AU5853999A

AU5853999A - Perforated bonded fiber fabric

Info

Publication number: AU5853999A
Application number: AU58539/99A
Authority: AU
Inventors: Dieter Groitzsch; Bernhard Klein; Gerhard Schaut
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 1998-10-12
Filing date: 1999-08-23
Publication date: 2000-05-01
Anticipated expiration: 2019-08-23
Also published as: CZ20011294A3; HUP0104008A2; AU748374B2; CA2346889C; RU2184182C1; PL201698B1; AR019243A1; NO20011880L; HUP0104008A3; KR100391040B1; CN1105203C; BR9914536A; TR200101807T2; CN1326521A; SK285887B6; BG105502A; JP2002527636A; WO2000022218A1; BR9914536B1; EP1121481A1

Description

Page 1 Perforated bonded fiber fabric and method of producing same Hygiene products for absorbing body fluids, like infant diapers, incontinence pads for adults or sanitary napkins are generally composed of an absorbent core, an impermeable backsheet comprising a film or a fiber/film laminate and facing the body a permeable structured surface comprising a thin, wear-resistant, soft fiber fabric or a vacuum perforated film with funnel-shaped, i.e. three-dimensional perforations. The vacuum perforated film surrounds the absorbent core with the largest opening of the perforation being oriented outwards, i.e. towards the body. The film material is constructed from a hydrophobic thermoplastic polymer, like polyethylene, polypropylene or a copolymer of ethylene and polyvinylacetate (EVA). As a result, the surface of the film will not be wetted by the body fluid, the body fluid will only flow in the direction of the absorbent core and the inwardly tapered perforations prevent backflow, e.g. in case of application of loads, movement or pressure. It is well known that the absorbent core, besides being comprised mainly of pulp, usually also contains superabsorbent particles (SAP). Superabsorbent polymers are characterized by the fact that they can absorb aqueous fluids in large quantity and, accompanied by a marked increase in volume, form a gel body with more or less minimal gel rigidity. The advantage of having SAP present is that weight can be saved, thereby allowing a reduction in the thickness of the absorbent core, and that the fluid cannot be released again by application of loads thus effectively preventing leaks. SAP does however have the disadvantage that it leads to the well-known phenomenon of gel blocking and that this effect becomes more pronounced the higher its content.

Page 2 The term gel blocking refers to the effect whereby further transport of fluid no longer becomes possible or is slowed down considerably. This problem too was able to be resolved through suitable construction of the absorbent hygiene product. In this case bulk fiber fabrics, or other very open structures that do not lead to blockages when in contact with fluid, are positioned between the absorbent core and the cover sheet. This intermediate layer absorbs fluid immediately, i.e. spontaneously removes it from the surface of the pad and distributes it uniformly. Fluid management is improved by such measures. By fluid management we mean the interplay of many contributing factors, some of which have been described above, with the aim of achieving the highest level of comfort when the hygiene article is worn on the body. It is well known that non-perforated spunbonded fiber fabrics and staple fiber fabrics based on polyolefins are also used as the structured surface for containing the absorbent material located on the side facing the body. Fluid management of urine in the case of infant diapers and incontinence pads and of menstrual fluids for feminine hygiene is regarded as highly advanced to mature. Future pads should however not only be capable of managing urine in an optimal manner but also highly fluid exudates from the intestines. Non-perforated bonded fiber fabric topsheets have proven to be unsuitable for this purpose. The body fluid involved is a multiphase system with solid particles of various shapes and consistency and a tendency for phase separation, in particular at active surfaces or surfaces having a filtrating or separating effect. These fluids will hereinafter be referred to as intestinal fluids. It has been found that non-perforated bonded fiber fabrics are unsuitable in allowing full passage of intestinal fluids and transport to the absorbent core. Rather there is a tendency for solid and/or highly viscous components of the intestinal fluid to collect on the surface of the pad as a result of separation and in such case act as an obstructing layer to subsequently arriving body fluid of a highly fluid consistency. Both the

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1 Page 3 separation of the coarser components in itself, and the associated blockage of further fluid transport, are serious disadvantages of conventional pads. Numerous solutions have therefore been proposed for improving the management of intestinal fluids, all of which are based on the requirement that perforated topsheets (fiber fabric coversheets) be used. The perforations in this case must be unobstructed. Individual or bundles of fibers across the opening or fiber bridges of any kind have proven to be disadvantageous. Besides perforated topsheets, the construction of the pad and the design of the open structured fiber fabric located between the fiber fabric topsheet and the absorbent core need to be adapted to suit the particular consistency and associated properties of the intestinal fluid. Both numerous perforation methods as well as fiber fabrics and composite fiber fabrics are known. The creation of perforations in fiber fabrics with the aid of a water jet technique is described in EP-A-0 215 684. Rather than known screens being used as the support medium for the fibers and water jet treatment, these have instead been replaced by drainage cylinders provided with protuberances. Said protuberances are responsible for producing the unobstructed perforations. A different perforation method and perforated product are described in US 5,628,097 in which the fiber fabric is slit ultrasonically or thermally in lengthwise direction and stretched in the crosswise direction by passing it between a pair of rollers consisting of two intermeshing rollers. The melt stabilized slit locations are separated and opened into perforations. Described therein are fiber fabrics made of staple fibers and continuous filaments, meltblown fiber fabrics and composites comprising staple fibers and continuous filaments with meltblown, referred to for example as SM (Spunbond/Meltblown composite) or SMS (Spunbond/Meltblown/Spunbond). A perforated bonded fiber fabric in the area of hygiene is expected not only to manage intestinal fluids but also possess a highest possible level of whiteness or a high opacity and a high degree of softness, at least on the side facing the body.

Page 4 It is well known that both properties are dependent on the flexibility and softness of the fibers themselves used. These properties are higher the lower the titer of the fiber so it clearly lends itself to use fine, very fine, or even super fine fibers. Super fine fibers are also known as microfibers. These can be based on woven or nonwoven fabrics. Meltblown fiber fabrics too are comprised of microfibers in the size range of approx. 1 10 microns. A diaper from the manufacturer Unicharm is known having a perforated bonded fiber fabric topsheet that has been manufactured by means of the special water jet perforation method briefly described above and comprising a PP/PE spunbond composite and a PP meltblown layer. Whilst this composite plastic construction has been able to contribute to better intestinal fluid management, good softness on the meltblown side (= facing the body) and high opacity, this composite construction and the method of producing same do however also exhibit serious disadvantages. The meltblown layer makes no contribution, or only a completely insignificant one, to the overall strength or integrity of the composite. The weights are considerably higher than customary these days. A reduction in weight to below approx. 30 g/m 2 would appear impossible due to the requirement for high strength in the machine direction in the manufacture of the diaper. The high material usage is costly. The meltblown layer, regarded on its own, is not wear resistant and in addition to the water jet treatment needs to be thermally anchored to the spunbond support fiber fabric to alleviate its tendency to delaminate. This in consequence requires bicomponent fibers (conjugated fibers) with a concentric or eccentric sheath component made from a lower melting-point polymer than that of the meltblown layer. This perforated SM composite nevertheless doesn't achieve on the soft M side anywhere near the wear resistance of a spunbond PP or PP stamp-bonded staple fiber fabric as used these days in diapers and sanitary napkins. For other applications, like impermeable sleeves on training pants or fiber fabrics for operating theatres, requiring same to be wear-resistant or lint-free, only SMS can be used. 71 Page 5 With the meltblown layer on the side facing the body covered in this way, the advantages of the meltblown layer would no longer manifest themselves. From document US 4,840,829 bonded fiber fabrics with a surface weight of between 10 and 150 g/m 2 are known, which are made from staple fibers of a length of between 20 and 100 mm and a titer between 0.555 and 16.65 dtex. These bonded fiber fabrics have circular or elliptical openings, which are obtained by water jet treatment on a support provided with protuberances. Furthermore, from document W098/23804 bonded fiber fabrics and methods for their production are known, which consist of multicomponent fibers and which during their bonding into bonded fiber fabric are separated and entangled into their individual component fibers. It is object of the present invention to create a perforated bonded fiber fabric that is superior to pre-existing fiber fabrics in regard to intestinal fluid management, that meets the requirements for high opacity and greater softness and gentleness on the surface facing the body, that doesn't necessitate a dual or multilayer construction and that can function with a fiber material weight considerably below that of the perforated bonded fiber fabrics currently used in diapers and sanitary napkins. It is also object of the present invention to improve the intestinal fluid management without adversely affecting the urine management. It is a further object of the present invention to achieve fluid passage through the perforated bonded fiber fabric without the use of detergents or otherwise to reduce the quantity of same used to a fraction of the customary quantities for non perforated bonded fiber fabric coversheets. The objects of the present invention have been attained by means of a perforated bonded fiber fabric having a surface weight of 7 to 25 g/m 2 and consisting of continuous intertwined microfiber filaments with a titer that ranges from 0.05 to 0.40 dtex. Said filaments are constructed of at least two Page 6 thermoplastic polymers with different hydrophobicities and a filament cross section in pie or hollow pie form from which the split filaments have been released whereby said perforations are unobstructed and devoid of split fiber filaments. The invented fiber fabrics exhibit very high strengths despite their extremely low weights and very distinct hole structures as a result of the low fiber mass. This makes it possible to guarantee fast passage of body fluids, in particular intestinal fluids, without or with only minimal use of surface-active substances with a low surface tension (wetting agents), and to create a dry topsheet surface in diapers and sanitary napkins. Each of the different filaments has a titer in the aforementioned range. The perforations are preferably regularly arranged and each exhibit a perforation area of 0.01 to 0.60 cm 2 . The invented perforated bonded fiber fabric exhibits in preference a strike through value after one minute of less than 3 sec. The maximum tensile strength in the lengthwise direction is in preference at least 30 N/5 cm. The rewet value is in preference less than 0.5 g. To construct the fiber fabric, two different filaments made from thermoplastic polymers and having a weight ratio in the range 20:80 to 80:20 could for example be used. The construction of the fiber fabric on the basis of two filaments F1 and F2 will be elaborated on in the following. The present invention also relates to a method for producing perforated bonded fiber fabrics of this kind by depositing to form a fiber fabric, splittable pie or hollow pie continuous fibers, the cross section of which exhibits at least two different thermoplastic polymers with different hydrophobicities in an alternating cake portion arrangement, subsequent splitting and entangling of the fibers with the aid of high 41, Page 7 pressure water jets to form continuous intertwined filaments, and subsequent perforation using higher pressure water jets of the fiber fabric thus formed. Said perforation occurs in preference on drainage and perforation-forming drums exhibiting protuberances on their surface. In the following, the polymers used to produce the invented fiber fabric will first be elaborated on and then the method to produce the same. Of the two fiber polymers F1 and F2 at least one of these is hydrophobic, preferably belonging to the polyolefin series, like polyethylene, polypropylene or copolymers thereof, one of the two being present in excess. The other can be either hydrophobic or hydrophilic, but is preference not hydrophilic but instead less hydrophobic than polypropylene. The more strongly hydrophobic fiber polymer will here be designated F1 and the more weakly hydrophobic fiber polymer F2. F1 will comprise in preference polypropylene (PP) or polyethylene (PE) or blends of the two. F2 could for example be a fiber belonging to the polyester series, like polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate or a copolyester with PE thereof. Neither F1 nor F2 are subject to any other restrictions as far as polymer selection is concerned other than that they must be able to be spun to form conjugated fibers by means of the known fabric spunbonding process. One or both of F1 and F2 can consist of thermoplastic elastomers. Examples of elastic polyolefins for spunbonded fiber fabrics can be found in EP-A-O 625 221 and for metallocene catalyzed LLDPE in EP-A-O 713 546 in which are also described representatives of the weaker hydrophobic elastomers, like polyurethane, ethylene-poly butylene copolymers, poly(ethylene-butylene) styrene copolymer (Kraton), polyadipate ester and polyester elastomer (Hytrel). It is known that these elastomers can be spun into spunbonded fiber fabrics in meltblown or SMS combinations. The use of such elastomers in F1 and/or F2 increases the softness and flexibility of the perforated microfiber fabric. It also turns out that only perforated bonded fiber fabrics consisting Page 8 of continuous intertwined microfiber filaments exhibit outstanding properties in respect to fluid management. Perforated bonded fiber fabrics made of microfiber staple fibers intertwined in the same manner do not achieve these improved properties. On account of the required processing on diaper machines alone (high tensile loads in the machine direction) the weight of same would have to be tripled compared to continuous fiber fabrics, leading to marked reductions in perforation quality, flexibility, softness, wear resistance and fluid management. It is also possible to add ingredients in the form of masterbatches to the fiber polymer melt for the purpose of antistatic finishing, spin dyeing, matting, plasticizing, making adhesive and flexibilizing the fibers, increasing or decreasing their repellent properties against fluids (like water, alcohols, hydrocarbons, oils), fats and multi-disperse systems like intestinal fluids and other fluid body exudates like urine and menstrual fluids. Ingredients to change the interface tension on the surface of the microfiber can also be applied after the generation or release of the microfiber filaments in the already perforated bonded fiber fabric. Substances of this kind can for example be wetting agents dissolved in water or in dispersed form as are often applied to fiber fabric diaper topsheets these days for the purpose of better urine management. The fiber fabrics in accordance with the present invention also function in preference without such wetting agents or with only a fraction of the quantities customarily applied up to now. The design of the perforations, i.e. their hole sizes, their shape, the layout of the individual perforations with respect to one another (e.g. by constant spacing or in rows) and the total perforation area on the one hand, as well as the extremely high flexibility of the web (the area between the perforations) made from continuous intertwined microfiber filaments and said webs very low weight enable this reduction in wetting agent to the point of fully eliminating its use. RA4Z '_ 14 Page 9 The invention is further elaborated with the aid of the illustration comprising Figs. 1 to 6. Figs. 1 to 6 show the shape of the individual perforations K and their layout in the surface structure. In Fig 1, K is an ideally represented perforation in the shape of an equilateral hexagon, where the edge length a is identical to b. The distance o is the shortest distance between the center c of the perforation K and the edge a. The edges a and b are both located at a constant distance 9 from each neighboring K. Surrounding each individual perforation K can be placed a larger, equilateral hexagon with edges e and f aligned in parallel to a and b respectively. In Fig. 1, e = f. This creates a honeycomb shaped layout of the perforations K. The edges a and b of a perforation K are aligned in parallel with the respective edges a and b of the neighboring perforations K. The distance h = 0.5 g. The vertices at the contacting edges a to a and a to b are present in rounded off form in the fiber fabric. These rounded-off vertices i and j for the case where i = j are shown in Fig. 1. As a result of this rounding-off of the vertices, the original distances d to e of the hexagon are reduced to q and r. In the case of Fig. 1, q = r again. In the extreme case, all the rounded-off vertices i and j can be so strongly developed that K assumes a circular shape, as shown in Fig. 2. The perforations K in Fig. 3 differ from those in Fig. 1 only in that b is noticeably longer than a and the rounding-off of the vertex i is more marked than for j. In the extreme case, the rounding-off of the vertices i and j can be so strongly developed that an elliptical shape results from the hexagon K, as shown in Fig. 4. Hexagonal shapes of the perforations K, or such shapes derived from them by rounding off of the vertices, and the layout of the same, as shown in Fig. 1 to Fig. 4, have proven to be particularly advantageous for fluid management. In particular equilateral

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1 Lii 7 IC,j Page 10 hexagonal perforations K and rounded-off derivatives thereof, provide the bodily fluid with the shortest path from the exterior into the interior of the pad. The invention does not however restrict itself to such regular shapes and layouts. Other polygons for K and rounded-off derivatives thereof are also conceivable along with irregular layouts of such or other perforations. Less suitable however are such perforations and layouts of the same that provide cause for hindering the fast drainage through the perforation K of the exudated bodily fluid situated furthest away from the edge of the perforation. Examples of such layouts are shown in Figs. 5 and 6. The distance from the furthest removed point w to the (rounded-off) corner of the square is considerably larger than the distance h. The ratio u/h of maximum distance to the perforation K to minimum distance, should be 1/1 in the ideal case and worst case no greater than 2/1. The individual perforation areas range from 0.01 to 0.60 cm 2 , preferably between 0.04 and 0.40 cm 2 . The individual perforation openings can all be of the same shape and have a uniform area throughout. They could however differ in both or just one of these two regards whilst still adhering to the above mentioned rule of u/h smaller than/equal to 2/1. The total area of the perforations is in the range of 8 to 40%, preferably between 12 and 35%. The microfine, continuous intertwined filaments S form a frame L around the openings. The perforated bonded fiber fabric can, as previously mentioned, contain surface-active agents making it washable, delayed washable or permanently hydrophilic. These are preferably applied by means of a wet-in-wet process after water jet perforation. The applied quantity ranges from 0 to 0.60 % by weight relative to the fiber fabric weight, preferably from 0 to 0.20 %. The required dosage depends on the area of the individual perforations and the total area of the perforations. The larger both of these are, the more Page 11 the content of such surfactants can be reduced. For reasons of optimum biocompatibility, a surfactant content of 0 % was strived for. It has proven to be particularly advantageous not to distribute the surface-active agent (surfactant) evenly over the entire frame but instead to restrict it to the immediate vicinity on the periphery of a perforation. From this location will then originate a suction effect on the fluid in the direction of the perforation. The multidisperse fluid system will thereby no longer be subjected to dewatering or phase separation. Clogging of the perforations and deposition on the frame will be prevented. The fluid absorption and distribution layer inserted between the absorbent core and topsheet, adjusted to also be wetting, further promotes the immediate removal of body fluid from the surface of the pad. Production of the perforated bonded fiber fabric (topsheet) The method involves depositing a splittable pie or hollow pie fiber with the aid of fabric spinbonding technology to form a fiber fabric made from continuous filaments. The cross sections of the unsplit fibers exiting the nozzle consist of two different polymer components Fl and F2 arranged next to one another in alternating sequence like portions of a cake (normally comprising 4 to 16 such cake portions). As a prerequisite for subsequent splitting, such two components, normally differing greatly in regard to their polymer chemistry, should preferably be used as exhibiting the least possible amount of adhesion at their mutual interface. Chemically similar polymer components, like for example polyethylene terephthalate and a copolyester or polypropylene and polyethylene, can however also be used provided measures have been taken to reduce adhesion at the interfaces of both, for example by the addition of a release agent to at least one of the fiber polymer components. When the fiber to be split is provided with a (round) hollow core on the inside, this is referred to as a hollow pie fiber, otherwise as a pie fiber. The titer of the continuous filaments in the spunbonded fabric before splitting is as a rule 1.0 to 4.0 dtex. The continuous filaments of the spunbonded fabric are subsequently, in a Page 12 first treatment stage, entangled in one another and at the same time split into the pie components using known high pressure water jet technique methods (see for example EP-A-0 215 684). For a pie fiber having a titer of 1.6 dtex and a total of 16 segments, comprising 8 segments each of the two fiber polymers, after splitting there will be microfibers with a titer of 0.10 dtex present. Since the present invention involves a very light fiber fabric, it is advantageous not to use a screen or a support with perforations as the support on which to deposit the fiber fabric, but rather a completely unperforated support. By reflecting the water jets on the support, the rebound properties of the latter can be exploited thereby minimizing energy losses. Following perforation, the fiber fabric is either dried immediately or before doing so, surfactant applied for the purpose of surface hydrophilation preferably using a wet-in-wet application method. This can occur using any known method of bath impregnation, single-sided slop padding, brush application or printing. In a particular embodiment the surfactant (wetting agent) is printed on as a pattern in such a way that only the edge region of the fiber borders around the perforations are affected. This requires the production of special printing templates that have to match the perforation pattern and special control measures to maintain the contour sharpness of the wetting agent imprint during production. Example 1: A spunbonded fiber fabric with a surface weight of 13 g/m 2 , consisting entirely of a pie fiber with a fiber titer of 1.6 dtex, is deposited onto a screen. The cross section of the pie fiber consists of 8 polypropylene segments and 8 polyethylene terephthalate segments in alternation. The size of the individual polypropylene segments is chosen so that the weight fractions of polypropylene and polyethylene terephthalate are 30 and 70% respectively. -v12) Page 13 The unsplit continuous filament fiber fabric is placed onto a 100 mesh drainage screen and oriented with a water jet pressure of 180 mbar; the continuous filaments are split into their 8 microfiber segments made of polypropylene and 8 microfiber segments made of polyethylene terephthalate. After splitting, there exist the same number of microfiber segments made of polypropylene and polyethylene terephthalate. Each microfiber segment made of polypropylene has a titer of 0.06 dtex and each segment made of polyethylene terephthalate has a titer of 0.14 dtex. Converting dtex into fiber diameter (idealized to round cross section) gives a value of 2.36 micron for the polypropylene (density of 0.91 g/cm3) and a value of 4.42 micron for the polyethylene terephthalate (density of 1.37 g/cm3). After splitting the fibers by means of water jets, the structured surface is subjected to perforation again with the aid of high pressure water jets and a pressure of 70 kg/cm 2 . This is done using the drainage and perforation-forming drums with protuberances on their surface, as described in EP-A-0 215 684, instead of the customary drainage screens. After drying, a very soft, cuddly fiber fabric with clearly formed perforations is produced. The individual holes of the perforations are (ideally) circular in shape and of the same size. The layout of the holes is in an orthogonal grid with a grid spacing a, onto which is superimposed a further grid with holes in face-centered alignment. The radius r is on average 1.4 mm and the distance a = 6.0 mm. The total perforated area OF is 34 % relative to the entire surface. The maximum tensile strength in lengthwise direction as per EDANA 20.289, the liquid strike through time as per EDANA 150.3-96 and the coverstock wet back (also called rewet) as per EDANA 151.1-96 were measured on all perforated fiber fabrics.

Page 14 The strike through was repeated twice in total after successive waiting periods of 1 minute without changing the filter paper layers. The specified values are in each case the average of a total of 3 individual measurements. Results: Maximum tensile strength in lengthwise direction: 32.3 N/5 cm 1st strike through (sec) 2nd strike through (sec) 3rd strike through (sec) immediately after 1 minute after a further minute 1.82 2.42 2.44 Rewet: 0.09 g Example 2 The perforated bonded fiber fabric from example 1 was impregnated with an aqueous emulsion of a non-ionic wetting agent based on polysiloxane in a Foulard using the so called full bath method. The applied quantity of solid was 0.042 weight % after drying. The following test results were obtained for this sample: Maximum tensile strength in lengthwise direction: 30.2 N/5 cm 1st strike through (sec) 2nd strike through (sec) 3rd strike through (sec) immediately after 1 minute after a further minute 1.58 2.10 2.11 Rewet: 0.31 g Page 15 Comparative example 1: Onto a stamp-bonded fiber fabric comprising polypropylene with continuous filaments of titer 2.2 dtex and a surface weight of 10 g/m 2 was spun a meltblown layer of 20 g/m 2 . The average diameter of the microfibers making up the meltblown layer was 3.82 micron. The bonded area of the stamp-bonded fiber fabric was 5.2 %. This double-layer laminate was water jet treated as per the method described in example 1 and then perforated on a conventional 20 mesh belt screen. The total perforated area was calculated to be 18.4 %. This double-layer fiber fabric was also very soft but displayed considerable deficiencies with regard to maximum tensile strength and strike through compared to the measured test values in examples 1 and 2. Strike through and rewet were both measured on the PP meltblown side. Maximum tensile strength in lengthwise direction: 25.4 N/5 cm 1st strike through (sec) 2nd strike through (sec) 3rd strike through (sec) immediately after 1 minute after a further minute 3.81 4.92 4.96 Rewet: 0.10 g The strike through values are considerably too high for a topsheet. Comparative example 2: Onto the sample from comparative example 1 was applied 0.40% of a non-ionic wetting agent based on polysiloxane. As the measured results show, whilst the strike through value can be reduced considerably by this means, the rewet value increases disproportionately. Such a high level of rewetting cannot be accepted in a diaper.

Page 16 Results: Maximum tensile strength in lengthwise direction: 24.6 N/5 cm 1st strike through (sec) 2nd strike through (sec) 3rd strike through (sec) immediately after 1 minute after a further minute 1.23 2.35 2.40 Rewet: 2.35 g The meltblown layer gives the topsheet a high degree of softness. In the presence of a wetting agent however this meltblown layer acts like a sponge. This type of construction therefore proved to be unsuitable as a coversheet for an absorbent layer. Comparative example 3: The double-layer construction described in comparative example 1 was subjected to a water jet treatment as per example 1. The average radius r of the holes after water jet perforation was r = 1.28 mm. The distance a remained the same at a = 6.0 mm. The resultant total perforation area OF = 28.6 %.

Page 17 Results: Maximum tensile strength in lengthwise direction: 24.2 N/5 cm 1st strike through (sec) 2nd strike through (sec) 3rd strike through (sec) immediately after 1 minute after a further minute 2.93 3.78 3.84 Rewet: 0.10 g The strike through values are again too high. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that the prior art forms part of the common general knowledge in Australia

Claims

1. Perforated bonded fiber fabric with a surface weight of 8 to 17 g/m consisting of continuous intertwined microfiber filaments with a titer that ranges from 0.05 to 0.40 dtex, said filaments are constructed of at least two thermoplastic polymers with different hydrophobicities and a filament cross section in pie or hollow pie form which the split filaments have been released, whereby said perforations are unobstructed and devoid of split fiber filaments.

2. Perforated bonded fiber fabric according to claim 1, characterized in that said perforations are regularly arranged with each exhibiting a hole of area 0.01 to 0.60 2 cm2

3. Perforated bonded fiber fabric according to claim 1 or 2, characterized in that within said fiber fabric the ratio of the maximum distance of points on the surface of the fiber fabric to the nearest perforation to the minimum distance is 1:1 to 2:1.

4. Perforated bonded fiber fabric according to any one of claims 1 to 3, characterized in that the total area of the perforations is 8 to 40 %.

5. Perforated bonded fiber fabric according to any one of claims 1 to 4, characterized in that said perforated bonded fiber fabric is constructed from polyolefin and polyester filaments with a weight ratio in the range of 20:80 to 80:20.

6. Perforated bonded fiber fabric according to any one of claims 1 to 5, characterized in that said fiber fabric has been impregnated with 0 to 0.6 weight % relative to the fiber fabric weight of at least one surface-active agent. ~.4/ Page 19

7. Perforated bonded fiber fabric according to any one of claims 1 to 6, characterized in that the strike through value after one minute is less than 3 seconds, the rewet value is less than 0.5 g and the maximum tensile strength in the lengthwise direction is at least 30N/5 cm.

8. Method for producing a perforated bonded fiber fabric according to any one of claims 1 to 7 by depositing splittable pie or hollow pie continuous fibers, cross section of said fibers displaying at least two different thermoplastic polymers with different hydrophobicities in an alternating cake portion arrangement, to form a fiber fabric, subsequent splitting and entangling of the split filaments into intertwined microfibre filaments with the aid of high pressure water jets, and subsequent perforation with high pressure water jets of the fiber fabric thus formed.

9. Method according to claim 8, characterized in that the perforation occurs on drainage and perforation-forming drums which exhibit protuberances on their surface.

10. Use of perforated bonded fiber fabric according to any one of claims 1 to 7 as a topsheet in hygiene products like diapers or sanitary napkins.

11. Perforated bonded fiber fabric as hereinbefore described with reference to the accompanyingdrawings. DATED THIS 14th day of February, 2002. CARL FREUDENBERG By Its Patent Attorneys DAVIES COLLISON CAVE RA/T