extruder proceeds directly into the feed region of a sequentially connected extruder and there exists no region of the process wherein the polymer is not in a continuously stirred condition. Additionally, there is no portion of polymer flow path that is not contained within the extruder. In this fashion, the melted polymer can be subjected to pressure, vacuum, mixing, conveying, reacting and/or reactant or non-reactant additions and or removal throughout the length of all so connected extruders. Likewise, no portion of the polymer melt phase is needlessly exposed to the atmosphere or requiring an inert gas blanket at the junction of any two extruders. The extruder assembly described herein is a unique family of extruder barrel mountings and connection transitions between sequential extruders. These connections and transitions accommodate the thermal expansion of the extruder barrel and screw shaft while maintaining a continuous flow path for the polymer without requiring the movement of an entire extruder and its complement gear drive, motor and base plate on wheels or bearings.  
         [0026]     The polymer flow path is at all times in a stirred condition and contained within the walls of the extruder to allow for continuous reactive and physical processes including grafting, fuctionalization, neutralization, heating, cooling, injection, solid inclusion, pressure, vacuum and volatile removal. A particularly beneficial aspect of the multiple extruder assembly disclosed herein is that extruder screw removal for cleaning or changing may be accomplished with no additional effort than that required with conventional extruders.  
         [0027]     The unique extruder assembly and connections can provide for two, three, four or more serially connected extruders. Each extruder of the combined assembly is driven by independent motors and gear reduction equipment. Thus, each extruder is capable of different revolutions per minute, shear rates and residence times. The assembly is specifically suited for the reactive extrusion of grafted polymers, viscosity modification, polymer neutralization, post-reactor polymerization and cross-linking, vacuum stripping, agent addition and multiple combinations of these. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0028]      FIG. 1  is an isometric and exploded view of a  3  extruder assembly according to one embodiment of the invention.  
         [0029]      FIG. 2  is a partially cut-away, top plan view of the embodiment illustrated in  FIG. 1 .  
         [0030]      FIG. 3  is a partially cut-away side elevation taken along the line indicated in  FIG. 2 .  
         [0031]      FIG. 4  is a partially cut-away top plan view of a junction device according to one embodiment of the invention at ambient temperature.  
         [0032]      FIG. 5  shows the embodiment of  FIG. 4  at operating temperature.  
         [0033]      FIG. 6  shows three different embodiments of extruder barrel supports according to the invention.  
         [0034]      FIG. 7  is a partially cut-away top plan view of an alternative embodiment of the invention.  
         [0035]      FIG. 8  is a partially cut-away side elevation of the embodiment of  FIG. 7  along the line shown therein.  
         [0036]      FIG. 9  is a partially exploded, isometric view of a 3 extruder assembly according to an alternative embodiment of the invention.  
         [0037]      FIG. 10  is a block diagram of the reactor conditions employed in Example 1.  
         [0038]      FIG. 11  is a block diagram of the reactor conditions employed in Example 2.  
         [0039]      FIG. 12  is a block diagram of the reactor conditions employed in Example 3.  
         [0040]      FIG. 13  is a block diagram of the reactor conditions employed in Example 4.  
         [0041]      FIG. 14  is a block diagram of the reactor conditions employed in Example 5.  
         [0042]      FIG. 15  is a block diagram of the reactor conditions employed in Example 6. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0043]     Referring to Figure One, three extruders “A”, “B”, and “C” are shown in isometric and expanded fashion to indicate the relative assembly and specific parts: drive motor  104 , gear reduction unit  107 , lantern section  3 , seal housing  4 , base pad  110 , rigid support  133 A, slide support  134 , screw assembly  101 , screw barrel  117 , feed port  129 , piston  131 , piston housing  132 , piston cap  136  and final outlet  130 . Polymer flow is from the feed port  129  to the final outlet  130  sequentially passing through each extruder “A” to “B” to “C” via the connection at the piston housings.  
         [0044]     Referring to Figure Two, the partial cut away, plan view of Figure One, the three twin screw extruders “A”, “B” and “C” are directly coupled sequentially together as to provide a total length to diameter ratio that is the sum of each individual machine length to diameter ratio. Each individual extruder is aligned so as the longitudinal axes of each pair of screw shafts  101 ,  102 , and  103  are substantially co-planer and perpendicular with one another. Each extruder is driven by independent motors  104 ,  105 , and  106  and gear reduction units  107 ,  108  and  109  that are in turn all rigidly attached to and supported on a common base plate or pad  110 . The gear reduction unit output shafts  111 ,  112  and  113  are rigidly connected to the driven end or input end of the extruder shaft pairs.  
         [0045]     The compounding extruders each have a barrel or housing  117 ,  118  and  119  within which is contained the screw shaft pairs  101 ,  102  and  103  extending from the inlet and driven end to the outlet end or discharge of the individual extruder. The shaft lengths are selected such that on heating each from ambient to the required operating temperatures, the individual shafts expand longitudinally and extend just to but not intersecting with the flights of the sequential extruder shaft flights.  
         [0046]     The driven ends of the shafts of each downstream extruder housing enter the extruder barrel through mechanical seals or packing gland seals  120  and  121 . These seals serve to contain the polymer flow and gases allowing the development of pressure or vacuum without un-wanted leakage from the expansion housing to the atmosphere.  
         [0047]     The barrel housings  117 ,  118  and  119  are rigidly attached to the gear reduction unit through the seal housing  122 ,  123  and  124  and the lantern section  125 ,  126  and  127 . The lantern section allows access for de-coupling the extruder screws from the gear reduction units. The lantern section may be water cooled with an internal water course  128  to reduce heat flow from the barrel to the gear reduction unit.  
         [0048]     The extruder barrels may be equipped with external heating supplied by steam, hot oil or electric resistance heaters. The barrels may also be equipped with access ports along the length of the screw shafts for the introduction of liquids or solids or the atmospheric or vacuum removal of liquids or volatile fractions as required by the specific polymer chemistry. The polymer enters extruder A in the inlet and driven end feed port  129 . During operation, various mixing, shearing and conveying screw designs process the polymer and any additives and reactants as is common to the art and specific to the reactions desired. As the polymer proceeds from the input of the first extruder  129  to the final output of the final connected extruder at  130 , variously located heating and cooling devices may be attached to or included within the extruder barrels to add or remove heat as required by the specific polymer chemistry. Final output of the extruder assembly is through the outlet end of the last connected extruder at  130  through devices appropriate for pumping, cooling and packaging of the polymer as are familiar to those experienced in the art.  
         [0049]     The rotation of the screws and the external heat sources supply the energy to melt the polymer. The barrel temperatures may increase from ambient to greater than 400° C. The thermal expansion along the axes of the barrels of an extruder of 4 meters in length may exceed 20 mm, and each extruder in the disclosed assembly operates independently and thus may expand in differing lengths, from 0 to greater than 20 mm per 4 meters. As the barrels are rigidly connected to the base or pad via the seal housings, lantern sections and the gear reduction units, the barrels must expand linearly away from the individual driven ends toward the respective individual outlet ends. On cooling, the barrels independently reverse the linear thermal expansion and contract away from the outlet ends toward the driven or inlet ends.  
         [0050]     The expansion and contraction of the sequential extruder barrels is accommodated with a unique transition connection assembly between connected extruders. Reference is made to Figure Three, the elevation and partial cut away section of  FIG. 2 . The input end of barrel  117  of extruder “A” is rigidly connected to the seal housing  122  and lantern section  11   1 . The lantern section  111  is rigidly connected to the gear reduction unit  107  that is rigidly connected to the base pad  1   10 . The input end of barrel  1   17  is also attached and supported rigidly to the base  1   10  via the fixed support  133 A. The remainder of barrel  117  of extruder A is supported longitudinally along the barrel by a multiple of low friction, linear mountings  134 . These linear mountings are aligned so as to prevent any rotational movement of the extruder barrel  117  about any axis and to allow linear motion only parallel to the axis of the extruder shaft  101  and thus parallel to the extruder barrel  117 .  
         [0051]     The outlet of the extruder barrel  117  of upstream extruder “A” abuts and is rigidly attached to expansion piston  131 . The piston is free to slide within the expansion piston housing  132 . The piston housing is rigidly attached to the downstream extruder “B” via seal housing  132 . Seal housing  132  is rigidly mounted to the base  110  via the rigid support  133 B.  
         [0052]     Reference is made to Figure Four, the partial cut away and expanded detail plan of the upstream extruder “A” and downstream extruder “B” connection in the ambient temperature state. Extruder “A” barrel  117  is rigidly attached to the expansion piston  131 . The piston housing  132  is rigidly attached to the upstream extruder “B” seal housing  123  and thus the downstream extruder “B” lantern housing  123  and thus to the downstream extruder “B” gear reduction unit  108  and thus the common assembly base plate  110 . The piston housing is also rigidly attached to the downstream extruder “B” barrel  118 . The piston is variously equipped with a series of ring grooves and elastomeric ring seals  134 . The clearance of the expansion piston  131  within the expansion piston housing  132  is sufficient to allow free movement of the piston  131  but tight enough to prevent leakage of polymer or gases. As the upstream extruder “A” barrel  117  expands linearly away from the upstream extruder “A” driven and input end and toward the outlet end, the upstream extruder “A” barrel  117  moves the expansion piston  131  across the expansion piston housing  132 . The piston  131  closes the space  135  provided for its movement and stops just near the piston housing cap  136 .  
         [0053]     Reference is made to Figure Five, the partial cut away and expanded detail plan of the upstream extruder “A” and downstream extruder “B” connection in the operating or elevated temperature state, or after the upstream extruder A barrel  117  and up stream extruder A screw shafts  101  have expanded longitudinally. The leading edge of the piston  131  now abuts the piston housing cap  136 . The piston housing cap  136  can be removed to allow removal of the upstream extruder shafts  117  through the piston  131  and piston housing  132 . The piston housing cap  136  may also be bored to allow controlled entry or removal of liquids, gases, solids or polymers during operation.  
         [0054]     On cooling, the up stream extruder “A” barrel  117  and shafts  117  contract and return to the position shown in Figure Four. This also returns attached expansion piston  131  to its original position shown in Figure Four. This connection is applicable to each extruder connection.  
         [0055]     Reference again is made to Figure Three. The extruder barrels are free to expand longitudinally from the inlet end and are supported by the base plate  110  on a multiple of low friction mountings  134 . These mountings allow movement only along the longitudinal or long axes of the extruder barrels. Rotational movement about any axis is restrained as is any barrel movement perpendicular to the long axis of the barrel. Reference is made to Figure Six Three distinct extruder barrel mountings  134 - 1 ,  134 - 2  and  134 - 3  are shown. In practice, any combination of these types may be used to support the extruder barrel. The slide friction mounting  134 - 1  consists of an attachment leg bearing pad  49  rigidly attached to the extruder barrel and that slides on and is restrained by low friction bearing surfaces  50  and  51  enclosed in the mounting housing  52 . As an alternative, the low friction bearing pads can be replaced by rollers as in  134 - 2 . The rod mounting  134 - 3  consists of an attachment leg and guide  56  rigidly attached to the extruder barrel. The attachment leg  56  is drilled and sleeved  57  to ride along the axes of multiple linear polished shafts  58 . All mountings completely restrain rotation of the mounted extruder barrel on all axes and allow linear movement of the extruder barrel only in a direction parallel to the extruder barrel.  
         [0056]     While the previously described piston and piston housing connection assembly will also serve to connect any number of sequential machines, an alternative connection assembly is also proposed for the specific connection between the first extruder and the second extruder only of a series of two or more extruders. Reference is made to Figure Seven and Figure Eight, elevation and partial cross-section of Figure Seven. The barrel  201  of the first extruder “D” is rigidly attached to the second extruder “E” barrel housing  202  through an opening window  203  located at the inlet end of the second extruder “E”. The first extruder “D” barrel  201  is not connected to the first extruder “D” gear reduction unit  204  or first extruder “D” lantern housing  205  and thus the feed section of extruder “D” is not rigidly attached to the base plate  209 . The second extruder “E” barrel  202  is rigidly connected to the second extruder “E” gear reduction unit  206  through the second extruder “E” seal housing  208  and thus the second extruder “E” lantern housing  207 . The second extruder “E” gear reduction unit  206  is rigidly connected to the base plate or pad  209 . Access to remove the first extruder “D” screw shaft pair  212  from the first extruder “D” barrel housing  201  is provided by removable plug  211  on the second extruder “E” barrel housing  202 . The removable plug may also be bored to allow controlled entry or removal of liquids, gases, solids or polymers during operation. The inlet end of second extruder “E” is sealed at all locations. Figure Eight details the support for the barrel housing  212  of Extruder “D”. The support connections  234  are identical in design and operation as those described previously in Figure Six. As first extruder “D” is heated, the first extruder “D” barrel housing  201  expands linearly away from the connection  203  at the second extruder “E”. This expansion is accommodated by the gap  220  provided between the first extruder “D” lantern section  205  and the first extruder “D” seal housing  210 . The first extruder “D” screw shafts  212  are rigidly attached to the first extruder “D” gear reduction unit  204  and thus expand linearly toward the second extruder “E”. The shaft lengths are selected such that on heating each from ambient to the required operating temperatures, the individual shafts expand longitudinally and extend just to but not intersecting with the flights of the sequential extruder shaft flights.  
         [0057]     Reference is made to Figure Nine. The isometric detail of a multiple extruder assembly “D” “E” and “F” is shown using the rigid connection method at the intersection of the first extruder “D” with the second extruder “E” and the piston connection method at the connection of second extruder “E” with third extruder “F”. The expansion gap  220  is provided for extruder “D” and the piston and piston housing  300  is provided for the connection of extruder “E” and “F”. The connection housing plug  211  is shown bored to accept feed assembly as is common to the art.  
         [0058]     Operation of each extruder in the multiple extruder assembly is performed through separate and independent control and drive systems. Each extruder can thus rotate at equal or differing screw revolutions per minute.  
       DETAILED DESCRIPTION OF THE PROCESSES  
       [0059]     As the disclosed assembly may accommodate large values of extruder length to diameter ratios, multiple rpm settings and is able to permit a continuous, uninterrupted series of stirred, melt phase polymer reactions and processes, it may be economically employed to produce a wide range of reacted and modified polymers.  
       EXAMPLE ONE  
       [0060]     Reference is made to Figure Ten. An ethylene-propylene copolymer rubber with 49 weight % ethylene, 50 Mooney viscosity measured at 100° C. (ML 1+4) and a moisture content of less than 2.0% is ground to an average particle size of approximately 0.25″diameter and fed into the feed zone “A” of a multiple twin screw extruder assembly with total length to diameter ratio, L/D, of 88 to 1 and screw diameter of 92 mm. The feed rate is 2,000 pounds per hour. Each of the coupled extruders is powered by a 700 horsepower motor. The RPM for L/D 0 to 44 is set at 310. The RPM for L/D 45 to 88 is set at 260. The barrel temperatures in ° C. are set as indicated in Figure Ten. Vacuum is pulled from “B”, “C” and maintained at greater than 18 inches of mercury.  
         [0061]     The discharge of the first extruder is fed into the second extruder that is serially connected to the first extruder with no un-mixed, uncontained or unregulated temperature zone between the two extruders. Rubber entering the second extruder at L/D of 44 has a moisture content of less than 0.06% and the Mooney viscosity essentially unchanged vis-à-vis the feed-stock rubber. Molten maleic anhydride is injected in locations “D” and “F” at equal rates of 27.5 lbs/hr each. Lastly, 2,5-dimethyl-2,2-di(tertiary-butyl peroxy)hexyne-3 is injected in locations “E” and “G” at equal rates of 2.5 lbs/hr. A vacuum of a minimum of 21 inches of mercury is pulled on location “H”. The final product at “J” is pelletized and has volatile content less than 0.1%, a melt Index (ASTM D-1238, 1900 C, 2160 grams.) of 4.5 grams/10 minutes and a grafted maleic anhydride=1.85%.  
         [0062]     The long L/D provided by the multiple extruder assembly allows for lower temperatures of the de-volatized rubber and longer, lower temperature reaction zones. The primary benefit of this process is a greatly reduced gel count. Samples of the product are dissolved in tetra-hydro furan at a ratio of 50 to 1 for 120 minutes. Samples are filtered through a 350 mesh screen and weight percentage of the residual, un-dissolved rubber is determined. Material processed using the long, 88:1 L/D multiple extruder assembly has un-dissolved rubber fractions of less than 0.05%.  
         [0063]     Optionally, solvent neutral oil is injected and mixed in location “K” to facilitate downstream amine capping in solution.  
       EXAMPLE TWO  
       [0064]     Reference is made to Figure Eleven. A polymer cement exiting a thin film evaporator is fed at the rate of 2,500 lbs/hr is fed into the feed zone “A” of a multiple twin screw extruder assembly with total length to diameter ratio, L/D, of 88 to 1 and screw diameter of 92 mm. Each of the coupled extruders is powered by a 700 horsepower motor. The RPM for L/D 0 to 44 is set at 150. The RPM for L/D 45 to 88 is set at 270. The barrel temperatures in ° C. are set as indicated in Figure Eleven. Vacuum is pulled from “B”, “C” and maintained at greater than 21 inches of mercury. The polymer cement feedstock has the following characteristics: weight % n-hexane=20%; weight % ethylene/propylene copolymer=80%. The ethylene/propylene copolymer has the following characteristics: weight % ethylene=49%; Mooney viscosity (ML1+4@ 1000 C)=50  
         [0065]     The discharge of the first extruder is fed into the second extruder that is serially connected to the first extruder with no un-mixed, uncontained, or unregulated temperature zone between the two extruders. Rubber entering the second extruder has a volatile content of less than  0 . 06 % and the Mooney viscosity essentially unchanged vis-a-vis the feed-stock rubber.  
         [0066]     Molten maleic anhydride is injected in locations “D” and “F” at equal rates of 27.5 lbs/hr each. Lastly, 2,5-dimethyl-2,2-di(tertiary-butyl peroxy) hexyne-3 is injected in locations “E” and “G” at equal rates of 2.6 lbs/hr. A vacuum of a minimum of 24 inches of mercury is pulled on location “H”. The final product at “J” is pelletized and has volatile content less than 0.06%, a melt Index (ASTM D-1238, 1900 C, 2160 grams.) of 5.5 grams/10 minutes and a grafted maleic anhydride=2.0%.  
         [0067]     The long L/D provided by the multiple extruder assembly allows for lower temperatures of the de-volatized rubber and longer, lower temperature reaction zones. The primary benefit of this process is a greatly reduced gel count. Samples of the product are dissolved in tetra-hydro furan at a ratio of 50 to 1 for 120 minutes. Samples are filtered through a 300 mesh screen and residual, un-dissolved rubber weight is determined. Material processed using the long, 88:1 L/D multiple extruder assembly has un-dissolved rubber fractions of less than 0.04%.  
         [0068]     Optionally, solvent neutral oil can be injected and mixed in location “K” to facilitate downstream amine capping in solution.  
       EXAMPLE THREE  
       [0069]     Reference is made to Figure Twelve. The process is the same as Example 1, except the following: The product exiting the second extruder is then continuously fed into a third extruder that is serially connected to the second extruder wherein no unmixed, uncontained or temperature unregulated zone between the second and third extruders exists. The output of the second extruder is monitored by an embedded FTIR probe and control loop at location “P”. The third extruder is a 700 horsepower, 44/1 L/D, and 92 mm twin-screw extruder. The extruder RPM and temperatures are as shown in Figure Eleven.  
         [0070]     Solvent neutral oil is pumped into locations “J” and “K” at the rate of 500 lbs/hr each. Molten N-phenyl para-phenylene diamine is injected in location “L” at the rate of approximately 70 lbs/hr as controlled by said FTIR probe at “P”. A vacuum of at least 24″ of mercury is pulled at location “M” to remove the water of reaction. The output of the third extruder is collected as a liquid in drums at “N”.  
         [0071]     The finished product of this example is an oil concentrate of maleated and amine capped ethylene/propylene copolymer. The nitrogen bound to the polymer is 0.53%. The polymer concentrate can be optionally further diluted with additional solvent neutral oil to a desired final polymer content.  
       EXAMPLE FOUR  
       [0072]     Reference is made to Figure Thirteen. The process is the same as Example 2, except the following: The product exiting the second extruder is then continuously fed into a third extruder that is serially connected to the second extruder wherein no unmixed, uncontained or temperature unregulated zone between the second and third extruders exists. The output of the second extruder is monitored by an embedded FTIR probe and control loop at location “P”. The third extruder is a 700 horsepower, 44/1 L/D, 92-mm twin-screw extruder. The extruder RPM and temperatures are as shown in Figure Eleven.  
         [0073]     Solvent neutral oil is pumped into locations “J” and “K” at the rate of 500 lbs/hr each. Molten N-phenyl para-phenylene diamine is injected in location “L” at the rate of approximately 77 lbs/hr as controlled by said FTIR probe at “P”. A vacuum of at least 24″ of mercury is pulled at location “M” to remove the water of reaction. The output of the third extruder is collected as a liquid in drums at “N”.  
         [0074]     The finished product of this example is an oil concentrate of maleated and amine capped ethylene/propylene copolymer. The nitrogen bound to the polymer is 0.59%. The polymer concentrate can be optionally further diluted with additional solvent neutral oil to a desired final polymer content.  
       EXAMPLE FIVE  
       [0075]     Reference is made to Figure Fourteen. Ethylene acrylic acid (EAA) co-polymer pellets with a melt index of 35 grams per 10 minutes at 190° C., 2160 grams per ASTM D1238 and with an acrylic acid content per ASTM D4094 of 8.7 weight % and sodium carbonate powder are fed into feed zone “A” of a multiple twin screw extruder assembly with total length to diameter ratio, L/D, of 88 to 1 and screw diameter of 92 mm and constructed of hardened carbon steel. The feed rate is 1,500 pounds per hour of EAA and 50 pounds per hour of sodium carbonate. Each of the coupled extruders is powered by a 700 horsepower motor. The RPM for L/D 0 to 44 is set at 475. The RPM for L/D 45 to 88 is set at 425. The barrel temperatures in ° C. are set as indicated in Figure Fourteen. Vacuum is pulled from “B”, “C” and maintained at greater than 22 inches of mercury. The product exits the assembly at “D”. The final product melt index is 1.2 grams per 10 minutes with free volatiles less than 0.04%. Gel rating is performed on an Optical Control Systems, GmbH, model FT Film Scan Testing System. Gel count and diameters are measured to be fewer than 900 0.2 mm, fewer than 70 0.3 mm, fewer than 51 0.4 mm and fewer than 37 0.6 mm, fewer than 4 0.8 mm and no more than 1 greater than 0.8 mm observed in  1 . 145  square meters.  
         [0076]     The multiple extruder continuous process assembly provided by the disclosed equipment herein allows for sufficient reaction time to completely react the sodium carbonate with the acid functionality of the EAA. Prior art uses sodium hydroxide, but at elevated temperatures, sodium hydroxide requires the extruder assembly to be constructed of exotic and expensive corrosion resistant alloys. Prior art using sodium carbonate employs high temperatures, often greater than 250° C. causing the increased formation of degraded or gelled final product.  
       EXAMPLE SIX  
       [0077]     Reference is made to Figure Fifteen. Ethylene acrylic acid (EAA) co-polymer pellets with a melt index of 60 grams per 10 minutes at 190° C., 2160 grams per ASTM D1238 and with a 13.5 weight % acrylic acid content per ASTM D4094 and zinc oxide powder are fed into feed zone “A” of a multiple twin screw extruder assembly with total length to diameter ratio, L/D, of 88 to 1 and screw diameter of 92 mm and constructed of hardened carbon steel. The feed rate is 2,000 pounds per hour of EAA and 23 pounds per hour of zinc oxide. Each of the coupled extruders is powered by a 700 horsepower motor. The RPM for L/D 0 to 44 is set at 475. The RPM for L/D 45 to 88 is set at 425. The barrel temperatures in OC are set as indicated in Figure Fifteen. Vacuum is pulled from “B”, “C” and maintained at greater than 22 inches of mercury. The product exits the assembly at “D”. The final product melt index is 14 grams per 10 minutes with free volatiles less than 0.04%. Gel rating is performed on an Optical Control Systems, GmbH, model FT Film Scan Testing System. Gel count and diameters are measured to be fewer than 900 0.2 mm, fewer than 70 0.3 mm, fewer than 51 0.4 mm and fewer than 37 0.6 mm, fewer than 4 0.8 mm and no more than 1 greater than 0.8 mm observed in 1.145 square meters.  
         [0078]     The multiple extruder continuous process assembly provided by the disclosed equipment herein allows for sufficient reaction time to completely react the zinc with the acid functionality of the EAA. Prior art uses sodium hydroxide, but at elevated temperatures, sodium hydroxide requires the extruder assembly to be constructed of exotic and expensive corrosion resistant alloys. Prior art using sodium carbonate employs high temperatures, often greater than 250° C. causing the increased formation of degraded or gelled final product.  
         [0079]     While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.