Sachet

Abstract

A sachet defining a volume. The sachet has a sheet of material fastened to itself and/or another sheet of material and contains a sufficient quantity of absorbent material such that when the sachet is exposed to liquid a swelled volume of the absorbent material exceeds the volume of the sachet, and wherein the fastening means weakens on exposure to liquid. The sheet material may be paper. The absorbent material may be a super absorbent polymer. The super absorbent material may be sodium polyacrylate.

Description

The present invention relates to a sachet.

Sachets comprising a super absorbent polymer material are used for sanitary purposes in the hospital environment to clean up spillages, vomit and other liquid human waste material. Super absorbent material is useful because it can absorb and retain large quantities of liquid relative to its own mass so even a small amount is an effective cleaning tool.

Conventional sachets are formed from water permeable paper or water soluble synthetic polymer such as polyvinlyl alcohol and contain a small quantity of powdered super absorbent material. The paper sachets are designed to burst or rupture when exposed to water containing liquid as a result of the expansion of the superabsorbent material whose volume eventually exceeds the volume of the sachet. It is important that the sachet ruptures when exposed to the liquid so that the superabsorbent material can continue to expand and is released and dispersed throughout the liquid. This maximises the effectiveness of the absorbent material and ensures that it absorbs as much water as possible. It is not a requirement that the polymer sachets rupture when exposed to water containing liquid because they will eventually dissolve and release the absorbent material.

Both types of sachets have advantages and disadvantages. Paper sachets can be produced at a higher rate (up to 100 times faster) than synthetic polymer sachets which tend to melt if they are run through manufacturing machines too quickly. Consequently, paper sachets can be manufactured more efficiently and cheaply than synthetic polymer sachets. However, paper sachets do not have a 100% burst rate which means that some sachets fail to release the absorbent material when exposed to liquid, especially thick liquids such as vomit. Since synthetic polymer sachets are not dependent upon bursting, they always release the absorbent material when exposed to water containing liquid and are not therefore subject to the same failure rate as paper sachets.

One proposed solution is to use a paper of lower tensile strength which is more likely to rupture when subjected to the forces exerted by swelled absorbent material. However, a problem with using such paper is that it cannot withstand the manufacturing process and tends to bum up or tear when run through manufacturing machines.

An object of embodiments of the invention is to provide a sachet that is cheap and efficient to manufacture and has a high rupture rate.

According to an aspect of the present invention, there is provided a sachet defining a volume, the sachet comprising a sheet of material fastened to itself and/or another sheet of material and containing a sufficient quantity of absorbent material such that when the sachet is exposed to liquid a swelled volume of the absorbent material exceeds the volume of the sachet, and wherein the fastening means weakens on exposure to liquid.

Advantageously, the likelihood of a sachet according to the invention failing to rupture when exposed to liquid is minimised. Therefore, embodiments of the invention made from paper and having a high rupture rate may be manufactured cheaply and efficiently.

The fastening means may comprise an adhesive. The adhesive may be a solvent based liquid. The or each sheet of material may be coated with adhesive. Alternatively, the or each sheet of material may be partially coated with adhesive at regions at which the or each sheet is fastened together. The adhesive may be applied at a rate of 1.5 gsm. The adhesive may be applied at a rate of 0.9 gsm. The adhesive may be water soluble. The adhesive may be heat activable. The adhesive may be a lacquer.

Alternatively or additionally, the fastening means may comprise a thread.

The or each sheet of material may comprise paper. The basis weight of paper may be 22 gsm. The paper may comprise machine glazed paper. The paper may be perforated with holes of diameter 300 microns to thereby allow liquid to pass through the walls of the sachet. The perforations may be covered with water soluble lacquer to thereby restrict the transfer of liquid across the sheets of material until exposed to sufficient liquid to cause the lacquer to dissolve and expose the perforations.

The quantity of absorbent material may be chosen such that the swelled volume is at least five times the volume of the sachet. The quantity of absorbent material may be chosen such that the swelled volume is at least ten times the volume of the sachet. The quantity of absorbent material may be chosen such that the swelled volume is at least fifty times the volume of the sachet.

The absorbent material may be water absorbent. The water absorbent material may be a super absorbent polymer. The polymer may be in granular, particulate or powder form. Alternatively, the polymer may be in sheet form. The polymer may be sodium polyacrylate.

The or each sheet of material may define a space within which the absorbent material is contained. The sachet may comprise a single sheet of material that has been folded and fastened together along the peripheral edges of the folded sides. Alternatively, the sachet may comprise two sheets of material fastened together along their respective peripheral edges. The or each sheet of material may be fastened to itself and/or another sheet of material such that the sachet is sealed along the entire length of the peripheral edges. Alternatively, the or each sheet may be fastened to itself and/or another sheet of material such that the sachet is partially sealed along the length of the peripheral edges. Those regions of the peripheral edges that are not sealed together may be sized such that super absorbent material cannot exit the sachet when not exposed to liquid.

In order that the invention may be more clearly understood embodiments thereof will now be described, by way of example, with reference to the accompanying drawings of which:

FIG. 1 is a plan view of a sachet according to the invention;

FIG. 2 is a cross sectional side view of the sachet shown in FIG. 1;

FIG. 3 is an enlarged side view of an end of the sachet shown in FIG. 2;

FIG. 4 is a cross sectional side view of the sachet shown in FIG. 2 shortly after being exposed to a liquid;

FIG. 5 is a cross sectional side view of the sachet shown in FIG. 4 when the absorbent material has breached the interface between the sides of the sachet;

FIG. 6 is a cross sectional side view of the sachet shown in FIG. 4 when the absorbent material has breached the interface between the sides of the sachet and also breached a side of the sachet; and

FIG. 7 is an enlarged side view of an end of a different embodiment of the sachet shown in FIG. 2;

Referring to the drawings, there is shown a burstable or rupturable sachet 1 for absorbing liquid made from two roughly square sheets of 22 gsm machine glazed bleached kraft paper 3,5 that have been sealed together along their peripheral edges 7, 9 to form an enclosed volume of space 11. Both sheets of paper 3, 5 are water permeable having holes of diameter 300 microns throughout their respective surfaces in a PI pattern. The two sheets are heat welded together along their four peripheral edges 7, 9 with a layer of water soluble, solvent based lacquer applied at 1.5 gsm 20 and disposed at the interface between the two edges to form a line of seal 20 surrounding the space 11. The sachet 1 is particularly suited to the hospital environment where it is desirable to safely clean up unwanted liquid chemicals, or liquid waste from patients such as blood, urine and vomit and with which, physical contact is undesirable.

A quantity of dry granules of sodium polyacrylate, a super absorbent polymer (SAP) 13 is sealed within the space 11 defined by the sachet 1. Sodium polyacrylate has the ability to absorb and retain 200 to 300 times its mass in water which causes the powdered granules to solidify and form a gel. The quantity of SAP 13 sealed within the sachet 1 is chosen such that, when the sachet is exposed to water containing liquid, a swelled volume of SAP exceeds the volume of the space 11 in which the SAP 13 is contained to thereby cause the sachet 1 to rupture.

Referring to FIG. 2, the volume of dry granules of SAP 13 is less than that of the space 11 defined by the sachet 1. When the sachet 1 is brought into contact with water containing liquid, the water permeable paper permits the liquid to enter the space 11 and come into direct contact with the SAP 13. As shown in FIG. 4, the exposure of the SAP granules 13 to water results in absorption of the water by the SAP granules 13 which causes them to swell and increase in volume to form a gel like consistency. If sufficient water comes into contact with the SAP granules 13, they swell to the extent that they fill the space 11 defined by the sachet 1 and exert force upon its walls 3,5.

Exposing the sachet 1 to water containing liquid also causes the water soluble lacquer 10 to dissolve which weakens the bond at the interface between the two sheets 3,5 of the sachet 1. As shown in FIG. 5, the weakening of the bond between the sheets 3, 5 coupled with the increased internal pressure of the sachet 1 resulting from the expansion of the SAP granules 13 causes the seal 20 to break at one or more locations. It can also result in the complete detachment of the two sheets 3, 5 from one another. The breaking of the seal 20 permits the SAP granules 13 to spread beyond the walls 3,5 of the sachet 1 and become dispersed throughout the liquid where they can continue their absorption and expansion. Thus the act of rupturing the bag and dispersing the SAP 13 through a liquid maximises the SAP's absorbing ability.

In addition to causing a breach at the weakened interface between the sheets 3,5 as with conventional paper sachets, the expansion of the SAP granules 13 can also result in a rupture at the surface of a sheet of material 3, 5 due to the pressure exerted by the SAP granules 13 overcoming the wet strength of the paper. Thus the combination of a paper sachet with a water soluble lacquer helps to maximise the chances of the sachet 1 bursting and releasing the SAP granules 13 contained within.

FIG. 7 illustrates a second embodiment in which the inner and outer facing sides of both sheets of the sachet are coated with a 1.5 gsm layer of water soluble lacquer, but in other respects the second embodiment is similar to the first. A sachet 1 with water soluble lacquer 22, 23 coating its sides provides added support and strength to the paper and therefore permits the use of a paper with a lower tensile strength than that of the first embodiment. A coated paper of lower tensile strength is more robust than the raw paper and can therefore be run through sachet manufacturing machines without tearing or burning.

When a sachet 1 according to the second embodiment is exposed to water containing liquid, the water soluble lacquer 22, 23 dissolves from the inner and outer surfaces thereby permitting the water to pass through the perforations in the sides of the sachet and come into contact with the SAP granules 13. Since the paper is of a lower tensile strength than that of the first embodiment, when the water soluble lacquer 22, 23 has partially or fully dissolved from the sachet 1, the lower strength paper is left exposed and therefore is more prone to rupture as a result of the rapidly expanding SAP granules 13.

In addition, since the perforations of the sachet 1 are covered by lacquer 22,23, the SAP granules 13 contained within are not activated until the lacquer has partially or fully dissolved which means that activation of the sachet 1 does not occur until the sachet 1 is exposed to a sufficient quantity of water. Thus accidental activation of a sachet I by small quantities of water is minimised.

It is of course to be understood that the above embodiments have been described by way of example only and that many variations are possible without departing from the scope of the invention.

Claims

1. A sachet defining a volume, the sachet comprising a sheet of material fastened to itself and/or another sheet of material and containing a sufficient quantity of absorbent material such that when the sachet is exposed to liquid a swelled volume of the absorbent material exceeds the volume of the sachet, and wherein the fastening means weakens on exposure to liquid.

2. A sachet as claimed in claim 1, wherein the fastening means comprises an adhesive.

3. A sachet as claimed in claim 2, wherein the adhesive is a solvent based liquid.

4. A sachet as claimed in claim 2, wherein the sheet material is coated with adhesive.

5. A sachet as claimed in claim 2, wherein the sheet material is partially coated with adhesive at regions at which the or each sheet is fastened together.

6. A sachet as claimed in claim 2, wherein the adhesive is applied at a rate of 1.5 gsm.

7. A sachet as claimed in claim 2, wherein the adhesive is applied at a rate of 0.9 gsm.

8. A sachet as claimed in claim 2, wherein the adhesive is water soluble and/or heat activable and/or a lacquer.

9. A sachet as claimed in claim 1, wherein the fastening means comprises a thread.

10. A sachet as claimed in claim 1, wherein the or each sheet of material comprises paper.

11. (canceled)

12. A sachet as claimed in claim 10, wherein the paper comprises machine glazed paper.

13. A sachet as claimed in claim 10, wherein the paper is perforated with holes which are shaped and sized to permit water to pass through the walls of the sachet and to restrict the absorbent material from passing through the walls.

14. A sachet as claimed in claim 13, wherein the walls are 300 microns in diameter.

15. A sachet as claimed in claim 13, wherein the perforations are covered with water soluble lacquer to restrict the transfer of liquid across the sheets of material until exposed to sufficient liquid to cause the lacquer to dissolve and expose the perforations.

16. (canceled)

17. (canceled)

18. (canceled)

19. A sachet as claimed in claim 1, wherein the absorbent material is water absorbent.

20. A sachet as claimed in claim 19, wherein the water absorbent material comprises a super absorbent polymer.

21. A sachet as claimed in claim 20, wherein the polymer is in granular, particulate or powder form.

22. A sachet as claimed in claim 20, wherein the polymer is in sheet form.

23. A sachet as claimed in claim 20, wherein the polymer is sodium polyacrylate.

24. A sachet as claimed in claim 1, wherein the or each sheet defines a space within which the absorbent material is contained.

25. (canceled)

26. (canceled)

27. (canceled)

28. (canceled)

29. (canceled)