EP1534883B1 - Articles comprising fibres and/or fibrids, fibres and fibrids and production method of same - Google Patents

Abstract

The present invention relates to novel articles, especially non-woven articles comprising fibers and/or fibrids. It also relates to novel fibers and fibrids and to a process for obtaining these fibers and fibrids.

Description

The present invention relates in particular to new articles, in particular nonwoven articles comprising fibers and / or fibrids. It also relates to new fibers and fibrids and a process for obtaining these fibers and fibrids.

In the field of electrical insulation in particular, it is sought to obtain products having good temperature resistance and good mechanical properties and / or good dielectric properties. These products may for example be nonwoven articles made from thermostable fibers. In such an article, a good cohesion of thermostable fibers is necessary to obtain a good level of mechanical properties, or even a homogeneous and dense structure of the article for obtaining dielectric properties. For this purpose, it is sought to obtain good cohesion of thermostable fibers at the article. It is also sought to obtain a homogeneous and compact structure at the article level. These articles, according to their structure (in particular their density) and / or their formulation, can have a function of mechanical and / or dielectric reinforcement.

The document US 2,999,788 For example, it is proposed to prepare particles of synthetic or "fibrous" polymers having a particular structure that can be used with fibers based on synthetic polymers for the production of fibrous structures that are coherent by the papermaking method. A hot pressing operation can be performed on these structures, causing a creep of the fibrids. But the preparation of such fibrids, carried out by precipitation in sheared medium is complicated and expensive. Moreover, these fibrids must remain in an aqueous medium for direct use. As a result, they can not be isolated or transported easily, which limits their use.

The document FR 2 163 383 proposes to prepare non-woven articles constituted by a sheet of fibers based on an infusible material or having a melting point greater than 180 ° C., the fibers being bound together by means of a polyamide-imide binder, used in proportion of 5 to 150% of the weight of dry fibers used. But the impregnation of the resin is in solution in a solvent, which has the consequence of adverse effects on the characteristics of the nonwovens.

To improve the feasibility of nonwoven webs, the document FR 2 156 452 proposes the wet preparation of nonwoven webs of fibers consisting of infusible material or having a melting point greater than 180 ° C, bonded together by powdered thermoplastic polymer.

If obtaining these sheets can, in theory, be carried out by paper, in practice, their industrial realization is difficult: in fact the mixture of synthetic fibers-resin-based binder has too little cohesion to be handled and in In particular, such a mixture does not have sufficient cohesion to be able to be prepared dynamically, for example on a commercial papermaking machine; such plies are feasible mainly on laboratory devices of the "Formette Franck" type, that is to say statically and discontinuously as is apparent from the examples.

The document FR 2,685,363 proposes to prepare by wet paper made of fibers having a thermal resistance greater than or equal to 180 ° C, bonded together by means of a fibrous binder and a chemical binder.

We know from the document EP.0.648.812 a gaseous separation membrane in the form of a film or hollow fibers, which is formed from a mixture of polyethersulfones with polyimides, polyamides or polyamide-imides. As hollow fibers, they are assembled using a binder, containing an epoxy resin.

The use of binders to ensure the cohesion of the fibers in articles such as non-woven entails particular difficulties and costs in the implementation of these binders.

The subject of the present invention is a process for the manufacture of articles consisting in particular of non-woven articles, not having the above-mentioned drawbacks, which method comprises the features of claim 1. The thermoplastic part of the fiber or fibride of the In particular, the invention plays the role of the chemical binder described above. It has the property of "flowing" under pressure and temperature constraints. Thus the cohesion of thermostable fibers in these articles is ensured, their level of thermal and mechanical properties is very satisfactory. These articles can have a homogeneous and dense structure, and therefore a good level of dielectric properties.

In another object, the invention proposes the use of the articles obtained by the above method in the field of electrical insulation.

The thermostable polymer of the invention is preferably infusible or has a glass transition temperature greater than 180 ° C, preferably greater than or equal to 230 ° C, or higher. The thermostable polymer of the invention has a thermal resistance (that is to say a conservation of its physical properties in particular) long-term at a temperature above 180 ° C. This thermostable polymer is preferably chosen from polyaramids and polyimides. Examples of polyaramids include aromatic polyamides such as the polymer known under the trade name Nomex®, or polyamide imides such as the polymer known under the trade name Kermel®. Examples of polyimides that may be mentioned are the polyimides obtained according to the document EP 0119185 , known under the trade name P84®. The aromatic polyamides can be as described in the patent EP 0360707 . They can be obtained according to the process described in the patent EP 0360707 .

The thermoplastic polymer is selected from the group of polysulfides and polysulfones. As an example of polysulfide, there may be mentioned polyphenylene sulphide noted PPS thereafter. By way of example of polysulfones noted PSU thereafter, mention may be made of the polyether sulfone noted PESU later or polyphenylene sulfone noted PPSU thereafter.

These thermoplastic polymers have a glass transition temperature of less than or equal to 250 ° C., which enables them to act in particular as a chemical binder in the articles of the invention and to "flow" under pressure and temperature stress. These polymers also have good thermostability because they belong to a thermal class (thermal index) greater than 130 ° C. This has an advantage for obtaining articles having good thermostability.

According to a preferred embodiment of the invention, the thermoplastic polymer and the thermostable polymer are soluble in the same solvent. Advantageously, the solvent is polar aprotic. It is more preferably chosen from DMEU, DMAC, NMP, DMF.

Advantageously, the fiber or fibride according to the invention comprises at least 10% by weight of thermoplastic polymer.

Fibrides are small non-granular fibrous or film-like particles that are not rigid. Two of their three dimensions are of the order of a few microns. Their small size and flexibility allow them to be deposited in physically interwoven configurations such as those commonly found in pulp papers.

The fiber according to the invention preferably has a titer of between 0.5 dtex and 13.2 dtex. The fiber of the invention preferably has a length of between 1 and 100 mm.

The fiber according to the invention may have various section shapes such as a round, trilobed, "flat" shape. By fiber of flat section is meant a fiber whose length / width ratio is greater than or equal to 2.

The fiber or fibride according to the invention can be treated by sizing.

According to a particular embodiment of the article of the invention, the fibers are obtained by mixing the thermostable polymer and the thermoplastic polymer, and then spinning the mixture.

Any means known to those skilled in the art for mixing two polymers can be used. Preferably, the polymer mixture is obtained by dissolving the polymers in at least one common solvent. The thermoplastic polymer and the heat-stable polymer may be dissolved together, simultaneously or successively in a solvent or a mixture of solvents miscible with each other, in a single reactor for example. The polymers can also be dissolved separately in the same solvent or in different solvents miscible with each other, for example in two different containers, then the polymer solutions mixed together.

The dissolution conditions, such as temperature, are determined by those skilled in the art depending on the nature of the polymers and the solvent (s) used. The dissolution may for example be carried out hot, with stirring, to facilitate dissolution.

The dissolution can be carried out at room temperature. Preferably the dissolution temperature is between 50 and 150 ° C.

The dissolution solvent (s) is (are) advantageously an aprotic polar solvent. Dimethylalkylene urea, for example dimethylethylene urea (DMEU) or dimethylpropylene urea, may be used. Preferably it is selected from DMEU, dimethylacetamide (DMAC), N-methyl pyrrolidone (NMP), dimethylformamide (DMF). The dissolution solvent can be a mixture of aprotic polar solvents, for example a mixture of dimethylethylene urea and an anhydrous aprotic polar solvent such as NMP, DMAC, DMF, tetramethylurea or γ-butyrolactone.

The solution of polymers obtained after dissolution is called collodion. The resulting solution is preferably clear.

The total concentration by weight of the polymers relative to the solution is preferably between 5 and 40%.

The solution may also include additives such as pigments, reinforcing agents, stabilizers, mattifying agents.

The solution must also have a viscosity allowing its spinning, generally between 100 and 1000 poise. For wet spinning, the viscosity is preferably between 400 and 800 poises measured using a viscometer known in the trade under the trademark EPPRECHT RHEOMAT 15. For dry spinning, the viscosity is preferably between 1500 and 3000 poise.

The polymer mixture can also be made in line during the spinning step, for example by online injection of each polymer-whether or not dissolved in a solvent-during the spinning process.

Any method of spinning a mixture of polymers, in particular a polymer solution, known to those skilled in the art can be used here within the scope of the invention.

Dry spinning, for example, in which the solution of polymers (fibrogenic substance in the solution state) is extruded through capillaries in an environment favorable to the elimination of the solvent, for example in an evaporating atmosphere maintained at a temperature near or above the boiling point of the solvent, allowing the solidification of the filaments. The filaments leaving the evaporation chamber are freed of their residual solvent. For this they can be washed with water, possibly boiling and under pressure; dried in the usual manner, preferably at a temperature above 80 ° C. They can also be heat treated at a temperature greater than or equal to 160 ° C under reduced pressure, and / or under an inert atmosphere. After being freed from their residual solvent, they may be drawn for example at a temperature above 250.degree. C., preferably above 300.degree. C., preferably in the absence of oxygen.

According to a particular embodiment of the invention, the spinning method is a wet spinning, in which the polymer solution (fibrogenic substance solution) is extruded into a coagulating bath.

The temperature of the spinning solution can vary within wide limits depending on the viscosity of the solution to be spun. For example, a solution having a low viscosity can easily be extruded at ordinary temperature, while it is preferable to extrude hot, for example at 120 ° C or even higher, a solution of high viscosity to avoid using too much. great pressures in the sector. The spinning solution is advantageously maintained between 15 and 40 ° C, preferably between 15 and 25 ° C.

The coagulant bath used in the process according to the invention is preferably an aqueous solution containing from 30 to 80% by weight, preferably from 40 to 70% by weight of a solvent or solvent mixture, preferably a dimethylalkylene urea (DMAU ) or DMF or their mixture, although it is often advantageous to use a bath containing more than 50% by weight of solvent to obtain filaments of better stretchability, thus better final properties.

Preferably, the polymers of the solution to be spun have close coagulation rates.

The spinning speed in the coagulant bath can vary within wide limits, depending on its solvent concentration and the distance of the filaments in this bath. This spinning rate in the coagulant bath can be easily selected between 10 and 60 m / min, for example, although higher speeds can be achieved. It is generally not advantageous to spin at lower speeds for reasons of cost efficiency of the process. Moreover, too high speeds of spinning in the coagulant bath reduce the stretchability of the filaments in the air. The spinning speed in the coagulant bath will therefore be chosen to take into account both the profitability and the desired qualities on the finished filament.

The filaments emerging from the coagulating bath in the gel state are then stretched, for example in air, at a rate defined by the ratio (V 2 / V 1) * 100, V 2 being the speed of the drawing rolls, V 1 that delivery rollers. The stretching rate of the son in the gel state is greater than 100%, preferably greater than or equal to 110% or even greater, for example greater than or equal to 200%.

After drawing, preferably in air, generally carried out by passage between two sets of rollers, the residual solvent of the filaments is removed by known means, generally by means of a washing with water flowing against the current or on washing rollers, preferably at room temperature.

According to another particular embodiment of the invention, the spinning method is dry spinning.

In the two spinning processes described above (dry spinning and wet spinning), the washed filaments are then dried by known means, for example in a drier or on rollers. The temperature of this drying can vary within wide limits as well as the speed which is greater as the temperature is higher. It is generally advantageous to perform a drying with gradual rise in temperature, this temperature being able to reach and even exceed 200 ° C. for example.

The filaments can then undergo a warm overetching to improve their mechanical properties and in particular their toughness, which can be interesting for some jobs.

This hot stretching can be carried out by any known means: oven, plate, roller, roller and plate, preferably in a closed enclosure. It is carried out at a temperature of at least 150 ° C, which can reach and even exceed 200 to 300 ° C. Its rate is generally at least 150% but it can vary within wide limits depending on the qualities desired for the finished yarn. The total draw ratio is then at least 250%, preferably at least 260%.

The stretching assembly and optionally super stretching can be carried out in one or more stages, continuously or discontinuously with the previous operations. In addition, overdrawing can be combined with drying. For this purpose, it is sufficient to provide, at the end of the drying, a zone of higher temperature which makes it possible to overetch.

The filaments obtained are then cut in the form of fibers according to a method known to those skilled in the art

According to another embodiment of the article of the invention, the fibrids are obtained by mixing the thermostable polymer and the thermoplastic polymer, and then precipitating the mixture under shear stress.

The mixture of the thermostable polymer and the thermoplastic polymer may be made in a manner analogous to that described above for the fibers. The fibrids of the invention can in particular be obtained by precipitating a solution of polymers in a fibridation apparatus of the type described in the patent US 3,018,091 wherein the polymers are sheared as they precipitate.

According to a particular embodiment of the invention, the articles are nonwoven articles. The nonwoven articles are in the form of sheets, films, felts and generally they denote any coherent fibrous structure involving no textile operation such as spinning, knitting, weaving.

The article can be obtained from a single type of fiber or on the contrary from fiber mixtures. The nonwoven article of the invention comprises at least in part fibers and / or fibrids according to the invention. The article of the invention may comprise fibers of different natures and / or fibrids of different natures. In addition to the fibers and / or fibrids according to the invention, the nonwoven article may comprise, for example, thermostable fibers and / or fibrids or reinforcements of the para-aramid, meta-aramid, polyamide imide, etc. type.

The nonwoven article may comprise, for example, fibers according to the invention and heat-stable fibers. In the case where the article comprises fibrids, the article may for example comprise fibers according to the invention and thermostable polymer fibrids according to a first embodiment; or the article may for example comprise thermostable fibers and fibrids according to the invention according to another embodiment.

The nonwoven article of the invention may be obtained by a method and apparatus for preparing a nonwoven article known to those skilled in the art. The article of the invention is generally obtained by implementing a "lapping" step, that is to say a step of distribution of the fibers and / or fibrids on a surface, then a step of "Consolidation" of the structure obtained.

According to an advantageous embodiment of the invention, the "lapping" step is carried out by "dry route"("drylaid"), for example from, in particular, the invention whose length is between 40 and 80 mm. The fibers may for example be processed using an ordinary carding machine.

According to another advantageous embodiment of the invention, the "nappage" step is carried out by "wet" or "papermaking" ("wetlaid"). The fibers used in this embodiment generally have a length between 2 and 12 mm, preferably between 3 and 7 mm, and their title, expressed in decitex is generally between 0.5 and 20. It is theoretically possible to use fibers longer than 12 mm, but in practice longer fibers become entangled, requiring a greater amount of water, making the process heavier and more complicated.

According to this embodiment, the nonwoven article is obtained by introducing into water, the various constituents of the article: the fibers and a fibrous binder composed of a pulp based on a synthetic polymer having a thermal resistance greater than or equal to 180 ° C (such as a para-aramid pulp) and / or fibrids based on a synthetic polymer having a heat resistance greater than or equal to 180 ° C and / or fibrids according to the invention, and optionally other adjuvants, additives or desired fillers.

The pulp based on a synthetic polymer having a heat resistance greater than or equal to 180 ° C. has generally been obtained from fibers of the usual length, in particular fibrils, in a known manner, to give it a large number of dots. snagging and thus increase its specific surface area. Of the synthetic fibers, only highly crystallized fibers can be fibrillated. This is the case of totally aromatic polyamides and polyesters, but other highly crystallized polymers are cleavable along the fiber axis or fibrillable.

To improve certain properties, adjuvants, additives or fillers can also be used in various proportions depending on the desired properties; for example mica can be introduced to further increase the dielectric properties of the article.

The "paper route" for preparing non-woven articles is known to those skilled in the art.

The "consolidation" step of the structure obtained by layering as described above is carried out by thermal pressing of the article: The thermal pressing temperature is greater than the glass transition temperature of the thermoplastic polymer of the fibers and / or fibrids according to the invention contained in the article. Preferably the thermal pressing temperature is between the glass transition temperature and the softening temperature of the thermoplastic polymer.

According to an advantageous embodiment of the invention, the thermal pressing temperature is between 200 and 350 ° C. The pressure is preferably greater than or equal to 5 bars.

This pressing ensures densification and consolidation of the article of the invention. It is generally accompanied by creep of the thermoplastic polymer fibers and / or fibrids according to the invention contained in the article through the structure of the article,

Thermal pressing is not limited to the level of its implementation. Any means of thermal pressing a nonwoven article can be used.

The pressing may for example be carried out using a press or a heated roller calender. It is possible to make several passes on the pressing apparatus so as to obtain the desired density.

The preferred thermal pressing method of the invention is calendering. According to a particular embodiment of the invention, the thermal pressing is carried out using a continuous press.

The articles obtained by this pressing are various and varied according to the conditions of the thermal pressing implemented - in particular the temperature, the pressure and the pressing time - and according to the formulation of the article - in particular the amount of fibers and / or fibrids according to the invention contained in the article and the amount of thermoplastic polymer present in these fibers and / or fibrldes-.

The choice of these parameters is made according to the type of articles and the properties sought on this article.

The articles of the invention can be implemented in particular in the field of electrical insulation.

The role of the articles varies according to their density and therefore according to their dielectric strength properties. They may for example be used in an insulation system in which the main insulation is an oil or a resin, such as "spacer" or "reinforcement" mechanical interposed between two parts to be electrically insulated. The articles can also be used directly as insulation in "dry" type insulation systems.

The invention also relates to the use of the articles obtained by the method of the invention as described above in the field of electrical insulation.

Other details and advantages of the invention will emerge more clearly from the view of the examples described below.

EXAMPLES Examples 1 to 3 Preparation of the Thermoplastic Polymer / Heat-stable Polymer Mix Example 1

180 kg of DMEU solvent are introduced into a heated and stirred reactor. This solvent is first heated to a temperature between 60 ° C and 120 ° C. The PESU polymer (MW 80000 to 90000 g / mol) in the form of lenticular granules is introduced into the hot solvent, in 10 equal fractions. The time required between each fraction is a function of the intensity of the agitation and the temperature. The polymer is introduced to represent 20 to 40% by weight of the mixture.

The polymer content in the medium affects its viscosity. By way of example, at 21% the viscosity at 25 ° C. is 350 poise; at 28% the viscosity is 460 poises.

The mixture of the thermoplastic polymer PESU with the polyamide imide Kermel® is produced by hot mixing, between 60 and 120 ° C., of the medium described above containing the PESU and a solution containing 21% by weight of Kermel® polyamide imide in the DMEU solvent (MW 150000 g / mol in polystyrene equivalents, viscosity: 600 poise at 25 ° C.). The proportion of the two solutions in the mixture is expressed in proportion of PESU polymer in the dry matter and is between 40 and 60%.

Example 2

A polyamide-imide Kermel® / PESU mixture is obtained directly by dissolving the PESU polymer in a solution containing 13% by weight of Kermel® polyamide imide in the DMEU solvent, using a high shear gradient mixing apparatus. , and high recycling rate.

Example 3

A medium containing PESU is prepared according to the procedure of Example 1. The mixture with Kermel® polyamide imide (in the form of a 21% by weight solution of Kermel® polyamide imide in DMEU solvent) is produced during spinning, by joint injection of the two solutions in a common pipe, upstream of static mixers implanted in this pipe which feeds the spinning loom. Respect of the proportions of the two solutions in the mixture is ensured by the adjustment of the rotational speeds of volumetric pumps.

Examples 4 and 5: Thermoplastic polymer / thermostable polymer blend spinning Example 4

• Filières 10.000 trous de 50µm
• Bain de coagulation à 55% de solvant, 19°C
• Vitesse de filage 14 m/min
• Taux d'étirage: 2 x
• Titre final obtenu : 4.4 dtex

The PESU / polyamide imide Kermel® mixtures of Examples 1 to 3 are spun by a wet spinning process. The proportion of PESU polymer is 40% by weight. The following conditions give as an example the spinning parameters used:

• Dies 10,000 holes of 50μm
• Coagulation bath with 55% solvent, 19 ° C
• Spinning speed 14 m / min
• Drawing ratio: 2 x
• Final title obtained: 4.4 dtex

The fiber is dried, crimped and cut under conventional conditions (fiber length = 60 mm).

Example 5

• Filières 10.000 trous de 40µm
• Bain de coagulation à 60% de solvant, 19°C
• Vitesse de filage 14 m/min
• Taux d'étirage : 2 x
• Titre final obtenu : 2.2 dtex

The PESU / polyamide imide Kermel® mixtures of Examples 1 to 3 are spun by a wet spinning process. The proportion of PESU polymer is 50%. The following conditions give as an example the spinning parameters used:

• Dies 10,000 holes of 40μm
• Coagulation bath with 60% solvent, 19 ° C
• Spinning speed 14 m / min
• Drawing ratio: 2 x
• Final title obtained: 2.2 dtex

The fiber is dried under conventional conditions. Crimping and cutting are done under conventional conditions

Examples 6 to 8: Articles

Non-woven articles of different grammages are prepared from the fibers of Example 4 by "dry route" and "consolidation" (carding, glazing, calendering) according to a method known to those skilled in the art.

• carde de type Garnett® à sortie parallèle
• nappeur Asselin®
• calandre KTM®

The equipment used is as follows:

• Garnett® type card with parallel output
• Asselin® lapper
• KTM® grille

Table 1 describes the operating conditions used and the characteristics of the articles obtained.

The mechanical properties of force and elongation at break are measured according to standard NF-EN 29073-3 of December 1992. The thickness of the articles is measured using a micrometer of Palmer® type. <u> Table 1 </ u> Examples Example 6 Example 7 (*) Example 8 Calender speed (m / min) 5 5 5 Calender temperature (° C) 250 250 270 Calender pressure (bar) 6 6 6 Weight (g / m ² ) 42 60 65 Thickness (μm) 50 65 70 Density (g / cm ³ ) 0.84 0.92 0.93 Force breaking machine direction (N / 5cm) 20.2 41 60.9 Elongation breaking machine direction (%) 1.4 2.1 2.9 (*) The article according to Example 7 has undergone two calendering passes. The creep and the density obtained after calendering are observed.

The figure 1 is a photograph of the surface of the article according to Example 8 after calendering.

The figure 2 is a photograph of the section of the article according to Example 8 after calendering.

Examples 9 to 12: Preparation of fibrids from a thermoplastic polymer / thermostable polymer blend

The PESU / polyamide imide Kermel® mixture of Example 1, diluted with DMEU to obtain the desired PESU / polyamide imide Kermel® polymer concentration, is precipitated under high shear, according to a method as described in US Pat. FR 1214 126 or US 4,187,143 in an aqueous coagulation bath comprising a given concentration of DMEU solvent. Table 2 describes the conditions of preparation of fibrids. <u> Table 2 </ u> Examples Proportion of PESU / polyamide imide Kermel® by weight (%) before precipitation Proportion of solvent in the coagulation bath by weight (%) 9 9.5 25 10 15 50 11 9.5 0 12 9.5 50

The characteristics of the fibrids were measured on MORFI apparatus (conventional apparatus for measuring paper cellulosic fibers). Table 3 describes these characteristics. <u> Table 3 </ u> Examples 9 10 11 12 Length (mm) 0,315 0.431 0.351 0.289 Width (μm) 40.2 44.6 49.7 30.3 Fine elements (% in length) 19.5 11.0 14.7 24.9 Fine element rate (% on the surface) 1.6 0.4 0.6 3.6

Examples 13 to 16: Articles obtained from fibrids

The fibrids of Examples 9 to 12 were mixed with an equal weight of Kermel® polyamide imide fibers 6 mm in length. These four preparations were used to make paper on FRANK-type form apparatus wet and in a conventional paper-making process. The target density of the samples is 80g / m ² . The characteristics of the papers are shown in Table 4.

Tableau 4 Exemples Fibrides Epaisseur en µm Masse introduite dans l'appareil (g) Masse après passage dans l'appareil (g) Taux de rétention (%) Grammag e (g/m²) Main (cm³/g) 13 Ex.9 199,6 2,506 2,448 98 77 2.6 14 Ex.10 238,8 2,516 2,478 98 81 2.9 15 Ex.11 199,5 2,517 2,342 93 74 2.7 16 Ex.12 191,3 2,525 2,500 99 77 2.5 The retention rate is defined as follows: $$\mathrm{Retention\; rate}(\%)=(1-\left[\left(\mathrm{mass\; introduced}\left(\mathrm{boy\; Wut}\right)-\mathrm{mass\; after\; passage}\left(\mathrm{boy\; Wut}\right)\right)/\mathrm{mass\; introduced}\left(\mathrm{boy\; Wut}\right)\right]*100$$

<u> Table 4 </ u> Examples fibrids Thickness in μm Mass introduced into the device (g) Mass after passing through the device (g) Retention rate (%) Grammage (g / m ² ) Main (cm ³ / g) 13 Ex.9 199.6 2,506 2,448 98 77 2.6 14 Ex.10 238.8 2,516 2,478 98 81 2.9 15 Ex.11 199.5 2,517 2,342 93 74 2.7 16 Ex.12 191.3 2,525 2,500 99 77 2.5

The papers obtained, after drying, were characterized by their mechanical properties (Table 5) and by their air permeability on the BENDTSEN apparatus under a pressure of 1.47 kPa (Table 6) according to the traditional methods of the industry. paper. <u> Table 5: Mechanical strength of papers </ u> Examples 13 14 15 16 Breaking force (N) 1.78 2.37 1.05 3.23 Tensile strength (N / m) 119 158 70 216 Resistance index 1.55 1.95 0.94 2.84 with traction (Nm / g) Elongation rupture (%) 1.89 2.61 1.16 2.09 Modulus of elasticity (MPa) 558 370 638 632 Tear (mN) 820 1600 560 1400 Tear index (Nm / g) 3.27 6.07 2.32 5.6 Example s 13 14 15 16 Average (ml / min) 50.5 58.7 876.8 1.4 Standard deviation 4.9 124.9 0.2

Examples 17 to 24: Articles obtained from fibrids, hot-pressed

• soit 10min sous 100 bars
• soit 5min sous 200 bars.

Tableau 7 : Epaisseur des papiers pressés Pression 100 bars Exemples 17 18 19 20 Article Ex.13 Ex.14 Ex.15 Ex. 16 Epaisseur moyenne (µm) 125,8 137,3 125,7 121,5 Main (cm³/g) 1,63 1,69 1,69 1,57 Pression 200 bars Exemples 21 22 23 24 Article Ex.13 Ex.14 Ex.15 Ex.16 Epaisseur moyenne (µm) 123,1 122 116,4 121,4 Main en cm³/g 1,59 1,50 1,57 1,58 The papers of Examples 13 to 16 were hot-pressed on a laboratory plate press at 280 ° C.

• 10min under 100 bars
• ie 5min under 200 bars.

<u> Table 7: Thickness of pressed papers </ u> 100 bar pressure Examples 17 18 19 20 article Ex.13 Ex.14 Ex.15 Ex. 16 Average thickness (μm) 125.8 137.3 125.7 121.5 Main (cm ³ / g) 1.63 1.69 1.69 1.57 Pressure 200 bars Examples 21 22 23 24 article Ex.13 Ex.14 Ex.15 Ex.16 Average thickness (μm) 123.1 122 116.4 121.4 Hand in cm ³ / g 1.59 1.50 1.57 1.58

Claims (19)

1. A method of manufacturing a consolidated fiber-based article, the method being characterized in that the article comprises at least fibers and/or fibrids formed from a mixture of polymers comprising at least a thermostable polymer, and a thermoplastic polymer selected from the group formed by polysulfides and polysulfones, and in that said article is consolidated by heat pressing at a temperature above the glass transition temperature of said thermoplastic polymer.
2. A method according to claim 1, characterized in that the thermostable polymer is selected from aromatic polyamides, aromatic polyamide imides and polyimides.
3. A method according to claim 1 or claim 2, characterized in that the thermoplastic polymer is selected from polyether sulfone and polyphenylene sulfone.
4. A method according to any preceding claim, characterized in that the thermoplastic polymer and the thermostable polymer are soluble in the same solvent.
5. A method according to any preceding claim, characterized in that the mixture of polymers comprises at least 10% by weight of thermoplastic polymer.
6. A method according to any preceding claim, characterized in that the fibers are obtained by mixing the thermostable polymer and the thermoplastic polymer, followed by spinning the mixture.
7. A method according to claim 6, characterized in that the mixture is produced by dissolving the polymers in a solvent.
8. A method according to claim 7, characterized in that the solvent is a polar aprotic solvent.
9. A method according to claim 8, characterized in that the solvent is selected from DMEU, DMAC, NMP and DMF.
10. A method according to any one of claims 6 to 8, characterized in that spinning is wet spinning.
11. A method according to any one of claims 6 to 8, characterized in that spinning is dry spinning.
12. A method according to any preceding claim, characterized in that the fibrids are obtained by mixing the thermostable polymer and the thermoplastic polymer then shear precipitating the mixture.
13. A method according to any one of claims 1 to 12, characterized in that heat pressing is performed in pressure and temperature conditions that impart hot flow to at least the thermoplastic polymer.
14. A method according to claim 13, characterized in that, during heat pressing, the temperature is in the range between the glass transition temperature and the softening temperature of the thermoplastic polymer.
15. A method according to claim 14, characterized in that, during heat pressing, the temperature is in the range 200°C to 350°C, and the pressure is 5 bars or more.
16. A method according to claim 1, characterized in that the article further comprises fibers and/or fibrids which are thermostable, in particular para-aramid, meta-aramid, polyamide imide fibers.
17. A method according to any one of claims 1 to 16, characterized in that the fibers have a size of 13.2 dtex or less.
18. The use of an article obtained by the method according to any one of claims 1 to 17, in the field of electrical insulation.
19. A use according to claim 18, characterized in that the article also includes mica.

Images