EP1420097A1 - Microfibrous nonwovens, complexes and manufacturing processes - Google Patents

Abstract

The non-woven fabric has a fibrous structure containing a majority of microfibres (10) and thermally bonded zones (13). The micro fibres are made from one or more materials that have a higher melting point than the thermally-bonded fibres, and at least a proportion of them has an oblong cross-section. The fibrous structure also includes cellulose or non-cellulose fibres with a yarn count of under 1 dtex, and is made up of at least 20 per cent by weight of microfibres, at least 10 per cent of a thermal bonding material and at least 10 per cent of cellulose fibres. The weight of the fabric is between 5 and 600 g/sq m and preferably under 30 g/sq m, and it is impregnated to enhance its dust-free properties. The thermal bonding is carried out by passing the fabric through an oven, over heated rollers, or by ultrasound.

Description

• des non-tissés de fibres courtes, à structure microfibreuse ;
• des complexes, incorporant de tels non-tissés dans leur structure ;
• des procédés de préparation desdits non-tissés et complexes.

The subject of the present invention is:

• short fiber nonwovens, with a microfibrous structure;
• complexes, incorporating such nonwovens into their structure;
• processes for the preparation of said nonwovens and complexes.

The nonwovens of the invention are particularly effective for degrease surfaces. They exhibit an interesting compromise of properties, especially in terms of mechanical resistance, flexibility, softness touch and mass volume.

• aisément,
• à des grammages aussi bien forts que faibles,
• avec un réglage aisé de leur résistance mécanique,
• avec utilisation optimale des précurseurs de microfibres, intervenant à titre de matière première.

They are particularly interesting in that they can be obtained:

• easily,
• at both strong and weak grammages,
• with easy adjustment of their mechanical strength,
• with optimal use of microfibers precursors, acting as raw material.

The process proposed for their preparation is indeed very efficient and optimizes the use of the microfibers precursors.

In patent application WO-A-98 238 04, the manufacture of a microfibrous nonwoven from a web of continuous filaments burstable multicomponents. The constituent filaments of said veil are previously thermally bonded before being burst by water jets. The preliage is implemented to stiffen the veil of filaments and to prevent said filaments are not encrusted in the support fabric. It consumes matter hot-melt, precursor of microfibers. It is shown, in said request WO-A-98 238 04, that the nonwoven obtained at the end of the manufacturing process described (thermobonding + bursting) is more airy (less dense) than that obtained without prior thermobonding, by simple bursting.

In this request, it is incidentally mentioned, without providing of no precision, the possibility of replacing the veil of continuous filaments multi-component bursts, a veil of multi-component cut fibers Explodable.

Anyway, according to the process described, the raw material used consists only of the microfibers precursor and the material hot melt is generated from it.

The most widespread microfibrous nonwovens in the trade are prepared from veils of crimped cut fibers, multicomponents, burst in microfibers by hydraulic means. Tablecloths, made up of several of these veils, are thus generally subjected to the action of water jets, which, while bursting the multicomponent fibers in microfibers, bind them by interlacing. The microfibrous nonwoven obtained is, or not, post-linked. It can thus be coated with a hydrophilic latex and / or embossed in a thermocalandre. The process in question, based on the action of the water jets, does not make it possible to obtain sheets of low grammage, in particular of a grammage lower than 30 g / m ² . Indeed, the water jets destroy such layers, by a blast effect.

In such a context, the inventors have developed a process original, very efficient, which makes it possible to obtain new nonwovens microfibrous with interesting properties. Said new nonwovens have a structure, which bears the signature of their production process.

The nonwovens of the invention are shortwoven nonwovens, the fibrous structure of which contains a majority in number of microfibers as well as zones of molten thermobonding. In this they can be considered as nonwovens of the type of those of the prior art. Of typically, the microfibers of the nonwovens of the invention are material (s) different from that (s) of the melted material thermobonding, which has a higher melting temperature (s) and they are located at the limit of said zones of molten material of thermobonding, grouped in bundles.

• la première, au niveau de la nature de leurs matériaux constitutifs : les microfibres, qui interviennent majoritairement (en nombre) dans leur structure, sont en un matériau, plus généralement en des matériaux (matériau(x) constitutif(s) des fibres multicomposantes utilisées comme matière première, précuseur desdites microfibres) différent(s) de celui ou ceux de la matière fondue de thermoliage (il est en effet susceptible d'intervenir un unique ou plusieurs matériaux, à titre de précurseur de la matière fondue de thermoliage. Il en intervient généralement un unique. Un tel précurseur (de tels précurseurs) est(sont) par ailleurs susceptible(s) d'intervenir sous différentes formes, telles que des fibres et/ou de la poudre...), qui présente(nt) une(des) température(s) de fusion supérieure(s) à celle(s) du(des) matériau(x) de la matière fondue de thermoliage. Ainsi, lesdites microfibres ou, plus précisément les fibres multicomposantes, précurseurs desdites microfibres ont elles pu conserver leur intégralité lors de la matière fondue de thermoliage (voir le procédé décrit plus avant dans le présent texte). Le thermoliage en cause n'entame pas la réserve de microfibres. Selon une variante préférée, les non-tissés de l'invention renferment des microfibres en deux matériaux différents (par exemple, des microfibres de polyester et des microfibres de polyamide) liées par intervention d'un seul matériau (par exemple, du polypropylène) ;
• la seconde, au niveau de l'arrangement des microfibres : en limite des zones de thermoliage, les microfibres se présentent, regroupées en faisceaux. Cette seconde caractéristique originale est la signature du procédé d'obtention des non-tissés de l'invention, procédé selon lequel le thermoliage est mis en oeuvre avant l'éclatement des fibres multicomposantes précuseurs des microfibres, avant la génération desdites microfibres.

The nonwovens of the invention therefore have two original characteristics:

• the first, in terms of the nature of their constituent materials: the microfibers, which are mainly involved (in number) in their structure, are made of a material, more generally of materials (material (s) constituting the multicomponent fibers used as raw material, precusor of said microfibers) different from that or those of the molten thermobonding material (it is indeed likely to intervene a single or several materials, as a precursor of the molten thermobonding material. There is generally only one. Such a precursor (such precursors) is (are) moreover capable (s) of intervening in different forms, such as fibers and / or powder, etc.), which has (are) a melting temperature (s) higher than that (s) of the material (s) of the molten thermobonding material. Thus, said microfibers or, more precisely multicomponent fibers, precursors of said microfibers were able to retain their integrity during the molten thermobonding material (see the process described later in this text). The thermobonding in question does not affect the supply of microfibers. According to a preferred variant, the nonwovens of the invention contain microfibers in two different materials (for example, polyester microfibers and polyamide microfibers) linked by the intervention of a single material (for example, polypropylene);
• the second, at the level of the arrangement of the microfibers: at the limit of the thermobonding zones, the microfibers appear, grouped in bundles. This second original characteristic is the signature of the process for obtaining the nonwovens of the invention, a process according to which the thermobonding is carried out before the bursting of the multicomponent precursor fibers of the microfibers, before the generation of said microfibers.

According to an advantageous variant, at least a fraction of the microfibers present, very advantageously all the microfibers present, have an oblong section, that is to say of an elongated shape. Said section may in particular be oval, flat, triangular or trapezoidal. She actually has one of its dimensions at least 1.5 times larger than the other. The presence of this type of fiber optimizes wiping performance nonwovens of the invention.

Microfibers involved in the fibrous structure of nonwovens of the invention may be of any material, in particular polyester, polyamide, polyethyleneterephthalate ...

The microfibers in issue are conventional microfibers whose title is less than 1 dtex, advantageously less than 0.6 dtex.

They (usually most, if not all) are obtained from conventional way, by bursting precursor fibers.

The molten thermobonding material is in one (of), advantageously one, material (s) compatible with the material (s) constituting the microfibers. The compatible adjective is used here with reference to the points of fusion of the materials in question. We have seen that the melt must have melted without alteration of the microfibers precursors. Said melt may in particular consist of polypropylene. It has already been indicated that said polypropylene advantageously binds polyester microfibers together and polyamide.

• ils renferment quasi exclusivement des microfibres liées par de la matière fondue (intervenue à l'état de poudre, fondue lors du thermoliage, antérieur à l'éclatement) ;
• ils renferment majoritairement des microfibres et d'autres fibres en un(des) matériau(x) thermofusible(s) qui a(ont) été ponctuellement fondu(s) dans les zones de thermoliage ;
• ils renferment, outre les microfibres, intervenant majoritairement, et les éventuelles fibres en matériau(x) thermofusible(s), d'autres fibres. De telles autres fibres peuvent notamment consister en des fibres cellulosiques (artificielles ou naturelles, telles des fibres de viscose, de Lyocell®, de coton, d'acétate de cellulose, de lin, de jute de ramie, de chanvre et/ou de bois...) et/ou des fibres non cellulosiques dont le titre est supérieur à 1 dtex. Les fibres cellulosiques, microfibres et/ou fibres plus grosses, sont susceptibles d'intervenir pour conférer de l'hydrophilie aux non-tissés de l'invention (pour les rendre ainsi capables d'absorber et de retenir l'eau). Lesdites fibres cellulosiques, par ailleurs, absorbent et retiennent l'huile, tout comme les fibres synthétiques. Enfin, leur présence rend les non-tissés de l'invention plus souples. De grosses fibres (dont le titre est supérieur à 1 dtex) non cellulosiques sont susceptibles d'intervenir pour conférer un caractère récurant et/ou abrasif aux non-tissés de l'invention.

The nonwovens of the invention can exist according to different variants and in particular according to those specified below:

• they almost exclusively contain microfibers linked by molten material (intervened in the powder state, melted during thermobonding, prior to bursting);
• they mainly contain microfibers and other fibers in one (or more) hot-melt material (s) which has (have) been temporarily melted (s) in the thermobonding zones;
• they contain, in addition to the microfibers, intervening mainly, and the possible fibers in material (X) hot-melt (S), of other fibers. Such other fibers may in particular consist of cellulosic fibers (artificial or natural, such as viscose, Lyocell®, cotton, cellulose acetate, flax, ramie jute, hemp and / or wood fibers ...) and / or non-cellulosic fibers with a titer greater than 1 dtex. The cellulosic fibers, microfibers and / or coarser fibers, are capable of intervening to impart hydrophilicity to the nonwovens of the invention (to thereby make them capable of absorbing and retaining water). Said cellulosic fibers, on the other hand, absorb and retain oil, just like synthetic fibers. Finally, their presence makes the nonwovens of the invention more flexible. Large non-cellulosic fibers (the titer of which is greater than 1 dtex) are capable of intervening to impart a scouring and / or abrasive character to the nonwovens of the invention.

According to an advantageous alternative embodiment, the fibrous structure nonwovens of the invention contain cellulosic fibers.

• au moins 20 % en poids de microfibres (et notamment de microfibres de polyester et de polyamide) ;
• au moins 10 % en poids de matière thermoliante, fondue et/ou non fondue (et notamment des fibres de polypropylène) ;
• au moins 10 % en poids de fibres cellulosiques.

According to a preferred variant embodiment, the fibrous structure of the nonwovens of the invention contains:

• at least 20% by weight of microfibers (and in particular of polyester and polyamide microfibers);
• at least 10% by weight of thermobonding material, melted and / or unmelted (and in particular polypropylene fibers);
• at least 10% by weight of cellulosic fibers.

The nonwovens of the invention can be obtained, having a high or low grammage. They generally have a grammage of between 5 and 600 g / m ² . They can in particular be obtained at a grammage less than 30 g / m ² . We have seen that the conventional hydraulic system of the prior art did not make it possible to obtain nonwovens of such a low grammage.

+ les liquides présentant une température d'ébullition ou de décomposition supérieure à 150°C ; et

+ les compositions adhésives présentant un pouvoir collant à température ambiante.

The nonwovens of the invention advantageously have their fibrous (essentially microfibrous) structure impregnated, so that their dusting power is reinforced. They are then, at the same time, wiping greasy traces (by the presence of microfibers within them) and dusting. They are thus advantageously impregnated with at least one non-volatile compound, chosen from:

+ liquids with a boiling or decomposition temperature above 150 ° C; and

+ the adhesive compositions having a tackiness at room temperature.

• ledit composé non volatil est choisi parmi les liquides présentant une température d'ébullition ou de décomposition supérieure à 150°C et intervient avantageusement en une quantité telle que sa masse représente au plus 50 %, avantageusement entre 25 et 30 %, de la masse dite de rétention dudit liquide par ledit support ; ou
• ledit composé non volatil est choisi parmi les compositions adhésives présentant un pouvoir collant à température ambiante et intervient avantageusement en une quantité telle que sa masse représente au plus 20 %, avantageusement au plus 10 %, de la masse dudit support non imprégné.

Their impregnation rate must be controlled so that the impregnation in question does not harm the wiping properties of greases. So :

• said non-volatile compound is chosen from liquids having a boiling or decomposition temperature greater than 150 ° C. and advantageously intervenes in an amount such that its mass represents at most 50%, advantageously between 25 and 30%, of the so-called mass retaining said liquid by said support; or
• said non-volatile compound is chosen from adhesive compositions having a tackiness at room temperature and is advantageously used in an amount such that its mass represents at most 20%, advantageously at most 10%, of the mass of said non-impregnated support.

les liquides ci-après :

• les polyols et notamment l'éthylèneglycol, le propylèneglycol, le 1,3-butylèneglycol, le 1,4-butylèneglycol, l'hexylèneglycol, le diéthylèneglycol, le triéthylèneglycol, le dipropylèneglycol et le glycérol ;
• les éthers de glycols et notamment le diéthylèneglycolmonoéthyléther, le diéthylèneglycolmono(iso)butyléther, le diéthylèneglycolmonohexyléther, l'éthylèneglycolmonohexyléther ;
• le formamide,
• le cinnamaldéhyde,
• l'hexanoate de 2-éthylhexyle,
• les huiles, minérales, végétales et animales, et notamment les dérivés terpéniques,
• leurs mélanges,

ou les compositions adhésives ci-après :

• les latex, de préférence à faible température de transition vitreuse et notamment des latex nitrile, acrylonitrile, acrylique, éthylènevinylalcool (EVA), styrènebutadiène (SBR) ;
• les polybutadiènes, polybutènes et terpolymères d'éthylène, de propylène et de diène (EPDM) :

• les paraffines et les cires ;
• les résines, notamment les résines cellophanes estérifiées, les résines hydrogénées, les résines terpéniques et les résines d'hydrocarbure polydiènes ;
• leurs mélanges.

Said non-volatile compound can in particular be chosen from:

the following liquids:

• polyols and in particular ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, hexylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol and glycerol;
• glycol ethers and in particular diethylene glycolmonoethyl ether, diethylene glycolmono (iso) butyl ether, diethylene glycolmonohexyl ether, ethylene glycolmonohexyl ether;
• formamide,
• cinnamaldehyde,
• 2-ethylhexyl hexanoate,
• oils, mineral, vegetable and animal, and in particular terpene derivatives,
• their mixtures,

or the following adhesive compositions:

• latexes, preferably at a low glass transition temperature and in particular nitrile, acrylonitrile, acrylic, ethylenevinyl alcohol (EVA), styrenebutadiene (SBR) latexes;
• polybutadienes, polybutenes and terpolymers of ethylene, propylene and diene (EPDM):

• paraffins and waxes;
• resins, in particular esterified cellophane resins, hydrogenated resins, terpene resins and polydienic hydrocarbon resins;
• their mixtures.

According to its second object, the present invention relates to complex, whose structure, at least two-component, includes at least one nonwoven of the invention. Said complexes can in particular be obtained by either of the methods specified below. They can also be obtained by any other method of joining at least one nonwoven to at minus another structure and in particular by sewing, gluing ...

• le thermoliage d'un voile ou d'une nappe (constituée de plusieurs voiles) de fibres courtes, dont la structure fibreuse renferme une quantité adéquate de matière thermofusible (susceptible d'intervenir notamment à l'état de poudre et/ou de fibres) et une quantité adéquate de fibres précurseurs de microfibres ; les matériaux constitutifs de ladite matière thermofusible (thermoliante) et desdites fibres précurseurs de microfibres étant différents, celui(ceux) constitutif(s) de ladite matière thermoliante présentant une température de fusion inférieure(s) ;
• le traitement du voile thermolié obtenu ou de la nappe thermoliée obtenue pour générer en son sein une majorité en nombre de microfibres.

According to its third subject, the present invention relates to a process for the preparation of nonwovens, as described above. Said method typically comprises the following two stages of thermobonding and treatment, carried out in the order indicated:

• the thermobonding of a veil or a sheet (made up of several veils) of short fibers, the fibrous structure of which contains an adequate quantity of hot-melt material (likely to occur in particular in the form of powder and / or fibers) and an adequate amount of microfibers precursor fibers; the constituent materials of said thermofusible (thermobonding) material and said microfibers precursor fibers being different, that (those) constituting (s) of said thermobonding material having a lower melting temperature (s);
• the treatment of the thermobonded veil obtained or of the thermobonded sheet obtained to generate within it a majority in number of microfibers.

Said veil (said sheet) is thermally bonded before being treated for generate microfibers within it. Thermobonding involves at least part of the hot-melt material, provided for this purpose. It does not consume microfibers precursor material. Said material is not altered by said thermobonding.

We have seen that the hot melt in question is susceptible to intervene in the form of powder and / or hot-melt fibers.

The thermobonding can in particular be implemented by passing the veil (of the tablecloth) in an oven or on heating drums. He can too be implemented by treating said veil (of said web) in a thermocalandre, smooth or patterned, or in an ultrasonic calender. These various thermobonding techniques are familiar to those skilled in the art.

It is incidentally recalled here that the veil or the tablecloth in question is likely to contain other fibers than said precursor fibers of microfibers and any thermobonding fibers, especially fibers cellulose. It is also not excluded that said veil or said tablecloth contains microfibers. These microfibers, initially present, are added, in the final microfibrous structure of the nonwovens of the invention, microfibers generated from the precursor fibers of microfibers.

The second stage of the process - the stage of treatment, of generation microfibers from precursors - is not per se original. His bet in use is obviously adapted to the nature of the precursor fibers of microfibers involved. It is actually usually a treatment thermal, chemical or mechanical. We prefer the implementation of a mechanical treatment, in particular of the hydraulic needling type, mechanical needling, sanding, "woolening", hammering; we prefer everything particularly the implementation of a mechanical treatment of the type hydraulic needling.

The process of the invention, characterized by the order in which its two main stages are implemented [1) thermobonding, 2) generation microfibers] can be completed. It can in particular include, in addition of said two steps, a complementary tying step (a post-tying step) and / or an impregnation step so as to strengthen the power dusting the nonwoven obtained.

For the preparation of a complex of the invention, one can prepare a nonwoven of the invention, as specified above and then secure it to another structure. You can also proceed as indicated below.

• on thermolie un voile ou une nappe de fibres courtes, tel que caractérisé plus haut (on reprend la première étape du procédé décrit ci-dessus) ;
• on dépose sur ledit voile thermolié ou ladite nappe thermoliée, un voile ou une nappe renfermant des fibres précurseurs de microfibres (fibres identiques ou non à celle du premier voile ou de la première nappe) ;
• on traite l'ensemble pour générer les microfibres ;
• on consolide éventuellement ledit ensemble traité.

According to a first variant:

• a veil or a sheet of short fibers is heat-sealed, as characterized above (the first step of the method described above is repeated);
• a veil or a tablecloth containing precursor fibers of microfibers (fibers which may or may not be identical to that of the first veil or of the first tablecloth) is deposited on said thermo-bonded web or said thermobonded web;
• the whole is processed to generate the microfibers;
• possibly consolidating said treated assembly.

• on thermolie un voile ou une nappe de fibres courtes, tel que caractérisé plus haut (on reprend la première étape du procédé décrit ci-dessus) ;
• on dépose sur ledit voile ou ladite nappe, un voile ou une nappe renfermant des microfibres ;
• on solidarise éventuellement l'ensemble ;
• on traite l'ensemble en vue de générer les microfibres et avantageusement d'assurer, au moins partiellement, la solidarisation dudit ensemble traité ;
• on solidarise éventuellement ledit ensemble traité.

According to a second variant:

• a veil or a sheet of short fibers is heat-sealed, as characterized above (the first step of the method described above is repeated);
• depositing on said veil or said tablecloth, a veil or a tablecloth containing microfibers;
• optionally the whole is joined;
• the assembly is treated in order to generate the microfibers and advantageously to ensure, at least partially, the joining of said treated assembly;
• said treated assembly is optionally joined.

In the context of these two variants, a microfibrous nonwoven of the invention is associated with a veil or a sheet of microfibers, previously constituted or not. Whatever the exact variant of implementation processing work (aimed at generating microfibers from fibers microfibers precursors), advantageously takes advantage of said treatment to link together the microfibers generated. This bond is more or less strong and may or may not be associated with complementary bindings, of the conventional type.

As part of the preparation of the complexes, the steps, prior to thermobonding, then of treatment, as indicated in upstream. The preparation of said complexes can likewise be supplemented by a final complementary binding step and / or a step impregnation.

The present invention is illustrated, without limitation, in reference to the appended figures.

In FIGS. 1A, 1B, 1C, the method of the invention has been illustrated.

In FIGS. 2A and 2B, the method of the prior art has been illustrated.

In Figure 3, we show a magnification (x 300) of an area of thermobonding of a nonwoven of the invention.

• des fibres bicomposantes 1 précurseurs de microfibres 1a, 1b (voir figure 1C) ;
• une fibre thermofusible 2.

FIG. 1A shows an interlacing of fibers at the level of a web, precursor of a nonwoven of the invention. It intervenes, in a characteristic way, in said interlacing:

• bicomponent fibers 1 microfibers precursors 1a, 1b (see FIG. 1C);
• a hot-melt fiber 2.

During the first step of the process of the invention (FIG. 1B), said hot-melt fiber 2 is punctually melted. We have referenced 3 the thermobonding zones. In said zones 3, said fibers 1 and 2 are joined together, said fibers 1 not having been affected. During the second step of the process of the invention (FIG. 1C), the fibers 1 are split into microfibers 1a and 2b. Said microfibers 1a and 1b are grouped in bundles at the limit of the thermobonding zones 3.

According to the method of the prior art, the microfibers 1'a and 1'b were generated, prior to the implementation of thermobonding (Figure 2A). AT after said thermobonding (Figure 2B), they are secured to the fiber 2 ' melt. They are thus, individually, secured to said fiber 2 '.

In photograph 3, the beams of microfibers 10, emerging from the thermobonding zones 13. In said zones of thermobonding 13, the fibers of hot-melt material 20 have been melted (prior to the bursting of the precursor fibers of the microfibers 10). We have referenced in 30 as a post-binding area. Fibers of hot-melt material 20 were punctually melted there after the bursting of said fibers precursors to microfibers 10.

The present invention is finally illustrated and positioned by compared to its closest prior art, in the examples below.

The products in question are characterized and evaluated, respectively, by the parameters and methods specified below.

Area mass or grammage: G (g / m ² )

The surface mass G is the mass of the conditioned sample M divided by its area S according to Edana 40.3-90 or ISO 9073-1.

Bulky or mass volume: B (cm ³ / g)

The mass volume is the ratio between the thickness E (mm) and the grammage G (g / m ² ) such that B (cm ³ / g) = 1000 * E (mm) / G (g / m ² ). The thickness is measured by a probe of 25 cm ² in diameter according to the Edana ERT 30.5-99 or ISO 9073-2 standard but under a pressure of 0.5 kPa.

Number of microfibers

The number of microfibers is evaluated by observation of photos of photograph taken under a scanning electron microscope. Fibers, including mean diameter is less than 10 µm, are considered to be microfibers of less than 1 dtex. The counting consists in drawing one or more several lines on the photograph, counting the number of fibers it (s) cut (s) and count among them those which are microfibers.

Mass fiber content:

Chemical analysis to determine the components of the nonwoven in percentage by mass such as cellulose and polyamide 6 which are soluble in hot hydrochloric acid. Polyamide 6.6 is soluble in hot formic acid. The polyester is soluble in a 50/50 mixture of chloroform and trichloroacetic acid, polypropylene in toluene or xylene at boiling point.

Differential thermal analysis differentiates points polyester and co-polyesters. From their enthalpies of merger, the weight content can be determined.

Water absorption time: T (s)

It is determined according to the Edana 10.3-99 method (or ISO 9073-6) as follows: a 5 g sample of nonwoven is rolled up and placed in a basket with a length of 8 cm and a mass of 3 g. Cart containing the sample is deposited on the surface of the water. The absorption time is the time necessary to note the disappearance of the basket under water.

Oil retention: Rh (%)

It is measured according to the following procedure, derived from the standard DIN 53814: a sample is pre-conditioned and weighed. It is immersed in SPC 68 WOM mineral oil (sold by the company SIP PETRO-CANADA, CAS n ° 8042-47-5) then placed in a centrifuge, at inside a suitable basket 19 cm in diameter. It is then spun at 2,000 gravities at the speed of 4350 rpm for 3 min. Fluid retention is the mass of liquid retained divided by the mass of the sample, expressed percentage.

Oil absorption: Ah (%)

A 10 x 10 cm sample is weighed, i.e. m (g), and then placed on a 2 cm wide mesh grid. The whole is immersed under 2 cm mineral oil SPC 68 WOM from SIP PETRO-Canada CAS n ° 8042-47-5 then drained for 2 minutes. The oil-impregnated sample is weighed, i.e. M (G). The percentage absorption is Ah = 100 x (M-m) / m.

Wiping off traces of oil

5 : Essuie sans laisser de trace ni de reflet d'huile.

4 : Légers reflets d'huile.

3 : Reflets d'huile affectant la brillance.

2 : Légères traces d'huile.

1 : Quelques traces d'huile.

0 : Traces d'huile et mauvais essuyage.

The procedure consists in depositing 10 μl of a mixture of 15% by mass of oil and 85% by mass of acetone on a black polymethacrylate (PMMA) plate whose haze haze measurement with the "Haze Gloss" device "from BYK CHEMIE is less than 10 units. After evaporation of the acetone for 20 seconds, the traces of oil are wiped by passing back and forth through a non-woven sample with a diameter of 30 mm fixed to an object holder exerting a pressure of 3 kPa. Then the Haze value of the residual oil haze is measured. This indicative value correlated with the observation is translated by a classification note:

5: Wipe without leaving any trace or reflection of oil.

4: Slight reflections of oil.

3: Oil reflections affecting the shine.

2: Slight traces of oil.

1: Some traces of oil.

0: Traces of oil and bad wiping.

Rigidity

The bending moment MF expressed in cg.cm of a test piece of 50 x 250 mm is determined according to Edana standard 50.2-80 (Bending length). The rigidity Rig is the logarithmic value of this measurement: Rig = logMF.

Breaking strength: Fr and breaking length: Lr (km)

The breaking length or resistance per kilometer is determined in perpendicular directions of the sample (S1 and S2) corresponding to the forward and cross directions of the sample by measuring the grammage G (g / m ² ) of the test pieces - Edana 40 standard -3-90 or ISO 9073-1: 1989 - then their breaking strengths in both directions, the average of which is Fr (daN / cm) - Edana standard 20.2-89-. The breaking length Lr (km) is calculated according to the formula Lr = 102xFr / G.

Example 1 (thermobonding on a grille then bursting with soda or by water jets)

de 50 % en poids de fibres de polypropylène de 2,2 dtex et 51 mm de long, et

de 50 % en poids de fibres bicomposantes éclatables de 3,3 dtex et 51 mm de long (fibres T-510 en polyester PET/polyamide PA6 50/50 commercialisées par la firme Fibres Innovation Technology Inc.) sont formés sur une carde.

Composed sails:

50% by weight of polypropylene fibers 2.2 dtex and 51 mm long, and

50% by weight of burstable two-component fibers 3.3 dtex and 51 mm long (T-510 fibers in polyester PET / polyamide PA6 50/50 marketed by the company Fibers Innovation Technology Inc.) are formed on a card.

They are thermally bonded at 165 ° C in a heating calender, according to patterns covering an area of 21%, by melting polypropylene.

The thermally bonded nonwovens obtained (TB 23 and TB 51) have a grammage of 23 and 51 g / m ^{2 respectively} . Their properties have been measured and are indicated in the tables below, respectively table 1A, column TB 23 and table 1B, column TB 51.

• par immersion dans la soude à 20 g/l à 90°C pendant 1 h 30 min. On obtient alors, à partir de non-tissés TB 23 et TB 51 respectivement, les non-tissés TB-S et TB-S'. Le dénombrement des microfibres est réalisé par comptage sur photographie. Le taux de microfibres est de plus de 80 %, voire 90 % ; ou
• par aiguilletage hydraulique sous deux rangées de jets d'eau à 120 ou 150 bars sur chaque face. On obtient alors, à partir des non-tissés TB 23 et TB 51, respectivement, les non-tissés TB-J (jets d'eau à 120 bars) et TB-J' (jets d'eau à 150 bars);

The T-510 fibers are broken up into 16 microfibers of approximately 0.21 dtex:

• by immersion in soda at 20 g / l at 90 ° C for 1 h 30 min. TB-S and TB-S 'non-woven fabrics are then obtained from TB 23 and TB 51 nonwovens respectively. The microfibers are counted by counting on photographs. The microfibers rate is more than 80%, even 90%; or
• by hydraulic needling under two rows of water jets at 120 or 150 bars on each side. We then obtain, from the nonwovens TB 23 and TB 51, respectively, the nonwovens TB-J (water jets at 120 bars) and TB-J '(water jets at 150 bars);

The properties of said nonwovens of the invention TB-S, TB-J, TB-S 'and TB-J' were measured and are indicated in the tables below. TB 23 TB-S TB-J weight (g / m ² ) 23 25 25 Thickness (Mm) 0.37 0.46 0.6 baggy (cm ³ / g) 16 18 25 Oil absorption (%) 1480 1920 2200 Oil retention (%) 32 36 45 Wiping off traces of oil (Score / 5) 3 4 4 Break length (S1 km) 0.84 0.76 1.1 (S2 km) 0.25 0.3 0.5 Rigidity - - - TB 51 TB-S ' TB-J ' weight (g / m ² ) 51 47 52 Thickness (Mm) 0.67 0.5 0.7 baggy (cm ³ / g) 13.1 10.6 13.8 Oil absorption (%) 1180 1030 1110 Oil retention (%) 37 52 60 Wiping off traces of oil (Score / 5) 2 5 5 Break length (S1 km) 1.36 1.6 2.6 (S2 km) 0.4 0.5 1.1 Rigidity 1.3 0.33 0.78

The nonwovens of the invention (thermally bonded and then burst) are at least as strong as the nonwovens of the prior art (exploded then thermally bonded).

The process of the invention makes it possible, in a particularly advantageous manner, to burst very light thermally bonded nonwovens (TB-23 of 23 g / m ² ), insofar as they have, before (bursting), been reinforced by thermobonding.

Bursting by hydraulic needling is currently revealed more efficient than chemical bursting: oil retention of nonwovens TB-J and TB-J 'are higher than those of the nonwovens TB-S and TB-S'.

Hydraulic needling which allows fibers to burst of the thermally bonded nonwoven ensures post-binding while retaining the absorption properties of the nonwoven in question: oil absorption (in% mass) is practically equal to the mass or bulk volume of the nonwoven, which shows that bursting (hydraulic needling) is not effect of increasing the bulk of the nonwoven of thermo-bonded carded fibers.

The nonwovens of the invention TB-S 'and TB-J' are both stronger and more flexible (less rigid) than thermobonded nonwoven, TB 51, from from which they are obtained.

Example 2 (thermobonding on a radiator grille then bursting with soda)

• de 50 % en poids de fibres de polypropylène de 2,2 dtex et 51 mm de long, et
• de 50 % en poids de fibres T-510 (voir l'exemple 1) est formé sur une carde. Ce voile est thermolié à 165°C, comme précisé dans l'exemple 1. Les propriétés du non-tissé thermolié obtenu (TB 102) sont mesurées et indiquées dans le tableau ci-après, tableau 2.
A veil of 100 g / m ² composed:
• 50% by weight of polypropylene fibers 2.2 dtex and 51 mm long, and
• 50% by weight of T-510 fibers (see Example 1) is formed on a card. This veil is thermally bonded at 165 ° C., as specified in Example 1. The properties of the thermally bonded nonwoven obtained (TB 102) are measured and indicated in the table below, table 2.

Splitting of T-510 fibers into 16 microfibers of 0.21 dtex approximately is achieved by immersion in soda at 20 g / l at 90 ° C for 1 hour 30 min. A nonwoven of the invention is then obtained, referenced TB-S. The enumeration of microfibers within it is carried out by counting on photography. The microfibers rate is more than 80%, even 90%. The properties of said TB-S nonwoven have been measured and are indicated in the table 2 below.

Counterexample (bursting with soda then thermobonding on a grille)

• Another nonwoven is prepared by the conventional method according to which the starting veil is first burst and then calendered. The bursting and calendering operations are carried out under the same conditions, on a web of the same characteristics. The nonwoven of the prior art obtained is referenced S-TB. Its properties have also been measured and are shown in Table 2 below. TB 102 TB-S S-TB weight (g / m ² ) 102 101 109 Thickness (Mm) 0.92 0.92 1.19 baggy (cm ³ / g) 9.0 9.1 11 Oil retention (%) 33 57 65 Wiping off traces of oil (Score / 5) 2 5 4 Tear resistant (S1 N / cm) 1.7 1.5 1.1 (S2 N / cm) 2.0 2.3 1.7 Break length (S1 km) 1.6 1.6 1.0 (S2 km) 2.1 2.3 1.6 Rigidity 2.18 1.87 2.44

The microfibrous nonwoven of the invention (TB-S) is particularly wiping (oil wiping score of 5). Its high oil retention (from 57% for 33% before bursting) shows the presence of microfibers.

Surprisingly, said TB-S nonwoven is more resistant and less rigid than the non-woven fabric of the prior art S-TB.

The bursting of the fibers within the TB 102 nonwoven does not modify significantly its structure because the bulk (TB-S / TB 102) is not significantly changed.

Example 3 (thermobonding on drum then bursting with soda).

de 15 % en poids de fibres de polypropylène jaune de 3,3 dtex et 51 mm de long, et

de 85 % en poids de fibres bicomposantes éclatables de 2,2 dtex et 51 mm de long (fibres, Eastlon SN 2250 SMS en polyester PET/ polyamide PA6.6 50/50, éclatables en 16 microfibres de 0,14 dtex) sont formés sur une carde.

Veils of compound fibers:

15% by weight of yellow polypropylene fibers 3.3 dtex and 51 mm long, and

of 85% by weight of burstable bicomponent fibers of 2.2 dtex and 51 mm long (fibers, Eastlon SN 2250 SMS in polyester PET / polyamide PA6.6 50/50, burstable in 16 microfibers of 0.14 dtex) on a card.

Said sails are covered with 12 plies and needled 1300 strokes / min. The sheet obtained is then thermobonded on cylinders heated to 180 ° C.

The thermally bonded nonwoven obtained TB 150 has a grammage of 150 g / m ² . It is exploded chemically in a sodium hydroxide solution (as specified in Example 1).

The properties of said thermally bonded nonwoven, TB 150 and of said exploded thermally bonded nonwoven TB-S were measured and are shown in Table 3 below. TB 150 TB-S weight (g / m ² ) 150 153 Thickness (Mm) 1.56 1.26 baggy (cm ³ / g) 10.4 8.25 Water absorption time (S) 3 5 Oil absorption (%) 898 1020 Oil retention (%) 27 91 Wiping off traces of oil (Score / 5) 3 4

The burst essentially modifies the usage properties of the nonwoven : it becomes more wiping (its oil retention increases significantly). The skeleton of the nonwoven, before and after bursting, remains unchanged because the volume parameters (bulk, absorption) do not hardly vary.

Addition of cellulosic fibers to partially replace fibers has been advantageously achieved, particularly in terms of economy, without appreciable modification of the properties of the final product (except the contribution of a certain hydrophilic character).

Example 4 (thermobonding on a grille then bursting with water jets)

de fibres de polypropylène (PP) de 1,7 dtex et de 40 mm de long,

de fibres bicomposantes éclatables de 3,3 dtex et de 50 mm de long (fibres T-510 de FIT, en polyester PET et polyamide PA 6-6 50/50, éclatables en 16 microfibres de 0,21 dtex), et

éventuellement de fibres cellulosiques de viscose de 1,7 dtex et de 40 mm de long (fibres LENZING), sont formés sur des cardes.

Veils of compound fibers:

polypropylene (PP) fibers 1.7 dtex and 40 mm long,

bicomponent fibers that are 3.3 dtex and 50 mm long (T-510 fibers from FIT, polyester PET and polyamide PA 6-6 50/50, burstable into 16 microfibers of 0.21 dtex), and

optionally 1.7 dtex viscose cellulosic fibers 40 mm long (LENZING fibers) are formed on cards.

These sails, of variable composition (see the first part of Table 4 below) are thermally bonded on a laboratory calender at 165 ° C, by partial melting of polypropylene fibers, according to patterns covering 21% from the surface. They are then bound and split, by passing at 10 m / min under water jets, at 100 and then 150 bars.

The properties of the nonwovens obtained were measured and are indicated in the second part of Table 4 below. 4a 4b 4c 4d 4th 4f 4g Percentage of fibers (% by mass) microfiber 40 30 50 30 25 20 35 PP 30 40 50 70 40 30 35 viscose 30 30 0 0 35 50 30 Percentage of microfibers (% number) 90 86 94 87 82 77 88 weight (g / m ² ) 51 58 58 53 38 47 41 baggy (cm ³ / g) 9.7 9.4 9.2 10.2 16.2 13.5 14.4 Oil absorption (%) 1030 940 975 950 1310 1105 1279 Oil retention (%) 75 65 73 63 47 42 53 Wiping off traces of oil (Score / 5) 5 5 5 5 5 5 5 Water absorption time (S) 45 85 > 600 > 900 37 7 80 Break length (S1 km) 2.00 1.65 3.00 2.65 1.40 1.25 1.35 (S2 km) 3.30 2.70 4.40 3.45 1.55 2.25 1.85 Rigidity 0.90 1.10 1.20 1.00 0.50 0.55 0.60

We immediately notice that all these nonwovens wipe the traces oil (since they all contain more than 20% by mass of microfibers, this which represents more than 77% by number). The more the nonwoven contains microfibers, the more it retains the oil.

The presence of viscose fibers improves flexibility (the product is less rigid) and hydrophilicity. Nonwovens, which do not contain fibers viscose, have very high water absorption times: they do not get wet not.

Example 5 (complex)

de 30 % en poids de fibres de polypropylène (PP) de 1,7 dtex et de 40 mm de long,

de 35 % en poids de fibres bicomposantes éclatables de 2,2 dtex et 50 mm de long (fibres Eastlon SN2250SMS de Far Eastern Textile, en polyester PE et polyamide PA 6.6 50/50, éclatables en 16 microfibres de 0,14 dtex),

et de 35 % en poids de fibres cellulosiques de viscose de 1,7 dtex et de 40 mm de long (fibres LENZING),

sont formés sur des cardes. Two veils of compound fibers:

30% by weight of polypropylene (PP) fibers 1.7 dtex and 40 mm long,

35% by weight of burstable bicomponent fibers of 2.2 dtex and 50 mm long (Eastlon SN2250SMS fibers from Far Eastern Textile, in polyester PE and polyamide PA 6.6 50/50, burstable in 16 microfibers of 0.14 dtex),

and 35% by weight of cellulosic viscose fibers of 1.7 dtex and 40 mm long (LENZING fibers),

are trained on cards.

20 % en poids de fibres de polypropylène,

40 % en poids de fibres éclatables et

40 % de viscose.

On each of these two fiber veils, thermally bonded on a calender at 160 ° C under linear pressure of 100 N / mm at 60 m / min, a veil composed of the same fibers is deposited:

20% by weight of polypropylene fibers,

40% by weight of burstable fibers and

40% viscose.

Each set is bound and split by hydraulic needling at 80 then 120 bars on each side.

The first thermo-bonded veil of each complex constitutes a nonwoven thermally bonded support, which facilitates passage under high-pressure water jets pressure (which tend, by their breath, to destroy a veil of carding, not linked).

Non-woven complexes of 47 (C1) and 72 g / m ² (C2) containing on average 38% by mass of microfibers, 24% by mass of polypropylene and 38% by mass of viscose, are thus produced industrially.

The properties of the complexes obtained have been measured and are indicated in Table 5 below. C1 C2 weight (g / m ² ) 47 72 Thickness (Mm) 0.58 0.83 baggy (cm ³ / g) 12.3 11.5 Water absorption time (S) 4 3 Oil retention (%) 48 44 Wiping off traces of oil (Score / 5) 5 5 Rigidity 0.75 1.50 Break length (S1 km) 3.3 3.4 (S2 km) 0.6 0.6 Rigidity 0.8 1.5

Within these complexes (C1 and C2), the presence of viscose ensures rapid water absorption. The high microfibers content (88% in number: polyester and polyamide) guarantees good wiping off of traces of oil.

Claims (15)

Nonwoven of short fibers, the fibrous structure of which contains a majority in number of microfibers (1a, 1b; 10) and zones of molten thermobonding material (3; 13), characterized in that said microfibers (1a, 1b; 10) are made of a material (s) different from that (s) of said molten thermobonding material, having a higher melting temperature (s) and
in that said microfibers (1a, 1b; 10) are located, at the limit of said zones of molten thermobonding material (3; 13), grouped in bundles. Nonwoven according to claim 1, characterized in that at least a fraction of said microfibers (1a, 1b; 10) have an oblong section. Nonwoven according to one of claims 1 or 2, characterized in that said fibrous structure also contains cellulosic fibers. Nonwoven according to any one of claims 1 to 3, characterized in that said fibrous structure also contains non-cellulosic fibers whose titer is greater than 1 dtex. Nonwoven according to any one of Claims 1 to 4, characterized in that the said fibrous structure contains: at least 20% by weight of microfibers, at least 10% by weight of thermobonding material, and at least 10% by weight of cellulosic fibers. Nonwoven according to any one of claims 1 to 5, characterized in that its grammage is between 5 and 600 g / m ² . Nonwoven according to any one of claims 1 to 6, characterized in that its grammage is less than 30 g / m ² . Nonwoven fabric according to any one of Claims 1 to 7, characterized in that its fibrous structure is impregnated so that its dusting power is reinforced. Complex whose structure, at least two-component, includes at least one nonwoven according to any one of the preceding claims. Process for the preparation of a nonwoven according to any one of the preceding claims, characterized in that it comprises: thermobonding a veil or sheet of short fibers, the fibrous structure of which contains an adequate quantity of hot-melt material (2; 20) and an adequate quantity of fibers (1) precursors of microfibers (1a, 1b; 10) ; the materials constituting said hot-melt material and said fibers (1) precursors of microfibers (1a, 1b; 10) being different, that (these) constituting (s) of said hot-melt material having a lower melting temperature (s); the treatment of the thermobonded veil obtained or of the thermobonded sheet obtained, to generate within it a majority in number of microfibers (1a, 1b; 10). Process for the preparation of a complex according to claim 9, characterized in that it comprises: thermobonding a veil or sheet of short fibers, the fibrous structure of which contains an adequate quantity of hot-melt material (2; 20) and an adequate quantity of fibers (1) precursors of microfibers (1a, 1b; 10) ; the materials constituting said hot-melt material and said fibers (1) precursors of microfibers (1a, 1b; 10) being different, that (these) constituting (s) of said hot-melt material having a lower melting temperature (s); depositing on said thermo-bonded web or said thermobonded web, a web or a web containing microfibers precursor fibers; processing the assembly in order to generate microfibers (1a, 1b; 10) from said fibers (1) microfibers precursors (1a, 1b; 10) of said web (s) and / or web (s); a possible consolidation of said treated set. Process for the preparation of a complex according to claim 9, characterized in that it comprises: thermobonding a veil or sheet of short fibers, the fibrous structure of which contains an adequate quantity of hot-melt material (2; 20) and an adequate quantity of fibers (1) precursors of microfibers (1a, 1b; 10) ; the materials constituting said hot-melt material and said fibers (1) precursors of microfibers (1a, 1b; 10) being different, that (these) constituting (s) of said hot-melt material having a lower melting temperature (s); depositing on said veil or said tablecloth, a veil or a tablecloth containing microfibers; the possible joining of the whole; the treatment of the assembly in order to generate microfibers (1a, 1b; 10) from said fibers (1) precursors of microfibers (1a, 1b; 10) of said veil or of said sheet and advantageously to ensure, at least partially, the joining of said treated assembly; the possible joining of said treated assembly. Process according to any one of Claims 10 to 12, characterized in that the said thermobonding is carried out: by passing said veil or said sheet through an oven or over heating drums; or by treating it or this in a smooth or patterned thermo-calender, or in an ultrasonic calender. Process according to any one of Claims 10 to 13, characterized in that the treatment with a view to generating microfibers is a thermal, chemical or mechanical treatment, advantageously a mechanical treatment of the mechanical needling type. Method according to any one of Claims 10 to 14, characterized in that it further comprises an additional bonding step and / or an impregnation of the nonwoven or of the complex obtained.

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