Method for making a spunbonded high loft nonwoven web

Abstract

The invention relates to a method for making a spunbonded high loft nonwoven web comprising crimped multicomponent fibers, the process comprising continuously spinning the fibers, directing the fibers to a spin-belt by deflectors and/or air streams, laying down the fibers on the spinbelt and pre-consolidating the fibers after laydown using one or more pre-consolidation rollers to form a pre-consolidated web, wherein a first component of the fibers comprises a PP homopolymer and a second component of the fibers comprises a PP/PE copolymer, wherein the pre-consolidation rollers are operated at a temperature of smaller 110 C. and/or a linear contact force of smaller 5 N/mm.

Claims

1. A method for making a high loft spunbonded nonwoven web comprising crimped multicomponent fibers, the process comprising continuously spinning the fibers, directing the fibers to a spin-belt by deflectors or air streams or both, laying down the fibers on the spin-belt and pre-consolidating the fibers after laydown using one or more pre-consolidation rollers to form a pre-consolidated web, wherein a first component of the fibers comprises a polypropylene (PP) homopolymer and a second component of the fibers comprises a polypropylene/polyethylene (PP/PE) copolymer, wherein the pre-consolidation rollers are operated at a temperature of below 100 C. and a linear contact force of below 5 N/mm.

2. The method of claim 1, wherein the pre-consolidation rollers are operated at a temperature of from 20 C. to less than 100 C.

3. The method of claim 1, wherein the pre-consolidation rollers are operated at a linear contact force of 1-4 N/mm.

4. The method of claim 1, wherein the content of ethylene-stemming repetitive units in the PP/PE copolymer is >0-5 wt %.

5. The method of claim 1, wherein the PP/PE copolymer is a random copolymer.

6. The method of claim 1, wherein the PP homopolymer is isotactic.

7. The method of claim 1, wherein the melt flow rates or the polydispersities of the PP homopolymer and the PP/PE copolymer or both differ by less than 30%.

8. The method of claim 1, wherein the melting points of the PP homopolymer and the PP/PE copolymer differ by 10 C. or more or by 20 C. or less, or both.

9. The method of claim 1, wherein the multicomponent fibers are bicomponent fibers and/or have a side-by-side configuration.

10. The method of claim 1, wherein the weight ratio of the first to second component in the multicomponent fibers is 40/60-80/20.

11. The method of claim 1 further comprising bonding the pre-consolidated web using one or more calandering rolls, at least one of which is embossed, and/or hot air through bonding.

12. The method of claim 11, wherein the calandering rolls are operated at a temperature of and/or the air used in hot air through bonding has a temperature of 120-145 C.

13. The method of claim 1, wherein the pre-consolidation rollers are operated at a temperature of 40-90 C.

14. The method of claim 1, wherein the pre-consolidation rollers are operated at a temperature of 55-75 C.

15. The method of claim 1, wherein the pre-consolidation rollers are operated at a linear contact force of 1-2.5 N/mm.

16. The method of claim 1, wherein the melt flow rates or the polydispersities of the PP homopolymer and the PP/PE copolymer or both differ by less than 20%.

17. The method of claim 1, wherein the weight ratio of the first to second component in the multicomponent fibers is 40/60-60/40.

Description

(1) Further details and advantages of the present invention are described with reference to the figures and following working examples. The figures show:

(2) FIG. 1: a process line for carrying out a method of the invention (single beam);

(3) FIG. 2: another process line for carrying out a method of the invention (2 spunbond beams and 2 meltblown beams);

(4) FIG. 3: the process line of FIG. 2 complemented with an Omega oven for hot air through bonding; and

(5) FIG. 4: sketches of side-by-side, eccentric sheath core and trilobal bicomponent fiber configurations.

(6) The following terms and abbreviations may be used in the working examples.

(7) MFR: Melt Flow Rate as measured according to ISO 1133 with values shown in g/10

(8) min and conditions being 230 C. and 2.16 Kg

(9) MD: Machine Direction

(10) CD: Cross machine Direction

(11) Denier: g/9000 m filament

(12) Change to thickness of a material was measured according to WSP.120.1 (R4), Option A.

(13) Crimp: typically helically crimped fibers

(14) Neck-in: a materials tendency to shrink widthwise when exposed to a certain tensile/force in MD

(15) Density: g/cm.sup.3 weight unit per volume unit

(16) GSM: gram per square meter

(17) TM: melting point in C. as determined according to DSC (Differential Scanning calorimetry) method ISO 11357-3

(18) GPC: Gel Permeation Chromatography

(19) Specific strength: To obtain the specific strength in the units of Ncm3/g2, the area weight was assumed in grams

(20) The values for molecular weight averages (M.sub.z, M.sub.w and M.sub.n), molecular weight distribution (MWD) and its broadness, described by polydispersity index, PDI=M.sub.w/M.sub.n (wherein M.sub.n is the number average molecular weight and M.sub.w is the weight average molecular weight) as used herein are to be understood as having been determined by GPC according to ISO 16014-1:2003, ISO 16014-2:2003, ISO 16014-4:2003 and ASTM D 6474-12 using the following formulae:

(21) $\begin{array}{cc}{M}_n=\frac{\underset{i=1}{\overset{N}{.Math.}}{A}_i}{\underset{i=1}{\overset{N}{.Math.}}\left(A_i/M_i\right)}& \left(1\right)\\ M_w=\frac{\underset{i=1}{\overset{N}{.Math.}}\left(A_i{M}_i\right)}{\underset{i=1}{\overset{N}{.Math.}}{A}_i}& \left(2\right)\\ M_z=\frac{\underset{i=1}{\overset{N}{.Math.}}\left(A_i{M}_i^2\right)}{\underset{i=1}{\overset{N}{.Math.}}\left(A_i{M}_i\right)}& \left(3\right)\end{array}$

(22) For a constant elution volume interval V.sub.i, where A.sub.i, and M.sub.i are the chromatographic peak slice area and polyolefin molecular weight (MW), respectively associated with the elution volume, V.sub.i, where N is equal to the number of data points obtained from the chromatogram between the integration limits.

(23) A high temperature GPC instrument, equipped with either infrared (IR) detector (IR4 or IR5 from PolymerChar (Valencia, Spain) or differential refractometer (RI) from Agilent Technologies, equipped with 3 Agilent-PLgel Olexis and 1 Agilent-PLgel Olexis Guard columns was used. As the solvent and mobile phase 1,2,4-trichlorobenzene (TCB) stabilized with 250 mg/L 2,6-Di tert butyl-4-methyl-phenol) was used. The chromatographic system was operated at 160 C. and at a constant flow rate of 1 mL/min. 200 L of sample solution was injected per analysis. Data collection was performed using either Agilent Cirrus software version 3.3 or PolymerChar GPC-IR control software.

(24) The column set was calibrated using universal calibration (according to ISO 16014-2:2003) with 19 narrow MWD polystyrene (PS) standards in the range of 0.5 kg/mol to 11 500 kg/mol. The PS standards were dissolved at room temperature over several hours. The conversion of the polystyrene peak molecular weight to polyolefin molecular weights is accomplished by using the Mark Houwink equation and the following Mark Houwink constants:
K.sub.PS=1910.sup.3 mL/g, a.sub.PS=0.655
K.sub.PE=3910.sup.3 mL/g, a.sub.PE=0.725
K.sub.PP=1910.sup.3 mL/g, a.sub.PP=0.725

(25) A third order polynomial fit was used to fit the calibration data.

(26) All samples were prepared in the concentration range of 0.5-1 mg/ml and dissolved at 160 C. for 2.5 hours.

(27) FIG. 1 illustrates a process line for carrying out a method of the invention, more specifically a bicomponent spunbond method. The process line is equipped with two independent extruders A1 and A2, which process different polymers. The polymers are guided to a coathanger in separate channels. Under the coathanger a die consisting of several guide plates is mounted, which enables to obtain various cross fiber segments.

(28) A typical configuration of bicomponent fibers is a sheath-core configuration. Other configurations can be where the two polymer streams are arranged in a side-by-side arrangement, eccentric sheath-core arrangement, trilobal etc. as illustrated in FIG. 4.

(29) Where extruder A1 is processing a homopolymer and extruder A2 is processing a random copolymer and the die is configured as a side-by-side configuration, helically crimped fibers are generated under certain spinning conditions.

(30) After exiting the die the filaments are cooled in unit 1 by means of conditioned process air. The same process air is used to draw the filaments in the stretching unit 2 on drawing to obtain the right fibers denier and thereby to generate internal strength in the fibers by arranging polymer chains in the same direction.

(31) After laydown of the fibers on the spunbelt 4, the process air is sucked away by vacuum chamber 3. The fibers are then exposed to a nip for pre-consolidation by means of a set of rollers, one compaction roller 5 and one counter roller 6 below the spinbelt.

(32) The resultant and pre-consolidated web 7 is after it exits the pre-consolidation process deposited on the spinbelt free of any forces, and with a light fiber to fiber integration enough to withstand further processing.

(33) It has been found that when processing two polymers where one first polymer being a regular PP homopolymer in combination with one second random PP/PE copolymer in a side-by-side arrangement the fibers are able to generate helical crimp.

(34) The resultant fabric 7 features a very soft touch comparable to the touch of the well-known microfleece. As the crimped fibers of this polymer combination offer very uniform and consistent crimp levels, the resultant fabric of such fibers will display high tensile properties.

(35) In one example, the first polymer a homopolymer used in A1 is a traditional spunbond grade with an narrow molecule distribution M.sub.w/M.sub.n (polydispersity) in the range of 4.33-4.93 measured with GPC as described in terms and conditions, and a MFR measured according to ISO 1133 range of 19-35 g/10 min and a T.sub.M of 159-161 C. measured with DSC according to ISO 11357-3. As the second polymer, a random copolymer with a M.sub.w/M.sub.n (polydispersity) value of 4.54 and hence a similar narrow molecule distribution as the polymer of A1 is used. The MFR of the polymer in A2 measured according to ISO 1133 is in the range of 30 g/10 min and the TM at 144 C. as measured with DSC according to ISO 11357-3. The second polymer is a PP/PE random copolymer containing a C2 level of approx. 4% and has been nucleated to a certain degree.

(36) The parameter settings at the consolidations rollers 5 and 6 have an important impact on the fabric quality. In prior art processes, consolidation rollers are typically operated at pressures and temperatures in the range of 5 N/mm linear contact forces and a temperature of 110-130 C. When processing crimped fibers as described above at such conditions, however, crimp is ironed out and the fabrics exhibit poor thickness and softness. According to the invention, the rollers 5 and 6 are hence operated at temperatures and linear contact forces lower than in the prior art.

(37) In FIGS. 2 and 3, complex lines for obtaining spunmelt nonwovens comprising a spunbond line as described in FIG. 1 are shown. Besides the line 10 as described in FIG. 1, the apparatuses further comprise meltblown lines 11 and a bonding apparatus 12 comprising an embossed calander roll 13 and a counter roll 14 as well as, in the case of FIG. 3, an Omega-oven 15 for hot air through bonding.

(38) All examples described below use a line as described in FIG. 1.

(39) In the examples discussed in the following, the polymers as indicated in Table 1 were used.

(40) TABLE-US-00001 TABLE 1 TM MFR (DSC) Mn Mw Mz Type g/10 min C. g/mol g/mol g/mol Mw/Mn Mw/Mz A1 Moplen Propylene 25 161 34300 160500 333500 4.68 2.08 HP561R Homopolymer Borealis Propylene 19 161 45150 195500 431000 4.33 2.20 HF420FB Homopolymer Exxon 3155 Propylene 35 159 30150 148500 307500 4.93 2.07 Homopolymer A2 Moplen Propylene 30 144 33600 152500 308000 4.54 2.02 RP248R Co-polymer

(41) In the comparative examples discussed in the following, the polymers as indicated in Table 2 were used.

(42) TABLE-US-00002 TABLE 2 TM MFR (GPC) Mn Mw Mz Type g/10 min C. g/mol g/mol g/mol Mw/Mn Mw/Mz A1 Moplen Propylene 25 161 34300 160500 333500 4.68 2.08 HP561R Homopolymer A2 Moplen Propylene 25 163 25900 176500 514000 6.81 2.91 RP552R Homopolymer Moplen Propylene 25 161 34300 160500 333500 4.68 2.08 HP561R Homopolymer

EXAMPLES 1-5

(43) General process conditions for the spunbond process in examples 1-5 are as follows.

(44) Approx. 4900 capillary holes/m

(45) Side by side die configuration

(46) Cabin pressure of 3700 Pa

(47) Process air temperature of approx. 20 C.

(48) Melt temperature of A1 and A2 between 245 and 250 C.

(49) Throughput per capillary hole in the range of 0.53 g/hole/min

(50) Titer range of 1.5-2.0 denier

(51) Consolidation roller: 2.5 N/mm linear contact force and temperature of 70 C.

(52) Calandering rollers 135 C. on the point bond emboss roll and 125 C. on the smooth roll linear contact force 60 N/mm

(53) Bond pattern 12.1% open dot bond pattern with a dot diameter of 0.8 mm and 24 dot/cm.sup.2 depth of engraving 0.75 mm

(54) Results are shown in Table 3.

(55) TABLE-US-00003 TABLE 3 A1 A2 Ratio Bw Caliper Density TSMD TSCD Example polymer polymer A1/A2 gsm mm g/cm3 N/50 mm TEMD % N/50 mm TECD % 10 Exxon RP248R 50/50 20.6 0.37 0.0557 29.2 74.9 17.5 78.0 3155 2 Exxon RP248R 70/30 21.2 0.33 0.0642 33.2 56.2 17.8 62.4 3155 3 HP561R RP248R 50/50 20.7 0.42 0.0493 27.8 104.0 17.0 119.0 4 HP561R RP248R 70/30 20.6 0.35 0.0589 36.7 96.8 25.4 116.8 5 HF420FB RP248R 50/50 20.0 0.44 0.0455 26.9 135 17.8 137.0

(56) In the above it is seen the outcome of tests of parameters of the resultant fabric with varying polymer combinations of A1/A2 in the MFR range of 35/30 g/10 min, 25/30 g/10 min and 19/30 g/10 min. As seen all combinations generate crimp in the sense that a caliper of 0.33 mm to 0.44 mm is measured. MD Tensile properties are positively high and elongation properties remain on an acceptable low level.

EXAMPLES 6-10

(57) General process conditions for the spunbond process in examples 6-10 are as follows.

(58) Approx. 4900 capillary holes/m

(59) Side by side die configuration

(60) Cabin pressure of 3700 Pa

(61) Process air temp approx. 20 C.

(62) Melt temperature of A1 and A2 between 245 and 250 C.

(63) Throughput per capillary hole in the range of 0.53 g/hole/min

(64) Titer range of 1.5-2.0 denier

(65) Consolidation roller: 2.5 N/mm linear contact force and temperature of 40 C.

(66) Calandering rollers 135 C. on the point bond emboss roll and 125 C. on the smooth roll linear contact force 60 N/mm

(67) Bond pattern 12.1% open dot bond pattern with a dot diameter of 0.8 mm and 24 dot/cm.sup.2 depth of engraving 0.75 mm

(68) Results are shown in Table 4.

(69) TABLE-US-00004 TABLE 4 A1 A2 Ratio Bw Caliper Density TSMD TSCD Example polymer polymer A1/A2 gsm mm g/cm3 N/50 mm TEMD % N/50 mm TECD % 6 HP561R RP248R 40/60 21.5 0.60 0.0358 21.4 121 12.7 129 7 HP561R RP248R 50/50 21.9 0.49 0.0447 32.3 137 17.5 129 8 HP561R RP248R 60/40 20.9 0.36 0.0581 35.4 112 21.4 131 9 HP561R RP248R 70/30 20.1 0.34 0.0591 45.3 112 26.0 125 10 HP561R RP248R 80/20 20.0 0.34 0.0588 48.3 100 26.7 103

(70) In the above example list is seen the outcome when varying the polymer ratios between A1 and A2 but keeping all other parameters constant, consolidation rollers are in all options operated with a contact force of 2.5 N/mm and with a temperature of approx. 40 C.

(71) It is noticed that a maximum crimp level is seen in the option with a 40/60 ratio where a caliper of 0.6 mm is measured, but also as noticed a relatively low tensile property in the range of 21.4 N/50 mm in MD and 12.7 N/50 m in CD is obtained with this ratio.

EXAMPLES 11-17

(72) General process conditions for the spunbond process in examples 11-17 are as follows.

(73) Approx. 4900 capillary holes/m

(74) Side by side die configuration

(75) Cabin pressure of 3700 Pa

(76) Process air temp approx. 20 C.

(77) Melt temperature of A1 and A2 between 245 and 250 C.

(78) Throughput per capillary hole in the range of 0.53 g/hole/min

(79) Titer range of 1.5-2.0 denier

(80) Consolidation roller: 2.5 N/mm linear contact force and temperature range from 50 C. to 110 C.

(81) Calandering rollers 135 C. on the point bond emboss roll and 125 C. on the smooth roll linear contact force 60 N/mm

(82) Bond pattern 12.1% open dot bond pattern with a dot diameter of 0.8 mm and 24 dot/cm.sup.2 depth of engraving 0.75 mm

(83) Results are shown in Table 5.

(84) TABLE-US-00005 TABLE 5 A1 A2 Ratio Bw Caliper Density TSMD TSCD Example polymer polymer A1/A2 CR C gsm mm g/cm3 N/50 mm TEMD % N/50 mm TECD % 11 HF420FB RP248R 50/50 50 20.0 0.476 0.0420 25.7 130 18.1 154 12 HF420FB RP248R 50/50 60 19.7 0.476 0.0414 27.0 136 17.1 138 13 HF420FB RP248R 50/50 71 20.0 0.470 0.0426 28.0 139 17.3 149 14 HF420FB RP248R 50/50 82 20.2 0.448 0.0451 27.3 130 17.4 156 15 HF420FB RP248R 50/50 91 19.8 0.432 0.0458 26.5 132 18.8 165 16 HF420FB RP248R 50/50 97 20.0 0.370 0.0541 27.6 135 17.7 152 17 HF420FB RP248R 50/50 110 19.8 0.358 0.0553 26.0 126 17.1 151

(85) In the above examples 11-17 all process parameters are kept the same except from the temperature on the consolidation roller. The roller are in all options operated with a contact force of 2.5 N/mm and the temperature are set to an increasing level from 50 C. to 110 C. in steps of approx. 10 C.

EXAMPLES 18-23

(86) General process conditions for the spunbond process in examples 18-23 are as follows.

(87) Approx. 4900 capillary holes/m

(88) Side by side die configuration

(89) Cabin pressure of 3700 Pa

(90) Process air temp approx. 20 C.

(91) Melt temperature of A1 and A2 between 245 and 250 C.

(92) Throughput per capillary hole in the range of 0.53 g/hole/min

(93) Titer range of 1.5-2.0 denier

(94) Consolidation roller: 2.5 N/mm linear contact force and a temperature of 40 C.

(95) Calandering rollers 135 C. on the point bond emboss roll and 125 C. on the smooth roll linear contact force 60 N/mm

(96) Bond pattern 12.1% open dot bond pattern with a dot diameter of 0.8 mm and 24 dot/cm.sup.2 depth of engraving 0.75 mm

(97) Results are shown in Table 6.

(98) TABLE-US-00006 TABLE 6 A1 A2 Ratio Bw Caliper Density TSMD TSCD Example polymer polymer A1/A2 Oven C gsm mm g/cm3 N/50 mm TEMD % N/50 mm TECD % 18 HF420FB RP248R 50/50 120 19.0 0.39 0.0487 28.8 113.6 16.8 132.2 19 HF420FB RP248R 50/50 125 19.3 0.42 0.0460 30.2 109.9 17.1 129.7 20 HF420FB RP248R 50/50 130 20.0 0.41 0.0488 29.5 99.6 15.9 122.0 21 HF420FB RP248R 50/50 135 20.9 0.38 0.0550 31.5 99.3 15.7 121.8 22 HF420FB RP248R 50/50 140 19.5 0.38 0.0513 30.1 97.1 14.9 137.1 23 HF420FB RP248R 50/50 145 20.0 0.40 0.0500 29.2 71.4 12.8 130.0

(99) In the above examples all process parameters are kept constant and the crimped consolidated and calander bonded web has been post activated in an oven with an air through bonding process where the airflow through the consolidated web is kept constant and the temperature of the air in the oven is varied from 120 C. to 145 C.

(100) General observations processing options listed from 1-23:

(101) Various combinations of polymer ratios have been processed without any negative observations. Process conditions were very stable and smooth to run including transitions from option to option. Spinning wise, the fiber curtain was steady at all conditions and no fiber breakage leading to droplets or drips were observed.

COMPARATIVE EXAMPLES 24-26

(102) General process conditions for the spunbond process in comparative examples 24-26 are as follows.

(103) Approx. 4900 capillary holes/m

(104) Side by side die configuration

(105) Cabin pressure of 4000 Pa

(106) Process air temp approx. 18 C.

(107) Melt temperature of A1 and A2 between 245 and 248 C.

(108) Throughput per capillary hole in the range of 0.58 g/hole/min

(109) Titer range of 1.5-2.0 denier

(110) Consolidation roller: 2.5 N/mm linear contact force and varying temperature from 41-88 C.

(111) Calandering rollers 160 C. on the point bond emboss roll and 145 C. on the smooth roll linear contact force 60 N/mm

(112) Bond pattern 12.1% open dot bond pattern with a dot diameter of 0.8 mm and 24 dot/cm.sup.2 depth of engraving 0.75 mm

(113) Results are shown in Table 7.

(114) TABLE-US-00007 TABLE 7 A1 A2 Ratio Bw Caliper Density TSMD TSCD Example polymer polymer A1/A2 CR C gsm mm g/cm3 N/50 mm TEMD % N/50 mm TECD % 24 HP561R HP552R/ 70/30 41 20.4 0.66 0.0309 18.1 91.3 9.4 123.9 HP561R (50/50) 25 HP561R HP552R/ 70/30 62 20.6 0.67 0.0307 15.1 107.1 10.4 132.7 HP561R (50/50) 26 HP561R HP552R/ 70/30 88 20.5 0.65 0.0315 15.8 109.5 9.5 126.9 HP561R (50/50)

(115) In the above is shown obtained data from reference options from known PP/PP based crimped consolidated fabric of the style aggressive crimp. The polymer ratios are 70/30 between A1 and A2, and the A2 extruder is feed with a polymer blend of 50% HP561R and 50% HP552R (narrow and broad distributed). All process parameters are kept constant except from the temperature of the consolidation roller. The consolidation roller is kept with a constant linear contact force of 2.5 N/50 mm but the temperature are varied from 41 C. to 88 C. Calander temperature is 160 C. on the embossing roller and 145 C. on the smooth roller.

EXAMPLES 27-31 AND COMPARATIVE EXAMPLE 32

(116) These examples serve to demonstrate the excellent specific strength of nonwoven materials produced according to the invention. The examples are summarized in Table 8.

(117) TABLE-US-00008 TABLE 8 A1 A2 Ratio Bw Caliper Density TSMD Specific strength Example polymer polymer A1/A2 gsm mm g/cm3 N/50 mm N cm3/g2 27 HP561R RP248R 40/60 21.5 0.60 0.0358 21.4 27.9 28 HP561R RP248R 50/50 21.9 0.49 0.0447 32.3 33.3 29 HP561R RP248R 60/40 20.9 0.36 0.0581 35.4 29.2 30 HP561R RP248R 70/30 20.1 0.34 0.0591 45.3 38.0 31 HP561R RP248R 80/20 20.0 0.34 0.0588 48.3 41.2 32 HF420FB NA 100 19.3 0.31 0.0623 50.4 42.1

(118) Comparative Example 32 is a reference monocomponent material, which was run with significant higher calander bonding temperatures with 162 C. (calander oil temperature) for the embossing roller and 145 C. (calander oil temperature) for the smooth roller. All other examples were run at 135 C. (calander oil temperature) for the embossing roller and 125 C. (calander oil temperature) for the smooth roller. All other process settings are identical.

(119) Of the above is seen that the maximum obtainable MD tensile is 50.4 N/50 mm which is measured for the option with no crimp (Comparative Example 32), this results in a specific strength of 42.1 N.Math.cm.sup.3/g.sup.2. It is seen that for the lower density options with different polymer ratios and lower density due to crimped fibers the absolute tensile is reduced which leads to a reduced specific strength. The optimum between crimp/softness/thickness and specific strength found with a polymer ratio of the homopolymer and the copolymer of 50/50 which results in a specific strength of 33.3 N.Math.cm.sup.3/g.sup.2.

(120) Specific strength compensates for the materials individual density and basis weight.

COMPARATIVE EXAMPLES 33-35

(121) These examples constitute high loft reference options for specific strength. The examples are summarized in Table 9.

(122) TABLE-US-00009 TABLE 9 A1 A2 Ratio Bw Caliper Density TSMD Specific strength Example polymer polymer A1/A2 CR C gsm mm g/cm3 N/50 mm N cm3/g2 33 HP561R HP552R 70/30 90 21.1 0.43 0.0500 21.1 22.7 34 Exxon 3155 HP552R 70/30 90 20.6 0.42 0.0490 21.4 21.3 35 HP561R HP552R/ 70/30 88 20.5 0.65 0.0315 15.8 24.5 HP561R (50/50)

(123) The following Table 10 compares specific strength parameters obtained for examples 27-35 mentioned above. Comparative Example 32 is considered to be optimum of what is feasible under the given process conditions, and this specific strength is set to 100% the ranges for other high loft options can be calculated as follows.

(124) TABLE-US-00010 TABLE 10 Specific Ratio strength Example A1 polymer A2 polymer A1/A2 N cm3/g2 Rating 32 HF420FB NA 100 42.1 100 27 HP561R RP248R 40/60 27.9 66.2 28 HP561R RP248R 50/50 33.3 79.1 29 HP561R RP248R 60/40 29.2 69.4 30 HP561R RP248R 70/30 38.0 90.2 31 HP561R RP248R 80/20 41.2 97.9 33 HP561R HP552R 70/30 22.7 53.7 34 Exxon 3155 HP552R 70/30 21.3 50.5 35 HP561R HP552R/ 70/30 24.5 58.2 HP561R (50/50)

(125) It has been found that materials of this invention have a high specific strength. As shown in Example 28 with a 50/50 ratio of the two different polymers, this appears to be the best rating on the scale when at the same time a low density/high caliper is prioritized. Obviously, when the ratio of the two polymers are changed from a 50/50 blend towards a more monocomponent blend that generates less crimp, the specific tensile increased and actually the option with a 80/20 blend are very close to a regular monocomponent material in terms specific strength.

(126) Comparing basic PP/PP crimped nonwovens made with two homopolymers with a difference in molecule distribution (one being narrow and the other being more broad), it is seen these options perform relative poor on the scale for specific strength. All options both with medium as well as aggressive crimp are between 50.5 and 58.2 on the scale where 100 is max value for a monocomponent material. Materials of this invention are for comparison close to 80% on the scale.