Source: http://www.google.com/patents/US6875394?dq=5527183
Timestamp: 2017-05-26 08:42:52
Document Index: 328041842

Matched Legal Cases: ['arts 21', 'arth 31', 'art 33', 'art 33', 'art 33', 'art 33', 'art 33', 'art 33', 'art 33', 'art 33', 'art 33']

Patent US6875394 - Method and device for transforming crystalline or semicrystalline polymers - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA method for processing thermoplastics in a shaping device, whereby before and/or during its passage in the shaping device the thermoplastic is submitted to a static electrical field....http://www.google.com/patents/US6875394?utm_source=gb-gplus-sharePatent US6875394 - Method and device for transforming crystalline or semicrystalline polymersAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS6875394 B2Publication typeGrantApplication numberUS 10/200,454Publication dateApr 5, 2005Filing dateJul 23, 2002Priority dateJan 24, 2000Fee statusLapsedAlso published asCA2398234A1, CA2398234C, CN1315633C, CN1404437A, DE60109425D1, DE60109425T2, EP1261469A2, EP1261469B1, US20030047842, WO2001053060A2, WO2001053060A3Publication number10200454, 200454, US 6875394 B2, US 6875394B2, US-B2-6875394, US6875394 B2, US6875394B2InventorsJoël SoulierOriginal AssigneeInternational Brain System S.A.Export CitationBiBTeX, EndNote, RefManPatent Citations (7), Referenced by (20), Classifications (33), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetMethod and device for transforming crystalline or semicrystalline polymers
US 6875394 B2Abstract
A method for processing thermoplastics in a shaping device, whereby before and/or during its passage in the shaping device the thermoplastic is submitted to a static electrical field.
1. A method for processing thermoplastic materials presenting a melting point and a solidification temperature,
wherein the thermoplastic material is heated to a temperature higher than the melting point, and wherein said heated material is processed in a forming device by lowering therein the temperature of the thermoplastic material from a temperature at least close to the melting point, to a temperature below the solidification temperature, said method comprising a treatment step selected from the group consisting of: step of subjecting the thermoplastic material, before its passage in the forming device, to a static electric field between a positive electrode in contact with the thermoplastic material and a reference electrode selected from the group consisting of negative electrode and earth, said reference electrode being in contact with the thermoplastic material; step of subjecting the thermoplastic material, during its passage through at least a part of the forming device, to a static electric field between a positive electrode in contact with the thermoplastic material and a reference electrode selected from the group consisting of negative electrode and earth, said reference electrode being in contact with the thermoplastic material; and step of subjecting the thermoplastic material, before and during its passage in the forming device, to a static electric field between a positive electrode in contact with the thermoplastic material and a reference electrode selected from the group consisting of negative electrode and earth, said reference electrode being in contact with the thermoplastic material. 2. The method of claim 1, in which the treatment step is carried out by subjecting the thermoplastic material to a static electric field of at least 800,000 V/m, between a positive electrode in contact with the thermoplastic material and a reference electrode selected from the group consisting of negative electrode and earth, said reference electrode being in contact with the thermoplastic material.
3. The method of claim 1, in which the treatment step is carried out by subjecting the thermoplastic material to a static electric field of at least 1,000,000 V/m, between a positive electrode in contact with the thermoplastic material and a reference electrode selected from the group consisting of negative electrode and earth, said reference electrode being in contact with the thermoplastic material.
4. The method of claim 1, in which the treatment step of subjecting the thermoplastic material to a static field is carried while the thermoplastic material moves between a positive electrode and a reference electrode selected from the group consisting of negative electrode and earth, said reference electrode being in contact with the thermoplastic material, whereby said field is substantially perpendicular to the flow of the material between the positive electrode in contact with the thermoplastic material and the reference electrode in contact with the thermoplastic material.
5. The method of claim 1, in which an electrostriction effect is created in the thermoplastic material between the positive electrode and the reference electrode.
6. The method of claim 1, in which the material is subjected to a static electric field at least in respect of a temperature range higher than the crystallization temperature.
7. A method for processing a thermoplastic material containing at least one compound selected among the group consisting of crystalline polymers, crystalline copolymers, semi-crystalline polymers and semi-crystalline copolymer, said compound presenting a melting point, a crystallization temperature lower than the melting point, and a glass transition temperature,
in which the material is heated to a temperature higher than the melting point of the compound, and in which said heated material is processed in a forming device by lowering therein the temperature of the material from a temperature higher than the crystallization temperature to a temperature lower than the glass transition temperature of the compound, said method comprising a treatment step selected from the group consisting of: step of subjecting the thermoplastic material, before its passage in the forming device, to a static electric field between a positive electrode in contact with the thermoplastic material and a reference electrode selected from the group consisting of negative electrode and earth, said reference electrode being in contact with the thermoplastic material; step of subjecting the thermoplastic material, during its passage in the forming device, to a static electric field between a positive electrode in contact with the thermoplastic material and a reference electrode selected from the group consisting of negative electrode and earth, said reference electrode being in contact with the thermoplastic material; and step of subjecting the thermoplastic material, before and during its passage in the forming device, to a static electric field between a positive electrode in contact with the thermoplastic material and a reference electrode selected from the group consisting of negative electrode and earth, said reference electrode being in contact with the thermoplastic material whereby the material is subjected to a static electric field at least in respect of a temperature higher than the glass transition temperature. 8. The method of claim 7, in which the material is subjected to a static electric field at least in respect of a temperature range higher than the crystallization temperature.
9. The method of claim 7, in which the material is subjected to an electric field at least whilst the temperature is being lowered from a temperature higher than the crystallization temperature, to a temperature lying between the glass transition temperature and the crystallization temperature.
10. The method of claim 7, in which the material is subjected to a static electric field at least whilst the temperature is being lowered from a temperature at least substantially equal to the crystallization temperature, to a temperature close to the glass transition temperature.
11. The method of claim 7, in which the material is subjected to a static electric field at least whilst the temperature is being lowered from a temperature higher than the crystallization temperature, to a temperature close to the glass transition temperature.
12. The method of claim 7, in which the material is subjected to a static electric field at least in respect of a temperature close to melting point.
13. The method of claim 12, in which the material is subjected to a static electric field at least in respect of a temperature close to melting point, as well as in respect of a temperature range extending between a temperature higher than the crystallization and a temperature lying between the crystallization temperature and the glass transition temperature.
14. The method of claim 7, in which the electric field has a strength of at least 1,000,000 volts/m.
15. The method of claim 7, in which the electric field has a strength of at least 2,000,000 volts/m.
16. The method of claim 7, in which the material is subjected to an electric field selected from the group consisting of at least radial electric fields and electrical fields at least substantially perpendicular to the direction in which the material flows.
17. The method of claim 7, in which that the material contains at least one additive to raise the dielectric characteristic.
18. The method of claim 7, in which the material is a PET, possibly contaminated or containing additives or fillers.
19. The method of claim 7, in which the forming device is selected from the group consisting of shaping fixtures of extruders, moulds and extruder dies.
20. The method of claim 7, for extruding an extruded product with an internal shape and an external shape, in which the forming device incorporates a mandrel rod designed to form the internal shape of the extruded product and a wall designed to form the external shape of the extruded product, whereby a radial electric field is created between the mandrel rod and the wall designed to form the external shape of the extruded product.
21. The method of claim 7, for extruding an extruded product with an internal shape and an external shape, in which the forming device incorporates a mandrel rod designed to form the internal shape of the extruded product and a wall designed to form the external shape of the extruded product, whereby a radial electric field is created between the mandrel rod and the wall designed to form the external shape of the extruded product, the mandrel rod constituting the reference electrode, whereas the wall constitutes the positive electrode.
22. The method of claim 7, in which an electrical insulating fluid is used to cool the positive electrode.
23. The method of claim 7, in which the thermoplastic material is subjected to a static electrical field while being submitted to a cooling such that the temperature of the thermoplastic is lower than the crystallization temperature in less than 60 seconds.
24. The method of claim 7, in which the thermoplastic material is subjected to a static electrical field while being submitted to a cooling such that the temperature of the thermoplastic is lower than the crystallization temperature in less than 15 seconds.
25. The method of claim 23, in which the thermoplastic material subjected to a static electrical field while being submitted to a cooling such that the temperature of the thermoplastic is lower than the crystallization temperature in less than 60 seconds is then pushed in a shaping device.
The present application is a Continuation in part of co-pending International application No. PCT/BE01/00012, with an international filing date of Jan. 24, 2001, published in French under PCT Article 21(2) on Jul. 26, 2001 which claims the benefit of the priority of Belgian Patent Application BE2000/0052 filed on Jan. 24, 2000.
The object of the present invention is a method for processing thermoplastic materials, more particularly materials containing at least one crystalline or semi-crystalline polymer or copolymer having a melting point, a crystallization temperature and a glass transition temperature.
The object of the present invention is a method that makes it possible, inter alia, to extrude crystalline or semi-crystalline polymer, more particularly polyethylene terephthalate, but equally a method that makes it possible to more readily extrude thermoplastic materials such as polyethylene, polypropylene, PVC, polycarbonate, etc.
The method according to the invention is especially applicable to the processing of crystalline or semi-crystalline polymer, preferably polymers or polymer mixes that present solid crystals below the crystallization temperature, advantageously presenting substantially only solid crystals below the crystallization temperature. In particular, the crystalline polymer or copolymer contains less than 40% by weight of non-crystalline or semi-crystalline polymer(s) or presenting liquid crystals below the crystallization temperature. More particularly, the crystalline or semi-crystalline polymer contains less than 20% by weight of liquid crystalline polymer and/or less than 20% by weight of polyolefin, in particular no or substantially no liquid crystalline polymers and polyolefins (for example less than 10% by weight of liquid crystalline polymer and less than 10% by weight of polyolefins). The liquid crystalline polymers are thermotropic polymers which present liquid crystals at a temperature lower than the crystallization temperature but higher than the hardening point.
The method according to the invention is a method for processing thermoplastic materials presenting a melting point and a solidification temperature,
said method being characterised by subjecting the thermoplastic material, before its passage in the forming device and/or during its passage in or through at least a part of the forming device, to a static electric field between a positive electrode and a negative electrode or earth, said electrodes or said electrode and earth being in contact with the thermoplastic material.
According to one preferred embodiment, the method according to the invention is a method involving processing a thermoplastic material that contains at least one crystalline or semi-crystalline polymer or copolymer having a melting point, a crystallization temperature lower than the melting point, and a glass transition temperature, said polymer or copolymer preferably presenting substantially only solid crystals below the crystallization temperature,
For example, the material is subjected to a static electric field over a temperature range that extends from a temperature higher than the crystallization temperature, down to a temperature at least 20° C. lower than the crystallization temperature, advantageously at least 50° C. lower than the crystallization temperature, and preferably at least 100° C. lower than the crystallization temperature.
According to one practical embodiment, a material containing at least one additive is processed so as to raise the dielectric characteristic, i.e. the dielectric constant or permittivity. This for example involves adding to the material a sufficient amount of additive to raise the dielectric constant or permittivity of the crystalline or semi-crystalline polymer or copolymer by at least 10%. Examples of suitable additives are titanium based compounds such as barium titanate, titanium dioxide (TiO2), etc.
The method according to the invention is particularly well suited to processing PET, possibly contaminated or containing additives or fillers, for example PET derived from PET preform or bottle manufacturing waste.
The forming device of the method according to the invention is advantageously a mould and/or a shaping fixture of an extruder, for example a shaping fixture operatively associated with a die for producing a profile, tube, etc. The forming device may also be a mould and/or die, or the injection runner or runners of a mould, so as for example to reduce the injection pressure and/or increase the number of cavities in the mould.
Another object of the invention is a product made from a crystalline or semi-crystalline polymer or copolymer (contaminated or otherwise) obtained by the method according to the invention. It is an advantage if the product is made from PET, possibly contaminated or containing additives or fillers. It was observed that by inducing an axial static electric field, especially one that is radial with respect to a wall of the product, it was possible to enhance the mechanical characteristics of said wall.
a die and/or shaping chamber which has a passage for introducing the material (for example at a temperature close to melting point, preferably higher than melting point, or at a temperature higher than the crystallization temperature or at a temperature lower than the crystallization temperature), said chamber or die having one or more walls in contact with the thermoplastic material (in order to shape it); a cooling means so as to cool one or more walls at least partially; and a means for connecting at least one wall or part-wall (part or portion of wall) of the chamber or die in contact with the thermoplastic wall to an electrical source in order to create a static electric field between at least said wall or part-wall (part of wall or portion of wall) and another wall or part-wall (part or portion of wall) of the chamber or die (walls or part-walls which are in contact with the thermoplastic material). It is an advantage if the device includes a first means for connecting a first wall or part of wall (part-wall) to a pole (for example the positive pole) of an electrical source, and a second means for connecting another wall or part-wall to another pole (for example the negative pole) of the electrical source or to earth, such that the first wall or part of wall (part-wall) forms a positive electrode.
According to one practical embodiment, the forming device, advantageous operatively associated with a die, presents a defined channel between one wall of a positive electrode and one wall of a negative electrode or earth, said channel presenting a passage for introducing thermoplastic material that is molten (or close to melting point) into the channel. Substantially the entire surface of the wall(s) of the channel of the forming device (plus, if appropriate, that/those of the die) in contact with the thermoplastic material is constituted by electrode walls or by electrode walls and the earth. It is an advantage if the electrodes and/or earth are positioned or disposed so that an electric field is applied substantially radially throughout the forming device, as well as in the die if appropriate. Where the forming device presents a passage for the shaped material to exit (for instance at a temperature lower than the crystallization temperature, for example a temperature lying between the glass transition temperature and the crystallization temperature), the electrodes (or the electrode(s) and earth) are advantageously disposed or arranged so as to create a radial electric field in the material, substantially extending from the passage for introducing the material into the forming device, as far as the passage for the material to leave the forming device.
According to one practical embodiment, the wall or walls of the forming device or of the shaping fixture or of the mould and/or of the die in contact with the material are provided with aluminium oxide, notably being covered with a layer containing aluminium oxide.
It is an advantage if the device has a positive electrode and a negative electrode that are arranged so as to form between them an electric field and constituting walls of the shaping chamber in contact with the thermoplastic material, the positive electrode advantageously being made from an aluminium alloy, the contact face of the electrode with the thermoplastic material preferably being provided with a layer of aluminium oxide at least 25 μm thick.
According to a detail of one embodiment, the length of the positive electrode or positive electrodes in contact with the material—said length being calculated in the direction in which the material advances in the shaping chamber or die—is more than 5 cm, advantageously more than 10 cm, and preferably more than 20 cm. This length is for example somewhere between 20 cm and 2 m, or even more. The length of the positive electrode or positive electrodes will be determined in response to the zones in which an electric field is to be applied, in response to the throughput rate of the material, in response to the grade of articles being produced, to the size and thickness of the articles, etc.
The device according to the invention is more particularly a device for shaping a material made of crystalline or semi-crystalline polymer or copolymer using a method according to the invention. The device comprises:
It is an advantage if the device according to the invention has a means for feeding the material into the shaping chamber adiabatically or substantially adiabatically (i.e. without heat exchange or transfer), at a temperature higher than the crystallization temperature.
According to one preferred form of embodiment, the means for creating an electric field is arranged relative to the cooling means so as to create an electric field at least in one zone of the shaping chamber in which the material passes from a temperature higher than the crystallization temperature to a temperature substantially the same as the glass transition temperature.
According to another possible form of embodiment, the device incorporates one or more means for creating an electric field at least in one zone of the die and at least in one zone of the shaping chamber, so as to apply an electric field to the material from a temperature higher than the melting point down to a temperature lower than the crystallization temperature, for example down to a temperature close to the glass temperature, or even lower than the glass temperature.
According to a detail of one embodiment, the device has a mandrel rod designed to form the internal shape of the article formed in the shaping chamber, said chamber having one wall designed to form the external shape of the article. The mandrel rod and the wall designed to form the external shape of the article constitute electrodes for creating a radial electric field, the mandrel rod advantageously constituting a negative electrode or earth, whilst the wall advantageously constitutes a positive electrode.
According to another detail of one embodiment, the device has a positive electrode and a negative electrode which are arranged so as to form an electric field between them and constituting walls of the shaping chamber in contact with the crystalline or semi-crystalline polymer or copolymer, the positive electrode advantageously being made from aluminum alloy, with the face that is in contact with the crystalline or semi-crystalline polymer or copolymer preferably being treated to receive a layer of aluminum oxide at least 25 μm thick.
FIG. 1 is a schematic view of an extruder equipped with a device according to the invention;
FIG. 2 is a sectional view of a detail of the extrusion die from FIG. 1;
FIG. 3 is a transverse sectional view through the extrusion die;
FIGS. 4 to 7 are views showing the positioning of the electrodes so as to obtain a particular field;
FIG. 8 is a schematic view of a mould according to the invention;
FIG. 9 represents the enthalpic curve of the PET obtained by the DSC (differential scanning calorimetry) method;
FIGS. 10 to 12 are schematic views of specific embodiments of the device according to the invention;
FIG. 13 represents an arrangement of electrodes in an injection runner of a mould;
FIG. 14 shows how the pressure required for POM to pass through a forming device evolves over time (where time 0 corresponds to the start time of introducing polymer into the device), with and without applying a radial electric field;
FIGS. 15 to 17 are graphs similar to the one in FIG. 14, except for the fact that the extruded material is respectively PET, high-density PE, and polypropylene;
FIG. 18 is a schematic view of a further embodiment of a device of the invention.
FIG. 1 shows an extruder 2 receiving crystalline or semi-crystalline polymer (for example PET in the form of granules or slivers) through the feed hopper 1. The polymer is melted in the extruder 2 and is forced into the head 3, which in zone A thereof is equipped with a mandrel rod 4 designed to produce the internal shape of the extrudate. The extrudate then passes into an adiabatic zone B (zone 5 where there is no, or substantially no, heat exchange). It is an advantage if this zone is convergent, i.e. if the throughput section of said zone decreases in the direction in which the material advances. The temperature of the polymer in this zone 5 is slightly higher than the crystallization peak, for example a temperature 1° to 20° C. higher than the crystallization peak. Next the melted polymer passes into zone C, which is subjected to strong cooling and to a strong electric field. Zone C thus constitutes a condenser 6. This electric field is maintained until the temperature of the polymer is the same or less than the glass transition temperature of the polymer (zone D). The stabilized product 7 accordingly exits from the extrusion die.
FIG. 2 is a sectional view of the extrusion die, extended by a forming device. The unit comprising the die/forming device 10 has an envelope 11 incorporating a passage along which extends the mandrel rod 4. The mandrel rod 4 forms a negative electrode or the machine's earth, whereas the envelope 11 forms the positive electrode. The electric field thereby created is a radial field directed towards the mandrel rod 4. This radial electric field (see FIG. 3) induces an electrostriction phenomenon in the crystallites, which manifests itself in a slight detachment of the polymer relative to the positive electrode (the temperature of the polymer being lower than the crystallization temperature or peak). The inside face of the envelope 11 is for example made from aluminum alloy, advantageously treated and coated with a layer of aluminum oxide Al2O3. This slight detachment makes it possible for the product to move in the extrusion die by the force of the extruder screw and enables the product to exit from the extrusion die. In the present case the electric field between the electrodes was a field of 5,000,000 V/m. The material for instance enters the unit 10 at a temperature higher than the melting point and exits at a temperature lower than the crystallization temperature.
During its passage or flow in the unit 10 (from its entry up to its outlet in the case of FIG. 2, i.e. its complete passage or flow in the unit 10), the thermoplastic material is submitted to a static radial electrical field.
`This insulating fluid therefore also serves as an electrical insulator for the positive electrode. This insulation is for example useful if the channels in which the fluid is flowing are formed between the positive electrode and an earth, but is likewise useful for insulating the positive electrode from the insulating fluid circulation system or cooling system.
In the case of FIG. 1, the product leaving the extrusion die is a tube with an external diameter of 9 cm and a wall 0.5 cm thick.
FIG. 4 represents a cross-section taken through an extrusion die similar to the one in FIG. 3, except for the fact that the mandrel rod constitutes the positive electrode and the envelope 11 constitutes the negative electrode.
FIG. 5 represents a cross-section taken through a die for extruding a hollow profile of rectangular cross-section. In this embodiment the mandrel rod of rectangular cross-section constitutes the positive electrode, while the envelope 11 constitutes the negative electrode.
FIG. 6 schematically represents a longitudinal section taken through an extrusion die, the envelope 11 of which has a series of distinct elements 12; 13 which form positive electrodes and negative electrodes, a positive electrode 12 being separated from a negative electrode 13 by an insulating element. The electrodes are disposed perpendicularly to the extrudate's axis of displacement, thereby subjecting the polymer to a longitudinal electric field, a field whose direction is parallel to the direction in which the extrudate is displaced.
FIG. 7 is a partly sectional view showing a die whose envelope 11 has a series of distinct elements 14, 15 forming positive electrodes and negative electrodes, one positive electrode 14 being separated from a negative electrode 15 by an insulating element 16. The electrodes are positioned relative to one another so as to define transverse electric fields, the direction of which is perpendicular to the direction in which the extrudate is displaced.
It goes without saying that it is possible to create electric fields that are constituted by operatively associating a radial electric field, a longitudinal electric field and/or a transverse electric field, by positioning the electrodes in an appropriate manner. If, for example, the mandrel rod is a negative electrode, radial and oblique electric fields will be created in the devices shown in FIGS. 6 and 7, in addition to the longitudinal or transverse fields.
FIG. 8 represents a mould 20 constituted by an outer envelope 21 comprising two parts 21A, 21B which may be separated from one another so as to enable the moulded part to be withdrawn. A cavity 23 is defined within said envelope 21. Into this cavity 23 extends a core, for example a cylindrical core 24, said core being fixed on the injection machine. The mould is advantageously equipped with cooling means. The envelope 21 for example constitutes a positive electrode, while the core 24 constitutes a negative electrode, or vice versa.
FIG. 9 represents a PET enthalpy curve, said curve depicting a (hollow) glass transition peak corresponding to the PET glass transition temperature, a crystallization peak corresponding to the PET crystallization temperature, and a (hollow) melting peak corresponding to the PET melting point.
FIG. 10 is a view showing a device according to the invention that is similar to the one in FIG. 1. This device features:
an extruder 2; an adiabatic zone 5; a die 10; a shaping fixture 6; and a traction system 11 which draws the product 7 outside of the shaping fixture. In the embodiment seen in FIG. 10, the shaping fixture 6 is equipped with means for applying a radial static electric field. The product obtained exhibited mechanical characteristics improved by 30% compared to the product obtained when no electric field was applied.
In the embodiment seen in FIG. 11, the device is similar to that in FIG. 10, except for the fact that there is no adiabatic zone 5 (the product exiting from the extruder passes straight into the die 10) and that a static electric field is applied to the material passing into the die 10 instead of into the shaping fixture 6. The electric field is advantageously radial. It was observed that by applying a radial electric field in the die, a lesser extruder pressure was sufficient to ensure the same throughput of extruded product as when no electric field was applied. In the case of crystalline polymer, it was observed that the extruder pressure could be reduced by a factor of 5 to 10 when a radial electric field of at least 5,000,000 volts/m was applied, while maintaining the same throughput as an extruder operatively associated with a die in respect of which no electric field is applied.
Finally, the device seen in FIG. 12 is similar to the one in FIG. 11, except for the fact that a radial electrical field is applied to the shaping fixture 6. This device makes it possible on the one hand to increase the production of an existing extruder and on the other hand to improve the mechanical characteristics of the extruded product.
FIG. 13 schematically shows one possible arrangement of electrodes (positive electrode 30, negative electrode or earth 31) in an injection runner 32 of a mould 33, having for example a fixed part 33A with respect to the head of an injector and a moving part 33B adapted to execute a relative motion with respect to part 33A, in order to enable the moulded article to be removed from the cavity or cavities 34. The injection runner 32 has a finger or means 36 for distributing the polymer flow to the various cavities 34 of the mould or to a plurality of locations in the mould cavity or cavities. The fixed part of the mould presents a positive electrode 30 which is insulated by an insulating layer 35 from the frame 33A1 of part 33A. The frame 33A1 is joined to the injector's earth. The moving part 33B is arranged so as to be connected to the injector's earth, at least when part 33B is resting against part 33A (with the mould in the closed position). The moving part 33B therefore also forms an earth at least when the mould 33 is in the closed position. In the embodiment shown, the finger or means 36 is carried by part 33B. The insulating layer 35 also provides insulation between the positive electrode and the injector head. If the injector head is provided with a positive electrode, the positive electrode of the mould is advantageously connected to the positive electrode of the injector, the positive electrode of the injector then being insulated from the frame 33A1.
FIG. 14 shows the pressures exerted by the screw of an extruder which is advancing polyoxymethylene (crystalline polymer) into a polarized forming device [radial field applied to the material from the time that the material is introduced into the device (temperature close to melting point) until it leaves the device at a temperature close to the glass transition temperature] and into the unpolarized forming device from the time that the material is introduced at a temperature close to melting point.
It can be seen from this Figure that where the forming device is not polarized (curve I), the flow is in a first adiabatic period (±15 seconds), after which a front or abrupt increase in the pressure is observed (due to the polymer's crystallization peak). Thereafter a pressure increment is observed up to a time of 30 seconds after the introduction of the material. The pressure then continues to rise until the maximum permissible pressure of the forming device and of the extruder is reached (120 bars). Due to the material having cooled, a plug of material has formed in the forming device and a pressure of 120 bars was not enough to force the material out of the forming device.
FIG. 15 is a figure similar to FIG. 14, but showing the effect of an electric field in the forming device for PET. It can be seen from this Figure that by applying an electric field (curve II), the maximum pressure required to pass the material through the device is reduced. Curve I shows the pressure needed when no electric field is applied.
Lastly, FIGS. 16 and 17 are figures similar to FIG. 14, but applied respectively to recycled high-density polyethylene and to polypropylene. This figure also shows that by applying an electric field (in this example radial: curve II) it is possible to reduce the maximum pressure needed to pass material through the forming device. Curve I shows the pressure necessary when no electric field is applied.
PET, POM and high-density PE test pieces were also prepared by applying a radial electric field of 5,000,000 volts/m in the forming device, together with other test pieces in the forming device without applying an electric field. Accordingly a resistance to traction was observed that was substantially the same for the test pieces with the electric field as for the test pieces without the electric field. However, as far as the modulus of elasticity is concerned, it was observed that the POM and PET test pieces had a modulus of elasticity approximately 60% higher when an electric field was applied than was the case with the modulus of the specimen prepared in the absence of an electric field. In the case where the test pieces prepared with an electric field were post-cured (post-curing carried out for 48 hours at a temperature 20° C. higher than the glass transition temperature), the test pieces prepared using the electric field and post-cured still had a modulus of elasticity approximately 20 to 30% higher than the modulus of elasticity of the test pieces that were not prepared using an electric field and post-cured.
The following Table gives Young's modulus of elasticity (expressed in MPa) for a test piece moulded without an electric field (A), a test piece moulded without an electric field but with post-curing (B), and a test piece prepared with an electric field.
Ratio of modulus
test piece X/test piece C
The method according to the invention may be used to manufacture many different parts, such as moulded parts, extruded parts, panels, rails, profiles, sheets, troughs (e.g. cable troughs), profiles with T-sections, profiles with U-sections, profiles with I-sections, profiles with L-sections, profiles with X-sections, etc.
FIG. 18 is a schematic view of an embodiment of a device of the invention. In said device, an extruder 2 receives crystalline or semi-crystalline polymer or copolymer with a low crystallization rate (such as a PET with a low crystallization rate) trough the feed hopper 1. The polymer or copolymer is melted in the extruder and is forced into a electrostriction converter 17 in which the temperature of the polymer or copolymer is rapidly reduced below the crystallization temperature. For example, the reduction of the temperature below the crystallization temperature is made in less than 60 seconds, advantageously in less than 30 seconds, preferably in less than 15 seconds, such as in less than 10 seconds, for example in about 8 seconds, 5 seconds, etc.
For ensuring the rapid cooling of the polymer or copolymer below the crystallization temperature, the converter 17 is shaped so as to ensure a quick cooling, for example a temperature reduction from about 270-290° C. up to 150° C.-170° C. in about 8 seconds for a PET polymer. The electrostriction effect is obtained by submitting the polymer or copolymer to a static electrical field of more than 1,000,000 volt/m, such as a static electric field of 5,000,000 Volt/m. For example, the converter is shaped so that the thickness of the polymer or copolymer (such as a PET polymer) between the positive electrode and the negative electrode or earth is less than 10 mm, advantageously less than 5 mm, preferably equal to about 2.5 mm, or even most preferably lower than 2.5 mm.
For example, when the device of FIG. 18 is used for shaping product with PET, the temperature of the PET at the entry of the converter is about equal to the melting point of the PET or is lower than said melting point, while at the outlet of the converter, the temperature of the PET is within the range of 150-170° C. The PET is then pushed in the cold die or shaping device 19 at a temperature of about 150° C.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS3943614 *Jul 17, 1974Mar 16, 1976Kureha Kagaku Kogyo Kabushiki KaishaMethod of polarizing high molecular weight filmsUS4683093 *Nov 6, 1985Jul 28, 1987Toray Industries, Inc.Method for holding a moving filmUS4810319 *Aug 25, 1986Mar 7, 1989Isner Robert EMethod of making a monofilament having on the surface embedded filamentons materialUS4810432 *Dec 28, 1987Mar 7, 1989Polaroid CorporationMethod and apparatus for establishing a uniform charge on a substrateUS5254297 *Jul 15, 1992Oct 19, 1993Exxon Chemical Patents Inc.Charging method for meltblown websEP0171017A2Jul 29, 1985Feb 12, 1986Bayer AgThermoplastic processing of thermotropic liquid crystalline polymers under the influence of electric and/or magnetic fieldsGB1086765A Title not available* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS7199508 *Aug 1, 2002Apr 3, 2007Matsushita Electric Industrial Co., Ltd.Coaxial flexible piezoelectric cable polarizer, polarizing method, defect detector, and defect detecting methodUS7381765Nov 8, 2004Jun 3, 2008Freudenberg-Nok General PartnershipElectrostatically dissipative fluoropolymersUS7445725Dec 8, 2006Nov 4, 2008Freudenberg-Nok General PartnershipSurface bonding in halogenated polymeric componentsUS7521486May 14, 2007Apr 21, 2009Freudenberg-Nok General PartnershipBranched chain fluoropolymersUS7862765 *Nov 20, 2008Jan 4, 2011Semes Co., Ltd.Method for synthesizing conductive compositeUS7863365Dec 20, 2006Jan 4, 2011Freudenberg-Nok General PartnershipRobust magnetizable elastomeric thermoplastic blendsUS8124679May 20, 2008Feb 28, 2012Freudenberg-Nok General PartnershipElectrostatically dissipative fluoropolymersUS20040251772 *Aug 1, 2002Dec 16, 2004Mitsuo EbisawaCoaxial flexible piezoelectric cable polarizer, polarizing method, defect detector, and defect detecting methodUS20060099368 *Nov 8, 2004May 11, 2006Park Edward HFuel hose with a fluoropolymer inner layerUS20060100333 *Nov 8, 2004May 11, 2006Park Edward HElectrostatically dissipative fluoropolymersUS20060100368 *Nov 8, 2004May 11, 2006Park Edward HElastomer gum polymer systemsUS20070036980 *Oct 19, 2006Feb 15, 2007Freudenberg-Nok General PartnershipPolytetrafluoroethylene compositesUS20070044906 *Aug 31, 2005Mar 1, 2007Freudenberg-Nok General PartnershipMultilayer polymeric composites having a layer of dispersed fluoroelastomer in thermoplasticUS20070045967 *Aug 31, 2005Mar 1, 2007Freudenberg-Nok General PartnershipAssemblies sealed with multilayer composite torsion seals having a layer of dispersed fluoroelastomer in thermoplasticUS20070048476 *Aug 31, 2005Mar 1, 2007Freudenberg-Nok General PartnershipAssemblies sealed with multilayer composite compression seals having a layer of dispersed fluoroelastomer in thermoplasticUS20070092731 *Nov 28, 2006Apr 26, 2007Freudenberg-Nok General PartnershipElectron beam curing in a composite having a flow resistant adhesive layerUS20070095790 *Dec 8, 2006May 3, 2007Freudenberg-Nok General PartnershipSurface bonding in halogenated polymeric componentsUS20070213423 *May 14, 2007Sep 13, 2007Freudenberg-Nok General PartnershipBranched chain fluoropolymersUS20090105385 *Oct 20, 2008Apr 23, 2009Freudenberg-Nok General PartnershipElastomer gum polymer systemsUS20100123274 *Nov 20, 2008May 20, 2010Semes Co., Ltd.method for synthesizing conductive composite* Cited by examinerClassifications U.S. Classification264/449, 425/3, 264/451, 264/452, 264/450International ClassificationB29C47/88, D01D10/00, D01D5/088, B29C47/12, B29C47/86, B29C47/20, B29B13/08, B29C35/10, B29C45/27, B29K67/00, B29C47/08, B29C33/02Cooperative ClassificationB29C47/003, B29C47/0019, B29C47/0023, D01D5/088, D01D10/00, B29C47/20, B29K2995/0041, B29K2105/253, B29C45/2701, B29C47/881, B29C47/8805European ClassificationB29C45/27B, B29C47/20, B29C47/88B2, D01D10/00, D01D5/088Legal EventsDateCodeEventDescriptionNov 8, 2002ASAssignmentOwner name: INTERNATIONAL BRAIN SYSTEM S.A., BELGIUMFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SOULIER, JOEL;REEL/FRAME:013481/0487Effective date: 20020826Dec 9, 2004ASAssignmentOwner name: INTERNATIONAL BRAIN SYSTEM S.A., BELGIUMFree format text: TO RE-RECORD ASSIGNMENT PREVIOUSLY RECORD ON NOVEMBER 8, 2002 AT REEL 13481 FRAME 487 TO CORRECT THE ASSIGNEE S ADDRESS AS NOTED ABOVE.;ASSIGNOR:SOULIER, JOEL;REEL/FRAME:016048/0894Effective date: 20020826May 26, 2008FPAYFee paymentYear of fee payment: 4Nov 19, 2012REMIMaintenance fee reminder mailedApr 5, 2013LAPSLapse for failure to pay maintenance feesMay 28, 2013FPExpired due to failure to pay maintenance feeEffective date: 20130405RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services