Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/78—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolycondensation products
  • D01F6/84—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolycondensation products from copolyesters
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/08—Melt spinning methods
  • D01D5/088—Cooling filaments, threads or the like, leaving the spinnerettes
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/78—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolycondensation products
  • D01F6/82—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolycondensation products from polyester amides or polyether amides

Definitions

• the present invention relates to polyester (amide) aromatic thermotropic fibers, more specifically to the monofilaments of such polymers, as well as to the processes for obtaining such monofilaments.
• thermotropic aromatic polyester amide
• fibers multiftlamentary made up of a large number of filaments of small elementary diameter (typically around 20 to 30 ⁇ m), or of large diameter unitary monofilaments (at least less than 40 ⁇ m)
• melt-spinning of the polymer generally followed of a so-called post-polycondensation heat treatment is a known technique.
• the raw spinning monofilament thus obtained is taken from a winding at a speed of 590 m / min, to then be subjected to the heat treatment of postpolycondensation on the receiving coil: this postpolycondensation phase particularly long on this type of polymer (several hours) in fact implies that the treatment is carried out on a reel, generally in an oven, and not on a moving single-wire continuous through this oven.
• the monofilaments have a diameter about 180 ⁇ m the following mechanical properties: initial modulus of 4300 cN / tex, 2.5% elongation at break and 130 cN / tex toughness.
• the monofilaments already have in the raw spinning state a module very high initial, greater than 4000 cN / tex, postpolycondensation heat treatment being essentially intended to increase the toughness of the spun products.
• the primary purpose of the invention is to overcome the aforementioned drawbacks by proposing a new monofilament in thermotropic aromatic polyester (amide) which, in the raw spinning state (“as-spun”), has the characteristic of not contracting hot.
• D is preferably included in a range from 80 to 230 ⁇ m, more preferably from 100 to 200 ⁇ m.
• the raw spinning monofilament of the invention has the advantage of having, for a given polymer and a given diameter D. a lower extension module combined with an elongation at break which is generally higher, which is an advantageous compromise.
• a lower extension module combined with an elongation at break which is generally higher, which is an advantageous compromise.
• the raw spinning monofilament of the invention verifies the relationships: Mi ⁇ 4000;Ar> 2,
• Mi being its initial modulus (in cN / tex) and Ar its elongation at break (in%).
• the raw spinning monofilament of the invention can be used as it is, or else treated thermally to obtain an aromatic polyester (amide) monofilament post-polycondensed thermotrope which constitutes another object of the invention.
• the invention further relates to the use of the monofilaments of the invention, whether in the state assembly or unitary wire, for the reinforcement of plastic and / or rubber, as well as its articles themselves, in particular the rubber tablecloths intended in the manufacture of tires and these tires themselves.
• the optical anisotropy of the polymers is tested by observing in the molten phase (i.e. above the polymer melting temperature) a drop of polymer between polarizer and analyzer crossed lines of a polarization optical microscope (Olympus type BH2), at rest that is to say in the absence of dynamic constraint.
• a polarization optical microscope Olympus type BH2
• the above preparation is optically anisotropic, that is to say that it depolarizes light: thus placed between crossed linear polarizer and analyzer, it has a light transmission (texture more or less colorful); an optically isotropic preparation, under the same conditions observation, does not have the above depolarization property, the field of microscope remaining black.
• the term "monofilament” or “monofilament” means a unitary filament whose diameter or thickness (i.e. the smallest transverse dimension of its section right when it is not circular), noted D, is at least equal to 40 ⁇ m (title 1.7 tex minimum).
• the above definition therefore covers both monofilaments of essentially cylindrical (ie with circular section) than oblong monofilaments, monofilaments of flattened shape, or strips or films of thickness D.
• pre-conditioning means the storage of monofilaments (after drying) for at least 24 hours, before measurement, in a standard atmosphere according to European standard DIN EN 20139 (temperature of 20 ⁇ 2 ° C ; humidity ⁇ 65 ⁇ 2%).
• the titer of the monofilaments is determined on at least three samples, each corresponding to a length of 50 m, by weighing this length of monofilament.
• the title is given in tex (weight in grams of 1000 m of monofilament - reminder: 0.111 tex equal to 1 denier).
• the tenacity (force-breaking divided by the title) and the initial modulus are indicated in cN / tex (centinewton per tex - reminder: 1 cN / tex equal to 0.11 g / den (gram per denier)).
• the module initial is defined as the slope of the linear part of the Force-Elongation curve, which comes just after a standard pretension of 0.5 cN / tex.
• the elongation at break is indicated as a percentage.
• the parameter D which then represents the smallest dimension of the monofilament in a plane normal to the axis of the latter, is no longer determined by calculation but experimentally, by optical microscopy on a cross section of this monofilament, the latter being for example previously coated in a resin to facilitate cutting.
• thermal variation test of length The thermal behavior of the monofilaments is analyzed, after conditioning prior, using a test called "thermal variation test of length" whose principle is well known to those skilled in the art in the field of textile fibers.
• the thermal variation in length denoted ⁇ L is measured by introducing the monofilaments. under a pretension of 0.2 cN / tex, in an oven previously balanced with temperature of 235 ° C ⁇ 5 ° C.
• a known commercial device of the "Testrite” type is used (model MK3 marketed by the company Testrite).
• the useful sample length (without significant impact on the measurement) is 254 mm.
• ⁇ L is measured automatically by the device, using mechanical sensors, and the measurement result is read on a digital display, after 2 minutes at a temperature of 235 ° C ⁇ 5 ° C; a positive ⁇ L variation corresponds to a dilation of the monofilaments, while a negative ⁇ L variation corresponds to a contraction of these last.
• the starting polymer is any polyester or thermotropic aromatic polyester-amide which can be spun to the molten state.
• polyesters or polyester-amides called “fully aromatic” are known to those skilled in the art and have been described in a very large number of documents.
• thermotropic aromatic polyester this polymer consists essentially of repeating units (A) of 6-oxy-2-naphthoyl and (B) of 4-oxybenzoyl: the A: B molar ratio being in a range from 10:90 to 90:10. preferably from 20:80 to 30:70.
• Such a polymer sold in particular by the company Hoechst Celanese under the name of Vectra, has been described in US 4,161,470 and can be obtained by copolymerization of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, these two acids possibly being substituted. It has, in known manner, an excellent compromise of properties in terms of thermal resistance, chemical resistance, ease of implementation and suitability for spinning, in particular due to a relatively low melting point (hereinafter denoted Tm).
• Tm relatively low melting point
• a polymer of this type - Vectra type 900 or 950 with molar ratio A: B equal to 27:73 - is widely known for conventional multifilament fibers (see for example J. Text. Inst., 1990, 81 No 4. pp. 561-574) and was also used for obtaining monofilaments of the prior art described in the aforementioned application WO92 / 12018.
• the starting polymer for example in the form of granules or powder, is dried under vacuum then introduced into an extruder having one or more heating zones different.
• the temperatures and the residence times imposed in these different zones are such that they allow complete melting of the polymer, rotation and screw torque conditions stable extrusion offering a regular supply to the spinning pump, and finally to avoid degradation of the polymer in the extruder.
• the molten polymer then at the temperature denoted Tx (temperature of extruder outlet). is transferred to a spinning pump which feeds a preceding die a filter.
• the die may include a single extrusion capillary or more depending on whether one wishes spinning a single monofilament or several monofilaments in parallel; we will consider below the case of a die with a single capillary.
• the diameter of the capillary is not a critical parameter of the process: it can vary in a wide range, for example from 200 to 1500 ⁇ m, or even more. according to the diameter D targeted.
• the invention also relates to the cases where the monofilaments have a cross section other than circular, such a shape being obtainable by example by modifying the cross section of the extrusion capillary; for such monofilaments, the parameter d then represents the smallest transverse dimension of the capillary, i.e. its smallest dimension measured in a plane normal to the direction flow of the polymer.
• the die temperature denoted Tf is lower than the temperature Tm (polymer melting temperature).
• a liquid extrudate is therefore obtained. (flow of polymer) consisting of an elementary liquid vein having the shape of a still liquid monofilament. This liquid polymer vein is then structured. oriented by stretching (see below FEF spinning factor) in a fluid layer gas, for a predetermined time ts, this before entering a liquid zone of thermal quenching.
• structuring duration means the total duration of passage from the flow of polymer in the layer of gaseous fluid, whatever the profile or gradient drawing the flow in this layer of gaseous fluid.
• the layer of gaseous fluid is preferably air, the thickness of which, denoted Ag, can vary by example from a few centimeters to several meters, depending on the specific conditions of placing of the invention, in particular according to the durations ts referred to.
• thickness Ag is meant from the layer of gaseous fluid the distance between the outlet of the die and the inlet of the zone thermal quenching liquid.
• Tc of the fluid layer gas is notably lower than Tf, Tc being generally close to the temperature ambient (about 20 ° C).
• a structuring time ts lower than the critical value to above is a condition necessary to guarantee, whatever the diameter D aimed, the obtaining of a raw monofilament of spinning not contracting hot (i.e. showing a variation ⁇ L ⁇ 0 on the variation test length).
• the following relation (2) is verified: 1.5.10 -6 D 2 ⁇ ts ⁇ 6.10 -6 D 2 .
• the spinning speed (see below Vf) is within a range of 500 to 1000 m / min and the thickness of the layer of gaseous fluid (Ag) is chosen to be greater than 0.50 meters and less than 2.0 meters.
• the flow of polymer thus structured, oriented enters the zone thermal quenching liquid where, in contact with the liquid agent, it solidifies and thus forms a monofilament.
• the liquid thermal quenching agent is water and its temperature noted Tl is preferably lower than ambient temperature, for example in the range of 10 to 15 ° C.
• liquid thermal quenching operation simple means can be used consisting for example of a bath containing the quenching liquid and through which flows the monofilament in formation.
• the liquid quenching time is not a critical parameter and can vary for example from a few milliseconds to a few tenths of a second, or even a few seconds, according to the specific conditions for implementing the invention.
• the stretch factor and the spinning speed can vary within a very wide range, for example from 2 to 50 for the FEF and from 100 to 1500 m / min for Vf.
• the raw spinning monofilament thus obtained is then wound at speed Vf, on a spool reception. It can optionally be dried before winding, for example by scrolling continuous on heating rollers, or else be wound in the wet state and then dried on a reel. for example in ambient air or at a higher temperature in an oven. before a pre-conditioning for the measurement of its thermal and mechanical properties.
• the initial modulus Mi and the elongation at break Ar of the monofilament of the invention can be largely modulated by the choice of the starting polymer and spinning conditions, the initial module in particular being all the higher as the rigidity of the polymer is greater (eg use of thermotropic polyester amides).
• the raw spinning monofilament of the invention verifies the following relationships: Mi ⁇ 4000;Ar> 2,
• Mi being its initial modulus (in cN / tex) and Ar its elongation at break (in%).
• their toughness in the raw state of spinning is preferably greater than 55 cN / tex, more preferably greater than 65 cN / tex; their initial module, at the raw spinning state is preferably between 2500 and 4000 cN / tex, more preferably at least equal to 3000 cN / tex and less than 4000 cN / tex.
• Post-polycondensation heat treatment after spinning, essentially allows increase the toughness available on monofilaments, by increasing the degree of polymerization of the polymer; in general, the more advanced the heat treatment, the higher the toughness obtained after treatment.
• Monofilaments are thus obtained in thermotropic aromatic polyester (amide) called postpolycondensed, which are directly derived from raw monofilament yarns described above.
• the coils of raw spinning monofilaments are treated in ovens in known manner, at high temperatures, under vacuum or under inert gas, for example under flow nitrogen, usually for several hours.
• the conditions of this processing postpolycondensation which in known manner varies depending on the nature of the polymer used, are similar to those used for conventional fibers multifilament. Special treatment conditions have been described, for example in US 4,161,470 for these conventional fibers, and in application WO92 / 12018 above for monofilaments with a diameter of 180 ⁇ m: such conditions are also given in the exemplary embodiments which follow.
• the post-polycondensed thermotropic aromatic polyester (amide) monofilament derived from the raw spinning monofilaments of the invention verifies the following relationships: Mi ⁇ 4000;Ar>2;Te> 100,
• Mi being its initial modulus (in cN / tex), Ar its elongation at break (in%), and Te sa tenacity (in cN / tex). More preferably, its Mi module is between 2500 and 4000 cN / tex, more preferably still at least equal to 3000 cN / tex and less than 4000 cN / tex ; its elongation at break Ar is preferably at least equal to 2.5.
• the raw spinning monofilaments of the invention such as those in the post-polycondensed state which are derived, can be used in various applications, in particular for manufacturing or reinforcement of various articles, in particular plastic articles and / or rubber, for example belts, hoses, tire casings.
• a diameter at least equal to 80 ⁇ m is preferred in view of the wiring costs (need to limit the number of wires in the cables, for a given breaking strength), while a diameter greater than 230 ⁇ m is generally to be avoided to limit damage in bending-compression (disadvantage of large diameters with a small radius of curvature).
• a diameter greater than 230 ⁇ m is hardly compatible with obtaining toughness sufficient, especially for reinforcing tires.
• thermotropic aromatic of determined diameter D, with the duration of structuring ts.
• thermotropic aromatic polyester used here is a known polymer of the Vectra A900 type, in the form of granules, marketed by the company Hoechst Celanese, consisting of recurring units (A) and (B) as defined above, according to a molar ratio A: B equal to about 27:73 (Tm equal to 280 ° C according to DSC analysis).
• the temperature Tf and the diameter d of the single capillary of the die are respectively equal to 270 ° C and 800 ⁇ m.
• the spinning conditions are adjusted in a known manner, by varying the speed of the spinning pump and on the speed of extrusion through the die, so as to obtain a monofilament with a diameter D of approximately 180 ⁇ m (titer equal to approximately 34.5 tex).
• the flow of polymer thus structured is thermally quenched by forced passage of the monofilament under a pulley immersed in a water bath at 15 ° C; the length of submerged monofilament is approximately 10 cm, which corresponds to a time of very short but sufficient thermal quenching of approximately 10 milliseconds.
• the monofilament is taken up and wound up in several turns on a drive device consisting of a call slab, at the speed Vf indicated above of 590 m / min.
• the monofilament is then taken from a reel in the wet state and allowed to dry at air for 24 hours, before conditioning for the measurement of its properties thermal and mechanical.
• the structuring time ts was thus varied according to the indications in Table 1 - either 0.02 to 0.40 s - gradually increasing the thickness Ag of the air-gap from 0.2 m (eg A-1) to 3.9 m (eg F-1), successively passing through Ag values of 0.55 m (eg B-1), 0.75 m (e.g. C-1), 1.10m (e.g. D-1) and 1.60m (e.g. E-1). All wiring conditions are in compliance to the invention, with the exception of the duration ts for example F-1 which does not verify the relation (1) above (ts ⁇ to).
• Table 1 also indicates the properties of the monofilaments obtained.
• Examples A-1 to D-1 further verify the following preferential relationships: Mi ⁇ 4000; Ar> 2.
• examples A-1 to B-1 obtained for the shortest structuring times ts, verify the following preferential relationships: ⁇ L ⁇ 0.20; Ar ⁇ 2.5.
• the initial module can thus be lowered to values between 2500 and 4000 cN / tex without affecting the toughness which remains in all cases greater than 65 cN / tex.
• the monofilaments B-1, C-1, D-1 and E-1 (diameter 180 ⁇ m), which are obtained according to a process verifying the above-mentioned relation (2), namely: 1.5.10 -6 D 2 (i.e. 0.049 s) ⁇ ts ⁇ 6.10 -6 D 2 (i.e. 0.194 s), all have the following preferred characteristic: 3000 ⁇ Mi ⁇ 4000.
• Example F-1 prepared according to a spinning process not in accordance with the invention (ts> to), it has a "hot" contraction ( ⁇ L negative) and is therefore not in accordance with the invention: also has a particularly high initial module. greater than 4000 cN / tex, and a Ar value less than 2%.
• the parameters ⁇ L, Mi and Ar are particularly sensitive to an increase in ts.
• the continuous increase in the initial module Mi with ts - and therefore with the thickness Ag of the air layer - appears rather unexpected in the extent that the skilled person could expect to observe on the contrary, for thicknesses air gap of up to several meters, a decrease in the initial module due to molecular relaxation process in the liquid crystal flow of the polymer.
• the monofilaments in accordance with the invention have significant thermal expansion ( ⁇ L ⁇ 0.2 for all examples: ⁇ L ⁇ 0.4 in most cases cases): advantageously, such properties may in particular authorize their winding under high tension, during spinning, before the subsequent treatment of post-polycondensation.
• Table 2 also indicates the properties of the raw spinning monofilaments thus obtained.
• Table 3 also indicates the properties of the monofilaments obtained. Note that the monofilaments of examples E-3, F-3 and G-3, prepared according to the process in accordance with the invention (ts ⁇ to), verify all the following relationships: D ⁇ 40; Te>45; ⁇ L ⁇ 0.
• These monofilaments in accordance with the invention also verify the following preferential relationships: Mi ⁇ 4000 and Ar> 2; the Te is greater than 55 cN / tex for the E-3 and F-3 monofilaments.
• Examples A-3 to D-3 prepared according to a process not in accordance with the invention (ts> to), if they certainly present, as for examples C-2 and D-2 above, a initial modulus Mi less than 4000 cN / tex (polymer less rigid than for test 1), they are all characterized by a negative ⁇ L variation, i.e. by a hot thermal contraction at length variation thermal test: they are therefore not in accordance with the invention.
• test 2 the monowires of Examples A-2 to D-2 above (test 2) are subjected to a postpolycondensation heat treatment.
• Table 4 indicates the properties of monofilaments in the post-polycondensed state A-4, B-4, C-4, D-4 thus obtained, respectively from the raw spinning monofilaments A-2, B-2, C-2, D-2.
• the raw spinning monofilaments according to the invention are those which, after heat treatment, lead to the products (A-4 and B-4) presenting the highest toughness (Te> 100 cN / tex) and highest elongation at break (Ar > 2.5%).
• the monofilaments C-4 and D-4 prepared according to the prior art have a significantly lower toughness, an elongation at break weaker, and a general aspect which is degraded: they contain in particular a number important of "kink-bands" at the crossing points of the turns, on the processing coil.
• This monofilament is then subjected to a post-polycondensation heat treatment, in placing the monofilament spool in an oven, under vacuum, and applying the rails and following thermal steps: thermal ramp of 2 ° C / min from room temperature to 195 ° C : then thermal ramp of 0.3 ° C / min from 195 ° C to 241 ° C; then 2 hours at 241 ° C; then crawl thermal from 0.1 ° C / min from 241 ° C to 285 ° C; finally 3 hours at 285 ° C.
• the oblong monofilament thus obtained in the post-polycondensed state has, for a titer of 227 tex, a toughness greater than 100 cN / tex (precisely 101 cN / tex, which corresponds to a breaking force about 23 daN), an initial Mi module between 3000 and 4000 cN / tex (precisely 3600 cN / tex) and an elongation at break Ar greater than 3% (precisely 3.4%).
• the monofilaments according to the invention in the form of unitary threads (in particular when these are oblong monofilaments or films) or in the form of cables or assemblies, are used preferably for the reinforcement of rubber articles, in particular plies of rubber intended for the manufacture of tires.
• the assemblies or monofilaments can undergo a preliminary treatment activation such as plasma therapy, for example, as described in the application WO92 / 12018 cited above or in application WO92 / 12285, for aramid monofilaments.
• a preliminary treatment activation such as plasma therapy, for example, as described in the application WO92 / 12018 cited above or in application WO92 / 12285, for aramid monofilaments.
• the monofilaments according to the invention can be used under an oblong shape, therefore not requiring wiring operations, to reinforce the carcass or the top of these radial tires, instead of conventional cables formed of several monofilaments twisted together.
• the very low thickness D of the oblong monofilaments compared to the cables, makes it possible to reduce in fact notably the thickness of the rubber plies which they reinforce, and therefore the manufacturing costs; a small thickness D is also favorable for endurance in bending-compression monofilaments, and therefore the endurance of the rubber plies themselves in the tires.
• the monofilaments rough spinning of the invention have a new and essential characteristic which is that not to contract hot.
• the raw spinning monofilaments of the invention such as those in the post-polycondensed state which derived therefrom, have the advantage over those of the prior art of having, for a given polymer (given stiffness and anisotropy), a lower modulus which is most often combined with higher elongation at break; it has been found that such combination gives monofilaments, for a determined diameter D, resistance in flexion-compression which is improved.
• an advantageous characteristic of the spinning method of the invention is that it allows the rate of thermal expansion of monofilaments to be adjusted practically on demand rough spinning, or even their initial modulus and their elongation at break, depending on the intended industrial application; such an adjustment is obtained by controlling the duration of structuring ts of the polymer flow before the liquid quenching, this duration of structuring ts being a direct function of the diameter D of the targeted monofilament.
• the raw spinning monofilaments of the invention can be used in the form of continuous monofilaments or of short fibers: they can optionally be combined with other fibers, threads or monofilaments , for example steel wires, to constitute for example hybrid reinforcing elements.
• N c test ts .DELTA.L You Mid Ar A-1 0020 + 0.55 68 2890 2.5 B-1 0,056 + 0.50 69 3000 2.5 C-1 0,076 + 0.45 70 3270 2.3 D-1 0.112 + 0.40 67 3230 2.3 E-1 0.163 + 0.20 70 3910 2.0 F-1 0.397 - 0.10 74 4340 1.9 Test No.

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