ABSORBENT CLOTH

Abstract: An absorbent textile fabric including hydrophilic textile fibres comprises a non-woven web needle punched with between 5 and 90 punches per cm<2>. Preferably the fabric comprises a blend of hydrophilic textile fibres and other textile fibres which are thermoplastic and at least partially melt at a temperature at which the said hydrophilic fibres remain intact. Use of such a low density of needle punching can provide increased liquid retention capacity in the non-woven fabric.

Description: ABSORBENT CLOTH Technical Field This invention relates to an absorbent fabric, more particularly to an absorbent fabric suitable for household use as a wiping cloth, and having high liquid retention properties. Background Art It is commonplace to make non-woven fabrics by a process comprising combining the relevant fibres together to form a loose web and thereafter needle-punching the web in order to interlace the fibres. In such processes the needling density is relatively high, typically of the order of 150 penetrations per sq cm. Such a process is commonly used for making inter alia blankets, carpets, felts and certain kinds of furnishing fabric, for example for covering seats. Lower needling densities are used for joining preformed layers which if non-woven will themselves have been needle punched at the typical density of 150 punches per cm 2 mentioned above. The manufacture of non-woven fabrics and the technique of needle punching are described in various texts including "Non-woven Bonded Fabrics" edited by Lunenschloss and Albrecht, published by Ellis Horwood, and "Needle-punching" by A.T.Purdy, a Textile Institute Monograph. Non-woven fabrics are in use as household absorbent cloths. Those sold for this purpose can have liquid retention capacities up to 10.5 grams of liquid per gram of dry fabric, but lower levels of around 8 g/g are more usual. Disclosure of the Invention Contrary to what might be predicted, we have now found that the liquid retention capacity of a non-woven fabric can be increased by using only a low density of needle punching. Broadly, in a first aspect, this invention provides an absorbent textile fabric which comprises hydrophilic textile fibres, the fabric being a non-woven web needle 2 punched with between 5 and 90 punches per cm . Preferably the fabric comprises a blend of (i) hydrophilic textile fibres and (ii) other textile fibres which are thermoplastic and at least partially melt at a temperature at which the said hydrophilic fibres remain intact. The ratio by weight of fibres (i) to (ii) preferably lies in a range from 50:50 to 95:5, better 60:40 to 90:10. In a second broad aspect this invention provides a method of making an absorbent fabric comprising hydrophilic textile fibres, the method comprising forming the fibres into a web without substantially interlacing the fibres and then needle punching the web with between 5 2 and 90 punches per cm . The needle punching density utilised in this invention is preferably at least 10, better at least 15 punches per cm 2, for the sake of achi.evi.ng fabri.c strength through this (low) level of interlacing. Good levels of water retention can be achieved with needle punch densities up to 80 or 90 punches per cm 2, but higher levels of water retention are obtained with needle punch densities of 20 to 60, even better 20 to 40 punches per cm . The formation of a web which is subjected to needle punching may be carried out by forming a plurality of thinner webs without substantially interlacing their fibres and then laying these on top of one another to form a thicker web, again substantially without interlacing the fibres prior to the needle punching. The steps of blending fibres, forming one or more webs from them and laying multiple webs one on top of another may all be carried out using conventional technology. Notably the fibres may be air-laid to form the web(s) . The needle punching may be carried out by conventional technology, modified by reducing the number and density of needles in the array of needles which is used, and/or increasing the cloth feed rate. This punching will reduce the thickness of the web to which it is applied, but not so greatly as does a conventional, higher density of needle punching. It is strongly preferred that the needle punched web is then compacted to the desired thickness by passing between calendering rollers. Suitably the web has a final dry bulk density of 3 between 0.95 aaind 0.125 g/cm , more suitably between 0.10 Preferably the fibres employed are a blend of (i) hydrophilic textile fibres and (ii) other fibres which are thermoplastic and at least partially melt at a temperature at which the fibres (i) remain intact. When such a blend of fibres is used, the needle punched web is, advantageously, subjected to a heat treatment step sufficient to effect at least partial melting of the thermoplastic fibres (ii) . The -softened or melted thermoplastic functions as an adhesive to bond fibres within the fabric, so enhancing the strength of the fabric. The preferred treatment is a heat treatment sufficient to at least partially melt the thermoplastic fibres (ii) followed directly by calendering at a lower temperature to solidify the thermoplastic while the fabric is compressed and hence set the fabric into a desired thickness. The heat treatment may be passage through an oven or passage between heated calendar rollers. It is preferred that both exterior surfaces of the fabric are provided by the non-woven material. This is particularly desirable for a cloth intended to be used either side up. A possibility would be to apply an exterior surface layer to one or even both sides, but this is not preferred. A further possibility which is preferred is to treat one or both exposed side surfaces with a binder material which will adhere fibres together at the surface but without substantially reducing the porosity of the fabric. Such a binder material may be applied by conventional methods, e.g. as a fine spray at a level of 1 to 50 grams per square metre of surface area, preferably 1 to 20 grams per square metre. At such a level the binder will not impregnate the porous fabric but will bind fibres together at the surface. Applying a binder in this way is beneficial in reducing linting of the fabric. The finished fabric, if intended for household use, will be cut into individual pieces of cloth which are packaged for sale. The size of such pieces of cloth is a matter of choice, but will generally not be less than an area of 100cm 2 or larger than lm2. The hydrophilic fibres which are employed are essential to the absorbency of the fabric which is formed and they constitute at least half, preferably a major fraction of any fibre blend. Suitably the hydrophilic fibres are cellulosic, e.g. cotton, viscose rayon or other regenerated cellulose or a mixture of them; other examples of cellulosic fibres which are not preferred are jute, hemp and sisal. The hydrophilic fibres could alternatively be non-cellulosic synthetic polymer fibres incorporating hydrophilic groups in the polymer chains or having hydrophilic material in the polymer matrix. Other fibres, able to melt at least partially while the hydrophilic fibres remain intact, will generally be synthetic organic polymer fibres. These do not need to be hydrophilic (although they may be if that happens to be convenient) . Preferred are polyethylene and polypropylene. Bicomponent fibres, also known as sheath-core fibres, may be used. If these are used it is desirable that a heat treatment step should melt the outer layer (sheath) of the fibres, to function as an adhesive within the fabric, while leaving the core of the fibres intact. It will be appreciated that a preferred blend of fibres will consist of hydrophilic fibres (i) which may or may not be thermoplastic and thermoplastic fibres (ii) which may or may not be hydrophilic. If both'categories of fibres happen to be thermoplastic and hydrophilic they will still be distinct categories because the fibres (ii) are required to be able to melt at least partially while the hydrophilic fibres (i) remain intact. The hydrophilic fibres (i) which remain intact through any heat treatment suitably have a length of at least 2mm. An average length between 30 and 60 mm can conveniently be used. Longer lengths are possible, e.g. up to 100mm or more. The fibre dtex may lie in a range up to 25 dtex, especially 1 to 6 dtex. Diameters substantially larger than this are not preferred as they would give a coarser feel. The other fibres (ii) may also have lengths and diameters within the above ranges. Either or both types of fibres (i) and (ii) can be hollow. Increased amounts of liquid can thus be absorbed by the fabric. Suitably any such hollow fibres have similar external dimensions to those recommended above for hydrophilic fibres. If desired at least some of any hollow fibres employed can be pre-filled with one or more ingredients which are released in use. Examples of suitable ingredients include surfactants for cleaning, hygiene agents for killing and/or preventing the build up of bacteria, viruses, fungi etc., perfumes, antistatic agents, polishes, conditioners etc. and mixture thereof. Such hollow fibres can form a significant proportion of the total fibres present without detriment to the overall properties of the fabric. Either instead of or in addition to the use of hollow fibres, the textile fabric can include fibres containing an embedded abrasive. Suitably such fibres can comprise up to 50wt% of the total fibres present, and could for example be present on one side only or one portion only of the fabric. A binder which is sprayed on to the needle punched fabric may be a polymeric emulsion and preferably this has the ability to cross link on heating. Examples are the vinyl acetate-ethylene copolymers such as Vinamul 32417 and Vinamul 32440 supplied by Vinamul Ltd. After curing by heating, these have glass transition temperature below room temperature, giving a soft handle to the fabric. The fabric of the present invention can be sold dry intended for use with a fluid applied in use or as a cloth to mop us spills, or alternatively the present fabric can be laden with a liquid prior to ' sale and appropriately packed and sold as a ready to use wipe. Embodiments of the Invention Embodiments of this invention will now be described. Fabrics embodying the invention were prepared by the following general procedure. Bales of the fibres were opened and the fibres weighed into the required ratios. The fibres was mixed, carded and laid to produce an initial web having a weight in the order of 10 gram/square metre. Lengths of this initial web were cross laid, one upon another to produce a thicker and wider web having a weight of 120-150 gram/square metre. This web was needle punched with each punch extending through the full thickness of the web. This needle punching contracted the web, to a weight of 140-150 gram/square metre. The needle punched web .was passed through a hot air tunnel oven and directly thereafter through a pair of cold calendar rollers. The resulting fabric was cut into individual cloth pieces of size 10 cm by 10 cm. The fibres employed were chosen from two cellulosic fibres and two synthetic thermoplastic fibres as follows: "Intermatt" ex Courtaulds, a viscose rayon of average 1.7 dtex and 51 mm length; Bleached cotton fibre, average 20μ diameter arid 38mm length; "ES" ex Danaklon AS, a polyethylene sheath over polypropylene core bicomponent fibre of average 3.3 dtex and 51mm length; "T151" Polypropylene fibre, average 3.3 dtex and 48mm length. 0 For all the fabrics the feed rate through the tunnel oven was 2 metres/minute through a heated zone 1.8 metres long and the cold calendar gap was 0.6mm. If "ES" bicomponent fibre was used the oven temperature was set at 150°C to melt the polyethylene sheath without melting the 5 polypropylene core. If polypropylene fibre was used the oven temperature was increased to 182°C to melt the polypropylene. After production, the thickness of the fabric was 0 measured with a Shirley thickness gauge applying 20 gram per cm 2 pressure. The water retenti.on capabi.li.ty was measured by means of a test specific by the European Disposables and Non-wovens Association as a test of liquid g absorptive capacity. In this test samples of fabric are weighed dry, immersed in water while attached to a wire gauze, removed after 60 seconds immersion, hung vertically and allowed to drain for 120 seconds, then weighed again. The test is repeated for five samples. The bulk density of the dry fabric was calculated from the thickness, surface area and dry weight of a sample. Using this determination of dry density, the absorption capacity of each cloth was calculated in grams 3 . . . . . of water per cm of cloth. This indicates the efficiency with which spaces between fibres are utilised for water absorption. Softness of the fabrics was also measured, using a test machine in which the fabric applies force to a piezoelectric sensor, the harsher the fabric, the higher the average voltage produced. Compositions of the fabrics, together with test results, are set out in the table below. Included at the end of the table are test results for various commercial cloths each of which was a non woven comprising a major proportion of cellulosic fibre and which appeared to have been made by conventional needle punching at a density of over 100 punches per cm 2. The composi.ti.ons of these- cloths are given, so far as they could be ascertained. TABLE Fabric Composition Needle Thickness Bulk Water Softness (% by weight) density (mm) Density retention (mV) (punches/ (g/cm 3 ) fq/cm 3 ) cm 2 ) Cloth 1 85% Intermatt viscose 30 1.45 0.103 1.11 129 15% ES bicomponent Cloth 2 75% Intermatt viscose 30 1.47 0.104 1.11 128 25% ES bicomponent 15 Cloth 3 85% cotton 30 1.10 0.104 1.14 15% T151 polypropylene Cloth 4 85% Intermatt viscose 50 1.15 0.114 1.17 20 15% T151 polypropylene Cloth 5 80% Intermatt viscose 50 1.26 0.118 1.14 20% ES bicomponent 25 Fabric Composition Needle Thickness Bulk Water Softness (% by weight) density (mm) Density retention (mV) (punches/ (q/cm 3 ) (g/cm 3 ) cm 2 ) Cloth A >100 1.12 0.111 0.98 204 Cloth B >100 1.44 0.102 0.93 140 10 Cloth L >100 1.12 0.125 0.99 188 Cloth M 85% viscose >100 1.46 0.095 1.00 142 15% polypropylene Cloth P >100 1.89 0.115 0.98 15 20 25

Claims: Claims 1. Absorbent textile fabric including hydrophilic textile fibres characterised in that the fabric is a non-woven web needle punched with between 5 and 90 punches 2. Absorbent textile fabric according to claim 1 wherein the fabric is a non-woven web needle punched with between 2 10 and 80 punches per cm . 3. Absorbent textile fabric according to claim 2 wherein the fabric is a non-woven web needle punched with between 2 20 and 60 punches per cm . 4. Absorbent textile fabric according to any one of the preceding claims wherein the fabric in addition to hydrophilic textile fibres includes other textile fibres which are thermoplastic and at least partially melt at a temperature at which said hydrophilic fibres remain intact. 5. Absorbent textile fabric according to claim 4 wherein the ratio by weight of hydrophilic textile fibres to said other textile fibres lies in a range from 50:50 to 95:5. 6. Absorbent textile fabric according to claim 1 wherein at least one exposed side surface has been treated with a binder material. 7. Method of making an absorbent textile fabric including hydrophilic textile fibres characterised by forming the fibres into a web without substantially interlacing the fibres and then needle punching the web 2 with between 5 and 90 punches per cm . 8. Method according to claim 7 comprising needle 2 punching the web with between 10 and 80 punches per cm . 9. Method according to claim 7 wherein the fabric in addition to hydrophilic textile fibres includes other textile fibres which are thermoplastic and at least partially melt at a temperature at which said hydrophilic fibres remain intact, the method comprising subjecting the needle punched web including such a blend of fibres to a heat treatment step sufficient to effect at least partial melting of the thermoplastic fibres. 10. Method according to claim 7 or claim 9 comprising compacting the needle punched web by passing between calendering rollers. 11. Method according to claim 7 comprising treating at least one exposed side surface with a binder material.

Inventors: SAVILL DEREK GUY, SAVILL, DEREK, GUY
Applicants: UNILEVER NV, UNILEVER PLC
Application year: 1990
Main classification: D04H1
IPC codes: D04H1