Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From aldehyde or derivative thereof as reactant
Patent
1997-10-09
1999-06-29
Truong, Duc
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From aldehyde or derivative thereof as reactant
528499, 528502A, 528503, 528163, 2641761, 521 65, 521187, C08G 1230
Patent
active
059169990
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for producing continuous 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 precondensate.
The production of fibers from MF condensation products was first described in DE-B-23 64 091. In this process, the aqueous solution of the precondensate is spun into a heated atmosphere in which, at one and the same time, the water evaporates and the precondensate cures. Since the curing process takes a comparatively long time, long piping is required downstream of the spinneret 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 alcohol. However, such polymers impair the flame resistance of the fibers and of textile materials produced therefrom.
EP-A-93 965 therefore proposes admixing MF precondensates (which may optionally contain N-alkyl-substituted melamines as cocondensed units) 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 precondensate at elevated temperature. The fibers obtained, however, have in consequence of their alkali metal salt content little hydrolysis 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 "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.
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 infusible fibers of high strength and good hydrolysis resistance at high spinning speed.
We have found that this object is achieved by the process of claim 1.
The process of the present invention starts from an MF precondensate. 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 preferably from 85 to 95, mol % of melamine and (b) from 1 to 70, preferably from 1 to 50, particularly preferably from 5 to 15, mol % 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 of moles of monomeric building blocks (a)+(b)+(c), of a phenol or of a mixture of phenols.
The condensation products of the present invention are obtainable by reacting components (a), (b) and optionally (c) with formaldehyde or formaldehyde-supplying compounds in a molar ratio of melamines+phenols to formaldehyde within the range from 1:1.15 to 1:4.5, preferably from 1:1.8 to 1:3.0.
Candidate substituted melamines (b) of the general formula I ##STR1## are those in which X, X' and X" are each selected from the group consisting of --NH.sub.2, --NHR and NRR', provided X, X' and X" are not all --NH.sub.2, and R and R' are each selected from the group consisting of hydroxy--C.sub.2 --C.sub.10 --alkyl, hydroxy--C.sub.2 --C.sub.4 --alkyl(oxa--C.sub.2 --C.sub.4 --alkyl).sub.n, where n is from 1 to 5, and amino--C.sub.2 --C.sub.12 --alkyl.
Preferred hydroxy--C.sub.2 --C.sub.10 --alkyl includes hydroxy--C.sub.2 --C.sub.6 --alkyl such as 2-hydroxyethyl, 3-hydroxy-n-propyl, 2-hydroxyisopropyl, 4-hydroxy-n-butyl, 5-hydroxy-n-pentyl, 6-hydroxy-n-hexyl, 3-hydroxy-2,2-dimethylpropyl, preferably hydroxy--C.sub.2 --C.sub.4 --alkyl such as 2-hydroxyethyl, 3-hydroxy-n-propyl, 2-hydroxyisopropyl and 4-hydroxy-n-butyl, particularly preferably 2-hydroxyethyl and 2-hydroxyisopropyl.
Preferred hydroxy--C.sub.2 --C.sub.4 --alk
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Berbner Heinz
Gihr Hartmut
Rachwalsky Uwe
Zettler Hans Dieter
BASF - Aktiengesellschaft
Truong Duc
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