GB2409827A

GB2409827A - Fire retardant for fabrics, comprising melamine coated ammonium polyphosphate

Info

Publication number: GB2409827A
Application number: GB0400417A
Authority: GB
Inventors: Peter Finan
Original assignee: Stephenson Group Ltd
Current assignee: Stephenson Group Ltd
Priority date: 2004-01-09
Filing date: 2004-01-09
Publication date: 2005-07-13
Also published as: GB0400417D0

Abstract

Preferably the fire retardant comprises ammonium polyphosphate coated with a melamine formaldehyde resin in an aqueous suspension. Preferably the composition also contains an acrylic binder, a benzalkonium salt preservative, a glycerine humectant, and xanthan gum and colloidal magnesium/lithium silicate thickeners. Preferably the fabric is heated after the composition has been applied. The composition is used to coat upholstery fabrics including curtains, awnings, window blinds, carpets, rugs, chair covers and sofa covers, especially those comprising cellulose base fibres, in particular cotton.

Description

if: . ... --a: Improvements in or Relating to Flame Retardancy This

invention relates to improvements in or relating to flame retardancy. It relates in particular to a method of treating a fabric to achieve improved flame retardancy, to a flame retardant composition for use on a fabric, and to a fabric treated with such a composition.

The term flame retardant in this specification denotes 0 a fabric which has been made more resistant to burning in any manner. That is, it includes a fabric whose ignition properties are favourably modified, and a fabric which, if ignited, is rendered more resistant to burning - and preferably being self-distinguishing It barely needs explaining that the ignition and burning properties of fabrics is of the utmost importance, most importantly in human terms. It is of course imperative that the flame retardancy of fabrics be improved. In research and business terms enormous efforts are being made, with that aim.

Traditionally there have been three methods of rendering a fabric, in particular a cellulosic-based fabric, flame-retardant: 1) Non-durable (i.e. not fast to washing) finishes such as solutions of various ammonium phosphates.

These may be applied by padding, spraying, etc. 2) Durable (i.e fast to washing) finishes such as phosphorus-containing compounds PYROVATEX CP (Ciba) ::. ... ::.

e:. :: A. and AFLAMMIT KWB (Thor). These may be applied by padding, spraying, etc. 3) Semi-durable finishes such as further ammonium phosphate-based products, for example FLAMMENTIN FMB (Thor) and AMGARD LR2 (Rhodia/Albright & Wilson). This category of flame retardants have been specifically designed to meet the requirements of BS5852 part 2: 1982 as modified by Schedule 3, Clause 1 of the Furniture and Furnishings (Fire) (Safety) Regulations 1988 S.I No. 1324 after the water soak procedure specified by Clause 4 of BS5651: 1978.

This third category requires that the flame-retardant finishes are durable only to a water-soaking procedure before testing.

The method of application of these semi-durable finishes have a number of drawbacks both in terms of processing and consumer desirability: High levels of chemical are required to be applied to the fabric The fabric frequently has to passed twice through a stenter/drying machine to ensure fixation During processing large amounts of fumes consisting of ammonia and urea derivatives are emitted The treated fabric is frequently much yellower than the untreated fabric The treated fabric is frequently much more tender, i.e it tears more easily than untreated fabric d, b , te,, The treated fabric is frequently harsher to the touch, and has what some processors describe as a "boardyn feel Reports from accredited testing houses suggest that samples submitted for testing meets the requirements of the relevant British Standard in barely 50% of cases.

Attempts to produce fabrics according to this third lo category have involved coating procedures, but these may use environmentally undesirable bromine and antimony compounds which are currently the subject of intense scrutiny from regulatory authorities in European Union countries. Some such compounds have already been banned in Scandinavian countries.

Padding procedures using these products have been attempted, but due to the nature of the active compounds the treatment procedure is often unpredictable. The heavy compounds have a tendency to settle in the treatment trough and a heavy-duty binder system is required to bind the compounds to the fabric making the fabric aesthetically undesirable.

This invention attempts to remedy most if not all of these shortcomings described above, and to produce a processing route and treated fabric with, in preferred embodiments, has one or more, and preferably all, of the following desirable characteristics: No fumes during processing Simple one-pass processing route

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No separate baking or washing-off procedures required No settling of product in the treatment trough No yellowing of treated fabric No loss of fabric strength Treated fabric is virtually indistinguishable from untreated fabric No antimony compounds used No bromine or other halogenated compounds used lo All ingredients biodegradable and non-hazardous Treated fabrics reliably meet the requirements of the British Standard.

Any method which could meet the above requirements would have many advantages both for the fabric processor and for the consumer.

We have now devised a method and composition which shows great promise for rendering fabrics flame retardant, and which offers at least some of the desirable characteristics described above.

In accordance with a first aspect of the present invention there is provided a method of treating a fabric to achieve improved flame retardancy, comprising the application to the fabric of a treatment composition comprising a melamine-coated ammonium polyphosphate compound.

Melamine-coated ammonium polyphosphates have been proposed before, but as flame retardant components of thermoplastic resin composition. Examples of such . : : . .. .e: :.. :. . :.e disclosures are given in US 5,430,080 and US 5,945,467.

In the present invention no claim is made to the use of a melamine-coated ammonium polyphosphate for the purpose of rendering flame retardant plastics resins per se.

Methods for the manufacture of melamine-coated ammonium polyphosphates are well known. In broad terms, melamine may be sublimated, and deposited onto the surface of ammonium polyphosphate particles. Typically the amount lo of melamine thus deposited is 0.5-20t w/w of the ammonium polyphosphate, preferably 2-10%. For further information US 5,534,291 or US 5,599,626 may be consulted.

In the present invention the melamine-coated ammonium polyphosphate compound is preferably applied to the fabric in a liquid treatment composition. Preferably the treatment composition is a dispersion in which particles of the melamine-coated ammonium polyphosphate compound are suspended. Preferably the dispersion is a stable one, resisting settlement even over an extended period, for example when stored without movement for one month under ambient conditions.

Preferably the melamine-coated ammonium polyphosphate compound is in the form of particles having a mean particle size of at least 3pm, preferably at least 5pm.

Preferably they have a mean particle size not exceeding 15ym, and preferably not exceeding loom. Mean particle size as defined herein may be as determined by Low Angle Laser Light Scattering (LALLS), using standard test method ISO 13320, carried out using a Malvern Mastersizer S apparatus, supplied by Malvern Instruments Ltd., of Malvern, UK. Typically the melamine-coated ammonium : : e e e polyphosphate is supplied as a powder, but the apparatus described above can measure mean particle size of a dry powder or of particles in a dispersion.

Suitably the treatment composition contains from 5 80%w/w of the melamine-coated ammonium polyphosphate compound, preferably 10-50%, more preferably 12-40%, and most preferably 15-30%.

lo Preferably the treatment composition contains a thickener which acts to thicken the treatment composition when phosphate groups are present. Preferably a thickener which causes thickening when the phosphate groups are present is present in an amount of from 0.01-2% w/w, more preferably 0.02-0.5% and especially 0.05-0.2%. We have found colloidal magnesium/lithium silicate to be very suitable for this purpose.

Preferably the treatment composition used in the method comprises a general thickener, by which we mean a thickener whose thickening action in not dependent upon any other component of the composition. Preferably a general thickener is present in the amount of from 0.01-2% w/w, more preferably 0.02-0.5% and especially 0.05-0.2%.

We have found fine food grades of xanthan gum to be very suitable for use as a general thickener.

Preferably the treatment composition includes a humectant. Preferably a humectant is present in an amount of from 0.1-4% w/w, preferably 0.5-2%. We have found glycerine to be very suitable as a humectant. .

e: . e. . : e A.. * ë Preferably, the treatment composition used in the method contains a preservative, for example a benzalkonium salt. Suitably a preservative is present in the amount of from 0.01-2% w/w, preferably 0. 02-0.5%, and especially 0.05-0.2%.

Preferably a binder is delivered to the fabric, together with the melamine-coated ammonium polyphosphate.

Preferably the binder is a thermoplastic material.

lo Preferably the binder is such that a heat treatment as mentioned above causes it to improve the adherence of the melamine-coated ammonium polyphosphate, on the fabric.

Preferably the binder is a thermoplastic material.

Preferably the binder is such that a heat treatment as mentioned above causes it to improve the adherence of the melamine-coated ammonium polyphosphate, on the fabric.

Preferably a binder is present in the treatment composition, suitably in an amount of from 1-30% w/w, preferably 2-20t, more preferably 3-10%, and most preferably 4-8% (by weight of binder molecules).

In some embodiments the binder may be such that the melamine-coated ammonium polyphosphate is retained on the fabric with a very high level of durability. In other, preferred, embodiments the binder is such that the retention of the melamine-coated ammonium polyphosphate is semi- durable. That is, it may persist for several normal domestic washes. Semi- durable adherence is quite sufficient in the case of many household fabrics. We have found that a fabric which has semi-durable adherence of a : .: : . e: : :e melamine-coated ammonium polyphosphate may have excellent flame retardancy, along with excellent fabric handle.

Preferably the treatment composition contains 30-90% 5water, more preferably 50-85%, most preferably 70-85% (w/w of composition).

A binder, comprising binder molecules, may suitably be applied to a fabric in an amount 1 part by weight binder lo molecules to 2-15 parts, preferably 5-12, parts melamine coated ammonium polyphosphate (w/w).

Preferably the treatment composition is pourable, and resistant to settlement, as defined above.

Preferably, the treatment composition used in the method has a solids content in the range 5-40% w/w, preferably 6-30%.

Preferably a treatment composition of the invention is one which is able to soak into the fabric being treated.

This ensures that the melamine-coated ammonium polyphosphate compound is delivered to the fabric with a high degree of penetration.

Preferably a fabric which is treated in accordance with the present invention is visually indistinguishable from a corresponding fabric which has not been treated.

In particular, preferably there is no yellowing of the fabric.

Preferably a fabric which is treated in accordance with the present invention has substantially the same . ::..:. ....: -. . . . strength as a corresponding fabric which has not been treated.

The treatment composition may be applied to a fabric in any convenient manner, for example by spraying, immersion, padding, coating and printing. Padding is a preferred method.

Preferably the addition of the treatment composition lo to the fabric involves initial weight add-on (including water) of 50-80%, preferably 6075%, on dry fabric weight (after any fabric nip or squeeze which is used, to remove excess treatment composition.

Preferably the method includes a heat treatment, wherein after the treatment composition has been applied to the fabric it is subjected to an elevated temperature, preferably in excess of 80 C, and most preferably in excess of 120 C. Preferably the elevated temperature is up to 200 C.

Preferably a stenter machine is used to apply the treatment composition to a fabric, and to convey the treated fabric through a heating zone.

When the treated fabric is passed through a heating zone, preferably only one pass is made through it; there are preferably no separate drying and baking passes, as are employed in prior processes.

Preferred fabrics treated by the method of the present invention are household upholstery fabrics, for example curtains, awnings, window blinds, carpets, rugs, chair : '. . ::: . : :: ee: covers and sofa covers. Other fabrics found in the house, for example clothes, bed linen and netting, are less preferred, in the application of the present invention, but their treatment is not excluded.

Preferably the method does not involve the application, to the treated fabric, of any bromine- containing compound.

0 Preferably the method does not involve the application, to the treated fabric, of any antimony containing compound.

Preferably the method does not generate any hazardous fumes. Preferably substantially the only compound which is driven off as vapour in the method is water.

In a preferred embodiment a precursor composition is prepared, containing all of the compounds to be applied to the fabric except the binder. The precursor composition is preferably a concentrate which is diluted with water at the point of use. Preferably any binder present is added at the point of use. We have found that this gives the most reliable results. Preferably 0.5-2 parts of the precursor composition, most preferably 1-1. 5 parts, are diluted with 1 part water (w/w).

Suitably the precursor composition contains from 10 90%w/w of the melamine-coated ammonium polyphosphate compound, preferably 15-70%, more preferably 25-55t, and most preferably 35-45%.

:... I: :.

Preferably the precursor composition contains from 0.02-4% w/w, more preferably 0.04-1%, and most preferably 0.1-0.5%, of a said thickener which acts to thicken the treatment composition when phosphate groups are present.

Preferably the precursor composition contains from 0.02-4% w/w, more preferably 0.04-1%, and most preferably 0.1-0.4% of a general thickener, as defined above.

loPreferably the precursor composition contains from 0.2-8% w/w, more preferably 0.5-6%, and most preferably 1 4%, of a humectant, as defined above.

Preferably, the precursor composition contains from 150.02-4% w/w, preferably 0.04-1%, and most preferably 0.1-0.4%, of a preservative, as defined above.

Preferably the precursor composition contains 40-75% water, more preferably 50-65% (w/w of precursor composition).

Preferably the solids content of the precursor composition is in the range 10-80% (w/w), more preferably 20-60%, and most preferably 30-50%.

The definitions of amounts of components given above and in the claims are stated on the basis that when there is more than one of a given component present (for example when more than one preservative) the above definitions apply to such components in combination.

Preferably the precursor composition does not contain a binder. A binder, when present in the treatment :. .. a.-:.. .:e ee.

composition, is preferably added separately at the point of use. However a precursor composition containing a binder, that composition merely requiring dilution with water for use, is not excluded.

Preferably a precursor composition as defined above is made by high shear mixing of the components.

A precursor composition as defined herein constitutes lo a second aspect of the present invention.

A treatment composition in a form to be applied to a fabric preferably constitutes a third aspect of the invention. Preferably this treatment composition contains a binder and a higher water content than the precursor composition of the second aspect.

In accordance with a fourth aspect to the present invention there is provided a fabric treated by the method of the present invention, in order to confer flame retardancy. Preferably the fabric is a cellulosic- based material, including manufactured cellulosic-based materials, for example viscose, and natural cellulosic- based materials, for example cotton. Most preferably the fabric is cotton or is cotton-rich (having at least 50% w/w cotton).

The invention will now be further described, by way of

example, as follows.

A precursor composition was made, containing the following ingredients, in the amounts stated.

. ::. :.e A: .. . Ingredient Function % w/w Water Inert neutral diluent 57. 5% LAPONITE RDS Li/Mg silicate. A phosphorous- 0.2% mediated thickener FR CROS C60 Flame retardant 40.0% Xanthan Gum GA Food grade - general thickener 0.15% Glycerine Humectant 2.0% SPECTRUS NX1170 Preservative 0. 15% LAPONITE RDS is available from Southern Clay Products, of Gonzales, TX, USA.

FR CROS C60 is particulate melamine-coated ammonium polyphosphate of mean particle size 7pm, believed to have a melamine coating: ammonium polyphosphate ratio of 5:95, and available in powder form from Budenheim KG, Germany.

SPECTRUS NX1170 is available from GE Water Technogies, of Trevose, PA, USA.

LAPONITE RDS, FR CROS C60 and SPECTRUS NX1170 are believed to be trade marks of the companies mentioned above.

The ingredients were blended together using a high shear mixer and formed a stable dispersion. No settlement was evident when a sample was placed in a transparent glass jar under ambient conditions for a period of one month.

The mixing tank of a stenter machine was loaded with water, an acrylic binder composition was added, and the precursor composition mentioned above. The relative e : . :: amounts were 40% w/w water, 12% w/w binder composition (50% w/w thereof being acrylic binder molecules) and 48% w/w the precursor composition. These components were mixed together by a simple paddle and easily formed a smooth fluid treatment composition. This was fed into a trough, and the fabric to be treated was taken through the trough. After padding the weight add-on to the fabric was of the order 63- 70% w/w. The fabric was fed to the heater zone of the stenter, where it was subjected to a lo temperature in the range 150-170 C.

The resulting fabric had an unchanged textile handle, and was of unchanged appearance, yet had been rendered flame retardant to a good level, maintained over several washes.

The fabric was subjected to British Standard test BS 5852: Part 2: 1982 "Methods of test for the ignitability of upholstered composites for seating by flaming sourcesa.

The fabric was a 100% cotton fabric of weight 220g/m2, squared i.e. plain weave (1 under, 1 over warp/weft) 60 threads per inch (24 threads per cm) in each direction.

The samples tested were of size in the range (120-160cm) by (120-160cm). The test was undertaken with and without a calendered finish. In each case the fabric was subject to a water soak specified by Clause 4 of BS 5651: 1978 as modified by Schedule 3, Clause 1 of The Furniture and Furnishings (Fire) (Safety) Regulations 1988 S.I.No.1324 using BS 5852: Part 2: 1982; and used E20 non-combustion modified foam with a density of 20-22 kg/m3. In all tests pass grades were obtained, in accordance with these British Standard tests.

Claims

. # Claims 1. A method of treating a fabric to achieve improved flame

retardancy, comprising the application to the fabric of a treatment composition comprising melamine-coated ammonium polyphosphate compound...CLME:
2. A method as claimed in claim 1 wherein the melamine-coated ammonium polyphosphate compound is in the lo form of particles having a mean particle size of at least 3pm and not exceeding lOpm.
3. A method as claimed in claim 1 or 2 wherein the treatment composition contains from 5-80%w/w of said melamine-coated ammonium polyphosphate compound.
4. A method as claimed in any preceding claim wherein the treatment composition comprising one or more of the following components preferably in the amounts stated: (a) a thickener which acts to thicken the treatment composition when phosphate groups are present, 0.01-2% w/w; (b) a general thickener, 0.01-2% w/w; (c) a humectant, 0.1-4% w/w; (d) a preservative, 0.01-2% w/w; (e) a binder, 1-30% w/w; (f) water, 50-90% w/w.
5. A method as claimed in any preceding claim wherein a binder is applied to a fabric in an amount 1 part by weight binder (as binder molecules) to 2-15 parts (w/w), preferably 5-12 parts, melamine-coated ammonium polyphosphate (as weight of chemical compound).

: t: . .
6. A method as claimed in any preceding claim wherein the treatment composition is a pourable suspension which is stable against settlement.
7. A method as claimed in any preceding claim wherein the treatment composition has a solids content in the range 5-40% w/w.

lo
8. A method as claimed in any preceding claim wherein the method includes a heat treatment, wherein after the treatment composition has been applied to the fabric the treated fabric is subjected to an elevated temperature, preferably in the range 80 to 200 C.
9. A method as claimed in any preceding claim wherein the fabric treated is selected from household upholstery fabrics including curtains, awnings, window blinds, carpets, rugs, chair covers and sofa covers.
10. A treatment composition for use in a method as claimed in any preceding claim.
11. A precursor composition for the preparation of a treatment composition as claimed in claim 10, the precursor composition being a concentrate which is mixed substantially at the point of use with water and with any binder which is to be present in the treatment composition; the precursor composition comprising one or more of the following components preferably in the amounts stated: :: a: : e e e (a) a melamine-coated ammonium polyphosphate compound, 1 0 - 9 0 %w/w; (b) a thickener which acts to thicken the treatment composition when phosphate groups are present, 0.02-4% w/w; (c) a general thickener, 0.02-4% w/w; (d) a humectant, 0.2-8% w/w; (e) a preservative, 0.01-2% w/w; (f) water, 40-75% w/w.
12. A fabric treated by a method as claimed in any of claims 1 to 9, in order to confer flame retardancy.
13. A method, composition or treated fabric in accordance with the present invention, in each case substantially as hereinbefore described with reference to

the example.