GB2242915A - Flame retardants - Google Patents

Description

1 1 1 FLAME RETARDANTS.

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 tetrakis (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 retained on the substrate after washing, and can enable adequate fire retardant properties to be provided for fabrics comprising non cellulosic fibres such as ones of cotton and polyester fibres.

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 silicon compound having at least two active-hydrogen-reactive groups (or precursor therefor), then subsequently with an aqueous solution of an organophosphorus compound, to provide a second impregnated substrate which is dried and cured heat and/or ammonia, to give a cured substrate.

The silicon compound 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 silicon compound to interact or react in the substrate before the second step.

The silicon compound (or a hydrolysis product thereof) contains at least two groups capable of reaction or interaction with active hydrogen groups especially in hydroxyl, amide or amine groups (including ammonia). Preferably the silicon compound contains at least one group designated R in the formula below which, as is or after hydrolysis, is capable of reaction or interaction with a hydroxyl group in an insoluble polymer, e. g. cellulosic hydroxy groups or polyester terminal hydroxyl groups or with an amide group in an insoluble polymer, e.g. a polyamide such as a nylon; and at least one group, designated R1 in the formula below, which is capable of reaction or interaction with hydroxymethyl groups e.g. ones which are attached to nitrogen, oxygen or especially phosphorus atoms, and/or ammonia or amide NH2 groups. The conditions of the reaction or interaction are usually under the influence of heat, and may be under acid, neutral or basic conditions, and are preferably such that when R (or a group formed by hydrolysis thereof) reacts or interacts, R1 will not so react.

Preferably the silicon compound is of formula (R) 2 54 R1 b R2c v i 1 1 1 wherein each of a and b, which is the same or different, is 0, 1, 2, 3 or 4 c is 0, 1 or 2 and a+b+c is 4. R and R1 are as defined above, while R2 is an inert organic group, e.g. one inert under the conditions of the first and second steps. Preferably a is 1, 2 or 3 especially 3, b is 3, 2 or 1 especially 1 and c is preferably 0. Group R may be hydrogen, halogen (e.g. chlorine or bromine), hydroxyl or an ether, acetal, ketal or ester thereof. Alternatively two groups R may together be divalent ether, acetal, ketal or ester groups, or three groups R may together form a trivalent ether or ester group. Preferably R is a hydrolyzable group. Examples of ether groups for R are alkoxides and alkoxy-alkoxides and aryloxides and aralkoxides e.g. of formula R30 wherein R3 is an alkyl e.g. of 1-10 or 1-6 carbon atoms (such as methoxide and ethoxide or 2ethylhexoxide), or an alkoxy alkoxylene group, with 1-8 carbon atoms in each of the alkoxy and alkylene groups, (such as 2-butoxy-ethylene or 2methoxy-ethylene). R3 may also be an ary] group, e.g. an aromatic hydrocarbyl group of 6-19 carbons (such as phenyl, toly] and xylyl), or an aralkyl group, such as an aralkyl hydrocarbyl group of 7-20 carbon atoms (such as benzy] and naphthyImethyl). Examples of ester groups for R are carboxylate ones, e.g. of formula R3C00- where R3 is as defined above, especially acetoxy. Preferred groups R are hydroxyl and especially alkoxide, such as methoxy, ethoxy, propoxy, isopropoxy and butoxy. Preferably the silicon compound is a tri alkoxy silane of formula RI Si(OR3)3. Thus group R is usually such that the silane is hydrolysed in the impregnation medium or as a prior step to the reaction or interaction, e.g during the first step to a hydroxy silane (or a cyclized product therefrom with the silanol and any amino group in R1). The use of hydroxy silane itself or cyclic product therefrom or the precursor therefor is also included. The impregnation medium is usually an aqueous solution, so the silicon compound (as is or after hydrolysis) is usually water soluble, e.g with a solubility of at least 109/1.

1 Group or groups RI may be an organic group e.g. of 1-12 carbon atoms (such as 1-6 carbon atoms) containing at least one substituent or group which contains at least one e.g. 1-4 and especially 2-4 active hydrogen atoms attached to one or more nitrogen, sulphur, oxygen, or silicon atoms, or a substituent or group which is an unsaturated or 3 atom ring group formed from a carbon atom and a carbon, nitrogen, sulphur or oxygen atom, said unsaturated group being electrophilic and capable of being attacked by nucleophiles, (such as a -CH2-OH group or ammonia). The substituent may also be a halide (e.g. chloride or bromide). Group R1 preferably contains a basic group or quaternary derivative thereof, so the silicon compound in the impregnation medium is advantageously a Zwitterion. Examples of the substituents are -OH, Cl, -NH2 -NH-, SH, Si-H, CH2=CH-, CH2=C(CH3)-, epoxy, -CN, and C=O. Examples of group R1 are ones of formula -R4_X, wherein R4 is an alkylene group e.g. 1-6 carbon atoms (such as methylene, ethylene, 1, 3- propylene), or an arylene group, e.g. of 6-13 carbon atoms (such as o, m, p-phenylene, tolylene or xylylene), or an aralkylene group, e.g. of 7-13 carbon atoms (such as benzyIene) R4 may also be a cyclo alkylene-alkylene or cycloalkenylene alkylene group, each of the latter groups being e.g. of 6-10 carbons (such as 2 cyclohexyl ethyl or 2-(cyclohexenyl) ethyl) or cycloalkylene, e.g. of 5-7 carbons such as cyclohexylene. X is one of the above substituents, especially Cl, -NH2, CN, -NHR5 (wherein R5 is an alkyl group of 1-6 carbon atoms, an aromatic or 4 4 5 aralkyl group, eg of 6-18 carbons, or of formula R NH2. -R NHR e.g. an amino alkylene group, e.g. of 2-10 carbon atoms (such as 2aminoethy], 6-aminohexyl), or an optionally substituted (e.g. vinyl substituted) benzylamino alkylene group with 2-6 carbon atoms in the alkylene group, (such as 2[p vinyl benzy] amino] ethyl or an amino carbonyl group). Amino functional silanes e.g. where X is an NH2 or NHR5 group are preferred; such silanes preferably have at least one NH2 group, and especially one NH2 and one or two -NH- groups in the molecule.

1 The olefinic, substitution or grbup - which may be an alkenyl or alkenylene group e.g. of 2-8 carbon atoms, (such as vinyl, or propenylene) or an ary] substituted alkenylene group e.g. of 8-14 carbons (such as vinyl-phenyl or 2-phenyl or 2-phenyl ethenylene) or a cycloalkenyl group, e.g. of 5-7 carbons, (such as cyclohexenylene), may be group RI itself or group X itself or may be part of a group X, as when RI represents R4X e.g. as in the vinyl substituted benzylamino group above, or as in a 2, 1 unsaturated carboxylic ester group such as a methacryloxy or an acryloxy group, attached for example to an alkylene group such as 1, 3 propylene. Examples of the 3 atom ring substituents are cyclopropane, epoxide, episulphide and optionally substituted ethylene imine groups. These groups may form R1 or part of X or X (as in OX) wherein X and R4 are as defined above, so R1 may be for example a 3- (glycidyloxy) propyl group or a 2(3, 4-epoxycyclohexyl) ethyl group. However preferably the group R4 contains only saturated C-C bonds.

Most preferred groups R are 1, 3 propylene with a 3-substituent of formula X which is glycidyloxy, methacryloxy, acryloxy, chlorine, amine, cyano, ureido and 2-(amino ethyl) amino, especially when 3 R groups represent three methoxy or ethoxy groups in a molecule of formula RI Si (OCH3)3 or RI Si (OC2H5h. Thus preferred silicon compounds are N-(2 aminoethyl) 3-amino propyl trimethoxy silane and 3-amino propyl trimethoxy silane. Vinyl tri alkoxy silanes are also preferred.

Group R2 is an inert organic group e.g. one of 1-19 carbon atoms such as one given above in relation to R3, preferably methyl, and is non reactive and non hydrolyzable.

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).

1 1 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. 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 3099% (such as 30-85%), particularly 62-78% or 25-55% cellulosic fibres. Substrates comprising at least 45% non cellulosic fibres, eg polyester fibres such as 45-100% polyester, are preferred as are ones comprising 3078% 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.

1 1 If desired the fibrous substrate may be one of the above non cellulosic ones having groups capable of interaction with the silicon compound. Thus the substrate may be a polyester, with the silicon compound reacting with hydroxyl or ester groups, or a polyamide with the silicon compound reacting with amide or amine or carboxyl or a polyacrylonitrile with reaction of the silicon compound 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. Okg/M2, e.g. 0.150-0.40kg/m2, or 0.05-0.20kg/M2, such as polyester cotton shirting or sheeting or curtain fabric.

Usually before the silicon compound treatment the fabric is substantially free from size or other finishing agents, such as softening agents and resins; thus size that may have been on the fabric is usually removed, eg by washing.

1 X The silicon compound may be applied undiluted to the substrate but is preferably applied in aqueous solution, e.g. of 0.1-10%, especially 0.57% w/w, and a pH 2-9. A weak acid such as acetic or phosphoric acid may be present also in the solution in amount of 0.1 - 1% by weight, to aid hydrolysis of the silicon compound if required. Preferably the solution is at pH 2-4. The weight of silicon compound applied is usually 0.01-10%, e.g. 0.1-5%, especially 0.5-4%, based on the weight of the untreated fabric. The silicon compound is usually impregnated into the fabric with a wet pick up of 40-150% 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 90-150'C (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). If desired, the silicon compound may be impregnated by a minimum add-on technique tb provide eg a 10-50% wet pick up. Thereafter the fabric may be dried or kept with a dwell time of, eg, 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. The silicon compound may be hydrolysed in the aqueous solution, or may be hydrolysed during the drying or heat treatment step to form a reactive silicon compound. In this treatment or fixing step, the silicon compound or reactive silicon compound is believed to react with the substrate, especially hydroxyl amide or ester groups thereon, in particular via the reactive group R or a hydrolysed version thereof (e.g. hydroxyl), to give a treated substrate which carries a silicon containing group, especially one with group RI, as defined above, intact. Thus the treated substrate preferably contains pendant -SiRlbR2c groups especially SiRl groups, attached usually to cellulosic hydroxy groups or terminal hydroxy groups of a polyester. Alternatively active hydrogen containing groups in R1 can react with ester or amide or nitrile groups in polyester or polyamides or polyacrylonitrile respectively. Unsaturated or 3 ring groups in R1 can react with the fibres by addition of hydroxyl or N-H groups on the fibres to the silicon compound.

In the second step of the process, the silicon treated substrate is then treated with the organophosphorus compound. In the tetra (hydroxyorgano) phosphonium compound, each hydroxyorgano group is preferably an alpha hydroxyorgano group of 1-9 carbons especially one of formula HOC- (R5R6) wherein each of R5 and R6 which is the same or different represents hydrogen or an alkyl group of 1 to 4 carbons e.g. methyl or ethyl. Preferably R5 is hydrogen, and R6 is methyl or especially hydrogen as in tetra kis (hydroxymethyl) phosphonium (THP) compounds. The use of tetra 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.

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.

$. 1 i 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 oftotal 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 maybe 5-70%, eg 5-35% or 35-70% (expressed by weight at THP+ion), but is preferably 20-35%.

If desired the solution may contain a wetting 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 0.12% 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 addon, eg foam, technique and a 10-50% wet pick up.

1 # 1 1 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 substrate, eg 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 80-120C for 10 to 1 min. 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 100-200'C, or 100-1800C, (such as 130-170C) for 10-0.5 minutes (e.g. 7-1 minutes). Higher temperatures with long curing times should be avoided with substrates containing at least a majority of cellulosic fibres especially 100% cotton. While a dried substrate may then be heat cured, preferably the drying and heat curing steps are combined in a single step with heating under the heat cure conditions. When heat cured fabric is subsequently 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 solids add-on (derived from the THP 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).

f 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 0.515% concentration, such as 1-5% strength, or sodium perborate solution, e. g. of 1-10% concentration, usually applied in excess, and usually for 0.110 mins at O-WC. 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. 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 protective clothing including uniforms, particularly from 30-70% (e.g. 55-70%) cotton and 70-30% (e.g. 45-30%) polyester, and household fabrics such as sheets and curtains particularly from 30-70% (e.g. 30-60%) cotton and 40-70% polyester.

1 1 13 - If the process of the invention is compared to the corresponding one without the silicon treatment step, the initial uptake of THP compound by the substrate in the impregnation may be increased, the cure efficiency may be increased, and the loss of cured P compound from the final substrate during washing in use may be reduced. Thus for a constant total weight phosphorus chemical applied to the substrate, the cured substrate of the invention 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 silicon compound. 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 pretreatment.

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 exacting flame retardancy standards e.g. BS6249 Part 1 1984 Index B, which may not be passed by the same original substrate cured without the initial treatment with silicon compound. The final substrate obtained by the process of the invention may also have less reduction in strength compared to corresponding substrates without the initial treatment.

In this specificiation 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 denizing treatment.

Examp] e 1 (a) A 67:33 intimate blend polyester cotton fabric of 0.246kg/m2 was impregnated with a 2% w/w aqueous solution of 3- (2 amino ethyl) amino propyl trimethoxy silane, sold by Dow Corning under the trademark Z6020. 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 siVane.

1 1 (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 to give a wet pick up of about 50%.

(c) The fabric was then heat cured at 1500C 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 and tested for flame retardancy before and after washing 40 times at 930C, 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 met the flammability requirements of BS 6249 Index B. The analysis results were as follows:

FABRIC %P M Final 2.39 2.19 After 40 washes 2.34 2.12 The fabric passed the ignition test even after 40 washes.

Examples 2-6

The process of Exl was repeated with 2 separate fabrics and 3 types of cure step (c). The fabrics were (A) a 100% print cotton of 0.240 kg/m2 fabric weight (B) the 67:33 polyester cotton fabric of Exl.

1 In each case the treated fabric was impregnated and treated as in steps (a), (b) of Ex 1 with wet pick ups in step (b) of 74.1%, 74.7%, 53.7% and 61.9% for Ex 2, and Ex 4-6 respectively. After step (b) fabric A was then cured by (i) heat cure at 1500C for 4 minutes or (ii) ammonia cured by drying the fabric for 2 minutes at 1000C and then passing ammonia through the fabric in a chamber as described in USP 4145463 or (iii) heat curing at 1500C for 4 minutes followed by ammonia cure by passing ammonia through the fabric in a chamber as described in USP 4145463. In ea ch case after step (b) with fabric B, the cure step (c) was by (i) or (ii) only.

After cure steps (i), (ii) or (iii) the operations of step (d) were performed. The flame retardancy and analyses test were done on the final fabric and the fabric after 40 washes at 93C. The results were as follows.

Final Fabric Ex Cure Fabric %P M Char Length Technique MM 2 Heat A 1.99 1.54 96 (i) 3 Heat B 2.17 1.64 50 (i) 4 Ammonia A 3.00 3.07 74 (ii)Ammonia B 2.12 2.09 60 (ii) 6 Heat and Ammonia A 2.82 2.84 78 (iii) 1 1 1 The analyses of the fabric after 40 washes were as follows:- EX %P M 2 1.66 1.35 3 1.55 1.17 4 2.90 2.86 2.19 2.12 6 2.77 2.61 Example 7-9

The processes of Ex 2-6 were repeated with the same 3 types of cure (i), (ii) or (iii) but with another fabric, namely a 67:33 polyester cotton intimate blend fabric of 0.095kg/m2. The final fabrics of Ex 7-9 and those on the corresponding final fabrics of Comp Ex A-C without the silicon pretreatment were analyzed for %P and M. The results were as follows.

Ex Cure %P M 8 Heat (i) 2.38 2.04 9 Ammonia (ii) 2.23 2.45 Heat and Ammonia iii 2.53 2.47 A (i) 1.78 1.56 B (ii) 1.96 2.18 c (iii) 2.00 2.11 Examples 10-13 The process of Exl was repeated with a different fabric namely an intimate blend 60:40 cotton polyester fabric of weight 0.268 kg/m2 and 4 concentrations of the silane in the first step. All the fabrics before and after washing passed the flammability tests. The other results were as follows:

AL 1 0 Final Fabric Fabric after 40 washes Ex % Silane % P % N Char % P % N Char Length Length 11 1 2.94 2.88 43 2.36 2.20 55 12 2 3.14 3.08 60 2.56 2.41 52 13 3 3.04 3.18 50 2.47 2.35 60 14 5 2.97 3.33 40 2.72 2.56 55 Exampl e 14 The process of Ex 1 was repeated with a 50:50 intimate blend polyester cotton fabric of weight 0.095 kg/m2 and a silane concentration in the solution of 5% by weight. The final fabric and that after 20 washes passed the flammability tests. The results were as follows. The final fabric had 3.09%P, 2.82% N and gave a char length of 84 mm, while after 20 washes the fabric had 2.58%P, 2.23M and 95 mm char length.

Example 15-17

The process of Ex 1 was repeated with 3 different silanes in the aqueous solution in step (a) namely (i) a 2% solution of 3-chloropropyltrimethoxy silane (ii) a 1% solution of 3-[2-[pvinylbenzylamino]ethyl]aminopropyl trimethoxy silane. (iii) (iv) a 0.25% solution and a 2% solution of 3-glycidyloxy propyl trimethoxy silane, the silanes being sold by Dow Corning under the trademarks Z6076, Z6032 and Z6040 respectively. All the final fabrics passed the flammability tests. The char lengths in mm for the final fabrics were as follows (ii) 74 mm (iii) 69 mm and (iv) 65 mm respectively.

HI - 1

Claims (1)

1. CLAIMS:

   2.

   3.

   5.

   A process for the flame retardant treatment of an organic fibrous substrate containing reactive groups, said process comprising impregnating the substrate with a silicon compound having at least two active-hydrogen-reactive groups (or precursor therefor), then subsequently with an aqueous solution of an organophosphorus compound, to provide a second impregnated substrate which is dried and cured, to give a cured substrate.

   A process according to Claim 1, in which the silicon compound is of general formula (R)a Si RIb R2 c wherein (i) each of a and b, which may be the same or different, S U d -tt is 0, 1, 2, 3 or 4, c is 0, 1, or 2, od a+b+c is 4, (ii) R, or its hydrolysis product, is capable of reaction of interaction with a hydroxyl or an amide group in an insoluble polymer',")R' is capable of reaction in interaction with hydroxymethyl groups and/or ammonia or amide NH2 groups, angv2 is an inert organic group.

   A process according to Claim 2 c in which said silicon compound has the general formula R1 Si(OH3)3 or R Si(OC05)3 wherein RI is 1, 3-propylene with a 3-substituent selected from the following groups: glycidyloxy, methacryloxy, acryloxy, chlorine, amine, cyano, ureido and 2-(aminoethyl) amino.

   A process according to Claim 3, in which said silicon compound is N-(2 aminoethyl)-3-aminopropyl trimethoxysilane, 3-aminopropyl trimethoxy silane or a vinyl trialkoxysilane.

   A process according to any one of Claims 1 to 4, in which said silicon compound is applied to the substrate in aqueous solution.

   f i l 1 q- 7.

   9.

   11 12 14.

   15.

   16.

   A process according to Claim 5, in which said aqueous solution has a concentration of 0.1-10% w/w.

   A process according to Claims 5 or 6, in which said aqueous solution also comprises a weak acid.

   A process according to Claim 7, in which said weak acid is present in an amount of 0.1 to 1% by weight.

   A process according to Claim 7 or 8, in which said weak acid is acetic or phosphoric acid.

   A process according to any one of Claims 1 to 9, in which the silicon compound is impregnated into the substrate with a wet pick-up of 40-150%.

   A process according to Claim 10, in which the impregnated substrate then is dried by means of beating at 80 to 100 C for 0.1 to 5 minutes.

   A process according to Claims 10 or 11, in which the substrate is then treated by heating at 90 to 150 C for 0.5 to 10 minutes.

   A process according to Claims 10 or 11, in which the impregnated substrate is then kept at ambient temperature for 10 to 60 hours, while being allowed to dry.

   A process according to any one of Claims 1 to 9, in which the silicon compound is applied to the substrate with a minimum add-on technique.

   A process according to Claim 14, in which the wet pick-up is 10 to 50%.

   A process according to Claim 14 or 15, in which said minimum add-on technique is a foaming technique.

   20- 17. A process according to any one of Claims 1 to 16, in which the organophosphorus compound is a tetrakis (hydroxyorgano) phosphonium compound.

   18. A process according to Claim 17, in which the hydroxyorgano group is an alpha-hydroxyorgano group of 1-9 carbons.

   19. A process according to Claim 18, in which the Al_pha-hydroxyorgano 6 group has the general formula HO-C(R5R6), wherein R and R ' which are the same or different, are hydrogen or an alkyl group of 1 to 4 carbons.

   20. A process according to Claim 17, 18 or 19, in which the organ ophosphoru s compound comprises a -tetrakis (hydroxymethyl) phosphonium (THP) compound, or a water-soluble self-condensate thereof, or a water soluble condensate thereof with an organic nitrogen compound, or a mixture of said organic nitrogen compound with phosphonium compound or condensate or self condensate. 21. A process according to Claim 20, in which the organic nitrogen compound is urea, biuret, guanidine, melamine or methylolated melamine. 22. A process according to Claim 21, in which the organic nitrogen compound is urea. 23. A process according to any one of Claims 1 to 22, in which the THP salt and the organic nitrogen compound comprise a precondensate such that the molar ratio of organic nitrogen compound to THP therein is 0.05:1 to 0.8:1. 24. A process according to Claim 23, in which the molar ratio of organic nitrogen compound to THP is 0.25:1 to OA:L 25. A process according to Claim 23 or 24, in which the molar ratio of organic nitrogen compound to THP is 0.4:1 to OA:L 26. A process according to any one of Claims 1 to 25, in which the impregnation solution has a pH of 2-7.5.

   i 2-1- iL A process according to Claim 26, in which the impregnation solution has a pH of 4-5.

   28. A process according to any one of Claims 1 to 27, in which the concentration of organophosphorus compound (by weight expressed as THP+ ion) in the impregnation solution is 5-70%.

   29. A process according to Claim 28, in which the concentration of organophosphorus compound (by weight expressed as THP+ ion) is 20-35%.

   30. A process according to any one of Claims 1 to 29, in which the impregnation solution also comprises a wetting agent.

   31. A process according to Claim 30, in which said wetting agent is nonionic.

   32. A process according to Claim 30 or 31, in which said wetting agent is present in an amount of 0.05-0.5% by weight of the impregnation solution.

   33. A process according to any one of Claims 1 to 32, in which the impregnation solution also comprises a fabric softener.

   34. A process according to Claim 33, in which said fabric softener is present in an amount of 0.1-2% by weight.

   35. A process according to any one of Claims 1 to 34, in which the impregnation solution also comprises a catalyst.

   36. A process according to Claim 35, in which said catalyst comprises a salt of a strong acid and a weak base.

   37. A process according to Claim 36, in which said catalyst comprises an ammonium or alkaline earth metal chloride or nitrate or an ammonium acid phosphate.

   22.

   td 39 40.

   41.

   42.

   43.

   44.

   45.

   46.

   47.

   48.

   A process according to Claim 35, 36 or 37, in which said catalyst is present in an amount of 0.1-5% by weight.

   A process according to any one of Claims 1 to 38, in which the treated substrate is impregnated to give an organophosphorus pick up of less than 40% (as THP+ ion based on the original weight of the substrate).

   A process according to Claim 39, in which said organophosphorus pick up is 20-30% (as THP+ ion based on the original weight of substrate).

   A process according to Claim 39 or 40, in which the wet substrate is squeezed to a wet pick up of 50-100% (by weight based on the original weight of substrate) A process according to any one of Claims ' 1 to 38, in which the treated substrate is impregnated with a concentrated impregnation solution via a minimum add-on technique.

   A process according to Claim 42, in which said minimum add-on technique is a foaming technique.

   A process according to Claim 42 or 43, in which the wet pick-up is 10-50% (by weight based on the original weight of the substrate).

   A process according to any one of Claims 1 to 44, in which the organophosphorus impregnated substrate is cured by means of heat and/or ammonia.

   A process according to Claim 45, in which said organophosphorus impregnated substrate is cured by means of ammonia alone.

   A process according to Claim 45, is which said organophosphorus impregnated substrate is cured by means of heat alone.

   A process according to Claim 45, in which the ammonia cure takes place after the heat cure.

   7; i i 23.

   A process according to Claim 45 or 47, in which the heat cure takes place in a stetner or baking oven at a temperature of from 100 to 200 C.

   50. A process according to Claim 49, in which the curing time is from to 0.5 minutes.

   51. A process according to any one of Claims 1 to 50, in which the cured substrate is subjected to further insolubilisation of the cured resin in the treated substrate.

   52. A process according to any one of Claims 1 to 51, in which the cured substrate is subjected to oxidation.

   53. A process according to Claim 52, in which said oxidation is achieved by means of an aqueous hydrogen peroxide solution of concentration of 0.5-15% w/w.

   54. A process according to Claim 52, in which said oxidation is achieved by means of an aqueous sodium perborate solution of concentration 1-10% w/w.

   55. A process according to Claim 52, 53 or 54, in which said oxidation is achieved by application of an oxidising agent in excess for 0.1-10 minutes at 0-40 C.

   56. A process according to Claim 52, wherein said oxidation is achieved by means of a gas containing molecular oxygen being drawn or blown through the substrate.

   A process according to any one of Claims 1 to 56, in which the organic fibrous substrate consists essentially of cellulosic fibres.

   58.

   A process according to any one of Claims 1 to 56, in which the organic fibrous substrate comprises cellulosic and non-cellulosic fibres.

   21 JA - 4. 5 i.

   60.

   61.

   62.

   64.

   65.

   A process according to any one of Claims 1 to 56, in which the organic fibrous substrate consist:s essentially of non-cellulosic fibres.

   A process according to any one of Claims 1 to 58, in which the cellulosic fibres are natural cotton, ramie, flax, paper or cardboard, viscose or cuprammonium fibres, or cellulose acetateor propionate.

   A process according to any one of Claims 1 to 56, or 58 or 59, in which the non-cellulosic fibres are polyester, polyamide or polyacrylonitrile fibres.

   A process according to any one of Claims 1 to 61, in which the 2 substrate is a fabric of weight of 0.05 to lkg/m A process for the flame retardant treatment of an organic fibrous substrate containing reactive groups, substantially as hereinbefore described with reference to any one of Examples 1 to 17.

   An organic fibrous substrate when treated by a process according to any one of Claims 1 to 63.

   A composition for the flame retardant treatment of an organic fibrous substrate made by the process of any one of Claims 1 to 64.

   Published 1991 at The Patent Offire. Concept House. Cardifr Road. Newport. Gwent NP9 I RH. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmfe"fach. Cross Keys. Newport. NP1 7HZ. Printed by Multiplex techniques)td. St Mary Cray. Kent- z 1 i i