CA1138612A - Method and apparatus for drying wet polymerized materials - Google Patents
Method and apparatus for drying wet polymerized materialsInfo
- Publication number
- CA1138612A CA1138612A CA000351506A CA351506A CA1138612A CA 1138612 A CA1138612 A CA 1138612A CA 000351506 A CA000351506 A CA 000351506A CA 351506 A CA351506 A CA 351506A CA 1138612 A CA1138612 A CA 1138612A
- Authority
- CA
- Canada
- Prior art keywords
- screw
- polymeric material
- abutment
- barrel
- die plate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B17/00—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement
- F26B17/18—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by rotating helical blades or other rotary conveyors which may be heated moving materials in stationary chambers, e.g. troughs
- F26B17/20—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by rotating helical blades or other rotary conveyors which may be heated moving materials in stationary chambers, e.g. troughs the axis of rotation being horizontal or slightly inclined
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B13/00—Conditioning or physical treatment of the material to be shaped
- B29B13/06—Conditioning or physical treatment of the material to be shaped by drying
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
- B29C48/50—Details of extruders
- B29C48/76—Venting, drying means; Degassing means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
- B29C48/50—Details of extruders
- B29C48/76—Venting, drying means; Degassing means
- B29C48/765—Venting, drying means; Degassing means in the extruder apparatus
- B29C48/766—Venting, drying means; Degassing means in the extruder apparatus in screw extruders
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
- B29C48/04—Particle-shaped
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Extrusion Moulding Of Plastics Or The Like (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
Abstract
METHOD AND APPARATUS FOR DRYING WET POLYMERIZED MATERIALS
Abstract of the Disclosure A method and apparatus for drying wet polymeric material wherein, after being compressed and heated in an extruder barrel, the material is extruded to form crumb through orifices in a multi-orifice die plate equipped with a rotatable die face cutter. The invention effects movement of some of the polymeric material across the downstream end of the extrusion screw constantly to replace the material between the end of the screw and the cutter mounting thereby preventing a stationary zone of the material or slowing down in movement of the material and hence avoiding its degrada-tion through overheating.
Abstract of the Disclosure A method and apparatus for drying wet polymeric material wherein, after being compressed and heated in an extruder barrel, the material is extruded to form crumb through orifices in a multi-orifice die plate equipped with a rotatable die face cutter. The invention effects movement of some of the polymeric material across the downstream end of the extrusion screw constantly to replace the material between the end of the screw and the cutter mounting thereby preventing a stationary zone of the material or slowing down in movement of the material and hence avoiding its degrada-tion through overheating.
Description
1~3~
, This invention relates to methods and apparatus for removing volatile substances from an extrudable polymeric material.
In a method of manufacturing synthetic polymers S which include synthetic rubber, the polymers are produced by a polymerization process in a reactor. Upon leaving the reactor, the polymeric material is subjected to a crumb forming process to produce a slurry of the crumb in water.
It is then necessary to--separate the polymer from the aqueous phase and finally produce dry polymer which may then be suitably packaged for commercial use.
Removal of the water is effected in a two stage water removal process. In a first stage, the slurry is passed through a dewatering machine which operates at a temperature up to 220F and removes water and other solvents present until the water and other solvent content is normally between 4% ànd 12% by weight of the total weight of the material. In a second stage, the wet polymeric material may be passed through a mechanical dryer. This is in the form of an extruder commonly referred to a~ an extruder dryer or expander dryer. While in the extruder dryer, the polymeric matesial is pressurized as it i8 fed along the extruder barrel by an extruder screw, back pressure to resist movement along the barrel being a~ least psrtly provided by a multi-orifice die plate at the outlet end of the dryer. Thetemperature of the polymeri.c material while in the extruder dryer increases to temperatures in excess of 350-360F and water and other volatile substances are removed to further reduce the total volatile content to around 1% or less by weight of the final extruded weight of extruded crumb.
, This invention relates to methods and apparatus for removing volatile substances from an extrudable polymeric material.
In a method of manufacturing synthetic polymers S which include synthetic rubber, the polymers are produced by a polymerization process in a reactor. Upon leaving the reactor, the polymeric material is subjected to a crumb forming process to produce a slurry of the crumb in water.
It is then necessary to--separate the polymer from the aqueous phase and finally produce dry polymer which may then be suitably packaged for commercial use.
Removal of the water is effected in a two stage water removal process. In a first stage, the slurry is passed through a dewatering machine which operates at a temperature up to 220F and removes water and other solvents present until the water and other solvent content is normally between 4% ànd 12% by weight of the total weight of the material. In a second stage, the wet polymeric material may be passed through a mechanical dryer. This is in the form of an extruder commonly referred to a~ an extruder dryer or expander dryer. While in the extruder dryer, the polymeric matesial is pressurized as it i8 fed along the extruder barrel by an extruder screw, back pressure to resist movement along the barrel being a~ least psrtly provided by a multi-orifice die plate at the outlet end of the dryer. Thetemperature of the polymeri.c material while in the extruder dryer increases to temperatures in excess of 350-360F and water and other volatile substances are removed to further reduce the total volatile content to around 1% or less by weight of the final extruded weight of extruded crumb.
- 2 -1 1 3~ 6 ~ ~
Some extruder dryers are provided with rotatable die-face cutters mounted coaxially UpGn the die plates.
W~ile the die plates are of multi-orifice design for extru-sion of crumb which is cut by the cutter into pieces of convenient size for conveying and baling, the central region of the die plate is devoid of orifices because of the area required for mounting of the cutter. The use of this design of die plate and cutter arrangement creates problems because the polymeric material as it is fed along the extruder barrel i~ forced by the screw against the whole of the facing sur-face of the die plate and becomes substantially stationary behind the orifice-devoid central region. Once material becomes substantially stationary in thi~ position, its residence ~ime in the dryer is increased as it is by-passed by other material moving radially outside it in the extruder barrel, which other material is capable of being extruded directly through the orificec. Some polymeric materials, such as bromobutyl, ha~e a low tem~erature degradation point which is close to their extrusion temperature in an extruder dryer. With such materials, the combination of the extrusion temperature and the residence time of substantially sta~ionary material behind the central region of the die plate is sufficient to cause degradation of the substantially stationary material by overheating. Hence the finally extruded crumb may be contaminated with a small percentage of degraded material which renders the use of this particular design of extruder dryer unsatisfactory for heat sensitive materials.
Similar disadvantages are found in other processes performed upon polymeric materials in which volatile sub-~138t~12 stances are removed by volatile removal apparatus of thesame basic design as the above described extruder dryer.
The present invention provides a method for removing volatile substances from a polymeric material wherein the residence time for material is reduced in the orifice-devoid central region behind the die plate. This is made possible by causing the material to flow radially across the end of the screw, between the screw and the mounting of the cutter.
Accordingly, the invention provides a method of removing volatile substances from an extrudable polymeric material comprising:-(a) entering the material into an inlet of an extruder barrel;
(b) rotating an e~truder screw with a free down-stream end within the barrel to feed the material along the barrel towards an outlet end of the barrel while compressing it and heating it to cause subsequent volatilization and release of the ~olatile substance when the material is subjected to a reduction in pressure and brought into contact with ambient atmosphere; and (c) by rotation of the extruder screw, continuously forcing the material in an axia~ direction through orifices provided in a die plate at the outlet end of the barrel and severing the extrudate ~o formed into discrete portions by the use of a cutter rotating upon a mounting upon the die plate while continuously applying a force to cause movement of material radially inwardly across the end of the screw constantly to replace material situated axiaLly between the
Some extruder dryers are provided with rotatable die-face cutters mounted coaxially UpGn the die plates.
W~ile the die plates are of multi-orifice design for extru-sion of crumb which is cut by the cutter into pieces of convenient size for conveying and baling, the central region of the die plate is devoid of orifices because of the area required for mounting of the cutter. The use of this design of die plate and cutter arrangement creates problems because the polymeric material as it is fed along the extruder barrel i~ forced by the screw against the whole of the facing sur-face of the die plate and becomes substantially stationary behind the orifice-devoid central region. Once material becomes substantially stationary in thi~ position, its residence ~ime in the dryer is increased as it is by-passed by other material moving radially outside it in the extruder barrel, which other material is capable of being extruded directly through the orificec. Some polymeric materials, such as bromobutyl, ha~e a low tem~erature degradation point which is close to their extrusion temperature in an extruder dryer. With such materials, the combination of the extrusion temperature and the residence time of substantially sta~ionary material behind the central region of the die plate is sufficient to cause degradation of the substantially stationary material by overheating. Hence the finally extruded crumb may be contaminated with a small percentage of degraded material which renders the use of this particular design of extruder dryer unsatisfactory for heat sensitive materials.
Similar disadvantages are found in other processes performed upon polymeric materials in which volatile sub-~138t~12 stances are removed by volatile removal apparatus of thesame basic design as the above described extruder dryer.
The present invention provides a method for removing volatile substances from a polymeric material wherein the residence time for material is reduced in the orifice-devoid central region behind the die plate. This is made possible by causing the material to flow radially across the end of the screw, between the screw and the mounting of the cutter.
Accordingly, the invention provides a method of removing volatile substances from an extrudable polymeric material comprising:-(a) entering the material into an inlet of an extruder barrel;
(b) rotating an e~truder screw with a free down-stream end within the barrel to feed the material along the barrel towards an outlet end of the barrel while compressing it and heating it to cause subsequent volatilization and release of the ~olatile substance when the material is subjected to a reduction in pressure and brought into contact with ambient atmosphere; and (c) by rotation of the extruder screw, continuously forcing the material in an axia~ direction through orifices provided in a die plate at the outlet end of the barrel and severing the extrudate ~o formed into discrete portions by the use of a cutter rotating upon a mounting upon the die plate while continuously applying a force to cause movement of material radially inwardly across the end of the screw constantly to replace material situated axiaLly between the
3~ end of the screw and the mounting of the cutter.
~3861Z
The continuous.ly applied force may be caused by an abutment provided upon either the end of the screw or upon the die plate and lying between screw end and die plate.
The invention also includes apparatus for removing volatile substances from an extrudable polymeric material comprising:
(a) an extruder barrel defining a barrel chamber and formed with an inlet for the polymeric material and an outlet spaced from the inlet;
(b) a multi-orifice die plate extending radially across the chamber at the outlet for extrusion of polymeric material flowing from the chamber;
(c) a cutter having a mounting and carried by the mounting upon the die plate for cutting extruded polymeric material as it i~ emitted from the extrusion orifices into discrete portions;
(d) and an extrusion screw with a free downstream end and rotatabLe within the chamber and having at least one screw flight fox feeding polymeric material along the barrel from the inlet to the outlet and through the die plate orifices while subjecting the material to compression to cause an increase in its temperature. for subsequent volatili-zation and release of volatile substance from the polymeric material, the extrusion screw having a downstream end towards the die plate and an abutment extending radially of the screw end, the screw flight having a downstream facing load-applying surface and, when considered in the direction of screw rota~ion, the abutment ha~ing a leading surface which - extends axially from the end of the screw and forming an extension of the load-applying surface from a position 11381~Z
adjacent the wall of the chamber at least partly across the end of the screw, said abutment sweeping around the axis of rotation of the screw during screw rotation to direct polymeric material to flow radially inwardly across said end of the screw thereby to move polymeric material across the end of the screw constantly to replace material situated axially between the end of the screw and the mounting of the cutter.
With this construction, polymeric material being fed downstream by the screw flight is partly conveyed directly against the leading surface and then by the leading surface is directed to flow radially across the end of the screw and behind the cutter mounting.
It is also to be preferred that the leading surface extends to a position adjacent the circumference of the chamber in such a manner that, when considered in the direction of screw rotation and forwardly of the leading surface, the outer end of the leading surface forms an obtuse angle with a tangent to the circumferential point of the chamber to which the outer end lies ad~acent. This then enables polymeric material to be moved by the leading surface across the screw end without a sudden change in direction of motion of the material from i~s axial and circumferential movement around the screw whereby resistance to such movement across the screw is minimized. The obtuse angle is con-veniently provided by a concave curva~ure of the leading surface as it e~ends across the screw end. Conveniently, the concavity may be provided by the leading surface following the shape of an involute which may be based upon a diameter substantially equal to the chamber diameter with the shape at 113~3612 .
the radially inner end of the surface corresponding to the root end of the involute and with said inner end lying substantially coincident with the axis of rotation of the screw. It is found with this involute shape, a pumping action takes place, as with the involute shaped vanes of a pump, to assist in directing flow of the polymeric material across the end of the screw.
Embodiments of the invention will now be described, ~ by way of example, with reference to the accompanying drawings in which:-FIGURE 1 is an axial cross-sectional view of part of an apparatus according to a first embodiment;
FIGURE 2 is a view in the direction of arrow II
in Figure 1 with a die plate partly cut away to show an end of an extruder screw;
FIGURE 3 is an isometric view on an enlarged scale of the end of the extruder screw removed from the apparatus;
FIGURE 4 is a view similar to that of Figure 1 of a second embodiment;
FIGURE 5 is an axial view on the end of a screw used in the second embodiment, considered in the direction of arrows VI in Figure 5 and on a larger scale;
FIGURE 6 is a cross-sectional view on line VI-VI
of Figure 5 of an end of the screw;
FIGURE 7 is a view slmilar to Figure 1 of a third embodiment;
FIGURE 8 is an isometric view on an enlarged scale 11386~2 of the end of a screw used ln the third embodiment; and FIGURE 9 is a view of the end of the screw in the direction of arrow IX in Figure 8.
In a first embodiment as shown in Figure 1, apparatus for removing water and other volatile substances from a polymeric material such as wet bromobutyl comprises an extruder 1 ha~ing a barrel 2 formed with a cylindrical barrel chamber 3. The barrel houses an extrusion screw 4 ha~ing a free downstream end and formed with a single screw flight 5 having a downstream load-applying æurface 6 for ~`
feeding the wet bromobutyl from an inlet (not shown) for the material to the outlet of the extruder at which position a die plate 7 extends radially across the chamber. The die pla~e is formed with a plurality of extrusion orifices 8 (see particularly Figure 2) for extrusion therethrough of the polymer. It is intended that orifices towards the radial center of the die plate are of larger cross-sectional area than other orifices and for this purpose orifices 8a on an inner pitch circle are of larger diameter as shown in Figure 2. Mounted upon the die plate is a cutter (not shown) which is rotatably held upon a mounting spindle 9 which extends coaxially out from the die plate and from the extruder and is held securely in position by a locking nut 10 disposed in a central recess on the upætream face of the die plate.
The barrel, die plate, cutter and mounting for the cutter together with the part of the extrusion screw 80 far des-cribed are all of conventional design and will be described in no greater detail. Suffice it to say that the extrusion screw i of the type that, during rotation, compresses the 3 ~6 1 ~
wet polymeric material to cause an increase in temperature of the material during its movement along the barrel by a mechanical working process and then suddenly releases the pressure conditions to result in volatilization of the volatile substances which then escape from the material upon exposure to ambient atmospheric conditions.
This embodiment differs from prior construc~ions and according to the invention by the extrusion screw having a downstream end towards the die plate and an abutment extending radially of the screw end, the screw flight having a downstream facing load-applying surface and, when considered in the direction of screw rotation, the abutment having a leading surface which extends axially from the end of the screw and forming an extension of the load-applying surface from a position adjacent the wall of the chamber at least partly across the end of the screw, this abu~ment sweeping around the axis of rotation of the screw during screw rotation to direct polymeric material to flow radially inwardly across said end of the screw thereby to move polymeric material across the end of the screw constantly to replace material situated axially between the end of the screw end and the cutter mounting. This abutment i8 a pro-jection 11 on the screw end and, in end view (F~gure 2), is generally in the form of a sector of a circle with two ~5 generally radially extending edges 12 and 13 meeting at the axis of rotation of ~he screw to make an included zngle slightly less than 90. As may be seen from Figures 2 and 3, the edge 12 is not intended to extend along a radial line of the screw. This edge 12 is that formed by a surface 14 (Figure 3) of the abutment and is a leading surface of the _ 9._ .
113~Z
abutment when considered in the direction of rotation of the screw and abutment around the rotational axis. The rotational direction is anticlockwise as viewed in Figure 2.
Figure 2 shows that the leading surface is of concave curvature as it extends radially outwards from the rotational axis to the radiaLly outer edge 15 of the abutment which is in the shape of an arc having a radius with a center coincident with the rotatîonal axis and equal in length to the outside radius of the screw fligh~. The concave curva-ture of the surface 14 may be of any desired shape to urgethe wet polymerlc material to move radially across the screw end face during screw rotation. However, in this embodiment the leading surface has a shape which follows the shape of an involute based upon a circle of diameter sub-stantially equal to the chamber diameter with the shape atthe radially inner end of /- _ _ _ _ _ _ _ _ 1 ~ 3~ 6 1 ~
the surface corresponding to the root end of the involute, i.e. the end commencing at the circum~erence of the circle from which the involute is formed. The reason for this involute shape will be given below. As may be seen from Figures 2 and 3, the radially outer end o the leading sur-face 14, considered forwardly of the surface, forms an obtuse angle to the tangent to the circumferential point of the chamber to which the outer end lies adjacent. Also, the surface 14 is an extension (albeit at a different inclination) of the downstream end of the load-applying surface 6 of the screw flight 5.
The part of the end face 16 of the screw which is devoid of the abutment is a planar face lying normal to the rotational axis. The abutment has a maximum depth at the edge 17 where the leading surface 14 meets the arcuate outer edge 15 of the abutment and at this position has a slight operating clearance from the upstream face of the die plate.
This depth is caused to decrease progressively across the abutment by a curved end surfacè 18 of the abutment which meets the end face 16 along the edge 13. Hence, rake is provided upon the abutment rearwardly, in the sense of its direction of rotation, from the edge 17.
The abutment 11 described above was added as a modification to an ex~ruder of otherwise conventional design and one which had previously had the problem of degradation of polymeric material between the mounting spindle and the end of the extrusion screw 4. This modification was provided by replacing an existing end cap (not shown) with an end cap 19 (Figure 3) having the end surface 16 and a radially inner region 20 of the abutment 11. A radially outer region 21 of ` ~ ~
1~319~i1Z
the abutment, having an arcuate interface 22 with the inner region, was formed by an extension to the screw flight S.
The curved end surface 18 enables the abutment to clear the nut 10 as shown in Figure 1. The end cap 19 is retained on the screw in conventional manner.
In use of the apparatus, wet bromobutyl is fed into the extruder inlet and is mo~ed under compression by the screw along the chamber 3 while increasing in temperature to at least 320F by mechanical working. The wet material is moved along the barrel by the surface 6 of the screw flight and upon reaching the end of the flight, most of the material is fed through the orifices 8 in the die plate where pressure reduction results in volatilization and removal of volatile substances, and is cut into smaLl pieces of manageable size for conveying and baling by the cutter.
Some of the polymeric material, however, i.e. that lying closest to the load-applying surface 6 at its downstream end, is directed by the radially outer end of the leading surface 14 of the abutment, to flow radially inwards across the end of the screw before being e~truded. The obtuse angle formed by the surface 14 with a tangent at any circumferential point of the chamber wall to which it lies adjacent assists in change in direction of flow of the polymeric material across the end face 16 because it tends to blend that flow direction with that around the chamber wall caused by the surface 6. Upon meeting the leading surface 14, the polymeric material is influenced to move radially inwards during screw rotation by the concave shape of the surface which at its outer end has a radially inwardly facing component. It is also believed that the involute shape of the leading surface ~ 1 38 ~ 1 ~
14 based upon a circle equal in diameter to the chamber diameter further assists in the inward movement of the material, as a pumping action is created by the surface in the radial inward direction in a manner similar to that which is understood to take place in pumps operating with involutely-shaped radially positioned vanes.
The leading surface 14 thus directs the material across the end face 16 of the screw so as constantly to force out and replace material in regions at and around the axis of rotation of the screw, i.e. directly behind the area occupied by the nut 10 at which position the die plate is devoid of extrusion orifices 8 or 8a. In addition, as the surface 14 decreases in height towards its inner end because of the inclined end surface 18, some of the material flows over the surface 14 and across surface 18.
The orifices 8a, being of larger diameter than orifices 8 in the die plate, encourage constant movement of material across the regions at and around the rotational axis of the screw as they are closest to this axis and their larger diameters encourage the extrusion of polymeric material through them.
In use of the apparatus of the above embodiment, mo~ement of polymeric material across all regions of the end face 16 and across the surface 18 is continuous and residence time for the material is reduced significantly. Because of this, bromobutyl dried by passage through this apparatus was found to be completely free of degraded material although normal extrusion pressures and temperatures were created within the apparatus.
In second and third embodiments now to be described, 1~38~i12 similar advantages are obtained to those obtained in the first embodiment.
In the second embodiment as shown in Figures 4, 5 and 6, apparatus for removing volatile substances from wet bromobutyl comprises an extruder having a barrel 23 with chamber 24, die plate 25 and mounting spindle 26 and locking nut 27 of construction si~ilar to that described in the first embodiment.
The construction of the second embodiment has a screw 28 with a screw flight 29 and an end cap 30 having four circumferentially spaced-apart axially extending abutments 31. These abutments are equally angularly spaced around the screw rotational axis and are arcuately shaped in end view (Figure 5) to present a convex leading surface 32 in the sense of the direction of screw rotation which is anti-clockwise in Figure 5. The whole of the end cap with the abutments lies radially within the base diameter of the screw flight. Each abutment is inclined from a peak 33 radially outwardly to blend with a chamfered edge 34 of the end cap.
Each abutment also extends inwards from its peak while tapering towards its inner end 35 to provide a clearance from the nut 27 as shown by Figure 4.
In use of the apparatus of the second embcdiment, as the polymeric material ifi forced along the ch~mber 28, it passes the end cap 30 and a large proportion of it is extruded directly through the extrusion orifices in the die plate. Any wet material which is caused to flow radially inwardly over the chamfered surface of the end cap is not directed in that direction as in the first embodiment but is merely urged in that direction by the screw flight. Upon 1~38~
moving radially within the vicinity of the sweep of the abutments 31, however, the material is subjected to dis-turbance caused by the rotation of the abutments. The abutments effect movement of material across the end cap merely by disturbance of the material so that the material is constantly replaced particularly in the radially central regions which lie immediately upstream of the locking nut 27.
In the third embodiment (Figures 7, 8 and 9), apparatus for removing volatile substances from polymeric material~ for instance wet bromobutyl, comprises an extruder 36 with a chamber 37 housing a rotatable screw 38. An inlet (not shown) for polymeric material to be dried is provided to the chamber and at an outlet end, a die plate 39 is provided which is formed with extrusion orifices 40. A
mounting spindle 41 extends coaxially from the outside of the die plate and is held in place by a locking nut 42. The die plate differs from that in previous embodiments in that it has a recess 43 in its rear face and which houses the locking nut in a manner completely submerged below the rear face.
The extrusion screw has a screw flight 45 formed with a downstream facing load-applying surface 46. An end cap 47 (Figure 8) is held onto the end of the screw in normal manner and comprises an end face 48 which is inclined relative to the rota~ional axis of the screw so as to extend across the screw and towards ~he die plate as it progresses away from the downstream end of the screw flight.
The end cap is formed with an abu~ment 49 in the form of a projection which is approximately semi-circular in end ~iew as shown in Figure 9. When considered in the direc~ion of screw rotation, i.e. anticlockwise in Figure 9, 1 1 3~ ~ 1 2 the abutment has a concave leading surface 50 extending towards the central radial regions of the end cap from a position at the outside diameter of the screw flight on one side of the end cap. The leading surface forms an obtuse angle forwardly of itself with a tangent to an adjacent point on the circumference of the chamber. In extending inwards it extends to a position close to the rotational axis of the screw while facing across the axis. The outer regions of the abutment lie at the maximum diameter of the screw flight for approximately three-quarters of their sectorial coverage and then decrease to the base diameter. As shown in ~igure 8, the leading surface extends axially along the end cap to terminate close to the screw flight at edge 53.
As may be seen from Figures 7 and 8, an end surface 54 of the abutment lies in a plane normal to the rotational axis and this together with the inclination of end face 48 causes a progressive reduction in depth of the surface 50.
The normal end surface 54 lies close to the upstream surface of the die plate as shown by Figure 7.
In use of the apparatus, some of the wet pol~meric material lying close to the load-applying surface 46 of the screw flight comes close to the leading surface S0 of the abutment upon reaching the end of the screw. The obtusely oriented surface at its outer end assists in directin~
material across the end face 48 and across the radially central regions so as to constantly replace material in these regions and prevent any undesirable dwell time which could result in degradation of the br~mobutyl. The inclined end face 48 assists in urging the polymeric material on the face towards the die plate during screw rotation.
~3861Z
The continuous.ly applied force may be caused by an abutment provided upon either the end of the screw or upon the die plate and lying between screw end and die plate.
The invention also includes apparatus for removing volatile substances from an extrudable polymeric material comprising:
(a) an extruder barrel defining a barrel chamber and formed with an inlet for the polymeric material and an outlet spaced from the inlet;
(b) a multi-orifice die plate extending radially across the chamber at the outlet for extrusion of polymeric material flowing from the chamber;
(c) a cutter having a mounting and carried by the mounting upon the die plate for cutting extruded polymeric material as it i~ emitted from the extrusion orifices into discrete portions;
(d) and an extrusion screw with a free downstream end and rotatabLe within the chamber and having at least one screw flight fox feeding polymeric material along the barrel from the inlet to the outlet and through the die plate orifices while subjecting the material to compression to cause an increase in its temperature. for subsequent volatili-zation and release of volatile substance from the polymeric material, the extrusion screw having a downstream end towards the die plate and an abutment extending radially of the screw end, the screw flight having a downstream facing load-applying surface and, when considered in the direction of screw rota~ion, the abutment ha~ing a leading surface which - extends axially from the end of the screw and forming an extension of the load-applying surface from a position 11381~Z
adjacent the wall of the chamber at least partly across the end of the screw, said abutment sweeping around the axis of rotation of the screw during screw rotation to direct polymeric material to flow radially inwardly across said end of the screw thereby to move polymeric material across the end of the screw constantly to replace material situated axially between the end of the screw and the mounting of the cutter.
With this construction, polymeric material being fed downstream by the screw flight is partly conveyed directly against the leading surface and then by the leading surface is directed to flow radially across the end of the screw and behind the cutter mounting.
It is also to be preferred that the leading surface extends to a position adjacent the circumference of the chamber in such a manner that, when considered in the direction of screw rotation and forwardly of the leading surface, the outer end of the leading surface forms an obtuse angle with a tangent to the circumferential point of the chamber to which the outer end lies ad~acent. This then enables polymeric material to be moved by the leading surface across the screw end without a sudden change in direction of motion of the material from i~s axial and circumferential movement around the screw whereby resistance to such movement across the screw is minimized. The obtuse angle is con-veniently provided by a concave curva~ure of the leading surface as it e~ends across the screw end. Conveniently, the concavity may be provided by the leading surface following the shape of an involute which may be based upon a diameter substantially equal to the chamber diameter with the shape at 113~3612 .
the radially inner end of the surface corresponding to the root end of the involute and with said inner end lying substantially coincident with the axis of rotation of the screw. It is found with this involute shape, a pumping action takes place, as with the involute shaped vanes of a pump, to assist in directing flow of the polymeric material across the end of the screw.
Embodiments of the invention will now be described, ~ by way of example, with reference to the accompanying drawings in which:-FIGURE 1 is an axial cross-sectional view of part of an apparatus according to a first embodiment;
FIGURE 2 is a view in the direction of arrow II
in Figure 1 with a die plate partly cut away to show an end of an extruder screw;
FIGURE 3 is an isometric view on an enlarged scale of the end of the extruder screw removed from the apparatus;
FIGURE 4 is a view similar to that of Figure 1 of a second embodiment;
FIGURE 5 is an axial view on the end of a screw used in the second embodiment, considered in the direction of arrows VI in Figure 5 and on a larger scale;
FIGURE 6 is a cross-sectional view on line VI-VI
of Figure 5 of an end of the screw;
FIGURE 7 is a view slmilar to Figure 1 of a third embodiment;
FIGURE 8 is an isometric view on an enlarged scale 11386~2 of the end of a screw used ln the third embodiment; and FIGURE 9 is a view of the end of the screw in the direction of arrow IX in Figure 8.
In a first embodiment as shown in Figure 1, apparatus for removing water and other volatile substances from a polymeric material such as wet bromobutyl comprises an extruder 1 ha~ing a barrel 2 formed with a cylindrical barrel chamber 3. The barrel houses an extrusion screw 4 ha~ing a free downstream end and formed with a single screw flight 5 having a downstream load-applying æurface 6 for ~`
feeding the wet bromobutyl from an inlet (not shown) for the material to the outlet of the extruder at which position a die plate 7 extends radially across the chamber. The die pla~e is formed with a plurality of extrusion orifices 8 (see particularly Figure 2) for extrusion therethrough of the polymer. It is intended that orifices towards the radial center of the die plate are of larger cross-sectional area than other orifices and for this purpose orifices 8a on an inner pitch circle are of larger diameter as shown in Figure 2. Mounted upon the die plate is a cutter (not shown) which is rotatably held upon a mounting spindle 9 which extends coaxially out from the die plate and from the extruder and is held securely in position by a locking nut 10 disposed in a central recess on the upætream face of the die plate.
The barrel, die plate, cutter and mounting for the cutter together with the part of the extrusion screw 80 far des-cribed are all of conventional design and will be described in no greater detail. Suffice it to say that the extrusion screw i of the type that, during rotation, compresses the 3 ~6 1 ~
wet polymeric material to cause an increase in temperature of the material during its movement along the barrel by a mechanical working process and then suddenly releases the pressure conditions to result in volatilization of the volatile substances which then escape from the material upon exposure to ambient atmospheric conditions.
This embodiment differs from prior construc~ions and according to the invention by the extrusion screw having a downstream end towards the die plate and an abutment extending radially of the screw end, the screw flight having a downstream facing load-applying surface and, when considered in the direction of screw rotation, the abutment having a leading surface which extends axially from the end of the screw and forming an extension of the load-applying surface from a position adjacent the wall of the chamber at least partly across the end of the screw, this abu~ment sweeping around the axis of rotation of the screw during screw rotation to direct polymeric material to flow radially inwardly across said end of the screw thereby to move polymeric material across the end of the screw constantly to replace material situated axially between the end of the screw end and the cutter mounting. This abutment i8 a pro-jection 11 on the screw end and, in end view (F~gure 2), is generally in the form of a sector of a circle with two ~5 generally radially extending edges 12 and 13 meeting at the axis of rotation of ~he screw to make an included zngle slightly less than 90. As may be seen from Figures 2 and 3, the edge 12 is not intended to extend along a radial line of the screw. This edge 12 is that formed by a surface 14 (Figure 3) of the abutment and is a leading surface of the _ 9._ .
113~Z
abutment when considered in the direction of rotation of the screw and abutment around the rotational axis. The rotational direction is anticlockwise as viewed in Figure 2.
Figure 2 shows that the leading surface is of concave curvature as it extends radially outwards from the rotational axis to the radiaLly outer edge 15 of the abutment which is in the shape of an arc having a radius with a center coincident with the rotatîonal axis and equal in length to the outside radius of the screw fligh~. The concave curva-ture of the surface 14 may be of any desired shape to urgethe wet polymerlc material to move radially across the screw end face during screw rotation. However, in this embodiment the leading surface has a shape which follows the shape of an involute based upon a circle of diameter sub-stantially equal to the chamber diameter with the shape atthe radially inner end of /- _ _ _ _ _ _ _ _ 1 ~ 3~ 6 1 ~
the surface corresponding to the root end of the involute, i.e. the end commencing at the circum~erence of the circle from which the involute is formed. The reason for this involute shape will be given below. As may be seen from Figures 2 and 3, the radially outer end o the leading sur-face 14, considered forwardly of the surface, forms an obtuse angle to the tangent to the circumferential point of the chamber to which the outer end lies adjacent. Also, the surface 14 is an extension (albeit at a different inclination) of the downstream end of the load-applying surface 6 of the screw flight 5.
The part of the end face 16 of the screw which is devoid of the abutment is a planar face lying normal to the rotational axis. The abutment has a maximum depth at the edge 17 where the leading surface 14 meets the arcuate outer edge 15 of the abutment and at this position has a slight operating clearance from the upstream face of the die plate.
This depth is caused to decrease progressively across the abutment by a curved end surfacè 18 of the abutment which meets the end face 16 along the edge 13. Hence, rake is provided upon the abutment rearwardly, in the sense of its direction of rotation, from the edge 17.
The abutment 11 described above was added as a modification to an ex~ruder of otherwise conventional design and one which had previously had the problem of degradation of polymeric material between the mounting spindle and the end of the extrusion screw 4. This modification was provided by replacing an existing end cap (not shown) with an end cap 19 (Figure 3) having the end surface 16 and a radially inner region 20 of the abutment 11. A radially outer region 21 of ` ~ ~
1~319~i1Z
the abutment, having an arcuate interface 22 with the inner region, was formed by an extension to the screw flight S.
The curved end surface 18 enables the abutment to clear the nut 10 as shown in Figure 1. The end cap 19 is retained on the screw in conventional manner.
In use of the apparatus, wet bromobutyl is fed into the extruder inlet and is mo~ed under compression by the screw along the chamber 3 while increasing in temperature to at least 320F by mechanical working. The wet material is moved along the barrel by the surface 6 of the screw flight and upon reaching the end of the flight, most of the material is fed through the orifices 8 in the die plate where pressure reduction results in volatilization and removal of volatile substances, and is cut into smaLl pieces of manageable size for conveying and baling by the cutter.
Some of the polymeric material, however, i.e. that lying closest to the load-applying surface 6 at its downstream end, is directed by the radially outer end of the leading surface 14 of the abutment, to flow radially inwards across the end of the screw before being e~truded. The obtuse angle formed by the surface 14 with a tangent at any circumferential point of the chamber wall to which it lies adjacent assists in change in direction of flow of the polymeric material across the end face 16 because it tends to blend that flow direction with that around the chamber wall caused by the surface 6. Upon meeting the leading surface 14, the polymeric material is influenced to move radially inwards during screw rotation by the concave shape of the surface which at its outer end has a radially inwardly facing component. It is also believed that the involute shape of the leading surface ~ 1 38 ~ 1 ~
14 based upon a circle equal in diameter to the chamber diameter further assists in the inward movement of the material, as a pumping action is created by the surface in the radial inward direction in a manner similar to that which is understood to take place in pumps operating with involutely-shaped radially positioned vanes.
The leading surface 14 thus directs the material across the end face 16 of the screw so as constantly to force out and replace material in regions at and around the axis of rotation of the screw, i.e. directly behind the area occupied by the nut 10 at which position the die plate is devoid of extrusion orifices 8 or 8a. In addition, as the surface 14 decreases in height towards its inner end because of the inclined end surface 18, some of the material flows over the surface 14 and across surface 18.
The orifices 8a, being of larger diameter than orifices 8 in the die plate, encourage constant movement of material across the regions at and around the rotational axis of the screw as they are closest to this axis and their larger diameters encourage the extrusion of polymeric material through them.
In use of the apparatus of the above embodiment, mo~ement of polymeric material across all regions of the end face 16 and across the surface 18 is continuous and residence time for the material is reduced significantly. Because of this, bromobutyl dried by passage through this apparatus was found to be completely free of degraded material although normal extrusion pressures and temperatures were created within the apparatus.
In second and third embodiments now to be described, 1~38~i12 similar advantages are obtained to those obtained in the first embodiment.
In the second embodiment as shown in Figures 4, 5 and 6, apparatus for removing volatile substances from wet bromobutyl comprises an extruder having a barrel 23 with chamber 24, die plate 25 and mounting spindle 26 and locking nut 27 of construction si~ilar to that described in the first embodiment.
The construction of the second embodiment has a screw 28 with a screw flight 29 and an end cap 30 having four circumferentially spaced-apart axially extending abutments 31. These abutments are equally angularly spaced around the screw rotational axis and are arcuately shaped in end view (Figure 5) to present a convex leading surface 32 in the sense of the direction of screw rotation which is anti-clockwise in Figure 5. The whole of the end cap with the abutments lies radially within the base diameter of the screw flight. Each abutment is inclined from a peak 33 radially outwardly to blend with a chamfered edge 34 of the end cap.
Each abutment also extends inwards from its peak while tapering towards its inner end 35 to provide a clearance from the nut 27 as shown by Figure 4.
In use of the apparatus of the second embcdiment, as the polymeric material ifi forced along the ch~mber 28, it passes the end cap 30 and a large proportion of it is extruded directly through the extrusion orifices in the die plate. Any wet material which is caused to flow radially inwardly over the chamfered surface of the end cap is not directed in that direction as in the first embodiment but is merely urged in that direction by the screw flight. Upon 1~38~
moving radially within the vicinity of the sweep of the abutments 31, however, the material is subjected to dis-turbance caused by the rotation of the abutments. The abutments effect movement of material across the end cap merely by disturbance of the material so that the material is constantly replaced particularly in the radially central regions which lie immediately upstream of the locking nut 27.
In the third embodiment (Figures 7, 8 and 9), apparatus for removing volatile substances from polymeric material~ for instance wet bromobutyl, comprises an extruder 36 with a chamber 37 housing a rotatable screw 38. An inlet (not shown) for polymeric material to be dried is provided to the chamber and at an outlet end, a die plate 39 is provided which is formed with extrusion orifices 40. A
mounting spindle 41 extends coaxially from the outside of the die plate and is held in place by a locking nut 42. The die plate differs from that in previous embodiments in that it has a recess 43 in its rear face and which houses the locking nut in a manner completely submerged below the rear face.
The extrusion screw has a screw flight 45 formed with a downstream facing load-applying surface 46. An end cap 47 (Figure 8) is held onto the end of the screw in normal manner and comprises an end face 48 which is inclined relative to the rota~ional axis of the screw so as to extend across the screw and towards ~he die plate as it progresses away from the downstream end of the screw flight.
The end cap is formed with an abu~ment 49 in the form of a projection which is approximately semi-circular in end ~iew as shown in Figure 9. When considered in the direc~ion of screw rotation, i.e. anticlockwise in Figure 9, 1 1 3~ ~ 1 2 the abutment has a concave leading surface 50 extending towards the central radial regions of the end cap from a position at the outside diameter of the screw flight on one side of the end cap. The leading surface forms an obtuse angle forwardly of itself with a tangent to an adjacent point on the circumference of the chamber. In extending inwards it extends to a position close to the rotational axis of the screw while facing across the axis. The outer regions of the abutment lie at the maximum diameter of the screw flight for approximately three-quarters of their sectorial coverage and then decrease to the base diameter. As shown in ~igure 8, the leading surface extends axially along the end cap to terminate close to the screw flight at edge 53.
As may be seen from Figures 7 and 8, an end surface 54 of the abutment lies in a plane normal to the rotational axis and this together with the inclination of end face 48 causes a progressive reduction in depth of the surface 50.
The normal end surface 54 lies close to the upstream surface of the die plate as shown by Figure 7.
In use of the apparatus, some of the wet pol~meric material lying close to the load-applying surface 46 of the screw flight comes close to the leading surface S0 of the abutment upon reaching the end of the screw. The obtusely oriented surface at its outer end assists in directin~
material across the end face 48 and across the radially central regions so as to constantly replace material in these regions and prevent any undesirable dwell time which could result in degradation of the br~mobutyl. The inclined end face 48 assists in urging the polymeric material on the face towards the die plate during screw rotation.
Claims (13)
1. A method of removing volatile substances from an extrudable polymeric material comprising:
(a) entering the material into an inlet of an extruder barrel;
(b) rotating an extruder screw with a free down-stream end within the barrel to feed the material along the barrel towards an outlet end of the barrel while compressing it and heating it to cause subsequent volatilization and release of the volatile substance when the material is subjected to a reduction in pressure and brought into contact with ambient atmosphere; and (c) by rotation of the extruder screw, continuously forcing the material in an axial direction through orifices provided in a die plate at the outlet end of the barrel and severing the extrudate so formed into discrete portions by the use of a cutter rotating upon a mounting upon the die plate while continuously applying a force to cause movement of material radially inwardly across the end of the screw constantly to replace material situated axially between the end of the screw and the mounting of the cutter.
(a) entering the material into an inlet of an extruder barrel;
(b) rotating an extruder screw with a free down-stream end within the barrel to feed the material along the barrel towards an outlet end of the barrel while compressing it and heating it to cause subsequent volatilization and release of the volatile substance when the material is subjected to a reduction in pressure and brought into contact with ambient atmosphere; and (c) by rotation of the extruder screw, continuously forcing the material in an axial direction through orifices provided in a die plate at the outlet end of the barrel and severing the extrudate so formed into discrete portions by the use of a cutter rotating upon a mounting upon the die plate while continuously applying a force to cause movement of material radially inwardly across the end of the screw constantly to replace material situated axially between the end of the screw and the mounting of the cutter.
2. A method according to Claim 1 wherein the polymeric material is caused to flow along the barrel by axial pressure imposed upon it by a downstream facing load-applying surface of a screw flight of the extruder screw, the material then being engaged at the end of the screw by an abutment surface extending at least partly across the end of the screw, projecting axially from said end and forming an extension to the downstream facing surface of the screw flight, the material being forced by the abutment surface to flow radially inwardly of the screw by rotational sweeping movement of the surface during screw rotation.
3. A method according to Claim 1 wherein the polymeric material contacts an abutment surface at the end of the screw, said surface projecting axially from said end, being a lead-ing surface when considered in the direction of screw rotation and also extending radially of the screw with a degree of concavity.
4. Apparatus for removing volatile substances from an extrudable polymeric material comprising:
(a) an extruder barrel defining a barrel chamber and formed with an inlet for the polymeric material and an outlet spaced from the inlet;
(b) a multi-orifice die plate extending radially across the chamber at the outlet for extrusion of polymeric material flowing from the chamber;
(c) a cutter having a mounting and carried by the mounting upon the die plate for cutting extruded polymeric material as it is emitted from the extrusion orifices into discrete portions;
(d) and an extrusion screw with a free downstream end and rotatable within the chamber and having at least one screw flight for feeding polymeric material along the barrel from the inlet to the outlet and through the die plate orifices while subjecting the material to compression to cause an increase in its temperature for subsequent volatiliza-tion and release of volatile substance from the polymeric material, the extrusion screw having a downstream end towards the die plate and an abutment extending radially of the screw end, the screw flight having a downstream facing load-applying surface and, when considered in the direction of screw rotation, the abutment having a leading surface which extends axially from the end of the screw and forming an extension of the load-applying surface from a position adjacent the wall of the chamber at least partly across the end of the screw, said abutment sweeping around the axis of rotation of the screw during screw rotation to direct polymeric material to flow radially inwardly across said end of the screw thereby to move polymeric material across the end of the screw constantly to replace material situated axially between the end of the screw and the mounting of the cutter.
(a) an extruder barrel defining a barrel chamber and formed with an inlet for the polymeric material and an outlet spaced from the inlet;
(b) a multi-orifice die plate extending radially across the chamber at the outlet for extrusion of polymeric material flowing from the chamber;
(c) a cutter having a mounting and carried by the mounting upon the die plate for cutting extruded polymeric material as it is emitted from the extrusion orifices into discrete portions;
(d) and an extrusion screw with a free downstream end and rotatable within the chamber and having at least one screw flight for feeding polymeric material along the barrel from the inlet to the outlet and through the die plate orifices while subjecting the material to compression to cause an increase in its temperature for subsequent volatiliza-tion and release of volatile substance from the polymeric material, the extrusion screw having a downstream end towards the die plate and an abutment extending radially of the screw end, the screw flight having a downstream facing load-applying surface and, when considered in the direction of screw rotation, the abutment having a leading surface which extends axially from the end of the screw and forming an extension of the load-applying surface from a position adjacent the wall of the chamber at least partly across the end of the screw, said abutment sweeping around the axis of rotation of the screw during screw rotation to direct polymeric material to flow radially inwardly across said end of the screw thereby to move polymeric material across the end of the screw constantly to replace material situated axially between the end of the screw and the mounting of the cutter.
5. Apparatus according to Claim 4 wherein, when considered in the direction of screw rotation and forwardly of the leading surface, the outer end of the leading surface forms an obtuse angle with a tangent to the circumferential point of the chamber to which said outer end lies adjacent.
6. Apparatus according to Claim 5 wherein the leading surface has a concave curvature as it extends across the screw end.
7. Apparatus according to Claim 6 wherein the leading surface extends radially outwards from a position substantially coincident with the axis of rotation of the screw and follows the shape of an involute based upon a diameter substantially equal to the chamber diameter with the shape at the radially inner end of the surface corresponding to the root end of the involute.
8. Apparatus according to Claim 5 wherein the leading surface lies between the end of the screw and the mounting of the cutter and extends to a position adjacent to the rotational axis of the screw while facing across the rotational axis.
9. Apparatus according to Claims 7 or 8 wherein the abutment has a downstream end which is inclined relative to the rotational axis of the screw to decrease the depth of the leading surface from its radially outer end towards its radially inner end.
10. Apparatus according to Claims 4 or 8 in which the end of the screw from which the abutment extends is inclined to extend axially towards the breaker plate from the screw flight.
11. Apparatus according to Claim 8 wherein, when considered in the direction of screw rotation and forwardly of the leading surface at any angular position of the screw, the outer end of the leading surface forms an obtuse angle with a tangent to the circumferential point of the chamber wall to which said outer end lies adjacent.
12. Apparatus according to Claim 4 wherein a plurality of radially extending, angularly spaced-apart abutments are provided upon the end of the screw, and when considered in the direction of screw rotation, each abutment extends radially inwardly of the screw end and has a leading surface for moving polymeric material across the end of the screw.
13. Apparatus according to Claim 4 wherein the die plate has some orifices closer to the cutter mounting than other orifices and said closer orifices are of larger cross-sectional area than the other orifices.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US4690879A | 1979-06-08 | 1979-06-08 | |
| US46,908 | 1979-06-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1138612A true CA1138612A (en) | 1983-01-04 |
Family
ID=21946038
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000351506A Expired CA1138612A (en) | 1979-06-08 | 1980-05-08 | Method and apparatus for drying wet polymerized materials |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5638244A (en) |
| BE (1) | BE883702A (en) |
| CA (1) | CA1138612A (en) |
| FR (1) | FR2458383A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2615781B1 (en) * | 1987-05-26 | 1989-07-28 | Biomass Dev Sa | IMPROVED COMPRESSION HEAD FOR A CONTINUOUS DENSIFYING MACHINE FOR PLANT MATERIALS |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1132898A (en) * | 1965-08-13 | 1968-11-06 | Werner & Pfleiderer | Multi-stage screw treatment device |
| DE2027564A1 (en) * | 1969-06-05 | 1970-12-10 | International Basic Economy Corp., New York, N.Y. (V.St.A.) | Method and apparatus for removing liquid from a polymer material |
| DE2120601B2 (en) * | 1971-04-27 | 1973-08-09 | Barmag Barmer Maschinenfabrik Ag, 5600 Wuppertal | METHOD AND DEVICE FOR PROCESSING AND DEGASSING THERMALLY SENSITIVE POWDERED THERMOPLASTICS |
-
1980
- 1980-05-08 CA CA000351506A patent/CA1138612A/en not_active Expired
- 1980-06-06 JP JP7656580A patent/JPS5638244A/en active Pending
- 1980-06-06 BE BE0/200944A patent/BE883702A/en not_active IP Right Cessation
- 1980-06-06 FR FR8012634A patent/FR2458383A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| FR2458383A1 (en) | 1981-01-02 |
| BE883702A (en) | 1980-12-08 |
| JPS5638244A (en) | 1981-04-13 |
| FR2458383B1 (en) | 1983-12-23 |
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