CA1070070A - Method and apparatus for the extrusion of foamable thermoplastic materials - Google Patents
Method and apparatus for the extrusion of foamable thermoplastic materialsInfo
- Publication number
- CA1070070A CA1070070A CA247,499A CA247499A CA1070070A CA 1070070 A CA1070070 A CA 1070070A CA 247499 A CA247499 A CA 247499A CA 1070070 A CA1070070 A CA 1070070A
- Authority
- CA
- Canada
- Prior art keywords
- channel
- extrusion
- composition
- foam
- shaping
- 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
Landscapes
- Extrusion Moulding Of Plastics Or The Like (AREA)
Abstract
ABSTRACT
Plastic foam is extruded into and from a channel where it expands from an extrusion orifice. A pressure controlled gas pocket provides support for the foaming material generally adjacent the extrusion die. The arrange-ment permits extrusion of foam having widely varying char-acteristics with a single apparatus.
Plastic foam is extruded into and from a channel where it expands from an extrusion orifice. A pressure controlled gas pocket provides support for the foaming material generally adjacent the extrusion die. The arrange-ment permits extrusion of foam having widely varying char-acteristics with a single apparatus.
Description
~L07~J107~
The present invention resides in an improved method and apparatus for the extrusion of expandable synthetic resi-nous foams. More specifically, the present invention resides in an improved method and apparatus for the extrusion of ex pandable synthetic resinous foams which can support the ex-panding extruded foam without the necessity of individual shaping plates for each product extruded.
Foamed plastics are well known items of commerce.
Particularly desirable forms of foam plastics are those having rectangular or other regular configurations which are suitable for structural purposes such as insulation. Bene-ficially such foamed plastics are employed as panel cores, building insulation as well as for decorative purposes such as for supports for floral arrangements. Many foams have a relatively low density usually Erom 1.5 to 3 pounds per cubic foot and are prepared by extruding a heat plastified mixture of a thermoplastic resin and a blowing agent. Such ~oamable plastic systems are well known in the art and some are set forth in the following U. S~ Patents: 2,387,730;
The present invention resides in an improved method and apparatus for the extrusion of expandable synthetic resi-nous foams. More specifically, the present invention resides in an improved method and apparatus for the extrusion of ex pandable synthetic resinous foams which can support the ex-panding extruded foam without the necessity of individual shaping plates for each product extruded.
Foamed plastics are well known items of commerce.
Particularly desirable forms of foam plastics are those having rectangular or other regular configurations which are suitable for structural purposes such as insulation. Bene-ficially such foamed plastics are employed as panel cores, building insulation as well as for decorative purposes such as for supports for floral arrangements. Many foams have a relatively low density usually Erom 1.5 to 3 pounds per cubic foot and are prepared by extruding a heat plastified mixture of a thermoplastic resin and a blowing agent. Such ~oamable plastic systems are well known in the art and some are set forth in the following U. S~ Patents: 2,387,730;
2,409,slO; 2,5~5,250; 2,537,977; 2,576,911; 2l6~0,515;
2,669,751; 2,774,991; 2,857,625; 2,884,386; 2,92~,130;
2,669,751; 2,774,991; 2,857,625; 2,884,386; 2,92~,130;
3,121,130; 3,121,911; 3,194,~54; 3,219,733; 3,299,192;
3,431,163; 3,431,164; 3,466,705 and 3,764,642.
The extrusion of plastic foams with the passage of time has become more sophisticated in order that the extruded product might have physical characteristics suitable for -~
a specific application. It is particularly desirable in the extrusion of foamed plastics that the cooled foam have a shape and size of the desired end product thus ;. :
. ~ .
;16,899A-F
, ,' . ~. ; :,, . '. . . - ' , ~7~
avoiding loss of material by trimming, shaping and the like. Tnerefore, it is desirable to extrude foam in such a way that such trim waste is minimized and to this end various extrude shaping devices have been employed~ The physical properties of the resultant foam can be varied quite significantly by such factors as the relative speed of extrusion and takeaway speed which affects cell orienta-tion. For many applications it has be~n found desirable to provide shaping plates generally adjacent the extrusion die~
Such shaping plates have varied from flat plates which are hinged adjacent the di~ to e3aborately curved plates which conform more or less to the natural configuration of the expanding foam. In some instances such plates have been replaced by a plurality of rolls. Such shaping aids axe intended to provide a finished product having a generally rectangular or other predetermined configuration and hope fully a generally uniform densi~y throughout the extruded shape. One can, with time and patience~ devise a curved -~
shaping plate which aids in obtaining the desired physical ~0 characteristics in the extruded product. However, such a shaping plate generally is satisfactory for only a single product and/or a narrow rancJe of operating conditions and when a different product or different operating conditions are desired two or more new shaping plates must be developed.
The present invention resides in a process for the preparation of synthetic resinous thermoplastic foam, comprising the s~eps of extruding a heat plastified syn-thetic resinous thermoplastic extrudable foamable compo sition through an extrusion orifice into a shaping channel, ;
16,8n9~ 2-.~
'i' .. . .
: :
~: .. .. - :
7~
of lower pressure, said channel having internal walls with a cross-sectional configuration generally corresponding to the shape of the product desired, the extrudable composition expanding to generally fill said shaping channel and contact the internal walls of said channel at a location adjacent a discharge opening thereof, withdrawing the foamed product from said channel at the discharge opening remote from the extrusion orifice, and providing within said channel, at a location ajacent to the extrusion orifice, a gas unde:r pres-sure, the gas pressure being sufficient to regulate the shape of the expanding composition at a location between the die and a location where the expanding composition contacts said channel walls.
Further features and advantages of the present invention will become more apparent from the following specification taken in connection with the drawing wherein:
Figure 1 is a schematic representation of a side view of apparatus in accordance with the invention.
Figure 2 is a partially cutaway fractional view of a portion of the apparatus of Figure 2.
16,899A-F -3~
~'7~
Figure 3 is an alternate embodiment of a channel for the apparatus of Figure 1.
Figure 4 shows a channel suitable for the prepara-tion of a foam having a circular cross-section.
In Figure 1 there is schematically depicted an appaxatus indicated by the reference numeral 10. The apparatus 10 comprises in co~perative combination a source 11 such as a plastics extruder which provides a heat plasti-fied stream of a synthetic resinous thermoplaskic extrudable ~oamable composition. The extruder 11 is operatively con-nected with a die 12. The die 12 has an extrusion orifice 13 having a generally slot-like configuration. The slot 13 i~ in ull communication with a hollow housing 15,. The housing 15 defines the~ein a space~ channel or shaping passage 16. The housing 15 has a discharge opening 17 remot~ly disposed from the die orifice 13. As depicted in Figure 1~ the spacs 16 within the housing 15 has a desired configuration; that is, rectangular. A conduit 18 is in operative communication with the space 16 at a location 19 generally adjacent the die 12. The conduit 18 is in com-munication with a conduit 21 which in turn comm~micat~s with a gas pressure regulating valve 23 and a discharge nozzle or bleed 24. Disposed within the space 16 is an expanded extruded syn~hetic re~inous composition or foam 26 which fills the cross-section o the space 16 adjacent the dis-charge opening 17 thereo~. The foam 26 is in contact with a major portion of the internal walls of the housing 15 and is shaped thereby. A gas space 27 surrounds an extruda~le foamable composition 26a at a location where the composition 16,899A-F -4-~C!1'7~JV~
is foaming which is generally adjacent to the extrusion orifice 13. The gas space 27 is defined by the housing 15 and foam 26a and 26. The extrudable composition 26a expands or foams to form foam 26. The foam 26 remoke from the orifice 15 peripherally engages the inner wall of the housing 15 which series retains gas in the space 27. Remote from the chamber 15 generally adjacent the ope.ning 17 are takeaway rolls or conveying means 27 and 28.
In F.igure ~ there is more clearly shown the ccn-figuration of the extrude 26a as it leaves the extrus:ion orifice 13 and expands into the foam 26. -In operation~ the foamable composition is extruded from the orifice 13, expands to form the foam 26 and is removed by the takeaway means 27 and 28. The gas pressure : :
regulating assembly consisting of components 1~, 21, 23 and 24 is adjusted by means of the valve 23 to provide a gas pressure within the space 27 sufficient ~o permit either rapid : .
expansion or delayed expansion of the composition 26a as desixed and provide the desired characteristics in the extruded foam. For example, if cells are desired which are elongated generally in directions normal to the direction .~:
of extrusion, a relatively low gas pressure is employed, whereas if orientation is desired in the direction of extrusion, a higher gas pressure is used 9 The gas pressure ; 25 tends to advance ~he foam from the chamber and overcomes frictional drag forces developed by contact of the foam with -the chamber walls. The particular pressure in the chamber will vary rom composition to composition and depends upon ~he charac~eristics desired in the foam~ The gas pressure 16,899A-F -5-,, , , . . ~
~)7~7~
usually will be within the range of fxom about 1 to 15 pounds per square inch gauge. The temp,erature of the supply gas is usually immaterial as the hea~ capacity and volume of the gas is small relative to the extrude and the volume.
In Figure 3 there is schematically depicted an alternate chamber suitable for use in the present invention designated by the reference numeral 35~ The chamber 35 comprises a housing 36 which has an open end 37~ a closed end 38 having defined therein an extrusion ori~ica 39. A
gas conduit 41 provides communication between the inside of the chamber and a source of gas under pressure. A side shaped fillet 43 is positioned in a corner of the housing genexally adjacent to the slot 39. An upper shapled fillet 44 and a lowex shaped fillet 45 are similarly disposed within corners of the housing. A Eourth side shaped fillet is disposed opposite the fillat 43 but is not shown. The arrangements of the fillets within the chamber 35 adjacent the extrusion slot provides a convenience in startup of extrusion hy eliminating sharp corners in which ini~ially extruded foam may adhere prior to the extrusion of sufi-cient foam material into the chamher to provide a cell which would permit gas pressure to increase to a su~ficient extent to shape the expanding portion of the extrude. The ~illets 43, 44r 45 and the fouxth side fillet (not shown~
do not contact the foam when steady sta~e operation is achieved. Optionally, the side fillets may, if desired~
be increased in size to contact the extruded foam at the rearmost edge portion and gas pressure support applied to only the major aces of the expanding composition.
16,899A-F -6-In Figure 4 there ls depicted a sectional view of a chamber su.itable for the practice of the pr~sent invention generally designated by the reference numeral 50O The chamber 50 has a jacketed housing 51. The housing 51 has an open end 52 7 an internal passageway 53 and a feed end or slot 54 remotely disposed from the open end 52. The housing 51 has defined therein a generally cylindrical passage which smoothly curves in a concave mannPr to the orifice 54. The conduit 55 is in communication with a source o~ pressure regulated gas~ not shown. Dotted lines indicated by ~he reference numeral 57 depict the shape of an extruded foam composition within the chamber when a cylindrical billet is being extruded. The housing may be heated, cooled or operated at ambient temperature depending upon the surface effects-desired in accord with conventional foam extrusion practices. :
Apparatus as depicted in Figures 1-4 is eminently satisfactory for the preparation of extruded thermoplastic foams including polystyrene, polyvinyl chloride, polyethylene, polypropylene and the like. .Rectangular, hexagonal and cir- :
; cular shape~ are readily prepared in a manner to give sub-stantial control of cell orientation The foregoing description is intended to be il-lustrati~e and is not to be cons trued or interpreted as 2S being restrictive or otherwise limiting o F the present invention.
16,899A-F -7-... .: . : . . . . - . - . .. .. . .. , . .:
3,431,163; 3,431,164; 3,466,705 and 3,764,642.
The extrusion of plastic foams with the passage of time has become more sophisticated in order that the extruded product might have physical characteristics suitable for -~
a specific application. It is particularly desirable in the extrusion of foamed plastics that the cooled foam have a shape and size of the desired end product thus ;. :
. ~ .
;16,899A-F
, ,' . ~. ; :,, . '. . . - ' , ~7~
avoiding loss of material by trimming, shaping and the like. Tnerefore, it is desirable to extrude foam in such a way that such trim waste is minimized and to this end various extrude shaping devices have been employed~ The physical properties of the resultant foam can be varied quite significantly by such factors as the relative speed of extrusion and takeaway speed which affects cell orienta-tion. For many applications it has be~n found desirable to provide shaping plates generally adjacent the extrusion die~
Such shaping plates have varied from flat plates which are hinged adjacent the di~ to e3aborately curved plates which conform more or less to the natural configuration of the expanding foam. In some instances such plates have been replaced by a plurality of rolls. Such shaping aids axe intended to provide a finished product having a generally rectangular or other predetermined configuration and hope fully a generally uniform densi~y throughout the extruded shape. One can, with time and patience~ devise a curved -~
shaping plate which aids in obtaining the desired physical ~0 characteristics in the extruded product. However, such a shaping plate generally is satisfactory for only a single product and/or a narrow rancJe of operating conditions and when a different product or different operating conditions are desired two or more new shaping plates must be developed.
The present invention resides in a process for the preparation of synthetic resinous thermoplastic foam, comprising the s~eps of extruding a heat plastified syn-thetic resinous thermoplastic extrudable foamable compo sition through an extrusion orifice into a shaping channel, ;
16,8n9~ 2-.~
'i' .. . .
: :
~: .. .. - :
7~
of lower pressure, said channel having internal walls with a cross-sectional configuration generally corresponding to the shape of the product desired, the extrudable composition expanding to generally fill said shaping channel and contact the internal walls of said channel at a location adjacent a discharge opening thereof, withdrawing the foamed product from said channel at the discharge opening remote from the extrusion orifice, and providing within said channel, at a location ajacent to the extrusion orifice, a gas unde:r pres-sure, the gas pressure being sufficient to regulate the shape of the expanding composition at a location between the die and a location where the expanding composition contacts said channel walls.
Further features and advantages of the present invention will become more apparent from the following specification taken in connection with the drawing wherein:
Figure 1 is a schematic representation of a side view of apparatus in accordance with the invention.
Figure 2 is a partially cutaway fractional view of a portion of the apparatus of Figure 2.
16,899A-F -3~
~'7~
Figure 3 is an alternate embodiment of a channel for the apparatus of Figure 1.
Figure 4 shows a channel suitable for the prepara-tion of a foam having a circular cross-section.
In Figure 1 there is schematically depicted an appaxatus indicated by the reference numeral 10. The apparatus 10 comprises in co~perative combination a source 11 such as a plastics extruder which provides a heat plasti-fied stream of a synthetic resinous thermoplaskic extrudable ~oamable composition. The extruder 11 is operatively con-nected with a die 12. The die 12 has an extrusion orifice 13 having a generally slot-like configuration. The slot 13 i~ in ull communication with a hollow housing 15,. The housing 15 defines the~ein a space~ channel or shaping passage 16. The housing 15 has a discharge opening 17 remot~ly disposed from the die orifice 13. As depicted in Figure 1~ the spacs 16 within the housing 15 has a desired configuration; that is, rectangular. A conduit 18 is in operative communication with the space 16 at a location 19 generally adjacent the die 12. The conduit 18 is in com-munication with a conduit 21 which in turn comm~micat~s with a gas pressure regulating valve 23 and a discharge nozzle or bleed 24. Disposed within the space 16 is an expanded extruded syn~hetic re~inous composition or foam 26 which fills the cross-section o the space 16 adjacent the dis-charge opening 17 thereo~. The foam 26 is in contact with a major portion of the internal walls of the housing 15 and is shaped thereby. A gas space 27 surrounds an extruda~le foamable composition 26a at a location where the composition 16,899A-F -4-~C!1'7~JV~
is foaming which is generally adjacent to the extrusion orifice 13. The gas space 27 is defined by the housing 15 and foam 26a and 26. The extrudable composition 26a expands or foams to form foam 26. The foam 26 remoke from the orifice 15 peripherally engages the inner wall of the housing 15 which series retains gas in the space 27. Remote from the chamber 15 generally adjacent the ope.ning 17 are takeaway rolls or conveying means 27 and 28.
In F.igure ~ there is more clearly shown the ccn-figuration of the extrude 26a as it leaves the extrus:ion orifice 13 and expands into the foam 26. -In operation~ the foamable composition is extruded from the orifice 13, expands to form the foam 26 and is removed by the takeaway means 27 and 28. The gas pressure : :
regulating assembly consisting of components 1~, 21, 23 and 24 is adjusted by means of the valve 23 to provide a gas pressure within the space 27 sufficient ~o permit either rapid : .
expansion or delayed expansion of the composition 26a as desixed and provide the desired characteristics in the extruded foam. For example, if cells are desired which are elongated generally in directions normal to the direction .~:
of extrusion, a relatively low gas pressure is employed, whereas if orientation is desired in the direction of extrusion, a higher gas pressure is used 9 The gas pressure ; 25 tends to advance ~he foam from the chamber and overcomes frictional drag forces developed by contact of the foam with -the chamber walls. The particular pressure in the chamber will vary rom composition to composition and depends upon ~he charac~eristics desired in the foam~ The gas pressure 16,899A-F -5-,, , , . . ~
~)7~7~
usually will be within the range of fxom about 1 to 15 pounds per square inch gauge. The temp,erature of the supply gas is usually immaterial as the hea~ capacity and volume of the gas is small relative to the extrude and the volume.
In Figure 3 there is schematically depicted an alternate chamber suitable for use in the present invention designated by the reference numeral 35~ The chamber 35 comprises a housing 36 which has an open end 37~ a closed end 38 having defined therein an extrusion ori~ica 39. A
gas conduit 41 provides communication between the inside of the chamber and a source of gas under pressure. A side shaped fillet 43 is positioned in a corner of the housing genexally adjacent to the slot 39. An upper shapled fillet 44 and a lowex shaped fillet 45 are similarly disposed within corners of the housing. A Eourth side shaped fillet is disposed opposite the fillat 43 but is not shown. The arrangements of the fillets within the chamber 35 adjacent the extrusion slot provides a convenience in startup of extrusion hy eliminating sharp corners in which ini~ially extruded foam may adhere prior to the extrusion of sufi-cient foam material into the chamher to provide a cell which would permit gas pressure to increase to a su~ficient extent to shape the expanding portion of the extrude. The ~illets 43, 44r 45 and the fouxth side fillet (not shown~
do not contact the foam when steady sta~e operation is achieved. Optionally, the side fillets may, if desired~
be increased in size to contact the extruded foam at the rearmost edge portion and gas pressure support applied to only the major aces of the expanding composition.
16,899A-F -6-In Figure 4 there ls depicted a sectional view of a chamber su.itable for the practice of the pr~sent invention generally designated by the reference numeral 50O The chamber 50 has a jacketed housing 51. The housing 51 has an open end 52 7 an internal passageway 53 and a feed end or slot 54 remotely disposed from the open end 52. The housing 51 has defined therein a generally cylindrical passage which smoothly curves in a concave mannPr to the orifice 54. The conduit 55 is in communication with a source o~ pressure regulated gas~ not shown. Dotted lines indicated by ~he reference numeral 57 depict the shape of an extruded foam composition within the chamber when a cylindrical billet is being extruded. The housing may be heated, cooled or operated at ambient temperature depending upon the surface effects-desired in accord with conventional foam extrusion practices. :
Apparatus as depicted in Figures 1-4 is eminently satisfactory for the preparation of extruded thermoplastic foams including polystyrene, polyvinyl chloride, polyethylene, polypropylene and the like. .Rectangular, hexagonal and cir- :
; cular shape~ are readily prepared in a manner to give sub-stantial control of cell orientation The foregoing description is intended to be il-lustrati~e and is not to be cons trued or interpreted as 2S being restrictive or otherwise limiting o F the present invention.
16,899A-F -7-... .: . : . . . . - . - . .. .. . .. , . .:
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the preparation of synthetic resinous thermoplastic foam, comprising the steps of ex-truding a heat plastified synthetic resinous thermoplastic extrudable foamable composition through an extrusion ori-fice into a shaping channel of lower pressure, said channel having internal walls with a cross-sectional configuration generally corresponding to the shape of the product desired, the extrudable composition expanding to generally fill said shaping channel and contact the internal walls of said channel at a location adjacent a discharge opening thereof, withdrawing the foamed product from said channel at the discharge opening remote from the extrusion orifice, and providing within said channel, at a location adjacent to the extrusion orifice, a gas under pressure, the gas pres-sure being sufficient to regulate the shape of the expanding composition at a location between the die and a location where the expanding composition contacts said channel walls.
2. The process of Claim 1, including the step of mechanically supporting edge portions of the expandable composition during expansion.
3. The method of Claim 1, wherein the channel has an elongate rectangular configuration.
4. The method of Claim 1, wherein the cross--sectional configuration of the shaping device is circular.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA247,499A CA1070070A (en) | 1976-03-09 | 1976-03-09 | Method and apparatus for the extrusion of foamable thermoplastic materials |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA247,499A CA1070070A (en) | 1976-03-09 | 1976-03-09 | Method and apparatus for the extrusion of foamable thermoplastic materials |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1070070A true CA1070070A (en) | 1980-01-22 |
Family
ID=4105430
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA247,499A Expired CA1070070A (en) | 1976-03-09 | 1976-03-09 | Method and apparatus for the extrusion of foamable thermoplastic materials |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1070070A (en) |
-
1976
- 1976-03-09 CA CA247,499A patent/CA1070070A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |