METHOD FOR PRODUCING DUROPLASTIC FINE-FIBER NON-WOVENS HAVING A HIGH FLAME-RETARDANT, THERMAL PROTECTIVE AND SOUND INSULATING EFFECT

PROCEDE DE PRODUCTION DE NON-TISSES THERMODURCISSABLES A FIBRES SUPERFINES CARACTERISES PAR UN EFFET PROTECTEUR ACCRU EN MATIERE D'IGNIFUGATION ET D'ISOLATION THERMIQUE ET ACOUSTIQUE

English Abstract

The invention relates to a method for producing duroplastic fine-fiber non-
wovens,
characterized in that: a) melts of reactive three-dimensionally cross-
linkable, non-linear
prepolymers are extruded by nozzles; b) the exiting melts are blown by means
of hot air
to form fine fibers; c) the fine fibers are separated by the flow of air and
deposited to
form a non-woven comprised of a fine-fiber weave; d) the non-woven is
subsequently
compacted, and ; e) the non-woven is treated with a medium that initiates a
three-dimensional
cross-linking, and the fine fibers in the non-woven are inherently bonded
and/or hardened in a subsequent thermal post-hardening. This enables
duroplastic fine-fiber
non-wovens to be economically produced that have both a high flame retardant
effect as well as a high thermal protection, sound insulation and filtering
capacity.

French Abstract

L'invention concerne un procédé de production de non-tissés thermodurcissables à fibres superfines, caractérisé en ce que a) des masses fondues de prépolymères réactifs non linéaires réticulables en trois dimensions sont poussées à travers des filières, b) les masses fondues sortant sont soufflées au moyen d'air chaud pour former des fibres superfines, c) ces fibres superfines sont séparées du flux d'air et déposées sous la forme d'un non-tissé constitué d'un entrelacement de fibres superfines, d) le non-tissé est compacté, e) il est traité au moyen d'un agent induisant une réticulation tridimensionnelle, puis les fibres superfines sont collées et/ou durcies à l'intérieur du non-tissé lors d'une étape de post-traitement thermique. Ce procédé permet de produire de façon économique des non-tissés thermodurcissables à fibres superfines qui possèdent un effet protecteur accru en matière d'ignifugation et d'isolation thermique et acoustique et un haut pouvoir filtrant.

Claims

14
We claim:
1. A process for producing thermoset microfibrous webs, wherein
a) melts of reactive, three-dimensionally crosslinkable, nonlinear prepolymers
are
pressed through dies,
b) the exiting melts are attenuated by hot air to form microfibers,
c) the microfibers are separated from the air stream and are deposited to form
a web
consisting of a microfibrous braid,
d) the web is subsequently compacted,
e) treated with a medium inducing a three-dimensional crosslinking and in a
subsequent thermal postcure the microfibers in the web are self-bonded and/or
cured
off.
2. The process according to claim 1, characterized in that reactive,
nonlinear
prepolymers three-dimensionally crosslinkable by a condensation reaction are
pressed
through dies situated in a tip of cones.
3. The process according to claim 2, characterized in that the exiting melt
is
attenuated directly at the die outlet to form microfibers by the hot air,
whose
temperature is above the starting temperature of the condensation reaction,
flowing at
a high rate of speed along the tip of cones.
4. The process according to claim 2 or 3, characterized in that the
microfibers are
separated from the air stream and are deposited as an unconsolidated web.

15
5. The process according to claim 4, characterized in that the
unconsolidated web
is subsequently compacted.
6. The process according to any one of claims 4 and 5, characterized in
that the
unconsolidated web has air comprising a component catalyzing the crosslinking
flowing through it at temperatures below the melting point of the prepolymer.
7. The process according to any one of claims 4 to 6, characterized in that
the
unconsolidated web subsequently has an inert medium flow through it and, in
the
process, the catalyzing component is completely removed from the spaces
between
the microfibers or neutralized with a basic gas.
8. The process according to any one of claims 4 to 7, characterized in that
the
unconsolidated web is self-bonded and/or cured off to a consolidated web by
elevating
the temperature.
9. The process according to claim 8, characterized in that the web has hot
air flow
through it and, in the process, is incrementally or continuously further
heated.
10. The process according to claim 8 or 9, characterized in that the web is
dwelled
at high temperatures.
11. The process according to any one of claims 1 to 10, characterized in
that the
reactive crosslinkable, nonlinear prepolymers consist of alcohol-etherified
melamine-
formaldehyde resins.
12. The process according to claim 11, characterized in that the alcohol-
etherified
melamine-formaldehyde resins consist of meltable 4- to 18-nucleus
oligotriazine ethers
in which the triazine segments contain

16
<IMG>
R1 = -NH2, -NH-CHR2-O-R3, -NH-CHR2-O-R4-OH, -CH3, -C3H7, -C6H5, -OH,
phthalimido-,
succinimido-, -NH-CO-C5-C18-alkyl, -NH-C5-C18-alkylene-OH
<IMG>
-NH-CHR2-O-R4-O-CHR2-NH-, -NH-CHR2-NH-, -NH-CHR2-O-C5-C18-alkylene-NH-,
-NH-C5-C18-alkylene-NH-, -NH-CHR2-O-CHR2-NH-,
R2 = H, C1-C7-alkyl;
R3 = C1-C18-alkyl, H;
R4 = C2-C18-alkylene, -[CH2-CH2-O-CH2-CH2]-, -[CH2-CH(CH3)-O-CH2-CH(CH3)]n-,
-[4-O-CH2-CH2-CH2-CH2-]n-, -[(CH2)2-8-O-CO-C6-C12-aryl-CO-O-(CH2)2-8-]n-
,
-[(CH2)2-8-O-CO-C6-C12-alkylene-CO-O-(CH2)2-8-]n-,
where n = 1 to 200;
sequences containing siloxane groups, of the type
C1-C4-alkyl C1-C4-alkyl, -(C1-C18)-alkyl-O-Si-O-[Si-]1-4-O-(C1-C18)-alkyl-, C1-
C4-alkyl, C1-
C4-alkyl
- polyester sequences containing siloxane groups, of the type
-[(A)r-O-CO-(B)s-CO-O-(A)r]-, in which
A = {(CH2)2-8-O-CO-(C6-C14)-arylene-CO-O-(CH2)2-8-} or

17
-{(CH2)2-8-O-CO-(C2-C12)-alkylene-CO-O-(CH2)2-8-};
C1-C4-alkyl C1-C4-alkyl
B = -{(C6-C14)-arylene-CO-O-({Si-O-[Si-O]y-CO-(C6-C14)-arylene-}
C1-C4-alkyl C1-C4-alkyl or
C1-C4-alkyl C1-C4-alkyl
{O-CO-(C2-C12)-alkylene-CO-O-({Si-O-[Si-O]z-CO-(C2-C12)-alkylene-CO-};
C1-C4-alkyl C1-C4-alkyl
r = 1 to 70; s = 1 to 70 and y = 3 to 50;
polyether sequences containing siloxane groups, of the type
C1-C4-alkyl C1-C4-alkyl
-CH2-CHR2-O-({Si-O-[Si-O]y-CHR2-CH2-
C1-C4-alkyl C1-C4-alkyl
where R2 = H; C1-C4-alkyl and y = 3 to 50;
sequences based on alkylene oxide adducts of melamine, of the type of 2-amino-
4,6-
di-C2-C4-alkyleneamino-1,3,5-triazine sequences;
phenol ether sequences based on dihydric phenols and C2-C8 diols, of the type
of
-C2-C8-alkylene-O-(C6-C18)-arylene-O-(C2-C8)-alkylene- sequences;
are linked by bridge members -NH-CHR2-O-R4-O-CHR2-NH- and -NH-CHR2-NH- and
also, where appropriate, -NH-CHR2-O-CHR2-NH-, -NH-CHR2-O-C5-C18-alkylene-NH-
and/or -NH-C5-C18-alkylene-NH- to form 4- to 18-nucleus oligotriazine ethers
of linear
and/or branched structure,
the terminal triazine segments in the oligotriazine ethers forming triazine
segments of
the structure
<IMG>
Y = -NH-CHR2-O-R3, -NH-CHR2-O-R4-OH and also if appropriate -NH-CHR2-O-O5-C18-
alkylene-NH2,

18
-NH-C5-C18-alkylene-NH2, -NH-C5-C18-alkylene-OH,
R1 = -NH2, -NH-CHR2-O-R3, -NH-CHR2-O-R4-OH, -CH3, -C3H7, -C6H5, -OH,
phthalimido-,
succinimido-, -NH-CO-R3, -NH-C5-C18-alkylene-OH, -NH-C5-C18-alkylene-NH2,
<IMG>
R2 = H, C1-C7-alkyl;
R3 = C1-C18-alkyl, H;
R4 = C2-C18-alkylene, -[CH2-CH2-O-CH2-CH2]-, -[CH2-CH(CH3)-O-CH2-CH(CH3)]n-,
-[-O-CH2-CH2-CH2-CH2-]n-, --[(CH2)2-8-O-CO-C6-C12-aryl-CO-O-
(CH2)2-8-]n-,
-[(CH2)2-8-O-CO-C6-C12-alkylene-CO-O-(CH2)2-8-]n-,
where n = 1 to 200;
sequences containing siloxane groups, of the type
C1-C4-alkyl C1-C4-alkyl, -(C1-C18)-alkyl-O-Si-O-[Si-]1-4-O-(C1-C18)-alkyl-, C1-
C4-alkyl, C1-
C4-alkyl
polyester sequences containing siloxane groups, of the type
-[(A)r-O-CO-(B)s-CO-O-(A)r]-, in which
A = {(CH2)2-8-O-CO-(C6-C14)-arylene-CO-O-(CH2)2-8-} or
-{(CH2)2-8-O-CO-(C2-C12)-alkylene-CO-O-(CH2)2-8-};
C1-C4-alkyl C1-C4-alkyl
B = -{(C6-C14)-arylene-CO-O-({Si-O-[Si-O]-CO-(C6-C14)-arylene-}
C1-C4-alkyl C1-C4-alkyl or
C1-C4-alkyl C1-C4-alkyl
{O-CO-(C2-C12)-alkylene-CO-O-({Si-O-[Si-O]z-CO-(C2-C12)-alkylene-CO-};
C1-C4-alkyl C1-C4-alkyl
r = 1 to 70; s = 1 to 70 and y = 3 to 50;
polyether sequences containing siloxane groups, of the type

19
C1-C4-alkyl
-CH2-CHR2-O-({Si-O-[Si-O]-CH R2-CH2-
C1-C4-alkyl C1-C4-alkyl
where R2 = H; C1-C4-alkyl and y = 3 to 50;
sequences based on alkylene oxide adducts of melamine, of the type of 2-amino-
4,6-
di-C1-C4-alkyleneamino-1,3,5-triazine sequences;
phenol ether sequences based on dihydric phenols and C2-C8 diols, of the type
of
-C2-C8-alkylene-O-(C6-C18)-arylene-O-(C2-C8)-alkylene- sequences;
in the oligotriazine ethers the molar ratio of the substituents R3: R4 = 20:1
to 1:20,
the proportion of the linkages of the triazine segments through bridge members
-NH-
CHR3-O-R4-O-CHR3-NH- is 5 to 95 mol%.
13. The process according to claim 11 or 12, characterized in that the
alcohol-
etherified melamine-formaldehyde resins contain further compounds influencing
the
reactivity of the prepolymers and the molecular structure of the cured
polymers.
14. The process according to any one of claims 1 to 13, characterized in
that the
reactive three-dimensionally crosslinkable, nonlinear prepolymers contain up
to 20%
by mass of further reactive polymers selected from the group consisting of
ethylene
copolymers, maleic anhydride copolymers, modified maleic anhydride copolymers,
poly(meth)acrylates, polyamides, polyesters and polyurethanes.
15. The process according to any one of claims 1 to 14, characterized in
that the
reactive three-dimensionally crosslinkable, nonlinear prepolymers contain up
to 20%
by mass of aliphatic diols of the HO-R-OH type and also up to 2% by mass of
fillers,
color pigments, stabilizers, UV absorbers and/or auxiliaries.

20
16. The process according to any one of claims 1 to 15, characterized in
that the
reactive, three-dimensionally crosslinkable, nonlinear prepolymers are melted
at about
70 °C to 130 °C for spinning.
17. The process according to any one of claims 1 to 16, characterized in
that the
dies have a diameter of 0.1 to 3 mm.
18. The process according to claim 17, characterized in that the dies have
a
diameter of 0.5 to 1 mm.
19. The process according to any one of claims 2 to 10, or any one of
claims 11 to
18 as dependent from claim 2, characterized in that the dies are situated on
and/or in
the tips of cones and the hot air flows along the die cones at a high rate of
speed.
20. The process according to claim 19, characterized in that the cones have
an
angle of 10 to 90°.
21. The process according to any one of claims 1 to 20, characterized in
that the
hot air has a temperature of 150 °C to 400 °C.
22. The process according to claim 21, characterized in that the hot air
has a
temperature of 180 °C to 300 °C.
23. The process according to any one of claims 1 to 22, characterized in
that the
microfibers are filaments or have a diameter/length ratio of greater than
1:50.
24. The process according to any one of claims 1 to 23, characterized in
that the
microfibers have an average diameter of 0.5 to 100 µm.
) 25. The process according to claim 24, characterized in that the
microfibers have
an average diameter of 1 to 7 µm.

21
26. The process according to any one of claims 1 to 25, characterized in
that the
microfibers have a disordered, small-scale crimped structure.
27. The process according to any one of claims 1 to 26, characterized in
that the
microfibers are separated from the air stream using a wire grid or braid
inserted into
the air/microfiber stream and at the same time an unconsolidated web forms.
28. The process according to claim 27, characterized in that the wire grid
or braid is
in the form of an endless belt.
29. The process according to claim 27 or 28, characterized in that the air
of the
air/rnicrofiber stream is aspirated away underneath the wire grid or braid.
30. The process according to any one of claims 1 to 29, characterized in
that the
web is compacted to the desired density by mechanical pressure or by forming.
31. The process according to any one of claims 1 to 30, characterized in
that a
three-dimensional crosslinking is induced or starts at temperatures below the
microfiber melting point.
32. The process according to any one of claims 1 to 31, characterized in
that the
medium inducing the three-dimensional crosslinking is gaseous HCI and/or
gaseous
HBr and/or formic acid neat or diluted with air or some other inert gas.
33. The process according to any one of claims 1 to 32, characterized in
that the
microfibers in which the medium is sorbed self-bond in the temperature range
between
100 °C and 120 °C.
34. The process according to any one of claims 1 to 33, characterized in
that the
thermal aftertreatment of the web is effected by incremental or continuous
heating with

22
hot air and at the same time, methanol is discharged together with detached
HCI
and/or HBr.
35. The process according to claim 34, characterized in that the thermal
aftertreatment of the web is effected in the temperature range from 200
°C to 320 °C
and the aftertreatment time is between 15 min and 120 min.
36. The process according to claim 35, characterized in that the web is
washed with
water after the aftertreatment.
37. The process according to claim 35 or claim 36, wherein the temperature
range
is from 250 °C to 280 °C.
38. The process according to any one of claims 35 to 37, wherein the
aftertreatment
time is between 20 min and 60 min.
39. The process according to any one of claims 1 to 38, characterized in
that the
reactive three-dimensionally crosslinkable, nonlinear prepolymers are before
processing in the form of cylindrical, lenticular, pastille-shaped or
spherical particles
having an average diameter of 0.5 to 8 mm.
40. The process according to any one of claims 1 to 39, characterized in
that the
medium catalyzes a condensation reaction.

Description

CA 02602171 2007-09-17
WO 2006/100041 PCT/E P2006/002597
METHOD FOR PRODUCING DUROPLASTIC FINE-FIBER NON-
WOVENS HAVING A HIGH FLAME-RETARDANT, THERMAL
PROTECTIVE AND SOUND INSULATING EFFECT
This invention relates to a process for producing thermoset microfibrous
webs.
The process of the present invention proceeds from reactive, three-
dimensionally crosslinkable, nonlinear prepolymers, preferably from
etherified melamine-formaldehyde resins. The melts of these prepolymers
are pressed through dies, the exiting melts are attenuated by hot air to form
microfibers, the microfibers are separated from the air stream and to form a
microfibrous braid. The, in particular, unconsolidated web is subsequently
compacted, treated with a medium inducing a three-dimensional
crosslinking and then thermally postcured, causing the web fibers to self-
bond and/or cure off. Web articles are formed which are widely used on
account of their high flame protection effect and also their good thermally
protecting, acoustically protecting and filtering ability.
It is particularly advantageous to deposit an unconsolidated web also
known as a random-laid ply of loosely aggregated fibers.
Microfibrous webs, which are very useful for filtration and also thermal and
acoustical protection, are produced in large amounts from meltable
polymers by the familiar meltblown process. In the meltblown process, a
low-viscosity molten jet of a thermoplastic polymer is extruded into a hot
stream of air moving at a high rate of speed. The melt disintegrates into
microfibers, which are cooled and laid down on a foraminous belt. The
disadvantage of this economical process is that it is limited to thermoplastic
polymers only, which have an inadequate flame protection effect. Flame-
retardant, thermoset polymers have hitherto not been processible into
fibers by such processes.
CONFIRMATION COPY

CA 02602171 2007-09-17
WO 2006/100041 PCT/EP2006/002597
2
It is well known to use cotton webs consolidated with thermoset phenolic
resin as acoustical and thermal protection in the automotive sector
(Becker/Braun, Kunststoff-Handbuch: Duroplaste, page 763, Hanser Verlag
Munich). The disadvantage of these webs is their high mass per unit area
and their insufficient resistance to flames.
Also known are thermoset melamine resin fibers and webs produced
therefrom, which have a very good flame protection effect. DE 19515277,
DE 10133787 or DE 19753834 describe the production of fibers from
aqueous melamine-phenol-formaldehyde precondensates. The aqueous
precondensate solution is pressed through spinneret dies, the resulting
fibers are subsequently dried and cured off at elevated temperature. The
fibers can subsequently be processed by existing processes into
nonconeustible webs. A significant disadvantage of such webs is that the
fibers interentangle only insufficiently in the web-forming step and hence
the strength of the webs is not sufficient. The addition of web-forming
auxiliary fibers such as cotton is often necessary.
A further disadvantage is the separation of the process stages of "fiber
production" and "web formation", making the web-producing process
unnecessarily complicated. It is further disadvantageous that hitherto only
aqueous melamine resin precondensate solutions are used to produce the
fibrous material, necessitating an energetically wasteful evaporation of the
water during the filament-forming operation.
EP 1 403 405 A2 describes continuous filaments obtainable by melting
amino resin polymers comprising oligo- and/or polytriazine ethers. The
amino resin melts are spun by means of dies and are subsequently
stretched into continuous filaments of a desired diameter while undergoing
curing. The cured amino resin filaments can be wound up, bundled to form
a strand or laid down to form a fabric. The disadvantage here is again the
complicated web-producing process wherein

CA 02602171 2013-05-17
3
it is necessary first to form the continuous filaments, then cut these into
fibers and
finally consolidate these fibers into a fabric.
In some cases, it may be desirable to develop a process whereby thermoset
microfibrous webs possessing not only high flame protection effect but also a
high
thermally protecting, acoustically protecting and filtering ability are
economically
obtainable.
In accordance with one aspect of the present invention, there is provided a
process for
producing thermoset microfibrous webs, wherein a) melts of reactive, three-
dimensionally crosslinkable, nonlinear prepolymers are pressed through dies,
b) the
exiting melts are attenuated by hot air to form microfibers, c) the
microfibers are
separated from the air stream and are deposited to form a web consisting of a
microfibrous braid, d) the web is subsequently compacted, e) treated with a
medium
inducing a three-dimensional crosslinking and in a subsequent thermal postcure
the
microfibers in the web are self-bonded and/or cured off.
Reference will now be made, by way of example only, to selected embodiments of
the
invention as illustrated in the accompanying drawings in which:
Figure 1 is a cross-section view of a die used in a process exemplary of the
present
invention;
Figure 2 is a scanning electron micrograph of a web formed of sample
microfibers; and
Figure 3 is a scanning electron micrograph of a web formed of sample
microfibers.
In some cases, it may be particularly advantageous when the microfibers are
separated from the air stream and are deposited as an unconsolidated web
(random-
laid ply).

CA 02602171 2013-05-17
3a
Surprisingly, although the reactive, three-dimensionally crosslinkable,
nonlinear
prepolymers in the solid state are very brittle and are easy to crumb without
particular
exertion, the process can convert the melts of these prepolymers after
departure from
the die, despite the severe turbulences and frictional forces in the meltblown
process
air or to be more precise in the fiber/air stream, into microfibers which,
without being
crumbed into microfine particles, can be in particular laid down to form an
unconsolidated web, which can be compacted or formed by application of force.
It is also surprising that the microfibers produced have a disordered, small-
scale
crimped structure which, however, is advantageous for web formation and web
coherency.

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4
It is further surprising that the microfibers produced can also be in the form
of continuous filaments.
It is also surprising that the microfibers, after being exposed to the medium
which induces the three-dimensional crosslinking, can self-bond to each
other in the web at their contact surfaces without additional binders having
been added.
The process is advantageously carried out when the reactive crosslinkable,
nonlinear prepolymers consist of alcohol-etherified melamine-formaldehyde
resins composed of meltable 4- to 18-nucleus oligotriazine ethers in which
the triazine segments contain
C C ---
\
R1 = -NH2, -NH-CHR2-0-R3, -NH-CHR2-0-R4-0H, -CH3, -C3H7,
-C6H5, -OH, phthalimido-,
succinimido-, -NH-CO-c5-015-alkyl, -NH-05-C18-alkylene-OH
CO - CHR2 -NH-CHR2-0-05-C18-alkylene-NH2,
-NH-CHR2-0-(CH2)54B-N
CO - CHR2, -NH-05-C16-alkylerte-NH2,
-NH-CHR2-0-R4-0-CHR2-NH-, -NH-CHR2-NH-, -NH-CHR2-0-
05-C18-alkylene-NH-,
-NH-05-C15-alkylene-NH-, -NH-CHR2-0-CHR2-NH-,
R2 7= H, C1-C7-alkyl;
R3 = H;

CA 02602171 2007-09-17
WO 2006/100041 PCT/EP2006/002597
R4= C2-GiEralky1ene, -[CH2-CH2-O-CH2-CH21,-, -{CH2-CH(CH3)-0-CH2-CH(CH3)rr,
-[-O-CH2-CH2-CH2-CH2+-,
-RCH2)2_8-0-CO-c6-012-aryl-00-0-(CH2)2-8-k,
TCH2)2-8-0-CO-cs-c12-alkylene-00-0-(C
5 where n = 1 to 200;
sequences containing siloxane groups, of the type
C1-C4-alkyl
alkyl-, C1-C4-alkyl, C1-C4-alkyl
polyester sequences containing siloxane groups, of the type
-{(A)r-O-00-(B)s-00-0-(A)d-, in which
A = {(CH2)2_8-0-00-(C5_C14)-arylene-00-0-(CH2)2_8-} or
-{(CH2)2-8-0-00-(C2-C12)-alkylene-00-0-(CH2)2-8-1;
C1-C4-alkyl C1-C4-alkyl
B = -{(C8-C14)-arylene-00-0-({Si-0-[Si-O]-00-(C8-C14)-arylene-}
C1-C4-alkyl Cl-C4-alkyl or
C1-C4-alkyl
(0-00-(C2-C12)-alkylene-00-0-({Si-O-pi-O]z-00-(C2-C12)-alkylene-00-1;
C1-C4-alkyl C1-C4-alkyl
r= 1 to 70; s = 1 to 70 and y = 3 to 50;
polyether sequences containing siloxane groups, of the type
C1-C4-alkyl
-CH2-CHR2-0-({Si-0-[Si-O]y-C1-1R2-CH2-
C1-C4-alkyl C1-C4-alkyl
where R2 = H; C1-C4-alkyl and y = 3 to 50;
sequences based on alkylene oxide adducts of melamine, of the
type of 2-amino-4,6-di-02-c4-alkyleneamino-1,3,5-triazine sequences;
phenol ether sequences based on dihydric phenols and C2-C8 diols,
of the type of
-C2-C8-alkylene-0-(C8-C18)-arylene-0-(C2-C8)-alkylene- sequences;
are linked by bridge members -NH-CHR2-0-R4-0-CHR2-NH- and
-NH-CHR2-NH- and also, where appropriate, -NH-CHR2-0-CHR2-NH-,
-NH-CHR2-0-C8-C18-alkylene-NH- and/or -NH-C8-C18-alkylene-NH- to
form 4- to 18-nucleus oligotriazine ethers of linear and/or branched
structure,

CA 02602171 2007-09-17
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6
the terminal triazine segments in the oligotriazine ethers forming
triazine segments of the structure
NN
N N
1 1 1
Y C C.--
\ //
Y = -NH-CHR2-0-R3, -NH-CHR2-0-R4-0H and also if appropriate
-NH-CHR2-0-05-C18-alkylene-NH2,
-NH-05-C18-alkylene-NH2, -NH-05-C18-alkylene-OH,
F21 = -NH2, -NH-CHR2-0-R3, -NH-CHR2-0-R4-0H, -CH3, -C3H7,
-C8H5, -OH, phthalimido-,
succinimido-, -NH-CO-R3, -NH-05-C18-alkylene-OH, -NH-05-C18-alkylene-NH2,
CO - CHR2 -NH-cHR2-O-
Cs-C18-alkylene-NH2,
.NH-cHR2-0-(CH2)la-\
CO - CHR2,
R2 = H, C1-C7-alkyl;
R3 = H;
R4 02-018-alkylene, -[CH2-CH2-0-CH2-CH21,-, -[CH2-CH(CH3)-0-CH2-
CH(CH3)]-, 4-0-CH2-CH2-CH2-CH2-ln-, -RCH2CO-cs-cizearyl-00-
0-(CH2)2-8-1n-, -RCI-12)2-8-0-CO-ce-c12-alkylene-00-0-(CH2)2-dri,
where n = 1 to 200;
sequences containing siloxane groups, of the type
01-04-alkyl C1-C4-alkyl, -(C1-018)-alkyl-O-Si-0-[Si-)14-0-(C1-C18)-
alkyl-, 01-C4-alkyl, C1-C4-alkyl
polyester sequences containing siloxane groups, of the type
-RA),--0-00-(B)s-00-0-(A)d-, in which
A = {(CH2)2_8-0-00-(C6_C14)-arylene-00-0-(CH2)2-8-} or
-{(CH2)2-8-0-00-(C2-C12)-alkylene-CO-0-(CH2)2-8-};
C1-C4-alkyl C1-C4-alkyl

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B = -{(C8-C14)-arylene-00-0-({Si-0-[Si-O]y-00-(C8-C14)-arylene-}
C1-C4-alkyl C1-C4-alkyl or
C1-C4-alkyl C1-C4-alkyl
{0-00-(G2-C12)-alkylene-00-0-({Si-O-pi-OVC0-(C2-C12)-alky1ene-00-1;
C1-C4-alkyl C1-C4-alkyl
r =1 to 70; s= 1 to 70 and y = 3 to 50;
polyether sequences containing siloxane groups, of the type
C1-C4-alkyl C1-C4-alkyl
-CH2-CHR2-0-({Si-0-[Si-O]-CHR2-CH2-
C1-C4-alkyl C1-C4-alkyl
where R2 = H; C1-C4-alkyl and y = 3 to 50;
sequences based on alkylene oxide adducts of melamine, of the
type of 2-amino-4,6-di-02-04-alkyleneamino-1,3,5-triazine sequences;
phenol ether sequences based on dihydric phenols and C2-C8 diols,
of the type of
-C2-C8-alkylene-0-(C6-C18)-arylene-0-(C2-C8)-alkylene- sequences;
in the oligotriazine ethers the molar ratio of the substituents R3R4
20:1 to 1:20,
the proportion of the linkages of the triazine segments through
bridge members -NH-CHR3-0-R4-0-CHR3-NH- is 5 to 95 mol%.
Triazines herein are aromatic nitrogen heterocycles of the empirical
formula C3H3N3 with three nitrogen atoms in a 6-membered ring. Triazine
segments herein are parts of a network described herein which are derived
from triazines.
The alcohol-etherified melamine-formaldehyde resins, as well as melamine
and formaldehyde, may contain further compounds influencing the
reactivity of the prepolymers and the molecular structure of the cured
polymers, and also up to 20% by mass of further reactive polymers
selected from the group consisting of ethylene copolymers,

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maleic anhydride copolymers, modified maleic anhydride copolymers,
poly(meth)acrylates, polyamides, polyesters and polyurethanes and/or up
to 20% by mass of aliphatic diols of the HO-R-OH type and also up to 2%
by mass of fillers, color pigments, stabilizers, UV absorbers and/or
auxiliaries.
Before being processed as a melt, the reactive, three-dimensionally
crosslinkable, nonlinear prepolymers are in the form of cylindrical,
lenticular, pastille-shaped or spherical particles having an average
diameter of 0.5 to 8 mm.
To spin the reactive, three-dimensionally crosslinkable, nonlinear
prepolymers they are melted at between 70 and 160 C and in particular
between 70 C and 130 C.
The diameter of the dies is 0.1 to 3 mm and preferably 0.5 to 1 mm.
Preferably, the dies are situated in or on the tips of cones and the hot air
flows along them at a high rate of speed. This makes it possible to elevate
the temperature of the meltblown air, which disintegrates the melts into
microfibers, far above the curing temperature of the reactive, three-
dimensionally crosslinkable, nonlinear prepolymers, which makes
particularly fine-denier fibers available without the dies becoming blocked.
It is further advantageous when the cones have an angle of 10 to 90 .
Preferably, the hot air has a temperature of 100 to 400 C preferably 180 to
300 C.
The microfibers laid down to form a web can be filaments or have a
diameter/length ratio of greater than 1:50. They have an average diameter
of 0.5 to 100 pm and preferably of 1 to 7 pm.

CA 02602171 2013-05-17
9
The microfibers are separated from the air stream by means of a wire grid or
braid
inserted into the air/microfiber stream, the wire grid or braid advantageously
taking the
form of an endless belt. At the same time, in the process, the unconsolidated
web
forms as a deposited random-laid ply.
Advantageously, the air of the air/microfiber stream is aspirated away
underneath the
wire grid/braid, causing the very loosely aggregated microfiber web which
forms to
undergo a first compaction.
The unconsolidated web can further be compacted to a desired degree by
mechanical
pressure or by forming.
The three-dimensional crosslinking is effected by a condensation reaction. The
condensation reaction is speeded (catalyzed) by, for example, gaseous HCI
and/or
gaseous HBr and/or gaseous formic acid neat or diluted with air or some other
inert
gas.
The sorption of the catalytically active components can advantageously induce
three-
dimensional crosslinking at temperatures below the microfiber melting point.
The thermal postcure, in which the microfibers in the web self-bond and/or
cure off, is
preferably carried out at temperatures of 60 to 320 C and more preferably at
250 to
280 C. It is advantageous in this connection when the temperature is gradually
raised
from 60 to 280 C and preferably from 80 to 280 C.
Example 1
A prepolymer prepared by reaction of melamine with formaldehyde and subsequent
etherification with methanol and polytetrahydrofuran Mn 250 and having a
viscosity of
53 Pa*s at 135 C is melted in a Randcastle extruder at a block temperature of
135 C
and the melt is forced through a heated die at 150 C which has a hole diameter
of

CA 02602171 2013-05-17
1 mm. The die is situated in the tip of a cone having an angle of 200. The
prepolymer
melt exiting from the die is attenuated into microfibers by hot air (190 C,
0.4 bar)
flowing along the die cone. The construction of the die used is depicted in
figure 1.
The meltblown fiber stream is steered onto a wire sieve situated above an
aspirating
5 system. The microfibers laid down on the wire sieve form a loose random-laid
web
(unconsolidated web) which is compacted by a roll. To induce the curing
reaction
(particularly a catalyzed one), a mixture of 25% HCI and 75% air is sucked
through the
web. The web is cured off by the action of hot air (raising the temperature).
The
temperature in the process is raised from 60 to 210 C over 30 minutes.
The fully cured microfibers forming the web have a length of 1 to 50 mm and a
diameter of 4 to 20 pm.
The web obtained has a basis weight of 34 g/m2 coupled with a thickness of 2
mm.
The structure of the web is documented in the scanning electron micrograph
figure 2.
In a modification of this embodiment, the temperature is raised from 60 to 280
C over
30 minutes. The web is dwelled at 280 C for a further 45 minutes.
Example 2
A prepolymer prepared by reaction of melamine with formaldehyde and subsequent
etherification with methanol and butanediol and having a viscosity of 15 Pa*s
at 135 C
is melted in a Randcastle extruder at a block temperature of 145 C and the
melt is
forced through a heated die at 150 C which has a hole diameter of 1 mm. The
die is
situated on or in the tip of a cone having an angle of 20 C. The prepolymer
melt exiting
from the die is attenuated into microfibers by hot air (280 C, 0.8 bar)
flowing along the
die cone. The construction of the die used is depicted in figure 1.
The meltblown fiber stream is steered onto a moving endless wire sieve
situated
above an aspirating system. The microfibers laid down on the wire sieve form a
stable

CA 02602171 2013-05-17
11
unconsolidated web which is compacted by a roll. To induce, in particular to
speed, the
curing reaction, a mixture of 75% HCI and 25% air is sucked through the
unconsolidated web.
__ The temperature is raised to start the condensation reaction. The methanol
released in
the course of the condensation reaction causes the microfibers to become
tacky. They
bond at their crossing points.
This creates a microfibrous web consolidated by self-bonding. The temperature
is
__ further raised from 800 to 200 C over 30 minutes.
In an alternative embodiment, further from 100 C to 250 C over a period of
30 minutes.
__ The fully cured microfibers forming the, in particular, consolidated web
obtained have
a length of 1 to 50 mm and a diameter of 1 to 7 pm. They, as depicted in
scanning
electron micrograph figure 3, are self-bonded at their crossing points.
The web obtained has an envelope density of 9 kg/m3
Example 3
A prepolymer prepared by reaction of melamine with formaldehyde and subsequent
etherification with methanol and butanediol and having a viscosity of 20 Pa*s
at 130 C
__ is melted in a Randcastle extruder at a block temperature of 135 C and the
melt is
forced through a heated die at 150 C which has a hole diameter of 0.5 mm. The
die is
situated in the tip of a cone having an angle of 20 C. The prepolymer melt
exiting from
the die is

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attenuated into microfibers by hot air (280 C, 0.8 bar) flowing along the die
cone.
The meltblown fiber stream is steered onto a moving endless wire sieve
above an aspirating system. The microfibers laid down on the wire sieve
__ form a stable unconsolidated web which is compacted by a roll. To speed
the curing reaction, a mixture of 0.2% HCI and 99.8% air is sucked through
the web.
Subsequently, further dry air is sucked through until HCI is no longer
detectable (determined using moist indicator paper).
__ Hot air is flowed through the unconsolidated web to raise the temperature
of the web. In the temperature range below the melting point of the
prepolymer, the prepolymer is rendered tacky by the methanol eliminated
in the course of the condensation reaction, and bonds at the crossing
points.
__ Hot air is further flowed through the web to further raise the temperature.
In
the process, the temperature is raised from 80 to 280 C over 30 minutes.
The methanol released by the condensation in the course of curing is
discharged together with residual HCI.
The fully cured microfibers forming the web have a length of 1 to 50 mm
__ and a diameter of 1 to 7 pm.
The web obtained has a decomposition point of 390 C, determined by
differential thermal gravimetry.
The web obtained has an envelope density of 9 kg/m3.
The web is subsequently if appropriate washed with water in a further
operation (temperature of wash water: 30 C). This raises the
decomposition point of the web, as determined by differential thermal
gravimetry, to 400 C.

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13
List of reference symbols for figure 1
1. Annular passage
2. MER melt
3. Meltblown air
4. Compressed air
5. Meltblown fiber stream

Representative Drawing