MXPA96006025A - Machine to form compounds by extrusion multiple detachments with elements of mixcladomodula - Google Patents

Abstract

The present invention relates to a multi-screw extrusion or compounding machine, characterized in that it comprises: a housing assembly including two adjacent and substantially cylindrical barrel sections, each having an inner wall surface; extrusion mixing screw positioned within each of the adjacent barrel sections, the screws being axially adjacent to each other and rotating in the same direction about an axis of rotation, each screw includes a plurality of transport screw elements removably mounted on and keyed to a rotary actionable arrow, the transport screw elements are interengaged, each screw includes at least one set of symmetrical modular mixing elements, each modular mixing element is removably mounted on and keyed to the arrow, each modular mixing element has or a plurality of asymmetrical wings, the modular mixing elements are interengranted, and each set of modular, asymmetric mixing elements includes at least one modular mixing element having a left turn, immediately mounted downstream and contiguous with at least one element Modular mixer that has a right turn

Description

MACHINE TO FORM COMPOUNDS BY EXTRUSION OF MULTIPLE SCREWS WITH MODULAR MIXING ELEMENTS DESCRIPTION The invention relates to the field of machines to form compounds by extrusion, multiple screws, interengranados, co-rotating for plastic material. More particularly, the invention relates to such machines having co-rotating screws that incorporate sets of modular mixing elements of non-symmetrical geometries, with relatively large wing-type spaces and in which such assemblies of modular mixing elements do not symmetrical, they can be mounted in any suitable axial location along their respective screw shafts, in which the use of mixing block or mixing discs can be avoided. The co-rotating double screw extruders, intergraded as is conventionally known in the art, use many different elements mounted along the respective extruder shafts according to a sequence of the functions of the process of which extruder will operate. In general, the screws in such an extruder include a number of transport screw elements (forward transport) designed to accept the plastic material and additives and to transport them to a special section of the dedicated extruder to transform the plastic material into a melt that forms a thermally homogeneous compound that includes the additives. This special section of the extruder conventionally includes many mixing elements usually in the form of blocks or discs, designed to impart high energy per unit volume in the plastic material with the additives. The rotational pulse energy imparted to the mixing elements in the screws of the extruder is dissipated in the plastic material causing heating and inducing mixing of the various additives in a melt of the plastic compound. These mixing elements conventionally employ a special cross section profile which is designed to provide "effective scraping" (very small spaces such as one millimeter or less) between the adjacent mixing elements and usually also scraping effective between an outside diameter of the Kneading element and the inner wall of the cylinder or barrel. As a result of this very small space geometry, the intense energy is dissipated in the kneading section of the extruder, producing localized extreme heating. This heat energy, if not removed quickly and continuously, results in overheating of the melt of the compound with possible degradation of the plastic material. Another problem associated with kneading discs in general is their ability to generate high localized pressures, especially in the vicinity of the tip of the mixing disc. These localized high pressures result in axis deflection forces, which push the screw shafts towards the inner surfaces of the cylinder walls, thus accelerating the wear of the extruder. From a process point of view, such localized high pressures can be re-melted together and agglomerated to previously separated solid particles, whereby they act contrary to the objective of obtaining a homogenous melt of the compound. Additionally, in such prior machines when dealing with dispersed or extensive mixing, several different fluid particles are being exposed to shear rates of highly non-uniform mixing. Accordingly, the shearing action of the mixing must be repeated many times to ensure that all fluid particles have been exposed to equal levels of shear and / or thermal stresses. The invention is contemplated in machines that are composed by extrusion that have interengaged, co-rotating screws that incorporate elements, modular mixing of identical geometries having relatively large spaces and in which non-symmetrical geometries provide dynamic wedge pressurization to drive relatively large circumferential flows of the plastic material through large shear space. In this way, advantageously, the large circumferential flows of plastic material are repeatedly directed by the action of dynamic wedge pressurization to pass repeatedly through the larger shear spaces. By virtue of these relatively large stress spaces, the plastic material that is being mixed at lower and more uniform temperatures that usually occur with the use of typical prior art mixing elements. In most plastic materials, viscosity decreases with rising temperatures. Accordingly, these lower temperatures allow the plastic material to be processed at higher viscosities than what typically occurs in prior art extrusion forming machines. Due to the higher viscosities of the plastic material of lower temperature, the stresses of shear in the material are greater, so that the dispersed mixing increases, despite the relatively large spaces, which are used.

Among other advantages of the illustrative embodiments of the invention, there are those that arise from the fact that by using several sets of modular mixing elements and by mounting them in selectable positions along the length of the screws, the operators they are provided with advantageous flexibility in adapting the machines to form extrusion compounds for optimum performance in relation to the particular plastic material and particular additives that are being formed in a composite. The modular mixing elements can be arranged and assembled in several assemblies in a wide range of axial positions and configurations to increase the processing characteristics, zone temperature levels and magnitudes and axial locations of wedge-shaped shear actions, dynamics within the twin cylinders and to couple these dynamic effects with the desired properties of the plastics materials and additives that are being formed into a composite. BRIEF DESCRIPTION OF THE DRAWINGS The invention, together with other objects, features, advantages and their aspects, will be understood more clearly from the following detailed description considered together with the attached drawings, which were not drawn to scale with the emphasis, on the contrary they are placed to clearly illustrate the principles of the invention. The ,--. Similar reference numbers indicate similar elements, similar components or similar geometric shapes in all different views. The attached drawings, which are incorporated in and constitute a part of the specification, currently illustrate preferred embodiments of the invention and together with the general description set forth in the foregoing and the detailed description of the preferred embodiments set forth in the following, serve to explain the principles of the invention. In the drawings: Fig. 1 is a sectional view in longitudinal, lateral elevation, schematic of a machine for forming an extrusion composite, of multiple screws having 15 twin co-rotating, interengaged screws (only one is observed in the Fig. 1) incorporating non-symmetrical modular mixing elements having relatively large wing-type spaces. Figs. ÍA and IB are enlargements of the 20 portions of Fig. 1 in which a respective set of modular mixing elements is shown in each FIGURE. Fig. 2 is an enlarged, cross-sectional view taken downwards taken along any of the planes 2-2 in Fig. 1 or along the planes 2-2 in Fig. IA or plane 2-2 of Fig. IB near the upstream ends of the respective modular mixing elements. Fig. 3 is another enlarged view of one of the modular mixing elements of Fig. 2 for purposes of explaining the advantageous non-symmetric geometric relationships provided in those modular mixing elements. Fig. 3A shows an upper half of Fig. 3 for purposes of another explanation. Fig. 3B is another enlargement of the upper half of Figs. 3 and 3A for explanation purposes. Figs. 4A and 4B are end elevation and side elevation views, respectively, of a modular, non-symmetrical mixing element with two axially extending wings, each having a clockwise rotation ("RH"). A RH rotation is a forward pumping turn, which can also be referred to as a downward pumping turn. Fig. 4A is an end view of the mixing element in Fig. 4B as seen upwards as indicated by the arrows 4A-4A. Fig. 4B is a side view of the mixing element of Fig. 4A, as shown by the arrows 4B-4B. Figs. 5A and 5B are views in end elevation and side elevation, respectively, of another non-symmetrical modular mixing element similar to that shown in Figs. 4A and 4B, except that the two wings that extend axially each have a left turn ("LH"). A turn LH is a reverse pumping turn, which can also be referred to as a pumping upward rotation. Fig. 5A is an end view of the mixing element of Fig. 5B as seen in the upward direction, as shown by arrows 5A-5A. Fig. 5B is a side view of the mixing element in Fig. 5A, as indicated by the arrows 5B-5B. Figs. 6A and 6B are views in end elevation and side elevation, respectively, of a rotational non-symmetrical modular mixing element RH similar to that shown in Figs. 4A and 4B, except that the element shown in Figs. 6 having two thirds of the axial length of the element shown in Figs. 4. Fig. 6A is an end view of the element in Fig. 6B as seen upwards, as indicated by arrows 6A-6A. Fig. 6B is a side view of the element in Fig. 6A as shown by arrows 6B-6B. Figs. 7A and 7B are views in end elevation and side elevation, respectively, of a non-symmetrical rotational mixing element LH similar to that shown in Figs. 5A and 5B, except that the element shown in Figs. 7 which is two thirds of the axial length of the element shown in Figs. 5. Fig. 7A is an end view of the element in Fig. 7B as seen indicating upstream, as indicated by arrows 7A-7A. Fig. 7B is a side view of the element in Fig. 7A as shown by the arrows 7B-7B. Fig. 8 is a cross-sectional profile view of a non-symmetrical modular mixing element taken along any of the respective planes 8-8 in Figs. 4B, 5B, 6B or 7B. This profile view of a modular mixing element is shown superimposed on an ideal self-sliding profile of two screws (shown in shaded form). Such "self-sliding profile of two screws" is the maximum proportional area of such profile, which can be used in co-rotation of the extruder with two screws, interengranated where the screw is continuously in contact with its co-twin. rotating and also continuously being in contact with the inner surface of the wall of a barrel in cylindrical form of an extruder housing. The comparison of the profiles in Fig. 8 serves to emphasize the relatively large spaces provided around these non-symmetrical modular mixing elements. Figs. 1, 2, 3 and 3A show a machine 20 for forming a compound by extrusion of multiple screws having double co-rotating, intermixing screws 21 and 22. Since Fig. 1 is a sectional view in side elevation, only one of the screws 21 is seen. A downward direction through the machine 20 is shown by an arrow 23. In the machine 20, a housing 24 for the screws 21 and 22 consist of a plurality of barrel segments 26-1 to 26-9 inclusive, which are removably interconnected in axially aligned positions by disconnectable fastening means, suitable as are known in the art. The first barrel segment 26-1 is shown to have an inlet opening 25 for feeding into the housing of suitable materials indicated by the arrow 27, which are to be processed. At the upward end of the housing 24, as seen to the left in Fig. 1, a suitable drive mechanism 28 is shown with mechanical connections indicated by the dotted line 29 to the respective round axes 30 (Fig. 2) of Screws 21 and 22 to turn both screws at the same speed in the same direction. Such a drive mechanism 28 and mechanical connections 29 with suitable thrust bearings are known in the art. For example, the direction of rotation of the screws 21 and 22 around their respective axes 31 and 32 may be in the counterclockwise direction, as indicated by the arrows 34 'as seen by indicating in the downward direction 23 along the screw axes 31 and 32. It is noted that the rotation in the counterclockwise direction shown by the arrows 34 'as seen when viewed downwards along these axes 31 and 32 is the same direction of rotation as the clockwise rotation shown by arrows 34 as seen when viewed upwards along these screw axes. The seventh barrel segment 26-7 is shown, having a vent hole 36 for releasing the volatile materials indicated by an arrow 37. The ninth barrel segment 26-9 at a downward end of the housing 24 defines the outlet orifice 38 of the housing, from which an extrudate formed in a compound indicated by the arrow 39 emerges. A tip end 33 down the axis 30 of the screw 21 is seen to the right in Fig. 1. It is understood that a suitable matrix (not shown) is normally mounted in the outlet orifice 38 and in the extruded member 39 leaves the machine 20 through such a die. Each screw shaft 30 includes one or more keys 40 (Fig. 2) extending longitudinally from the respective axis parallel with the respective axis 31 or 32 to receive the keys 42 in engagement in the corresponding keys 44, in the elements mounted in the shaft to provide a positive rotational driving connection between each axis of round screws 30 and the elements mounted removably therein. In the region of the inlet opening 25 (Fig. 1), each screw 21 and 22 includes a plurality of co-rotating, intergranular conveying screw elements 45 and 46 mounted end-to-end in and keyed to their respective axes. It is noted that the transport screw elements 46 are larger than the screw elements 45 and the wings 49 of the helical screw of the elements 46 have a cable proportionally larger than the fins of the helical screw 47 of the elements 45 for fast transport of the feed materials 27 downstream of the inlet 25. Each of the transport screw elements 45 and 46, are shown having two helical screw flaps 47 or 49, respectively. Each of such fins extends around their respective axis 31 or 32 for a complete turn, that is, 360 °. Since the helical screw flaps 47 in each conveying element 45 have a one-turn configuration, the result is to provide helical screw flaps without interrupting, extending over the entire full axial length of all transport elements 45. and 46 assembled, continuous when those transport elements are sequentially mounted in and keyed to the respective screw shaft 30 in an end-to-end relationship as shown in Fig. 1.

The feed materials 27 include suitable plastic material and suitable additives to be formed into a composite and mixed in the machine 20. The transport screw elements 45 and 46 in the respective screws 21 and 22 transport these materials to be processed to a first set 50-1 of modular mixing elements 51 and 52 mounted end-to-end on their respective axes 30. Such mixing assembly 50-1 as shown includes a modular, non-symmetrical rotary mixing element RH 51 contiguous with and placed immediately upward of a non-symmetrical rotary mixing element LH 52. It is noted, as seen more clearly in FIG. 1 that the two helical screw flaps 47 of the transport screw element 45 which is positioned immediately upwards of the modular mixing element 51, are aligned with the respective wing tips 60 (Figs. 4A and 4B) of the wings 62 (Figs 2, 4A and 4B) of this mixing element 51. In this way, the two tips of the wing 60 of the mixing element 51 effectively form downward continuations of the two fins of the screw helical 47, but the angle of the propeller and the front of the tips of the wing 60 are different from the angle of the helix and front of the fins of the screw 47. In other words, there is an acute change (decrease) in the turn h elicoidal at the junctions where the fins of the respective helical screw 47 are located at the tips of the respective flange 60. Downstream of the first mixing assembly 50-1 at the respective screw 21 or 22, is another mixing assembly 50-2 (Fig. . IB) showing that it comprises non-symmetrical modular mixing elements 53 and 54 (Figs 6A, 6B and 7A, 7B, respectively). Between the mixing assemblies 50-1 and 50-2 there is a plurality of sequentially contiguous assembled transport screw elements 45 mounted and keyed to the respective axis 30. Four of the elements 45 are shown plus a short screw transport member 48, in which its two helical screw flaps 47 each extend around their respective axis 31 or 32 for one half of a full turn, i.e. 180 °. It is noted, as seen more clearly in FIG. 1A, that the two helical fins 47 of the transport screw element 45 positioned immediately downward from the modular mixing element 52 are aligned with the tips of the wing 60 of the two. wings 64 (5A and 5B) of this mixing element 52. In this way, the two wings of the helical screw 47 of this adjacent transport element, downwardly, 45 effectively forms downward continuations of the wing tips 60 of the wings 64 of the mixing element 52, but there is an acute inversion in the helical turn at the junction of these helical downwind screw wings 47 and the tips 60 of the upstream pump wings 64. The two fins 47 of the short screw transport element 48 are aligned with the tips of the wing 60 of the wings 66 (Figs 2, 6A and 6B) of the modular mixing element 53, such that these wing tips form effectively continuations downwardly of these screw fins 47, but there is an acute change (decrease) in the helical turn at the junctions between these screw fins and the tips of the flange 60 downward, contiguous. Between the second mixing assembly 50-2 and the exit of the extruder 38 there is a final sequence of screw transport elements, comprising in sequence: two screw elements 45, two elements of longer thyme 46, with fins 49 of the passage smaller helical and greater advance located near the ventilation 36 and seven screws elements plus 45. This final sequence of seven screw elements 45 serve for the pressure formed to extrude the extrudate 39 through a matrix (not shown) in the hole 38 out. The longest screw elements 46 with their longest advances, usually provide increased transport speed downward to avoid complete filling of the barrels near the vent 36 to facilitate the release of volatile materials 37. It is noted that each end of the arrow 33 includes a suitable fastening means, such as for example such as a fastening nut, with a washer, threaded on the end of the shaft to capture and retain the chain of assembled elements 45, 46, 51, 52, 45, 48, 53, 54, 45, 46 and 45 mounted on their respective axes 30 to form the screws 21 and 22. In each screw 21 and 22, the two fins 47 of the transport element 45 placed immediately downwards from the modular mixing element 54 of the second mixing assembly 50-2 as seen more clearly in Fig. IB, they are aligned with the tips 60 of the wings 68 (Figs 7A and 7B) of this mixing element effectively forming continuations downwardly of the tips 60 of the wing flange 68. There is an in sharp version in the helical turn in the joint, where each screw flap 47 that transports downward, finds each tip 60 of the pumping wing upwardly of the modular mixing element 54. To describe the characteristics of the various nodular mixing elements, Non-symmetrical 51, 52, 53 and 54, it is helpful to use certain defined terms as explained in the following. As used herein, the following terms, dimensions, factors and relationships are intended to have respective meanings as follows: "horizontal", "vertical", "upper", "lower", "upward", "downward" , "vertically upwards" and "vertically downwards" are terms used for convenience and clarity in the description of the components, elements, parts or directions as seen or shown with reference to the various FIGURES of the drawings, assuming that the drawings receptive are placed in their normal vertical orientations. It should also be understood that these terms are not intended to be limiting, since during the operation of the machine 20, the components, elements, parts or directions in the machine can be moved or rotated in orientations or angular positions different from those shown in the drawing. . "material" is intended to include both the singular and plural for convenience in avoiding the use of "material (s)". "Plastic material" is intended to include any suitable plastic materials or materials, which may include any of the suitable additives to form the composite in the machine 20 which forms the composite by extrusion. "keyed", "key" and "keyed" are intended to be interpreted broadly enough to include other equivalent means, for example, such as a spline, to provide a positive rotational momentum relationship between a rotationally driven shaft and a spline element. transport screw or a non-symmetrical modular mixing element mounted removably on such axis and rotationally driven by the shaft. The reference symbols listed in the following have the respective meanings as are further listed in these symbols. D Internal diameter (ID) of a barrel wall, which can also be referred to as the diameter of the barrel hole or the inner diameter of the barrel d space of the tip and width of the tip in the circumferential direction in Figs. 3, 3A and 3B. f width of the angular tip f-j_ width of the angular tip on the front side in the circumferential direction <; r / > 2 width of the angular tip on the rear side in circumferential direction Rß inner radius of the barrel RQ radius of the tip Q half of the width of the base R-j_ radius of the front surface X coordinates of the center point of the front surface, normal to the wing y- ^ coordinate of the center point of the front surface, normal to the base «a; wedge angle of the front surface R2 radius of the rear surface x2 coordinate of the center point of the back surface, normal to the wing y2 coordinate of the center point of the back surface, normal to the base ß angle of the wedge surface later. All linear distances in the established equations are further defined in the following to the inner radius of the barrel Rß. The following relationships were defined: a = e / d aspect ratio of the tip space b = XQ / RQ aspect ratio of the wing e = f-j_ / f coefficient of symmetry of the tip There are 18 geometric variables without dimension: 12 distance relations, 5 angles and 1 angle relation. The following 6 variables are considered main or independent design variables, which can be selected by any particular non-symmetric modular mixing element: d / Rß, a, b, e, a, ß. The other 12 variables are considered dependent variables calculated by simultaneously solving the 12 equations established in the following. It is noted that "atan" is an abbreviation of the computer for the "tangent arc": (10) ef FY- \ + e (11) F F > - l + e C12) d RB Once the ranges for the six independent variables are selected, then the resulting ranges for the dependent variables can be calculated. It should be noted that the six independent variables can not be selected arbitrarily, if they are not constrained by parameters, such as f = 0, etc., which results in a series of complex limits for all of them. In addition, according to the present invention, more preferred and more preferred ranges for the six independent variables, as will be explained below, are to increase the processing characteristics of machines that form an extrusion compound in handling various plastic materials. and additives that are formed in a compound. With another reference to Fig. 2, the housing assembly 24 is shown including two adjacent barrel sections 83 and 84 having respective substantially cylindrical inner surfaces 81 and 82 (inner surfaces of the barrel) which intersect. These cylindrical surfaces 81 and 82, as seen in the cross section in Fig. 2, appear as two intersecting circles in the form of a figure of eight. Each modular, non-symmetrical mixing element 51, 52, 53 or 54 has an axial hole 56 for mounting on an axis 30. The transport screw elements 45, 46 and 48 have holes and keys (not shown) similar to those shown in Fig. 2 for the modular mixing elements. It is shown more clearly in Figs. 3, 3A and 3B a profile 57 of a modular, non-symmetrical mixing element 51, 52, 53 or 54. Each modular mixing element 51, 52, 53 or 54 is shown in Fig. 3, having two non-symmetrical wings 62, 64, 66 or 68, respectively. Also in Fig. 3 the diameter D of the inner cylindrical surface 81 or 82 of a barrel section 83 or 84, respectively, is shown in the housing assembly 24. The dimensions of the various components of a mixing element can be expressed subsequently in terms of this inner diameter of the barrel D, such that these dimensions are set in universal terms in relation to D to be applicable to extrusion compound forming machines of various sizes, or alternatively such dimensions can be expressed in terms of the previous radius of the Rß barrel for similar reasons that are going to be established in universal terms. Each of the wings 62, 64, 66 or 68 includes a convex front surface 70 of the radius R- ^, which is located on the surface of the wing tip 60 along a corner 71. This convex front surface 70 merges at a point 72 with a tangent, straight portion 73 (called "FLAT PART") of the non-symmetrical profile 57. As shown in Fig. 3A, this merging of the tangent point 72 is located above a baseline X by the same distance as the coordinate distance y- ^ in which the center point 74 of the front surface is located above this baseline. The pair of base half-widths XQ is positioned along the base line X on opposite sides of the axis 31 or 32. Each of the wings 62, 64, 66 or 68 includes a convex rear surface 76 of the radius R2, which finds the surface of the tip 60 of the wing along a corner 77. The radius of the rear surface R2 is preferably always greater than the radius of the front surface R- ^ for the reasons explained below. A center point 78 for the radius of the rear surface R is separated by a distance from the small coordinate y2 above the base line X. The distance of the coordinate x-_ for the center point of the front surface 74 and the distance of the coordinate x2 for the center point of the back surface 78 are measured normal to a centerline 75 (main chord) of the two non-symmetrical wings 62, 64, 66 or 68 of each modular mixing element 51, 52, 53 or 54. This main line 75 of the center line is called a "center line" because it extends through the axes 31 or 32. coordinate is always greater than x-,, and the y2 coordinate is always less than y1. Since the center point of the back surface 78 is slightly spaced above the base line X, it is noted that the flat surface 73 extends a slight distance beyond the base line X and merges into a tangent point of fusion 79 with the convex rear surface 76.

To extend an advantageous wedge angle a between the convex front surface 70 of a non-symmetrical wing 62, 64, 66 or 68 and the surface of the inner wall of the barrel 81 or 82, reference will now be made to Fig. 3B. A second radius R- | _ is being needed. This second radius R-j_ is a line segment 86 extending from the front center point 70 which intersects the surface of the wing tip 60. Since this line segment 86 extending from point 74 to corner 71 is a radius of arched front surface 70, it is normal (perpendicular) to point 71 to a tangent for that convex front surface 70 at point 71. A line 90 is indicated extending from the axis 31 or 32 to the corner 71, and this line 90 is shown by shading 91 of points which are understood up to a point 92 on the inner surface of the barrel 81 or 82. Since this extended line 90, 91 is radiated from the axis 31 or 32 (which is on the axis of the inner surface of the barrel and you also see the axis of the screw assembly 21 or 22), this extended line 90, 91 is a radius of the surface inside the barrel and therefore is perpendicular at point 92 to the tangent with respect to the inner surface of the barrel at point 92. The dotted line 93 is drawn tangent to the front surface 70 at the corner point 71. Another line dotted 94 is drawn so people to the inner surface of barrel 81 or 82 at point 92. The angle a between the tangent lines 93 and 94 is called the wedge angle of the front surface, because it provides an essentially constant and uniform wedge action, which begins near the melting point 72 of the flat surface to the curve and which continues to the front corner 71 of the wing tip. Since they are perpendicular to the respective tangents 93 and 94, the line segment 86 and line 90 also define among themselves the same front surface wedge angle, as shown in Fig. 3B. By a geometrical principle, it is observed that the lines 86 and 90, which are respectively perpendicular to two lines of intersection (tangents 93 and 94), define among themselves the same angle as between the lines of intersection. By a similar reasoning, it is observed that a line segment 87 extending from the center point of the rear surface 78 to the rear corner of the wing tip 77 is another radius R2 of the arcuate rear surface 76. Therefore, the line 87 is perpendicular to a tangent 95 (shown in dashed line) to the rear surface curve 76 at the corner point 77. A line segment 96 exiting the axis 31 or 32 to the corner point 77 is extended as it is shown by dotted line 97 at a point 98 on the inner surface of barrel 81 or 82. In this way, a tangent 99 (shown in dashed line) to the inner surface of barrel 81 or 82 at point 98 is perpendicular to line 96, 97. The angle between the tangents 95 and 97 is called the rear surface wedge angle and is always greater than the wedge angle ex of the front surface. Lines 87 and 96 also define the same angle between themselves as tangents 95 and 99 do, due to the same geometric principle mentioned above for angle a. By the dynamic wedge action created by the wedge angle α in the wedge area 85 (Fig. 3B) between the front surface 70 and the inner surface of the barrel 81 or 82, the plastic material 27 (Fig. 1) that is being formed in a compound is subject to dynamic wedge pressurization in this area 85, which drives relatively large circumferential flows of this material, as shown by the arrow 88, through a relatively greater shear stress space d the tip of the wing 60. In this way, large circumferential flows 88 of plastic material are repeatedly driven by the action of dynamic wedge pressurization, to repeatedly pass through shear spaces d. Because these relatively large shear spaces, the plastic material that is being mixed at lower and more uniform temperatures than what usually occurs with the use of typical prior art mixing elements. Since the viscosity in most plastic materials decreases with elevated temperatures, the lower temperatures which are achieved allow the plastic material to be processed at higher speeds than what typically occurs in machines to form former extrusion compounds. Due to the higher viscosities of the plastic material of lower temperature, the shear stresses in the material are greater, increasing the dispersive mixing despite the relatively large spaces d, which are being used. Also, due to the fact that the wedge angle ß of the back surface is chosen to be greater than the wedge angle of the front surface, the plastic material experiences a sudden release, ie a reduction in the speed of circumferential flow and in the cutting speed after the corner 77 of the tip of the rear wing has passed. This sudden release of the plastic material in the rear wedge release area 89, after the corner conduit 77, causes in effect a separation of the plastic from the inner surface 81 or 82 of the barrel, almost like the plastic material "bounced" "separating it from this inner surface. Accordingly, less energy is needed in starting in this area of the rear wedge angle 89, so it conserves energy and keeps the plastic material at a lower temperature than what occurs with mixing blocks or symmetrical mixing discs. A sequence of seven experimental tests run on polypropylene material that has an index of Melt Flow Flow (MFI) of 2.5 as measured according to the ASTM D1238 test procedure (conditions 230 ° C) (446 ° F) with the piston weight of 2.16 kilograms). The machine that forms the compound by extrusion as run, included the screw assemblies 21 and 22 arranged as shown in Figs. 1, ÍA, IB, 2, 3, 3A and 3B. The results of these seven experimental tests are summarized in columns 1 to 7 of Table I, established in the following. "SEI" is the specific energy input, which is the calculated result of dividing the energy input measured between the flow velocity of the resulting mass in kilograms per hour. The temperatures of the successive eight barrel segments 26-2 to 26-9 were measured for suitable temperature detectors, one of which is indicated by T with the detector 100 shown inserted in the barrel segment 26-6, so that be sensitive to the temperature of the respective barrel segment. The outlet temperature and the pressure are respectively the temperature of the extrudate 39 and the pressure at which it is being extruded through the matrix. The front temperature is. the temperature of the front outlet at the downward end of the final barrel segment 26-9. The temperature of the matrix is the temperature of the matrix (not shown) through which the extrudate 39 is ejected. There are two temperatures set in each test column for eight segments of Barrel and the Front. The value of the left temperature in each column is the set point (or target) and the value on the right is the temperature actually obtained as shown by the respective measured temperatures. It is observed that the relatively low and relatively uniform temperatures are achieved along the full length of the barrel in all seven test runs.

T A B A I Material: PP MR = 2.5 f Figs. 4A and 4B show end elevational and lateral elevation views of the non-symmetrical modular mixing element 51, which was described with reference to Figs. 1 and ÍA. It is shown with two wings 62 located in angular positions diametrically opposite in relation to the screw axis 31 or 32. The wings 62 with their wing tips 60 are shown having a rotation RH of 90 ° in the axial length L of the element 51. As will be appreciated from a close view in Fig. IA, which shows a barrel segment 26-3, the axial length L is shown to be one half the axial length of a barrel segment. With two opposing keys 44 as shown and with a 90 ° turn such elements 51 are capable of being assembled in multiple assemblies and combinations, with their wing tips 60 which are in alignment to form the propeller without interrupting their end joints. to extreme. Figs. 5A and 5B show views of end elevation and lateral elevation of the non-symmetrical modular mixing element 52, which was described with reference to Figs. 1 and ÍA. This mixing element 52 is shown with two wings 64 located in angular positions diametrically opposite in relation to the screw axis 31 or 32. The wings 64 and their wing tips 60 are shown having a LH rotation of 90 ° in the axial length L (one half of the axial length of a barrel segment). With two opposing keys 44 as shown and with a 90 ° turn, such elements 52 are allowed to be assembled in multiple assemblies and combinations with their wing tips 60 which are aligned end to end to form an uninterrupted helix. Also, elements 51 and 52 can be assembled in assemblies 50-1 (Figs.1 and IA) as described. Their wing tips are aligned in a joint 104 (Fig. IA), but there is an abrupt inversion in the turn that forms a horn in this joint 104. Figs. 6A and 6B show views in end elevation and lateral elevation of the non-symmetrical modular mixing element 53 observed in Figs. 1 and IB. The element 53 is shown with two diametrically opposed wings 66. These wings 66 with their wing tips 60 are shown having a rotation RH of 90 ° within an axial length of two thirds L. In this way, the length of the element 53 is shown to be one third of the length of a barrel segment. With two opposing keys 44 as shown and with a 90 ° turn, such elements 53 are capable of being assembled into multiple assemblies and combinations with their wing tips that are in alignment at their end-to-end joints to form a propeller without interrupt. In addition, the rotary mixing elements 51 and 53 are capable of being assembled with their wing tips in alignment to provide changes in the helical pitch RH at their joints. The rotational mixing elements RH 51 and 53 are capable of being assembled upwardly of the rotary mixing elements LH with the tips of the wing in alignment, but there is an abrupt inversion in the turning that forms a horn in its joints. Figs. 7A and 7B show views in end elevation and in lateral elevation of the rotating modular mixing element LH 54 not symmetrical of a 90 ° turn. This mixing element 54 is also seen in Figs. 1 and IB. It has an axial length of two thirds L and is similar to mixing element 53, except that the turns of its helix are of the same pitch but in the opposite direction. In this way, mounted end-to-end in a set of 50-2 as shown in Fig. IB, they form a horn 106 which has a stepped V-shape that the horn 104 (Fig. IA) since the lengths axial are shorter, so they create a larger helix angle (shorter front end) at their wing tips 60, than the helix angle for the wing tips 60 of the larger mixing elements 51 and 52. In FIG. 8 the profile 57 of a non-symmetrical modular mixing element is shown superimposed on an ideal self-slip profile of double screw. (shown shaded). As explained above, such an ideal self-slip profile of double screw, is the maximum proportional area of such self-slip profile, which can be used in a co-rotating co-rotating double screw extruder in which the screw remains continuously in sliding contact with its co-rotating twin and also continuously remains continuously in sliding contact with an inner wall surface 81 or 82 of the barrel in a cylindrical shape. The substantial proportional amount of the shaded area between the profiles 107 and 57 shows the relatively large spaces provided around the non-symmetrical profiles 57 of those modular mixing elements. During the operation of the machine 20, the downward flow is mainly the channel flow in the regions along a barrel where the transport screw elements 45, 46 or 48 are interengaged. This channel flow occurs along the valleys of the helix between the successive screw fins 47. To distinguish this channel flow, there are relatively large amounts of circumferential flow produced in the regions along a barrel where sets of modular mixing elements 51, 52, 53 or 54 not symmetrical are mounted. By their dynamic wedge action and their relatively large cutting spaces, they produce relatively large proportional amounts of circumferential flow as shown by the arrows 88 in Fig. 3B. It is recognized that the entire mass of plastic material in the barrel is progressing downward, but nevertheless the non-symmetrical configurations as shown and described produce relatively large proportional amounts of circumferential flow. 88 so they produce repeated passes of the material through the relatively large tip spaces to efficiently and effectively produce the homogeneous composite of the plastic material. The analyzes lead to the selection of the following preferred ranges for the independent design variables, which were discussed in the foregoing for the non-symmetrical profile 57: TABLE II ratio of the tip space d to the inner radius of the barrel RB = from approximately 0.01 to about 0.15 aspect ratio of tip space a = from about 1 to about 8 wing aspect ratio b = from about 0.5 to about 0.8 point symmetry coefficient e = from about 0 to about 1 wedge angle ar from the front surface = from about 5 ° to about 25 ° angle ß of the wedge of the back surface = from about 10 ° to about 90 ° and ß is at least 1 ° greater than.

The most preferred ranges for these independent design variables for the non-symmetric profile 57 are as follows: TABLE III d / Rg = from about 0.02 to about 0.12 a = from about 1.5 to about 6 b = from about 0.55 to about 0.75 e = from about 0.25 to about 0.75 = from about 10 ° to about 20 ° β = from about 20 ° to about 30 ° β is at least about 5 ° higher than the most preferred ranges of values for the independent design variables for the The unsymmetrical profile 57 is as follows: TABLE IV d / RB = from about 0.03 to about 0.10 a = from about 2 to about 5 b = from about 0.6 to about 0.7 e = from about 0.4 to about 0.6 = from about 12 ° to approximately 16 ° ß = from approximately 22 ° to approximately 28 ° ß is at least approximately 7 ° greater than «I Directing attention again to Figs. 4A and B, 5A and B, 6A and B, 7A and B, the propeller angles for the wing tips 60 of the modular mixing elements, are preferably in the range of about 20 ° to about 60 °. . The front part of the tips of the helical wing is preferred to be in the range of approximately 2D to approximately 8D. As well, it is noted that the 90 ° turn shown for the modular mixing elements 51, 52, 53 and 54 are related to their two-pin configuration. With a three-key configuration, the 60 ° turning angles are usable to provide alignment of the wing tips 60 at the end-to-end joints. With a four-pin configuration, either 90 ° or 45 ° turning angles can be used to provide such alignment of the wing tips in the joints, and so on. Since other changes and modifications vary to adjust the operating requirements of the machine forming an extrusion compound, particular and environments will be recognized by those skilled in the art, the invention is not considered limited to the examples chosen for the purposes of and includes all changes and modifications in the machines to form compounds by extrusion, which do not constitute a separation of the true spirit and scope of this invention, as claimed in the following claims and equivalents for the claimed elements.

Claims (21)

1. CLAIMS 1. A machine for forming an extrusion compound, of multiple screws characterized in that it comprises: a housing assembly including two attached and substantially cylindrical barrel sections, each having an interior wall surface; a screw for forming the extrusion compound placed within each of the adjacent barrel sections with the screws that are axially adjacent to each other and rotatable in the same direction about an axis of rotation; each screw includes a plurality of transport screw elements removably mounted on and keyed to a rotatably operable shaft; the transport screw elements intergraded; each screw that includes at least one set of modular, non-symmetrical mixing elements; each modular mixing element that is removably mounted on a key for the shaft; each modular mixing element has a plurality of non-symmetrical wings; the modular mixing elements are interengranted; and each set of modular, non-symmetrical mixing elements that include at least one modular mixing element that has a left turn, mounted immediately downward and contiguous with at least one modular mixing element having a rotation to the right. The machine for forming an extrusion composite according to claim 1, characterized in that: each wing has a front surface and a rear surface with a wing tip positioned between front and rear surfaces; the front surface defines a wedge angle α of the front surface with the surface of the inner wall of the barrel; the rear surface defines a wedge angle ß of the rear surface with the interior wall surface of the barrel; and the angle ß is at least about 5 ° greater than the angle a. 3. The machine for forming compounds by extrusion according to claim 2, characterized in that; the front surface wedge angle a is in a range of about 5 ° to about 25 °; and the rear surface wedge angle ß is in a range of about 10 ° to about 50 °. 4. The machine for forming compounds by extrusion according to claim 3, characterized in that: the tip of the wing has a tip space d of the surface of the inner wall of the barrel; the surface of the inner wall of the barrel has an inner radius of the barrel Rß; and the ratio of the space of the tip d to the inner radius Rβ of the barrel is approximately from 2 percent to approximately 15 percent. 5. The machine for forming compounds by extrusion according to claim 4, characterized in that: the tip of the wing has a circumferential extension e; an aspect ratio of tip space a is defined as the ratio of the circumferential extension of the tip of the wing to the tip space; and the aspect ratio of the tip space is in a range of about 1 to about 8. The machine for forming extrusion compounds according to claim 5, characterized in that: the surface of the inner wall of the barrel is concentric around the axis of rotation; and the circumference of the tip of the wing e is concentric about the axis of rotation; and the tip space d is constant along the circumferential extension e. The machine for forming extrusion compounds according to claim 2, characterized in that: the angle alpha of the wedge of the front surface is in the range of approximately 12 ° to approximately 18 °; the wedge angle ß of the back surface is in a range of about 20 ° to about 36 °; and the angle ß is at least about 6 ° greater than the angle. 8. The machine for forming compounds by extrusion according to claim 3, characterized in that: the tip of the wing has a space of the tip d of the surface of the interior stop of the barrel; the surface of the inner wall of the barrel has an inner radius of the barrel Rß; and the ratio of the space of the tip d to the inner radius of the barrel Rβ is from about 3 percent to about 14 percent. The machine for forming compounds by extrusion according to claim 8, characterized in that: the tip of the wing has a circumferential extension e; an aspect ratio of the tip space a is defined as the ratio of the e circumferential extension of the tip of the wing to the tip space d; and the aspect ratio of the tip space is from about 1.5 to about 6. The machine for forming compounds by extrusion according to claim 6, characterized in that: the aspect ratio of the extension e circumferential of the tip of the wing to space of the tip d is in a range of approximately 1.5 to approximately 6. 11. A machine for forming an extrusion composite, of multiple screws according to claim 1, characterized in that: the surface of the inner wall has an inner diameter D; the plurality of non-symmetrical wings extend axially and have an angular rotation about the axis of rotation; and the angular rotation of the wings having a front part in the range of approximately 2D to approximately 8D. The multi-screw extrusion forming machine according to claim 11, characterized in that each of the non-symmetrical modular mixing elements has an axial length; each of the modular mixing elements has an axial hole, with a plurality of keys therein; the wings in each modular mixing element have an end-to-end amount of rotation about the axis of rotation; and the amount of end to end of the turn is equal to 180 ° divided by the number of keys. The multi-screw extrusion forming machine according to claim 11, characterized in that: a first plurality of transport screw elements are removably mounted on and keyed to the shaft placed upwards of each set of mixing elements modular non-symmetrical; a second plurality of transport screw elements are removably mounted on and keyed down the axle of each set of non-symmetrical modular mixing elements; Downward ends of the screw fins of a transport screw element, contiguous with an upward end of the modular mixing element woven to the right in an assembly, are aligned with the upward ends of the wings of the modular mixing element of turning to the right in the set. A multi-screw extrusion forming machine according to claim 13, characterized in that: the upstream ends of the screw fins of a transport screw element, contiguous with a downward end of the mixing element Modular to the left is aligned with downward ends of the wings of the left-hand modular mixing element. 15. A non-symmetrical modular mixing element for removably mounting on a shaft of a rotationally driven screw of a machine to form an extrusion compound in keyed relationship with the shaft characterized in that: the non-symmetrical modular mixing element has an axial hole for receive the shaft; the axial hole having at least one key; the non-symmetric mixing element having a plurality of non-symmetrical wings; each of the wings having a front surface and a rear surface with a tip of the intermediate wing to the front and rear surfaces; and the rear surface having a smaller radius of curvature than the rear surface. 16. The modular, non-symmetrical mixing element for removably mounting on the shaft of the rotationally driven screw of a machine to form compounds by extrusion in keyed relation to the shaft, characterized in that: the non-symmetrical modular mixing element has an axial hole for receiving the y-axis has a concentric rotation axis with the axial hole; the axial hole has at least one keygNE ; the modular, non-symmetrical mixing element that is configured for removable mounting on such a screw shaft, for installation in a machine to form extrusion compounds desi for two co-rotating screws, interengaged to be placed in respective barrel sections of two sections barrel substantially cylindrical and adjacent each having an inner radius of the barrel surface Rg; the non-symmetrical modular mixing element having two non-symmetrical wings located on opposite sides of the axis of rotation; each of the wings having a front surface and a rear surface with a tip of the intermediate wing on the front and rear surfaces; the front surface having a convex portion adjacent to the tip of the wing; the convex portion of the front surface having a radius R1 extending from the center point of the front surface; a portion of the radius R ^ extending from the center point of the front surface to a point on the convex portion of the front surface defining an angle a with a first radial line extending from the axis of rotation to the point on the convex portion of the front surface; the rear surface meets the tip of the wing along a corner; a geometric straight line extends from the back surface to the corner and is a straight extension of the back surface at the corner to a point on the inner surface of the barrel that defines an angle ß with a tangent to the inner surface of the barrel in the point; and the angle ß is greater than the angle. 17. The modular, non-symmetrical mixing element according to claim 16, characterized in that: the angle ß is at least about 5 ° greater than the angle. 18. The modular, non-symmetrical mixing element according to claim 17, characterized in that: the tip of the wing is at a radial distance RQ from the axis of rotation; and the non-symmetric modular mixing element is configured so that the radial distance RQ is smaller than the inner radius of the barrel surface Rß by a space at the tip d having a space ratio of the tip d to the inner radius of the barrel. the surface of the barrel Rß in a range of about 0.01 to about 0.15. The modular, non-symmetrical mixing element according to claim 16, characterized in that: the convex portion of the front surface attaches to the tip of the wing along a first corner at the point; the first radial line extending from the center point of the front surface extends to the first corner; the angle a is in a range of about 5 ° to about 25 °; and the angle ß which is in a range of about 10 ° to about 90 °. 20. The modular, non-symmetric mixing element according to claim 19, characterized in that: the tip of the wing is at a radial distance RQ from the axis of rotation; the non-symmetrical modular mixing element has a base half the width X0 measured perpendicular to the radial distance RQ; and the non-symmetric modular mixing element has an aspect ratio of the X0 / RQ wing in a range of about 0.5 to about 0.8. 21. The non-symmetrical modular mixing element according to claim 20, characterized in that: the center point of the front surface is offset by a distance X-j_ measured perpendicular to the racial distance R0; and the base of half the width XQ equal to the radius R-L of the convex portion of the front surface minus the displacement distance X1. ABSTRACT Machines to form compound by extrusion, of multiple screws that have assemblies of cogiratorios screws that incorporate sets of modular mixing elements of non-symmetrical geometries with relatively large wingtip spaces. These non-symmetrical modular mixing element assemblies are removably mounted from any of the axial locations along their rotationally driven screw shafts to optimize performance in relation to the plastic material and the particular additives to be formed in a compound. The non-symmetrical geometries provide dynamic wedge pressurization to repeatedly drive relatively large circumferential flows of the plastic material through large cutting spaces. Due to the relatively large cutting spaces, the plastic material is mixed at lower temperatures and more uniform than what usually happens with the use of the mixing blocks with previous symmetrical mixing discs. At lower temperatures, more plastic materials have increased viscosities. Thus, the resulting increased viscosities allow the plastic material to be processed at higher shear stresses to increase dispersion mixing, despite the relatively large spaces, which are being used. In this way, the operators of the machines for forming compounds by extrusion are provided with advantageous flexibility in adapting them for the increased operation in the processing of a coupling machine that works with the characteristics and processing parameters of the plastic materials and the additives. that are going to form in a compound.