Note: Descriptions are shown in the official language in which they were submitted.
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Amended page (dated 28.12.92) 1 PCT/DK91/00383
Method of manufacturing insulating boards composed of interconnected
-shaped mineral fibre elements
This invention relates to n method of manufacturing insulating
boards composed of interconnected rod-shaped mineral fibre elements
(in the following referred to as lamellae) comprising converting a
melt of a mineral fibre forming starting material into fibres,
supplying a binder to said fibres, collecting the fibres on a
conveyor belt so as to form a primary fibre web.
A method of the type defined above is disclosed in DE patent
publication No. 2307577 C3. In this prior art method the melt is
converted into fine mineral fibres by being thrown out from onQ or
more rapidly rotating spinning wheels under the simultaneous supply
of a binder capable of being cured, and the fibres thus formed are
caught on an endless belt in the form of a fibre web wherein the
fibres predominantly are oriented parallel to the surface of the
web. In this prior art method the fibre web is cut longitudinally
into lamellae and the lamellae thus formed are turned 90' about
their longitudinal axis whereafter the lamellae thus oriented are
bonded together to form a web-1 ike product which is then cut into
desired lengths to farm board elements. Due to the turning of the
lamellae the fibres of the finished boards will predominantly be
oriented in a plane perpendicular to the surfaces of the boards and
as a result thereof boards having a considerable stiffness and
strength parpkndicularly to the surfaces of the boards are obtained.
CA-A-1209893 discloses a method of producing a fibrous material
product made from a laminar mat of glass fibres containing a bonding
substance and having fibre lamination Qxtending parallel to the
surface of the mat, said method comprising the steps of a) crimping
the mat in the longitudinal direction so as to dispose a major
portion of said laminations in directions extending across the
thickness of the mat, b) heat-curing the bonding substance, c)
cutting the mat in the longitudinal direction to form mat strips, d)
rotating the strips 90' and e) securing adjacent strips to each
other to form a board,
In the longitudinal compression of the mat an inner folding
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X095532
""' Amended page (dated 28.12.92) la PCT/DK91/00383
structure is produced in the fibre web, the foldings extending
perpendicularly to the longitudinal direction of the fibre web.
4ihen such a web is cut longitudinally into lamellae and the lamellae
are turned 90' and bonded together to form a lamella board, each
lamella will exhibit a folded layer structure, the folds extending
perpendicularly to the main surfaces of the lamella board and
thereby imparting a greater stiffness and strength (area strength]
to the lamella board than in the case where a lamella board is
composed of rectilinear layers.
Boards produced by the prior art methods described above are
suitable for many applications, but for certain applications, e.g.
exterior insulation of roofs and/or building fronts and insulation
of floors, the boards possess an insufficient stiffness or strength
and/or insulating property.
It has now baQn found that these properties can be considerably
improved so as to allow the boards to be used for purposes far which
the prior art boards are not suitable by using the method of the
lnvQntion which is~characterized in forming a secondary fibre web by
doubling of the primary web by laying it in a number of layers
transversely to the longitudinal direction of said secondary web,
cutting the secondary fibre web in the longitudinal direction to
form lamellae, cutting said lamellae into desired lengths, turning
the lamellae 90' about their longitudinal axis and bonding thorn
together to form boards, and sub~QCting the lamellae to a surface
compression followed by a longitudinal compression eithQr before or
after the fibre web is cut into lamellae.
Thv invention is based on the disccvery that a board, wherein both
the foldings formed by a longitudinal compression of the web to be
cut to form lamellae and the individual fibres are positioned
perpendicularly to the plane of the board, has superior stiffness
and strength over a board, wherein only faldings extend
perpendicularly to the surface of the board, whereas the fibres are
positioned with arbitrary orientation in a plane perpendicular to
the surface of the board.
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Amended page (dated 28,12.92) lb PCT/DK91/00383
Also, the invention is based on the discovery that a board having
such a construction may be provided by using lamellae made from a
secondary fibre web formed by transverse doubling of a primary web
having a fibre orientation parallel to the surface of the web and
predominantly in the longitudinal direction of the web.
The method of the invention has provided a possibility of producing
a 1am411a board having a grQatly increased stiffness and area
strength compared to lamellae boards made from primary fibre webs,
i0 wherein the fibres are positioned with arbitrary orientation in a
plane parallel to the plane of the web.
A particularly high stiffness is obtained with boards made from
lamellae obtained by cutting ~ sQCOndary web longitudinally and
subsequently turning them 90' about their longitudinal axis because
the fibres boing predominantly oriented transversely to the
secondary web will be positioned perpendicularly to the plane of the
board.
By compressing the fibre web longitudinally before turning the
lamellae 90', the compressive strength of the finished lamellae is
increased and thQ above mentioned increase in stiffness and the
increase in compression strength appear to support one another,
which is evidenced by the fact that the two measures apparently
produce a total effect which is greater than the sum of effects
produced by the measures separately.
35
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-- Amended page (dated 28.12.92) 2 PCT/DK91/00383
Instead of increasing the strength it may be desirable to reduce the
density as this rnay cause an Increase in the Insulating capacity.
Thus, it is well known that boards of rock wool made from lamellae
having a content of shots of about 30%, the shots being greater than
63 um, have an optimum insulating capacity at a density of about 40
kg/ms.
It is well known that a fibre web can be produced by Initially
producing a relatively thin primary web and subsequently doubling
the primary web to form a secondary relatively thick fibre web
comprising partially overlapping layers of the primary web, see DE
patent
2J
30
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Amended page (dated 28.12.92) 3 PCT/DK91/00383
publication No. 3501897.
When a fibre wQb is doubled tho fibres ar8 collected on a
high-velocity conveyor belt, e_g, running with a velocity of 130
m/min, in tho form of a thin fibre layer, e.g. having a weight of
0.3 kg/mz. When collected in this manner, the fibres will be
dQposited on the conveyor belt in directions parallel to the surface
of the web and predominantly parallel to thQ direction of movQmQnt
of the belt. As a result thereof the fibre web will obtain a tensile
IO strenght which is about twicQ as high in the longitudinal direction
of the fibre web as in the transverse direction. The secondary fibre
web is formed by laying by means of pendulum belts the thin primary
web in a number of layers, e.g. 20, transvQrsoly to the longttudinal
direction of tho secondary web, the number of layors being
determined by the desired area weight of the secondary web.
In the doubled web the fibres are predominantly oriented
transversely to the web when the layers of the primary web extend
transversQly to the secondary web.
24
The purpose of doubling a fibre web is ordinarily to obtain a
secondary web having a relatively great thickness and having a small
variation in density in the longitudinal direction.
In the method according to the invention lamellae made from a
doubled fibre web comprising from 4 to 25 layers and having a
surface weight of from 1 to 8 kg/m= are preferably used.
35
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AmendQd page (d;ted 28.12.92) 4 PCf/OK91/00383
Methods for longitudinally compressing fibre webs are known per se.
In a preferred prior art method, cf. CH patent specification No.
620861, a mineral fibre web is introduced into the space between two
parallel conveyor belts which travel with a velocity V1 and
subsequently Into the space between two further conveyor bolts which
travel with a velocity 112, which is lower than V1. Depending on the
relationship botwaan V1 and V2, thQ fibre web is morn or less
compressed longitudinally. The relatiansship between Y1 and V2 is
selected so that folds are farmed by the longitudinal compression,
said folds extending transversely to the longitudinal direction of
the web. In another prefQrred method, cf. US patent specification
No. 2,500,690, the longitudinal compression is effected by means of
a row of roller sets, said rollers rotating with a velocity which
decreases in the longitudinal direction of thQ fibre web.
It is prefQrred to compress the fibre web longitudinally before
cutting it into lamellae but the longitudinal Compression may also
be effected when the web has bean cut into lamellae..
For use in the method according to the invention lamellae made from
fibre webs which have been compressed longitudinally in a ratio of
from 1.5:1 to ~:1 arQ preferred.
As mQntioned above, the longitudinal compression should be effected
following the vertical compression and when using a heat curable
binder, the said longitudinal compression is effected before the
fibre web is introduced into a curing oven.
Methods for subjecting a fibre web to a surface compression are also
35
AMENDED PAGE (dated 29.05.92) 5 PCT/DK91/00383
well known. In such a prior art method the fibre web to be
compressed is introduced into the space between the rollers in a
series of roller sets, the spacing between the rollers in the roller
sets decreasing in the direction of movement of the fibre web.
For use in the method according to the invention lamellae made from
a fibre web which has been surface compressed in a ratio of from 3:1
to 6:1 are preferred.
The cutting of the fibre web to form lamellae is preferably effected
by means of saws which may have the form of compass saws, cf. DE
patent publication No. 2307577, or circular saws, cf. SE published
patent application No. 441764 and DE patent publication No. 2032624.
In a preferred embodiment of the method according to the invention
the rod-shaped fibre elements are cut into desired lengths before
being turned 90° and combined into lamella boards. Such turning may
e.g. be effected in connection with the transfer of the cut lamellae
from one conveyor belt upon which they are advanced in the
longitudinal direction of the lamellae onto another conveyor belt
moving perpendicularly to the first belt and upon which the lamellae
are conveyed in a direction perpendicularly to their longitudinal
direction.
This embodiment is advantageous in that the apparatus used for such
turning of the lamellae requires little space.
Alternatively the turning of the lamellae can be effected during the
cutting of the web into lamellae, e.g. as described in DE patent
publication No. 2307577 or DE 2032624.
The properly oriented lamellae which are to form a lamella board can
be bonded together, preferably by means of a binder which is applied
to the upper side of the fibre web and optionally to the lower side
thereof, and preferably before the web is cut into lamellae.
However, it is not necessary to add an additional binder as the
binder which is supplied to the fibres in connection with their
formation is also present at the surfaces of the lamellae and it may
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09553
AMENDED PAGE (dated 29.05.92 6 PCT/DK91/00383
be sufficient to bond together the lamellae if they are pressed
intimately together during the curing of the binder in the curing
oven, cf. DK patent application No. 3526/75.
If a heat curable binder has been supplied to the fibres in
connection with their formation and if a heat curable binder is also
used for bonding together the lamellae, the binders can be cured in
one step by conveying the properly oriented and combined lamellae
through a curing oven in which they are heated to curing
temperature, which is preferably between 210 and 260°C when phenol
formaldehyd resin is used as a binder.
However, the binder for bonding together the lamellae may also be
suppl i ed after the f i bre web/1 amel 1 ae have been heated i n a curi ng
oven to cure the binder supplied to the fibres in connection with
their formation.
By supplying binder after the curi.n. ven other binders than heat
curable binders can be used.
The invention will now be described in further detail with reference
to the drawing which schematically shows a plant for carrying out
the method according to th invention.
In the drawing 1 designates an oven for manufacturing a mineral
fibre forming melt which is supplied to a spinner 3 having four
rapidly rotating spinning wheels 4 via a melt outlet 2.
Simultaneously with the introduction of melt onto the outer surfaces
of the spinning wheels and binder is sprayed, a strong gas stream is
passed across the surfaces of the spinning wheels in the axial
direction, thereby causing the formation of fibres 5 which are
collected on an endless perforated conveyor belt 6 which is
supported by three rollers 7, one of which is driven by driving
means (not shown). As a result thereof a fibre web 8 (the primary
web) is formed and this web is introduced into the space between two
pendulum belts 10 and 11 by means of a further endless conveyor belt
9. The lower ends of the pendulum belts are located pivotally in a
direction perpendicularly to~the direction of movement of a further
endless conveyor belt 12 which is supported by two rollers 13, one
~.
. ~,~~5~32 _
' AMENDED PAGE (dated 29.05.92) 7 PCT/DK91/00383
of which is driven by driving means (not shown).
The ampl i tude of the osci 11 at i on of the 1 ower part of the pendul um
belts 10 and 11 corresponds to the width of the conveyor belt 12 and
a doubled fibre web 14 of partially overlapping fibre layers 8 is
thus formed on the belt 12.
The fibre web 14 is subsequently introduced into a surface
compression section consisting of three sets of co-operating rollers
15, 16 and 17, the spacing between the rollers in the roller sets
decreasing in the longitudinal direction of the fibre web.
Subsequently the fibre web 14 is introduced into the longitudinal
compression section which also consists of three roller sets 18, 19
and 20, the rollers of the latter sets of rollers rotating with the
same velocity, which velocity is lower than that of the sets of
rollers 15, 16 and 17.
The fibre web which has been compressed longitudinally is then
introduced into a curing oven 21 in which it is heated to a
temperature which is sufficiently high to cure the binder and to fix
the fibres relatively to one another.
After having passed the curing oven the heat treated fibre web 14 is
cut in the longitudinal direction by means of saws 22 so as to form
lamellae 23 which are subsequently cut transversely by means of a
transverse saw 24. The lamellae 23 thus cut are then turned 90° and
combined to form a board element 25 on a conveyor belt 26 and at the
same time a binder is applied to the contact surfaces by means of an
application apparatus (not shown) to bond together the lamellae 23.
As indicated in the drawing the fibre layers formed from the primary
web 8 extend substantially perpendicularly to the surface of the
finished board element, and as they are also folded they are highly
resistant against compression.
Instead of being bonded together the lamellae can be joined together
by means of e.g. strips, strings, non-woven fabric or paper on one
side or both sides of the boards.
