Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF PREPARING DRY-LAID FIBROUS PRODUCTS
This invention relates to a method of preparing dry-
laid fibrous products comprising the steps of passing a
gaseous medium containing a suspended fibrous material
through a gas permeable forming surface so as to form a
fibrous layer thereon, and incorporating a binder in said
fibrous layer. A prior ar-t method of this is disclosed in
British patent specification No. 1.518.284.
In a prior art method of the above mentioned type the
binder is incorporated in the fibrous layer by spraying the
fibrous layer with a binder or a binder solution, e.g. an
aqueous solution of a binder. Subsequently, the solvent, if
any, is removed and the binder is caused to set or cure.
: By spraying the binder onto the fibrous layer it is
difficult to obtain a predetermined distribution of binder
within the fibrous layer. Thus, it may be desirable to
provide a relatively high concentration of binder in the
middle of the fibrous layer and relatively low binder
concentrations at the surfaces thereof. In other cases .it
may be desirable to provide a relatively high concentration
of binder at one surface and a relatively low concen-tration
of binder in the remaining portions of -the fibrous layer.
The main object of the invention is to obtain pre-
determined binder concentrations in any portions of the
fibrous layer.
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Another object is to obtain a lmiform distribution of binder within
the fibrous layer so as to reduce or eliminate the tendency of delamination.
A further object is to allow the introduction of substantial amounts
of filler in a fibrous product prepared by a method of the above mentioned type
and to retain said filler in the final product.
The present invention provides a method of preparing a dry-laid cellu-
losic fibrous web, wherein a gaseous medium containing a suspended cellulosic
fibrous material is supplied to a distributor means, passed through rotating
stirring impellers, passed through a perforated distributor means bottom wall,
passed through a foraminous forming surface so as to form a fibrous layer
thereon and finally into a suction box located below said foraminous forming
surface and said perforated distributor means bottom wall, and wherein a binder
in powder form is supplied to the gaseous medium containing a suspended cellu-
losic fibrous material before said gaseous medium is supplied to said distribu-
tor means.
The method of the invention is particularly suitable for use in the
manufacture of fibrous products composed of two or more fibrous layers which
are formed separately by separate fibre distributors. Thus, by varying the
amount and/or, optionally the type of binder used, products can be obtained by
such a multideposition technique wherein the binder concentration varies within
a given cross section of the product. However, the method of the invention can
also be used in the production of products, wherein the binder concentration
varies in the machine and/or cross machine direction of the product.
By supplying the binder to the fibrous material before or cluring the
folmation of the fibrous layer, the binder become uniformly distributed in said
layer and, consequently~ the tendency of delamination withirl such layer is
eliminated or reduced.
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In a pre:Eerred embodiment of the method of the invention the binder is
in the orm of a powder and it is introduced into a defibrator used for the
defibration of the fibrous starting material together with said starting mater-
ial. The powdered binder may also be introduced into the fibre distributor
together with or independently of
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the defibrated fibrous material.
A fibre distributor which is particularly suitable for
use in the method of the invention is described in British
patent specifications ~os. 1.207.556 and 1.518.28~.
The powdered binder may also be supplied to the fibrous
material by introducing said binder into the zone between
the fibre distributor and the forming surface. When intro-
ducing the binder in this manner, the binder concentration
may be varied from one zone to another in the machine and/or
cross machine direction of the product. Thus, a desired
distribution of binder can be obtained by introducing the
powdered binder into separate streams of air, each providing
a zone of a relatively high binder concentration in the
fibrous layer formed during -the deposition of the fibres on
the forming surface.
The introduction of the binder in this manner is par-
ticularly suitable when using binders having low melting
points or low softening points, because such binders or-
dinarily cannot be introduced into t~1e defibrator or the
fibre distr:ibutor in which substantially frictional heat is
generated.
The problems caused by heat generation may also be
solved by using two defibrators arranged in series and by
introducing -the binder into the second defibrator and
operating said defibrator in such a manner that only a
reduced defibration and cor.sequently heat generation take
place therein.
The binder may also be supplied to the fibrous product
by treating the starting material, e.g. a fibrous pulp, with
a binder solution, slurry, suspension, or a binder foam, and
by subsequently drying the pulp thus trea-ted to remove
volatile subs-tances, if any, before -the pulp is defibrated.
Thus, the pulp may be hea-ted by using infrared light.
In some cases, a separate hea-t treatment is superfluous
because the heat generated i~ the defibrator may be suffi-
cient to increase the temperature to such an extent that
most volatile substances, if any, are removed by evaporation.
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The ~inder may be any substance or mixture of sub-
stances capable of binding the fibres together or to a
reinforcing net, if any.
Thus, thermoplastic as well as thermocuring organic
binders of the polymer type are suitable. Examples of such
binders are polyolefines, melamin urea and phenolic resins,
and lattices. Another type of organic binders are starch
binders and binders based on modified starch, i.e. partial-
ly hydrolyzed and/or chemically treated starch. By subjec-
-ting starch to such treatments, it is made soluble and in
the converted form it is suitable for use in a binder so-
lution.
Also inorganic binders, such as water glass, are
suitable for use in the method of the invention.
Various waste materials, e.g. powdered polyethylene,
may be used as binders. Such was-te materials are availahle
in large amounts in the industry and as a waste product
from households.
Cellulosic fibres are particularly suitable for use
in the method of the invention. The cellulosic fibres used
may be virgin fibres, i.e. fibres prepares from fresh cel-
lulosic pulp, or waste fibres, i.e. fibres prepared from
cellulose-containing waste ma-terials, such as paper. Also
partially defibrated fibrous materials can be used. Such
materials impart to the fibrous product a high flexibility
without significantly reducing the hydroscopicity of the
product. Therefore, such materials are useful in the pro-
duction of building materials for indoor as well as outdoor
use and pac~aging materials. Apart Erom natural vegetable
fibres, such as cellulosic fibres, synthetic organic fibres
having a relatively high melting or softening point may be
used in the me-thod of the invention. The synthetic organic
fibres used should prefera~ly ilave a melting or softening
point which is higher than that of the binder when using
termoplastic binders.
Inorganic fibres, such as mineral fibres, may be used
in admixture with organic fibres. Examples of such
mineral fibres are rockwool fibres, glass fibres, flbres
of crystallizable glass, fibres of devitrified glass, and
S slag wool fibres.
The costs of producing the product of the invention
may be reduced by introducing therein a mineral powder
in an amount of up to about 70 per cent by weight based
on the total weight of the fibrous product. For instance
devitrified glass powder having particle sizes of up to
500 ~m may be used as an additive.
Examples of other mineral additives are kaolin, dolo-
mite, glass, chalk etc.
The addition of a mineral powder to the mixture of
fibres and binder is particularly useful if it is desired
to produce products having a long life time.In such
cases, the product may consist of about 33 per cent by
weight of fibres, preferably cellulosic fibres, about 33
per cent by weight of a thermoplastic or thermocuring
binder having a particle size of below 100 ~Im and prefer-
ably 10-20 ~m, and about 33% of mineral powder having
a particle size of below 100 ~Im and preferably below 50 ~m.
However, also relatively smaller amounts of binder, e.g.
about 15 per cent by weight, may be used.
When used in the method of the invention, the mineral
powder is preferably introduced into the fibre distributor
together with the stream of air containing suspended fib-
; res. ~lowever, it may also be introduced into the defibra-
tor together with the pulp. Furthermore, the mineral pow-
der may be in-troduced directly in the zone between the
fibre dis-tribu-tor and -the forming surface so as to mix
with the fibre suspension passing from the fibre distri-
butor towards the forming surface.
The binder and the mineral powder are preferably in-
timately mixed so as to obtaln a binder CGating on themineral particles. When the mineral particles are coa-ted
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with the binder, the subsequent heat treatment will cause
the particles to form a solid skeleton. The particle size
of the mineral powder is preferably between 50 and 100 ~m.
When the mixing process is essentially completed/ a
small amount of solvent may be added in order to improve
the coating of the mineral particles.
It may also be desirable to add other auxiliary
agents, e.g. water repelling agents, to reduce -the water
absorption of the fibrous product when said product is to
be used as a packaging material or a building material.
Such auxiliary agents are well known, and examples
thereof are silicones, wa-ter repelling oils, waxes, as-
phalt, etc. By incorporating into the fibrous layer as-
phalt in an amount of 1-2% by weight, a product is obtain-
ed which is suitable for use as a roof covering element.
The addition of water repelling agents may be effectedafter the formation of the fibrous layer and as part of
the further treatment of the product formed. Ordinarily,
it is preferred to add such agents during the last steps
of the method of preparing such a product.
The water absorption of a produc-t prepared by the
method of the invention can be reduced in a manner which
is well known per se by subjecting said product to a
finishing treatment so as to close the pores of the mate-
rial. In this manner a mechanical barrier agains-t water
absorption is provided.
However, a porous structure is not necessarily a dis-
advantageous property of a product for use as a building
material. Thus, it is well known that in order to provide
a pleasant indoor climate, building materials should pre-
ferably present some degree of porosity and should be
permeable for air and/or moisture.
Such a porous product may be prepared by using a
mineral powder, e.g. powder of devi-trified glass con-tain-
ing no very fine particles. Such a product may consist ofparticles which preferably have a particle size of 100 ~Im
and above.
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When preparing a flbrous product from cellulose
pulp, the s-tarting material ordinarily contains about 10%
of moisture.
During the deEibration and the fibre distribution,
frictional heat is generated, and the moisture content of
the fibrous ma-terial is reduced to 2-3% by weight.
Therefore, it may be preferable to add moisture
during the defibration or during the formation of the
fibrous layer. The addition of mois-ture may be effected
by adjusting -the moisture content in the room wherein the
defibration and/or fibre distribution takes place at a
relatively high value, e.g. at a relative humidity of 55-
65%.
When using relatively high concentrations of binder,
it is particularly easy to add moisture. Thus, in such
cases the moisture con-tent of the fibrous material may be
increased to 30%. If the method of the inventian is to be
carried ou-t at such a high moisture content, -the adhesion
of the powdered binder and/or filler to the surfaces of
-the fibres is increased, and consecluently an increased
amount of binder and/or filler may be applied to the sur-
faces of the individual fibres. By coating the fibres
with large amounts of binder in the manner described
above, a product containing up to about 75% of binder and
containing fibres and optionally filler uniformly distri-
buted therein can be obtained. When hea-ting such a product
-to an elevated temperature, a strongly coherent product
is obtained.
The method of the invention permits the produc-tion
of fibrous products in whicn ratio oE fibres to binder
varies within wide ranges.
Thus, by using two or more fibre distributors to
form a Eibrous layer composed of two or more indiv:idual
layers, fibrous products can be obtained having a binder
concentra-tion varying within-a cross section throucJh the
product. Thus, by introducing a relatively large amount
of binder in one of the above mentioned layers, a product
is formed which at one surface con-tains a relative high
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concentration of binder, whereas the binder concentration
at the other surface is relatively low. Consequently, the
said other surface is more porous than the first surface.
It is also possible by using three or more fibre di-
stributors to prepare a sheet ma-terial having surface
layers of a relatively loose s-truc-ture and a dense core
layer.
Such a product can be obtained either by introducing
a relatively large amount of binder into the fibre distri-
butor used for the formation of the intermediate layer ofthe product or by rolling or compressing the fibrous
layer formed by said fibre distributor at a temperature
above the melting or softenlng point of the binder. During
said compression the binder is caused -to flow and forms a
dense layer of fibres.
The method of the invention is particularly suitable
for the production of shee-t materials and more specifical-
ly a fibrous layer formed on an essentially flat forming
surface. It should be mentioned, however, that a forming
surface, such as a wire having a non-planar surface, e.g.
comprising depressions and projections can also be used.
A similar pattern may be provided in the surface of a
fibrous product by passing the fibrous product through a
set of embossing rollers.
As will appear from the following description, the
method of the invention is particular]y useful for the
production of containers. The term "container" is to be
understood as any kind of articles which are capable of
containing solid materials or liquids. Such containers
can be produced by using a forming surface having pro-
jections or dispersions of a shape corresponding to -that
of the con-tainer to be produced.
The fibrous products prepared by the method of the
invention may be composed of fibres which are fixed rela-
tive to one another in a rela-tively loose structure by
the binder.
Such products may be converted by compression or
embossing into a wide range of products having properties
which vary from one par-t oE a cross section to another or
vary from one zone to another in the machine or cross
machine direction of the product.
Products in which the properties vary from one part
of the cross section to another are preferably produced
by using differen-t binder concen-trations when forming the
individual layers forming said fibrous product or by
using different compression or embossing condi-tions.
When using the same compression or embossing condi-
tions, the highest density of the compressed or embossed
product is obtained in such zones wherein the binder
concentration is highest.
On the other hand, by using the same binder concen-
tration, the highest density is obtained in zones wherein
the product has been subjected to the most severe compres-
sion or embossing, i.e. the most severe pressure and
-temperature conditions. As a result of the relatively
loose structure of the fibrous product defined above, even
a flat product can be converted into a hollow article when
suitably compressed or embossed.
A fibrous material of the above men-tioned type and
consisting of cellulosic fibres and a polyethylene binder
may be subjected to compression at a temperature of about
110C. The material thus obtained can be used as a star-t-
ing material for a number of products, e.g. diapers, sani-
tary napkins and other products for the care of the human
body.
In order to prevent liquids, such as blood, from
penetrating such a ma-terial, anticoagulating composi-tions
may be introduced into said material. It is also possible
to apply to one of the surfaces of such a layer a poly-
ethylene menbrane or another mois-ture barrier.
The polyethylene membrane may be provided on the sur-
face of such a product by in-troducing large amounts of
binder into the fibrous layer which is to form the surface
layer of the fibrous product.
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When using such a fi.brous product for the care of
the body, the fibrous product is arranged so that the
membrane does not contact the skin.
In order to prevent -the cellulosic fibres from being
disengaged from the fibrous product during the use there-
of, the surface of the product which is to contact the
human body is preferably coated with a layer of non-woven
textile material, e.g. a layer which is commercially
available under the trade name "Cerex". Thi.s commercially
available product is a spun-bonded material.
A special advantage obtained by using a material of
-the above mentioned -type for the manufacture of diapers
and other products for the care of the human body, e.g.
sanitary napkins, is that the fibres are fixed relative
to one another in an open structure having a large volume
which allows considerable amounts of liquid to be absorb-
ed, not only within the fibres, but also in the inter-
stices between the fibres.
When fibres are fixed relative to one another in an
open structure, the product does not fluff even when the
binder concentration is small. Therefore, such products
do not have to be packed or rol.led into an envelope, e.g.
a separately produced non-woven material, as is the case
with pri.or art products of a similar kind.
However, it is ordinarily preferable to apply to one
surface sheet material of the invention, viz. the surface
which is to contact the skin, a Cerex layer.
However, even without such a protecting layer, a
fibrous product according to the inventi.on may be in
direct contact with the skin without causing irritation of
the skin.
By using the fibrous product according to the inven-
tion, a serious drawback of the prior art diapers and
sanitary nap]cins may be eliminated. Due to the manner in
which such prior art products are prepared i-t is diffi-
cul-t to prepare products having an anatomic correct shape.
Since the fibrous products of the invention are capable
of being converted in-to products of different shapes, they
are suitable for use in -the produc-tion of diapers and sa-
ni-tary nap]cins having a shape which is adjusted to the
portion of the human body with which they are to be in
contact.
In a product according -to the inven-tion the fibres can
be fixed relative to one another throughout the product.
Therefore, when used for -the care of the human body -thev
remain in the desired position during such use, and thev
maintain their softness. Therefore, such sanitary napkins
and diapers do not require the use of adhesive tapes or
other fastening means.
By varying binder contents in the machine or cross
machine directions of fibrous produc-ts of the invention,
sanitary napkins and diapers can be prepared in wh:ich the
binder concentrati.on is high in the edge ~.ones.
A fibrous product containing a latex binder in a
relatively high concentration at one surface of the pro-
duct is particularly suitable :Eor the production of car-
. 20 pets and carpet underlays.
Fibrous products having a shape si.milar to that o:E
quilted products can be prepared by heating fibrous pro-
ducts of the invention to an eleva-ted temperature within
narrow zones forming a linear pattern so as to bond the
opposite surfaces of the product together within said
zones.
A product of this type affords an excellent heat in-
sula-tion and is a soft and pleasan-t product having ex-
cellent strength properties.
Since such produc-ts can be prepared in a relatively
s.imple manner, they are also sui-table as d.isposable pro-
ducts, e.g. for camping purposes, military purposes, for
use in hospitals and :Eor nursing purposes.
If it is desired to make such products more stable,
a layer of a spun-bonded material, such as the above men-
tioned "Cerex" produc-t, may be incorporated therein.
Fibrous products prepared by the above mentioned
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12
me-thod can be converted in-to valuable semi-manufactured
produc-ts by subjecting the flbrous layer formed on the
forming surface to a compression to increase the densi-ty
o:E the product.
Such compression is preferably effected at tempera-
tures close to the softening temperature of the binders
used.
A semi-manufactured product of the above mentioned
type is sui.table for the manufacture of compression mould-
ed packing materials, cups, trays, containers etc.
The fibrous product should preferably be only slight-
ly compressed during the i.nitial compression, because a
slightly compressed fibrous product is more suitable for
a subsequent strong deformation than a more dense fibrous
product. It is preferable to effect the initial compres-
sion of the fibrous material and the final shaping there-
of immeaiately following the -formation of the fibrous
layer on the forming su.rface, e.g. by using heated rol-
lers and by reducing the thickness from about 2 cm to
2-3 mm or belbw.
In the production of ordinary plates and soup pla-tes,
the fibrous product should preferably be reduced to
0.6-0.7 mm dependent on the binder concentra-tion and the
conditions under which the plates are to be used.
The production rate may be increased by preheating
the material to a temperature at which the binder is soft.
The tools for compressing semi-manufactured fibrous
products are preferably heated to a temperature of 150-
200C, and the pressure exerted is preferably between 1
and 10 kg per cm depending on the desired strength of the
final procluct. When using fibrous products which have
been heated to a temperature above the softening point
of the binder, e.g. to a temperature of 150C, it is pre-
ferable to use cold tools for the moulding operation.
Plates, cups, trays, etc. which are -to be subjected
to high temperatures, are preferably manufactured by com-
pressing fibrous products under temperature conditions
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producing a maximum strength.
The moulded products are preferably introduced into
an oven, e.g. a tunnel oven, at a temperature of e~g.
150C for a period of abou-t 5 minutes.
Products having a high binder concentration may be
considered as a fibre reinforced plastics material. Such
products have a high ductility and flexibility and a sa-
tisfactory -tear strength and are par-ticularly suitable
for the production of the disposable packing materials,
cups, plates, book jackets, and printing materials.
Furthermore, such fibrous products are more suscept-
ible to printing inks than plastics materials, because
the fibres make the products opaque and improve the ad-
herence of printing inks.
A fibre reinforced plastics material can be bended
many times wi-thout breaking and, therefore, such produc-ts
are suitable for the manufacture of con-tainers wi-th inte-
gral lids.
A fibre reinforced product based on cellulosic fib-
res is decomposable when stored nature. ~ibre reinforcedproduc~s containing about 50 per cent by weight of cellu-
losic fibres and 50 per cent by welght of binder in the
form of an urea binder or a mix-ture of an urea and mela-
min binder have sufficien-tly low water absorption pro-
perties to be suitable for use as packaging materialsfor e.g. food products. On the other hand, such products
are decomposed more rapidly than the prior art plastics
materials if they are under the influence of moisture
for longer periods of time, e.g. by being stored in
nature.
Such produc-ts present the further advantage tha-t
they are more stable when exposed to sunlight or ultra-
violet light than many plastics materials.
It is well known to introduce in-to a plastics mate-
rial compositions which when-e~posed to ultraviolet
light cause the plastics ma-terial -to be decomposed.
Articles prepared from such plastics materials are not
1 'I
fully satisfactory, because they may undergo such
changes that they do not longer perform satisfactori-
ly when they reach the consumers.
Plastics materials reinforced with cellulosic
fibres and containing -the above mentioned compositions
in the binder are decomposed in an ideal manner. Thus,
the fibres decompose only after having absorbed moisture
and the decomposition of the binder is accelerated only
in the presence of moisture in -the fibres. If a partial
decomposition of the binder is initiated under the in-
fluence of ultraviolet light, the fibres will still im-
part to the material good strength properties, and a
final decomposition does not take place until the pro-
: duct is subjected to the influence of both ultraviolet
light and moisture. Packaging materials prepared fromthe fibrous products based on cellulosic fibres prefer-
ably contain well known compositions for decomposing
plastics materials.
As mentioned above -the fi.brous products according
to -the invention are preferably prepared in the form of
sheets or webs. However, they may also have a shape
corresponding to the shape of a non-planar formi.ng sur-
face. If it is desired to convert a sheet or web mate-
: rial into a product having a three-dimensional struc-
ture, it is desirable to effect a pre-moulding by using
a forming surface having a configuration such that the
shape of the initial fibrous product formed on said form-
ing surface does not differ significantly from the shape
of t.he final product.
Thus, the product according -to the invention may
comprise projections and/or depressions corresponding to
the projections and/or depressions desired in the final
product.
The produc-t accordiny to -the invention is suitable
for the production of packinys for frozen products, e.g.
food, eggs, chocolate or meat which are to be maintained at
a low temperature, or for heated products which are to be
~,
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maintained in a heated condition during transporta-tion.
In a method of preparing sueh products it is pre-
ferable to combine the dry moulding technique with a va-
cuum moulding technique.
A vacuum moulding is a method in whieh a thin layer
of a thermoplastie material in heated condition and at a
temperature close to the softening point of said mate-
rial is caused to deform and assume a desired shape.
According to the invention this vacuum moulding
technique may be used to provide a packing comprising
different compartments for the s-torage of various pro-
ducts, such as foods and chocolate. The vaeuum moulding
teehnique ean also be used for the produetion of pro-
duets, e.g. bags and trays whieh eombine a desired soft-
ness with desired insulation properties and resistanee. tomousture penetration.
Such a combined dry-laying and vacuum moulding opera-
tion may be effected in the following manner. The thiek-
ness of fibrous layer leaving the forming surface is re-
dueed to abou-t 50% of its original thiekness so as to fix
the fibres relative -to one another.
The product thus prepared is coated on one surface,
e.g. the top surfaee, with a thin layer of a thermoplastie
resin, e.g. polyethylene. Sueh eoating may be effeeted by
a well known extrusion or coating process or by merely
placing a layer of polyethylene on the top surface of
the product. It is also possible to use a loose separate
film of an elastomeric material. In the latter embodiment
the film may be used repeatedly.
The composite produet is then vaeuum moulded in a
vaeuum mould. By seleeting suitable temperatures for the
vaeuum moulding operation the eomposite produet is de-
formed and a bond be-tween the polyethylene layer and the
fibrous layer is established in one s-tep. The produet
thus obtained :is a laminate whieh is suitable ~or many
purposes.
A laminated produet whieh eomprises a core layer of
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16
fibres and wherein one or both surfaces are coated with
a layer of a thermoplastic material can be prepared in a
similar mannner. Such a produet which eomprises a moist-
ure impervious layer and a moisture absorbing layer is
not only suitable as a packing material but can also be
used for the production of diapers, sanitary napkins and
bandage materials.
By a similar lamination method produc-ts may be pre-
pared wherein the layer of thermoplastic material is
located within the material and is covered on both sides
by fibrous layers.
In order to use the above mentioned technique for the
moulding of laminated materials, the fibrous layer should
be pervious to air and the polyethylene film should be im-
pervious to air.
A fibrous product having a relatively high binder con-
centration at one surface is particularly suitable for the
production of containers for hot and cold products, such
as coffee and iee-eream, respectively. ~hen preparing such
eontainers, the starting material used is preferably a
fibrous produet wherein the layer which is to form the in-
terior surface oE the eontainer has a high binder concen-
tration, e.g. up to 75 per cent by weight. The binder may
be polyethylene or a melamin resin.
By providing a surface layer having a high binder eon-
eentration, no special eoating at the interior surfaee of
the container is needed and the strength and rigidity of
the container is inereased.
As mentioned above, a product comprising a surfaee
layer having a relatively high binder coneentration may be
prepared by using two or more fibre distributors and by
introdueing diEferent amounts of binder into said fibre
distributors.
Containers prepared from -the above mentioned product
are impervious to both liquid and gaseous produets inelu-
ding oils and fats.
In order to heat insulate such zones of containers,
17
such dS CUpS, for hot or cold products which are -to be
contacted by the hands, the said zones are preferably
composed of a fibrous material having a significan-tly
lower density than -that of the remaining zones. Such
cups may e.g. be provided with a band shaped zone extend-
ing over about 1/3 of -the total height of the cup.
Instead of providing such a limited 7one on the ex-
terior side of the container, -the exterior surface of
the whole side wall and, if desired, also the bottom
thereof may be composed of a fibrous material of a low
density. Such con-tainers are particularly suitable for
packing deep-froæen goods. When fibres are fixed relative
to one another in such a loose structure, -the rigidity
of the product formed also becomes satisfactory. Further-
more, such containers can be provided with ornamentswhich serve decora-tive purposes and which also increase
the friction so that e.g. cups prepared from said pro-
duct do not slide out of the hand.
Containers of the above mentioned type in the form
of trays or boxes are suitable for the storage of eggs
and for the storage of deep-frozen products during derim-
ing of refrigera-tors.
Contalners of this type are also suitable for the
transportation of deep-fro~en articles from shops to the
homes of the consumers.
The containers are preferably construc-ted in a man-
ner so that they can be closed and preferably comprise a
lid which is integral with the bottom par-t and is capable
of being folded over the bottom part.
Drinking cups may be prepared from blanks of a flat
sheet rnaterial of the invention, said blanks being suit-
ably shaped to form cups and overlapping portions being
joined by an adhesive.
Instead of preparing cups or similar articles from
flat fibrous materials, it is also possible to use forming
surfaces having portions of a shape corresponding -to that
of the articles to be prepared.
By using such forming surfaces and by successively
18
introducing said forming surfaces in-to gas s-treams con-
taining suspended fibres, a final fibrous layer which af-
ter compression and curing of the binder has the desired
properties can be formed thereon.
When compressing a product of the above mentioned
type, the mixture of fibres and binder is ordinarily com-
pressed in the direction of compression only.
However, a product may also be obtained wherein the
mixture of fibres and binder is compressed both in -the
direction of compression and in a direction perpendicular
thereto.
This e~fect is obtained by a me-thod wherein a fibrous
layer is compressed and simultaneously penetrated by heat~
ed needles. By using such a large number of needles that
the total cross sectional area thereof consti-tutes a con-
siderable portion of -the area of the product wherein -the
compression takes place, e.g. of the order of 50~, -the
said compression will resul-t in a considerable compression
not only ln the direc-tion of compression but also in a
direction perpendicular thereto.
By using heated needles having a diameter of between
e.g. 5 and lO mm and a fibrous product in which the bind-
er is uniformly distributed, a product is obtained in
which the fibres and the binder are concen-trated in the
zones adjacen-t to the holes. Therefore, the product ob-
tained is resistant to compression in the longitudinal
direction of said holes.
When using closely spaced needles, the product obtain-
ed becomes rigid and, conse~uently, a high flexural
strength is produced.
A product of the above mentioned -type may also be
coated on its surfaces with sheets of paper, boxboard or
similar materials so as to close the open ends of the
holes obtained by said needling. Such a coa-ting may be ap-
plied onto one or both surfaces of the material. When ap-
plying a coating onto both surfaces of the material, the
rigidity of the product is further increased. II} many re~
spects such a material possesses properties similar to
19
those of corrugated paper. These materials may advanta-
geously be used for the insulation purposes because they
are excellen-t insulating materials both as ~ar as heat
and noise is concerned.
The material described is also suitable for the pack-
ing of fragile articles, such as articles of ~lass/ and
instruments.
The me-thod of the inven-tion may be used for the pro-
duction of fibre layers containing binders which may be
activated with heat and/or moisture, e~g. binders based
on starch and water glass. Such fibre layers are suitable
for the production of fibrous products having a structure
corresponding to that of corrugated paper.
A product of the invention is also suitable for the
production of a buffer ma-terial for use in automobiles
etc.
Such a material may be prepared from a fibrouc; layer
having a thickness of e.g. 5 cm and consisting of fibres
and about 20% of a mixture of urea and melamin resins or
other thermosetting bin~er. This material is compressed
so as to form zones of alternating thickness and density.
Thus, the thickness within some zones is reduced to 3 cm,
whereas it is reduced to 0.6 cm in other zones.
By using mineral fibres, the material is made fire
resistant.
If desired, an artificial leather coating, e.g. made
of polyurethane, may be applied to the top surface of the
product.
The method of the invention is also suitable for the
production o~ corrugated fibrous proclucts and in particu-
lar a corrugated product consis-ting of a defibrated
fibrous waste ma-terial con~aining binders originating from
the production of said fibrous material and optionally
additional amounts of binder added during the production
of the corrugated product.
Due -to the excellen-t moulding pro~erties of a fibrous
product prepared by the method of the invention, such cor-
rugated product can be obtained by passing the fibrous
..,
3~
product through a set of rollers having a surface configu-
ra-tion which results in the obtaining of a corrugated pro-
duct. The binder used in the production of such corrugated
product is preferably a phenolic resin.
Examples of waste ma-terials which may be used in the
production of corrugated products are waste clippings of
corrugated paper, newsprin-t materials and sawdust in ad
mixture with mechanical pulp.
A corrugated product prepared from these ma-terials
preferably contains about 2% by weight of a phenolic resin,
said resin being introduced into the fibrous material in
-the form of a powder.
The corrugated products prepared in this manner may
be products in which the corrugations extend :longitudinal-
ly or transversely of the web.
The fibrous products of -the invention may also be
used for -the production of laminates. ~ preferred type of
laminates may be prepared by preparing a fibrous product
of a loose structure, compacting said product and coating
the compac-ted ma-terial with a chipboard. A decorative
sheet of melamin resin may be applied to the top surface
of said chipboard.
These layers may be formed individually in different
forming stations and subse~uently compressed before being
bonded together to form a laminate.
The top surface layer may also be a decorated layer
of paper.
In order to obtain final products having a uniform
distribution of binder, it may be desirable first to pre-
pare an intermediate produc-t and to introduce said inter-
mediate product into a defibrator and a distribu-tor so as
to prepare the final product.
The intermediate product prepared by -the method of
the invention is preferably compacted by being passed
through one or more sets of rollers which are moderately
heated, e.g. -to a temperature below the setting point of
the resin used as birder.
Due to the repeated defibration of the fibrous mate-
21
rial, irregulari-ties in the distribution of binder in the
intermediate product can be fully eliminated.
The binder used in the intermediate product is pre-
ferably of the thermocuring type.
The invention will now be described in further detail
with reference to the drawings, in which:
Figs. 1-9 illustrate various fibrous products obtain-
ed by the method of the invention and
Fig. lO schematically illustrates a method of pre-
paring a fibrous product comprising cup-
shaped portions.
Fig. 1 shows a cross sectional view of a product pre-
pared by the method of the invention. This product compris-
es a relatively loose fibrous layer l having a top layer 2
made from a fibrous material having a high binder concen-
tration.
r~he composite product has heen embossed so as to
form depressions 3.
The product illustrated in Fig. 2 comprises three
fibrous layers of which the outer layers 4 and 5 have a
loose structure and the core layer 6 is dense. The dense
core layer 6 may be prepared from a fibrous layer having
a relatively high binder concentration or by rolling or
compressing a fibrous layer at a temperature above the
melting or softening point of the binder used.
The fibrous product illustrated in Fig. 3 comprises
a relatively loose fibrous layer 7 which is coated on
one side by a polymer film 8, such as a polyethylene
film.
E'ig. 4 illustrates a fibrous product in which the
binder concen-tratiorl increases from -the upper surface -to-
wards the lower sur~ace.
Fig. 5 illustrates a fibrous product prepared by the
method of the invention, sai~ product comprising parallel
zones 9 of a high binder concentra-tion, said zones being
applied to the product in i-ts machine direction.
The fibrous product illustrated in Fig. 6 comprises
22
a loose fibrous layer lO located between two non-woven
nets 11.
The fibrous product shown in Fig. 7 is a fibrous pro-
duc-t provided with crossing grooves 12 so as to form a
product which is similar -to the well known quilted tex-
tile products.
Fig. 8 illustrates a box 13 having an in-tegral hing-
ed lid 14, said box and lid being prepared from a rolled
fibrous product ob-tained by the produc-t of the invention.
Fig. 9 shows a cross sectional view of a pre~erred
packing ma-terial prepared by embossing a fibrous product
of the invention in a pa-ttern comprising alternating
rounded projections and depressions.
Fig. 10 shows portion of an endless forming wire 15
mounted on at least two rollers of which only one 16 is
shown. The apparatus shown also comprises two cooperating
rollers 17 and 18 which are provided with intermeshing
projections l9. The forming wire 15 is provided with cup-
shaped projections 20 on which a fibrous layer 21 contain-
ing a binder is deposi-ted in a manner which is well ]~nown
per se.
The fibrous layer 21 is removed from the forming
wire 15 and is introduced into the nip between the two in-
termeshing rollers 17 and 18. During the passage -through
said nip the fibrous layer is compressed to form dense
cup-shaped elemen-ts which are subse~uently removed from
the roller 18 and separated from one another.
