Underwear abstract
Compositions which greatly diminish, or eliminate, unpleasant smells
associated with the use of underwear and diapers are described.
These compositions are composed of superabsorbent polymers of the
p6lyacrylic type and of certain boron derivatives, in particular
sodium tetraborate pentahydrate. The sanitary articles which incorporate
these compositions do not develop unpleasant smells, ammoniacal
or otherwise.
Underwear claims
We claim:
1. A superabsorbent composition intended for the production of
sanitary articles selected from the group consisting of underwear,
diapers and disposable diapers, wherein the articles do not develop
unpleasant smells, wherein the composition consisting essentially
of:
a superabsorbent polymer resulting from the polymerization, with
partial crosslinking, of water-soluble ethylenically unsaturated
monomers; and
sodium tetraborate pentahydrate, in the proportion 0.1 to 10% by
weight of sodium tetraborate pentahydrate, with respect to the superabsorbent
composition,
wherein the sodium tetraborate pentahydrate is impregnated in the
polymer.
2. The composition of claim 1, wherein the superabsorbent polymer
comprises polymers formed from monomers selected from the group
consisting of acrylic acids, methacrylic acids, and alkali and alkaline
earth salts derived from said acrylic acids and methacrylic acids.
3. The composition of claim 2, wherein the particle sizes of the
polymer are in the range 100 to 800 .mu.m.
4. The composition of claim 1, wherein the sodium tetraborate pentahydrate
is in the proportion 0.5 to 5% by weight with respect to the superabsorbent
composition.
5. The composition of claim 4, wherein the particle sizes of the
polymer are in the range 100 to 800 .mu.m.
6. The composition of claim 1, wherein the particle sizes of the
polymer are in the range 100 to 800 .mu.m.
7. The composition of claim 1, not containing pine oil.
8. A process for the production of a superabsorbent composition
intended for the production of sanitary articles selected from the
group consisting of underwear, diapers and disposable diapers, wherein
the articles do not develop unpleasant smells, wherein the process
comprises
polymerizing with partial crosslinking, water-soluble ethylenically
unsaturated monomers to from a polymeric product in the presence
of sodium tetraborate pentahydrate, in the proportion 0.1 to 10%
by weight of sodium tetraborate pentahydrate, with respect to the
superabsorbent composition.
9. The process of claim 8 wherein the sodium tetraborate pentahydrate
is introduced into the polymer by means of an aqueous solution.
10. An article of manufacture selected from the group consisting
of disposable diapers for babies, disposable diapers for young children,
disposable diapers for adults, and disposable diapers for elderly
people comprising an absorbent element comprising superabsorbent
composition which consisting essentially of:
a superabsorbent polymer resulting from the polymerization, with
partial crosslinking, of water-soluble ethylenically unsaturated
monomers and sodium tetraborate pentahydrate, wherein the proportion
of the sodium tetraborate pentahydrate is 0.1 to 10% by weight of
the superabsorbent composition, and the sodium tetraborate pentahydrate
is impregnated in the polymer.
11. The article of claim 10 wherein the superabsorbent polymer
comprises polymers formed from monomers selected from the group
consisting of acrylic acids, methacrylic acids, and alkali and alkaline
earth salts derived from said acrylic acids and methacrylic acids.
12. The article of claim 10, wherein the sodium tetraborate pentahydrate
is in the proportion 0.5 to 5% by weight with respect to the superabsorbent
composition.
13. The article of claim 10 wherein the particle sizes of the polymer
are in the range 100 to 800 .mu.m.
Underwear description
The invention relates to the production of sanitary articles intended
to absorb and retain body fluids.
When the absorbing article in place is impregnated with such body
fluids, in particular urine, powerful and unpleasant smells are
produced. The predominant smells among these are ammoniacal smells
due to the ammonia originating from the hydrolysis of urea by the
ureases of bacteria (Proteus, Acinetobacter, and the like) present
on the skin and in the digestive tract.
For the purpose of suppressing these smells, widespread recourse
has been had to absorbents of smells or ammonia (U.S. Pat. No. 3,340,875,
Scott Paper Company), optionally in combination with deodorants,
fragrances, and the like. The use of pH buffers (WO-A-94 25077),
of oxidants (hydrogen peroxide, chlorine dioxide), of biocides (metals
or of metal cations), as well as of bactericides (quaternary ammoniums,
in particular), of antibiotics, of complexing agents or of surfactants,
both alone and in combination with one another, has also been recommended.
These various products present the general problem of an irritant
effect on the skin and mucosal mebranes. Absorbents of smells or
of ammonia are certainly less dangerous in this respect but they
leave the field free for a bacterial growth which remains worrying
and which it would be advisable to control from the outset. The
way which appeared necessary for the control of the bacterial emission
of ammonia from urea consists in inhibiting the enzymes which are
responsible for it, that is to say the ureases.
The use of urease inhibitors of low or moderate activity has until
now only been envisaged in combination with ammonia scavengers (JP
61-179155). Some powerful urease inhibitors, such as hydroxamic
acid derivatives (U.S. Pat. No. 3,920,015, Allied Chem. Corp.),
are advantageous but their toxicity excludes them from the targeted
use. Others, such as phenyl phosphorodiamidate (PPDA) or dimethyldithiocarbamate
(DTC), are compounds which are very effective against the formation
of ammonia but give rise, during their use, to other very unpleasant
sulfurous or alliaceous smells which are perhaps related, at least
in part, to their own decomposition by the bacterial flora present.
The search for a solution to this problem is all the more pressing
since, nowadays, the absorption capacity for body fluids of protection
articles has been very substantially increased by incorporating
superabsorbent polymers (SAP) into them, in particular hydrophilic
polymers and copolymers of acrylic acid, and since, by the same
token, the time during which they are maintained in place has been
increased, all conditions which promote the development of microbial
and enzymatic activity and of the smells which result therefrom.
It has now just been found that it is possible to formulate superabsorbent
polymers with certain boron derivatives in order to prepare therefrom
compositions which, although impregnated with urine or with biological
fluids containing it and maintained under conditions of use which
are especially propitious for bacterial growth, give rise neither
to significant evolution of ammonia nor to repellent or simply unpleasant
smells and which communicate this property to the sanitary articles
which contain. them.
The invention thus consists of a superabsorbent composition intended
for production of sanitary articles of the underwear, diaper or
disposable diaper type which do not develop unpleasant smells which
comprises a polymer, which is superabsorbent with respect to water,
saline solutions and body fluids, and sodium tetraborate or sodium
metaborate in the proportion of 0.1 to 10% of boron derivative,
preferably 0.5 to 5%, with respect to the superabsorbent composition.
Superabsorbent polymers within the meaning of the present invention
are polymers which result from the polymerization, with partial
crosslinking, of watersoluble ethylenically unsaturated monomers,
in particular acrylic and methacyrlic acids and their alkaline salts,
whether they are obtained by an inverse suspension or solution polymerization
process. These polymers possess a very high capacity for absorption
and retention of water and aqueous solutions and are nowadays widely
available commercially in the form of powders with particle sizes
of between 100 and 800 .mu.m. The literature relating to them is
very extensive; reference may be made, for example, to EP-A-0,312,952
(The Dow Chem. Co.) and to EP-A-0,441,507 (Sumitomo Seika Chem.).
Within the meaning of the present invention, sodium tetraborate
(Na.sub.2 B.sub.4 O.sub.7) is the anhydrous, pentahydrate or decahydrate
(borax) salt and the metaborate (NaBO.sub.2) is also regarded independently
of its degree of hydration. These boron compounds are mixed with
the polymer in the powder form in proportions indicated above.
The preparation of the composition according to the invention is
very easy, since it is sufficient to incorporate the boron derivative
in the powder form, preferably with a particle size also of between
100 and 800 .mu.m, in the superabsorbent polymer powder by simple
mixing. However, it has been observed that, if the boron derivative
was introduced within the superabsorbent polymer particles, an odor-preventing
efficiency was obtained, at equivalent concentration, which is greater
than by simple mixing of the powders. This results in an alternative
form of the process, which also forms part of the invention, whereby
the polymer powder is swollen using an aqueous solution of boron
derivative and then the water thus introduced is evaporated.
The superabsorbent compositions of the invention become gelled
on contact with water, aqueous saline solutions or body fluids,
like the superabsorbents of the prior art, and the gels thus formed
behave in a substantially identical way. They do not suffer from
any counterindication, the boron derivatives which are the means
of the invention being rightly regarded as inoffensive and being
widely used in various mild antiseptic compositions at contents
of the order of 1% by weight. They are used in place of the ordinary
superabsorbents in the manufacture of sanitary articles such as
disposable diapers for babies, for young children, for adults or
for elderly people of both sexes. This use also constitutes a subject
of the present invention.
Assessment of -the true effectiveness of odor-preventing products
is difficult to carry out. Since the invention comes within the
context of urease inhibitors, the candidate compounds which can
be envisaged for their anti-urease activity are therefore generally
classified by an IC.sub.50 value according to the results of an
enzymatic test which will be described later. Since the process
which generates smells is a biological process, it is necessary
to be able to estimate the effectiveness of various urease inhibitors
for their ability to limit the biological emission, by urea-fermenting
microorganisms, of at least the most common odorous compound, in
this case ammonia. This effectiveness is understood of the inhibitor
just as it is or In the presence of various substances with which
it is combined in the production of diapers and other sanitary articles,
in particular superabsorbent polymers. The results of this test
correlate fairly well with the IC.sub.50 values. Finally and particularly,
it is necessary to be able to decide on the satisfactory overall
result by olfactive tests under conditions which give acceptable
simulation of the conditions of use of the products in which the
superabsorbent composition which is believed to inhibit smells is
incorporated. They are carried out by impregnating a disposable
diaper with urine under standardized conditions, by heating the
combination in an oven at a low temperature and by subjecting the
object to a nose panel for overall assessment of its possible unpleasant
smells.
Such tests are described in the examples given below, which illustrate
the unexpected effectiveness of the products according to the invention.
In these tests, the superabsorbent polymer used is a partially neutralized
polyacrylic acid marketed under the name of AquaKeep.RTM.D (Elf
Atochem S.A.).
EXAMPLE 1
IC.sub.50 values of several molecules believed to operate as urease
inhibitors.
The test comprises the decomposition of a neutral solution of urea
at 1 g/l (0.016 M) in a 0.1M triethanolamine buffer, to which solution
has or has not been added the compound whose anti-urease activity
it is desired to estimate, by a solution of soybean urease (1500
U from Sigma) at 1 mg/ml in the buffer+10 mM of glutathion under
the following conditions. 400 .mu.l of urease solution and 10 ml
of urea solution are mixed. The mixture is maintained at 37.degree.
C. 1 ml samples are taken with time and assayed for NH.sub.3 by
the Nessler method: each 1 ml sample is added to 24.5 ml of dilute
Nessler reagent (0.5 for 24) and, after incubating for 10 minutes,
the absorbance at 425 nm is measured. An IC.sub.50 value is determined,
which value is the concentration of inhibitor in the mixture, expressed
as .mu.M, capable of reducing the urease activity by 50% under the
conditions of the test.
The IC.sub.50 values for several urease inhibitors known in the
literature are reported in the following table.
Compound IC.sub.50 (.mu.M) Phenyl phosphorodiamidate (PPDA) 0.05
Boric acid 450 Sodium metaborate 260 Sodium tetraborate 5H.sub.2
O 160 Sodium pyrophosphate 8000 Hydroquinone 500 Dimethyldithiocarbamate
(DTC) 10 Salicylhydroxamic acid 310 Glycolic acid 450 Acetohydroxamic
acid 600 Nitrilotriacetic acid 5000
Example 2
SAP/sodium tetraborate pentahydrate synergy
The IC.sub.50 value is determined as described above. The tests
are carried out by comparison both with a control medium and with
media containing respectively solely SAP, sodium tetraborate pentahydrate
(Na.sub.2 B.sub.4 O.sub.7.5H.sub.2 O) and SAP to which has been
added 3.9% by weight of sodium tetraborate pentahydrate, which was
obtained by mixing 29 kg of Na.sub.2 B.sub.4 O.sub.7.5H.sub.2 O
with 718.5 kg of superabsorbent polymer, so as finally to obtain
750 kg of boratecontaining composition. The results are reported
in the following table.
Residual urease activity Composition % Control (without SAP and
100 without inhibitor) SAP alone 100 (10 mg/15 ml of medium) SAP
alone 100 (100 mg/15 ml of medium) Borate-containing SAP 50 (10
mg/15 ml of medium) Borate-containing SAP 0 (100 mg/15 ml of medium)
The effectiveness of the borate-containing SAP is clearly demonstrated
by the test.
It was noted that the curve of the urease activity as a function
of the additive-containing SAP content in the medium was a smooth
curve. Under these conditions, the point of 50% residual urease
activity for this SAP containing 3.9% of tetraborate pentahydrate
can be interpreted in terms of IC.sub.50 with respect to the tetraborate
and is calculated at 90 .mu.M. This figure will be compared with
the value of 160 .mu.M for the tetraborate pentahydrate alone in
the table in Example 1 in order to observe that the IC.sub.50 which
can be attributed to sodium tetraborate pentahydrate in the presence
of SAP is superior to that which is calculated with the tetraborate
alone. This synergic effect between the SAP and the tetraborate
with respect to its anti-urease activity is most unexpected and
remains unexplained.
Example 3
Inhibiting effect on formation of ammonia.
The introduction is carried out, into a 100 ml Erlenmeyer flask
equipped (cf. FIG. 1) with a Prolabo No. 02.436.112 1 measuring
tube (these are graduated glass tubes containing a reagent for ammonia
which changes from violet to yellow, the position of the demarcation
between the two colorings giving an indication of the amount of
ammonia evolved), of urine 2 and of a mixture of defibrated cellulose
pulp and of SAP 3 in the following proportions:
fresh urine 50 ml fermented urine (inoculum) 2 ml superabsorbent
0.5 g defibrated cellulose pulp (fluff) 0.5 g
The inoculum is necessary because the fresh urine is sterile. This
inoculum is prepared in the following way: 0.25 g of urea and 1
g of soiled fluff originating from a used baby disposable diaper
are added to 100 ml of fresh urine (for greater convenience, the
medium could be inoculated with, in place of the used fluff, a strain
of Bacillus, Proteus or Acinetobacter). This solution, withdrawn
after 24 hours at room temperature, constitutes the inoculum.
In this test, the odor inhibitor is not introduced separately,
but with the superabsorbent formulated as indicated above and with
a content in the superabsorbent such that its dose in the medium
to be fermented is 10 times its IC.sub.50.
The system is left for 18 hours at 40.degree. C., after which the
position of the region of transition of violet/yellow coloring in
the measuring tube is noted, which thus provides a comparative estimation
of the evolution of ammonia and thus of the influence on this evolution
of the products which have been subjected to the test. After this,
the Erlenmeyer flask is carefully opened and the experimenter gives
his assessment of the smell of the contents. The results are recorded
in the table below.
Reading on the Substrate/inhibitor measuring tube Smell Control
(neither SAP nor >500 Strong ammoniacal inhibitor) SAP alone
>500 Strong ammoniacal SAP + Na.sub.2 B.sub.4 O.sub.7.5H.sub.2
O 90 No perceptible ammonia smell. Neutral smell of fresh urine
SAP + PPDA 120 Unpleasant smell of rotten cabbage SAP + DTC 1070
Unpleasant smell of rotten cabbage SAP + hydroquinone 120 Slight
nauseating
Example 4
Comparative test of an odor-preventing treatment by mixing powders
or by impregnation.
The introduction is carried out, in the device of Example 3, of
a synthetic urine inoculated by B. pasteunii (ATCC 11859) and of
a mixture of defibrated cellulose pulp and of SAP containing 4%
borax, one being produced by mixing SAP and borax powders and the
other by impregnation of SAP by the necessary amount of aqueous
borax solution at 80.degree. C. (22% by weight solution). The comparative
amounts of NH.sub.3 evolved (in ppm) at different moments are reported
below:
SAP + 4% borax SAP + 4% borax so- t (hours) SAP alone powder lution
0 0 0 0 6 7 7 7 8 20 18 10 10 off the scale 24 12 30 off the scale
off the scale 13
These results show the advantage, particularly with respect to
relatively long time periods, of tetraborate impregnation compared
with simple mixing.
Example 5
The test is carried out by using, as substrates, disposable diaper
material not containing SAP. Such a blank disposable diaper, with
a size of 31.times.11 cm, is taken and opened and 4 grams of SAP
are spread over it over a surface area of approximately 15.times.9
cm. The Centre of the disposable diaper is moistened with a mixture
of 50 ml of fresh urine and 2 ml of inoculum. The disposable diaper
is enclosed in a plastic bag which is welded. The whole assembly
is placed in a ventilated oven at 37.degree. C. for 12 hours. At
the end of this period, the bag is opened and an estimation of the
smell is made by a nose panel (8 people). In a system of notation
which confers the grade 0 in the complete absence of smell to 5
for a very strong smell of ammonia, the following are obtained:
Control disposable diaper 4.6 Disposable diaper with ordinary SAP
4.6 4% of "powder" borax 3.3 4% of "liquid"
borax 2.8
There has thus been found:
a strong smell of ammonia with the control disposable diaper,
a strong smell of ammonia with the disposable diaper carrying an
ordinary polyacrylic superabsorbent,
no smell of ammonia with the disposable diaper with a polyacrylic
superabsorbent containing 3.9% of sodium tetraborate pentahydrate.
A test of the same type, carried out with a synthetic urine, confirms,
with greater clarity, the above results:
Control disposable diaper 5 Disposable diaper with ordinary SAP
5 4% of "powder" borax 4 4% of "liquid" borax
3 |