WO1990004456A1

WO1990004456A1 - Superabsorbant package

Info

Publication number: WO1990004456A1
Application number: PCT/AU1989/000456
Authority: WO
Inventors: John Kenneth Bethune
Original assignee: John Kenneth Bethune
Priority date: 1988-10-19
Filing date: 1989-10-19
Publication date: 1990-05-03

Abstract

A package comprising a first housing (2) having at least one fluids permeable surface and a second housing (3) located inside the first housing, the second housing isolating particulate superabsorbent polymer material (1) and having at least one degradable surface which weakens or dissolves in the presence of moisture. The package may be used, for example, as an absorbant mat for food packaging or medical waste, or as a slow water release device in agriculture.

Description

SOTERABSQRaAOT PACKAGE

FIELD OF THE INVENTION

The invention relates to a packaging system for particulate material. In particular the system is adapted for use with particles designed to interact with the environment surrounding the package.

BACKGROUND OF THE INVENTION

Dispersion systems have been developed over a number of years for use in applications including the production of "superabsorbent" tissue. By dispersing amongst the fibres of cellulose particles using superabsorbent polymers, it is possible to produce a tissue with a greatly increased liquid absorbance capacity. Applications for such tissues include incorporation in nappies to remove urine from adjacent to a baby's skin, removal of pollutants or contaminants from liquid mixtures, the removal of spilled liquids from surfaces and the storage of liquids in a dispersed form in soils for slow release into such soils.

However, considerable difficulty has been encountered in developing methods of incorporation of the superabsorbents into the carrier medium. It is essential to ensure the superabsorbent is properly located for optimal use. For example, nappies should be sprayed at key points whilst the cellulose fibres are being laid into a sheet. In another example, superabsorbent polymer is incorporated into a mat for use in packaging seafood and this polymer must be located in the area to which moisture is likely to gravitate.

Well documented properties of polyacrylate and polyacrylamide particles include their ability to quickly absorb large amounts of liquids such as water from their immediate environment. For agricultural applications these types of superabsorbent polymers may be modified to allow them to release the liquid back into the environment at a predetermined rate.

In the manufacture of such a superabsorbent tissue, a major problem is that, in its dehydrated form, the superabsorbent polymer particles are too small to be retained within the matrix. To overcome this problem, methods have been developed to modify the polymer particles so as to cause them to adhere to the material making up the matrix. A major disadvantage of these methods is that the modifications of polymer particles required to achieve the desired adhesive properties have been found to adversely affect their superabsorbent and liquid retention properties.

The invention has arisen from a study of packaging systems currently in use and a desire to achieve a maximal retention rate of particulate material within a package but permit the package to be subsequently used so as to take advantage of the superabsorbent properties of the particulate material. For the purposes of the following description of the invention when reference is made to particulate material, a superabsorbent particular polymer particles is meant.

DESCRIPTION OF THE INVENTION

According to the invention, there is provided a package comprising a housing having at least one fluids permeable surface and particulate material (as hereinbefore defined) located therein. For example the fluids permeable material may be paper, plastic or cellulose.

The housing may be a container such as a bag which will initially hold the particulate material within it. When contacted with fluids, the fluids permeable surface allows the fluids to enter the bag. Simultaneously, the particulate material will begin to hydrate.

The fluids permeable surface is typically a degradable surface, for example, cellulose tissue or a non-degradable surface such as the material sold by Dupont under the trade mark TYVECK. As the degradable surface weakens or is dissolved it will open under the force of the swelling particulate material. This material will freely fill any void in the degradable surface. If the fluids degradable surface is a woven or non-woven matrix, the swelling particles being of a size greater than the matrix will not escape from the housing. Typically, the particulate material is placed within the package or mat which is itself then sealed. In another preferred embodiment, the particulate material e.g. anhydrous polyacrylate and/or polyacrylamide particles, are placed within a water-soluble paper sachet which is then itself sealed and incorporated into a fibrous matrix, such as a non-woven or fabric matrix. Upon the non-woven matrix being placed in water, the water penetrates both the non-woven matrix and the package and is absorbed by the polyacrylate and/or polyacrylamide particles. . The polyacrylate and/or polyacrylamide particles absorb water and swell whilst the container surface breaks down and dissolves. By this time the polyacrylate and/or polyacrylamide particles have swollen to such a size that they may be independently retained within the non-woven matrix without needing to be enclosed within the now dissolved package.

In another preferred embodiment, hydrated particles are placed within a water-insoluble but water-permeable sachet which is then itself sealed and incorporated into a fabric which may, among other things, be of a spun bonded manufacture. Upon the fabric being placed in a dry environment, water is released from the hydrated particles through the sachet membrane and then by a process of dispersion away from the fabric. Upon such release of water from the hydrated particles, the polymer particles shrink in size but continue to be retained within the fabric by reason of the continuing presence of the water-insoluble but water-permeable sachets incorporated into the fabric. The fabric may at a later time be "re-charged" by soaking the fabric, and thus the polymer particles contained in the sachets incorporated into it, in water. This latter arrangement may have considerable application in the agricultural field for irrigation purposes. For example the particulate material can be placed into an elongated sachet or bag and located beneath the surface of the ground. Water may be caused to periodically pass through the sachet or bag to hydrate the particulate material. By appropriate selection of the particulate material it is possible to achieve the release of the water to the surrounding ground in a regulated way. The sachet or bag also includes fillers to ensure the sachet or bag does not collapse under the weight of the overlying ground when the particulate material becomes dehydrated. Typical fillers are synthetic beads or balls made of substantially water impermeable materials such as polystyrene.

In a further preferred embodiment, hydrated particles are placed within a water-insoluble but water-permeable sachet without being itself sealed and incorporated into a fabric.

A further example of the application of the invention is the manufacture of spun bonded "root bags" incorporating sachets as described above containing hydrated polyacrylate and/or polyacrylamide particles, which root bags would be wrapped around the root systems of plants for the purposes of retaining a replenishable yet constant water supply to the plant.

Accordingly, by utilizing the package as described above it is possible to easily and economically encapsulate the particulate material allowing it to be incorporated into existing packaging or other applications such as in agriculture or horticulture.

Applications of sachets where one or both surfaces are disintegrating paper (cellulose) include:

(a) absorbent mats for food packaging;

(b) absorbent sachets for the airline industry;

(c) medical waste containers; and

(d) sea containers to allow free moisture absorption;

Such sachets where one or both surfaces are disintegrating paper can be used for flood damage control and for fire damage clean up.

Applications of sachets or tube where both surfaces are non-degradable but water permeable surfaces for flow moisture transfer to the surrounding environs include:

(a) pot plant watering devices;

(b) tree watering devices; and

(c) irrigation tunnels for broadscale horticulture and agriculture. DESCRIPTION OF THE DRAWINGS

The invention will now be further illustrated with reference to the accompanying drawings:

Figure 1 is a plan view of a sachet unit series showing the cross-sectional line A-B.

Figures 2 and 3 are cross-sectional views of the sachet as shown in Figure 1.

As shown in Figure 2, a cross-sectional view A-B of a sachet is shown having sides A and B where 1 is the superabsorbent polymer, 2 is the non-woven or TYVECK water-permeable non-degradable membrane, 3 is the non-woven, TYVECK, cellulose or degradable plastics membrane which can be both water permeable and non-degradable or completely degradable, and 4 is the heat sealed joint.

Figure 3 is the cross-sectional view A-B of the sachet as shown in Figure 1 which depicts a degradable water permeable membrane 3 breaking down allowing expanded superabsorbent polymer particles to fill the void available.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A package comprising a housing having at least one fluids permeable surface and particulate material (as hereinbefore defined) located therein.

2. The package according to claim 1 wherein the at least one fluids permeable surface is paper, plastic or cellulose.

3. The package according to claim 1 wherein the at least one fluids permeable surface is a degradable surface.

0 4. A package comprising a first housing having at least one fluids permeable surface and a second housing located in the first housing, the second housing isolating particulate material (as hereinbefore defined) and having at least one degradable surface

- _. which weakens or dissolves in the presence of moisture.

5. The package according to claim 4 wherein the first housing is a woven or non-woven material having an opening less than the diameter of the particulate material when partially hydrated.

20 6- A method of providing moisture to an area over a predetermined period of time comprising the steps of (a) locating a package according to claims 1 to 5 in the area.

(b) hydrating the particulate material; and

(c) at the end of the predetermined period of time again hydrating the particulate material •

7. The method of claim 6 wherein step (b) precedes step (a).

8. A package according to claims 1 to 3 wherein the housing additionally includes filler.

9. A package according to claims 4 and 5 wherein the first housing additionally includes filler.

10. A package according to either claims 8 or 9 wherein the filler is synthetic beads or balls.