CA1069268A - Process and apparatus for employing a high percentage of scrap resin in an extruder - Google Patents
Process and apparatus for employing a high percentage of scrap resin in an extruderInfo
- Publication number
- CA1069268A CA1069268A CA244,969A CA244969A CA1069268A CA 1069268 A CA1069268 A CA 1069268A CA 244969 A CA244969 A CA 244969A CA 1069268 A CA1069268 A CA 1069268A
- Authority
- CA
- Canada
- Prior art keywords
- resin
- extruder
- feed inlet
- scrap
- barrel
- 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
- 229920005989 resin Polymers 0.000 title claims abstract description 177
- 239000011347 resin Substances 0.000 title claims abstract description 177
- 238000000034 method Methods 0.000 title claims abstract description 33
- 230000005484 gravity Effects 0.000 claims abstract description 22
- 235000003642 hunger Nutrition 0.000 claims abstract description 16
- 230000037351 starvation Effects 0.000 claims abstract description 15
- 229920013716 polyethylene resin Polymers 0.000 claims abstract description 4
- 239000000463 material Substances 0.000 claims description 63
- 229920005992 thermoplastic resin Polymers 0.000 claims description 37
- 238000000227 grinding Methods 0.000 claims description 22
- 238000001125 extrusion Methods 0.000 claims description 20
- 239000000203 mixture Substances 0.000 claims description 16
- 239000008188 pellet Substances 0.000 claims description 13
- 229920001169 thermoplastic Polymers 0.000 claims description 7
- 239000004416 thermosoftening plastic Substances 0.000 claims description 7
- 238000002156 mixing Methods 0.000 claims description 5
- 230000006835 compression Effects 0.000 claims description 4
- 238000007906 compression Methods 0.000 claims description 4
- 238000011144 upstream manufacturing Methods 0.000 claims description 3
- 238000007664 blowing Methods 0.000 claims description 2
- 235000012438 extruded product Nutrition 0.000 claims description 2
- 238000006243 chemical reaction Methods 0.000 claims 1
- 239000004698 Polyethylene Substances 0.000 abstract description 10
- -1 polyethylene Polymers 0.000 abstract description 10
- 229920000573 polyethylene Polymers 0.000 abstract description 9
- 229920001903 high density polyethylene Polymers 0.000 abstract 1
- 239000004700 high-density polyethylene Substances 0.000 abstract 1
- 229920003023 plastic Polymers 0.000 description 5
- 239000004033 plastic Substances 0.000 description 5
- 238000004064 recycling Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000011800 void material Substances 0.000 description 2
- 101150034533 ATIC gene Proteins 0.000 description 1
- 235000010627 Phaseolus vulgaris Nutrition 0.000 description 1
- 244000046052 Phaseolus vulgaris Species 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 239000010408 film Substances 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
Landscapes
- Extrusion Moulding Of Plastics Or The Like (AREA)
- Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An apparatus for and method of employing a high per-centage of reground polyethylene resin scrap in an extruder, wherein fluffy, low-density, polyethylene scrap resin is preferably admixed with a granular high-density polyethylene virgin resin, and the admixture fed by gravity into a first feed inlet in a screw-type conveyor, and granular polyethylene virgin resin fed by gravity into a second feed inlet generally adjacent to and downstream of the first feed inlet of the extruder. The admixture fed to the first feed inlet is in-sufficient to fill the volume of the extruder tube, while the virgin resin automatically fed by gravity fills up the total volume in the extruder tube, thereby preventing starvation of the resin to the extruder die in the event of blockage of the fluffy scrap resin, which technique permits high amounts of from 20 to 40% of scrap resin to be blended with virgin resin.
An apparatus for and method of employing a high per-centage of reground polyethylene resin scrap in an extruder, wherein fluffy, low-density, polyethylene scrap resin is preferably admixed with a granular high-density polyethylene virgin resin, and the admixture fed by gravity into a first feed inlet in a screw-type conveyor, and granular polyethylene virgin resin fed by gravity into a second feed inlet generally adjacent to and downstream of the first feed inlet of the extruder. The admixture fed to the first feed inlet is in-sufficient to fill the volume of the extruder tube, while the virgin resin automatically fed by gravity fills up the total volume in the extruder tube, thereby preventing starvation of the resin to the extruder die in the event of blockage of the fluffy scrap resin, which technique permits high amounts of from 20 to 40% of scrap resin to be blended with virgin resin.
Description
926~3 ... ... . .. .
BACKGROUND OF THE INVENTION
The employment of scrap thermoplastic resins in an extrusion process is a common method of efficiently and profit-ably recycling scrap resin. Typically the scrap re~in material is ground up and then fed into a screw-type extruder through a feed hopper, and often in admixture with a virgin resin material.
By such recovery and recycle techniques, scrap-to-virgin resin ratios above to about 20% or higher have bean reported, however and typically the ~crap-to-virgin resin ratios usually obtained have been up to about 10%, and more generally 5%.
One prime difficulty in the recycle of scrap poly-ethylene re~in or a similar resin, is that on regrinding of the solid resin, the resin becomes a very low-density, fine particle-size fluffy material. The reground resin is thus difficult to feed in a feed hopper in a continuous manner to an extruder and, further, is difficult by virtue of the differ-ence in density, to admix properly with a granular virgin resin for a proper and continuous feed to an extruder. Thus, when the fluffy scrap resin, alone or with virgin resin is attempted to be fed at high ratios into an extruder, quite often blockage ~ `
of the feed hopper occurs, with the result that the extruder die is then starved for resin material. Such difficulties have often resulted in expensive down time for the extruder, while restricting the practical amount of the ~-rap resin to be ; employed in a recycling proces~ to not more than about 5%.
Thus, there exists a need for an apparatus and method by which ; thermoplastic scrap resin material, such as polyethylene, may be effectively a,nd efficiently employed in an extruder at high ratlos, without the difficulties occasioned by the prior art.
BACKGROUND OF THE INVENTION
The employment of scrap thermoplastic resins in an extrusion process is a common method of efficiently and profit-ably recycling scrap resin. Typically the scrap re~in material is ground up and then fed into a screw-type extruder through a feed hopper, and often in admixture with a virgin resin material.
By such recovery and recycle techniques, scrap-to-virgin resin ratios above to about 20% or higher have bean reported, however and typically the ~crap-to-virgin resin ratios usually obtained have been up to about 10%, and more generally 5%.
One prime difficulty in the recycle of scrap poly-ethylene re~in or a similar resin, is that on regrinding of the solid resin, the resin becomes a very low-density, fine particle-size fluffy material. The reground resin is thus difficult to feed in a feed hopper in a continuous manner to an extruder and, further, is difficult by virtue of the differ-ence in density, to admix properly with a granular virgin resin for a proper and continuous feed to an extruder. Thus, when the fluffy scrap resin, alone or with virgin resin is attempted to be fed at high ratios into an extruder, quite often blockage ~ `
of the feed hopper occurs, with the result that the extruder die is then starved for resin material. Such difficulties have often resulted in expensive down time for the extruder, while restricting the practical amount of the ~-rap resin to be ; employed in a recycling proces~ to not more than about 5%.
Thus, there exists a need for an apparatus and method by which ; thermoplastic scrap resin material, such as polyethylene, may be effectively a,nd efficiently employed in an extruder at high ratlos, without the difficulties occasioned by the prior art.
- 2 -1069Z6~
SUMM~RY OF THE INVENTION
My invention relates to an apparatus for and method of efficiently and profitably employing scrap thermoplastic resin in an extruder. In particular my invention relates to an apparatus for and a method of emp]oying a high percenta~e of a thermoplastic scrap resin, such as reground polyethylene scrap resin, with additional virgin thermoplastic resin, such as virgin polyethylene scrap resin, in a screw-type extruder.
- My invention provides for the profitable and effective utilization of scrap resin at much higher ratios than that achieved by the prior art, and, for example, greater than I0%
and typically from 20 to 40% or higher. My discovery overcomes many of the disadvantages of the prior art in the use and hand-ling of reground scrap resin, while preventing the starvation of an extruder die of an extruder by the blockage of feed of the low-density, fluffy, reground resin scrap. In my invention, the blockage of the feed of the fluffy scrap resin, alone or in admixture with virgin resin granules, does not result in the starvation of the extruder die of the extruder, which, in the past has limited conventional extruders and recycle tech-niques through the use of very low ratios of scrap-to-virgin resin in practice.
My apparatus includes a means to regrind a solid scrap resin material, such as an olefinic resin like polypropylene or polyethylene resin, into the form of a fine particle-size material charac'terized by very low-density and a fluffy snow-like nature. In my invention, the reground scrap resin may be used alone, or preferably admixed with an additional virgin thermoplastic resin of the same or different resln from the same or different source. Preferably the virgin resin is the same or similar in compositLon and derived ~rom a common ''' ~ .
~69Z~8 source, such as the same or similar extruding machine or process. The reground resin or admixture is then conveyed, such as by a blower, into a feed hopper or other storage bin, preferably a cyclone-type truncated hopper. trhe reground scrap resin or a combination of the scrap resin and ~rirgin resin material is then fed from the feed hopper by gravity or a low-pressure difference into a first feed inlet into the barrel of a single or multiple screw extruder. The extruder typically comprises an extruder barrel having a rotating lead screw housed therein to form a mixing and compressing section and later a heated extrusion section wherein the resin is he~ted to a molten stage, and then through an extrusion die wherein the heated or molten resin is extruded intq a product, such as a blown tubular form in one embodiment, to be slit subsequently and formed into a thermoplastic thin-film roll. In the extruder, rotation of the lead screw therein in the mixing and compr~ssing sections compresses the plastic material and propels it foxward.
The fluffy scrap resin material often has a-tendency, because of it~ low density and resistance to flow, to become compressed and blocked in the feed hopper throat, thereby starving the extruder die for resin material. Although this may happen in-frequently in the prior art, such blockages are annoying, time-consuming and expensive. ;
The scrap resin or admixture fed to the barrel of theextruder is in such a quantity as to be insufficient to fill completely the ~rolume of the lead screw barrel, and typically fills about 40 t:o 70/0 of the lead screw. Of course, if too much resin is fed int:o the lead screw; that is, greater than the out-put of the extr~lder die, then backup of the scrap resin or admlxture occur~; in the feed hopper.
My apparatus contains a second or auxiliary feed hopper ':
.~:
~92~;8 adapted to contain a granular thermoplastic re~in material such as a medium or low-density virgin polyethylene resin in pellet or granular form, but typically of the same or similar-type resin as that admixed with the fluffy scrap resin after re-grinding. At a further diqtance generally adjacent to and quite close to the first feed inlet along the barrel, there is provided a second feed inlet for the introduction, typically by gravity, of the virgin resin material from the second feed hopper into the extruder. The granular virgin resin material from the auxiliary hopper is fed into the second feed inlet to fill all or substantially all of the volume of the barrel. The relationship and position of the first and second feed inlets to the mixing and compressing sections of the extruder is such that the second feed inlet is positioned at least one helical turn distance, and often no more than three helical turns distance, from the first feed inlet. The fluffy snow-like resin from the first feed hopper fed into the lead ~crew is guickly compressed and reduced in volume by one helical turn of the screw permitting the feed of additional fluffy s,crap resin from the first hopper, and permitting the easy intro- ' duction by gravity of the virgin resin material from the second feed hopper in the second feed inlet. Due to the low density and fluffy characteristics of the scrap re~in or admixture, the opening of the fi'rst feed inlet is preferably larger, ~uch ' as from two to four times, than the area of the second feed inlet, wherein ealsy-to-handle, colored or granular-type virgin plastic material of high density is introduced into the lead screw. The size of the respective openings and,the positions thereof, therefore, permit the proper feed of the scrap and vlrgin material, while permitting a void in the volum0 of the ; barrel between the first and second feed in~ets ~ufficient to '' . ~
. -. . . : . ::
- .. . ~ ~ . . . : .
permit the auto~atic feed by gravity of the virgin material into the extruder. Further and importantly, the first feed hopper is preferably a cyclone or conical-type hopper so that the fluffy scrap material is urged by gravity and the low pressure in the eed throat easily into the extruder tube~
The scrap and virgin material which may be the same or of a slightly different size, fo~ example, ranging from l/16th of an inch to l/4th of an inch in average particle size i5 o considerable e.g. 3 to 10 times, di~ference in density.
The entire admixture of the scrap and the virgin resin material so introduced into the lead screw is fed by the rotation of the lead screw after mixing and compressing into a heating section of the extruder barrel, where the compressed and mixed blend i5 heated to a temperature for extrusion and then subsequently into an extrusion die wherein the heated material is extruded into the desired form.
In the event that the first feed hopper containing a qcrap resin material becomes temporarily blocked due to the lack of sufficient density of the scrap material my discovery permits the extrusion die to continue in full production, since the amount of virgin resin fed from the second feed hopper into the extruder will increase automatically to ~ill the void in the feed tube caused by the blockage, thus permitting the cont-inuou5 operation of the extruder. The virgin resin fed from the qecond or auxil-iary feed hopper, therefore makes up in quantity or the amount of scrap and/or virgin resin which has been temporarily blocked from feeding int:o the extruder from the first hopper. By my appa-ratus and method, the costly starveouts of the extruder die and production shut~lowns are prevented, since the use of high scrap `' '..
~ . ~
. . ,, . - , .
.
~6~Z68 content in the feed inlet of conventlonal extruder machines ~-increases the liklihood of such resin starveouts of the extruder die, and conventional extruders and scrap-recycling techniques are limited to low scrap ratios of the virgin material.
In my invention, the salvagable resin may be fed into the grinding means in any form suitable for grinding, while the admixture of the granular virgin resin with the low-density reground resin may vary as desired, but typically ranges in a scrap-to-virgin resin ratio of from about 1:1 to 6:1, but particularly, rrom about 2-4:1, such that the amount of scrap material in the final extruded product is greater than 20% or as - .
high as tolerable, depending on the extrusion speed, resin and other factors. : .
In accordance with a specific embodiment of the :
invention, a/process for the use of high amounts of fluffy, low density, scrap resin, in an extruder, which extruder comprises a barrel with a rotating helical lead screw therein, said process comprising:
a) feeding a fine fluffy thermoplastic resin scrap 20 material of a character having a tendency to block an extruder .
barrel feed inlet directly into an extruder barrel first feed .
inlet in an amount insufficient to fill the extruder barrel; ..
b) feeding a second thermoplastic resin in pellet form into a second feediinlet in the extruder barrel, said second feed inlet being downstream from the first inlet and spaced there- .- .~
from by the length of at least one helical turn of the screw, . .
said pellets being introduced in an amount sufficient to keep ::
the extruder b~rrel substantially full of resin at all~times, and c) extruding the~scrap re.3in and second resin as a ~. ..-mixture;througll an extruder die, whereby starvation of the extruder die is prevented in the event of plugging of the first .. :,.
extruder inlet. - -I ~ . .
: ~ ~ - 7 ~
~69~
In accordance with a further embodiment, a process for the use of high amounts of fluffy, low density scrap resin, in an extruder, which extruder comprises a barrel with a rotating helical lead screw therein, said process comprising:
a) grinding thermoplastic resin scrap into a fine fluffy material of a character having a tendency to block an extruder barrel feed inlet;
b) feeding said material directly into an extruder barrel first feed inlet in an amount insufficient to fill the ~ .
extruder barrel;
c) feeding a second thermoplastic resin in pellet form into a second feed inlet in the extruder barrel, said second feed inlet being downstream from the first inlet and spaced therefrom by the length of at least one helical turn of the screw, said pellets being introduced automatically by gravity feed in an amount sufficient to keep the extruder barrel substantially full of resin at all times; and ..
d~ extruding the scrap resin and second resin as a mixture through an extruder die, whereby starvation of the extruder : -.
die is prevented in the event of plugging of the first extruder .;~
inlet.
From a different aspect and in accordance with an embodiment of the invention, a thermoplastic resin extruder ~
apparatus which permits the use of high amounts of fluffy scrap .
resin to be employed without resin starvation of the extruder die . .
comprises:
a) a thermoplastic resin extruder which comprises i. an extruder barrel, , ii. an extruder die at one end of the extruder ~30 for the extrusion of a resin product, iii. a lead screw in the barrel for movement of thermoplastic resin material through the barrel to the extruder die, ~ .
:~
iv. a first feed inlet in the barrel for the introduction of a fluffy low-density scrap resin into the barrel and compression of the fluffy resin in the barrel by the lead screw, v. a second feed inlet in the barrel for the introduction of a granular high-density resin into the barrel, the second feed inlet down-stream of the first feed inlet by at least one :
lead screw length, and generally adjacent and :
close to the first feed inlet along the barrel, vi. the first feed inlet larger in inlet area than the second feed inlet, and vii. a heated extruder section downstream of the : ~
second feed inlet to heat the thermoplastic : -:
resin prior to the extrusion of the heated resin in the extruder die; : .
b) a means upstream of said extruder barrel to grind :-a scrap thermoplastic resin onto a low-density .-fluffy scrap resin, - ~ .
c) a first feed hopper operable to contain the fluffy scrap resin and having an open throat area at ~:
the lower portion thereof communicating directly . ~j .
with the first feed inlet, whereby fluffy resin :
. , .in the first feed hopper is introduced by gravity . or low~pressure into the first feed inlet and com-; pressed~in part by the lead screw prior to the second feed inlet, : .
d~ means operatively associated with said grinding ~ ;:
means to convey the~fluffy scrap resin from the grinding:means to the first feed hopper, and ... ~,, .
.
~ ~ ;: ,,. ,:
:~ ~ - 7b ::
' `~ ,., ,:
SUMM~RY OF THE INVENTION
My invention relates to an apparatus for and method of efficiently and profitably employing scrap thermoplastic resin in an extruder. In particular my invention relates to an apparatus for and a method of emp]oying a high percenta~e of a thermoplastic scrap resin, such as reground polyethylene scrap resin, with additional virgin thermoplastic resin, such as virgin polyethylene scrap resin, in a screw-type extruder.
- My invention provides for the profitable and effective utilization of scrap resin at much higher ratios than that achieved by the prior art, and, for example, greater than I0%
and typically from 20 to 40% or higher. My discovery overcomes many of the disadvantages of the prior art in the use and hand-ling of reground scrap resin, while preventing the starvation of an extruder die of an extruder by the blockage of feed of the low-density, fluffy, reground resin scrap. In my invention, the blockage of the feed of the fluffy scrap resin, alone or in admixture with virgin resin granules, does not result in the starvation of the extruder die of the extruder, which, in the past has limited conventional extruders and recycle tech-niques through the use of very low ratios of scrap-to-virgin resin in practice.
My apparatus includes a means to regrind a solid scrap resin material, such as an olefinic resin like polypropylene or polyethylene resin, into the form of a fine particle-size material charac'terized by very low-density and a fluffy snow-like nature. In my invention, the reground scrap resin may be used alone, or preferably admixed with an additional virgin thermoplastic resin of the same or different resln from the same or different source. Preferably the virgin resin is the same or similar in compositLon and derived ~rom a common ''' ~ .
~69Z~8 source, such as the same or similar extruding machine or process. The reground resin or admixture is then conveyed, such as by a blower, into a feed hopper or other storage bin, preferably a cyclone-type truncated hopper. trhe reground scrap resin or a combination of the scrap resin and ~rirgin resin material is then fed from the feed hopper by gravity or a low-pressure difference into a first feed inlet into the barrel of a single or multiple screw extruder. The extruder typically comprises an extruder barrel having a rotating lead screw housed therein to form a mixing and compressing section and later a heated extrusion section wherein the resin is he~ted to a molten stage, and then through an extrusion die wherein the heated or molten resin is extruded intq a product, such as a blown tubular form in one embodiment, to be slit subsequently and formed into a thermoplastic thin-film roll. In the extruder, rotation of the lead screw therein in the mixing and compr~ssing sections compresses the plastic material and propels it foxward.
The fluffy scrap resin material often has a-tendency, because of it~ low density and resistance to flow, to become compressed and blocked in the feed hopper throat, thereby starving the extruder die for resin material. Although this may happen in-frequently in the prior art, such blockages are annoying, time-consuming and expensive. ;
The scrap resin or admixture fed to the barrel of theextruder is in such a quantity as to be insufficient to fill completely the ~rolume of the lead screw barrel, and typically fills about 40 t:o 70/0 of the lead screw. Of course, if too much resin is fed int:o the lead screw; that is, greater than the out-put of the extr~lder die, then backup of the scrap resin or admlxture occur~; in the feed hopper.
My apparatus contains a second or auxiliary feed hopper ':
.~:
~92~;8 adapted to contain a granular thermoplastic re~in material such as a medium or low-density virgin polyethylene resin in pellet or granular form, but typically of the same or similar-type resin as that admixed with the fluffy scrap resin after re-grinding. At a further diqtance generally adjacent to and quite close to the first feed inlet along the barrel, there is provided a second feed inlet for the introduction, typically by gravity, of the virgin resin material from the second feed hopper into the extruder. The granular virgin resin material from the auxiliary hopper is fed into the second feed inlet to fill all or substantially all of the volume of the barrel. The relationship and position of the first and second feed inlets to the mixing and compressing sections of the extruder is such that the second feed inlet is positioned at least one helical turn distance, and often no more than three helical turns distance, from the first feed inlet. The fluffy snow-like resin from the first feed hopper fed into the lead ~crew is guickly compressed and reduced in volume by one helical turn of the screw permitting the feed of additional fluffy s,crap resin from the first hopper, and permitting the easy intro- ' duction by gravity of the virgin resin material from the second feed hopper in the second feed inlet. Due to the low density and fluffy characteristics of the scrap re~in or admixture, the opening of the fi'rst feed inlet is preferably larger, ~uch ' as from two to four times, than the area of the second feed inlet, wherein ealsy-to-handle, colored or granular-type virgin plastic material of high density is introduced into the lead screw. The size of the respective openings and,the positions thereof, therefore, permit the proper feed of the scrap and vlrgin material, while permitting a void in the volum0 of the ; barrel between the first and second feed in~ets ~ufficient to '' . ~
. -. . . : . ::
- .. . ~ ~ . . . : .
permit the auto~atic feed by gravity of the virgin material into the extruder. Further and importantly, the first feed hopper is preferably a cyclone or conical-type hopper so that the fluffy scrap material is urged by gravity and the low pressure in the eed throat easily into the extruder tube~
The scrap and virgin material which may be the same or of a slightly different size, fo~ example, ranging from l/16th of an inch to l/4th of an inch in average particle size i5 o considerable e.g. 3 to 10 times, di~ference in density.
The entire admixture of the scrap and the virgin resin material so introduced into the lead screw is fed by the rotation of the lead screw after mixing and compressing into a heating section of the extruder barrel, where the compressed and mixed blend i5 heated to a temperature for extrusion and then subsequently into an extrusion die wherein the heated material is extruded into the desired form.
In the event that the first feed hopper containing a qcrap resin material becomes temporarily blocked due to the lack of sufficient density of the scrap material my discovery permits the extrusion die to continue in full production, since the amount of virgin resin fed from the second feed hopper into the extruder will increase automatically to ~ill the void in the feed tube caused by the blockage, thus permitting the cont-inuou5 operation of the extruder. The virgin resin fed from the qecond or auxil-iary feed hopper, therefore makes up in quantity or the amount of scrap and/or virgin resin which has been temporarily blocked from feeding int:o the extruder from the first hopper. By my appa-ratus and method, the costly starveouts of the extruder die and production shut~lowns are prevented, since the use of high scrap `' '..
~ . ~
. . ,, . - , .
.
~6~Z68 content in the feed inlet of conventlonal extruder machines ~-increases the liklihood of such resin starveouts of the extruder die, and conventional extruders and scrap-recycling techniques are limited to low scrap ratios of the virgin material.
In my invention, the salvagable resin may be fed into the grinding means in any form suitable for grinding, while the admixture of the granular virgin resin with the low-density reground resin may vary as desired, but typically ranges in a scrap-to-virgin resin ratio of from about 1:1 to 6:1, but particularly, rrom about 2-4:1, such that the amount of scrap material in the final extruded product is greater than 20% or as - .
high as tolerable, depending on the extrusion speed, resin and other factors. : .
In accordance with a specific embodiment of the :
invention, a/process for the use of high amounts of fluffy, low density, scrap resin, in an extruder, which extruder comprises a barrel with a rotating helical lead screw therein, said process comprising:
a) feeding a fine fluffy thermoplastic resin scrap 20 material of a character having a tendency to block an extruder .
barrel feed inlet directly into an extruder barrel first feed .
inlet in an amount insufficient to fill the extruder barrel; ..
b) feeding a second thermoplastic resin in pellet form into a second feediinlet in the extruder barrel, said second feed inlet being downstream from the first inlet and spaced there- .- .~
from by the length of at least one helical turn of the screw, . .
said pellets being introduced in an amount sufficient to keep ::
the extruder b~rrel substantially full of resin at all~times, and c) extruding the~scrap re.3in and second resin as a ~. ..-mixture;througll an extruder die, whereby starvation of the extruder die is prevented in the event of plugging of the first .. :,.
extruder inlet. - -I ~ . .
: ~ ~ - 7 ~
~69~
In accordance with a further embodiment, a process for the use of high amounts of fluffy, low density scrap resin, in an extruder, which extruder comprises a barrel with a rotating helical lead screw therein, said process comprising:
a) grinding thermoplastic resin scrap into a fine fluffy material of a character having a tendency to block an extruder barrel feed inlet;
b) feeding said material directly into an extruder barrel first feed inlet in an amount insufficient to fill the ~ .
extruder barrel;
c) feeding a second thermoplastic resin in pellet form into a second feed inlet in the extruder barrel, said second feed inlet being downstream from the first inlet and spaced therefrom by the length of at least one helical turn of the screw, said pellets being introduced automatically by gravity feed in an amount sufficient to keep the extruder barrel substantially full of resin at all times; and ..
d~ extruding the scrap resin and second resin as a mixture through an extruder die, whereby starvation of the extruder : -.
die is prevented in the event of plugging of the first extruder .;~
inlet.
From a different aspect and in accordance with an embodiment of the invention, a thermoplastic resin extruder ~
apparatus which permits the use of high amounts of fluffy scrap .
resin to be employed without resin starvation of the extruder die . .
comprises:
a) a thermoplastic resin extruder which comprises i. an extruder barrel, , ii. an extruder die at one end of the extruder ~30 for the extrusion of a resin product, iii. a lead screw in the barrel for movement of thermoplastic resin material through the barrel to the extruder die, ~ .
:~
iv. a first feed inlet in the barrel for the introduction of a fluffy low-density scrap resin into the barrel and compression of the fluffy resin in the barrel by the lead screw, v. a second feed inlet in the barrel for the introduction of a granular high-density resin into the barrel, the second feed inlet down-stream of the first feed inlet by at least one :
lead screw length, and generally adjacent and :
close to the first feed inlet along the barrel, vi. the first feed inlet larger in inlet area than the second feed inlet, and vii. a heated extruder section downstream of the : ~
second feed inlet to heat the thermoplastic : -:
resin prior to the extrusion of the heated resin in the extruder die; : .
b) a means upstream of said extruder barrel to grind :-a scrap thermoplastic resin onto a low-density .-fluffy scrap resin, - ~ .
c) a first feed hopper operable to contain the fluffy scrap resin and having an open throat area at ~:
the lower portion thereof communicating directly . ~j .
with the first feed inlet, whereby fluffy resin :
. , .in the first feed hopper is introduced by gravity . or low~pressure into the first feed inlet and com-; pressed~in part by the lead screw prior to the second feed inlet, : .
d~ means operatively associated with said grinding ~ ;:
means to convey the~fluffy scrap resin from the grinding:means to the first feed hopper, and ... ~,, .
.
~ ~ ;: ,,. ,:
:~ ~ - 7b ::
' `~ ,., ,:
3~69Z68 e) an auxiliary feed hopper op~rable to contain a granular high-density thermoplastic resin, and having an open throat area which communicated with the second feed inlet, whereby, on occasional plugging of the first feed inlet by the fluffy resin, granular resin is fed by gravity from the auxiliary hop~er to the barrel throug'n the second feed inlet, preventing resin starvation of the extruder die.
In accordance with a further embodiment of the second aspect, a thermoplastic resin extruder apparatus which permits the use of high amounts of fluffy scrap resin to be employed without resin starvation of the extruder die comprises: ;
; a) a thermoplastic resin extruder which comprises: -; i. an extruder barrel, ii. an extruder die at one end of the extruder for the extrusion of a tubular resin product, ; iii. a lead screw in the barrel for movement of thermoplastic resin material through the barrel ` 20 to the extruder die, -~
iY. a first feed inlet in the barrel for the introduction of a fluffy low-density scrap resin into the barrel and compression of the j fluffy resin in the barrel by the lead screw.
v. a second feed inlet in the barrel for the introduction of a granular high-density resin into the barrel, the s~econd feed inlet down-stream of~the~first feed inlet by from about one to three lea~d screw lengths, vi. the first feed inlet about two to six times larger in inlet area than the second feed inlet, and 7c -~ . ,-:- :
... . . .. . . .. . . . ..
:~1369268 vii. a heated extruder secjtl~n~jdownstream of the second feed inlet to heat the thermo-plastic resin prior to the extrusion of the heated resin in the extruder die, b) a means up-stream of said extruder barrel to grind scrap thermoplastic resin film into a low-density fluffy scrap r sin' :
c) a first cyclone-type feed hopper operable to contain the fluffy scrap resin and having an open throat area at the lower portion thereof communicating directly with the first feed inlet, the hopper free of any screw conveyor :~ for the fluffy resin therein, whereby fluffy - resin in the first feed hopper is introduced .
-, by gravity or low pressure into the first feed ~; ...
inlet and compressed in part by the lead screw ; :
prior to the second feed inlet, ~ ~.
` d) means operatively associated with said grinding means to convey the fluffy scrap resin by air from the grinding means to the first feed hopper .
which includes an air blower and conveyor tube;
Q) a means operatively associated with said grinding , means to admix high-density granular resin with the fluffy scrap resin from the grinding means ~ :
prior to introduction of the admixture into the : :
first feed hopper, and ~) an auxiliary cyclone-type~feed hopper operable ;;~
to contain a granular high-~density thermoplastic resin, and having an~open throat area which communicates with the second~feed inlet, whereby, on occasional plugging of the first feed inlet ~.
: 9~ ~ .:
. .
1 (~6~ 6~
by the fluffy resin, gra~ular resin is fed by gravity from the auxiliary hopper to the barrel through the second feed inlet, preventing resin starvation of the extruder die.
My apparatus and method will be described for the purposes of illustration only in connection with the employment of a polyethylene scrap resin and virgin resin admixtures in a single sc ew-type extruder. However, as will be apparent to those skilled in the art, various and obvious changes may be made in the various embodiments of the invention as illustrated, and it is not intended that the matter contained herein and as described in the specific embodiments be so limited in scope.
BRIEF DESCRIPTION OF THE DRAWINGS
My invention and the objects and features thereof may be understood with reference to the following detailed ~
description of an illustrative embodiment of my apparatus in the - -drawings in which:
` Fig. lA is a partial diagrammatic sketch of my ;
apparatus for the grinding of scrap resin and the feeding of scrap resin and a virgin resin admixture into an extrusion die in accordance with my invention: and -~ r~,.. ...
,. ,~ ' ' . .. ,: .' '. .,'', , ..'.. . ~ ., . . ' '' ' ,, ; ' ' ' ..'. . '.
. ' . '' ' ' '' : ..... '- .: ' ' ' : ' ''. ' - . '' . .
2~8 Fig. lB is a partial diagrammatic sketch of the remainder of the diagrammatic sketch of Fig. lA.
DESCRIPTION OF THE PREFERRED EMBODIMENIS
Fig. lA and FigO lB illustrate an apparatus in which rolls 11 of polyethylene re;3in material to be salvaged are fed by feed rolls 12 into grinder 13 wherein the sheet material is ground into a low-density fine particle-size fluff material e.g. about 1/8th of an inch in size. The reground polyethylene material 33 flows into exit tube 2~
where it is mixed with hard, high-density, pellet or granular virgin plastic material 15, fed into hopper 16, and into exit tube 24. The ratio of virgin material to scrap material at this stage is preferably in the order of one part of virgin material to 3.5 to 4.5, e.g. 4, parts of scrap ground material, forming the mixture 14 in tube 24.
Blower unit 17 draws in the mixture of material 14 and ejects it through exhaust tube 18 into hopper 19 where it flows by gravity to the hopper throat and feed inlet 26 leading into the extruder barrel 20. Feed screw 21 rotating in barrel 20, is rotated by motor unit 22. The feed screw 21 acts to mix compre~s and force the material in barrel 20 to the extruder heater and aie section 35 as shown in Fig. lB.
Pellet virgin polyethylene reain e.g. a low or medium-density resin like the resin 15, is added to auxiliary feed hopper 23 where it flows by gravity through tube 31 to throat 25 joining barrel 20 to mix with the,initial mixture 14 of scrap and virgin material in the tube, forming mixture 34.
Under normal operation, the ratio of virgin ~0 material added by the auxiliary hopper 23 to the mixture 14 ~-in the barrel 20 i~ in the ratio of one part of virgin material ;, .. '~'.: , ,...
- 8 - ~
~369;~6~3 15 to one part of mixture 14 resulting in a mixture 34 which is composed of about six parts of virgin material to four parts of reground scrap material. Mixture 34 is fad through barrel 20 by feed screw 21 to extrusion d:ie unit 35 mounted on support unit 37, where the materia:L 34 is extruded into plastic products 36.
As illustrated the feed hopper 19 comprises a cyclone or conical-type hopper hav:ing tapered sides leading to the first feed inlet or hopper throat 26, where by virtue of the blowing of the scrap resin into the feed hopper, there .
is a pressure difference which induces movement of the scrap : . -admixture 14 from the hopper 19 through the flute 26 and into the barrel 20. As illustrated, the feed hopper 19 is position-ed such that the.throat communicates directly with the feed .
inlet, while the first feed inlet and throat.of the hopper ~6 is upstream of and adjacent to the second inlet from the gravity feed of hopper 23 for the virgin material 15. Typically, the throat section 26 would have an area two to six times greater than the second feed inlet area 25 in order to permit passage of the fluffy scrap admixture into the barrel 20. In one illustrated embodiment, the hopper 26 would comprise a generally rectangular opening of about six by four inches, while the second feed inlet or throat 25 would comprise a circular inlet of about three to four inches in diameter, with the distance between the centers of the first and second throats in a single ~ extruder being about six inches.
.~ . . . . ' .
It i.s not unusual for the fine fluff of the re- ;:
ground scrap mat~rial in hopper 19 to separate from the heavier virgin material i.n the hopper 19 and to block up the thr~at of ::~
the hopper, causi.ng the incomlng material ~n tube 1~ to back up ~ -and flow out of t:he hopper top 32. In conventional apparatus, ..
such blockage would prevent sufficient material from flowing into :.
.. '. '.
_ g ~
~L~6~68 the barrel 20 to force properly sufficient material through the extrusion die unit 35 a condition known as extruder starveout.
Such a condition is very costly because the material in the ex-truder die area becomes overheated and must be scrapped, result-ing in expensive down time for the machine.
With the apparatus of my invention, a blockage of adequate flow from hopper 19 of mixture 14 of scrap and virgin plastic is compensated for by an automatic increase of flow of virgin pellets 15 from auxiliary hopper 23 feeding through throat 25 into barrel 20. Thi~ increased flow of virgin material 15 occurs since the barrel 20 is fed automatically by gra~ity from hopper throat 25, with the limit on the feed of virgin material 15 from hopper 23 being the actual filling of volume of the barrel 20 under throat 25.
The difference in positions between the throats 25 and ~6 as illustrated of one helical turn permits the fluffy resin admixture 14 to be compressed and reduced in volume prior to the introduction of the virgin resin 15. It is essential in my in-vention that the fluffy scrap resin be,added to the first feed in-let and compressed at least in part by the lead screw prior to the introduction of the virgin resin.
; The blockage of the scrap mixture 14 in hopper 19 does not cause extruder starveout, and the extrusion die 35 con- -tinues in operation during such a blockage in hopper 19. Block- , age in hopper 19 may be cleared by temporarily stopping blower ' 17 and allowing t:he material in hopper 19 to settle together or separately with necessary manual agitation of the contents of hopper 19. After the blockage has been cleared, the grinder unit 13 and the blower unit 17 may be restarted to resume the'origin-al feeding schedule. During this interruption, the extru~i,on , process continue~s, with the only change during the blockage being the temporarily increased ratio of virgin material to scrap mater- -ial utilized in l:he finished product. , , ~
- 10 - , . ., ~
In accordance with a further embodiment of the second aspect, a thermoplastic resin extruder apparatus which permits the use of high amounts of fluffy scrap resin to be employed without resin starvation of the extruder die comprises: ;
; a) a thermoplastic resin extruder which comprises: -; i. an extruder barrel, ii. an extruder die at one end of the extruder for the extrusion of a tubular resin product, ; iii. a lead screw in the barrel for movement of thermoplastic resin material through the barrel ` 20 to the extruder die, -~
iY. a first feed inlet in the barrel for the introduction of a fluffy low-density scrap resin into the barrel and compression of the j fluffy resin in the barrel by the lead screw.
v. a second feed inlet in the barrel for the introduction of a granular high-density resin into the barrel, the s~econd feed inlet down-stream of~the~first feed inlet by from about one to three lea~d screw lengths, vi. the first feed inlet about two to six times larger in inlet area than the second feed inlet, and 7c -~ . ,-:- :
... . . .. . . .. . . . ..
:~1369268 vii. a heated extruder secjtl~n~jdownstream of the second feed inlet to heat the thermo-plastic resin prior to the extrusion of the heated resin in the extruder die, b) a means up-stream of said extruder barrel to grind scrap thermoplastic resin film into a low-density fluffy scrap r sin' :
c) a first cyclone-type feed hopper operable to contain the fluffy scrap resin and having an open throat area at the lower portion thereof communicating directly with the first feed inlet, the hopper free of any screw conveyor :~ for the fluffy resin therein, whereby fluffy - resin in the first feed hopper is introduced .
-, by gravity or low pressure into the first feed ~; ...
inlet and compressed in part by the lead screw ; :
prior to the second feed inlet, ~ ~.
` d) means operatively associated with said grinding means to convey the fluffy scrap resin by air from the grinding means to the first feed hopper .
which includes an air blower and conveyor tube;
Q) a means operatively associated with said grinding , means to admix high-density granular resin with the fluffy scrap resin from the grinding means ~ :
prior to introduction of the admixture into the : :
first feed hopper, and ~) an auxiliary cyclone-type~feed hopper operable ;;~
to contain a granular high-~density thermoplastic resin, and having an~open throat area which communicates with the second~feed inlet, whereby, on occasional plugging of the first feed inlet ~.
: 9~ ~ .:
. .
1 (~6~ 6~
by the fluffy resin, gra~ular resin is fed by gravity from the auxiliary hopper to the barrel through the second feed inlet, preventing resin starvation of the extruder die.
My apparatus and method will be described for the purposes of illustration only in connection with the employment of a polyethylene scrap resin and virgin resin admixtures in a single sc ew-type extruder. However, as will be apparent to those skilled in the art, various and obvious changes may be made in the various embodiments of the invention as illustrated, and it is not intended that the matter contained herein and as described in the specific embodiments be so limited in scope.
BRIEF DESCRIPTION OF THE DRAWINGS
My invention and the objects and features thereof may be understood with reference to the following detailed ~
description of an illustrative embodiment of my apparatus in the - -drawings in which:
` Fig. lA is a partial diagrammatic sketch of my ;
apparatus for the grinding of scrap resin and the feeding of scrap resin and a virgin resin admixture into an extrusion die in accordance with my invention: and -~ r~,.. ...
,. ,~ ' ' . .. ,: .' '. .,'', , ..'.. . ~ ., . . ' '' ' ,, ; ' ' ' ..'. . '.
. ' . '' ' ' '' : ..... '- .: ' ' ' : ' ''. ' - . '' . .
2~8 Fig. lB is a partial diagrammatic sketch of the remainder of the diagrammatic sketch of Fig. lA.
DESCRIPTION OF THE PREFERRED EMBODIMENIS
Fig. lA and FigO lB illustrate an apparatus in which rolls 11 of polyethylene re;3in material to be salvaged are fed by feed rolls 12 into grinder 13 wherein the sheet material is ground into a low-density fine particle-size fluff material e.g. about 1/8th of an inch in size. The reground polyethylene material 33 flows into exit tube 2~
where it is mixed with hard, high-density, pellet or granular virgin plastic material 15, fed into hopper 16, and into exit tube 24. The ratio of virgin material to scrap material at this stage is preferably in the order of one part of virgin material to 3.5 to 4.5, e.g. 4, parts of scrap ground material, forming the mixture 14 in tube 24.
Blower unit 17 draws in the mixture of material 14 and ejects it through exhaust tube 18 into hopper 19 where it flows by gravity to the hopper throat and feed inlet 26 leading into the extruder barrel 20. Feed screw 21 rotating in barrel 20, is rotated by motor unit 22. The feed screw 21 acts to mix compre~s and force the material in barrel 20 to the extruder heater and aie section 35 as shown in Fig. lB.
Pellet virgin polyethylene reain e.g. a low or medium-density resin like the resin 15, is added to auxiliary feed hopper 23 where it flows by gravity through tube 31 to throat 25 joining barrel 20 to mix with the,initial mixture 14 of scrap and virgin material in the tube, forming mixture 34.
Under normal operation, the ratio of virgin ~0 material added by the auxiliary hopper 23 to the mixture 14 ~-in the barrel 20 i~ in the ratio of one part of virgin material ;, .. '~'.: , ,...
- 8 - ~
~369;~6~3 15 to one part of mixture 14 resulting in a mixture 34 which is composed of about six parts of virgin material to four parts of reground scrap material. Mixture 34 is fad through barrel 20 by feed screw 21 to extrusion d:ie unit 35 mounted on support unit 37, where the materia:L 34 is extruded into plastic products 36.
As illustrated the feed hopper 19 comprises a cyclone or conical-type hopper hav:ing tapered sides leading to the first feed inlet or hopper throat 26, where by virtue of the blowing of the scrap resin into the feed hopper, there .
is a pressure difference which induces movement of the scrap : . -admixture 14 from the hopper 19 through the flute 26 and into the barrel 20. As illustrated, the feed hopper 19 is position-ed such that the.throat communicates directly with the feed .
inlet, while the first feed inlet and throat.of the hopper ~6 is upstream of and adjacent to the second inlet from the gravity feed of hopper 23 for the virgin material 15. Typically, the throat section 26 would have an area two to six times greater than the second feed inlet area 25 in order to permit passage of the fluffy scrap admixture into the barrel 20. In one illustrated embodiment, the hopper 26 would comprise a generally rectangular opening of about six by four inches, while the second feed inlet or throat 25 would comprise a circular inlet of about three to four inches in diameter, with the distance between the centers of the first and second throats in a single ~ extruder being about six inches.
.~ . . . . ' .
It i.s not unusual for the fine fluff of the re- ;:
ground scrap mat~rial in hopper 19 to separate from the heavier virgin material i.n the hopper 19 and to block up the thr~at of ::~
the hopper, causi.ng the incomlng material ~n tube 1~ to back up ~ -and flow out of t:he hopper top 32. In conventional apparatus, ..
such blockage would prevent sufficient material from flowing into :.
.. '. '.
_ g ~
~L~6~68 the barrel 20 to force properly sufficient material through the extrusion die unit 35 a condition known as extruder starveout.
Such a condition is very costly because the material in the ex-truder die area becomes overheated and must be scrapped, result-ing in expensive down time for the machine.
With the apparatus of my invention, a blockage of adequate flow from hopper 19 of mixture 14 of scrap and virgin plastic is compensated for by an automatic increase of flow of virgin pellets 15 from auxiliary hopper 23 feeding through throat 25 into barrel 20. Thi~ increased flow of virgin material 15 occurs since the barrel 20 is fed automatically by gra~ity from hopper throat 25, with the limit on the feed of virgin material 15 from hopper 23 being the actual filling of volume of the barrel 20 under throat 25.
The difference in positions between the throats 25 and ~6 as illustrated of one helical turn permits the fluffy resin admixture 14 to be compressed and reduced in volume prior to the introduction of the virgin resin 15. It is essential in my in-vention that the fluffy scrap resin be,added to the first feed in-let and compressed at least in part by the lead screw prior to the introduction of the virgin resin.
; The blockage of the scrap mixture 14 in hopper 19 does not cause extruder starveout, and the extrusion die 35 con- -tinues in operation during such a blockage in hopper 19. Block- , age in hopper 19 may be cleared by temporarily stopping blower ' 17 and allowing t:he material in hopper 19 to settle together or separately with necessary manual agitation of the contents of hopper 19. After the blockage has been cleared, the grinder unit 13 and the blower unit 17 may be restarted to resume the'origin-al feeding schedule. During this interruption, the extru~i,on , process continue~s, with the only change during the blockage being the temporarily increased ratio of virgin material to scrap mater- -ial utilized in l:he finished product. , , ~
- 10 - , . ., ~
Claims (19)
1. A process for the use of high amounts of fluffy, low density, scrap resin, in an extruder, which extruder comprises a barrel with a rotating helical lead screw therein, said process comprising:
a) feeding a fine fluffy thermoplastic resin scrap material of a character having a tendency to block an extruder barrel feed inlet directly into an extruder barrel first feed inlet in an amount insufficient to fill the extruder barrel;
b) feeding a second thermoplastic resin in pellet form into a second feed inlet in the extruder barrel, said second feed inlet being downstream from the first inlet and spaced there-from by the length of at least one helical turn of the screw, said pellets being introduced in an amount sufficient to keep the extruder barrel substantially full of resin at all times; and c) extruding the scrap resin and second resin as a mixture through an extruder die, whereby starvation of the extruder die is prevented in the event of plugging of the first extruder inlet.
a) feeding a fine fluffy thermoplastic resin scrap material of a character having a tendency to block an extruder barrel feed inlet directly into an extruder barrel first feed inlet in an amount insufficient to fill the extruder barrel;
b) feeding a second thermoplastic resin in pellet form into a second feed inlet in the extruder barrel, said second feed inlet being downstream from the first inlet and spaced there-from by the length of at least one helical turn of the screw, said pellets being introduced in an amount sufficient to keep the extruder barrel substantially full of resin at all times; and c) extruding the scrap resin and second resin as a mixture through an extruder die, whereby starvation of the extruder die is prevented in the event of plugging of the first extruder inlet.
2. The process of claim 1 which includes feeding the second thermoplastic resin in pellet form automatically by gravity feed to keep the extruder barrel substantially full of resin at all times.
3. The process of claim 1 wherein the thermoplastic resin is an olefinic resin.
4. The process of claim 1 wherein the thermoplastic resin is a polyethylene resin.
5. The process of claim 1 wherein the scrap resin is derived from the operation of a film extruder.
6. The process of claim 1 which includes the step of mixing the ground fluffy resin scrap with a granular thermo-plastic resin of higher density to obtain an admixture in a ratio of scrap-to-virgin resin of from about 1:1 to 6:1, and feeding the admixture into the first feed inlet.
7. The process of claim 1 wherein the amount of granular resin and fluffy scrap resin employed in the process provides for an extruded product when the first feed inlet is not plugged by scrap resin comprising from about 20 to 40% by weight of scrap resin.
8. The process of claim 1 wherein the scrap resin is admixed with high-density virgin resin, and, after being fed into the feed inlet and compressed in the barrel, comprises an admixture of scrap resin and virgin resin, which occupies at least one-half of the volume of the barrel of the extruder.
9. The process of claim 1 which includes the step of extruding the mixture through an extrusion die into a thin blown tube product.
10. The process of claim 1 which includes blowing the scrap resin into a first inverted cyclone feed hopper having a throat outlet which directly communicates with the first feed inlet of the extruder.
11. A process for the use of high amounts of fluffy, low density scrap resin, in an extruder, which extruder comprises a barrel with a rotating helical lead screw therein, said process comprising:
a) grinding thermoplastic resin scrap into a fine fluffy material of a character having a tendency to block an extruder barrel feed inlet;
b) feeding said material directly into an extruder barrel first feed inlet in an amount insufficient to fill the extruder barrel;
c) feeding a second thermoplastic resin in pellet form into a second feed inlet in the extruder barrel, said second feed inlet being downstream from the first inlet and spaced therefrom by the length of at least one helical turn of the screw, said pellets being introduced automatically by gravity feed in an amount sufficient to keep the extruder barrel substantially full of resin at all times; and d) extruding the scrap resin and second resin as a mixture through an extruder die, whereby starvation of the extruder die is prevented in the event of plugging of the first extruder inlet.
a) grinding thermoplastic resin scrap into a fine fluffy material of a character having a tendency to block an extruder barrel feed inlet;
b) feeding said material directly into an extruder barrel first feed inlet in an amount insufficient to fill the extruder barrel;
c) feeding a second thermoplastic resin in pellet form into a second feed inlet in the extruder barrel, said second feed inlet being downstream from the first inlet and spaced therefrom by the length of at least one helical turn of the screw, said pellets being introduced automatically by gravity feed in an amount sufficient to keep the extruder barrel substantially full of resin at all times; and d) extruding the scrap resin and second resin as a mixture through an extruder die, whereby starvation of the extruder die is prevented in the event of plugging of the first extruder inlet.
12. A thermoplastic resin extruder apparatus which permits the use of high amounts of fluffy scrap resin to be employed without resin starvation of the extruder die, which apparatus comprises:
a) a thermoplastic resin extruder which comprises i. an extruder barrel, ii. an extruder die at one end of the extruder for the extrusion of a resin product, iii. a lead screw in the barrel for movement of thermoplastic resin material through the barrel to the extruder die, iv. a first feed inlet in the barrel for the introduction of a fluffy low-density scrap resin into the barrel and compression of the fluffy resin in the barrel by the lead screw, v. a second feed inlet in the barrel for the introduction of a granular high-density resin into the barrel, the second feed inlet down-stream of the first feed inlet by at least one lead screw length, and generally adjacent and close to the first feed inlet along the barrel, vi. the first feed inlet larger in inlet area than the second feed inlet, and vii. a heated extruder section downstream of the second feed inlet to heat the thermoplastic resin prior to the extrusion of the heated resin in the extruder die;
b) a means upstream of said extruder barrel to grind a scrap thermoplastic resin onto a low-density fluffy scrap resin;
c) a first feed hopper operable to contain the fluffy scrap resin and having an open throat area at the lower portion thereof communicating directly with the first feed inlet, whereby fluffy resin in the first feed hopper is introduced by gravity or low pressure into the first feed inlet and compressed in part by the lead screw prior to the second feed inlet;
d) means operatively associated with said grinding means to convey the fluffy scrap resin from the grinding means to the first feed hopper; and e) an auxiliary feed hopper operable to contain a granular high-density thermoplastic resin, and having an open throat area which communicates with the second feed inlet, whereby, on occasional plugging of the first feed inlet by the fluffy resin, granular resin is fed by gravity from the auxiliary hopper to the barrel through the second feed inlet, preventing resin starvation of the extruder die.
a) a thermoplastic resin extruder which comprises i. an extruder barrel, ii. an extruder die at one end of the extruder for the extrusion of a resin product, iii. a lead screw in the barrel for movement of thermoplastic resin material through the barrel to the extruder die, iv. a first feed inlet in the barrel for the introduction of a fluffy low-density scrap resin into the barrel and compression of the fluffy resin in the barrel by the lead screw, v. a second feed inlet in the barrel for the introduction of a granular high-density resin into the barrel, the second feed inlet down-stream of the first feed inlet by at least one lead screw length, and generally adjacent and close to the first feed inlet along the barrel, vi. the first feed inlet larger in inlet area than the second feed inlet, and vii. a heated extruder section downstream of the second feed inlet to heat the thermoplastic resin prior to the extrusion of the heated resin in the extruder die;
b) a means upstream of said extruder barrel to grind a scrap thermoplastic resin onto a low-density fluffy scrap resin;
c) a first feed hopper operable to contain the fluffy scrap resin and having an open throat area at the lower portion thereof communicating directly with the first feed inlet, whereby fluffy resin in the first feed hopper is introduced by gravity or low pressure into the first feed inlet and compressed in part by the lead screw prior to the second feed inlet;
d) means operatively associated with said grinding means to convey the fluffy scrap resin from the grinding means to the first feed hopper; and e) an auxiliary feed hopper operable to contain a granular high-density thermoplastic resin, and having an open throat area which communicates with the second feed inlet, whereby, on occasional plugging of the first feed inlet by the fluffy resin, granular resin is fed by gravity from the auxiliary hopper to the barrel through the second feed inlet, preventing resin starvation of the extruder die.
13. The apparatus of claim 12 wherein the extruder die is a tubular-forming extruder die to form a tubular product for conversion into film.
14. The apparatus of claim 12 wherein the area of the first feed inlet and the throat area of the first feed hopper are from about two to six times the area of the second feed inlet.
15. The apparatus of claim 12 wherein the second feed inlet is positioned downstream from one to three screw lengths of the first feed inlet.
16. The apparatus of claim 12 wherein the means to convey the fluffy scrap resin comprises an air blower and conveyor tube, whereby fluffy resin from the grinding means is conveyed by air through the conveyor tube to the first feed hopper.
17. The apparatus of claim 12 wherein the means to grind the scrap resin comprises a film-grinding means, whereby salvageable resin film is ground into a low-density fluffy scrap resin.
18. The apparatus of claim 12 which includes a means operatively associated with said grinding means to admix high-density granular resin with the fluffy scrap resin from the grinding means prior to introduction of the admixture into the first feed hopper.
19. A thermoplastic resin extruder apparatus which permits the use of high amounts of fluffy scrap resin to be employed without resin starvation of the extruder die, which apparatus comprises:
a) a thermoplastic resin extruder which comprises:
i. an extruder barrel, ii. an extruder die at one end of the extruder for the extrusion of a tubular resin product, iii. a lead screw in the barrel for movement of thermoplastic resin material through the barrel to the extruder die, iv. a first feed inlet in the barrel for the introduction of a fluffy low-density scrap resin into the barrel and compression of the fluffy resin in the barrel by the lead screw, v. a second feed inlet in the barrel for the introduction of a granular high-density resin into the barrel, the second feed inlet down-stream of the first feed inlet by from about one to three lead screw lengths, vi. the first feed inlet about two to six times larger in inlet area than the second feed inlet, and vii. a heated extruder section downstream of the second feed inlet to heat the thermoplastic resin prior to the extrusion of the heated resin in the extruder die;
b) a means up-stream of said extruder barrel to grind scrap thermoplastic resin film into a low-density fluffy scrap resin;
c) a first cyclone-type feed hopper operable to contain the fluffy scrap resin and having an open throat area at the lower portion thereof communicating directly with the first feed inlet, the hopper being free of any screw conveyor for the fluffy resin therein, whereby fluffy resin in the first feed hopper is introduced by gravity or low pressure into the first feed inlet and compressed in part by the lead screw prior to the second feed inlet;
d) means operatively associated with said grinding means to convey the fluffy scrap resin by air from the grinding means to the first feed hopper which includes an air blower and conveyor tube;
e) a means operatively associated with said grinding means to admix high-density granular resin with the fluffy scrap resin from the grinding means prior to introduction of the admixture into the first feed hopper; and f) an auxiliary cyclone-type feed hopper operable to contain a granular high-density thermoplastic resin, and having an open throat area which communicates with the second feed inlet, whereby, on occasional plugging of the first feed inlet by the fluffy resin, granular resin is fed by gravity from the auxiliary hopper to the barrel through the second feed inlet, preventing resin starvation of the extruder die.
a) a thermoplastic resin extruder which comprises:
i. an extruder barrel, ii. an extruder die at one end of the extruder for the extrusion of a tubular resin product, iii. a lead screw in the barrel for movement of thermoplastic resin material through the barrel to the extruder die, iv. a first feed inlet in the barrel for the introduction of a fluffy low-density scrap resin into the barrel and compression of the fluffy resin in the barrel by the lead screw, v. a second feed inlet in the barrel for the introduction of a granular high-density resin into the barrel, the second feed inlet down-stream of the first feed inlet by from about one to three lead screw lengths, vi. the first feed inlet about two to six times larger in inlet area than the second feed inlet, and vii. a heated extruder section downstream of the second feed inlet to heat the thermoplastic resin prior to the extrusion of the heated resin in the extruder die;
b) a means up-stream of said extruder barrel to grind scrap thermoplastic resin film into a low-density fluffy scrap resin;
c) a first cyclone-type feed hopper operable to contain the fluffy scrap resin and having an open throat area at the lower portion thereof communicating directly with the first feed inlet, the hopper being free of any screw conveyor for the fluffy resin therein, whereby fluffy resin in the first feed hopper is introduced by gravity or low pressure into the first feed inlet and compressed in part by the lead screw prior to the second feed inlet;
d) means operatively associated with said grinding means to convey the fluffy scrap resin by air from the grinding means to the first feed hopper which includes an air blower and conveyor tube;
e) a means operatively associated with said grinding means to admix high-density granular resin with the fluffy scrap resin from the grinding means prior to introduction of the admixture into the first feed hopper; and f) an auxiliary cyclone-type feed hopper operable to contain a granular high-density thermoplastic resin, and having an open throat area which communicates with the second feed inlet, whereby, on occasional plugging of the first feed inlet by the fluffy resin, granular resin is fed by gravity from the auxiliary hopper to the barrel through the second feed inlet, preventing resin starvation of the extruder die.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA244,969A CA1069268A (en) | 1976-01-30 | 1976-01-30 | Process and apparatus for employing a high percentage of scrap resin in an extruder |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA244,969A CA1069268A (en) | 1976-01-30 | 1976-01-30 | Process and apparatus for employing a high percentage of scrap resin in an extruder |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1069268A true CA1069268A (en) | 1980-01-08 |
Family
ID=4105147
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA244,969A Expired CA1069268A (en) | 1976-01-30 | 1976-01-30 | Process and apparatus for employing a high percentage of scrap resin in an extruder |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1069268A (en) |
-
1976
- 1976-01-30 CA CA244,969A patent/CA1069268A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |