U.S. patent application number 10/497445 was filed with the patent office on 2005-02-10 for wound dressings.
Invention is credited to Bray, Roger, Caskey, Philip Roy, Patel, Champa.
Application Number | 20050033213 10/497445 |
Document ID | / |
Family ID | 9926921 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050033213 |
Kind Code |
A1 |
Bray, Roger ; et
al. |
February 10, 2005 |
Wound dressings
Abstract
A wound dressing comprises a wound-contacting layer composed of
a mixture of honey and a moisture-absorbing agent; a
water-permeable fabric backing layer; and an intermediate layer
comprising water-permeable fabric impregnated with a mixture of
honey and a moisture-absorbing agent.
Inventors: |
Bray, Roger; (Nuneaton,
GB) ; Patel, Champa; (Coventry, GB) ; Caskey,
Philip Roy; (Cambridge, NZ) |
Correspondence
Address: |
HOWSON AND HOWSON
ONE SPRING HOUSE CORPORATION CENTER
BOX 457
321 NORRISTOWN ROAD
SPRING HOUSE
PA
19477
US
|
Family ID: |
9926921 |
Appl. No.: |
10/497445 |
Filed: |
October 4, 2004 |
PCT Filed: |
December 2, 2002 |
PCT NO: |
PCT/GB02/05441 |
Current U.S.
Class: |
602/48 |
Current CPC
Class: |
A61L 15/44 20130101;
C08L 5/04 20130101; C08L 5/00 20130101; C08L 1/28 20130101; A61L
2300/404 20130101; A61L 2300/608 20130101; A61L 15/225 20130101;
A61L 15/225 20130101; A61L 15/225 20130101; A61L 2300/30 20130101;
A61L 15/225 20130101 |
Class at
Publication: |
602/048 |
International
Class: |
A61F 013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 2001 |
GB |
0128936.2 |
Claims
1. A wound dressing having honey and a moisture-absorbing agent,
comprising a wound-contacting layer including a mixture of honey
and a moisture-absorbing agent; a water-permeable fabric backing
layer; and an intermediate layer comprising water-permeable fabric
impregnated with a mixture of honey and a moisture-absorbing
agent.
2. A wound dressing according to claim 1, wherein said dressing is
substantially impervious to liquid water but substantially
permeable to water vapour.
3. A wound dressing according to claim 2, wherein said dressing
remains substantially impervious to liquid water but substantially
permeable to water vapour even after gamma-irradiation.
4-18. (canceled).
19. A method of manufacturing a wound dressing, comprising the
steps of: providing a layer of a water-permeable fabric material;
providing a mixture of honey and a moisture-absorbing agent;
spreading said mixture over said fabric layer; allowing a portion
of said mixture to impregnate an upper sub-layer of said fabric
layer; and allowing said mixture to set, thereby to produce a
dressing comprising a wound-contacting layer including a mixture of
honey and a moisture-absorbing agent, a water-permeable fabric
backing layer, and an intermediate layer comprising fabric
impregnated with said mixture of honey and moisture-absorbing
agent.
20. A method according to claim 19, wherein said mixture of honey
and moisture-absorbing agent is allowed to impregnate said fabric
layer to a depth of 100 .mu.m to 1,000 .mu.m.
21-23. (canceled).
24. A method according to claim 19, further comprising the step of
attaching to said fabric layer an adhesive layer extending
laterally outwardly beyond a periphery of said wound-contacting
layer and being provided with adhesive material on such outward
extension of its surface oriented towards said wound-contacting
layer to provide adhesion of said adhesive layer to an area of skin
of a patient to whom the dressing is applied, surrounding a wound
to be treated.
25. A method according to claim 24, wherein said adhesive layer
does not overlie at least a substantial portion of said fabric
layer.
26. A method according to claim 19, further comprising the step of
subjecting the dressing to gamma-irradiation.
27. A method according to claim 19, wherein the mixture of honey
and the moisture-absorbing agent is provided by continuous mixing
in a twin-screw extruder.
28. A method according claim 27, wherein said mixing is carried out
in a twin-screw extruder having a series of temperature zones down
a length of said extruder.
29. A method according to claim 27, wherein the mixture of honey
and the moisture-absorbing agent is provided at a temperature such
that gelling starts to occur immediately on extrusion through said
twin-screw extruder.
30. A method according to claim 27, wherein the mixture of honey
and the moisture-absorbing agent is provided at a temperature of
about 75.degree. C. to about 80.degree. C.
31. A method according to claim 27, wherein the mixture of honey
and the moisture-absorbing agent is laid onto a support paper.
32. A method according to claim 31, wherein the mixture of honey
and the moisture-absorbing agent laid onto the support paper is
passed in direct contact with the layer of the water-permeable
fabric material through calendar rolls, to thereby achieve partial
impregnation of the fabric material with the mixture.
33. A method according to claim 32, wherein the layer of the
water-permeable fabric material is passed through calendar rolls
together with a backing release paper.
34. A wound dressing according to claim 1, wherein an identity of
said moisture-absorbing agent and a ratio of honey with respect to
said agent are chosen so that said wound-contacting layer forms a
substantially homogeneous solid sheet.
35. A wound dressing according to claim 1, wherein said
wound-contacting layer and said intermediate layer form a first
continuous phase, and wherein said fabric layer and said
intermediate layer form a second continuous phase, said first and
second continuous phases overlapping to form said intermediate
layer.
36. A wound dressing according to claim 35, wherein said
intermediate layer has a thickness of between 100 .mu.m and 1,000
.mu.m.
37. A wound dressing according to claim 36, wherein said
intermediate layer has a thickness of between 200 .mu.m and 500
.mu.m.
38. A wound dressing according to claim 35, wherein said
wound-contacting layer is free from fabric and said fabric layer is
free from honey.
39. A wound dressing according to claim 1, wherein a weight ratio
of moisture-absorbing agent to honey in said wound-contacting and
intermediate layers is between 1:2 and 1:14.
40. A wound dressing according to claim 39, wherein said ratio is
in the range 1:4 to 1:10.
41. A wound dressing according to claim 40, wherein said ratio is
in the range 1:4 to 1:5.
42. A wound dressing according to claim 1, wherein said
moisture-absorbing agent is an alginate or carboxymethyl cellulose
powder.
43. A wound dressing according to claim 42, wherein said
moisture-absorbing agent is sodium alginate.
44. A wound dressing according to claim 1, wherein said dressing
has a 24-hour moisture vapour transmission rate of at least 20 g
per 100 cm.sup.2 and a 24-hour total fluid handling capacity of at
least 35 g per 100 cm.sup.2.
45. A wound dressing according to claim 1, further comprising an
adhesive layer attached to or integral with said fabric backing
layer, said adhesive layer extending laterally outwardly beyond a
periphery of said wound-contacting layer and being provided with
adhesive material on such outward extension of its surface oriented
towards said wound contacting layer to provide adhesion of said
adhesive layer to an area of skin of a patient to whom the dressing
is applied, surrounding a wound to be treated.
46. A wound dressing according to claim 45, wherein at least a
substantial portion of the fabric backing layer is not overlain by
said adhesive layer.
47. A wound dressing according to claim 1, wherein the dressing has
been gamma-irradiated.
48. A wound dressing according to claim 47, wherein the dressing is
gamma-irradiated by at least 25 kGy.
Description
FIELD OF THE INVENTION
[0001] This invention relates to wound dressings containing
honey.
[0002] It has been long known that honey possesses antimicrobial
properties that make it suitable for use in treating a range of
infections and skin disorders. This antimicrobial activity can be
attributed to a number of factors, in particular the natural
presence in honey of hydrogen peroxide (H.sub.20.sub.2), its high
saccharide content (which tends to dehydrate bacteria by osmosis)
and its relative acidity (normally around pH 4). Additionally,
those honeys produced by bees that have fed on nectar from manuka
blossom possess enhanced antimicrobial potency, due to the presence
in such honeys of an as yet unidentified substance known simply as
"unique manuka factor" (UMF).
[0003] The antimicrobial properties possessed by all honeys (and
particularly those containing UMF) also render honey suitable for
use in the dressing of wounds, where it assists in preventing
infection, the debridement of necrotic tissue, the deodorising of
malodorous wounds and the minimisation of scar formation. However,
an obvious problem associated with the use of honey in such
circumstances is that it is a rather runny substance, with the
result that the use of natural honey in a wound dressing is messy
and impractical and the wound dressing has no absorbing capacity,
so that on an exuding wound it rapidly becomes unevenly liquefied
and runs off the wound. This
BACKGROUND ART
[0004] Attempts have been made in the past to overcome this problem
by combining honey with viscosity-enhancing additives. Several such
formulations are mentioned in WO 01/41776. WO 00/09176 discloses a
wound treatment composition comprising an adsorbent material for
adsorbing moisture on or around a wound and a saccharide or
polysaccharide or derivative thereof. WO 02/00269 (published on
3.sup.rd Jan. 2002) also discloses a wound dressing comprising a
honey composition and a base material and optionally further layers
for adhesion.
DISCLOSURE OF THE INVENTION
[0005] We have carried out experimental work that has confirmed
that it is possible to create a moisture-absorbing agent (such as
sodium alginate powder) and allowing the mixture to set. When
sheets of such material were subjected to a "Paddington Cup test"
(as described in the 1996 Addendum to the British Pharmacopoeia,
p1943), in which a saline solution is applied to the upper surface
of a sample sheet clamped between a pair of flanges, it was found
that the material readily breaks down and that saline passes
through the sheet in less than 24 hours. Saline liquid also passes
through a fabric layer in the same test in less than 24 hours. It
has further been found that a fabric impregnated with pure honey is
liquid water-permeable. Most surprisingly in view of these
findings, however, it was discovered that a three-layer structure
in which a honey-containing sheet of the type mentioned above is
supported by a water-permeable fabric backing layer, with an
intermediate layer of fabric impregnated with the honey mixture,
can be substantially impervious to liquid water and aqueous saline
liquid. Moreover, such substantially liquid-impervious composite
material still has a significant liquid-absorption capacity,
together with a high degree of permeability to water vapour
generally, being capable of achieving a 24-hour moisture-vapour
transmission rate of at least 20 g per 100 cm.sup.2 and a 24-hour
total fluid handling capacity of at least 35 g per 100
cm.sup.2.
[0006] In the context of this invention, the term "impervious" is
used in relation to the composite structure in the sense that
liquid water (or an aqueous liquid such as saline solution) does
not penetrate all the way through the structure and emerge in the
liquid phase at the opposite face. The above-mentioned "Paddington
Cup test" can serve as a test for this purpose, a composite being
considered impervious if the liquid saline does not pass through it
within 24 hours under that test.
[0007] The composite material is therefore ideally suited for use
as a moist wound dressing, which assists in the healing of exuding
wounds, since it retains its structural integrity in moist
conditions, is able to form a barrier to liquid water, and yet both
absorbs liquid water and transmits substantial amounts of water
vapour at a steady rate. Both liquid absorbency and vapour
transmission can be important. Absorbed liquid will include other
wound fluid components and wound debris, as well as water. Moisture
vapour transmission is an on-going property of the dressing whereas
liquid absorption (absorbency) is a property which attains a
maximum level.
[0008] The invention therefore provides, in one aspect, a wound
dressing comprising: a wound-contacting layer composed of a mixture
of honey and a moisture-absorbing agent; a water-permeable fabric
backing layer; and an intermediate layer comprising water-permeable
fabric impregnated with a mixture of honey and a moisture-absorbing
agent. The wound dressings of the invention preferably are
substantially impervious to liquid water but permeable to water
vapour as manufactured, preferably even after sterilisation.
[0009] Generally speaking the wound-contacting and intermediate
layer are in direct physical contact as are the intermediate layer
and backing layer, although liquid and vapour contact is
sufficient.
[0010] To provide structural integrity and strength, the honey
mixture in the wound-contacting and intermediate layers preferably
forms a continuum, as does the fabric in the backing and
intermediate layers. In other words, the wound-contacting layer and
the intermediate layer preferably form a first continuous phase and
the fabric layer and intermediate layer preferably form a second
continuous phase, the first and second continuous phases
overlapping to form the intermediate layer. This may be achieved,
for example, by spreading the honey mixture over a layer of fabric
and allowing the mixture only partially to impregnate the fabric
before it sets. This structural integrity also assists in removal
of a used dressing in one piece.
[0011] The invention therefore provides, in another aspect, a
method of manufacturing a wound dressing, comprising the steps of:
providing a layer of a water-permeable fabric material; providing a
mixture of honey and a moisture-absorbing agent; spreading said
mixture over said fabric layer; allowing a portion of said mixture
to impregnate an upper sub-layer of said fabric layer; and allowing
said mixture to set; thereby producing a dressing comprising a
wound-contacting layer composed of a mixture of honey and a
moisture-absorbing agent, a water-permeable fabric backing layer,
and an intermediate layer comprising fabric impregnated with said
mixture of honey and moisture-absorbing agent.
[0012] In preferred embodiments, the three-layer structure is well
defined, with the wound-contacting layer being free (or
substantially free) from fibres such as fabric fibres from the
backing layer and the fabric backing layer being free (or
substantially free) from honey. The thickness of the intermediate
layer e.g. as formed by partial impregnation of the fabric backing
layer by the honey mixture may, for example, be from 100 .mu.m to
1,000 .mu.m, preferably from 200 to 500 .mu.m.
[0013] Preferably, the honey layer forms a substantially
homogeneous solid phase gel sheet. To ensure this, the ratio of
honey to moisture-absorbing agent in the wound-contacting layer
needs to be controlled within certain limits. Generally, the weight
ratio of moisture-absorbing agent to honey should be within the
range from 1:2 or 1:3 to 1:14 and preferably in the range from 1:2
or 1:3 or 1:4 to 1:10.
[0014] The preferred ratio of moisture-absorbing agent to honey has
been found to be affected by irradiation, which is the preferred
method for sterilising the wound dressings of the invention after
manufacture and prior to use. Either gamma-irradiation or
electron-beam irradiation can be used. The dressing can be
irradiated by 25 kGy or more, or by lower amounts sufficient to
achieve sterilisation. Surprisingly, it has been found that the
ability of the honey layer to absorb liquid is diminished
substantially and to a similar degree by both gamma-irradiation and
electron-beam irradiation, if the ratio of moisture-absorbing agent
to honey is very low, i.e. in compositions containing a relatively
low proportion of moisture-absorbing agent. To ensure that the
composite material retains its optimal properties, that is to say
it is substantially impervious to liquid water but permeable to
water vapour and with good liquid absorbency, even after
irradiation, it is preferred that the weight ratio of
moisture-absorbing agent to honey is in the range from 1:2 or 1:3
or 1:4 to 1:5. In preferred embodiments, the liquid absorbency is
at least 15 g per 100 cm.sup.2 after irradiation.
[0015] The identity of the moisture-absorbing agent and its
molecular weight will also affect the constitution of the honey
mix, and the precise identity and molecular weight of the agent
used for best results may easily be determined by experiment. The
moisture-absorbing agent may be selected from those which are
non-toxic and pharmaceutically acceptable. Suitable
moisture-absorbing agents include alginate salts such as sodium
alginate (e.g. Keltone.TM. HVCR sodium alginate) and modified
cellulose polymers such as carboxymethylcellulose (CMC), generally
in powder form.
[0016] The water-permeable fabric for the intermediate and backing
layers is preferably a needled non-woven fabric, but woven fabric
may also be used. It is preferably a calcium alginate fabric, but
other fabric materials such as carboxymethylcellulose or polyester
may be used. As mentioned above, the same fabric is preferably used
for both layers. The fabric density is preferably in the range 100
to 200, for example 150 to 180 gsm (gm.sup.-2), although use of a
lighter or heavier fabric may be possible. However, with lighter
weight fabrics, for example of 70 gsm or less, it may be more
difficult to produce dressings substantially impervious to
liquid.
[0017] The amount of the mixture of honey and water-absorbing agent
applied to the water-permeable fabric is desirably in the range
1000 to 5000 gsm (gm.sup.-2), preferably 1500 to 4500 gsm, more
preferably 2200 to 4200 gsm, although lower or higher amounts may
be used. When the amount of the mixture is substantially below 1500
gsm, for example down to 1350 gsm or less, the dressings may not be
substantially impervious to liquid.
[0018] A particularly preferred dressing is composed of non-woven
calcium alginate fabric of 130-170 gsm, preferably about 150 gsm,
impregnated with 2000-3000 gsm, preferably about 2500 gsm, of a
mixture of sodium alginate and honey in a ratio by weight of 1:3 to
1:5, preferably about 1:4, so as to form a wound-contacting layer
of the sodium alginate/honey mixture, an intermediate layer of the
fabric impregnated with the sodium alginate/honey mixture and a
backing layer of the fabric.
[0019] The dressings may also include one or more active
pharmaceutical components to augment or supplement the properties
of the dressing, particularly those components whose activity
supplements those of honey, so that the wound-contacting layer need
not be composed solely of honey and the moisture-absorbing agent.
For example, an antimicrobial agent, or an antibiotic, or an
anaesthetic, or an anti-inflammatory agent, or a wound-healing
agent, or a skin-protective agent, or a substance intended to
negate malodours, can be incorporated. Suitable antimicrobial
agents include silver or silver-containing compounds, povidone
iodine and substances or formulations which release hydrogen
peroxide. Honey already contains an amount of glucose oxidase which
acts in combination with glucose, also present in honey, to produce
hydrogen peroxide. Additional amounts of glucose oxidase can be
added artificially to supplement this natural activity. Suitable
anaesthetics include lidocaine hydrochloride. Suitable
wound-healing agents include zinc oxide.
[0020] The composite of honey-containing wound-contacting layer,
intermediate layer and fabric backing layer may be produced by
mixing the honey and water-absorbing agent batchwise or
continuously in appropriate proportions, for example in an extruder
such as a twin-screw extruder, for an appropriate period until a
mixture is formed, extruding the mixture at an appropriate
temperature and calendering the extruded mixture in contact with
the fabric backing layer so as to achieve partial impregnation of
the backing layer by the mixture. The mixing may be carried out for
from 2 to 60 minutes, a mixing period of 10 minutes or more being
preferred to induce some degree of set in the mixture. The mixing
temperature is preferably in the range 40 to 50.degree. C. A final
heat treatment to set the honey may be desirable. At heat setting
temperatures of about 80.degree. C. setting occurs in less than 1
minute but at 50.degree. C. setting can take up to 30 minutes.
[0021] To create a self-adhesive wound dressing, an adhesive layer
may be attached to or formed integrally with the fabric backing
layer. Conveniently, the adhesive layer may extend laterally
outwardly beyond the periphery of the wound-contacting layer and is
provided with adhesive material on such outward extension of its
surface oriented towards the wound-contacting layer. The adhesive
layer may thereby be caused to adhere to an area of the skin of a
patent to whom the dressing is supplied surrounding a wound to be
treated, while the honey layer is brought into contact with the
wound. In preferred embodiments, the adhesive layer is disposed in
a window-frame-type arrangement around the periphery of the fabric
backing sheet, leaving at least a substantial portion of the fabric
backing sheet uncovered, i.e. not overlain by the adhesive layer.
This arrangement has the advantage of allowing the wound dressing
to "breathe", thus permitting moisture absorbed in the honey layer
to be transpired to the atmosphere.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The invention will hereinafter be described in more detail,
by way of example only, with reference to the accompanying drawing
in which:
[0023] FIG. 1 is a diagrammatic representation of an embodiment of
wound dressing according to the invention; and
[0024] FIG. 2 is a scanning electron microgram of a cross-section
of a wound dressing manufactured according to the invention.
[0025] The stylised wound dressing depicted in FIG. 1 illustrates
the basic structure of an embodiment of wound dressing 10 according
to the invention, in which a fabric backing layer 12 is partially
impregnated with a mixture of honey and sodium alginate to form an
intermediate layer 16, with the remainder of the honey/alginate
mixture forming a wound-contacting layer 14. A flexible adhesive
fabric 18 is attached to the periphery of the underside of the
fabric layer 12 and is provided on its upper surface with an
adhesive substance suitable for adhering the dressing to the
patient's skin. The adhesive fabric 18 is mounted to the fabric
backing layer 12 in a window-frame-type arrangement, leaving a
central hole 20, through which water vapour absorbed into the
dressing is able to transpire.
[0026] The invention is further illustrated by reference to the
following Examples
EXAMPLE 1
[0027] A test sample of a composite three-layer structure according
to the invention was manufactured by the following procedure. 50 g
of honey was warmed to 50.degree. C. and added to 10 g of
Keltone.TM. HVCR sodium alginate powder (viscosity 600-900 cP 1.25%
aq. solution at 25.degree. C. on spindle 3 of an LV Brookfield
viscometer at 60 rpm). The mixture was stirred for 10 s and
transferred to a petri dish. A disc of 150 gsm (gm-.sup.2) calcium
alginate fabric was placed on top of the honey/sodium alginate
mixture, followed by a closely fitting support member. The assembly
was then inverted and placed under pressure to spread the
honey/sodium alginate mixture evenly over the fabric carrier, and
heated at 50.degree. C. for 1 hour. The assembly was then cooled
and the resulting composite product removed. The sample was
prepared for electron microscopy by immersion in liquid nitrogen
and cut with a scalpel to produce a suitable cross-sectional
surface, which was then coated with gold/palladium and analysed
under a Hitachi S4000 field emission scanning electron microscope
operating at 2 kV. The resulting electron microgram appears as FIG.
2 and clearly reveals a distinct three-layer structure comprising
(from left to right in the figure) honey layer, honey/fibre
impregnated layer, and fabric backing layer.
EXAMPLE 2
[0028] In order to test the fluid handling capabilities of
dressings manufactured according to the invention, several further
samples were produced, using varying ratios of sodium alginate to
honey. The effect of gamma-irradiation was also studied. All of the
samples were produced using 150 gsm needled calcium alginate
non-woven fabric carrier and Keltone.TM. HVCR sodium alginate
powder. The weight ratio of alginate powder to honey varied between
1:4 and 1:10. Half of the samples were gamma-irradiated (to 25 kGy)
after manufacture. The samples were subjected to the Paddington Cup
test, and their liquid absorbency, moisture vapour transmission
rate ("MVTR"--i.e. the mass of water vapour transpired through the
sample) and total fluid handling capacity ("TFHC"--i.e. the sum of
MVTR and liquid absorbency) were measured in terms of grams of
water per 100 cm.sup.2 surface area of sample per 24 hours. The
results are set out in Table 1 below:
1 TABLE 1 Non-Irradiated Irradiated (25 kGy) g/m.sup.2 of G/m.sup.2
of sodium sodium Weight alginate alginate ratio of and and sodium
honey honey alginate mixture mixture to in the in the honey
dressing Absorbency MVTR TFHC dressing Absorbency MVTR TFHC 1:4
2251 44 43 87 2730 22 39 62 2578 43 42 86 2401 29 39 68 1:4 4660
53.5 24.1 77.6 4090 35.2 33.7 68.9 3516 52.8 33.1 85.9 3878 33.0
31.9 64.9 1:5 2259 40 45 85 2201 22 42 63 2622 51 46 96 2572 23 39
62 1:5 3142 462 32.0 78.2 3504 18.7 36.0 54.7 3258 48.3 27.4 75.7
3000 19.9 37.8 57.7 1:5 3808 45.9 30.0 75.9 3437 22.2 32.4 54.6
3753 45.8 31.5 77.3 3491 19.7 36.7 56.4 1:5 3920 44.4 35.5 79.9
4153 19.1 26.5 45.6 4120 51.2 30.1 81.3 1:10 3067 46.1 37.4 83.5
3154 12.8 37.6 50.4 3079 34.6 33.5 68.1 3320 8.3 37.1 45.4
[0029] These results indicate that, in non-irradiated samples, all
of the samples demonstrated good liquid absorbency and TFHC and
that variations of alginate: honey weight ratio within the range
1:4 to 1:10 had little effect. Gamma-irradiation tended
significantly to reduce liquid absorbency as the amount of honey in
the alginate/honey mixture increased.
[0030] Products were made with a honey sheet having a 1:4 sodium
alginate: honey ratio and with (a) 150 gsm calcium alginate needled
fabric and 1350 gsm honey sheet, and (b) 70 gsm calcium alginate
needled nonwoven fabric and 2500 gsm honey sheet, and these were
gamma sterilized at 25 kGy. They were subsequently tested using the
Paddington Cup test and, after 24 hours, showed leakage of liquid
through to the back of the dressing, i.e. they were not impervious
to liquid, due to the "thinness" of the product, i.e. low honey
level or low fabric density.
EXAMPLE 3
[0031] To test whether the identity of the fabric carrier had any
effect on fluid handling capability, four samples were produced
using a 1:5 alginate:honey weight ratio, as before. Two of the
samples were manufactured using 150 gsm calcium alginate needled
non-woven fabric and two using Hydrocel.TM.
(carboxymethylcellulose) 100 gsm needled non-woven fabric. Liquid
absorbency, MVTR and TFHC after 24 hours were measured as
previously, and the results are set out in Table 2 below:
2TABLE 2 Fabric carrier type .fwdarw. Calcium Calcium Property
.dwnarw. alginate alginate CMC CMC Weight of Honey Sheet
(g/m.sup.2) 3430 4190 4190 4100 Nice Dome Yes Yes Yes Yes 24 Hr
absorbency g/100 cm.sup.2 44.0 40.0 43.0 39.0 24 Hr MVTR g/100
cm.sup.2 31.0 28.0 27.0 29.0 24 Hr TFHC g/100 cm.sup.2 75.0 68.0
70.0 68.0
[0032] These results indicate that there is no significant
difference between fabric carrier types or between sheet weights
within the scope of the tests. The "dome" mentioned in the Table is
a reference to the honey layer swollen by absorption of saline, a
"nice dome" therefore being indicative, at least qualitatively, of
good absorption.
EXAMPLE 4
[0033] A further test was carried out, using calcium alginate and
polyester 150 gsm needlebonded non-woven fabrics, to test fluid
handling over an extended period (48 hours). The results are set
out in Table 3 below:
3TABLE 3 Wt Fabric honey TFHC MVTR carrier sheet Absorbency
Absorbency g/100 cm.sup.2 g/100 cm.sup.2 type g/cm.sup.2 g/100
cm.sup.2/24 hr g/100 cm.sup.2/48 hr 24 hr 48 hr 24 hr 48 hr
Alginate 3400 44 44 74 109 30 65 Polyester 3600 46 41 72 101 26
60
[0034] These results demonstrate that liquid absorbency and vapour
transmission rate are maintained over a period of 48 hours, there
being no significant difference in absorbency between the two
fabrics over that period.
EXAMPLE 5
[0035] 16 kg of Manuka honey was placed into a Z-blade mixer with
front and rear blades rotating at 32 rpm and 25 rpm respectively
and with a circulating water jacket at 55.degree. C. After 30
minutes, when the honey had reached a temperature of 45.degree. C.,
4 kg sodium alginate powder (Keltone.TM. HCVR) was added to the
mixer over a 2-minute period. After a further 3.5 minutes, by which
time the honey mixture was homogeneous and had reached a
temperature of 48.degree. C., the mixture was extruded through a
fish-tail device by means of a screw feeder rotating at 2.5 rpm.
The extruded sheet of honey mixture was 1.2 mm thick and was laid
onto a support paper and then passed through calender rolls, heated
to 55.degree. C. by circulating water, with a gap set to produce
the required final thickness of material. Prior to passing the
extruded material through the calender rolls, 150 gsm calcium
alginate needled nonwoven fabric, together with a backing release
paper, was placed directly against the honey mixture. The action of
the calender rolls was to achieve partial impregnation of the
alginate fabric with the honey mixture. A final heat treatment, at
50.degree. C. for 1 hour, set the honey mixture.
[0036] The above Example was repeated but this time allowing 30
minutes mixing time for the honey and powder, in order to induce a
degree of set prior to extrusion. It was found that setting of the
honey mixture was achieved without the need for a final heating
treatment.
EXAMPLE 6
[0037] Instead of the batch operation described in Example 5,
continuous mixing can be employed. A twin-screw extruder having a
series of temperature zones down its length can be fed with sodium
alginate powder together with downstream addition of honey at one
or more injection points and mixing and heating to a series of
temperature points carried out to produce a consistent mixture at a
high temperature, for example of 75-80.degree. C., so that it would
start to gel immediately on extrusion, and fed to forming and
calendering equipment similar to that already described in Example
5. Optimisation of the temperature profile enables the final heat
treatment to set the honey mixture to be omitted.
* * * * *