Note: Descriptions are shown in the official language in which they were submitted.
~0~)3~
- 1 -
DESCRIPTION
BI~XIALLY ORIENTED POLYAMIDE FILM AND
METHOD FOR PRODUCING THE SAME
Technical field:
The present invention relates to blaxially oriented
polyamide film, and more particularly, to biaxially ori-
ented polyamide film which has a low degree of anisotropy
in heat shrinkage over the entire width of the mill roll.
This biaxially oriented polyamide film can be made into
bags which are hardly liable to distortion when subjected
to heat treatment with hot water or retorting.
Background art: .
Biaxially oriented film of polyamide typified by
nylon ~ has outstanding pinhole resistance, heat
resistance, low-temperature resistance, and gas barrier
property. Owing to these characteristic properties, it is
generally used as a packaging material, in the form of
composite film with polyethylene sealant, for frozen
foods, refrigerated foods, and retort foods.
The production of biaxially oriented polyamide film
involves the steps of subjecting a polyamide resin to melt
extrusion, cooling and solidifying the extruded film,
reheating the unoriented film and subjecting 't to drawing
in the machine direction (MD) and trans~erse direclion
(TD), and heat-setting the drawn film. Drawing is usually
accomplished by sequential biaxial drawing in flat form,
simultaneous biaxial drawing in flat form, or simultaneous
biaxial drawing in tubular torm.
After biaxial drawing, biaxially oriented polyamide
film undergoes heat setting under tension at a temperature
close to the melting point of the film. Heat setting
makes the film resistant to shrinkage that takes place
during storage or in the subsequent steps such as printing
and lamination.
After heat setting, biaxially oriented polyamide
film is combined with a sealant such as polyethylene and
polypropylene by the aid of an adhesive and fabricated
into composite bags, which are used for food packaging.
Food packages usually undergo heat treatment at 70-80~C or
above in hot water, boiling water, or pressurized hot
water for the purpose of sterilization of foods.
Unfortunately, biaxially oriented polyamide film has
a disadvantage that it greatly shrinks during hot water
treatment even after heat setting. This is true particu-
larly of the case in which packaging bags are made from
the marginal part of the heat-set film. Such packaging
bags are subjec~ to distortion during hot water treatment
for sterilization. This distortion deteriorates the
~0~
appearance of the packaye and hence lowers the commercial
value of the package. In addition, such packaging bags
are liable to S-curling (bag distortion) that takes place
before hot water treatment, and this often hinders the
automatic filling operations.
The distortion of packaging bags occurs because the
film as the raw material is anisotropic in heat shrinkage.
In other words, the film shrinks in hot water in the
machine direction (MD) differently than in the transverse
direction (TD). (The maximum shrinkage takes place in the
direction of film advance.) When a film with a high
degree of anisotropy is made into bags by folding, the
resulting bags are subject to distortion because the front
side and back side shrink in different directions.
In the present invention, the anisotropy is expressed
in terms of the difference between the degrees of shrink-
age (caused by hot water) in the directions 45~ and 135
deviated to the left from the machine direction (MD).
The above-mentioned distortion is liable to occur in
the case where packaging bags are made from marginal parts
of film drawn in the flat form by the tenter method. By
contrast, such anisotropy does not exist in film drawn in
the tubular form. However, this film becomes anisotropic
when it undergoes heat setting by the tenter method for
the reduction of shrinkage in hot water. This tendency
becomes significant in the case of heat setting which is
carried out a~ a temperature close to the melting point of
the resin from which the film is made. It is known well
that this phenomenon is attributable to bowing. ~owing
occurs when film undergoes uneven drawing in the tentering
process. Bowing can be visuali7ed when film is tentered,
with a straight line drawn across the film width. As the
film undergoes orientation by tentering, the straight line
bends, with the center cor.caved backward (with respect to
the direction of film advance). Bowing occurs because the
edges of the film are moved forward compulsorily by the
grips, whereas the central part of the film is pulled
backward by the tension in the film surface. A film spec-
imen taken from the film which has experienced bowing will
not shrink evenly in all directions when heated, for
example, in hot water at lOO~C. In other words, the
direction of the maximum shrinkage does not coincide with
MD or TD. If the magnitudes of shrinkage in all the
directions are represented by vectors diverging from a
center, the ends of the vectors will form an ellipse, with
its major axis inclined with respect to the machine direc-
tion.
If a wide film undergoes heat setting on a tentering
machine~ severe bowing occurs, with the result that the
central part of the film has a comparatively low degree of
~(~035~
anisotropy and the maLginal parts of the film have a
remarkably high degree or anisotropy. Therefore, only the
central part of the film can be used for making
distortion-free bags, and the marginal parts of the film
have to be discarded. This leads to unpracticably poor
yields.
It was found that there are many commercial grades of
heat-set polyamide film which have a high degree of aniso-
tropy.
On the other hand, it was also found that oriented
film heat-set by the tubular process (which blows up a
tubular film with air) has a much lower degree of aniso-
tropy in heat shrinkage than oriented film made by the
tentering method. Heat setting by the tubular process,
however, is not practicable for oriented film in the form
of a large tube. Usually, tubular film undergoes heat setting
in the foldedform or the cut-open flat form, and heat setting
in this manner poses a problem associated with anisotropy as
mentioned above. Many attempts have heen made to solve
these problems; but they are not successful so far.
Disclosure of the invention:
Heat setting by the conventional tentering method
provides polyamide film which is anisotropic in heat
shrinkage. In other words, the marginal parts of the film
~0~5~
have a high degxee of anisotropy in heat shrinkage, and
only the central part of the film can be used for applica-
tions which need a low degree of anisotropy.
It is an object of the present invention to provide
an improved method of heat~setting biaxially oriented
polyamide film in flat form. According to the method of
the present invention, biaxially oriented polyamide film,
with the edges thereof gripped, is heated to an adequate
temperature, which is lQ-40~C lower than the melting point
of the film,by bringing it into close contact with the
surface of a heating body such as heat roll and heat belt,
and immediately thereafter the film is cooled to a temper-
ature at which the film does not deform easily.
It is another object of the present invention to
provide biaxially oriented polyamide film which has a
uniform heat shrinkage across the entire width of the
film. The shrinkage by hot water at 100~C is smaller than 5.0
% in all the directions in the plane, and the anisotropy
H (%) in hot water shrinkage which is calcuiated from the
formula below is less than 30%, preferably less than 20%,
across the entire width of the film.
I S~s ~ Sl3s 1
H (%) = x 100
S~s + Sl3s
~:0~:)3511
(where S~5 and Sl35 respectively denote the shrinkage
(by hot water at 100~C) in the directions deviated left
ward 95~ and l35r from the machine direction.)
With a degree of anisotropy H (%) higher than 30%,
the film will provide packaging bags which are of no prac-
tical use on account of extreme distortion. A preferred
degree of anisotropy H (%) should be smaller than 20%.
The method of the present invention performs heat
setting on biaxially oriented polyamide film to give uni-
formly thick heat-set film which, when exposed to hot
water at 100~C, exhibits a degree of anisotropy H (%)
smaller than 30% at any position across the entire width
of the film and undergoes shrinkage smaller than 5.0% in
all the directions. The heat-set film can be made into
bags after lamination with a sealant material, and the
resulting bags are substantially free from distortion even
after sterilization by boiling or retorting, no matter
what part of the film is used for the bags.
Best mode for carrying out the invention:
The heat-setting method of the present invention is
not effective for the biaxially oriented film of thermo-
plastic resin other than polyamide which has originally a
low hot water shrinkage; however, it produces a pronounced
~0~351~
effect on polyamide film which has a large hot water
shrin~age and undergoes heat treatment with hot water or
retorting in most of its applications.
The polyamide film in the present invention is pro-
duced from aliphatic polyamide resins (such as nylon 6,
nylon 66, nylon 12, and nylon 11), polyamide copolymer
resins composed mainly of the monomer constituting said
aliphatic polyamide resins, aromatic polyamide resins, and
blends of these polyamide resins.
The melting point of the resin is measured by the DSC
method provided in JIS K-7121 (Method for measuring the
transition point of plastics), Section 3(2).
The melting point of a blend resin is a weighted mean
(proportional to the blending ratio) of the melting points
of the individual resins comprising the blend. In the
case where a copolymer resin has two or more melting
points, the melting point of such a copolymer resin is a
weighted mean proportional to the peak areas of the indi-
vidual melting points.
The heat-setting method of the present invention can
be advantageously applied to biaxially oriented polyamide
film formed by the tubular stretching method, which has a
low degree of anisotropy. This is because heat setting
~o~
does not reduce anisotropy in heat shrinkage and the film
for heat setting should originally have a low degree of
anisotropy in heat shrinkage.
The heat setting in the present invention may be
carried out using any heating body which has a smooth
surface. The heating body is not necessarily made of a
metal. A preferred heating body is a heat roll or heat
belt which provides an endless surface suitable for indus-
trial continuous production In addition, the surface of
a heating body should preferably be smooth for close
contact with the film; but it may have small irregulari-
ties which do not prevent close contacting.
The heating body is heated to a temperature close to
the ordinary heat setting temperature. According to the
heat setting method of the present invention, the heat
setting temperature should be in the range of the melting
point minus 10~C to the melting point minus 40~C. With a
heat setting temperature higher than the upper limit, the
film undergoing heat setting softens and sticks to the
surface of the heating body (such as a heat roll and heat
belt). This blocking deteriorates the smoothness and
clarity of the film, making the film of no practical use.
Conversely, with a heat setting temperature lower than the
lower limit, the film does not undergo sufficient heat
setting.
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To effect heat setting, the film is kept in close
contact with the surface of the heating body for a certain
length of time, which is properly selected according to
the kind of polyamide resin and thickness and heat-setting
temperature of the film. The thinner the film or the
higher the heat-setting temperature, the shorter the
contact time. Contact for about 0.5 second is usually
sufficient. When the film is brought into close contact
with the surface of the heating body, the edges of the
film are gripped to ensure the close contact by preventing
shrinkage in the widthwise direction. If the oriented
film is simply brought into contact with the heating body
(such as heat roll and heat belt), close contact is not
obtained because the film undergoes heat shrinkage. Any
oriented film which is liable to shrinkage in the width-
wise direction is of no practical use because shrinkage
gives rise to the thickening of edges. The above-
mentioned heat setting may be carried out in multiple
stage. In this case, the temperature in the later stage
should be higher than that in the previous stage.
In the last stage of heat setting, the film should
preferably be cooled to a temperature at which the film
does not deform easily. Such a temperature is, for
example, the melting point minus 135~C. For the minimum
film deformation, the film should be cooled below the
13511
glass transition point (Tg) of the film. Such cooling is
practically effected by bringing the film into contact
with the surface of a cooling body such as a water-cooled
roll. Without sufficient cooling, the film is deformed by
tension and the process cannot be controlled smoothly.
Transfer of the film from the heating unit to the cooling
unit should be carried out in such a way as to prevent
shrinkage in the widthwise direction, because the heat-set
film leaving the heating unit is still very hot. This
object is achieved if a rubber roll (or the like) of com-
paratively low temperature is placed between the heating
unit and the cooling unit, so that the heat-set film
moves, keeping itself in close contact with the surface of
the rubber roll. The rubber roll should preferably be
close to the heat roll (or heat belt) and the cooling
roll, so that the heat-set film does not become completely
or nearly free during its transfer.
The above-mentioned heat setting should preferably be
preceded by a preheating stage. Preheating protects the
film from blocking and whitening when the film comes into
contact with a heating body at a high temperature. Thus,
preheating permits efficient heat setting at a high tem-
perature. Preheating should be carried out at tempera-
tures ranging from the melting point minus 40~C to the
)3~
, ~
melting point minus ~35~C (preferably 105~C). Wlth a tem-
peratu-e lower than the lower limit, preheating produces
almost no effect. Preheating may be carried out in multi-
ple stages by means of a heat roll or heat belt at a tem-
perature lower than the heat-setting temperature. In the
case where preheating is carried out in two or more
stages, the preheating temperature should be increased
sequentially from one stage to another. Preheating in the
stage at a comparatively low temperature may be carrled
out by the tentering method. The preheating steps should
preferably be followed immediately by quenching.
EXAMPI,ES
The invention will be described in more detail with
reference to the following examples, which are not
intended to restrict the scope of the invention.
n the examples, the characteristic properties of
film were measured according to the following methods.
(1) Shrinkage by hot water at 100~C and anisotropy
Shrinkage in all the directions is represented by
shrinkage in the machine direction (MD), transverse direc-
tion (TD), and directions deviated 45~ and 135~ leftwards
from the machine direction (MD).
A square film specimen, measuring 120 mm by 120 mm,
is cut from the film which has undergone heat setting.
(The center of the square film specimen coincides with a
)35~
, -~
prescribeci position measured in the widthwise direction of
the film.) At the square film specimen is drawn a circle,
lO0 mm in diameter. Marking lines, 100 mm long, passing
through the center of the circle are drawn in the MD
direction, the TD directior" and the directions deviated
45~ and 135~ leftward from the MD direction (referred to
as MD-45~ direction and MD-135~ direction, respectively,
hereinafter). After conditioning at 20'C and 65 %RH for 1
day, the length of the marking lines on the film specimen
are accurately measured.
The film specimen is dipped in hot water (at 100~C)
for 30 minutes. After wiping and conditioning at 20~C and
65 %RH for 1 day, the length of the marking lines on the
film specimen are accurately measured again. Hot water
shrinkage S (%) in each direction is calculated from the
following formula.
Mo -- M
S (%) = x 100
MD
(where M denotes the length of the marking line mea-
sured before dipping, and Mo denotes the length of the
marking line measured after dipping.)
Then, a degree of anisotropy H (%) in hot water
shrinkage is calculated from the following formula.
_ Is _
~ S13'~ 1
r ) = X 1 00
S45 + S135
SMD/ STD~ S45~ and S135 denote the hot water
shrinkage S (%) in the MD direction, TD direction, MD-45~
direction, and MD-î35~ direction, respectively.
(2) Distortion of filled bag caused by hot water treat-
ment
A composite film is formed by dry lamination fromsample film and 40-~m thick LLDPE film (having a melting
point of 126~C and a density of 0.935), with one side
corona-treated, using a urethane resin adhesive ("AD-
305/AD-355", 1:1 wet ratio, made by Toyo Morton Co.,
Ltd.), with the corona-treated side facing inward.
The composite film is folded in two and cut at the
fold. Two pieces of the composite film placed one over
the other undergo bag making in such a manner that two
bags of three-sided seal type are formed slde by side at
one time. (One bag is formed from the marginal part of the
film, and the other bag is formed from the central part of
the film.) Thus there are obtained three-sided seal bags
each measuring 250 mm (ln the MD direction) and 200 mm (in
the TD direction). The bag made from the marginal part of
the film is filled with 150 cc of water and heat-sealed.
335~.~
The filled bag is dipped in hot water (at 100~C) for 30
minutes. After heat treatment, the filled bag is visually
examined for distortion according to the following crite-
ria.
A : no distortion
B : almost no distortion
C : slight distortion
D : severe distortion
(3) Edge thickness
The edge thickness of the heat-set film is expressed
by an average value of measurements made at five points at
intervals of 60 mm in the MD direction, 120 mm inward from
the edge.
Example 1
Nylon 6 (having a melting point of 215~C) was made
into a lay-flat tube (having a film thickness of 150 ~m
and a lay-flat width of 600 mm) by melt extrusion from a
tubular die, followed by quenching and solidification.
The lay-flat tube was passed through two sets of nip
rolls running at different ci.rcumferential speeds to
effect simultaneous biaxial orientation (3 x 3 times) at
80-100~C by utilizing the pressure generated in the tube.
Thus there was obtained biaxially oriented film having a
)35~1
lay-flat width of 1800 mm and a film thickness of 17 ~m.
This film was separated into two webs by cutting the
edges, and the webs were wound onto two separate cores.
The film was unwound and passed at a rate of 80 m/min
through a 1-m long tenter oven at 120~C for preheat treat-
ment, with the edges of the film gripped by tenter chucks
to keep the film width constant. Imrnediately after the
passage through the tenter oven, the film was cooled by a
water-cooled roll. The film was introduced to a 1-m long
endless heat belt at 180~C. The film was brought into
close contact with the surface of the heat belt for heat
treatment. During this heat treatment, the edges of the film were
fixed by heat resistant endless pressing belts so as to protect
the film from heat shrinkage in the widthwise direction.
The film was transferred to a rubber roll running in
contact with the surface of the heat belt and the surface
of the cooling roll (mentioned later). The film was
further transferred to a cooling roll ~300 mm in diameter)
whose surface is kept at 90~C by cooling water circulating
therein. The film was kept in contact with the cooling
roll for 0.5 second so that the film was quenched below
80~C. Thus the heat setting was cornpleted. The heat-set
film was wound up.
5~1
E'rom the heat-set film was ta~en a square film speci-
men (120 mm by 120 mm). The center of the square film
specimen is at the position 120 mm inward from the edge of
the film web. The square film specimen was tested for S~,
ST~ S45, and S1~5 according to the above-mentioned method.
The heat-set film was subsequently cut into two
parts, each 840 mm in width, and the edges, 60 mm each,
damaged by grips were cut off using a siitter. The two
webs of the film were wound onto separate cores. The film
of the right web as viewed in the MD direction was made
into a composite film as mentioned above. The resulting
composite film was made into bags and the bags were filled
with water as mentloned above. The filled bags were
tested for distortion by hot water as mentioned above.
The results are shown in Table l.
Examples 2 and 3 and Comparative Examples 1 and 2
Various kinds of nylon 6 film were prepared in the
same manner as in Example 1, except that the temperature
of the heat belt was changed to 190~C, 200~C, 170~C, and
210~C, respectively. They were evaluated in the same
manner as in Example 1. The results are shown in Table l.
~0~51~
Example 4
The same procedure as in Example 2 was repeated to
give heat-set film, except that the preheating temperature
was changed to 160~C. The film was evaluated in the same
manner as in Example 1. The results are shown in Table 1.
Example 5
The same procedure as in Example 2 was repeated to
give heat-set film, except that the rubber roll between
the heat-set roll and the cooling roll was removed and a
120-mm long unsupported zone was formed. The film was
evaluated in the same manner as in Example 1. The results
are shown in Table 1.
Example 6
Nylon 6 film was prepared in the same manner as in
Example 1, except that the preheating tenter oven was not
heated and the temperature of the heat belt was changed to
200~C. The film was eva]uated in the same manner as in
Example 1. The results are shown in Table 1.
Examples 7 and 8 and Comparative Examples 3 and 4
In Example 7, there was obtained biaxially oriented
lay-flat nylon 6 film, 1800 mm wide, in the same manner as
in Example 1. The nylon film was cut into two parts. For
preheating, the film was passed on an endless be]t, heated
at 150~C, in contact with the film over a length of 1
meter. During this heat treatment, the edges of the film
~0~1351~
- ~ g
~!ere fixed by endless pressir)g belts so as to protect the
film from heat shrinkaye in the widthwise direction. The
film was transferred to a water-cooled roll whose surface
was kept at 40~C. Subsequently, the film was passed over
a heat roll (400 mm in diameter) heated at 190~C for heat
treatment. During this heat treatment, the film was
brought into contact with the heat roll by means of heat
reslstant belts which press edges of the film against the
heat roll over two-thirds of the circumference oî the heat
roll. The film was passed through the rubber roll and
then cooling roll in the same manner as in Example 1. The
heat-set film was wound up.
The same procedure as in Example 7 was repeated in
Example 8 and Comparative Examples 3 and 4, except that
the temperature of the heat belt for preheating was
changed to 180~C, 170~C, and 180~C, respectively, and the
temperature of the heat roll for heat setting was changed
to 200~C, 170~C, and 210~C, respectively. The thus
obtained heat set film was evaluated in the same manner as
in Example 1. The results are shown in Table 1.
Comparative Examples 5 to 7
The same procedure as in Example 7 was repeated to
give various ~inds of heat-set film, except that the film
underwent heat setting by passing through a hot air tenter
at 200~C, 210~C, and 220~C, respectively, for 6 seconds,
till.
( )
with the ed~es of tne film gripped by tenter chucks. The
thus obtained heat set film was evaluated in the same
manner as in Ex~mple 1. The results are shown in Table 1.
Example 9 and Comparative Examples 8 and 9
Biaxially oriented film was prepared in the same
manner as in Example 1 from a 30/70 blend of nylon 6
(having a melting point of 215~C) and nylon 66 (having a
melting point of 260~C), with the weighted average melting
point being 247CC.
This film underwent preheat treatment in a tenter
oven at 130~C and then heat~set by means of a heat belt in
the same manner as in Example 1, except that the tempera-
ture of the heat belt was changed to 230~C, 200~C, and
240~C, respectively. The thus obtained heat set film was
evaluated in the same manner as in Example 1. The results
are shown ln Table 1.
Table 1 shows the following. The method of the
present invention provides film which has a low hot-water
shrinkage and a low degree of anisotropy in hot-water
shrinkage, even in the marginal parts. This film is
obtained by heating biaxially oriented film in close
contact with a heat roll at a temperature which is 10-40~C
lower than the melting point of the film, with the edges
of the film gripped, and then quenching the film at a tem-
perature which is 135~C lower than the melting point,
~(~03~
the~eby heat-setting the film. The thus obtained heat-set
film ca~ be made into hags which are hardly subject to
distortion by hot water treatment. This is true even in
the case where the marginal parts of the film are used.
By contrast, the film which was heat-set by means of the
conventional hot air tenter has a high degree of aniso-
tropy in hot water shrinkage and provides bags which are
subject to distortion (as in Comparative Examples 5 and
6).
In the case where the heat-set temperature is lower
than the melting point minus 40~C, the resulting film has
a hot-water shrinkage greater than 5.0~ on account of
insufficient heat setting. Such film gave rise to great
overall shrinkage in the distortion test (as in Compara-
tive Examples 1, 3, and 8). On the other hand, in the
case where the heat-set temperature is higher than the
melting point minus lO C, blocking to the heat roll
occurred (as in Comparative Examples 2, 4, and 9). In the
case where a tenter was used, whitening occurred (as in
Comparative Example 7).
In the case where heat setting is carried out at a
higher temperature side in the range from the melting
point minus 10 to the melting point minus 40~C, it is
~(~035~L~
desirable tv subject the ~ilm to pretreatment at a temper-
ature lower than the above-mentioned range. This pre-
treatment prevents the blocking tendency of the film.
(E~ample 4).
In the case where preheating is carried out at a high
temperature by the tenter method, the film becomes to have
a high degree of anisotropy in heat shrinkage (as in
Example 4). Therefore, preheating by a tenter should not
be carried out at an excessively high temperature.
Referential Example
Two rolls of biaxially oriented polyamide film (860
mm wide and 700 mm wide) obtained from the market were
tested for hot-water shrinkage. Specimens were taken from
the left edge, the center, and the right edge across the
width. Anisotropy (H') in hot water shrinkage was calcu-
lated from the following formula. The results are shown
in Table 2.
I S4'j - S13s 1
H' (%) = x 100
S4s + S135
(where S45 and S13s respectively denote the shrinkage
(by ho-t water at 100~C) in the directions deviated left-
ward 45~ and 135~ from the machine direction.)
It is noted that the two kinds of the film tested
have a high degree of anisotropy. It is presumed that the
film of roll 1 coincides with the center of the mi,ll roll
at the intermediate between the left edge and the center.
It is also presumed that the film of roll 2 coincides with
the center of the mill roll at an imaginary point beyond
the right edge. In other words, it is presumed that the
film of roll 1 was obtained from that part of the web that
coincides with the center of the mill roll, and the film
of roll 2 was obtained from that part of the web which is
very close to the edge of the mill roll.
~00~35~
a~ -E ~ N ~ -- N -- -- -- -- -- -- C'~ --'
a~
-
a' E ~~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~ O C~ m ~ ~ m 6 .~ I C o o I m ~
-- 0 N _ ~ N ~ ~D I ~ Il~
N ~t (D ~ N ~ ~
C~N N N N ~r ' N ' N '-t ~ N N _ ~ ~ 10
~_ o ~t _ 0 N ~ ~D N~ U~ 1 ~ N ~t ~ U'~ U~
U) ~ C~ N t'~ N 10 ~ N ~ N 117 ~ N ~r ~~ ' ~ tSI
O 0~ 0 el ~D ~ 0 , N ~ N r' Ctl " ID 0
C'~ N N N N ~ ~ N ' N ~t ~ N ~ N
O N N 11~ 07 N ~ ~ ~' N U') C~
D C/~ ~ ~ N N C~ N ~ N U) ' N ~ C'') ' N U')
E ~ ~ 0 o 0 0 ~ ~ o~ 0 ~o o Oo O o NO C" o O
' ~Y
~ I I I I I I I I I I I I )-- ~ 1-- I I I
E t ~ ~ ON NO ~D N NO N I 10 ~ ~ 0 10 Lt~ U~ C')
~- O O O O O O O ~ m m m m m m m o O
E-- N N N N N N N N N N N N N N N N N N
a~
E ~ N C'~ ~r U'i _ N ID ~ ~ ~r ~ 1 L~'> _ _ _ _
U
51~
- 25 -
Ncte to Tabl~ 1
Parenthesi~ed example Nos. indicate Comparative E~.amples.
HR : Heat roll, HB : Heat belt, TO : Tenter oven
*1 : Partial blocking to HB.
*2 : Tendency toward blocking to HB.
*3 : Blocking to HR.
*4 : Partial whitening.
*5 : Blocking to HB.
*6 : Great overall shrinkage.
~t~J~
Table 2
Filmwidth Roll 1 (860 mrn) Roll 2 (700 mm)
Widthwise position Left Center Right Left Center Right edge edge edge edge
Shrinkage MD 3.4 3.4 3.53.5 3.2 3.4
Shrinkage MD4s 2.6 2.93.3 3.8 3.3 3.3
Shrinkage TD 2.2 2.3 2.02.0 2.0 1.9
Shrinkage MD13s 2.8 2.42.0 1.6 1.9 2.1
Anisotropy H' (%) -7 19 49 81 54 44
