EP0769584A2

EP0769584A2 - Flame retardant compositions

Info

Publication number: EP0769584A2
Application number: EP96116404A
Authority: EP
Inventors: Rebecca Sally Jane Day
Original assignee: Albright and Wilson UK Ltd
Current assignee: Solvay Solutions UK Ltd
Priority date: 1995-10-21
Filing date: 1996-10-14
Publication date: 1997-04-23
Also published as: GB9521640D0; NO964429L; GB2306477A; EP0769584A3; NO964429D0

Abstract

The use of non-salt ammonia neutralisate of a nitrilo-tris (alkylene phosphonic acid), especially nitrilo-tris (methylene phosphonic acid), having a pH of 6.5 to 7.0 at 25°C, as, or in connection with, a flame-retardant.

Description

The present invention relates to the use of non-reactive, non-salt, non-durable ammonia neutralisates of nitrilotris (alkylenephosphonic acids), especially of nitrilotris methylenephosphonic acid, as a flame retardant composition. In particular it relates to the use of said neutralisates as, or in connection with a flame retardant for amongst other applications fabrics, timber, paper, and timber coatings. Fabrics, including natural, man made or synthetic fibres and blends thereof, treated with the aforementioned neutralisates exhibit excellent flame retardant properties, good fabric strength, handle and drape, do not bloom and are of low fogging characteristics even under conditions of high humidity. Such treated fabrics are particularly suitable for use in automotive and aerospace applications (where such low blooming and/or fogging characteristics are required), and are also suitable for use in soil furnishings, clothing and the like.
Flame retardants are incorporated into many products on the grounds of safety in order to control the spread of fire through the product. Flame retardants can, for example, act by causing rapid extinguishing of flames, or by making the product difficult to set alight. Flame retardants have conventionally been used to treat inter alia fabrics and soft furnishings, especially within the home furnishings, automotive, aerospace and construction industries. The use of flame retardants within these and other industries in conventional applications is increasing in response to more stringent fire control and safety legislation, and as a consequence thereof many new applications for flame retardants are now being found.
Non-durable flame retardant compositions are applied to many fabrics, either during the manufacture of the fabric by means of a particular process stage or as a separate treatment after the manufacture of an article prepared from a fabric, eg, the post manufacture treatment of curtains to render them flame retardant. Non-durable flame retardant compositions are not permanent in their application to fabric, and are removed by washing. However, non-durable flame retardants do exhibit same durability to dry cleaning.
It is an important feature of flame retardant treated fabrics that the feel or the 'handle' of the fabric is not excessively harsh to the touch, especially if the fabric is to be used for applications such as safety clothing and soft furnishings. Furthermore, such treated fabrics should maintain good flexibility after treatment, ie, show good drape characteristics, especially if the fabric is to be used for applications such as curtains etc.
Some flame retardants, especially salt based flame retardants, may produce or contain volatile components which upon contact with glass, especially cold glass, cause fogging. This is particularly undesirable where the flame retardant is to be used in automative or aerospace applications.
Alternatively, or in the case of some flame retardants, additionally, the flame retardant may under certain conditions 'bloom' on the fabric to which it has been applied, and is then visible. This blooming is especially problematic in conditions of high humidity. As well as being unsightly on the fabric, blooming can result in poor fabric handle.
The ammonia neutralisate of nitrilotris (methylenephosphonic acid) is a water soluble phosphonate which is known as a scale-inhibitor for use in water treatment and also as a deflocculating and dispersing agent, due to its ability to form calcium and magnesium complexes, and very stable complexes with heavy metals. Said neutralisate has also previously found use in other applications such as cooling water treatment, corrosion control, oil-field water treatment, bottle washing and textile bleaching. However, hitherto said neutralisate has not been used as, or in connection with, flame retardant compositions. The aforementioned ammonia neutralisate has been available commercially as BRIQUEST 301-34N^*1.
^*1 'BRIQUEST' is a registered trademark of Albright & Wilson UK Limited.
Flame retardants for fabrics should ideally exhibit excellent flame retardancy on natural, man made and synthetic fibres and blends thereof, and not result in unacceptable levels of loss of strength of the treated fabric. The problem of the loss of strength is particularly prevalent with acid sensitive fibres such as cotton, in cases where an acidic flame retardant is used. Such strength loss results in a decreased useful life of the fabric due to its premature wear and tear. Also, the flame retardant treated articles should, if the application requires, exhibit good drape and/or hand characteristics. In particular salt based flame retardants, eg ammonium polyphosphate, are known to be susceptible to precipitation which may cause blooming, and also produce unacceptable fogging levels under conditions of high humidity. For the reasons mentioned hereinabove, blooming and unacceptable fogging levels caused by the use of flame retardants is undesirable.
There is therefore a need to provide a non salt-based flame retardant, which exhibits excellent flame retardancy on natural, man made and synthetic fabrics and blends thereof but which does not result in excessive loss of strength of the fabric after treatment, and which does not exhibit unacceptable levels of blooming and/or fogging, and which retains or improves handle and drape characteristics of the fabric.
We have now discovered that an ammonia neutralisate of a nitrilotris (alkylenephosphonic acid), in particular a nitrilotris (methylenephosphonic acid) may be used as, or in connection with, a flame retardant composition. Said neutralisates provide excellent flame retardancy on natural, man made, and synthetic fabrics and blends thereof, do not result in unacceptable levels of loss of strength of the fabric, impart excellent blooming and fogging control characteristics (even in conditions of high humidity) and fabrics treated with said flame retardant compositions exhibit good handle and drape characteristics. We have further discovered that said neutralisates are suitable in some circumstances for use as, or in connection with, flame retardants inter alia for timber, paper and timber coatings.
It is believed, although we do not wish to be limited thereto, that the neutralisation by a nitrogen containing base may aid the flame retardancy characteristics of the neutralisate, or provide a synergistic effect.
Accordingly, in a first embodiment, the present invention provides the use of an ammonia neutralisate of nitrilotris (alkylenephosphonic acid) as, or in connection with, a flame retardant composition. In particular an ammonia neutralisate of nitrilotris methylene phosphonic acid is provided.
Preferably, the ammonia neutralisate of nitrilotris (alkylenephosphonic acid), has a pH of from 6.5 to 7.0 at 25°C.
In the use of the ammonia neutralisates of the present invention, the flame retardant may be contacted with a fabric either before, during or after the manufacture of said fabric, or applied to an article made from said fabric. The present invention further provides articles rendered flame retardant by the use of the neutralisate described in the two immediately preceding paragraphs.
The ammonia neutralisate of the nitrilotris (alkylenephosphonic acids) are non-reactive, non-durable, non-salt compounds prepared by the neutralisation of nitrilotris (alkylenephosphonic acids) with ammonia. It is preferred that the ammonia neutralisate is prepared by the neutralisation of nitrilotris (methylenephsophonic acid), with the corresponding ethylenephosphonic acids, and propylene phosphonic acids also being suitable.
Typically the nitrilotris (alkylenephosphonic acid) is neutralised by the addition of ammonia to an aqueous solution of said acid. Typically said aqueous solution of said acid is used at an active concentration of 1 to 99% by weight, preferably 10% to 80%, most preferably 25% to 65%, eg, 35% to 55% by weight, such as 50% by weight active concentration. The ammonia may be added as an aqueous solution, at any suitable active concentration, typically as a saturated ammonia solution, (ie, 88% by weight ammonia solution).
The neutralisation of the nitrilotris (alkylenephosphonic acid) may be undertaken according to any suitable method. Typically, the ammonia solution is slowly added to the nitrilotris (alkylenephosphonic acid) with stirring, for example at a rate of 1 drop of ammonia solution per second, until the requisite pH is obtained and maintained. No further ammonia solution is then required to be added.
The ammonia neutralisate of the nitrilotris (alkylenephosphonic acid) typically has a pH in the range of 6.5 to 7.0, preferably 6.52 to 6.95, most preferably 6.55 to 6.9, when measured at 25°C.
Said ammonia neutralisate is typically used in an amount sufficient to render the fabric or article to which it is applied sufficiently flame retardant to meet recognised flammability standards, eg, the British Safety Standards Council's BS5867 Part 2 Types A and B for curtains, BS476 Parts 6 and 7 for wall coverings and BS7175 for mattress tickings.
Typically said ammonia neutralisate is used at a concentration of 0.5% to 20%, expressed as % dry chemical add on (with respect to phosphorus content) to the fabric, preferably 1% to 16%, most preferably 3% to 15%, eg, 3.5% to 13%. The actual amount of said neutralisate required will depend upon the nature, construction and weight of the fabric to be treated, the uniformity of the application and the flame retardant performance required.
The concentration of said ammonia neutralisate when used as a bath composition for treating fabric typically lies within the range of 100g/l to 600g/l, preferably 150g/l to 500g/l, most preferably 175g/l to 400g/l, eg, 204g/l to 370g/l, dependent upon the factors recited in the immediately preceding paragraph.
The addition of an excessive amount of said ammonia neutralisate may result in a poor handle of the fabric, and should preferably be avoided if an acceptable level of flame retardancy can be achieved with a lower level of said neutralisate. However, in virtually all cases excellent flame retardancy and good fabric handle may be achieved at a low application level of said neutralisate.
The aforementioned ammonia neutralisate may be applied to the fabric to be treated by any suitable method. Said fabric should be clean, absorbent, and free from alkali, or otherwise reduced uptake of the flame retardant will occur as a result of the presence of soils, natural waxes or applied finishes. The application of said ammonia neutralisate to the fabric may be effected any suitable method, for example by brushing, dipping, spraying or by a pad dry technique.
The treated fabric may be dried at ambient or at elevated temperatures. If the fabric is heat dried, it is preferred that a temperature of between 70°C and 160°C is used, preferably between 80°C and 150°C. Alternatively the treated fabric may be dried by infa-red heating, as the ammonia neutralisate is not prone to arcing and subsequent scorching, as is commonly encountered with salt type flame retardants.
Where the ammonia neutralisate flame retardant compositions of the present invention are used as an application bath composition for the treatment of fabrics, said reaction bath composition may optionally include minor amounts of other ingredients such as water and/or oil repellent fluorocarbons, fabric softeners, to impart said respective characteristics to the treated fabric or other article. Furthermore, other minor ingredients such as binders, or surfactants may be used with or in connection with, the ammonia neutralisate as required. Suitable binders include acrylics, vinyl chloride and polyvinyl alcohol. Suitable surfactants include anionic, cationic, amphoteric and especially non-ionic surfactants. Particularly preferred non-ionic surfactants include fatty acid alkylolamines; ethylene oxide condensates of fatty alcohols, fatty acids and alkylolamides; fatty acid esters; and ethylene oxide/propylene oxide block copolymers. Typically the aforementioned optional ingredients are present in said reaction bath compositions in total amounts of up to 80g/l, preferably up to 60g/l, eg, up to 50g/l or up to 25% by weight based on the total weight of the active flame retardant composition, preferably up to 20%, most preferably up to 10% by weight.
The ammonia neutralisate of nitrilotris (alkylenephosphonic acid) may be used as, or in connection with, a flame retardant composition for natural, man made, or synthetic fibres, and blends thereof, for example wool, wool blends, cotton, cotton blends, and polyesters.
The use of the aforementioned neutralisate as, or in connection with a flame retardant, finds particular application in areas where low fogging and blooming characteristics of the treated fabric are required. Such applications include amongst others, the aerospace and automotive industries, in particular for seat and carpet fabrics. Other uses include mattress tickings, wall coverings and other soft furnishings, eg, curtains and settee covers. The excellent drape and handle characteristics imparted to fabrics by treatment with said neutralisate, makes treated fabrics also suitable for non durable safety clothing, etc. Furthermore, said neutralisate may be used in some circumstances as, or in connection with, a flame retardant compositon for timber, paper, timber coatings and the like.
The ammonia neutralisates of the present invention may be used as a flame retardant additive for suitable applications.
The flame retardants of the present invention will be further illustrated by reference to the following examples, although is not to be construed as being limited thereto.

Example 1: Method of preparation of the ammonia neutralisate of nitrilotris (methylene phosphonic acid)

To a 50% by weight aqueous solution of nitrilotris (methylenephosphonic acid) (1 litre, 500g of acid, 1.67 moles), an 88% ammonia solution (113g, 6.64 moles) was added dropwise at a rate of 1 drop per second with constant stirring. The ammonia addition was maintained until the pH of the solution reached, and stabilised at pH 6.5 (as measured at 25°C).

Example 2: Level of the flame retardant composition required on different fabrics

Table 1 below shows the typical concentration of the flame retardant composition required on different fabrics to meet recognised flammability standards. The concentration is expressed as percentage dry chemical add on, with respect to the fabric. TABLE 1

% dry add on for different fabrics

Fabrics % dry add-on

Cotton 6-12%

70 parts cotton / 30 parts polyester 6-12%

polyester 8-12%

wool 4-10%

wool/polyester 4-10%
For each of the above fabrics the amount of the flame retardant composition required is relatively low, and the loss of strength of the fabric due to the treatment was within acceptable limits.

Example 3: Typical bath compositions for the treatment of fabrics

Table 2 shows the typical bath composition concentration used to treat various fabrics to render them sufficiently flame retardant to meet the relevant flammability standard stated.

TABLE 2

Typical bath composition concentration
	Ammonia neutralisate of nitrilotris methylenephosphonic acid	^*2 EMPILAN KI8/65	Fabric to be treated	Safety Standard requirements fulfilled
	g/l	g/l
A	370	4	136g/m² 100% polyester	USA Standard FMVSS302 automotice end use
B	204	4	405g/m² 100% wool	EC Standard CAA 8/2 aircraft upholstery end use
C	320	4	232g/m² 100% cotton, pigment printed	UK Standard BS5867 Part 2 Type B - curtains
D	360	4	409g/m² 42% polyamide, 40% polyester, 18% viscose, colour woven fabric	UK Standard BS5867 Part 2 Type B - curtains

^*2 EMPILAN KI8/65 is a C₁₃ alcohol 8 mole ethoxylate surfactant.
EMPILAN is a registered trade mark of Albright & Wilson UK Limited

The above table shows that the flame retardant compositions of the present invention are effective in the treatment of various types of fabrics, and such treated cloth easily fulfils the requirements of recognised flammability standards.

Example 4: Water/oil repellent and flame retardant finishes

The following typical bath composition provides a flame retardant and water/oil repellent finish to the treated fabric. The composition is particularly effective for treating 100% cotton:

Ammonia neutralisate of nitrilotris (methylenephosphonic acid) 340g/l

Water and oil repellant ^*3 44g/l

Amine oxide surfactant ^*4 4g/l

^*3 available commercially as SCOTCHGARD FC251, a dispersion of a fluroalkyl copolymer.

^*4 available commercially as MYKON NRW-3.

SCOTCHGARD and MYKON are trade marks.
Cotton treated with the above composition has an oil repellancy rating of 6, and a spray rating of 80 (BS3702 : 1982).

Example 5: Flame retardant and fabric softening finishes

The following typical bath composition provides a flame retardant and fabric softening finish to the treated fabric:

Ammonia neutralisate of nitrilotris (methylenephosphonic acid) 340g/l

Fabric Softener ^*5 44g/l

^*5 available commercially as Patsoft 1220, a fatty amine/polyolefin blend.

PATSOFT is a trade mark

Example 6: Comparison of blooming and fogging characteristics

The bloom control characteristics of the ammonia neutralisate of the present invention was tested under controlled conditions against two conventional salt based flame retardants (AMGARD TR^*6 and AMGARD FSD^*7) and a commercially available non-salt flame retardant (FLOVAN CGN^*8).
The flame retardants were applied to various fabrics as listed below in Table 3. The fabrics were stored under conditions which would typically induce blooming by leaving the samples on a draughty windowsill, with the samples being regularily inspected. A small draught from the window was maintained with the temperature of the test varying between -5°C to 25°C over a 6 month period.
The fogging characteristics of the ammonia neutralisate of the present invention were tested by determining the gravimetric weight gain on aluminium foil from the test material. A Haake fogging apparatus (instrument Nos 00032, 00033, 00034 and 00035) was used. Samples were cut in to 80mm diameter pieces, with the thickness measured to the nearest 0.02mm, and kept in a desicator until required. Immediately prior to use the samples were removed from the desicator, placed into beakers and weighted with metal rings. Silicone rubber rings were placed on each of the beakers and covered by 105mm x 105mm pieces of aluminium foil, followed by glass plates, filter papers and condensors. The beakers were placed in the fogging apparatus, and the condensors pushed down to ensure the beakers were level with the top of the oil bath part of the apparatus. The fogging apparatus was heated to 100°C +/- 0.3°C, and the test was run for 16 hours +/- 10 minutes. After this time the condensors, glass plates, aluminium foil were removed and the foil stored in a desicator for 3½ to 4 hours, prior to being weighed to the nearest 0.01mg. The fogging value was recorded as mg/10mm of foam, taken as an average of five results.
A result of greater than 1mg/10mm of foam represents unacceptable fogging characteristics, and a result of less than 1mg/10mm of foam represents low fogging characteristics. Obviously the lower the value of mg/10mm of foam, the more acceptable are the fogging characteristics.
The handle of the fabrics subjected to the 'bloom' experiment was assessed by simply feeling the fabric. The ammonia neutralisate treated fabric was judged to have the most acceptable hand, followed by the FLOVAN treated fabric which exhibited some degree of stiffening. Both the aforementioned products were judged to provide a superior hand when compared to the AMGARD treated fabrics. Furthermore, the fabric strength loss and the flame retardant performance of the ammonia neutralisate and FLOVAN treated fabric were found to be comparable. The fogging control characteristics of the ammonia neutralisate and the FLOVAN were excellent, whilst the conventional salt based flame retardants exhibit poor control characteristics.

Example 7: Flame retardancy

The flame retardancy of fabric treated with the ammonia neutralisate of the nitrilotris (methylenephosphonic acid) was tested and compared against conventional flame retardants, on the fabrics given below in Table 4.

TABLE 4

Flame retardancy on different fabric types
FABRIC TYPE	COMPOSITION & CONSTRUCTION	WEIGHT G/M²
1	100% Cotton plain woven fabric	155
2	50/50 Polyester/wool blended woven fabric	223
3	100% polypropylene plain woven fabric	220
4	100% acrylic plain woven fabric	270
5	100% polyamide plain woven fabric	90
6	100% polyester satin weave fabric	102

The flame retardants used as a comparison to the above ammonia neutralisate are given below in Table 5.
Comparative testing to BS 5867, Part 2 Type B, for flame retardancy was carried out on the finished textiles.

The flame retardancy, of the fabrics of table 4, treated with the various flame retardants is given below in Table 5.

TABLE 5

Flame retardancy results
SAMPLE AND FABRIC TYPE		AFTERFLAME (SECONDS)	AFTERGLOW (SECONDS)	CHAR LENGTH (MM)
AMGARD FSD
Fabric type	1	0.0	0.0	76.0
	2	0.0	0.0	68.0
	3	0.0	0.0	94.0
	4	> 35.0	0.0	T/E
	5	47.8	0.0	T/E
	6	0.0	0.0	106.0

AMGARD TR
Fabric type	1	0.5	0.0	70.0
	2	1.6	0.0	63.0
	3	18.9	0.0	108.0
	4	> 35.0	0.0	T/E
	5	28.5	0.0	T/E
	6	0.0	0.0	106.0

FLOVAN CGN
Fabric type	1	0.3	0.0	76.0
	2	1.6	0.0	64.0
	3	0.0	0.0	101.0
	4	> 35.0	0.0	T/E
	5	15.6	0.0	T/E
	6

Ammonia neutralisate of nitrilotris (methylenephosphonic acid)
Fabric type	1	0.0	0.0	58.0
	2	3.5	0.0	67.0
	3	22.5	0.0	T/E
	4	> 35.0	0.0	T/E
	5	48.5	0.0	T/E
	6	0.0	0.0	106.0

* T/E Top Edge Ignites

Results

Fabric types 1, 2 and 6 met the requirements of BS 5867 Part 2 Type B when treated with any of the five chemical finishes, whereas fabric types 4 and 5 did not meet said requirements when treated with any of the conventional flame retardants, or the flame retardant of the present invention.
Both the conventional Amgard products produced a salty handle to the fabric, and the Flovan product a stiff or sticky handle. The flame retardant of the present invention was considered to give the best handle of the flame retardant compositions tested, when manually compared.

Example 8: Tensile strength of the treated fabrics

Samples were taken from both the warp and weft directions of fabric types 1, 2, 5 and 6 of Example 7, and were tested to BS 2576 Tensile Strength and BS 4303 Wing Rip Tear. Each result was compared to the result obtained for the untreated fabric, with the difference in Tensile Strength being recorded as a % change in strength and tear strength when compared to the untreated fabric. The ammonia neutralisate used was that of the nitrilotris (methylenephosphonic) acid. The results are given in Table 6.
The results in table 6 show all the treated fabrics exhibit some change in the strength thereof, with the loss of strength for the ammonia neutralisate being within acceptable limits and comparable to the conventional flame retardants.

Example 9: Drape characteristics

Each of the samples of Example 6 was tested for the assessment of the drape characteristics according to BS 5058 : 1993 after the aforementioned 6 month storage period. The samples were not reconditioned prior to testing. The ammonia neutralisate was of the nitrilotris (methylenephosphonic) acid. The results are given below in Table 7. It should be noted that small samples of fabric were used for the test and therefore the drape co-efficient values obtained are comparative with respect to each other, and represent higher co-efficients than would typically be obtained. TABLE 7

Drape Characteristics

FLAME RETARDANT DRAPE CO-EFFICIENT

Amgard FSD 89.3

Amgard TR 89.1

Flovan CGN 88.9

Ammonia Neutralisate 86.8
In each case the smallest test size was carried out. The samples all show comparable drape characteristics. A drape co-efficient of 100.0 shows a stiff fabric.

Claims

A method for treating a flammable material with a flame-retardant, characterised by the use of a non-salt ammonia neutralisate of a nitrilotris (alkylene phosphonic acid) as, or in connection with, said flame-retardant.
Use according to Claim 1, characterised in that the neutralisate is an ammonia neutralisate of nitrilotris (methylene phosphonic acid).
Use according to Claim 1 or 2, characterised in that the neutralisate has a pH of from 6.5 to 7.0 at 25°C, for example 6.52 to 6.95 at 25°C and especially 6.55 to 6.9 at 25°C.
Use according to any of Claims 1 to 3, characterised in that said flammable material comprises a fabric and said ammonia neutralisate is contacted with said fabric either before, during or after the manufacture of said fabric.
Use according to any one of Claims 1 to 4, characterised in that said ammonia neutralisate is used at a concentration of 0.5% to 20% (expressed as % dry chemical add on with respect to the phosphorus content).
Use according to Claim 5, characterised in that said concentration is from 1% to 16%, for example 3% to 15% and especially 3.5% to 13%.
Use according to any one of Claims 1 to 6, characterised in that said ammonia neutralisate is applied to said flammable material by brushing, spraying or pad-drying.
Use according to Claim 7, characterised in that said ammonia neutralisate is at a concentration of 100g/l to 600g/l, for example 150g/l to 500g/l, 175g/l to 400g/l, or 204g/l to 370g/l.
Use according to any one of Claims 1 to 8, characterised in that said ammonia neutralisate is used together with one or more further ingredients, e.g. water- and/or oil-repellent fluorocarbons, fabric softeners, binders or surfactants.
Use according to Claim 9, characterised in that said one or more further ingredients are used in an amount, based on the total weight of the neutralisate and said further ingredients, of up to 25% by weight, for example up to 20% by weight and especially up to 10% by weight.