WO2011004386A2

WO2011004386A2 - An extruder

Info

Publication number: WO2011004386A2
Application number: PCT/IN2010/000414
Authority: WO
Inventors: Babu Padmanabhan; Pradeep Bakshi; Durgesh Bakshi
Original assignee: Steer Engineering Private Limited
Priority date: 2009-06-17
Filing date: 2010-06-17
Publication date: 2011-01-13
Also published as: WO2011004386A3

Abstract

An extruder capable of manufacturing fiber reinforced thermoplastics is disclosed. The extruder includes a barrel having two parallel bores of equal diameter, the centre distance between the two bores lesser than the diameter of the bore; and a shaft located within each bore, each shaft configured for rotation in the same direction; the shaft forming three zones within the barrel, the zones including a fiber entry zone configured for receiving fibers from an extruder inlet; a fiber incorporation zone configured for incorporation the fibers into a polymer mix, the fiber entry zone and fiber incorporation zone generate waves in the polymer mix; and a wave disruption zone capable of cutting of fibers to a desired length; wherein the fiber entry zone and the fiber incorporation zone includes at least one extruder wave element; and the wave disruption zone includes at least one wave disruption element

Description

AN EXTRUDER

The present disclosure generally relates to an extruder. More particularly the disclosure relates to an extruder for the manufacture of fiber reinforced thermoplastics.

BACKGROUND

Fiber reinforced thermoplastics are used for various types of applications such as automobile parts including bumpers, side panels and dashboards and for office automation equipment. Fiber reinforced thermoplastics are best suited for designs that demand weight saving, precise engineering, finite tolerance and simplification of parts in both production and operation. Moulded fiber reinforced thermoplastic products are cheaper, faster and easier to manufacture than cast aluminium or steel products with similar tolerance and material strength. One factor that determines the strength and elasticity of a fiber reinforced thermoplastic is the length of the fibers present in the final product. It is observed that when longer fibers are used to reinforce thermoplastic, the mechanical strength and elasticity of the thermoplastic increases.

Various methods are known for the manufacture of fiber reinforced thermoplastics, hi one method chopped fibers are added to melted plastic in an extruder. The chopped fibers may be added prior to or after the addition of the melted plastic in the extruder. This has a disadvantage as the fibers and the melted plastic do not mix uniformly when they meet, but form zones of fiber concentration and plastic concentration that must then be blended downstream by mixing means in order to achieve uniform mixing and impregnation of the fibers. As excessive mixing is required downstream, it causes breakage and damage to the fibers.

Another method involves feeding a continuous roving of fiber into the plastic melt in an extruder. In such systems the fibers are rapidly pinched off or cut off between the screw flights and the barrel wall at the point of entry. These fibers form entanglements which are not completely impregnated, and are therefore very difficult to break up and mix with the remaining plastic melt. Such systems therefore require intensive and/or long mixing and kneading or shearing zone. The result of this is that a very high proportion of very short fibers or fines are produced in the final product.

Both the methods described above require the use of mixing or kneading extruder elements in the fiber entry zone and in the fiber mixing or impregnation zone (the zone downstream to the fiber entry zone) in the extruder. Such mixing or kneading elements mix compounds primarily through a folding mechanism. This folding mechanism results in the breakage of the fibers resulting in shorter fibers in the product. Moreover, the fibers produced have an uneven length due to the folding mechanism of these mixing or kneading elements.

Therefore there is a need for extruder elements and an extruder that would allow for efficient mixing of the fiber with the plastic melt without causing breakage of fibers. The extruder elements and the extruder should be such that it would allow for the production of fiber reinforced thermoplastic compositions in which long fibers make up as large a population as possible and the smallest or short fibers make up as small a proportion as possible of the product. Moreover, the extruder elements and the extruder should be such that a substantial portion of the fibers in the product have a specific distribution of fiber length.

SUMMARY

The invention relates to an extruder capable of manufacturing fiber reinforced thermoplastics. The extruder includes a barrel having two parallel bores of equal diameter, the centre distance between the two bores lesser than the diameter of the bore; and a shaft located within each bore, each shaft configured for rotation in the same direction; the shaft forming three zones within the barrel, the zones including a fiber entry zone configured for receiving fibers from an extruder inlet; a fiber incorporation zone configured for the incorporation of fibers into a polymer mix, the fiber entry zone and fiber incorporation zone generate waves in the polymer mix; and a wave disruption zone capable of cutting of fibers to a desired length; wherein the fiber entry zone and the fiber incorporation zone include at least one extruder wave element, the extruder wave element has a continuous outer surface in the form of a helical wave; and the wave disruption zone includes at least one wave disruption element, the wave disruption element has an outer surface in the form of a helical wave with a plurality of grooves formed on the crest of the helical wave.

The invention also relates to an extruder capable of manufacturing fiber reinforced thermoplastics including a barrel having two parallel bores of equal diameter, the centre distance between the two bores lesser than the diameter of the bore; and a shaft located within each bore, each shaft configured for rotation in the same direction; the shaft forming four zones within the barrel, the zones including a pre-plasticizing zone configured for preparing a polymer melt; a fiber entry zone configured for receiving fibers from extruder inlet; a fiber incorporation zone configured for incorporating the fibers into the polymer mix, the fiber entry zone and fiber incorporation zone generate waves in the polymer mix; and a wave disruption zone capable of cutting the fibers to a desired length; wherein the fiber entry zone and the fiber incorporation zone include at least one extruder wave element, the extruder wave element has a continuous outer surface in the form of a helical wave; and the wave disruption zone includes at least one wave disruption element, the wave disruption element having an outer surface in the form of a helical wave with a plurality of grooves formed on the crest of the helical wave.

The invention also relates to a method of incorporating fibers in a thermoplastic. The method includes feeding fibers into an extruder, the extruder comprising a barrel having two parallel bores of equal diameter, the centre distance between the two bores lesser than the diameter of the bore; and a shaft located within each bore, each shaft configured for rotation in the same direction; the shaft forming three zones within the barrel, the zones including a fiber entry zone configured for receiving fibers from an extruder inlet; a fiber incorporation zone configured for incorporation of the fibers into a polymer mix, the fiber entry zone and fiber incorporation zone generate waves in the polymer mix; and a wave disruption zone capable of cutting the fibers to a desired length; wherein the fiber entry zone and the fiber incorporation zone includes at least one extruder wave element, the extruder wave element has a continuous outer surface in the form of a helical wave; and the wave disruption zone includes at least one wave disruption element, the wave disruption element has an outer surface in the form of a helical wave with a plurality of grooves formed on the crest of the helical wave; the method comprising adding fibers to a plastic melt into the fiber entry zone of the extruder; mixing the fibers with the plastic melt by passing the mixture of the fibers and plastic melt through the fiber incorporation zone; and reducing the length of the fibers in the mixture to a desired length by passing the mixture though the wave disruption zone of the extruder.

The invention also relates to an element for an extruder, wherein the element has a continuous outer surface in the form of a helical wave.

The invention also relates to an element for an extruder, wherein the element has a continuous outer surface in the form of a helical wave having an axial length in the range of 0.5 to 6 times the outer diameter of the element (10), a helical pitch in the range of 0.5 to 20 times the outer diameter of the element (10) and the ratio of element outer diameter to element root diameter ranges from 1.25 to 1.95. The invention relates to an element for an extruder. The element has an outer surface in the form of a helical wave with a plurality of grooves formed on the crest of the helical wave.

The element may be used in an extruder for processing long fibre reinforced thermoplastics.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

The accompanying drawings illustrate the preferred embodiments of the invention and together with the following detailed description serve to explain the principles of the invention.

Figure 1 illustrates an isometric perspective view of an extruder shaft in accordance with an embodiment.

Figure 2 illustrates a top view of an extruder illustrated in figure 1.

Figure 3 illustrates a left hand view of an extruder illustrated in figure 1.

Figure 4 illustrates a right hand view of an extruder illustrated in figure 1.

Figure 5 illustrates an isometric perspective view of an extruder wave element in accordance with an embodiment.

Figure 6 illustrates a front view of the extruder wave element of figure 5.

Figure 7 illustrates a left hand side view of the extruder wave element of figure 6.

Figure 8 illustrates a right hand side view of the extruder wave element of figure 6.

Figure 9 illustrates a top view of an extruder wave element illustrated in figure 5.

Figure 10 is a pictorial representative of the extruder wave element in accordance with an embodiment.

Figure 11 illustrates on isometric perspective view of an extruder wave disruption element in accordance with an embodiment.

Figure 12 illustrates a front view of the extruder wave disruption element of figure 11.

Figure 13 illustrates a left hand side view of the extruder wave disruption element of figure 12.

Figure 14 illustrates a right hand side view of the extruder wave disruption element of figure 12.

Figure 15 illustrates a top view of an extruder wave disruption element illustrated in figure 11.

Figure 16 is a pictorial representative of the extruder wave disruption element in accordance with an embodiment. Figure 17 illustrates an extruder comprising of a pre-plasticizing zone in accordance with an embodiment.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.

An extruder for the manufacture of fiber reinforced thermoplastics is disclosed. The extruder is a co-rotating twin screw system comprising of a long barrel having two bores that intersect each other. Two shafts that are both driven in the same direction are placed in the bore. Extruder elements are mounted one after the other in a continuous chain on the shaft that transmits the rotary motion without slippage to the extruder elements.

Figures 1 to 4 illustrate the two shafts (50) and (60) of the extruder in accordance with an embodiment. The shafts (50, 60) comprise of a fiber entry zone (12) configured for receiving fibers from an inlet, a fiber incorporation zone (14) configured for incorporating the fibers received from the fiber receiving zone (12) into a plastic melt and a wave disruption zone (16) configured for cutting the fibers to obtain fibers of desired length.

In accordance with an embodiment, the extruder may further comprise of a pre- plasticizing zone configured for spreading out and melting the polymer. The pre-plasticizing zone may also be configured with conventional extruder elements for melting and mixing the polymer constituents.

The length of a zone may be determined based on the length and the nature of the fibers to be incorporated into the polymer composite and on the required length of the fibers required in the end product. In accordance with an aspect the length of the fiber entry zone (12) is in the range of 0.5 times to 20 times the barrel diameter. The length of the fiber incorporation (14) is in the range of 0.5 times to 20 times the barrel diameter. The length of the wave disruption zone (16) is in the range of 0.5 times to 20 times the barrel diameter.

The fiber entry zone (12) and the fiber incorporation zone (14) comprises of a first type of element capable of forming waves in the extruder mixture. In accordance with an aspect a wave extruder element that has a continuous outer surface in the shape of a helical wave is deployed in these zones. A continuous surface as used herein refers to a smooth surface without any abrupt changes in profile and without the formation of a distinct land.

With reference to figures 5 and 10, an extruder wave element (100) for an extruder shaft in accordance with an embodiment is illustrated. The extruder wave element (100) comprises of a grooved axial bore (118) in which splines of the drive shaft are engaged. The extruder wave element (100) has a continuous outer surface (112) in the form of a helical wave extending between the first end (114) and second end (116) of the extruder wave element (100).

The outer wave surface refers to an outer surface such that the flight depth of the element varies between a maximum and a minimum value to form wave crests periodically along the element (100). Flight depth refers to the depth of the channel or the distance from the edge of the flight to the core of the element (100). The flight depth is equal to one half the ratio of element outer diameter (D) to element root diameter, hi accordance with an aspect the ratio of the element outer diameter (D) to element root diameter is in the range of 1.25 to 1.95.

The continuous outer surface (112) in the shape of a helical wave refers to an outer wave surface forming periodic crests in a direction both along and perpendicular to the element axis, as depicted in figures 5 and 9.

With reference to figure 6, a front view of the extruder . wave element (100) is illustrated, wherein the element (100) is shown to form a wave pattern along the element axis. The distance between two successive crests of the wave is a factor of the outer diameter [D] of the element (100). The distance between two successive crests of the wave is known as the pitch of the helical wave.

In accordance with an aspect, the distance between two successive crests or the pitch of the helical wave may vary from being half the outer diameter [0.5 D] to twenty times the outer diameter [20 D], depending on the nature of the application. For processes involving the treatment of long fibers, the pitch or the distance between two successive crests is preferably at least one and a half times the outer diameter [1.5 D]. In the embodiment illustrated, the pitch or the distance between two successive crests is twice the outer diameter of the element [2D].

In accordance with an embodiment, the extruder wave elements (100) used in the fiber incorporation zone (14) have a smaller distance between two successive crests than the extruder wave elements (100) of the fiber entry zone (12).

In accordance with an embodiment, the extruder wave elements (100) used in the fiber entry zone (12) have a larger screw- screw clearance than the extruder wave elements (100) used in the fiber incorporation zone (14). Due to the larger screw- screw clearance the extruder wave elements (100) in the fiber entry zone (12) are intermeshing elements, but are not completely wiping. This allows for the entry of fibers into the extruder without causing breakage of fibers. In the embodiment illustrated the screw-screw clearance of the extruder wave elements (100) used in the fiber entry zone (12) is 2 mm.

In the fiber incorporation zone (14) due to the smaller screw-screw clearance the extruder wave elements (100) are wiping in nature. The wiping extruder wave elements (100) in the fiber incorporation zone (14) prevents winding of fibers on the extruder wave elements (100) thus preventing the jamming of the extruder. In the embodiment illustrated the screw- screw clearance between the extruder wave elements (100) used in the fiber incorporation zone (14) is 0.5 mm.

In accordance with an aspect the fiber entry zone (12) of the extruder is configured for heating the thermoplastic polymer allowing for its melting and mixing during the process of fiber entry in the extruder.

In accordance with another embodiment, the fiber incorporation zone (14) may include extruder wave elements (100) having a smaller distance between two successive crests followed by wave extruder elements (100) having a larger distance between two successive crests.

In accordance with another embodiment, the elements in the fiber entry zone (12) and the fiber incorporation zone (14) may be configured on the extruder to form alternate zones of wave elements (100) having larger and smaller distance between two successive crests.

Figures 7 and 8 illustrate the left hand and right hand side views of the extruder wave element (100) in accordance with an embodiment. In the embodiment illustrated the wave completes a cycle, and the two end points (114, 116) represent the start and completion of a wave along the element axis. However, the extruder wave element may be formed where a wave cycle is not completed between the two end points of the element, which would also depend on the distance between two successive crests forming the wave and the length of the wave element. In accordance with an aspect, the axial length of the extruder wave element (100) is in the range of 1.25 to 1.95 times the outer diameter [D] of the element.

Figure 9 illustrates a top view' of the extruder wave element (100) of figure 5. As may be seen in the top view, a wave surface is formed in a direction perpendicular to the element axis. In the embodiment illustrated, one crest of the wave is formed on the element in a direction perpendicular to the axis of the element, between two crests formed along the element axis. The outer surface of the extruder wave element (100) is a continuous surface including the crests formed both along and perpendicular to the element axis and thereby forming the continuous helical wave outer surface.

Again with reference to figure 1 and 2, the wave disruption zone (16) comprises of a second type of element capable of disrupting the waves formed in the mixture and breaking fiber length to desired size. In accordance with an, aspect a wave disruption element (200) configured for reducing the size of the fibers to the desired fiber length is used in the wave disruption zone (16).

With reference to figures 11 and 16, the wave disruption element (200) for the extruder shaft in accordance with an embodiment is illustrated. The wave disruption element (200) comprises of a grooved axial bore (218) in which splines of the drive shaft are engaged. The wave disruption element (200) has an outer surface (212) in the form of a helical wave extending between the first end (214) and second end (216) of the element.

An outer wave surface refers to an outer surface such that the flight depth of the element varies between a maximum and a minimum value to form wave crests periodically along the element. Flight depth refers to the depth of the channel or the distance from the top edge of the flight to the core of the element. The flight depth is equal to one half the ratio of element outer diameter (D) to element root diameter. In accordance with an aspect the ratio of the element outer diameter (D) to element root diameter is in the range of 1.25 to 1.95.

The outer surface in the shape of a helical wave refers to an outer wave surface forming periodic crests in a direction both along and perpendicular to the element axis, as depicted in figures 11 and 16. The crests formed along the element axis and crests formed perpendicular to the element axis are connected by the continuous outer surface (212) of the helical wave profile such that a continuous helical crest (220) is formed along the outer surface of the wave disruption element (200). The continuous helical crest (220) does not form a land on the outer surface (212). A plurality of grooves (222) is present along the continuous helical crest (220) of the wave disruption element (200). The grooves (222) may be present in a continuous manner on the crest (220) of the helical wave on the outer surface (212). Alternatively the grooves (222) may be distributed in a pre-determined pattern.

In accordance with an embodiment the grooves (222) are substantially perpendicular to the continuous crest axis, the continuous crest axis being the helical axis passing through the highest point of the continuous helical crest (220).

In accordance with an embodiment, the grooves (222) are substantially parallel to each other.

In accordance with an aspect, the grooves (222) are placed equidistant from each other. Alternatively the distance between grooves (222) may be varied. The grooves (222) may also be placed such that at least two grooves (222) are grouped together. A plurality of such groups may be present along the continuous helical crest (220). In the embodiment illustrated the grooves (222) are placed equidistant from each other.

In accordance with an embodiment, grooved area is less than 50 percent of the total outer surface area of the element (200).

In accordance with an embodiment, grooves (222) may extend to a flight depth of not more than 30 percent of the total flight.

With reference to figure 12, a front view of the wave disruption element (200) is illustrated, wherein the element (200) is shown to form a wave pattern along the element axis. The distance between two successive crests of the wave is a factor of the outer diameter [D] of the element. The distance between two successive crests of the wave is also known as the pitch of the helical wave.

In accordance with an aspect, the distance between two successive crests or the pitch may vary from being half the outer diameter [0.5D] to twenty times the outer diameter [20 D], depending on the nature of the application. For processes involving the treatment of long fibers, the pitch or the distance between two successive crests is preferably at least one and a half times the outer diameter [1.5 D]. In the embodiment illustrated, the pitch or the distance between two successive crests is twice the outer diameter of the element [2D].

Figures 13 and 14 illustrate the left hand and right hand side views of the wave disruption element (200) in accordance with an embodiment, hi the embodiment illustrated the wave completes a cycle, and the two end points (214, 216) represent the start and completion of a wave along the element axis. However, the wave disruption element (200) may be formed where a wave cycle is not completed between the two end points of the element (200), which would also depend on the distance between two successive crests forming the wave and the length of the element (200).

In accordance with an aspect, the axial length of the element (200) is in the range of 1.25 to 1.95 times the outer diameter of the element (200).

Figure 15 illustrates a top view of the wave disruption element (200) of figure 11. As may be seen in the top view, a wave surface is formed in a direction perpendicular to the element axis. In the embodiment illustrated, one crest of the wave is formed on the element in a direction perpendicular to the axis of the element, between two crests formed along the element axis. The outer surface of the element is a continuous surface including the crests formed both along and perpendicular to the element axis and thereby forming the continuous helical wave outer surface.

While a specific configuration of the wave elements (100) and the wave disruption elements (200) on the extruder is illustrated, various similar configurations may be formed by positioning the extruder wave element (100) and the wave disruption element (200) in an extruder system. By way of example, the wave disruption zone (14) may be followed by another zone including the wave extruder elements (100).

Figure 17 illustrates an extruder having a pre-plasticising (70) zone in accordance with an embodiment. The pre- plasticising zone (70) comprises of an intake zone (80) configured for receiving the polymer and additive and a melting zone (90) configured for melting and mixing the polymer. The intake zone (80) and the melting zone (90) may be configured with conventional extruder elements for melting and mixing the polymer constituents.

In accordance with an aspect, the extruder element configuration of the intake zone (80) and the melting zone (90) may be modified depending on the application to be processed and on the choice of polymer for the application.

By way of specific example, for applications where the final product is formed by a compression molding process, it is necessary that the fibers are wetted completely by the polymer in the mixing zone. For such applications, a polymer of higher Melt Flow Index (MFI), i.e. of lower viscosity, is chosen and the melting zone (90) is correspondingly 'weakened' by reducing the number of elements resulting in high shearing action thus reducing the work done on the polymer to obtain a suitable melt viscosity for wetting the fibers completely. Alternatively, the long fiber reinforced plastic materials may be processed into profiles. In such applications, a lower Melt Flow Index (MFI) polymer, i.e. a polymer with higher viscosity, is required. For such applications the melting zone (90) of the extruder is correspondingly 'strengthened' by increasing the kneading blocks and high shearing elements in the screw configuration, thus increasing the work done on the polymer in the existing length of the melting zone of the screw to obtain the melt viscosity of the polymer suitable for wetting the fibers completely.

A method of incorporating fibers in a thermoplastic is disclosed. The process comprising adding fibers to a plastic melt at the fiber entry zone of an extruder, mixing the fibers with the plastic melt in a fiber incorporation zone of the extruder to obtain a mixture of fibers and plastic, and reducing the length of fibers in the mixture to a desired length by passing the mixture through a wave disruption zone of the extruder. The fiber entry zone and the fiber incorporation zone are provided with extruder wave elements configured for incorporating the fibers into the plastic melt by producing waves in the mixture. The wave disruption zone is provided with wave disruption elements configured for disrupting the waves in the mixture and cutting the fibers to a desired length to obtain a fiber reinforced thermoplastic composite.

In accordance with an embodiment, the process comprises of pre-preparing a plastic melt in the extruder followed by the incorporation of fibers. The process comprises of adding to a pre-plasticizing zone of the extruder polymer constituents, melting the polymer constituents and mixing the melted constituents to obtain a plastic melt, the pre-plasticizing zone configured with conventional extruder elements for melting and mixing the polymer constituents.

In accordance with an aspect, the process further comprises of passing the fiber reinforced thermoplastic composite through a pelletizing system to obtain pellets of fiber reinforced thermoplastic composite.

In accordance with an aspect the fiber reinforced thermoplastic composite may also be used directly for forming other structures including tubes and sheets using suitable moulds and dies.

In accordance with an aspect, the fiber reinforced thermoplastic composite may be pushed into a single screw extruder arranged in a cascaded or a series arrangement. This fiber reinforced thermoplastic obtained from the single screw extruder may be extruded into a profile by using suitable dies and moulds. The fibers that may be incorporated into the thermoplastic may include but are not limited to glass fibers, carbon fibers, natural fibers or their combination. The length of the fibers is in the range of 5 mm to 100mm.

The thermoplastic composite may include but is not limited to polypropylene, polyethylene, polyamides, polyamines, polycarbonate, polystyrene, styrene-acrylonitrile copolymers, acrylonitrile-butandiene-styrene terpolymers, polysulphones, polyesters, polyurethanes, polyphenylene sulfides, polyphenylene ethers or their combinations.

Specific embodiments are described below:

An extruder capable of manufacturing fiber reinforced thermoplastics comprising a barrel having two parallel bores of equal diameter, the centre distance between the two bores lesser than the diameter of the bore; and a shaft located within each bore, each shaft configured for rotation in the same direction; the shaft forming three zones within the barrel, the zones including a fiber entry zone configured for receiving fibers from an extruder inlet; a fiber incorporation zone configured for incorporation the fibers into a polymer mix, the fiber entry zone and fiber incorporation zone generate waves in the polymer mix; and a wave disruption zone capable of cutting of fibers to a desired length; wherein the fiber entry zone and the fiber incorporation zone includes at least one extruder wave element, the extruder wave element has a continuous outer surface in the form of a helical wave; and the wave disruption zone includes at least one wave disruption element, the wave disruption element has an outer surface in the form of a helical wave with a plurality of grooves formed on the crest of the helical wave.

An extruder capable of manufacturing fiber reinforced thermoplastics comprising a barrel having two parallel bores of equal diameter, the centre distance between the two bores lesser than the diameter of the bore; and a shaft located within each bore, each shaft configured for rotation in the same direction; the shaft forming four zones within the barrel, the zones including a pre-plasticizing zone configured for preparing a polymer melt; a fiber entry zone configured for receiving fibers from extruder inlet; a fiber incorporation zone configured for incorporating the fibers into the polymer mix, the fiber entry zone and fiber incorporation zone generate waves in the polymer mix; and a wave disruption zone capable of cutting the fibers to a desired length; wherein the fiber entry zone and the fiber incorporation zone includes at least one extruder wave element, the extruder wave element has a continuous outer surface in the form of a helical wave; and the wave disruption zone includes at least one wave disruption element, the wave disruption element having an outer surface in the form of a helical wave with a plurality of grooves formed on the crest of the helical wave.

Such extruder(s) wherein the pitch of the extruder wave element in the fiber entry zone is greater than the pitch of the extruder wave element in the fiber incorporation zone.

Such extruder(s) wherein the pitch of the extruder wave element in the fiber entry zone is at least one time the barrel diameter.

Such extruder(s) wherein the pitch of the extruder wave element in the fiber incorporation zone is in the range of 0.5 times to 20 times the barrel diameter.

Such extruder(s) wherein the wave disruption element has a pitch in the range of 0.5 times to 20 times the barrel diameter.

Such extruder(s) wherein the screw-screw clearance between the extruder wave element in the fiber entry zone is greater than the screw-screw clearance between the extruder wave element in the fiber incorporation zone.

Such extruder(s) wherein length of the fiber entry zone is in the range of 0.5 to 20 times the barrel diameter.

Such extruder(s) wherein the length of the fiber incorporation zone is in the range of 0.5 to 20 times the barrel diameter.

Such extruder(s) wherein the length of the fiber disruption zone is in the range of 0.5 to 20 times the barrel diameter.

Such extruder(s) wherein the fiber incorporation zone is configured for mixing and melting the polymer mix in the extruder.

Such extruder(s) wherein the pre-plasticizing zone comprises of an intake zone configured for receiving the polymer constituents; and a melting zone configured for melting and mixing the polymer constituents.

Further Specific embodiments are described below:

A method of incorporating fibers in a thermoplastic comprising feeding fibers into an extruder, the extruder comprising a barrel having two parallel bores of equal diameter, the centre distance between the two bores lesser than the diameter of the bore; and a shaft located within each bore, each shaft configured for rotation in the same direction; the shaft forming three zones within the barrel, the zones including a fiber entry zone configured for receiving fibers from an extruder inlet; a fiber incorporation zone configured for incorporation the libers into a polymer mix, the fiber entry zone and fiber incorporation zone generate waves in the polymer mix; and a wave disruption zone capable of cutting of fibers to a desired length; wherein the fiber entry zone and the fiber incorporation zone includes at least one extruder wave element, the extruder wave element has a continuous outer surface in the form of a helical wave; and the wave disruption zone includes at least one wave disruption element, the wave disruption element has an outer surface in the form of a helical wave with a plurality of grooves formed on the crest of the helical wave; the method comprising adding fibers to a plastic melt into the fiber entry zone of the extruder; mixing the fibers with the plastic melt by passing the mixture of the fibers and plastic melt thorough the fiber incorporation zone; and reducing the length of the fibers in the mixture to a desired length by passing the mixture though the wave disruption zone of the extruder.

Such method(s) wherein the method further comprises of forming a plastic melt in the extruder, the extruder including a pre-palletizing zone prior to the fiber entry zone, the method comprises adding to a pre-plasticizing zone of the extruder polymer constituents; and melting and mixing the polymer constituents to obtain a plastic melt.

Such method(s) wherein the fibers are any one of glass fibers, carbon fibers, natural fibers or their combination.

Such method(s) wherein the thermoplastic composite is any one of polypropylene, polyethylene, polyamides, polyamines, polycarbonate, polystyrene, styrene-acrylonitrile copolymers, acrylonitrile-butandiene-styrene terpolymers, polysulphones, polyesters, polyurethanes, polyphenylene sulfides, polyphenylene ethers or their combinations.

Such method(s) wherein the length of the fibers is in the range of 5 mm to 100mm.

Such method(s) wherein the method further comprises of passing the long fiber reinforced thermoplastic composite through a pelletizing system to obtain pellets of the fiber reinforced thermoplastic composite.

Long fiber reinforced thermoplastic composite obtained by such method(s).

Further Specific embodiments are described below:

An element (10) for an extruder, wherein the element(lθ) has a continuous outer surface (12) in the form of a helical wave.

Such element(s) for an extruder wherein the pitch of the helical wave is in the range of 0.5 to 20 times the outer diameter of the element (10).

Such element(s) for an extruder wherein the axial length of the element is in the range of 0.5 to 6 times the outer diameter of the element (10). Such element(s) for an extruder wherein the ratio of element outer diameter to element root diameter ranges from 1.25 to 1.95.

An element for an extruder, wherein the element has a continuous outer surface in the form of a helical wave having an axial length in the range of 0.5 to 6 times the outer diameter of the*element (10), a helical pitch in the range of 0.5 to 20 times the outer diameter of the element (10) and the ratio of element outer diameter to element root diameter ranges from 1.25 to 1.95.

Further Specific embodiments are described below:

An element (10) for an extruder, wherein the element (10) has an outer surface (12) in the form of a helical wave with a plurality of grooves(22) formed on the crest of the helical wave.

Such element(s) for an extruder wherein the grooves (22) are continuous.

Such element(s) for an extruder wherein the grooves (22) are substantially perpendicular to the helical wave on the outer surface (12).

Such element(s) for an extruder wherein the grooves (12) are substantially parallel to each other.

Such element(s) for an extruder wherein the grooves (22) are equidistant from each other.

Such element(s) for an extruder wherein two or more grooves (22) are arranged in a group.

Such element(s) for an extruder wherein the grooved area is less than 50 per cent of the total outer surface.

Such element(s) for an extruder wherein the depth of the groove (22) is not more than 30 percent of the total height of the crest of the helical wave.

Such element(s) for an extruder wherein the pitch of the helical wave is in the range of 0.5 to 20 times the outer diameter of the element.

Such element(s) for an extruder wherein the axial length of the element (10) is in the range of 0.5 to 6 times the outer diameter of the element.

Such element(s) for an extruder wherein ratio of element outer diameter to element root diameter ranges from 1.25 to 1.95.

Such element(s) for an extruder used in an extruder for processing long fibre reinforced thermoplastics. INDUSTRIAL APPLICABILITY

The extruder as disclosed allows for the manufacture of a fiber reinforced plastic in a simple and efficient manner.

Moreover, the wave element as disclosed serves to generate waves in the material being processed by the extruder. In particular, such elements having a continuous outer surface in the form of a helical wave serve to convey the material without adversely affecting the length of the fiber used for reinforcement.

Moreover, the wave disruption element as disclosed serves to disrupt a wave that is generated in the material that is being processed by the extruder. In particular, such elements having grooves allow the length of the fibers to be cut to a desired length to obtain a reinforced plastic having a specific distribution of fiber lengths.

The use of the wave extruder element and the wave disruption element in an extruder system allow for the incorporation of fibers in the plastic in an efficient manner with a substantial number of fibers retaining their desired length.

The extruder as disclosed allows for the use of a single extruder to carry out the entire process for the incorporation of fibers in the plastic including melting of the polymer, compounding the polymer with the additives and mixing the plastic melt with the fibers.

The process as disclosed allows for the production of fiber reinforced thermoplastic compositions in which a substantial portion of the fibers in the product has a specific distribution of fiber length.

Claims

WE CLAIM:

1. An extruder capable of manufacturing fiber reinforced thermoplastics comprising:

a barrel having two parallel bores of equal diameter, the centre distance between the two bores lesser than the diameter of the bore; and

a shaft located within each bore, each shaft configured for rotation in the same direction; the shaft forming three zones within the barrel, the zones including

a fiber entry zone configured for receiving fibers from an extruder inlet;

a fiber incorporation zone configured for incorporation the fibers into a polymer mix, the fiber entry zone and fiber incorporation zone generate waves in the polymer mix; and

a wave disruption zone capable of cutting of fibers to a desired length;

wherein the fiber entry zone and the fiber incorporation zone includes at least one extruder wave element, the extruder wave element has a continuous outer surface in the form of a helical wave; and

the wave disruption zone includes at least one wave disruption element, the wave disruption element has an outer surface in the form of a helical wave with a plurality of grooves formed on the crest of the helical wave.

2. An extruder capable of manufacturing fiber reinforced thermoplastics comprising:

a shaft located within each bore, each shaft configured for rotation in the same direction; the shaft forming four zones within the barrel, the zones including

a pre-plasticizing zone configured for preparing a polymer melt; a fiber entry zone configured for receiving fibers from extruder inlet;

a fiber incorporation zone configured for incorporating the fibers into the polymer mix, the fiber entry zone and fiber incorporation zone generate waves in the polymer mix; and

a wave disruption zone capable of cutting the fibers to a desired length;

wherein the fiber entry zone and the fiber incorporation zone includes at least one extruder wave element, the extruder wave element has a continuous outer surface in the form of a helical wave; and the wave disruption zone includes at least one wave disruption element, the wave disruption element having an outer surface in the form of a helical wave with a plurality of grooves formed on the crest of the helical wave.

3. An extruder as claimed in any preceding claim, wherein the pitch of the extruder wave element in the fiber entry zone is greater than the pitch of the extruder wave element in the fiber incorporation zone.

4. An extruder as claimed in claim 1, 2 or 3 wherein the pitch of the extruder wave element in the fiber entry zone is at least one time the barrel diameter.

5. An extruder as claimed in any preceding claim wherein the pitch of the extruder wave element in the fiber incorporation zone is in the range of 0.5 times to 20 times the barrel diameter.

6. An extruder as claimed in claim 1 or 2, wherein the wave disruption element has a pitch in the range of 0.5 times to 20 times the barrel diameter.

7. An extruder as claimed in claim 1 or 2, wherein the screw-screw clearance between the extruder wave elements in the fiber entry zone is greater than the screw-screw clearance between the extruder wave elements in the fiber incorporation zone.

8. An extruder as claimed in claim 1 or 2 wherein length of the fiber entry zone is in the range of 0.5 to 20 times the barrel diameter.

9. An extruder as claimed in claim 1 or 2 wherein the length of the fiber incorporation zone is in the range of 0.5 to 20 times the barrel diameter.

10. An extruder as claimed in claim 1 or 2 wherein the length of the fiber disruption zone is in the range of 0.5 to 20 times the barrel diameter.

11. An extruder as claimed in claim 1 or 2, wherein the fiber incorporation zone is configured for mixing and melting the polymer mix in the extruder.

12. An extruder as claimed in claim 2, wherein the pre-plasticizing zone comprises of an intake zone configured for receiving the polymer constituents; and a melting zone configured for melting and mixing the polymer constituents.

13. A method of incorporating fibers in a thermoplastic comprising feeding fibers into an extruder, the extruder comprising:

a fiber entry zone configured for receiving fibers from an extruder inlet;

a wave disruption zone capable of cutting of fibers to a desired length;

the wave disruption zone includes at least one wave disruption element, the wave disruption element has an outer surface in the form of a helical wave with a plurality of grooves formed on the crest of the helical wave;

the method comprising

adding fibers to a plastic melt into the fiber entry zone of the extruder; mixing the fibers with the plastic melt by passing the mixture of the fibers and plastic melt thorough the fiber incorporation zone; and

reducing the length of the fibers in the mixture to a desired length by passing the mixture though the wave disruption zone of the extruder.

14. A method as claimed in claim 13, wherein the method further comprises of forming a plastic melt in the extruder, the extruder including a pre-palletizing zone prior to the fiber entry zone, the method comprises adding to a pre-plasticizing zone of the extruder polymer constituents; and melting and mixing the polymer constituents to obtain a plastic melt.

15. A method as claimed in claim 13 or 14, wherein the fibers are any one of glass fibers, carbon fibers, natural fibers or their combination.

16. A method as claimed in claim 13 or 14, wherein the thermoplastic composite is any one of polypropylene, polyethylene, polyamides, polyamines, polycarbonate, polystyrene, styrene-acrylonitrile copolymers, acrylonitrile-butandiene-styrene terpolymers, polysulphones, polyesters, polyurethanes, polyphenylene sulfides, polyphenylene ethers or their combinations.

17. A method as claimed in claim 13 or 14, wherein the length of the fibers is in the range of 5 mm to 100 mm.

18. A method as claimed in claim 13 or 14, wherein the method further comprises of passing the long fiber reinforced thermoplastic composite through a pelletizing system to obtain pellets of the fiber reinforced thermoplastic composite.

19. Long fiber reinforced thermoplastic composite obtained by a method as claimed in any of claims 13 to 18.

20. An element for an extruder, wherein the element has a continuous outer surface in the form of a helical wave.

21. An element for an extruder as claimed in claim 20, wherein the pitch of the helical wave is in the range of 0.5 to 20 times the outer diameter of the element.

22. An element for an extruder as claimed in claim 20 or 21, wherein the axial length of the element is in the range of 0.5 to 6 times the outer diameter of the element.

23. An element for an extruder as claimed in claim 20, wherein the ratio of element outer diameter to element root diameter ranges from 1.25 to 1.95.

24. An element for an extruder, wherein the element has a continuous outer surface in the form of a helical wave having an axial length in the range of 0.5 to 6 times the outer diameter of the element (10), a helical pitch in the range of 0.5 to 20 times the outer diameter of the element (10) and the ratio of element outer diameter to element root diameter ranges from 1.25 to 1.95.

25. An element for an extruder, wherein the element has an outer surface in the form of a helical wave with a plurality of grooves formed on the crest of the helical wave.

26. An element for an extruder as claimed in claim 25, wherein the grooves are continuous.

27. An element for an extruder as claimed in claims 25 or 26, wherein the grooves are substantially perpendicular to the helical wave on the outer surface.

28. An element for an extruder as claimed in any of claims 25 to 27, wherein the grooves are substantially parallel to each other.

29. An element for an extruder as claimed in any of claims 25 to 28, wherein the grooves are equidistant from each other.

30. An element for an extruder as claimed in claim 25 or 26, wherein two or more grooves are arranged in a group.

31. An element for an extruder as claimed in any of claims 25 to 30, wherein the grooved area is less than 50 per cent of the total outer surface.

32. An element for an extruder as claimed in claim 25, wherein the depth of the groove is not more than 30 percent of the total height of the crest of the helical wave.

33. An element for an extruder as claimed in any of claims 25 to 32, wherein the pitch of the helical wave is in the range of 0.5 to 20 times the outer diameter of the element.

34. An element for an extruder as claimed in any of claims 25 to 33, wherein the axial length of the element is in the range of 0.5 to 6 times the outer diameter of the element.

35. An element for an extruder as claimed in claim 25, wherein ratio of element outer diameter to element root diameter ranges from 1.25 to 1.95.

36. An element for an extruder claimed in any of claims 20 to 35 used in an extruder for processing long fibre reinforced thermoplastics.