Note: Descriptions are shown in the official language in which they were submitted.
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TEXT WITH AMENDMENT UNDER CHAPTER II
METHOD FOR MANUFACTURING A MULTI-LAYERED PULP PRODUCT
COMPRISING A FILLER BETWEEN LAYERS
TECHNICAL FIELD OF THE INVENTION
The present invention refers to a procedure for the
manufacture of a multi-layer pulp product, in particular a
product selected from between paper and cardboard and which
presents the essential characteristic of incorporating a
l0 filler between layers.
BACKGROUND OF THE INVENTION
Many products such as paper and cardboard are constituted
- by the superposition of layers of fibres which can be of
the same type or of different qualities. In multi-layer
pulp products the outer layers which grant that paper or
cardboard its final appearance are distinguished from the
inner layers, which can be constituted by virgin paste,
recycled paste or mixtures of the two. In general, the
inner layers have a dark colour which sometimes needs to be
masked with the outer layers, for which one or several
layers of white fibres (virgin or recycled) are usually
added, with a layer of pigment being able to be applied to
the surface afterwards.
In the manufacture of products such as paper or cardboard,
the fillers are of vital importance since by means of them
a saving can be achieved in the amount of virgin or
recycled fibre that is used. The object of adding fillers
during manufacture is also to improve or acquire certain
properties that are desired in the end product: improvement
3o in optical properties such as whiteness, opacity,
brightness and colour; improvement in properties relating
to permeability to fluids, such as penetration of water or
ink, penetration of oil and porosity or resistance to the
passage of air. The addition of fillers to the paper also
permits the speed of the machine to be increased, which
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improves its production.
Independently of whether the type of machine for the
manufacture of paper or cardboard is a Fourdrinier machine
- flat table - or a cylinder machine, or a combination of
the two, different ways of introducing fillers into the
paper are described in the art.
International application WO-9600816 describes a method and
a device for applying a film of a coating material on a
network or tissue of fibres in a paper or cardboard
l0 machine . The coating material is applied on the surface of
the mesh of the pulp product by means of a spraying system
at low pressure and high flow. The system is equipped with
a series of spray guns adjacent to the mesh of the pulp
product. Nevertheless, this procedure is solely intended
for the manufacture of mono-layer paper. The mono-layer
paper coating thus described has the drawback that it is
complicated to achieve a correct distribution of the filler
over the entire section of the paper since the penetration
of the filler within the fibre mesh will vary radically
depending on the point of application.
The application for European patent EP-0 373 276-A1
describes a procedure and device for the continual spraying
of adjuvants on a permeable fibre mesh arranged on a belt
which is displaced. The system permits spraying of the
adjuvants in different states of humidity of the sheet
undergoing formation by means of one or various spraying
ramps. Each of them is supported by a movable support frame
transversely arranged in relation to the direction of
displacement of the belt. This ramp is constituted by two
ducts provided with nozzles for the transport of the
adjuvants, with starch being the product that is sprayed
and which penetrates throughout the entire thickness of the
sheet.
In spite of the above examples, known techniques for
introducing fillers into the interior of the fibre mass
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present drawbacks such as the low transference of that
filler, with a major loss of raw materials taking place
which has repercussions on the manufacturing costs. Another
drawback consists of the reduction in the mechanical
properties of the paper, which become more important as the
content of filler increases.
It is therefore necessary to be able to have a procedure
with which the transference of filler to the paper manages
to be increased, which will also improve its optical
properties (whiteness, opacity, etc.) and which does not
lead to any major reduction in mechanical properties. All
these factors will result in an overall improvement of the
manufacturing process.
In the case of mufti-layer paper, the above objectives can
be achieved by means of the manufacturing procedure of the
present invention. This procedure is innovative since,
among the known techniques for the manufacture of multi
layer paper, no description has yet been made of the
application of a filler between layers of fibre (which can
2o be of different compositions and can contain different
additives), and which acquire the filler prior to being
joined together.
OBJECT Oh THE INVENTION
The present invention refers to a procedure for the
manufacture of a mufti-layer pulp product. Said procedure
essentially consists of applying a filler between at least
two layers of fibre material in motion prior to the final
joining of them together.
DESCRIPTION OLD THE INVENTION
The present invention refers to a procedure for the
manufacture of a mufti-layer pulp product, characterised in
that it consists of:
- the continuous exit of fibre material from one or more
entrance boxes of a pulp product manufacturing machine,
- the depositing of said fibre material on one or several
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sections of the pulp product manufacturing machine,
obtaining one or several moving fibre meshes and
forming different layers of the fibre material in one
or several layer formation sections,
- the draining of those layers during their trajectory on
the layer formation section,
- the introduction of filler, by certain application
means, between the layers of said fibre material which
is being displaced via a conveying means, and
- the joining together of those layers.
The 'position of the one or more application means with
respect to the layer formation section of fibre material
' can be variable. The fillers can be proportioned by the
application means on one or another layer.
The introduction of filler is done at a distance of between
1 and 70 cm above the moving fibre mesh and preferably
between 5 and 40 cm.
The fillers used in the procedure of the present invention
are applied by one or several means which are transversely
located on the moving fibre mesh, with those application
means being arranged in one or several series at different
distances from the entrance box for the pulp product
manufacturing machine.
The means of filler application can also be arranged with
an angle of inclination with respect to the plane of the
moving fibre mesh of between 0 and 90 degrees, this angle
preferably being 2S degrees.
The final configuration of the application system
essentially depends on the speed and configuration of the
3o pulp product manufacturing machine.
According to the procedure of the present invention, the
application means of the filler are located in a transverse
direction with respect to the direction of displacement of
the moving belt. The application of filler can be done by
various application means, being able to be introduced in a
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single application or in successive layers of filler.
The means of filler application preferably consist of
nozzles, the filler being applied by spraying of a
suspension of the filler between layers of pulp material
(the moving fibre mesh is displaced at a speed between 50
and 2000 metres a minute).
The use of nozzles permits the introduction of filler
according to a shape selected from between jets of conical
shape and plane jets with variable angles of opening,
to preferably 60 ° .
The spraying can be done by means of a system that includes
nozzles and a return, which provides effective control of
the flow or stream in the nozzles. The flow in the nozzles
can be adjusted by control means and the said return. The
IS control means are preferably selected from between a
pressure regulator, a flow regulator and a pump fitted with
a frequency shifter.
The filler is introduced with a transference efficiency of
greater than 70%, preferably between 90% and 100%.
2o The filler can penetrate into the interior of the moving
fibre mesh with a depth that is determined by the distance
of the application means of the filler with respect to the
entrance box. The filler is preferably sprayed at the end
of the formation of the sheet at a distance from the
25 entrance box that guarantees little penetration (in order
to achieve the best coating of the inner layers).
The manufacturing machine for the product is preferably a
paper or cardboard machine, and the mufti-layer pulp
product is paper or cardboard.
3o The procedure of the present invention can be carried out
in any kind of paper or cardboard machine, so said machine
can be a Fourdrinier type of machine, a cylindrical machine
or a machine which is a combination of both.
The filler is preferably of inorganic origin, though it can
35 include organic components.
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- Among fillers of inorganic origin in the procedure of
the present invention, use is preferably made of
calcium sulphate, calcium carbonate, titanium dioxide,
talc, kaolin, alumina trihydrate or a mixture of two or
more of these components.
- The carbonate can be selected from between a natural
calcium carbonate or a precipitated calcium carbonate.
- In an especially preferred embodiment of the procedure
of the present invention, the filler that is used is an
l0 anhydrous calcium sulphate of high whiteness.
The calcium sulphate is selected from:
natural anhydrous calcium sulphate,
- anhydrous calcium sulphate coming from chemical
synthesis, and
- anhydrous calcium sulphate obtained by dehydration of a
calcium sulphate selected from:
- natural calcium sulphate hemihydrate,
- natural calcium sulphate dihydrate,
- calcium sulphate dihydrate coming from chemical
synthesis, and
calcium sulphate hemihydrate coming from chemical
synthesis.
The calcium sulphate is preferably dispersed in water (by
means of vigorous stirring) in proportions of up to 60% by
weight in relation to the total mass of the suspension.
The granulometry of the filler is also an important factor
for the procedure of the invention. The fine granulometry,
coating power and high refractive index of calcium sulphate
improve the opacifying capacity of the white layer.
3o The calcium sulphate used in the invention has a mean
granulometry of between 0.5 and 50 um. The filler
preferably has a particle size lying between 0.5 and 10 um.
The filler can include a dispersant in a proportion between
0.01% and 1% of the weight of dry filler.
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The filler is applied as an aqueous suspension, the
quantities of water and filler being controlled preferably
by weighing. Also, said filler is applied by generally
controlling the stream by means of a flow regulator and/or
by means of a pressure controller.
The rheological properties of calcium sulphate enable a
wide range of dry extracts to be worked with, and the
optimum quantity of filler between layers can thus be
determined for each type of quality to be manufactured.
l0 In a preferred embodiment the filler is applied as an
aqueous suspension consisting of between 99% and 40% of
water. It preferably consists of between 90% and 70% of
water.
The quantity of filler deposited on the fibre mesh lies
between 0.5 g/m2 and 50 g/m2, and very preferably between 5
g/mz and 15 g/m2.
The filler can optionally include one or more additives.
Fox example, it can include various types of starches or
mixtures of them.
The fibrous material constituting the multi-layer pulp
product produced by the procedure of the present invention
can be constituted by a paste selected from among virgin
paste, recycled paste, paste that has been de-inked or not,
all kinds of paste whitened or not, and mixtures of the
above .
The present invention has as an additional object a paper
or cardboard product produced according to the described
procedure.
The advantages obtained with the procedure of the present
invention are multiple:
- A saving in filler is achieved owing to filler
retentions of higher than 70% being attained without
the use of outside chemical agents.
- Another additional advantage of the procedure of the
present invention is that it permits inner and outer
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layers of the end product to be of inferior quality,
thus considerably reducing the cost of the end product.
If the same quality is maintained for the inner and
outer layers, then the application of filler between
layers permits an end product to be obtained that has a
better overall quality.
- Another additional advantage of the procedure of the
present invention is that the white prelayer or
prelayers (if the end product is constituted by several
l0 outer white layers) can be replaced, with the desired
optical properties being maintained.
Another additional advantage of the procedure of the
present invention is that it also permits a reduction
in the grammage of the white layer, maintaining the
desired optical properties of the end product, thereby
considerably reducing the cost of the manufactured
product.
- Another additional advantage of the procedure of the
present invention is that by means of using calcium
2o sulphate an improvement in the efficiency and
homogeneity of the coating between layers is achieved.
The following figures and example show in a more detailed
manner certain aspects of the invention.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 show a series of positions of a device conceived
for the introduction of fillers according to the procedure
of the invention and suitable for different configurations
of machine. In that figure:
- 1 represents an application means of filler,
- (a) shows a section of a combination of
Fourdrinier machines and cylindrical machines,
- (b) shows a section of a combination of
cylindrical machines, and
- (c) shows a section of combination of Fourdrinier
machines.
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Figure 2 shows a system of introducing filler by spraying,
said system consisting of a series of nozzles permitting
the suspension of filler to be sprayed in jets with a
conical or plane shape. Represented in that figure is a jet
with a plane shape 2 or conical shape 3.
Figure 3 shows a possible configuration of the application
means of filler with respect to the moving fibre mesh. In
that figure:
- "h" represents the distance between the means of
to application and the surface of the fibre mesh
- 4 represents the sprayed filler
- 5 represents the pulp product and
- - 6 represents the support for the moving pulp product
(fabric)
Figure 4 shows a diagram of the preparation, storage and
spraying of filler in the form of suspension. In that
figure 4 can be seen a section of storage of the filler 7,
a section of dilution of the preparation 8, a section of
storage of the filler suspension 9, a sprinkling system 10
which includes a final batch 10a, and a section of the
device for the introduction of filler between the layers of
pulp product lob.
Figure 5 shows the section or sprinkling system 10 of
figure 4. It is a standard diagram of the introduction of
filler in the form of suspension. In figure 5 can be seen a
filler filter 11, the flow control point 12, the positions
of the flow meters 12a and 12b, and the section of the
filler spraying ramp 13 between the pulp product layers.
This system can be subject to specific: modifications
permitting both the elimination or addition of elements and
the modification by means of other more sophisticated
components.
DESCRIPTION OF AN EMBODIMENT OF THE INVENTION
Described below is the use of the present invention in the
manufacture of multi-layer paper, specifically white
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BlCIaSS.
Provided on a conveyor belt of a Fourdrinier type paper
machine being displaced at 142 m/s is a mesh of cellulose
fibres coming from recycled white paper. At a distance of
40 cm (h in figure 3) above the surface of the fibre mesh a
filler spraying system is provided, having 14 nozzles like
those shown in figure 2. The angle of inclination a - as
shown in figure 3 - of the nozzles with respect to the
moving fibre mesh is 25°.
to By means of an installation similar to that described in
figure 4 and under conditions of vigorous stirring, a 25%
aqueous suspension is prepared of anhydrous calcium
sulphate (coming from the dehydration of calcium sulphate
dihydrate) with an average particle size of 3 um. The
quantities of water and filler are controlled by weighing.
By means of the spraying system described in the above
figure, 17 g/m2 of anhydrous calcium sulphate are
proportioned on the surface of the moving paper (10% by
weight on the white layer production). The flow of filler
2o is controlled by means of an automatic flow regulator, the
spraying point being located at the end part of the
formation table and after the water line. At the end of the
formation table the joining of the white layer with the
grey support takes place.
In this way, a 90% transference of filler takes place, and
a very considerable increase in the whiteness of the outer
white layer of the paper can be observed.
The results obtained by the application means of anhydrous
calcium sulphate in the interlayer following the procedure
3o described above were compared with the results obtained
using kaolin as filler in the mass of the white layer. The
conclusions of the comparison are as follows:
- For an objective whiteness value of 77, the grammage of
the white layer was reduced from 81 to 65 g/m2, with the
consequent economic saving.
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- For the same value of grammage of the white layer (81
g/mz) and maintaining the same mechanical properties as
were achieved with kaolin, it was possible to increase
the percentage of ash from 18% to 23% by means of
spraying with calcium sulphate.
- The transference of filler went from 40% for kaolin to
90% for calcium sulphate. The spraying with calcium
sulphate avoided the use of the retention agents needed
in the case of kaolin.
l0 - The values of delaminating and of "Dennison" waxes
remained similar at all times 0.199 joules/m2 (95
ft.lb/in2) and 0.01892 joules/m2 (9 ft.lb/in2)
' respectively, for the two cases.
- As calcium sulphate is a filler with superior whiteness
and opacity characteristics to the kaolin used in the
mass, this permitted the use of recycled paper of
poorer quality (and therefore much more economical).
Using kaolin, recycled white paper with a minimum
whiteness of 75.5 had to be used, while with calcium
sulphate it was possible to reduce this whiteness to
72.5.
The whiteness of the final paper by means of spraying
with calcium sulphate between layers increased
potentially as a function of the percentage of filler
applied.
Having illustrated and described the principles of the
invention and its application to a particular case, it can
be appreciated that it is in no way limited to the example
presented here. Numerous modifications can be made to the
3o method and the apparatus in order to adapt it to diverse
cases and configurations without departing from the
principles of the invention described in the following
claims.
