U.S. patent application number 13/331905 was filed with the patent office on 2012-06-21 for flame retardant cellulosic man-made fibers.
This patent application is currently assigned to LENZING AG. Invention is credited to Clemens BISJAK, Gert Kroner, Hartmut RUF.
Application Number | 20120156486 13/331905 |
Document ID | / |
Family ID | 45478011 |
Filed Date | 2012-06-21 |
United States Patent
Application |
20120156486 |
Kind Code |
A1 |
BISJAK; Clemens ; et
al. |
June 21, 2012 |
FLAME RETARDANT CELLULOSIC MAN-MADE FIBERS
Abstract
The invention relates to flame-retardant cellulosic man-made
fibers containing a flame-retardant substance in the form of an
oxidized condensate of a tetrakis hydroxyalkyl phosphonium salt
with ammonia and/or a nitrogenous compound which contains one or
several amine groups whereby the fiber has a tenacity of more than
18 cN/tex in a conditioned state. Production process and the use of
the fibers according to the invention are further objects of the
invention.
Inventors: |
BISJAK; Clemens; (Weyregg,
AT) ; Kroner; Gert; (Lenzing, AT) ; RUF;
Hartmut; (Schorfling, AT) |
Assignee: |
LENZING AG
Lenzing
AT
|
Family ID: |
45478011 |
Appl. No.: |
13/331905 |
Filed: |
December 20, 2011 |
Current U.S.
Class: |
428/375 |
Current CPC
Class: |
C09K 21/10 20130101;
D01F 2/06 20130101; D01D 5/06 20130101; C09K 21/12 20130101; Y10T
428/2933 20150115; D01F 2/08 20130101; D01F 2/00 20130101; Y10T
428/249921 20150401; D01D 5/26 20130101; Y10T 442/696 20150401;
D01F 2/02 20130101; D01F 1/07 20130101 |
Class at
Publication: |
428/375 |
International
Class: |
B32B 23/00 20060101
B32B023/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2010 |
AT |
A2096/2010 |
May 23, 2011 |
AT |
A742/2011 |
Claims
1. A flame-retardant cellulosic man-made fiber comprising a
flame-retardant substance in the form of an oxidized condensate of
a tetrakis hydroxyalkyl phosphonium salt with ammonia and/or a
nitrogenous compound which contains one or several groups of amine
groups, wherein the fiber has a strength of more than 18 cN/tex in
a conditioned state.
2. The flame-retardant cellulosic man-made fiber according to claim
1, wherein the nitrogenous compound is selected from the group
consisting of urea, ammonia, thiourea, biuret, melamine, ethylene
urea, guanidine and 2-cyanoguanidine.
3. The flame-retardant cellulosic man-made fiber according to claim
1, wherein the tetrakis hydroxyalkyl phosphonium salt is a tetrakis
hydroxymethyl phosphonium salt.
4. The flame-retardant cellulosic man-made fiber according to claim
1, wherein the fiber is a viscose or modal fiber.
5. The flame-retardant cellulosic man-made fiber according to claim
1, wherein the cellulosic man-made fiber is a cupro or carbamate
fiber.
6. The flame-retardant cellulosic man-made fiber according to claim
1, wherein the fiber is a lyocell fiber.
7. The flame-retardant cellulosic man-made fiber according to claim
1, wherein the share of flame-retardant substance in the cellulose
fiber is between 5-50 weight percent.
8. The flame-retardant cellulosic man-made fiber according to claim
1, wherein the fiber strength is from 18 cN/tex to 50 cN/tex.
9. The flame-retardant cellulosic man-made fiber according to claim
1, wherein the fiber comprises additives.
10. A process for the production of flame-retardant cellulosic
man-made fibers according to of claim 1 from a spinning mass
comprising the steps producing of a viscose of cellulose
xanthogenate adding a modification agent adding of 5 weight percent
to 50 weight percent of a flame-retardant agent in relation to the
cellulose in the form of a aqueous dispersion of the pigment
spinning of spinning mass through a spinneret into a spinning bath
stretching of precipitated filaments after-treating via washing,
bleaching, finishing cutting to staple fibers, and wherein for the
production of the fiber the pulp used has a R-18 content of 93-98%
the cellulose content of the viscose is between 4 and 7% the alkali
ratio is between 0.7 and 1.5 the carbon disulphide used equals 36
weight percent to 42 weight percent in relation to the cellulose
between 1 weight percent and 5 weight percent of a modifying agent,
in relation to the cellulose, is added to the viscose the spinning
gamma value of the viscose lies between 50 und 68, preferably
between 55 and 58 die spinning viscosity equals 50 to 120 falling
ball seconds the temperature of the spin bath is between 34 to
48.degree. C. the following spin bath concentrations are used
H.sub.2SO.sub.4 68-90 g/l Na.sub.2SO.sub.4 90-160 g/l ZnSO.sub.4
30-65 g/1 the final drawing-off from the spinning bath is performed
at a speed of between 15 und 60 m/min.
11. A process for the production of flame-retardant cellulosic
man-made fibers according to claim 1 according to the lyocell
process, wherein a flame-retardant substance is added prior to the
extrusion of the spinning mass and the share of flame-retardant
substance in the cellulose fiber is 5 weight percent to 50 weight
percent.
12. A process for the production of flame-retardant cellulosic
man-made fibers according to claim 1, wherein the flame-retardant
substance is washed with acid and finally with water before adding
to the spinning mass as such, respectively before producing a
dispersion thereof.
13. A yarn comprising a flame-retardant cellulosic man-made fiber
according to claim 1.
14. A textile material comprising a flame-retardant cellulosic
man-made fiber according to claim 1.
15. A textile material comprising a flame-retardant cellulosic
man-made fiber according to one of claim 1, wherein the textile
fabric respectively the non-woven fulfils the demands in accordance
with EN ISO 14 116 classification "limited flame spread index 3",
when testing according to EN ISO 15025:2002 Process B--edge
flaming.
16. A yarn or textile fabric comprising a flame-retardant
cellulosic man-made fiber according to one of claim 1, wherein the
flame-retardant cellulosic fiber is blended with fibers of a
natural or synthetic origin.
17. The yarn or textile fabric claim 16, wherein the blend
comprises fibers, which themselves are inherently flame-retardant
or treated with a flame-retardant agent.
18. The yarn or textile fabric according to claim 16, wherein the
flame-retardant cellulosic man-made fiber is present in a blend
with polyester, modacryl, para- and meta-Aramide, polyamidimide,
flame-retardant wool, polybenzimidazol, polyimide, polyamide,
polyamide, flame-retardant acrylic fibers, melamine fibers,
polyphenylene sulphide, polytetrafluorethylene, glass fibers,
cotton, silk, carbon fibers, oxidized thermally stabilized
polyacrylonitrile fibers and electrically conductive fibers and
blends of these fibers.
19. A yarn or textile fabric comprising a flame-retardant
cellulosic man-made fiber according to claim 1, wherein the
flame-retardant cellulosic man-made fiber is present in a blend
with meta- or para-polyaramide--respectively polyimide fibers.
20. A flame-retardant cellulosic man-made fiber according to claim
1, wherein the fiber comprises an oxidized condensate from a
tetrakis hydroxyalkyl phosphonium compound and a nitrogenous
compound, and wherein a molar ratio of tetrakis hydroxyalkyl
phosphonium compound to the nitrogen compound is in the range of 1:
(0.05 to 2.0).
21. The flame-retardant cellulosic man-made fiber according to
claim 20, wherein the nitrogenous compound is selected from the
group consisting of urea, ammonia, thiourea, biuret, melamine,
ethylene urea, guanidine and dicyandiamide.
22. The flame-retardant cellulosic man-made fiber according to
claim 20, wherein the nitrogenous compound is urea or ammonia.
23. The flame-retardant cellulosic man-made fiber according to
claim 20, wherein the hydroxyalkyl group of the tetrakis
hydroxyalkyl phosphonium compound is selected from the group
consisting of hydroxymethyl, hydroxyethyl, hydroxypropyl or
hydroxybutyl groups.
24. The flame-retardant cellulosic man-made fiber according to
claim 20, wherein the tetrakis hydroxyalkyl phosphonium compound is
a tetrakis hydroxymethyl phosphonium salt.
25. The flame-retardant cellulosic man-made fiber according to
claim 7, wherein the share of flame-retardant substance in the
cellulose fiber is between 10-30 weight percent.
26. The flame-retardant cellulosic man-made fiber according to
claim 7, wherein the share of flame-retardant substance in the
cellulose fiber is between 15-25 weight percent.
27. The flame-retardant cellulosic man-made fiber according to
claim 9, wherein the additives are selected from the group
consisting of color pigments or bactericides.
28. The process according to claim 11, wherein the share of
flame-retardant substance in the cellulose fiber is 10 weight
percent to 30 weight percent.
29. The process according to claim 11, wherein the share of
flame-retardant substance in the cellulose fiber is 15 weight
percent to 25 weight percent.
30. The textile material according to claim 15, 16, 17, 18 or 19
wherein the textile material is a non-woven material.
31. The flame-retardant cellulosic man-made fiber according to
claim 20, wherein the molar ratio of tetrakis hydroxyalkyl
phosphonium compound to the nitrogen compound is in the range of 1:
(0.5 to 1.5).
32. The flame-retardant cellulosic man-made fiber according to
claim 20, wherein the molar ratio of tetrakis hydroxyalkyl
phosphonium compound to the nitrogen compound is in the range of 1:
(0.65 to 1.2).
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The invention relates to cellulosic man-made fibers with
permanently flame-retardant properties whereby the flame-retardant
property is arrived at by adding an oxidized condensate of tetrakis
hydroxyalkyl phosphonium salt with ammonia and/or a compound
containing nitrogen which contains one or several amine groups, to
the spinning mass and/or the spinning solution and the fiber
reveals a strength (tensile strength) in the conditioned state of
more than 18 cN/tex.
[0002] The cellulosic man-made fibers can be viscose/modal, cupro,
or lyocell fibers. Lyocell fibers are defined by BISFA (The
International Bureau for the Standardization of Man-made Fibers) as
cellulosic man-made fibers which are spun from an organic solvent
without the derivatization of the cellulose (the direct spinning
process). This also means fibers which are spun from solutions of
cellulose in ionic liquids.
[0003] An overview of the methods used to render cellulosic
textiles flame-retardant and the mechanisms used for this is
supplied by the publication: Horrocks, A. R.; Kandola, B. K. "Flame
Retardant Cellulosic Textiles" Spec. Publ.--Royal Society of
Chemistry, volume 224, year 1998, pages 343-362. The methods
described differ in the element responsible for the
flame-retardation (mainly phosphorus, however, nitrogen, boron and
sulphur as well), the place of the application (surface treatment
mainly with cotton, additive in fiber production with man-made
fibers) and the permanency (degree of resistance of flame-retardant
properties after laundering treatments).
[0004] A large share of the permanently flame-retardant cellulosic
textiles is produced by finishing cotton fabrics with tetrakis
(hydroxymethyl)phosphonium derivatives (e.g. Proban.RTM. finish)
respectively with N-methylol dialkylphosphonopropionamides (e.g.
Pyrovatex CP.RTM.). The finished textiles do, however, have a very
hard hand.
[0005] Among the cellulosic man-made fibers, a large number of
substances were suggested as flame-retardant additives for viscose
fibers in fiber production.
[0006] In U.S. Pat. No. 3,266,918 Tris(2,3-bromopropyl)phosphate is
suggested as the flame-retardant agent. A fiber of this kind was
produced for some time on an industrial scale. Production was,
however, discontinued due to the toxicity of the flame-retardant
agent.
[0007] A class of substances used as a flame-retardant agent is
that of substituted phosphazenes. A flame-retardant viscose fiber
was produced at industrial level on the basis of these substances
(U.S. Pat. No. 3,455,713). The flame-retardant agent is however in
liquid form and can only be spun into viscose fibers with a lower
yield (approx. 75 weight percent) and it tends to migrate out of
the fiber thus giving the fiber an undesirable stickiness.
[0008] Similar compounds were described in patents but were never
tried for viscose fibers on an industrial scale (BP 1,521,404; U.S.
Pat. No. 2,909,446, U.S. Pat. No. 3,986,882; JP 50046920; DE
2,429,254; GB 1,464,545; U.S. Pat. No. 3,985,834; U.S. Pat. No.
4,083,833; U.S. Pat. No. 4,040,843; U.S. Pat. No. 4,111,701; U.S.
Pat. No. 3,990,900; U.S. Pat. No. 3,994,996; U.S. Pat. No.
3,845,167; U.S. Pat. No. 3,532,526; U.S. Pat. No. 3,505,087; U.S.
Pat. No. 3,957,927). All of these substances are in liquid form and
demonstrate the same disadvantages as in U.S. Pat. No.
3,455,713.
[0009] Apart from the above named Tris(2,3-bromopropyl)phosphate, a
series of other organophosphates respectively phosphonic acid
amides and esters were described as flame-retardant agents for
viscose fibers (DE 2,451,802; DE 2,622,569; U.S. Pat. No.
4,193,805; U.S. Pat. No. 4,242,138; JP 51-136914; DE
4,128,638).
[0010] Of this class of substances, until now only the compound
2,2'-oxybis[5,5-dimethyl-1,3,2-dioxaphosphorinane]2,2 fulfils the
requirements with regard to the effectiveness (the necessary amount
of incorporation in order to fulfill EN ISO 15025:2002),
quantitative yield in the spinning process and not containing
halogen.
[0011] Apart from the phosphorus compounds mentioned above,
flame-retardant viscose fibers were described which contain silicic
acid (EP 619,848; EP 1,753,900; EP 1,918,431). These fibers pass
the flame test described above, however, only with high contents of
silicic acid. Due to the high content of pigment which does not
contribute to the tenacity, the fibers do not attain the necessary
fiber tenacities required for textile applications.
[0012] In a series of patent applications, ways were described to
impart flame-retardant properties to cellulosic fibers, which are
produced according to the amine oxide-process. WO 93/12173
describes triazine compounds containing phosphorus as a
flame-retardant agent for plastic materials, in particular
polyurethane foam. Cellulose is mentioned in claim 18, spun from a
solution in a tertiary amine oxide, without citing an example with
regard to the actual suitability of the compounds as
flame-retardant agents for cellulose.
[0013] WO 94/26962 describes the addition of a tetrakis
hydroxymethyl phosphonium chloride (THPC)--urea--pre-condensate to
the wet fiber prior to drying, ammonia-treatment, condensation,
oxidation and drying after a second washing step. However,
condensation reactions at fiber level significantly impair the
fiber properties (embrittlement).
[0014] In WO 96/05356, lyocell fibers are treated with phosphoric
acid and urea and kept at 150.degree. C. for 45 minutes. This
process also damages the mechanical properties of the fibers to a
considerable extent.
[0015] EP 0 836 634 describes the incorporation of compounds
containing phosphorus as flame-retardant agents for regenerated
cellulose fibers, particularly lyocell fibers.
1,4-diisobutyl-2,3,5,6-tetrahydroxy-1,4-dioxophosphorinane is cited
as an example. The process has the disadvantage that the
incorporation yield of the flame-retardant agent only equals 90%
and thus problems occur in the closed solvent loops involved in the
lyocell process.
[0016] U.S. Pat. No. 6,893,492 and WO 2007/022552 describe clay
minerals (montmorillonite and/or hectorite) as an additive for
lyocell fibers. The flame-retardant effect of these additives does
not, however, suffice for textile products, which have to pass the
vertical flame test, according to EN ISO 15025:2002 process B--edge
flaming.
[0017] In the Korean patent application, Kongkae Taeho Kongbo
2009/025979, a flame-retardant agent containing phosphorus is
bonded to the cellulose via a silicon-oxygen group. This bond is,
however, sensitive to hydrolysis and so the product is not suitable
for washables.
[0018] None of the methods described for the lyocell process has
become important in technical terms. One important reason for this
is that the closed solvent loops in this process place special
demands on the yield when incorporating a solid or liquid additive
in the spinning mass. The recovery of solvent equals more than 99%.
Even small amounts of impurities which get into the spinning
bath/washing water build up in the closed solvent loops as a result
of the non quantitative yield of incorporation and lead to problems
when spinning and when reprocessing/cleaning the solvent.
[0019] No patent applications have been announced to date for
flame-retardant lyocell fibers, made from ionic liquids ("ionic
liquids". Likewise no patent applications are known for fibers
according to the cupro or carbamate process. According to BISFA,
cupro fibers are a separate fiber genre. In the following, fibers
according to the carbamate process are called carbamate fibers.
[0020] The use of tetrakis hydroxymethyl phosphonium chloride
(THPC)--urea--pre-condensates for the flame-retardant finishing of
in particular cotton, involving the process steps impregnation with
the precondensate--treatment with ammonia--condensation--oxidation
(e.g. the Proban.RTM.-process), is known.
[0021] The use of fully condensed products is described in U.S.
Pat. No. 3,645,936. According to the teaching of the patent, the
incorporation of an ammonia/tetrakis hydroxymethyl phosphonium
chloride-polymer (THPC/NH.sub.3-polymer) solely with the amount of
incorporation which is required to pass the flame test (20%), leads
to fibers of insufficient tenacity (1.08 g/den=approx. 9.7
cN/tex).
[0022] Surprisingly it has been found that flame-retardant
cellulosic man-made fibers possessing a higher tenacity can be
obtained by applying a flame-retardant substance as a
flame-retardant agent, which is based on a class of compounds known
from U.S. Pat. No. 3,645,936.
SUMMARY OF THE INVENTION
[0023] The flame-retardant cellulosic man-made fibers in accordance
with the invention contain a flame-retardant substance in the form
of an oxidized condensate from a tetrakis hydroxyalkyl phosphonium
salt with ammonia and/or a nitrogen-rich compound which contains
one or several amine groups, and are characterized in that the
fiber reveals a strength of more than 18 cN/tex in the conditioned
state.
[0024] The nitrogenous compound is preferably urea or ammonia.
[0025] The flame-retardant cellulosic man-made fibers in accordance
with the invention can be viscose fibers or modal fibers. Other
fibers according to the invention can be produced using the cupro
or carbamate process.
[0026] The production of viscose and modal fibers is generally
known. In this respect the addition of functional additives is
generally performed by means of adding an aqueous dispersion to the
spinning mass (viscose).
[0027] A process which involves the following steps is particularly
well suited [0028] production of a viscose from cellulose
xanthogenate [0029] by adding a modification agent [0030] addition
of 5 weight percent up to 50 weight percent in relation to the
cellulose of the flame-retardant substance in the form of an
aqueous dispersion of the pigment [0031] spinning of the spinning
mass though a spinneret into the spin bath [0032] stretching of the
precipitated filaments [0033] after-treatment after washing,
bleaching, finishing [0034] cutting to staple fibers,
[0035] and is characterized in that for the production of fiber
[0036] the pulp used has an R-18 content of 93-98% [0037] the
cellulose content of the viscose lies between 4 weight percent and
7 weight percent [0038] the alkali ratio lies between 0.7 and 1.5
[0039] the carbon disulphide input equals 36 weight percent to 42
weight percent in relation to the cellulose [0040] between 1 weight
percent and 5 weight percent of a modification agent is added in
relation to the cellulose [0041] the spinning gamma value of the
viscose lies between 50 and 68, preferably between 55 and 58 [0042]
the spinning viscosity equals 50 to 120 falling ball seconds [0043]
the temperature of the spinning bath equals 34.degree. C. to
48.degree. C.
[0044] the following spinning bath concentrations are used [0045]
H.sub.2SO.sub.4 68-90 g/l [0046] Na.sub.2SO.sub.4 90-160 g/l [0047]
ZnSO.sub.4 30-65 g/1 [0048] the final drawing off from the spinning
bath is performed at a speed of between 15 and 60 m/min.
[0049] Another flame-retardant cellulosic man-made fiber in
accordance with the invention is a lyocell fiber which is produced
using a direct spinning process, wherein the direct solvent for the
cellulose is preferably a tertiary amine oxide. N-methyl morpholine
oxide (NMMO), which is already being used at commercial level, is
particularly well suited as a direct solvent.
[0050] Likewise ionic liquids, such as those known from
DE102005062608, can be used as a direct solvent for cellulose.
DETAILED DESCRIPTION OF THE INVENTION
[0051] The production of lyocell fibers according to the amine
oxide process is performed in the following steps:
[0052] 1) Contacting the disintegrated pulp with an aqueous
N-methyl morpholine oxide (NMMO) solution.
[0053] 2) Evaporation of excess quantity of water when shearing
until a fiber-free spinning mass has formed.
[0054] 3) Extrusion of the spinning mass through spinnerets,
stretching in an air gap, precipitation of the cellulose in an
aqueous spinning bath containing NMMO, washing and drying.
[0055] As an alternative, the production of the spinning mass can
also be performed via the direct dissolution of the pulp in NMMO,
containing approx. 13% water (NMMO monohydrate) in e.g. an
extruder.
[0056] The addition of the flame-retardant agent can be performed
in powder form or as a dispersion in water or in aqueous NMMO in
step 1.
[0057] The flame-retardant agent can also be added to the spinning
mass in the form of a dispersion in NMMO, whereby the NMMO has a
water content of between 13 weight percent and 20 weight
percent.
[0058] As an alternative, the flame-retardant agent can be added in
powder form in an extruder.
[0059] The average particle size of the flame-retardant agent
should be clearly below half the fiber diameter, preferably under
10% of the fiber diameter.
[0060] A flame-retardant agent, which was subjected to an
additional purification step with diluted acid, has proven to be
particularly well suited to the lyocell process.
[0061] One highly suited process for the production of a
flame-retardant agent for use in cellulosic fibers comprises the
following steps:
[0062] (a) Reaction of at least one tetrakis hydroxyalkyl
phosphonium compound with at least one nitrogen compound, selected
from the group of urea, thiourea, biuret, melamine, ethylene urea,
guanidine and 2-cyanoguanidine, to obtain a polymer whereby the
molar ratio of the tetrakis hydroxymethyl phosphonium compound to
the nitrogen compound lies in the range of 1: (0.05 to 2.0),
preferably in the range of 1: (0.5 to 1.5) and most preferably in
the range of 1: (0.65 to 1.2),
[0063] (a') Cross-linking of the polymer obtained in process step
(a) with the help of ammonia and
[0064] (b) Oxidation of the phosphorus contained in the
cross-linked polymer as a result of adding an oxidation agent in
order to obtain the flame-retardant agent.
[0065] The first step of the production process (a) and/or the
steps (a) and (a') serves respectively serve to produce a polymer
by reacting the at least one tetrakis hydroxyalkyl phosphonium
compound with at least one nitrogen compound selected from the
group of ammonia, urea, thiourea, biuret, melamine, ethylene urea,
guanidine and 2-cyanoguanidine.
[0066] The hydroxyalkyl groups of the tetrakis hydroxyalkyl
phosphonium compounds are hydroxymethyl, hydroxyethyl,
hydroxypropyl or hydroxybutyl groups.
[0067] The at least one tetrakis hydroxyalkyl phosphonium compound,
preferably is a tetrakis hydroxymethyl phosphonium compound,
hereinafter also named "THP", with the general formula
(P.sup.+(CH.sub.2OH).sub.4).sub.tX.sup.-, or also the blends of
compounds of this kind whereby X.sup.- stands for an anion and t
for the valence of this anion. t can thereby stand for a whole
number of 1 or 2. For example sulphate, hydrogen sulphate,
phosphate, mono or dihydrogen phosphate, acetate or halogen anions,
such as fluoride, chloride and bromide, are suitable as anion
X.sup.-.
[0068] With the at least one nitrogen compound, which is reacted in
the process steps (a) and (a') with the tetrakis hydroxyalkyl
phosphonium compound, meant one compound, two compounds, three
compounds or several compounds selected from the group of ammonia,
urea, thiourea, biuret, melamine, ethylene urea, guanidine and
2-cyanoguanidine. In accordance with a preferred embodiment of the
invention, the nitrogen compound is urea. In accordance with one
particularly preferred embodiment of the invention, in process step
(a) at least one nitrogen compound, selected from the group urea,
thiourea, biuret, melamine, ethylene urea, guanidine and
2-cyanoguanidine is reacted and the resulting polycondensation
product is cross-linked with ammonia in a subsequent process step
(a').
[0069] The reaction (conversion) in process step (a) and as the
case may be also in process step (a'), is performed in a solvent in
accordance with one preferred embodiment of the invention. The
solvent preferably used is water. The content of the at least two
compounds to be converted in process step (a) respectively (a') can
vary across a wide range and in general it equals 10 weight percent
to 90 weight percent, preferably 20 weight percent to 40% weight
percent in relation to the overall mass of the reaction mixture
used in process step (a) respectively (a'), containing at least the
two compounds to be reacted and the solvent.
[0070] The molar ratio of the tetrakis hydroxyalkyl phosphonium
compound to the nitrogen compound can vary across a wide range and
generally lies in the range of 1: (0.05 to 2.0), preferably 1: (0.5
to 1.5), most preferably 1: (0.65 to 1.2). As a result of
deliberately selecting this molar ratio, it is ensured that the
flame-retardant agent produced in accordance with the invention
does not dissolve or only dissolves to a limited extent in the
solvents used for the production of flame-retardant cellulose
fibers.
[0071] The conversion in process step (a) and/or (a') is generally
preferred at a temperature in the range of 40 to 120.degree. C.,
preferably at a temperature in the range of 80 to 100.degree. C.
over a period of 1 to 10 hours and preferably over a period of 2 to
6 hours.
[0072] In accordance with a general embodiment of the invention,
following process step (a), one can cool the reaction mixture which
contains the polymer to room temperature, i.e. to a temperature in
the range of around 15 to 25.degree. C., and preferably to a
temperature of 20.degree. C., prior to further cross-linking of the
polymer in process step (a') with ammonia.
[0073] In accordance with a preferred embodiment of the invention,
one adds one or several dispersing agents to the polymer after
performing process step (a) and prior to performing process step
(a'), and thus prior to carrying out cross-linking using ammonia.
These dispersing agents are preferably selected from the group of
poly-vinylpyrrolidone, C.sub.14-C.sub.17-alkyl sulfonates,
hydroxylpropyl cellulose (HPC) and polyethylene glycol (PEG). The
dispersing agent thereby serves to stabilize the components in the
composition and prevents the agglomeration of polymers in the
subsequent cross-linking reaction in process step (a'). Typically
the at least one dispersion agent is in a concentration in the
range of 0.01 weight percent to 3 weight percent, preferably in the
range of 0.1 weight percent to 1 weight percent, in relation to the
reaction mixture.
[0074] If the production of the polymer is performed in two stages,
with process steps (a) and (a'), then ammonia is added in process
step (a') in a molar ratio to the tetrakis hydroxymethyl
phosphonium compound in the range of (1 to 4.0): 1, preferably in
the range of (1.2 to 3.5): 1, most preferably in the range of (1.5
to 2.0): 1. In this respect ammonia is added according to a
preferred embodiment of the invention, until the reaction mixture
reaches a pH-value in the range of 7 to 10, preferably in the range
of 8 to 9. In this way the polymer obtained in step (a) is
cross-linked by means of ammonia in process step (a') and a
precursor of the flame-retardant agent is obtained, which is
oxidized in the subsequent step, process step (b). The duration of
the conversion in process step (a') generally lies in the range of
1 min. to 60 min.
[0075] The oxidation in process step (b) can be done with the help
of the usual oxidation agents such as hydrogen peroxide, ammonium
persulphate, air (oxygen) and perchloric acid. The molar ratio
between the preliminary stage of the flame-retardant agent and the
oxidation agent is generally around 1:1 to 1:1.2.
[0076] The flame-retardant agent obtained in process step (b) is
washed with an acid in a subsequent process step (c) in accordance
with a preferred embodiment of the invention. In this respect the
flame-retardant agent can be pre-purified, using common methods
known to the specialist, for example by means of filtration. The
acid employed in process step (c) is generally selected from the
group of HCl, H.sub.2SO.sub.4, H.sub.3PO.sub.4 and acetic acid. The
acid is generally used in a concentration of around 1 to 75%,
preferably in a concentration of around 1 to 20%, most preferably
in a concentration of around 1 to 9%, diluted in a solvent selected
from the group of water, methanol, ethanol, N,N-dimethylformamide
(DMF) and N-methyl morpholine oxide (NMMO) or a mixture of these.
The solvent given preference for diluting the acid is water. The
quantity of acid used to wash the flame-retardant agent obtained in
process step (b), can vary across a wide range. In general, one
part by volume of acid per part by volume of flame-retardant agent
is used for washing. According to one preferred embodiment of the
invention two parts by volume are used and according to one
specially preferred embodiment of the invention, three parts by
volume of acid are used for washing.
[0077] The flame-retardant agent obtained in process step (b) can
subsequently be washed with an acid, as described before, and then
washed with a solvent one or several times whereby one to two parts
by volume of solvent, in relation to the volume of the
flame-retardant agent, are used. For washing a solvent is
preferably used which is selected from the group of water,
methanol, ethanol, N,N-dimethylformamide (DMF), N-Methyl morpholine
oxide (NMMO), or a mixture of these. Washing with water is
preferable.
[0078] The flame-retardant agent can now be subsequently separated
from the solvent used by means of a separation process, such as
filtration. In general the remaining content of solvent then equals
0 to 40 weight percent, preferably 0 to 20 weight percent and most
preferably 0 to 10 weight percent.
[0079] To improve the ability to be incorporated into fibers
respectively fiber materials, by way of example within the
framework of the lyocell or viscose process, it is of advantage to
grind the flame-retardant agent for example in a ball, sand, glass
pearl or a quartz pearl mill to an average particle size of 0.5 to
5 .mu.m, preferably 1 .mu.m. Grinding can either be done by means
of wet grinding or dry grinding.
Production example 1
Production of a Product with a Mol Ratio of Urea to Tetrakis
Hydroxylmethyl Phosphonium Sulphate (THPS) of 1 to 0.77
[0080] 66.2 kg of water, 10.5 kg of urea and 59.5 kg THPS (75%
volume percentage) are mixed and subsequently heated for a period
of 3 hours at 95 to 98.degree. C. whilst being stirred. The
reaction mixture is thereafter cooled down to a temperature below
30.degree. C., 2.1 kg of Duralkan.TM. TL 844 (PVP 25%) and 30 kg of
ammonia (25 volume percentage) are introduced. Using ammonia, the
pH-value is set at a value of around 8 and the reaction mixture is
allowed to react for 1 min. Following this, 21.3 kg of hydrogen
peroxide solution (30 volume percent) is introduced. The solid
contained (flame-retardant agent) is separated via a drum filter at
a temperature of 40.degree. C., and finally washed with a quantity
of water equivalent to the volume of the solid. A white product is
obtained with a solid matter content of 35 weight percent.
Production Example 2
Production of a Product with a Molar Ratio of Urea to THPS of 1 to
0.77
[0081] 68 kg of water, 10.5 kg of urea and 59.5 kg THPS (75 volume
percent) are mixed and subsequently stirred for a period of 5 hours
at a temperature of 95 to 98.degree. C. The reaction mixture is
then cooled down to a temperature below 30.degree. C., 0.5 kg
Hostapur.TM. SAS and 30 kg ammonia (25% volume percent) are
subsequently added. Using ammonia, the pH-value of the reaction
mixture is set at a value of 8 and the reaction mixture is left to
react for 1 min. Then 21.3 kg of hydrogen peroxide solution (30
volume percentage) is introduced. The solid contained
(flame-retardant agent) is separated at a temperature of 40.degree.
C. via a drum filter, washed with a quantity of water equivalent in
volume, then washed with a quantity of 3 volume percent
hydrochloric acid equivalent in volume and finally washed with a
quantity of water at least equivalent in volume. A white product is
obtained with a solid content of 35 weight percent.
[0082] The oxidized condensates which are produced in this way from
a tetrakis hydroxyalkyl phosphonium salt with a nitrogenous
compound are suitable as a flame-retardant agent in a cellulosic
molded body.
[0083] Urea or ammonia are preferred as the nitrogenous
compound.
[0084] The tetrakis hydroxyalkyl phosphonium compound is preferably
a tetrakis hydroxymethyl phosphonium salt.
[0085] The share of flame-retardant agent in the cellulosic
man-made fiber, in the form of a viscose or lyocell fiber, can be
between 5 weight percent and 50 weight percent, preferably between
10 weight percent and 30 weight percent, most preferably between 15
weight percent and 25 weight percent in relation to the fiber. When
the share is too low, the flame-retardant effect is insufficient,
with shares above this limit, the mechanical properties of the
fiber deteriorate excessively. A flame-retardant cellulosic
man-made fiber can be obtained with these shares which is
characterized by the fact that the tenacity in a conditioned state
equals from 18 cN/tex to 50 cN/tex.
[0086] In addition, the flame-retardant cellulosic man-made fiber
can contain additional additives, such as dyestuffs or
bactericides.
[0087] In the final product (textile fabric), the cellulosic
man-made fiber in accordance with the invention fulfils the
requirements according to EN ISO 14 116 (previously EN 533)
classification "limited flame spread index 3", when testing in
accordance with EN ISO 15025:2002 process B--edge flaming.
[0088] In the test procedure according to EN ISO 15025:2002, a
defined flame from a stipulated burner is directed at the surface
(process A) or the lower edge (process B) of vertically arranged
textile samples for 10 s. The spreading of the flame and the
afterglowing as well as the formation of particles dropping off and
burning particles dropping off, are to be recorded.
[0089] The requirements in EN ISO 14 116 for the "limited flame
index 3", are as follows: [0090] The flame is not allowed to reach
the upper edge on any of the test bodies [0091] None of the test
bodies should release burning particles [0092] The afterglow should
not spread from the carbonized part of the test body to the
undamaged part [0093] The subsequent burning time must be below two
seconds
[0094] A yarn can be spun from the fiber in accordance with the
invention which can be further processed to a textile fabric. The
fiber in accordance with the invention can also be used to produce
non-wovens.
[0095] The textile fabric resp. non-woven produced from the fiber
in accordance with the invention fulfilled the requirements of EN
ISO 14 116 classification "limited flame spread index 3", when
testing according to EN ISO 15025:2002 process B--edge flaming.
[0096] The yarn, textile fabric or nonwoven containing the
flame-retardant cellulosic man-made fiber in accordance with the
invention can be blended with fibers of natural or synthetic
origin. The fibers of natural or synthetic origin can be either
inherently flame-retardant or be finished in this way. Examples of
this are (flame-retardant) polyester, modacryl, para- and
meta-polyaramide, polyamide-imide (Kermel.RTM.), (flame-retardant)
wool, polybenzimidazol (PBI), polyimide (P84.RTM.), polyamide,
(flame-retardant) polyamide, flame-retardant acrylic fibers,
melamine fibers, polyphenylene sulphide (PPS),
polytetrafluorethylene (PTFE), glass fibers, cotton, silk, carbon
fibers, oxidized thermally stabilized polyacrylonitrile fibers
(PANOX.RTM.) and electrically conductive fibers and blends of these
fibers.
[0097] In particular para- and meta-polyaramide- and/or polyimide
fibers are particularly well suited for blending with the
flame-retardant man-made fibers according to the invention.
[0098] The applicational purpose of the fiber in accordance with
the invention or fiber blends containing the fiber in accordance
with the invention, is in all kinds of protective clothing such as
e.g. fireman uniforms, protective clothing against contact with
molten metals, underwear and uniform parts in the military sector,
textile materials in the public sector such as e.g. curtains and
seat covers, textiles in means of transportation such as e.g.
airline seats, flame-retardant outer and intermediate sheets (fire
blocker) consisting of a textile or non-woven material e.g. for
mattresses.
Example 1
[0099] A viscose with a composition of 6.0% cellulose/6.5% NaOH was
made from a beech pulp (R18=97.5%) using 40% CS.sub.2. To the
viscose with a spinning gamma value of 62 and a viscosity of 120
falling ball seconds, a modifying agent (2% dimethylamine and 1%
polyethylene glycol 2000, always in relation to cellulose) and 22%
in relation to cellulose of the flame-retardant agent according
Production example 1, in the form of a 12 weight percent dispersion
in 60 weight percent NMMO, were added. The modified viscose was
spun with 60 .mu.m spinnerets into a spinning bath with the
composition 72 g/l sulphuric acid, 120 g/l sodium sulphate and 60
g/l zinc sulphate with a temperature of 38.degree. C., stretched to
120% inside a second bath (water with 95.degree. C.) and finally
drawn off at 42 m/min. The after-treatment (hot diluted
H.sub.2SO.sub.4/water/desulphurizing/water/bleaching/water/finishing
agent) was performed according to well known methods.
[0100] The dried fibers were processed to a yarn of Nm 30 and these
were in turn processed to a knitted stocking with a mass per unit
area of 200 g/m.sup.2, using a circular knitting machine.
[0101] The knitted stocking was subjected to the vertical flame
test according to EN ISO 15025:2002 process B--edge flaming. The
results of the flame test are shown in Table 3 and the fiber data
in Table 1.
TABLE-US-00001 TABLE 1 Tensile strength Breaking elongation Fiber
thickness conditioned conditioned Example [dtex] [cN/tex[ [%[ 1
2.17 20.1 12.3
Example 2
[0102] 22% in relation to cellulose of the flame-retardant agent
according to production Example 1 in the form of a 12 weight
percent dispersion in 60 weight percent NMMO were added to the
slurry (mixture of pulp/aqueous NMMO) and water was evaporated to
yield a fiber-free spinning solution with the composition 12%
cellulose/77% NMMO/11% water. A sulphate-high alpha pulp was used
as pulp.
[0103] The spinning mass was spun to 2.2 dtex fibers, using the
well-known wet-dry spinning process with a spinning temperature of
110.degree. C. with the help of a 100 nm spinneret into a spinning
bath containing 25% NMMO with a temperature of 20.degree. C. The
washed and dried fibers were processed as described in Example 1 to
a knitted stocking and then subjected to the vertical flame test
according to EN ISO 15025:2002 process B--edge flaming. The results
of this flame test are shown in Table 3 and the fiber data are
shown in Table 2.
Example 3
[0104] The same procedure was followed as in Example 2, however, a
flame-retardant agent was used according to Production example 2.
The results of the flame test can be found in Table 3 and the fiber
data in Table 2.
TABLE-US-00002 TABLE 2 Yield Tensile Breaking Flame-retardant
strength elongation agent conditioned conditioned Example [%] of
input [cN/tex] [%] 2 95.1 34.1 13.4 3 99.3 34.3 11.6
TABLE-US-00003 TABLE 3 Burning behaviour according to EN ISO 15025:
2002 Phosphorus- After-burning Degree of content time destruction
Example [%] [s] [mm] 1 2.1 0 186 2 2.2 0 69 3 2.5 0 7
* * * * *