Continuous-filament spunbond

Abstract

The invention relates to a spunbonded fabric of endless filaments made of thermoplastic plastic, wherein the endless filaments are designed as multi-component filaments having a core/sheath configuration. The filaments contain at least one lubricant, the lubricant being present exclusively or at least to 90 wt. % in the core component. The mass ratio between the core component and the sheath component is 65:35 to 80:20. The proportion of the lubricant is 250 to 5500 ppm with respect to the total filament.

Claims

1. A nonwoven spunbonded of filaments, wherein the filaments are of continuous, thermoplastic multicomponent and spunbond construction having a core/sheath configuration, the filaments contain at least one lubricant, the lubricant is present in the core exclusively or in a quantity of at least 98 wt % of lubricant in the filament, a mass ratio between the core and the sheath being is from 50:50 to 75:25, the core consists essentially of homopolypropylene, the sheath consists essentially of a polypropylene copolymer with a molar mass distribution of 3.5 to 5, or a mixture of homopolypropylene and a polypropylene copolymer with a molar mass distribution of 3.5 to 5, and the proportion of the lubricant with respect to the overall filament corresponds to 250 to 5500 ppm.

2. The spunbonded nonwoven defined in claim 1, wherein the mass ratio between the core and sheath is 67:33 to 73:27.

3. The spunbonded nonwoven according to claim 1, wherein the lubricant comprises fatty acid ester, fatty acid alcohol, or fatty acid amide.

4. The spunbonded nonwoven according to claim 1, wherein the lubricant is at least one stearate or at least one erucic acid amide or at least one oleamide.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention is explained in greater detail with reference to an embodiment shown in the sole FIGURE of the drawing.

SPECIFIC DESCRIPTION OF THE INVENTION

(2) Below, spunbonded nonwovens of bicomponent filaments having a core/sheath configuration were prepared according to the spunbond process described above. The materials used for the two components (core and sheath) were homopolypropylenes and polypropylene copolymers. In all of the embodiments, the spunbonded nonwoven deposited on the screen deposit belt was compacted using a calender having a U5714A engraving (12% embossing surface, round engraving points, 25 Fig/cm.sup.2). The fineness of the filaments of all examples was about 1.6 to 1.8 denier. All samples were produced using a spinning system with the same or similar throughputs.

Comparative Example

(3) Monocomponent filaments of homopolypropylene (Borealis HG455FB with MF125) were produced. The calendering was carried out with a surface temperature of the calender rolls of about 148° C. The spunbonded nonwoven produced has good strength, but, but no satisfactorily soft feel compared to the subsequent embodiments.

Embodiment 1

(4) A spunbonded nonwoven of bicomponent filaments was produced according to the first embodiment of the invention, with both the core and the sheath being made of homopolypropylene (Borealis HG455FB with MF125) with 8% of an “L-MODU X901 S” polypropylene from the company Ldemitsu as a soft polypropylene additive. The mass ratio between the core and the sheath was 70:30. Only the erucic acid amide-based SL05068PP lubricant from Constab was contained. The content of the lubricant was 2000 ppm with respect to the overall filament. The spunbonded nonwoven was calendered with a surface temperature of the calender rolls of about 142° C. The spunbonded nonwoven produced from these continuous filaments had a smooth, soft feel after one day of storage.

Embodiment 2

(5) The spunbonded nonwoven of this embodiment was also produced according to the first embodiment of the invention. The bicomponent filaments of this spunbonded nonwoven contained homopolypropylene (Basell Moplen HP561R with MF125) in both the core and the sheath with 10 wt % of a soft copolypropylene additive (Exxon Vistamaxx VM 6202). Here as well, the mass ratio between the core and the sheath was 70:30. Again, the lubricant used was the erucic acid amide-based SL05068PP lubricant from Constab. This lubricant was contained only in the core, and the content of the lubricant was 2500 ppm with respect to the overall filament. The calendering of the spunbonded nonwoven was performed with a surface temperature of the calender rolls of 132° C. The feel of the filament produced had to be classified as blunt at first, but soft feel appeared after one day of storage. This illustrates the delayed migration of the lubricant.

Embodiment 3

(6) This spunbonded nonwoven was produced according to the second embodiment of the invention. The bicomponent filaments contained homopolypropylene (Borealis HG475FB) in the core and polypropylene copolymer (Basell Moplen RP248R with MEI 30) in the sheath. The mass ratio between the core and the sheath was 70:30. The polypropylene copolymer of the sheath contains a nucleating agent and an antistatic agent. The calendering of the spunbonded nonwoven was carried out at a surface temperature of the calender rolls of 121° C. The feel of the spunbonded nonwoven produced had to be classified as blunt at first, but the spunbonded nonwoven acquired a soft feel after one day of storage. This illustrates again a delayed migration of the lubricant or antistatic agent here.

Embodiment 4

(7) The spunbonded nonwoven was produced according to the second embodiment of the invention. The core of the bicomponent filaments consisted of homopolypropylene (Borealis HG475FW with MF125) and the sheath consisted of polypropylene copolymer (Basell Moplen RP248R with MF130).

(8) The mass ratio between the core and the sheath was 50:50. The polypropylene copolymer contained a nucleating agent and an antistatic agent. The compaction was carried out with calender rolls having a surface temperature of 121° C. The feel of the spunbonded nonwoven produced was blunt at first, and a smooth, soft feel developed after one day of storage. This again illustrates the delayed migration of the stearate that was used as lubricant. Compared to embodiment 3, a reduced strength of the nonwoven fabric was observed (see table below) that can be attributed to the greater proportion of polypropylene copolymer compared to homopolypropylene.

Embodiment 5

(9) The bicomponent filaments of this spunbonded nonwoven had homopolypropylene (Borealis HG475FB with MF125) in the core and polypropylene copolymer in the sheath. The mass ratio of the core to the sheath was 70:30. The polypropylene copolymer used is comparable to the Moplen RP248R copolymer but has no nucleating agent and no antistatic agent. Compaction was performed with calender rolls having a surface temperature of 121° C. Even after three days of storage time, the spunbonded nonwoven produced in this way did not achieve the smooth, soft feel of embodiment 3. This shows that the use of polypropylene copolymer alone is not sufficient and that a migrating lubricant is required in order to achieve the properties according to the invention.

(10) In the table below, the weights per unit area of the spunbonded nonwovens are given in g/m.sup.2, and the strengths in the machine direction (MD) and transverse to the machine direction (CD) are given in N/5 cm for the above examples. The strengths were measured according to EDANA ERT 20.2-89 with a 100 mm clamping length and 200 mm/min draft speed. Comparative example V is compared here with embodiments 1 to 5:

(11) TABLE-US-00001 Example Weight/area Strength MD Strength CD “V” 22 49 35 1 22 44 28 2 22 39 31 3 20 55 31 4 20 48 30 5 20 55 35

(12) It should be emphasized that the spunbonded nonwovens of embodiments 3 to 5 were compacted at a substantially lower calender temperature than in comparative example V. Nevertheless, comparable strengths are observed, so that the energy input was able to be reduced in the production of the spunbonded nonwovens according to embodiments 3 to 5. The lower calender temperature promotes the soft feel and thus makes it possible to reduce the additional lubricant to be added.

Embodiment 6

(13) This embodiment concerns the difference in the degree of hardness or in relation to the hardness measurements listed. Measurements of the degree of hardness were carried out on a spunbonded nonwoven S1 according to the invention and on a nonwoven of reference V1 using a commercially available TSA (Tissue Softness Analyzer) measuring device from Emtec, Leipzig, Germany. The method of measurement has already been explained above. The measuring head was pressed against the nonwoven surface with a force of 100 M.sub.n. It was measured here on the spunbonded nonwoven surface facing away from the screen deposit belt. The measuring head was equipped with eight rotating or rotatable measuring blades, and the speed during the measurement was 2/sec. A sound intensity/frequency spectrum was recorded for the spunbonded nonwoven according to the invention and the nonwoven of reference, respectively, and the sound intensity of the peak maximum (TS7 value) was determined at 6550 Hz in each case. In each case, 5 individual measurements were averaged. The two spunbonded nonwovens were made using the same spunbond apparatus, precompacted in the same manner (i.e., under the same calender compaction conditions), and both spunbonded nonwovens had filaments of the same titer of 1.8 denier. The difference between the filaments of the two spunbonded nonwovens was the distribution of the lubricant in the polymer melt as it exited the spinning plate before the respective filament was spun. In the spunbonded nonwoven S1 according to the invention, the filaments consisted of a homogeneous mixture of homopolypropylene and polypropylene copolymer. The raw materials for the bicomponent filaments were selected analogously to embodiment 2 above, the lubricant content with respect to the overall filament was 2000 ppm, and a “U2888” calender engraving with a 19% surface ratio was used. The content of the core was 50% (mass ratio between core and sheath 50:50). Accordingly, 4000 ppm of lubricant were added to the core of the bicomponent filaments. A spunbonded nonwoven of filaments made of the same components was used as nonwoven V1 of reference, but the lubricant was homogeneously distributed over the filament cross section at 2000 ppm. For both nonwovens S1 and V1, the sound intensity values (TS7 values) were determined for three times, namely 15 minutes, 2 hours, and 96 hours after the filaments were deposited on a screen deposit belt. Sound intensity values for the spunbonded nonwoven S1 according to the invention and for the nonwoven V1 of reference are shown in the following table:

(14) TABLE-US-00002 L (dBV.sup.2 rms) in % S1 V1 S1 V1 15 min 4.31 3.98 108.2 100  2 hours 4.42 4.16 106.3 100 96 Hours 3.93 3.84 102.2 100

(15) The sole FIGURE shows the sound intensity values TS7 (in dBV2 rms) of the peak maximum at 6550 Hz as a function of the time of measurement. The TS7 value that was determined 15 minutes after depositing of the filament is shown at the far left, and the TS7 value that was determined 2 hours after depositing of the filament is shown to the right of that. The TS7 value that was determined 4 days or 96 hours after the depositing of the filament is shown at the far right. The solid line characterizes the TS7 values for the spunbonded nonwoven S1 according to the invention, and the dashed line shows the TS7 values for the nonwoven V1 of reference. It can be seen here that the spunbonded nonwoven S1 according to the invention initially (after 15 minutes and after 2 hours) has a substantially higher sound intensity and thus a lower degree of softness or higher degree of hardness than the nonwoven V1 of reference. This is because the lubricant migrates much more slowly to the filament surface in the filaments of the spunbonded nonwoven S1 according to the invention. By contrast, a relatively fast migration takes place in the nonwoven of reference, so that high degrees of softness and low degrees of hardness are already achieved relatively early. The rise in the curve between 15 minutes and 2 hours for both spunbonded nonwovens is explained by the initial recrystallization of the polypropylene blend that stiffens the filaments. This shape of the curves can be considered to be typical of this combination of raw materials. As expected, both migration of the lubricant and recrystallization simultaneously affect softness. Since migration speeds can also change depending on the respective crystallinity, there is no universally applicable curve progression; this is raw material-specific. After 96 hours, the sound intensity values and thus the degrees of softness or degrees of hardness of the spunbonded nonwoven S1 according to the invention on the one hand and of the nonwoven V1 of reference on the other hand coincide or virtually coincide. The delayed migration of the lubricant to the filament surface in the spunbonded nonwovens according to the invention has the advantage that, during manufacture of the filaments, substantially less outgassing of lubricant from the filaments takes place, so the system components are correspondingly less contaminated. At the same time, this has a positive influence on winding characteristics. Apart from that, it can be seen from the percentage data in the table that the sound intensity value of the spunbonded nonwoven according to the invention is more than 3% higher than the sound intensity value of the nonwoven V1 of reference within the first 150 minutes after the depositing of the filament and, accordingly, the degree of hardness of the spunbonded nonwoven S1 according to the invention is more than 3% higher than the degree of hardness of the nonwoven V1 of reference. It can also be seen that the finished spunbonded nonwovens have become softer, independent of any subsequent recrystallization that demonstrates the effect and purpose of the lubricant.

Embodiment 7

(16) With the same system and compaction as in embodiment 6, the combination of raw materials was chosen in keeping with embodiment 5, but with a lubricant. A Moplen HP561R homopolypropylene was used in the core, and the random CoPP with MFR 30 from embodiment 5 was used in the sheath. A core/sheath ratio of 70:30 was set, and the same calender temperature was used as in embodiment 6. In the spunbonded nonwoven S2 according to the invention, 2900 ppm of lubricant were added only in the core. In nonwoven V2 of reference, 2000 ppm of lubricant were added both to the core and to the sheath. A similar relationship is again observed here in the TS7 values to that observed in embodiment 6; however, the sheath raw material used here results in a different temporal course due to its different base softness and crystallization and migration speed. The TS7 difference becomes particularly apparent here after 2 hours.

(17) TABLE-US-00003 L (dBV.sup.2 rms) S2 V2 15 min 5.03 4.91  2 hours 5.64 4.86 96 Hours 4.33 4.19

(18) Here, too, the deposited spunbonded nonwoven is softer (has a lower TS7 value) than the newly produced spunbonded nonwoven.

(19) The following table shows the TS7 relationship of spunbonded nonwovens S according to the invention to nonwovens V of reference (embodiments 6 and 7) after 15 minutes, 2 hours, and 96 hours, as well as the strength values after production and the weights per unit area of the spunbonded nonwovens. Strengths and weights per unit area were determined according to the methods described above using a draft speed of 200 mm/min for the strength measurement.

(20) TABLE-US-00004 Sample V1 S1 V2 S2 TS7 (15 min) [%] 100 108.2 100 102.4 TS7 (2 hrs) [%} 100 106.3 100 116.1 TS7 (96 hrs) [%} 100 102.2 100 102.5 Strength MD 41.6 39.4 44.2 42.3 [ND/5 cm] Strength CD 23.7 23 28.1 28.4 [N/5 cm) Weight/Area g/m.sup.2 20.6 20.3 20.6 20.3

(21) A strength advantage is observed in the embodiment 7 compared to embodiment 6. This demonstrates the advantage as well as the possibilities of bicomponent technology.