Note: Descriptions are shown in the official language in which they were submitted.
203~9~
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TREATMENT OF FABRIC8
This invention relates to a fabric treatment process, in
particular one rendering fabrics flame retardant with organo
phosphorus compounds.
The flame retardant treatment of cotton fabric with tetra kis
(hydroxymethyl) phosphonium compounds (hereafter called THP
compounds) or precondensates thereof with urea has been described in
USP2983623, 4068026, 4078101, 4145463 and 4494951. The treatment
processes involved impregnation of the fabric with an aqueous solution
of the chemicals, followed by drying, treatment with ammonia to cure
the phosphorus compounds in order to insolubilize the phosphorus onto
the fabric, finally with oxidation and washing to leave a treated
fabric whose flame resistance is retained even after many washes in
use.
However the cure efficiency which is a measure of the
effectiveness of the cure in insolubilizing the phosphorus on the
fabric, is not always ideal and a percentage of the expensive
phosphorus chemicals applied in the impregnation step is not cured and
is washed off the fabric after the cure and wasted. The cure
efficiency for cotton fabrics is higher than for cotton polyester
fabrics and especially polyester cotton fabrics and in some cases
adequate fire retardant properties cannot be provided to the latter
with THP compounds. Furthermore, while some techniques enable the
necessary fire retardant properties to be provided to the fabric when
first cured, those properties often diminish significantly on repeated
washing.
We have discovered a process which can increase the amount of P
compound fixed on the substrate especially ones comprising non
cellulosic fibres, and can enable adequate fire retardant properties
to be provided for fabrics comprising non cellulosic fibres such as
cotton polyester blends.
~ ~ . ~, . . . . ....
- 2 - 203~ ~ 2~
The present invention provides a process for the flame retardant
treatment of an organic fibrous substrate containing reactive groups,
which process comprises impregnating said substrate with a nitrogen
containing polymer (or precursor therefor) and with an aqueous
solution of an organophosphorus compound, to provide an impregnated
substrate which is dried and cured, to give a cured substrate.
The nitrogen containing polymer may be applied to the substrate
at the same time as the organophosphorus compound, but preferably the
polymer or precursor is applied in a first step to give a first
impregnated substrate and then the organophosphorus compound is
applied in a second step. The first impregnated substrate is usually
maintained to allow the polymer to interact with the substrate before
the second step.
The nitrogen containing polymer is preferably free of P atoms and
may be capable of reaction with cellulose on heating eg at 150C. It
is preferably a polyelectrolyte containing a plurality of N atoms
(especially in tertiary or quaternary form), which may interrupt a
carbon polymeric chain, but preferably are in groups pendant from a
hydrocarbon polymeric chain. The hydrocarbon polymer backbone is
preferably made of structural units derived from mono or di
ethylenically unsaturated compounds containing one or more N atoms.
Examples of mono ethylenically unsaturated compounds are vinyl
compounds with a heterocyclic N ring, (such as N- vinyl pyridine,
N-vinylpyrrolidine, N-vinyl pyrrolidone and their C-ring alkyl
derivatives), and also acrylic and methacrylic compounds with amide or
amine groups such as acrylamide, methacrylamide, ammonium acrylate and
methacrylate, and their mono, di, tri or tetra N-alkyl derivatives,
especially those in which the alkyl group contains 1-6 carbon atoms
(such as methyl or ethyl). The polymer may be a homo or copolymer of
monomers, each of which contains the N atom or atoms, or may be a
copolymer with other N- free ethylenically unsaturated monomers such
as acrylic or methacrylic acid or corresponding esters, eg with
alkanols of 1-6 carbon atoms.
~03~
- 3 -
The weight proportion of N containing monomers to N-free monomers
is usually 50-100:50-0 ~eg 70-90:30-10), but especially 80-100:20-0,
such as 80-95:20-5. Examples of the di ethylenically unsaturated
compounds are di allyl amines, especially quaternized di allylamine
(such as N,N -dialkyl-N, N-diallyl ammonium halides), in which each
alkyl group contains 1-6 carbon atoms such as ethyl, isopropyl, propyl
or butyl but especially methyl. Examples of copolymers are those of
acrylic acid and acrylamide, and acrylamide and dialkyl diallyl
ammonium chlcride. Polymeric dialkyl diallyl ammoniu~ chlorides may
be made as described in USP 3472740, the disclosure of which is hereby
incorporated by reference. Otherwise the polymers from ethylenically
unsaturated compounds may be made by conventional means, such as free
radical polymerization, especially in aqueous solution or aqueous
emulsion.
The nitrogen containing polymer may also contain the N atom in
the polymeric backbone and may be made by polymerization involving a
ring opening operation (such as the known polymerization of ethylene
imine to give polyethylene imine).
The average molecular weight of the nitrogen containing polymer
is usually 10000 - 5 million eg (100000 - 3 million), and it is water
soluble, (eg with a solubility in water at 20C of at least 10g/1) or
water dispersible.
Other nitrogen containing polymers which may be used are water
soluble or water dispersible ones made by condensation polymerization
and capable of further condensation with cellulose, such as
polyamines, polyamides and polyamine/polyamide epichlorohydrin
reaction products.
A precursor capable of forming the nitrogen containing polymer on
heating may be used, in particular a monomer which can be polymerized
to form the polymer, eg in situ in the fabric during a drying or dwell
time either after one~or after two step impregnation or between
impregnations in/a two step impregnation (as herein before described),
or especially during any heat cure.
203~
- 4 -
Particularly useful monomers are di ethylenically unsaturatedcompounds, such as the di allylamine salts mentioned above. The
monomer may also react with the substrate or the organophosphorus
compound rather than polymerizing to polymer which itself interacts.
The precursor is preferably added in a first step separate from the
organophosphorus treatment.
The organic fibrous substrate is especially one comprising or
consisting essentially of cellulosic fibres. The cellulosic fibres
are preferably natural cotton, but may be ramie, flax, paper or
cardboard or regenerated fibres (e.g. viscose or cuprammonium fibres)
or partly etherified or esterified cellulose (e.g. cellulose acetate
or propionate). The substrate may be substantially completely
cellulosic eg 100% cotton or may contain both cellulosic and non
cellulosic organic fibres, or just contain non cellulosic organic
fibres eg 100% polyester fibres. Inorganic fibres such as glass
fibres are usually absent.
The non cellulosic fibres are preferably polyester or polyamide
fibres but may also be acrylic. The polyamide may be an aliphatic
one, such as copolymers of a polyamine (such as a diamine) preferably
an alkylene diamine, eg of 4-12 carbon atoms and a poly carboxylic
acid eg a dicarboxylic acid, of 4-14 carbon atoms such as an alkylene
dicarboxylic acid (e.g. Nylon 66), or polylactams such as Nylon 6.
Alternatively the polyamide may be an aromatic one, such as aramids
based on aromatic dicarboxylic acids and phenylene diamines. The
acrylic polymer may be polyacrylonitrile homopolymer or copolymer with
vinyl chloride, as in modacrylic fibres. The substrate can contain at
least 20% of cellulosic fibres and up to 80% of coblendable fibres
e.g. 10-80% especially 25-80% of coblendable fibres such as
polyamides. However preferably the substrate comprises cellulosic
fibres and polyester fibres. The substrate usually contains up to 80%
(e.g up to 70%) polyester fibres and from 20% (e.g. from 30%) upwards
of cellulosic fibres, e.g. 1-80% or 1-70%, such as 15-70% particularly
22-38% or 45-75% polyester fibres and 20-99% or 30-99% (such as
30-85%), particularly 62-78% or 25-55% cellulosic fibres.
2039624
- 5 -
Substrates comprising at least 45% non cellulosic fibres, eg
polyester fibres such as 45-100% polyester, are preferred as are ones
comprising 30-78% cellulosic fibres and 22-70% polyester fibres, or
30-62% cellulosic fibres and 38-70% polyester fibres. The polyester
is usually a condensation product containing structural units from an
aliphatic alcohol, e.g. dihydric alcohol, especially ethylene glycol
or butane diol (or mixtures thereof) and an aromatic dicarboxylic
acid~ e.g. terephthalic acid, or a mixture thereof with other
dicarboxylic acids, such as isophthalic acid, or sebacic acid.
!~ If desired, the fibrous substrate may be one of the above noncellulosic ones having groups capable of interaction with the cationic
compound. Thus the substrate may be a polyester, with the cationic
polymer interacting with hydroxyl groups, or a polyamide with the
-cationic polymer interacting with carboxyl or a polyacrylonitrile,
with interaction of the cationic polymer with nitrile groups. The
polyester may be described above, while the polyamide may be a
reaction product of a polyamine, e.g. a diamine, e.g. 4-12 carbons,
with a polyarboxylic acid, e.g. a dicarboxylic acid of 4-14 carbon
atoms. The polyacrylonitrile may be a homopolymer or copolymer with
vinyl chloride as in modacrylic fibres.
The substrate fibres may be in the form of thread or non woven
fabric, but are preferably as woven fabric. Mixtures of fibres e.g.
of cellulosic and other fibres may be an intimate or non intimate
mixture, but the fibres are preferably in the form of blend of
cellulosic fibres and the other fibres, e.g. polyester fibres, as in
cospun blends such as cotton polyester or polyester cotton staple
fibre, but may be in the form of core spun yarn with a core of the
other fibre, e.g. polyester sheathed in cotton fibres. In a fabric,
the warp and weft fibres are preferably the same, but may be
different, e.g. one may be from cotton fibres and the other from e.g.
polyester cotton fibres. Thus in this specification the term "blend"
also includes unions and union/blends as well as core sheath fibres.
The substrate is preferably a fabric with a weight of 0.05-1.0kg/m2
(e.g. 0.150-0.40kg/m2) or 0.05-0.20kg/m2, such as polyester cotton
shirting or sheeting or curtain fabric.
6 2039~2~
The nitrogen containing polymer (or precursor) is usually applied
in aqueous solution or dispersion, e.g. of 0.1-30% (such as 0.2-15%),
especially 0.5-4% w/w and at pH 2-9 eg. 2-4. The weight of nitrogen
containing polymer (or precursor) applied is usually 0.01-20% (e.g.
0.1-10%), especially 0.5-5% based on the weight of the untreated
fabric. The nitrogen containing polymer (or precursor) may be
impregnated into the fabric with a wet pick up of 50-150% and then,
after initial drying if desired (e.g. with the impregnated fabric
heated at 80-100c for 0.1-5 minutes), the impregnated fabric is then
treated by heating at 90-150C (e.g. 90-130C) for 0.5-10 minutes
(e.g. 1-5 minutes). Instead of the heating step, the impregnated
fabric may be kept, e.g at ambient temperature for 10-60 hours (e.g
10-30 hours) preferably while being allowed to dry. If desired the
polymer (or precursor) may be applied with a minimum add-on technique
to provide a 10-50% wet pick up; thereafter the fabric may be dried or
kept with a dwell time of eg 0.2-24 hours before the second step. A
foam minimum add on technique may be used, with a cationic or
amphoteric foaming agent and a stabilizer. In this treatment or
fixing step the nitrogen containing polymer is believed to interact
with the substrate, especially hydroxyl, amide or ester groups
thereon, to give a treated substrate having the cationic polymer bound
or attracted thereto by ionic bonds.
In the preferred form of the process, after the treatment with
the nitrogen-containing-polymer, the substantially dry substrate is
then treated with the organophosphorus compound. In the tetrakis
(hydroxyorgano) phosphonium compound, each hydroxyorgano group is
preferably an alpha-hydroxyorgano group of 1-9 carbons. Especially
said alpha-(hydroxyorgano) group is one of formula HOC- (R1R2),
wherein each of Rl and R2 (these being the same or different)
represents hydrogen or an alkyl group of 1 to 4 carbons, e.g. methyl,
or ethyl. Preferably R1 is hydrogen, and R2 is methyl or especially
hydrogen, as in tetrakis (hydroxymethyl) phosphonium (THP) compounds.
The use of tetrakis hydroxyorgano phosphonium compounds in general
will hereafter be exemplified with respect to THP compounds with -
corresponding molar amounts of the other compounds used instead of the
THP compound.
.:
2039~2~
The substrate is treated with an impregnation solution which is
an aqueous solution of a THP salt mixed with a nitrogen compound
condensable therewith to form a water soluble precondensate, or a
solution of a precondensate of said salt and nitrogen compound, or a
solution of THP salt, or water soluble self-condensate thereof, or at
least partly neutralised THP salt, (e.g. THP hydroxide), with or
without the nitrogen compound. The impregnation solution may
alternatively comprise a solution of said precondensate and further
nitrogen compound (eg urea), as in a solution with a molar ratio of
total nitrogen compound (free and combined) to THP group (free and
combined) of 0.8-2:1, eg 0.8-1.5:1. The nitrogen compound is
preferably one with at least two NH groups (such as 2-4), but
advantageously contains two NH or especially two NH2 groups. The
nitrogen compound is usually bifunctional and may be an amine but is
especially an amide. Examples of suitable nitrogen compounds are
biuret, guanidine, melamine and methylolated melamines, but urea is
the preferred species for the purposes of this invention, especially
in the absence of melamine or a methylolated melamine. The nitrogen
compound is preferably urea whenever it is present in the
precondensate.
In a preferred embodiment of this invention, the solution
contains a precondensate of THP salt, e.g. chloride or sulphate, and
the nitrogen compound in a molar ratio of nitrogen compound to THP of
0.05-0.8:1, e.g. 0.05-0.6:1, or 0.22-0.8:1, such as 0.25-0.6:1,
especially 0.4-0.6:1. The pH of said solution is usually 2-7.5, such
as 4-6.5, e.g. 4-5. The atom ratio of total N atoms in the nitrogen
compound or condensate to the total P atoms from THP salt or
condensate in the impregnation solution is usually not greater than
4:1, eg 1-3:1.
The concentration of organophosphorus compound in the aqueous
solution may be 5-70% eg 5-35% or 35-70% (expressed by weight as THP+
ion), but is preferably 20-35%.
203962~
- 8 -
If desired the solution may contain a wett;ng agent such as a
nonionic one, eg in amount of 0.05-0.5% by weight of the impregnation
solution, a fabric softener such as a polyethylene one and in
preferred amount of 0.1-2% by weight, and a salt of a strong acid and
weak base (such as an ammonium or alkaline earth metal chloride or
nitrate or ammonium acid phosphate) as catalyst for the heat cure, and
in amount of 0.1-5% by weight.
The treated substrate is impregnated to give an organo phosphorus
pick up of less than 40% e.g. 10-40%, (such as 10-30%) especially
20-30% (as THP ion based on the original weight of the substrate).
The substrate can be impregnated with solution and the wet substrate
e.g. fabric usually squeezed to a wet pick up of 50-130%, e.g. 60-100/~
(based on the original weight of the substrate). Alternatively the
treated substrate may be impregnated with a concentrated impregnation
solution via a minimum add-on, eg foam, technique and a 10-50% wet
pick up.
The organophosphorus impregnated substrate is then dried, e.g. to
a moisture content of 0-20%, e.g. 5-15% such as about 10%, for
subsequent ammonia cure and to substantial dryness for subsequent heat
cure (the percentage being derived from the increase in weight of the
fabric and the weight of chemicals impregnated). The drying may be in
a stenter oven or over heated cans e.g. steam cans, and may involve
heating at 80-160C for 10 min to 10 secs e.g. at 100-120C for 3min
to 30 secs . The dried substrate is then cured. The cure may be by
treatment with ammonia, usually gaseous ammonia, which diffuses
through the substrate and/or is forced through the substrate, e.g. by
passage of the fabric over a perforated tube through which ammonia has
is emitted. Examples of apparatus and techniques suitable for the
ammonia cure are given in USP 4145463, 4068026 and 4494951, the
disclosure of which is hereby incorporated by reference.
Alternatively or preferably prior to the ammonia cure, the dried
organophosphorus impregnated substrate may be heat cured, e.g. at a
temperature of at least 100C (such as 100-200C) or 100-180C (such
as 130-170C) for 10-0.5 minutes e.g. 7-1 minutes.
:
- 9 - 2039~2~
'':
Higher temperatures with long curing times should be avoided with
substrates containing at least a majority of cellulosic fibres,
especially 100% cotton. While the dried substrate may then be heat
cured, preferably the drying and heat curing steps are combined with
just heating under the heat cure conditions. When a heat cured fabric
is subseqently to be cured with ammonia, the heat cured fabric is
preferably submitted to a humidity equilibration step to allow the
fabric to recover its moisture content before the ammoniation.
The cured substrate usually has a solids add-on (derived from the
organo phosphorus impregnation and cure stages) of 10-50%, or 10-40%,
(e.g. 10-30%) such as 10-25% or 15-30%, especially 20-30%, (by weight
of the original substrate), based on a total organophosphorus compound
pick up of 16-36%, e.g. 20-28% (expressed as THP ion on the same
basis).
The cured substrate is then usually subjected to at least one of
the following operations: further insolubilization of the cured resin
in the treated substrate, oxidation in order to convert at least some
trivalent phosphorus to pentavalent phosphorus in the cured resin, or
washing with aqueous base and washing with water. The oxidation is
preferably by contact with an aqueous solution of an oxidising agent,
preferably a peroxy compound, such as aqueous hydrogen peroxide
solution e.g. of 0.5-15% concentration, such as 1-5% strength, or
sodium perborate solution, e.g. of 1-10% concentration, usually
applied in excess, and usually for 0.1-10 mins at 0-40C.
Alternatively the oxidation may be performed with a gas containing
molecular oxygen, preferably air, and particularly with the gas being
drawn or blown through the substrate. Thus the substrate in the form
of fabric can be passed over a vacuum slot or perforated tube though
which the gas is blown or sucked.
After the oxidation, or instead thereof, the cured substrate may
be washed with an aqueous medium, preferably an aqueous solution
of base, e.g. sodium carbonate solution and/or rinsed with water. The
oxidation preferably reduces the residual content of formaldehyde on
the cured substrate.
203~62~
- 10 -
Alternatively the cured substrate may simply be rinsed with water
or submitted to other operations to reduce its content of water
soluble materials. Finally the cured fabric is dried, to give a final
substrate.
The final substrate e.g. fabric can be used for making workwear
such as overalls, boiler suits and protect;ve cloth;ng ;nclud;ng
un;forms, part;cularly from 30-70% e.g. 55-70% cotton and 70-30% e.g.
45-30% polyester, and household fabr;cs such as sheets and curtains
particularly from 30-70% e.g. 30-60% cotton and 40-70% polyester.
If the process of the invent;on is compared to the corresponding
one without the nitrogen containing polymer (or precursor) step, the
init;al uptake of THP compound by the substrate in the ;mpregnat;on
may be ;ncreased, the cure eff;c;ency may be ;ncreased and the loss of
cured P compound from the f;nal substrate dur;ng washing ;n use may be
reduced. Thus for a constant total we;ght phosphorus chem;cal
appl;ed to the substrate, the cured substrate of the ;nvent;on usually
has a higher percentage of bound phosphorus and may also have a better
handle than the corresponding cured substrate without the initial
treatment with the n;trogen containing polymer. There is thus less
wastage of phosphorus chemical. The flame retardant properties e.g
the char length, are usually improved enabling fabrics to pass more
severe flammability tests than without the treatment with nitrogen
containing polymer (or precursor).
The final substrate obtained by the process of the invention may
; also have enough cured and bound phosphorus containing-resin to enable
it to reach the exacting flame retardancy standard~ e.g. BS6249 Part 1
1984 Part B, which may not be passed by the same orig;nal substrate
cured w;thout the initial treatment with nitrogen conta;ning polymer
(or precursor). The f;nal substrate obta;ned by the process of the
;nvent;on may also have less reduct;on in strength compared to
corresponding substrates without the initial treatment.
~'
- 11 2039 6 24
In this specification, unless otherwise noted parts and
percentages are by weight.
The invention is illustrated in the following Examples in which
all the fabrics had been previously submitted to a desizing treatment.
Example 1
An aqueous dispersion of poly (dimethyl diallyl ammonium chloride) was
obtained by a reaction in which into a reactor with stirrer and
condenser were added toluene (50g) and a nonionic surfactant (15g) and
the reactor heated to 80C followed by simultaneous addition of an
aqueous solution of dimethyl diallyl ammonium chloride (50g) in water
(50g) and di-(4 tert butylcyclohexyl) peroxydicarbonate (0.15g). The
reactor contents were stirred at 80C for 3 hours to leave an
emulsion, which was then heated to remove the toluene by distillation
with water, with addition of extra water in lieu of the toluene and
water distilled. The product was a stable aqueous dispersion of
the average molecular weight of the polymer was about 1 million.
(a) A 67:33 intimate blend polyester cotton fabric of 0.246kg/m2 was
impregnated with a 2% w/w aqueous dispersion of the above polymeric
dimethyl diallyl ammonium chloride. The excess of liquid was then
separated from the fabric, which was allowed to dry at room
temperature overnight to leave a treated fabric comprising about 1.6%
of the polymer.
(b) The treated fabric was then impregnated with an aqueous solution
of 1:2 molar condensate of urea and tetrakis (hydroxy methyl)
phosphonium chloride containing 25.2% solids (expressed by weight as
THP+ ion and the excess of liquid squeezed from the fabric.
- 12 - 2 0 3 ~ 6 2
(c) The fabric was then heat cured at 150C for 3 minutes, and then
its water content returned to normal by equilibration in a humidity
controlled room overnight. The heat cured fabric was then cured
further with ammonia gas which was passed through the fabric in a
chamber as described in USP 4145463.
(d) After the ammonia cure, the fabric was washed with 10% hydrogen
peroxide solution, rinsed with water, washed with aqueous sodium
carbonate and then rerinsed and dried, to give a final fabric.
The final fabric was then analysed for P and N; it was also
tested for flame retardancy before and after washing 40 times at 93C,
the washing being as in the manner described in DIN 53920 procedure 1
with soft water. The test method used was according to BS 5438 (1989)
Test 2A. In all cases the fabrics passed the flammability
requirements of BS 6249 Index B. The analysis results were as
follows:
FABRIC XP XH
Cured (step c) 1.94 1.56
Final fabric (step d) 1.81 1.65
The fabric passed the ignition test even after the 40 washes.
Example 2
The process of Ex 1 was repeated with a different fabric, namely a
60:40 cotton/polyester intimate blend fabric of weight 0.268kg/m2, and
with a different pretreatment agent, namely monomeric d; (allyl) di
(methyl~ ammonium chloride added in 2%, 5% or 10% aqueous
concentration to give a wet pick up of about 70-90%. The
flammability, % P and %N analyses were done on the final fabric as
- such and after 20 washes. The results were as follows.
- 13 - ~39~24
F~nal Fabric Fabr~c after 20 washes
% Agent 1n solution XP %N Char %P NX Char
length Length
~ 0n
2 3.05 3.05 60 ~.63 2.4050
2.9 2.90 54 2.43 2.2447
2.98 2.90 58 2.38 2.1942
ExamDles 3 - 9
The process of Ex 1 was repeated with two different polymeric nitrogen
compounds, namely (Ex 3-6) a water soluble copolymer of acrylamide and
acrylic acid in about 90:10 ratio and (Ex7-9) a water soluble
polyethylene imine. The final fabrics and those after 20 washes were
tested for flammability. All passed the flammability tests the
results of these on the final fabrics being as follows.
Example % polymer Char
1n solut~on length
ln step (a) mm
3 1 81
4 2 76
79
6 10 75
7 0.5 90
8 1.5 85
9 2 87
