Extruded thermoplastic, liquid crystalline polymers and blends thereof having a planar morphology

The present invention relates to articles of manfacture, such as films, tubes, and coatings, comprising a multiaxially oriented film having a planar morphology, wherein the article of manfacture comprises at least one thermoplastic flexible polymer, at least one thermotropic liquid crystalline polymer, or a blend thereof. Recyclable articles of manufacture having improved barrier properties are also provided.

FIELD OF THE INVENTION 
This invention relates to the extrusion of multiaxially oriented articles 
of manufacture having a planar morphology from thermoplastic flexible 
polymers, thermotropic liquid crystalline polymers, (homopolymers, 
copolymers, and the like) and blends containing thermoplastic flexible 
polymers and thermotropic liquid crystalline polymers. Preferred 
thermoplastic flexible polymers include polyimide, polypropylene, 
polycarbonate and polystyrene. Preferred thermotropic liquid crystalline 
polymers include those commercially available thermotropic polymers sold 
under the trade names of XYDAR.RTM. LCP and VECTRA.RTM. LCP. 
BACKGROUND 
There is a growing demand for high temperature and high performance 
polymers. It is particularly desirable to be able to control the molecular 
orientation of such polymers and to tailor the coefficient of thermal 
expansion (CTE) to optimize properties. 
Polymers having improved properties have been obtained by the incorporation 
of reinforcing fibers, such as, glass, carbon and aramid, to form fiber 
reinforced polymers. However, disadvantages well known to those of 
ordinary skill in the art accompany the use of each of these reinforcing 
fibers. 
Performance gains over fiber reinforced polymers have been achieved by 
blending thermoplastic flexible polymers with thermotropic rigid-rod 
polymers which are also called thermotropic liquid crystalline polymers 
(TLCPs). These blends are sometimes referred to as polymer 
microcomposites. 
Thermoplastic polymers used in making reinforced polymer composites, such 
as those described above, include a wide range of thermoplastics, such as 
polyimides, polyethylene, polystyrene and copolymers thereof, polyamides, 
polycarbonates, polyetherimide and polyesters such as polybutylene 
terephthalate. These thermoplastic polymers are either amorphous or 
semi-crystalline and may be called flexible chain polymers, since 
individual monomer units in the polymer chain are free to rotate with 
respect to each other so that the polymer chain may assume a random shape. 
Thermotropic LCPs are a relatively new class of polymeric materials which 
combine the advantages of melt processability and outstanding mechanical 
properties. Due to their rigid-rod molecular conformation and capability 
to form highly oriented crystalline structures, i.e., an ordered phase 
when subjected to shear above their melting point, they form products with 
properties similar to fiber reinforced composites. However, if the 
orientation of the polymer is in only one direction, such products are not 
suitable for applications requiring strength in more than one direction. 
Because of their rigid backbone structure with flexible spacer groups, 
commercially available TLCPs have far higher tensile strength and flexural 
moduli than conventional polymers. 
Thermotropic LCPs can be processed in the melt state and they are capable 
of forming a highly oriented fibrillar structure when subjected to shear 
above their melting point. Methods for producing such highly oriented 
fibrillar structures are disclosed in U.S. Pat. Nos. 4,973,442; 4,939,325; 
4,963,428; and 4,966,807 (hereinafter referred to collectively as the "CRD 
Patents"). The disclosure of each of these patents is incorporated herein 
by reference. A brief discussion of this methodology follows. 
A schematic diagram of the process disclosed in the CRD Patents is shown in 
FIGS. 1A and 1B. A combination of shear and elongational flows during the 
extrusion process orients the TLCP polymers. This controlled orientation 
can be accomplished with the counter-rotating die shown in FIG. 1A that 
aligns TLCP molecules along at least two distinct axes within a single 
ply. The angle that the TLCP fibrils make with the longitudinal axis of 
the film is .+-.theta, where theta can be varied from near zero to over 50 
degrees. By rotating the mandrels, a transverse shear flow is superimposed 
on the axial shear developed as the polymer melt is extruded through the 
die. It is possible to obtain films in accordance with the CRD Patents 
having a thickness ranging from about 0.0001 to 0.060 inches. 
In the CRD Patents, the objective was to obtain extruded articles, such as 
films and tubular components, having optimized tensile strength, tensile 
modulus, coefficient of thermal expansion, and other properties related to 
in-plane stresses and deflections of the film. As disclosed in the CRD 
Patents, such properties can be controlled and enhanced by alignment, 
orientation and organization of the rigid thermotropic LCP molecules. In 
the technology disclosed in the CPD Patents, reinforcement is achieved by 
the LCPs in fibrillar form. This morphology was observed directly 
microscopically and indirectly through effect on mechanical properties. 
In such methods, subsequent post-die processing enhances the orientation 
already present as the material exits the die. For example, post 
processing such as post-die draw in the transverse and/or machine 
direction can be performed on the extruded article to further optimize 
properties or obtain a finished product. 
Because TLCPs form an ordered phase in the melt (hence, the name 
thermotropic), they have shear viscosities far lower than other polymers, 
This property gives them potential importance as a processing aid. 
Thermotropic liquid crystalline polymers have received increasing attention 
in the scientific and technical literature as in situ reinforcements in 
polymer blends and microcomposites. The range of high performance 
thermoplastic flexible polymers blended with TLCPs include polyimides, 
polyamides, PES, PEI, PEEK, polycarbonate, PET, PPS, and polyarylace. The 
blending of thermoplastic flexible polymers and LCPs occur at various size 
scales down to the molecular level to form the systems referred to as 
polymer microcomposites (PMC). 
The microstructure of a polymer microcomposite is similar to 
fiber-reinforced composites except that the fibers are at a micron to 
submicron scale. Blends of thermoplastic polymers and TLCPs are disclosed, 
e.g., in U.S. Pat. Nos. 4,386,174; 4,728,698; 4,835,047; and 4,871,817, 
the disclosures of which are incorporated herein by reference. 
The potential advantages of blending thermoplastic matrix polymers with 
thermotropic LCPs are well recognized. Yet, despite the potential 
advantages of combining thermoplastics with TLCPs, traditional processing 
steps have failed to yield the optimal properties desired in blends. To 
achieve the optimal properties with such blends, processing techniques are 
used that permit the controlled orientation of the rigid-rod polymer in 
melt state and subsequent freezing in the desired morphology. 
Although fibers and films of LCP blends have shown the most promise in 
terms of properties, they typically have consisted of a highly uniaxially 
oriented structure with correspondingly inferior transverse properties. 
This anisotropy is the bane of thermotropic LCP blends, limiting their use 
primarily to spun fibers. To extend the applications of thermoplastic 
flexible polymers/TLCP blends to two and three dimensional articles, the 
fibrillar orientation of the TLCP reinforcing phase must be controlled. 
Indeed, the processing of such blends into films, tubes, and other 
structures has been severely hindered by the difficulties encountered in 
con-rolling the orientation and CTE of the final product. 
Until recently it had not been possible to form articles, such as films and 
tubes, comprising blends of thermoplastic flexible polymers and TLCPs and 
to obtain controlled multiaxial orientation of such articles. Such 
articles and methods of obtaining them are disclosed in application Ser. 
No. 07/678,080, filed Apr. 1, 1991, now abandoned. One such method 
involves use of a counter-rotating die (CRD) and the technology disclosed 
in the CRD Patents, supra. 
In general, a multiaxially oriented article is produced which has a 
tailored CTE and comprises at least one thermotropic LCP and at least one 
thermoplastic flexible. The method comprises: 
(i) extruding a melt of the polymer or polymers, under conditions which 
impart axial and transverse shear thereto to form a multiaxially oriented 
article; and 
(ii) maintaining the article under conditions to enable solidification of 
the orientation formed in step (i). 
The method may further comprise the step of subjecting the article to 
post-die draw in the axial and/or transverse direction between steps (i) 
and (ii). When it is desirable to increase the bend and fracture toughness 
of the article, e.g., the film or tube, the film or tube is stretched at 
above the Tg of the thermoplastic flexible polymer. 
Co-pending Ser. No. 07/678,080 filed Apr. 11, 1991, now abandoned teaches 
that LCP-thermoplastic blends can be processed as disclosed in the CRD 
Patents to achieve fibrillar morphology and to orient the fibrils during 
processing to greatly improve mechanical properties with only small 
amounts of LCP (10% for example) in the blend. 
A major problem currently exists in the packaging industry because of the 
relatively poor barrier properties of plastic materials used in films, 
bags, bottles, cars and ocher containers. Packaging materials have long 
since been developed with excellent barrier properties, but they do so 
with multiple layers, typically three to seven layers, including separate 
layers for oxygen and moisture barriers. Although special co-extrusion 
machinery has been developed to make such films, they are still perceived 
as being environmentally "unfriendly" because they cannot be recycled. 
Also, co-extrusion requires the use of secondary "tie" layers to bond the 
other layers together, and the machinery is generally more expensive to 
build and operate than equipment for extrusion and processing of single 
polymer materials. 
Furthermore, it is not possible to recycle most of such multiple layer 
packaging materials, because the components of the multi-layers are 
irreversibly melted together during thermoplastic recycling. Plastic 
materials which can be recycled (such as polyethylene) are not very good 
barriers to gases such as oxygen, air and water vapor, and therefore 
cannot be used for long storage times. Accordingly, materials which 
combine excellent barrier properties with ability to recycle, creating a 
new generation of food and beverage packaging materials are being sought. 
SUMMARY OF THE INVENTION 
The present invention provides multiaxially oriented articles, such as 
films, tubes and coatings, having a planar or laminar morphology and 
comprising at least one thermoplastic flexible polymer, at least one 
thermotropic rigid-rod polymer, i.e., thermotropic liquid crystalline 
polymer (TLCP), and blends thereof. 
It has unexpectedly beer found that the processing technology disclosed in 
the CRD Patents and in Ser. No. 07/678,080 filed Apr. 1, 1991, now 
abandoned, can be controlled to produce multiaxially oriented articles 
having a planar rather than fibrillar morphology. It has also unexpectedly 
been discovered that the highly oriented planar or laminar morphology of 
the present invention provides enhanced barrier properties over the 
fibrillar morphology disclosed in the CRD Patents and in Ser. No. 
07/678,080 filed Apr. 1, 1991, now abandoned. 
By the fibrillar morphology disclosed in the CRP Patents and in Ser. No. 
07/678,080 filed Apr. 1, 1991, now abandoned, is meant that discrete 
fibrils are formed and oriented as illustrated in FIG. 2C, i.e., 
multiaxially oriented. FIGS. 2A and 2C illustrate the various orientations 
imparted to rigid-rod polymers by stress conditions. Typically, LCP 
polymers subjected to shear stress assume a uniaxial orientation as 
illustrated in FIG. 2A. Ordered polymers in solution have the scattered or 
random nematic orientation illustrated in FIG. 2B. FIG. 2C illustrates the 
twisted nematic (or cholesteric) orientation imparted to ordered polymers 
by processing under the method of the CRD Patents and Ser. No. 07/678,080 
filed Apr. 1, 1991, now abandoned. 
In contrast, in a planar or laminar morphology or microstructure as shown 
in FIG. 3A, the two-dimensional laminar layers are much less thick than 
the entire film, they overlap one another, and they extend over the entire 
length and width of the film. In comparison, a composite film made by 
conventional compounding and extrusion methods will contain discrete 
polymer regions which are not laminar and do not overlap. In many cases, 
such as the blending of LCPs and thermoplastics, workers report droplets 
of one component in the other, as shown in FIG. 3B. Such a droplet, if 
extruded under conditions to produce a fibrillar microstructure, e.g. as 
disclosed in the CRD patents, will not improve the barrier properties of 
the composite as does the planar morphology of the present invention. 
By using transverse shear and control of temperature during extrusion in 
accordance with the teachings of the present invention, the polymer layers 
are put in series providing the best barrier, rather than in parallel (see 
FIG. 8) where gases can permeate through the path of least resistance. In 
other words, shear forces applied to the polymers during film extrusion 
impart a planar or laminar arrangement of the polymer molecules, much like 
a deck of cards, resulting in high resistance to gas permeation through 
the film The planar morphology provides improved resistance to gas 
permeability through the thickness of the articles of the present 
invention. This morphology also enhances dielectric properties, such as, 
dielectric constant, dielectric breakdown strength and tan delta. 
Accordingly, the present invention also provides articles of manufacture, 
e.g., films, tubes and coatings having improved barrier and dielectric 
properties. 
Some advantages provided by the planar morphology of the present invention 
over other barrier layers are: it can replace multi-layer materials with a 
single layer resulting in the ability to recycle and reduce manufacturing 
costs, it can reduce the thickness of the barrier layer resulting in a 
cost savings and reduction of material to dispose or recycle, since it 
contains no metal layers it can be used with microwave cooking, and it can 
be used with many conventional fabrication methods (such as heat sealing) 
common to the food packaging industry. Other benefits of the invention 
will be apparent from the discussion and examples. 
Thermoplastic flexible polymers suitable for use in the present invention 
include polyimide, polypropylene, polycarbonate and polystyrene, and 
blends thereof. Polyimide represent one type of preferred polymers. See 
FIG. 4A. Polyimides such as LARC-TPI,.RTM. and ARUM..RTM. formerly known 
as NEW-TPI,.RTM. are particularly preferred polymers for use in the 
present invention. The structure of LARC-TPI,.RTM. is shown in FIG. 4B and 
of ARUM.RTM. is shown in FIG. 4C. LARC-TPI.RTM. and ARUM.RTM. are 
available from Mitsui-Toatsu Chemicals, Inc. 
Thermotropic LCPs suitable for use in the present invention include, e.g., 
wholly and partially aromatic polyester and copolyesters. XYDAR.RTM. see 
FIG. 5A, is one such preferred polymer for use in the present invention 
(available from Amoco Performance Products, Inc.) and is based on 
terephthalic acid, p,p'-dihydroxybiphenyl, and p-hydroxybenzoic acid. 
VECTRA.RTM. see FIG. 5B and 5C, is another preferred TLCP for use in the 
present invention (available from Hoechst Celanese Corp.) and can be 
characterized as primarily aromatic polyesters based on parahydroxybenzoic 
acid and hydroxynaphthoic acid. Both types of polyesters contain 
relatively rigid chains of long, flat monomer units which undergo ordering 
in the melt. They are also referred to as nematic, anisotropic, or 
self-reinforcing polymers. 
In embodiments of the present invention wherein the article comprises a 
blend of thermotropic LCP and thermoplastic flexible polymer the 
proportion of polymers selected will depend upon the intended use of the 
final article produced therefrom. In preferred blends, the thermoplastic 
flexible polymer is present at from about 99 to 50 weight % and the 
thermotropic rigid-rod polymer is present at from about 1 to 50 weight %. 
In one particularly preferred embodiment, the thermoplastic polymer is 
present at about from less than 95 percent to greater than 80 percent and 
the TLCP is present at about from greater than 5 percent to less than 20 
percent. 
In selecting thermoplastic flexible polymers and TLCPs for use in the 
blends of the present invention, both the thermodynamic and rheological 
properties of these polymers must be considered. 
In particularly preferred embodiments of the present invention, 
LARC-TPI,.RTM. ARUM.RTM. and mixtures thereof, are blended with XYDAR.RTM. 
or VECTAO.RTM. TLCPs and melt extruded by utilizing a counter-rotating die 
to produce a multiaxially oriented film having a planar morphology through 
varying the processing parameters, particularly the temperature and 
transverse shear, in accordance with the teachings of the present 
invention. These films have a multiaxial orientation in the TLCP phase and 
have a planar morphology, as well as improved barrier properties. 
An immediate advantage of such composite films is that the barrier 
properties are as good or better than "environmentally unfriendly" 
multi-layer laminated packages that can not be recycled. 
This development is of interest to the food and beverage packaging 
industry, because it can replace the complex, multi-layer laminated 
structures typical of packaging where strength, toughness and barrier 
properties are all required, such as snack food bags, juice boxes, frozen 
foods packaging and beverage bottling. 
Films comprising the TLCP/thermoplastic blends of the present invention 
should exhibit the low permeability properties of multi-layer packaging, 
but should be fully recyclable. A film processed using the teachings of 
the present invention is two orders of magnitude less permeable to oxygen 
and water vapor that PVDC and is not thought co be toxic, based on 
currently available information. This unique combination makes it possible 
to produce containers for carbonated fluids, for example, with extended 
shelf-life. Furthermore, the TLCP/thermoplastic flexible polymer blends of 
the present invention are recyclable. These recyclable LCP blends provide 
other key advantages over multi-layer packages, including: 
Potentially lower product cost 
Wider range of performance (higher temperature, strength) 
Ability to form into articles of manufacture not possible with multi-layer 
films 
The cost of TLCP/thermoplastic flexible polymer blend packaging should be 
less than multi-layers because less complex and expensive extrusion 
equipment will be needed. Also, the barrier performance of the LCP portion 
of the blend is 100 to 1,000 times higher than the base plastic portion, 
so the cost per unit performance of the blend is actually less than the 
basic plastic itself. 
The properties of LCP blends of the present invention are likely to be 
better than most packaging materials, based on the strength, high 
temperature capability, chemical inertness, tear resistance, wet strength, 
and fatigue strength of the LCP's.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention provides multiaxially oriented structures, such as 
films, coatings, and tubes, having a planar or laminar morphology, and 
methods of making such structures. The structures of the present invention 
comprise at least one thermotropic LCP, at least ore thermoplastic 
flexible polymer, or are formed from a blend comprising at least one 
thermoplastic flexible polymer and at least one thermotropic rigid-rod 
polymer. 
The following definitions of multiaxially oriented film characteristics are 
useful in understanding the present invention: 
______________________________________ 
balanced biaxial 
a film having maximum strength and 
stiffness at approximately .+-. 45 deg. to the 
machine direction, but exhibiting the least 
angular dependence of these properties. 
predominantly 
a film having maximum strength and 
stiffness in the uniaxial machine 
direction, but also with some strength 
within .+-. 20 deg. of the machine direction. 
nearly uniaxial 
a film having maximum strength and 
stiffness in the machine direction, with 
some strength within only .+-. 5 deg. of the 
machine direction. 
______________________________________ 
As used herein, the generic term for those orientations not meeting 
specific definitions above, but providing strength to a film in both the 
machine and transverse directions is "multiaxial." 
Thermoplastic flexible polymers useful in the practice of the present 
invention, include polyimide, polypropylene, polycarbonate, and 
polystyrene. Such thermoplastic polymers are selected, in part, on the 
basis of properties, such as melt viscosity and thermal stability. 
Thermoplastic flexible polymers for melt extrusion in accordance with the 
present invention typically have a melt viscosity in the range of about 
10E4 to 10E5 poise. Additives may be incorporated into these polymers to 
bring the viscosity into the appropriate range. 
The thermal stability of such polymers must be taken into consideration 
because the polymer must not significantly degrade during extrusion. 
Extrusion at lower temperatures can reduce the thermal degradation of a 
particular thermoplastic. However, this must be balanced against any 
increase in polymer viscosity caused by dropping the temperature. Other 
desirable characteristics include low outgassing and good flow. 
Although polyimides will be used to illustrate thermoplastic flexible 
polymers in the present invention, the invention is not so limited. 
Preferred thermoplastic polyimides for use in this invention include those 
polyimides having the general structure shown in FIGS. 4A, 4B, and 4C. 
LARC-TPI.RTM. and ARUM.RTM. thermoplastic polyimides, commercially 
available from Mitsui-Toatsu Chemicals, Inc., have excellent flow 
properties and thermal stability, and are particularly preferred 
thermoplastic polymers for use in the present invention. By combining such 
polyimides with thermotropic LCPs as taught herein, the orientation can be 
controlled and the CTE can be tailored. 
The chemistry of LARC-TPI.RTM. is shown in FIG. 4B. In the imide form it 
can be formed, laminated, or molded in the substantial absence of solvents 
or evolved materials. LARC-TPI.RTM. achieves its processability and its 
suitability for lamination through chemistry based upon a polyamic acid 
precursor capable of imidization by further heating. The imidized film 
offers good adhesion, flow and flexibility at moderate temperatures, with 
the chemical and thermal resistance increasing dramatically after heat 
treatment (increased imidization). As a linear aromatic polyimide, 
LARC-TPI exhibits the chemical insensitivity, high thermal resistance, low 
moisture sensitivity, radiation and thermo-oxidative resistance and good 
mechanical properties of other materials of this class (e.g., ULTEM.RTM., 
bismaleimide, THERMID.RTM.). These properties are relevant to aircraft and 
aerospace applications, where lightweight, stiff structures are needed; 
and to electronic circuit board applications, where the high temperature 
(soldering) resistance and dimensional stability are most attractive. 
Two especially preferred classes of thermotropic liquid crystalline 
polymers exhibiting desired performance characteristics for use in the 
present invention are Amoco's XYDAR.RTM. TLCPs and Hoechst-Celanese's 
VECTRA.RTM. TLCs polymers. The general chemical structures of these 
polymers are shown in FIG. 5. 
Processing characteristics and compatibility are considerations in 
selecting the appropriate thermoplastic polymers and TLCP(s) for use in 
the blends in accordance with the present invention. By compatibility is 
meant both thermodynamic miscibility and the relative Theological 
properties between the phases. Usually, polymer blends are immiscible, and 
none more so than rigid-rod LCPs with flexible chain polymers. However, 
too great a miscibility may eliminate the hierachical fibrillar structure 
present, thereby reducing the effectiveness of the reinforcement provided 
by the high modulus TLCP. 
Other conventional ingredients are optionally included in the polymer 
blends of the present invention. Such ingredients include, pigments, 
fillers, stabilizers and so forth, well-known to those of ordinary skill 
in the art of polymer processing. 
The processability of the polyimide was greatly enhanced through reduction 
in the melt viscosity by virtue of the incorporation of the TLCP into the 
blend. When processed in accordance with the teachings of the present 
invention, high shear forces and temperature control applied to such 
blends during extrusion, impart a laminar arrangement of the polymer 
molecules, much like a deck of cards, resulting in high resistance to gas 
permeation through the film. 
The present invention will be illustrated by multiaxially oriented films 
having a planar morphology wherein the film comprises XYDAR.RTM. LCP or a 
blend of XYDAR.RTM. LCP and a polyimide. However, it is understood that 
the present invention is not so limited. 
In accordance with the present invention a laminar layered type of 
morphology is achieved to obtain improved barrier properties. Special 
processing means are more effective at producing layered morphology than 
the previously disclosed means for making fibrillar reinforcement, i.e. , 
disclosed in the CRD Patents and in co-pending Ser. No. 07/678,080. 
The following are processing parameters which will produce a planar layered 
morphology in the LCP regions of the blend: 
1. High transverse shear produced by rotation raze of the circular die. 
Rotation rate should be higher than that used to produce film with the 
best mechanical properties in the extrusion direction. The rotation rate 
for production of film with the best barrier properties, i.e., planar 
morphology, could be 2 to 5 times higher than that for the best mechanical 
properties, i.e., fibrillar morphology. 
2. The LCP phase must be melted and be at a low viscosity relative to the 
thermoplastic phase. 
3. The film should be drawn equally in two orthogonal directions after 
extrusion from the die, while the LCP-thermoplastic blend is in a 
partially solidified state. In contrast, film with high mechanical 
properties is typically drawn preferentially in one of two orthogonal 
directions. 
4. Laminar flow conditions (rather than turbulent conditions) are 
maintained in the die. 
Although some of the conditions used to produce the layered morphology of 
the present invention are the same as the conditions disclosed in the CRD 
Patents to produce the fibrillar morphology, more specialized controls are 
needed. This is because a fibrillar (one-dimensional) morphology is easier 
to achieve via extrusion than a planar (two-dimensional) one. The fibrils 
are discrete and have a small diameter and can be thought of as 
one-dimensional, i.e., having length only. In contrast in the planar 
morphology, the individual "layers" are formed of many fibers and can, 
thus, be thought of as two-dimensional, i.e., as having width, in addition 
to length. 
The counter-rotating die itself is not sufficient to create planar 
morphology. Temperature, shear rate, total shear strain, axial flow rate, 
pressure, and draw ratios must all be controlled in as taught herein to 
produce the layered LCP microstructure, rather than a fibrillar 
arrangement of the LCP molecules. 
Extrusion conditions described in TABLE 3 are for the production of films 
comprising TLCP/polyimide blends having a fibrillar morphology. These 
conditions were modified to produce the planar morphology of the present 
invention. The 10% XYDAR.RTM./90% ARUM.RTM. film shown in FIG. 7B and the 
XYDAR.RTM. LCP film shown in FIG. 7A were produced under the following 
conditions. 
______________________________________ 
Feed Screw 
Rate Speed Temperature (.degree. F.) 
Powder (g/min) (rpm) Zone 1 
Zone 2 Zone 3 
Die 
______________________________________ 
10% 28 98 700 720 730 725 
XYDAR .RTM. 
90% 
ARUM .RTM. 
XYDAR .RTM. 
25 110 610 650 640 630 
______________________________________ 
Additionally, a glass tube cooling ring was used outside the die to quench 
the melt and :he screw compression ratio was 6:1 rather than 4:1 as 
described in the Examples which follow. 
In general, high shear and control of temperature are important to achieve 
the planar morphology in the LCP region of the blend. High transverse 
shear is produced by controlling the rotation rate of the GRD as described 
above. The temperature is controlled by controlling both the die and the 
exit temperature. Upon the die the extrudate was blown against a chilling 
ring which controls the temperature at that point. 
The exit temperature of the extrudate should be slightly below the melt, 
i.e., the exiting polymer is partially solidified. If it is in the fully 
molten phase, it does not have melt strength (strength of extrudate) to be 
blown. It must be tacky enough to be capable of orientation and have 
enough strength to be blown without exploding. 
To get the planar morphology, the temperature of the extrudate is slightly 
lower then for obtaining the standard fibrillar film. 
FIG. 6 compares the barrier properties of a film comprising XYDAR.RTM. 
thermotropic LCP polymer, processed in accordance with the present 
invention with some standard barrier films produced using conventional 
extrusion technology, i.e., not by use of the technology disclosed in the 
CRD Patents or in the present application. 
In FIG. 6, the block labeled "FMI LCP", represents XYDAR.RTM. TLCP 
processed in accordance with the present invention to produce a planar 
morphology. The block labeled "Vendor LCP" represents an LCP produced 
using conventional extrusion technology. It can be seen that oxygen 
permeability is improved by an order of magnitude and water vapor 
permeability is improved by eight, as compared with Vendor LCP. 
FIG. 7A show electron micrographs of the FMI LCP described above. The 
bottom layer is shown at 1, the top layer is shown at 2, and an 
intermediate layer is shown at 3. 
The barrier properties of films comprising blends of thermoplastic flexible 
polymers and thermotropic LCPs produced in accordance with the present 
invention were compared with the barrier properties of (i) a film 
comprising the thermotropic LCP extruded using conventional extrusion 
technologies and (ii) a film comprising a blend of thermoplastic flexible 
polymer and thermotropic LCP, also extruded using conventional extrusion 
technology. 
These studies were conducted with films of ARUM.RTM./XYDAR.RTM. blends 
containing up to 30 wt percent LCP. 
The barrier properties of a thermoplastic film processed through the CRD 
substantially improve with the addition of an LCP phase. For example, by 
processing a blend of polyimide and LCP, the permeability of the film to 
oxygen decreased by eightfold and to water vapor by over sixteenfold by 
adding as little as 10 wt percent XYDAR.RTM. LCP to the polyimide. An 
electron micrograph of this film is shown in FIG. 7. 
The reason for this improved barrier performance is that the LCP regions 
are thought to form a laminar arrangement in the blend. It is estimated 
that these layers are approximately 0.1 to 1.5 micron thick, and overlap 
one another. In comparison, a composite film not made using the technology 
in the CRD Patents, will contain discrete LCP regions which form particles 
that are neither laminar not overlapping. This particulate arrangement as 
shown in FIG. 3B contributes little to better barrier performance, unless 
the amount of LCP is very high, over 70% by volume. 
CRD processed blend films put the laminar LCP layers. "in-series" to the 
permeation direction; the conventional process places the LCP region "in 
parallel" with the permeation direction. FIG. 8A shows "in-series" 
arrangement and FIG. 8B shows "in-parallel" arrangement. This has a 
significant effect on the barrier properties of the composite, such that 
the F-M "series" composites are 10 to 100 times better than the "parallel" 
composites. Barrier properties in "series" can be represented by the 
equation Bc=V1B1+V2B2 and barrier properties "in parallel" can be 
represented by the equation Pc=V1P1+V2P2, where: 
B--Barrier Property 
P--Permeability (-i/B) 
V--Volume Fraction 
c--Composite 
1--Thermoplastic 
2--LCP 
FIG. 9 shows the permeability relationships for the two types of composite 
films. In the "parallel" composite, tine permeability of the composite is 
the arithmetic sum of the permeability of each component. The permeability 
of each component is given by the volume fraction times the inherent 
permeability of the material. In the "series" composite, the barrier 
property (reciprocal of permeability) of the composite is the arithmetic 
sum of the barrier property of each component. This results in an 
idealized hyperbolic relationship between composite permeability and 
volume fraction of the LCP. Since the permeability of the LCPs is 100 to 
1,000 times lower than that of the base thermoplastic resin, the 
difference between "series" and "parallel" relationships is dramatic. The 
data of 10% LCP in the polyimide indicates that a "series" composite 
barrier film was achieved using the modification of the methodology of the 
CRD Patents. 
Examples 1 to 4, which follow, describe experiments which are disclosed in 
co-pending Ser. No. 07/678,080 in which a fibrillar morphology was 
produced. These examples are included to aid in the understanding of the 
present invention. Standard commercially available reagent grade chemicals 
were used whenever possible. 
A 3/4 in. single screw extruder with three heating zones was used in the 
Examples. A counter-rotating die (CRD), were used to produce multiaxial 
films and multiaxial tubes by melt processing XYDAR.RTM. fully imidized 
LARC-TPI.RTM. powder, and blends thereof. Extrusion grades of the polymers 
were used wherever possible. 
EXAMPLE 1--ROD DIE EXTRUSION 
As explained above, prior to melt extrusion, an appreciation of the 
polymers Theological properties is necessary, both in order to select 
appropriate polymers for blending and to select extrusion conditions. If 
these properties are not available, e.g., in the literature or from the 
manufacturer, they may be determined in accordance with well-established 
methodology. 
The melt viscosities of polymers used in the examples were obtained from 
the manufacturers, from literature, and, where needed, measured by 
Foster-Miller using a parallel plate rheometer and conventional 
methodology. 
A rod die was used to help identify the most suitable LARC-TPI.RTM. type 
polymer for use in the present invention (i.e., Mitsui grades versus 
DURIMID.RTM.) and to determine the general conditions for multiaxial 
extrusion through the CRD. Both the rod die and the CRD were used with the 
same extruder, so the information gained from one could be related to the 
other system. The rod die had a die gap of 0.635 cm (0.25 in.) and a 
temperature capability of 370.degree. C. (700.degree. F.). 
In all, the following polymers were extruded through the rod die: 
Neat DURIMID.RTM. 
DURIMID.RTM. containing 10 weight percent 6F Diimide 
DURIMID.RTM. containing 5 weight percent VECTRA.RTM. 
Mitsui 1500 -LARC-TPI.RTM. 
Mitsui 2000 LARC-TPI 
The extrusion conditions for these systems are summarized in Table 1 below. 
TABLE 1 
__________________________________________________________________________ 
EXTRUSION CONDITIONS FOR LARC-TPI POWDERS 
PROCESSED THROUGH A ROD DIE 
Feed 
Screw 
Rate 
Speed 
Temperatures (.degree. F.) 
Powder (g/min) 
(rpm) 
Zone 1 
Zone 2 
Zone 3 
Die Comments 
__________________________________________________________________________ 
Durimid 
30 75-100 
695 695 700 685 Unable to produce any 
extrudate 
Durimid + 10% 
30 75-100 
520 550 550 525 Material experienced 
6F Diimide long residence times 
and became degraded 
Durimid + 20% 
30 75-100 
460 470 470 470 Degraded 
6F Diimide 
Durimid + 
30 75-85 
620 630 630 620 Low integrity extrudate 
Vextra resulted due to 
incompatible melt 
temperatures and poor 
flow of the Durimid 
Mitsui 1500 
30 75-100 
630 650 650 660 Excellent extrudate, 
good flow and low 
residence times will 
allow the production of 
good quality films 
Mitsui 2000 
30 75-100 
590 595 600 585 Poor extrudate, unable 
to produce quality rods 
due to instability of the 
material 
__________________________________________________________________________ 
Extrusion temperature Zone 1: where material is fed into the extruder to 
soften the material. 
Extrusion temperature Zone 2: where material is mixed and sheared and 
begins to melt; also referred to as the transition zone. 
Extrusion temperature Zone 3: where material is fully melted under shear 
and travels to the die. 
Extrusion temperature Zone 4: where the temperature is near that of Zone 
3 to allow good flow and film formation. 
Residence time the length of time the material is exposed to high 
temperature and shear in the extruder. (Long residence times cause the 
material to degrade.) 
Screw Speed the speed at which the screw turns. 
Feed Rate the speed at which material is fed into the extruder. 
Takeup speed the speed at which extrudate is pulled from the die. 
These conditions, along with the quality of the extrudates, were used to 
select the preferred materials for multiaxial extrusion, and, to set 
initial extrusion temperature, residence time, screw speed, feed rate, and 
takeup speed. The most promising grade of LARC-TPI.RTM. for extrusion 
purposes was the Mitsui 1500 which exhibited a consistent rheology and 
thermal stability. It was also least dependent on residence time which 
made it more attractive than other grades of LARC-TPI.RTM.. 
DURIMID.RTM. and Mitsui 2000 LARC-TPI.RTM. was not successfully extruded 
through the rod-die extruder due to their high melt viscosity (&gt;10.sup.7 
poise) and their volatile nature. The DURIMID.RTM. powder was not 
end-capped, resulting in a molecular weight increase in the extruder 
during processing. To avoid this, a residence time in the extruder of less 
than one minute was required, but this did not allow complete melting of 
the powders inside the extruder. The Mitsui 2000 LARC-TPI.RTM. is also not 
extrusion grade and is less stable than Mitsui 1500 LARC-TPI.RTM.. The 
resulting rods exhibited poor mechanical integrity and large voids, which 
indicated some outgassing had occurred. Addition of 6F Diimide and LCP 
VECTRA.RTM. markedly lowered the viscosity of DURIMID.RTM., but 
volatilization still occurred. Based on these studies of LARC-TPI.RTM. 
type polyimides, Mitsui 1500 LARC-TPI.RTM. polyimide was selected for 
extrusion through the CRD. 
EXAMPLE 2--MELT EXTRUSION OF FILMS COMPRISING LARC-TPI.RTM. AND 
LARC-TPI.RTM./XYDAR.RTM. BLENDS 
Two types of films, neat Mitsui 1500 polyimide LARC-TPI.RTM. and Mitsui 
1500 LARC-TPI.RTM./XYDAR.RTM. blends, were extruded through a CRD similar 
to that shown in FIG. 1A. Two volume fractions XYDAR.RTM. at 10 and 30 
volume percents were produced. 
The 1500 LARC-TPI.RTM. used for this study was a fully imidized polyimide 
with an average particle size of 5 to 7 micrometers. Since it was not 
available in large quantities, several 5-lb batches had to be used for the 
different extrusion experiments. However, because this was an experimental 
grade material, the glass transition temperature varied from batch to 
batch and its melting point was in the range of about 285 to 305.degree. 
C. The T.sub.g of each batch was determined using a differential scanning 
colorimeter (DSC), followed by parallel plate rheometry co determine the 
polymer's viscoelastic properties. 
Two types of neat LARC-TPI.RTM. films were extruded through the CRD. In the 
first case, highly drawn near-uniaxial film was processed. In the second 
case, film was extruded with more transverse orientation. FIGS. 10A-10C 
summarize preferred conditions for the extrusion of multiaxially oriented 
Mitsui 1500 LARC-TPI.RTM.. 
The extrusion process involved first drying the LARC-TPI.RTM. polyimide 
powder at 150.degree. C. for 12 hours to remove moisture. Next, as 
illustrated in FIG. 10, the powder was introduced into the feed-hopper 1, 
a nitrogen purged enclosed chamber where powders were protected against 
moisture during the extrusion process. Next, the powder was fed into the 
extruder 2 at a rate of 25 to 30 g/min and carried inside the extruder 
where it was heated. The heated polyimide was carried forward in the 
barrel via the screw 3, applying shear during the process. The amount of 
shear depends on two variables, screw speed and the screw compression 
ratio. Compression ratio is the ratio between the depth of the grooves 
(teeth) in the back versus the tip of the screw. A 4 to 1 compression 
ratio to screw was used in this work. For comparison, liquid crystalline 
polymer XYDAR.RTM. is often processed using a 6 to 1 compression ratio 
screw. The shear rate constantly increased as the material was moved 
forward in the barrel. The LARC-TPI.RTM. eventually exhibited viscoelastic 
(flow) behavior as a result of a combination of heat and high shear. The 
viscosity of the LARC-TPI.RTM. at this stage was in the range of 1E4 to 
1E5 poise. At this point, the polyimide went through a pump block 10 (FIG. 
10A) and into the counter-rotating die 20 (FIG. 10A). Once inside the CRD 
20, the counter-rotating mandrels 21, 22 applied more shear to the 
extrudate, thus imparting additional orientation to the exiting film. The 
exiting film was cooled once it is exposed to room temperature conditions. 
It was then nipped via nip-rollers which take up the extruded film at a 
designated rate based on the desired angular orientation. The angular 
orientation of the finished film was a function of the amount of material 
entering the die, the rate at which the CRD spins and the rate of take up. 
See FIG. 10B. 
Of the LCPs considered for this works XYDAR.RTM. and VECTRA.RTM., 
XYDAR.RTM. was considered the most suitable match for LARC-TPI.RTM.. It is 
available in powder form, and can be extruded at temperatures close to 
that of LARC-TPI.RTM.. 
XYDAR.RTM. and LARC-TPI.RTM. powders were mechanically mixed and dried at 
150.degree. C. for 12 hours prior to extrusion as described above. To 
determine the extrusion conditions, sample powders of the mixture were 
characterized using a differential scanning colorimeter (DSC) and parallel 
plate rheometry. FIGS. 10B and 10C summarize the extrusion conditions for 
10 weight percent and 30 weight percent XYDAR.RTM., respectively. The 
extrusion process was the same as described herein above. Two types of 
films, near-uniaxial, and more transverse, were extruded. The properties 
of these blended films are summarized in Table 2. 
TABLE 2 
__________________________________________________________________________ 
Orientation 
TM (GPa) 
TS (MPa) 
CTE ppm .degree. C. 
Polymer (Degree) 
MD TD MD TD MD TD Elongation 
__________________________________________________________________________ 
100% LARC-TPI 
.+-. 24 
2.8 
2.8 
97 104 
34 34 10-20% 
Near 3.2 
2.4 
130 
105 
27 38 10% 
Uniaxial 
10% XYDAR/ 
.+-. 24 
5.1 
3.2 
140 
98 12 38 -- 
90% LARC-TPI 
30% XYDAR 
.+-. 24 
3.2 
-- 156 
-- 3-4 40 -- 
70% LARC-TPI 
Near 3.0 
-- 101 
-- 12 -- -- 
Uniaxial 
30% XYDAR 
Near 3.15 
2.25 
143 
100 
3 15 50 
12% LARC-TPI 
Uniaxial 
58% NEW-TPI 
10% XYDAR 
.+-. 24 
3.12 
1.8 
135 
110 
24 33 100% 
90% NEW-TPI 
100% XYDAR 
.+-. 24 
6.2 137 
100 
+2 +8 5% 
100% NEW-TPI 
.+-. 45 
2.14 
2.15 
97 97 44 45 150% 
__________________________________________________________________________ 
EXAMPLE 3--MELT EXTRUSION OF NEW-TPI.RTM. AND TERTIARY BLENDS 
NEW-TPI.RTM. polyimide provided by Mitsui Taotsu Corporation was used in 
pellet form. ARUM.RTM. is highly processable and is a thermally stable 
polyimide. 
FIG. 11 presents a schematic illustration of the tertiary blends studied. A 
combination of NEW-TPI.RTM. and LARC-TPI.RTM. was used in order to exploit 
the best properties of each system. LARC-TPI.RTM. is a higher modulus 
material which is better characterized than NEW-TPI.RTM.. NEW-TPI,.RTM. on 
the other hand, is available in pellet form, making it easier to process. 
It also yields a tougher finished product. Their combination resulted in 
easily reproducible and processable blends. The ratio of the NEW-TPI.RTM. 
to LARC-TPI.RTM. was fixed at 0.75 to 0.25 for all the tertiary systems. 
Only the weight percent LCP and its type were altered. These differences 
are discussed below. 
A mixture of 0.75 to 0.25 NEW-TPI.RTM. to LARC-TPI.RTM. was prepared for 
tertiary blend formulations. LARC-TPI.RTM. powder was compacted. The 
compacts were broken into pieces sufficiently small to mix with 
NEW-TPI.RTM. pellets. The resulting mixture was then mixed with either 
XYDAR.RTM. pellets or VECTRA.RTM. pellets. Films with LCP content of 10 
and 30 weight percent were produced using the method of Example 3 and 
characterized. See Table 2, supra. 
EXAMPLE 4--BLENDS OF OTHER THERMOPLASTIC FLEXIBLE POLYMERS 
Blends of VECTRA.RTM. between about 5 and 20% and the thermoplastic 
polymers polypropylene, polycarbonate and polystyrene between about 95 to 
80% were also extruded under conditions similar to those described above, 
the main difference being a lower extrusion temperature. Balanced biaxial 
(.+-.45 degrees) films varying in thickness from 0.001 inches (1 mil) to 
0.005 inches (5 mil) were extruded. 
The present invention has been described in detail, including the preferred 
embodiments thereof. However, it will be appreciated that those skilled in 
the art, upon consideration of the present disclosure, may make 
modifications, and/or improvements in this invention and still be within 
the scope and spirit of this invention as set forth in the following 
claims.