NONWOVEN LAMINATE FABRIC COMPRISING MELTBLOWN AND SPUNDBOND LAYERS

Abstract

The invention relates to a nonwoven laminate fabric comprising a meltblown nonwoven layer sandwiched between first and second spundbond nonwoven layers, wherein at least one of the spundbond layers is a high loft spunbond nonwoven layer comprising or consisting of crimped multicomponent fibers.

Claims

1. A nonwoven laminate fabric comprising a meltblown nonwoven layer sandwiched between first and second spundbond nonwoven layers, wherein at least one of the spundbond layers is a high loft spundbond nonwoven layer comprising crimped multicomponent fibers.

2. The fabric of claim 1, wherein both spundbond layers are high loft spundbond nonwoven layers comprising crimped multicomponent fibers.

3. The fabric of claim 1, wherein the bond area of the fabric is 10-15%.

4. The fabric of claim 1, wherein the bonding zones are constituted by discrete dots, wherein further the dot area is 1-5 mm.sup.2 or 1.5-3 mm.sup.2 and/or the dot diameter is 0.5-1.5 mm or 0.7-1.0 mm.

5. The fabric of claim 4, wherein the fabric comprises 20-30 dots per cm.sup.2.

6. The fabric of claim 1, wherein the basis weight of the meltblown layer is less than 4.0 g/m.sup.2.

7. The fabric of claim 1, wherein the basis weight of the meltblown layer makes up 5-15% of the overall basis weight of the fabric.

8. The fabric of claim 1, wherein the average diameter of the meltblown fibers of the meltblown layer is below 3.0 m.

9. A method of manufacturing a fabric, the method comprising: (a) forming a first spundbond nonwoven layer upon depositing spundbond fibers on a moving belt; (b) forming a meltblown nonwoven layer upon depositing meltblown fibers on a surface of the first spundbond nonwoven layer; and (c) forming a second spundbond nonwoven layer upon depositing spundbond fibers on a surface of the meltblown nonwoven layer; wherein the first spundbond nonwoven layer and/or the second spunbond nonwoven layer is a high loft spundbond nonwoven layer and wherein at least part of the spundbond fibers deposited on the moving belt and/or the meltblown layer are crimped multicomponent spundbond fibers.

10. A hygiene product comprising a nonwoven laminate fabric, the nonwoven laminate fabric comprising: a meltblown nonwoven layer sandwiched between a first spundbond nonwoven layer and a second spundbond nonwoven layer, the first spundbond nonwoven layer and/or the second spundbond nonwoven layer being a high loft spundbond nonwoven layer comprising crimped multicomponent fibers.

11. The hygiene product of claim 10, further comprising an absorbent core and a backsheet film, the high loft spundbond nonwoven layer being positioned between the absorbent core and the backsheet film.

12. The hygiene product of claim 11, wherein the absorbent core comprises granular absorbent material.

13. The hygiene product of claim 12, wherein the granular absorbent material comprises super absorbent granulate/polymers (SAP).

14. The hygiene product of claim 11, wherein the backsheet film comprises a water impermeable film.

15. The hygiene product of claim 14, wherein the high loft spundbond nonwoven layer is positioned adjacent to the water impermeable film.

16. The hygiene product of claim 10, wherein each of the first nonwoven spundbond layer and the second nonwoven spundbond layer is a high loft spundbond nonwoven layer comprising crimped multicomponent fibers.

17. The hygiene product of claim 10, wherein a bond area of the nonwoven laminate fabric is 10-15%.

18. The hygiene product of claim 10, wherein bonding zones are constituted by discrete dots, wherein further the dot area of each of the discrete dots is 1-5 mm.sup.2 or 1.5-3 mm.sup.2 and/or the dot diameter of each of the discrete dots is 0.5-1.5 mm or 0.7-1.0 mm.

19. The hygiene product of claim 18, wherein the nonwoven laminate fabric comprises 20-30 dots per cm.sup.2.

20. The method of claim 9, further comprising consolidating, using a compaction roller, the crimped spundbond fibers.

Description

[0040] 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:

[0041] FIG. 1: a schematic illustration of an apparatus for producing an SMS-type nonwoven laminate according to one embodiment of the present invention;

[0042] FIG. 2: a schematic illustration of a section of a crimped multicomponent fiber as comprised in a high loft spunbond layer of such laminate; and

[0043] FIG. 3: schematic illustrations of different possible configurations of bicomponent fibers.

[0044] FIG. 1 illustrates an apparatus for producing SMS-type nonwoven laminates of the present invention. Specifically, the machine is configured for producing an S.sub.HMMS.sub.H type laminate. It comprises, as main components, a moving belt 1, a first spinning machine 2 for forming a first high loft spunbond layer, a first meltblowing machine 3 for forming a first meltblown layer, a second meltblowing machine 4 for forming a second meltblown layer, and a second spinning machine 5 for forming a second high loft spunbond layer. Both spinning machines 2 and 5 are configured to produce bicomponent fibers, as symbolized by the two polymer reservoirs 2a, 2b and 5a, 5b, respectively, for each machine. Downstream each spinning machine 2 and 5 there is a precompaction roller 6 and 7, respectively. Downstream of the machines 2-5 and the precompaction rollers 6-7 there is a calander roll 8 for firmly bonding the layers of the laminate to each other. Reference numeral 9 designates the SAS gaps of both spinning machines 2 and 5.

[0045] FIG. 2 is a schematic illustration of a section of crimped endless fibers as present in high loft spunbond layers of a fabric of the invention. The crimped fiber sections form circles with a certain crimp radius and hence define a certain crimp area. The crimp area, for example, can be 20,000-50,000 m.sup.2, corresponding to a crimp radius of approximately 80-125 am.

[0046] FIG. 3 shows schematic illustrations of different possible configurations of bicomponent fibers. The fibers comprise first and second polymeric components arranged in distinct zones within the cross-section of the fiber that extend continuously along the length of the fiber. A side-by-side arrangement is depicted in FIG. 3a. An eccentric sheath/core arrangement is depicted in FIG. 3b, where one component fully surrounds the other but is asymmetrically located in the fiber to allow fiber crimp. The fibers can also be hollow as shown in FIG. 3c and 3d or can be multilobal fibers as shown in FIG. 3e.

[0047] A number of S.sub.H-M-M-S.sub.H laminate nonwoven sheets have been produced on a machine as shown in FIG. 1 to demonstrate the beneficial properties of laminates of the present invention. The expression S.sub.H denotes a high loft spunbond layer consisting of helically crimped side-by-side bicomponent fibers. All sheets have been prepared using a Reicofil spunbondmeltblown machine. The spunbond spinneret had approximately 5000 holes per meter. The meltblown spinneret was a single row die having 35-42 holes per inch (Reicofil Single Row Technology). In the following Table 1, an overview over the configurations of the different sheets is given.

TABLE-US-00001 TABLE 1 1.sup.st 2.sup.nd BW BW 1.sup.st S M M 2.sup.nd S M Ex. g/m.sup.2 g/m.sup.2 g/m.sup.2 g/m.sup.2 g/m.sup.2 % Bonding A 15 7.5 S 0 0 7.5 S 0 18.8% Oval B 15 7.5 S 0 0 7.5 S 0 13.6% Open Dot C 17 8.5 S.sub.H 0 0 8.8 S.sub.H 0 13.6% Open Dot D 15 6.5 S 1.0 1.0 6.5 S 13.3 13.6% Open Dot 1 15 6.6 S.sub.H 0.9 0.9 6.6 S.sub.H 12.0 13.6% Open Dot 2 15 6.7 S.sub.H 0.8 0.8 6.7 S.sub.H 10.7 13.6% Open Dot 3 15 6.8 S.sub.H 0.7 0.7 6.8 S.sub.H 9.33 13.6% Open Dot 4 17 7.6 S.sub.H 0.9 0.9 7.6 S.sub.H 10.6 13.6% Open Dot 5 17 7.7 S.sub.H 0.8 0.8 7.7 S.sub.H 9.4 13.6% Open Dot 6 17 7.8 S.sub.H 0.7 0.7 7.8 S.sub.H 8.2 13.6% Open Dot

EXAMPLES A-D ARE COMPARATIVE EXAMPLES

[0048] Example A is a regular 15 g/m.sup.2 SS nonwoven based on uncrimped fibers without meltblown layers. The calander settings were such as to obtain an 18.8% oval bond. The S layers each have a basis weight of 7.5 g/m.sup.2. The PP polymer Sabic 511A with an MFR of 25 was used for the S layers.

[0049] Example B corresponds to Example A but with different calander settings to obtain an open dot bonding with a bonding area of 13.6% and 24 dots per cm.sup.2. Each bonding point is circular and had a diameter of 0.85 mm.

[0050] Example C is 17 g/m.sup.2 S.sub.HS.sub.H spunbond nonwoven based on high loft spunbond layers having helically crimped fibers without meltblown layers. The S layers each have a basis weight of 8.5 g/m.sup.2. The helically crimped fibers of the S.sub.H layers comprised two different polymers in a 50/50 relation and side-by-side configuration. Sabic 511A was used for one side. The PP/PE random copolymer Molplen RP248R with an MFR of also 25 was used for the other side. Bonding is as in Example B.

[0051] Example D is 15 g/m.sup.2 SMMS nonwoven based on uncrimped fibers and with two meltblown layers each 1.0 g/m.sup.2. The S layers each have a basis weight of 6.5 g/m.sup.2. Bonding is again as in Examples B and C. The PP polymer Borealis HL708FB with an MFR of 800 was used for the M layers. The settings when producing the M layers were as follows: die temperature: 280 C.; air temperature 275 C.; airflow: 3200 m.sup.3/h; distance between die and spinbelt: 98 mm.

EXAMPLES 1-6 ARE INVENTIVE EXAMPLES

[0052] Example 1 is a 15 g/m.sup.2 S.sub.HMMS.sub.H spunbond nonwoven based on based on high loft spunbond layers having helically crimped fibers and with two layers of meltblown fibers sandwiched in between. The helically crimped fibers of the S.sub.H layers were as in Example C. Borealis HL708FB was used for the M layers, as in Example D. The S.sub.H layers each have a basis weight of 6.6 g/m.sup.2. The M layers each have a basis weight of 0.9 g/m.sup.2. The settings when producing the M layers were as in Example D. Bonding was as in Examples B, C and D.

[0053] The difference of Example 2 to the otherwise identical Example 1 is the area weight of the S.sub.H layers and M layers. The S.sub.H layers each have a basis weight of 6.7 g/m.sup.2. The M layers each have a basis weight of 0.8 g/m.sup.2.

[0054] The difference of Example 3 to the otherwise identical Examples 1 and 2 is the area weight of the S.sub.H layers and M layers. The S.sub.H layers each have a basis weight of 6.8 g/m.sup.2. The M layers each have a basis weight of 0.7 g/m.sup.2.

[0055] The differences of Examples 4-6 to the otherwise identical Examples 1-3 are the overall basis weights and, consequently, the basis weights of the individual layers. The overall basis weight in all Examples 4-6 is 17 g/m.sup.2. In Example 4, the S.sub.H layers each have a basis weight of 7.6 g/m.sup.2 and the M layers each have a basis weight of 0.9 g/m.sup.2. In Example 5, the S.sub.H layers each have a basis weight of 7.7 g/m.sup.2 and the M layers each have a basis weight of 0.8 g/m.sup.2. In Example 6, the S.sub.H layers each have a basis weight of 7.8 g/m.sup.2 and the M layers each have a basis weight of 0.7 g/m.sup.2.

[0056] In order to determine the fiber size for both the spunbond fibers and the meltblown fibers in each of the Examples D and 1-3, samples of each example have been analyzed by scanning electron microscopy (SEM) with a Phenom ProX machine and Fibermetric v2.1 evaluation software applying a 400 magnification for the S fibers and a 3000 magnification for the M fibers. 100 data points have been measured per example, each for spunbond and meltblown. The results are given in Table 2 below.

TABLE-US-00002 TABLE 2 Spunbond Meltblown Example Mean [m] Std. Dev. [m] Mean [m] Std. Dev. [m] D 18.1 1.19 1.71 0.591 1 17.8 1.39 1.69 0.546 2 17.0 0.963 1.55 0.479 3 16.9 0.928 1.35 0.439

[0057] All process settings for reference Example D and Examples 1-6 are the same. Only the level of meltblown fibers is different. In Example D, the level is 1 g/m.sup.2 per individual M laydown. In Examples 1-3, the level is 0.9 g/m.sup.2, 0.8 g/m.sup.2 and 0.7 g/m.sup.2 per individual M laydown, respectively. In Examples 4-6, again, the level is 0.9 g/m.sup.2, 0.8 g/m.sup.2 and 0.7 g/m.sup.2 per individual M laydown, respectively.

[0058] It can be recognized from the results that reducing the level of meltblown basis weight at otherwise constant parameters, in particular at constant airflow, will lead to a smaller fiber diameter. The mean diameter in Example D with a level of 1.0 g/m.sup.2 each is 1.71 m and becomes slightly lower with decreasing levels of 0.9 g/m.sup.2, 0.8 g/m.sup.2 and 0.7 g/m.sup.2, respectively, in the set of Examples 1-3 (1.69 m, 1.55 m, 1.35 m).

[0059] Different tests for physical properties have been carried out for each of the Examples A-D and 1-6.

[0060] The tests for hydrostatic head properties were carried out according to WSP80.6. In this test the nonwoven fabric is mounted to form a cover on a test head reservoir. The fabric is then subjected to a standardized water pressure increase at a constant rate until leakage appears on the outer surface of the nonwoven. The test results for the hydrostatic water pressure test are measured at the point where the first drops appear in three separate areas on the specimen. The rate of increase of the water pressure (height of the water column) used was 603 cm H.sub.2O/min. The test head used was a 100 cm.sup.2 test head. Reading of test result was done when three droplets appeared on the surface of the test specimen. The pressure (height of the water column) obtained in millimeters was reported.

[0061] Tensile strength in machine direction (TSMD), tensile elongation in machine direction (TEMD), tensile strength in cross-machine direction (TSCD) and tensile elongation in cross-machine direction (TECD) were measured according to WSP 110.4.

[0062] The fabric caliper was measured according to WSP 120.6.

[0063] The results are reported in Table 3 below.

TABLE-US-00003 TABLE 3 Hydro- TSMD TSCD static BW Caliper N/50 TEMD N/50 TECD head Example g/m.sup.2 mm mm % mm % mm A 15 0.18 29 40 14 50 90.4 B 15 0.22 17.5 111 9.68 151 111 C 17 0.24 20.6 109 11.5 133 117 D 15 0.22 13.8 85.9 6.00 118 167 1 15 0.26 17.6 88.2 8.63 122 194 2 15 0.24 17.3 94.7 7.90 118 192 3 15 0.23 18.2 95.0 8.72 122 211 4 17 0.23 19.2 95.8 9.8 121 205 5 17 0.24 22.8 102 10.7 124 212 6 17 0.25 21.1 98.2 10.6 131 198

[0064] The traditional spunbond-only SS nonwovens of Example A based on uncrimped fibers and bonded with an 18.8% bond area exhibited a higher value in TSMD and TSCD than the spunbond-only SS nonwovens of Examples B-C. The elongation values for Example A, on the other hand, are lower than the elongation values for Examples B-C. Both these observations are suspected to be attributable to the combined application of uncrimped fibers and a higher bond area.

[0065] Hydrostatic head of Example A was measured at 90.4 mm, which is a comparatively low value. This is believed to be attributable to a crisp material with little flexibility, in line with low elongation values, and, of course, due to the missing M layers. Example B exhibits a higher hydrostatic head value of 111 mm. It is believed that this is because the material is more flexible, as also seen in elongation values. Example C shows a still higher hydrostatic head value of 117 mm. It is believed that this is because the helically crimped individual fibers are more flexible and this emphasizes a beneficial effect of the open dot bonding on hydrostatic head.

[0066] Example D comprises a meltblown layer and hence has a much higher hydrostatic head value (167 mm) than otherwise similar Example B. Tensile strength and elongation properties are lower due to the replacement of some spunbond material with meltblown material.

[0067] All Examples 1-3 demonstrate a significantly higher hydrostatic head value when compared to Example D, even though the meltblown content is indeed lower (and the tensile strength hence higher). It is believed that the effect of the significantly higher hydrostatic head value of Examples 1-3 when compared to Example D can be attributed to the higher flexibility of the helically crimped individual fibers in combination with the open dot bonding. What can furthermore be observed when comparing Examples 1-3 to each other is that the hydrostatic head becomes slightly higher with decreasing meltblown content. This effect is believed to be attributable to the smaller average meltblown fiber diameter at decreasing level of meltblown basis weight at otherwise constant parameters, in particular at constant airflow, as reported in Table 2.

[0068] The same trend is observed for the nonwovens of Examples 4-6, which have a higher spunbond basis weight (and hence content) than the nonwovens of Examples 1-3, but are otherwise identical.

[0069] An overview on the most important findings above is given in Table 4 below, which additionally calculates a meltblown efficiency value for the individual nonwoven laminates, which is hydrostatic head (mm) of the laminates divided by overall meltblown basis weight (g/m.sup.2) of the laminates.

TABLE-US-00004 TABLE 4 Hydro- M 1.sup.st 2.sup.nd static Ex- BW 1.sup.st S M M 2.sup.nd S head efficiency ample g/m.sup.2 g/m.sup.2 g/m.sup.2 g/m.sup.2 g/m.sup.2 mm mm/(g/m.sup.2) A 15 7.5 S 0 0 7.5 S 90.4 B 15 7.5 S 0 0 7.5 S 111 C 17 8.5 S.sub.H 0 0 8.8 S.sub.H 117 D 15 6.5 S 1.0 1.0 6.5 S 167 83.5 1 15 6.6 S.sub.H 0.9 0.9 6.6 S.sub.H 194 108 2 15 6.7 S.sub.H 0.8 0.8 6.7 S.sub.H 192 120 3 15 6.8 S.sub.H 0.7 0.7 6.8 S.sub.H 211 151 4 17 7.6 S.sub.H 0.9 0.9 7.6 S.sub.H 205 114 5 17 7.7 S.sub.H 0.8 0.8 7.7 S.sub.H 212 133 6 17 7.8 S.sub.H 0.7 0.7 7.8 S.sub.H 198 141

[0070] It can be gathered from Table 4 that the meltblown efficiency values for the meltblown layers in the fabrics of the invention according to Examples 1-6 is generally and sometimes significantly above 100 mm per g/m.sup.2, whereas it is significantly below in comparative Example D. Considering that a low meltblown content can be advantageous from the standpoint of mechanical behaviour, level of softness and cost of the sheet, a high meltblown efficiency as exhibited by the inventive sheets is hence very desirable.

[0071] To summarize the findings of the examples, using the nonwoven webs of the invention have a very desirable softness characteristics due to the outer high loft spunbond layers. At the same time, the barrier properties measured as hydrostatic head have been found to be higher when compared to prior art SMS structures that have the same or even higher meltblown contents.