Many personal care articles are used to retain body excretions. Examples include bedpan liners, incontinence bags, diapers, ostomy bags and sanitary napkins. It would be advantageous to fabricate articles of these types from materials that may be easily disposed of via a toilet bowl of a WC and a number of prior proposals have been made in this regard.

Thus a number of patents describe the construction of"so-called"disposable ostomy bags utilizing film laminates comprised of a layer of a water soluble polymer and a layer of a water insoluble polymer. In the final bag, the water insoluble layer (usually polyvinylidine chloride) is innermost and serves to collect and retain the body excretion and protect the outer water-soluble layer against contact with the aqueous media contained in the excretion which would act either as solvent or plasticiser (depending on the exact nature of the water soluble polymer). Polyvinyl alcohol is usually the material of choice for the water soluble polymer due to its excellent barrier properties to malodorous gasses. Examples of ostomy bags of this type are disclosed, for example, in GB-A-2 083 762, US-A-4 772 279 and US-A-4 917 689.

There is however a disadvantage with the constructions described in the previous paragraph in that although the outer polyvinyl alcohol layer will dissolve or disintegrate on exposure to water in the toilet bowl, the inner water impermeable layer will remain intact and may lead to blockage of the plumbing system.

Another toilet disposable ostomy bag construction is described in US 5 674 578, wherein a blend of polyethylene oxide and plasticized polyvinyl chloride is bonded to a barrier layer of polyvinylidene chloride. The presence of polyethylene oxide renders the first layer water degradable. This approach again has the drawback that the second layer of polyvinylidene chloride is non-water degradable.

One approach that has been postulated to overcome this problem is disclosed in US-A-5 769 831 which describes a flushable ostomy appliance having pH sensitive films either side of a hydrophilic material. The pH sensitive material may be a flexible polyurethane (presumably an anionic polyurethane dispersion grade) which is dissolved by application of alkaline media, either to the pouch or to the toilet bowl. A similar approach is outlined in US-A-5 009 647 in which the use of a carboxylated resin such as poly (acrylic acid) may be used in a laminate construction.

It is however a disadvantage of the constructions described in the preceding paragraph that in the event of the body excretion being of an alkaline (rather than the usual acidic) nature the article will begin to degrade in situ when worn by a person and this is clearly undesirable.

It is an object of the present invention obviate or mitigate the above mentioned disadvantages.

According to a first aspect of the present invention there is provided a film-like material for use in the manufacture of a disposable article, said material comprising a blend of a hydrophilic polyurethane and a hydrophobic polymer.

The term polyurethane as used herein also embraces polyurethane ureas.

We have found that the blend of a hydrophilic polyurethane and a hydrophobic polymer provides a material that will degrade in the presence of an acidified, aqueous solution of a chlorine-containing bleach but not water or body excretions (be they acid or alkaline). Examples of bleach which may be used for this purpose include sodium dichloroisocyanurate (e. g. provided by PRECEPT sterilizing tablets (ex Johnson & Johnson)) although in essence any bleaching agent that is capable of liberation of hypochlorous acid on acidification to low pH may be used. Examples of such agents are hypochlorites, such as sodium hypochlorite or calcium hypochlorite, compounds containing N-chloro groups, such as the aforementioned sodium dichloroisocyanurate or N-chlorosuccinimide, or commercially available bleaches wherein the nature of the bleaching agent is not disclosed such as Vortex (supplied by Procter & Gamble).

Essentially any acid (or concentration thereof) may be used to produce hypochlorous acid as long as a sufficiently low pH (2.5-5, typically 3.5) is generated.

Thus the present invention renders it possible to fabricate articles which when used may be disposed of by treatment with an acidified, aqueous solution of a chlorine- containing bleach. Such disposable articles provide a second aspect of the invention.

The article may for example comprise a bag, pouch, or the like (herein referred to collectively as a bag) fabricated from the material of the first aspect of the invention.

The article may for example be for the collection/retention of body excretions and may for example be a bedpan liner, incontinence bag, diaper, ostomy bag or sanitary napkin. It is however also contemplated that articles in accordance with the invention may be used for the collection of other waste products.

The bag of the article may be fabricated solely from the material of the first aspect of the invention. In certain instances however it may be desirable for the bag to be fabricated from a laminate of a first layer of this material (which is innermost of the bag) and a second film-like layer of a water degradable (e. g. water-soluble or water-dispersible polymer). Such a laminate, which provides a third aspect of the invention, will likewise degrade in aqueous acidified bleach as described above. Thus, for example, in the case of an ostomy or incontinence bag, it will generally be preferred that the bag comprises an inner, first layer of the material of the first aspect of the invention and a second layer of polyvinyl alcohol which is used for its barrier properties to malodorous gasses.

Therefore it is possible to dispose of articles such as ostomy bags and incontinence bags produced from the laminate by placing the (used) article with its contents in the bowl of a WC, adding an acidified chlorine containing bleach and allowing the material to degrade before flushing the WC.

We recognize that polyurethane has previously been proposed for use in disposable articles. Thus, for example, US-A-5 009 647 (see above) cites polyurethane as having low odour barrier properties and being of use for bags that cannot be disposed of via a WC. Polyurethanes have also been used as adhesives to bond layers of polyvinylidene chloride and polyvinyl alcohol together in laminate structures for disposable personal care items (EP-A-0 589 437). However, to our knowledge, the present invention is the first proposal to utilise the good mechanical and barrier properties of polyurethanes for disposable items and yet have a convenient means of breaking down the article to render it easily disposable.

Preferred embodiments of the invention will now be described with specific reference to laminate of the third aspect of the invention in which polyvinyl alcohol is used as the water soluble, second layer as well as articles produced therefrom which are intended to be disposed of in a WC. Examples of such articles include ostomy bags and incontinence bags.

The length of time taken for the laminate structure to degrade in the presence of a bleach to a point where the laminate has been broken down sufficiently to be flushed down the toilet without blockage problems will depend of factors such as the relative amounts of the hydrophilic polyurethane and the hydrophobic polymer within the first layer and also on the nature and concentration of the bleach.

It is preferred that the first layer is formulated (and of a thickness) such that it is breached by a 2% solution of sodium dichloroisocyanurate (SDIC) acidified to a pH of 3.5, e. g. with 1-2% w/w of 35% hydrochloric acid in a time scale of 5 to 20 minutes.

Longer time scales mean that the disposed article must remain for an inordinate amount of time in the bowl before the WC can be flushed. A shorter time scale means that the polyurethane may be too hydrophilic or of insufficient thickness to be suitable as a barrier to prevent moisture vapour compromising the properties of polyvinyl alcohol. Another implication may be that the molecular weight of the material is below that which is satisfactory as for a coherent film and may be breached by physical rupture in use.

This"breach"test, outlined above, may be carried out by securing the material of the first layer (without the second layer being present) over the mouth of a 250ml beaker and applying ca 2g of the acidified SDIC solution and measuring the time taken for the solution to breakthrough the polymer film.

Although the first layer is capable of being degraded in the presence of an acidified aqueous solution of a bleach, it will nevertheless retain its integrity in the presence of the aqueous media of body excretions. Thus a disposable article comprised of a bag of the laminate with the first layer being innermost and intended for the collection/retention of body excretions will retain its integrity until disposed of in the manner described above. More particularly, the aqueous media of the body excretion is not able to breach the first layer and cause dissolution of the polyvinyl alcohol second layer.

Generally the first layer will be comprised of 20% to 60% by weight of the hydrophilic polyurethane and 80% to 40% by weight of the hydrophobic polymer although the exact proportions (which may be outside these ranges) will depend on the nature of the polymers and the desired final properties of the second layer. Generally the composition of the first layer will be governed by the thickness of the layer. Thus for a first layer of 40-50 thickness a composition of 40-60% by weight of the hydrophilic polyurethane and 60%-40% by weight of the hydrophobic polymer is generally appropriate. If the thickness is reduced to 20-3 Ou. however, the above composition is unsuitable as the moisture vapour barrier properties are no longer adequate and a composition of 20-35% by weight of the hydrophilic polyurethane and 80%-65% by weight of the hydrophobic polymer is more appropriate.

Typically the first layer will have a thickness of 10-60p, more preferably 20-501l.

The second layer preferably has a thickness of 30-80p, more preferably 40-60p.

Hydrophilic polyurethanes for use in accordance with the invention will generally have a soft block incorporating poly (ethyleneoxide) (ethylene glycol) units. Such groups within the backbone of a polyurethane render the capability of water binding and enable the polymer to swell and transmit moisture vapor. Suitable hydrophilic polyurethanes will comprise hard and soft blocks with the latter incorporating poly (ethyleneoxide) units desirably having a molecular weight of at least 400 and preferably in the range 400 to 8000. Generally also the overall content of poly (ethyleneoxide) units in the hydrophilic polyurethane will be at least 10% by weight within the polyol mixture used to produce the softblock.

The swell of these types of polyurethane are the key to their ability to be rapidly broken down by aqueous bleaching agents. As the material being challenged by the bleaching agent swells the degradation process proceeds throughout the whole thickness profile of the sample and disintegration will occur more rapidly. Thus a polyether- urethane having a soft block structure solely based on ethylene glycol units may break down within 30 seconds, whereas one having hydrophobic ether units in addition to ethylene glycol would take longer, from 30 seconds to several minutes. The exact time of breakdown will be governed inter alia by the relative lengths of the hydrophobic polyether and ethylene glycol units, the ratio of hard to soft blocks within the polyurethane, the molecular weight of the polyurethane and the thickness of the sample tested.

Hydrophilic polyurethanes for use in the invention may be step-growth polymers formed via the reaction of an organic diisocyanate (OCN-R-NCO) and appropriate chemical species having two active hydrogen substituents capable of reacting with such diisocyanate groups. A suitable polyurethane may be formed by the initial reaction of an aliphatic or aromatic diisocyanate with a relatively low molecular weight polymer (MW 400-8,000, preferably 1,000-2,000) incorporating poly (ethylene oxide) units and having end groups comprising an active hydrogen species (e. g. OH or NH2), in the ratio of n+1 : n moles respectively to form a pre-polymer.

Representative examples of such diisocyanates include: (i) hexamethylene diisocyanate, 4,4 dicyclohexylmethane diisocyanate, isophorone diisocyanate, 4,4 diphenylmethane diisocyanate, toluene diisocyanate, 1,5 naphthalene diisocyanate, tetramethyl xylene diisocyanate, and mixtures thereof.

Representative examples of the relatively low molecular weight polymers that may be used include: (ii) polyethylene glycol having terminal hydroxyl or amine functionality, a block co-polymer (AB, ABA etc) of ethylene glycol and a hydrophobic polyol (such as propylene glycol or polytetramethylene glycol) having terminal hydroxyl or amine functionality or mixtures thereof.

Such low molecular weight polymers (or mixtures thereof) as listed under (ii) may be used individually to react with diisocyanates to form a pre-polymer. Alternatively the low molecular weight polymers, e. g. as exemplified under (ii) above may be used in conjunction with a further low molecular weight (e. g. 250-8000, preferably 1000-2000) polyol not containing poly (ethylene oxide) units. Examples of such further polymers include: (iii) polytetramethylene glycol, polypropylene glycol, polycaprolactone polyol, polyethylene adipate polyol, polytetramethylene adipate polyol, polyethylene- tetramethylene adipate polyol, polyhexamethylene adipate polyol, polyethylene- hexamethylene adipate polyol, polyhexamethylene carbonate glycol, polyethylene- hexamethylene carbonate glycol, and mixtures thereof. For the purposes of this definition the term polyol has been used to refer to a polyester material containing terminal hydroxyl functionality and glycol a polyether (or polycarbonate) material containing terminal hydroxyl functionality. In each of the above examples the terminal hydroxyl functionality may be replaced by terminal amine functionality.

The pre-polymer is then extended by reaction with a low molecular weight aliphatic compound comprising difunctional groups with active hydrogen species (e. g.

OH or NH2) and a diisocyanate in the ratio of x: x-lmoles per mole of prepolymer. Such low molecular weight aliphatic compounds comprising difunctional groups with active hydrogen species may be either diols or diamines or alkanolamines, representative examples of which include: (iv) ethylene glycol, ethylene glycol, triethylene glycol, 1,2 propylene glycol, 1,3 propylene glycol, 1,4 butane diol, 1,3 butane diol, 2,3 butane diol, 1,6 hexane diol, 2,5 hexane diol, and mixtures thereof.

(v) ethylene diamine, propane diamines, butane diamine, pentane diamine, 2, methyl pentane diamine, 1,4 cyclohexyl diamine or mixtures thereof.

(vi) ethanolamine.

In an alternative to the above described procedure, the prepolymer may be produced by reaction of n+1 moles of the diisocyanate (e. g. as listed under (i)) with (n) moles of a polyether glycol as identified under (iii) above. The product of this reaction is then further reacted with 2 molar equivalents of a hydroxyl or amine terminated low molecular weight polymer containing poly (ethylene oxide) units such as exemplified under (ii) above (i. e. one mole of prepolymer is reacted with 2 moles of a poly (ethylene oxide) containing polymer) The extension reaction of the prepolymer is then effected with a low molecular weight aliphatic compound having two active hydrogen substituents, e. g. as exemplified by compounds (iv)- (vi) above and a diisocyanate (such as exemplified by (i) above) in the ratio of x : x+1 moles per mole of prepolymer.

The hydrophilic polyurethane will generally have a hard block content of 18-35%.

Generally the hard block will be derived from an aromatic diisocyanate and a butane diol.

The soft block will be derived from an aromatic diisocyanate and a polyethylene oxide of the type described above. The polyethylene oxide may be capped with amine groups.

The hydrophobic polymer used in admixture with the hydrophilic polyurethane may for example be a hydrophobic polyurethane. The hydrophobic polyurethane will not contain any ethylene glycol units in the soft block structure and will therefore undergo limited swelling by aqueous bleaching agents. Units of short ethylene glycol units (as identified above) may be incorporated into the hard block of a polyurethane without producing a material with appreciable hydrophilic properties (swelling in water) providing that there are not longer chains of polyethylene glycol in the soft block of the material. The rate of degradation of the material is now confined to the surface of the polyurethane and will therefore be much slower. In general the time for disintegration of materials of this type will be greater than 20 minutes and more probably one to several hours. The exact time of breakdown will be governed inter alia by the relative length of the hydrophobic units in the soft block, the ratio of hard to soft blocks within the polyurethane, the molecular weight of the polyurethane and the thickness of the sample tested.

Hydrophobic polyurethanes for use in the invention may be produced by initial formation of a prepolymer from n+1 moles of an organic diisocyanate (such as exemplified by the compounds listed under (i) above and n moles of a compound having a hydrophobic moiety and two active hydrogen substitutents, e. g. as exemplified by the compounds listed under (iii) above.

The pre-polymer may then be extended by reaction with a low molecular weight aliphatic compounds comprising difunctional groups with active hydrogen species (e. g.

OH or NH2) (e. g. as exemplified under (iv)- (vi) above) and a diisocyanate (e. g. as exemplified by (i) above) in the ratio of x : x-1 moles.

The hydrophobic polyurethane may for example have a hard block content of 20- 45%, more preferably 25-35%. The hard block may be derived by reaction of an aromatic diisocyanate with a butane diol. The soft block may be derived from an aromatic diisocyanate and polytetramethylene diol.

As contemplated above, the polymer is produced in a"two-shot"reaction (i. e. the pre-polymer formation step if carried out in the first stage before the extension step is effected in the second step). Alternatively the reaction may be carried out a bulk"one- shot"reaction (i. e. all reactants are mixed together in a single stage reaction).

The polyurethane polymers may be melt-processed from bulk or dissolved in a convenient solvent and fabricated by solvent casting. Alternatively, the pre-polymer may be diluted by an appropriate solvent and the extension stage of a"two-shot"polyurethane reaction effected in solution. Examples of solvents that may be used in such reactions are dependent on the nature and concentration of the reactants used but may include toluene, tetrahydrofuran, methyl ethyl ketone, dimethylformamide, dimethylacetamide, N-methyl pyrrolidone, dimethylsulphoxide or mixtures thereof.

As an alternative to the use of a polyurethane as the hydrophobic polymer it is possible to employ polyvinyl chloride, polyvinylidine chloride or polymethylmethacrylate.

The polyvinyl alcohol layer of the preferred laminate of the third aspect of the invention may either be a grade that is hot or cold water soluble. In general polyvinyl alcohol having a degree of hydrolysis greater than 88% will be hot water soluble, whilst a lower degree of hydrolysis (85-88%) will produce a cold water soluble material. Airvol 103 (Air Products) is an example of the former while L330 (Aquafilm) is an example of the latter. Both types may be used in this application. A cold water soluble polyvinyl alcohol grade will be more readily broken down in a toilet bowl but will have a greater sensitivity towards water. A hot water soluble polyvinyl alcohol grade will be less susceptible towards water but will require hot water to be added to it to ensure dissolution over an acceptable timeframe. The molecular weight of polyvinyl alcohol will also have an effect on the performance of the material. The molecular weight may be low (number average molecular weight 7,000-13,000), medium (number average molecular weight 15,000-33,000), high (number average molecular weight 35,000-68,000) or very high (number average molecular weight 70,000-101,000). Higher molecular weight materials will tend to have improved water sensitivity, but potentially any grade may be useful providing it is used with a layer having appropriate barrier properties towards water or moisture vapour.

The laminate material of the third aspect of the invention may be comprised solely of the first and second layers. Alternatively the material may be a trilaminate structure comprising a central polyvinyl alcohol, ("second") layer between two"first" layers each comprised of a blend of a hydrophilic polyurethane and a hydrophobic polymer. Other constructions are also possible. The individual layers of the material may be laminated together be bonding (e. g. heat sealing) over the entire area of the interfacial surfaces of the films, or as patterned (crosshatch) sealed areas or by bonding only at the edges of the films.

The material in accordance with the first aspect of the invention (with or without a layer of polyvinyl alcohol or other water soluble polymer) may be used, for example, for the manufacture of disposable, personal care articles, e. g. ostomy bags, bed pan liners, incontinence bags, diapers and sanitary napkins. If no second layer is present then the preferred features described above for the first layer are still applicable. Currently both diapers and sanitary napkins have moisture impermeable outer film layers (usually polyethylene, perforated to confer some breathability) bonded to absorbent layers that are usually based on cellulose. Thus while the cellulosic layers will swell and disintegrate when in contact with water in a toilet bowl the impermeable layer will remain intact. The use of the material in accordance with the first aspect of the invention (in place of the conventional polyethylene layer) will render articles such as diapers and sanitary napkins easily disposable.

It will be appreciated that whilst the present invention is applicable particularly to disposable, personal care articles, the material of the first aspect of the invention may also be used for bags to dispose of materials such as agrochemicals, detergents and household goods as disclosed in US-A-5 486 526.

The invention is illustrated by reference to the following non-limiting Example.

Example 1 Films of various thicknesses were produced by solvent-casting of hydrophobic polyurethanes, hydrophilic polyurethanes and blends thereof. The polyurethanes used are listed in Table 1 which also gives the relative properties of the polyurethanes and the film thicknesses used.

All films were prepared by solvent casting the particular polyurethane (or blend thereof) from dimethylforamide.

Table 1 Polyurethane film Hydrophilic or Film thickness p Time to code hydrophobic breakthrough Hyphob 1 Hydrophobic 40 > 600 seconds Hyphob 2 Hydrophobic 40 >600 seconds Hyphil 3 Hydrophilic 50 49 seconds Hyphil 2 Hydrophilic 50 487 seconds Hyphil 1 Hydrophilic 50 45 seconds Hyphob 1/Hyphil 1 40 540 seconds blend (1: 1) Hyphob 1 is an aromatic polyether-urethane, having a hard block content of 26- 29% and Hyphob 2 is an aromatic polyether-urethane having a hard block content of 40- 43%. Both materials are based upon a polyol of molecular weight 2,000.

Hyphil 1 is an aromatic polyether-urethane-urea, having a hard block content of 20-24% with a soft block structure of both hydrophilic and hydrophobic polyols each having a molecular weight of 2,000. Hyphil 2 is an aromatic polyether-urethane-urea, having a hard block content of 26-30% with a soft block structure of both hydrophilic and hydrophobic polyols, the former having a molecular weight of 2,000 and the latter of 1,400. Hyphil 3 is an aromatic polyether-urethane-urea, having a hard block content of 18-23% with a soft block structure of both hydrophilic and hydrophobic polyols, the former having a molecular weight of 2,000 and the latter of 1,000.

The stability of the films towards bleach was determined using a 2% by weight solution of sodium dichloroisocyanurate (SDIC) acidified by 1-2% w/w with 35% hydrochloric acid. The source of SDIC was PRECEPT sterilizing tablets (ex Johnson & Johnson), each of which contains 2.5g of SDIC.

A first test was conducted by securing the polyurethane film under test over the mouth of a beaker (250ml) and applying ca 2g of the acidified SDIC solution and measuring the time taken for the solution to break through the polymer film. If no breakthrough had occurred after 10 minutes the test was terminated. The results are present in the final column of the above Table.

The results clearly show that while the hydrophilic grades of polyurethane films are broken down within a time frame that would be adequate for the disposal of a personal care article, their rapid rate of moisture transmission would make them unsuitable as stand alone films in their own right. The rapid rate of moisture transmission of many hydrophilic polyurethane grades are unsuitable for applications where there is a requirement for the film to act as a barrier to moisture vapour. The blend of hydrophilic polyurethanes with hydrophobic polyurethanes are however appropriate. The hydrophobic films are not sufficiently degraded over this time period however.

The blend of the hydrophilic and hydrophobic polymers provided to be particularly suitable, the breakthrough time being 540 seconds.

Further tests were carried out on the above films be immersing the films in acidified SDIC (1%) at a pH of 2.5-5.0, typically 3.5, and assessment of the time to disintegration of the film was carried out. The results are set out in Table 2 below. Polymer Film Film Thickness Wt (g) Solution Observation (microns) Hyphob 1 40 0.1 lOg of 1% No evidence of acidified SDIC breakdown after 600 seconds. Film clumps Hyphob 1 10 0.1 lOg of 1% No evidence o acidified SDIC breakdown afte 600 seconds. Fil tacky. Hyphil 1 40 0.1 lOg of 1% Breakdown of acidified SDIC film into fine particulate matter within 300 seconds Hyphob 1/40 0.1 lOg of 1% Breakdown of Hyphil 1 blend acidified SDIC film after 590 (1: 1) seconds The results of this study confirm that the hydrophilic film breaks down far more readily than the hydrophobic film and that the blended polyurethane film is broken down within a potentially useful timeframe. The difference between hydrophobic and hydrophilic polyurethanes is that the latter contain polyethylene glycol units that have the ability to bind water molecules. However this also confers much greater permeability to oxygen and moisture vapor upon the films. A further test was therefore carried out by heat sealing a film of Hydrophil 1 polyurethane to a film of polyvinyl alcohol and placing -2g of water on the surface of the hydrophilic polyurethane film. The water was found to have permeated through the polyurethane layer and attack the polyvinyl alcohol within 1 hour, indicating that the barrier properties of the polyurethane film were inadequate for the application. When heat sealed to a film of polyvinyl alcohol, the film of the blend of hydrophilic and hydrophobic polyurethanes proved an effective barrier to water when tested by the method described above. After 24 hours no sign of attack on the polyvinyl alcohol layer was visible.