AU2022272011A1

AU2022272011A1 - Wafer for an ostomy bag

Info

Publication number: AU2022272011A1
Application number: AU2022272011A
Authority: AU
Inventors: Luke Harry BATCHELOR; Duale Abdirahman Mohamed MAHDI
Original assignee: Welland Medical Ltd
Current assignee: Welland Medical Ltd
Priority date: 2021-05-12
Filing date: 2022-05-11
Publication date: 2023-11-09
Also published as: WO2022238697A1; EP4337271A1; GB2607564A

Abstract

A wafer for an ostomy bag comprises a film having an adhesive coating, wherein the adhesive comprises a composition comprising carboxymethyl cellulose (CMC) and a two-part addition-curing composition comprising silicone.

Description

Wafer for An Ostomy Bag

The present invention relates to a wafer for an ostomy bag.

Background of the Invention

Ostomy bags are medical devices that are worn by an individual and they can be used for the collection of waste from a surgically diverted bowel or urinary system of the individual. They are used to collect waste that is output from a stoma created in the ostomate's skin and connected to the intestine or urinary system.

Known ostomy bags comprise a pouch, which is also referred to as a collection bag, and, in some cases, the collection bag is attached mechanically or with adhesive to a wafer, commonly referred to as a mounting plate, a flange or a baseplate. The wafer is fixed to the skin of an individual and the ostomy bag allows the waste to drain from a stoma into the collection bag while protecting the surrounding skin from contamination by the waste.

Ostomy bags should be air-and water-tight and they should allow the individual to lead an active normal lifestyle that can include all forms of sport and recreation. However, there is a need to make ostomy bags discreet.

The need to provide discreet ostomy bags must be balanced with the need to provide a sufficiently large wafer so that it adheres to the skin and supports a collection bag which is sufficiently large so that unexpected deposits can be accommodated by the bag. The wafer must provide a secure attachment to the skin of an ostomate but it must also be discreet and allow for the ostomy bag to be removed for emptying or disposal. Typically, ostomy bags are emptied at least once per day.

The wafer is commonly manufactured of a hydrocolloid pressure sensitive adhesive, referred to hereinafter as hydrocolloid, which serves as an adhesive to attach the ostomy bag to the skin. The known wafers, comprising a hydrocolloid, are relatively thick and do not conform well to the body.

In addition, known wafers can become detached from the body when the ostomate moves. This can result in loss of, or decline in, adhesion of the ostomy bag. Loss of, or decline in, adhesion can have potentially difficult and embarrassing consequences for an ostomate due to the nature of the waste in the pouch and unpredictable output from the stoma.

The present invention seeks to provide a wafer suitable for securing an appliance such as an ostomy bag to the skin of a patient about a stomal opening, wherein the wafer addresses one or more of the problems presented by prior art arrangements. In particular, the present invention seeks to provide a wafer for an ostomy bag which addresses major concerns of ostomates in conformability, comfort, security and discreetness.

In light of the problems discussed above, various proposals have been made, but there remains a need for an improved device which address one or more of the problems presented by prior art arrangements. In this regard, the present invention seeks to provide an alternative device which preferably addresses one or more of the problems presented by prior art arrangements.

Summary of the Invention

In accordance with a first aspect of the present invention there is provided a wafer for an ostomy bag, which comprises a film having an adhesive coating, wherein the adhesive comprises a composition comprising carboxymethyl cellulose (CMC) and a two-part addition-curing composition comprising silicone.

The two-part addition curing composition is a two part composition which requires the mixture of a silicone polymer with a catalyst, which initiates curing of the composition. Preferably, a first part of the two part composition comprises a vinyl terminated polydimethylsiloxane. Preferably, a second part of the two part composition comprises hydrogen functional siloxane. Preferably, one of the two parts includes a platinum catalyst. In an embodiment, the second part of the composition comprises a platinum catalyst. In an alternative embodiment, the first part of the composition comprises a platinum catalyst. The two-part composition of the invention offers several advantages over one part systems, especially in production environments. Since it is the catalyst and not moisture, as in the case of a condensation curing silicone, that causes the composition to cure, this provides the advantage that they have no issue with section thickness.

Preferably, the platinum catalyst catalyses a hydrosilylation reaction, preferably wherein ~Si-H + ~Si-Vi Si-C H -Si~. In this regard, there are two competing reaction paths: chain extension between vinyl and Si-H terminated polymer and crosslinking between vinyl and Si-H of polymer.

Preferably, the platinum catalyst comprises a divinylsiloxane-platinum complex. Preferably, it comprises less than about 30 ppm platinum.

Preferably, the two-part addition-curing composition comprises about 40% to about 60% of the first part by weight. In addition, preferably, the two-part addition-curing composition comprises about 60% to about 40% of the second part by weight. More preferably, the two-part addition-curing composition comprises about 50% of the first part by weight and about 50% of the second part by weight.

Remarkably, it has been found that the presence of CMC improves the cohesion of the adhesive and reduces the amount of silicone needed. It also helps achieve an immaculate release when the wafer is released from a liner. The adhesive does not leave residue on the liner when CMC is present.

Preferably, the CMC is sodium carboxymethyl cellulose.

Preferably, the composition comprises from about 25% to about 35% CMC by weight. More preferably, composition comprises about 32% CMC by weight. Preferably, the adhesive is cast to have a thickness of about 200 mih to about 350 mih onto the film.

Preferably, the film is of thermosetting elastomer. More preferably, it is of polyurethane (PU).

Preferably, the film has a thickness of about 6 pm to about 9 pm. More preferably, the film has a thickness of about 7 pm.

Preferably, the adhesive is covered with a release liner after curing. This provides the advantage of protecting the adhesive until use. The release liner is removed prior to use to allow the adhesive to be applied to the skin of an ostomate.

Preferably, the release liner comprises a low density polyethylene (LDPE). LEPE is a thermoplastic made from the monomer ethylene and defined by a density range of 917-930 kg/m³ at standard conditions (a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 10⁵ Pa (100 kPa, 1 bar)).

Preferably, the release liner is embossed and placed so the embossed features project away from the adhesive. This provides the advantage of reducing the total contact area between the release liner and the adhesive.

Preferably, the embossed features are defined by pyramids or frustopyramids. The embossed features provide void space and thus less contact area between the release liner and the adhesive. Advantageously, having the embossed features project away from the adhesive makes it easier to peel the release liner away from the adhesive.

Preferably, the release liner has a thickness of about 90 pm to about 110 pm. More preferably, the release liner has a thickness of about 100 pm. Preferably, the polyurethane elastomer film is attached to the pouch of an ostomy bag via an interfacial material. Therefore, preferably, the wafer includes an interfacial material.

Preferably, the interfacial material comprises a low melting point co-polyamide (CoPA) layer laminated with a polyethylene (PE) layer. Preferably, the CoPA has a melting point at atmospheric pressure of about 105°C to about 115°C. Preferably, the PE has a melting point at atmospheric pressure of about 100°C to about 110°C. Advantageously, this material solves the problem of joining a delicate thin silicone adhesive and thin PU backing film to a pouch of an ostomy bag by forming an intermediate layer.

Preferably, the CoPA layer is positioned between the film and the PE layer.

Preferably, in use, the PE layer of the interfacial material is bonded to the pouch of an ostomy bag.

This joining of the outer most film of a pouch to the wafer is not only limited by the fact that the PU elastomer film of the wafer is a thermoset material unlike the thermoplastic of the outer most film of the pouch, but the limitations in terms of temperature and pressure presented those skilled in the art with a need for an innovative solution.

In a second aspect, the invention provides an ostomy bag comprising a wafer according to the invention together with a pouch defined by two opposing surfaces of two walls.

Brief Description of the Drawings

The invention will now be further described with reference to the accompanying drawings in which:

Figure 1 shows an exploded view of a wafer according to the invention. Detailed Description of the Invention

It will be appreciated that aspects, embodiments and preferred features of the invention have been described herein in a way that allows the specification to be written in a clear and concise way. However, unless circumstances clearly dictate otherwise, aspects, embodiments and preferred features can be variously combined or separated in accordance with the invention. Thus, preferably, the invention provides a device having features of a combination of two or more, three or more, or four or more of the aspects described herein. In a preferred embodiment, a device in accordance with the invention comprises all aspects of the invention.

Within the context of this specification, the word "about" means preferably plus or minus 20%, more preferably plus or minus 10%, even more preferably plus or minus 5%, most preferably plus or minus 2%.

Within the context of this specification, the word "comprises" means "includes, amongst other things" and should not be construed to mean "consists of only".

Within the context of this specification, the word "substantially" means "preferably at least 90%, more preferably 95%, even more preferably 98%, most preferably 99%.

The invention provides a wafer for an ostomy bag.

As shown in Figure 1, an embodiment of a wafer (10) of the invention comprises a plurality of layers. A first layer (1) suitable for applying to the skin of an ostomate comprises an adhesive comprising silicone. The first layer (1) is coated onto a second layer (2) which comprises a PU film. A third layer (3), which abuts the second layer (2), comprises a multi-layer film comprising of a co-polyamide layer (4) combined with a polyethylene layer (5). The third layer (3) is bonded to the outer layer (6) of a pouch of an ostomy bag. The pouch may, for example, comprise a vapour barrier film such as PVDC (polyvinylidene chloride) that has been multi-layered with an EVA film (6). Advantageously, the wafer (10) of the invention can be used with all three types of stoma (ileostomy, colostomy and urostomy) and products described as 'stoma caps'.

The adhesive comprises about 32% by weight sodium carboxy methylcellulose and a two-part addition-curing composition comprising silicone.

The two-part addition-curing composition comprises about 50% by weight of a first part and about 50% by weight of a second part. The two parts of the two-part addition-curing composition can vulcanize slowly at room temperature or rapidly at temperatures of about 120°C. One part of the two-part composition contains a vinyl terminated polydimethylsiloxane and a second part contains a hydrogen functional siloxane. One of the two parts contains a platinum catalyst. At lab bench scale the two mixed components can be cast onto a backing material using a film applicator. For mass production a coating line can be used were the composition comprising silicone is stored in a reservoir prior to coating.

This composition comprising silicone acts as an adhesive and it is coated onto a polyurethane (PU) elastomer film (2) having a thickness of about 7 pm. The polyurethane (PU) elastomer film (2) acts as a backing and the composition comprising silicone (1) can be cast with a thickness of about 200 pm to about 350 pm onto this PU backing.

When the curing process is complete a liner must be attached to preserve the surface of the adhesive created. In one embodiment, it was found through peel testing and wear testing that the most suitable liner was a 100 micron LDPE embossed release liner with the texture orientated away from the composition comprising silicone to reduce surface area contact. In an alternative embodiment, such as a smooth featureless LDPE release liner, a bond with the thin delicate construction was found to be too strong. In this regard, removal of some of the release liners tested resulted in damage to the adhesive layer of the wafer. In this regard, cohesive failure occurred and chunks of the adhesive layer were removed with the release liner when the release liner was removed from the wafer. Advantageously, the invention provides a very thin wafer (10) with advantages from being so thin and using a silicone adhesive. The silicone is a highly biocompatible US Pharmacopia (USP) class 6 material due to is chemical simplicity and cross linked macro-molecular structure. The silicone also has atraumatic removal from the skin of an ostomate in part due to its elastomeric properties and silicone chemistry.

During wear testing it was discovered that the very thin and conformable construction prevented forces from accumulating in one place of the wafer (10). This actually improves security and reduces the need for adhesive strength that can cause skin cell stripping.

The adhesive composition has carboxymethylcellulose (CMC) added before curing. This improves the cohesion of the silicone and reduces the amount of silicone needed. It also helps achieve an immaculate release from the release liner. The adhesive composition does not leave residue on the release liner when CMC is present.

The wafer (10) must be attached to an ostomy pouch (6) so that stoma waste can be collected. There are two interconnected technical problems that must be overcome to do this.

Firstly, the polyurethane backing (2) is a thermoset material due to its cross-linked elastomeric structure. It cannot be directly heat-welded onto a thermoplastic pouch film (6).

Secondly, the resulting construction of the backing layer (2) and composition comprising silicone (1) is very thin and soft. The thin silicone layer is very susceptible to damage from the heat and pressure of a heat weld. In this regard, the silicone is soft and contains very little cross-links due to its required adhesive properties. In addition, the backing material (2) is very thin and does little to shield the silicone in a heat weld process. This problem has been addressed by providing an interfacial material (3) with a low melting point on the wafer side and pouch side.

Various films have been tested as an interfacial layer (3). The first film comprised a thermoplastic polyurethane laminated with an adhesive EVA layer. A partial bond was created using this film. The difficulty was a consequence of the high bonding temperature required of the TPU at 160C°. It was difficult to achieve a complete bond over the entire surface without causing damage to the silicone. The EVA part of the technical film more easily achieved a bond with a pouch film since it only required 80 C° to achieve an adhesive state.

A second technical film comprised a further lamination of a co-polyamide (Nylon) combined with a polyethylene. These materials required temperatures of 105C° and 100C° respectively to form a bond by welding. A strong bond was generated easily when heat welded at 120C°.

Examples

Example 1

After the Silpuran RTV gels had been investigated for what amounts of CMC they could hold the next step was to establish what these combinations performed like when peel tested from human skin.

A comparison was made of the peel strength of various compositions comprising silicone with a hydrocolloid composition having a known formula. The hydrocolloid was of a known, non-integrated type consistent with composition described in US3339546 having a thickness of 1mm.

A product (Silpuran 2130) that could hold the most CMC and still be formed into a thin coating did not have a very high peel strength. This was due to the low viscosity as specified for the product. A product having 35% by weight CMC had a peel strength much closer to the peel strength of the known hydrocolloid composition for the three wear times tested. A double layer concept had an outermost layer comprising Silpuran 2114 with just 25% by weight CMC and it matched the peel strength of the hydrocolloid for the 10 and 240 minutes wear time. Later, wear testing would suggest that when the wafer is very thin and conformable, the adhesive bond is challenged by movement less and the need for strong adhesive is eliminated. A product having Silpuran 2142 produced higher peel strengths but there was residue and inconsistencies between cohesive and adhesive bond failure with the same specimens. Results are shown in table 1. Table 1

Silpuran 2114, Silpuran 2130 and Silpuran 2142 are examples of two-part addition curing compositions comprising silicone. The different Silpuran products are defined by the viscosity of the two parts of the product. The units of viscosity in mPa s and the viscosity for the two parts A+B is as follows: Silpuran 2114 is 12000 and 10000, Silpuran 2130 is 1,100 and 1000, Silpuran 2142 is 80000 and 40000.

Example 2

A 180 degree FINAT peel test was used as a more precise way to determine how CMC influences cohesion during peeling. Silpuran 2114 was chosen for its stability and relatively high peel strength. It required 25% CMC for the bond with polyester strips to fail in adhesion and not cohesion. It has been determined that this combination will release from a 1.84 N/25mm bond and a composition comprising 35% CMC by weight is much stronger at resisting failure in cohesion. Results are shown in table 2. Table 2

Exam le 3 The same castings were tested for tackiness and compared with the 0.45N peel force achieved by a known hydrocolloid layer. These results are shown in table 3. Extrapolation suggests that the CMC content should be 32% to satisfy perception of tack. Table 3

Example 4

The moisture handling properties of thin silicone films were investigated in terms of moisture vapour transition rate (MVTR). Testing was carried out as defined in the Fluid Handling Capacity section of the British Pharmacopoeia 1993 Addendum 1996 - Semi- Permeable Hydrocolloid Dressings. The results are displayed in three sets of data due to how Paddington cups used in the test method were placed in the oven on the same day to prevent variation in the sets.

The results show how a very thin 7 micron PU and a lower quantity of 25% CMC by weight contribute towards this property. The 40 micron PU is a thicker more commonly used thickness of PU. Testing the MVTR of a lower proportion of CMC in the adhesive composition justifies the use of a larger CMC proportion in the adhesive composition. For this type of thin film construction, a high MVTR is achieved quickly with little absorption. The MVTR results are shown in table 4 and saline absorption results in table 5.

Table 4

Table 5 Example 5

Moisture vapour transition can be combined with absorption by weighing the specimens attached to the Paddington cup. This can be used to differentiate the amount absorbed from that which transpired. There are two sets of data shown in table 6.

Table 6

Exam le 6 The biophysical measurements made on the skin after wearing the thin silicone variants are shown in table 7.

The four sets of data are shown in their groups of data collected together. Four patches were worn on the arms at the same time for each 24 hour study. Results are reported as the difference between the base measurement and the measurement made after patch wearing. The skin probes include trans-epidermal water loss (TEWL) which was measured immediately after patch removal unlike when barrier function is measured after a period of time. In effect this is a second measure of hydration that supports the skin permittivity measurements for hydration. They form a very strong evidence for moisture handling of adhesives since they are quantitating the same thing via totally different measurement techniques. The TEWL probe measures the moisture that enters a chamber which is different from measuring the electrical capacitance of the skin surface. The results show a very clear advantage for the invention over a known hydrocolloid product and four known products. The thin silicone variants have a ATEWL of about 4 g/m² which is substantially less than the hydrocolloid (11 g/m²) and the four known products. The hydration measurements show a significant superiority in moisture handling of the thin silicone variants compared with the other five adhesives. If the negative values reported are not real reductions in hydration then it might be the case that the silicone has somehow altered the electrical properties of the skins surface. Erythema measurements have a large variation and little can be concluded with the data. Wearing patches for 24 hours does very little to elicit erythema. The melanin changes do seem to correlate with skin hydration to some extent. The skin becomes whiter when more hydrated. The D pH gives no indication of a trend and there does seem to be differences between groups and there separate calibrations.

Table 7

This invention is intended to be used in an ileostomy, colostomy or urostomy products. It can also be used for a stoma cap. This invention allows a very thin silicone wafer construction to be attached to an ostomy pouch film without damaging the thin wafer when its backing material is a thin thermosetting elastomer.

The combination of a room-temperature-vulcanising silicone cast to the stated thickness and backed with 7pm is unique among ostomy products.

The above described embodiments have been given by way of example only, and the skilled reader will naturally appreciate that many variations could be made thereto without departing from the scope of the invention.

Claims

1. A wafer for an ostomy bag, which comprises a film having an adhesive coating, wherein the adhesive comprises a composition comprising a carboxymethyl cellulose (CMC) and a two-part addition-curing composition comprising silicone.

2. The wafer according to claim 1, wherein a first part of the two part composition comprises a vinyl terminated polydimethylsiloxane.

3. The wafer according to claim 1 or claim 2, wherein a second part of the two part composition comprises hydrogen functional siloxane.

4. The wafer according to any one of the preceding claims wherein at least one of the two parts of the two-part addition-curing composition comprises a catalyst.

5. The wafer according to claim 4, wherein the catalyst comprises a divinylsiloxane-platinum complex.

6. The wafer according to claim 4 or 5, wherein the catalyst comprises less than about 30 ppm platinum.

7. The wafer according to any one of the preceding claims, wherein the two-part addition-curing composition comprises about 40% to about 60% of the first part by weight.

8. The wafer according to any one of the preceding claims, wherein the two-part addition-curing composition comprises about 60% to about 40% of the second part by weight. The wafer according to any one of the preceding claims, wherein the CMC is in the form of sodium carboxymethyl cellulose. The wafer according to any one of the preceding claims, wherein the composition comprises from about 25% to about 35% CMC by weight. The wafer according to any one of the preceding claims, wherein the adhesive is cast to have a thickness of about 200 pm to about 350 pm onto the film. The wafer according to any one of the preceding claims, wherein the film is of thermosetting elastomer. The wafer according to any one of the preceding claims, wherein the film is of polyurethane (PU). The wafer according to any one of the preceding claims, wherein the film has a thickness of about 6 pm to about 9 pm. The wafer according to any one of the preceding claims, wherein the adhesive is covered with a release liner after curing. The wafer according to claim 15, wherein the release liner comprises a low density polyethylene (LDPE). The wafer according to claim 15 or claim 16, wherein the release liner is embossed and placed so the embossed features project away from the adhesive. The wafer according to claim 17, wherein the embossed features are defined by pyramids or frustopyramids. The wafer according to any one of claims 15 to 18, wherein the release liner has a thickness of about 90 miti to about 110 miti. The wafer according to any one of the preceding claims wherein the film is attached to the pouch of an ostomy bag via an interfacial material. The wafer according to claim 20, wherein the interfacial material comprises a low melting point co-polyamide (CoPA) layer laminated with a polyethylene (PE) layer. An ostomy bag comprising a wafer according to any one of the preceding claims and a pouch defined by two opposing surfaces of two walls.