Note: Descriptions are shown in the official language in which they were submitted.
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HARD SURFACE CLEANING ARTICLE COMPRISING AN ADHESIVE
FIELD OF THE INVENTION
The present invention relates to an article for cleaning hard surfaces
comprising an
adhesive. The adhesive is able to quickly trap and retain dust, lint, hairs,
sand, food
crumbs, grass and the like. In particular, said adhesive is able to retain
those particles and
hairs which are normally not captured by usual articles not comprising an
adhesive and
which need to be collected with a vacuum cleaner or a broom. This is achieved
by
carefully selecting the chemical composition and rheological characteristics
of the
adhesive.
BACKGROUND OF THE INVENTION
Hard surface cleaning articles comprising an adhesive to retain particles and
hairs are
known in the art. For example PCT patent application WO 01/62132 by The
Procter &
Gamble Company describes cleaning sheets comprising an additive that enhances
the
pick up and retention of particulate material from surfaces, while minimizing
the amow.lt
of residue left on the surface being cleaned. Adhesives are mentioned among
the additives
which can be used. The mentioned application also describes a cleaning
implement
comprising a mop head having a resilient bottom surface, a portion of which
preferably
has a substantially smooth curved profile or crown which engages a removable
cleaning
sheet. The application also describes how the adhesive can be applied to the
cleaning
sheet only in selected zones, in order to avoid excessive tackiness and
preserve the ability
of the cleaning sheet to smoothly glide across surfaces
Patent application WO 03/075735 by 3M Company, describes a wipe for capturing
ordinary dust or dirt and heavier particles such as sand that includes a
wiping member
having discrete valleys and peaks, and wherein an adhesive is provided in the
valleys and
not on the peaks. The adhesive can contact a surface sufficiently to pick up
sand and other
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heavy particles, but not to so great a degree that the coefficient of friction
between the
wipe and the surface is unduly high, which can make wiping difficult.
Similarly to the 3M application, US 6,550,092 from S.C. Johnson describes a
cleaning
sheet including a fabric layer with a plurality of cavities secured to a
flexible backing
layer so as to define an outer fabric surface with a plurality of cavities
therein. The
cavities can include a tacky bottom surface capable of enhancing the retention
of dust and
other particles. Cleaning implements and methods of cleaning surfaces using
the cleaning
sheet are also described.
The hard surface cleaning articles described in the prior art can be further
inlproved,
especially as concerns their efficiency in capturing and retaining particles
and hairs.
Based on the above state of the art it is an objective of the present
invention to provide
hard surface cleaning articles having a better efficiency in capturing and
retaining
particles and hairs. It is another objective of the present invention to
provide hard surface
cleaning articles which are more effective in picking up large particles such
as
breadcrumbs and the like.
All cited prior art applications describe hard surface cleaning articles
comprising generic
adhesives. We have surprisingly found that by selecting a specific range of
adhesive
materials having peculiar rheological properties, hard surface cleaning
articles can be
obtained having an improved efficiency of particles/hairs pickup. This
translates in a
much easier handling of the article, in a faster cleaning action and also in
more effective
cleaning, including the ability of collecting bigger particles.
SUMMARY OF THE INVENTION
In one embodiment the present invention relates to a hard surface cleaning
article
comprising an adhesive having:
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a. An elastic modulus G'25 measured at 25 C and 0.1 rad/s below 15000 Pa,
preferably below 10000 Pa, most preferably below 5000 Pa
and
b. An elastic modulus percent increase AG'25 measured between 0.1 and 100
rad/s of more than 100%, preferably more than 130%, more preferably more
than 150%.
In another einbodiment the present invention relates to a method of cleaning a
hard
surface which comprises contacting said surface with an article comprising an
adhesive as
described above.
A further embodiment of the present invention relates to the use of an article
comprising
an adhesive as described above, for cleaning a hard surface in order to remove
more
effectively big particles and hairs.
DETAILED DESCRIPTION OF THE INVENTION
The Adhesive
The characteristics which have been considered in this context are the elastic
modulus G'
describing the elastic behaviour of the material and the viscous modulus G"
which
describes the viscous behaviour of the adhesive material. G' and G" are
measured in
Pascal (Pa) and all values must specify the temperature ( C) and the frequency
(rad/s) at
which it has been measured since both G' and G" can change significantly with
these two
parameters.
The viscous behaviour of the adhesive can be interpreted to represent an
indication of the
ability of the adhesive to quickly attach and securely adhere. The elastic
behaviour can be
interpreted as an indication of the "hardness" of the adhesive. Its value is
also critical for
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good initial =attachment. Their combination is believed to be'an indicator of
the required
force upon removal. The ratio between viscous and elastic and modulus is
considered to
be an indication of which fraction of the reinoval energy will be dissipated
within the
adhesive and which fraction is available to trigger the actual removal.
In order to provide the desired properties of quickly adhere, embed and retain
dirt
particles the dynamic behaviour of the elastic modulus at different
frequencies,
representative of the conditions in which the adhesive respectively
adheres/embeds dirt
particles and retains them, is of key importance. The ratio between the
viscous modulus
and the elastic modulus is important as well in order to further optimize the
adhesive
selection.
All rheological properties in the discussion below are measured at 25 C since
the
adhesives in question are meant to be used in household cleaning articles and
therefore
the normal operating temperature is expected to be about 25 C in most cases.
An adhesive to be used in the present invention has an elastic modulus G'25 at
a
temperature of 25 C and a viscous modulus G"25 at a temperature of 25 C of
wherein
each of these values is measured at a specified frequency in rad/s. The
adhesive further
has a dynamic elastic behaviour expressed in terms of elastic modulus percent
increase
AG'25 which is defined in this case as the percent increase of G'25 from a
frequency of 0.1
rad/s to a frequency of 100 rad/s:
AG,25 = G'25 (100rad / s) - G'25 (0. lrad / s) X100
G'25 (0. lrad / s)
The adhesive also has a "crossover frequency" which is defined as the
frequency in rad/s
at which the value of G'25 is equal to G"25 .
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The adhesive to be used in the present invention satisfies the following
conditions.
= G'25 (0.1 rad/s) is below 15000 Pa
preferably below 10000 Pa,
most preferably below 5000 Pa.
and
= A G'25 is higher than 100 %
preferably higher than 130%
most preferably higher than 150%.
In a preferred embodiment, the adhesive to be used in the present invention
also has a
crossover frequency below 1000 rad/s, preferably below 700 rad/s most
preferably below
500 rad/s.
It is in general preferred that the adhesives of the present invention are in
the form of hot
melt adhesives.
Provided the above rheological conditions are satisfied the adhesives will
also preferably
satisfy conditions such as sufficient cohesiveness (to prevent residue of
adhesive on the
treated surfaces) which are critical for commercial use of such adhesives and
apparent to
those skilled in the art.
Often the criteria of hygienic appearance and pleasant feel upon contact are
important
such that adhesive composition which are transparent or white, are preferred.
It was surprisingly found that hard surface cleaning articles comprising an
adhesive as
described above have an improved efficacy in trapping large particles and
hairs.
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While not whishing to be bound by theory, it is believed that adhesives work
by two main
mechanisms, i.e. 1) energetic interactions between the surface of the adhesive
and the
surface of the particle / substrate to be adhered (adherend) and 2) mechanical
grafting or
embedding by the adhesive of the particle / substrate to be adhered
(adherend). When
both mechanisms are possible the effectiveness of the adhesion achieves a
maximum.
For activating both mechanisms and for providing optimal conditions of bonding
it is
important that the adhesive is sufficiently soft -i.e. that its absolute value
of G' is
sufficiently low- at the typical frequencies at which the bond formation
occurs, e.g.
between 0.01 and 1 rad/s.
Absolute low values of G' at this frequency range in fact allow both the
establishment of
a very intimate contact between the adhesive and the adherend -with activation
of
energetic interactions between the surfaces of the adhesive and the adherend -
and favors
also the mechanical grafting / embedding of the adherend . The lower is the
value of G'
the better is the activation of both these phenomena which fact leads to a
strong adhesion.
On the other side, adherends not only need to be bonded by the adhesive but
they need
also to be retained by it in a stable way, resisting as much as possible all
external stresses
that may lead to the break of the adhesive bond. Consequently, it is essential
that the
adhesive, while sufficiently soft in the conditions of bond formation -i.e. at
low
frequencies- is able to harden and resist possible breaks of the bond at
higher frequencies,
for examples 100 rad/s, which typically represent the conditions in which
debonding
occurs.
This ability of the adhesive of both forming excellent bonds and resisting
debonding by
hardening upon increase of frequency, is well expressed by the increase of its
G' between
a typical frequency of bonding -e.g. 0.1 rad/s- and a typical frequency of
debonding-e.g.
100 rad/s.
While, as said, the absolute values and the dynamic variations of G' are
important in
achieving a good bond formation and a sufficient resistance to debonding, also
the
viscous modulus G" and his dynamic variation with frequency have a certain
importance
in determining the overall adhesive behaviour in hard surface cleaning
applications. Good
adhesives have typically not only a high variation of G' across the considered
frequencies
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but also there is often an even higher variation of G" which can get close or
become
greater than the value of G'.
Without wishing to be bound by theory, this can be interpreted as meaning that
a high
fraction of the energy applied for the debonding is dissipated within the
adhesive (so it is
not effective in causing the debonding) while this fact causes macroscopically
the
recording of a very high level of adhesive force.
Therefore good adhesives according to the present invention, show a crossover
of the
moduli G' and G" as a function of applied frequency, i.e the frequency at
which G" is
equal to G' and goes over it, that occurs at frequencies which are below a
certain limit.
This phenomenon can be summarized by saying that in general the lower is the
crossover
frequency of an adhesive, the stronger is its adhesive strength.
Chemical composition of the adhesives
All compositions are expressed in wt% unless otherwise stated. In order to
provide
adhesive compositions which satisfy the requirements of the above rheological
and
physical characteristics of an adhesive the following formulation criteria can
be used in
addition. It should be noted that most compositions useful as adhesive have a
substantially gel-like structure and are preferably gels. Gels are materials
wherein a three
dimensional network caused by physical or chemical links formed between the
molecules.
Gels commonly comprise a relatively large amount (30-80 wt%) of low molecular
weight
components like plasticizers and tackifiers which are often liquid at room
temperature and
an amount of a macromolecular or polymeric component which is generally less
than
50% in weight of the gel.
The adhesive compositions to be used in the present invention preferably
comprise:
- From 0.5 % to 49 % %, preferably 5 % to 40 %, more preferably 7 % to 35 % by
weight of a polymer or a mixture of polymers. Polymers which can be used for
the
present invention include natural and/or synthetic polymers, such as
polyolefins and
their copolymers (like e.g. polyethylene-vinyl acetate or polyethylene-
acrylates
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copolymers); natural and syntlletic rubbers (like polyisoprene, polybutadiene,
butyl
rubber and polyisobutylene, SBR, NBR etc.); thermoplastic block copolymers;
polyurethanes; polyacrylates; polyesters; polyamides; polyvinyl-pyrrolidone
and its
copolymers; cellulose ethers and esters; natural gums and gelatins; alginates;
starch
and dextrin and their chemically modified derivatives. Particularly preferred
in this
application are Thermoplastic Block Elastomers and preferably Styrenic Block
Copolymers like Styrene/Butadiene Block Copolyrners, such as SBS and (SB),,;
Styrene/Isoprene Block Copolymers, such as SIS and (SI),,, Styrene/Isoprene-
Butadiene Block Copolymers such as SIBS; Styrene/Ethylene-Butylene Block
Copolymers such as SEBS, and Styrene/Ethylene-Propylene Block Copolymers such
as SEPS.
- from 51 % to 99.5 % by weight, preferably 65 % to 95%, more preferably 75 %
to 93
% of a plasticizer or mixture of plasticizers which are preferably liquid at
room
temperature. As non limiting examples such plasticizers may be mineral and
vegetable
oils and their chemically modified derivatives such as epoxidized and
polymerized
oils; liquid polybutenes; liquid taclcifiers such as liquid rosins and rosin
esters; esters
such as phtalates, citrates, phosphates; liquid polyesters; monocarboxilic
fatty acids (C8
- C22) and their derivatives; glycols and polyglycols. When hydrophilic
polymers are
used, said plasticizer can preferably be water, glycerol or glycerol esters.
- from 0 % to 48.5 % by weight of a tackifier or mixture of tackifiers having
a softening
point of 160 C or less, preferably of 125 C or less and more preferably of
100 C or
less. As non limiting examples such tackifiers may be rosins and rosin esters;
hydrocarbon resins; apliphatic resins; terpene and terpene-phenolic resins;
aromatic
and aromatically modified resins; synthetic C5 resins and C5 - C9 resins.
Preferably the adhesives to be used in the present invention are gels based on
a
hydrophobic polymer, otherwise called "oil gels".
Common additives known in the art as preservatives, antioxidants, anti UV,
pigments,
mineral fillers, rheology modifiers etc. can also be comprised in quantities
up to 10 % by
weight each.
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The Article
Articles according to the present invention are hard surface cleaning
articles. For the
purposes of the present invention hard surfaces are all common surfaces which
are
present inside or outside a house and which are not covered by fabrics, fibers
or
earth/grass and include floors, walls, doors, furniture, appliances and the
like. Hard
surfaces can be made with almost any material including resin, rubber,
plastic, gres,
marble, ceramics, porcelain, stone, metals (steel, aluminum), cement, bricks
etc. More
specifically the term hard surfaces, as defined in the present invention,
include linoleum
and resin surfaces and excludes carpet surfaces. In one embodiment the present
invention
relates to a hard surface cleaning article comprising an adhesive as described
above. The
article can be any known hard surface cleaning article, for example as those
described in
the prior art documents cited in the Background of Invention section of the
present patent
application.
The adhesive can be applied onto a portion of the article or be incorporated
as a
removable cartridge or sheet. In one embodiment the articles of the present
invention are
disposable sheets like wipes or pads which can be used directly by hand or
preferably
affixed onto the head of a mop such as, for example, those described in figure
1 and 2 of
patent application WO01/62132 so that once the sheet has been used it can be
disposed
and substituted with a new one. Alternatively the sheets can be attached to
any type of
implement which can aid wiping said sheet onto a surface including for example
a
cylindrical support which can be rolled onto a surface in order to clean it.
Sheets according to the present invention can be made according to all known
designs and
construction for cleaning sheets such as but not limiting to those mentioned
in the already
cited patent applications WO01/62132 by Procter & Gamble, WO 03/075735 by 3M
and
US 6550092 by S.C. Johnson. Accordingly sheets comprise as a substrate any
natural or
synthetic fibrous material in the form of a woven fabric or a knit fabric, a
non woven
fabric, a laminate of a fabric and a polymeric film and combinations thereof.
Methods of
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making such substrate are also well know in the art and are not described in
detail herein.
Preferably said substrate is a non woven fabric.
In general it is preferred that, upon use, the adhesive comprised in the
articles of the
present invention does not directly contact the hard surface, or at least does
not contact it
to a large extent, otherwise the article could stick to the hard surface and
prevent gliding.
It is in fact preferred that the adhesive is present in a recessed area of the
article so that
particles and hairs which need to be removed can get in contact with the
adhesive while
the article is quickly passed onto the surface to be cleaned and be trapped
into it. It will be
understood by the skilled man how important the rheological characteristics of
the
adhesive are in order to reach this result, in fact the adhesive may contact
the particle or
the hair for a fraction of second and only on a small portion of their
surface, so it is
crucial that the adhesive has the right "softness" features as described above
in order to
stick to the particle or hair and to trap it fast enough.
In the embodiment of the present invention wherein said article is a sheet,
said sheet can
have any configuration wherein the adhesive has a limited contact or no
contact at all
with the surface to be cleaned. In one embodiment the articles of the present
invention are
sheets having a three dimensional structure comprising valleys and peaks
wherein the
adhesive in the valleys only. In another embodiment the articles of the
present invention
are multi-layer sheets comprising a layer of adhesive sandwiched between 2
layers
wherein one of the layers is an open structure. The adhesive may be applied
uniformly on
the surface of one sheet layer, or it may be applied in discrete areas. The
adhesive may be
applied by any suitable method known in the art, such as for example spraying,
blowing,
slot coating. A preferred method is blowing using equipment such as the Spyro
Glue
Heads from Nordson or alternatively, ITW Dynafiber from Dynatech. The adhesive
can
be applied at an add-on level of 0.5 gsm or higher, preferably at an add-on
level of 2-20,
even more preferably 5 to 15 gsm. The layer having an open structure can be
for example
a fabric layer having holes. An example of such a fabric layer is an apertured
nonwoven
layer. Preferably, the apertures have an opening of 0.5 mm to 8 mm, or open
areas of 0.19
mmz to 50 mma. The apertures are preferably spaced apart at a distance of 2 to
25 mm. A
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more preferred apertured nonwoven layer is a nonwoven layer comprising
rounded,
conical protruberances. The protruberances may face the other layer of the
sheet, but are
preferably in the opposite direction such that they face the surface to be
cleaned. The
most preferred nonwoven layer is a nonwoven with ill-formed or aperture-lilce
structures.
The aperture-like structures exhibit fibers that span the ill-formed aperture.
These
spanning fibers can hold adhesive and are affective in increasing hair capture
when
located near the surface to be cleaned. Processes of making apertured
nonwovens, or
nonwovens with protruberances are well known in the art and need not be
further
described. When using nonwovens with conical protruberances, it is preferred
that
adhesive is applied inside, and at or near the top of the protruberance.
Another example of
an open structure layer is a polymeric net. Suitable polymeric nets are
described in detail
in U.S. Patent.No. 4,636,419. They can be derived from a polyolefin such as
polyethylene
or polypropylene, copolymers thereof, poly butylene terephtalate, polyethylene
terephtalate, Nylon 6, Nylon 66, and the like. In use, the polymeric net is
contacting the
surface to be cleaned and prevents the adhesive to directly contact that
surface. When
cleaning a surface, hair can penetrate the holes and be trapped and locked in
place by the
adhesive, while the open structured layer prevents direct contact of the
adhesive with the
surface.
In another embodiment the article of the present invention are sheets wherein
a layer of
adhesive is covered by a very light fibrous layer which is resilient enough to
avoid, wlien
in use, contact of the adliesive with the surface to be treated and wherein
the space
between the fibers of said fibrous layer is large enough to allow particles
and hairs to
reach the adhesive and be trapped into that. In another embodiment the
articles of the
present invention are sheets having non uniform thickness, comprising at least
two raised
areas and a recessed area, wherein the adhesive is applied onto the recessed
area so that
when the sheets is placed onto an hard surface only the raised portions will
contact said
surface.
In an alternative embodiment the article of the present invention is a brush
for removing
particles such as breadcrumbs, comprising means to pick up particles from a
hard surface
and means to collect them to an inner compartment of said article where an
adhesive as
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described above is applied (preferably in the form of a disposable sheet) so
that it can
capture and retain said particles. In this embodiment the adhesive is
preferably in a
removable cartridge or sheet which, when exhausted, can be disposed with the
trapped
particles.
The articles of the present invention in all embodiments can also optionally
comprise a
cleaning lotion. In the case of sheets said sheets can be impregnated with a
cleaning
lotion, e.g. a wax, a solvent or a water based solution. Cleaning lotions, if
present,
preferably comprise a surfactant. Noticeably, the adhesives used in the
present invention,
due to their rheological properties, are able to retain particles also in the
presence of
cleaning lotions which reduce the tackiness of the adhesive surface.
While mentioned embodiments are just some of the many possible articles
according to
the present development, it will be appreciated that other possible
embodiments may be
derived from the prior art simply by introducing an adhesive as described
herein in a prior
art article wherein a generic adhesive was used. Many changes and
modifications to the
einbodiments described so far may be made without departing from the present
invention,
for example by applying an article according to the present invention to any
known
cleaning implement such as a stick, a broom, a roll, a solid support having or
not having
an handle, or by making the article as a durable object rather than a
disposable one.
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EXAMPLE
Dry adhesive wipe
An adhesive wipe according to the present invention was made using a
commercially
available spundbond polypropylene nonwoven web having a basis weight of
20grams per
square meter, available from Avgol Corporation of Holon, Israel. The adhesive
was
applied into recessed areas of the nonwoven by an embossing and adhesive
printing
process as described in our patent US 6,881,471. With reference to Fig.3 of
the cited
patent, the substrate was embossed between male and female rolls 15 and 16.
The rolls
were engaged between 1 to 1.5 mm (0.04 to 0.06 inches). The enibossed
substrate,
maintaining contact and registration with the male roll 15 rotated toward the
glue transfer
nip. The adhesive transfer nip 17 was a second female role having a 0.13mm
(0.0005
inch) FEP release coating and an embossed pattern that is in register and had
0.4mm
(0.016 inch) engagement with the male pattern role.
The adhesive was extruded onto the surface of the first adhesive application
metering roll
via a slot die 22. The application temperature for both the adhesive and the
slot die was
set at 130 C. The adhesive passed through metering rolls 22 and was
transferred to the
land areas of the adhesive transfer nip 17. Interaction between last metering
roll 22 and
embossing roll 17 was controlled to ensure adhesive application to the lands
of the first
embossing roll 17, without pressing the adhesive into the recesses or pockets
between
lands. The adhesive was applied on the second female roll at a basis weight of
2 grams
per square meter. The combined adhesive/substrate was then pressed by a rubber
covered
niproll.
The applied adhesive is a hot melt supplied by National Starch under the trade
name
Softge1555-8819. The G' at 0.1 rad/s and 25 C of this adhesive material is
2700 Pa.
