APPARATUS FOR DETERMINING PROPERTIES OF ABSORBENT ARTICLES

Abstract: There is disclosed apparatus for determining properties of absorbent articles, comprising: a) a test surface upon which an article to be investigated can be located and arranged with respect to a liquid challenge application position; b) pressure applying means adapted to apply a predetermined pressure around the liquid application position on an article located on the test surface; c) controlled hydrostatic head liquid applying means adapted to apply liquid for absorption by an article on the test surface; and d) measurement means adapted to effect a measurement of liquid movement through the articles; characterised in that the pressure applying means are provided in modular component form, the modules being combinable in different ways to apply a plurality of different predetermined pressures.

Description: APPARATUS FOR DETERMINING PROPERTIES OF ABSORBENT ARΗCLES This invention relates to determining properties of absorbent articles such, for example, as infants' nappies (diapers), training pants, adult incontinence pads and garments and sanitary napkins, especially such as contain superabsorbent materials or hydrogels contained within a structure which transports liquid from the surface to the core of the article so as to present a dry or relatively dry skin contact area and components of such articles. For purposes of comparison between different designs of such articles, possible for research and development as for consumer advice, as well as for quality control reasons, measurements are made of their properties, specifically, but not exhaustively, the amount of liquid they can absorb and the rate at which they absorb it, under different conditions. Different manufacturers use different tests based on different criteria, using different test equipment, and test equipment suitable for one type of product is not necessarily suitable for any other. The present invention provides test apparatus and procedures that are applicable to all such products currently available which are capable of objective measurements of performance and objective comparisons. The invention comprises, in one aspect, apparatus for determining properties of absorbent articles, comprising: a) a test surface upon which an article to be investigated can be located and arranged with respect to a liquid challenge application position; b) pressure applying means adapted to apply a predetermined pressure around the liquid application position on an article located on the test surface; c) controlled hydrostatic head liquid applying means adapted to apply liquid for absorption by an article on the test surface; and d) measurement means adapted to effect a measurement of liquid movement through the article; characterised in that the pressure applying means are provided in modular component form, the modules being combinable in different ways to apply a plurality of different predetermined pressures. The controlled hydrostatic head liquid applying means may comprise a reservoir for a supply of challenge fluid and may comprise valve means adapted to maintain a constant hydrostatic head of liquid on the article. The valve means may comprise an electrically actuated valve such as a solenoid pinch valve, which may be controlled by a liquid level sensor such as an electrode which completes an electric circuit when in contact with the challenge liquid. A first module may comprise both said controlled hydrostatic head liquid applying means and said measurement means. Said measurement means may comprise a timer, which may be controlled, for example by the presence or absence of challenge liquid applied to the article. The timer may be controlled from electrodes between which a circuit is made or broken by the presence or absence of challenge liquid applied to the article. The timer may be contained in an upper housing of said first module, which may be mounted on an open support arrangement upstanding from a base member comprising said controlled hydrostatic head liquid applying means. The support arrangement may comprise legs serving as conductors for liquid-sensing electrodes. Said base member may have provision for interchangeable inserts with different apertures for challenge liquid application to different product categories. At least one other module may be accommodated within the open support arrangement. The apparatus may comprise module securing means securing modules together, which may be magnetic for ready assembly and disassembly. The apparatus may be adapted to load an article under a range of predetermined pressures between 0.17 psi and 1.0 psi - the pressures may be achieved by a selection of modules and areas over which the modules apply pressure. The various determinations that can be carried out using apparatus according to the invention are derived from prior art determination devised by different manufacturers and applied to their own products. The prior art determinations are made using test procedures and equipment intended to stimulate actual conditions of use as regards quantities and flow rates of liquid as well as pressures on the articles concerned that affect rates of take-up of liquid and the possibility of squeezing or wicking out liquid already absorbed. There is, however, no independent standard test procedure or equipment, and no consensus that any one procedure or apparatus simulates any more realistically than any other. The present invention could fill the need for a standard testing apparatus adapted for evaluation of a range of products upon which a standard test protocol could be established. To that end, and by way of illustration, one embodiment of apparatus for determining properties of absorbent article and a set of tests to be carried out therein will now be described with reference to the accompanying drawings, in which: Figure 1 is a view of the apparatus from one side; Figure 2 is a view of the apparatus from the opposite side of Figure 1 ; Figure 3 is a view like Figure 1 with a module removed; Figure 4 is a view like Figure 2 with the same module removed as in Figure 3; Figure 5 is a part view like Figure 3 with a further portion removed; Figure 6 is a part view like Figure 3 showing electrodes; Figure 7 is a view from below showing electrodes; Figure 8 is a view of a first insert; Figure 9 is a view of a second insert; Figure 10 is a view of a fluid transfer module exerting a pressure of 0.1 psi; and Figure 11 is a view of a fluid extraction module exerting a pressure of 0.7 psi. The drawings show apparatus for determining properties of absorbent articles, comprising: a) a test surface 11 - which may be of a base supplied with the apparatus or may, as illustrated, be a surface of a workbench or worktable - upon which an article 12 to be investigated can be located and arranged with respect to a liquid challenge application position (the determination of which will be referred to further below); b) pressure applying means 12, 14, 15 adapted to apply a predetermined pressure around the liquid application position on a article 12 located on the test surface 11 ; c) controlled hydrostatic head liquid applying means 16 adapted to apply liquid for absorption by an article 12 on the test surface 11 ; and d) measurement means 17, 18 adapted to effect a measurement of liquid movement through the article 12; characterised in that the pressure applying means 14, 15 are provided in modular form, the modules being combinable in different ways to apply a plurality of different predetermined pressures. The controlled hydrostatic head liquid applying means 16 comprises a reservoir 19 for a supply of challenge liquid, and solenoid pinch valve means 21 acting on flexible delivery tube 22, the valve means 21 being controlled by a liquid level sensor - electrode 23 - which closes the valve means 21 when liquid on the surface of the article 12 reaches it to make an electrical circuit. Set at a height of 20 mm above the article 12, the hydrostatic head of liquid on the article is controlled to a limit of 0.03 psi. This is in contrast to some procedures where the hydrostatic head of liquid is uncontrolled or relatively so, leading to inaccurate simulation or poor reproducibility. Various challenge liquids are used in the various procedures used by different manufacturers, for example, a simulated urine and a simulated plasma. While such may add verisimilitude to the procedures by simulating the fluids expected to be encountered by e.g. nappies (diapers) in incontinence garments on the one hand and sanitary napkins on the other, their different densities can adversely affect the value of the results obtained. In the 'standard' tests proposed in connection with the apparatus of the invention, a solution of KC1 or NaCl at a concentration of 0.9% w/w in de-ionised water is proposed for all procedures simulating urine resulting in an electrically conductive challenge liquid of standard density and standard viscosity. For feminine sanitary protection, a synthetic plasma is used for better simulation of viscosity. The control circuit for the valve means 21 comprises the electrode 23 and a second electrode 24 (see Figures 6 and 7). The liquid applying means 16 and measurement means 17, 18 are comprised in a first pressure-applying module 14 comprising a base member 25 with an open support arrangement consisting of legs 26 upstanding from the base member 25 supporting an upper housing 27 which contains a countdown timer 28 with setting buttons 29 and on/off and control switches 31 and which also contains a d.c. power source for the apparatus, and a controller (not shown) for the countdown timer which causes it to run for so long as electrode 24 and another electrode 32, both of which terminate at the base of module 14 (and are therefore level with the top of an article when the base is placed directly on the article 12, i.e. without the intermediary of module 13) are connected electrically by the challenge liquid, but which stops when there is no liquid between electrodes 24 and 32, i.e. when any liquid applied to the article 12 has been absorbed thereby. A test step comprises challenging the article 12 with a measured amount of electrolyte, challenge liquid by placing the same in reservoir 19, whence it falls through tube 22 until it reaches the level of the electrode 23 whereon pinch valve 21 closes until the level drops below electrode 23. The valve 21 through repeated opening and closing admits challenge liquid to the article 12 until the amount charged into the reservoir 19 has been exhausted therefrom, the liquid meanwhile being absorbed into the article. The countdown clock starts counting down a preset time as soon as the first liquid lands on the article 12 and continues to count until all the water from the reservoir 19 has been absorbed, then stops, automatically recording the absorption time. The legs 26 serve as conductors in circuits from the sensors 24, 32. Module 15 is simply a plastic cover, with weighting, that rests on the base 15 of module 14 to give additional pressure on the article 12. Module 13 is a rubber skirt to reduce leakage for products which hydrate unevenly. In addition to adjusting the pressure on the article 12 by adding or changing modules 14, 15, inserts 33 (Figure 8) and 34 (Figures 9) are used in base 25 of module 14 to modify the area of the base and hence modify the pressure (weight/area). The apparatus is sometimes used as illustrated in Figure 1 with modules 14, 15 in service. Module 40 is, however, only called into service in connection with fluid transfer out of an article under low pressure. Module 40 is used on its own to apply pressure to filter papers placed on the wetted article, the fluid transfer after a given time lapse being measured by determining the increased filter paper weight or high pressure (fluid extraction) when module 41 is used on its own to the same end. Since the apparatus permits of the specification of standard test procedures, in terms of the pressure regime, dosage regime (aliquots dosed, number of doses) - and time cycles, it would be beneficial to ensure that there were standards relating to precisely where, on the articles under tests, the doses(s) of challenge liquid should be applied. The apparatus facilities precise location with regard to a marked position on the article as it is easy to centralise the base 25 (or, if attached to the module 13) which has a control aperture. It is proposed for example, that a standard dose point determination be made, perhaps as follows:- It is also proposed that standard procedures, such as measuring absorption rate by feeding four aliquots of challenge fluid at 10 minute intervals, noting the absorption time for each aliquot on the timer 28 and summing the four absorption times, under prescribed standard pressures, be agreed on the basis of trials yielding procedure parameters that best simulate actual conditions and best characterise actual performance for the products in question, all this possibly on the basis of inter-laboratory trials and to result in consistency of evaluation regardless of differences in location, testing personnel and other factors that could influence the results.

Claims: CLAIMS 1. Apparatus for determining properties of absorbent articles, comprising: a) a test surface upon which an article to be investigated can be located and arranged with respect to a liquid challenge application position; b) pressure applying means adapted to apply a predetermined pressure around the liquid application position on an article located on the test surface; c) controlled hydrostatic head liquid applying means adapted to apply liquid for absorption by an article on the test surface; and d) measurement means adapted to effect a measurement of liquid movement through the article; characterised in that the pressure applying means are provided in modular component form, the modules being combinable in different ways to apply a plurality of different predetermined pressures. 2. Apparatus according to claim 1, in which the controlled hydrostatic head liquid applying means comprises a reservoir for a supply of challenge liquid. 3. Apparatus according to claim 1 or claim 2, in which the controlled hydrostatic head liquid applying means comprises valve means adapted to maintain a constant hydrostatic head of liquid on the article. 4. Apparatus according to any one of claims 1 to 3, in which the liquid applying means comprises a solenoid pinch valve. 5. Apparatus according to any one of claims 1 to 4, in which the controlled hydrostatic head liquid applying means is controlled by a liquid level sensor. 6. Apparatus according to any one of claims 1 to 5, in which a first module comprises said controlled hydrostatic head liquid applying means and said measurement means. 7. Apparatus according to claim 6, in which said measurement means comprise a timer. 8. Apparatus according to claim 7, in which said timer is controlled. 9. Apparatus according to claim 8, in which said timer is controlled by the presence or absence of challenge liquid applied to the article. 10. Apparatus according to claim 9, in which the said timer is controlled from electrodes between which a circuit is made or broken by the presence or absence of challenge liquid applied to the article. 11. Apparatus according to any one of claims 7 to 10, in which the timer is contained in an upper housing of said first module. 12. Apparatus according to claim 11, in which said upper housing is mounted on an open support arrangement upstanding from a base member comprising said controlled hydrostatic head liquid applying means. 13. Apparatus according to claim 12, in which said open support arrangement comprises legs serving as conductors for liquid-sensing electrodes. 14. Apparatus according to claim 12 or claim 13, in which said base member has provision for interchangeable inserts with different apertures for challenge liquid application. 15. Apparatus according to any one of claims 12 to 14, in which at least one other module is accommodated within the open support arrangement. 16. Apparatus according to any one of claims 1 to 15, in which there are three modules. 17. Apparatus according to any one of claims 1 to 16, comprising module securing means securing modules together. 18. Apparatus according to claim 17, in which said module securing means are magnetic. 19. Apparatus according to any one of claims 1 to 18, adapted to load an article under a range of predetermined pressures between 0.6KPa and 50.1KPa.

Inventors: KELLY NEIL, KELLY, NEIL
Applicants: DATASORB LIMITED, KELLY NEIL, KELLY, NEIL
Application year: 1999
Main classification: A61F13
IPC codes: A61F13