CA1064210A - Process and apparatus for heat setting biaxially oriented tubular polyethylene terephthalate films - Google Patents
Process and apparatus for heat setting biaxially oriented tubular polyethylene terephthalate filmsInfo
- Publication number
- CA1064210A CA1064210A CA237,232A CA237232A CA1064210A CA 1064210 A CA1064210 A CA 1064210A CA 237232 A CA237232 A CA 237232A CA 1064210 A CA1064210 A CA 1064210A
- Authority
- CA
- Canada
- Prior art keywords
- film
- heat setting
- tubular
- heating
- heat
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
- B29C71/02—Thermal after-treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/28—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of blown tubular films, e.g. by inflation
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S264/00—Plastic and nonmetallic article shaping or treating: processes
- Y10S264/90—Direct application of fluid pressure differential to shape, reshape, i.e. distort, or sustain an article or preform and heat-setting, i.e. crystallizing of stretched or molecularly oriented portion thereof
- Y10S264/902—Production of continuous length
Abstract
PROCESS AND APPARATUS FOR
HEAT SETTING BIAXIALLY ORIENTED
TUBULAR POLYETHYLENE TEREPHTHALATE FILMS
Abstract of the Disclosure A process for continuously heat setting a tubular film of biaxially oriented polyethylene terephthalate in a state expanded with a gaseous material and taking the heat set film up on a winder which comprises carrying out the heat setting in a heat setting chamber wherein the temperature is controlled so as to be initially in the range of about 220°C.-240°C. in the first zone of heat setting and thereafter declines to about 195°C.-215°C. in the final zone while the length of the film is increased about 2% - 7% and the diameter of the film is reduced about 5 - 15% from the corresponding dimensions of the film before heat setting, the film then being taken up by a rotary winder. An apparatus for carrying out the described process is also provided which comprises a heating chamber having heat-ing means dividing the chamber into zones so as to supply a hot blast in each zone of a different temperature from the other zones and rotatable means for controlling the stretch and shrink-age of the tubular film in the heating chamber and handling the film after it leaves the chamber comprising adjustable pinch rolls, film collapsing means and a winder, all mounted in fixed relation to one another.
HEAT SETTING BIAXIALLY ORIENTED
TUBULAR POLYETHYLENE TEREPHTHALATE FILMS
Abstract of the Disclosure A process for continuously heat setting a tubular film of biaxially oriented polyethylene terephthalate in a state expanded with a gaseous material and taking the heat set film up on a winder which comprises carrying out the heat setting in a heat setting chamber wherein the temperature is controlled so as to be initially in the range of about 220°C.-240°C. in the first zone of heat setting and thereafter declines to about 195°C.-215°C. in the final zone while the length of the film is increased about 2% - 7% and the diameter of the film is reduced about 5 - 15% from the corresponding dimensions of the film before heat setting, the film then being taken up by a rotary winder. An apparatus for carrying out the described process is also provided which comprises a heating chamber having heat-ing means dividing the chamber into zones so as to supply a hot blast in each zone of a different temperature from the other zones and rotatable means for controlling the stretch and shrink-age of the tubular film in the heating chamber and handling the film after it leaves the chamber comprising adjustable pinch rolls, film collapsing means and a winder, all mounted in fixed relation to one another.
Description
F.N. 911,858 1064Z~0 PROCESS AND APPARATUS FOR
HEAT SETTING BIAXIALLY ORIENTED
~UBULAR POLYETHYLENE TEREPHTHALATE FILMS
Background of the Invention The present invention relates to a process and an apparatus for producing heat set polyester films 1n an advan-tageous manner from a biaxially oriented tubular polyethylene terephthalate film.
It is necessary that packaging films have good dimen-sional stability. This dimensional stability is given to flat webs of biaxially oriented polyethylene terephthalate fllms by a heat setting process. Usually heat setting is carried out in a tenter stretching process wherein the film web ls stretched ` and then heat set by hot air while being supported at its edges by means of clips of the tenter device used in the process.
On the other hand, in a tubular stretchlng process, heat setting by enclosing the air in the interior of a tubular film and expanding the result~ng bubble by air pressure ls known, as are heat setting by 1nsertion of a mandrel 1n the interior of the film tube and sliding the tube over the mandrel, and heat setting a tubular film in a folded state in an oven after stretching.
In the process for heat settlng a tubular film while expanding with ~nternal alr pressure, it is difficult to maln-taln the fllm bubble in a deflnite shape because the tubular fllm to be heat set is unsupported and a conslderable fllm shrinkage stress occurs durlng heatlng; consequently it ls d1fficult to carry out continuously stable heat setting of the fllms. ~here ls the further problem in that physlcal proporties whlch are unlform ~ust after stretchlng are rather lnJured by the heat setting process~ng because of sway of the tubular f11m during heat settlng.
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Accordingly, heat setti~g of biaxially oriented tubu-lar films has not been carried out advantageously industrially because of having the above described defects, even thou~il the prior art of tubular heat setting is existent.
S In Japanese Patent Publication No. 12,038/1968 a process which comprises heat setting a tubular film by heating means which are divided into multistage rooms along the running d1rection of the tubular film, wherein a su1table pressure 1s applied to each room, while an exterior pressure 1s applied to the tubular film so that the diameter of the tubular film after the heat processing means is smaller than a diameter of the stretched tubular film just prior to heat setting. However, this process is difficult to put in practical use because con-trol of the pressure is complicated.
SummarY of the Invention The present invention relates to a process for pro-ducing heat set tubular films having uniform physical proper-ties, which films are unmarred by stripes caused by folding and which films have an excellent appearance.
The invention comprises a continuous process for heat setting of a tubular film of biaxially oriented polyethyl~ -ene terephthalate in an expanded state by the use of gas pressure wherein the film is initially heated by a hot blast in the range of 220C. - 240C., which temperature is then gradually reduced until it it is in the range of about 195C. - 215C. During heating the diameter of the f11m tube is decreased in the range of about 5X - 15X wh11e the film is stretched in the range of about 2~ - 7~ 1n the running direction of the film. The heat set film is then ~ken up by using a rotary w1nder which inhibits sway of the film during heat sett1ng. An apparatus for producing the heat set tubular b1ax1ally oriented film 1s also provided, which comprises a heating chamber having first and second pairs of nip rolls located respectively at the entrance to and exit from the heat setting chamber. Heating means are provided in the chamber to create a plurality of heating zones in the chamber for the tubular film bubble supported by and between said pairs of nip rolls, each heating means being capable of - -blowing a hot blast against the tubular film bubble in the heating chamber, the temperatu~e of the heating units being independently adjustable; film collapsing means and winding means for simultaneously rotating in a fixed relationship to each other are provided at the film chamber outlet for winding the heat set tubular film.
According to the invention there is provided in the process for producing polyethylene terephthalate film which comprises a step for heat ~, . .
, setting a tubular biaxially oriented polyethylene terephthalate film by continuously heating a film bubble expanded by a gas pressure, the improve-i ment comprising said heating being carried out by blowing hot gaseous blasts against the surface of the film bubble the temperature of the hot blasts on the film being about 220C. -240C. at the first stage of heat setting and declining to about 195& .-215C. at the final stage of heat setting, and the diameter of the tubular film during heat setting being reduced -about 5%-15~ of that before heating and the length thereof being stretched ~ -~ about 2%-7% of that before heating.
- According to another aspect of the invention, there is provided ~,~ an apparatus for producing tubular biaxially oriented films which comprises a heat setting chamber which has a plurality of means for blowing hot blasts, each of said hot blast blowing means having its own heating controls j ~ whereby said chamber is adapted for division into at least two heating 3 stages; two pairs of nip rolls for supporting and conveying the tubular film, one pair of said nip rolls being located at the inlet to said heat setting chamber and the other pair of said nip rolls being located at the ~ ~ -outlet of said hoat setting chamber; means for moving the outlet nip rolls toward and away from the outlet side of said heat setting chamber to control diametric shrinkage of the film during heat setting; cooling means mounted ~ - 3 -B ~:
-between said outlet pair of nip rolls and said heat setting chamber for cooling the film heated by said hot blast blowing means; and rotatable means mounted adjacent said cooling means for taking up the heat set film after cooling, said rotatable means having film collapsing means and widening means fixedly mounted thereon in fixed relationship to said cooling means.
i Figure 1 is a plan of the heating chamber of the tubular heat setting process.
Figure 2 is a diagram of the heat setting apparatus.
Figure 1 is a section plan of the essential point of the process for carrying out tubular heat setting, wherein a biaxially --oriented tubular film 1 is supported by a pair of nip rolls 2, the air is then enclosed in the film and the film is heated by introducing into " `
heat setting chamber 4a. The film is then taken by another pair of - nip rolls 3, and is collapsed and taken up on a winder. Though the , ~ tubular film supplied to the heat setting means rapidly shrinks with a shrinkage stress due to heating to reduce its diameterJ the film gradually expands again as heat setting proceeds and the shrinkage stress decreases. The re-expansion finishes when the shrinkage stress disappears, and the film passes through the latter half part of the ` chamber at its final definite diameter to conclude the heat setting.
The heat setting temperature of a biaxially oriented ; ,.
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i ~064Z10 polyethylene terephthdlate film having a meltlng point of 265C.
is usually in a range of 180 - 240C. If the heat setting is started at 180C. and the temperature is gradually elevated and ~ -kept finally at 240C., the tubular film exhibits a behavior wherein the diameter of the film becomes minimum at an inlet area of the heating zone of the heat setting means and then it gradually increases by expansion. However, a phenomenon of period~c sway occurs on the tubular f11m as it is being heat - set. This sway occurs intermittently, and un~form heat sett1ng cannot be carried out due to the film sway, which sway prevents the achievement of a definite uniform final film shape. Con- -sequently, physical properties of the film products, such as ; the degree of shrinkage, deteriorate.
We have found that if the highest heating 1s achteved as the film is introduced into the heat setting chamber at the beginning of the heat setting cycle and the temperature is gradually reduced thereafter during the balance of the cycle, the diameter o~ the tubular film rapidly decreases with shrink-age as soon as the film is introduced into the heat sett1ng means and thereafter gradually expands until the diameter ' reaches a definite value after the film passed through about ~ ~
l/3 of the whole ?ength of the chamber, wtth hardly any change - ~ -~-~ in d1ameter thereafter. While the sway phenomenon still occurs, the 1nterval between sway undulations increases and the degree of sway decreases suff1cientiy to provide better un1form1ty of phystcal properties 1n the f1nal product.
In the case that the 1nterior of the chamber is main-~; ta~ned at a defin1te temperature throughout its length, ~.e.~
1n the runn1ng d~rect1On of the tubular fllm, the fllm sway 1S
s9 pronounced that un1form heat settlng cannQt be carr1ed out.
It has been ascerta1ned that the above descr~bed swayphenomenon during the heat settlng depends upon not only a ~ 4 -, -,, . , . - : .
temperature of heating the film but is related to dimensional changes of the film. Thus, where the diameter of the tubular film after heat setting is equalized with the diameter thereof , just after stretching and prior to heat setting, the sway of the film does not stop. As the result of studying dimensional changes in the longitudinal and transverse d~rections from the viewpo~nt of the sway, it has been found that smooth and un~form heat setting can be carried out continuously without generatlon of the sway and a residual shrinkage stress, if the film as it is being heat set is stretched about 2% - 7% and preferably about 2% - 4~ in the running direction (machine direction) and shrunk about 5X - 15% and preferably about lOX - 15% in the diameter direction (transverse direction) while the temperature , is gradually reduced from about 220C. - 240C. and preferably about 230C. - 240C. to about 195C. - 215C. and preferably about 195C. - 205C.
Control of dimensiona1 changes, i.e., stretch and shrink, of the film bubble during heat setting is brought about initially by adjusting the air volume inside the tubular fi1m at start up and thereafter by changing the angle of collapse of the bubble as it exits from the heat setting chamber, e.g., by moving .... ;
the lower nip rolls toward or away from the chamber exit. Within ~ -the stretch and shrink limits sway is inhibited greatly and uni-~ , - form product results even with the high temperatures used in heat setting. While little or no sway occurs at low heat setting temperatures, e.g. 180-200C., striping of the tubular film is ..
not removed and the phystcal properties of the heat set film are impaired.
In carrying out biaxial stretching of the tubular fllm, a non-stretched tubular film is reheated between low speed nip rolls provided at the inlet of the stretching means and high speed nip rolls provided at the outlet while the film is ~, . . - , - :. :.
... ..
,: . ,, :
10642~0 expanded with an interior gas pressure.
Accordingly, since the low-speed and high-speed nip rolls nip the film with tolerably high pressure so as to prevent leakage of the interior gas pressure, the folds of the non-stretched film at passing through the low-speed nip rolls and the folds of the biaxially oriented film at passing through the high-speed nip rolls whiten in stripe-like due to stress crack. Still, there is the process which does not carry out nipping at the low-speed roll part. In this case, however, it is also inevitable that the folds at the high-speed n~p roll part whiten.
In the case of taking up the tubular film as a tubular state or as two flat films by slitting both film edges, it has been known to carry out rotary winding by which unevenness of a film roll shape does not occur because of dispersion of uneven thickness of the film in the transverse direction of the final roll. Since the unevenness of film roll shape remarkably injures flatness of the film, it is not too much to say that the rotary wlnding is practically indispensable in the case of rlgid films such as a blaxially oriented polyester film. However, it is not possible to produce the film roll which can be practically used, because the tubular film after biaxial stretching has stripes ; caused by foldlng as descr1bed above and the stripes always move from one film list to the other list along the axis of the fllm roll at rotary winding when the stripes do not disappear during heat setting.
If the rotary winding ls not carried out, the str1pes caused by folding are always exlstent on both film lists (ln the case of taking up as a tubular fllm). While they can be remo~ed by sllttlng ~in the case of taking up as two flat fllms after sllttlng both film lists), it is inevltable that the unevenness of fllm roll shape on the film roll wlll occur, evldenclng a ~ .
.
remarkable deterioration of flatness of the fi1m roll.
Thus, experiments hdve made clear the importance of removing co~pletely the stripes caused by folding on the film at the heat setting step in order to produce films having a good flatness. Therefore,it is indispensable to have a zone wherein the heating temperature is at least about 220C. and preferably above about 230C. in the heat sett~ng section or chamber of the apparatus.
It is not necessary that the whole of the heat setting chamber through which the tubular film passes has a temperature above about ~20C. It is sufficient for stripe removal that the tubular film pass through such a high temperature zone for only a few seconds. It is preferred that only the first l/3 - l/5 of the whole length of the heat setting chamber have a tempera-ture above about 220C. As noted previously, where the entireheat setting apparatus has a constant temperature above about 220C., the sway of the film is remarkably enhanced.
~ The non-stretched film can be produced by the process ; which comprises extruding molten polyethylene terephthalate from an annular die and cooling directly by apply1ng cold water on both surfaces of the fllm. Further, the biaxial stretching ls carr1ed out by the process which comprises expanding a tubular film by heating while enclosing the air in the interior of the film to stretch in the transverse direction and stretching at the same time in the longltudinal direction by a difference of speeds of the nip rolls located at the upper posltion and the lower position. (For example, biaxial stretching ~s carried out by the process described in U.S. Patent 3,788,503). ~-In the following, the heat settlng apparatus and the process for heat setting are illustrated with reference to Figure 2, As descrlbed above, a biaxlally orlented tubular film l :' ... .. .
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is introduced lnto a heat settlng apparatus 4 through nlp rolls 2. The film after heat setting by heating with hot air blasts blown from a holed plate 7 is collapsed and folded by ; collapsing frames or rolls 13, drawn by nip rolls 3 and taken up on a winder by a rotary winding means lO to produce a finished product ll. The nip rolls 3 are movable upwards and downwards to control the final d7ameter of the tubular film in the heat setting apparatus. The heat setting apparatus 4 1s equipped with air heating means comprising heaters 6 and fans 5 by which hot air blasts at the desired temperature are blown 1nto the chamber 4a. Further, in this Figure, the apparatus is divided into four zones, wherein the temperature of each zone can be ad~usted independently with the air heating means for that zone. Each zone is equipped with an exhaust system by wh1ch the 15 influence of the hot blast of each zone upon the other zones ls ;~
minimized. In order to carry out uniform blowing of the hot blasts, the holed plate 7 is located parallel to or concentric with the film surface. Hot blast suction nozzles 8 and 8' at -~ the heating chamber 4a inlet and outlet respect1vely provide an 20 alr curtain so that exterior air streams do not flow into the ;
heat setting chamber 4a of the apparatus 4. Cooling ring 9 beneath the nozzles 8 provide means for cooling the heat set fllm. Collapser 13, ntp rolls 3 and a winder 14 are mounted on ~t~ a turn table 12 and rotate or oscillate simultaneously therewith Z5 ln a fixed relationsh1p to each other. The rotary w1nder moans :::
:~ or assembly lO comprises the winder 14, gu~de rolls 15 and tho . turn table 12.
Tho biaxially orientod film l is heated in the f1rst zono of tho heat setting apparatus 4 with, for example, a hot blast of 240C., heated ~n the second, third and last zones wlth hot blasts each having a lower temperature than the one precoding 1t, the fourth zone having, for example, d hot blast of 200C.
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The above descri~ed temperature of the hot blasts means an averdge temperature of the hot blast in each zone. But it is preferred that the distribution of the temperature range in each zone be as narrow as possible. Though hot blasts are used for heating the film, they may be combined with infrared ray heaters, if desired.
In carry~ng out heat sett~ng, the revolv~ng rate of - the nip rolls 3 is about 2% - 7% higher than that of the nip rolls 2. At the same time, the diameter of the fllm at the out-let part of the heat setting apparatus is reduced about 5~ - lS~
smaller than that of the film at the inlet part by adjust~ng the vertical position of the nip rolls 3.
Though it is possible to osc~llate the rotary winder lO, it is preferred to rotate it in a definite direction. The rota-tion cycle depends on the speed of the runn1ng film and generally is about 20 minutes. The heat set film is then taken up on the w1nder in a collapsed tubular state. However, if necessary, the film may be taken up on the winder respectively after slitting both film edges to make two sheets.
The heat settlng apparatus may be a stand1ng vertical -type one as illustrated or it may be a horlzontal type one.
However, in the horizontal apparatus, the heating temperature for the film should vary only about lO~C. 1n the circumferential direction from inlet to outlet to bring about a uniform heat .3 25 setting operation. Accordingly, the standing type apparatus is preferred since the film runs downwards and greater leeway 1s poss1ble in temperature declination changes from the higher inlet temperature to the lower outlet temperature along the running direction of the film.
Thus, uniformly heat set polyethylene terephthaTate biax1ally oriented tubùlar film can be produced continuously and - smoothly.
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:, " 1064Zl~
Though the heat sett1ng chamber ls d1v1ded 1nto four zones in the above drawing, the number of zones is not lim~ted to four. But at least two zones are necessary.
In the following, the present invention is illustrated 5 in detail with reference to Examples.
,, Example 1 i Polyethylene terephthalate having a relat~ve v~scos1ty of 0.70 was melted at 287C. by us1ng an extruder and extruded from an annular die having a slit diameter of 75 mm. The ex-lO truded material was slid on a mandrel having a diameter of 66 mm.
~- which was placed just below the die. Cooling water was main-- tained at 20C. circulated inside the mandrel. At the same time the tube of film was cooled with cooling water in an external cooling bath at 20C. to produce a non-stretched film tube havlng r~, 15 a d1ameter of 66 mm. and a thickness of llO microns.
The film was then introduced into the stretching apparatus equipped with two pairs of nip rolls, and air was enclosed lnside the film to expand in the diametrlc d1rectlon by an alr pressure to make 200 mm. in the diameter. At the same 20 tlme the film was stretched 3.0 times in the longitudinal direc-. .
`~ tion by a difference of resolving rates of the nlp rolls to carry out biaxial stretching.
`, The resulting biaxially oriented f~lm was introduced , into the heat setting apparatus shown ln F~gure 2 at a feed rate`~ 25 of 20 m./min. to carry out heat sett1ng. In carrying out heat sett1ng, the hot blast temperature was 240C. 1n the first zone, 230C. in the second zone, 215C. in the thlrd zone and 200C.
ln the fourth zone and a blowing rate of the hot blasts was 12 m./m1n. This corresponds wlth a fllm heat transfer co-30 efflclent of about 50.
The diameter of the film tube was reduced during heat setting to 175 mm., whlch meant about 12.5X shrlnkage ln the ".
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transverse direction. The fllm take-up rate was 20.6 m./m~n , which was 3~ faster than the ~eed rate of the film to the heat setting apparatus. The inside diameter of the heat setting apparatus used was 400 mm. and the length thereof was 3.5 m.
The shape of the film bubble was maintained in a definite state during heat setting and no sway of the bubble was observed. Further, it was possible to operate safely and continuously for about 8 hours.
The resulting tubular biaxially oriented polyethylene terephthalate film was 15.5 microns thick, had a haze reading of 1.75, a tensile strength in the longitudinal direction of 1,980 kg./cm.2 and a tensile strength of 1,880 kg./cm.2 in the transverse direction, which was near1y a l to l ratio.
The heat shrinkage of the heat set tubular film, lS measured after dipping the film in silicone oil for lO seconds at 150C., was 0.4% in the longitudinal direction and 0.7% in the transverse direction, showing a good dimensional stability.
The film taken up by the rotary winder had a uniform appearance, all stripes caused by folding of the non-stretched film having disappeared.
Examples 2 - 5 The same biaxially oriented film as in Example l was ; heat set under conditions shown in Table l by means of the same; apparatus as shown in Figure 2 or an apparatus where1n the heatsetting chamber was divided in three or two stages. Physical .. ~
properties of the heat set film are shown in Table l.
The shape of the film bubble during heat setting was maintained in a def1nite state and no sway of the bubble was observed. Further, 1t was possible to operate safely and con-t1nuously for a long period of time.
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i Example No. 2 3 4 5 Heat setting conditions Film feeding rate m./min.20 15 lS 18 Film taking-up rate m./min.21.415.4 15.9 18.7 Percent stretching in % 7 2.7 6 3.9 longitudinal direction Diameter of film mm. 200 200 200 200 before heat setting - 10 Diameter of film mm. 190 185 172 180 after heat setting Percent shrinkage in % 5 7.5 14 10 transverse direction Number of hot blast 4 3 3 2 zones Temperature of hot blast 1st zone 240 220 220 230 2nd zone 230 210 210 215 3rd zone 215 200 195 -4th zone 200 - - -Properties of heat set film Thickness micron14 15 15.5 lS
Haze 1.8 1.8 1.8 1.85 Tensile strength Longitudinal dtrection kg./cm.22,0001,9501,970 1,950 Transverse direction kg./cm.2 1,900 1,850 1,800 1,850 Heat shrinkage Longitudinal direction X O.S 0.6 0.7 0.6 ~ Transverse direction % 0.9 0.9 0.8 0.8 .~ :
Table 2 following tabulates the results of a series of tubular fllm runs on the apparatus utll~zed in Examples 2 ~ 5 and is included for comparison purposes. The runs are numbered seria1ly from 1 through 20.
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Notes to Table 2 _ _ _ _ _ _ _ _ _ (Note l) The sway of film represents a degree of sway: --+ Little ++ Medium +++ Much (Note 2~ X : Stripes did not disappear * : Stripes disappeared (Note 3) Heat shrinkage ratio after steep1ng in s~licone oil at 150C. for lO seconds.
With respect to run l, where the heat setting was carr1ed out at 180C. without any stretching (or shrink~ng) of the tubular film in any directiion, considerable sway occurred and the stripes caused by folding at the nlp rolls 2 did not disappear.
With respect to run 2, the film was stretched and shrunk during heat setting as in the present ~nvention and the degree of sway decreased markedly, but the stripes caused by fold~ng did not disappear.
With respect to run 3, the film was stretched and shrunk during heat setting as in the present lnvent~on but heat setting was carried out at a definite temperature of 200C. and considerable sway occurred.
In runs 4 through 9 the film was passed through at least one heating zone of above 220C. during heat settlng but ~ithout stretch~ng or shrinking and vigorous sway occurred. In , run 5, the sway continued for 20 seconds, In runs 8, lO and ll wherein the film was treated at the declining temperature ranges of the present 1nventlon but w1thout stretchtng (or shrink1ng), the degree of sway decreased and the t~me of each sway was only about 4 seconds.
In runs 12 and 13 stretch~ng or shr1nking was carried out as 1n the present invent~on but at a fixed temperature , ~ ' ~' . ' - : .
. . . .
... .
~ 0642~0 above 220C. (230C. or 240C.), the str1pes caused by fold1ng were not observed but considerable swdy occurred.
In runs 14 - 20 where the ~1lm was heat set at the declining temperature ranges of the present invention bùt stretching and shrinking were carried out under conditions outside of the present invent10n, Swdy was not re~oved.
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HEAT SETTING BIAXIALLY ORIENTED
~UBULAR POLYETHYLENE TEREPHTHALATE FILMS
Background of the Invention The present invention relates to a process and an apparatus for producing heat set polyester films 1n an advan-tageous manner from a biaxially oriented tubular polyethylene terephthalate film.
It is necessary that packaging films have good dimen-sional stability. This dimensional stability is given to flat webs of biaxially oriented polyethylene terephthalate fllms by a heat setting process. Usually heat setting is carried out in a tenter stretching process wherein the film web ls stretched ` and then heat set by hot air while being supported at its edges by means of clips of the tenter device used in the process.
On the other hand, in a tubular stretchlng process, heat setting by enclosing the air in the interior of a tubular film and expanding the result~ng bubble by air pressure ls known, as are heat setting by 1nsertion of a mandrel 1n the interior of the film tube and sliding the tube over the mandrel, and heat setting a tubular film in a folded state in an oven after stretching.
In the process for heat settlng a tubular film while expanding with ~nternal alr pressure, it is difficult to maln-taln the fllm bubble in a deflnite shape because the tubular fllm to be heat set is unsupported and a conslderable fllm shrinkage stress occurs durlng heatlng; consequently it ls d1fficult to carry out continuously stable heat setting of the fllms. ~here ls the further problem in that physlcal proporties whlch are unlform ~ust after stretchlng are rather lnJured by the heat setting process~ng because of sway of the tubular f11m during heat settlng.
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Accordingly, heat setti~g of biaxially oriented tubu-lar films has not been carried out advantageously industrially because of having the above described defects, even thou~il the prior art of tubular heat setting is existent.
S In Japanese Patent Publication No. 12,038/1968 a process which comprises heat setting a tubular film by heating means which are divided into multistage rooms along the running d1rection of the tubular film, wherein a su1table pressure 1s applied to each room, while an exterior pressure 1s applied to the tubular film so that the diameter of the tubular film after the heat processing means is smaller than a diameter of the stretched tubular film just prior to heat setting. However, this process is difficult to put in practical use because con-trol of the pressure is complicated.
SummarY of the Invention The present invention relates to a process for pro-ducing heat set tubular films having uniform physical proper-ties, which films are unmarred by stripes caused by folding and which films have an excellent appearance.
The invention comprises a continuous process for heat setting of a tubular film of biaxially oriented polyethyl~ -ene terephthalate in an expanded state by the use of gas pressure wherein the film is initially heated by a hot blast in the range of 220C. - 240C., which temperature is then gradually reduced until it it is in the range of about 195C. - 215C. During heating the diameter of the f11m tube is decreased in the range of about 5X - 15X wh11e the film is stretched in the range of about 2~ - 7~ 1n the running direction of the film. The heat set film is then ~ken up by using a rotary w1nder which inhibits sway of the film during heat sett1ng. An apparatus for producing the heat set tubular b1ax1ally oriented film 1s also provided, which comprises a heating chamber having first and second pairs of nip rolls located respectively at the entrance to and exit from the heat setting chamber. Heating means are provided in the chamber to create a plurality of heating zones in the chamber for the tubular film bubble supported by and between said pairs of nip rolls, each heating means being capable of - -blowing a hot blast against the tubular film bubble in the heating chamber, the temperatu~e of the heating units being independently adjustable; film collapsing means and winding means for simultaneously rotating in a fixed relationship to each other are provided at the film chamber outlet for winding the heat set tubular film.
According to the invention there is provided in the process for producing polyethylene terephthalate film which comprises a step for heat ~, . .
, setting a tubular biaxially oriented polyethylene terephthalate film by continuously heating a film bubble expanded by a gas pressure, the improve-i ment comprising said heating being carried out by blowing hot gaseous blasts against the surface of the film bubble the temperature of the hot blasts on the film being about 220C. -240C. at the first stage of heat setting and declining to about 195& .-215C. at the final stage of heat setting, and the diameter of the tubular film during heat setting being reduced -about 5%-15~ of that before heating and the length thereof being stretched ~ -~ about 2%-7% of that before heating.
- According to another aspect of the invention, there is provided ~,~ an apparatus for producing tubular biaxially oriented films which comprises a heat setting chamber which has a plurality of means for blowing hot blasts, each of said hot blast blowing means having its own heating controls j ~ whereby said chamber is adapted for division into at least two heating 3 stages; two pairs of nip rolls for supporting and conveying the tubular film, one pair of said nip rolls being located at the inlet to said heat setting chamber and the other pair of said nip rolls being located at the ~ ~ -outlet of said hoat setting chamber; means for moving the outlet nip rolls toward and away from the outlet side of said heat setting chamber to control diametric shrinkage of the film during heat setting; cooling means mounted ~ - 3 -B ~:
-between said outlet pair of nip rolls and said heat setting chamber for cooling the film heated by said hot blast blowing means; and rotatable means mounted adjacent said cooling means for taking up the heat set film after cooling, said rotatable means having film collapsing means and widening means fixedly mounted thereon in fixed relationship to said cooling means.
i Figure 1 is a plan of the heating chamber of the tubular heat setting process.
Figure 2 is a diagram of the heat setting apparatus.
Figure 1 is a section plan of the essential point of the process for carrying out tubular heat setting, wherein a biaxially --oriented tubular film 1 is supported by a pair of nip rolls 2, the air is then enclosed in the film and the film is heated by introducing into " `
heat setting chamber 4a. The film is then taken by another pair of - nip rolls 3, and is collapsed and taken up on a winder. Though the , ~ tubular film supplied to the heat setting means rapidly shrinks with a shrinkage stress due to heating to reduce its diameterJ the film gradually expands again as heat setting proceeds and the shrinkage stress decreases. The re-expansion finishes when the shrinkage stress disappears, and the film passes through the latter half part of the ` chamber at its final definite diameter to conclude the heat setting.
The heat setting temperature of a biaxially oriented ; ,.
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i ~064Z10 polyethylene terephthdlate film having a meltlng point of 265C.
is usually in a range of 180 - 240C. If the heat setting is started at 180C. and the temperature is gradually elevated and ~ -kept finally at 240C., the tubular film exhibits a behavior wherein the diameter of the film becomes minimum at an inlet area of the heating zone of the heat setting means and then it gradually increases by expansion. However, a phenomenon of period~c sway occurs on the tubular f11m as it is being heat - set. This sway occurs intermittently, and un~form heat sett1ng cannot be carried out due to the film sway, which sway prevents the achievement of a definite uniform final film shape. Con- -sequently, physical properties of the film products, such as ; the degree of shrinkage, deteriorate.
We have found that if the highest heating 1s achteved as the film is introduced into the heat setting chamber at the beginning of the heat setting cycle and the temperature is gradually reduced thereafter during the balance of the cycle, the diameter o~ the tubular film rapidly decreases with shrink-age as soon as the film is introduced into the heat sett1ng means and thereafter gradually expands until the diameter ' reaches a definite value after the film passed through about ~ ~
l/3 of the whole ?ength of the chamber, wtth hardly any change - ~ -~-~ in d1ameter thereafter. While the sway phenomenon still occurs, the 1nterval between sway undulations increases and the degree of sway decreases suff1cientiy to provide better un1form1ty of phystcal properties 1n the f1nal product.
In the case that the 1nterior of the chamber is main-~; ta~ned at a defin1te temperature throughout its length, ~.e.~
1n the runn1ng d~rect1On of the tubular fllm, the fllm sway 1S
s9 pronounced that un1form heat settlng cannQt be carr1ed out.
It has been ascerta1ned that the above descr~bed swayphenomenon during the heat settlng depends upon not only a ~ 4 -, -,, . , . - : .
temperature of heating the film but is related to dimensional changes of the film. Thus, where the diameter of the tubular film after heat setting is equalized with the diameter thereof , just after stretching and prior to heat setting, the sway of the film does not stop. As the result of studying dimensional changes in the longitudinal and transverse d~rections from the viewpo~nt of the sway, it has been found that smooth and un~form heat setting can be carried out continuously without generatlon of the sway and a residual shrinkage stress, if the film as it is being heat set is stretched about 2% - 7% and preferably about 2% - 4~ in the running direction (machine direction) and shrunk about 5X - 15% and preferably about lOX - 15% in the diameter direction (transverse direction) while the temperature , is gradually reduced from about 220C. - 240C. and preferably about 230C. - 240C. to about 195C. - 215C. and preferably about 195C. - 205C.
Control of dimensiona1 changes, i.e., stretch and shrink, of the film bubble during heat setting is brought about initially by adjusting the air volume inside the tubular fi1m at start up and thereafter by changing the angle of collapse of the bubble as it exits from the heat setting chamber, e.g., by moving .... ;
the lower nip rolls toward or away from the chamber exit. Within ~ -the stretch and shrink limits sway is inhibited greatly and uni-~ , - form product results even with the high temperatures used in heat setting. While little or no sway occurs at low heat setting temperatures, e.g. 180-200C., striping of the tubular film is ..
not removed and the phystcal properties of the heat set film are impaired.
In carrying out biaxial stretching of the tubular fllm, a non-stretched tubular film is reheated between low speed nip rolls provided at the inlet of the stretching means and high speed nip rolls provided at the outlet while the film is ~, . . - , - :. :.
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10642~0 expanded with an interior gas pressure.
Accordingly, since the low-speed and high-speed nip rolls nip the film with tolerably high pressure so as to prevent leakage of the interior gas pressure, the folds of the non-stretched film at passing through the low-speed nip rolls and the folds of the biaxially oriented film at passing through the high-speed nip rolls whiten in stripe-like due to stress crack. Still, there is the process which does not carry out nipping at the low-speed roll part. In this case, however, it is also inevitable that the folds at the high-speed n~p roll part whiten.
In the case of taking up the tubular film as a tubular state or as two flat films by slitting both film edges, it has been known to carry out rotary winding by which unevenness of a film roll shape does not occur because of dispersion of uneven thickness of the film in the transverse direction of the final roll. Since the unevenness of film roll shape remarkably injures flatness of the film, it is not too much to say that the rotary wlnding is practically indispensable in the case of rlgid films such as a blaxially oriented polyester film. However, it is not possible to produce the film roll which can be practically used, because the tubular film after biaxial stretching has stripes ; caused by foldlng as descr1bed above and the stripes always move from one film list to the other list along the axis of the fllm roll at rotary winding when the stripes do not disappear during heat setting.
If the rotary winding ls not carried out, the str1pes caused by folding are always exlstent on both film lists (ln the case of taking up as a tubular fllm). While they can be remo~ed by sllttlng ~in the case of taking up as two flat fllms after sllttlng both film lists), it is inevltable that the unevenness of fllm roll shape on the film roll wlll occur, evldenclng a ~ .
.
remarkable deterioration of flatness of the fi1m roll.
Thus, experiments hdve made clear the importance of removing co~pletely the stripes caused by folding on the film at the heat setting step in order to produce films having a good flatness. Therefore,it is indispensable to have a zone wherein the heating temperature is at least about 220C. and preferably above about 230C. in the heat sett~ng section or chamber of the apparatus.
It is not necessary that the whole of the heat setting chamber through which the tubular film passes has a temperature above about ~20C. It is sufficient for stripe removal that the tubular film pass through such a high temperature zone for only a few seconds. It is preferred that only the first l/3 - l/5 of the whole length of the heat setting chamber have a tempera-ture above about 220C. As noted previously, where the entireheat setting apparatus has a constant temperature above about 220C., the sway of the film is remarkably enhanced.
~ The non-stretched film can be produced by the process ; which comprises extruding molten polyethylene terephthalate from an annular die and cooling directly by apply1ng cold water on both surfaces of the fllm. Further, the biaxial stretching ls carr1ed out by the process which comprises expanding a tubular film by heating while enclosing the air in the interior of the film to stretch in the transverse direction and stretching at the same time in the longltudinal direction by a difference of speeds of the nip rolls located at the upper posltion and the lower position. (For example, biaxial stretching ~s carried out by the process described in U.S. Patent 3,788,503). ~-In the following, the heat settlng apparatus and the process for heat setting are illustrated with reference to Figure 2, As descrlbed above, a biaxlally orlented tubular film l :' ... .. .
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is introduced lnto a heat settlng apparatus 4 through nlp rolls 2. The film after heat setting by heating with hot air blasts blown from a holed plate 7 is collapsed and folded by ; collapsing frames or rolls 13, drawn by nip rolls 3 and taken up on a winder by a rotary winding means lO to produce a finished product ll. The nip rolls 3 are movable upwards and downwards to control the final d7ameter of the tubular film in the heat setting apparatus. The heat setting apparatus 4 1s equipped with air heating means comprising heaters 6 and fans 5 by which hot air blasts at the desired temperature are blown 1nto the chamber 4a. Further, in this Figure, the apparatus is divided into four zones, wherein the temperature of each zone can be ad~usted independently with the air heating means for that zone. Each zone is equipped with an exhaust system by wh1ch the 15 influence of the hot blast of each zone upon the other zones ls ;~
minimized. In order to carry out uniform blowing of the hot blasts, the holed plate 7 is located parallel to or concentric with the film surface. Hot blast suction nozzles 8 and 8' at -~ the heating chamber 4a inlet and outlet respect1vely provide an 20 alr curtain so that exterior air streams do not flow into the ;
heat setting chamber 4a of the apparatus 4. Cooling ring 9 beneath the nozzles 8 provide means for cooling the heat set fllm. Collapser 13, ntp rolls 3 and a winder 14 are mounted on ~t~ a turn table 12 and rotate or oscillate simultaneously therewith Z5 ln a fixed relationsh1p to each other. The rotary w1nder moans :::
:~ or assembly lO comprises the winder 14, gu~de rolls 15 and tho . turn table 12.
Tho biaxially orientod film l is heated in the f1rst zono of tho heat setting apparatus 4 with, for example, a hot blast of 240C., heated ~n the second, third and last zones wlth hot blasts each having a lower temperature than the one precoding 1t, the fourth zone having, for example, d hot blast of 200C.
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The above descri~ed temperature of the hot blasts means an averdge temperature of the hot blast in each zone. But it is preferred that the distribution of the temperature range in each zone be as narrow as possible. Though hot blasts are used for heating the film, they may be combined with infrared ray heaters, if desired.
In carry~ng out heat sett~ng, the revolv~ng rate of - the nip rolls 3 is about 2% - 7% higher than that of the nip rolls 2. At the same time, the diameter of the fllm at the out-let part of the heat setting apparatus is reduced about 5~ - lS~
smaller than that of the film at the inlet part by adjust~ng the vertical position of the nip rolls 3.
Though it is possible to osc~llate the rotary winder lO, it is preferred to rotate it in a definite direction. The rota-tion cycle depends on the speed of the runn1ng film and generally is about 20 minutes. The heat set film is then taken up on the w1nder in a collapsed tubular state. However, if necessary, the film may be taken up on the winder respectively after slitting both film edges to make two sheets.
The heat settlng apparatus may be a stand1ng vertical -type one as illustrated or it may be a horlzontal type one.
However, in the horizontal apparatus, the heating temperature for the film should vary only about lO~C. 1n the circumferential direction from inlet to outlet to bring about a uniform heat .3 25 setting operation. Accordingly, the standing type apparatus is preferred since the film runs downwards and greater leeway 1s poss1ble in temperature declination changes from the higher inlet temperature to the lower outlet temperature along the running direction of the film.
Thus, uniformly heat set polyethylene terephthaTate biax1ally oriented tubùlar film can be produced continuously and - smoothly.
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Though the heat sett1ng chamber ls d1v1ded 1nto four zones in the above drawing, the number of zones is not lim~ted to four. But at least two zones are necessary.
In the following, the present invention is illustrated 5 in detail with reference to Examples.
,, Example 1 i Polyethylene terephthalate having a relat~ve v~scos1ty of 0.70 was melted at 287C. by us1ng an extruder and extruded from an annular die having a slit diameter of 75 mm. The ex-lO truded material was slid on a mandrel having a diameter of 66 mm.
~- which was placed just below the die. Cooling water was main-- tained at 20C. circulated inside the mandrel. At the same time the tube of film was cooled with cooling water in an external cooling bath at 20C. to produce a non-stretched film tube havlng r~, 15 a d1ameter of 66 mm. and a thickness of llO microns.
The film was then introduced into the stretching apparatus equipped with two pairs of nip rolls, and air was enclosed lnside the film to expand in the diametrlc d1rectlon by an alr pressure to make 200 mm. in the diameter. At the same 20 tlme the film was stretched 3.0 times in the longitudinal direc-. .
`~ tion by a difference of resolving rates of the nlp rolls to carry out biaxial stretching.
`, The resulting biaxially oriented f~lm was introduced , into the heat setting apparatus shown ln F~gure 2 at a feed rate`~ 25 of 20 m./min. to carry out heat sett1ng. In carrying out heat sett1ng, the hot blast temperature was 240C. 1n the first zone, 230C. in the second zone, 215C. in the thlrd zone and 200C.
ln the fourth zone and a blowing rate of the hot blasts was 12 m./m1n. This corresponds wlth a fllm heat transfer co-30 efflclent of about 50.
The diameter of the film tube was reduced during heat setting to 175 mm., whlch meant about 12.5X shrlnkage ln the ".
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transverse direction. The fllm take-up rate was 20.6 m./m~n , which was 3~ faster than the ~eed rate of the film to the heat setting apparatus. The inside diameter of the heat setting apparatus used was 400 mm. and the length thereof was 3.5 m.
The shape of the film bubble was maintained in a definite state during heat setting and no sway of the bubble was observed. Further, it was possible to operate safely and continuously for about 8 hours.
The resulting tubular biaxially oriented polyethylene terephthalate film was 15.5 microns thick, had a haze reading of 1.75, a tensile strength in the longitudinal direction of 1,980 kg./cm.2 and a tensile strength of 1,880 kg./cm.2 in the transverse direction, which was near1y a l to l ratio.
The heat shrinkage of the heat set tubular film, lS measured after dipping the film in silicone oil for lO seconds at 150C., was 0.4% in the longitudinal direction and 0.7% in the transverse direction, showing a good dimensional stability.
The film taken up by the rotary winder had a uniform appearance, all stripes caused by folding of the non-stretched film having disappeared.
Examples 2 - 5 The same biaxially oriented film as in Example l was ; heat set under conditions shown in Table l by means of the same; apparatus as shown in Figure 2 or an apparatus where1n the heatsetting chamber was divided in three or two stages. Physical .. ~
properties of the heat set film are shown in Table l.
The shape of the film bubble during heat setting was maintained in a def1nite state and no sway of the bubble was observed. Further, 1t was possible to operate safely and con-t1nuously for a long period of time.
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i Example No. 2 3 4 5 Heat setting conditions Film feeding rate m./min.20 15 lS 18 Film taking-up rate m./min.21.415.4 15.9 18.7 Percent stretching in % 7 2.7 6 3.9 longitudinal direction Diameter of film mm. 200 200 200 200 before heat setting - 10 Diameter of film mm. 190 185 172 180 after heat setting Percent shrinkage in % 5 7.5 14 10 transverse direction Number of hot blast 4 3 3 2 zones Temperature of hot blast 1st zone 240 220 220 230 2nd zone 230 210 210 215 3rd zone 215 200 195 -4th zone 200 - - -Properties of heat set film Thickness micron14 15 15.5 lS
Haze 1.8 1.8 1.8 1.85 Tensile strength Longitudinal dtrection kg./cm.22,0001,9501,970 1,950 Transverse direction kg./cm.2 1,900 1,850 1,800 1,850 Heat shrinkage Longitudinal direction X O.S 0.6 0.7 0.6 ~ Transverse direction % 0.9 0.9 0.8 0.8 .~ :
Table 2 following tabulates the results of a series of tubular fllm runs on the apparatus utll~zed in Examples 2 ~ 5 and is included for comparison purposes. The runs are numbered seria1ly from 1 through 20.
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Notes to Table 2 _ _ _ _ _ _ _ _ _ (Note l) The sway of film represents a degree of sway: --+ Little ++ Medium +++ Much (Note 2~ X : Stripes did not disappear * : Stripes disappeared (Note 3) Heat shrinkage ratio after steep1ng in s~licone oil at 150C. for lO seconds.
With respect to run l, where the heat setting was carr1ed out at 180C. without any stretching (or shrink~ng) of the tubular film in any directiion, considerable sway occurred and the stripes caused by folding at the nlp rolls 2 did not disappear.
With respect to run 2, the film was stretched and shrunk during heat setting as in the present ~nvention and the degree of sway decreased markedly, but the stripes caused by fold~ng did not disappear.
With respect to run 3, the film was stretched and shrunk during heat setting as in the present lnvent~on but heat setting was carried out at a definite temperature of 200C. and considerable sway occurred.
In runs 4 through 9 the film was passed through at least one heating zone of above 220C. during heat settlng but ~ithout stretch~ng or shrinking and vigorous sway occurred. In , run 5, the sway continued for 20 seconds, In runs 8, lO and ll wherein the film was treated at the declining temperature ranges of the present 1nventlon but w1thout stretchtng (or shrink1ng), the degree of sway decreased and the t~me of each sway was only about 4 seconds.
In runs 12 and 13 stretch~ng or shr1nking was carried out as 1n the present invent~on but at a fixed temperature , ~ ' ~' . ' - : .
. . . .
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~ 0642~0 above 220C. (230C. or 240C.), the str1pes caused by fold1ng were not observed but considerable swdy occurred.
In runs 14 - 20 where the ~1lm was heat set at the declining temperature ranges of the present invention bùt stretching and shrinking were carried out under conditions outside of the present invent10n, Swdy was not re~oved.
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Claims (6)
1. In the process for producing polyethylene tere-phthalate film which comprises a step for heat setting a tubular biaxially oriented polyethylene terephthalate film by continu-ously heating a film bubble expanded by a gas pressure, the improvement comprising:
(a) said heating being carried out by blowing hot gaseous blasts against the surface of the film bubble, the tempera-ture of the hot blasts on the film being about 220°C.-240°C.
at the first stage of heat setting and declining to about 195°C.-215°C. at the final stage of heat setting, and (b) the diameter of the tubular film during heat setting being reduced about 5%-15% of that before heating and the length thereof being stretched about 2%-7% of that before heating.
(a) said heating being carried out by blowing hot gaseous blasts against the surface of the film bubble, the tempera-ture of the hot blasts on the film being about 220°C.-240°C.
at the first stage of heat setting and declining to about 195°C.-215°C. at the final stage of heat setting, and (b) the diameter of the tubular film during heat setting being reduced about 5%-15% of that before heating and the length thereof being stretched about 2%-7% of that before heating.
2. In the process as set forth in Claim 1, the tubular heat set film being taken up on a winder in a folded state while rotating said tubular film around the axis of the film.
3. In the process which comprises heat setting a tubular biaxially oriented polyethylene terephthalate film by continuously heating a film bubble expanded by a gas pressure, and taking up on a winder, the improvement comprising:
(a) said heating being carried out by blowing hot gaseous blasts against the surface of the film bubble with the temperature of the hot blasts against the film being about 220°C.-240°C. at the first stage of heat setting and declining to about 195°C.-215°C. at the final stage of heat setting, (b) the diameter of the tubular film during heat setting being reduced about 5%-15% of that before heating and the length thereof being stretched about 2%-7% of that before heating.
and (c) the tubular heat set film being taken up on a winder in a folded state while rotating said tubular film around the axis of the film.
(a) said heating being carried out by blowing hot gaseous blasts against the surface of the film bubble with the temperature of the hot blasts against the film being about 220°C.-240°C. at the first stage of heat setting and declining to about 195°C.-215°C. at the final stage of heat setting, (b) the diameter of the tubular film during heat setting being reduced about 5%-15% of that before heating and the length thereof being stretched about 2%-7% of that before heating.
and (c) the tubular heat set film being taken up on a winder in a folded state while rotating said tubular film around the axis of the film.
4. In the process for producing polyethylene tere-phthalate films which comprises a step for heating setting a tubular biaxially oriented polyethylene terepththalate film by continuously heating a film bubble expanded by a gas pressure, the improvement comprising:
(a) said heating being carried out by blowing hot air blasts against the surface of the film bubble with the tempera-ture of the hot blast on the film being about 230°C.-240°C.
at the first stage of heat setting and with subsequent blasts thereafter gradually declining in temperature to about 195°C.-205°C. at the final stage of heat setting, and (b) the diameter of the tubular film during heat setting being reduced about 10%-15% of that before heating and the length thereof being stretched about 2%-4% of that before heating.
(a) said heating being carried out by blowing hot air blasts against the surface of the film bubble with the tempera-ture of the hot blast on the film being about 230°C.-240°C.
at the first stage of heat setting and with subsequent blasts thereafter gradually declining in temperature to about 195°C.-205°C. at the final stage of heat setting, and (b) the diameter of the tubular film during heat setting being reduced about 10%-15% of that before heating and the length thereof being stretched about 2%-4% of that before heating.
5. In the process which comprises heat setting a tubular biaxially oriented polyethylene terephthalate film by continuously heating a film bubble expanded by a gas pressure and taking up on a winder, the improvement comprising:
(a) said heating being carried out by blowing hot air blasts against the surface of the film bubble at a temperature of about 230°C.-240°C. at the first stage of heat setting, the temperature thereafter declining to about 195°C.-205°C.
at the final stage of heat setting, (b) the diameter of the tubular film during heat setting being reduced about 10%-15% of that before heating and the length thereof being stretched about 2%-4% of that before heating, and (c) the heat set tubular film being taken up on a winder in a folded state while rotating said tubular film around the axis of the film.
(a) said heating being carried out by blowing hot air blasts against the surface of the film bubble at a temperature of about 230°C.-240°C. at the first stage of heat setting, the temperature thereafter declining to about 195°C.-205°C.
at the final stage of heat setting, (b) the diameter of the tubular film during heat setting being reduced about 10%-15% of that before heating and the length thereof being stretched about 2%-4% of that before heating, and (c) the heat set tubular film being taken up on a winder in a folded state while rotating said tubular film around the axis of the film.
6. An apparatus for producing tubular biaxially oriented films which comprises:
(a) a heat setting chamber which has a plurality of means for blowing hot blasts, each of said hot blast blowing means having its own heating controls whereby said chamber is adapted for division into at least two heating stages;
(b) two pairs of nip rolls for supporting and conveying the tubular film, one pair of said nip rolls being located at the inlet to said heat setting chamber and the other pair of said nip rolls being located at the outlet of said heat setting chamber;
(c) means for moving the outlet nip rolls toward and away from the outlet side of said heat setting chamber to control diametric shrinkage of the film during heat setting;
(d) cooling means mounted between said outlet pair of nip rolls and said heat setting chamber for cooling the film heated by said hot blast blowing means; and (e) rotatable means mounted adjacent said cooling means for taking up the heat set film after cooling, said rotatable means having film collapsing means and winding means fixedly mounted thereon in fixed relationship to said cooling means.
(a) a heat setting chamber which has a plurality of means for blowing hot blasts, each of said hot blast blowing means having its own heating controls whereby said chamber is adapted for division into at least two heating stages;
(b) two pairs of nip rolls for supporting and conveying the tubular film, one pair of said nip rolls being located at the inlet to said heat setting chamber and the other pair of said nip rolls being located at the outlet of said heat setting chamber;
(c) means for moving the outlet nip rolls toward and away from the outlet side of said heat setting chamber to control diametric shrinkage of the film during heat setting;
(d) cooling means mounted between said outlet pair of nip rolls and said heat setting chamber for cooling the film heated by said hot blast blowing means; and (e) rotatable means mounted adjacent said cooling means for taking up the heat set film after cooling, said rotatable means having film collapsing means and winding means fixedly mounted thereon in fixed relationship to said cooling means.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11519874A JPS5529809B2 (en) | 1974-10-08 | 1974-10-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1064210A true CA1064210A (en) | 1979-10-16 |
Family
ID=14656774
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA237,232A Expired CA1064210A (en) | 1974-10-08 | 1975-10-07 | Process and apparatus for heat setting biaxially oriented tubular polyethylene terephthalate films |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US4061707A (en) |
| JP (1) | JPS5529809B2 (en) |
| CA (1) | CA1064210A (en) |
Families Citing this family (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5586719A (en) * | 1978-12-25 | 1980-06-30 | Chisso Eng Kk | Manufacturing device for tubular biaxial stretching film |
| GB2138349B (en) * | 1983-04-22 | 1987-06-03 | Metal Box Plc | Dimensionally stable thermoplastic tubular articles |
| DE3227945C2 (en) * | 1982-07-27 | 1986-07-24 | Naturin-Werk Becker & Co, 6940 Weinheim | Single-layer elastic tubular film made of polyamide for packaging pasty substances, in particular foods, which are packaged hot or are subjected to a heat treatment after being packaged, and a process for their production |
| US4536365A (en) * | 1983-12-22 | 1985-08-20 | American Cyanamid Company | Process for the manufacture of equally biaxially oriented film |
| JPS6160502U (en) * | 1984-09-26 | 1986-04-23 | ||
| DE8501177U1 (en) * | 1985-01-18 | 1986-05-22 | Alpine Ag, 8900 Augsburg | Pull-off device for plastic tubular films |
| DE3508626C1 (en) * | 1985-03-11 | 1986-02-27 | Windmöller & Hölscher, 4540 Lengerich | Flat lay and take-off device for a tubular film web made of plastic in a blowing process |
| DE3516244A1 (en) * | 1985-05-06 | 1986-11-06 | Tomi Machinery Mfg. Co. Ltd., Tsunashimahigashi, Yokohama | COOLING AND GUIDE DEVICE FOR FILMS MADE OF THERMOPLASTIC RESIN |
| DE69002295T2 (en) * | 1989-09-25 | 1993-11-04 | Schneider Usa Inc | MULTILAYER EXTRUSION AS A METHOD FOR PRODUCING BALLOONS FOR VESSEL PLASTICS. |
| JP2866727B2 (en) * | 1990-09-27 | 1999-03-08 | 三菱樹脂株式会社 | Heat shrinkable tubing |
| US5124094A (en) * | 1991-03-21 | 1992-06-23 | Minnesota Mining And Manufacturing Company | Apparatus and method for constraining a rotating tube of material |
| US5128076A (en) * | 1991-03-21 | 1992-07-07 | Minnesota Mining And Manufacturing Company | Apparatus and method for producing an elongate strip of material |
| US5195969A (en) | 1991-04-26 | 1993-03-23 | Boston Scientific Corporation | Co-extruded medical balloons and catheter using such balloons |
| US5310329A (en) * | 1992-02-05 | 1994-05-10 | Cree Robert E | Air shroud device for a blown film extrusion line |
| JPH05259709A (en) * | 1992-03-10 | 1993-10-08 | Fukushima Nippon Denki Kk | Matching circuit using high specific dielectric constant board |
| WO1995009667A1 (en) * | 1993-10-01 | 1995-04-13 | Boston Scientific Corporation | Medical device balloons containing thermoplastic elastomers |
| US6896842B1 (en) | 1993-10-01 | 2005-05-24 | Boston Scientific Corporation | Medical device balloons containing thermoplastic elastomers |
| DE602004020449D1 (en) | 2003-02-26 | 2009-05-20 | Boston Scient Ltd | BALLOON CATHETER |
| US7166099B2 (en) | 2003-08-21 | 2007-01-23 | Boston Scientific Scimed, Inc. | Multilayer medical devices |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2916764A (en) * | 1956-08-31 | 1959-12-15 | Ici Ltd | Apparatus including tube flattening rollers for inflating tubular film |
| NL281373A (en) * | 1961-07-28 | |||
| US3257489A (en) * | 1961-11-28 | 1966-06-21 | Du Pont | Process for improving gauge of organic, thermoplastic, crystallizable polymeric film by stretching during heat treating |
| US3548042A (en) * | 1966-07-22 | 1970-12-15 | Reynolds Metals Co | Method and apparatus for cooling extruded tubing |
| NL6807357A (en) * | 1967-06-01 | 1968-12-02 | ||
| US3814785A (en) * | 1969-01-03 | 1974-06-04 | Ici Ltd | Heat stabilization of oriented thermoplastic films |
| US3788503A (en) * | 1969-12-30 | 1974-01-29 | Kohjin Co | Method for producing biaxially molecule-oriented poly-{68 -caproamide resin film |
-
1974
- 1974-10-08 JP JP11519874A patent/JPS5529809B2/ja not_active Expired
-
1975
- 1975-10-06 US US05/619,818 patent/US4061707A/en not_active Expired - Lifetime
- 1975-10-07 CA CA237,232A patent/CA1064210A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5141772A (en) | 1976-04-08 |
| JPS5529809B2 (en) | 1980-08-06 |
| US4061707A (en) | 1977-12-06 |
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