Note: Descriptions are shown in the official language in which they were submitted.
Z043380
This invention relates to a coating and impregnation
composition especially one for treating fabrics to render them flame
retardant.
Cotton fabrics can be rendered flame retardant by incorporation
therein of a wide variety of chemicals, which can provide durable or
non durable flame retardance. Among these chemicals are antimony
compounds, organo halogen compounds and organic or non organic P
compounds such as water insoluble and soluble ammonium
polyphosphates, which can be cured into the fabric by heating (eg
see GB-P-1504507). In the treatment of many fabrics, especially for
upholstery uses, it is essential that the look and handle of the
fabric be substantially unaffected by any fire retardant treatment.
For this reason many upholstery fabrics are fire retarded by back
coating especially with a resin composition containing antimony
oxide and an organo bromine compounds. Such compositions are
undesirable for environmental reasons and secondly are only suitable
for low fabric weight fabrics.
We have discovered a back coating composition, which is
suitable for a wide range of fabric weights and is more acceptable
to the environment.
The present invention provides a composition for flame
retarding fabrics which comprises (i) an at least partly water
insoluble ammonium polyphosphate, (ii) an antifoam agent (iii) a
heat curable resin and (iv) water. It is especially preferred that
the composition contains (v) a surfactant. Preferably the
composition also contains (vi) a water soluble ammonium
polyphosphate and/or (vii) a carbamic acid derivative. There is
also provided a method of flame retarding a fabric substrate which
comprises impregnating the fabric with a composition comprising
components (i) to (iv), and especially also (v), (vi) and/or (vii~,
and then heat curing the impregnated fabric.
:.
'
- 2 - 2043380
The invention also provides a fabric which as been flame
retarded by impregnation with a composition comprising components i)
to (iv) and preferably also (v), (vi) and/or (vii) and curing the
impregnated fabric.
The at least partly water insoluble (hereinafter referred to as
insoluble) ammonium polyphosphate usually has a water solubility of
less than 10 g/lOOg water at 20C, especially less than 8 or 5
9/1009, such as 0.1-5, 0.5-3 or 1.5-7g/100g water, wherein the
solubility is as measured by the Manders test as defined by the
Manders Paint company for ammonium polyphosphates used in paints and
as hereinafter described. It may be considered as comprising a
mixture of truly soluble and insoluble components, the soluble
components of which can leach out on addition of or to water to
produce an insoluble fraction of very high surface area to volume
ratio e.g. as a very fine powder and/or a honeycomb structure. It
may be made by heating at, eg 200-400C, mono or di ammonium
polyphosphate alone or mixed with phosphorus pentoxide or ammonia.
The phosphorus pentoxide may be replaced at least in part by
phosphoric acid and the source of ammonia may be urea (see eg BP
1103772, 1184878, 1309873 and EP 49763). The insoluble
polyphosphate may have a straight or branched chain structure and
may be of general formula (NH4)a Hb a+2 Pb3b+1~ where b has an
average value of greater than 10, a/b is 0.7-1.1 and the maximum
value of a is b+2. The molecular weight of the insoluble
polyphosphate is usually greater than 10,000, eg 10,000 to 2
million, such as 10,000 to 1,000,000 or 200,000 to 1.5 million. The
water insoluble ammonium polyphosphate usually has a mean particle
size of less than SO microns preferably less than 30 microns such as
1-50, 5-50 or 10-30 microns; preferably at least 60% of the
particles are of less than 30 microns and especially at least 40%
less than 10 microns. The polyphosphate usually contains 20-35% P,
such as 23-32%P, preferably 25-32%P.
Examples of suitable insoluble polyphosphates are these sold by
Albright & Wilson Limited under the Trade Marks AMGARD MC or AMGARD
PI.
- 3 - 2043380
The composition usually contains (based on the weight of components
(i-vii)) 15-30%, eg 10-25%, or 19-23% of the water insoluble
ammonium polyphosphate, while containing 15-30%, such as 20-28 or
21-25, and especially 24-27%, of the polyphosphate (based on the
weight of components (i-iv)).
An antifoam agent is a material which interacts with a liquid
which is foaming or capable of doing so and which contains a
surfactant by interacting with the surfactant molecules and/or the
liquid/vapour interface in order to destroy the foam or prevent its
formation. Examples of such agents are soaps, alkyl phosphate
esters and mineral oil, wax, vegetable oil or silicone based
formulations. The silicone based formulations comprise polysiloxane
liquids which may be fluoro or alkyl siloxanes optionally
prossessing amino substituents and are preferably dimethyl siloxane
polymers and preferably also contain finely divided silica which may
be formed in situ by the hydrolysis of tetra alkoxy silanes. A
preferred antifoam agent for use in the current invention is that
sold by Wacker-Chemie GmbH under the name S132.
The composition usually contains 0.01-0.5%, e.g. 0.02-0.4%,
preferably 0.05-0.2%, of the antifoam agent.
The resin tiii) is derived from at least one ethylenically
unsaturated monomer and may be a homopolymer but is preferably is a
copolymer. Examples of suitable monomers are ethylene and mono
substituted ethylenes eg vinyl carboxylate esters eg of 4-8 carbons
such as vinyl acetate, mono and di carboxy substituted ethylenes and
esters thereof such as acrylic acid, methacrylic acid, maleic acid
and their esters such as ethyl acrylate, chloreothylenes such as
vinyl chloride and cyaneothylenes such as acrylonitile. Preferred
resins are copolymers comprising acrylic monomer units with each
other or acrylonitrile or vinyl chloride, or vinyl acetate/ethylene
copolymers. Examples of suitable resins are those sold under the
trade marks REVACRYL 274 by Harlow Chemical Co, England VINAMUL 3306
sold by Vinamul Ltd, Surrey, England LUTOFAN LA560S and LUTOFAN 300d
and ACRONAL DS 2272 sold by BASF, West Germany.
. .
- 4 - 20433~3
The resin is usually commercially available as an aqueous dispersion
or emulsion which usually contains an emulsifier, which may be
anionic such as an alkyl sulphate and/or alkyl ether sulphate, a
mixture of which is present in the case of the REVACRYL 274 resin,
or non-ionic as in the case of the ethylene/vinyl acetate copolymer
sold as VINAMUL 3306. The dispersions usually contain 40-55% solids
content of the resin. While the emulsifier added with the resin may
be sufficient to provide the sole emulsifier for use in the
compositions of this invention (as in the case of the vinyl chloride
acrylic copolymer sold as LUTOFAN 5605), a separate emulsifier can
be added as well. The resins are usually ones with TG f less than
30C, eg -40 to +30C, and especially O to - 30C. The resins are
self curable by heat, eg at 80-180C, but especially 120-170C. The
compositions of the invention usually contain 10-30% or 15-30%, such
as 20-25%, 21-24% or 21.5-23.5% resin (expressed as resin solids on
the total weight of the components (i-vii)), or 10-30%, eg 14-23%
such as 17-21% or 14-18% (based on the weight of a composition
containing components (i-v) but not (vi) or (vii)).
The compositions also contains as component (iv) water in
weight amount usually of 40-51%, such as 42-50 or 44-49% (based on
the weight of components (i-vii)) or 50-60% such as 56-58% (based on
the weight of components (i-iv) in the absence of (v), (vi) and
(vii)). These figures include any water added with the other
components such as resin or surfactant, as well as water added
separately.
The surfactant (v) is usually a poor wetting agent but with
some surface activity. It preferably comprises strong foaming
agent, especially one stabilizing oil in water emulsions with an
hydrophilic lipophilic balance (HLB) figure of greater than 12, e.g.
12-20 eg 12-16, but may alternatively be suitable for stabilizing
water in oil emulsion with an HLB of figure less than 12, eg 1-8,
especially 3-7. The composition may comprise a mixture of
surfactants, e.g. as an emulsifier for the resin.
20433~3
The surfactant may comprise at least one anionic, non-ionic,
cationic, amphoteric and/or semi-polar component.
Surfactants for use in our invention typically contain
hydrophobic groups such as alkenyl, cycloalkenyl, alkyl, cycloalkyl,
aryl, alkyl/aryl or more complex aryl (as in petroleum sulphonates)
moieties having from 8 to 22, preferably lO to 20, typically 12 to
18, carbon atoms and a hydrophilic moiety. Other hydrophobic groups
included in the invention are polysiloxane groups.
The surfactant may for example consist substantially of an at
least sparingly water-soluble salt of sulphonic or mono esterified
sulphuric acids, e.g. an alkylbenzene sulphonate, alkyl sulphate,
alkyl ether sulphate, olefin sulphonate, alkane sulphonate,
alkylphenol sulphate, alkylphenol ether sulphate, alkylethanolamide
sulphate, alkylethanolamide ether sulphate, or alpha sulpho fatty
acid or its esters, each having at least one alkyl or alkenyl group
with from 8 to 22, more usually 10 to 20, aliphatic carbon atoms.
The expression "ether" hereinbefore refers to compounds
containing one or more glyceryl groups and/or an oxyalkylene or
polyoxyalkylene group, especially a group containing from l to 20
oxyethylene and/or oxypropylene groups. One or more oxybutylene
groups may additionally or alternatively be present. For example,
the sulphonated or sulphated surfactant may be sodium dodecyl
benzene sulphonate, potassium hexadecyl benzene sulphonate, sodium
dodecyl dimethyl benzene sulphonate, sodium lauryl sulphate, sodium
tallow sulphate, potassium oleyl sulphate, ammonium lauryl
monoethoxy sulphate, or monoethanolamine cetyl 10 mole ethoxylate
sulphate.
.
Other anionic surfactants useful according to the present
invention include alkyl sulphosuccinates, such as sodium di-2-
ethylhexylsulphosuccinate and sodium dihexylsulphosuccinate, alkyl
ether sulphosuccinates, alkyl sulphosuccinamates, alkyl ether
sulphosuccinamates, acyl sarcosinates, acyl taurides, isethionates,
- 6 - 20433~30
soaps such as stearates, palmitates, resinates, oleates, linoleates,
and alkyl ether carboxylates. Anionic phosphate esters, alkyl
phosphonates and alkyl amino and imino methylene phosphonates may
also be used. In each case the anionic surfactant typically contains
at least one aliphatic hydrocarbon chain having from 8 to 22,
preferably 10 to 20 carbon atoms, and, in the case of ethers, one or
more glyceryl and/or from 1 to 20 oxyethylene and/or oxypropylene
and/or oxybutylene groups.
Preferred anionic surfactants are sodium salts. Other salts of
commercial interest include those of potassium, lithium, ammonium,
monoethanolamine, diethanolamine, triethanolamine and alkyl amines
containing up to seven aliphatic carbon atoms.
The surfactant may optionally contain or consist of nonionic
surfactants. The nonionic surfactant may be, e.g. a C10-22
alkanolamide of a mono or di- lower alkanolamine, such as coconut
monoethanolamide. Other nonionic surfactants which may optionally
be present, include tertiary acetylenic glycols, polyethoxylated
alcohols, polyethoxylated mercaptans, polyethoxylated carboxylic
acids, polyethoxylated amines, polyethoxylated alkylolamides,
polyethoxylated alkylphenols, polyethoxylated glyceryl esters,
polyethoxylated sorbitan esters, polyethoxylated phosphate esters,
and the propoxylated or ethoxylated and propoxylated analogues of
all the aforesaid ethoxylated nonionics, all having a C8 22 alkyl or
alkenyl group and up to 20 ethyleneoxy and/or propyleneoxy groups.
Also included are polyoxypropylene/polyethylene oxide copolymers,
polyoxybutylene/polyoxyethylene copolymers and polyoxybutylene/
polyoxypropylene copolymers. The polyethoxy, polyoxypropylene and
polyoxybutylene compounds may optionally be end-capped with, e.g.
benzyl groups to reduce their foaming tendency.
Compositions of our invention preferably contain at least one
amphoteric surfactant.
20~33~0
-- 7 --
The amphoteric surfactant may for example be a betaine, e.g. a
betaine of the formula:- R3N+CH2COO-, wherein each R is an alkyl,
cycloalkyl, alkenyl or alkaryl group and preferably at least one,
and most preferably not more than one R, has an average of from 8 to
20, e.g. 10 to 18, aliphatic carbon atoms and each other R has an
average of from 1 to 4 carbon atoms. Particularly preferred are the
quaternary imidazoline betaines of the formula:
CH2 CH2
N +N - CH2COO-
~c/l
Rl
R
wherein R and Rl are alkyl, alkenyl, cycloalkyl, alkaryl or
hydroxyalkyl groups having an average of from 1 to 20 aliphatic
carbon atoms. R preferably has an average of from 8 to 20, e.g. 10
to 18, aliphatic carbon atoms and R1 preferably has 1 to 4 carbon
atoms. Other amphoteric surfactants for use according to our
invention include alkyl amine ether sulphates, sulphobetaines and
other quaternary amine or quaternised imidazoline sulphonic acids
and their salts, and other quaternary amine or quaternised
imidazoline carboxylic acids and their salts and Zwitterionic
surfactants, e.g. N-alkyl taurines, carboxylated amido amines such
as RCONH(CH2)2N+(CH2CH2CH3)2CH2C02-, and amino acids having, in each
case, hydrocarbon groups capable of conferring surfactant properties
(e.g. alkyl, cycloalkyl, alkenyl or alkaryl groups having from 8 to
20 aliphatic carbon atoms). Typical examples include 2-tallow
alkyl l-tallow amido alkyl l-carboxymethyl imidazoline and 2-coconut
alkyl N-carboxymethyl 2-(hydroxyalkyl) imidazoline. Generally
speaking any water soluble amphoteric or Zwitterionic surfactant
compound which comprises a hydrophobic portion including a C8 20
alkyl or alkenyl group and a hydrophilic portion containing an amine
or quaternary ammonium group and a carboxylate, sulphate or
sulphonic acid group may be used in our invention.
2043380
- 8 -
Compositions of our invention may also include cationic
surfactants.
The cationic surfactant may for example be an alkylammonium
salt having a total of at least 8, usually 10 to 30, e.g. 12 to 24,
aliphatic carbon atoms, especially a tri or tetra-alkylammonium
salt. Typically alkylammonium surfactants for use according to our
invention have one, or at most two, relatively long aliphatic chains
per molecule (e.g. chains having an average of 8 to 20 carbon atoms
each, usually 12 to 18 carbon atoms) and two or three relatively
short chain alkyl groups having 1 to 4 carbon atoms each, e.g.
methyl or ethyl groups, preferably methyl groups. Typical examples
include dodecyl trimethyl ammonium salts. Benzalkonium salts having
one C8 20 alkyl group, two C1 4 alkyl groups and a benzyl group are
also useful.
Another class of cationic surfactants useful according to our
invention are N-alkyl pyridinium salts wherein the alkyl group has
an average of from 8 to 22, preferably 10 to 20 carbon atoms. Other
similarly alkylated heterocyclic salts, such as N-alkyl
isoquinolinium salts, may also be used.
Alkylaryl dialkylammonium salts, having an average of from 10
to 30 aliphatic carbon atoms are useful, e.g. those in which the
alkylaryl group is an alkyl benzene group having an average of from
8 to 22, preferably 10 to 20, aliphatic carbon atoms and the other
two alkyl groups usually have from 1 to 4 carbon atoms, e.g. methyl
groups.
Other classes of cationic surfactant which are of use in our
invention include alkyl imidazoline or quaternised imidazoline salts
having at least one alkyl group in the molecule with an average of
from 8 to 22, preferably 10 to 20, carbon atoms. Typical examples
include alkyl methyl hydroxyethyl imidazolinium salts, alkyl benzyl
hydroxyethyl imidazolinium salts, and 2-alkyl-1-alkylamidoethyl
imidazoline salts.
g Z~43380
Another class of cationic surfactant for use according to our
invention comprises the amido amines such as those formed by
reacting a fatty acid having 8 to 22 carbon atoms or an ester,
glyceride or similar amide forming derivative thereof, with a di or
poly amine, such as, for example, ethylene diamine or diethylene
triamine, in such a proportion as to leave at least one free amine
group. Quaternised amido amines may similarly be employed.
Typically the cationic surfactant may be any water soluble
compound having a positively ionised group, usually comprising a
nitrogen atom, and either one or two alkyl groups each having an
average of from 8 to 22 carbon atoms.
The anionic portion of the cationic surfactant may be any anion
which confers water solubility, such as formate, acetate, lactate,
tartrate, citrate, chloride~ nitrate, sulphate or an alkylsulphonate
ion having up to 4 carbon atoms such as a methanesulphonate. It is
preferably not a surface active anion such as a higher alkyl
sulphate or organic sulphonate.
Polyfluorinated anionic, nonionic or cationic surfactants may
also be useful in the compositions of our invention. Examples of
such surfactants are polyfluorinated alkyl sulphates and
polyfluorinated quaternary ammonium compounds.
Compositions of our invention may contain a semi-polar
surfactant, such as an amine oxide, e.g. an amine oxide containing
one or two (preferably one) C8 22 alkyl group, the remaining
substituent or substituents being preferably lower alkyl, e.g. C1 4
alkyl, groups or benzyl groups.
Mixtures of two or more of the foregoing surfactants may be
used. In particular mixtures of non-ionic surfactants with cationic
and/or amphoteric and/or semi polar surfactants or with anionic
surfactants may be used.
Z043380
- 10 -
The surfactant is usually present in the resin-containing
emulsion but made additionally or alternatively be added separately,
if desired.
The compositions usually contain 0.1-5%, eg 1.0-3.5%~ of the
surfactant (or surfactant mixture), especially with 0.2-1.5%, eg
0.4-1%, added surfactant in addition to any emulsifier present in
the resin dispersion, which may be in amount of 0.2-3.5%~ such as
0.5-2.5%~ of components (i-vii). Added emulsifier may be 0.5-0.9%
based on components (i-v). The emulsifier in the resin dispersion
is preferably non ionic or anionic, eg an alkyl sulphate and/or
alkyl ether sulphate.
The water soluble ammonium polyphosphate (vi), which is
preferably present in the compositions of the invention, is usually
made by reaction of a condensed phosphoric acid with ammonia or an
organic amine or quaternary ammonium hydroxide to give a water
soluble product. The condensed phosphoric acid usually has a mean
degree of condensation of more than 3, e.g. 3-30, and usually has a
linear branched or cyclic structure. Preferably the salts contain N
and P in an atomic ratio of 0.5-2:1~ especially about 1:1. The
polyphosphate salt is preferably a mixture of the ammonium salts of
a plurality of polyphosphoric acids, which mixture has been produced
by a process of reacting an aqueous solution of phosphoric acids
containing 80-86% by weight of phosphorus pentoxide with ammonia or
a basic derivative thereof at a temperature of 15-70C, e.g.
15-40C, and at a pH of 4-12~ e.g. 5-12~ such as 5-9~ 6-8 or
6.5-7.5. Ammonium polyphosphate mixtures which may be used are
described in BP 1504507 and may be made as described therein. This
added ammonium polyphosphate usually has a (true) water solubility
of at least 50 g/l, e.g. at least lOOg/l, in water at 20C.
Examples of suitable soluble polyphosphates are these mixed with
urea and sold by Albright ~ Wilson Ltd under the Trade Mark AMGARD
LR2. The compositio~ usually contains 0-10%, such as 2-8%, eg 4-6%~
of the water soluble ammonium polyphosphate.
Z043380
- 11 -
S, The flame retardant composition of the invention usually
contains a carbamic acid derivative (vii) having 2 amino groups per
molecule in a weight percentage (expressed as urea) to the ammonium
polyphosphate (expressed by weight as ammonium polyphosphate itself)
of 0.5%-300%, such as 0.5-50%, eg 5-30%, such as 7-20% or 10-20%.
However 50-300%, e.g. 50-200%, and especially 75-125% are preferred.
The carbamic acid derivative may be guanidine or dicyandiamide, but
is preferably urea. The weights are expressed as urea but
equivalent weights of the other carbamic acid derivative can be
used. The presence of the carbamic acid derivative reduces any
tendency to discoloration of the fabric after heat curing. The
composition usually contains 0-10%, such as 2-8%, eg 4-6%, of the
carbamic acid derivative (expressed as urea).
The compositions of the invention are usually thixotropic
pastes, which are pourable when freshly made, form a gel on standing
but are converted to a pourable emulsion on shearing. The stable
emuls;ons may be water in oil emulsions, but are preferably oil in
water emulsions. On contact with a cotton fabric under the
influence of gravity only, the compositions tend not to pass through
the fabric nor to lose water rapidly into the fabric. On shearing
the composition in contact with the fabric, eg under the pressure of
a knife edge it is believed that the compositions shear allowing
them to penetrate the fabric, wherein they regel rapidly, but do not
pass through the fabric and exude from the opposite side. The
compositions may be made by mixing the components in any order, but
usually in order of resin first, then insoluble ammonium
polyphosphate, followed preferably by soluble ammonium polyphosphate
and carbamic acid derivative, then water and finally the defoamer.
The mixing is usually done with a high speed stirrer.
The compositions of the invention containing components (i)
(iv) usually contain these in weight proportions of 20-28 : 0.01-5 :
14-30 : 50-60. The compositions of the invention containing
components (i-vii) usually contain these in weight proportions of
15-30 : 0.01-5 : 15-30 : 40-51 : 0.1-5 : 2-8 : 2-8.
- 12- 2043~
The substrates to which the composition is applied may be woven
or non woven. They are usually cellulosic based substrates, e.g.
textile fabrics, such as cotton, linen, jute, hessian or regenerated
cellulosic materials, such as rayon or viscose, alone with other
fibres coblendable or mixable therewith, e.g. polyester, nylon,
acrylics, acetate, polypropylene, silk or wool. These blends or
mixtures of fibres may contain at least 10%, or at least 20%~ such
as 15-100% or 30-90%, but preferably at least 40%, such as 40-75%,
of the cellulosic material.
Preferred are fabrics from intimate blends or non blended
mixtures of cellulosic material, eg cotton, and synthetic polymer,
eg polyester, nylon or acrylics. The fibres used to form at least
part of the fabrics may if desired be of core sheath construction
but are preferably not so. The fabrics may be of union
construction, for example with at least one of the weft and
especially the warp being predominantly (eg 50-100%), especially
essentially completely, of synthetic polymer fibres. Those with a
warp predominantly of polyester or nylon and cotton weft, especially
with embossed cotton designs and/or colour woven cotton are
preferred. The flame retardant compositions of the invention and
the method of the invention enables one more uniformly to flame
retard, at least semidurably, such union fabrics, preferably
embossed ones, but especially ones with non uniform distribution of
synthetic polymer and cellulosic material on a surface thereof
(hereinafter called "differential surface fabrics"). Particularly
important differential surface fabrics are ones with a front side
with a different (usually lower) proportion of the cellulosic
material to synthetic material from that on the back side, as well
usually as having a face or front side having significant areas of
predominantly (eg 50-100%) fibres of synthetic polymer on the
surface, as well usually as significant areas of predominantly (eg
50-100%) fibres of the cellulosic material. ~xamples of such
differential surface fabrics are ones with a polyester warp and dyed
cotton weft, especially with more than one differently coloured
cotton weft, with the fabrics woven with front designs of such dyed
cotton on a background of the polyester warp and a nondesigned back
with a substantial cotton surface.
204338()
- 13 -
Such differential surface fabrics may be used as upholstery fabrics.
Other useful fabrics are pile fabrics, especially with a cotton base
fabric back and an acrylic pile face. In the cases of the union
fabrics and pile fabrics each having a face and a back, the
compositions are applied to the back of the fabrics.
In addition to upholstery fabrics, the flame retardant
composition can be applied to other furnishing fabrics, such as
curtains, which are not subjected to frequent washing, and which are
for use in, for example, domestic, office, institutional or public
buildings. The ability to treat different types of fabric makes it
useful where various fabrics bear the same, or similar, designs for
use in situations which have "colour-coordinated" decor.
Fabric weights can be 0.050-1.0kg/m2, e.g. 0.080-0.700kg/m2, or
0.400-0.700 kg/m2, typically 0.200-0.400 kg/m2, espec;ally with
fabrics containing at least 30% of non cellulosic fibres. Each of
the components of the fabric may be plain or undyed or may be dyed
especially with white or pastel shades. The fabric before
impregnation is usually free of dirt, sizes, natural waxes and
applied finishes though it may contain an optical brightening agent.
The flame retardant composition may also be used to treat
carpeting (by back coating) which can weigh up to 2kg/m2.
The flame retardant composition usually at pH 2-8, e.g.
5.5-7.5, is applied to the fabric substrate by a back coating
procedure such spreading with a knife over a roller or air to give
an application rate of 35-150% or 50-150% (on weight of fabric),
such as 60-80% on pile fabrics or 80-120% on intimate blend or union
fabrics. The minimum application rate necessary to provide adequate
flame retardant properties is typically that required to saturate
the fabric (especially the pores of the fabric) or a minimum of 95%,
whichever amount is the lesser.
- 14 - 204:~;}8C~
If desired after impregnation, the substrate may be dried, e.g.
at 80-120C for 0.1 to 10 minutes. The drying may be performed in
any conventional drier, e.g. a forced air drier or stenter.
The impregnated substrate after dry;ng, if desired, is then
heat cured, eg by heating at a temperature of at least 80C, such as
at least 120C, e.g. 120-170C, preferably 140-170C or 140-165C,
e.g. for 6 to 0.5 minutes, the combination of longer times and
higher temperature preferably being avoided to decrease any tendency
to discoloration. Preferably the drying and curing steps are
combined.
The curing, which is usually continuous, may be performed by
radiant, e.g. infra red, heating but preferably the curing is by
heating from impact of hot air on the surface of the substrate,
preferably on both surfaces to ensure uniformity of heating. Thus
preferably, the substrate is passed continuously on a stenter
through a thermostated oven in which heated air flows are passed on
to the top and bottom surfaces of the substrate. The stenter gives
the most uniform curing with minimum scorching. In the case of the
stenter oven, the cure temperature of the substrate is essentially
the same as that of the heated air flow. Usually at the end of the
curing the substrate is cooled rapidly by passing or drawing cool
air through it.
The cured fabric as finished usually has a solids content of
30-60%, such as 35-45% for pile fabrics or 50-60% for union or other
non pile fabrics, and usually contains 3-10% P, preferably 5-8% P.
The fabric as finished has a reduced flammability compared to the
untreated substrate and can pass the BS 5852 test with ignition
sources 0 and 1. The fabric after leaching once in hard water at
40C according to BS 5651 without final ironing can pass the
flammability test of BS 5852 Part 1 with ignition sources 0 and 1.
The reduced flammability finish can be durable for 1-3 washes in
soft water at 74C or to 10 dry cleaning operations depending
primarily on the nature of the resin.
.
- 15 - Z04338
The fabric as finished usually has a face handle not significantly
changed from that of the untreated fabric, and shows no surface salt
deposits or resin marks. It usually has a colour not significantly
changed from that of the untreated fabric.
The synergistic combination of the components (i)-(iv)
especially with components (v), (vi) and (vii), can give treated
fabrics with improved flame retardant properties and, particularly
with fabrics having a face and back, without salt or resin deposits
on the face, when the composition is applied to the back. It is
believed that some of the water and any water soluble ammonium
polyphosphate, added as such or as part of the water insoluble
polyphosphate, migrates from the back towards the face but does not
reach the face.
In this specification all parts and percentages are by weight.
The invention is illustrated in the following Examples in which
the following fabrics were used:
Fabric A was a 50:50 cotton polyester union fabric with cotton
weft and polyester warp of 0.240 kg/m2 weight.
Fabric B was a 65:35 cotton polyester union fabric with cotton
weft and polyester warp of 0.470 kg/m2 weight.
In each case the composition of the invention was prepared and
applied to the fabric on a supporting surface with the aid of a
knife which spread the composition onto the fabric and forced it
into the fabric. The supporting surface under the fabric became
cool but not damp in this procedure, showing that water did not
exude from the underside of the fabric. The impregnated fabric was
then heated in a stenter at 150C for 90 secs to provide a combined
drying and curing operation. The cured fabric was then tested for
flame retardancy as finished and after one leach in hard water at
40C according to BS 5651 part l without final ironing.
2043~
- 16 -
The solubility of the water insoluble ammonium polyphosphate as
used in the text and Examples is that determined by the Manders
test, in which 59 of solid is shaken with 50ml of water at ambient
temperature and then 10 ml of solution is removed, weighed and
evaporated to dryness to leave a residue. The solubility is given
as 10 times the weight in 9 of the residue.
Example 1
A composition was made up by thoroughly mixing in the following
order the following ingredients : 48 parts of a 45.5% solids content
aqueous emulsion of a self cross linking heat curable acrylic
copolymer containing some acrylonitrile monomer units, whose TG was
-24C, sold as REVACRYL 274 by Harlow Chemical Co. England (an
emulsifier comprising alkyl ether sulphate and alkyl benzene
sulphonate was also present in the emulsion); 20 parts of a water
insoluble ammonium polyphosphate with a particle size distribution
of 98% less than 32 microns, containing 30.2% P and a solubility of
about 3.59/1009 at 20C; 4.9 parts of urea; 4.9 parts of water
soluble ammonium polyphosphate made according to the process of BP
1504507; 8.4 parts of water; and 0.1 parts of a 50:50 silicone
oil(poly dimethyl siloxane)/hydrophobic silica antifoam agent, sold
as S132 by Wacker-Chemie GmbH. The insoluble polyphosphate was
obtained by milling the product sold by Albright & Wilson Limited
under the trade mark AMGARD MC.
The composition was a pourable stable emulsion which on
standing thickened to a gel, which itself was reconverted to the
emulsion on shearing and was applied to fabric A with an
application rate of 90%.
,:
The cured fabric samples passed the ignition source 0 and
tests and showed no salt deposits or resin marks on their faces or
on the surface opposed to that on which the composition was applied.
The face handle of the fabric was substantially unaffected by the
treatment.
204;~80
- 17 -
Example 2
By proceeding in a similar manner to Example 1, but replacing
the insoluble ammonium polyphosphate by 24 parts of one having a
phosphorus content of 27.1%, a size distribution of 100% c32 ~m and
a solubility of 6.32g/lOOg, and using an application rate of
94%,cured samples of fabric A again passed the FR tests, showed no
salt or resin marks and exhibited an essentially unchanged handle.
Examples 3-16
Samples of fabric B were treated with compositions similar to
those in Examples 1 and 2, but containing 20 or 24 parts of
insoluble ammonium polyphosphate having the following properties:-
Examples %P Solubility Particle Size
(g/lOOg) (100% less than)
3,4 27.1 6.32 30 ~m
5, 6 26.7 5.55 32 ~m
7, 8 27.3 3.55 32 ~m
9, 10 27.5 3.33 32 ~m
11, 12 27.9 3.16 32 ~m
13, 14 27.3 2.96 32 ~m
15, 16 27.9 2.58 32 ~m
All cured samples again passed the FR tests, and exhibited nosalt or resin marks or adverse change in handle.
