SK4922001A3 - Perforated bonded fiber fabric - Google Patents

Abstract

Disclosed is a perforated bonded fiber fabric with a surface weight of 8-17g/m<2>. The inventive fabric consists of continuous intertwined microfiber filaments with a titer that ranges from 0.05 0.40 dtex. Said filaments consist of at least two different types of filaments made from thermoplastic polymers with different hydrophobicities and a fiber cross section resembling the portions of a cake. The filaments are devoid of any conglutinations or fusions, especially in the region of the perforations.

Description

Technical field

Hygiene articles absorbing body fluids, such as baby diapers, adult diapers, or sanitary napkins, are essentially comprised of an absorbent core, a foil or backing sheet / laminate, and a permeable flat face of thin and soft fleece on the body side. abrasion resistant or vacuum perforated foil with three-dimensional funnel-shaped openings. The vacuum-perforated film forms a core-absorbent shell, with the larger aperture opening facing outwards, i.e., to the body. The film material is a hydrophobic thermoplastic such as polyethylene, polypropylene, or ethylene-polyvinyl acetate (EVA) copolymer. This ensures that the surface of the film is not wetted by body fluids, body fluids are directed solely in the direction of the absorbent core, and their backward displacement, for example under load, movement or pressure, is prevented by a tapering inward. As is known, the absorbent core usually contains superabsorbent (SAP) particles in addition to the predominant pulp. Polymer superabsorbents are characterized in that they can absorb body fluids in considerable amounts, while forming a gel structure with a more or less reduced gel stability with a significant increase in volume. The presence of SAP has the advantage of saving weight and therefore reducing the thickness of the absorbent core, and that the liquid cannot be released again at, for example, pressure, and thus can largely prevent leakage. known blockage of the gel, the more the greater its proportion. By gel blocking is meant the effect that the liquid can no longer be transported, or only at a considerable slowdown. However, a suitable design of absorbent sanitary articles has also resolved this problem by placing bulky webs (nonwovens) or other very open and non-blocking structures between the absorbent core and the backing layer. means that it removes spontaneously from the surface of the diaper and distributes it evenly This measure greatly improves fluid control ······························································· · · · · · · · · · · · · · · · · · · (Fluid management). By fluid control we understand the cooperation of many of the previously mentioned factors to create the best possible comfort when wearing hygiene products on the body.

Non-perforated spunbonds and polyolefin-based staple fibers are also known to be used as flat textile layers for covering the absorbent material on the body side.

Fluid control is considered to be very advanced to overworked in the case of baby diapers and adult diapers, as well as in menstrual fluids for sanitary napkins. However, the diaper of the future should not only be able to optimally control urine but also sparse intestinal products. however, they appear inappropriate for this purpose. This body fluid is a multi-phase solid particulate system in various forms and consistencies with a tendency to phase separation, particularly on active surfaces or surfaces with filtering and separating effect. For these fluids, the term intestinal fluids is used hereinafter. It has been shown that non-perforated webs are not suitable for the intestinal fluid to leak perfectly to the absorbent core. In addition, there is a tendency that solid and highly viscous proportions of intestinal fluid due to separation are deposited on the diaper surface and the resulting layer subsequently acts as a closure for the next bodily fluid with a thin consistency Separation of coarser components and the associated blockage of further fluid transport are significant drawbacks of current diapers. Therefore, there are many solutions to improve the control of intestinal fluids, all of which are based on the assumption that perforated nonwoven fabrics must be used. It is necessary to create perforations in clean contours. Transverse reinforcements with individual fibers, fiber bundles or some fiber bridges are adversely affected. Perforated cover webs should both conform to the diaper construction and the open structure web structure sandwiched between the cover web and the absorbent core to the properties of the intestinal fluid.

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BACKGROUND OF THE INVENTION

As with many perforation methods, several types of nonwoven and composite webs are known. EP-A-0 215 684 discloses the perforation of the webs using the water jet technique. Known sieves, which are replaced by dewatering rollers with ridges (spines), are not used to store the fibers in the waterjet treatment. Their purpose is to create clean perforations U.S. Pat. No. 5,628,097 discloses another perforation method and its products in which the web is longitudinally sonicated or thermally dissected and expanded laterally by passing through one of a pair of rollers formed by two interlocking raster calenders. Welds and open as perforations Described are nonwoven fabrics of staple fibers and filaments, meltblown fleece and composite products of staple fibers and filaments with meltblown, referred to as SM (spunbond / meltblown composite) or SMS (spunbond / composite) meltblown / spunbond)

In the hygiene field, the perforated fleece is required not only to control intestinal fluids but also to provide the highest whiteness and good hiding power and very high softness at least on the side facing the body. It is known that both properties depend on the flexibility and softness of the fibers used. This is the higher the lower the fiber titer, so it is possible to use fine, finest or even ultra-fine fibers. Ultrafine fibers are also referred to as microfibers. They can be used in fabrics and nonwovens. Also, the meltblown webs are microfibers in the range of about 1 to 10 μιη.

A baby diaper of Unicharm is known, covered with a perforated nonwoven fabric produced according to the above-described special method of special water jet perforation and consisting of a composite spunbond PP / PE and a meltblown PP layer. Indeed, this composite construction provides better intestinal fluid control, good softness on the body-facing meltblown side and high hiding power. However, this composite construction and its method of manufacture exhibit significant drawbacks. The meltblown layer does not contribute (or only slightly) to the overall strength or compactness of the system, respectively. Weights are well above today's usual values Weight reduction below about 30 g / m ² for high temperatures It is not possible to make high demands on the mechanical production of diapers. Considerable material consumption increases costs. The Meltblown layer is not abrasion-resistant in itself and must still be anchored in the spunbonded nonwoven prior to perforation with a water jet to prevent delamination. This in turn requires bicomponent fibers with a central or eccentric sheath component of a polymer set at a lower temperature than the meltblown layer. Nevertheless, this perforated SM system on the soft meltblown side does not nearly reach the abrasion strength of the spunbond-PP or staple fiber fleece associated with the PP screen roller, which is now used in both diapers and sanitary napkins. For applications other than sealed diaper cuffs or OP non-woven fabrics where abrasion resistance or non-loose textile dust is required, only SMS can be used. With similar coverings of the meltblown layer on the body side, the advantages of the meltblown layer would no longer be apparent.

U.S. Pat. No. 4,840,829 discloses webs having a basis weight of 10 to 150 g / m ² , made from staple fibers of a length of 20 to 100 mm and a titre of from 0.555 to 16.65 dtex. These webs have circular or elliptical perforations, which are obtained by treatment with water rays on the mandrel substrate.

in

Furthermore, WO 98/23804 discloses reinforced webs and a process for making them, consisting of multicomponent fibers which, when stiffened to a non-woven fabric, are fiberized into individual constituent fibers while being coiled.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION It is an object of the present invention to provide a perforated web that is superior to the prior art webs in controlling intestinal fluids, meets the requirements for high capacity and higher whiteness and fineness on the body side, makes two- or multilayer systems unnecessary. weight of perforated webs today for diapers and sanitary napkins used. Another object of the invention is to improve intestinal fluid control without impairing urinary control. In addition, it is an object of the present invention to provide a fluid passage through a perforated nonwoven fabric without the use of surfactants, as described herein. Or reduce their amount to a fraction of the amount present in unperforated coated webs common.

According to the invention, these tasks are achieved by a perforated web of intertwined filaments having a basis weight of 7 to 25 g / m ² of intertwined interwoven filaments of microfibers with a titre in the range of 0.05 to 0.40 dtex, made of at least two thermoplastic polymers having a different hydrophobicity and having a fiber cross-section in the form of pie or hollow-pie from which it is possible to release the chopped fibers, the perforations being cleanly formed and free of the chopped fibers.

The webs according to the invention exhibit very high strength characteristics despite the extremely low weight and, due to the low fiber mass, also a very clean opening structure. It is therefore possible to ensure rapid passage of body fluids, especially intestinal fluids, without low surfactant surfactants. cover web for diapers and sanitary napkins.

However, the different fibers exhibit a titer in the above range. Perforations, each having a surface area of 0.01 to 0.60 cm ² , are preferably spaced regularly.

The perforated web of the present invention preferably exhibits a strikethrough value of 1 minute below 3 seconds. The maximum tensile force in the longitudinal direction is preferably at least 30 N / 5 cm. The rewet value is preferably below 0.5 g

For example, two different thermoplastic polymer fibers in a weight ratio of 20 can be used to prepare the web. 80 to 80: 20. The following explains the production of a non-woven fabric F1 and F2.

The invention also relates to a process for the production of similar perforated webs by processing into pie or hollow-pie filament webs in which the cross-sections contain at least two different thermoplastic polymers. · With different hydrophobicity in the arrangement of alternating slits cake, followed by splitting and entangling the fibers into entangled filaments by means of high pressure water rays and subsequent perforation of the web formed by high pressure water rays.

In this case, the perforation takes place preferably on drainage and punching drums provided with mandrels on the surface.

Next, the polymers used to produce the nonwoven fabrics of the present invention, and then the respective manufacturing processes, are mentioned first.

Of the two fiber-shaped polymers F1 and F2, at least one is hydrophobic and preferably belongs to polyolefins such as polyethylene, polypropylene or copolymers thereof, one of which is in excess. The second polymer may be hydrophobic as well as hydrophilic, but it is preferred that it is not hydrophilic but less hydrophobic than polypropylene. The stronger hydrophobic polymer fiber will be referred to herein as F1 and the weaker hydrophobic as F2. F1 may preferably be of polypropylene (PP) or polyethylene (PE), or both. For example, F 2 may be a fiber from the group of polyesters such as polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, or a copolymer thereof with polyethylene. Otherwise, F1 and F2 are not subject to any restrictions in the choice of polymer, except that they can be coupled to bicomponent fibers in a known manner.

The filaments F1 and F2 may also be both or one of the thermoplastic elastomers. Examples of elastic polyolefins for spunbonded fiber webs can be found in EP-A-0 625 221 and for metallocene catalyzed LLDPE in EP-A-0 713 546, which also discloses representatives of weaker hydrophobic elastomers such as polyurethanes, ethylene-butylene copolymers. , poly (ethylene-butylene) -styrene (Kraton) copolymer, adipate polyester and elastomeric polyether ester (Hytrel). These elastomers are known to be spunbonded in combination with meltblown or SMS. The use of such elastomers in the fibers F1 and / or F2 increases the softness and flexibility of the perforated microfiber webs. In addition, it has been shown that only the perforated webs of intertwined microfibre filaments interconnect each other. Perforated webs of equally intertwined microfibre staples do not exhibit these improved properties. ujú ujú ujú ujú ujú ujú ujú ujú ujú ujú ujú ujú ujú ujú Per Per With regard to processing on diaper machines (high demands on tensile strength in the machine direction), their weight would have to triple on average compared to continuous filament webs, leading to a significant deterioration in perforation quality, flexibility, softness, abrasion resistance and fluid control.

It is also possible to add polymer fiber melt additives in the form of parent polymer blends to impart antistatic properties, additive dyeing, matting, softening, tackiness and fiber flexibility, increasing and reducing non-wettability to liquids (water, alcohols, hydrocarbons, oils), greases and a multidisperse system such as intestinal fluids and other liquid body secretions such as urine and menstrual blood.

The interfacial tension-altering additives on the microfiber surfaces can additionally be applied after the microfiber fibers have been formed or released in the already perforated web. Such substances are, for example, wetting agents dissolved in water or in dispersed form, with which many spunbonds having a covering function in diapers are already treated in order to better control the urine.

The webs according to the invention, however, are preferably sufficient without such wetting agents, possibly with only a small fraction of the amounts usually applied so far. The perforations, i.e. the size of the holes, their shape, the arrangement of the individual perforations with each other (e.g. in a row or with gaps) and with respect to the open area, as well as the extremely high flexibility in the space between perforations of interwoven microfibers and very low weight this reduction in the amount of wetting agent used up to 100% savings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1 to 6 complete the explanation of the invention.

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Figures 1 to 6 show the shape of the individual holes K and their arrangement in plan view. Figure 1 is an idealized shown hole in the form of an equilateral hexagon in which the side length a is the same as b The distance o is the shortest distance edge and. The edges a and b have a constant distance g from each adjacent K A larger equilateral hexagon with sides e and f can now be formed around the individual openings K. In Figure 1, e = f. This results in a honeycomb arrangement of the openings K The edges a and b of the opening K are now parallel to the adjacent edges a and b of the adjacent openings K. The distance h = 0.59. The vertices of the touching sides a and a and b respectively are rounded in the web. These rounds of i and j peaks are presented in Figure 1 for case i = j. These roundings shorten the original distances d and e in the hexagon to q and r In the case of Figure 1 again q = r

In the extreme case, the radiuses i and j can extend so much that the opening K becomes circular in shape, as shown in Figure 2.

The apertures to Figure 3 differ from the apertures in Figure 1 only in that b is significantly longer than a and the rounding i is more pronounced than j.

The radiuses i and j can, in extreme cases, expand so much that an elliptical shape is formed from the hexagon K, as shown in Figure 4.

The hexagonal shapes of the orifices K or those which arise therefrom and their assemblies as shown in Figures 1 to 4 have proved to be particularly advantageous for fluid control. Especially in the case of openings K in the shape of equilateral hexagons and their drains with rounded peaks, body fluid will always find the shortest path from the diaper surface to its interior.

However, the invention is not limited to such regular forms and arrangements. Other polygons and their rounded derivatives as well as the irregular spacing of such or other openings are conceivable for K. However, such apertures and their arrangement are less suitable that the part of the excreted body fluid that is furthest from the edge of the aperture interferes with rapid aperture through the aperture.

K. Such arrangements are shown, for example, in Figures 5 and 6.

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The distance of the furthest point w to the rounded apex of the quadrilateral is significantly greater than the distance h. The ratio u / h, i.e. the maximum distance to the opening K to the minimum distance should ideally be 1/1 and in the worst case not exceed 2/1.

The area of the individual perforation is in the range of 0.01 to 0.60 cm ² , preferably between 0.04 to 0.40 cm ² . The individual holes of the perforations may all have the same shape and uniformly the same perforation area. Also, however, the area and shape may be different or only different in shape or area, provided that an u / h ratio of less than 2/1 or the same is maintained.

The open area of the perforation is in the range of 8 to 40%, preferably between 12 to 40%

5%.

The micro-fine interwoven filaments S form a frame L of the perforations. As mentioned above, the perforated web may comprise surfactants which impart a washable, delayed washable or permanent hydrophilic nature to it. They are conveniently applied after perforation with a water jet in a wet process. The amount applied is 0 to 0.60% by weight of the web, preferably between 0 and 0.30%

0.20%. The dosage depends on the surfaces of the perforations and the overall rpm • · Vorenus ^{in the} area so that the two values, the greater the possible content of these surfactants reduce. For environmental reasons, a detergent content of 0% is sought

It has proven to be particularly advantageous if the surfactant does not spread evenly over the entire perforation frame but is limited to the immediate vicinity of the perforation edge. From this point it then exerts a forced suction effect on the fluids towards the perforation. Thereafter, the multi-dispersion fluid system does not dewater and phase separate. This prevents the perforations from clogging and settling on them. The fluid absorbing and distributing layer positioned between the absorbent core and the cover web, which is also wetted by them, then promotes the immediate removal of body fluids from the diaper surface.

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Production of perforated fleece (topsheet)

The method consists in processing the pie-fiber cleavable fiber into a spunbond of filaments. The cross sections of the uncleaved fibers exiting the nozzle consist of two different polymer components F1 and F2, which alternate in sequence as round cake slices (normally 4 to 16 such slices). In the interest of downstream cleavage, it is preferable to use those (mostly two) polymeric and chemically strongly different components which exhibit as little adhesion to each other on the common interface as possible. However, chemically similar polymeric components such as polyethylene terephthalate and copolyester or polypropylene and polyethylene may be used provided that the adherence to the bonding surfaces of the two is reduced, for example by adding a separator to at least one polymeric fiber component. and on the cross-section of a round space, we are talking about pie-fiber (hollowpie-fiber).

As a rule, the spunbond filament titer in the spunbond is 1.0 to 4.0 dtex, preferably 1.6 to 3.3 dtex, before splitting. water jet under pressure (see, for example, EP-A-0.21 5.684). In the case of cake fibers with a titre

Thus, 1.6 dtex with 16 segments, composed of 8 segments for each of the two polymers, will therefore produce microfibers having a titer of 0.10 dtex upon cleavage. Since the web according to the invention is a very light web, it is preferable not to use a web or perforated substrate, but a non-perforated substrate as the substrate on which the web is laid. Thus, by reflecting water rays on this substrate, it is possible to utilize its elasticity and thereby minimize energy loss.

The perforation is followed by drying, or preferably, and preferably, prior to wet drying, a surfactant may be applied for surface hydrophilization. This is done by known methods, dipping, painting and printing. In a particular embodiment, the surfactant is printed according to a template so that only the border regions of the fibrous frame of the perforations are suppressed. To · · · I · I I I I I I I I I I I I I I I I I I I I I I · It requires special printing templates that must conform to the perforation pattern as well as special control measures to achieve sharp surfactant contours in this operation.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

Spunbond with a basis weight of 13 g / m ² consisting of 100% pie-fiber with a titre of 1.6 dtex is placed on a sieve. The cross-sectional pie-fiber consists of 8 propylene segments and 8 polyethylene terephthalate segments alternately. The size of the individual polypropylene segments is selected such that the weight proportion of polypropylene is 30% and the weight proportion of polyethylene terephthalate is 70%.

The uncleaved filament web is deposited on a 100 mesh dewatering screen and compacted under 180 mbar water pressure, splitting the filament into 8 polypropylene microfibre elements and 8 polyethylene terephthalate microfibre elements.

After cleavage, the same amount of polypropylene segments is now formed as the polyethylene terephthalate microfibers The polypropylene fiber segments exhibit a titer of 0.06 dtex and the polyethylene terephthalate microfibre segments have a titer of 0.14 dtex. Conversion of dtex to fiber diameter (idealized to circular diameter) gives polypropylene (density 0.91 g / cm -1) a diameter value

2.36 pm and for polyethylene terephthalate (density 1.37 g / cm ³ ) 4.42 pm.

After the fibers have been split with water rays, the flattened web is also perforated by high pressure water rays under a pressure of 70 kg / cm ² . In this case, drainage and perforation drums according to EP-A-0 215 684 with mandrels on the drum surface are used instead of otherwise conventional drainage screens.

After drying, a very soft adhesive fleece with purely shaped perforations is formed. The individual perforations have all (idealized) circular circumference and the same size. The perforations are arranged in a rectangular grid with a spacing of: · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Individual perforations and which are then overlapped by another perforated grid so as to overlap the perforations. The perforation radius r is on average

The open area OF represents 34% of the total area

The functional parameters of the perforated web were measured, namely the highest pulling force in the longitudinal direction according to EDANA 20 289, the liquid strike through team (EDANA 150,3 - 96) and the capacity characteristic of the coverstock wet back (also called rewet) according to EDANA 151, 1 - 96.

The strike through parameter was measured twice more after a waiting time of 1 minute without changing the filter paper layer. The measured values are now mean values from a total of 3 measurements.

The results :

Maximum tensile force in the longitudinal direction: 32.3 N / 5 cm

2 strike through (sec) 3.strike through (sec) 2 strike through (sec) immediately after 1 minute after another 1 minute 1.82 2.42 2.44

Rewet 0,09 g

Example 2

The perforated web of Example 1 was soaked in fulard by immersion in an aqueous emulsion of a non-ionic polysiloxane-based detergent. After drying, the applied amount of reagent was found to be 0.042% by weight. The following experimental results were obtained with this sample

Highest tensile force in longitudinal direction: 30.2 N / 5 cm ················· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·

2 .strike through (sec) 3.strike through (sec) 2 strike through (sec) immediately after 1 minute after another 1 minute 1.58 2.10 2.11

Rewet: 0.3 1 g

Comparative Example 1

A spunbond of polypropylene having a filament of 2.2 dtex titer with a basis weight of 10 g / m ² bonded to the screened roller formed a spunbond layer of meltblown with a basis weight of 20 g / m ² . The average diameter of the microfibers in the meltblown layer was 3.82 pm. The welded area of the spunbond thus bonded was 5.2%.

The bilayer laminate was solidified by a pressurized water jet as described in Example I and subsequently perforated on a conventional 20 mesh web. An open area of 18.4% was found by calculation. This two-layer web was also very soft, but showed significant drawbacks in terms of the highest tensile strength and strike through compared to the measured experimental values in Examples 1 and 2. Strike through and rewet were measured on the meltblown side of the polypropylene layer.

Maximum tensile force in longitudinal direction: 25.4 N / 5 cm.

2.strike through (sec) 1 strike through (sec) 2.strike through (sec) immediately after 1 minute after another 1 minute 3.81 4.92 4.96

Rewet · 0.10 g

The strike through values are significantly too high for the cover fleece.

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Comparative Example 2

0.40% of a non-ionic polysiloxane-based humectant was applied to the sample of Comparative Example 1. As the measurement results show, the strike through can be significantly reduced, but the rewet value is increased disproportionately.

Such high rewet values cannot be accepted for diapers.

The results :

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Maximum tensile force in longitudinal direction · 24.6 N / 5 cm

2 strike through (sec) 3.strike through (sec) 2 strike through (sec) immediately after 1 minute after another 1 minute 1.23 2.35 2.40

Rewet 2.35 g

The meltblown layer gives the fleece top cover a high softness. However, in the presence of a wetting agent, this meltblown layer functions as a sponge. This construction therefore appears to be unsuitable as a covering web on the layer.

Comparative Example 3

The bilayer system described in Comparative Example 1 was subjected to a water jet treatment as in Example 1

The average radius r of the perforations was, after water jet perforation, r = 1.28 mm. The spacing of the perforations was unchanged and was a = 6.0 mm.

An open area OF = 28.6% was found.

The results:

Highest tensile force in the longitudinal direction · 24.2 N / 5 cm · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ··· ··

2.strike through (sec) 3.strike through (sec) 2.strike through (sec) immediately after 1 minute after another 1 minute 2.93 3.78 3.84

Rewet: 0.10 g

Again, strike through values are too high

Claims (1)

PATENT CLAIMS Perforated fleece with a basis weight of 8 to 17 g / m ² from each other4. 4th 5th 5th microfibre knitted filaments with a titre ranging from 0,05 to 0,40 dtex, consisting of at least two thermoplastic polymers of different hydrophobicity and having a cross-section of the pie or hollowpie fiber from which the filaments are released wherein the perforations are cleanly formed and free of split fibers Perforated fleece according to claim 1, characterized in that the perforations are regularly arranged and the area of the individual perforation is 0.01 to 0.60 cm ² Perforated web according to claim 1 or 2, characterized in that in the web the ratio of the maximum distance of the points on the web surface to the nearest perforation and their minimum distance is 1: 1 to 2: 1. Perforated fleece according to claims 1 to 3, characterized in that the open area of the perforation is 8 to 40%. Perforated web according to claims 1 to 4, characterized in that in the perforated web there are polyolefin and polyester fibers in a weight ratio ranging from 20: 80 to 80. 20 Perforated web according to claims 1 to 5, characterized in that the web is impregnated with at least one surfactant in an amount that is in a ratio of 0 to 0.60% to the weight of the web. ··················································· · · · · · · · Ί. The perforated web of claims 1 to 6, wherein the strike through value is below 3 seconds after one minute, the rewet value is less than 0.59 and the maximum tensile force in the longitudinal direction is at least 30 N / 5 cm. Method for producing a perforated web according to one of Claims 1 to 7, characterized in that it comprises processing a web of fissile pie or hollow-pie filaments whose cross section has at least two different thermoplastic polymers of different hydrophobicity alternately embossed in a manner of cutting the cake, then splitting and intertwining the fissile fibers into intertwined microfibre fibers by means of high pressure water rays, and then perforating the formed webs with high pressure water rays Method according to claim 8, characterized in that the perforation takes place on drainage and punching drums which have mandrels on their surface. Use of a perforated web as claimed in any one of claims 1 to 7 as a topsheet in sanitary articles such as diapers and sanitary napkins.