Patent Application
20100228216
The present invention relates to reusable diaper compositions and more specifically to a reusable and absorptive mat for the absorption, dispersion and retention of a liquid manufactured so as to minimize interference with the inherent absorbent properties of viscose rayon fibres.
The majority of diapers in use today, both for adults and children are of the disposable type. Over time, disposable diapers have presented improved comfort levels, fluid absorption and dispersion and typically include a layer in contact with the skin that feels dry over extended periods of time. These advances in disposable diapers, at one point rendered conventional cotton or flannel diapers almost obsolete.
A major drawback of disposable diapers is that they are not readily biodegradable and with ever increasing use, this has resulted in an overload at garbage and landfill sites to the point of causing serious environmental problems. Furthermore, disposable diapers or incontinence pads from hospitals are treated as infectious waste and must be disposed of at special landfill sites, thereby adding to the critical storage at such sites.
With the recent increase in public awareness and concern with environmental issues along with a move towards reducing waste, there has been renewed interest in washable and reusable diapers. This interest is however constrained by the performance of reusable and washable diapers when compared with the advances in disposable diapers. To date, disposable diapers and incontinence pads are used in the overwhelming majority of cases as their comfort, dryness and absorption qualities have been superior to those of reusable diapers and incontinence pads. Due to the competitive marketplace and high demands and expectations of users, there is a need in the art for an improved reusable and washable diaper which provides equivalent comfort, dryness and absorption qualities as disposable diapers.
One prior art reusable diaper, disclosed in U.S. Pat. No. 5,267,991 (Dec. 7, 1993) to Gillies et al. (hereinafter, the '991 Patent), attempted to match the performance of disposable diapers with the inclusion of an absorbent mat produced using a viscose rayon fibre developed by Cortaulds Limited and produced under the GALAXY™ and GALAXY I™ brands. The GALAXY I™ fibre, having a trilobal configuration, was found to have a relatively even fluid dispersion characteristic making it ideal for use in reusable diapers. Both the aforementioned fibres exhibited a water imbibition characteristic of from 100-345%.
While the use of viscose rayon fibres in applications requiring high absorption, such as tampons, was known, the '991 Patent disclosed a method for forming the viscose rayon fibres into a washable and reusable mat, thus allowing them to be used in reusable diaper or incontinence pad applications. The method included providing a plurality of non-woven layers of carded and cross-laid viscose rayon fibres having a cross-section of substantially rigid, multi-limbed configuration and stitchbonding said layers into a cohesive web with a thread under medium tension to stabilize and maintain the web such that the fibres that are gripped by the threads are not bunched up and tightened in a manner that would interfere with uniform absorption and dispersion of a fluid being absorbed.
The carding and cross-laying steps are well known in the art of producing fabrics. Cross-laying involves laying the fibres in layers offset by ninety degrees until a desired thickness is reached. With the viscose rayon fibres, this allows for fluid dispersion optimized along each fibre and therefore fluid is drawn substantially along the two axes as they are cross-laid. This dispersion, while far superior to traditional cotton diapers, needs to be improved upon to match the absorption and dispersion characteristics of current disposable diapers. There is thus a need in the art for a reusable and washable diaper which provides improved fluid absorption and dispersion.
The stitchbonding step of the '991 Patent was carried out using a MALLYMO® stitchbonding machine made by Textina Inc. As is well known and common practice in the art, prior to stitchbonding, the fabric or web to be stitchbonded is temporarily bonded or otherwise held cohesively such that the web can be maintained in a given shape and fed easily through the stitchbonding machine. This results in a stitchbonded mat having a substantially controlled shape. Typically, as in the manufacture of felt, such pre-stitchbonding processing steps involve a chemical or thermal bonding; however these preliminary steps were found by the inventor to interfere with the absorbency of the viscose rayon fibres, and were for this reason unsuitable for use in the method of the '991 Patent. The alternative, as carried out when using a MALLYMO® stitchbonding machine is to use a needle punch machine, (which, contrary to the suggestion of its name, uses no thread) prior to feeding the web therethrough for stitchbonding. A needle punch machine causes some fibres to break or to entangle with others, thereby constraining the web for easier feeding through the stitchbonding machine.
It has also been found by the inventor that the needle punch step, while not limiting absorbency to the same degree as chemical or thermal bonding, still results in less than optimal absorbency and fluid dispersion due to breakage and entanglement of the fibres that make up the web. This is so, as it has been found that fluid dispersion is optimized along the length of a given individual fibre. Accordingly, broken web fibres result in the stitchbonded threads not gripping entire fibres, with a resultant loss of directionality of individual fibres within the web. Similarly, entangled fibres lose the original directionality with which they were laid within the web. Both effects combine to cause reduced fluid dispersion through the web away from a potential source of wetting. Thus, using a needle punch to pre-process a fibrous web prior to stitchbonding has the effect of reducing the overall moisture absorption capacity of the web. Such reduced moisture retention capacity has been a barrier to more widespread use of reusable diapers, as they continue to underperform in comparison to disposables.
Another problem associated with prior art reusable diapers is the loss of integrity after repeated washings. This can be caused by shrinking, change of shape, or degradation in the quality of the absorbent mat.
There is therefore a need in the art for a reusable and washable diaper or mat composition which provides improved fluid absorbency and fluid dispersion characteristics over the prior art and comparable to those of disposable diapers. Moreover, there is a further need for a reusable and washable diaper which can maintain its size, shape and form after repeated washings.
In accordance with a first embodiment of the present invention there is disclosed a reusable and absorptive mat for the absorption, dispersion and retention of a liquid comprising a plurality of non-woven layers, of carded and randomly laid viscose rayon fibres having a cross-section of substantially rigid multi-limbed configuration, said layers stitchbonded in an as laid state, thereby substantially limiting entanglement and breaking of individual fibres, with a thread under limited tension so as to maintain uniformity of the absorptive mat.
In accordance with one aspect of the first embodiment, the viscose rayon fibres are of a trilobal configuration and have a water imbibition characteristic of from 100 to 345 percent.
In accordance with a further aspect of the first embodiment, the layers are stitchbonded with a polyester thread in rows approximately 2 to 10 rows per inch, each of said rows having from 6 to 200 stitches per inch.
In accordance with a further aspect of the first embodiment, said absorptive mat is pre-shrunk.
In accordance with a second embodiment of the present invention, there is disclosed a reusable diaper comprising, a layer of a hydrophobic web of polyester fibres, an impermeable pant-like garment and a reusable and absorptive mat as herein disclosed, said absorptive mat disposed within said garment and said hydrophobic web adjacent to said absorptive mat.
In accordance with a third embodiment of the present invention, there is disclosed a washable and reusable incontinence pad for the absorption, dispersion and retention of liquids, said pad comprising an interior layer of hydrophobic material including a receiving surface, at least one median layer adjacent the interior layer opposite the receiving surface and comprising a plurality of non-woven layers, of carded and randomly laid viscose rayon fibres having a cross-section of substantially rigid multi-limbed configuration, said layers stitchbonded in an as laid state, thereby substantially limiting entanglement and breaking of individual fibres, with a thread under limited tension so as to maintain uniformity of the absorptive mat, and an outer layer of substantially waterproof polyurethane film adjacent the median layer.
In accordance with one aspect of the third embodiment, said interior layer, said at least one median layer, and said outer layer are joined only along outer edges thereof.
In accordance with a further aspect of the third embodiment, said interior layer and said outer layer are joined to form an interior pocket for holding said at least one median layer.
In accordance with a further aspect of the third embodiment, said at least one median layer comprises two median layers.
In accordance with a further aspect of the third embodiment, said viscose rayon fibres include recycled viscose rayon fibres.
In accordance with a further aspect of the third embodiment, said viscose rayon fibres are blended with between 5% and 40% polyester fibres.
In accordance with a further aspect of the third embodiment, said viscose rayon fibres are of trilobal configuration and have a water imbibition characteristic of from 100 to 345%.
In accordance with a further aspect of the third embodiment, said layers of viscose rayon fibres are stitchbonded with polyester thread along a series of rows spaced approximately 2 to 10 rows per inch with each of said rows having from 6 to 200 stitches per inch.
In accordance with a further aspect of the third embodiment, said interior layer is characterized by being warp knit tricot stitched, and said receiving surface is napped finish.
In accordance with a further aspect of the third embodiment, wherein said outer layer comprises a first lamina of pre-stretched film of polyurethane bonded to a second lamina comprising a web of warp knit tricot stitched polyester fibres and in which said first lamina is positioned adjacent said median layer.
In accordance with a further aspect of the third embodiment, said median layer is preshrunk.
In accordance with a further aspect of the third embodiment, said pad is contoured in an hourglass shape for wearing as a diaper and has a fastener device for securing said pad about a wearer.
In accordance with a further aspect of the third embodiment, the median layer as hereinbefore disclosed in combination with a mesh liner for receiving and disposing of solid excrement, said mesh liner placed adjacent said receiving surface of said interior layer.
In accordance with a fourth embodiment of the present invention, there is disclosed a method for manufacturing a reusable and washable article for the absorption, dispersion and retention of a liquid comprising providing a plurality of viscose rayon fibres having a cross-section of substantially rigid multi-limbed configuration, carding said plurality of viscose rayon fibres, randomly laying the carded plurality of viscose rayon fibres into a continuous random web structure to form a desired thickness, and stitchbonding said continuous random web structure in an as laid state thereby limiting entanglement or breakage of individual fibres to form an absorptive mat.
In accordance with one aspect of the fourth embodiment, said viscose rayon fibres are of a trilobal configuration and have a water imbibition characteristic of from 100 to 345 percent.
In accordance with a further aspect of the fourth embodiment, said stitchbonding step comprises stitchbonding with polyester thread in rows approximately 2 to 10 rows per inch, each of said rows having from 6 to 200 stitches per inch.
In accordance with a further aspect of the fourth embodiment, subjecting the stitchbonded mat to a heat treatment to reduce shrinkage when washed after use.
In accordance with a further aspect of the fourth embodiment, said heat treatment is at approximately 110° C.
In accordance with a further aspect of the fourth embodiment, providing an interior layer of hydrophobic material having a receiving surface, said interior layer adjacent said absorptive mat opposite the receiving surface and providing an outer layer of substantially waterproof polyurethane film adjacent said absorptive mat.
In accordance with a further aspect of the fourth embodiment, adjoining said interior layer, said absorptive mat and said outer layer along the outer edges thereof to form a pad of unitary construction.
In accordance with a further aspect of the fourth embodiment, adjoining said interior layer and said outer layer to form an envelope, said absorptive mat located within said envelope.
In accordance with a further aspect of the fourth embodiment, said article is contoured in an hourglass shape for wearing as a diaper and further providing a fastener for securing said diaper about a wearer.
It is thus an object of this invention to obviate or mitigate at least one of the above mentioned disadvantages of the prior art.
Other advantages, features and characteristics of the present invention, as well as methods of assembly, use, operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following detailed description and the appended claims with reference to the accompanying drawings, the latter of which is briefly described hereinbelow.
a of the drawings is a top perspective view of a diaper according to a second embodiment of present invention.
b of the drawings is a bottom perspective view of the diaper of
A reusable and washable absorptive mat 10 constructed according to the present invention has been found to have improved absorption and dispersion characteristics over the prior art by virtue of improvements to the structure of the absorptive mat and the method of manufacture as detailed below. The reusable and washable absorptive mat 10, while described for use in a diaper 200, or in an incontinence pad 100, is not limited as such, and can be used in any application requiring a reusable and absorptive mat for the absorption, dispersion and retention of a fluid.
As shown in either
A reusable and washable absorptive mat 10 for the absorption, retention and dispersion of a fluid according to the present invention is produced from viscose rayon fibres 15 having a cross-section of substantially rigid multi-limbed configuration, for example those produced by Courtaulds Limited of London, England under the GALAXY I™ brand. In their pre-processed state, multi-limbed viscose rayon fibres, either trilobal or multilobal were found to have a water imbibition characteristic of 100 to 345 percent, measured by dividing a wet weight by a dry weight of a given sample of the fibre. The fibres are to be formed into a non-woven mat.
The viscose rayon fibres 15 as described above are processed into the absorptive mat 10 according to the present invention as herein described. Referring now to
Next, referring to step 50, the carded viscose rayon fibres are randomly laid into a continuous random web structure until a desired thickness is reached. The randomly laying of the carded fibres can be done using a Rando-Webber® or as part of the Rando-Web® process developed by the Rando® Machine Corporation of Macedon, N.Y., USA.
Alternatively, the carded fibres can be laid into a radial web, wherein the fibres of each successive layer are offset at a given angle from the previous layer. The result is a web laid in a radial manner.
Referring now to step 60, the carded and randomly laid random web structure is then stitchbonded in an as laid state. For the purposes of the present invention, application, specification, and claims, an “as laid state” is defined as the state of the continuous random web structure immediately after being laid into the desired thickness, without the inclusion of any preparatory steps to aid in the stitchbonding process. More specifically, the “as laid state” is defined expressly to exclude any needling or needle punching of the web or any other process known in the art to provide for easier feeding into a stitchbonding machine at the expense of potentially altering the state of individual fibres within the web, such as by breaking or entangling them.
The prior art step of needling is carried out in the prior art to provide a more cohesive web to be transferred from the carding machine, for subsequent feeding through the stitchbonding machine. This step is well established and thought necessary in the prior art to provide for a more uniform web for feeding through the stitchbonding machine. It was found by the present invention, however, that needle punching results in significant breaking or entanglement of individual fibres, thereby hampering the fluid dispersion and absorption characteristics of the absorptive mat; accordingly, this pre-processing step is explicitly and expressly excluded from the present invention. In order to eliminate the temporary binding and shaping of the web provided by needling, greater care must be taken in transporting the web from the carding machine and subsequently feeding same into the stitchbonding machine.
If transporting the non-needled web from the carding machine to the stitchbonding machine is required, mechanical means may be used to assist therein, which means does not cause breakage or entanglement of individual fibres. One such mechanical means is the Menzel “A-Frame”, manufactured by Menzel (USA) of Sparttanburg, S.C., which can be used for transferring un-needled webs. The Menzel “A-Frame” is designed to wind and unwind a wide variety of fabrics or webs on and off of fixed mounted cores. The versatility of the Menzel “A-Frame” does not require the web to be bonded or held cohesively to be transported to, or fed into, a stitchbonding machine without damage. Optionally, the web may be surrounded by a polyethylene, or similar material, film to maintain cohesiveness in transporting onto and off from the Menzel “A-Frame”. Other means which do not cause or limit the breakage or entanglement of individual fibres, including but not limited to, mechanical clamping means, other mechanisms for winding onto and from a core, and manual feeding of the web, are all within the scope of the present invention.
Preferably, the stitchbonding step 60 is thereafter carried out using a polyester thread having a thickness of approximately 150 denier. Some variation in the thickness of the thread, or an optimal thickness for a given mat size, as determined by routine experimentation, is contemplated by the present invention. The stitchbonding is preferably carried out using multiple needles to provide a series of stitch rows spaced apart to give approximately 2 to 10 rows per inch, with approximately 5 rows per inch, being the most preferable for diaper purposes. Each row contains approximately 60 to 200 stitches per inch, with 120 stitches per inch being the most preferred.
The non-woven web is stitchbonded under limited, or relatively light, tension so that the fibres gripped by the thread are not bunched up and tightened in a manner that would interfere with the uniformity of the absorptive mat 10. Maintaining a high degree of uniformity in the absorptive mat 10 ensures minimal interference with uniform absorption and dispersion. As can be appreciated, bunching at the stitchbonded areas results in regions of higher concentration of fibres and disrupts the even and uniform absorption and dispersion of fluids. The limits on the thread tension are dependent on the thickness of web, or intended thickness of the final absorptive mat 10, for a given application, and can optionally be determined by visually observing the web for regions of bunching or fluffiness.
After stitchbonding, the absorptive mat is pre-shrunk by subjecting it to an air heat treatment, preferably at approximately 110° Celsius. This allows the diaper to maintain a consistent size, shape and form after repeated washings.
To further increase the strength of the absorptive mat 10 and to improve its lifespan after repeated washings, the fibre used to create the absorptive mat 10 may be a blend of the multi-limbed viscose rayon fibres discussed above together and a polyester fibre. It is possible to use between 5% and 40% polyester fibre with a preferred composition of 80% trilobal fibre and 20% polyester fibre. The addition of polyester fibres results in a reduction in the absorbency characteristics of the absorptive mat 10, but provides for increased strength, if required.
Referring particularly to
In application as an incontinence pad 100 as shown in
To give a thick and comfortable appearance to the inner surface of the inner layer 120 or 220, it was found most desirable that the polyester fibre be knitted to a thickness of approximately 3 to 5 oz. per sq. yd., with a particularly preferable thickness being 4.4 oz. per sq. yd.
Referring now to
The outer, impermeable pant-like garment layer 225, or outer layer 125, provides further waterproofing, particularly for any outer clothing that might be worn over the diaper 200 or incontinence pad 100. The respective outer layer 125 or 225 is mounted to cover the bottom surface 105 or 205 of the viscose rayon median layer 110 or 210 and preferably includes a polyurethane film 130 or 245 that contacts the median layer 110 or 210, thereby preventing absorbed fluid from passing through the median layer 110 or 210. The outer layer 125 or 225 is preferably formed by means of a web of polyester fibre, which is preferably a warp knit tricot material stitched with a pre-stretched polyurethane film 130 or 245 bonded to the knitted polyester fibre. The pre-stretching gives the outer layer 125 or 225 a thick bumpy appearance, and provides additional strength. The thickness of the fibre portion of the outer layer 125 or 225 is normally between about 2.0 and 4.0 oz. per sq. yd., and preferably about 2.2 oz. per sq. yd.
The three layers 120, 110, 125 or 220, 210, 225 are preferably stacked together to form the incontinence pad 100 or diaper 200, respectively, and are preferably stitched together only around the periphery of their mated edges. Illustrated and described with reference to the diaper 200, and as shown in
A diaper 200 according to the present invention can further include a mesh liner 240 which is removably placed onto the inner layer 220. The mesh liner 240 is used to collect solid excrement and can, together with the solid excrement, be flushed down the toilet for disposal in the sewage system. As such, the liner 240 is preferably made from a biodegradable fibrous mesh material. Alternatively, the liner 240 can be made from a polyester mesh material which can be washed and reused.
The diaper 200 of
Various other modifications and alterations may be used in the design and manufacture of the improved reusable diaper composition according to the present invention without departing from the spirit and scope of the invention, which is limited only by the accompanying claims. For example, the reusable and absorptive mat herein described can be adapted for various other applications or uses beyond the diaper or incontinence pad as disclosed. The inner and outer layers may be made of any suitable material and include various finishes or additives to provide desired characteristics. These may include odour masking additives, prints or other designs for aesthetic reasons, additional waterproofing layers, or additional layers for added comfort to the wearer. In addition, a plurality of reusable and absorptive mats or median layers as described may be combined to provide a greater degree of liquid absorption and retention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2657077 | Mar 2009 | CA | national |
