U.S. patent application number 15/766255 was filed with the patent office on 2018-10-11 for composite fibre.
This patent application is currently assigned to UNIVERSITY OF LEEDS. The applicant listed for this patent is UNIVERSITY OF LEEDS. Invention is credited to Parikshit Goswami, Andrew Hebden, Stephen Russell, Timothy Smith.
Application Number | 20180291529 15/766255 |
Document ID | / |
Family ID | 55130751 |
Filed Date | 2018-10-11 |
United States Patent
Application |
20180291529 |
Kind Code |
A1 |
Goswami; Parikshit ; et
al. |
October 11, 2018 |
Composite Fibre
Abstract
A composite fibre comprising polyurethane and a particulate,
wherein the particulate has mean particle diameter in the range 50
nm-100 .mu.m. A web comprising this fibre, and the use of the web
for non-slip applications or antimicrobial applications, together
with a method for making the fibre.
Inventors: |
Goswami; Parikshit; (Leeds,
Yorkshire, GB) ; Smith; Timothy; (Leeds, Yorkshire,
GB) ; Hebden; Andrew; (Leeds, Yorkshire, GB) ;
Russell; Stephen; (Leeds, Yorkshire, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UNIVERSITY OF LEEDS |
Leeds, Yorkshire |
|
GB |
|
|
Assignee: |
UNIVERSITY OF LEEDS
Leeds, Yorkshire
GB
|
Family ID: |
55130751 |
Appl. No.: |
15/766255 |
Filed: |
October 6, 2016 |
PCT Filed: |
October 6, 2016 |
PCT NO: |
PCT/GB2016/053112 |
371 Date: |
April 5, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D01F 1/103 20130101;
D01F 1/10 20130101; D01F 6/70 20130101; D01D 5/0985 20130101; D01F
1/04 20130101; D01D 5/003 20130101 |
International
Class: |
D01F 1/04 20060101
D01F001/04; D01F 1/10 20060101 D01F001/10; D01F 6/70 20060101
D01F006/70; D01D 5/098 20060101 D01D005/098; D01D 5/00 20060101
D01D005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 8, 2015 |
GB |
1517791.8 |
Claims
1. A composite fibre comprising polyurethane and a particulate,
wherein the particulate has mean particle diameter in the range 50
nm-50 .mu.m.
2. A fibre according to claim 1, wherein the particulate modifies
the friction co-efficient of the fibre.
3. A fibre according to claim 1, wherein the particulate comprises
a particle selected from a pigment particulate, an inorganic
compound, a metal, a polymer or combinations thereof.
4. A fibre according to claim 3, wherein the metal is selected from
silver, copper, gold, titanium, zinc, iron, aluminium or
combinations thereof.
5. A fibre according to claim 1, comprising in the range 0.1-25 wt
% particulate.
6. A fibre according to claim 1, wherein the particulate comprises
particles of mean particle size in the range 0.05-10 .mu.m.
7. A fibre according to claim 1, wherein the particulate comprises
particles of multimodal particle size distribution.
8. A fibre according to claim 1, of mean diameter in the range
0.1-20 .mu.m.
9. A fibre according to claim 1, wherein a ratio of particle size
to mean fibre diameter is in the range 0.05:1-2:5.
10. A web comprising a plurality of fibres according to claim
1.
11. A web according to claim 10, wherein the particulate is a
pigment particulate.
12. A method, comprising: using a web according to claim 10, for
non-slip applications.
13. A method, comprising: using a web according to claim 12 for
non-slip applications in the presence of water.
14. A method, comprising: using a web according to claim 4, for
antimicrobial applications.
15. A method of making a fibre according to claim 1, comprising
forming the polyurethane and particulate composite fibre using a
technique selected from electrospinning or melt blowing.
Description
FIELD
[0001] The invention relates to a polyurethane fibre/web, in
particular to composite fibres/webs of polyurethane and a
particulate, together with uses and processes for manufacture.
BACKGROUND
[0002] With the advent of synthetic polymeric fibres, such as Nylon
came the possibility to create a vast range of fibres, including
copolymers, with different physical properties. Nonwoven fabrics
made from these fibres soon became popular and are used in
applications across numerous technical arenas.
[0003] The invention relates to the provision of non-slip products,
for instance, but not limited to, for applications in which
silicone bands are currently used. These include hosiery (hold-ups
for instance), and intimate apparel (for instance brassieres and
shapewear), where silicon bands are provided to prevent the garment
shifting out of place during wear. For example, hold ups are only
possible as a product because of the silicone band replacing the
suspender belt which would otherwise retain the stocking on the
leg. Further applications include sportswear (such as swimwear and
strap tops) and medical clothing applications (for instance
compression garments or supports, such as knee or ankle supports).
However, there is a desire to improve upon the current technology
as silicone bands can cause allergies in some wearers, can lack
flexibility leading to discomfort, and are not easily coloured. In
addition, the lack of breathability and concerns about silicone
leaching can deter some consumers from wearing products including
silicone bands. The invention is intended to overcome or ameliorate
at least some aspects of this problem.
SUMMARY
[0004] Accordingly, in a first aspect of the invention there is
provided a polyurethane and particulate composite fibre of mean
particle diameter in the range 50 nm-50 .mu.m. It has been found
that adding particulates (particles) to a polyurethane fibre
modifies the friction properties of the fibre, generally resulting
in an increase in the frictional coefficient relative to prior art
polyurethane fibres and, as a result, in a web which has good
non-slip/gripping properties, even where moisture is present, such
as water, perspiration or other aqueous solutions so that the skin
is wet. Further the webs have excellent shape recovery properties,
preventing sagging of the garment in use, and loss of fit over
time. These webs are porous providing for improved comfort to the
wearer because of the increased flexibility offered relative to the
use of silicone bands, and the breathability. In addition, the
product has been shown to be colour fast, where coloured, and there
is no evidence of leaching, one reason why it is believed that the
fibres cause fewer allergies than silicone technologies, and do not
carry the stigma of the silicone bands in medical terms. An added
advantage is that the fibres, and resulting webs, have been found
to be antimicrobial, where an appropriate additive is present.
[0005] As noted above, the particulate modifies the friction
co-efficient of the fibre, making it suitable for use in non-slip
applications. As used herein the term "modify" is intended to mean
that the friction co-efficient of the fibre is modified by at least
.+-.1.8% relative to the value for any substrate when compared to
present commercial polyurethane containing products (i.e.
polyurethane without particulate matter). Typically, the friction
co-efficient will be increased, for instance by at least .+-.1.8%,
although often the modification will be far greater, for instance
.+-.20%, or .+-.50% or even .+-.100%; often the modification will
be an increase.
[0006] The particulate may be any particulate which modifies the
friction coefficient of the fibre, typically to increase this.
However, it can be desirable to use an antimicrobial particle, and
so the particle may be selected from a metal, such as silver,
copper, gold, titanium, zinc, iron, aluminium or combinations
thereof. Silver will often be used to enhance the antimicrobial
properties of the fibre. Alternatively, pigment particulates may be
used, as these can colour the fibre in addition to modifying the
friction properties thereof. Further, inorganic compounds such as
silica (such as Celite), calcium phosphate (such as ivory black),
ceramic or glass microparticles may be used as these are
inexpensive, safe on the skin, non-toxic and have been shown to
give high friction values. Polymeric particles may also be added,
for instance polyethylene or cellulose acetate particles for the
same reasons.
[0007] The use of silver particles in the size range 5-10 .mu.m has
been found to offer particularly high static friction coefficients,
as has silver in the range 0.5-1 .mu.m, this latter particle size
being especially effective when used at low levels, such as in the
range 1-3 wt % or around 2 wt %.
[0008] Often the fibre will comprise in the range 1-25 wt %
particulate, often in the range 2-10 wt %. At these ranges the
particulate has been found to increase the friction coefficient of
the fibre and resulting web, without, it is believed, reducing
overall fibre strength significantly. The range 2-10 wt % particles
has been found to be particularly effective at providing a web
which had good non-slip properties.
[0009] It will generally be the case that the particulate comprises
particles of mean particle size in the range 50 nm-50 .mu.m, often
in the range 0.5-25 .mu.m, in the range 0.5-10 .mu.m or in the
range 0.7-1.5 .mu.m. Particle size is important as it is believed
that this offers one of the advantages over known technologies, in
that particle sizes in this range offer a web with a very fine
surface topography, such that the particles can settle in the
grooves of the skin, providing intimate contact, without loss of
comfort. This micro-scale contact is much more effective at
preventing slipping of the web across the skin than the macro-scale
friction based contact provided by silicone band technologies.
Similarly, it will often be the case that the particles will be in
the micro- or sub-micro scale rather than the nano-scale to ensure
that toxicity is avoided.
[0010] To increase the number of skin types with which the web
works effectively, and to improve the grip of the web still further
by offering contact with a wider range of grooves in the skin, it
can be beneficial to provide a fibre in which the particulates have
a multimodal, in some cases bimodal, particle size
distribution.
[0011] As used herein the term "diameter" is intended to refer to
the width of the fibre or particle across the largest part of its
cross-section. Typically the fibre will be of mean diameter in the
range 0.05-20 .mu.m, often in the range 0.2-15 .mu.m, or 1.5-5
.mu.m. The diameter of the fibre can be controlled through careful
selection of the manufacturing method, for instance, melt blowing
processes generally produce fibres of larger diameter than
electrospinning techniques. Fibres of the diameters described above
have been found to offer increased contact with the skin, because
of the large surface area relative to fibres of larger diameters.
The provision of fibres with diameters in this range also allows
for more particulate to be present at the surface of the fibre,
improving the friction properties of the fibre relative to fibres
of larger diameters. An advantage of these techniques is that they
inherently produce fibres with a range of diameters. This allows
them to interact more effectively with the skin, as the range of
fibre diameters is well suited to interacting with the range of
groove sizes found in the skin.
[0012] It will often be the case that a ratio of particle size to
mean fibre diameter is in the range 0.05:1-2:5 This is desirable
because at such ratios the friction with the skin is excellent.
[0013] In a second aspect of the invention there is provided a web
comprising a plurality of fibres according to the first aspect of
the invention.
[0014] In a third aspect of the invention there is provided the use
of a web according to the second aspect of the invention, this use
may be for non-slip applications, applications where fabric
breathability is important and/or antimicrobial applications among
others. For instance, the web may be used in hosiery (hold-ups for
instance), and intimate apparel (for instance brassieres and
shapewear). Further applications include sportswear (such as
swimwear and strap tops) and medical clothing applications (for
instance compression garments or supports, such as knee or ankle
supports). A particular advantage of the invention is that the
fibres offer their friction modification properties regardless of
whether the substrate, for instance skin, is wet or dry. This makes
them particularly suitable for use in swimwear and sportswear
applications.
[0015] In a fourth aspect of the invention there is provided a
method of making a fibre according to the first aspect of the
invention, the method comprising forming the polyurethane and
particulate composite fibre using a technique selected from but not
limited to electrospinning or melt blowing. Often electrospinning
will be used, such that the webs produced will be electrospun.
Electrospinning offers the advantage that the fibre diameters are
smaller than other methods, including melt-blowing. It is often the
case that the fibre is sufficiently thin to interact with the
grooves of the skin, working with the particulate to modify the
friction co-efficient of the web. Often the method will comprise:
[0016] providing a 7.5-12.5 wt %, often a 9-11 wt %, or 10 wt %
solution of polyurethane; [0017] combining the polyurethane
solution and a particulate; and applying an electrospinning
technique.
[0018] These concentrations of polyurethane have been found to
provide the optimal balance between fibre diameter and consistency
of fibre diameter. Higher concentrations of polyurethane in the
solution may produce fibres of undesirably thick diameter, reducing
the surface area, surface availability of the particles and
weakening the strength of the fibre matrix. Lower concentrations of
polyurethane can lead to webs with uncontrolled fibre diameters
along fibre lengths reducing the uniformity of the web. Where
melt-blowing is used, the method will often comprise: [0019]
combining polyurethane and a particulate; and [0020] applying a
melt-blowing technique.
[0021] There is therefore provided a polyurethane and particulate
hybrid fibre of mean particle diameter in the range 50 nm-50 .mu.m
wherein the particulate modifies the friction coefficient of the
fibre. In the fibre, the particulate comprises 1-25 wt % of the
fibre, and may be a particle selected from a pigment particulate,
an inorganic compound (optionally selected from silica, calcium
phosphate, ceramic or glass microparticles), a metal (optionally
selected from silver, copper, gold, titanium, zinc, iron, aluminium
or combinations thereof), a polymer or combinations thereof.
Generally, the particulate comprises particles of mean particle
size in the range 50 nm-50 .mu.m. Alternatively, the particulate
comprises particles of multimodal, in some cases, bimodal particle
size distribution. Generally, the fibre will be of mean diameter in
the range 0.2-20 .mu.m, and a ratio of particle size to mean fibre
diameter is in the range 0.05:1-2:5.
[0022] Unless otherwise stated each of the integers described may
be used in combination with any other integer as would be
understood by the person skilled in the art. Further, although all
aspects of the invention preferably "comprise" the features
described in relation to that aspect, it is specifically envisaged
that they may "consist" or "consist essentially" of those features
outlined in the claims. In addition, all terms, unless specifically
defined herein, are intended to be given their commonly understood
meaning in the art.
[0023] Further, in the discussion of the invention, unless stated
to the contrary, the disclosure of alternative values for the upper
or lower limit of the permitted range of a parameter, is to be
construed as an implied statement that each intermediate value of
said parameter, lying between the smaller and greater of the
alternatives, is itself also disclosed as a possible value for the
parameter.
[0024] In addition, unless otherwise stated, all numerical values
appearing in this application are to be understood as being
modified by the term "about".
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In order that the invention may be more readily understood,
it will be described further with reference to the figures and to
the specific examples hereinafter.
[0026] FIG. 1 is an SEM image of an electrospun polyurethane web
(4480.times. magnification, mean fibre diameter 1.8 .mu.m);
[0027] FIG. 2 is an SEM image of an electrospun polyurethane web
similar to that of FIG. 1, but with the incorporation of silver
particles to form a hybrid fibre (4970.times. magnification, mean
fibre diameter 1.8 .mu.m, particle size range 0.5-1 .mu.m);
[0028] FIG. 3 is a graph illustrating the static friction of a
range of web compositions when tested against a plain cotton
sample;
[0029] FIG. 4 is a graph illustrating the static friction of a
range of web compositions when tested against a cotton muslin
sample;
[0030] FIGS. 5a, 5b and 5c are graphs illustrating the static
friction of a range of web compositions when tested against dry pig
skin;
[0031] FIG. 6a is a graph illustrating the static friction of a
range of web compositions when tested against wet pig skin, FIG. 6b
is a graph comparing the static friction of a range of web
compositions when tested with dry and with wet pig skin (left hand
graph is dry, right hand graph is wet);
[0032] FIG. 7 is a graph illustrating the static friction of web
compositions comprising silver particles in selected size ranges
against a pig skin sample;
[0033] FIG. 8 shows the results of antimicrobial testing for an
electrospun membrane, 10% polyurethane with 10% (0.5-1 .mu.m)
silver particles membrane tested against [A] S. aureus and [B] E.
coli;
[0034] FIG. 9 is a schematic showing the dimensional stability
template pattern in a wash fastness test; and
[0035] FIGS. 10a-10d are graphs showing the colour fastness results
of polyurethane webs with a) 10% red pigment, b) 10% violet
pigment, c) 10% blue pigment and d) 10% blue pigment with
Celite.
EXAMPLES
Materials
[0036] Selectophore.TM. polyurethane, Tecoflex.TM. polyurethane,
dimethylformamide (DMF), silver microparticles (5.0-8.0 .mu.m) and
(2.0-3.5 .mu.m), Celite.RTM. 545 (particle distribution=0.02-0.10
mm, median size=36 .mu.m) were purchased from Sigma Aldrich.
Tetrahydrofuran (THF) was purchased from VWR. Silver micro
particles (0.7-1.3 .mu.m) and (4.0-7.0 .mu.m) were purchased from
Alfa Aesar. The various powdered pigments were all purchased online
from L. Cornelissen & Son. Plain cotton optic white 150 cm,
CD12 (100% cotton) was purchased from Whaleys Bradford Ltd. Pig
skin from belly pork was obtained from a local butcher (Crawshaw
butchers, Leeds). Melt blown polyurethane TPU Estane 58237 was
purchased from velox.com.
Preparation of Polyurethane Solutions
[0037] Polyurethane (Selectophore.TM., at the desired wt %) was
dissolved in DMF:THF (15 ml, 60:40 (v:v)) with stirring over 24
hours. The particulate was added as defined in Table 1 below,
slowly with stirring and allowed to disperse over the period of an
hour.
TABLE-US-00001 TABLE 1 Polyurethane Additive 1 - Additive 2 -
Sample label wt % weight/name weight/name Polyurethane only 10 n/a
n/a 2% Ag 0.5-1.0 .mu.m 10 0.3 g/Ag n/a 0.5-1.0 .mu.m 10% Ag
0.5-1.0 .mu.m 10 1.5 g/Ag n/a 0.5-1.0 .mu.m 10% Ag 0.7-1.3 .mu.m 10
1.5 g/Ag n/a 0.7-1.3 .mu.m 10% Ag 2.0-3.5 .mu.m 10 1.5 g/Ag n/a
2.0-3.5 .mu.m 10% Ag 5.0-8.0 .mu.m 10 1.5 g/Ag n/a 5.0-8 .mu.m 10%
Ag 4.0-7.0 .mu.m 10 1.5 g/Ag n/a 4.0-7.0 .mu.m 5% Celite 0.02- 10
0.75 g/Celite 545 n/a 0.1 mm 10% Celite 0.02- 10 1.5 g/Celite 545
n/a 0.1 mm 10% Charcoal 10 1.5 g/Charcoal - n/a 100 mesh 10% Ivory
Black 10 1.5 g/Ivory black n/a 10% Violet only 10 1.5 g/Ultramarine
n/a violet 10% Blue only 10 1.5 g/Cobalt blue n/a 10% Blue + 10% 10
1.5 g/Cobalt blue 1.5 g/ Celite 0.02-0.1 mm Celite 545 10% Red only
10 1.5 g/Cadmium red n/a 10% Red + 10% Ag 10 1.5 g/Cadmium red 1.5
g/ 5-8 .mu.m Ag 5-8 .mu.m 10% Red + 10% 10 1.5 g/Cadmium red 1.5 g/
Celite 0.02-0.1 mm Celite 545 10% Yellow + 10% 10 1.5 g/Cadmium 1.5
g/ Celite 0.02-0.1 mm yellow middle Celite 545
Electrospinning General Procedure (Nanospider)
[0038] A 10 wt % solution of Selectophore.TM. polyurethane was
prepared using a 60:40 DMF:THF solvent ratio. Selectophore.TM.
polyurethane (1.5 g) was added to 15 ml of the solvent mixture with
stirring and left to dissolve overnight. Once dissolved
particle/pigment additive was then added to the solution with
continuous stirring for 10 minutes (according to Table 1), the
solution was then added to the 10 ml syringe and electrospun for
approximately 4 hours. The aluminium foil collection plate was
periodically rotated 90 degrees resulting in more uniform fibre
coverage. The syringe and needles were wiped clean using tissue and
then washed using acetone, followed by distilled water.
Melt-Blowing General Procedure
[0039] 500 g batches of hybrid polyurethane pellets were prepared
by adding 25 g (5 wt %) and 50 g (10 wt %) of silver or 50 g (10 wt
%) and 100 g (20 wt %) of Celite respectively. Melt-blowing
experiments were carried out using a pilot scale melt blowing
machine. A 43 hole 250 .mu.m diameter spinneret was used throughout
the testing. Polyurethane webs of 75 g m.sup.-2 (fibre diameter
range 11.25-18.50 .mu.m mean=14.69 .mu.m) and 94 g m.sup.-2 (fibre
diameter range 6.69-14.88 .mu.m mean=11.11 .mu.m) were
produced.
Methodology
[0040] Friction Test:
[0041] The friction coefficient was determined in accordance with
European Standard EN ISO 8295:2004. Applied force (F.sub.p) of
1.96N via an 80 g sled, and a 120 g weight for a total weight of
200 g. The speed was 100 mm/min. Sample size was 90.times.755 mm.
The coefficient of static friction can be defined by the
equation:
Coefficient of static friction .mu. S = F s F p ##EQU00001##
Where F.sub.p=1.96N (the normal force which comes from 200 g of
weight applied to the top of the sample). F.sub.s represents the
static friction force (N) measured by the machine and is always
proportional to the static friction coefficient. The static
friction force arises from the interlocking of surface
irregularities between the polyurethane sample and the test
surface. As a force is applied horizontally to the test sample this
interlocking force will increase to prevent any relative movement
of the sled. This force increases until a threshold force is
reached where motion of the sled begins. It is this threshold point
of motion which defines the static force.
[0042] Hydration, lipid films as well as surface structure of the
skin will all affect frictional behaviour when in contact with
textiles. For example, moist skin has an elevated frictional
coefficient and dry skin has lower frictional coefficient. Age has
been seen to have little effect on the frictional coefficient of
human skin, while the anatomical region the skin is located has a
large influence. Regarding gender; skin viscoelasticity was found
to be comparable however, the friction of female skin shows
significantly higher moisture sensitivity than that of men. It
should be noted that as pig skin is a natural product, test results
will vary from batch to batch. Therefore, each set of comparative
tests were carried out on a single sample of pig skin to ensure the
validity of the test. However, absolute values of static friction
would be expected to (and have been observed to) vary slightly with
each pig skin sample.
[0043] Webs:
[0044] The tested webs were electrospun polyurethane with added
particulates.
[0045] Antimicrobial Tests:
[0046] These followed AATCC 100. 3 mm diameter samples of the web
were tested against E. Coli, (MacConkey agar plates) and S. Aureus
(blood agar plates) by 24 hour incubation at 37.degree. C. The
plates were inoculated with 30 .mu.l of 0.5 McFarland standard E.
coli or S. aureus diluted in 3 ml of PBS or saline solution.
Anaerobic testing used the above methods, however C. difficile was
the model bacteria selected (CCEYL plates) and the incubation
period was 48 hours at 37.degree. C. in an anaerobic incubator. All
tests were repeated three times.
[0047] Scanning Electron Microscopy:
[0048] The structure and morphology of the electrospun fibre mats
produced were examined by scanning electron microscopy (SEM; Carl
Zeiss EVO) at the Leeds Electron Microscopy and Spectroscopy
(LEMAS) centre. SEM images were taken at different magnifications
for all electrospun fibres for comparison.
[0049] Fibre Analysis:
[0050] Media Cybernetics Image Pro Analyser Plus was used to
analyse images captured via SEM. The software was used to measure
fibre diameters of samples; a minimum of 75 fibre diameters were
recorded for each sample and digitised in order to obtain values
for the mean, maximum and minimum fibre diameters for each
sample.
[0051] Colour Fastness:
[0052] These measurements were carried out on a datacolor
Spectraflash SF600 Plus-CT using a medium aperture measuring
between 360 nm-700 nm, where the front face of each sample was
tested a minimum of four times in different positions over the
membrane to create a fair mean of the measurements across the
material. K/S is a measure of the colour strength of a particular
sample and can be calculated by measuring the reflection values of
a material and applying these to the equation:
K/S=((1-R).sup.2/2R)
Where R is the reflectance value at a specific wavelength, K is
absorbance coefficient and S is the scattering coefficient.
[0053] Wash Fastness:
[0054] These tests were carried out on a Roaches washtec machine
following the international standard--ISO 105-006:2010. A section
of SDC multifibre was secured adjacent to each polyurethane sample,
the multifibre used contained sections of cotton, wool, polyester,
acetate, nylon and acrylic to compare the colour transfer to
various fabric types. In addition simultaneous dimensional
stability measurements were carried out on the samples, to
establish the shrinkage potential of these electrospun membranes.
Dimensional stability was used to establish a level of shrinkage
occurring in the samples after washing. This was done using a
template pattern to set out fixed measurement points on the
unwashed piece of material (FIG. 8), then after washing these
distances were remeasured and finally compared to the original.
[0055] Breathability:
[0056] Breathability tests were carried out following the BS
7209:1990 standard for 20 hours in a climate controlled laboratory
(temperature 20.+-.2.degree. C. and relative humidity 65.+-.5%).
Test samples were placed over a weighed amount of distilled water
and the water allowed to evaporate slowly (through the fabric)
prior to reweighing after a set time. This calculation of water
loss can be applied to the following equation which allows the
relative breathability of the fabric to be assessed.
WVP = 24 .DELTA. m At ##EQU00002##
WVP is the water vapour permeability (g/m.sup.2/day), .DELTA.m is
the change in mass of water in grams, A is the area of the test
material in m.sup.2 and t equals the time in hours for the
experiment.
[0057] Following this calculation for the polyurethane membranes
and the polyester reference fabric the below equation is then
applied to give the WVP index for each sample. The WVP index is a
breathability ratio which compares the test samples to the
reference fabric.
I = WVP S WVP R .times. 100 ##EQU00003##
I is the water vapour permeability index of the material, WVP.sub.s
is water vapour permeability of a particular test sample whilst
WVP.sub.R is the water vapour permeability value calculated for the
polyester reference fabric. The experiments were conducted over 20
hours using test dishes with a diameter of 76 mm which gives a
material test area of 0.004537 m.sup.2.
Example 1: Friction Test with Cotton
[0058] The friction test was applied to a medium weight cotton
weave fabric (100% plain cotton optic white 150 cm CD12) as a skin
substitute. It is known that for a fabric to adhere to the skin, a
static force (N) of at least 2.0 and a friction coefficient (.mu.S)
of at least 1.1 be observed. The test results are shown in Table 2
below and summarised in FIG. 3.
TABLE-US-00002 TABLE 2 Electrospun Fibre Composition Static Force
(N) Friction Coefficient (.mu.S) Polyurethane 2.01 1.03 2 wt %
silver particles of 1.97 1.01 size range 0.5-1 .mu.m 10 wt % silver
particles of 2.70 1.38 size range 0.5-1 .mu.m 10 wt % ivory black
2.29 1.17 particles
[0059] The friction test was also applied to a cotton gauze (CX202
cotton gauze L/State 96 cm, CC28). The gauze is a lighter weight
muslin style fabric in which the fibre surfaces are sized so that
they are smoother. It would be expected that a lower friction be
observed in these tests. The results are shown in Table 3 and FIG.
4.
TABLE-US-00003 TABLE 3 Electrospun Fibre Composition Static Force
(N) Friction Coefficient (.mu.S) Polyurethane 2.04 1.04 2 wt %
silver particles of 2.01 1.03 size range 0.5-1 .mu.m 10 wt % silver
particles of 1.98 1.01 size range 0.5-1 .mu.m 10 wt % silver
particles of 2.04 1.04 size range 0.7-1.3 .mu.m 10 wt % ivory black
1.99 1.02 particles
[0060] The inventive samples have good friction properties
indicating utility in non-slip apparel applications.
Example 2: Friction Tests with Pig Skin
[0061] Porcine (pig) skin models are a useful tool to predict human
interactions with compounds because both human and porcine skin
have a spare hair coat, a thick well differentiated epidermis, a
dermis that has a well-differentiated papillary body and a large
content of elastic tissue, alongside similar size, distribution and
communication of the dermal blood vessels. There are also
immunohistochemical and biochemical similarities between to two
organisms. The porcine and human skin differ in the type of sweat
glands present in majority (apocrine vs. eccrine). In humans,
apocrine glands are located mainly in the armpits, genital area and
around the nipples, the prevalence of apocrine glands in porcine
skin samples makes porcine skin an excellent model for human skin
in these areas. The results of these tests are shown in Tables 4-6
and FIGS. 5a-c below:
TABLE-US-00004 TABLE 4 (data for graph of FIG. 5a) Electrospun
Fibre Composition Static Force (N) Static Coefficient (.mu.S)
Polyurethane 3.17 1.62 2 wt % silver particles of 3.82 1.95 size
range 0.5-1 .mu.m 10 wt % silver particles of 1.82 0.93 size range
0.5-1 .mu.m 10 wt % silver particles of 2.18 1.11 size range
0.7-1.3 .mu.m 10 wt % silver particles of 4.49 2.29 size range 5-8
.mu.m 10% Celite 0.02-0.1 mm 2.88 1.47 Silicone 2.28 1.16
TABLE-US-00005 TABLE 5 (data for graph of FIG. 5b) Electrospun
Fibre Composition Static force (N) Static coefficient (.mu.S)
polyurethane only 4.74 2.42 10% Ag 4.0-7.0 .mu.m 5.06 2.58 2%
Celite 0.02-0.1 mm 2.25 1.15 5% Celite 0.02-0.1 mm 2.54 1.30 10%
Celite 0.02-0.1 mm 2.75 1.40 10% Charcoal 2.27 1.16 10% Blue only
5.29 2.70 10% Blue + 10% Celite 3.22 1.64 0.02-0.1 mm 10% Red only
6.51 3.32 10% Red + 10% Ag 5.0-8.0 .mu.m 5.70 2.91 10% Red + 10%
Celite 3.11 1.59 0.02-0.1 mm 10% Yellow + 10% Celite 4.65 2.37
0.02-0.1 mm Silicone 2.68 1.37
TABLE-US-00006 TABLE 6 (data for graph of FIG. 5c) Electrospun
Fibre Composition Static Force (N) Static Coefficient (.mu.S)
Polyurethane (Tecoflex) 4.27 2.18 Vermillion Red 1.5% wt 3.73 1.91
Ultramarine Pink 7.5% wt 4.15 2.12 Teratop Pink crude 1.5% wt 4.33
2.21 Woven PU Fibre 2.07 1.06 Silicone 3.14 1.60
[0062] In some cases, the static friction observed is significantly
higher than the minimum values for skin adherence, for instance 10%
silver at 5-8 .mu.m provides an excellent static friction
coefficient. Further, the FIG. 5c clearly shows that the fibres of
the invention outperform both conventional silicone systems and
(specifically a woven elastane, Nylon and polyurethane system in
which the polyurethane is present in the warp only). polyurethane
systems. This series of tests also showed that pigment particles
can successfully form composite fibres, and that the pigment
particles are sufficient, when used alone with polyurethane, to
increase the friction properties of the web.
Example 3: Friction Tests with Wet Pig Skin
[0063] To determine the potential for the use of webs formed from
the composite fibres in swim wear or other sports gear where high
levels of sweat or moisture are possible, further tests were
completed using wet porcine samples. The friction test method was
identical to previous tests with the only modification being 1 ml
of distilled water (skin area=184 cm.sup.2, 0.005 ml cm.sup.-1)
sprayed onto skin surface before each sample run. After each sample
was measured a folded tissue was laid onto the skin to remove the
excess water and the method was repeated between each sample. The
results are shown in Table 7 and FIG. 6a below. This data was
generated from the same pig skin sample as the data for Table 4 and
FIG. 5a
TABLE-US-00007 TABLE 7 (data for graph of FIG. 6a) Electrospun
Fibre Composition Static force (N) Static coefficient (.mu.S)
polyurethane only 4.19 2.14 2% Ag 0.5-1.0 .mu.m 4.56 2.33 10% Ag
4.0-7.0 .mu.m 5.60 2.86 10% Ag 5.0-8.0 .mu.m 4.48 2.29 10% Charcoal
4.16 2.12 2% Celite 0.02-0.1 mm 4.81 2.45 5% Celite 0.02-0.1 mm
4.95 2.52 10% Celite 0.02-0.1 mm 3.75 1.92 10% Blue only 4.90 2.50
10% Blue + 10% Celite 5.09 2.60 0.02-0.1 mm 10% Red only 4.85 2.48
10% Red + 10% Ag 5.0-8.0 .mu.m 5.17 2.64 10% Red + 10% Celite 5.11
2.61 0.02-0.1 mm 10% Yellow + 10% Celite 6.71 3.42 0.02-0.1 mm
Silicone 2.26 1.15
[0064] FIG. 6a and the table above shows that the samples in this
test performed well, compared to the silicone product of the prior
art ("silicone") indicating that this material can provide higher
friction in wet conditions. The main contributing factor to the
good frictional resistance in wet conditions is believed to be the
porous nature of the electrospun material. The water present on the
skin surface is able to leach into the membrane (between the
fibres) effectively removing some surface water and allowing the
membrane to interact with the skin surface.
[0065] FIG. 6b shows that for the same pig skin sample, that
performance in the wet is superior to that in the dry. The static
friction values between all these samples are less variable than
the dry tests. This supports the argument that it is the porosity
of the material and not the added particles that leads
predominantly to the high friction values in wet conditions. The
results are shown in Table 8 below:
TABLE-US-00008 TABLE 8 Electrospun Fibre Composition Static force
(N) Static coefficient (.mu.S) DRY 10% Ag 5-8 .mu.m 3.74 1.91 10%
Celite 2.75 1.40 10% Blue + 10% Celite 3.22 1.64 Silicone 2.68 1.37
Woven Nylon and elastane 1.42 0.73 Retail product WET 10% Ag 5-8
.mu.m 4.48 2.29 10% Celite 3.75 1.91 10% Blue + 10% Celite 5.09
2.59 Silicone 2.26 1.15 Woven Nylon and elastane 1.02 0.52 Retail
product
Example 4: Friction Tests with Dry Pig Skin with Multimodal
Particles
[0066] To determine the effect of including multimodal particles in
the webs, further tests were completed. The friction test method
was identical to previous tests with the only modification being
the particles selected. The samples were as shown below:
TABLE-US-00009 Weight % Sample particle Composition Ag 0.7-1.3
.mu.m 10 wt % 7 g of Ag 0.7-1.3 .mu.m powder in 70 ml of PU
solution Ag 5-8 .mu.m 10 wt % 7 g of Ag 5-8 .mu.m powder in 70 ml
of PU solution Ag 635 mesh (up 10 wt % 7 g of Ag -635 mesh powder
in 70 ml to 20 .mu.m) of PU solution Combination of 10 wt % 7 g
total (2.33 g of Ag 0.7-1.3 .mu.m + above three 2.33 g of Ag 5-8
.mu.m + 2.33 g Ag -635 particle sizes mesh) in 70 ml of PU
solution. One third of each particle size.
[0067] An average result was taken from three identical samples.
The results of the test runs, are shown in Table 9 and FIG. 7
below.
TABLE-US-00010 TABLE 9 Sample Static Force (N) Ag 0.7-1.3 .mu.m
1.93 Ag 5-8 .mu.m 2.69 Ag 635 mesh (up to 20 .mu.m) 2.91
Combination of three sizes 3.02
[0068] The data clearly shows that the presence of multimodal
particle sizes offers a static friction at least comparable to
single particle sizes, and that this can be higher compared to when
a single particle size is used; although it is known that the
nature of the skin sample can have a significant effect on the
overall frictional value.
Example 5: Antimicrobial Properties
[0069] As shown in FIG. 8, the web has an antimicrobial effect on
contact with the bacteria. There is no zone of inhibition around
the web, indicating that there is no leaching of the particles from
the web.
Example 6: Wash Fastness
[0070] The template pattern of FIG. 9 was used to determine
dimensional stability. The results are shown in Table 10.
TABLE-US-00011 TABLE 10 Electrospun Fibre % of shrinkage
Composition MD MD1 CD % change in K/S Polyurethane only 6.3 7 2.5
6.3 10% Ag 5.0-8.0 .mu.m 5 5 0 4.0 10% Blue + Celite 5.7 6 2.5 10.4
10% Celite 0.02-0.1 1.4 2 0 1.5 mm only 10% Blue only 9.3 10 7.5
9.3 10% Violet only 21.4 22 20 21.4 10% Red only 20 21 20 20.0
[0071] These tests have revealed that no transfer of pigments to
the SDC multifibre is observed for any of the samples examined.
This suggests that the incorporated pigments within the electrospun
membrane are stable and do not transfer readily in standard wash
conditions.
[0072] Dimensional stability measurements have revealed that
shrinkage occurs in all the samples tested after the first
wash.
[0073] Electrospun fibrous polyurethane webs can be produced whilst
simultaneously incorporating colour into the product in a single
step, which provides a significant economic advantage in production
relative to known multi-step methods.
[0074] It can be seen from Table 10 and FIGS. 10a-10d that the
colour strength (K/S) values of five of the seven samples are seen
to increase after washing and drying. Wash fastness testing of dyed
products usually reveals a loss in colour from the material
compared to the original sample, due to not all the dye or pigment
staying fixed within the polymer matrix. Firstly this suggests that
no loss of pigment is occurring from within the electrospun
membranes and successfully demonstrates the one step method of
spinning and colouring together. The one step manufacturing process
of these coloured membranes mean that pigments can mix within the
polymer solution before it has solidified. Upon solidifying into
fibres the pigment molecules become "locked in" and stable, making
removal only possible by melting or dissolving the polyurethane
membrane. Secondly the observed increase in colour strength cannot
be explained by the samples obtaining more pigment, this must arise
from shrinkage.
Example 7: Water Vapour Permeability
[0075] Table 11 shows the results of the WVP testing:
TABLE-US-00012 TABLE 11 WVP (g/m.sup.2/day) WVP Index (I) Polyester
reference material 907.76 100.00 10% Electrospun 969.57 106.81
polyurethane only 10% Electrospun PU with Ag 874.76 96.36 5.0-8.0
.mu.m 10% Electrospun PU with 941.28 103.69 Celite 0.02-0.1 mm only
Melt blown polyurethane 992.36 109.32 only (75 g/m.sup.2) Melt
blown polyurethane 974.81 107.39 only (94 g/m.sup.2) Melt blown 1%
Ag 944.95 104.10 5.0-8.0 .mu.m
[0076] It can be seen that the samples are at least as breathable,
and generally more so, than the polyester reference sample.
[0077] It should be appreciated that the processes and apparatus of
the invention are capable of being implemented in a variety of
ways, only a few of which have been illustrated and described
above.
* * * * *