WO1989006142A1

WO1989006142A1 - pH CONTROLLING ABSORBENT PRODUCT AND METHOD FOR PREPARING THE SAME

Info

Publication number: WO1989006142A1
Application number: PCT/GB1989/000013
Authority: WO
Inventors: Liam Patrick Forde
Original assignee: Liam Patrick Forde
Priority date: 1988-01-05
Filing date: 1989-01-03
Publication date: 1989-07-13

Abstract

In a diaper the absorbent material is acidic and capable of releasing H+ ions to lower the pH of urine in contact therewith to below that in which bacteria producing ammonia can grow (about 5.5). The material can be naturally acidic such as sphagnum moss or peat but preferably a neutral absorbent material is protonated.

Description

PH CONTROLLING ABSORBENT PRODUCT AND METHOD FOR PREPARING THE SAME

This invention relates to diapers, incontinent pads or sheets, and other sanitary products which come in contact with urine or the like, in which undesirable bacteria can grow.

Various types of absorbent materials such as wood pulp, starches, towelling, absorbent powders and synthetic polymers are used at present to absorb babies' urine and urea of incontinent and incapacited persons in items such as diapers and bed sheets.

One-piece disposable diapers comprise, in order, a liquid-permeable or semi-permeable material adapted to be in contact with the skin, a relatively thick absorbent substrate, and an outer layer of an impermeable material, the whole suitably shaped and usually including means for fastening the nappy about the baby's waist. Relatively "old-fashioned" towelling diapers provide an absorbent substrate, and are often used together with, on the inside, a separate layer of a liquid-permeable or semi-permeable material, a separate pair of impermeable pants, and separate fastening means such as a safety pin. The general arrangement of materials is the same in both cases.

It is known that bacteria can grow in urine above a pH of about 5.5 and metabolise the urea in the urine, in the process producing ammonia. The ammonia in contact with the skin, can cause 'nappy-rash', or with incontinent people, bed-sores. Many attempts have been made to combat this problem, such as by using acidic compounds to capture or neutralise the ammonia, or lowering the pH of the urine to below 5.5 to inhibit the growth of the ammonia-producing bacteria.

A typical way in which these acidic compounds are added to the diaper is described in patent nos. GB 1484501, US 424242, US 4273786, US 3964486 and US 3920015. In these patents, the acidic compound is admixed with or lies powdered on the surface of the absorbent material, and dissolves when contacted with the urine. It is, however, possible to have areas of absorbent or infill material which is nor treated, and there is also a tendency with powders to concentrate in particular areas, for example the outer edge or the diaper, leading to variations in the pH of the urine such as acid deficient spots where the bacteria can still grow, or highly acidic spots which can cause discomfort to the baby.

It is an object of the present invention to obviate or mitigate the aforesaid disadvantages. According to the first aspect of the present invention there is provided in a diaper, incontinant bedding and the like, the absorbent material of which is capable of releasing hydrogen ions to maintain the at of urine in contact, therewith to between 2 and 5.5 for a practicable period The absorbent material itself is now acidic rather than having for example an acidic powder on the surface thereof. Therefore H⁺ ions can be released uniformly throughout the contacting urine mitigating the effect of pH variances. Furthermore final pH of the urine is more predictable and controllable. The invention may further aid in the absorbancy quality of the acidic material. Preferably the H ⁺ ions are carried by a hydroxyl base, and more preferably the absorbent material is a polymer of glucose. The limits of the desired urine pH are defined by pH value below which the bacteria producing the ammonia cannot, survive (about 5.5 and below); and by the pH value where the acidic urine causes acid burns or otherwise substantially irrates the skin (below about pH2). Preferably the invention works in the pH range of 2.5 to 3. Obviously, however, because of the specificity that can be obtained, the absorbent material could be designed to give most desired urine pH values, such as for example, that required to capture the ammonia. The acidic absorbent material can be admixed with other non-acidic absorbent materials, and naturally acidic or more preferably is substantially an absorbent material which has been protonated since it would not otherwise be suf f iciently acidic . Naturally acidic materials preferably include suitably sterilised sphagnum moss or peat (dead sphagnum moss). Both of these materials are also highly absorbent and sphagnum moss contains phenolic acid which has antiseptic qualities and lanolin which has soothing qualities. It should be noted, however, that sphagnum moss can contain, for example, heavy metals and, the moss should therefore be treated and sterilised to render the moss suitable for use. Preferably the natural material such as the sphagnum moss and peat are bleached, which steriles, makes the material more attractive and does not substantially affect its acidic character. The sphagnum moss or peat can be mixed with a relatively neutral material such as wood pulp at, at least 10%, preferably 20% to 30% by weight of the moss or peat.

A high degree of pH control can be obtained if an insufficiently acidic absorbent material is protonated. Most absorbent materials in use are polymers of glucose, such as cellulose or starch based materials, and the free hydroxyl groups can act as bases. The degree of protonation and thus final urine pH will depend, for example, on the concentration and time of exposure of the H⁺ ions, as well as the strength of the base.

Preferably the absorbent material is soaked in an aqueous solution of any suitable acid, of pH for example from 1.8 to 6.5 and preferably from 3.5 to 6. Advantageously sulphuric or hydrochloric acid is used.

The process of protonating an absorbent material forms a second aspect, of the invention. According to second aspect of the invention, there is provided, a process of preparing an acidic absorbent material for a diaper, incontinant bedding or the like, comprising protonating an absorbent material capable of taking up hydrogen ions and of maintaining the pH of urine in contact therewith to from 2 to 5.5 for a practicable period. The acidic absorbent material as defined in the first aspect, and made in accordance with the second aspect of the invention, forms the third aspect of the present, invention. The invention will now be illustrates by way o f the following examples. Series 1

Samples of sphagnum moss and peat were bleacheo. Each of these, and a sample of non-acid wood pulp were then contacted with urine under simulated body conditions and incubated for some time. Two sets of tests were run (see tables I and II) and in each case the sample weight used was 5g and the weight of fresh urine was 27g. In the second run (table II) the results were taken over several days.

It is well known that above about pH 5.5, gram negative and gram positive bacteria will grow with the accompanying generation of ammonia. No ammonia (NH₄) was detected in the sphagnum moss or peat samples, whereas with the wood pulp, ammonia was detected after 6 hrs in the first sample (urine ph 5.3) and after 3/4 hr in the second sample (urine pH 6.6). Series 2

A typical commercial product, i.e. a baby's diaper as sold by a supermarket, was taken and the absorbent infill was removed and. examined.

It was found that the infill product was wood pulp, and this was weighed to record its dry weight. Various solutions of dilute sulphuric acid were prepared having the following pH values.

Sample No. 1 pH 2.00

Sample No. 2 pH 3.10

Sample No. 3 pH 3.80

Sample No. 4 pH 6.50 The wood pulp infill was divided into eight equal parts and two parts were used with each of the sample acids.

The first of the two portions of wood pulp was completely submerged in the. dilute sulphuric acid f or a period of 30 seconds. It was found that during this 30 seconds the wood pulp soaked up dilute acid and became completely and totally saturated. The second of the two portions of wood pulp was allowed to remain i n the di lu te acid for a period of up to three hours, at which stage it was completely saturated. This was repeated f or each of the other three acid solutions.

On removal from the dilute acid the wood pulp was squeezed to remove as much as possible of excess acid, and the sample was then dried at 102ºC, until it was found to be 100% dry. The sample was then weighed and its weight checked against the original dry weight.

Eight samples of wood pulp infill from a commercial diaper were prepared in this manner. A properly calibrated pH meter and pH paper were both used in the following tests on the treated samples. A concentrated solution of ammonia pH 10.4 was used to test the acidic qualities of the treated samples. Ordinary water pH 7.8 was also used to determine the acidic qualities of the treated samples.

The following results were achieved using wood pulp samples which had been immersed. Sample No. 1 (in dilute acid for only 30 seconds).

Acid pH 2.00 Ammonia pH 10.4 reduced to pH 8.2 Water pH 7.8 reduced to pH 2.8 Sample No. 2

Acid pH 3.4

Ammonia pH 10.4 reduced to pH 8.9 Water pH 7.8 reduced to pH 4.0

Sample No. 3

Acid pH 3.8

Ammonia pH 10.4 reduced to pH 9.1

Water pH 7.8 reduced to pH 4.8 Sample No. 4

Acid pH 6.5

Ammonia pH 10.4 reduced to pH 10.0 Water pH 7.8 reduced to pH 7.2

These tests were then repeated on the wood pulp samples which had been immersed in dilute acid for a period of three hours and the same results were obtained in all cases.

The reason that the wood pulp became protonated was because starch and cellulose are polyers of glucose. The glucose molecule has three free OH groups. The hydrogen ions from the acid attach themselves to the oxygen if the hydroxyl group forming on ionic compound.

Whenever water enters the glucose molecule the hydrogen ions prefixed to the OH group are released and combine immediately with the hydrogen in the water molecule forming H₃O. Any sulphate ions present, are in a very stable condition and are thus harmless.

The concentration of hydrogen ions in the infill material can be varied by submerging it in different strengths of the dilute acid. By this means, a controlled neutralisation process can be achieved. The last wash of the wood pulp at the wood pulp factory, prior to drying, can be carried out in a dilute acid solution, to suit a diaper manufacturer's requirements.

Where, for example, sphagnum is bleached, it can also be protonated if necessary. Series 3

Infill material from a diaper were protonated and tested as before, but in this instance using hydrochloric acid and using fresh urine 27g or 250ml excreted by a two year old child. A fresh sample of protonated wood pulp weighted 5g.

As before the pH of the urine should be maintained below about 5.5 (to prevent growth of bacteria) until a soiled diaper would be changed, for example up to ten hours. It should be noted that at urine pH of about 6.2there are buffers present which mitigate the acidic effect of the infill material, and although such a urine pH is not usual, infill material of stronger pH would have to be used. The results of these experiments are shown in Table III . Series 4 of experiments are shown in Table IV.

Claims

1. In a diaper, incontinent bedding and the like, the absorbent material of which is capable of releasing hydrogen ions to maintain the pH of urine in contact therewith, from 2 to 5.5 fora practicable period.

2. A diaper, incontinent bedding and the like as claimed in claim 1 wherein the absorbent material is a polymer of glucose, the free hydroxyl groups carrying the hydrogen ions.

3. A diaper, or incontinent bedding and the like, as claimed in claim 2 wherein an absorbent material was protonated to form the acidic absorbent material.

4. A diaper, or incontinent bedding and the like, as claimed in claims 1 or 2 wherein the absorbent material is naturally acidic.

5. A diaper, or incontinent bedding and the like, as claimed in claim 4 wherein the absorbent material is sterilised sphagnum moss or peat.

6. A diaper, or incontinent bedding and the like, as claimed in claim 5 wherein the sphagnum moss or peat a re bleached.

7. A diaper, or incontinent bedding and the like, as claimed in any one of the preceding claims wherein the urine maintained pH is from 2.5 to 3.

S. A process of preparing an acidic absorbent material for a diaper, incontinent bedding o r the like, comprising protonating an absorbent material capable of taking up hydrogen ions so that it is capable of maintaining the pH of urine in contact therewith to from 2 to 5.5 for a practicable period.

9. A process as claimed in claim 8 wherein the absorbent material includes free hydroxyl groυps which take up and release the hydrogen ions.

10. A process as claimed in claip 9 whereir the absorbent material is soaked in an acid solution to protonate it.

11. A process as claimed in claim 10 wherein the acid is sulphuric or hydrochloric acid.

12. An absorbent material as defined in any one of claims 1 to 7 or made in accordance with a method of claims 7 to 11.