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Title:
POLYMER FILM
Document Type and Number:
WIPO Patent Application WO/2015/107095
Kind Code:
A1
Abstract:
The present invention relates to a process for preparing a polymer film comprising a liquid-crystal polymer and either at least one thermoplastic polymer or a low-melting liquid crystal- polymer (LM-LCP), or a mixture thereof. The process comprises the steps of pressing either the liquid- crystal polymer alone or the polymer blend comprising said liquid-crystal polymer and the thermoplastic polymer through the inner part of a die, and the thermoplastic polymer or the LM-LCP or a mixture thereof through the outer part of a die to obtain polymer fibers; or the polymer blend comprising said liquid crystal polymer and the thermoplastic polymer through a die to obtain polymer fibers; or the mixture of the liquid-crystal polymer and the LM-LCP and optionally the thermoplastic polymer through a die to obtain polymer fibers. The polymers or polymer blend have a processing temperature of 250°C to 350°C; and b) guiding the polymer fibers obtained in step a) while still in melt through an opening to form a polymer film, characterized in that the polymer film obtained in step b) is pressed between a first pair of press rollers while the polymer film has a temperature between 220°C and 350°C and wherein the pair of press rollers has either a temperature of 220°C to 350°C or a temperature of 5 to 20°C.

Inventors:
FARHA SAID (CH)
Application Number:
PCT/EP2015/050622
Publication Date:
July 23, 2015
Filing Date:
January 15, 2015
Export Citation:
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Assignee:
CEDAR ADVANCED TECHNOLOGY GROUP LTD (CH)
International Classes:
C08J5/18; B29C48/08; B29C48/21; B29C48/305; B29C48/31; B29C48/49; B29C69/00; D01D5/30; D04H1/54
Domestic Patent References:
WO2010063846A22010-06-10
Foreign References:
JP2000159904A2000-06-13
US5225488A1993-07-06
US6364652B12002-04-02
EP0568083A11993-11-03
EP0045575A11982-02-10
Attorney, Agent or Firm:
SCHAAD BALASS MENZL & PARTNER AG (Zuerich, CH)
Download PDF:
Claims:
Claims

Process for preparing a polymer film comprising

a liquid-crystal polymer and

either at least one thermoplastic polymer or

a low-melting liquid crystal-polymer (LM-LCP) , or a mixture thereof,

wherein the thermoplastic polymer selected from the group consisting of polystyrene, polyethylene, polypropylene, polyethylene terephthalate , recycled polyethylene terephthalate, polymethylmethacrylate, maleated polypropylene polycarbonate, acrylonitrile- butadiene-styrene (ABS) , polyethylene naphthalate, polyester, polyetherimide, polyimide and polyamide or a mixture thereof, by

a) pressing

i . the liquid-crystal polymer alone or the polymer blend comprising said liquid-crystal polymer and the thermoplastic polymer is pressed through the inner core part of a die and the thermoplastic polymer is pressed through the outer jacket part of a die; or

ii . the liquid-crystal polymer alone or the polymer mixture comprising said liquid-crystal polymer, the low-melting liquid crystal polymer (LM-LCP) and optionally further comprising a thermoplastic polymer is pressed through the inner core part of a die, and the low-melting liquid crystal polymer as well as optionally a thermoplastic polymer is pressed through the outer jacket part of a die; or

iii. the polymer blend comprising the liquid-crystal polymer and at least one thermoplastic polymer is pressed through a die, or iv. a mixture of the liquid-crystal polymer and the low-melting liquid crystal polymer and optionally a thermoplastic polymer is pressed through a die

to obtain the polymer fibers,

whereby the polymers or polymer blend have a processing temperature of 250°C to 350°C; and

b) guiding the polymer fibers obtained in step a) while still in melt through an opening to form a polymer film, characterized in that the polymer film obtained in step b) is pressed between a first pair of press rollers while the polymer film has a temperature between 220°C and 350°C and

wherein the pair of press rollers has either a temperature of 220°C to 350°C or a temperature of 5 to 20°C.

Process according to claim 1, wherein the film comprises the liquid-crystal polymer and at least one thermoplastic polymer.

Process according to any of the preceding claims, wherein before pressing one of the compositions (i) to (iv) through the die, an IR-absorber is added to the thermoplastic polymer or the low-melting crystal- polymer, whereby said IR-absorber is preferably selected from the group consisting of black pigments, yellow pigments, orange pigments, brown pigments, red pigments, purple pigments, blue pigments, green pigments, fluorescent pigments, metal powder pigments, polymer bond pigments, insoluble azo pigments, azo lake pigments, condensation azo pigments, chelate azo pigment, phthalocyanine pigments, anthraquinone pigments, perylene pigments, perynone pigments, thioindigo pigments, quinacridone pigments, dioxazine pigments, isoindolinone pigments, quinophthalone pigments, colored lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, inorganic pigments, carbon black, Paris Blue, Prussian Blue and a combination thereof, and most preferably carbon black.

Process according to claim 3, wherein after adding the IR-absorber and the before pressing one of the compositions (i) to (iv) through the die, the thermoplastic polymer comprising the IR-absorber or the low-melting liquid crystal polymer comprising the IR- absorber are heated by IR radiation, preferably in an extruder .

Process according to claims 3 to 4, wherein the polymer film is heated by IR radiation before and/or while pressing it between the first pair of press rollers.

Process according to any of the preceding claims, characterized in that the pair of press rollers has a temperature of between 220°C and 320°C, preferably between 250°C and 300°C, and most preferably between 270°C and 290°C.

Process according to any of the preceding claims, characterized in that the pair of press rollers has a temperature 5 to 20 °C.

Process according to any of the preceding claims, characterized in that the liquid crystal polymer is extruded in a first extruder and the thermoplastic polymer is extruded in a second extruder, and the melt stream of the liquid crystal polymer and the melt stream of the thermoplastic polymer are joined together at a T- junction forming the polymer blend. - 2 \

Process according to any of the preceding claims, whereby the liquid-crystal polymer alone or the polymer blend comprising said liquid-crystal polymer is pressed through the inner part of a die and the thermoplastic polymer through the outer part of a die.

Process according to claim 9, whereby the polymer blend comprising said liquid-crystal polymer is pressed through the inner part of a die and the thermoplastic polymer through the outer part of a die.

Process according to any of claims 1 to 8, whereby the polymer blend is pressed through a die to obtain polymer fibers .

Process according to any of the preceding claims, characterized in that in that the polymer film has a temperature between 250°C and 300°C, preferably 270°C and 290°C.

Process according to any of the preceding claims, characterized in that the first pair of press rollers has essentially the same temperature as the polymer film during the pressing process.

Process according to any of the preceding claims, characterized in that in transportation direction one or two additional pairs of press rollers are arranged, said additional pair of press rollers whereby the temperature of each pair of press rollers decreases between 10 and 30°C in transportation direction.

Process according to any of the preceding claims, wherein the polymer film is quenched after leaving the last pair of press rollers in transportation direction. Process according to any of the preceding claims, wherein the pair of press rollers is made of steel, bimetallic steel / Ampcoloy or Ampcoloy.

Process according to any of the preceding claims, characterized in that the at least one thermoplastic polymer is selected from the group consisting of polycarbonate, polyethylene terephthalate , recycled polyethylene terephthalate, polyethylene naphthalate and polyethylene, preferably of polycarbonate.

Process according the any of the preceding claims, characterized in that the polymer blend comprises 1 to 99% by weight of the liquid crystal polymer and 1 to 99°% by weight of the thermoplastic polymer.

Process according to any of the preceding claims, characterized in that the die comprises a spinneret part having a plurality of orifices, the orifices having an inlet and an outlet and a second part having an opening for receiving fibers from the orifice outlets, the opening having an outlet facing away from the orifice outlets .

Process according to claim 19, characterized in that surface area of the outlet of the opening complies with the following formula

SA < N x D2

wherein

SA represents the surface area of the outlet of the opening;

N represents the number of orifice outlets of the spinneret; and

D represents the diameter of the orifice outlets of the spinneret .

Description:
Polymer film

The present invention relates to a process for preparing a polymer film from a polymer blend, said polymer blend comprising a liquid-crystal polymer and at least one thermoplastic polymer selected from the group consisting of polystyrene, polyethylene, polypropylene, polyethylene terephthalate, recycled polyethylene terephthalate, polymethylmethacrylate, polycarbonate, acrylonitrile-butadiene-styrene (ABS) , polyethylene naphthalate, polyester, polyethylene imide, maleated polypropylene, grafted polyesters, polyetherimide , polyimide and polyamide or a mixture thereof .

Liquid crystal polymers are well-known in the art. These polymers exhibit anisotropy in the liquid phase. They may be characterized as thermotropic (i.e., liquid crystal in the melt) or lyotropic (i.e., liquid crystal in solution) . Liquid crystal polymers have very stiff, rod-like molecules. In the quiescent state, the molecules line up in an ordered array in local regions, thereby forming domains. The individual domains, however, are not lined up into any particular ordered array; instead, they exhibit random orientations.

US 4' 332' 759 discloses a process comprising the steps of providing a fluid stream of liquid crystal polymer wherein the stream has a flow pattern comprising substantial shear flow; converting the flow of the fluid stream of liquid crystal polymer to a substantially elongational flow in the substantial absence of shear flow; and extruding the fluid stream of liquid crystal polymer to form a shaped article having the polymer molecules oriented substantially parallel to the flow direction. However, with said process it was not possible to produce very thin films of liquid crystal polymers.

US 6,364,652 discloses an apparatus and method for making liquid crystal polymer films. The apparatus comprises two preferably embossed rollers which oscillate oppositely with respect to each along their respective rotational axes.

US 5,225,488 relates to a mixing process for the generating in situ reinforced thermoplastics. US 6 268 026 discloses a multilayer laminate comprising at least one layer of wholly aromatic liquid crystalline polymer which is stretchable at a temperature below 200° C, and at least one layer of non-liquid crystalline polyester. The multilayer laminate is stretched to at least 100 percent elongation while at a temperature below 200° C and below the temperature of the molten state of said layer of wholly aromatic liquid crystalline polymer so as to achieve molecular orientation in layer.

WO 2010/063846 discloses dies for preparing liquid crystal polymer films. Said dies have a first section for orienting material being pressed through the die and a second section for shaping the oriented material into a desired form. The obtained film comprises liquid crystal polymer fibers which are stretch oriented in one direction. The individual fibers are created as the liquid crystal polymer passes through the die head which has a plurality of 100 to 500 micron holes. High shear and pressure promote crystallinity and orientation of the liquid crystal polymer fibers. The orifices in the die direct the strands to each other to form the sheet. The single direction oriented film is extremely strong in the machine direction, however lacks adhesion in the non-machine direction. This makes the liquid crystal polymer film difficult to handle without tearing the film.

Therefore, it was an object of the present invention to provide a process resulting in a thin film comprising a liquid crystal polymer and at least a thermoplastic polymer being extremely strong in the machine direction, while having excellent adhesion properties on the other hand. The problem is solved with a process according to claim 1. Further preferred embodiments are subject of dependent claims .

The process according to the present invention relates to a process for preparing a polymer film comprising a liquid-crystal polymer and either at least one thermoplastic polymer or a low- melting liquid crystal-polymer (LM-LCP) or a mixture thereof. The thermoplastic polymer is selected from the group consisting of polystyrene, polyethylene, polypropylene, polyethylene terephthalate, recycled polyethylene terephthalate , polymethylmethacrylate, polycarbonate, acrylonitrile-butadiene- styrene (ABS) , polyethylene naphthalate, polyester, polyethylene imide, maleated polypropylene, grafted polyesters, polyetherimide , polyimide, polyamide, and any suitable adhesive promoting polymers or a mixture thereof. The liquid-crystal polymer and the thermoplastic polymer may be processed separate from each other or they may form a blend.

The process is carried out by the following steps: First, either

(i) the liquid-crystal polymer alone or the polymer blend comprising said liquid-crystal polymer and the thermoplastic polymer is pressed through the inner core part of a die and the thermoplastic polymer is pressed through the outer jacket part of a die; or the liquid-crystal polymer alone or the polymer mixture comprising said liquid-crystal polymer, the low-melting liquid crystal polymer (LM-LCP) and optionally further comprising a thermoplastic polymer is pressed through the inner core part of a die, and the low-melting liquid crystal polymer as well as optionally a thermoplastic polymer is pressed through the outer jacket part of a die; or (iii) the polymer blend comprising the liquid-crystal polymer and at least one thermoplastic polymer is pressed through a die, or

(iv) a mixture of the liquid-crystal polymer and the low- melting liquid crystal polymer and optionally a thermoplastic polymer is pressed through a die to obtain polymer fibers. The polymers (that is the liquid- crystal polymer and thermoplastic polymer and/or the low-melting liquid-crystal polymer) or the polymer blend have a processing temperature of 250°C to 350°C.

Second, the polymer fibers obtained in step a) are guided while still in melt through an opening to form a polymer film. Afterwards the polymer film obtained in step b) is pressed between a pair of press rollers while the polymer film has a temperature between 220°C and 350°C and the pair of press rollers has either a temperature of 220°C to 350°C or a temperature of 5 to 20 °C.

Within the context of the present invention the expression liquid crystal polymer stands for liquid crystal polymers having a melting temperature of 300 °C and more and the expression low- melting liquid crystal polymer stands for liquid crystal polymers having a melting temperature of less than 300 °C.

Due to the process according to the present invention the adhesion between the thermoplastic polymer and the liquid crystal polymer is significantly increased, since the two components are tightened mechanically. In addition, polymer films according to the present invention are self-reinforcing and have mechanical properties superior to liquid crystal polymer films known in the art. Preferably, before pressing one of the compositions (i) to (iv) though the die, an IR-absorber is added to the thermoplastic polymer or to the low-melting liquid crystal polymer. The presence of such an IR absorber allows a lower process temperature, since the IR heat is better absorbed. Hence, the thermoplastic polymer or the low-melting liquid crystal polymer are melted faster. In the presence of such an IR-absorber the processing temperature of the polymers (that is the liquid crystal polymer and the thermoplastic polymer and/or the low- melting liquid-crystal polymer or the polymer blend) is preferably between 250°C and 300°C.

In composition (i) and (ii) the IR-absorber is preferably added to the thermoplastic polymer or the liquid-crystal polymer which are intended to be pressed through the outer jacket part of the die. Preferably, they are mixed together in an extruder. The polymer melt may be additionally heated by IR radiation within the extruder. In composition (iii) the IR-absorber is preferably added to the polymer blend. Preferably, they are mixed together in an extruder. The polymer melt may be additionally heated by IR radiation within the extruder.

In composition (iv) the IR-absorber is preferably added to low- melting liquid crystal polymer or to the optional thermoplastic polymer. Preferably, they are mixed together in an extruder. The polymer melt may be additionally heated by IR radiation within the extruder.

Preferably, the IR-absorber one or more selected from the group consisting of black pigments, yellow pigments, orange pigments, brown pigments, red pigments, purple pigments, blue pigments, green pigments, fluorescent pigments, metal powder pigments, polymer bond pigments, insoluble azo pigments, azo lake pigments, condensation azo pigments, chelate azo pigment, phthalocyanine pigments, anthraquinone pigments, perylene pigments, perynone pigments, thioindigo pigments, quinacridone pigments, dioxazine pigments, isoindolinone pigments, quinophthalone pigments, colored lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, inorganic pigments, carbon black, Paris Blue, Prussian Blue and a combination thereof, and most preferably carbon black .

In one embodiment of the process according to the present invention the liquid-crystal polymer alone or the polymer blend comprising said liquid-crystal polymer and the at least one thermoplastic polymer is pressed through the inner core part of a die and the thermoplastic polymer is pressed through the outer jacket part of a die. In this embodiment the thermoplastic polymer partially or fully encapsulates or coats the LCP in strands or the blend comprising the LCP formed at the die. Most preferably a polymer blend comprising said liquid-crystal polymer and the at least one thermoplastic polymer is pressed through the inner core part of a die and the thermoplastic polymer is pressed through the outer jacket part of a die. In this case, the adhesion takes place between polymer fibers comprising essentially the same material (thermoplastic polymer vs blend comprising thermoplastic polymer and LCP) . Under heat and compression strong adhesion can occur because the polymers adhering are identical to each other.

In another embodiment of the process of the present invention the polymer blend is pressed through a die to obtain polymer fibers. Also here the adhesion takes place between polymer fibers comprising the same material. Under heat and compression strong adhesion can occur because the polymers adhering are identical to each other.

The polymer blend may be produced by extruding the liquid crystal polymer in a first extruder and the thermoplastic polymer in a second extruder. This step allows in particular the melting of polymers not having overlapping thermal processing temperatures. Afterwards, the melt stream of the liquid crystal polymer and the melt stream of the thermoplastic polymer are joined together, for example at a T-junction forming the polymer blend. Preferably, they are mixed together in a static mixer (such as a Koch mixer) which distributes the streams such that long, continuous fibrils of the liquid crystal polymer are formed, that is oriented fibers which are formed in situ in a matrix of the thermoplastic polymer. Optionally, a melt pump can be used to feed the melt into the die in order to create more pressure as long as the pressure is chosen in such a way that it does not disturb the crystal shape or structure of the fibrils. Said fibrils reinforce the matrix polymer and provide enhanced strength and stiffness characteristics. The so obtained polymer blend emanating from the static mixer can then subsequently pass through the die to obtain the polymer fibers. A film obtained from such a blend is not brittle anymore.

Preferably, the polymer film obtained in step b) is pressed between a pair of press rollers while the polymer film has a temperature between 220°C and 350°C and the pair of press rollers has a temperature of 220°C to 350°C. Due to the fact, that the polymer film from the polymer blend comprising the liquid crystal polymer and the thermoplastic polymer is compressed together by the at least one pair of press rollers while the polymer blend is still very hot, that is, near to processing temperature, the contact between to two components is very strong. In particular, the temperature of the polymer film during the pressing process is higher than the melting point of the thermoplastic polymer, but lower than or slightly below the melting point of the liquid crystal polymer. Due to the fact that the pair of press rollers compresses the film at high temperatures the shear forces occurring between the two different polymeric materials can be substantially reduced. Therefore, no or only a few bond ruptures between said two components can be observed which can cause the loss of adhesion. Especially for very thin films, that is films having a post roller thickness of less than 50 micrometer, roller temperatures of 220°C to 350°C are preferred. Alternatively, the polymer film obtained in step b) is pressed between a pair of press rollers while the polymer film has a temperature between 220°C and 350°C and the pair of press rollers has a temperature of 5°C to 20°C, preferably about 10°C. The residual heat in the melt can promote immediate adhesion under pressure and the quenching will boost throughput. Especially for thicker films, that is, films having a post roller thickness of 100 to 150 micrometer, roller temperatures of 5°C to 20°C are preferred. Within the context of the present invention the expression liquid-crystal polymers, generally abbreviated as LCP's, stands for a class of aromatic polyester polymers. They are extremely unreactive and inert, and highly resistant to fire. Preferably, the liquid crystal polymer is selected from the group consisting of polyaramide, e.g. poly (p-phenylene terephthalamide) , co- polyester, i.e. polybenzoate-naphthalate , polybenzoate- terephthalate-bisphenol-isophthalate , polybenzoate- terephthalate-ethylene glycol, polynaphthalate-amino terephthalate, or poly (p-phenylene benzobisoxazole) . Commercial examples of some of the above-mentioned polymers are, for instance, those available under the trademarks Kevlar ® , Twaron ® , Vectra ® , M5 ® , and Zylon ® . Preferred LCP's are sold by different manufacturers under a variety of trade names. These include: Vectra (by Ticona) , which is chemically an aromatic polyester produced by the polycondensation of 4-hydroxybenzoic acid and 6- hydroxynaphthalene-2-carboxylic acid, Zenite (by Ticona) , Kevlar (by DuPont) , Sumikasuper (by Sumimoto Chemical Industry) or by Xydar (by Solvay) .

In a most preferred embodiment the liquid crystal polymer of the polymer blend used in the process according to the present invention is Vecta ® supplied by Ticona. It is believed to comprise about 25 to 27 mole percent of 6-oxy-2-naphthoyl moieties and 73 to 75 mole percent of p-oxybenoyl moieties. It is a liquid crystal polymer with a melting temperature of about 280°C, and a density (at 25°C) of about 1.4 g/cm.

An example for a low melting liquid-crystal polymer (LM-LCP) is hydroquinone/ isophthalic acid / 2 , 6-naphthalenedicarboxylic acid/4-hydroxybenzoic acid in a mole ratio of 100/70/30/270.

The thermoplastic polymer used for the polymer film according to the present invention is preferably selected from the group consisting of polystyrene, polyethylene, polypropylene, polyethylene terephthalate, recycled polyethylene terephthalate, polymethylmethacrylate, polycarbonate, acrylonitrile-butadiene- styrene (ABS) , polyethylene naphthalate, polyester, polyethylene imide, maleated polypropylene, grafted polyesters (such as acrylic grafted polyester) or maleic anhydride grafted polypropylene, polyetherimide, polyimide and polyamide or a mixture thereof. Suitable polyesters are for example polybutylene terephthalate (PBT) (Celanex®) which is produced by melt polycondensation of terephthalic acid dimethyl ester with 1 , 4-butanediol , polyethylene terephthalate (PET) (Impet ® ) is produced by melt polycondensation of terephthalic acid or terephthalic acid dimethyl ester with ethylene glycol, thermoplastic polyester-blends such as Vandar ® which is a range of elastomer-modified polybutylene terephthalate grades, and polycyclohexylene-dimethylene terephthalate (Thermx ® ) .

In addition, the polymer film may comprise any suitable recognized adhesive promoters / compatibilizers to promote adhesion between the liquid crystal polymer and the thermoplastic polymer.

The processing temperature for the extrusion process of the polymer blend, in particular the pressing through the die, is mainly determined by the choice of the thermoplastic polymer. Preferably, the processing temperature of the polymer blend is chosen according to the following table: Thermoplastic polymer in Preferred Most preferred the polymer blend processing processing

temperature temperature

Polystyrene 250°C - 280°C 250°C - 270°C

Polyethylene 250°C - 300°C 270°C - 300°C

Polypropylene 250°C - 300°C 270°C - 300°C

Polyethylene 260°C - 300°C 280°C - 300°C terephthalate

Polymethylmethacrylate 250°C - 280°C 250°C - 260°C

Polycarbonate 280°C - 320°C 300°C - 320°C

Polyethylene naphthalate 280°C - 320°C 300°C - 320°C

Polyamide 250°C - 290°C 270°C - 280°C

The distance from the opening to the pair of press rollers should preferably be kept as short as possible to avoid a strong temperature decrease of the polymer film. Therefore, the pair of press rollers is preferably arranged within 10 cm after the opening of the die, most preferably within 5 cm, within 3 cm, within 1 cm, or even within 0.5 cm. Most preferably, the location of the rollers is determined by where the strongest adhesion occurs for a given film thickness and temperature retention to promote adhesion.

The pair of press rollers according to the process of the present invention consists of two rollers with a gap between them, said rollers rotating in opposite direction. The gap between the pair of press rollers is adjustable so that films of different thicknesses may be produced. Preferably, the gap between the two press rollers is less than 150 micrometer, most preferably less than 50 micrometer, and for example 125 micrometer, 100 micrometer 75 micrometer, 50 micrometer, 25 micrometer or 10 or even 1 micrometer. Preferably however, the gap will be determined by the desired film thickness. The rollers are both preferably the same diameter and are both driven at the same surface speed through the gap. Preferably, - li

the roller rotation speed is adjustable in order to optimize both compression and pull orientation of the film. In the process of the present invention, the pressure applied to the film to be press rollers is preferably from about 15 to about 150 kg/cm 2 as expressed in terms of linear pressure. If the pressure is less than about 15 kg/cm 2 , the effect of mechanical tightening is sometimes not satisfactory. If the pressure exceeds about 150 kg/cm 2 , the film substantially changes its size and tends to break. In view of minimization of adverse effect on film and production, the pressure is more preferably in an approximate range of from 50 to 100 kg/ cm 2 . However, the optimum pressure is determined by materials, film thickness and pull orientation ratio.

For the process according to the present invention standard center feed dies can be used to extrude the films. A large manifold is preferred to distribute the melt of the blend evenly across the die. Preferably, the die head has a plurality holes having a size of 100 to 1000 μιτι, most preferably 500 to 1000 μιτι.

In another embodiment of the present invention the die has a circular shape. The die comprises an inner core part, which is preferably also circular, and an outer jacket part, which is preferably circular as well. The inner core part comprises preferably one single orifice forming one single central strand, that is, a first central layer. The outer jacket part of the die forms a hollow tube-shaped cylinder, that is, a second layer, which encloses the first central layer. The liquid-crystal polymer alone or, most preferably, the polymer blend comprising said liquid-crystal polymer is pressed through the inner core part of such a die and the thermoplastic polymer is pressed through the outer jacket part of a die.

In another embodiment of the present invention the die has a circular shape. The die comprises an inner core part, which is preferably also circular, and an outer jacket part, which is preferably circular as well. The inner core part comprises preferably multiple orifices forming one multiple central strands building first central layer. Preferably, the inner core part of such a die comprises more than 20, most preferably more than 100 and ideally more than 500 orifices. The outer jacket part of the die forms a hollow tube-shaped cylinder, that is, a second layer, which encloses the first central layer. The liquid-crystal polymer alone or, most preferably, the polymer blend comprising said liquid-crystal polymer is pressed through the inner core part of such a die and the thermoplastic polymer is pressed through the outer jacket part of a die.

In another embodiment of the present invention the die has the shape of a half circle or semi-circle die or a stacked die. Such a die can be used to create cross lamination or bi-axial orientation of the LCP film. Such a die allows the alignment of a first film over a second film, or in case of a stacked die the alignment of several films over each other. Said two or more films can be laminated slightly disaligned and pressed by the pair of press rollers to achieve an optimal adhesion between the two films and as well as between the polymer fibers within the films. Alternatively such a die can be used for a "bidirectional extrusion" with another material, such as another polymer blend or neat resins. The pair of press rollers creates a film with high strength in both the machine direction and non- machine direction. Preferably, the polymer film has a temperature between 250 °C and 300°C, most preferably between 270°C and 290°C when it is pressed between the pair of press rollers. Such a temperature range enhances the bonding of the components and results in excellent adhesion properties of the film. The pair of press rollers has preferably a temperature between 220°C and 320°C, preferably between 250°C and 300°C and most preferably between 270°C and 290°C, allowing the thermoplastic polymer to be in a molten state during the pressing process which increases the adhesion between the thermoplastic polymer and the liquid crystal polymer. Most preferably, the polymer film is heated by IR radiation before and/or and while pressing it between the first pair of press rollers in order to further increase the adhesion of the liquid crystal polymer and the thermoplastic polymer. In addition, it keeps the polymer film undistorted while pressing it between the first pair of press rollers .

Preferably, the pair of press rollers has essentially the same temperature as the polymer film during the pressing process. The expression "essentially the same temperature" means that the temperature of the pair of press rollers and the temperature of the polymer film differ in less than 10°C.

It is possible that the machine for carrying out the process according to the present invention does not only comprise one pair of press rollers, but for example one or two additional pair of press rollers. Said additional pairs of press rollers are sequentially arranged in transportation direction. After the pressing process between the first pair of press rollers the film is processed to the second pair of press rollers and after being released by said second pair of press rollers the film is conveyed to the optional third pair of press rollers. The temperature of each pair of press rollers decreases between 10 and 30°C in transportation direction. The pairs of press rollers with varying temperatures help the adhesion of the filaments to create a polymer film being extremely strong in machine direction and having excellent adhesion properties on the other hand. For example the first pair of press rollers can have a temperature of 290°C, the second pair of press rollers a temperature of 270°C and the third pair of press rollers a temperature of 250°C.

In another embodiment of the present invention the film is processed after the pressing process between the first pair of press rollers to the second pair of press rollers and after being released by said second pair of press rollers the film is conveyed to the optional third pair of press rollers or any cooling / quenching devise capable of cooling / quenching the film as needed, such as water bath or contact with cold service. The process of cooling can also be gradual by a series of single rollers downstream of press rollers or quenched either at or downstream of the press rollers by a series of singles rollers at 5 to 20 C. If such rollers are chosen, then the temperature of second pair of press rollers 10 to 30°C is less than the temperature for the first pair of press rollers. The third pair of press has a temperature of 10 to 20°C in order to quench the obtained polymer film. Therefore, the purpose of the first pair of press rollers is the thickness calibration and the high adhesion, the purpose of the second pair of press rollers is the better stabilization as well as the high adhesion and the purpose of the third pair of press rollers is the rapid cooling of the polymer film.

Alternatively, the polymer film is quenched, for example by cooling, removal of the solvent, or both, after leaving the last pair of press rollers in transportation direction. The expression last pair of press rollers means the first pair of press rollers if no additional pairs of press rollers are present or if further pairs of press rollers are present, the last one in transportation direction.

The pair of press rollers is preferably made of steel, bi- metallic steel / Ampcoloy ® (an alloy comprising copper and beryllium) or Ampcoloy 940 ® . If the film is quenched by press rollers, they are preferably made of Ampcoloy®. In addition, the press rollers may have a specific surface treatment or impregnation to avoid the polymer film from sticking to the rollers. Examples are TiN, TEFLON, vapor hone, bead blast, hard chrome, draw stone, nickel, dycronite, tribold or anodize.

Most preferably, the at least one thermoplastic polymer is selected from the group consisting of polycarbonate, polyethylene terephthalate, recycled polyethylene terephthalate, polyester, polyethylene naphthalate and polyethylene, most preferably of polycarbonate, since the optimal processing temperature of said thermoplastic polymers is rather high and therefore, the film can be pressed at high temperatures which results in very good adhesion properties.

Alternatively, the at least one thermoplastic polymer is recycled polyethylene terephthalate or a mixture of recycled polyethylene terephthalate and virgin polyethylene terephthalate, since a large amount of PET waste is generated every year, which can be recycled and then being an excellent raw material when combined with a liquid crystal polymer.

Preferably, the polymer blend comprises 1 to 99, most preferably 80 to 99% by weight of the liquid crystal polymer and 1 to 99, most preferably 1 to 20% by weight of the thermoplastic polymer. It was shown, that a film comprising 80 to 99% by weight of the liquid crystal polymer maintains the key properties of a liquid crystal polymer film with regard to its unique combination of high barrier to oxygen, aromas, and water vapor, together with chemical resistance superior to that of conventional barrier resins like ethylene vinyl alcohol. In addition, it remains inert, stable under heat. However, the presence of 1 to 20% of by weight of a thermoplastic polymer makes it easier to be processed as well as economical, since the liquid crystal polymer is a very expensive material. In addition, the thermoplastic polymer increases the bending ability of the polymer film without hampering the superior characteristics of the liquid crystal polymer.

Alternatively, it is also possible that the polymer blend comprises 80 to 99% of the thermoplastic polymer and 1 to 20% of the liquid crystal polymer if the thermoplastic polymer is reinforced with the liquid crystal polymer.

In addition, the polymer blend may additionally comprise montmorillonite clay (MMT) , which improves the thermal stability of the polymer film obtained with the process according to the present invention.

For the process according to the present invention standard dies which are generally appropriate for the extrusion of liquid crystal polymers may be used. Preferably, it is possible to control the temperature over the entire head and the die area. In addition, the melt pressure may be monitored and maintained as uniformly as possible. Most preferably, the die comprises a spinneret part having a plurality of orifices, the orifices having an inlet and an outlet. The spinneret part assists in orienting the liquid-crystal polymer as well as the thermoplastic polymer passing through the die. The die further comprises a second part for receiving fibers from the orifice outlets. Said second part assists in joining the plurality of fibers into a desired shape, that is preferably into a film. Preferably, the second part is in the shape of a slit.

Preferably, the die comprises a spinneret part having a plurality of orifices, the orifices having an inlet and an outlet and a second part having an opening for receiving fibers from the orifice outlets, the opening having an outlet facing away from the orifice outlets. Preferably, the surface area of the outlet of the opening complies with the following formula

SA < N x D 2 wherein SA represents the surface area of the outlet of the opening;

N represents the number of orifice outlets of the spinneret; and

D represents the diameter of the orifice outlets of the spinneret .

Such a die is disclosed in detail in WO 2010/063846, said specification is incorporated herein by reference. Said die is especially preferred when combining it with the embodiment, wherein polymer blend is produced by extruding liquid crystal polymer in a first extruder and the thermoplastic polymer in a second extruder and afterwards joining the two melt streams together forming the polymer blend. This allows the formation of fibrils as mentioned above. The above mentioned die maintains the structure of said fibrils and forms fibers which are joined together into a film.

The process according to the present invention may be used for the production of a polymer film comprising a liquid-crystal polymer and at least one thermoplastic polymer selected from the group consisting of polystyrene, polyethylene, polypropylene, polyethylene terephthalate , polymethylmethacrylate, polycarbonate, acrylonitrile-butadiene-styrene (ABS) , polyethylene naphthalate, polyester, polyethylene imide, maleated polypropylene, grafted polyesters, polyetherimide , polyimide and polyamide or a mixture thereof.

Preferably, the polymer film obtained by the process according to the present invention has a thickness of less than 150°C, e.g. less than 100 micrometer, less than 50 micrometer, less than 25 micrometer, less than 10 micrometer or even less than 5 micrometer .

The polymer film obtained by the process according to the present invention may be post-treated, e.g. annealed, further stretched, crosslinked. The film obtained according to the present invention may be used alone- in the form of a discrete layer or of a cross-laminated film - or in combination with another material, e.g. as a laminate with a thermoplastic film or paper. If several layers of the polymer film obtained by the process of the present invention are laminated, these layers may be oriented in different directions. For instance, varying angles between 3 and 10° may be used. - I S

The polymeric film obtained by the process according to the present invention is suited for different medical, chemical, electronic, beverage and food packing applications. It is more impermeable to water vapor, oxygen, carbon dioxide and other gases than typical barrier resins.

The film obtained by a process according to the present invention is particularly preferred as a protection barrier for containers for storing coffee or similar products used for the preparation of beverages in a suitable machine. Therefore, in a preferred embodiment the film obtained by the process of the present invention is part of a flexible & rigid containers or capsule for the preparation of liquid food. The film according to the present invention allows not only for protecting the contained product from oxygen and other gases, but also for perserving its aroma.

Further, the polymer film according to the present invention may be used as barrier material for microwave containers. Due to the polymer material obtained by the process according to the present invention it is no longer necessary to use energy consuming metal foils or metalized films comprising aluminum.

In another embodiment of the present invention the polymer film may be a barrier material in a pouch or a food bag and in particular in reusable pouches. Due to the presence of the thermoplastic polymer the bending characteristics of the polymer film are excellent, allowing the pouch to be closed and reopened without having cracks in the barrier material which reduced the quality of the food stuff.

In addition, due to its better adhesion properties in comparison with liquid crystal polymer films mentioned in the state of the art they are especially preferred for medical applications. The films are also suitable for thermally demanding applications such as films for printed wiring boards. Further features and advantages of the invention will become apparent from the following description in conjunction with the drawings. In the drawings show:

Fig. 1 a schematic drawing from the side of an apparatus for carrying out the process according to the present invention;

Fig. 2 A-D an embodiment of a spinneret part of a die.

Fig. 3 an alternative schematic drawing of an apparatus for carrying out the process according to the present invention with a cylindrical die

Fig. 4 an embodiment of a specific die

Fig. 5 an other embodiment of a further specific die.

Fig. 6 a schematic drawing from the side of another embodiment of an apparatus for carrying out the process according to the present invention;

In figure 1 an extruder 10 supplies the polymer material 15 through a die 20 to obtain polymer fibers. Afterwards the polymer fibers are guided while still in melt through an opening 25 to form a polymer film 30. Directly downstream after the opening 25 a pair of press rollers 35a and 35b is arranged. The press rollers 35a and 35b have a gap 40 between them, said gap being approximately equal to the thickness of the polymer film 30. The polymer fibers of the polymer film 30 are compressed by the pair of press rollers 35a, 35b while the polymer film 30 has a temperature between 220°C and 300°C and the pair of press rollers 35a, 35b has a temperature of 220°C to 300°C. The film contacts approximately simultaneously the surfaces 45a and 45b of the press rollers 35a and 35b, respectively. The press rollers 35a, 35b are driven in rotation in transport direction as shown in figure 1. The polymer film 30 exits the gap 40 from between the press rollers 35a, 35b for the further processing.

Figure 2A is a perspective view of a spinneret part 100 having a circular base 110 and a curved part 120 in the form of half a cylinder. The curved part 120 comprises a plurality of orifices 130 (Fig 2B) . The orifices 130 are arranged over curved part 120 in staggered arrays. The orifices have an inlet 140 (see Fig 2C) for receiving material during use (e.g. molten or dissolved polymers) and opposite orifice outlets 150 (see Fig 2C) . Figure 2B is a top view of the same spinneret part 100 of Fig 2A. Figure 2C is a sectional view of spinneret part 100 across the dotted line A-A depicted in Figure 2B. Figure 2D is a sectional view of spinneret part 100 across the dotted line B-B in Figure 2B. Referring to Fig 2C, orifices 130 have orifice inlets 140 and corresponding orifice outlets 150, and channels 160 between the orifice inlets and orifice outlets. In this example, as evident from Figure 2C, the channels are straight.

Figure 3a shows the side view and figure 3b the top view of another embodiment of the present invention. Two extruders 210a and 210b melt the liquid crystal polymer 215a and the thermoplastic polymer 215b.

In one embodiment the liquid crystal polymer and the thermoplastic polymer are blended before pressing the blend through a die 220 (not shown) to obtain polymer fibers. In another embodiment the liquid crystal polymer is guided into the inner part 221 a/b of a circular die 220a as shown in figures 3c and 3d, and the thermoplastic polymer is guided into the outer part 222a/b of the circular dies forming a first inner layer with LCP and a second outer layer with the thermoplastic polymer. The first layer may consist of one single LCP strand (figure 3c) or multiple LCP stands (figure 3d) . In another embodiment the liquid crystal polymer is blended with a part of thermoplastic polymer (not shown) before said blend is guided into the inner part 221 a/b of a circular die in figures 3c and 3d. The rest of the thermoplastic polymer, which is not blended with the LCP is guided into the outer part 222 a/b of the circular dies forming a first inner layer with LCP and a second outer layer with the thermoplastic polymer. The first layer may consist of one single strand comprising the blend of LCP and the thermoplastic polymer or multiple strands comprising the blend of LCP and the thermoplastic polymer.

Afterwards the polymer fibers are guided while still in melt through an opening 225, preferably in form of a slit, to form a polymer film 230. Directly downstream after the opening 225 a pair of press rollers 235a and 235b is arranged. The press rollers 235a and 235b have a gap 240 between them, said gap being approximately equal to the thickness of the polymer film 230. The polymer fibers of the polymer film 230 are compressed by the pair of press rollers 235a, 235b while the polymer film 230 has a temperature between 220°C and 300°C and the pair of press rollers 235a, 235b has a temperature of 220°C to 300°C. The film contacts approximately simultaneously the surfaces 245a and 245b of the press rollers 235a and 235b, respectively. The press rollers 235a, 235b are driven in rotation in transport direction as shown in figure 1. The polymer film 230 exits the gap 240 from between the press rollers 235a, 235b for the further processing.

Figure 3c shows a circular die 220a with an inner part 221a and an outer part 222a. The inner part 221a comprises one single orifice forming one LCP strand or one strand comprising the blend of LCP and the thermoplastic polymer. The outer part 222a of the die 220a forms a tube-like second layer, which encloses the LCP stand or the strand comprising the blend.

Figure 3d shows a circular die 220b with an inner part 221b and an outer part 222b. The inner part 221b comprises a plurality of orifices forming multiple LCP strands or multiple strands comprising the blend of LCP and the thermoplastic polymer. Preferably, the inner part 221b of such a die comprises more than 20, most preferably more than 100 and ideally more than 500 orifices. The outer part 222b of the die 220b forms a tube-like second layer, which encloses the multiple LCP stands or the multiple strands comprising the blend.

Figure 4a shows front view and figure 4b shows a top view of another embodiment of a die used for the process according to the present invention. The stacked die 420 comprises three modules (however, also more than three modules are possible) , a top part 430, a bottom part 435 and a middle part 440 which is arranged between the top part 430 and the bottom part 435. Each module may be provided with a thermal insulation to provide extra protection for the thermally sensitive polymers while being processed in the same system with other high melting resins. As shown in Fig. 4A the top part comprises more than 20, most preferably more than 100 and ideally more than 500 orifices 445, however, it is also possible that this arrangement of orifices is in the middle part 440 or in the bottom part 435 (not shown) . The middle part 440 and the bottom part 435 comprise an opening 450 a and 450 b in form of a slit (also these modules are exchangeable) , however, different shapes of the opening 450a and 450b are possible and known to a person skilled in the art. A first extruder 450, optionally comprising a melt pump (not shown) , feeds the top part 430 of the die 420 forming the liquid crystal polymer fibers. A second and a third extruder (455, 460) feed the middle and the bottom part with a thermoplastic polymer. The resulting fibers form a polymer film 470 having three layers, which is pressed between a first pair of press rollers 475.

Figure 5a shows front view and figure 5b shows a top view of another embodiment of a die 500 used for the process according to the present invention, a so called semi-circle die. The die 500 comprises two rows 505, 510 of horizontally arranged orifices 515, one at the top side 520 and one at the bottom side 525. One row 505 is built by two sets 530a, 530b of orifices 515, whereby between these two sets a central part 535 comprises no orifices. The second row 510 comprises only orifices in the central part 540 but no orifices at the beginning and end part of the row. Only a small part (1 and 1') of the orifices 515 are overlapping in vertical direction. Preferably, the row 510 comprising the orifices 515 in the central part is feed with the liquid crystal polymer, whereas the row 505 comprising two sets 530a, 530b of orifices is feed with the thermoplastic polymer.

Such a die allows the alignment of a first film 545 over a second film 550 and the second film 550 over a third film 555. Said three films can be laminated slightly disaligned and pressed by the pair of press rollers 560 to achieve an optimal adhesion between the three films and as well as between the polymer fibers within the films.

Figure 5c shows the top view of a half circle die 565, allowing the alignment of a first film 545a over a second film 550a. The concept is the same as that described for the semi-circle die described above.

In figure 6 an extruder 610 supplies the polymer material 615 through a die 620 to obtain polymer fibers. The extruder 610 comprises one, preferably two, infrared heating element (s) 680a, 680b, which allow to lower the process temperature of the polymer material, which preferably comprises and IR absorber, such as carbon black. The polymer fibers are guided while still in melt through an opening 625 to form a polymer film 630. During the transportation and/or while forming the polymer film the polymer fibers may additionally be heated by one or more infrared heating elements 685a, 685b. Directly downstream after the opening 25 a pair of press rollers 635a and 635b is arranged. The press rollers 635a and 635b have a gap 640 between them, said gap being approximately equal to the thickness of the polymer film 630. The polymer fibers of the polymer film 630 are compressed by the pair of press rollers 635a, 635b while the polymer film 630 has a temperature between 220°C and 300°C and the pair of press rollers 635a, 635b has a temperature of 220°C to 300 °C. The film contacts approximately simultaneously the surfaces 645a and 645b of the press rollers 635a and 635b, respectively. The press rollers 635a, 635b are driven in rotation in transport direction as shown in figure 1. The polymer film 630 exits the gap 640 from between the press rollers 635a, 365b for the further processing.

Example

The polymer material comprises 90% by weight of Vectra(TM) A950 as liquid crystal polymer and 10% by weight polycarbonate as thermoplastic polymer. Polymer films were produced by continuous extrusion at a processing temperature 300°C, using a single screw extruder, equipped with a die similar according to figure 2, having a slit with a length of 120mm and a width of 0.07 mm, and the spinneret part having 990 orifices with inlets and outlets both of 0.1mm in diameter (arranged in a substantially similar way as the orifices of the spinneret part in figure 2, but over a length of 120mm.

The polymer film comprising the fibers is conveyed to a pair of press rollers, which is arranged as shown in figure 1. Said press rollers were arranged within 5 cm after the opening of the die in transportation direction. The rollers were 10 cm in diameter and 20 cm wide, and the surfaces were faced with Teflon. Preferably, the surfaces of the press rollers were embossed. The rotational speeds of the rollers were manually controlled using a variable speed drive motor. The pair of press rollers was preferably heated simultaneously by electrical heater .