EP0637641B1 - Nonwoven containing an acid lactic polymer derivate, process of making and use thereof - Google Patents

Abstract

The subject of the present invention is a nonwoven based on polymers derived from lactic acid, the process for the production of and the use of such a nonwoven. Nonwoven consisting of filaments of a polymer material, characterised in that all the filaments composing it are made entirely from a polymer or from a polymer mixture derived from lactic acid. <IMAGE>

Description

The present invention relates to the field of nonwovens, in particular at least partially degradable nonwovens, and a for a totally degradable non-woven fabric which can be assimilated by the environment, its manufacturing process and its different uses.

Currently, most nonwovens produced are made based on synthetic polymers, such as propylene, polyethylene, polyesters or polyamides, which are practically non-degradable, in particular non-biodegradable, this especially since they often incorporate stabilizers or other additives that extend their life.

In an attempt to overcome this drawback, it has been proposed to include photosensitive agents in the composition of the filaments nonwovens to trigger a photo-oxidation reaction.

It has also been proposed to produce nonwovens from of thermoplastic polymers derived from starch or else based on polycaprolactones or polyhydroxybutyrates / polyhydroxyvalerates.

However, the nonwoven products obtained do not exhibit any sufficiently satisfactory properties (mechanical strength, physicochemical properties) allowing their implementation and, in in addition, their cost price is too high compared to polymers synthetic.

In addition, the filaments obtained from these materials have always important titles, rarely less than 10 dtex, due to the nature and characteristics of the materials used.

The problem posed with the present invention therefore consists in design a fully biodegradable, compostable and assimilable by the environment, whose filaments have a very low security and with low production costs and substantially mechanical and physicochemical properties equivalent to those of synthetic polymers.

For this purpose the present invention relates to a nonwoven made of filaments of a polymer material, characterized in that all the filaments that compose it are made entirely of a polymer or a mixture of polymers, derived from acid lactic.

The use of polymers derived from lactic acid is known in biodegradable products none of the documents teach constituted nonwovens of filaments produced solely on the basis of lactic acid.

EP-A-0530 987 describes a composition based on starch and lactic acid. All the examples relate to the manufacture of films from these compositions containing lactic acid and starch. The presence of starch is necessary in this invention. There is no indication in this document that lactic acid could be used alone. Likewise, if it is mentioned that filaments can be made from these starch-containing compositions, all the examples only show films. EP-A-0510 999 describes an article which in the appearance of a nonwoven obtained by the formation of a film comprising bubbles based on a composition of lactic acids which when they disappear give way to a structure in network. The product described in this document looks like a nonwoven but is not a nonwoven. In addition to form the bubbles there is a need for a "foaming" product (0.2-10 parts by weight per 100 parts by weight of the composition based on lactic acid.) Which is found in the final product.

The invention also relates to a method for the production of a nonwoven as mentioned above, characterized in what it basically involves is introducing a solid mass of polymers or a mixture of polymers, derived from acid lactic, in a heated extruder, to heat so controlled said mass by working it, in order to obtain a mass homogeneous fondue with a specific viscosity, then transport said melt to a device for die for the formation of filaments, to cool and stretch the filaments thus obtained, to deposit said filaments, without orientation preferential, on a circulating collecting mat, so as to form a non-woven tablecloth or veil and, finally, if necessary, to be joined said filaments of said web or of said web between them at the level at least part of their mutual crossing points and / or at treating said filaments of said sheet by immersion, coating, impregnation or spraying.

la figure 1 représente schématiquement un ensemble extrudeuse-filière pour la mise en oeuvre du procédé conforme à l'invention;

la figure 2 représente un dispositif pour la mise en oeuvre du procédé selon un premier mode de réalisation de l'invention;

la figure 3 représente un dispositif pour la mise en oeuvre du procédé selon un second mode de réalisation de l'invention;

les figures 4 et 5 représentent des courbes montrant, respectivement, l'évolution de la viscosité et de la contrainte de cisaillement en fonction du taux de cisaillement pour deux polymères dérivés de l'acide lactique et utilisés pour la réalisation d'un non-tissé selon l'invention.

The invention will be better understood thanks to the description below, which relates to preferred embodiments, given by way of nonlimiting examples, and explained with reference to the appended schematic drawings, in which:

FIG. 1 schematically represents an extruder-die assembly for implementing the method according to the invention;

FIG. 2 represents a device for implementing the method according to a first embodiment of the invention;

FIG. 3 represents a device for implementing the method according to a second embodiment of the invention;

Figures 4 and 5 show curves showing, respectively, the change in viscosity and shear stress as a function of the shear rate for two polymers derived from lactic acid and used for the production of a nonwoven according to the invention.

In accordance with the latter, all the filaments making up the nonwoven are made entirely (100% of their composition) into a polymer or a mixture of polymers, derived from acid lactic.

According to a first characteristic of the invention, said or said polymers constituting said filaments is (are) derived (s) lactic acid L or lactic acid D or a mixture L and D lactic acids

Said polymer or said mixture of polymers derived from lactic acid advantageously has a molecular mass between 100,000 g / mol and 200,000 g / mol and an index of polydispersity between about 1 and about 3.

In addition, said polymer (s) derived from lactic acid has a glass transition temperature between 45 ° C and 55 ° C and a melting temperature between 165 ° C and 180 ° C.

By way of example, a polymer A, which can be used for the production of a nonwoven according to the invention, can be obtained by reacting in a lactic acid reactor with a catalyst, in the form of stannous octoate mixed with said acid lactic with a rate of 0.11% by weight.

The above polymer, having at the outlet of the reactor a temperature of 209 ° C., has an average molecular mass in weight of 132,000 g / mol, a polydispersity index of 1.9, a glass transition temperature of 51.5 ° C and a temperature of 170.3 ° C melting.

It is also possible to obtain, with the conditions indicated above, a polymer B, derived from acid lactic and can be used to make a nonwoven according to the invention, said polymer B having a mass weight average molecular weight of 158,000 g / mol, an index of polydispersity of 2.1, a glass transition temperature of 49 ° C and a melting temperature of 171.6 ° C.

Certain other characteristics of polymers A and B will appear to those skilled in the art upon seeing Figures 4 and 5 of attached drawings.

The above-mentioned polymers A and B, as well as other polymers derived from lactic acid and capable of serving as a material for basis for the production of nonwovens according to the invention are described in more detail, with regard to obtaining and characteristics, in Finnish patent application No. 923167 filed on July 9, 1992 by Nesté Oy.

In accordance with another characteristic of the invention, the titer of the filaments constituting the nonwoven is between 0.5 and 10 dtex, advantageously between 1 and 5 dtex and preferably between 2.5 and 4.5 dtex, said nonwoven being able, moreover, to increase the mechanical strength and resistance of the veil or of the nonwoven web, have welds of different geometries between filaments on about 5% to 50% of its surface, obtained by hot calendering, preferably on 12%, 24% or 48%.

Furthermore, the filaments constituting the nonwoven according to the invention can also be treated with a view to acquiring particular physico-chemical properties and, for example, present hydrophilic or hydrophobic properties, obtained by impregnation or spraying of surfactants.

The nonwoven according to the invention, as described above, may be advantageously used as a partial component or as the sole constituent of a disposable article, in particular for use unique, and more particularly, following an adapted treatment, in as a hydrophilic component, in particular surface veil, of a disposable hygiene product, for example a diaper or disposable towel or as a component hydrophobic, in particular barrier surface, of a hygiene product disposable, for example a diaper or a period towel single use, by making a nonwoven on the basis of polymer A cited above.

Using the aforementioned polymer B, it will be possible to produce a non-woven fabric which can be used as mulch or haze protection for crops.

The subject of the invention is also, as shown by the Figures 1, 2 and 3 of the accompanying drawings, a method of producing a nonwoven as described above, said method consisting basically to introduce, from a tank, for example, and in granular or powdery form, a solid mass of polymers or a mixture of polymers, derived from lactic acid, in a heated extruder 2, to heat said mass in a controlled manner by working it, in order to obtain a homogeneous melt and having a determined viscosity, to then transport said melt to a 3, 3 'die device for forming of filaments, to cool and stretch the filaments thus obtained, to depositing said filaments, without preferential orientation, on a carpet collector 4 circulating, so as to form a sheet or a veil nonwoven and, finally, if necessary, to fasten said filaments of said sheet between them at at least part of their mutual crossing points and / or to treat said filaments of said sheet by immersion, coating, impregnation or spraying, if necessary via a calendering 5 and / or a treatment station 6 corresponding to through which the fleece or nonwoven web can pass after its training.

Of course, the veil or the nonwoven web is finally put in width and rolled up at a suitable winding station 7.

The extruder 2 used advantageously has a single screw 2 '(see Figures 2 and 3) and its body is surrounded by a plurality of heating collars defining, in said body, heating zones Z1 to Z5 (see Figure 1) which may have increasing temperature values between the supply input of the extruder 2, connected to the reservoir 1, and the outlet of said extruder 2.

According to a first alternative embodiment of the invention, and as shown in Figure 2 of the accompanying drawings, the method consists pushing the molten material from the extruder 2 through a sector 3 composed of several fields, advantageously seven, then to cool the filaments from each field with an air flow 8, then stretching said filaments, by Venturi effect, in nozzles 9 and, finally, to deposit the drawn filaments on a circulating collecting mat 4 without preferential orientation and homogeneously, by through separators 10.

Such a process is more generally known by the designation LURGI in the production of standard nonwovens.

According to the invention, the extruder 2 is preferably maintained at a temperature between 185 ° C and 204 ° C, giving the mass of polymer (s) derived from lactic acid a specific viscosity allowing its manipulation and its transport, without however altering the constituent (s).

According to a second alternative embodiment of the invention, and as shown in Figure 3 of the accompanying drawings, the process can also consist of pushing the molten material from the extruder 2 through a 3 ′ monobloc die, then to cool the filaments obtained by means of an air flow 8 and in stretching them in a slot 11 and, finally, depositing said stretched filaments on said collecting mat 4 or scrolling, without preferential orientation and homogeneously.

In addition, a suction device 11 'is located under the carpet collector 4, creating a suction effect on the latter, intended to press the filaments against it.

Such a process is more generally known by the designation S-Tex for the realization of synthetic nonwovens.

In accordance with a characteristic of the invention, the temperature of the extruder 2 is advantageously understood, for this second embodiment, between 245 ° C and 295 ° C.

According to a third alternative embodiment of the invention, not shown in the accompanying drawings, the process according to the invention may also consist in pushing the molten material through a die with a multitude of holes in line, then to stretch the filaments obtained by means of hot air currents circulating around the die and towards the collecting belt, and, finally, to project said filaments, without preferential orientation and to homogeneously, on said moving collecting mat.

Advantageously, the temperature of the molten material from the extruder 2 is fixed, on the one hand, by a first circuit of heating 12 comprising a first heat transfer fluid, during its transport from the extruder 2 to the die 3, 3 'and, on the other hand, by a second heating circuit 13 comprising a second fluid heat transfer fluid, distinct from said first devices and fluids, level of the die 3, 3 ′, said molten material thus being able to be brought to different temperatures depending on the operations at undergo.

The first heat transfer fluid, for example of the type known under the designation marlo, may give the melt a sufficient temperature for its transfer from the extruder 2 to the die 3, 3 ', while the second heat transfer fluid, for example type known as dyphil, will bring said melt to a higher temperature allowing its spinning.

In order to guarantee a constant quality of the veil or the non-woven sheet, it is preferable to feed the die 3, 3 'at volumetric pump means 14 connected to the outlet of the extruder 2 (Figures 2 and 3) or via a booster pump 15 (figure 1).

In accordance with a characteristic of the invention, the rate of drawing the filaments is advantageously between 100% and 1000%, and the obtained fleece or fleece can be treated by impregnation or by spraying with surfactants.

As a practical example of implementing the process according to the invention, the values of the various essential operating parameters involved in the process for manufacturing the nonwovens according to the invention obtained according to the first variant are indicated below. of embodiment (Table 1) or according to the second alternative embodiment, mentioned above (Table 2), mentioned above. Nature of parameters Place / object concerned Units Values test speed extruder (screw) rpm 15 to 90 volum pumps. rpm 4 to 20 carpet m / min > 6 debit extruder kg / h 25 to 140 temperature zone 1 ° C 190 ± 5 zone 2 ° C 200 ± 5 zone 3 ° C 200 ± 5 zone 4 ° C 200 ± 5 zone 5 ° C 200 ± 5 1 ° heating circuit ° C 210 ± 5 Faculty ° C 195 ± 5 2 ° cir. heated ° C 210 ± 5 pressure extruder bars 14 overpressure bars 84 volum pumps. bars 50 Faculty bars 50 2nd circ. heated bars 3 temperature air speed air suction speed filament rate stretch cooling ° C 15 ± 5 m / s 0.5 to 2.5 mm / CE 75 drawing m / s 10 to 90 % 200 to 900 T ° studs ° C 105 ± 15 Smooth temperature grille ° C 105 ± 15 pressure daN / cm 50 ± 10 speed scrub rate prod. active type impregnation treatment m / min 3 % 12 / silvet Nature of parameters Place / object concerned Units Values speed extruder (screw) rpm 15 to 80 volumet pumps. rpm 4 to 22 carpet m / min 5 to 200 debit Kg / h <140 temperature zone 1 ° C 250 ± 5 zone 2 ° C 290 ± 5 zone 3 ° C 290 ± 5 zone 4 ° C 290 ± 5 zone 5 ° C 290 ± 5 1st circ. heated ° C 200 ± 5 Faculty ° C 240 ± 5 2nd circ. heated ° C 245 ± 5 pressure extruder bars 37 overpressure bars 46 volum pumps. bars 24 Faculty bars 18 aspiration mm of CE 50 lives. filament. drawing m / s 2 <<30 stretch rate % 150 <<900 T ° pins ° C 132 ± 5 Smooth temperature grille ° C 132 ± 5 pressure daN / cm 50 scrub speed treatment m / min 3 production rate active impregnation % 12 type / silvet

The median values of the operating parameters indicated in Table 1 make it possible to obtain nonwovens which can be used for agricultural and hygienic applications and which have the characteristics mentioned in Tables 3 and 4 below, depending on the polymer. , respectively A (table 3) and B (table 4), used for their realization. weight g / m ² 20 25 voltage md N / 5cm 22 26.5 CD N / 5cm 8.5 10 elongation md % 2.5 2.5 CD % 2.5 2.4 air permeability (10 pa) 1 / m ² / s 1500 1300 absorption time s <3 <3 filament title dtex 2.2 2.5 mfr (I2 190 ° C) / / 400 weight g / m ² 50 100 voltage md N / 5cm 60.2 110.5 CD N / 5cm 23.5 40.5 elongation md % 3.1 3.5 CD % 2.9 3.5 air permeability (10 pa) 1 / m ² / s 650 300 absorption time s <3 <3 filaments title dtex 2.2 2.2 mfr (I2 190 ° C) / 400 400

Tables 3 and 4 above indicate, in addition to the conventional characteristics such as weight, tensile strength and elongation (in the machine direction: md and perpendicular to the latter: cd) and the title of the filaments of the nonwoven obtained, certain characteristics particular of said nonwoven such as air permeability (under a depression of 10 Pascal), absorption coefficient (passage time of 5 cm ³ of urine through the fleece or nonwoven web - Edam standard 150-1-90) or even the fluidity index (mfr - Standard ISO 1133 at T = 190 ° C).

The four nonwovens described in Tables 3 and 4 were treated, as shown in Table 1 above, using a surfactant known under the designation SILVET (brand) by the Union Carbide company.

To test the degree and speed of degradability of nonwovens in accordance with the invention, samples showing the characteristics mentioned in table 3, intended more particularly hygiene articles, have been mixed with vegetable food waste and transformed into compost and humus in a composter type reactor.

For eight days, the temperature in the reactor was fixed at 55 ° C, the humidity of the mixture maintained at 50% and the supply of air assured.

After this period, it was found that the nonwoven had considerably degraded and only a few filaments were still visible.

The compost was then removed from the reactor and spread in the open air for 10 weeks. At the end of this second period no more filament was not apparent and the decomposition of the nonwoven was total.

Likewise, nonwovens having the characteristics mentioned in table 4 were used as mulch sails in vegetable and horticultural crops to fight bad crops herbs, replacing phytosanitary products.

• contrôle des mauvaises herbes sans utilisation d'herbicides (examen du nombre d'adventices et de leur taille),
• activation des microorganismes du sol, les non-tissés constituant un excellent substrat de culture,
• limitation de l'évaporation (hygrométrie supérieure à 80% à 22°C).

By testing these nonwovens on young coniferous and lettuce plants, the following properties were found:

• weed control without the use of herbicides (examination of the number of weeds and their size),
• activation of soil microorganisms, nonwovens constituting an excellent growing medium,
• limitation of evaporation (humidity higher than 80% at 22 ° C).

The degradability of the nonwoven is ensured both by watering, rain and the activity of microorganisms.

The samples taken from the sails under test made it possible to find that the mechanical properties fell by 10% in 2 months.

Claims (22)

1. Non-woven fabric made up of filaments formed from a polymeric material, characterised in that all of the filaments which comprise it are formed entirely from a polymer, or from a mixture of polymers, derived from lactic acid.
2. Non-woven fabric according to claim 1, characterised in that said polymer or said polymers making up said filaments is (are) derived from L or D lactic acid.
3. Non-woven fabric according to claim 1, characterised in that said polymer or said polymers making up said filaments are obtained from a mixture of L and D lactic acids.
4. Non-woven fabric according to any of claims 1 to 3, characterised in that said polymer or said mixture of polymers derived from lactic acid has a molecular mass of between 100 000 g/mol and 200 000 g/mol and a polydispersity index of between about 1 and about 3.
5. Non-woven fabric according to any of claims 1 to 4, characterised in that said polymer or said polymers has or have a vitreous transition temperature of between 45°C and 55o C and a fusion temperature of between 165° C and 180° C.
6. Non-woven fabric according to any of claims 1 to 5, characterised in that the titer of the filaments making up said non-woven fabric is between 0.5 and 10 dtex, advantageously between 1 and 5 dtex and preferably between 2.5 and 4,5 dtex.
7. Non-woven fabric according to any of claims 1 to 6, characterised in that it comprises different geometrical seams between filaments over about 5% to 50% of its surface, obtained by hot calendering.
8. Non-woven fabric according to any of claims 1 to 7, characterised in that the filaments have hydrophilic or hydrophobic properties, obtained by impregnation or pulverisation of surfactants.
9. Method of manufacturing a non-woven fabric according to any of claims 1 to 8, characterised in that it essentially comprises introducing a solid mass of polymers or of a mixture of polymers, derived from lactic acid, into a heated extruder (2), heating said mass in a controlled manner while working it, in order to obtain a molten mass which is homogeneous and has a specific viscosity, subsequently transporting said molten mass to a die (3, 3') for forming filaments, cooling and extracting the filaments thus obtained, laying said filaments, without preferential orientation, on a circulatory collecting belt (4), so as to form a non-woven cloth or sheet and, finally, if necessary, interlocking said filaments of said cloth at the level of at least a portion of their mutually intersecting points and/or treating said filaments of said cloth by immersion, coating, impregnation or pulverisation.
10. Method according to claim 9, characterised in that it comprises pushing the molten material produced from the extruder (2) through a die (3) composed of a plurality of sections, advantageously seven, then cooling the filaments produced from each section by a flow of air (8), subsequently extracting said filaments, by Venturi effect, into nozzles (9) and, finally, laying the extracted filaments on a circulatory collecting belt (4), without preferential orientation and in a homogeneous manner, through the intermediary of separators (10).
11. Method according to claim 10, characterised in that it comprises maintaining the extruder (2) at a temperature of between 185° C and 205° C.
12. Method according to claim 9, characterised in that it comprises pushing the molten material produced from the extruder (2) through a one-piece die (3'), then cooling the filaments obtained by means of a flow of air (8) and extracting them in a slot (11) by means of suction generated by a device (14) adapted under the collecting belt (4) at the level of the slot (11) and, finally, laying said extracted filaments on said collecting belt (4) or separating means, without preferential orientation and in a homogeneous manner.
13. Method according to claim 12, characterised in that it comprises maintaining the extruder (2) at a temperature of between 245° C and 295° C.
14. Method according to claim 9, characterised in that it comprises pushing the molten material through a die having a plurality of holes in alignment, then extracting the filaments obtained by means of hot air currents circulatory around the die and in the direction of the collecting belt and, finally, projecting said filaments, without preferential orientation and in a homogeneous manner, onto said moving collecting belt.
15. Method according to any of claims 9 to 14, characterised in that the temperature of the molten material produced from the extruder (2) is fixed, on the one hand, by a first heating circuit (12) comprising a first heat-carrying fluid, during its transportation from the extruder (2) to the die (3, 3') and, on the other hand, by a second heating circuit (13) comprising a second heat-carrying fluid, distinct from said first devices and fluids, at the level of the die (3, 3'), said molten material thus being able to be carried at different temperatures depending on the operations to be carried out.
16. Method according to any of claims 9 to 15, characterised in that it comprises feeding the die (3, 3') by means of volumetric pumps (14) connected to the outlet of the extruder (2) or through the intermediary of a high-pressure pump (15).
17. Method according to any of claims 9 to 16, characterised in that the rate of extraction of the filaments is between 100% and 1000%.
18. Method according to any of claims 9 to 17, characterised in that the sheet of nonwoven fabric obtained is treated by impregnation or by pulverisation with surfactants.
19. Use of a non-woven fabric according to any of claims 1 to 8 as a partial component of or as a single constituent of a disposable article, more especially for single usage.
20. Use of a non-woven fabric according to any of claims 1 to 8 as a hydrophilic component, more especially a surface sheet, of a disposable hygienic product, for example a nappy or sanitary towel for single usage.
21. Use of a non-woven fabric according to any of claims 1 to 8 as a hydrophobic component, more especially a barrier surface, of a disposable hygienic product, for example a nappy or sanitary towel for single usage.
22. Use of a non-woven fabric according to any of claims 1 to 8 as a matting or protection sheet for cultures.

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