U.S. patent application number 09/731656 was filed with the patent office on 2001-04-12 for apparatus and method for direct injection of additives into a polymer melt stream.
This patent application is currently assigned to BASF Corporation. Invention is credited to Burlone, Dominick A., Helms, Charles F. JR., Huff, James L., Kessler, Thomas.
Application Number | 20010000234 09/731656 |
Document ID | / |
Family ID | 22764614 |
Filed Date | 2001-04-12 |
United States Patent
Application |
20010000234 |
Kind Code |
A1 |
Helms, Charles F. JR. ; et
al. |
April 12, 2001 |
Apparatus and method for direct injection of additives into a
polymer melt stream
Abstract
This invention provides an apparatus and method for injecting an
additive directly into a polymer melt stream. The method comprises
supplying a melt flow of a polymeric host material to a die
assembly having a thin-plate assembly and injecting at least one
additive into at least one predetermined location in a
cross-section of the melt flow of the polymeric host material while
the melt flow passes through the die assembly. The method achieves
uniform dosing of the one or more additives in the extrusion
direction in the polymeric host material without homogeneously
mixing the one or more additives and the polymeric host material.
The apparatus for directly injecting one or more additives into a
polymer melt stream comprises a pumping system, a die assembly
having a thin-plate assembly, and a distribution line.
Inventors: |
Helms, Charles F. JR.;
(Asheville, NC) ; Burlone, Dominick A.;
(Asheville, NC) ; Huff, James L.; (Mars Hill,
NC) ; Kessler, Thomas; (Schifferstadt, DE) |
Correspondence
Address: |
Nixon & Vanderhye P.C.
8th Floor
1100 N. Glebe Rd.
Arlington
VA
22201
US
|
Assignee: |
BASF Corporation
|
Family ID: |
22764614 |
Appl. No.: |
09/731656 |
Filed: |
December 8, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09731656 |
Dec 8, 2000 |
|
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|
09206011 |
Dec 4, 1998 |
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Current U.S.
Class: |
428/131 ;
428/402 |
Current CPC
Class: |
Y10T 137/85938 20150401;
Y10T 428/2933 20150115; B29K 2105/16 20130101; B29C 48/2886
20190201; B29C 48/08 20190201; Y10T 428/2982 20150115; B29C 48/07
20190201; Y10T 428/24273 20150115; Y10T 428/2975 20150115; B29C
48/95 20190201; B29B 7/72 20130101; B29B 9/06 20130101; Y10T
428/2929 20150115; B29C 48/29 20190201; B29K 2105/0005 20130101;
B29B 7/88 20130101 |
Class at
Publication: |
428/131 ;
428/402 |
International
Class: |
B32B 003/10 |
Claims
What is claimed is:
1. A method of directing at least one additive to a cross-section
of a host polymeric melt flow comprising the steps of: (a)
supplying a melt flow of a polymeric host material to a die
assembly comprising a thin-plate assembly; and (b) injecting at
least one additive into at least one predetermined location in a
cross-section of the melt flow of the polymeric host material while
passing the melt flow of the polymeric host material through the
die assembly, wherein the at least one additive is injected into
the at least one predetermined location in the cross-section of the
melt flow of the polymeric host material to achieve uniform dosing
of the additive in the extrusion direction in the at least one
predetermined location of the cross-section of the polymeric host
material.
2. The method of claim 1, wherein the thin-plate assembly comprises
at least a first thin plate and a second thin plate, the first thin
plate having channels formed on a surface thereof.
3. The method of claim 1, wherein the polymeric host material is
selected from the group consisting of polyamides, polyesters,
polystyrene, acrylics, polyolefins, and combinations thereof.
4. The method of claim 3, wherein the polymeric host material is
polyamide.
5. The method of claim 4, wherein the polyamide is nylon 6.
6. The method of claim 1 wherein the additive is selected from the
group consisting of antistatic agents, blowing agents,
delusterants, dye regulating agents, fillers, flame retardants,
heat stabilizers, light stabilizers, lubricants, pigments, and
plasticizers and combinations thereof.
7. The method of claim 1, wherein the additive is a lubricant.
8. The method of claim 7, wherein the lubricant is selected from
the group consisting of zinc stearate and calcium stearate.
9. The method of claim 1, wherein the additive is placed into the
core of the melt flow of the polymeric host material.
10. The method of claim 1, wherein the additive is placed into the
melt flow of the polymeric host material in an islands-in-a-sea
arrangement.
11. The method of claim 1, wherein the additive is placed in a
pattern of stripes on the surface of the melt flow of the polymeric
host material.
12. An apparatus for injecting at least one additive directly into
a cross-section of a host polymer melt flow comprising: (a) a
pumping system; (b) a die assembly comprising a thin-plate
assembly, wherein the thin-plate assembly comprises at least a
first thin plate and a second thin plate, the first thin plate
having channels formed on a surface thereof; and (c) a first
distribution line.
13. The apparatus of claim 12, wherein the pumping system comprises
an additive supply, a recirculation pump, and a metering pump.
14. The apparatus of claim 12, wherein the pumping system comprises
an additive supply, a weight scale, a metering pump, and a second
distribution line.
15. The apparatus of claim 12, wherein the pumping system comprises
an additive supply, a flow sensor, a metering pump, and a second
distribution line.
16. The apparatus of claim 12, wherein the first distribution line
comprises heat traced, high-pressure tubing.
17. The apparatus of claim 12, wherein the die assembly further
comprises a distribution plate and a die head plate, the thin
plates being located between the distribution plate and the die
head plate.
18. A method of making pellets from at least one polymeric host
material comprising the steps of: (a) supplying a melt flow of at
least one polymeric host material to a die assembly comprising a
thin-plate assembly; (b) directing the injection of at least one
additive in at least one predetermined location in a cross-section
of the melt flow of the polymeric host material while passing the
melt flow through the die assembly to form polymer strands, wherein
the at least one additive is injected into the at least one
predetermined location in the cross-section of the melt flow of the
polymeric host material to achieve uniform dosing of the additive
in the extrusion direction in the at least one predetermined
location of the cross-section of the polymeric host material; and
(c) cutting the polymer strands to form pellets.
19. The method of claim 18, wherein the thin-plate assembly
comprises at least a first thin plate and a second thin plate, the
first thin plate having channels formed on a surface thereof.
20. The method of claim 18, wherein the polymeric host material is
selected from the group consisting of polyamides, polyesters,
polystyrene, acrylics, polyolefins, and combinations thereof.
21. The method of claim 18, wherein the polymeric host material is
polyamide.
22. The method of claim 21, wherein the polymeric host material is
nylon 6.
23. The method of claim 18, wherein the additive is selected from
the group consisting of antistatic agents, blowing agents,
delusterants, dye regulating agents, fillers, flame retardants,
heat stabilizers, light stabilizers, lubricants, pigments, and
plasticizers and combinations thereof.
24. The method of claim 23, wherein the additive is a
lubricant.
25. The method of claim 24, wherein the lubricant is selected from
the group consisting of zinc stearate and calcium stearate.
26. The method of claim 18, wherein the additive is placed into the
core of the melt flow of the polymeric host material.
27. The method of claim 18, wherein the additive is placed into the
melt flow of the polymeric host material in an islands-in-a-sea
arrangement.
28. The method of claim 18, wherein the additive is placed in a
pattern of stripes on the surface of the melt flow of the polymeric
host material.
29. A thin plate having formed on a surface thereof at least one
first channel defining a perimeter about a center and having in
fluid flow communication therewith at least one second channel
radiating from said first channel toward said center and
terminating in at least one through hole.
30. A thin plate according to claim 29, wherein said at least one
first channel is spherical.
31. A thin plate according to claim 30, wherein said at least one
first channel is circular.
32. A thin plate according to claim 29, wherein two or more second
channels radiate from said first channel.
33. A thin plate according to claim 32, wherein said two or more
second channels terminate in a single through hole.
34. A thin plate according to claim 32, wherein each of said two or
more second channels terminate at a separate, respective through
hole.
35. A thin plate according to claim 29, wherein four-second
channels radiate from said first channel.
36. A thin plate according to claim 35, wherein said four channels
terminate in a single through hole.
37. A thin plate according to claim 35, wherein each of said four
channels terminate at its own through hole.
38. A pellet comprising a polymeric host material with an additive
embedded therein, said additive selected from the group consisting
of antistatic agents, blowing agents, delusterants, dye regulating
agents, fillers, flame retardants, heat stabilizers, light
stabilizers, lubricants, pigments, and plasticizers and
combinations thereof, wherein the additive is uniformly dosed, in
the extrusion direction, in the cross-section of the pellet in at
least one predetermined location.
39. A pellet according to claim 38, wherein the additive is a
lubricant.
40. The pellet of claim 39, wherein the lubricant is selected from
the group consisting of zinc stearate and calcium stearate.
41. The pellet of claim 40, wherein the additive domain comprises
the core of the pellet.
42. The pellet of claim 40, wherein the polymeric host material and
the additive are in an islands-in-a-sea arrangement and the
additive comprises the islands in the sea of the polymeric host
material.
43. The pellet of claim 40, wherein the additive domain comprises
stripes on the surface of the polymeric host material.
44. A pellet according to claim 38, wherein the polymeric host
material is selected from the group consisting of polyamides,
polyesters, polystyrene, acrylics, polyolefins, and combinations
thereof.
45. The pellet of claim 44, wherein the polymeric host material is
polyamide.
46. The pellet of claim 45, wherein the polyamide is nylon 6.
Description
FIELD OF THE INVENTION
1. This invention relates to the introduction of additives into a
polymer. More specifically, this invention relates to an apparatus
and method for the direct injection of additives into a polymer
melt stream.
BACKGROUND OF THE INVENTION
2. The addition of additives to molten polymers has been
accomplished by several means. One such means is blending the
additives and the polymer chips together in the polymer chip dryer
or in the storage hopper prior to extruding the polymer chips and
the additives into strands for pelletizing. Another method for
introducing additives into a polymer melt stream is to inject the
additives at the throat, the mixing zones, or the vent of the
extruder and to allow the extrusion process to fully blend the
additives into the polymer components. A third method of
introducing additives into a polymer melt stream involves injecting
the additives into static mixing elements located downstream of the
extruder to fully blend the additives into the polymer
components.
3. Problems arise, however, in that some additives may be heat
sensitive and may also cause polymer degradation or other
undesirable reactions with the polymer if blended with the polymer
before extrusion into polymer strands. Moreover, some additives
such as, for example, zinc stearate, can cause extruder screw
slippage.
4. A way to overcome such problems is to introduce the additives
into a polymer melt stream after extrusion of the polymer into
strands for pelletizing. One such method is to coat the polymer
pellets with the additives after the polymer extrusion process has
occurred. A problem arises, however, in that for additives that
amount to less than about 1 percent of the concentration of the
total polymer product, this method does not generally result in a
good uniform dosing of additive to polymer.
5. A need, therefore, exists for a method of introducing additives
into the polymer that overcomes the above-discussed
limitations.
SUMMARY OF THE INVENTION
6. It is a primary object of the present invention to introduce one
or more additives directly into a polymer melt stream.
7. Another object of the present invention is to strategically
place one or more additives at specific locations within an
extruded polymer strand using a thin plate die assembly.
8. Thus, according to one embodiment of the present invention,
there is provided a method of directly injecting one or more
additives into a polymer melt stream comprising the steps of
supplying a melt flow of a polymeric host material to a die
assembly having a thin-plate assembly and injecting at least one
additive into at least one predetermined location in a
cross-section of the melt flow of the polymeric host material while
passing the melt flow of the polymeric host material through the
die assembly. The one or more additives is injected into one or
more exact locations within the cross-section of the polymeric host
to achieve uniform dosing, in the extrusion direction, of the one
or more additives within the polymeric host material without
homogeneously mixing the one or more additives and the polymeric
host material into a single phase.
9. According to another aspect of the present invention there is
provided an apparatus for carrying out the direct injection of one
or more additives into the melt flow of a polymeric host material
comprising a pumping system, a die assembly having a thin-plate
assembly, and a distribution line.
10. According to yet another embodiment of the present invention
there is provided a method of making pellets from polymers
comprising the steps of supplying a melt flow of at least one
polymeric host material to a die assembly comprising a thin-plate
assembly, directing the injection of at least one additive into at
least one predetermined location in a cross-section of the melt
flow while passing the melt flow through the die assembly to form
strands, and cutting the polymer strands into pellets. The
resulting pellets have a precise amount of additive dosed at the at
least one predetermined location in the cross-section of the
polymeric host material. The uniform dosing of the one or more
additives is achieved without homogeneous mixing of the additive
and the polymeric host material.
11. By precisely injecting low concentrations of one or more
sensitive polymer additives into the polymeric host material at the
die, degradation and chemical reactions in the extruder are
avoided, handling of additive material is simplified, and
uniformity of the additive in the strand of polymeric host material
is improved. Moreover, accurate placement of additives in the
cross-section of a strand of polymeric host material is
achieved.
12. The above and other objects, effects, features, and advantages
of the present invention will become more apparent from the
following detailed description of the preferred embodiments
thereof, particularly when viewed in conjunction with the
accompanying drawings wherein like reference numbers in the various
figures are used to designate like components.
BRIEF DESCRIPTION OF THE DRAWINGS
13. FIG. 1a is a schematic of the apparatus of the present
invention.
14. FIG. 1b is a schematic of an alternate pumping system useful in
the apparatus of the present invention.
15. FIG. 1c 1b is a schematic of a second alternate pumping system
useful in the apparatus of the present invention.
16. FIG. 2 is an exploded view of one configuration of the
thin-plate assembly in the die assembly used in the apparatus of
the present invention.
17. FIG. 3 is an exploded view of a second configuration of the
thin-plate assembly in the die assembly used in the apparatus of
the present invention.
18. FIG. 3a is a schematic diagram of one of the plates of the
thin-plate assembly shown in FIG. 3.
19. FIG. 4 is an exploded view of a third configuration of the
thin-plate assembly in the die assembly used in the apparatus of
the present invention.
20. FIG. 4a is a schematic diagram of one of the plates of the
thin-plate assembly shown in FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
21. To promote an understanding of the principles of the present
invention, descriptions of specific embodiments of the invention
follow, and specific language is used to describe the same. It will
nevertheless be understood that no limitation of the scope of the
invention is intended by the use of this specific language and that
alterations, modifications, equivalents, and further applications
of the principles of the invention discussed are contemplated as
would normally occur to one of ordinary skill in the art to which
the invention pertains.
22. In one embodiment, the present invention is a method of
directly injecting one or more additives into a polymer melt
stream. The method comprises the steps of supplying a melt flow of
a polymeric host material to a die assembly having a thin-plate
assembly and injecting at least one additive into at least one
predetermined location in a cross-section of the melt flow of the
polymeric host material while passing the melt flow of the
polymeric host material through the die assembly. The one or more
additives is injected into one or more exact locations within the
cross-section of the polymeric host to achieve uniform dosing in
the extrusion direction of the one or more additives within the
polymeric host material without homogeneously mixing the one or
more additives and the polymeric host material into a single
phase.
23. In another embodiment, the present invention is an apparatus
for directly injecting one or more additives into a polymer melt
stream. The apparatus comprises a pumping system, a die assembly
having a thin-plate assembly, and a distribution line. The
apparatus of the present invention is designed to inject one or
more additives into the melt flow of a polymeric host material at
one or more specific locations in the cross-section of the
polymeric host material as the polymeric host material passes
through a die assembly and is shaped into polymer strands. While
the resulting pellets have a precise amount of one or more
additives dosed at one or more specific locations of the
cross-section of the polymeric host material, the polymer and the
one or more additives are not homogeneously mixed as a single
phase.
24. In yet another embodiment, the present invention is a method of
making pellets from polymers comprising the steps of supplying a
melt flow of at least one polymeric host material to a die assembly
comprising a thin-plate assembly, directing the injection of at
least one additive into at least one predetermined location in a
cross-section of the melt flow while passing the melt flow through
the die assembly to form strands, and cutting the polymer strands
into pellets.
25. Virtually any suitable polymer may be usefully employed in the
practice of this invention. In this regard, suitable classes of
polymeric materials that may be employed in the practice of this
invention include polyamides, polyesters, polystyrene, acrylics,
polyolefins, and combinations thereof.
26. One particularly preferred class of polymers useful in this
invention is polyamide polymers. In this regard, those preferred
polyamides useful in the practice of this invention are those that
are generically known by the term "nylon" and that are long chain
synthetic polymers containing amide (--CO--NH--) linkages along the
main polymer chain. Suitable polyamides include those polymers
obtained by the polymerization of a lactam or an amino acid and
those polymers formed by the condensation of a diamine and a
dicarboxylic acid. Examples of particularly useful polyamides are
nylon 6, nylon 6/6, nylon 6/9, nylon 6/10, nylon 6T, nylon 6/12,
nylon 11, nylon 12, nylon 4/6, and copolymers or mixtures thereof.
Polyamides can also be copolymers of nylon 6 or nylon 6/6 and a
nylon salt obtained by reacting a dicarboxylic acid component such
as terephthalic acid, isophthalic acid, adipic acid, or sebacic
acid with a diamine such as hexamethylene diamine, methaxylene
diamine, or 1,4-bisaminomethylcyclohexane. Most preferred is nylon
6. The polymers are generally supplied in the form of powders,
chips, or granules.
27. Additives that may be injected according to the present
invention include a variety of additives such as, for example,
antistatic agents, blowing agents, delusterants, dye regulating
agents, fillers, flame retardants, heat stabilizers, light
stabilizers, lubricants, pigments, plasticizers, and combinations
thereof. It is especially preferred to add lubricants such as, for
example, zinc stearate and calcium stearate, by the process of the
present invention because of the problems associated with adding
lubricants to the polymer melt stream before extrusion.
28. Referring now to the drawings, there is shown in FIG. 1a the
apparatus of the present invention. The apparatus includes a die
assembly, a pumping system, and a distribution line. The pumping
system comprises additive supply 10, recirculation pump 11, and
metering pump 12. Additive supply 10 may be a tank or an extruder.
One or more additives is maintained at the proper temperature
within additive supply 10 and pumps 11, 12 using heat tracing and
insulation (not shown). In general, pumps 11, 12 deliver the one or
more additives to die assembly 20 located at the end of extruder
60. More specifically, pump 11 circulates the one or more additives
from additive supply 10 to metering pump 12, and any additive that
is not taken away by metering pump 12 is returned back to additive
supply 10 by way of recirculation line 13. The recirculation of the
one or more additives provides ample pressure, i.e., from about 30
to about 5,000 psig, to feed inlet 14 of metering pump 12. From
metering pump 12, the one or more additives is transferred to die
assembly 20 by means of distribution line 15, which may be heat
traced, high-pressure tubing or piping. Die assembly 20, which will
be described in more detail below, preferably contains distribution
plate 21, thin-plate assembly 22, and die head plate 23 (FIGS.
2-4). Simultaneously, solid particles of polymer are fed into
hopper 61 and flow from hopper 61 into extruder 60 where the
polymer is extruded. The extruded polymer melt flow is then fed to
die assembly 20 where the one or more additives is injected into
one or more predetermined locations along the cross-section of the
polymer melt flow as the melt flow passes through die assembly 20
and is shaped into strands.
29. In another embodiment, as seen in FIG. 1b, the pumping system
can be a weight loss feeder system such as those known in the art
of chemical dispensing. An example of a commercially available
weight loss feeder system is a K-Tron Soder liquid loss-in-weight
feeder system made by K-Tron International of Pitman, N.J. In this
embodiment, additive supply 10 is placed upon weight scale 70 that
measures the weight of additive supply 10 and its liquid contents.
A heated distribution line 71 connects additive supply 10 to
metering pump 12 without interfering with the movement of the
weight scale. Metering pump 12 delivers the one or more additives
to die assembly 20 (FIG. 1) via distribution line 15. A control
system 72 calculates the loss in weight of additive supply 10 over
a given period of time, which is the metering pump delivery rate. A
time period of from 0 to 60 seconds is generally sufficient to
provide accurate flow delivery. The control system, therefore, can
control the pump speed in order to provide the proper delivery rate
of one or more additives to die assembly 20. Control system 72 may
include weight transmitter 73, weight loss controller 74, and
metering pump drive motor inverter 75, which is connected to
metering pump motor 76, metering pump motor gear box 77, and
metering pump drive shaft 78.
30. FIG. 1c illustrates yet another embodiment of the pumping
system. In this embodiment, a flow sensor may be used in place of
the weight scale to measure the flow and to control the pump. As
shown in FIG. 1c, heated distribution line 71 connects additive
supply 10 to flow sensor 79 and then to metering pump 12. Metering
pump 12 delivers the one or more additives to die assembly 20 (FIG.
1) via distribution line 15. A control system 80 determines the
flow rate, which is the metering pump delivery rate. The control
system, therefore, can control the pump speed in order to provide
the proper delivery rate of one or more additives to die assembly
20. Control system 80 may include flow transmitter 81, flow
indicating controller 82, and metering pump drive motor inverter
75, which is connected to metering pump motor 76, metering pump
motor gear box 77, and metering pump drive shaft 78.
31. The thin-plate assembly used in the present invention contains
at least two thin plates. Each plate in the thin-plate assembly
preferably is as flat as possible and is free of scratches. The
number of thin plates in the assembly will depend on the complexity
of the component distribution desired in the final product.
Typically, from 1 to about 5 plates are used, although more plates
can be used in the method and apparatus of this invention. Each
thin plate typically has a thickness of less than about 0.25 inch
and, more preferably, of from about 0.001 to about 0.10 inch.
32. The thin plates are preferably made from metal. Suitable metals
for use in the thin plates include, for example, stainless steel,
aluminum and aluminum-based alloys, nickel, iron, copper and
copper-based alloys, mild steel, brass, titanium, and other
micromachineable metals. Because it is relatively inexpensive,
stainless steel is preferably used.
33. Each thin plate has a first facial surface and an opposite
second facial surface, wherein on either or both of the first
facial and second facial surfaces, multiple distribution paths are
formed by an etching (or micromachining) process. The multiple
distribution flow paths have a flow pattern effective to distribute
and arrange the polymer melt flow and the one or more additives in
a predetermined spatial configuration. The specific flow pattern
will depend on the desired placement of the one or more additives
into or on the polymer melt flow.
34. Typically, the multiple distribution flow paths in the thin
plates are composed of multiple distribution flow channels and
multiple distribution flow apertures (or "through holes"), wherein
the distribution flow channels have a lesser depth than the
thickness of the thin plates, and further wherein the distribution
flow apertures communicate between the first facial surface and the
second facial surface of the thin plates. Preferably, at least some
of the distribution flow apertures are in communication with
respective distribution channels.
35. The multiple distribution flow paths are formed in the first
and/or second facial surfaces of the thin plates by etching (or
micromachining) processes such as, for example, photochemical and
laser etching, stamping, punching, pressing, cutting, molding,
milling, lithographing, particle blasting, reaming, or combinations
thereof. According to the current preference, the flow paths may be
photochemically etched into the surfaces.
36. The advantages of thin plates are well known in the art and
include, for example, relative ease in producing, cleaning, and
inspecting the plates. Thin plates are also inexpensive,
disposable, easily changeable, and capable of distributing and
combining a plurality of components in a predetermined
configuration with respect to each other.
37. As noted above, the configuration of thin-plate assembly 22 of
die assembly 20 depends on the desired placement of the one or more
additives in the polymer. While the number of through holes and
distribution channels in the thin plates varies, what follows are
descriptions of the preferred embodiments of the thin plates. FIG.
2 is an exploded view of one configuration of die assembly 20 used
in the apparatus of the present invention. In this configuration,
thin-plate assembly 22 is designed such that one or more additives
may be placed into the core of three separate polymer strands, as
in a core/sheath configuration.
38. In FIG. 2, die assembly 20 has a thin-plate assembly 22 that
includes thin plates 24, 25 sandwiched between distribution plate
21 and die head plate 23. Dowel pin 16 is used to align thin plates
24,25 with distribution plate 21. Die assembly 20 is connected to
the die head (not shown) of extruder 60 (FIG. 1) using a plurality
of bolts 51. Distribution line 15 is connected to inlet connection
17 located on the side of die head plate 23 using a high-pressure
tubing connector (tubing fitting) 18. Distribution line 15 may be
high-pressure tubing or piping. Tubing connector 18 may also be a
welded connector, threaded connector, or another commonly used
connector. The one or more additives in metering pump 12 (FIG. 1)
is transferred to die assembly 20 via distribution line 15 and
enters die assembly 20 through inlet connection 17 in die head
plate 23. The one or more additives then flows through hole 26 in
die head plate 23, through hole 27 in thin plate 24, and through
hole 28 in thin plate 25. At thin plate 25, the one or more
additives hydraulically splits into three equal streams through
three channels 29, 30, 31 in thin plate 25. Channels 29, 30, 31,
which are all of equal length, direct the additive streams into
holes 32, 33, 34 in thin plate 25 and then into the cores of the
three different strands of the polymeric host material via holes
35, 36, 37 in thin plate 24. Simultaneously, polymeric host
material supplied from extruder 60 is directed into central channel
38 of distribution plate 21. Distribution plate 21 divides the
polymeric host material into three sections of four polymer streams
each using distribution holes 39a-d, 40a-d, 41a-d that have been
drilled into distribution plate 21. The polymer streams then flow
through holes 42a-d, 43a-d, 44a-d in thin plate 25 to thin plate 24
where the polymer streams are combined with the additive streams
using "X" patterns 45, 46, 47 in plate 24 to converge the four
separate polymer streams in each region into a sheath of polymeric
host material that surrounds an additive core.
39. In FIG. 3, there is shown an exploded view of a second
configuration of the thin-plate assembly 22 of die assembly 20. In
this configuration, thin-plate assembly 22 allows for placement of
one or more additives inside of each of three strands of the
polymeric host material in an islands-in-a-sea arrangement. The one
or more additives in metering pump 12 (FIG. 1) is transferred to
die assembly 20 via distribution line 15 and enters die assembly 20
through inlet connection 17 located on the side of die head plate
23. The one or more additives then flows through hole 26 in die
head plate 23, through hole 27 in thin plate 24, and through hole
28 in thin plate 25a where the one or more additives then
hydraulically splits into three equal streams and flows through
channels 29, 30, 31 in thin plate 25a. From each of channels 29,
30, 31, the additive streams are transferred to distribution
channels 48, 49, 50 located around the regions of polymer holes
48i-l, 49i-l, 50i-l (FIG. 3a). Distribution channels 48, 49, 50
preferably are spherical (e.g., circular, oval-shaped,
ellipse-shaped, etc.), though any shape that allows for
distribution of the additive streams is contemplated. Next, from
distribution channels 48, 49, 50, the additive streams are
transferred to channels 48a-d, 49a-d, 50a-d (FIG. 3a). Channels
48a-d, 49a- d, 50a-d, which are similar to spokes on a wheel, are
of equal length. Channels 48a-d, 49a-d, 50a-d direct the additive
streams from each of distribution channels 48, 49, 50 to holes
48e-h, 49e-h, 50e-h (FIG. 3a) in thin plate 25a. The additive
streams then flow into holes 45, 46, 47 in thin plate 24 so that
the additive steams may be placed as four islands in each of the
polymer strands. Simultaneously, the polymeric host material
supplied by extruder 60 is directed into central channel 38 of
distribution plate 21. Distribution plate 21 divides the polymer
stream into three sections, each section having four polymer
streams, using distribution holes 39a-d, 40a-d, 41a-d drilled into
distribution plate 21. The polymer streams then flow through holes
48i-l, 49i-l, 50i-l (FIG. 3a) in thin plate 25a and are combined
with the additive islands in thin plate 24. Thin plate 24 has "X"
patterns 45, 46, 47 that converge the four separate polymer streams
of each region to form the sea that encapsulates the four additive
islands.
40. FIG. 4 shows yet another configuration of thin-plate assembly
22 of die assembly 20 useful in the method and apparatus of the
present invention. In FIG. 4, thin-plate assembly 22 is configured
such that one or more additives may be placed in a pattern of four
stripes on the surface of each polymer strand. The one or more
additives in metering pump 12 (FIG. 1) is transferred to die
assembly 20 via high-pressure tubing or piping 15 and enters die
assembly 20 through inlet connection 17 located on the side of die
head plate 23. The one or more additives then flows through hole 26
in die head plate 23 and hole 28 in thin plate 25b where the one or
more additives hydraulically splits into three equal streams in
channels 29, 30, 31 in thin plate 25b. From each of channels 29,
30, 31, the additive streams are transferred to distribution
channels 48, 49, 50. Distribution channels 48, 49, 50 preferably
are spherical (e.g., circular, oval-shaped, ellipse-shaped, etc.),
though any shape that allows for distribution of the additive
streams is contemplated. Next, from distribution channels 48, 49,
50, the additive streams are transferred to channels 48a-d, 49a-d,
50a-d (FIG. 4a). Channels 48a-d, 49a-d, 50a-d, which are similar to
spokes on a wheel, are of equal length. Channels 48a-d, 49a-d,
50a-d direct the additive streams around the outside of the polymer
strand holes 32, 33, 34. Simultaneously, the polymeric host
material supplied by extruder 60 is directed into central channel
38 of distribution plate 21. Distribution plate 21 divides the
polymeric host material into three sections of four polymer streams
each using distribution holes 39a-d, 40a-d, 41a-d drilled into
distribution plate 21. The polymer streams then flow into "X"
patterns 45, 46, 47 in thin plate 24 which converge the four
separate polymer streams of each region into a single polymer
strand before the additive stripes are added as the polymer strand
passes by thin plate 25b.
41. With each thin-plate assembly, after the one or more additives
is incorporated into the polymer melt flow, the strands of
polymeric host material containing the one or more additives exit
die assembly 20 and may then pass through water bath 62 and into
pelletizer 63, which cuts the polymer strands into pellets or
chips.
42. The invention will be further described by reference to the
following detailed examples. The examples are set forth by way of
illustration and are not intended to limit the scope of the
invention.
EXAMPLE 1
43. A die containing a thin-plate assembly of the four
islands-in-a-sea configuration is designed to inject a low
molecular weight lubricant (zinc stearate) into nylon 6 (Ultramid
B3 available from BASF Corporation of Mount Olive, N.J.), while the
passing the nylon 6 through a die and shaping it into strands for
pelletizing. The zinc stearate is injected into the nylon 6 having
a relative viscosity (in sulfuric acid) of 3.0. At the beginning of
the experiment, the metering pump is started a few minutes before
the extruder to prevent the nylon 6 from plugging up the holes in
the thin plates for the zinc stearate. The following settings are
used:
1 Extruder: ZSK25 Werner & Pfleiderer co-rotating twin screw
Screw speed: 300 rpm Barrel temperature: 259.degree. C. Die head
temperature: 300.degree. C. Extruder output: 20 kg/hour (333
g/minute) of nylon 6 Metering pump size: 0.16 cc/rev Metering pump
temperature: 150.degree. C. Additive supply temperature:
150.degree. C. Transfer tubing temperature: 180.degree. C.
44. Examination of the cross-section of the resulting polymer
strands shows that while the four islands appear to have collapsed
into a single core, the zinc stearate is uniformly dosed along the
length (i.e., in the extrusion direction) of the cross-section but
not mixed with the nylon 6 to form a single phase. The collapse of
the four islands into a single core is thought to be the result of
the differences in the viscosity of the zinc stearate and the nylon
6, i.e., the component having the lower viscosity migrates to the
center.
EXAMPLE 2
45. A die containing a thin-plate assembly is designed to inject
polypropylene wax dyed with 1 percent Heliogenblue (blue dye) onto
the surface and into the melt core of polystyrene 168N strands. The
thin plate assembly for samples 2 and 3 is a sheath/core
configuration, and the thin plate assembly for samples 4 and 5 is a
four stripes configuration. At the beginning of the experiment, the
metering pump is started a few minutes before the extruder to
prevent the polystyrene 168N from plugging up the distribution
holes in the thin plates for the polypropylene wax. The following
settings are used:
2 Extruder: ZSK25 Werner & Pfleiderer co-rotating twin screw
Screw speed: 300 rpm Barrel temperature: 250.degree. C. Die head
temperature: 300.degree. C. Extruder output: 20 kg/hour (500
g/minute) of polystyrene 168N Metering pump size: 0.16 cc/rev
Metering pump temperature: 150.degree. C. Additive supply
temperature: 130.degree. C. Transfer tubing temperature:
170.degree. C.
46. Examination of the cross-sections of the resulting polymer
strands of samples 2 and 3 shows two separate domains, a
"star-shaped" core domain of polypropylene wax surrounded by a
nylon 6 sheath domain. The "star-shaped" core is thought to be
caused by the viscosity differences between polystyrene 168N and
polypropylene wax.
47. Examination of the cross-sections of the resulting polymer
strands of samples 4 and 5 indicates four stripes of polypropylene
wax on the outside surface of the polystyrene core.
EXAMPLE 3
48. A die containing a thin-plate assembly is designed to inject a
low molecular weight lubricant (zinc stearate) into nylon 6
(Ultramid B3 supplied by BASF Corporation of Mount Olive, N.J.),
while passing the nylon 6 through a die and shaping it into strands
for pelletizing. The thin plate assembly for samples 6 and 7 is a
four stripes configuration, and the thin plate assembly for sample
8 is a four islands-in-a-sea configuration. At the beginning of the
experiment, the metering pump is started a few minutes before the
extruder to prevent the Ultramid B3 polymer from plugging up the
distribution holes in the thin plates for the zinc stearate. The
following settings are used:
3 Extruder: ZSK25 Werner & Pfleiderer co-rotating twin screw
Screw speed: 300 rpm Barrel temperature: 260.degree. C. Die head
temperature: 260.degree. C. Extruder output: 30 kg/hour (500
g/minute) of Ultramid B3 Metering pump size: 0.16 cc/rev Metering
pump temperature: 140.degree. C. Additive supply temperature:
130.degree. C. Transfer tubing temperature: 140.degree. C.
49. Examination of the cross-sections of the resulting polymer
strands of samples 6 and 7 indicates four stripes of zinc stearate
on the outside surface of the nylon 6 core. Sample 8 produced a
cross-section having a single core of zinc stearate in the center
of the cross-section surrounded by a sheath of nylon 6, as in
Example 1.
50. While the invention has been described in connection with what
is presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not to be
limited to the disclosed embodiment, but on the contrary, is
intended to cover various modifications and equivalents
arrangements included within the spirit and scope of the appended
claims.
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