U.S. patent application number 11/909300 was filed with the patent office on 2008-08-28 for method for producing duroplastic fine-fiber non-wovens having a high flame-retardant, thermal protective and sound insulating effect.
This patent application is currently assigned to AMI AGROLINZ MELAMINE INTERNATIONAL GBMH. Invention is credited to Hartmut Bucka, Bernd Riedel.
Application Number | 20080203602 11/909300 |
Document ID | / |
Family ID | 36381443 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080203602 |
Kind Code |
A1 |
Riedel; Bernd ; et
al. |
August 28, 2008 |
Method for Producing Duroplastic Fine-Fiber Non-Wovens Having a
High Flame-Retardant, Thermal Protective and Sound Insulating
Effect
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.
Inventors: |
Riedel; Bernd;
(Unterwellenborn, DE) ; Bucka; Hartmut;
(Eggendorf, AT) |
Correspondence
Address: |
WORKMAN NYDEGGER
60 EAST SOUTH TEMPLE, 1000 EAGLE GATE TOWER
SALT LAKE CITY
UT
84111
US
|
Assignee: |
AMI AGROLINZ MELAMINE INTERNATIONAL
GBMH
Linz
AT
|
Family ID: |
36381443 |
Appl. No.: |
11/909300 |
Filed: |
March 21, 2006 |
PCT Filed: |
March 21, 2006 |
PCT NO: |
PCT/EP2006/002597 |
371 Date: |
December 20, 2007 |
Current U.S.
Class: |
264/103 |
Current CPC
Class: |
D01D 5/0985 20130101;
D04H 3/02 20130101; D04H 3/03 20130101; C08G 12/42 20130101; D04H
1/56 20130101; D04H 1/4326 20130101; C08G 12/32 20130101; D01F 6/74
20130101 |
Class at
Publication: |
264/103 |
International
Class: |
D04C 1/00 20060101
D04C001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 21, 2005 |
DE |
10 2005 013 420.3 |
Claims
1. A process for producing thermoset microfibrous webs, comprising:
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, wherein reactive, nonlinear
prepolymers three-dimensionally crosslinkable by a condensation
reaction are pressed through dies situated in the tip of cones.
3. The process according to claim 2, wherein 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
tips of the die cones.
4. The process according to claim 2, wherein the microfibers are
separated from the air stream and are deposited as an
unconsolidated web (random-laid ply).
5. The process according to claim 4, wherein the unconsolidated web
is subsequently compacted.
6. The process according to claim 4, wherein 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 claim 4, wherein 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 fibers or if appropriate neutralized with a
basic gas.
8. The process according to claim 4, wherein 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, wherein 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 wherein the web is dwelled at
high temperatures.
11. The process according to claim 1, wherein the reactive
crosslinkable, nonlinear prepolymers consist of alcohol-etherified
melamine-formaldehyde resins.
12. The process according to claim 11, wherein the
alcohol-etherified melamine-formaldehyde resins consist of meltable
4- to 18-nucleus oligotriazine ethers in which the triazine
segments contain ##STR00005## R.sub.1=--NH.sub.2,
--NH--CHR.sub.2--O--R.sub.3, --NH--CHR.sub.2--O--R.sub.4--OH,
--CH.sub.3, --C.sub.3H.sub.7, --C.sub.6H.sub.5--OH, phthalimido-,
succinimido-, --NH--CO-.sub.C5-C18-alkyl,
--NH--C.sub.5-C.sub.18-alkylene-OH ##STR00006##
--NH--CHR.sub.2--O--R.sub.4--O--CHR.sub.2--NH--,
--NH--CHR.sub.2--NH--,
--NH--CHR.sub.2--O--C.sub.5-C.sub.18-alkylene-NH--,
--NH--C.sub.5-C.sub.18-alkylene-NH--,
--NH--CHR.sub.2--O--CHR.sub.2--NH--, R.sub.2.dbd.H,
C.sub.1-C.sub.7-alkyl; R.sub.3=C.sub.1-C.sub.18-alkyl, H;
R.sub.4=C.sub.2-C.sub.18-alkylene,
--[CH.sub.2--CH.sub.2--O--CH.sub.2--CH.sub.2].sub.n--,
--[CH.sub.2--CH(CH.sub.3)--O--CH.sub.2--CH(CH.sub.3)].sub.n--,
--[--O--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2--].sub.n--,
--[(CH.sub.2).sub.2-8--O--CO-.sub.C6-C12-aryl-CO--O--(CH.sub.2).sub.2-8---
].sub.n--,
--[(CH.sub.2).sub.2-8--O--CO-.sub.C6-C12-alkylene-CO--O--(CH.su-
b.2).sub.2-8-].sub.n--, where n=1 to 200; sequences containing
siloxane groups, of the type C.sub.1-C.sub.4-alkyl
C.sub.1-C.sub.4-alkyl,
--(C.sub.1-C.sub.18)-alkyl-O--Si--O--[Si--].sub.1-4--O--(C.sub.1-C.sub.18-
)-alkyl-, C.sub.1-C.sub.4-alkyl, C.sub.1-C.sub.4-alkyl polyester
sequences containing siloxane groups, of the type
-[(A).sub.r-O--CO--(B).sub.s--CO--O-(A).sub.r]-, in which
A={(CH.sub.2).sub.2-8--O--CO--(C.sub.6-C.sub.14)-arylene-CO--O--(CH.sub.2-
).sub.2-8--} or
--{(CH.sub.2).sub.2-8--O--CO--(C.sub.2-C.sub.12)-alkylene-CO--O--(CH.sub.-
2).sub.2-8--}; C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl
B=--{(C.sub.6-C.sub.14)-arylene-CO--O---({Si--O--[Si--O].sub.y--CO--(C.su-
b.6-C.sub.14)-arylene-} C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl
or C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl
{O--CO--(C.sub.2-C.sub.12)-alkylene-CO--O--({Si--O--[Si--O],
--CO--(C.sub.2-C.sub.12)-alkylene-CO--}; C.sub.1-C.sub.4-alkyl
C.sub.1-C.sub.4-alkyl r=1 to 70; s=1 to 70 and y=3 to 50; polyether
sequences containing siloxane groups, of the type
C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl
--CH.sub.2--CHR.sub.2--O--({Si--O--[Si--O].sub.y--CHR.sub.2--CH.sub.2--
C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl where R.sub.2.dbd.H;
C.sub.1-C.sub.4-alkyl and y=3 to 50; sequences based on alkylene
oxide adducts of melamine, of the type of
2-amino-4,6-di-.sub.C2-C4-alkyleneamino-1,3,5-triazine sequences;
phenol ether sequences based on dihydric phenols and
C.sub.2-C.sub.8 diols, of the type of
--C.sub.2-C.sub.8-alkylene-O--(C.sub.6-C.sub.18)-arylene-O--(C.sub.2-C.su-
b.8)-alkylene-sequences; are linked by bridge members
--NH--CHR.sub.2--O--R.sub.4--O--CHR.sub.2--NH-- and
--NH--CHR.sub.2--NH-- and also, where appropriate,
--NH--CHR.sub.2--O--CHR.sub.2--NH--,
--NH--CHR.sub.2--O--C.sub.5-C.sub.18-alkylene-NH-- and/or
--NH--C.sub.5-C.sub.18-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 ##STR00007##
Y=--NH--CHR.sub.2--O--R.sub.3, --NH--CHR.sub.2--O--R.sub.4--OH and
also if appropriate --NH--
CHR.sub.2--O--C.sub.5-C.sub.18-alkylene-NH.sub.2,
--NH--C.sub.5-C.sub.18-alkylene-NH.sub.2,
--NH--C.sub.5-C.sub.18-alkylene-OH, R.sub.1=--NH.sub.2,
--NH--CHR.sub.2--O--R.sub.3, --NH--CHR.sub.2--O--R.sub.4--OH,
--CH.sub.3, --C.sub.3H.sub.7, --C.sub.6H.sub.5, --OH, phthalimido-,
succinimido-, --NH--CO--R.sub.3,
--NH--C.sub.5-C.sub.18-alkylene-OH,
--NH--C.sub.5-C.sub.18-alkylene-NH.sub.2, ##STR00008## R.sub.2=H,
C.sub.1-C.sub.7-alkyl; R.sub.3=C.sub.1-C.sub.18-alkyl, H;
R.sub.4=C.sub.2-C.sub.18-alkylene,
--[CH.sub.2--CH.sub.2--O--CH.sub.2--CH.sub.2].sub.n--,-[CH.sub.2--CH(CH.s-
ub.3)--O--CH.sub.2--CH(CH.sub.3)].sub.n--,
--[--O--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2--].sub.n--,
--[(CH.sub.2).sub.2-8--O--CO-.sub.c6-c12-aryl-CO--O--(CH.sub.2).sub.2-8-]-
.sub.n--,
--[(CH.sub.2).sub.2-8--O--CO-.sub.c6-c12-alkylene-CO--O--(CH.sub-
.2).sub.2-8--].sub.n--, where n=1 to 200; sequences containing
siloxane groups, of the type C.sub.1-C.sub.4-alkyl
C.sub.1-C.sub.4-alkyl,
--(C.sub.1-C.sub.18)-alkyl-O--Si--O--[Si--].sub.1-4--O--(C.sub.1-C.sub.18-
)-alkyl-, C.sub.1-C.sub.4-alkyl, C.sub.1-C.sub.4-alkyl polyester
sequences containing siloxane groups, of the type
-[(A).sub.r-O--CO--(B).sub.s--CO--O-(A).sub.r]-, in which
A={(CH.sub.2).sub.2-8--O--CO--(C.sub.6-C.sub.14)-arylene-CO--O--(CH.sub.2-
).sub.2-8--} or
--{(CH.sub.2).sub.2-8--O--CO--(C.sub.2-C.sub.12)-alkylene-CO--O--(CH.sub.-
2).sub.2-8--}; C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl
B=--{(C.sub.6-C.sub.14)-arylene-CO--O--({Si--O--[Si--O].sub.y--CO--(C.sub-
.6-C.sub.14)-arylene-} C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl
or C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl
{O--CO--(C.sub.2-C.sub.12)-alkylene-CO--O--({Si--O--[Si--O],
--CO--(C.sub.2-C.sub.12)-alkylene-CO--}; C.sub.1-C.sub.4-alkyl
C.sub.1-C.sub.4-alkyl r=1 to 70; s=1 to 70 and y=3 to 50; polyether
sequences containing siloxane groups, of the type
C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl
--CH.sub.2--CHR.sub.2--O--({Si--O--[Si--O].sub.y--CHR.sub.2--CH.sub.2--
--C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl where R.sub.2.dbd.H;
C.sub.1-C.sub.4-alkyl and y=3 to 50; sequences based on alkylene
oxide adducts of melamine, of the type of
2-amino-4,6-di-.sub.C2-C4-alkyleneamino-1,3,5-triazine sequences;
phenol ether sequences based on dihydric phenols and
C.sub.2-Cdiolsa, of the type of
--C.sub.2-C.sub.8-alkylene-O--(C.sub.6-C.sub.18)-arylene-O--(C.su-
b.2-C.sub.8)-alkylene-sequences; in the oligotriazine ethers the
molar ratio of the substituents R.sub.3:R.sub.4=20:1 to 1:20, the
proportion of the linkages of the triazine segments through bridge
members --NH--CHR.sub.3--O--R.sub.4--O--CHR.sub.3--NH-- is 5 to 95
mol %.
13. The process according to claim 11 wherein 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 claim 1, wherein 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 claim 1, wherein 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. The process according to at least one of the
aforementioned claims, 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.
16. The process according to claim 1, wherein the reactive,
three-dimensionally crosslinkable, nonlinear prepolymers are melted
at about 70.degree. C. to 130.degree. C. for spinning.
17. The process according to claim 1, wherein the dies have a
diameter of 0.1 to 3 mm.
18. The process according to claim 17, wherein the dies have a
diameter of 0.5 to 1 mm.
19. The process according to claim 1, wherein 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, wherein the cones have an
angle of 10 to 90.degree..
21. The process according to claim 1, wherein the hot air, in
particular the hot air flowing along the tips of the die cones at a
high rate of speed, has a temperature of 150.degree. C. to
400.degree. C.
22. The process according to claim 21, wherein the hot air, in
particular the hot air flowing along the tips of the die cones at a
high rate of speed, has a temperature of 180.degree. C. to
300.degree. C.
23. The process according to claim 1, wherein the resulting fibers,
in particular microfibers, are filaments or have a diameter/length
ratio of greater than 1:50.
24. The process according to claim 1, wherein the microfibers have
an average diameter of 0.5 to 100 .mu.m.
25. The process according to claim 24, wherein the microfibers have
an average diameter of 1 to 7 .mu.m.
26. The process according to claim 1, wherein the fibers have a
disordered, small-scale crimped structure.
27. The process according to claim 1, wherein 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, wherein the wire grid or
braid is in the form of an endless belt.
29. The process according to claim 27 wherein the air of the
air/microfiber stream is aspirated away underneath the wire grid or
braid.
30. The process according to claim 1, wherein the web is compacted
to the desired density by mechanical pressure or by forming.
31. The process according to claim 1, wherein a three-dimensional
crosslinking is induced or starts at temperatures below the
microfiber melting point.
32. The process according to claim 1, wherein the component
inducing the three-dimensional crosslinking, in particular the
component catalyzing the condensation reaction, is gaseous HCl
and/or gaseous HBr and/or formic acid neat or diluted with air or
some other inert gas.
33. The process according to claim 32, wherein the microfibers in
which the catalyzing components are sorbed self-bond in the
temperature range between 100 and 120.degree. C.
34. The process according to claim 1, wherein the thermal postcure
of the web is effected by incremental or continuous heating with
hot air and at the same time, the methanol released is discharged
together with detached HCI and/or HBr.
35. The process according to claim 34, wherein the thermal postcure
of the web is effected in the temperature range from 200.degree. C.
to 320.degree. C. and preferably in the temperature range from
250.degree. C. to 280.degree. C. and the postcure time is between
15 min and 120 min and preferably between 20 min and 60 min.
36. The process according to claim 35, wherein the web is washed
with water after the postcure.
Description
[0001] This invention relates to a process for producing thermoset
microfibrous webs.
[0002] 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.
[0003] It is particularly advantageous to deposit an unconsolidated
web also known as a random-laid ply of loosely aggregated
fibers.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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 it is necessary first to form the
continuous filaments, then cut these into fibers and finally
consolidate these fibers into a fabric.
[0009] It is an object of the present invention 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.
[0010] We have found that this object is achieved when melts of
reactive, three-dimensionally crosslinkable, nonlinear 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 are deposited to form a web consisting of a microfibrous
braid. The web is subsequently compacted, treated with a medium
inducing a three-dimensional crosslinking and in a subsequent
thermal postcure the microfibers are self-bonded and/or cured
off.
[0011] It is particularly advantageous when the microfibers are
separated from the air stream and are deposited as an
unconsolidated web (random-laid ply).
[0012] 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 of the present invention converts 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.
[0013] 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.
[0014] It is further surprising that the microfibers produced can
also be in the form of continuous filaments.
[0015] 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.
[0016] 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
##STR00001## [0017] R.sub.1=--NH.sub.2,
--NH--CHR.sub.2--O--R.sub.3, --NH--CHR.sub.2--O--R.sub.4--OH,
--CH.sub.3, --C.sub.3H.sub.7, --C.sub.6H.sub.5, --OH, phthalimido-,
[0018] succinimido-, --NH--CO-.sub.C5-C18-alkyl,
--NH--C.sub.5-C.sub.18-alkylene-OH
[0018] ##STR00002## [0019]
--NH--CHR.sub.2--O--R.sub.4--O--CHR.sub.2--NH--,
--NH--CHR.sub.2--NH--,
--NH--CHR.sub.2--O--C.sub.5-C.sub.18-alkylene-NH--, [0020]
--NH--C.sub.5-C.sub.18-alkylene-NH--,
--NH--CHR.sub.2--O--CHR.sub.2--NH--, [0021] R.sub.2.dbd.H,
C.sub.1-C.sub.7-alkyl; [0022] R.sub.3.dbd.C.sub.1-C.sub.18-alkyl,
H; [0023] R.sub.4=C.sub.2-C.sub.18alkylene,
--[CH.sub.2--CH.sub.2--O--CH.sub.2--CH.sub.2].sub.n--,
--[CH.sub.2--CH(CH.sub.3)--O--CH.sub.2--CH(CH.sub.3)].sub.n--,
[0024] --[--O--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2--].sub.n--,
[0025]
--[(CH.sub.2).sub.2-8--O--CO-.sub.C6-C12-aryl-CO--O--(CH.sub.2).sub.2-8---
].sub.n--, [0026]
--[(CH.sub.2).sub.2-8--O--CO-.sub.C6-C12-alkylene-CO--O--(CH.sub.2).sub.2-
-8--].sub.n--, [0027] where n=1 to 200; [0028] sequences containing
siloxane groups, of the type [0029] C.sub.1-C.sub.4-alkyl
C.sub.1-C.sub.4-alkyl,
--(C.sub.1-C.sub.18)-alkyl-O--Si--O--[Si--].sub.1-4--O--(C.sub.1-C.sub.18-
)-alkyl-, C.sub.1-C.sub.4-alkyl, C.sub.1-C.sub.4-alkyl [0030]
polyester sequences containing siloxane groups, of the type [0031]
--[(A).sub.r-O--CO--(B).sub.s--CO--O-(A).sub.r]--, in which [0032]
A={(CH.sub.2).sub.2-8--O--CO--(C.sub.6-C.sub.14)-arylene-CO--O--(CH.sub.2-
).sub.2-8--} or [0033]
--{(CH.sub.2).sub.2-8--O--CO--(C.sub.2-C.sub.12)-alkylene-CO--O--(CH.sub.-
2).sub.2-8--}; [0034] C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl
[0035]
B=--{(C.sub.6-C.sub.14)-arylene-CO--O--({Si--O--[Si--O].sub.y--CO--(C.sub-
.6-C.sub.14)-arylene-} [0036] C.sub.1-C.sub.4-alkyl
C.sub.1-C.sub.4-alkyl or [0037] C.sub.1-C.sub.4-alkyl
C.sub.1-C.sub.4-alkyl [0038]
{O--CO--(C.sub.2-C.sub.12)-alkylene-CO--O--({Si--O--[Si--O].sub.Z--CO--(C-
.sub.2-C.sub.12)-alkylene-CO--}; [0039] C.sub.1-C.sub.4-alkyl
C.sub.1-C.sub.4-alkyl [0040] r=1 to 70; s=1 to 70 and y=3 to 50;
[0041] polyether sequences containing siloxane groups, of the type
[0042] C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl [0043]
--CH.sub.2--CHR.sub.2--O--({Si--O--[Si--O].sub.y--CHR.sub.2--CH.sub.2--
[0044] C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl [0045] where
R.sub.2.dbd.H; C.sub.1-C.sub.4-alkyl and y=3 to 50; [0046]
sequences based on alkylene oxide adducts of melamine, of the type
of 2-amino-4,6-di-.sub.C2-C4-alkyleneamino-1,3,5-triazine
sequences; [0047] phenol ether sequences based on dihydric phenols
and C.sub.2-C.sub.8 diols, of the type of
--C.sub.2-C.sub.8-alkylene-O--(C.sub.6-C.sub.18)-arylene-O--(C.sub.2-C.su-
b.8)-alkylene-sequences; [0048] are linked by bridge members
--NH--CHR.sub.2--O--R.sub.4--O--CHR.sub.2--NH-- and
--NH--CHR.sub.2--NH-- and also, where appropriate,
--NH--CHR.sub.2--O--CHR.sub.2--NH--,
--NH--CHR.sub.2--O--C.sub.5-C.sub.18-alkylene-NH-- and/or
--NH--C.sub.5-C.sub.18-alkylene-NH-- to form 4- to 18-nucleus
oligotriazine ethers of linear and/or branched structure, [0049]
the terminal triazine segments in the oligotriazine ethers forming
triazine segments of the structure
[0049] ##STR00003## [0050] Y=--NH--CHR.sub.2--O--R.sub.3,
--NH--CHR.sub.2--O--R.sub.4--OH and also if appropriate [0051]
--NH--CHR.sub.2--O--C.sub.5-C.sub.18-alkylene-NH.sub.2, [0052]
--NH--C.sub.5-C.sub.18-alkylene-NH.sub.2,
--NH--C.sub.5-C.sub.18-alkylene-OH, [0053] R.sub.1=--NH.sub.2,
--NH--CHR.sub.2--O--R.sub.3, --NH--CHR.sub.2--O--R.sub.4--OH,
--CH.sub.3, --C.sub.3H.sub.7, [0054] --C.sub.6H.sub.5, --OH,
phthalimido-, [0055] succinimido, --NH--CO--R.sub.3,
--NH--C.sub.5-C.sub.18-alkylene-OH,
--NH--C.sub.5-C.sub.18-alkylene-NH.sub.2,
[0055] ##STR00004## [0056] R.sub.2=H, C.sub.1-C.sub.7-alkyl; [0057]
R.sub.3=C.sub.1-C.sub.18-alkyl, H; [0058]
R.sub.4=C.sub.2-C.sub.18-alkene,
--[CH.sub.2--CH.sub.2--O--CH.sub.2--CH.sub.2].sub.n--,
--[CH.sub.2--CH(CH.sub.3)--O--CH.sub.2--CH(CH.sub.3)].sub.n--,
--[--O--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2--].sub.n--,
--[(CH.sub.2).sub.2-8--O--CO.sub.C6-C12-aryl-CO--O--(CH.sub.2).sub.2-8--]-
.sub.n--,
--[(CH.sub.2).sub.2-8--O--CO-.sub.C6-C12-alkene-CO--O--(CH.sub.2-
).sub.2-8--].sub.n--, [0059] where n=1 to 200; [0060] sequences
containing siloxane groups, of the type [0061]
C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl,
--(C.sub.1-C.sub.18)-alkyl-O--Si--O--[Si--].sub.1-4--O--(C.sub.1-C.sub.18-
)-alkyl-, C.sub.1-C.sub.4-alkyl, C.sub.1-C.sub.4-alkyl [0062]
polyester sequences containing siloxane groups, of the type [0063]
-[(A).sub.r-O--CO--(B).sub.S--CO--O-(A).sub.r]--, in which [0064]
A={(CH.sub.2).sub.2-8--O--CO--(C.sub.6-C.sub.14)-arylene-CO--O--(CH.sub.2-
).sub.2-8-} or [0065]
--{(CH.sub.2).sub.2-8--O--CO--(C.sub.2-C.sub.12)-alkylene-CO--O--(CH.sub.-
2).sub.2-8-}; [0066] C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl
[0067]
B=--{(C.sub.6-C.sub.14)-arylene-CO--O--({Si--O--[Si--O].sub.y--CO--(C.sub-
.6-C.sub.14)-arylene-} [0068] C.sub.1-C.sub.4-alkyl
C.sub.1-C.sub.4-alkyl or [0069] C.sub.1-C.sub.4-alkyl
C.sub.1-C.sub.4-alkyl [0070]
{O--CO--(C.sub.2-C.sub.12)-alkene-CO--O--({Si--O--[Si--O].sub.z--CO--(C.s-
ub.2-C.sub.12)-alkylene-CO--}; [0071] C.sub.1-C.sub.4-alkyl
C.sub.1-C.sub.4-alkyl [0072] r=1 to 70; s=1 to 70 and y=3 to 50;
[0073] polyether sequences containing siloxane groups, of the type
[0074] C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl [0075]
--CH.sub.2--CHR.sub.2--O--({Si--O--[Si--O].sub.y--CHR.sub.2--CH.sub.2--
[0076] C.sub.1-C.sub.4-alkyl C.sub.1-C.sub.4-alkyl [0077] where
R.sub.2=H; C.sub.1-C.sub.4-alkyl and y=3 to 50; [0078] sequences
based on alkylene oxide adducts of melamine, of the type of
2-amino-4,6-di-.sub.C2-C4-alkyleneamino-1,3,5-triazine sequences;
[0079] phenol ether sequences based on dihydric phenols and
C.sub.2-C.sub.8 diols, of the type of
--C.sub.2-C.sub.8-alkylene-O--(C.sub.6-C.sub.18)-arylene-O--(C.sub.2-C.su-
b.8)-alkylene-sequences; [0080] in the oligotriazine ethers the
molar ratio of the substituents R.sub.3:R.sub.4=20:1 to 1:20,
[0081] the proportion of the linkages of the triazine segments
through bridge members
--NH--CHR.sub.3--O--R.sub.4--O--CHR.sub.3--NH-- is 5 to 95 mol
%.
[0082] Triazines herein are aromatic nitrogen heterocycles of the
empirical formula C.sub.3H.sub.3N.sub.3 with three nitrogen atoms
in a 6-membered ring. Triazine segments herein are parts of a
network described herein which are derived from triazines.
[0083] 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, 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.
[0084] 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.
[0085] To spin the reactive, three-dimensionally crosslinkable,
nonlinear prepolymers they are melted at between 70 and 160.degree.
C. and in particular between 70.degree. C. and 130.degree. C.
[0086] The diameter of the dies is 0.1 to 3 mm and preferably 0.5
to 1 mm.
[0087] 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.
[0088] It is further advantageous when the cones have an angle of
10 to 90.degree..
[0089] Preferably, the hot air has a temperature of 100 to
400.degree. C. preferably 180 to 300.degree. C.
[0090] 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 .mu.m and preferably of 1 to 7
.mu.m.
[0091] 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.
[0092] 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.
[0093] The unconsolidated web can further be compacted to a desired
degree by mechanical pressure or by forming.
[0094] The three-dimensional crosslinking is effected by a
condensation reaction. The condensation reaction is speeded
(catalyzed) by, for example, gaseous HCl and/or gaseous HBr and/or
gaseous formic acid neat or diluted with air or some other inert
gas.
[0095] The sorption of the catalytically active components can
advantageously induce three-dimensional crosslinking at
temperatures below the microfiber melting point.
[0096] 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.degree. C. and more preferably at 250 to
280.degree. C. It is advantageous in this connection when the
temperature is gradually raised from 60 to 280.degree. C. and
preferably from 80 to 280.degree. C.
EXAMPLE 1
[0097] 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.degree. C. is melted in a Rand Castel extruder at a block
temperature of 135.degree. C. and the melt is forced through a
heated die at 150.degree. C. which has a hole diameter of 1 mm. The
die is situated in the tip of a cone having an angle of 20.degree.
C. The prepolymer melt exiting from the die is attenuated into
microfibers by hot air (190.degree. C., 0.4 bar) flowing along the
die cone. The construction of the die used is depicted in FIG.
1.
[0098] The meltblown fiber stream is steered onto a wire sieve
situated above an aspirating 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% HCl 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.degree. C. over 30 minutes.
[0099] The fully cured microfibers forming the web have a length of
1 to 50 mm and a diameter of 4 to 20 .mu.m.
[0100] The web obtained has a basis weight of 34 g/m.sup.2 coupled
with a thickness of 2 mm. The structure of the web is documented in
the scanning electron micrograph FIG. 2.
[0101] In a modification of this embodiment, the temperature is
raised from 60 to 280.degree. C. over 30 minutes. The web is
dwelled at 280.degree. C. for a further 45 minutes.
EXAMPLE 2
[0102] 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.degree. C. is
melted in a Rand Castel extruder at a block temperature of
145.degree. C. and the melt is forced through a heated die at
150.degree. 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.degree.
C. The prepolymer melt exiting from the die is attenuated into
microfibers by hot air (280.degree. C., 0.8 bar) flowing along the
die cone. The construction of the die used is depicted in FIG.
1.
[0103] 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 unconsolidated web which
is compacted by a roll. To induce, in particular to speed, the
curing reaction, a mixture of 75% HCl and 25% air is sucked through
the unconsolidated web.
[0104] 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.
[0105] This creates a microfibrous web consolidated by
self-bonding. The temperature is further raised from 80.degree. to
200.degree. C. over 30 minutes.
[0106] In an alternative embodiment, further from 100.degree. C. to
250.degree. C. over a period of 30 minutes.
[0107] 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 .mu.m. They, as depicted in scanning electron
micrograph FIG. 3, are self-bonded at their crossing points.
[0108] The web obtained has an envelope density of 9 kg/m.sup.3
EXAMPLE 3
[0109] 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.degree. C. is
melted in a Rand Castel extruder at a block temperature of
135.degree. C. and the melt is forced through a heated die at
150.degree. 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.degree. C. The
prepolymer melt exiting from the die is attenuated into microfibers
by hot air (280.degree. C., 0.8 bar) flowing along the die
cone.
[0110] 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% HCl and
99.8% air is sucked through the web.
[0111] Subsequently, further dry air is sucked through until HCl is
no longer detectable (determined using moist indicator paper).
[0112] 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.
[0113] Hot air is further flowed through the web to further raise
the temperature. In the process, the temperature is raised from 80
to 280.degree. C. over 30 minutes. The methanol released by the
condensation in the course of curing is discharged together with
residual HCl.
[0114] The fully cured microfibers forming the web have a length of
1 to 50 mm and a diameter of 1 to 7 .mu.m.
[0115] The web obtained has a decomposition point of 390.degree.
C., determined by differential thermal gravimetry.
[0116] The web obtained has an envelope density of 9
kg/m.sup.3.
[0117] The web is subsequently if appropriate washed with water in
a further operation (temperature of wash water: 30.degree. C.).
This raises the decomposition point of the web, as determined by
differential thermal gravimetry, to 400.degree. C.
LIST OF REFERENCE SYMBOLS FOR FIG. 1
[0118] Annular passage [0119] MER melt [0120] Meltblown air [0121]
Compressed air [0122] Meltblown fiber stream
* * * * *