Classifications

• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/70—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres
  • D04H1/74—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being orientated, e.g. in parallel (anisotropic fleeces)
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/425—Cellulose series
  • D04H1/4258—Regenerated cellulose series
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4266—Natural fibres not provided for in group D04H1/425
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4282—Addition polymers
  • D04H1/4291—Olefin series
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4326—Condensation or reaction polymers
  • D04H1/435—Polyesters
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/44—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties the fleeces or layers being consolidated by mechanical means, e.g. by rolling
  • D04H1/46—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties the fleeces or layers being consolidated by mechanical means, e.g. by rolling by needling or like operations to cause entanglement of fibres
  • D04H1/492—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties the fleeces or layers being consolidated by mechanical means, e.g. by rolling by needling or like operations to cause entanglement of fibres by fluid jet
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/70—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres
  • D04H1/76—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres otherwise than in a plane, e.g. in a tubular way
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H18/00—Needling machines
  • D04H18/04—Needling machines with water jets

Definitions

• This invention relates to cleaning articles, substrates therefor, and a process for the manufacture of such substrates.
• the invention has particular application to substrates which are to be used to produce so-called wet wipes, i.e. small sheets, moistened with a liquid having cleansing or other relevant properties.
• Such wipes are sold, for example, in the form of baby wipes, adult incontinent wipes, and facial/skin cleaning wipes.
• the invention is also applicable to other forms of product used for cleaning areas of the human person, for example moist toilet paper and dry wipes, and is also applicable to wipes intended for cleaning other surfaces, for example kitchen and bathroom surfaces, and surfaces which require cleaning in industry, for example surfaces of machinery or of automobiles.
• some, though not all, of the advantages afforded by the present invention and embodiments thereof are relevant to cleaning such inanimate surfaces.
• Wet wipes commonly comprise a substrate of a non ⁇ woven fibrous material, wetted by a suitable liquid.
• the non- woven substrate material is formed to have a high strength. Some limitations may be imposed on the strength of the substrate if it is desired that its density should be low enough to permit the presence of pores in which a significant amount of the wetting liquid can be held. However, this is not much of a limitation, and it may be no limitation at all, since all or most of the wetting liquid can be held by virtue of the strongly hydrophilic surfaces of the fibres, rather than by the capillary action of any open pores between the fibres. This is true, for example in the case of cellulose/pulp air laid tissues.
• a known wet wipe substrate will have a breaking tensile strength of about 50 or 60 N in MD and about 8N in CD, where MD and CD refer to machine direction (i.e. the direction of travel of the substrate through the machine which is producing it) and cross direction (a direction in the plane of the substrate and at 90_ to machine direction) .
• a web of fibres for example a carded web, travels beneath at least one array of orifices, and preferably a plurality of from successive arrays, from which jets of water are emitted.
• Each array extends transversely with respect to the path of travel of the web, and provides a large number of closely spaced jets.
• jets act like sharp needles, and entangle the fibres to form a substrate. This entanglement holds the fibres in a coherent substrate, without the need for adhesives or thermal bonding.
• the orifices typically have a diameter of from about 80 to about 180 micrometers, preferably about 90 to 150 micrometers, and there may typically be from about 800 to 1700 nozzles per metre of orifice array.
• the water is supplied to the orifice arrays at a pressure which generally increases stepwise from the first array, where it may be as little as 30 bar, to the last array, where it may be as much as about 250 bar. This stepwise increase is provided to allow for the fact that the fibres are progressively more and more difficult to move as entanglement proceeds.
• the total energy supplied to the web by the liquid jets from all the orifice arrays combined is 0.5 to 1.0 kWh/kg of fibre material.
• wet wipes can be produced which have superior properties to known wet wipes, both as regards as their cleaning ability and as regards the softness which the user perceives them to have, if the substrate is one which is significantly less strong than the substrates of known wet wipes, and provided certain other conditions are fulfilled.
• the lower strength can be achieved by reducing total energy input of liquid jets.
• the water can be replaced by another liquid, or by a gas, for example air or steam.
• the fluid "needles” can be replaced by mechanical needles, in a process known as needlepunching.
• needlepunching In this barbed needles, e.g. of steel, are punched through the web, hooking tufts of fibres across it and thereby bonding it in the needlepunched areas. The needles enter and leave the web while it is trapped between two plates, the web being pulled through the apparatus by draw rolls.
• thermal bonding in which the fibres are of thermoplastic material, or have an outer layer of thermoplastic material, and are bonded together in discrete spots by heat.
• This bonding can be achieved using a drum which has at least one heating element in the interior thereof, and which has an exterior surface carrying an embossed pattern with which the fibrous layer is pressed into contact.
• a substrate produced in this way is unlikely to be as soft as one produced by hydrogentangling, or needlepunching, and may have a substantially proportion of completely loose fibres.
• Yet another method involves wet-laying a mixture of fibres and chemical binder, somewhat in the manner employed, for example, in paper making.
• Needlepunching, thermal bonding, and wet-laying are all well known per se and will therefore not be described in detail below.
• Hydroentangling is also well known per se, but is described further below, because it is the preferred method and for the purpose of mentioning a number of modifications to the hydrogentangling procedure as it is usually practised.
• a non-woven fibrous substrate for use in a cleaning article, wherein the substrate has a major surface for rubbing on a surface to be cleaned, a low strength in at least one direction, and comprises at least a proportion of long fibres which are capable of protruding from the said major surface as a result of said rubbing whilst remaining attached to the substrate.
• the substrate, as made has a toughness of less than 0.6Nm in at least one direction, more preferably not more than 0.5 Nm.
• the toughness is preferably less than 1.2 Nm in each of two mutually perpendicular directions.
• the tensile strength is preferably not more than 45 N.
• the toughness is preferably reduced by at least 15%, and is preferably less than 0.5 Nm, in at least one direction, and less than 0.6 in each of two mutually perpendicular directions, the tensile strength after rubbing is preferably not more than ION in at least one direction, and not more than 3ON in each of two mutually perpendicular directions.
• the invention further provides a wet wipe comprising a substrate as aforesaid and a cleaning liquid.
• the invention also provides a method of producing a non-woven, fibrous substrate for use in a cleaning article, and having a major surface for rubbing on a surface to be cleaned, wherein a fibrous layer comprising fibres of which at least a proportion are long fibres, is subjected to hydroentangling by means of jets of liquid which apply to the fibrous layer a force sufficient to produce a coherent substrate but low enough for at least some of said long fibres to be capable of protruding from said major surface as a result of said rubbing, whilst remaining attached to the substrate.
• a substrate according to the invention must thus possess two significant characteristics identified as (a) and (b) below, and should desirably possess two others, identified as (c) and (d) . These are:
• the low strength may be in MD or CD or both.
• At least a certain proportion of the fibres are sufficiently long that even though they extend from the surface plane of the substrate as a result of the friction produced by rubbing, they nevertheless remain attached to the body of the substrate.
• substantially all the fibres are long fibres. Such fibres can either remain attached at one end, with the other end extending from the substrate surface, or they can remain attached at both ends, but have a central portion extending from the substrate surface.
• the fibres referred to herein as "long” have a length of at least 2cm, normally from 2 to 6cm, and more preferably at least 3cm, normally from 3 to 5cm.
• the tensile strength should therefore preferably not exceed 30cN, and more preferably should not exceed 20cN.
• the substrate is to be used for an article, such as a wet wipe, containing a cleaning liquid which is either an aqueous solution or an emulsion in which the continuous phase is aqueous
• a cleaning liquid which is either an aqueous solution or an emulsion in which the continuous phase is aqueous
• the desired effect may be achieved if those fibres are hydrophobic, and thus resist the absorption of the cleaning liquid which the wet wipe contains.
• Fibre materials which have suitably hydrophobic properties include polyolefins such as polypropylene and polyethylene, polyamides such as nylon, and polyethylene terephthalate.
• the fibres could be caused to protrude from the surface of the substrate by their being hydrophilic, and suitable fibre materials for this purpose include viscose fibres and cotton fibres.
• suitable fibre materials for this purpose include viscose fibres and cotton fibres.
• the cleaning liquid is a silicone emulsion, in which case the fibres must be such as will continue to protrude from the substrate in the presence of such an emulsion.
• Figure 1 is a diagrammatic perspective view of an example of an apparatus which can be used to produce a substrate according to the present invention, using hydroentangling;
• Figure 2 is a set of graphs showing the strength of various substrates, some according to the invention and some not;
• Figures 2 and 3 are photographs with a 1.75:1 magnification, showing a substrate according to the invention before and after rubbing;
• Figures 6 and 5 are cross section, magnified x25, through a substrate according to the invention and a comparative substrate;
• Figures 6a to 6f are graphs generated by an Instron machine test (described further below) of various substrates.
• Figure 7 shows a Lissajous curve, referred to below in connection with a rubbing test referred to below.
• the apparatus 10 shown in Figure 1 comprises a continuous belt 12, on the upper run of which the hydrogentangling process takes place. As viewed in Figure 1, the upper run travels in a rightward direction and preferably does so at a speed of 25-75 m/min, more preferably 40-60 m/min.
• the belt is apertured, as described in more detail below.
• a layer of fibres 14, such as a nonwoven batt or other initial fibrous layer is fed on to the belt, as indicated diagrammatically by arrow 16.
• the initial fibrous layer may consist of any suitable web, mat or batt of loose fibres, disposed in random relationship with one another, or in any degree of alignment, such as might be produced by carding or the like.
• the initial fibrous layer may be made by any desired technique, such as by carding, random laydown, air or slurry deposition or the like.
• Each array extends transversely across the line of travel of the belt 12 and fibrous layer 14. In the drawing, five such arrays 18 are shown, but it must be emphasised that the number of arrays could be more or less than this, say from 2 to 15. There might be only a single nozzle array, but a plurality is preferable.
• Each array 18 has a perforated plate on the underside thereof in which is formed at least one row of orifices. Typically, there is a single row or a pair of parallel rows, and where there is a pair of rows the orifices in one row may be staggered with respect to the orifices in the other row.
• the row, or each row, as the case may be, runs parallel to the length of the array 18.
• the orifices used in one preferred form of the present invention have a diameter of from 100-120 micrometers, and are arranged, for example, at about 0.6mm centres.
• Water is fed to the arrays via a high pressure line 20 and individual pressure regulators 22, one per array.
• the pressure can differ from array to array.
• the pressure may increase stepwise from one array to the next, as considered from the upstream end to the downstream end of the belt.
• the sum total of the pressure applied to individual arrays is preferably from 40-1100 bars, more preferably from 40-200 bars.
• the water flow rate through each array is preferably from 2-5 m 3 /hr for each metre length of the array.
• the flow velocity of each water jet is from 40 to 110 m/sec, more preferably from 40 to 100 m/sec, and the energy flow per water jet is preferably from 300-14000 bars.m/sec, more preferably at least 800 bars.m/sec.
• the total power input to the web from all the arrays combined is preferably from 1.0-120 kW/ of web width, and is more preferably not more than 100 kW/m.
• the total energy input to the web is preferably from 0.005 to 0.8 kWh/kg of material, and preferably less than 0.5 kWh/kg. More preferably it is in a range of from 0.1 to less than 0.5 kWh/kg. Still more preferably the upper limit of this range is 0.4 or 0.3, and the lower limit of the range may be 0.2.
• Vacuum boxes 24, one for each array 18, are provided beneath the belt, for the purpose of taking away the water after it has passed through the belt.
• the belt is in the form of a wire grid, preferably a rectangular, and, more preferably, square, grid, defining a corresponding array of apertures.
• a grid may be used in which there are from 12 to 30 apertures per cm 2 , preferably from 20 to 30 apertures per cm 2 , it must be understood, however, that finer or coarser grids may be used, and that the apertures may be arranged in ways which do not constitute square or rectangular grids.
• the water is used to supply an amount of energy which is low compared to that conventionally used, though sufficient to effect hydroentangling.
• One effect of this is that the substrate thus formed does not have openings extending through it even at the locations where, during its formation, it is immediately above the wire crossing points in the belt, at least as regards a substantial proportion of those locations.
• not more than 50% of the locations form open apertures, and more preferably not more than 30%.
• at least a few percent of the locations will provide open apertures, say at least 5%.
• the substrate consists of areas of reduced thickness formed above the wire crossing points and ridges elsewhere.
• the absence of large numbers of openings in the substrate is an advantage where, for example, it is to be used as the substrate for a wet wipe. If many openings were present these could permit dirt and other undesirable materials to pass through the substrate from the surface being cleaned to, for example, the hand of the user.
• the existence of the above mentioned ridges in the substrate has at least two significant advantages. One is that it increases the caliper of the substrate material without a proportionate increase in the amount of material required to make it. The other is that the ridges form initiation areas where friction produced during rubbing can start the partial break-up of the surface of the substrate, with the attendant desirable effects already described.
• the amount, and nature, of the entangling produced by the water jets depends, inter alia on the belt speed and the direction of the jets.
• the direction of belt travel (MD) as the y direction the direction transverse thereto in the plane of the belt (CD) as the x direction, and the direction perpendicular to the plane of the belt as the z direction, the greater the difference between the component of belt velocity in the x or y direction, and the component of jet velocity in the same direction, the greater will be the entangling effect in that direction.
• the respective strength in these two directions can be altered by angling the jets upstream (increasing the y direction entangling) , downstream (decreasing the y direction entangling) , laterally (increasing the x direction entangling), or in some combination thereof.
• the jets can be angled upstream or downstream by up to 45_ with respect to the normal to the belt, and/or laterally by up to 45_.
• some jets could point in different directions to other jets, either within a given array or from one array to another. Further, some or all of the orifices could be shaped to give a swirling motion to the jets issuing therefrom.
• the surface on which hydroentangling takes place has been referred to as a belt. It is to be understood, however, this is only by way of example, and the surface could be any suitable travelling surface, whether travelling linearly or, in the case of a drum for example, circularly.
• the apparatus shown in Figure 1 has water jets only on one surface of the substrate. It may be desirable to effect hydroentangling from both surfaces.
• the web of Figure 1 can be passed through a second, oppositely disposed assembly of orifices arrays and vacuum boxes.
• the initial web can pass through an assembly in which orifice arrays on one side of the web alternate with orifice arrays on the other side.
• Hydroentangling equipment suitable for use in carrying out the present invention is obtainable from ICBT Perfojet, Z.A. Pre- Millet, 38330 Mont Bonnot, France.
• compositions can be used to produce the substrate, though preferably the composition should include sufficient fibres which have the desired ability to protrude from the surface of the substrate.
• examples of fibre compositions which can be used include mixtures of a hydrophilic fibre material (e.g. viscose, cotton or flax) and a hydrophobic fibre material (e.g. polyethylene terephthalate or polypropylene) , which may be present in any desired proportions, or purely hydrophilic or purely hydrophobic materials.
• Two particularly preferred compositions are 50% viscose/50% PP and 50% viscose/50% PET.
• One advantage provided by having such a large amount of viscose fibres is that their surfaces are ridged, having ridges of the order of 10 micrometers high, and their ridges provide additional friction to help initiate partial break-up of the substrate.
• the substrate preferably has a basis weight of at least 30 gm -2 .
• a basis weight of more than 150 gm" 2 will be required, though in theory higher basis weights could be employed.
• the basis weight is preferably in the range of 30- 130 gm "2 more preferably 30-70 gm" 2 , and still more preferably 55 to 65 gm ⁇ 2 .
• a product having a basis weight of 55 to 65 gm" 2 when made according to the present invention by a hydroentangling process, and with a textured surface, typically has a caliper of about 0.8mm, including the texturing.
• the texturing as already mentioned can be achieved by carrying out the hydroentangling on an apertured surface. If the overall caliper is less than about 0.4 mm it may be difficult to incorporate a textured surface, and such a surface is advantageous, for the reasons already given.
• the caliper of the substrate is from 0.4mm to 2.0mm, more preferably from 0.4 to 0.95mm.
• the bulk density of the substrate is preferably not more than O.lg/cm 3 , preferably not more than 0.9g/cm 3 , and still preferably not more than 0.8g/cm 3 .
• the volume of the substrate is calculated using the caliper of the substrate including the texturing.
• a substrate produced according to the present invention results in superior cleaning properties to those obtained by substrates according to the prior art.
• the principle reason for this is believed to be the fact that the fibres which protrude from the substrate surface as the cleaning process proceeds provide additional cleaning surfaces.
• the actual cleaning mechanism may involve other effects in addition to, or instead of, the one just described, and no reliance is to be placed on the particular theoretical explanation just given.
• the second relevant mechanism is believed to be that as fibres are caused to protrude from the substrate they can be felt by the skin with which the substrate is in contact, and since these fibres, even if relatively stiff, are then free to bend, the sensation to the user is one of softness.
• the increased in perceived softness may result from other effects in addition to, or instead of, those just described, and no reliance is to be placed on the particular theoretical explanation just given.
• Example 5 Four substrates according to the invention (Examples 1 to 4) will now be described, together with a comparative example (Example 5) of a substrate not according to the invention.
• Examples 1 to 4 were made from the same fibre composition, namely 50% viscose and 50% polypropylene, all the fibres having a length of 4cm and a diameter equivalent to 1.7dtex. Examples 1 to 4 were all made in the same way. The only difference between them was basis weight of the substrate, which was as follows (the basis weight of Example 5 also being given for completeness) :
• Example 5 used the same fibre composition and fibre diameter as Examples 1-4.
• the apparatus used in Examples 1 to 4 had an apertured belt with 25 apertures/cm arranged in a square grid. The line travelled at about 50 m/min. 13 orifice arrays were used, each having about 1666 orifices per metre of their length, with each orifice being about 100 micrometers in diameter.
• Example 5 was made using a belt which was not apertured. In all of Examples 1-5 the jets were directed perpendicularly to the fibrous web.
• Other process conditions for Examples 1 to 4 and comparative Example 5 are set out in the following Table 1.
• Jet velocity (m/sec) 60-90 60-90 Energy flux per jet (bars, m/sec) 3000-7500 2000- 8000
• Example 6 which, like Examples 1-4, was a hydroentangled substrate, but, unlike comparative Example 5, was apertured.
• Example 6 was produced using more energy than for Examples 1 to 4.
• Example 6 had a basis weight of 53.9 gm" 2 . The results of these tests are set out in Table 2. The way in which the various tests were carried out is described later in this specification. TABLE 2
• modulus is those for initial modulus, as is also the case in Table 2 below.
• the initial CD modulus is very low, and that even though there are relatively few apertures the density is also low.
• Example 2 substantially alters the properties of Example 2 (which is according to the invention) , but has a much less marked effect on Examples 5 and 6 (which are not) .
• the alteration in Example 2 is consistent with its being significantly weaker than Examples 5 and 6, the effect of rubbing being to cause the substrate to beak up to an extent sufficient to produce the desired sensation to the user, but not such as to cause complete disintegration (which is undesired) .
• Example 2 attention is drawn to the fact that in Example 2 the caliper is significantly increased and the toughness is significantly decreased, both of which reflect the partial break-up of the substrate.
• FIG. 2 A comparison of Figures 2 and 3 shows the extent to which rubbing causes a substrate according to the invention (Example 2) to being to break up.
• each array may have a region of, say, 1cm, in which there are orifices spaced at 100 micrometer centres, alternately with regions of, say, 0.5cm in which there are no orifices.
• the effect of this is to produce a substrate which has alternating strips of entangled fibres and non-entangled fibres.
• the former provide strength to the substrate, and the latter provide fibres which readily come loose from the substrate as a result of the friction of rubbing.
• the substrate could be multi-layer.
• One possible construction is a sandwich in which a central layer (which may be of hydroentangled fibres, but could be of virtually any material, e.g. a woven material, with external layers of fibres formed therein by hydroentangling according to the invention. This would have the cleaning properties and softness associated with the present invention, but the possibility of other properties, e.g. added strength, from the central layer.
• Another possible construction is one of two layers, of which at least one layer is formed by hydroentangling according to the invention.
• the following tensile properties of the previous examples are evaluated with an Instron tester under the following conditions. All tests are conducted at laboratory conditions of 21 C and 65% relative humidity.
• the Instron gauge length is 10 cm. Elongation rate is lOcm/min or 100%/minute.
• the Instron "jaws" that secure the sample are flat and rubber coated.
• Tensile strength, initial modulus and toughness in both the MD and CD directions are determined from 1 M wide strips cut to 15 cm in length and fixed without slack but without tension on the Instron tester within jaws set at 10 cm distance.
• the energy input from the Instron machine to the sample is then plotted over time with the y axis indicating the force applied to the sample in Newtons and the x axis indicating the % elongation of the sample at the indicated elongation rate.
• the tensile strength number is defined as the peak force from this force over elongation curve.
• the initial modulus number is obtained from the graph produced from the same test. It is the initial slope of the force/elongation curve and is indicated as the y axis in units of Newtons/% elongation.
• the toughness is the number obtained also from this same test and results graph. Toughness is defined as the area under the entire curve indicated in Newtons by % elongation.
• Substrate caliper is measured using standard EDANA non-woven industry methodology, reference method #30-4- 89.
• Entanglement frequency is evaluated from the following data produced on the Instron tester with strips of varying widths, as indicated.
• Strip Width Avg CD Strip Instron Elongation Rate indication TensileStrip Width Gauge (in/minute) Example 2 fin'. Leneth Cm) wO 8.0 0.8 0 0.5 wl 8.2 0.3 1.5 5 w2 17.1 1.9 1.5 5
• test substrate to be evaluated is clamped into a fixed, taught but not stretched position on a horizontal surface.
• the circular clamp holding this material in place is 5" in diameter.
• the rubbing test is then conducted on the area of the sample within this fixed circular clamp.
• a second sample of the test material is then clamped taught but not stretched in a fixed position on a 1.75" diameter flat and solid ended cylinder. This second sample is then rubbed on the first sample for the purpose of the test.
• the vertical force, or absolute mass (weight) of the second sample against the first sample is 0.68 Kg.
• the second sample with this weight is then rubbed against the first sample in a repeating pattern, known as a Lissajous pattern, that fully covers the test sample, as shown in Figure 7.
• One cycle is represented by the full pattern shown above.
• One cycle consists of 15 oscillations in one direction and a second 15 oscillations at right angles to the first set of oscillations.
• One full cycle of these 30 oscillations is done over 18 seconds.
• the substrate within the 5" fixed ring is then considered the treated sample.
• this piece of substrate is then cut in the CD or MD direction into strips of the appropriate width and length for the Instron test.
• this treated strip is cut to 1" wide by 15 cm long strips.
• Figure 6a to 6e are curves of the type just mentioned derived from three different materials, as follows:
• the ordinate in each the graphs is in N, and the abscissa is in % elongation of the sample.
• the % value is converted into m by %/100 x 0.1m, with 0.1m being the length of the strips being tested.

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