Process for making continuous films of ordered poly(ether ketone ketones)

A process for extruding a smooth and uniform film or sheet of an ordered poly(ether ketone ketone) having a thickness of about 2.5 to 250 micrometers, wherein the molten extrudate is quenched on a drum maintained at a temperature of about 100.degree.-170.degree. C.

BACKGROUND OF THE INVENTION 
This invention relates to a process for making strong, tough, high gloss, 
transparent, uniform, substantially amorphous films from ordered 
poly(ether ketone ketones) sometimes referred to hereinafter as PEKKs. 
PEKKs are well known and are described, i.a., in U.S. Pat. No. 3,065,205 
(Bonner); U.S. Pat. No. 3,441,538, (Marks), U.S. Pat. No. 3,442,857 
(Thornton), and U.S. Pat. No. 3,516,966 (Berr). PEKK films and a 
melt-casting process for making PEKK films are described in detail in U.S. 
Pat. No. 3,637,592 (Berr) and British Patent 1,340,710 (Angelo). 
The PEKK principally employed in melt-casting films according to the above 
art was a copolymer of terephthalyl chloride (T), isophthalyl chloride 
(I), and diphenyl ether (DPE). The polymer, made by a one-step process was 
characterized by an essentially random distribution of the T and I groups 
along the chain backbone. 
More recently, U.S. Pat. No. 4,816,556 (Gay et al.) described a two-step 
ynthesis of PEKK resin characterized by an ordered (nonrandom) 
distribution of T and I groups along the chain backbone. In these PEKKs, 
the T and I groups either alternate or are in blocks, and the resins are 
described as ordered polyetherketones. The first step in that process is 
an oligomerization step in which either only the T or only the I comonomer 
react: with DPE to form an oligomeric structure -DPE-T-DPE- or 
-DPE-I-DPE-. In the second step, this oligomeric intermediate is contacted 
with further T and I to form the final product. These ordered PEKKs have a 
higher heat of fusion, a smaller difference between the melting 
temperature and the temperature of onset of crystallization, and a melting 
temperature greater than the melting temperature of PEKKs having the same 
gross composition wherein the repeat units occur in random sequence. These 
ordered PEKKs are more suitable in manufacturing lecause of their better 
melt processing characteristics than their random counterparts. 
Both Berr (U.S. Pat. No. 3,637,592) and Angelo (British Patent 1,340,710) 
describe a process for making films from random PEKK by continuous 
extrusion and melt casting of PEKK resin onto a quench (or, casting) drum. 
In order to obtain amorphous film, both Berr and Angelo consider it 
necessary to cool the casting drum to or below room temperature. 
However, when a thin film of ordered PEKK resin of Gay et al. is cast onto 
a drum cooled to below about 100.degree. C., especially below 80.degree. 
C., it buckles and cannot be laid down smoothly upon the drum, this effect 
being more severe at progressively lower temperatures. Yet, smooth 
lay-down is required for producing uniform film. In the absence of smooth 
lay-down, ridges, large bumps, and waviness occur in the film. In addition 
to its other shortcomings, the three-dimensional character of the 
resulting film renders wind-up of a good quality film package or roll 
virtually impossible in ordinary film winding equipment. 
It, therefore is desirable to provide a process for melt casting ordered 
PEKK resins into a smooth, essentially two-dimensional, high quality film 
or sheet. 
SUMMARY OF THE INVENTION 
According to the present invention, there is now provided a continuous 
process for melt casting a high quality film or sheet having a thickness 
of about 2.5 to 250 micrometers from an ordered poly(ether ketone ketone) 
resin consisting essentially of two repeating units (a) and (b) 
represented by the following formulas 
##STR1## 
and 
##STR2## 
where A is the p,p' -Ph-O-Ph- group, and Ph stands for the phenylene 
radical; 
B is p-phenylene and 
D is m-phenylene 
where the (a) and (b) units occur at a ratio in the range of 80:20 to 
25:75; 
said resin having an inherent viscosity at 30.degree. C., determined for a 
0.5 g/100 ml solution in concentrated sulfuric acid of about 0.6-1.2; 
said process comrising the consecutive stages of melt-extruding te resin at 
a temperature of at most 400.degree. C. at a die pressure of at least 1.4 
MPa, directing the molten extrudate onto the surface of a rotating quench 
drum maintained at a temperature between 100.degree. and 170.degree. C. so 
that the resin forms a thin layer thereon, maintaining the molten resin 
layer in contact with the surface of the quench drum until the resin 
solidifies into a film or sheet, and removing the film or sheet from the 
quench drum.

DETAILED DESCRIPTION OF THE INVENTION 
The PEKK resins to which this invention is applicable are the same as those 
claimed in the above-cited U.S. Pat. No. 4,816,556 (Gay et al.). They are, 
according to that patent, made by a sequential reaction of diphenyl ether 
with terephthalyl chloride and isophthalyl chloride. The repeating units 
obtained by reaction with terephtalyl chloride are represented by the 
formula (a), above, while those obtained by reaction with isophthalyl 
chloride are represented by the formula (b). The ratio of (a) units to (b) 
units is, therefore, normally referred to as the T/I ratio. Because those 
groups have the same molecular weights and differ only by their 
substitution positions, their mole ratios and weight ratios are the same. 
The preferred T/I ratio is 70:30 to 25:75. 
It is essential to the success of the process of this invention that the 
surface of the quench drum be maintained above about 100.degree. C. Below 
that temperature, and especially below about 80.degree. C., all the 
undesirable effects of buckling, ridge formation, and waviness occur to a 
greater or lesser degree. The preferred quench drum temperature is about 
110.degree.-160.degree. C. 
In the practice of this invention, the PEKK resin in the form of powder, 
flakes, or preferably pellets is fed to a conventional plastics extruder, 
either single or twin screw, wherein the resin is thoroughly melted and 
conveyed to a film extrusion die PG,6 wherefrom it is extruded onto the 
quench drum and thence conveyed by a series of guides to a wind-up. 
It is known in the art that inherent viscosities (I.V.), or dilute solution 
viscosities, can be used for determining the relative molecular weights of 
polymers which are similar in composition. The inherent viscosities are 
determined from the equation: 
EQU I.V.=1n[.eta.1(solution)/.eta.2(solvent)] 
where the viscosities, .eta.1 and .eta.2 are determined as described above 
in the Summary of the Invention. The preferred PEKK inherent viscosities 
are within the range of 0.7 to 1.1, especially 0.8-1.0. 
At the lower end of the broadest viscosity range, it may be difficult to 
generate enough die pressure to fill the die uniformly and obtain stable 
flow. Thus, both the machine direction and transverse direction thickness 
control often are difficult to achieve, while substantial edge weave and 
build-up and slough-off from the die edges may be encountered. At the high 
end of the broadest viscosity range, mechanical working of the melt may 
result in melt temperatures in excess of 90.degree. C., where some 
degradation may occur. 
The resin should be thoroughly devolatilized, preferably by extraction 
under vacuum during extrusion, prior to film casting. This is accomplished 
preferably in a separate pelletization step but may also be accomplished 
in the film extruder if the film extruder is provided with a vacuum 
extraction port for removing volatile contaminants from molten resin. The 
devolatilized resin should then be maintained in a low-moisture 
environment, or dried thoroughly before film processing. Drying at 
120.degree. C. for 16 hours has proved to be effective for reducing the 
moisture to acceptable levels for film fabrication, e.g., 300 ppm or less. 
In some circumstances, it is desirable to begin the extrusion under 
so-called "starve-feed" conditions, and then to inrrease the feed rate 
until the condition of "flood-feed" is attained. "Flood-feed" represents 
the highest degree of throughput consistent with a given extruder screw 
design and speed. It has also been found that excellent feeding is 
obtained when the compression ratio of screw flight depth in the feed zone 
to that ratio in the compression/metering zone is less than about 3.5. 
Further, the temperature in the feed throat should not exceed about 
200.degree. C. to avoid clumping of the feed. 
The drawing shows schematically a typical suitable arrangement for the 
practice of the present invention, wherein a single screw extruder is 
used. In the drawing, A is the feed hopper; B is the feed zone; C is the 
compression/metering zone; D is the adapter; E is the die; I are the die 
lips; F is the quench drum; G are the guides; and H is the wind-up device. 
The die pressure, measured by a probe placed at or near the point of entry 
of the melt into the die, must be maintained at a suitably high level to 
cause the polymer to fill the die uniformly. The prefered die pressure is 
at least about 2.8 MPa, especially at least about 4.2 MPa. Die pressure 
varies inversely with die lip opening, directly with extruder screw speed 
(under flood feed conditions), and directly with resin melt viscosity. The 
usual die lip opening is about 100-500 micrometers. 
The temperatures of the extruder barrel and die should be set in a manner 
consistent with obtaining a uniformly flowing melt, without causing 
polymer degradation. Melt temperatures preferably should be kept below 
390.degree. C., especially below 380.degree. C. 
For ordered PEKK resins having a T/I ratio of 70:30, the extruder 
temperatures are preferably in the range of 340.degree.-370.degree. C., 
especially 350.degree.-370.degree. C.; for ordered PEKK resins having a 
T/I ratio of 60:40, the extruder temperatures are preferably 
310.degree.-370.degree. C., and especially 330.degree.-360.degree. C. When 
working with a resin which has an inherent viscosity near the lower end of 
the range suitable for the practice of this invention, it is particularly 
preferred to operate at temperatures close to the low end of the 
appropriate temperature range in order to maximize melt viscosity and 
thereby die pressure. 
The films of ordered PEKK resins produced by the process of this invention 
preferably have a thickness of about 10 to 125 micrometers. 
Those films are readily obtained by drawing down in the melt from die lips 
preset at a separation of about 250 micrometers. Little orientation, as 
indicated by tensile properties, appears to result from the melt 
draw-down. 
For resins at the low end of the acceptable range of inherent viscosities, 
when a film of a thickness of 2.5-125 micrometers is desired, it is 
preferable to adjust the die lip opening to less than 250 micrometers, 
e.g. to 200 micrometers, in order to achieve satisfactory die pressures. 
The film exiting from the film die usually is brought into contact with the 
quench drum as quickly as possible. The distance between the lips of the 
die and the quench drum preferably is 2.5 cm or less, and in general, the 
closer the better consistent with safety. 
The cast film can be maintained in contact with the quench drum by any 
suitable technique. For example, electrostatic pinning across the full 
width of the cast film provides good lay-down, but may create a matrix of 
fine dots on the surface of the film. Such matrix of fine dots sometimes 
is considered useful because it increases the slippage of the film, thus 
facilitating film handling. It is believed to be caused by an interaction 
of unknown origin between the elctrostatic pinner and residual 
polymerization solvent (normally, o-dichlorobenzene). Use of an air pinner 
has been found to be less effective. Casting may also be performed into a 
nip, usually consisting of two highly polished chrome rolls or one chrome 
and one rubber roll, in either case the rolls being separated by the 
desired thickness of the film. 
These films are useful in a wide variety of applications such as packaging, 
particularly as a component of so-called microwave susceptors, as a 
preferred film substrate in the production of continuous fiber composites, 
wherein the film is melt-bonded to a layer of fibrous material, as a 
component layer of laminates to enhance solvent resistance or thermal 
properties of other resins, as a substrate or adhesive in flexible printed 
circuit boards, and as a capacitor dielectric. 
These amorphous films of ordered PEKKs are quite similar or superior in 
properties to the amorphous films of random PEKKs described by Berr and by 
Angelo, yet, surprisingly, cannot be made by practicing the art of Berr or 
of Angelo. The ordered PEKK resin, however, has processing advantages over 
random PEKK resin, as discussed above. Ordered PEKKs, like random PEKKs, 
must be processed at melt temperatures above 300.degree. C. at the point 
of extrusion from the film die lips. In a typical industrial film quench 
configuration, the high temperature melt comes into contact with the 
quench drum within less than one second from the time it is extruded, 
imparting a substantial quantity of heat to the drum. To achieve a quench 
drum temperature within the range of the present invention, it is 
practical to employ a circulating hot oil bath to supplement the transfer 
of heat from the molten polymer. This is contrary to the prior art 
practice with random PEKK resins, which required cooling of the quench 
drum. To the extent that the prior art processes required refrigeration in 
order to bring the drum temperature to the desired low level, the process 
of the present invention is less cumbersome and more energy-efficient. 
It is known in the art of making thick sheets of PEKK resins, having a 
thickness of at least about 625 micrometers, that very significant 
processability differences exist among such resins having different T/I 
ratios. A particularly large difference in processability of such resins 
is noted between those having T/I ratios of 60:40 and 70:30, the former 
being melt processable over a much wider range of conditions and, 
therefore, being highly preferred in this art. 
It is, therefore surprising that the excellent results obtained according 
to the present invention do not significantly depend on the PEKK resin's 
T/I ratio, and especially so for the resins having respective T/I ratios 
of 70:30 and 60:40. It is particularly surprising that both types of 
ordered PEKK resins having 70:30 and 60:40 T/I ratios have the same 
critical minimum quench drum temperature below which good quality film 
cannot be made. Such a minimum quench drum temperature unexpectedly is 
found for thin films and sheets but not for thick PEKK resin sheets. 
This result is of great practical utility because it makes a wide range of 
PEKK resin compositions equally available for applications for which each 
is best suited. For example, 70:30 T/I PEKK resin film is preferred for 
applications requiring higher temperature resistance or post-casting 
annealing to achieve, for example, higher strength and stiffness, such as 
certain fiber-reinforced composites. On the other hand, the 60:40 T/I PEKK 
resin film is preferred for applications in which its lower melting 
temperature is advantageous, e.g., in certain other fiber-reinforced 
composite structures, or where greater toughness is required. 
It is to be noted that the preferred quench drum temperature range for the 
practice of this invention is independent of the inherent viscosity of 
ordered PEKK over the range of acceptable inherent viscosities, although 
the minimum drum temperature at which the process becomes operable will 
increase somewhat with increasing inherent viscosity. 
Quench drum temperature will preferably lie within the range of 
110.degree.-160.degree. C., especially 120.degree.-150.degree. C. 
This invention is now illustrated by representative examples of certain 
preferred embodiments thereof, wherein all parts, proportions, and 
percentages are by weight unless otherwise indicated. 
All the PEKK resins were made according to the teachings of the Gay at al. 
patent. Their properties were determined according to the following ASTM 
procedures: 
Tensile strength, tensile modulus, tensile elongation: ASTM D-882 
Tear Strength (Elmendorf): ASTM D-1922 
Impact Strength (Spencer): A8TM D-3420 
Fold Endurance (MIT): ASTM D-2176 
Impact Strength (Pneumatic Ball Impact): ASTM D-3099 
All the units not originally measured or obtained according to SI have been 
converted to SI units. The abbreviation MD/TD means machine 
direction/transverse direction. 
In Examples 1-9, film was fabricated using a Werner & Pfleiderer 28 mm twin 
screw extruder equipped with a 25 cm vertical coathanger die manufactured 
by Extrusion Dies Incorporated. The die lip opening was preset at 250 
micrometers. It is to be noted, however, that the die lip opening is 
normally adjusted during the running to create a transverse lip opening 
profile which compensates for minor flow differences in the die in order 
to produce a film of uniform thickness. A screenpack consisting of 
841-177-99-841 micrometer screens or, alternatively, 841-177-149-841 
micrometer screens was placed, except where noted, between the extruder 
and the die. A polished, chrome-plated quench drum was employed. The drum 
was heated or cooled, as required, by continuously circulating oil pumped 
by an external pump through a heat exchanger. The line speed was in the 
range of 7.5-9.8 m/min. An electrostatic pinner was employed to maintain 
uniform film/drum contact. 
EXAMPLE 1 
The PEKK T/I ratio was 70:30 and its inherent viscosity 0.77. No screen 
pack was employed. The finished film thickness was about 38 micrometers; 
the drum temperature was 122.degree. C., the melt temperature 362.degree. 
C., and the die pressure 1.4 MPa. 
EXAMPLE 2 
In Example 2 and in Comparative Example 1, the T/I ratio of the PEKK resin 
was 70:30; the inherent viscosity was 0.78. 
The drum temperature was 163.degree. C., the melt temperature 355.degree. 
C.; the die pressure was 2.8 MPa; the film thickness was 32 micrometers. 
Film was flat on drum, exhibiting high gloss, and good uniformity in 
appearance. No crystallinity was found by examination of the cast film 
using wide angle x-ray diffraction method. Properties of the film, as 
cast, are shown in Table I. 
TABLE I 
______________________________________ 
Thickness (micrometers) 
32 
Tensile Strength MD/TD (MPa) 
89.6/84.8 
Tensile Modulus MD/TD (MPa) 
2530/2592 
Elongation MD/TD (%) 170/150 
Elmendorf Tear (g/mm) 
1457/2362 
Spencer Impact (J) 0.19 
MIT Fold (Cycles) 4250 
Pneumatic Ball Impact (J) 
0.18 
______________________________________ 
COMATIVE EXAMPLE 1 
The drum temperature was 60.degree. C., the minimum temperature attainable 
in this configuration; the circulating oil was at 35.degree. C. The melt 
temperature was about 358.degree. C.; the die pressure was 3 MPa; the film 
thickness was 33 micrometers. The film was forming bumps and ripples, and 
was no longer in perfect contact with the drum surface. No crystallinity 
was found by examination of the film as cast using wide angle x-ray 
diffraction. Properties of the cast film are shown in Table II. 
TABLE II 
______________________________________ 
I.V. 0.78 
Thickness (micrometers) 
32.3 
Tensile Strength MD/TD (MPa) 
97.2/84.1 
Tensile Modulus MD/TD (MPa) 
2482/2564 
Elongation MD/TD (%) 172/130 
Elmendorf Tear (g/mm) 
2087/1693 
Spencer Impact (J) 0.44 
MIT Fold 4220 
Pneumatic Ball Impact (J) 
0.19 
______________________________________ 
COMATIVE EXAMPLE 2 
In Comparative Example 2 and in Example 3, the T/I ratio of the PEKK resin 
was 70:30 and the inherent viscosity 0.93. 
The surface temperature of the drum was 63.degree. C.; the temperature of 
the circulating oil was 30.degree. C. The melt temperature was 361.degree. 
C.; the die pressure was 5.5 MPa; the film thickness was about 35 
micrometers. The resulting film exhibited a large number of ripples and 
was not laying down flat on the quench drum. The degree of rippling was 
significantly more severe than in Comparative Example 1. 
EXAMPLE 3 
This is the preferred embodiment of the present invention. 
The drum temperature was 122.degree. C.; the melt temperature was 
360.degree. C.; the die pressure was 5.4 MPa; the film thickness was 34 
micrometers. The film was laying down with no apparent ripples or 
wrinkles. It was glossy, transparent, strong, tough and uniform. No 
crystallinity was found by wide angle x-ray diffraction. Properties of 
this film are shown in Table III. 
TABLE III 
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I.V. 0.93 
Thickness (micrometers) 
32 
Tensile Strength MD/TD (MPa) 
149.6/131.7 
Tensile Modulus MD/TD (MPa) 
3399/3427 
Elongation MD/TD (%) 192/165 
Elmendorf Tear (g/mmm) 
2047/2008 
Spencer Impact (J) 0.81 
MIT Fold 15550 
Pneumatic Ball Impact (J) 
0.25 
______________________________________ 
COMPRATIVE EXAMPLE 3 
In Comparative Example 3 and in Example 4, the T/I ratio of the PEKK resin 
was 60:40, and its inherent viscosity was 0.68. 
Melt temperature was 343.degree. C.; the die pressure was 1.6 MPa; the film 
thickness was 25-40 micrometers. The extrusion was started with the quench 
drum at room temperature. At that point, the film was badly ridged. As the 
drum warmed, the ridges decreased. At about 100.degree.-110.degree. C., 
the ridges largely disappeared. 
EXAMPLE 4 
The drum temperature was 125.degree. C.; the melt temperature was 
330.degree. C.; the die pressure was 1.8 MPa; the film thickness was 33 
micrometers. The film was laying down without ripples. No crystallinity 
was found by wide angle x-ray diffraction. Properties of the cast film are 
shown in Table IV. 
TABLE IV 
______________________________________ 
I.V. 0.68 
Thickness (microm) 33 
Tensile Strength MD/TD (MPa) 
85.5/75.1 
Tensile Modulus MD/TD (MPa 
2413/2461 
Elongation MD/TD (%) 175/14 
Elmendorf Tear (g/mil) 
1220/1220 
Spencer Impact (J) 0.15 
MIT Fold (cycles) 1350 
Pneumatic Ball Impact (J) 
0.11 
______________________________________ 
COMATIVE EXAMPLE 4 
In Comparative Example 4 and in Example 5, the T/I ratio was 60:40, and the 
inherent viscosity was 0.92. 
Melt temperature was 359.degree. C.; die pressure was 6.3 MPa; the film 
thickness was not determined but it was no more than 250 micrometers. The 
oil temperature controller was set at 140.degree. C., and the drum 
temperature leveled out at 125.degree. C. The film was smooth, laying down 
without ripples. The oil temperature controller was reduced to a set point 
of 115.degree. C., and the quench drum leveled out at 103.degree. C.; 
small ripples began to appear in the film. Oil temperature control was 
further reduced to 90.degree. C. As the drum cooled, the film became badly 
disrupted by ripples and ridging. Temperature was increased, with the drum 
leveling out at 115.degree. C.; most but not all signs of rippling 
disappeared. As the drum temperature was further increased to 130.degree. 
C., rippling was essentially gone. 
EXAMPLE 5 
Drum temperature was 125.degree. C.; melt temperature was 361.degree. C.; 
die pressure was 6.0 MPa; film thickness was 35 micrometers. The film lay 
down smoothly and uniformly. Some haziness was noted. However, no 
crystallinity was found by examination of the cast film using wide angle 
x-ray diffraction. Properties of the cast film are given in Table V. 
TABLE V 
______________________________________ 
I.V. 0.93 
Thickness (micrometers) 
36 
Tensile Strength MD/TD (MPa) 
93/85 
Tensile Modulus MD/TD (MPa) 
2372/2358 
Elongation MD/TD (%) 176/163 
Elmendorf Tear (g/mm) 
2835/2441 
Spencer Impact (J) 0.47 
MIT Fold (cycles) 5265 
Pneumatic Ball Impact (J) 
0.26 
______________________________________ 
EXAMPLE 6 
PEKK of a T/I ratio of 70:30 and an I.V. of 0.78 was fed to a 5.1 cm 
single-screw extruder manufactured by Davis Standard and was fed through a 
91.4 cm-wide horizontal coat-hanger die. The quench drum was at 
124.degree. C.; the die pressure was 2.0 MPa; the film thickness was 9 
micrometers. The film quality was excellent with no sign of rippling on 
the drum.