Nonwoven Fabric Comprising A High Loft Spunbond Layer

Abstract

The invention relates to a fabric comprising at least one high loft spunbond nonwoven layer having crimped multicomponent fibers, wherein a first component of the multicomponent fibers comprises a first polymer A and a second component of the multicomponent fibers comprises a blend of the first polymer A and a second polymer B, wherein the melt flow rate of polymer A is at least 25% higher than the melt flow rate of polymer B and wherein the second component comprises at least 40 wt.-% of polymer B.

Claims

1. A fabric comprising at least one high loft spunbond nonwoven layer (S.sub.H) having crimped multicomponent fibers, characterized in that a first component of the multicomponent fibers comprises a first polymer A and a second component of the multicomponent fibers comprises a blend of the first polymer A and a second polymer B, wherein the melt flow rate of polymer A is at least 25% higher than the melt flow rate of polymer B and wherein the second component comprises at least 40 wt.-% of polymer B.

2. The fabric of claim 1, wherein the melt flow rate of polymer A is at least 35% higher than the melt flow rate of polymer B and/or wherein the melt flow rate of polymer B is smaller or equal 26 g/10 min and the melt flow rate of polymer A is 34 g/10 min or greater.

3. The fabric of claim 1, wherein the fabric further comprises at least one meltblown layer (M) or at least one standard loft spunbond layer (S.sub.S) or both, where these additional layers form a nonwoven laminate with the at least one high loft layer spunbond layer (S.sub.H).

4. The fabric of claim 1, wherein the first polymer A or the second polymer B or both are thermoplastic polymers.

5. The fabric of claim 3, wherein the melt blown layer (M) or the standard loft spunbond layer (S.sub.S) or both are made of a thermoplastic polymer.

6. The fabric of claim 1, wherein the second polymer B has a different molecular weight distribution than the first polymer A.

7. The fabric of claim 1, wherein the difference in polydispersity indices between the polymers A and B is greater than 0.5.

8. The fabric of claim 1, wherein the polydispersity index of polymer A is between 4.0 and 6.0.

9. The fabric of claim 1, wherein the weight ratio of the first to second component in the multicomponent fibers is 40/60 to 90/10.

10. The fabric of claim 1, wherein the polymer of the first component or the polymer blend of the second component or the polymer of the S.sub.S layer or the polymer of the M layer or any combination thereof comprises an additive which is capable of enhancing the softness of the fiber.

11. The fabric of claim 1, wherein the linear mass density of the crimped multicomponent fibers is 1.4 to 2.6 or wherein the average crimp diameter of the crimped multicomponent fibers is 50 to 500 μm or both.

12. The fabric of claim 1, wherein the density of the high loft spunbond layer (S.sub.H) is 0.02 to 0.08 g/cm.sup.3.

13. A hygiene product comprising the fabric of claim 1 and optionally further comprising granular absorbent material.

14. A method of manufacturing an SMS-type nonwoven laminate according to claim 3, which comprises the steps of: (a) providing the at least one standard loft spunbond layer (S.sub.S) or high loft spunbond layer (S.sub.H); (b) forming the at least one meltblown layer (M) upon depositing meltblown fibers on the surface of the standard loft spunbond layer (S.sub.S) or high loft spunbond layer (S.sub.H) provided under (a); and (c) forming the at least one high loft spunbond layer (S.sub.H) or standard loft spunbond layer (S.sub.S) upon depositing spunbond fibers on the surface of the meltblown layer (M) formed under (b).

15. A method of manufacturing an S.sub.HS.sub.SS.sub.H-type nonwoven laminate according to claim 3, which comprises the steps of: (a) providing the at least one high loft spunbond layer (S.sub.H); (b) forming the at least one standard loft spunbond layer (S.sub.S) upon depositing spunbond fibers on the surface of the high loft spunbond layer (S.sub.H) provided under (a); and (c) framing the at least one high loft spunbond layer (S.sub.H) upon depositing spunbond fibers on the surface of the standard loft spunbond layer (S.sub.S) formed under (b).

16. A method of manufacturing an S.sub.HS.sub.S-type nonwoven laminate according to claim 3, which comprises the steps of: (a) providing the at least one standard loft spunbond layer (S.sub.S); (b) forming the at least one high loft spunbond layer (S.sub.H) upon depositing spunbond fibers on the surface of the standard loft spunbond layer (S.sub.S) formed under (a).

17. The fabric claim 1, wherein the fabric further comprises at least one meltblown layer (M) or at least one standard loft spunbond layer (S.sub.S) or both, where these additional layers form an S.sub.HMS.sub.S-type nonwoven laminate.

18. The fabric claim 1, wherein the fabric further comprises at least one meltblown layer (M) or at least one standard loft spunbond layer (S.sub.S) or both, where these additional layers form an S.sub.HS.sub.SS.sub.H-type nonwoven laminate.

19. The fabric claim 1, wherein the fabric further comprises at least one meltblown layer (M) or at least one standard loft spunbond layer (S.sub.S) or both, where these additional layers form an S.sub.HS.sub.S-type nonwoven laminate.

Description

[0064] Further details and advantages of the present invention will be described with reference to the working examples and figures described in the following. The figures show:

[0065] FIG. 1: a schematic illustration of the structure of an SMS-type nonwoven laminate according to one embodiment of the present invention;

[0066] FIG. 2: a schematic illustration of an apparatus for producing such laminate;

[0067] FIG. 3: a schematic illustration of a section of a crimped multicomponent fiber as comprised in a high loft spunbond layer S.sub.H of such laminate;

[0068] FIG. 4: a micrograph of a high loft spunbond layer S.sub.H of such laminate;

[0069] FIG. 5: a micrograph of a standard loft spunbond layer S.sub.S of such laminate;

[0070] FIG. 6: TSA test results for the upper side of such laminate; and

[0071] FIG. 7: TSA test results for the lower side of such laminate.

[0072] 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 (Gel Permeation Chromatography) according to ISO 16014-1:2003, ISO 16014-2:2003, ISO 16014-4:2003 and ASTM D 6474-12 using the following formulae:

[00001] $\begin{matrix} M_{n} = \frac{{.Math.}_{i = 1}^{N} .Math. A_{i}}{{.Math.}_{i = 1}^{N} .Math. (A_{i} / M_{i})} & (1) \\ M_{w} = \frac{{.Math.}_{i = 1}^{N} .Math. (A_{i} \times M_{i})}{{.Math.}_{i = 1}^{N} .Math. A_{i}} & (2) \\ M_{z} = \frac{{.Math.}_{i = 1}^{N} .Math. (A_{i} \times M_{i}^{2})}{{.Math.}_{i = 1}^{N} .Math. (A_{i} \times M_{i})} & (3) \end{matrix}$

[0073] For a constant elution volume interval ΔV.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.

[0074] 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 μL 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.

[0075] 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=19×10.sup.−3 mL/g, a.sub.PS=0.655

K.sub.PE=39×10.sup.−3 mL/g, a.sub.PE=0.725

K.sub.PP=19×10.sup.−3 mL/g, a.sub.PP=0.725

[0076] A third order polynomial fit was used to fit the calibration data.

[0077] All samples were prepared in the concentration range of 0/5-1 mg/ml and dissolved at 160° C. for 2.5 hours.

[0078] The melt flow rates indicated in all examples correspond to those obtained according to ISO 1133-1 at 230° C. under 2160 g load.

EXAMPLES 1 TO 4

[0079] The following examples 1 to 4 demonstrate the surprising effect that when producing a spunbond nonwoven fabric the mixing of two polymers A and B in one polymer stream and maintaining polymer A in the other polymer stream of a side-by-side bicomponent fiber it is possible to create more crimp and thereby more bulk in the resulting web. The examples also demonstrate that this surprising effect is particularly emphasized when the melt flow rates of the two polymers A and B are different.

[0080] In each of these examples, a laminate comprising a standard loft spunbond layer and a high loft spunbond layer has been produced.

[0081] In examples 1 and 2, the standard loft spunbond bottom layer (S.sub.S) first produced was formed entirely from a single PP Homopolymer with an MFR of 25, a PD of 4.68 and a quotient M.sub.z/M.sub.w of 2.08 (Trade Name Moplen HP561R). In examples 3 and 4, the standard loft spunbond bottom layer (S.sub.S) first produced was formed entirely from a single PP Homopolymer with an MFR of 35, a PD of 4.93 and a quotient M.sub.z/M.sub.w of 2.07 (Trade Name Exxon 3155). In either case, 0.3 wt.-% of a colorant (TiO.sub.2) was added as the only additive and the titer of the fibers was in the range of 1.6 to 1.8 denier.

[0082] In either of the examples 1 to 4, a high loft spunbond upper layer (S.sub.H) formed entirely from circular side-by-side bicomponent fibers comprising 70 wt.-% of a first component and 30 wt.-% of a second component was laid onto the standard loft spunbond bottom layer (S.sub.S) thus obtained. In either case, the first component comprised 69.7 wt.-% of polymer and 0.3 wt.-% of a colorant (TiO.sub.2) as the only additive. In either case, the titer of the fibers was in the range of 1.6 to 1.8 denier.

[0083] In examples 1 and 2, the first component was formed entirely from the same polymer as used for the standard loft spunbond layer (S.sub.S), the PP homopolymer having the trade name Moplen HP561R. Also in examples 3 and 4, the first component was formed entirely from the same polymer as used for the standard loft spunbond layer (Se), in this case the PP homopolymer having the trade name Exxon 3155.

[0084] In examples 1 and 3 (both comparative), the second component was formed from a single polymer, a PP homopolymer with an MFR of 25, a PD of 6.81 and a quotient M.sub.z/M.sub.w of 2.91 (Trade Name Moplen HP552R).

[0085] In examples 2 (comparative) and 4 (inventive), the second component was formed from a 50/50 (by weight) blend of the same polymer as used for the first component (Moplen HP561R in example 2 and Exxon 3155 in example 4) and of the polymer Moplen HP552R. The melt flow rate of polymer Moplen HP561R is similar to the melt flow rate of polymer Moplen HP552R. The melt flow rate of polymer Exxon 3155 is 40% different the melt flow rate of polymer Moplen HP552R.

[0086] All four examples 1 to 4 were carried out under the same process conditions using the same machinery.

[0087] The physical properties of the webs obtained according to these examples are summarized in Table 1.

TABLE-US-00001 TABLE 1 Example 1 (Comparative) 2 (Comparative) Lower spunbond layer (S.sub.S) 8.4 g/m.sup.2 99.7 wt.-% HP561R 99.7 wt.-% HP561R (monocomponent fiber) 0.30 wt.-% TiO.sub.2 0.30 wt.-% TiO.sub.2 Upper spunbond layer (S.sub.H) 8.4 g/m.sup.2 69.7 wt.-% HP561R 69.7 wt.-% HP561R (bicomponent fiber) 0.30 wt.-% TiO.sub.2 0.30 wt.-% TiO.sub.2 30 wt.-% HP552R 15 wt.-% HP552R 15 wt.-% HP561R Overall caliper [mm] 0.23 0.28 Overall density [g/cm.sup.3] 0.073 0.060 Upper layer density [g/cm.sup.3] 0.056 0.042 TSMD [N/50 mm] 24.51 22.47 TEMD [%] 69.67 67.44 TSCD [N/50 mm] 14.16 12.02 TECD [%] 75.61 70.09 Example 3 (Comparative) 4 (Inventive) Lower spunbond layer (S.sub.S) 8.4 g/m.sup.2 99.7 wt.-% Exxon 3155 99.7 wt.-% Exxon 3155 (monocomponent fiber) 0.30 wt.-% TiO.sub.2 0.30 wt.-% TiO.sub.2 Upper spunbond layer (S.sub.H) 8.4 g/m.sup.2 69.7 wt.-% Exxon 3155 69.7 wt.-% Exxon 3155 (bicomponent fiber) 0.30 wt.-% TiO.sub.2 0.30 wt.-% TiO.sub.2 30 wt.-% HP552R 15 wt.-% HP552R 15 wt.-% Exxon 3155 Overall caliper [mm] 0.23 0.36 Overall density [g/cm.sup.3] 0.072 0.046 Upper layer density [g/cm.sup.3] 0.055 0.029 TSMD [N/50 mm] 18.68 23.56 TEMD [%] 56.93 67.58 TSCD [N/50 mm] 10.57 12.54 TECD [%] 65.95 74.95

[0088] TS means tensile strength. TE means tensile elongation. MD means machine direction. CD means cross machine direction.

[0089] Thickness of a material was measured according to WSP.120.6 (R4), Option A.

[0090] The overall density was calculated from the basis weight and caliper.

[0091] The upper layer density was calculated on the same basis, upon previously assuming that the lower layer comprises a caliper (thickness) at given basis weight according to standard spunbond materials (i.e., a thickness of approximately 0.08 mm) and subtracting this caliper from the value determined for the overall web.

[0092] Upon comparing the values for the upper layer density in the pairs of comparative and inventive examples 1/2 and 3/4, it becomes apparent that blending polymers according to the invention in the second component leads to an increase in loft. Surprisingly, this increase is particularly emphasized in the case of examples 3 and 4, where the components A and B have different melt flow rates.

[0093] With reference to examples 3 and 4, where the components A and B have different melt flow rates, it can further be observed that the tensile properties surprisingly improve in example 4 over example 3 irrespective of the higher loft.

EXAMPLES 5 TO 7

[0094] In all these examples SMMS nonwoven laminates are produced by identical spunmelt processes.

[0095] In either example, the first layer is a standard spunbond layer (S.sub.S) comprising monocomponent fibers having a titer of 1.7 denier. The polymer used for these fibers is the polymer Exxon 3155 already described in connection with examples 1 to 4.

[0096] The two center layers M1 and M2 consist of meltblown fibers with a size of 3 to 5 μm. The polymer used is a PP homopolymer (HL508FB).

[0097] The top layers are formed by a high loft spunbond upper layer (S.sub.H) which is formed entirely from circular side-by-side bicomponent fibers comprising 70 wt.-% of a first component and 30 wt.-% of a second component as described in table 2. The titer of the fibers was 1.7 denier.

[0098] Ercuamide is a slip-agent which has been added to both components in example 7.

[0099] In order to evaluate the composites materials barrier property the materials Hydrohead, Air Permeability and Pore size has been measured together with the materials basis weight and calliper.

[0100] As apparent from table 2, hydrohead air permeability and pore size has proven essentially unaffected for both inventive examples 6 and 7 as compared to the reference material of comparative example 5.

[0101] At the same time, however, the bulk/calliper has been increased by more than 100% for both inventive examples 6 and 7 as compared to the reference material of comparative example 5.

TABLE-US-00002 TABLE 2 Example 5 (Comparative) 6 (Inventive) Lower spunbond layer (S.sub.S) 6.5 g/m.sup.2 99.7 wt.-% Exxon 3155 99.7 wt.-% Exxon 3155 (monocomponent fiber) 0.30 wt.-% TiO.sub.2 0.30 wt.-% TiO.sub.2 First meltblown layer (M1) 1 g/m.sup.2 100 wt.-% HL508FB 100 wt.-% HL508FB Second meltblown layer (M2) 1 g/m.sup.2 100 wt.-% HL508FB 100 wt.-% HL508FB Upper spunbond layer (S.sub.H) 6.5 g/m.sup.2 69.7 wt.-% Exxon 3155 69.7 wt.-% Exxon 3155 (bicomponent fiber) 0.30 wt.-% TiO.sub.2 0.30 wt.-% TiO.sub.2 30 wt.-% Exxon 3155 15 wt.-% HP552R 15 wt.-% Exxon 3155 Overall caliper [mm] 0.16 0.34 Overall density [g/cm.sup.3] 0.095 0.045 Air permeability [l/m.sup.2/s] 2018 1997 Hydrohead [mm H.sub.2O] 171.0 161.4 Pore size [%] 98.8 98.3 Example 7 (Inventive) Lower spunbond layer (S.sub.S) 6.5 g/m.sup.2 98.9 wt.-% Exxon 3155 (monocomponent fiber) 0.30 wt.-% TiO.sub.2 0.80 wt.-% Erucamide First meltblown layer (M1) 1 g/m.sup.2 100 wt.-% HL508FB Second meltblown layer (M2) 1 g/m.sup.2 100 wt.-% HL508FB Upper spunbond layer (S.sub.H) 6.5 g/m.sup.2 68.9 wt.-% Exxon 3155 (bicomponent fiber) 0.30 wt.-% TiO.sub.2 0.80 wt.-% Erucamide 14.6 wt.-% HP552R 14.6 wt.-% Exxon 3155 0.80 wt.-% Erucamide Overall caliper [mm] 0.33 Overall density [g/cm.sup.3] 0.046 Air permeability [l/m.sup.2/s] 2034 Hydrohead [mm H.sub.2O] 164.2 Pore size [%] 98.7

[0102] A schematic illustration of the nonwoven materials of examples 6 and 7 is given in FIG. 1. A schematic illustration of an apparatus which may be used to obtain such laminates is given in FIG. 2. The different layers are labelled S.sub.H, S.sub.S, M1 and M2 as above.

[0103] FIG. 3 is a schematic illustration of a section of a crimped endless fiber as present in the S.sub.H layer. FIG. 4 is a micrograph of the S.sub.H layer of example 7 where helically crimped sections of some fibers have been highlighted. As apparent, the crimped fiber sections form circles with an area of approximately 20.000 μm.sup.2 to 50.000 μm.sup.2 resulting in a crimp radius of between approximately 80 μm to 125 μm. Exemplary data actually measured are given in table 3 below:

TABLE-US-00003 TABLE 3 Area [μm.sup.2] Radius [μm] 34.000 103 21.000 81 25.000 89 27.000 92 35.000 106 48.000 124 29.000 97 42.000 115

[0104] FIG. 5 is a micrograph of the S.sub.H layer as of example 5 to 7. It shows the traditional spunbond fibers. It is seen that these fiber have a straight character with no tendency to crimp. In the background, the 3 to 5 μm thin meltblown fibers from layers M1 and M2 can be seen.

[0105] For examples 5 to 7, the surface structure and softness was tested according to the measurement as described in the TSA Leaflet Collection No. 11 of 13 Nov. 2014 issued by emtec Electronic GmbH, Leipzig, DE. The results for the upper surface (S.sub.H in the inventive examples) of the laminate for each example are illustrated in FIG. 6. The results for the lower surface (S.sub.S in the inventive examples) of the laminate for each example are illustrated in FIG. 7.

[0106] As apparent from FIG. 6, the value of first peak for the reference material of example 5 is in the range of 13 dB and the values for inventive examples 6 and 7 are in the range of 22 to 24 dB and hence significantly higher. This shows that the surface of this side of the nonwovens with helically crimped/curled fibers has a more open surface topography with a bigger variance and more hills and valleys, indicative of the low density of this side of the material.

[0107] The value of the second peak is indicative of the softness of the individual fibers. Here it is seen that the individual fibers of the comparative example 5 and inventive example 6 are on same softness level, but the fibers of inventive example 7 containing Erucamide display a reduction in the peak value, which is an indication that the individual fibers are softer. The second peak value of examples 5 and 6 are approximately 8.3 dB and the value for example 7 containing Erucamide is approximately 7.0 db. Hence, upon addition of this agent, a reduction of almost 16% in individual fiber stiffness or an increase of almost 16% in individual fiber softness is observed.

[0108] As apparent from FIG. 7, the first peak values for all examples are within about 1 dB and in line with the first peak value of the upper side of reference example 5, meaning that in example 5 the two sides have an identical surface topography.

[0109] In the second peak value the values are within a narrow span, which indicates similar fiber softness. However, also in this graph it becomes apparent that example 7, where the lower S.sub.S layer contains Erucamide, displays the lowest value, which indicates that this option has the softest individual fiber.

Nonwoven Fabric Comprising A High Loft Spunbond Layer

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D04H3/147

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A61F13/5148

HUMAN NECESSITIES

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D04H1/56

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D04H1/50

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D02G3/04

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D04H3/007

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A61F13/51478

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D04H3/16

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D04H1/74

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D04H1/74

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D04H1/56

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D02G3/04

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Abstract

Claims

Description