Note: Descriptions are shown in the official language in which they were submitted.
'~ 0050/45800 CA 02216872 1997-10-20
Production of continuous filament fibers from melamine-formalde-
hyde condensation prodùcts
5 The present invention relates to a process for producing continu-
ous filament fibers from melamine-formaldehyde (MF) condensation
products by spinning a highly concentrated aqueous solution of
the MF precondensate, evaporating the water and curing the pre-
condensate.
The production of fibers from MF condensation products was first
described in DE-B-23 64 091. In this process, the aqueou~ solu-
tion of the precondensate is spun into a heated atmosphere in
which, at one and the same time, the water evaporates and the
15 precondensate cures. Since the curing process takes a compara-
tively long time, long piping is required downstream of the spin-
neret if nontacky fibers are to be obtained. In addition, this
process gives adequate spinning speeds only if the MF condensate
is admixed with fiber-forming polymers, for example polyvinyl al-
20 cohol. However, such polymers impair the flame resistance of thefibers and of textile materials produced therefrom.
EP-A-93 965 therefore proposes a~ ing MF precondensates (which
may optionally contain N-alkyl-substituted melamines as cocon-
25 densed unit~) with from 1 to 20~ by weight of alkali metal salts,preferably sodium metabisulfite, spinning the solution into a
heated atmosphere, evaporating the water and curing the precon-
densate at elevated temperature. The fibers obtained, however,
have in consequence of their alkali metal salt content little hy-
30 drolysis resistance.
EP-A-221 330, 408 947 and 523 485 describe hydroxyalkylmelamine-
modified MF condensates which can likewise be spun into fibers.
Suitable spinning processes are said to be on the one hand the
35 "dry reaction spinning process" of DE-A-23 64 091 and, on the
other, a centrifugal spinning process. However, the latter does
not afford continous filament fibers, but only comparatively
short fibers of nonuniform length.
40 It is an object of the present invention to provide a technically
simple process for producing thin continuous filament fibers from
MF condensation products which affords incombustible and infus-
ible fibers of high strength and good hydrolysis resistance at
high spinning speed.
0~50/45800 CA 02216872 1997-10-20
We have found that this object is achieved by the process of
claim 1.
The process of the present invention starts from an MF preconden-
5 sate. This MF precondensate comprises as a monomeric building
block from 90 to 99.9 mol% of a mixture consisting essentially of
(a) from 30 to 99, preferably from 50 to 99, particularly prefer-
ably from 85 to 95, mol% of melamine and (b) from 1 to 70, pre-
ferably from 1 to 50, particularly preferably from 5 to 15, mol%
10 of a substituted melamine I, or mixtures of substituted melamines
I.
A preferred MF precondensate comprises as further monomeric
building block (c) from 0.1 to 10 mol%, based on the total number
15 of moles of monomeric building block~ (a) + (b) + (c), of a phe-
nol or of a mixture of phenols.
The condensation products of the present invention are obtainable
by reacting components (a), (b) and optionally (c) with formalde-
20 hyde or formaldehyde-supplying compounds in a molar ratio of me-
lamines + phenols to formaldehyde within the range from 1:1.15 to
1:4.5, preferably from 1:1.8 to 1:3Ø
Candidate substituted melamines (b) of the general formula I
X
N ~ N
X~ ~
' N X''
are those in which X, X' and X'' are each selected from the group
consisting of -NH2, -NHR and NRR', provided X, X~ and X'~ are not
all -NH2, and R and R' are each selected from the group consisting
35 of hydroxy-C2-C1o-alkyl, hydroxy-Ca-C4-alkyl-
(oxa-C2-C4-alkyl)n, where n is from 1 to 5, and amino-C2-C12-alkyl.
Preferred hydroxy-C2-C10-alkyl includes hydroxy-C2-C6-alkyl such
as 2-hydroxyethyl, 3-hydroxy-n-propyl, 2-hydroxyisopropyl,
40 4-hydroxy-n-butyl, 5-hydroxy-n-pentyl, 6-hydroxy-n-hexyl,
3-hydroxy-2,2-dimethylpropyl, preferably hydroxy-c2-cg-alkyl such
as 2-hydroxyethyl, 3-hydroxy-n-propyl, 2-hydroxyisopropyl and
4-hydroxy-n-butyl, particularly preferably 2-hydroxyethyl and
2-hydroxyisopropyl.
0050/45800 CA 02216872 1997-10-20
Preferred hydroxy-c2-c~-alkyl(oxa-c2-cg-alkyl)n groups are those
with n from 1 to 4, preferably those with n = 1 or 2, such as
5-hydroxy-3-oxapentyl, 5-hydroxy-3-oxa-2,5-dimethylpentyl, 5-hy-
droxy-3-oxa-1,4-dimethylpentyl, 5-hydroxy-3-oxa-1,2,4,5-
5 tetramethylpentyl, 8-hydroxy-3,6-dioxaoctyl.
Amino-C2-C12_alkyl is preferably amino-C2-Cg-alkyl such as
2-aminoethyl, 3-aminopropyl, 4-aminobutyl, 5-aminopentyl,
6-aminohexyl, 7-aminoheptyl and also 8-aminooctyl, particularly
10 preferably 2-aminoethyl and 6-aminohexyl, very particularly pre-
ferably 6-aminohexyl.
Substituted melamines particularly suitable for the purposes of
the present invention are the following compounds:
15 2-hydroxyethylaminomelamine such as 2-hydroxyethylaminomelamine,
2,4-di(2-hydroxyethylamino)melamine, 2,4,6-Tris(2-hydroxy-
ethylamino)melamine, 2-hydroxyisopropylaminomelamine such as
2-(2-hydroxyisopropylamino)melamine, 2,4-di(2-hydroxyisopropyl-
amino)melamine, 2,4,6-Tris(2-hydroxyisopropylamino)melamine,
ao 5-hydroxy-3-oxapentylaminomelamine such as 2-(5-hydroxy-3-oxa-
pentylamino)melamine, 2,4-di(5-hydroxy-3-oxa-pentyl-
amino)melamine, 2,4,6-Tris(5-hydroxy-3-oxapentylamino)melamine
and also 6-aminohexylaminomelamine such as 2-(6-aminohexylamino-
pentylamino)melamine, 2,4-di(6-aminohexylamino)melamine,
25 2,4,6-Tris(6-aminohexylamino)melamine or mixtures thereof, for
example a mixture of 10 mol-% of 2-(5-hydroxy-3-oxapentyl-
amino)melamine, 50 mol-% 2,4-di(5-hydroxy-3-oxapentyl-
amino)melamine and 40 mol-% of 2,4,6-Tris(5-hydroxy-3-oxa-
pentylamino)melamine.
Suitable phenols (c) include phenols with one or two hydroxyl
groups, such as unsubstituted phenols, phenols substituted by
radicals selected from the group consisting of Cl-Cg-alkyl and hy-
droxyl, and also Cl-C4-alkanes substituted by two or three phenol
35 groups, di(hydroxyphenyl) sulfones, and mixtures thereof.
Preferred phenols include phenol, 4-methylphenol, 4-tert-butyl-
phenol, 4-n-octylphenol, 4-n-nonylphenol, pyrocatechol, resorci-
nol, hydroquinone, 2,2-bis(4-hydroxyphenyl)propane, 4,4'-dihy-
40 droxydiphenyl sulfone, particularly preferably phenol, resorcinoland 2,2-bis(4-hydroxyphenyl)propane.
Formaldehyde is typically used in the form of an aqueous solution
having a concentration of, for example, from 40 to 50% by weight
45 or in the form of compounds that supply formaldehyde in the
course of the reaction with (a) and (b), for example as
CA 022l6872 l997-l0-20
0050/45800
oligomeric or polymeric formaldehyde in solid form, such as para-
formaldehyde, l,3,5-trioxane or 1,3,5,7-tetroxocane.
A preferred MF precondensate is produced using from 1 to 50, pre-
5 ferably 5 to 15, in particular from 7 to 12, mol% of the substi-
tuted melamine and also from 0.1 to 9.5, preferably from 1 to 5,
mol% of one of the above-recited phenols or mixtures thereof.
The precondensate is produced by polycondensing melamine, substi-
10 tuted melamine and phenol together with formaldehyde or a formal-
dehyde-supplying compound, either by having all components pres-
ent from the start or adding them portionwise and gradually to
the reaction and subse~uently adding further melamine, substi-
tuted melamine or phenol to the precondensates formed.
The polycondensation is typically carried out in a conventional
manner (see EP-A-355 760, Houben Weyl, Vol. 14/2, p. 357 ff).
The reaction temperatures used are generally within the range
20 from 20 to 150 c, preferably from 40 to 140 C.
The reaction pressure is typically uncritical. In general, the
pressure employed is within the range from 100 to 500 kPa, pre-
ferably from 100 to 300 kPa.
as
The reaction can be carried out with or without solvent. Typical-
ly, no solvent is added when aqueous formaldehyde solution is
used. If formaldehyde bound in solid form is used, water is used
as solvent, and the amount used is typically within the range
30 from 5 to 40, preferably from 15 to 25, % by weight based on the
total amount of monomer used.
Furthermore, the polycondensation is generally carried out within
a pH range above 7. Preference is given to the pH range from 7.5
35 to 10.0, particularly preferably from 8 to lO.
Moreover, the reaction mixture may contain small amounts of cus-
tomary additives, for example amines and also aminoalcohols such
as diethylamine, ethanolamine, diethanolamine or 2-diethylamino-
40 ethanol.
Suitable further additives include fillers, for example metalpowders, metal salts or silicates, for example kaolin, talc, ba-
ryte, quartz or chalk, and also pigments and dyes.
0050/45800 CA 022l6872 l997-l0-20
The polycondensation can be carried out batchwise or continuous-
ly, for example in a stirred tank or in an extruder (see EP-
A-355 760).
5 In an advantageous embodiment, first a precondensate solution is
prepared in a continuous extruder or kneader and then passed into
a heatable stirred tank where it is devolatilized at low viscos-
ity and then further condensed to viscosities of 2000-50,000 Pas,
preferably 3000-10,000 Pas. However, it is also possible to carry
10 out all the steps of mixing, condensing and devolatilizing in an
extruder. It is further possible to prepare the solution com-
pletely in a batchwise stirred tank.
The process of the present invention is then carried out in the
15 following successive steps:
A. First the aqueous solution of the precondensate with a water
content of from 5 to 40, preferably from 10 to 25, % by
weight is filtered, removing coarse particles and impurities.
This can be done using a depth filter, for example.
B The aqueous solution is then forced by means of a pump
through a spinneret. This spinneret has from 500 to 5000
holes which each have a diameter from 40 to 400, especially
from 50 to 200, ~m. Individual holes are preferably arranged
in the form of a ring on a rectangular plate. The pressure
drop in the spinneret in the case of hole diameters of
100 ~m, for example, is about 50 bar.
30 C. The individual filaments emerging from the spinneret are
bathed for from 0.5 to 60 sec in dry air in a drying shaft.
The air is passed cocurrently to the emerging filaments and
it has a temperature within the range from 20 to 200 C, pre-
ferably from 50 to 150 C. This measure preferably removes
from 10 to 90% of the water present in the filaments, so that
their residual water content is less than 10, preferably less
than 5, % by weight.
In a preferred embodiment of the present invention, from 0.1
to 3% by weight, based on the precondensate, of a curing cat-
alyst are introduced into the drying shaft together with the ,
air. Preferred curing catalysts include organic acids, for
example formic acid, acetic acid, sulfamic acid and amino
acids.
0050/45800 CA 022l6872 l997-l0-20
On emerging from the drying cell the filament bundle can be
drawn off by means of godets, twisted by means of a twisting
nozzle through sideways blowing with air, laid down as a con-
tinuous filament material, or cut directly to a certain sta-
ple length. This is the point at which, if desired, surfaceauxiliaries, for example antistick agents and silicone oils,
can be added.
D. The dried filaments are then treated for from 10 to 200, pre-
ferably from 40 to 90, min in a tempering oven. It is essen-
tial that the temperature in this oven gradually increase.
This can be achieved for example by successive temperature
zones in the oven. In this way the oven can be kept compara-
tively short. If desired, a further catalyst can be added to
the warm circulating air. The r~xi lm temperature should be
from 160 to 250 C, preferably from 200 to 230 C. The precon-
densate i6 fully cured, so that nontacky continuous filament
fibers are obtained.
20 E. These continuous filament fibers are finally wound up or cut.
The take-off speed can be varied within wide limits. It is
customarily within the range from 200 to 250 m.min~1.
The continuous filament fibers produced according to the present
25 invention can be processed into incombustible and infusible wo-
vens and nonwovens.
The drawing shows a preferred embodiment of the present inven-
tion, the reference numerals of which are explained in the Exam-
30 ple which follows.
Example:
The resin is prepared without bubbles in a stirred tank (1). The
35 water content at the start of the reaction is 18%. The viscosityof the resin to be spun is about 9000 Pas/25 C.
The resin is conveyed by a pump (2) and filtered with the aid of
depth filters (3) made of metal and forced by means of a further
40 pump (4) through the spinneret orifices (6). The spinneret has
900 holes 100 ~m in diameter. The throughput of resin per hole is
6 g/h.
0050/45800 CA 022l6872 l997-l0-20
In the drying shaft (5) the fibers (8) are dried within 1.5 s by
an air stream (7) with an air inlet temperature of 95 C and an air
outlet temperature of about 125 C. The take-off speed is 200 m/
min.
The fibers are laid down as continuous filament material, tem-
pered in a drying cabinet (9) in four temperature stages
(100 C/130 C/160 C/220 C) each 20 min in length, and finally wound
up at (10).
The individual fiber has a diameter of 17 ~m, a tenacity of
2.8 cN/dtex and a breaking exten~ion of 32%.
