U.S. patent application number 10/757424 was filed with the patent office on 2004-08-26 for bacteria trapping fibrous material.
Invention is credited to Andreasson, Bo, Berland, Carolyn, Besemer, Arie, Himmelmann, Gunilla, Malmgren, Kent, Van Brussel-Verraest, Dorine Lisa, Verwilligen, Anne-Mieke.
Application Number | 20040166144 10/757424 |
Document ID | / |
Family ID | 32871874 |
Filed Date | 2004-08-26 |
United States Patent
Application |
20040166144 |
Kind Code |
A1 |
Besemer, Arie ; et
al. |
August 26, 2004 |
Bacteria trapping fibrous material
Abstract
The invention concerns the use of a fibre modified with
functions capable of interacting with microbial cell wall proteins
for immobilising micro-organisms in hygiene products. Those
functions are particularly capable of interacting with anionic
groups and amine groups, and are especially cationic groups and
aldehydes, respectively. The fibres may be synthetic or cellulosic.
Also hygiene products containing these fibres are described.
Inventors: |
Besemer, Arie; (Amerongen,
NL) ; Van Brussel-Verraest, Dorine Lisa; (Bodegraven,
NL) ; Verwilligen, Anne-Mieke; (Zeist, NL) ;
Himmelmann, Gunilla; (Molnlycke, SE) ; Malmgren,
Kent; (Sundsvall, SE) ; Andreasson, Bo;
(Sundsvall, SE) ; Berland, Carolyn; (Molndal,
SE) |
Correspondence
Address: |
YOUNG & THOMPSON
745 SOUTH 23RD STREET 2ND FLOOR
ARLINGTON
VA
22202
|
Family ID: |
32871874 |
Appl. No.: |
10/757424 |
Filed: |
January 15, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60440028 |
Jan 15, 2003 |
|
|
|
Current U.S.
Class: |
424/443 |
Current CPC
Class: |
A61L 15/26 20130101;
A61L 15/28 20130101; A61L 15/40 20130101; A61L 15/28 20130101; A61L
15/26 20130101; C08L 67/02 20130101; C08L 1/02 20130101 |
Class at
Publication: |
424/443 |
International
Class: |
A61K 009/70 |
Claims
1. A process of immobilising micro-organisms a hygiene product
comprising contacting a medium suspected of containing
micro-organisms with a hygiene product containing a fibre modified
with functions capable of interacting with microbial cell wall
biopolymers.
2. The process according to claim 1, wherein the functions capable
of interacting with microbial cell wall biopolymers are functions
capable of interacting with anionic groups or amine groups.
3. The process according to claim 1, wherein the modified fibre
comprises a cationic fibre.
4. The process according to claim 3, wherein the cationic fibre
contains 2-20, especially 3-10 cationic charges per 100 monomer
units of the fibre.
5. The process according to claim 3, wherein the cationic fibre
comprises cationic cellulose obtainable by oxidation of the
cellulose to introduce aldehyde groups, followed by reaction of
aldehyde groups with a nitrogen-containing reagent carrying a
cationic group.
6. The process according to claim 3, wherein the cationic fibre
comprises cationic cellulose obtainable by reacting the fibre with
a nitrogen-containing reagent carrying a cationic group.
7. The process according to claim 1, wherein the modified fibre
comprises a fibre containing aldehyde groups.
8. The process according to claim 7, wherein the
aldehyde-containing fibre contains 0.5-50 aldehyde groups per 100
monomer units of the fibre.
9. The process according to claim 7, wherein the
aldehyde-containing fibre is obtainable by oxidation of the
fibre.
10. The process according to claim 7, wherein the
aldehyde-containing fibre is obtainable by coupling an
aldehyde-containing polymer to the fibre.
11. The process according to claim 7, wherein the fibre comprises
cellulose.
12. The process according to claim 1, wherein the fibre comprises
polyethylene terephthalate.
13. A layered hygiene product comprising at least one layer
containing a fibre modified with cationic and/or aldehyde groups
and at least one layer not containing a modified fibre.
14. A hygiene product according to claim 13, wherein the layer
containing a modified fibre is an outer layer.
15. A hygiene product according to claim 14, containing at least
three layers.
16. A hygiene product according to claim 13, wherein the modified
fibre is a cellulosic fibre.
17. A hygiene product according to claim 13, wherein the modified
fibre is a synthetic fibre.
18. A hygiene product according to claim 13, wherein said layers
are plies of a multi-ply sheet.
19. A hygiene product according to claim 13, which is a tissue
paper or non-woven.
20. A hygiene product according to claim 19, which is an absorbent
article comprising an outer casing layer, an inner casing layer and
a layer containing a liquid-absorbing material.
21. A hygiene product according to claim 20, wherein the layer
containing the liquid-absorbing material contains the modified
fibre.
Description
[0001] The present invention relates to disposable fibrous
materials for immobilising microbes for the purpose of removing or
inactivating the microbes, and to a process for producing such
fibrous material. The invention furthermore relates to cleaning
products and hygiene products containing these fibrous materials
for the purpose of removing or controlling micro-organisms.
BACKGROUND
[0002] Bacterial contamination in hygiene products is commonly
controlled by incorporating antibacterial agents. Similarly,
antibacterial action of cleaning material can be enhanced by
incorporation of bactericides. WO 00/58092 (U.S. Pat. No.
6,258,455) discloses an antimicrobial cleaning cloth comprising a
cationic polyamide microfibre and an antibacterial cellulose
acetate fibre containing an antimicrobial agent, spun together with
a polyester fibre for increasing strength. The cloth can be used
for scraping bacteria from a surface. In contrast, EP 1247534
describes the use of non-pretreated, dry paper or nonwoven for
wiping bacteria from the hands.
[0003] U.S. Pat. No. 4,791,063 describes a fibrous separation
device for trapping bacteria, wherein the fibre is a cellulose to
which a cationic polymer is covalently attached. The cationic
polymer can be a poly(meth)acrylate having diethylaminoethyl (DEAE)
acrylate units as cationic groups and glycidyl acrylate units as
cellulose-binding groups. The DEAE groups may be quaternised. These
cellulose derivatives are described as having improved protein
absorbing capacity. The cationic polymer can also be a polyionene
coupled to cellulose with a crosslinker such as butanediol
diglycidyl ether. The resulting cationic cellulose is used as a
column material for filtering bacteria from a solution.
[0004] Cationic cellulosic fibre is a known product. U.S. Pat. No.
4,505,775 discloses a cationic cellulose obtained by reaction of
cellulose fibre with a condensate of epichlorohydrin and
dimethylamine. The cationic fibre has improved dye retention
characteristics. A more recent survey of cationic cellulose fibres
is given in Gruber et al. in Cellulose Derivatives, Modification,
Characterisation and Nanostructures, Ed. T. J. Heinze and W. G.
Glasser, A.C.S., Washington D.C., 1998.
[0005] WO 01/92632 (EP 1291460) describes the coupling of basic
amino acids such as lysine and arginine to cellulose fibres
resulting in low degrees of functionalisation (1.7 and 1.8
substituent group, respectively, per 100 recurring units of the
cellulose). The treated fibres are for use as an antibacterial
product. U.S. application Ser. No. 2002/0,177,828 (WO 03/039602)
describes wound dressings having a coating grafted with cationised
polymethacrylate. The products have antimicrobial properties.
[0006] Aldehyde-functionalised cellulosic and other fibres are also
known, e.g. from WO99/23117, WO00/50462, WO00/50463 and WO01/34656.
They have e.g. improved wet strength when used as a paper or tissue
material. Small molecules containing carbonyl groups such as linear
(C6-C12) aldehydes, formaldehyde, glyoxal, glutar-aldehyde,
acetone, diethyl ketone etc. are known for use as microbiocide or
preservative (e.g. EP 0018504, WO01/39739, U.S. Pat. No.
5,807,587).
SUMMARY OF THE INVENTION
[0007] It was found that bacteria, moulds and other micro-organisms
can be effectively controlled in hygiene products by immobilising
them onto fibrous materials of the hygiene products without
necessarily killing them. The immobilisation can be effected
according to the invention by modifying the fibres with functional
groups capable of interacting with the bacterial cell walls. Such
functional groups include cationic groups and carbonyl groups,
which can be introduced into the fibres by direct chemical
modification of the fibrous material. The fibrous material can be
part of cleaning cloths, napkins, personal hygiene products and the
like. No bactericidal additives are necessary or even desired.
DESCRIPTION OF THE INVENTION
[0008] The invention pertains to hygiene products containing
fibrous materials carrying functional groups capable of interacting
with the bacterial cell walls. The hygiene articles can be products
for absorbing body fluids which have the risk of bacterial growth.
Examples include sanitary napkins and the like having a layer of
modified fibre capable of immobilising microorganisms, and thus
inhibiting their growth, and sanitary napkins and the like having
modified fibres. Another type of products are tissues and other
cloth-like articles suitable for cleaning surfaces and containing
or consisting of modified fibre.
[0009] Functional groups capable of interacting with bacterial cell
walls are understood to be functional groups capable of reacting
with polar groups on the cell walls, especially on cell-wall
proteins. Such groups include carboxyl groups, amino groups,
hydroxyl groups and the like, especially (anionic) carboxyl groups
and phosphoryl groups such as present in proteins (e.g. glutamic
acid, aspartic acid residues), glyco-proteins, and certain
polysaccharides, and amino (guanidino etc.) groups such as present
in proteins (e.g. lysine, arginine residues). The (anionic)
carboxyl and phosphoryl groups exhibit electrostatic interaction
with cationic groups present on the modified fibres, while amino
groups can interact with e.g. aldehyde groups in the modified
fibres of the invention.
[0010] The fibres containing the functional groups capable of
interacting with bacterial cell walls can also be denoted as
electrophilically modified, which refers to chemical modification
resulting in the presence of electrophilic functional groups. The
electro-philic groups can be the electropositively charged groups,
i.e. cationic groups, wherein the positive charge has the
electrophilic function, or they can be non-charged groups that have
an internal charge separation wherein the positively charged centre
is capable of reacting with electron-rich functions.
[0011] Examples of electropositive groups include common cationic
groups such as ammonium groups, phosphonium groups, sulphonium
groups and certain metal-containing groups. Examples of non-charged
groups with internal charge separation include carbonyl groups,
such as aldehydes, ketones, and the like. For example, the internal
charge separation in an aldehyde can be represented by the variant
form R--HC.sup.+--O.sup.- of the conventional neutral formula
R--HC.dbd.O. The partially charged carbon atom is capable of
reacting with nucleophiles such as hydroxyl groups and amino
groups.
[0012] Although the inventors do not wish to be bound by theory, a
possible explanation of the bacteria-trapping property of the
modified fibres is their capability of associating with outer
layers of the bacteria having electron-rich functions, such as
carboxyl groups, amino groups and the like. Thus, a common feature
of the cationic functions and the non-charged electrophilic
functions may well be their capability to associate carboxyl groups
or the like. Herebelow, the functional (electrophilic) groups of
the modified fibres of the invention are further illustrated as
cationic groups and aldehyde groups, but other functional
(electrophilic) groups capable of interacting with cell wall
biopolymers can be used similarly.
[0013] The functional groups may be the same throughout the
modified fibre. Also, the same fibres may contain different
functional groups such as cationic groups and carbonyl groups in
the same molecule, but they may also be a fibre containing
different molecules, e.g. one type containing cationic groups,
another containing carbonyl groups. Also the fibre may partly
consist of modified fibres containing the functional groups capable
of interacting with protein functions, and partly of non-modified
fibre, or fibre containing functional groups having less or no
interaction with cell wall bio-polymer functions, such as
hydroxyalkyl or acyl groups.
[0014] The invention more particularly relates to layered products,
in which at least one layer, preferably a surface layer, contains
modified fibre. Thus, the product can be an absorbing or wiping
sheet having different layers, wherein at least one layer contains
the modified fibre, and at least one layer preferably does not
contain the modified fibre. If the layers are designated as E for
(electrophilically) modified fibre layer and N for non-modified
fibre layer, the layered structure can be of the types E-N, E-N-E,
E-N-N, E-E-N, N-E-N, E-N-N-N, E-N-N-E and the like, wherein those
structures having an external modified fibre layer (E) are
preferred.
[0015] The product of the invention can also be a homogeneous
product containing a mixture of modified fibres and non-modified
fibres. The basic fibres can than be the same, e.g. cellulosic, or
they can be different, e.g. a non-modified synthetic fibre combined
with a modified cellulosic fibre or vice versa. Also, the product
can be layered, wherein one or more layers may consist of a mixture
of modified and non-modified fibres as described above.
[0016] The product of the invention can also be a multiple sheet
product, i.e. a layered structure consisting of distinct superposed
sheets, each sheet containing one or more layers. In such multiple
sheet products, one top sheet can entirely consist of
electro-philically modified fibre, or may only contain an
electrophilically modified surface layer together with one or more
non-modified layers. Also, both external sheets may have a top
layer with electrophilically modified fibre, and one or more inward
layers without electrophilically modified fibre. Such multiple
sheet products can be produced by conventional means, e.g. using a
multi headbox as described e.g. in U.S. Pat. No. 5,538,595. The
products can be of a tissue type or a non-woven.
[0017] The product of the invention can be a layered
liquid-absorbing product, such as a sanitary napkin, a diaper or
other hygiene product, containing one or more internal layers
containing liquid-absorbing material and a modified outer layer.
Alternatively, the product of the invention can be a layered
product having a modified absorbent core with a non-modified outer
layer.
[0018] The modified fibre is especially a cellulosic fibre. The
cellulosic fibre may be directly obtained from wood pulp, or it may
have been pretreated so as to enhance its absorbing capacity or its
processability, e.g. in the case of lyocell or viscose fibres. The
fibre may also be of a synthetic type such as polyester,
polypropylene, polyvinylalcohol, polyamide (nylon), polylactic
acid., and the like. Polypropylene and especially poly-esters such
as polyethylene terephthalate (PET) are preferred for non-wovens.
Fibres containing aromatic or other unsaturated groups are
particularly preferred, as they are susceptible to oxidation
resulting in aldehyde or ketone groups. Different types of
synthetic fibres can be used: staple fibres, splittable fibres and
continuous filaments.
[0019] Where the fibre contains cationic groups, the fibre or
fibrous carrier, e.g. paper and paper product, tissue and the like,
is positively charged by cationic derivatisation. The cationic
derivatisation can be performed by amino- or azido-alkylation, or
oxidation to introduce aldehyde functions followed by reaction with
amines or other nitrogen-containing reagents. The cationic
derivatisation is performed to an extent that allows sufficient
coupling of opposite charges, depending on the particular use of
the coupling product. In general, a degree of ionisation of 0.1-50
ionic charges per 100 monomer units of the carrier, preferably from
0.5 to 20, most preferably from 1 to 10 charges per 100 units.
[0020] Thus, the cationic fibre to be used according to the
invention can be a cellulosic material containing at least 0.1
cationic group, preferably at least 1 cationic group, up to e.g. 50
cationic groups per 100 anhydroglucose unit (AGU). In particular
the fibre contains between 2 and 20, cationic groups, more in
particular between 3 and 10 cationic groups per 100 AGU. The
cationic groups may be any charged groups, wherein the charge may
be acid-independent, such as in trisubstituted ammonium,
trisubstituted phosphonium and disubstituted sulphonium groups,
wherein the substituents may be alkyl, alkenyl, aryl and their
substituted analogues such as hydroxyalkyl, ammonioalkyl,
alkylaryl, arylalkyl, and their cyclic analogues such as in
N-pyridylium. Instead, the charge may be acid-dependent such as in
amino, and mono- and disubstituted amino groups. An
acid-independent charge means that the charge is always present,
also under non-acidic conditions (high pH), requiring that the
charge-carrying atom (usually nitrogen, sulphur or phosphorus) does
not directly carry hydrogen atoms. An acid-dependent charge is only
present at sufficiently acidic conditions, i.e. usually when the
charge-carrying atom directly binds one or more hydrogen atoms.
Acid-independent cationic groups are preferred. Examples of
acid-independent charged groups include tri-methylammonio,
triethylammonio, N,N-dimethylhydroxyethylammonio,
N,N-dimethyl-benzylammo- nio, 1-methyl-1-piperidinio, 1-pyridinio,
tributylphosphonio, triphenyl-phosphonio, dimethylsulphonio and the
like. Examples of acid-dependent charged groups include amino,
ethylamino, dimethylamino, pyrrolidino, morpholino, and the like.
The preferred charged group is trimethylammonio
(CH.sub.3).sub.3N.sup.+--.
[0021] The cationic cellulosic fibre can be prepared by first
introducing aldehyde groups. A first, convenient method of
introducing aldehyde groups consists of oxidation of
dihydroxyethylene groups --CHOH--CHOH--, i.e. the 2,3-positions of
the cellulosic AGU, using periodate (MIO.sub.4 or M.sub.5IO.sub.6,
wherein M is e.g. hydrogen or an alkali metal or alkaline earth
metal or a combination thereof) or similar oxidising agents,
resulting in two aldehyde groups. Another useful method involves
oxidation of hydroxymethyl groups --CH.sub.2OH, i.e. the 6-position
of the AGU, using nitric oxides, in particular nitroxyl-mediated
("TEMPO") oxidation using hypochlorite, hydrogen peroxide, peracids
such as peroxosulphuric acid, or oxygen as reoxidators, optionally
using metal compounds, metal complexes or redox enzymes as
cocatalysts. These oxidations have been described in U.S. Pat. No.
3,364,200, NL 9301172, WO 00/50462, WO 00/50463, WO 01/34657 and WO
01/00681, for example. The aldehydes can also be introduced by a
combination of oxidation methods, e.g. TEMPO-mediated oxidation
followed by periodate oxidation, resulting in aldehydes at
positions 2, 3 and 6 of the AGU (see WO 01/34656).
[0022] Introduction of carbonyl groups (aldehydes and/or ketones)
in both cellulosic and non-cellulosic fibres can be effected by
oxidation of unsaturated groups, such as aromatic groups, e.g.
phenylene groups in polyesters and polyamides. Suitable oxidation
leading to carbonyl functions can be performed with ozone.
[0023] The aldehyde-functionalised fibre can conveniently be
reacted with an agent having both an unsubstituted amino group
(--NH.sub.2) for coupling with the aldehyde function, and a
cationic group, such as a trialkylammonio group, or a potentially
cationic groups such as an amino group, preferably a tertiary amino
group (e.g. N.sup.3,N.sup.3-dimethyl-1- ,3-propanediamine). The
amino group can be present on an aliphatic (alkyl) position, e.g.
as --CH.sub.2NH.sub.2, which upon condensation with the aldehyde
function (O.dbd.CH--) results in an imine (--CH.sub.2N.dbd.CH--),
which is then preferably stabilised by reduction to an amine
(--CH.sub.2NH--CH.sub.2--), e.g. by borohydride reduction,
dithionite reduction, or metal-catalysed hydrogenation. Preferably,
however, the starting amino group is stabilised, e.g. as a
hydrazine (--NH--NH.sub.2), a carboxamide (--CO--NH.sub.2), a
sulphonamide (--SO.sub.2--NH.sub.2) or the like, especially a
hydrazide (--CO--NH--NH.sub.2) or sulphohydrazide
(--SO.sub.2--NH--NH.sub.2), resulting, upon reaction with the
aldehyde, in stable coupling, e.g. as a hydrazone
(--CO--NH--N.dbd.CH--). Very suitable reagents are Girard's
reagents T, trimethylammonioacetic hydrazide
((CH.sub.3).sub.3N.sup.+CH.s- ub.2CONHNH.sub.2; betaine hydrazide
hydrochloride) and P, pyridinioacetic hydrazide. The reaction of
Girard's reagents with carbohydrates is known per se, from U.S.
Pat. No. 4,001,032.
[0024] The reaction with the stabilised amine reagent such as
Girard's reagent can be performed by treatment with 1-30 wt. % of
reagent with respect to the fibre dry weight to a suspension (0.5-5
wt. %, especially 1-2 wt. %) of the aldehyde-functionalised fibre
in water. The pH is usually between 2 and 7, in particular between
4 and 5, the reaction time is typically from 2 minutes to two hours
and the temperature is between 20 and 100.degree. C., especially
between 36 and 90.degree. C. The fibres are then washed with water
to remove excess reagent.
[0025] As an alternative, the cationic fibres can be obtained by
directly cationising the fibres. Thus, the fibres may be cationised
by reaction with a cationising agent, such as
2-chloroethyltrimethylammonium,
3-chloro-2-hydroxypropyltrimethylammonium, or glycidyl
trimethylammonium chloride or other epoxide reactants having
cationic functions. Further alternatives include binding of
cationic polymers, such as poly-ethyleneimines and
polyamine-amines, to the fibres, optionally using a crosslinker or
a binder material, or grafting of cationic monomers, such as
diallyldimethylammonium chloride (DADMAC), on to cellulose
fibres.
[0026] Where the fibre contains functional groups in the form of
aldehydes, the aldehyde groups may be introduced by methods known
in the art as described above. In case of cellulosic fibres,
aldehyde functions may thus be introduced by oxidation. A suitable
known example of oxidation of cellulosic material is periodate
oxidation (2-3 oxidation) as described above, resulting in a degree
of oxidation of choice, e.g. between 0.1 and 30%, wherein a degree
of oxidation of 1% means that 1 out of 100 mono-saccharide units
has been oxidised to a dialdehyde, i.e. containing 2 aldehyde
groups per 100 units. Preferably, the fibre contains 0.5-50
aldehyde (or ketone) groups per 100 units, most preferably 1-20.
Another preferred method of introduction of aldehyde groups is
6-oxidation using e.g. TEMPO as described above. Furthermore,
carbonyl groups can be introduced by ozone treatment of cellulose
fibres. This oxidation method is non-specific and also gives rise
to degradation of the cellulose. Cellulose derivatives containing
unsaturated groups can be converted to aldehyde-containing
derivatives by ozone treatment in a more controlled manner;
examples of such an unsaturated substrate include the addition
product of allyl glycidyl ether to cellulose as described in WO
01/87986 and the esterification product of unsaturated carboxylic
acids with cellulose as described in WO 97/36037. For synthetic
fibres, carbonyl groups can be introduced by ozone treatment of
polymers containing C--C double bonds or vicinal diols. Carbonyl
groups may also be introduced by corona treatment of fibres such as
described in EP-A 1158087, or by plasma treatment such as described
in WO 00/36216.
[0027] Another suitable method of producing aldehyde-modified
fibres consists of coupling the fibre with an aldehyde-containing
compound, e.g. an aldehyde-containing polymer or oligomer as can be
used as a wet-strength agent. Examples of the latter include
dialdehyde starch (DAS), cationised dialdehyde starch, and
glyoxalated amide polymers such as glyoxalated polyacrylamide
(G-PAM). These compounds preferably have a relatively high aldehyde
content, e.g. between 5 and 100, especially between 20 and 80
(di)aldehyde groups per recurring unit. These agents can be
incorporated in the fibre in relative proportions between e.g. 0.5
and 50 % by weight of the fibre, preferably between 2 and 20 % by
weight.
[0028] Modified fibres according to the invention include fibres
containing two or more different types of functions capable of
interacting with cell wall proteins. For example cellulosic fibres
containing both aldehyde groups and cationic groups are also
suitable in the products of the invention. For example a polymer
fibre may contain 1-20 aldehyde groups and 1-20 cationic groups per
100 monomer units. These mixed functions are accessible e.g. by
introduction of aldehyde groups in a manner described above,
followed by only partial further reaction of the aldehyde groups to
cationic groups.
[0029] The fibres thus prepared can be used for making paper,
tissues or non-wovens. A tissue paper is defined as a soft
absorbent paper having a basis weight below 65 g/m.sup.2 and
typically between 10 and 50 g/m.sup.2. Its density is typically
below 0.60 g/cm.sup.3, preferably below 0.30 g/cm.sup.3 and more
preferably between 0.08 and 0.20 g/cm.sup.3. Moist tissue paper
webs are usually dried against one or more heated rolls. A method,
which is commonly used for tissue paper is the so-called Yankee
drying, through-air drying (TAD) or impulse drying as described in
WO 99/34055. The tissue paper may be creped or non-creped. The
creping may take place in wet or dry condition. It may further be
foreshortened by any other methods, such as so-called rush transfer
between wires.
[0030] Apart from cationic or aldehyde-functionalised fibres
according to the invention, the tissue paper may comprise pulp
fibres from chemical pulp, mechanical pulp, thermo-mechanical pulp,
chemo-mechanical pulp and/or chemo-thermo-mechanical pulp (CTMP).
The fibres may also be recycled fibres. The tissue paper may also
contain other types of fibres enhancing e.g. strength, absorption
or softness of the paper. Such fibres may be made from regenerated
cellulose or synthetic material such as polyolefin, polyesters,
polyamides etc.
[0031] The tissue paper may comprise one or more layers. In the
case of more than one layer this is accomplished either in a
multi-layered headbox, by forming a new layer on top of an already
formed layer or by couching together already formed layers, or by
depositing dry fibres on a wet formed fibre as described in EP-A 0
332 618. These layers cannot or only with considerable difficulty
be separated from each other and are joined mainly by hydrogen
bonds. The different layers may be identical or may have different
properties regarding for example fibre composition and chemical
composition. One or more layers may comprise cationic and/or
aldehyde-modified fibres according to the invention.
[0032] The tissue paper coming from the tissue machine as a
single-ply paper sheet may be converted to the final tissue product
in many ways, for example embossed, laminated to a multi-ply
product, rolled or folded. A laminated multi-ply tissue product
comprises at least two tissue plies, which are often joined either
by an adhesive or mechanically. One or more plies may comprise
cationic and/or aldehyde-modified fibres according to the
invention. In the case of a tissue paper or nonwoven, preferably
the outer layers comprise modified fibres as according to the
invention. The adhesive may be applied all over the paper or just
in regions, for example dots or lines, or only along the edges of
the product. The mechanical methods are mainly embossing either
over the entire area of the plies or only along the edges, so
called edge embossing. In the final product the plies as mostly
easy detectable and can often be separated from each other as
single plies.
[0033] In some more detail, a two layered, two-ply web can be
comprised of two plies in juxtaposed relation, each ply having an
inner layer and an outer layer. Outer layers may contain short
paper making-fibres; whereas inner layers may contain long paper
making fibres. In another embodiment, tissue paper products are
formed by placing three single-layered tissue paper webs in
juxtaposed relation. In this example, each ply is a single-layered
tissue sheet made of softwood or hardwood fibres. The outer plies
preferably comprise the short hardwood fibres and the inner ply
preferably comprises long softwood fibres. The three plies are
combined in a manner such that the short hardwood fibres face
outwardly. In a variation of this embodiment each of two outer
plies can be comprised of two superposed layers. In another
embodiment, tissue paper products are formed by combining three
layers of tissue webs into a single-ply. In this example, a
single-ply tissue paper product comprises a three-layer tissue
sheet made of softwood and/or hardwood fibres. The outer layers
preferably comprise the short hard-wood fibres and the inner layer
preferably comprises long softwood fibres. The three layers are
formed in a manner such that the short hardwood fibres face
outwardly.
[0034] The term nonwoven is applied to a wide range of products,
which in term of their properties are located between the groups of
paper and cardboard on the one hand, and textiles on the other
hand. As regards nonwoven a large number of extremely varied
production processes are used, such as the air-laid, wetlaid,
spunlaced, spunbond, melt-blown techniques etc. Nonwovens represent
flexible porous fabrics that are not produced by the classical
methods of weaving or knitting, but by intertwining and/or by
cohesive and/or adhesive bonding of typical synthetic textile
fibres, which may for example be present in the form of endless
fibres or fibres prefabricated with an endless length, as synthetic
fibres produced in situ or in the form of staple fibres.
Alternatively they may be made from natural fibres or from blends
of synthetic fibres and natural fibres.
[0035] The invention further provides an absorbent article such as
a pant-type diaper, which will effectively enable diapers to lie
sealingly against and shape conformingly to the wearer's body, even
when the pad is full of liquid. Other absorbent articles in which
the modified fibre of the invention may be incorporated include
incontinence devices, sanitary towels, sanitary napkins and the
like The modified fibres according to the invention allow to reach
a sufficient degree of bacteria-trapping activity in such absorbent
articles and especially the absorption pad while maintaining it
biodegradable. A pant diaper according to the invention may include
an elongated absorbent pad which is enclosed between an inner
liquid-permeable casing layer and an outer liquid-impermeable
casing layer. The inner casing layer and/or the outer casing layer
may comprise modified fibres according to the invention. It is to
be understood that it is well within the scope of the invention to
put the modified fibres in distinct layers or mixed with regular
cellulosic fibres or polymeric hydrocolloidal material or mixed
even with both cellulosic fibres and polymeric hydrocolloidal
material. Different combinations with mixed layers and distinct
layers are also possible.
[0036] The liquid absorbing material in the absorbent article is
suitably manufactured by one or more layers of cellulose pulp. The
pulp may originally be in the form of rolls, bales or sheets, which
at the manufacture of the sanitary towel is dry-defibrated and
transmitted in fluffed form to a pulp mat, sometimes including
so-called super-absorbents, which are polymers having the ability
to absorb water or bodily fluids in an amount of several times
their own weight. An alternative to this is to dry-form a pulp mat,
such as described in WO94/10956. Examples of other usable absorbent
materials are different kinds of natural fibres, such as cotton
fibres, peat or the like. Naturally, it is also possible to use
absorbent synthetic fibres, or particles of a high-absorbing
polymer material of the type, which at absorption chemically bind
large amounts of liquid, during the formation of a
liquid-containing gel, or mixtures of natural fibres or synthetic
fibres. The liquid absorbing material may further comprise
additional components, such as form-stabilising means,
fluid-spreading means, or binders, such as for example
thermoplastic fibres, which have been heat-treated to hold short
fibres and particles to a connecting unit. It is also possible to
use different types of absorbing foam materials in the absorbent
body.
[0037] It is possible to add antimicrobial agents to the modified
fibres according to the invention, but the use of such additional
agents is not absolutely necessary and may even be disadvantageous
in some cases.
[0038] Where the product containing the modified fibre according to
the invention is an absorbent hygiene product, such as a diaper or
a sanitary napkin, the further composition and use of the product
can be as conventional. Where the product is a wiping tissue, it
can be used for cleaning or treating surfaces that are suspected to
carry microorganisms, such as kitchen tables, bathroom equipment
and other household and industrial surfaces. The cleaning treatment
may comprise simple wiping, or it may involve additional
treatments, such as wetting, using disinfectants, cleaning agents
or the like.
EXAMPLE 1
Preparation and Characterisation of Cationic Lyocell Fibres by
Treatment with Glycidyl Trimethyl Ammonium Chloride
[0039] Sample Preparation
[0040] Sample A: Lyocell fibres, manufactured by Lenzing with a
length of 38 mm and a fibre weight/length unit of 1.3 dtex, were
carded. The fibres were then modified as follows: 10 g fibres were
mixed with a solution of 6.7 g NaOH in 28.5 ml H.sub.2O in an
ice-bath for 30 min. Thereafter, 46.74 g of glycidyl trimethyl
ammonium chloride (GTAC; Sigma Aldrich, Sweden) was added with 20
ml H.sub.2O to the fibre suspension, which then was heated to
80-85.degree. C. using a water bath. After 30 min. the fibres were
washed with 4% NaCl by repeated decanting. When the washing liquid
showed a neutral pH, the fibres were added to 2.5 l of a 4% HCl
solution and kept overnight in this medium. Then the fibres were
washed with a 2% NaCl solution, and the fibres were washed until a
neutral pH was achieved.
[0041] Samples B-E: Lyocell fibres were treated as Sample A except
that the following amounts of GTAC were used.
1 absolute relative to sample A Sample B: 23.37 g 0.50 Sample C:
16.36 g 0.35 Sample D: 9.35 g 0.20 Sample E: 4.67 g 0.10
[0042] Charge Characterisation of Cationic Fibres
[0043] For determination of the fibre charge, polyelectrolyte
titration was used. 0.5 g fibre was added to 100 ml of a
polyacrylate solution. Sodium polyacrylate with a molar weight of
8000 g/mol (Sigma Aldrich, Sweden) was used in these tests. The
concentration of the polymer solutions was from 50 mg/l to 375 mg/l
and several fibre/polymer blendings were prepared for each charge
determination.
[0044] The pH was adjusted to 8.5 for each sample. Then the samples
were thoroughly mixed by shaking for 10 minutes followed by
separation of fibres and liquid achieved by filtration on a Buchner
funnel equipped with a Munktell filterpaper (pre weighted) of the
grade Munktell no 3. The fibres were dried in an oven at a
temperature of 105.degree. C. and weighed in order to determine the
amount of analysed fibre. The liquid was titrated with a 0.1 g/l
Polybrene.RTM. solution and the equivalence point was determined by
the aid of a Muitec LPCD (particle charge detector) (1), which
measures the zeta potential. The point of equivalence is indicated
by a zero zeta-potential. By this procedure the amount of adsorbed
polyacrylate/g fibre can be determined as a function of the
polyacrylate concentration in the solution and hereby an adsorption
isotherm could be achieved. The fibre charge can then easily be
determined by extrapolation of the plateau to zero concentration.
This value is then multiplied with the charge/weight unit of
polyacrylate at the present pH.
[0045] The following results were achieved:
2 Sample Fibre charge (.mu. equivalents/g) A 770 B 642 C 556 D 257
E 60
[0046] Determination of Bacteria-Removing Capability
[0047] The ability of the fibres to absorb Lactobacillus plantarum
was tested by adding the dry fibres to a solution of bacteria and
allowing the fibres to absorb bacteria for 10 minutes. The fibres
were then removed from the bacteria solution and the reduction of
the concentration of the bacteria solution was measured. Unmodified
carded lyocell fibres were used as a reference.
[0048] In addition to Lactobacillus, which are non-pathogenic
bacteria, also Staphylococcus aureus and Escherichia coli were
tested. S. aureus was chosen as a representative of the gram
positive bacteria because it may cause problems both in health care
and in food preparation. In addition this is one of the standard
bacteria used in testing disinfectants and other cleaners. The
bacteria E. coli was chosen as a representative of the gram
negative bacteria for similar reasons. The day to day variation of
the amount adsorbed by the reference fibers is due to natural
variation in the bacteria. For comparing the results, a normalised
reduction was defined as `reduction in bacteria obtained by a
modified fibre/reduction obtained by the reference fibre measured
on the same day`. The results were as follows:
3 SAMPLE Concentration (abs units) Normalised Reduction in bacteria
(Lactobacillus plantarum) Reference (day 1) 0.110 .+-. 0.040 1 B
0.513 .+-. 0.029 4.7 E 0.097 .+-. 0.036 0.9 Reference (day 2) 0.052
.+-. 0.011 1 C 0.220 .+-. 0.067 4.2 D 0.196 .+-. 0.064 3.8
Reduction in bacteria (Staphylococcus aureus) Reference (day 3)
0.024 .+-. 0.013 1 B 0.196 .+-. 0.019 12.0 Reduction in bacteria
(Escherichia coli) Reference (day 4) 0.133 .+-. 0.068 1 B 0.165
.+-. 0.072 1.2
Example 2
Preparation and Characterization of Cationic Lyocell Fibres by
Periodate Oxidation Followed by Reaction with Girard's Reagent
T
[0049] Sample Preparation
[0050] Lyocell fibres (40 g), carded as described in example 1,
were suspended in 4 litres of a solution of sodium periodate (5.3
g, 25 mmol) with the pH adjusted to 5. The suspension was left in
the dark at room temperature for 6 days. Then, the sodium iodate
formed during the reaction was removed by washing the fibres with
water.
[0051] Subsequently, the fibres were resusupended in 2 litres of
water, Girard's reagent T (trimethylammonioacetic hydrazide) was
added (8 g, 50 mmol) and the mixture was stirred for 2 hours at
40.degree. C. Then the fibres were thoroughly washed with water,
dewatered as much as possible and dried in a fluidised bed dryer at
40.degree. C.
[0052] Determination of Charge
[0053] The charge of the fibres was determined according to the
method described in Example 1. The charge of the modified fibres
was 320/.mu.eq/g.
[0054] Determination of Bacterial Removing Capability
[0055] The ability of the fibres to adsorb bacteria was measured
using the method described in Example 1 with the following
results.
4 Reduction in bacteria concentration Sample (abs units)
(normalised) Reference (day 5) 0.070 .+-. 0.018 1 Cationic fibre
0.218 .+-. 0.017 3.1
[0056] Examples 1 and 2 clearly illustrate that all fibres with
charge greater than 60 .mu.eq/g (samples B,D,E, and Lyocell
prepared with Girard's reagent) adsorbed significantly more
bacteria than the reference (untreated Lyocell). The treated fibres
were prepared using two different chemical routes demonstrating
that the effect is not specific to a particular type of cationic
modification.
Example 3
Preparation and Characterization of Aldehyde Lyocell Fibres by
Periodate Oxidation
[0057] Lyocell fibres, manufactured by Lenzing with the length 38
mm and the fibre weight/length unit 1.3 dtex, were carded. These
fibres were oxidised to a degree of 10% as follows: fibres (40 g;
247 mmol) were suspended in 4 litres of a solution of sodium
periodate (5.3 g, 25 mmol) with the pH adjusted to 5. The
suspension was left in the dark at room temperature for 6 days.
Then, the sodium iodate formed during the reaction was removed by
washing the fibres 3 times with excess water. Lyocell with higher
oxidation degrees (30%, 50%) were prepared in a similar way, except
that more sodium periodate was used (15.9 g for 30% and 26.5 g for
50%). The aldehyde content was determined by titration with
hydroxylamine. Hydroxylamine hydrochloride (Sigma) (1 g) was
dissolved in 40 mL water and heated at 50.degree. C. The pH was
adjusted to 3.2. The oxidised lyocell (500 mg) was added. Due to
reaction of the aldehydes with hydroxylamine, a pH-drop was
observed. From the amount of sodium hydroxide (0.5M) solution
needed to keep the pH at 3.2, the aldehyde content could be
calculated. The resulting aldehyde contents were as follows:
[0058] Aldehyde lyocell 10%: 750 .mu.mol/g aldehyde (=6%)
[0059] Aldehyde lyocell 30%: 3500 .mu.mol/g aldehyde (=28.5%)
[0060] Aldehyde lyocell 50%: 5110 .mu.mol/g aldehyde (=41.5%)
[0061] Determination of Bacterial Removing Capability:
[0062] The ability of the fibres to absorb Lactobacillus plantarum
was tested by adding the dry fibres to a solution of bacteria and
allowing the fibres to absorb bacteria for a period of 10 minutes.
The fibres were then removed from the bacteria solution and the
reduction of the concentration of the bacteria solution was
measured. Besides Lactobacillus, which is a non-pathogenic
bacteria, also Staphylococcus aureus and Escherichia coli were
tested. Staphylococcus aureus was chosen as a representative of the
gram positive bacteria because it is a bacteria that may cause
problems both in health care and in food preparation settings. In
addition this bacteria is one of the standard bacteria used in
testing disinfectants and other cleaners. The bacteria Escherichia
coli was chosen as a representative of the gram negative bacteria
for similar reasons. The results were as follows:
5 SAMPLE Concentration (abs units) Normalised Reduction in bacteria
(Lactobacillus plantarum) Lyocell fibre (Day 1) 0.070 .+-. 0.018 1
Aldehyde lyocell (10%) 0.255 .+-. 0.035 3.6 Lyocell fibre (Day 2)
0.067 .+-. 0.012 1 Aldehyde lyocell (10%) 0.157 .+-. 0.016 2.3
Aldehyde lyocell (30%) 0.165 .+-. 0.009 2.5 Aldehyde lyocell (50%)
0.105 .+-. 0.030 1.6 Reduction in bacteria (Staphylococcus aureus)
Lyocell fibre (Day 3) 0.022 .+-. 0.018 1 Aldehyde lyocell (10%)
0.196 .+-. 0.019 8.9 Aldehyde lyocell (30%) 0.164 .+-. 0.048 7.5
Reduction in bacteria (Escherichia coli) Lyocell fibre (Day 4)
0.241 .+-. 0.047 1 Aldehyde lyocell (10%) 0.355 .+-. 0.047 1.47
Aldehyde lyocell (30%) 0.371 .+-. 0.056 1.54
[0063] The modified samples all removed significantly more (1.5 up
to 8.9 times more) bacteria than the reference.
Example 4
Characterisation of Aldehyde-Modified Tork 606 Sheets by Periodate
Oxidation
[0064] Tork 606 is a non-woven material that is produced from 35 %
polyester (PET, 15 mm, 0.6 dtex), 15 % Lyocell (12 mm, 1.4 dtex)
and 50 % Vigor cellulose pulp. This material was modified with
aldehydes by periodate oxidation (oxidation degree 2% and 10%,
aldehyde content 240 .mu.eq/g and 540 .mu.eq/g, respectively). The
aldehydes are introduced on the cellulose fraction of the sheets.
Both oxidation and aldehyde titration were performed as described
in Example 3 for the lyocell fibres.
[0065] In the wiping test, a steel plate is covered with a mixture
of 1 egg yolk and 1 dl of 3% milk and a solution of bacteria
(Staphylococcus aureus). The plates are dried and then 1 mL of
water is placed on the upper edge of the plate. The test paper is
wrapped around a paper holder with a specific weight and is placed
over the line of water and pulled once vertically and once
horizontally across the soiled area without pressing on the holder.
The plate is than covered with agar and incubated for 2 days. The
colonies of bacteria are then counted. The number of colonies
remaining after wiping with a test paper was compared with the
number remaining after wiping with unmodified Tork 606. In the case
of periodate oxidation, the reference used was unmodified Tork 606
washed with water, since periodate oxidation is performed in
aqueous medium.
[0066] As can be seen in the table below, the 2% oxidised Tork 606
removed more bacteria than the reference. Periodate oxidised Tork
606 samples became stiffer and less absorbing, especially at higher
oxidation degrees (10%), which may explain the lower performance at
higher oxidation degree (10%).
6 Wiping result (number of remaining bacteria after wiping) (median
of 5 test samples/ SAMPLE median of 5 references) Tork 606 1 Ref:
Washed Tork 606 (Test day 1) 1.5 Periodate ox. Tork 606 2% (Test
day 1) 0.8 10% (Test day 1) 3.5 Ref: Washed Tork 606 (Test day 2)
16.8 Periodate ox. Tork 606 2% (Test day 2) 14.4 10% (Test day 2)
54.5
Example 5
Preparation and Characterisation of Aldehyde-Modifled Tork 606
Sheets by Ozonation
[0067] A Tork 606 sheet was placed in a round bottom flask on a
rotation evaporator equipment. Ozone gas generated with an ozone
generator from oxygen was passed through a 10% acetic acid solution
and was then passed in the flask with the Tork 606 sheet. The dose
was 6.4 g/hour. After reaction, excess ozone and acetic acid was
removed by evaporation in the fume hood. By ozonation, aldehydes
(and ketones) are introduced in the cellulose fraction of the
sheets as well as in the synthetic fibre (PET). The aldehyde
content was determined by titration with hydroxylamine as described
in example 3 and was between 100 and 150 ueq/g.
[0068] The bacteria removing properties were determined using the
wiping method as described in Example 4.
[0069] As can be seen in the results table below, 3 out of 5
ozonated Tork 606 removed significantly more bacteria than the
reference Tork 606 does. One removed an equal amount of bacteria
and one removed less bacteria.
7 Wiping result (median of 5 test samples/ SAMPLE median of 5
references) Tork 606 1 Ozonated Tork 606 (Test day 1) 0.1 (Test day
2) 8.5 (Test day 3) 0.2 (Test day 4) 0.5 (Test day 5) 1.1
* * * * *