EP3088585B1 - Method and device for manufacturing a spunbonding fabric made of filaments and spun fabric - Google Patents

Description

The invention relates to a method for producing a spunbonded nonwoven web or spunbonded nonwoven web from filaments, in particular filaments made of thermoplastic material, wherein the filaments are spun by means of at least one spinning device, then cooled and then passed through a stretching device with primary air. The invention further relates to a corresponding apparatus for producing a spunbonded nonwoven fabric and a spunbonded nonwoven fabric of filaments or endless filaments.

Methods and apparatus of the type described above are known in practice in various embodiments. It is also known to direct the filaments stretched by means of the stretching device through at least one diffuser as a depositing device and then to deposit it on a filing screen belt. The spunbonded nonwoven web produced in this way is then preconsolidated or solidified by means of a calender in many processes.

The spunbond webs produced can be characterized on the one hand by their strength or tensile strength in the machine direction (MD) and on the other hand by their strength or tensile strength transverse to the machine direction (CD). The machine direction (MD) corresponds to the conveying direction of the deposited spunbonded nonwoven web. The stated strengths are also referred to as longitudinal strengths and transverse strengths. In the known methods spunbonded nonwovens are generally produced in which the ratio of the longitudinal strength to the transverse strength is in the range of 1.5 to 2. This means that the machine direction (MD) longitudinal strength is higher than the cross machine direction (CD) strength. at Spunbonded fabrics with higher basis weights can also be achieved lower values of the aforementioned ratio. It would be desirable to improve the isotropy of spunbonded nonwovens in terms of their longitudinal and transverse strengths.

Accordingly, the technical problem underlying the invention is to specify a method of the type mentioned at the outset, with which it is possible to achieve isotropic or approximately isotropic strengths of the spunbonded nonwoven in the longitudinal direction and transverse direction. The invention is further based on the technical problem of specifying a suitable device. In addition, the invention deals with the technical problem of specifying a spunbonded fabric with isotropic strengths with respect to the longitudinal direction and transverse direction. Furthermore, in addition to the isotropic or approximate isotropic strength properties, a homogeneous deposition of the filaments should also be ensured.

To solve this technical problem, the invention teaches a method for producing a spunbonded filaments, in particular from filaments of thermoplastic material, wherein the filaments are spun by means of at least one spinning device, then cooled and then passed with primary air through a drawing device, wherein the primary air emerges from the drawing device with a primary air volume flow V _P , wherein the filaments are passed to the drawing device through a diffuser, wherein between drafting device and diffuser secondary air with a secondary air flow V _{S is introduced} into the diffuser, the filaments on a subsequent to the diffuser Storage device are stored, and wherein the method is performed with the proviso that the ratio of the primary air flow rate V _P to the secondary air flow rate V _S and the secondary air ratio V _P / V _S more than 4.5, preferably more than 5, and more preferably more than 5.5. According to particularly preferred embodiments of the invention, the secondary air ratio V _P / V _{S may} also be more than 6 or more than 6.5.

It is within the scope of the invention that the filaments are continuous filaments produced by a spunbond process. For cooling the spun filaments a cooling device with at least one cooling chamber is expediently provided, in which the filaments are exposed to cooling air. It is within the scope of the invention that the stretching device and the diffuser extend transversely to the machine direction over the production width or over the width of the spunbonded nonwoven web to be produced. In the context of the invention, primary air means the process air which is passed through the drawing device or through the drawing channel of the drawing device and which exits the drawing device or from the drawing shaft into the diffuser. Subsequently, the primary air is also referred to as process air. The volume flow V _{S of} the secondary air entering the diffuser between the drafting device and the diffuser is, according to the recommended embodiment of the invention, less than 20% of the volume flow V _P of the primary air flow or process air flow emerging from the drafting device.

It is within the scope of the invention that the filaments are passed for cooling by a cooling device with at least one cooling chamber and then introduced into the drawing device, and that the unit of cooling device and drawing device is designed as a closed system in which except the supply of cooling air or process air no further air supply is provided. It is further within the scope of the invention that the drawing shaft of the drawing device connects to the cooling device such that between cooling device and drawing device no more air can enter the system. The above-described closed system is very particularly preferred within the scope of the invention and has proven itself here. In principle, however, the method according to the invention could also be used for an open system.

A recommended embodiment of the invention is characterized in that a first air inlet gap and a second air inlet gap downstream of the first air inlet gap in the machine direction are provided between the drafting device or the drafting shaft and the diffuser. It is possible that the height or the vertical height of the two air inlet gaps differ from one another, so that an air inlet gap has a different distance to the depositing device than the other air inlet gap. Preferably, the volume flow V _{S1 of} the secondary air introduced through the first air inlet gap is different from the volume flow V _{S2 of} the secondary air introduced by the second air inlet gap. In this case, according to a preferred embodiment, the two air inlet gaps extend transversely to the machine direction over the production width or over the width of the spunbonded nonwoven web to be produced. The above-mentioned asymmetry of the volume flows V _S1 and V _S2 has proven itself in the context of the method according to the invention. The volume flows V _S1 and V _{S2 of} the secondary air are combined to form the total secondary air volume flow Vs (V _S = V _S1 + V _S2 ). The opening width of the air inlet gap or the air inlet gap can be constant over the width of the device or over the width of the spunbonded nonwoven web to be produced. According to a preferred embodiment variant, the opening width of the air inlet gap or the air inlet gap and thus also the local secondary air volume flow can vary across the width of the device. It is particularly within the scope of the invention that the opening width in the edge regions of the opening width in Deviates mean range and that is expediently the opening width of the air inlet gap or the air inlet column in the edge region lower than in the central region. For this reason, the term "opening width" is used below to mean the average opening mode, and when the secondary air volume flows are specified, the average secondary air volume flow is preferably meant. Expediently, the opening width of the first air inlet gap and of the second air inlet gap is in each case 0.8 to 20 mm, preferably 1 to 15 mm, preferably 1 to 10 mm. According to a recommended embodiment, this opening width is 0.8 to 4 mm, preferably 1 to 3 mm.

It is therefore within the scope of the invention that a smaller amount of secondary air flows through the one air inlet gap between drawing device and diffuser than through the other air inlet gap between drawing device and diffuser. Preferably, a secondary air volume flow is at least 10%, preferably at least 20% and very preferably at least 25% smaller than the other secondary air volume flow. A secondary air volume flow is expediently less than the other secondary air volume flow by at most 90% and recommended by at most 80%. - It is within the scope of the invention that the opening width of the two arranged between drafting and diffuser air inlet column is independently adjustable. Conveniently, the opening width of an air inlet gap is set smaller than the opening width of the other air inlet gap.

The embodiment with two air inlet gaps and thus two secondary air volume flows allows for spunbonds for normal hygiene applications the possibility of achieving relatively light basis weights and a uniform web structure at a ratio of the tensile strength of the spunbonded machine direction (MD) to the tensile strength of the spunbonded nonwoven Transverse direction (CD) above 1.5. This embodiment is thus very variable. - An embodiment with only one air inlet gap is suitable for the production of spunbonded nonwovens with basis weights above about 40g / m ² and with ratios of said tensile strengths by 1. Here are also secondary air numbers V _P / V _S above 4.5 relevant.

A particularly recommended embodiment of the invention is characterized in that one or at least one arranged between drafting and diffuser air inlet gap is preceded by an air chamber, said air chamber has at least one air inlet - expediently 1 to 6 air inlet openings and wherein the secondary air supply through the air inlet gap on the at least one air inlet opening or via the plurality of air inlet openings of the air chamber is adjusted or metered. Expediently, at least one air chamber, which has the at least one air inlet opening - expediently 1 to 6 air inlet openings - is connected upstream of the two air inlet gaps arranged between the drafting device and the diffuser. It is recommended that the secondary air supply through the air inlet column is then set or controlled via the air inlet openings of the air chambers. - The realization of this embodiment is based on the finding that the air inlet gaps between drawing device and diffuser can be easily clogged by impurities. Then the secondary air supply over the production width is no longer constant and this has a detrimental effect on the deposition process of the filaments. The pre-connection of the air chambers allows a precise and reproducible supply of secondary air. In particular, filters for cleaning the supplied air can be easily mounted in the air chambers or at the air inlet openings. These filters can easily be replaced or cleaned. In contrast, the cleaning of the Both air inlet gaps for the secondary air problematic and this also applies to the attachment of filters over the entire plant width. The few air inlet openings of the air chambers allow a very accurate adjustment of the supplied secondary air. It should be noted that narrow or small air inlet gaps between drawing device and diffuser can not be set very accurately compared to larger air inlet columns. With the help of the upstream air chambers relatively large easily adjustable air inlet column can be realized and the secondary air supply can instead be dosed adjusted at the air inlet openings of the air chambers. This adjustment or metering of the inflowing secondary air can be realized functionally reliable, for example with the help of flaps and similar control elements. According to one embodiment of the method according to the invention, a negative pressure can be maintained in the air chambers, so that in particular an increasing pressure consumption of an upstream filter can be compensated. Advantageously, the negative pressure formed in the air chambers is measured and preferably regulated or kept constant with the aid of the upstream flaps or similar control elements. In this way, the contamination of filters and the concomitant reduction of the volume flows is avoided. The air chambers upstream of the air inlet gaps have proven particularly useful in the context of the invention.

A recommended embodiment of the method according to the invention is characterized in that the diffuser is followed only by a diffuser with diffuser walls diverging towards the depositing device. Diverging here means in particular that the width of the entrance slit of the diffuser in the machine direction is smaller than the width of the exit slit of the diffuser in the machine direction. It is within the scope of the invention that the diffuser or that its diffuser walls over the entire Plant width or production width extends / extend. According to a preferred embodiment of the invention, the opening angle α of the diffuser is in the range between 2 ° and 4.5 °, expediently in the range of 2.5 ° to 4 °. In principle, however, also opening angle α greater than 4 ° or greater than 4.5 ° can be adjusted. The opening angle α of the diffuser is measured between the median plane M with the height of the lower ends of the drawing shaft of the drawing device and the lower ends of the diffuser walls of the diffuser. This will be explained in more detail below.

Preferably, the width B of the outlet gap of the diffuser in the machine direction is at least 250%, preferably at least 300% of the width b of the exit gap of the drawing shaft of the drawing device. It is recommended that the width B is 250% to 450%, preferably 300% to 400% of the width b. The width B or b is measured as the distance of the lower ends of the Verstreckschachwände or as a distance between the lower ends of the diffuser walls. When bent or rounded lower ends of the diffuser walls thus the distance of the respective deepest points of the diffuser walls is meant. If the angle of the beveled diffuser walls is about 90 °, then in particular the distance of the canted lines is meant. It is within the scope of the invention that the surface of the outlet gap of the diffuser is at least 250%, preferably at least 300%, of the area of the outlet gap of the drawing shaft of the drawing device. In this case, it is assumed that the lower ends of the drawing shaft or the diffuser walls have the same distance to the depositing device over the width of the plant or production width, and the surface thus results from the distance of the lower ends of the drawing shaft or from the distance between the lower ends of the diffuser walls and the length of the drawing shaft or the diffuser calculated.

A preferred embodiment of the method according to the invention is characterized in that the diverging diffuser walls or diffuser inner walls of the diffuser are adjustable asymmetrically with respect to a center plane M extending through the device. Preferably, the diffuser wall or diffuser inner wall positioned closer to the center plane M is assigned to the side of the diffuser, at which no or the lower secondary air volume flow enters the diffuser. In the case of two air inlet gaps, the diffuser wall or diffuser inner wall positioned closer to the center plane M is expediently assigned to the air inlet gap whose opening width is smaller or smaller than the opening width of the other air inlet gap. Means that a diffuser wall is associated with an air inlet gap means within the scope of the invention that seen in the machine direction first diffuser wall is associated with the first seen in the machine direction air inlet gap and the in Seen machine direction second diffuser wall is associated with the second air inlet gap seen in the machine direction. If, for example, a smaller secondary air volume flow flows through the second air inlet gap than through the first air inlet gap, the second diffuser wall is positioned closer to the center plane M than the first diffuser wall. If, according to one embodiment of the invention, only one air inlet gap is present, the diffuser wall farther from the center plane M is assigned to this one air inlet gap. - Expediently, the difference of the distance of the diffuser walls or diffuser inner walls to the center plane M on at least one horizontal height position is at least 5% or at least 5 mm.

Preferably, the filing device for the filaments or for the spunbonded nonwoven web is designed to be permeable to air and, according to the recommended embodiment, an air-permeable filament filter belt is used as the filing device. It is within the scope of the invention that suction air is sucked through the depositing device from the underside of the depositing device facing away from the filaments. This suction serves on the one hand to remove the process air and on the other hand also to fix the unconsolidated spunbonded web on the filing device or on the Ablagesiebband. For this purpose, at least one suction fan is expediently provided. In the method according to the invention, a mixture of process air or primary air and secondary air as well as ambient air is generally sucked through the depositing device or through the filing belt. A very preferred embodiment of the method according to the invention is characterized in that the suction air velocity v _L or the average suction air velocity v _{L of} the suction air below the outlet gap of the diffuser and directly above the storage device or directly above the Ablagesiebbandes 5 to 25 m / sec, preferably 5 to 20 m / sec and very preferably 10 to 20 m / sec. In order to determine the mean suction air velocity v _L , the suction air volume flow through the surface below the outlet gap B is considered.

It is within the scope of the invention that the spunbonded web is preconsolidated or solidified from the deposited filaments after their deposition. The pre-consolidation or solidification is carried out as recommended by means of at least one calender. Preferably, the calender has two calender rolls, of which at least one calender roll is heated. It is recommended that the calender has an embossing surface between 5 and 22%, preferably between 15 and 22%. Conveniently, the figure density of Calender or at least one calender roll of the calender 35 to 60 Fig./cm ² .

To solve the technical problem, the invention further teaches an apparatus for producing a spunbonded filaments, in particular of filaments of thermoplastic material, - with a spinning device for spinning the filaments, with a cooling device for cooling the spun filaments and with a subsequent to the cooling device stretching device with drawing shaft for stretching the filaments, wherein the filaments emerge from the drawing shaft of the drawing device together with a primary air volume flow V _P , wherein at least one diffuser is connected downstream of the drawing device or the stretching shaft and at least one air inlet gap for secondary air is arranged between the drawing shaft and the diffuser , wherein the primary air volume flow V _{P is} greater or significantly greater than the inflowing through the at least one air inlet gap secondary air flow Vs and wherein the width B of the off Tread of the diffuser at least 250%, preferably at least 300% of the width b of the exit slot of the drawing shaft is. That the primary air volume flow V _{P is} significantly greater than the secondary air volume flow Vs means within the scope of the invention in particular that the ratio or the secondary air number V _P / V _S more than 4.5, preferably more than 5 and very preferably more than 5.5 is.

It is recommended that the width B of the outlet gap of the diffuser is 50 to 170 mm, preferably 60 to 150 mm and expediently 70 to 140 mm. Particularly preferably, the width B of the outlet gap of the diffuser is 80 to 100 mm. The width B of the exit slit has already been defined above. It is the distance between the lower ends of the diffuser walls of the diffuser. - According to particularly proven embodiment According to the invention, the distance a or the vertical distance a between the diffuser and the depositing device amounts to 30 to 300 mm, preferably 50 to 250 mm and particularly preferably 70 to 200 mm. The distance a is measured from the lowest end of the diffuser or the diffuser walls to the surface of the storage device or the preferably used Ablagesiebbandes.

The subject of the invention is also a spunbonded fabric which has been produced in particular by the method described above and / or with the device described above. This is expediently a calendered spunbonded nonwoven. In this spunbonded or calendered spunbonded nonwoven according to the invention, it is recommended that the ratio of the tensile strength of the spunbonded fabric in the machine direction (MD) to the tensile strength of the spunbonded nonwoven in the transverse direction (CD) is less than 1.3, preferably less than 1.2, and more preferably this ratio is between 0 , 8 and 1,2. The tensile strengths are determined in particular by measuring the respective maximum tensile force. The measurement of the maximum tensile force is expediently carried out according to the standard DIN EN 29073-3 in N / 5 cm. The spun-bonded nonwovens according to the invention have in particular a coefficient of variation of the strength of less than 15%, preferably of less than 10%. The coefficient of variation results from the quotient of the standard deviation and the mean, separately determined for the longitudinal and transverse directions, and is the average of these two values. In each case, six samples are preferably measured per direction. The spunbonded nonwovens produced according to the invention are distinguished by a particularly homogeneous support. In particular, the coefficient of variation of the basis weight is less than 15%, preferably less than 10%. The coefficient of variation expediently refers to a Measuring surface with a diameter of 25 mm, when using 25 equidistant test surfaces.

In the context of the invention, both monocomponent filaments and bicomponent filaments or multi-component filaments can be used as filaments for the spunbonded nonwoven fabric produced according to the invention. In the case of the bicomponent filaments or multi-component filaments, it is above all recommended to have a core-shell configuration. According to a particularly preferred embodiment of the invention, the filaments spun for the spunbonded nonwoven consist of at least one polyolefin, preferably polypropylene and / or polyethylene. In principle, however, other raw materials such as polyamide or polyethylene terephthalate (PET) and the like can be used. Incidentally, the deposited spunbonded nonwoven web can also be preconsolidated or solidified in a different manner, in addition to a calender. In principle, the spunbonded fabric could also be further changed in subsequent processes, such as being transversely stretched in a tenter, for example. However, the abovementioned properties-in particular the measured strengths or tensile strengths-and the resulting MD / CD ratio relate to the state of the spunbonded fabric after the first preconsolidation or solidification, ie if the filament orientation has not yet been subsequently targeted-for example by stretching or transverse stretching - was influenced.

The invention is based on the finding that spun nonwovens having a relatively high strength or tensile strength transversely to the machine direction (CD direction) can be produced with the method according to the invention or with the device according to the invention. In particular, according to the invention, the strengths can be adjusted so that no great differences between the strengths or tensile strengths in the machine direction on the one hand and across on the other hand are detectable to the machine direction. Consequently, a tensile strength ratio MD / CD of 0.8 to 1.2, and preferably 0.9 to 1.1 can be easily adjusted. This setting is simple, reliable and reproducible possible. Furthermore, with the method according to the invention and with the device according to the invention, it is also possible to achieve a very homogeneous and uniform deposition of the filaments. This means that optimum coverage or opacity of the spunbonded fabric is achieved. Defects or holes in the filament tray can be easily avoided. In summary, it should be noted that with the method according to the invention and with the device according to the invention an optimal compromise between a balanced strength ratio MD / CD on the one hand and a very homogenous deposit on the other hand can be achieved in a simple and reliable way. For spunbonded nonwovens with basis weights below 40 g / m ² - which are preferably used for hygiene applications - especially good coverage or opacity of the spunbonded fabric is essential. The realization of these advantageous properties was at the expense of transverse strengths (CD strengths) in the previously known spunbonded nonwovens. With the method according to the invention or with the device according to the invention, both good coverage or opacity and sufficient transverse strength can be achieved for these light spunbonded nonwovens. For spunbonded fabrics with basis weights above 40 g / m ² , high transverse strengths are essential. The realization of these high transverse strengths was at the expense of the homogeneity of the filament deposit in the previously known methods. Especially with larger opening angles of the diffuser unacceptable inhomogeneous Filamentablagen emerged. With the measures according to the invention, both high transverse strength (CD strength) and acceptable homogeneous filament deposition can be achieved for these heavier spunbonded nonwovens. It should also be emphasized that the measures according to the invention relatively simple and inexpensive means can be realized. The invention is explained in more detail below with reference to an exemplary embodiment. Spunbonded nonwovens according to Examples 1 to 4 were produced, all spunbonded nonwoven filaments consisting of homo-polypropylene from Borealis (HF420FB) having a melt flow index of 19 g / min. All spunbonded nonwovens were calendered or calendered with a calender consisting of two calender rolls with an embossing surface of 20% and a roll temperature of both rolls of 155 ° C. The basis weight of all spunbonded nonwovens was 65 g / m ² and the filament fineness was 1.7 denier. Example 1 relates to the production of a spunbonded fabric according to the prior art with a secondary air number V _P / V _S of significantly less than 4.5, namely 3.0. In contrast, Examples 2 to 4 relate to spunbonded nonwovens which have been produced by the process according to the invention with a secondary air number V _P / V _S of greater than 4.5. In the table, in addition to the secondary air number V _P / V _S, the total secondary air volume flow Vs is given in m ³ / h and the volume flow V _{S1 of} the secondary air (in m ³ / h) introduced through the first air inlet gap and the volume flow V introduced through the second air inlet gap _{S2 of} the secondary air (in m ³ / h). In addition, the opening angle α of the diffuser and the average suction air velocity v _L in m / sec of the suction air below the outlet gap of the diffuser and above the Ablagesiebbandes listed. Further, the ratio of the tensile strength of the spunbonded fabric in the machine direction (MD) to the transverse direction tensile strength of the spunbonded nonwoven (CD) is indicated as MD / CD, and the coefficient of variation CV _{T of} the tensile strength and the coefficient of variation cv _{FL of} the basis weight. It can be seen here that Example 3 according to the invention has the best results. Here, an asymmetrical secondary air volume feed was used and with a secondary air number V _P / V _S greater than 4.5. The opening angle α of the diffuser here is 3 ° and is thus within the very preferred range of 2.5 ° to 4 °. The volume flows refer to Widths of the air inlet column of 1.25 m. In Example 4, only one air inlet gap is provided or active. This gives a less homogeneous spunbonded filing. Nonetheless, this spunbonded fabric is suitable for a wide variety of applications. A device with only one air inlet gap offers the advantage of a simpler construction and is less complex with regard to the settings and the care required. example V _S V _S1 V _S2 V _P / V _S α v _L MD / CD CV _T CV _FL 1 2400 1200 1200 3.0 3 ° 15-30 1.26 4.75 8.9 2 1200 600 600 6.2 7.5 ° 10-20 0.84 29.97 16.8 3 900 300 600 7.9 3 ° 10-20 1,03 5.94 9.8 4 600 0 600 11.9 3 ° 10-20 1,03 11.58 13.6

Fig. 1

einen Vertikalschnitt durch eine erfindungsgemäße Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens bei Einsatz von zwei Lufteintrittspalten,

Fig. 2

einen vergrößerten Ausschnitt A aus der Fig. 1,

Fig. 3a, b

einen Diffusor nach dem Stand der Technik und einen Diffusor der erfindungsgemäßen Vorrichtung und

Fig. 4

einen vergrößerten Ausschnitt B aus der Fig. 1.

The invention will be explained in more detail below with reference to a drawing, which shows only one exemplary embodiment.

Fig. 1

4 a vertical section through an apparatus according to the invention for carrying out the method according to the invention when using two air inlet gaps,

Fig. 2

an enlarged detail A from the Fig. 1 .

Fig. 3a, b

a diffuser according to the prior art and a diffuser of the device according to the invention and

Fig. 4

an enlarged detail B from the Fig. 1 ,

In the figures, an inventive device for carrying out the method according to the invention for the production of a spunbonded fabric 1 of filaments 2, in particular of filaments 2 made of thermoplastic material is shown. In the context of the method according to the invention, the filaments 2 are first by means of a in Fig. 1 discernible spinning device 3 spun. The filaments are then passed through a cooling device 4 for cooling. To the cooling device 4 preferably and in the embodiment, an intermediate channel 5 connects, which connects the cooling device 4 with a drawing device 6 and with a drawing shaft 7 of the drawing device 6. The drawing device 6 is followed by a diffuser 8 in the flow direction of the filaments. According to a preferred embodiment and in the embodiment, the unit of the cooling device 4 and the stretching device 6 or the unit of the cooling device 4, the intermediate channel 5 and the drawing device 6 is formed as a closed system. Apart from the supply of cooling air in the cooling device 4 no further air supply takes place in this unit. The guided through the drawing device or through the drawing shaft 7 air is referred to here as the primary air or process air.

It is within the scope of the invention that between the drawing device 6 and between the drawing shaft 7 and the diffuser 8 two opposite with respect to the machine direction (MD) opposite air inlet gaps 9, 10 are arranged. Through these air inlet gaps 9, 10, a secondary air volume flow Vs is introduced into the diffuser 8. In this case flows through the first air inlet gap 9 a first secondary air volume flow V _S1 and by the first air inlet gap 9 downstream in the machine direction second air inlet gap 10 flows a second secondary air flow V _S2 . It is within the scope of the invention that the drafting shaft 7, the air inlet gaps 9, 10 and the diffuser 8 extend across the plant width or production width transversely to the machine direction. According to the invention, the method is performed such that the primary air volume flow V _{P of} the primary air emerging from the drawing shaft 7 is significantly greater than the total secondary air volume flow Vs (V _S = V _S1 + V _S2 ). According to the invention, this ratio of primary air volume flow V _P to secondary air volume flow V _S or the secondary air number V _P / V _{S is} more than 4.5, preferably more than 5 and very preferably more than 5.5. According to a particularly recommended embodiment of the invention, the secondary air number is more than 6 and according to a variant more than 6.5.

It is furthermore within the scope of the invention that the secondary air volume flow V _S1 introduced through the first air inlet gap 9 is different from the secondary air volume flow V _S2 introduced through the second air inlet gap 10. The asymmetry of the secondary air volume flows V _S1 and V _S2 has proven particularly useful in the context of the invention. The opening width or gap width of the air inlet gaps 9, 10 is expediently between 5 and 15 mm. A particularly recommended embodiment of the invention is characterized in that a secondary air volume flow by at least 10%, preferably by at least 20% and very preferably by at least 25% and suitably by at most 90%, proven to be at most 80% smaller than the other secondary air volume flow. It is thus advisable that flows through an air inlet gap 9, 10, a smaller amount of secondary air than through the other air inlet gap 9, 10. Conveniently, the opening width of the two is between Drawing shaft 7 and diffuser 8 arranged air inlet column 9, 10 independently adjustable and according to a recommended embodiment of the invention, the opening width of an air inlet gap 9, 10 set smaller than the opening width of the other air inlet gap 9, 10th

An embodiment of the invention, not shown in the figures, is characterized in that the air inlet chamber 9, 10 is arranged upstream of the drafting shaft 7 and the diffuser 8, wherein the air chamber expediently has a number of air inlet openings, for example six air inlet openings distributed over the system width. The secondary air supply through the air inlet gaps 9, 10 can be adjusted dosed via these air inlet openings. The secondary air volume flows V _S1 and V _S2 can then be controlled and / or regulated at these air inlet openings, for example by means of flaps, sliders, blowers and the like. According to an advantageous embodiment, in each case at least one filter for filtering the inflowing secondary air can be present in the air chambers or at the air inlet openings. In this way effectively clogging of the air inlet gaps 9, 10 can be avoided.

According to a particularly recommended embodiment and in the exemplary embodiment, only one diffuser 8 with two diffuser walls 12, 13 diverging to a depositing device 11 for the filaments 2 is arranged following the stretching device 6. It is recommended that the opening angle α of the diffuser 8 is greater than 2 ° and expediently greater than 2.5 °. According to a particularly preferred embodiment, the opening angle α of the diffuser 8 is in the range between 2.5 ° and 4 °. The measurement of the opening angle α is in the Fig. 2 illustrated. In this case, the opening angle α - as in Fig. 2 illustrated - through the exit slit 14 of the drawing shaft 7 and the exit slit 15 of the diffuser 8 measured. By the way, the width B of the exit slit 15 of the diffuser 8 is preferably at least 250%, preferably at least 300%, of the width b of the exit slit 14 of the drawing shaft 7.

The Fig. 3a and 3b show a diffuser 8 as a storage system for the filaments deposited to the spunbonded 1 2. It is in the Fig. 3a a filing of the filaments 2 shown in the prior art. Here you can see homogeneous filament density over the cross section of the diffuser 8. In contrast, in the Fig. 3b a filing of the filaments 2 shown by the method according to the invention. In this case, the secondary air volume flows V _S1 and V _S2 entering through the first air inlet gap 9 and through the second air inlet gap 10 are different from each other (V _S1 ≠ V _S2 ). It is according to the embodiment Fig. 3b the secondary air volume _flow V _S2 greater than the secondary air volume _flow V _S1 . As a result, the filaments 2 are deposited in the left area of the diffuser with high filament density and homogeneously. From this homogeneous and narrow deposit results in a good opacity of the spunbonded fabric. On the other hand, a small filament density can be observed in the right-hand region of the diffuser 8, and the filaments 2 are deposited here far or with large radii. This leads to advantageous high transverse strength. In that regard, a good compromise between high transverse strength on the one hand and homogeneous filament deposition on the other hand can be achieved by the procedure according to the invention.

According to the recommended embodiment and in the embodiment (see in particular Fig. 4 ), the diverging diffuser walls 12, 13 of the diffuser 8 are adjustable asymmetrically with respect to a center plane M passing through the device. The center plane M is preferred and in the embodiment through the center of the drawing shaft 7 with respect to the Machine direction. Appropriately, and in the embodiment ( Fig. 4 ), the diffuser wall 12, which is arranged below the first air inlet gap 9 with the smaller inflowing secondary air volume flow V _S1 , is positioned closer to the center plane M. In the embodiment, the opening width of the first air inlet gap 9 is set smaller than the opening width of the second air inlet gap 10, so that the closer to the center plane M positioned diffuser wall 12 is disposed below the narrower air inlet gap 9. It is within the scope of the invention that the difference of the distance of the diffuser walls 12, 13 from the center plane M at least at a height position is at least 5% or at least 5 mm.

After a very preferred embodiment, the depositing device 11 of the device according to the invention is designed as an air-permeable Ablagesiebband 16. A particular recommended embodiment of the invention is characterized in that suction air is sucked through the depositing device 11 or through the filing screen belt 16 from the underside of the depositing device 11 or the air-permeable filing screen belt 16 facing away from the spunbonded web 1. The suction air velocity v _L or the average suction air velocity v _{L of} the suction air below the outlet gap 15 of the diffuser 8 and above the depositing device 11 or above the laying screen belt 16 is expediently 5 to 25 m / sec, preferably 5 to 20 m / sec and very preferably 10 to 20 m / sec. By sucking air or process air is removed from the system and also the unconsolidated spunbonded tape is fixed to the storage device 11. Incidentally, secondary air and ambient air are also drawn through the deposit screen belt 16 with the process air or primary air.

Conveniently, the spunbonded web is preconsolidated from the filaments 2 after their deposition and although preferred and in the embodiment by means of a calender 17 having two calender rolls 18, 19. Of these calender rolls 18, 19, at least one calender roll 18 is expediently heated. In the calendered spunbonded nonwoven fabric 1 thus prepared, the ratio of the tensile strength of the spunbonded fabric 1 in the machine direction (MD) to the tensile strength of the spunbonded nonwoven fabric 1 in the cross machine direction (CD) is less than 1.3. This ratio MD / CD is in a particularly preferred embodiment between 0.8 and 1.2.

By preference, and in the exemplary embodiment, the width B of the outlet gap 15 of the diffuser 8 is otherwise 50 to 170 mm, preferably 60 to 150 mm and very preferably 70 to 140 mm. Empfohlenermaßen the distance a between the diffuser 8 and the Ablagesiebband 16 is in the range between 50 and 150 mm. In this case, the distance a is expediently measured between the lowest point of the diffuser 8 or between the lowest end of a diffuser wall 12, 13 and the surface of the deposit screen belt 16.

Claims (17)

1. A method for producing a spunbonded fabric (1) from filaments (2), particularly from filaments (2) of thermoplastic polymer, wherein the filaments (2) are spun by means of at least one spinning device (3), subsequently cooled and then conveyed through a drawing device (6) with primary air, wherein the primary air exits the drawing device (6) with a primary air volume flow V_P, wherein the filaments (2) are guided through at least one diffusor (8) downstream of the drawing device (6), wherein secondary air is introduced into the diffusor (8) with a secondary air volume flow V_S between the drawing device (6) and the diffusor (8), wherein the filaments (2) are deposited on a delivery device (11) arranged downstream of the diffusor (8), and wherein the method is carried out in such a way that the ratio of the primary air volume flow V_P to the secondary air volume flow V_S or the secondary air coefficient V_P/V_S is respectively greater than 4.5, preferably greater than 5, particularly greater than 5.5.
2. The method according to claim 1, wherein the filaments (2) are cooled by being guided through a cooling device (4) with at least one cooling chamber and subsequently introduced into the drawing device (6), and wherein the unit consisting of the cooling device (4) and the drawing device (6) is realized in the form of a closed system, in which no additional air supply other than the supply of cooling air is provided.
3. The method according to one of claims 1 or 2, wherein a first air inlet gap (9) and a second air inlet gap (10) are provided between the drawing device (6) and the diffusor (8), and wherein the volume flow V_S1 of secondary air introduced through the first air inlet gap (9) preferably differs from the volume flow V_S2 of secondary air introduced through the second air inlet gap (10).
4. The method according to claim 3, wherein one secondary air volume flow is smaller than the other secondary air volume flow by at least 10 %, preferably at least 20 %.
5. The method according to one of claims 3 or 4, wherein one secondary air volume flow is smaller than the other secondary air volume flow by no more than 90 %, preferably no more than 80 %.
6. The method according to one of claims 1 to 5, wherein the opening widths of the two air inlet gaps (9, 10) arranged between the drawing device (6) and the diffusor (8) can preferably be adjusted independently of one another, and wherein the opening width of one air inlet gap (9, 10) is preferably adjusted smaller than the opening width of the other air inlet gap (9, 10).
7. The method according to one of claims 1 or 2, wherein only one air inlet gap (9 or 10) is provided between the drawing device (6) and the diffusor (8).
8. The method according to claim 7, wherein the opening width of the air inlet gap (9 or 10) arranged between the drawing device (6) and the diffusor (8) is adjustable.
9. The method according to one of claims 1 to 8, wherein at least one air chamber is arranged upstream of at least one air inlet gap (9, 10) arranged between the drawing device (6) and the diffusor (8), wherein the air chamber features at least one air inlet opening, preferably one to six air inlet openings, and wherein the supply of secondary air through the air inlet gap (9, 10) is respectively adjusted or metered by means of the at least one air inlet opening or the multiple air inlet openings.
10. The method according to one of claims 1 to 9, wherein the opening angle α of the diffusor (8) is adjusted to more than 2°, preferably more than 2.5°.
11. The method according to one of claims 1 to 10, wherein the width B of the outlet gap (15) of the diffusor (8) amounts to at least 250 % of the width b of the outlet gap (14) of the drawing shaft (7) of the drawing device (6).
12. The method according to one of claims 1 to 11, wherein the diffusor walls (12, 13) of the diffusor (8) can be adjusted asymmetrically referred to a center plane M extending through the device, and wherein the diffusor wall (12, 13) positioned closer to the center plane M is preferably assigned to the side of the diffusor (8), at which the smaller or no secondary air volume flow is introduced into the diffusor (8).
13. The method according to one of claims 1 to 12, wherein the delivery device (11) for the filaments (2) is realized air-permeable, wherein suction air is drawn through the delivery device (11) from the underside of the delivery device (11) that faces away from the filaments (2), and wherein the suction air velocity v_L or the average suction air velocity v_L of this suction air preferably amounts to 5 to 25 m/sec, preferably 5 to 20 m/sec, particularly 10 to 20 m/sec.
14. The method according to one of claims 1 to 13, wherein the spunbonded fabric web consisting of the filaments (2) is prebonded or bonded after it has been deposited, preferably by means of at least one calender (17).
15. A device for producing a spunbonded fabric (1) from filaments (2), particularly from filaments (2) of thermoplastic polymer, with a spinning device (3) for spinning the filaments (2), with a cooling device (4) for cooling the spun filaments (2) and with a drawing device (6), which is arranged downstream of the cooling device (4) and features a drawing shaft (7) for drawing the filaments (2), wherein the filaments (2) exit the drawing shaft (7) of the drawing device (6) together with a primary air volume flow V_P,
    wherein at least one diffusor (8) is arranged downstream of the drawing device (6) or the drawing shaft (7), wherein at least one air inlet gap (9, 10) for secondary air is arranged between the drawing shaft (7) and the diffusor (8), wherein the primary air volume flow V_P is significantly higher than the secondary air volume flow V_S introduced through the at least one air inlet gap (9, 10), and wherein the width B of the outlet gap (15) of the diffusor (8) amounts to at least 250 % of the width b of the outlet gap (14) of the drawing shaft (7).
16. The device according to claim 15, wherein the width B of the outlet gap (15) of the diffusor (8) amounts to 50 to 170 mm, preferably 60 to 150 mm, particularly 70 to 140 mm.
17. The device according to claim 15 or 16, wherein the distance a between the diffusor (8) and the delivery device (11) amounts to 30 to 300 mm, preferably 50 to 250 mm, particularly 70 to 200 mm.

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