CA1234958A - Vacuum pinning of molten thermoplastic film to a roughened casting roll - Google Patents
Vacuum pinning of molten thermoplastic film to a roughened casting rollInfo
- Publication number
- CA1234958A CA1234958A CA000466837A CA466837A CA1234958A CA 1234958 A CA1234958 A CA 1234958A CA 000466837 A CA000466837 A CA 000466837A CA 466837 A CA466837 A CA 466837A CA 1234958 A CA1234958 A CA 1234958A
- Authority
- CA
- Canada
- Prior art keywords
- roll
- film
- micrometers
- quench
- web
- 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
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- Extrusion Moulding Of Plastics Or The Like (AREA)
Abstract
TITLE
VACUUM PINNING OF MOLTEN THERMOPLASTIC FILM
TO A ROUGHENED CASTING ROLL
ABSTRACT
A process is disclosed for increasing the casting speed in manufacturing thermoplastic film and in increasing the quality of film made thereby. The film is cast, in molten form during manufacture, by means of a vacuum, onto a quench roll (casting roll) having a surface roughness of at least 3 microinches (0.08 micrometers).
VACUUM PINNING OF MOLTEN THERMOPLASTIC FILM
TO A ROUGHENED CASTING ROLL
ABSTRACT
A process is disclosed for increasing the casting speed in manufacturing thermoplastic film and in increasing the quality of film made thereby. The film is cast, in molten form during manufacture, by means of a vacuum, onto a quench roll (casting roll) having a surface roughness of at least 3 microinches (0.08 micrometers).
Description
3~ ~3 TITLE_ VACUUM PINNING OF MOLTEN THF~.RMOPLASTIC FILM
TO A ROUGHENED CASTING ROLL
BACKGROUND
5The subject invention relates to the extrusion of molten thermoplastic film onto a quench roll casting drum.
In the production of film from certain thermoplastic polymers in which such film is formed at temperatures above or near the pol~mer melting point, it is important to quickly cool the freshly formed film to a temperature below the second order transition temperature, i.e., that temperature at which, as temperature decreases, the polymer goes from a flexible state to a more rigid, glassy state, in order to prevent crystallization which would interfere with subsequent orientation of the film.
It is, therefore, important to achieve quickl intimate contact between the extruded film and the quench roll, hence preventing excess a.ir fxom being trapped between the film and the roll. A number oE
devices have been employed to create more intimate contact between the extruded film and the quench roll, the most prominent being, generally, forced air pinning, electrostatic pinning, and vacuum pinning~
Forced air pinning, where the molten film is urged against the quench roll by means of air pressure exerted against the upper, or leading surface of the extruded film, is of limited use during high speed operation due to inherent limitations in the magnitude of air pressure which can be applied to a film with low melt tensions. Electrostatic pinning~
where the extruded film i5 held to the quench roll by means of electrostatic forces, has also been limited D-5266 35 to slower operation as air bubbles are trapped under the film at high speeds.
In the recent past, the removal of air -~
proximate the line of contact between the extruded ~-film and the ~uench roll has been attempted by use Qr various vacuum box devices, for example, the vacuum devices disclosed in U.S. Patent 3,347,962 (Dieck et al) and U.S. Patent 4,310,295 tHeyer)~ A major ~tation of such vacuum devices, however, is the narrow operating range of vacuum leve ls that can be exerted on the lower, or ~railing surface of ~he molten film for any given casting speed, particularly in the manufacture of thin gauge films. As detailed below, a variation in vacuum levels or variation in casting speed outside of this delicate operating range results in dramatic irregularities in cast film quality.
SUMMARY OF THE INVENTION
_ _ The subject invention is a process for the preparation of thermoplastic polymeric film comprising extruding a web of said polymeric material in melt form onto a quench roll having a surface roughness of at least three microinches (0008 micrometers) while simult~neously applying a vacuum force to the line of contact between the web and the roll therby preventing excess air from being entrapped between the film and the roll.
BRIEF DESCRIPTION -OF DRAWINGS
Fig. 1 is a log/log graph of the ranges of vacuum level vs~ quench roll (casting roll) peripheral speed useful in the vacuum assisted casting of 7.~ mil (183 micrometers) molten thermoplastic film onto a highly polished quench roll (unless otherwise specified, all film thicknesses herein are as cast film thicknesses).
L/9~3~ ~
Fig. 2 is a log/log graph o:E the ranges of vacuum level vs. ~uench roll (cas~ing roll) peripheral speed useful in the vacuum assisted casting of 11.25 mil (28S micrometers) molten thermoplastic ~ilm onto a highly polished quench roll.
Fiq. 3 is a log/log graph of the ranges of vacuum level vs. ~uench roll (casting roll) peripheral speed useful in the vacuum assisted casting of both 7.2 and 11.25 mil molten thermoplastic film onto a quench roll having a glass bead-blasted surface roughness of 6-7 microinches (0.15-0.18 micrometers).
DETAILED DESCRIPTION
The subject invention is a process for the preparation of thermoplastic polymeric film comprising extruding a web of said polymeric material in melt form onto a quench roll having a surface roughness of at least 3 microinches (0.08 micrometers) while simultaneously applyin~ a vacuum force to the line of contact between the web and the rollO
Of the various vacuum box devices available in the art for a~sisting the casting of molten thermoplastic film onto a quench roll, the device depicted in the figures and detailed in the disclosure of U.S. 4,310,295 is preferred for purposes of ~he subject invention due to the quiescent nature of the vacuum forces applied thereby to the trailing face o~ the film proximate the line of contact between the film and the quench roll. Of course, any other of the many vacuum devices well known in the art useful in eliminating air from the line of contact between the film and the quench roll can be employed as well in the practice of the subject invention~
~3~
The process of the subject invention can be utilized for casting any thermoplastic polymer Eilm which is capable of being melt casted in film form.
For example, such polymers include polyesters such as polyethylene terephthalate, polyethylene-2,6-naphthalate, polytetramethylene-1,2-dioxybenzoate and polyethylene-1,5-naphthanate; polyamides such as polyhexamethylene adipamide, polyhexamethylene sebacamide and polycaproamide; and vinylidene chloride. While the above polymeric materials are generally crystallizable, the invention is equally applicable to those organic thermoplastic polymers which are normally amorphous and which do not crystallize, such as polystyrene and polymethyl methacrylate.
Of critical impact in the process of the subject invention is the nature of the surface o~ the quench roll. Vacuum devices have heretofore been utilized in conjunction with smooth surfaced quench rolls, the surfaces o these rolls more conventionally referred to as highly polished surfaces, whereas the process of the subject invention utilizes a quench roll having a roughened surface. Processes useEul to roughen the surface of processing rolls are well known and include surface grinding and bead blasting~ The former is accomplished by conventional grinding tools capable of forming continuous or non-continuous circumferential grooves in the surface of the roll.
The latter is accomplished by blasting hard, particulate matt~Pr, preferably spherical glass beads, against the surface of the roll, for example, using conventional air pressure blasting equipment. After grinding or blasting/ the surface of the roll may be polished to remove sharp, irregular edges from the 1.2~ 3!"`j~
newly formed surface grooves or pits. Blasted surfaces are preferred for use in the practice of the subject inven~ion because the roughness created thereby is two-dimensional comprised of interconnecting pits which allows multiple escape paths for any air entrapped between the film and the surface of the roll. In contrast, the roughness on ground surfaces is one-dimensional comprised of circumerential grooves which allows only one escape path for air en~rapped between the film and the surface of the roll. More importantly, there exists more points o~ contact between the extruded web and a quench roll having a blasted surface as compared to one having a ground surface.
The degree of roughness on the surface of the roll is also critical in the practice of the subject invention. Surface roughness is conventionally measured in microinches, herein specified as an Ari~tic Average (A~), as detailed in the IS~ Journal 10, p. 51-56 (February~ 1963). The lower lu~ of the operable roughness for purposes of the subject invention is 3 microinches (0.08 micrometers) In theory, there is no upper limit as to the degree of operable roughness for purposes of the subject invention. For practical purposes, however, to avoid detrimental film surface irregularities, the roughness of the quench roll surface should be between 3 and 64 microinches (0O08-1.6 micrometers~, preferably 3 to 32 microinches (0008 to 0.8 micrometers), and most preferably 4 to 16 microinches ~0~1 to 0.4 micrometers). This latter range ensures that any surface irregularities on the surface of the cast film will have a narrow size distribution, an important quality if the film is to be useful in ~ 3~
microEllm applications or as a computer, audio or video base film~
The surprising discovery resulting from utilization of a roughened quench roll in conjunction with va~uum assisted film casting is two-fold.
First, the "mottle" threshold is lowered. Mottle manifests itself when ~here is incomplete contact of the film with the surface of the quench roll. The few points on the film surface that do come into intimate contact with the quench roll during mottle cause dimples to be formed on the opposite surface of the film, that film surface thereby resembling the surface of an orange peel. Second, the "bursting~
threshold is raised. "Bursting" relates to the use Of vacuum assisted film casting and is simply the result of too high a vacuum force exerted on the trailing sur~ace of an extruded film at the line of contact between the film and the quench roll, causing the film to be drawn toward the vacuum device and away from the quench roll surface. In operatlng any of the vacuum devices disclosed in the art, a balance need be struck such that, a~ any given roll speed, there is sufficient vacuum force applied to the line of contact between the film and the quench roll to prevent excess air from being entrapped between the film and the roll (i e., to prevent mottle), but not so high a vacuum force that the film is pulled toward the vacuum device away from the quench roll ti.e., to prevent bursting). As will be seen in the Example below, ~he operating range, or window, within which this balance is struck is very narrow when utilizing vacuum assisted casting and a highly polished quench roll, particularly in the manufacture of ~hin gauge films. In contrast, when a quench roll having a roughened surface is utilized in conjunction with any of the prior art vacuum devices, the mottle thLeshold is lowered and the bursting threshold is raised thereby drastically enlarging the operating window which defines the conditions under which a thermoplastic film may be cast, as illustrated in Figures 1 and 2 and more fully detailed in the Example.
In addition to lowering the mottle threshold and raising the bursting threshold in a vacuum assisted casting process, the subject invention allows thin gauge films to be produced which both could never have been produced heretofore on continuous processing lines, and could not have been heretofore produced at commercially acceptable speeds. Surprisingly, films having cast thicknesses of between about 4 and 10 mils (100-250 micrometers) can be produced by the process of the subject invention at peripheral quench roll speeds of greater than about 125 f~/min ~38 m/min), and Eilms having cast thicknesses of between about 10 and 15 mils (250-380 micrometers) can be produced by ~he process of the subject invention at peripheral quench roll speeds of greater than about 150 ft/min (46 m/min).
Such thin film production has heretofore been unattainable using vacuum assisted casting on highly polished quench rolls.
The attributes of the subject invention will be more fully appreciated by reference to the following Example.
EXAMPLE
For control purposes, polyethylene terephthalate having an intrinsic viscosity of 0.51-0.52 was melt extruded in film form from a conventional .070-O090 inch (1.8-2.3 mm) slit die and cast onto a quench roll having a highly polished (1 2 23fl~"3'-j~
AA) sur~ace spaced 0.125 inches (3.2 mm) from the die lip. This casting was assisted by a vacuum device as depicted in the Figures of U.S. ~.,310,295. By varying both the vacuum pressure and the quench roll speed, the mottle threshold and bursting threshold were determined empirically for 7.2 mil (183 micrometer) film and 11.25 mil ~286 micrometer~ ~ilm (as cast), the results graphically illustrated in Fig. 1 and Fig. 2 respectively.
Thereafter, to illustrate the benefits of the subject invention, polyethylene terephthalate having an intrinsic viscosi~y of 0.52-0.545 was melt extruded in film form from a conventional ~09 inch (2 3 mm) slit die and cast onto a quench roll having a surface roughness of 6-7 AA. The mottle and bursting thresholds were again determined empirically for 7.2 and 11.25 mil films, the results graphically illustrated in Fig. 3.
It is apparent that the operatinc~ window for ~he process utilizing vacuum assisted casting and a roughened quench roll is surprisingly larger than that evidenced utilizing vacuum assisted casting and a highly polished quench roll. It is also apparent that, by utilizing the process of the subject invention, thin gauge films can be produced at high commercial rates heretofore unattainable.
TO A ROUGHENED CASTING ROLL
BACKGROUND
5The subject invention relates to the extrusion of molten thermoplastic film onto a quench roll casting drum.
In the production of film from certain thermoplastic polymers in which such film is formed at temperatures above or near the pol~mer melting point, it is important to quickly cool the freshly formed film to a temperature below the second order transition temperature, i.e., that temperature at which, as temperature decreases, the polymer goes from a flexible state to a more rigid, glassy state, in order to prevent crystallization which would interfere with subsequent orientation of the film.
It is, therefore, important to achieve quickl intimate contact between the extruded film and the quench roll, hence preventing excess a.ir fxom being trapped between the film and the roll. A number oE
devices have been employed to create more intimate contact between the extruded film and the quench roll, the most prominent being, generally, forced air pinning, electrostatic pinning, and vacuum pinning~
Forced air pinning, where the molten film is urged against the quench roll by means of air pressure exerted against the upper, or leading surface of the extruded film, is of limited use during high speed operation due to inherent limitations in the magnitude of air pressure which can be applied to a film with low melt tensions. Electrostatic pinning~
where the extruded film i5 held to the quench roll by means of electrostatic forces, has also been limited D-5266 35 to slower operation as air bubbles are trapped under the film at high speeds.
In the recent past, the removal of air -~
proximate the line of contact between the extruded ~-film and the ~uench roll has been attempted by use Qr various vacuum box devices, for example, the vacuum devices disclosed in U.S. Patent 3,347,962 (Dieck et al) and U.S. Patent 4,310,295 tHeyer)~ A major ~tation of such vacuum devices, however, is the narrow operating range of vacuum leve ls that can be exerted on the lower, or ~railing surface of ~he molten film for any given casting speed, particularly in the manufacture of thin gauge films. As detailed below, a variation in vacuum levels or variation in casting speed outside of this delicate operating range results in dramatic irregularities in cast film quality.
SUMMARY OF THE INVENTION
_ _ The subject invention is a process for the preparation of thermoplastic polymeric film comprising extruding a web of said polymeric material in melt form onto a quench roll having a surface roughness of at least three microinches (0008 micrometers) while simult~neously applying a vacuum force to the line of contact between the web and the roll therby preventing excess air from being entrapped between the film and the roll.
BRIEF DESCRIPTION -OF DRAWINGS
Fig. 1 is a log/log graph of the ranges of vacuum level vs~ quench roll (casting roll) peripheral speed useful in the vacuum assisted casting of 7.~ mil (183 micrometers) molten thermoplastic film onto a highly polished quench roll (unless otherwise specified, all film thicknesses herein are as cast film thicknesses).
L/9~3~ ~
Fig. 2 is a log/log graph o:E the ranges of vacuum level vs. ~uench roll (cas~ing roll) peripheral speed useful in the vacuum assisted casting of 11.25 mil (28S micrometers) molten thermoplastic ~ilm onto a highly polished quench roll.
Fiq. 3 is a log/log graph of the ranges of vacuum level vs. ~uench roll (casting roll) peripheral speed useful in the vacuum assisted casting of both 7.2 and 11.25 mil molten thermoplastic film onto a quench roll having a glass bead-blasted surface roughness of 6-7 microinches (0.15-0.18 micrometers).
DETAILED DESCRIPTION
The subject invention is a process for the preparation of thermoplastic polymeric film comprising extruding a web of said polymeric material in melt form onto a quench roll having a surface roughness of at least 3 microinches (0.08 micrometers) while simultaneously applyin~ a vacuum force to the line of contact between the web and the rollO
Of the various vacuum box devices available in the art for a~sisting the casting of molten thermoplastic film onto a quench roll, the device depicted in the figures and detailed in the disclosure of U.S. 4,310,295 is preferred for purposes of ~he subject invention due to the quiescent nature of the vacuum forces applied thereby to the trailing face o~ the film proximate the line of contact between the film and the quench roll. Of course, any other of the many vacuum devices well known in the art useful in eliminating air from the line of contact between the film and the quench roll can be employed as well in the practice of the subject invention~
~3~
The process of the subject invention can be utilized for casting any thermoplastic polymer Eilm which is capable of being melt casted in film form.
For example, such polymers include polyesters such as polyethylene terephthalate, polyethylene-2,6-naphthalate, polytetramethylene-1,2-dioxybenzoate and polyethylene-1,5-naphthanate; polyamides such as polyhexamethylene adipamide, polyhexamethylene sebacamide and polycaproamide; and vinylidene chloride. While the above polymeric materials are generally crystallizable, the invention is equally applicable to those organic thermoplastic polymers which are normally amorphous and which do not crystallize, such as polystyrene and polymethyl methacrylate.
Of critical impact in the process of the subject invention is the nature of the surface o~ the quench roll. Vacuum devices have heretofore been utilized in conjunction with smooth surfaced quench rolls, the surfaces o these rolls more conventionally referred to as highly polished surfaces, whereas the process of the subject invention utilizes a quench roll having a roughened surface. Processes useEul to roughen the surface of processing rolls are well known and include surface grinding and bead blasting~ The former is accomplished by conventional grinding tools capable of forming continuous or non-continuous circumferential grooves in the surface of the roll.
The latter is accomplished by blasting hard, particulate matt~Pr, preferably spherical glass beads, against the surface of the roll, for example, using conventional air pressure blasting equipment. After grinding or blasting/ the surface of the roll may be polished to remove sharp, irregular edges from the 1.2~ 3!"`j~
newly formed surface grooves or pits. Blasted surfaces are preferred for use in the practice of the subject inven~ion because the roughness created thereby is two-dimensional comprised of interconnecting pits which allows multiple escape paths for any air entrapped between the film and the surface of the roll. In contrast, the roughness on ground surfaces is one-dimensional comprised of circumerential grooves which allows only one escape path for air en~rapped between the film and the surface of the roll. More importantly, there exists more points o~ contact between the extruded web and a quench roll having a blasted surface as compared to one having a ground surface.
The degree of roughness on the surface of the roll is also critical in the practice of the subject invention. Surface roughness is conventionally measured in microinches, herein specified as an Ari~tic Average (A~), as detailed in the IS~ Journal 10, p. 51-56 (February~ 1963). The lower lu~ of the operable roughness for purposes of the subject invention is 3 microinches (0.08 micrometers) In theory, there is no upper limit as to the degree of operable roughness for purposes of the subject invention. For practical purposes, however, to avoid detrimental film surface irregularities, the roughness of the quench roll surface should be between 3 and 64 microinches (0O08-1.6 micrometers~, preferably 3 to 32 microinches (0008 to 0.8 micrometers), and most preferably 4 to 16 microinches ~0~1 to 0.4 micrometers). This latter range ensures that any surface irregularities on the surface of the cast film will have a narrow size distribution, an important quality if the film is to be useful in ~ 3~
microEllm applications or as a computer, audio or video base film~
The surprising discovery resulting from utilization of a roughened quench roll in conjunction with va~uum assisted film casting is two-fold.
First, the "mottle" threshold is lowered. Mottle manifests itself when ~here is incomplete contact of the film with the surface of the quench roll. The few points on the film surface that do come into intimate contact with the quench roll during mottle cause dimples to be formed on the opposite surface of the film, that film surface thereby resembling the surface of an orange peel. Second, the "bursting~
threshold is raised. "Bursting" relates to the use Of vacuum assisted film casting and is simply the result of too high a vacuum force exerted on the trailing sur~ace of an extruded film at the line of contact between the film and the quench roll, causing the film to be drawn toward the vacuum device and away from the quench roll surface. In operatlng any of the vacuum devices disclosed in the art, a balance need be struck such that, a~ any given roll speed, there is sufficient vacuum force applied to the line of contact between the film and the quench roll to prevent excess air from being entrapped between the film and the roll (i e., to prevent mottle), but not so high a vacuum force that the film is pulled toward the vacuum device away from the quench roll ti.e., to prevent bursting). As will be seen in the Example below, ~he operating range, or window, within which this balance is struck is very narrow when utilizing vacuum assisted casting and a highly polished quench roll, particularly in the manufacture of ~hin gauge films. In contrast, when a quench roll having a roughened surface is utilized in conjunction with any of the prior art vacuum devices, the mottle thLeshold is lowered and the bursting threshold is raised thereby drastically enlarging the operating window which defines the conditions under which a thermoplastic film may be cast, as illustrated in Figures 1 and 2 and more fully detailed in the Example.
In addition to lowering the mottle threshold and raising the bursting threshold in a vacuum assisted casting process, the subject invention allows thin gauge films to be produced which both could never have been produced heretofore on continuous processing lines, and could not have been heretofore produced at commercially acceptable speeds. Surprisingly, films having cast thicknesses of between about 4 and 10 mils (100-250 micrometers) can be produced by the process of the subject invention at peripheral quench roll speeds of greater than about 125 f~/min ~38 m/min), and Eilms having cast thicknesses of between about 10 and 15 mils (250-380 micrometers) can be produced by ~he process of the subject invention at peripheral quench roll speeds of greater than about 150 ft/min (46 m/min).
Such thin film production has heretofore been unattainable using vacuum assisted casting on highly polished quench rolls.
The attributes of the subject invention will be more fully appreciated by reference to the following Example.
EXAMPLE
For control purposes, polyethylene terephthalate having an intrinsic viscosity of 0.51-0.52 was melt extruded in film form from a conventional .070-O090 inch (1.8-2.3 mm) slit die and cast onto a quench roll having a highly polished (1 2 23fl~"3'-j~
AA) sur~ace spaced 0.125 inches (3.2 mm) from the die lip. This casting was assisted by a vacuum device as depicted in the Figures of U.S. ~.,310,295. By varying both the vacuum pressure and the quench roll speed, the mottle threshold and bursting threshold were determined empirically for 7.2 mil (183 micrometer) film and 11.25 mil ~286 micrometer~ ~ilm (as cast), the results graphically illustrated in Fig. 1 and Fig. 2 respectively.
Thereafter, to illustrate the benefits of the subject invention, polyethylene terephthalate having an intrinsic viscosi~y of 0.52-0.545 was melt extruded in film form from a conventional ~09 inch (2 3 mm) slit die and cast onto a quench roll having a surface roughness of 6-7 AA. The mottle and bursting thresholds were again determined empirically for 7.2 and 11.25 mil films, the results graphically illustrated in Fig. 3.
It is apparent that the operatinc~ window for ~he process utilizing vacuum assisted casting and a roughened quench roll is surprisingly larger than that evidenced utilizing vacuum assisted casting and a highly polished quench roll. It is also apparent that, by utilizing the process of the subject invention, thin gauge films can be produced at high commercial rates heretofore unattainable.
Claims (16)
1. A process for preparing thermoplastic polymeric film comprising extruding a web of said polymeric material in melt form and casting the web onto the surface of a quench roll having a surface roughness of at least three microinches (0.08 micrometers) and yielding a line of contact between the web and the quench roll while simultaneously applying a vacuum force to the line of contact between the web and the roll thereby preventing air from being entrapped between the film and the roll.
2. The process of Claim 1 wherein the polymeric film is of polyethylene terephthalate.
3. The process of Claim 1 wherein the surface roughness of the quench roll is 3 to microinches (0.08 to 1.6 micrometers).
4. The process of Claim 3 wherein the polymeric film is of polyethylene terephthalate.
5. The process of Claim 1 wherein the surface roughness of the quench roll is 3 to 32 microinches (0.08 to 0.8 micrometers).
6. The process of Claim 5 wherein the polymeric film is of polyethylene terephthalate.
7. The process of Claim 1 wherein the surface roughness of the quench roll is 4 to 16 microinches (0.1 to 0.4 micrometers).
8. The process of Claim 7 wherein the polymeric film is of polyethyelne terephthalate.
9. The process of Claim 1 wherein the roughness comprises interconnecting pits on the surface of the roll.
10. The process of Claim 1 wherein the roughness comprises circumferential grooves on the surface of the roll.
11. The process of Claim 9 wherein the web, once cast onto the surface of a quench roll, has a thickness between about 100 and 250 micrometers.
12. The process of Claim 9 wherein the web, once cast onto the surface of a quench roll, has a thickness between about 250 and 380 micrometers.
13. The process of Claim 10 wherein the web, once cast onto the surface of a quench roll, has a thickness between about 100 and 250 micrometers.
14. The process of Claim 10 wherein the web, once cast onto the surface of a quench roll, has a thickness between about 250 and 380 micrometers.
15. The process of Claim 11 wherein the roll has a peripheral speed greater than about 38 m/min.
16. The process of Claim 12 wherein the roll has a peripheral speed greater than about 46 m/min.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000466837A CA1234958A (en) | 1984-11-01 | 1984-11-01 | Vacuum pinning of molten thermoplastic film to a roughened casting roll |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000466837A CA1234958A (en) | 1984-11-01 | 1984-11-01 | Vacuum pinning of molten thermoplastic film to a roughened casting roll |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1234958A true CA1234958A (en) | 1988-04-12 |
Family
ID=4129058
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000466837A Expired CA1234958A (en) | 1984-11-01 | 1984-11-01 | Vacuum pinning of molten thermoplastic film to a roughened casting roll |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1234958A (en) |
-
1984
- 1984-11-01 CA CA000466837A patent/CA1234958A/en not_active Expired
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