WO2013092842A2

WO2013092842A2 - Treating textile material

Info

Publication number: WO2013092842A2
Application number: PCT/EP2012/076356
Authority: WO
Inventors: Robert Hicklin; Geoffrey Hand
Original assignee: Rhodia Operations
Priority date: 2011-12-23
Filing date: 2012-12-20
Publication date: 2013-06-27
Also published as: WO2013092842A3; GB201122310D0; GB2497974A

Abstract

The invention provides the use of acetoacetamide or an N-alkylated derivative thereof as a post treatment agent to reduce formaldehyde levels in a textile material that has undergone a flame-retardancy treatment, wherein the derivative is either mono- or di- substituted and the or each alkyl substituent is independently a C1-3 alkyl group. Also provided is a method of treating textile material to obtain a textile material having flame-retardant properties whilst having low formaldehyde levels, the method comprising the steps of: providing a textile material that has undergone a flame- retardancy treatment; impregnating the material with a post-treatment agent which is acetoacetamide or an N-alkylated derivative thereof, wherein the derivative is either mono- or di- substituted and the or each alkyl substituent is independently a C1-3 alkyl group; and drying the material.

Description

TREATING TEXTILE MATERIAL

The present invention relates to treating textile material to obtain a textile material having flame-retardant properties whilst having low formaldehyde levels, and to the use of acetoacetamide or an N-alkylated derivative thereof to reduce formaldehyde levels in a textile material that has undergone a flame-retardancy treatment.

Formaldehyde scavengers are known in the art. These include urea and acetoacetamide, and derivatives of acetoacetamide, such as monomethyl acetoacetamide and dimethyl acetoacetamide.

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H2M— C— CH 2— C—Me Acetoacetamide These formaldehyde scavengers are generally used during a process that generates airborne formaldehyde, to remove this formaldehyde from the reaction system. Formaldehyde scavenging will generally be carried out to remove formaldehyde as it is generated during a high temperature curing stage. Acetoacetamide is used as a scavenger in the manufacture of composition board (chip board) and of press finished textiles; see for example US 5, 1 12,562. In both cases the formaldehyde source is from N-methylol based resins. Derivatives of acetoacetamide (e.g. monomethyl, dimethyl, monoethyl and diethyl- acetoacetamide) have also been found to also be effective scavengers.

In all cases the acetoacetamide or derivative is applied in combination with the resin, before any curing.

A known process for the flame-retardant treatment of textile materials, including cellulosic (e.g. cotton) materials, consists of impregnation of the material with an aqueous solution of a treatment agent which is a poly(hydroxyorgano) phosphonium compound. This compound may be a salt, for example a tetrakis (hydroxyorgano) phosphonium salt. Alternatively, the compound may be a condensate, for example a condensate of a tetrakis (hydroxyorgano) phosphonium salt with a nitrogen- containing compound such as urea. Following impregnation, the material is dried and then cured with ammonia to produce a cured, water-insoluble polymer which is mechanically fixed within the fibres of the material. After curing, the polymer is oxidised to convert trivalent phosphorus to pentavalent phosphorus and the material is washed and dried. Such a process is described in, for example, GB2205868, GB2290562 and GB2294479.

In the curing process ammonia gas may be passed directly into a chamber through which the material passes, or, preferably, ammonia gas is forced through the material inside the chamber. GB 1439608 and GB 1439609 describe apparatus for use in such a process, which consists of a closed chamber, entry and exit seals thereto through which the material moves, a duct located in the chamber and having one or more orifices through which gaseous ammonia issues and subsequently passes through the material passing over each orifice, the chamber having means to prevent condensed water from dripping on to the material. This type of unit is referred to in the art as a standard cure unit.

A high speed cure unit is described in GB2252570, where the ammonia feed rate is precisely controlled relative to the amount of material being processed and the curing chamber is pre-filled with ammonia to provide a reservoir of ammonia to allow for any slight variation in the ammonia usage relative to the ammonia input. This type of unit is known in the art as a high speed cure unit.

However, known methods of treating textile materials to have flame-retardant properties result in formaldehyde being generated as a by-product and it can therefore be present in the treated material. Industry standards may place limits on the amount of formaldehyde that can be included in textile materials. It is known to carry out treatments to ensure that the free formaldehyde content in the end textile product is at acceptable levels. However, these treatments involve high temperature processing, which increases cost. Further, it is known that textile materials that contain formaldehyde can, when stored, be found to exhibit increased formaldehyde levels over time. Therefore materials that initially had a formaldehyde content within an acceptable range could, after time, be above the maximum acceptable level. The current methods tend to use a metal bisulfite (e.g. sodium bisulfite) treatment during the wash off stage, at a temperature of about 80°C or higher. This treatment results in a formaldehyde adduct being formed, which can be washed off, and so the free formaldehyde levels are decreased. However, the bisulfite treatment requires a long dwell time to ensure that the formaldehyde levels are reduced to a sufficiently low level. Generally, multiple treatment baths will be used in the wash off stage to ensure a sufficient reduction in free formaldehyde levels. This is therefore a treatment process that requires a lot of water, energy and chemicals and it requires careful control.

In addition, the bisulfite material is a reducing agent. Therefore it can have a negative effect on dyed textile materials. In particular, some dyestuffs rely on redox reactions for fixing the dye, and therefore it would be desirable to reduce the need to add significant amounts of bisulfites during the wash off stage of the flame retardancy treatment.

Further, any formaldehyde adduct remaining in the material can break down over time, and therefore after storage the textile material will gradually exhibit higher free formaldehyde levels.

It is therefore desired to have a more straightforward and cost-effective solution to the problem of the free formaldehyde generated in textile materials during flame retardancy treatments. It is also desired to have a solution that is reliable and long term. Summary of the Invention

The invention presents, in a first aspect, the use of acetoacetamide or an N-alkylated derivative thereof as a post treatment agent to reduce formaldehyde levels in a textile material that has undergone a flame-retardancy treatment, wherein the derivative may be either mono- or di- substituted and the or each alkyl substituent is independently a C I -3 alkyl group.

It may be that the use provides an initial reduction of formaldehyde levels and also retains reduced formaldehyde levels after storage. It may be that the use provides an initial reduction of formaldehyde levels and also provides a further reduction in the formaldehyde levels after storage.

The storage may be for one week or more, e.g. one month or more, or two months or more, or three months or more.

The use may be to achieve both an initial reduction of formaldehyde levels and a long term reduction of formaldehyde levels. The long term reduction may be after one week, or after one month, or after two months, or after three months, or more.

The skilled person will understand that formaldehyde levels in a textile material can suitably be measured using test method Japan Law 1 12.

It may be that the initial reduction of formaldehyde levels is by 25% or more, such as 30%) or more, or 35% or more, or 40% or more, or 45% or more, or 50% or more, when compared to the levels in the textile material before the post treatment. It may be that the long term reduction (after storage) of the formaldehyde levels is by 25% or more, such as 30% or more, or 35% or more, or 40% or more, or 45% or more, or 50% or more, when compared to the levels in the textile material before the post treatment. It may be that the long term reduction (after storage) is by 5% or more, such as 10% or more, or 15% or more, or 20% or more, or 25% or more, when compared to the levels in the textile material immediately after the post treatment.

It may be that the formaldehyde levels are initially reduced by the post treatment to be 95ppm or less, such as 85ppm or less, preferably 75ppm or less, or 70ppm or less, or 60ppm or less, or 50ppm or less. It may be that the formaldehyde levels remain at a level after storage of 95ppm or less, such as 85ppm or less, preferably 75ppm or less, or 70ppm or less, or 60ppm or less, or 50ppm or less. Preferably the acetoacetamide or an N-alkylated derivative thereof is used to treat the textile material after a flame-retardant material has been applied and fixed to the material and residual chemicals have been washed off.

The invention therefore also presents, in a second aspect, a method of treating textile material to obtain a textile material having flame-retardant properties whilst having low formaldehyde levels, the method comprising the steps of:

• providing a textile material that has undergone a flame-retardancy treatment;

• impregnating the material with a post-treatment agent which is acetoacetamide or an N-alkylated derivative thereof, wherein the derivative may be either mono- or di- substituted and the or each alkyl substituent is independently a

C I -3 alkyl group; and

• drying the material.

In one embodiment, the method comprises the steps of:

(1 ) impregnating the material with a flame-retardancy treatment agent;

(2) fixing the flame-retardancy treatment agent to the material;

(3) washing off residual chemicals from the material;

(4) impregnating the washed material with a post-treatment agent which is acetoacetamide or an N-alkylated derivative thereof, wherein the derivative may be either mono- or di- substituted and the or each alkyl substituent is independently a C I -3 alkyl group; and

(5) drying the material.

In one such embodiment, the method comprises the steps of:

(a) impregnating the material with an aqueous solution of a treatment agent which is a poly (hydroxyorgano) phosphonium compound;

(b) drying the impregnated material;

(c) curing the dried impregnated material with ammonia to produce a cured, water-insoluble polymer which is mechanically fixed within the fibres of the material; (d) oxidising the cured polymer to convert trivalent phosphorus to pentavalent phosphorus;

(e) washing the material;

(f) impregnating the washed material with a post-treatment agent which is acetoacetamide or an N-alkylated derivative thereof, wherein the derivative may be either mono- or di- substituted and the or each alkyl substituent is independently a C l - 3 alkyl group; and

(g) drying the material. The invention also provides, in a third aspect, a treated textile material obtainable by the method of the second aspect.

The invention also provides, in a fourth aspect, an item of clothing produced from the material of the third aspect.

The clothing may in one embodiment be protective clothing. The clothing may, for example, be a coat, trousers, a hat, an apron, a top, a shirt, or gloves.

The present invention has surprisingly identified that certain compounds can be used as a post treatment for flame-retardant treated textile materials to reduce the formaldehyde content. The effect is seen in the short term (immediately after the post treatment) and is also seen longer term, after storage of the textile material. The compounds in question are acetoacetamide and N-alkyl derivatives thereof. It is surprising that acetoacetamide and its derivatives have this effect when added as a post treatment. Although acetoacetamide is one of a group of agents known for exhibiting a formaldehyde-scavenging effect when used during a process that generates airborne formaldehyde, the present invention has found that other known formaldehyde-scavenging agents, such as urea, do not show any real benefit when used as a post treatment.

Also, even though metal bisulfites are effective when used during the wash off stage of the flame retardant treatment, it has been found that they are not effective when used in the post treatment regime of the invention. Therefore there is a surprising benefit of using a post treatment regime that is specific to acetoacetamide and its derivatives. The mechanism of action is therefore not a conventional formaldehyde-scavenging action, which will generally occur at high temperature during a curing stage.

Further, the post treatment does not require an elevated temperature and can be carried out at neutral pH values. Less harsh conditions are effective (e.g. room temperature and pressure can be used) as compared to the conditions used during a resin curing step.

The longer term reduction of formaldehyde levels is also a significant benefit of the invention that is not predictable from the prior art. The levels of formaldehyde can be reduced to an acceptable level and will then stay at acceptable levels longer term. Therefore there is no need to reduce formaldehyde levels to be significantly below the acceptable maximum in order to allow for a later increase in the levels.

Some metal bisulfite treatment (or other formaldehyde-scavenging treatment) could still be used in the chemical wash off stage of the flame retardancy treatment, but it can certainly be reduced, if not completely removed. This will reduce costs and complexity and the need for strict monitoring during the wash off stage.

The post treatment regime of the invention provides consistently good results and therefore the desired level of formaldehyde in the end product can be achieved with a greater degree of confidence. There is a greater degree of control possible with the post treatment regime.

Detailed Description of the Invention

The post treatment agent used in the present invention is acetoacetamide or an N- alkylated derivative thereof. The derivative may be either mono- or di- substituted and the or each alkyl substituent is independently a C I -3 alkyl group. In one embodiment the derivative may be either mono- or di- substituted and the or each alkyl substituent is independently a C l -2 alkyl group. Therefore the post treatment agent may be acetoacetamide, N-monomethyl acetoacetamide, Ν,Ν-dimethyl acetoacetamide, N- monoethyl acetoacetamide or Ν,Ν-diethyl acetoacetamide. In one preferred embodiment the post treatment agent is acetoacetamide, N- monomethyl acetoacetamide or Ν,Ν-dimethyl acetoacetamide. Most preferably, the post treatment agent is acetoacetamide.

Whilst it is preferred, for simplicity, to use a single post treatment agent in the present invention, it may be that two or more (e.g. two or three) post treatment agents may be used in combination in the present invention. For example, acetoacetamide could be used in combination with N-monomethyl acetoacetamide. When reference is made to "post treatment agent" in this application, it is intended that this could be a single agent selected from acetoacetamide and N-alkylated derivatives thereof, wherein the derivative may be either mono- or di- substituted and the or each alkyl substituent is independently a C I -3 alkyl group, or could be a combination of two or more agents selected from acetoacetamide and N-alkylated derivatives thereof, wherein the derivative may be either mono- or di- substituted and the or each alkyl substituent is independently a C I -3 alkyl group.

The post treatment agent may suitably be applied to the textile material in a fluid formulation and in particular in the form of a liquid, gel or foam. In one embodiment the post treatment agent is applied in the form of a solution or suspension, preferably an aqueous solution.

The post treatment agent may be applied to the textile material in any suitable manner. It could, for example, be padded onto the material (e.g. with a pad mangle), sprayed onto the material, applied as a foam onto the material, or the material could be dipped into the post treatment agent.

The post treatment agent may be used to treat the textile material at any stage after the flame retardant treatment has been effected.

The textile material may therefore be treated with the post treatment agent after the flame-retardancy treatment agent has been fixed to the textile material and a suitable washing of the textile material has been carried out. This washing will suitably be an aqueous wash and may comprise a conventional wash off stage, as known in the art, to remove chemicals from the textile material. It may involve washing with water and/or it may involve use of a metal bisulfite (e.g. sodium bisulfite) treatment and/or it may involve a temperature of about 80°C or higher.

The textile material may optionally undergo a drying treatment before it is treated with the post treatment agent, but this is not essential. In one embodiment the textile material remains wet from the flame retardant treatment/wash off until after the post treatment agent of the invention has been impregnated into the textile material.

In one option, it may be that the post treatment of the present invention is combined with a top softener treatment stage. Such a treatment stage is already known in the art to condition the flame-retardant treated textile material. This option can be beneficial in terms of ease and straightforwardness of the overall treatment. The post treatment agent can therefore be padded, or otherwise applied, onto the treated textile material together with a softening agent.

The post treatment agent and the softening agent can be applied simultaneously, sequentially or separately within the top softener treatment stage. When applied sequentially or separately the post treatment agent can be applied first or the softening agent can be applied first.

In one embodiment, the post treatment agent may be provided in a top softener formulation that is applied to the textile material after the flame retardant treatment has been effected. In other words, the post treatment agent is pre-mixed with the components of a top softener formulation.

This top softener formulation may therefore comprise water and softening agent in combination with the post treatment agent, and may optionally include buffering agents or pH adjusters. It may also comprise one or more other conventional additives known for use in a top softening treatment, such as wetting agents, water repellents, anti microbial agents, and the like. Additives that can be mentioned include alkanol polyglycol ethers and neutral phosphoric acid esters with non-ionic emulsifiers.

It may be that this top softener formulation will consist essentially of softening agent, the post treatment agent and water, plus any optional wetting agents, water repellents, anti microbial agents, buffering agents or pH adjusters. In another embodiment, the post treatment agent may be added to the top softener formulation during the top softener treatment stage. This top softener formulation may comprise water and softening agent, and may optionally also comprise one or more other conventional additives known for use in a top softening treatment, such as wetting agents, water repellents, anti microbial agents, and the like. Optional buffering agents or pH adjusters may be present in the top softener formulation or may be added to the top softener formulation during the top softener treatment stage. Any suitable softening agent or combination of two or more softening agents may be used and these agents are well known in the art. They include, but are not limited to, polyolefin fatty alcohols (e.g. polyethylene fatty alcohols), alkoxylated fatty alcohols (e.g. ethoxylated fatty alcohols), alkoxylated fatty acids (e.g. ethoxylated fatty acids), alkoxylated fatty amides (e.g. ethoxylated fatty amides), silicones, castor oil ethoxylates, amine oxides, betaines, quaternary ammonium salts, amine salts, imidazolines and alkylsulphonates.

In an alternative option, the post treatment agent may be added in a separate post treatment stage, which is distinct from any top softener treatment stage that is carried out. Therefore a post treatment formulation can be padded, or otherwise applied, onto the treated textile material. When there is a top softener treatment stage, this post treatment formulation can be carried out either before the top softener treatment stage or after the top softener treatment stage. The post treatment formulation may, for example, comprise the post treatment agent and water, and may optionally include buffering agents or pH adjusters. In one embodiment this post treatment formulation may consist essentially of the post treatment agent and water plus any optional buffering agents or pH adjusters. The post treatment agent may suitably be added to the textile material in a liquid formulation, e.g. an aqueous formulation. This applies for the post treatment formulation and the top softener formulation options. The formulation may have a concentration of post treatment agent of l g/1 or more, e.g. 5g/l or more. It may be from l g/1 to 200g/l, e. g. from 2g/l to l OOg/1, or from 5g/l to 80g/l, or from l Og/1 to 70g/l, or from 15g/l to 60g/l, or from 20g/l to 50g/l. In one embodiment, the post treatment agent may be added to the textile material to achieve a weight gain on the textile material of 0. 1 % or more, such as 0.2% or more, 0.33%) or more, 0.5%> or more. For example, the weight gain may be from 0. 1 %> to 10%), or from 0.5 %> to 5%, or from 0.6%> to 3 %>. The skilled person would appreciate that the weight gain will depend on the concentration of the post treatment agent in the formulation as added, the amount of formulation as added and the wet-pickup rate. In practice a pickup rate of about 60%> may readily be achievable.

The post treatment agent may be added to the textile material in a formulation with any suitable pH, e. g. from 4 to 10. Preferably the pH is in the range of from 4.5 to 9.5, more preferably from 5 to 9, such as from 5.5 to 8.5, and most preferably from 6 to 8, e. g. from 6.5 to 7.5. In one embodiment the pH is about 7. Values of pH that are clos e to neutral are preferred in light of subsequent contact of skin with the textile material.

The post treatment agent may be added to the textile material in a formulation that is buffered. The inclusion of suitable buffering agents makes the treatment more reliable and repeatable. Buffering agents are well known in the art and include, for example, phosphate buffering agents, such as monosodium phosphate and disodium phosphate.

The post treatment agent may be applied to the textile material at any suitable temperature. In one embodiment, the temperature is 80°C or less, preferably 70°C or less, such as from 10 to 65°C, or from 15 to 60°C. In a preferred embodiment, the temperature is 50°C or less, preferably 45°C or less, such as from 1 0 to 40°C, or from 15 to 35°C. Most preferably, the temperature is 30°C or less, such as from 15 to 30°C, or from 20 to 27°C. It is generally preferred that the temperature is around room temperature, as this reduces costs. The skilled person will appreciate that during the stage where the post treatment agent is added (whether this be as part of a top softener treatment stage or as a separate post treatment stage) the temperature could vary (e. g. it could vary within the range of from 15 to 30°C), and in fact a key aspect of the present invention is that there is no need for temperature control and monitoring because the invention does not require elevated temperatures when the p ost treatment agent is applied in order to be effective. In contrast to conventional formaldehyde scavenger treatments, which are carried out during a high temperature curing stage, there is no requirement for any heating or curing to be carried out when the post treatment agent is applied to the textile material in the present invention.

The post treatment agent may be added to the textile material at any suitable pressure. In one embodiment, the pressure is l Oatm or less, preferably 5atm or less, such as from 0.1 to 5atm, or from 0.5 to 3 atm. Preferably, the pressure is 2atm or less, such as from 0.5 to 1.5atm, or from 0.8 to 1.2 atm. It is generally preferred that the pressure is around atmospheric pressure, as this reduces costs. The skilled person will appreciate that during the stage where the post treatment agent is added (whether this be as part of a top softener treatment stage or as a separate post treatment stage) the pressure could vary, and in fact a key aspect of the present invention is that there is no need for pressure control and monitoring because the invention does not require elevated pressures to be effective.

After the post treatment agent of the invention has been impregnated into the textile material the material may undergo any conventional treatments known in the art of textile treatment. One or more of these treatments may be used. These conventional treatments include, but are not limited to, a drying treatment, a shrink resistance treatment (e.g. sanforization), a water repellence treatment, a softening treatment, and a crease resistance treatment.

In one embodiment, after the post treatment agent of the invention has been impregnated into the textile material the material may undergo a drying treatment. The drying treatment may suitably dry the material to achieve a level of moisture within the range that is normal for the textile material in question.

It may be that the material is dried to have a residual moisture content of from 0 to 20%, such as from 1 to 15%. In one embodiment the material is dried to a residual moisture content of from 3 to 10%>, such as from 4 to 8%. These values are actual moisture content values, rather than values as obtained from a conductivity meter. As the skilled person would understand, moisture values taken using a conductivity meter have to be adjusted to take into account the contribution from ions present. The drying may involve heating, e.g. at a temperature of 70°C or more, such as from 80°C to 180°C, preferably from 90°C to 150°C and more preferably from 100°C to 140°C. The drying treatment may be carried out for any suitable period of time, such as from 10 seconds to 5 minutes, preferably from 20 seconds to 3 minutes, more preferably from 30 seconds to 2 minutes, e.g. about 1 minute.

The drying may be carried out using any suitable equipment for drying of textile material, such as an oven (e.g. a fan assisted oven), or a gas or oil fired heating unit, or over heated cans e.g. steam cans.

The textile material that is treated preferably comprises cellulosic fibres. It preferably comprises 10% or more cellulosic fibres, more preferably 20% or more cellulosic fibres and most preferably 30% to 100%) cellulosic fibres. The amounts given are by weight.

The cellulosic fibres may be natural cellulosic material (e.g. cotton, linen, jute, hessian, flax, coir, hemp, nettle, ramie), or may be regenerated cellulosic material, such as modal, lyocell, or rayon (e.g. viscose rayon or cuprammonium rayon fibres), or any combination thereof. The cellulosic fibres are preferably natural cotton.

The textile material that is treated may comprise substantially 100%) cellulosic fibres. Alternatively, the textile material may comprise both cellulosic fibres and non- cellulosic fibres. Therefore it may comprise cellulosic fibres together with non- cellulosic fibres that are co-blendable or co-weaveable with the cellulosic fibres. The non-cellulosic fibres may be, for example, wool or silk fibres or they may comprise synthetic fibres such as polyester, polyamide (including aramid), or acrylic fibres.

The non-cellulosic fibres are preferably synthetic, e.g. polyester or polyamide fibres, or acrylic (especially modacrylic) fibres. The polyester may be a condensation product containing structural units from an aliphatic alcohol (e.g. a dihydric alcohol such as ethylene glycol) and an aromatic dicarboxylic acid (e.g. terephthalic acid). The polyamide fibres may be aliphatic, such as copolymers of alkylene diamines and alkylene dicarboxylic acids (e.g. nylon 66) or polylactams (such as nylon 6), or may be aromatic, such as aramid, based on aromatic dicarboxylic acids and phenylene diamines. The aramid fibres may be meta-aramid materials, such as Nomex® and Kermel®.

The textile material can in one embodiment comprise 30% or more cellulosic fibres and up to 70% of co-blendable or co-weaveable fibres (e.g. from 10-70%> and especially from 25-60%> of co-blendable or co-weaveable fibres).

Suitable textile materials are blended materials containing cellulosic fibres (especially cotton fibres) and polyester fibres or polyamide fibres (especially polyester or aramid fibres). The textile material suitably contains up to 70% (e.g. up to 60%) of polyester or polyamide fibres and from 30%, e.g. from 40% upwards, of cellulosic fibres (e.g. 1 - 70% or 1 -60%, such as 15-60%, particularly 22-38% or 38-60% polyester or polyamide fibres and 30-99% or 40-99% such as 40-85%, particularly 62-78% or 40- 62% cellulosic fibres).

The textile material may be non-woven or woven. The cellulosic and other fibres may be an intimate or non-intimate mixture, but the fibres are preferably in the form of a blend of cellulosic fibres and other fibres (e.g. polyester fibres), as in a co-spun blend such as cotton/polyester staple fibre. Alternatively, the fibres may be in the form of core-spun yarn, with a core of, for example, polyester sheathed in cotton fibres. In a textile material, the warp and weft fibres are preferably the same, but may be different e.g. one may be of cotton fibres and the other of polyester/ cotton fibres. Thus in this specification the term "blend" also includes unions and union/blends as well as core- sheath fibres.

The textile material is preferably one with a weight of from 50 to 1000 g/m², e.g. from 150 to 400 g/m².

The flame-retardancy treatment may be any process for the flame-retardant treatment of textile materials, including cellulosic (e.g. cotton) materials, such as those which consist of impregnation of the material with an aqueous solution of a treatment agent which is a poly(hydroxyorgano) phosphonium compound, followed by drying and curing with ammonia to produce a cured, water-insoluble polymer which is mechanically fixed within the fibres of the material, with subsequent oxidisation of the polymer to convert trivalent phosphorus to pentavalent phosphorus. In one embodiment, the flame retardant treatment may be a method comprising the steps of:

(i) impregnating the material with an aqueous solution of a treatment agent which is a poly (hydroxyorgano) phosphonium compound;

(ii) drying the impregnated material;

(iii) curing the dried impregnated material with ammonia to produce a cured, water-insoluble polymer which is mechanically fixed within the fibres of the material;

(iv) oxidising the cured polymer to convert trivalent phosphorus to pentavalent phosphorus; and

(v) washing the material.

The flame retardant treatment may be carried out in a standard cure unit or in a high speed cure unit.

The poly (hydroxyorgano) phosphonium compound used in step (i) may suitably be a tetra (hydroxyorgano) phosphonium compound. In the poly (hydroxyorgano) phosphonium compound, each hydroxyorgano group is preferably an alpha hydroxyorgano group of 1 -9 carbons, especially one of formula:

H0C-(R1 R2)- wherein each of Rl and R2, which may be the same or different, represents hydrogen or an alkyl group of 1 to 4 carbons e.g. methyl or ethyl. Preferably Rl is hydrogen and in one embodiment both Rl and R2 are hydrogen, as in tetrakis (hydroxymethyl) phosphonium (THP) compounds.

The poly (hydroxyorgano) phosphonium compound may in one preferred embodiment be a tetrakis (hydroxyalkyl) phosphonium salt. Alternatively, in another preferred embodiment the poly(hydroxyorgano) phosphonium compound may be a condensate of a tetrakis (hydroxyalkyl) phosphonium salt with a nitrogen-containing compound.

Preferably, the method uses a THP salt or a THP condensate.

In principal, any water soluble THP salt with an anion which does not interact adversely with other components present may be used. Preferably, a tetrakis(hydroxymethyl)phosphonium salt of formula THPX, wherein X is chloride, sulphate, bromide, iodide, phosphate, acetate, oxalate, citrate, borate, chlorate, lactate, nitrate, fluoride, carbonate or formate is used. THP condensates are water soluble or sparingly water soluble copolymers of THP with organic nitrogen compounds, such as urea or an amine. In one embodiment, the condensate is a copolymer of THP with urea, a C 1 -C20 alkylamine, dicyandiamide, thiourea or guanidine. The molar ratio of THP to nitrogen compound may be, for example, 2: 1 or higher, such as 3 : 1 or higher, preferably 4: 1 or higher, such as 5 : 1 or higher, for instance from 5 : 1 to 7: 1 molar THP:nitrogen compound.

THP condensates may contain two or more phosphorus atoms, so long as the phosphorus compound is water soluble to a concentration of at least 0.5 g/1 at 25°C. Such phosphorus compounds contain a total of at least two hydroxymethyl groups, usually at least one per phosphorus atom, and preferably at least two hydroxymethyl groups per phosphorus atom. In the THP condensate the group or groups joining the phosphorus atoms together may be of the formula -R-, -R-0-, -R-0-R-, -R-NH-R or - R-R"-R where R is an alkylene group of 1 to 4 carbon atoms and R" is the residue formed by removal of two hydrogen atoms, bonded to nitrogen, from a di or polyamide or an amine or di or polyamine, such as urea, a C 1 -C20 alkylamine, dicyandiamide, thiourea or guanidine. Such compounds with two or more, e.g. three, hydroxyalkyl groups per phosphorus atom may be made by self condensation of THP salts with a compound of general formula R"H₂ such as urea, or a C 1 -C20 alkylamine, e.g. by heating at 40 to 120°C.

The skilled person would readily be able to select appropriate amounts of poly (hydroxyorgano) phosphonium compound to be used in step (i), based on the textile material to be treated (in particular the textile material density) and its intended end use (in particular the standard and durability criteria the treated textile material will need to meet).

The amount of poly (hydroxyorgano) phosphonium compound used in the aqueous impregnating solution in step (i) will usually be calculated so as to give a 30 to 50% add on. This will require an appropriate concentration of poly (hydroxyorgano) phosphonium compound in the treatment solution to be selected, based on the pick up rate. For example, a 40% add on would be achieved by use of a 50% solution with an 80%) pick up rate.

The amount of poly (hydroxyorgano) phosphonium compound used in the aqueous impregnating solution in step (i) may, for example, be from 5 to 50% (expressed by weight as THP+ ion). If desired, the solution may contain a wetting agent, e.g. a nonionic or cationic wetting agent.

In step (ii) the material may be dried to any suitable level, such as from 0 to 20%, the percentage being calculated from the increase in weight of the fabric and the weight of chemicals impregnated. In one embodiment the material is dried to a residual moisture content of from 3 to 15%>, such as from 4 to 8%. These values are actual moisture content values rather than values as obtained from a conductivity meter. As the skilled person would understand, moisture values taken using a conductivity meter have to be adjusted to take into account the contribution from ions present.

The drying may be any suitable drying apparatus, such as in a stenter oven or over heated cans e.g. steam cans. It may involve heating, e.g. at from 80 to 120° C, for a suitable period of time, such as from 1 minute to 10 minutes.

Any suitable batching time may be used after step (iii) and before step (iv). The material may, for example, be batched for 30 minutes or more prior to oxidation. In a standard cure unit a batching time of from 30 minutes to 8 hours may suitably be used, such as from 1 to 8 hours. In a high speed cure unit a batching time of from 0 to 8 hours may suitably be used, such as from 1 to 8 hours.

In step (iii) the ammonia gas may be passed directly into a chamber through which the material passes, or the ammonia gas may be injected through the material inside the chamber.

Typically a standard cure unit may be operated at a temperature of from 50 to 60°C, whilst a high speed cure unit may be operated at a temperature of from 45 to 80°C.

The fresh ammonia gas is preferably undiluted, but may be diluted with up to 30% by volume of steam or air. The ammonia gas issuing from the duct into the chamber may be at from 10 to 120°C but is preferably at a temperature below 100°C, e.g. from 40°C to 50°C.

The textile material as obtained by the method of the invention may subsequently be used to manufacture an item of clothing or other textile item. Therefore in one embodiment the method comprises the further step of manufacturing a textile item, such as an item of clothing, from the treated textile material after it has undergone the post treatment and has been dried. The item may be protective clothing. The clothing may, for example, be a coat, trousers, a hat, an apron, a top, a shirt, or gloves.

The invention will be further described, by means of the following non-limiting examples.

Examples Experiment 1 Method

Textile material samples were cut from a roll of 300 g/m² 100% cotton twill workwear textile material that had been treated with an ammonia cure THPC-urea (2: 1 molar) pre-condensate flame retardant system, to give a phosphorus content of approximately 3% and nitrogen content of 3%.

The free formaldehyde content of the textile material was measured using test method Japan Law 1 12.

Samples of the material were then treated with water, 50g/l urea and 50 g/1 acetoacetamide respectively. The treatments were carried out using a BENZ laboratory pad mangle to give a wet pick-up of approximately 60%, the wet textile materials were then dried in a BENZ laboratory dryer at a temperature of 130°C. The treatment gave a weight gain of about 0.9%>. The free formaldehyde content of the textile materials after the treatment was again measured using test method Japan Law 1 12.

Results

Conclusion

The results show that the use of acetoacetamide gives a significantly greater reduction in formaldehyde levels than a water treatment, i.e. it is not just a rinsing effect. Surprisingly, a urea treatment is less effective than both the acetoacetamide treatment and the water treatment.

Therefore the formaldehyde reducing effect that is being seen with the acetoacetamide treatment is not the same as a formaldehyde scavenging treatment carried out during a process that generates formaldehyde, because urea is known to be effective in such a scavenging treatment.

Experiment 2

Method

Using the method of Experiment 1 , a further five flame retardant workwear textile materials of approximately 300 g/m², all dyed, were treated with (a) a water treatment, as a control, and (b) an acetoacetamide solution of 30 g/1 concentration. Results

Conclusion

The results show that the acetoacetamide treatment gives significant reductions in free formaldehyde levels. This effect is achieved on both 100%) cotton and cotton/polyester blend textile materials. Experiment 3

Method

Using the method of Experiment 1 , treatments were carried on three textile materials which had been previously tested in Experiments 1 &2.

The materials were: the 100% cotton twill from Experiment 1 , the vat blue twill 100% cotton textile from Experiment 2, and the navy twill 75 :25 cotton/polyester textile from Experiment 2.

The treatments used a concentration of 15 g/1 acetoacetamide at different buffered pH values. The phosphate buffering was with monosodium phosphate + di-sodium phosphate (10 millimoles/litre).

The free formaldehyde levels in the textile material samples were determined (i) after treatment and (ii) after 3 months' storage post-treatment.

Results

Sample pH of buffer in HCHO HCHO 3

acetoacetamide immediately months after treatment after treatment treatment

(ppm) (ppm)

100%) cotton twill Control - no treatment 148 *

100%) cotton twill 7 1 10 73

100%) cotton twill 7.5 1 15 68

Vat blue twill 100% Control - no treatment 130 *

cotton textile

Vat blue twill 100% 5 98 64

cotton textile

Vat blue twill 100% 5.5 98 65

cotton textile

Vat blue twill 100% 6 95 62

cotton textile

Vat blue twill 100% 6.5 92 60 cotton textile

Vat blue twill 100% 7 97 65

cotton textile

Vat blue twill 100% 7.5 105 70

cotton textile

Vat blue twill 100% 8 107 65

cotton textile

Vat blue twill 100% 8.5 104 67

cotton textile

Vat blue twill 100% 9 101 65

cotton textile

Navy twill 75 :25 Control - no treatment 170 *

cotton/polyester textile

Navy twill 75 :25 5 130 83

cotton/polyester textile

Navy twill 75 :25 5.5 126 82

cotton/polyester textile

Navy twill 75 :25 6 134 84

cotton/polyester textile

Navy twill 75 :25 6.5 136 83

cotton/polyester textile

Navy twill 75 :25 7 144 85

cotton/polyester textile

Navy twill 75 :25 7.5 147 85

cotton/polyester textile

Navy twill 75 :25 8 148 86

cotton/polyester textile

Navy twill 75 :25 8.5 142 85

cotton/polyester textile

Navy twill 75 :25 9 143 85

cotton/polyester textile

* - For all the controls, the levels of formaldehyde either stayed approximately constant or increased after the 3-month storage Conclusion

The results indicate that the acetoacetamide treatment significantly reduced the formaldehyde level on all three selected textile materials over a buffered pH range of 5 - 9.

Furthermore, storage of the treated textile materials resulted in a further significant reduction of the formaldehyde level in all cases

Experiment 4 Method

Using the method and textile material of Experiment 1 , four acetoacetamide solutions of concentration 5, 10, 20, 40 g/litre were applied to treat the material.

The released formaldehyde level was measured for each sample and for an untreated sample of the textile material as control. The measurements were taken according to AATCC Test Method 1 12-2008 (Formaldehyde Release From Fabric, Determination of: - Sealed Jar Method, Developed in 1965 by AATCC Committee RR68).

Results

Conclusion

The results show that the acetoacetamide treatment has reduced the amount of formaldehyde released from the textile material. In the case of the treatment using the highest acetoacetamide concentration, a tenfold reduction has been achieved. Experiment 5

Method

Using the method and textile material of Experiment 1 , a treatment was carried out using a 50 g/1 acetoacetamide solution.

In order to see whether there was an effect on textile material flammability, both treated and untreated samples of the textile material were tested using a Limiting Oxygen Index apparatus and LOI (%) values were determined. LOI is defined as the minimum percentage of oxygen which allows a sample to sustain combustion under specified conditions in a candle-like fashion.

Results

Conclusion

These results show clearly that the flame retardant performance has not been impaired by the acetoacetamide treatment.

Experiment 6 - Further testing

A treatment of fabric using sodium bisulfite instead of acetoacetamide was carried out. This showed that the sodium bisulfite did not have any significant effect to reduce the free formaldehyde levels in the flame-retardant material. A treatment was also carried out where acetoacetamide was added into the beginning of the flame-retardant treatment process, instead of as a post-treatment, by mixing it with the THPC-urea condensate solution. Surprisingly, the significant percentage reduction in formaldehyde that was observed using the post-treatment regime was not observed.

Summary of the Examples The examples demonstrate formaldehyde reductions in every case where treatment with acetoacetamide was applied to the flame-retardant material. The results were significant both when testing using test method Japan Law 1 12 and when using AATCC test method (formaldehyde). This reduction of formaldehyde levels is a technical benefit that is not predictable from the prior art and that, surprisingly, is not exhibited by a post treatment with urea or sodium bisulfite.

Repeat analysis for the samples treated with acetoacetamide after storage also shows an improvement, with the formaldehyde levels being further reduced. This longer term reduction of formaldehyde levels is also a benefit that is not predictable from the prior art.

LOI testing shows that the acetoacetamide treatment has no negative impact on flame retardancy properties for the textile material.

Claims

1. The use of acetoacetamide or an N-alkylated derivative thereof as a post treatment agent to reduce formaldehyde levels in a textile material that has undergone a flame-retardancy treatment, wherein the derivative is either mono- or di- substituted and the or each alkyl substituent is independently a C I -3 alkyl group.

2. The use of claim 1 to provide an initial reduction of formaldehyde levels and also to either (a) retain a reduced formaldehyde level after storage or (b) provide a further reduction in the formaldehyde levels after storage, wherein the storage is for one month or more.

3. The use of claim 1 or 2 wherein the initial reduction of formaldehyde levels is by 25% or more when compared to the levels in the textile material before the post treatment.

4. The use of any one of claims 1 to 3 wherein the long term reduction, after storage, in the formaldehyde levels is by 25% or more when compared to the levels in the textile material before the post treatment.

5. The use of any one of claims 1 to 4 wherein the long term reduction, after storage, in the formaldehyde levels is by 5% or more when compared to the levels in the textile material immediately after the post treatment.

6. The use of any one of claims 1 to 5 wherein the post treatment agent is used to treat the textile material after a flame-retardant material has been applied and fixed to the material and residual chemicals have been washed off.

7. The use of any one of claims 1 to 6 wherein the flame-retardancy treatment comprises impregnating the material with an aqueous solution of a treatment agent which is a poly (hydroxyorgano) phosphonium compound; drying the impregnated material; curing the dried impregnated material with ammonia to produce a cured, water-insoluble polymer which is mechanically fixed within the fibres of the material; oxidising the cured polymer to convert trivalent phosphorus to pentavalent phosphorus; and washing the material.

8. A method of treating textile material to obtain a textile material having flame- retardant properties whilst having low formaldehyde levels, the method comprising the steps of:

· providing a textile material that has undergone a flame-retardancy treatment;

• impregnating the material with a post-treatment agent which is acetoacetamide or an N-alkylated derivative thereof, wherein the derivative is either mono- or di- substituted and the or each alkyl substituent is independently a C I -3 alkyl group; and

· drying the material.

9. The method of claim 8 wherein the method comprises the steps of:

(1 ) impregnating the material with a flame-retardancy treatment agent;

(2) fixing the flame-retardancy treatment agent to the material;

(3) washing off residual chemicals from the material;

(4) impregnating the washed material with a post-treatment agent which is acetoacetamide or an N-alkylated derivative thereof, wherein the derivative is either mono- or di- substituted and the or each alkyl substituent is independently a C I -3 alkyl group; and

(5) drying the material.

10. The method of claim 9 wherein the method comprises the steps of:

(b) drying the impregnated material;

(c) curing the dried impregnated material with ammonia to produce a cured, water-insoluble polymer which is mechanically fixed within the fibres of the material;

(d) oxidising the cured polymer to convert trivalent phosphorus to pentavalent phosphorus;

(e) washing the material;

(f) impregnating the washed material with an aqueous solution of a post- treatment agent which is acetoacetamide or an N-alkylated derivative thereof, wherein the derivative is either mono- or di- substituted and the or each alkyl substituent is independently a C I -3 alkyl group; and

(g) drying the material.

1 1. The use or method of any one of claims 1 to 10 wherein the post treatment agent is acetoacetamide, N-monomethyl acetoacetamide, N,N-dimethyl acetoacetamide, N-monoethyl acetoacetamide or Ν,Ν-diethyl acetoacetamide, or combinations thereof.

12. The use or method of claim 1 1 wherein the post treatment agent is acetoacetamide.

13. The use or method of any one of claims 1 to 12 wherein the post treatment agent is provided in an aqueous formulation.

14. The use or method of claim 13 wherein the formulation has a concentration of post treatment agent of from l g/1 to 200g/l.

15. The use or method of any one of claims 1 to 14 wherein the post treatment agent is provided in a formulation having a pH in the range of from 5 to 9.

16. The use or method of any one of claims 1 to 15 wherein the post treatment agent is applied onto the treated textile material together with softening agent.

17. The use or method of claim 16 wherein the post treatment agent is provided in a top softener formulation that is applied to the textile material after the flame retardant treatment has been effected, with the top softener formulation comprising water, softening agent and post treatment agent.

18. The use or method of any one of claims 1 to 17 wherein the post treatment agent is applied to the textile material at a temperature of:

(a) 80°C or less; or

(b) 70°C or less; or

(c) from 10 to 65°C; or

(d) from 15 to 60°C; or

(e) 50°C or less; or

(f) 45°C or less.

19. The use or method of claim 18 wherein the post treatment agent is applied to the textile material at a temperature of from 10 to 40°C.

20. The use or method of any one of claims 1 to 19 wherein the post treatment agent is added to the textile material in a formulation with a pH of:

(a) from 4 to 10; or

(b) from 4.5 to 9.5; or

(c) from 5 to 9; or

(d) from 5.5 to 8.5.

21. The use or method of claim 20 wherein the post treatment agent is added to the textile material in a formulation with a pH of from 6 to 8.

22. The use or method of any one of claims 1 to 21 wherein the textile material comprises cellulosic fibres and optionally further comprises non-cellulosic fibres.

23. The method of any one of claims 8 to 22 which comprises the further step of manufacturing a textile item from the textile material, after it has undergone impregnation with the post-treatment agent and has been dried.

24. A treated textile material obtainable by the method of any one of claims 8 to 23.

25. An item of clothing produced from the material of claim 24.