Abrasive pad, which can substitute for a steel wool pad, and/or scouring pad and process for producing same

A pad which can be abrasive, scouring or both, is formed as a block of foam between two nonwovens. The foam is a polyurethane foam and the nonwovens are based on a mixture of polyamide and polyester fibers. The polyamide fibers have physical properties similar to those of the polyurethane foam. The nonwovens and the foam block are bonded together at their periphery by thermal-welding. The pad can be coated with abrasive fillers. It can also be used for scouring delicate surfaces when it contains little or no abrasive fillers.

FIELD OF THE INVENTION 
The present invention relates to the field of cleaning in general and more 
particularly to an abrasive pad, substitute for steel wool, and/or a 
scouring pad. The invention also relates to a process for obtaining such 
pad. 
BACKGROUND OF THE INVENTION 
Steel wool has been used for a long time now in pad form for scouring 
kitchen utensils such as cooking pots and pans. 
These steel wool pads, however, have the disadvantage of rusting, of 
disintegrating quickly, and of being difficult to clean. Moreover, they 
are unpleasant to the touch. 
SUMMARY OF THE INVENTION 
It is one object of the present invention to provide a pad which is 
abrasive on both faces and which constitutes a substitute for steel wool, 
without any of its disadvantages, and which, in particular, will last 
longer, while preserving its original aspect and properties. 
The invention also provides scouring or mixed pads, i.e. pads that are 
scouring on one face and abrasive on the other. 
The abrasive and/or scouring pad according to the invention is composed of 
a block of foam between two nonwovens. The term "non woven" is used in the 
art to refer to sheets or webs composed of materials which are bonded 
together and not woven. Its characteristics are as follows : 
the foam is a polyurethane foam; 
the nonwovens are based on a mixture of polyamide and polyester fibers, the 
polyamide having physical properties similar to those of said polyurethane 
foam; 
said nonwovens and foam are bonded together at their periphery by 
thermal-welding. 
The specific nature of the materials composing the pad according to the 
invention gives it advantageous properties as regards its cleaning and 
scouring action, with the added possibility for said pad of being produced 
by thermal-welding (or thermal-sealing), which is a very reliable method. 
Indeed, the thermal-welding produced with such material is strong, 
non-brittle and has no sharp edges, nor has it any tendency to break off.

DETAILED DESCRIPTION 
In the drawing is seen a pad composed of a block of foam 2 between two non 
woven webs 1,1' and bonded together at the periphery of the pad at 3, for 
example, by thermal welding. Hereafter, the webs 1,1' will be referred to 
as nonwovens. 
The foam 2 used in the pad according to the invention is a polyurethane 
foam whose composition is based on polyols and isocyanates. Said foam is 
stabilized inside the pad body since bonded to the two nonwovens 1,1' over 
its periphery. 
Suitable nonwovens according to the invention are webs containing a mixture 
of polyamide/polyester fibers. Polyamide has physical properties --bonding 
temperature, melting point-- similar to those of the polyurethane foam 
used. 
The fibers composing the nonwovens have been selected, according to the 
invention, for their mechanical properties --resistance to abrasion, 
mechanical strength-- and for their physical characteristics 
--heat-fisibility--. Said fibers are polyamide and polyester fibers. 
Polyamide fibers exhibit a good resistance to abrasion and a good 
mechanical resistance. Polyester fibers also exhibit a good resistance to 
abrasion with a high mechanical resistance. The fibers selected according 
to the invention preferably have a unit weight less than 50 dtex. The term 
"weight" of a fiber is used to mean "mass per unit length" and is measured 
in decitex (grams per 10,000 meters). Such fibers have a good covering 
rate and produce supple nonwovens which are not unpleasant to the touch. 
For practical reasons, the usable polyamide fibers generally have a unit 
weight ranging between 0.7 and 44 dtex, and the polyester fibers a unit 
weight ranging between 4.4 and 40 dtex. 
The physical properties of these fibers are fundamental. They enable the 
formation by thermal-welding of a supple bond on the periphery of the pad. 
Polyamide, which has the lowest transformation temperatures --bonding 
temperature, melting point-- is used as a bonding agent. Said 
transformation temperatures are close to those of the polyurethane foam. 
Therefore, a heating to the adequate temperature, during the welding 
operation causes the formation of an intimate "liquid" mixture of 
polyamide and polyurethane, within which mixture the polyester fibers 
begin to soften. Indeed, the polyester fibers are more heat-resistant than 
the polyamide fibers. It is then possible to obtain a reliable bond, which 
has a certain suppleness and also enables the stabilization of the foam 
inside the pad. 
According to the invention, the materials are judiciously selected : 
polyamide. polyester polyurethane foam. The combination of these 
materials, by a simple technique, gives abrasive and/or scouring pads of 
high performance. 
Advantageously, the nonwovens are based on a mixture containing 50 to 90% 
by weight of polyamide fibers and 50 to 10% by weight of polyester fibers. 
The quantities of polyamide and polyester used can indeed be optimized, as 
a function of the target results, in particular where the bonding is 
concerned. 
On this point, it has been found that polyamide acts as a bonding agent and 
polyester as a supplying agent. 
Preferably, the nonwovens are based on a mixture containing about 80% by 
weight of polyamide fibers and about 20% by weight of polyester fibers. 
Regarding the fibers used, the Applicant has also shown the advantage that 
there is in using, in the proportions by weight indicated above, polyester 
fibers of low unit weight and/or mixtures of polyester fibers, and more 
particularly polyamide fibers, of different unit weights. 
When using polyester fibers of low unit weight, a greater quantity of 
fibers is used giving then a very special homogeneousness and a remarkable 
suppleness of the material throughout its surface and also in the welding. 
For example, polyester fibers of unit weight ranging between 4.4 and 17 
dtex, ends included, are advantageously used. 
Similarly, by mixing polyamide fibers of at least two different weights, it 
is possible --the bonding factor at joint level being identical-- to 
improve the surface condition of the pad. 
Advantageously, fibers in polyamide 6 are used in the nonwovens of the pads 
according to the invention. However, other polyamide fibers may also be 
used. It is necessary, as indicated hereinabove, that the polyamide used 
has similar physical properties to those of the selected polyurethane 
foam. 
It is specified, by way of indication, that the nonwovens contained in the 
pads according to the invention, can advantageously be based on a mixture 
of : 
20% by weight of fibers of polyamide 6 of 44 dtex, 
60% by weight of fibers in polyamide 6 of 22 dtex, 
20% by weight of polyester fibers of 17 dtex. 
The nonwovens constituting the faces of the pads according to the 
invention, based on the above-referred mixtures of fibers, are pre-bonded 
mechanically before being chemically-bonded, preferably with a synthetic 
latex such as, for example, a thermal-setting latex. 
Said chemical binder is designed to give to the mixture of fibers a fairly 
high internal cohesion without however causing obstruction in the welding 
plane, during the thermal-welding operation. The quantity used, therefore, 
should be controlled. The weight of binder deposited with respect of the 
weight of fibers should be between 0.2 and 0.6. Said weight generally 
varies between 10 and 60 g/m.sub.2 (in dry weight). 
A bonded web of fibers is thus obtained after heating. 
Said web can be used as is, to constitute the faces of a scouring pad 
according to the invention. It is however, generally preferred to subject 
it to a further treatment, i.e. to a spraying of a formulation, possibly 
containing abrasive fillers. Such formulation is normally based on a 
synthetic latex : phenolic resin or acrylic latex. 
This spraying, which is quite controlled, can only be applied to one face 
of the nonwoven, i.e. the face intended to constitute the outer surface of 
the pad. Also, assuming that the formulation contains abrasive fillers, it 
is important that it should not penetrate deeply into the nonwoven. Both 
these conditions should be met in order to obtain a reliable and regular 
welding at the periphery of the pad. 
Whether or not abrasives are used, in great or small quantities, and 
composed of more or less hard materials, depends obviously on the 
properties required for the pad, and more precisely for each face of the 
pad according to the invention. 
The pads according to the invention can, indeed, have either two abrasive 
faces, or only one abrasive face or no abrasive face. It is merely a 
question of using nonwovens having on one of their faces the required 
surface condition. 
The pads according to the invention, with abrasive fillers, are an 
advantageous substitute for steel wool. 
The pads according to the invention, with little or no abrasive fillers, 
are advantageously used for scouring delicate surfaces. 
Examples of suitable abrasive fillers are: silicon carbide, alumina, 
silica, talc or mixtures thereof. 
Such abrasive fillers are deposited on the bonded web in the proportion of 
about 50 to about 200 g/m.sub.2 (dry weight) of the formulation containing 
them. 
It will be recalled that even without such fillers, the nonwovens based on 
polyamide and polyester fibers, bonded and optionally subjected to a 
spraying treatment, advantageously constitute either the faces or at least 
one of the faces of the pad according to the invention. 
According to a variant embodiment of the invention, the pad also contains 
soap. 
Advantageously, said soap contained in the pad, is distributed in the 
polyurethane foam, in solid form. The solid particles can be of variable 
granulometry. The pad according to the invention can also be coated on at 
least one of its outer faces, with a "film" of soap. 
The present invention also relates to the process for producing pads such 
as described hereinabove. 
Said process consists : 
in producing the nonwoven/foam/nonwoven assembly, in such a way that the 
abrasive and/or scouring faces of said nonwovens are facing outwardly; 
in placing the resulting assembly between the upper and lower molds of a 
thermoshaping tool; 
in thermal-welding the resulting sandwich form at a temperature close to 
the melting temperatures of the polyurethane foam and of the polyamide 
fibers; 
and finally, in individualizing the resulting pads, by cutting. 
The nonwoven are obtained, as described hereinabove, from a web of fibers, 
pre-bonded mechanically and chemically-bonded preferably by a synthetic 
latex, and optionally sprayed over with a phenolic resin. Said resin may 
optionally contain abrasive fillers. 
The polyurethane foam is placed between said nonwovens and the resulting 
assembly is placed between the upper and lower molds of a thermoshaping 
tool. Said thermoshaping tool is mounted on a press. 
The shape of the molds will define the shape of the resulting pads. These 
can, for example, be in the form of small cushions, or cylinders, etc. 
The nonwoven/foam/nonwoven sandwich is thermal-welded and the resulting 
pads are individualized by cutting. 
The thermal-welding operation is carried out at a temperature close to the 
melting point of the polyurethane foam and of the polyamide fibers. 
This creates at the periphery of the pad a zone of intimate mixture of said 
materials, within which the polyester fibers begin to soften. This 
compressed zone, when cooled, constitutes the bond between the two faces 
of the pad. The heating in the thermoshaping tool is obtained by any 
suitable means, for example by electric elements, heat-carrying fluids, or 
by micro-waves or high frequency techniques, etc. 
The accurate operational conditions of the thermoshaping are obviously 
dependent on the exact nature of the materials involved and on their 
thickness. Their optimization is within the scope of any one skilled in 
the art. 
DETAILED DESCRIPTION OF THE INVENTION 
The following example is given to illustrate the invention in more detail. 
An abrasive pad according to the invention is produced from a web of 
fibers, comprising : 
20% by weight of fibers of polyamide 6 of 44dtex, 
60% by weight of fibers in polyamide 6 of 22 dtex, 
20% by weight of polyester fibers of 17 dtex. 
Said web weighs 90 g/m.sup.2. It is impregnated in a bath with a binder 
-acrylic latex- containing the agents necessary for the use to be made of 
it. 
The dry weight of latex deposited is about 40 g/m.sup.2 (the ratio of the 
weight of latex deposited to the weight of fibers is around 0.50). 
The impregnated web is dried in two ovens successively, the temperature 
inside these ovens reaching from 50.degree. to 100.degree. C. 
The web is then subjected on one of its faces to a spraying operation, with 
a solution of phenolic resin containing a mixture of silica and alumina. 
In this solution, the filler/binder ratio is equal to 3. The quantity of 
dry product sprayed on the web is about 150 g/m.sup.2. After drying, said 
web can be cut to the required dimensions. The web then weighs about 280 
g/m.sup.2, and its thickness is about 6.6 mm. 
The process used for producing a pad according to the invention consists in 
making a sandwich by inserting a polyurethane foam block between two 
layers of the aforesaid type. The thickness of the foam block is 8 mm. The 
sandwich is thermal-welded in the molds of a thermoshaping tool mounted on 
a press. The essential parameters of this thermal-welding are as follows: 
temperature=about 220.degree. C. 
Pressure=15.10.sup.5 at 2.multidot.10.sup.6 Pa (15 to 20 bars) 
Time=1 min. 
The thermal-welding temperature corresponds to the start of melting zones 
of the polyamide 6 and of the polyurethane foam, and to the start of the 
polyester bonding and softening zone. 
The polyester fibers, having reached the softening limit, are bonded under 
the action of the pressure on their periphery by the 
polyamide-polyurethane "solution". The resulting bond being then perfectly 
homogeneous. 
The pads are then individualized. 
They are characterized by a remarkable efficiency and lasting power. They 
last for example four times longer than the conventional steel wool pad. 
Concerning their abrasive power, this can be measured by the Taber test. 
The Taber test is a test for assessing the abrasive power of the nonwovens; 
such assessment is performed by measuring the loss of weight of aluminum 
wheels, applied to the nonwoven with a certain pressure (1.5 kg), the 
nonwoven being imparted with a rotation movement. 
The faces of the pad have an abrasive power of 315 mg/1000 turns (initial 
abrasive power at 50 turns), of 215 mg/1000 turns (abrasive power at 200 
turns).