FIELD OF THE INVENTION

The present invention relates to a method for making a textile article flame-resistant as well as to textile articles obtained by said method. The method comprises providing at least part of the textile article with a non-cellulose-reactive, phosphorous-containing, flame-retardant compound and also providing at least part of the article with a cellulose-reactive, phosphorous-containing, flame-retardant compound.

BACKGROUND OF THE INVENTION

Numerous professions require individuals to risk exposure to extreme heat and/or flames. Typical examples are industrial workers, fire fighters, police and military personnel. Such personnel are, wherever possible, provided with appropriate flame-protective garments. These garments are distinctly different from normal, every-day-use garments as they are at least partly constructed from flame-resistant textiles.

Said garments must pass minimum thermal performance requirements such as flame- and/or heat- resistance, low percentage of (estimated) body burns in thermal manikin testing, limited after-flame time and high resilience against combustion, as well as protection against radiant heat. Other important performance requirements are tensile and tear strength, elongation at break, abrasion resistance, snagging resistance and resistance to penetration by water and liquid chemicals. In addition it is considered important that the garment provides adequate comfort, for instance by allowing vapour to be transported away from the body and ensuring that the garment is not too stiff. Also the garment must be durable in the sense that the above disclosed parameters last at least for the lifetime of the product. Furthermore the garment must be printable or dyeable with a durable result such that, for instance, the garment can be dyed to increase visibility. An often used standard for performance requirements for flame-resistant clothing made from flexible materials is ISO 1 1612.

Flame- and/or heat-resistance relates to a generic property of an article and indicates how resilient the article is against flames or high heat without suffering damage. The term flame-retardant is generally used to describe a treatment, which may be used to render an article flame-resistant. For instance, the article may be a flame-resistant garment that protects the wearer of the garment against flames or heat. A suitable manner to measure and quantify the flame- and/or heat-resistance is the thermal manikin test (ISO test 13506). In this test a manikin equipped with temperature sensors is submitted to a high heat-fluxfor a short time. Based on the read-out of the temperature sensors, an accurate prediction of the bum injury can be made. This includes a calculation of the second- and third-degree burn injury areas as well as the total burn injury area resulting from the exposure. In addition the after-flame can be assessed with this test. The after-flame time is that amount of time that a visible flame is present after the heat source has been removed. A limited or zero after-flame time is especially important when working in confined spaces, which is the case for helicopter and tank crews. In these cases a decrease in after-flame of only a few seconds can make an important difference. This includes the direct protection against burning garments, as well as the reduction of the chance that the prolonged flame sets off an external fire. As described above, the afterflame can be assessed using the thermal manikin test. Alternatively, and perhaps more accurately, the afterflame time can be determined using ISO 15025. In this test a vertically oriented, flexible material is subjected to a defined flame for a specific time. In this context procedure A refers to surface ignition - i.e. the case where the burner is orthogonal to the fabric and the flame is directed to the middle of the fabric - and procedure B refers to bottom ignition - i.e. the case where the burner is positioned 30° from the vertical axis and the flame is directed to the bottom of the fabric. The time that the material continues to burn after the flame has been removed is measured and recorded as the after-flame time.

Also the resilience against combustion upon exposure to a substantial level of thermal energy is a key property. Typically this is referred to as resilience against exotherm. This property relates to the level of thermal energy to which a system may be exposed before the system starts to produce a significant release of heat/combustion energy or, put in other words, before the system starts to“exotherm”. The exotherm can be assessed using the above mentioned manikin test (ISO test 13506) and varying for instance the heat flux density and/or the exposure time. The higher the exotherm, the lower the level of thermal energy that can be withstood prior to combustion. For a flame-resistant fabric, the intensity and initiation timing of the exotherm is dependent on intensity of thermal exposure, fabric mass, level of flame-retarding phosphorous contained in the fabric, and finally the way flame-retarding phosphorous is bonded with fibres in the fabric. It is theorized that upon exposure to an ignition source of sufficient magnitude, for example ~8.0 cal/cm ² with a 2.0 cal/cm ² /sec exposure flux on a 300 g/m ² fabric, the“free” cellulose in a treated system begins to rapidly oxidize, or burn. It is further theorized that phosphorous-containing compounds are then released from the in-situ resin, which react with radicals that fuel the combustion process, thereby, extinguishing the combustion when the heat source is removed. When the cellulose ignites during this process, the resultant exotherm that occurs prior to self-extinguishment may cause significantly increased burn injuries for garment wearers. Especially for individuals that risk exposure to intense heat or flash fires, such as firemen, it is crucial that the fabric does not exhibit a high exotherm so to reduce the risk that the fabric will combust.

Another important property of flame-resistant materials is the limiting oxygen index (LOI). This is the minimum concentration of oxygen, in admixture with nitrogen that will support combustion of small vertical test specimens under specified test conditions. This property is determined by putting a small test specimen vertically in a transparent chimney where a mixture of oxygen and nitrogen is flowing upward (ISO test 4589). The upper end of the specimen is ignited and the subsequent burning behaviour is observed. By repeating the test with varying oxygen concentrations, the minimum oxygen concentration at which the specimen combusts (the LOI) is estimated. Using the LOI the burning behaviour under specific circumstances can be understood. For instance, the normal amount of oxygen in air is about 21 %, which means that materials with indexes below 21 will burn continuously at normal conditions.

A known treatment for rendering cellulosic fibres or textile articles comprising cellulosic fibres flame-resistant is the Proban® treatment. This treatment comprises padding a textile article with an aqueous solution comprising tetrakishydroxyalkylphosphonium (THP) salt which is pre-reacted with urea and pH adjusted to 5-8. THP can be manufactured according to the process disclosed in US 4,31 1 ,855 of which examples 1 and 2 are hereby incorporated herein by reference. Subsequently the textile article is brought into contact with gaseous ammonia. More details can be found in examples 3 and 4 of US 4,31 1 ,855 or in the example covering columns 3 and 4 of US 4,078,101 , all of which are incorporated herein by reference.

THP does not react substantially with the cellulosic fibre, nor does it substantially react with the textile article comprising said fibre, but instead forms an enveloping network around and/or throughout the molecular structure of the cellulosic fibre. Hence the Proban® treatment is a non-cellulose-reactive treatment which means that there is substantially no chemical reaction between the THP and the cellulosic fibre.

It is generally accepted that this known process yields a durable end product that has no hydrolysable links adjacent to the phosphorous and that can withstand 100 industrial launderings using an alkaline detergent. The treatment is done gently on the alkaline side and as a result there is very little damage to the cellulose. The loss in tensile strength (measured using ISO 13934-1 ) and the loss in tear strength (measured using ISO 13937-2) is typically less than in the case of reactive treatments as discussed below. When the treated fabric is exposed to a flame, it chars and does not melt or exhibit flame spread. Proban® treated garments are generally considered to be well-performing flame-resistant fabrics useful for protecting various individuals such as industrial workers. However there is still room for improvement. Proban® treated fabrics or garments can exotherm which means that these fabrics or garments may not sufficiently protect against very intensive heat or longer-duration flash fires, e.g. flash fires that last for 3 seconds or longer at 2.0 cal/cm ² /sec heat flux.

It is known to perform multiple successive Proban® treatments on a textile article, which will result in a textile article with a high phosphorous content and possibly with some associated benefits relating to flame- resistant properties. However, due to the multiple treatments there is the risk that the fabric will become heavy and stiff, losing even more tensile and tear strength compared to a single treatment. In addition it is not possible to sufficiently improve the exotherm behaviour using multiple Proban® treatments.

In the case of regenerated cellulose fibres, there is also the option to render them flame-resistant during production by incorporating a flame-retardant chemical. Such a flame-retardant compound is usually provided as a solid particulate or masterbatch which has been ground into fine particles that are added to the spinning solution prior to extrusion or spinning of the fibre. As a result the particulates are dispersed throughout the fibre yielding a very durable flame protection. In this process too, there is no reaction between the fibres and the particulates, and it is hence a non-fibre-reactive or non-cellulose-reactive process. An example of such a fibre is Lenzing FR® which comprises an organic, non-halogenated, phosphorous containing flame-retardant such as Exolit® 5060 PK. A downside of such a process is that the strength of the fibre deteriorates with the inclusion of solid particulates.

An alternative flame-retardant treatment is a treatment with a N-methylol phosphonate compound, such as N-methylol dialkyl phosphonopropionamide. Commercially such treatments are offered under the brands Pyrovatex® CP and Aflammit® KWB. In this case the flame-retardant compound is grafted onto the cellulose by a reaction on the C(6) hydroxylgroup of the cellulose resulting in grafted protective phosphonopropionamide molecules on the outside of the cellulose fibre. This is therefore an example of a cellulose-reactive, phosphorous-comprising compound as there is a reaction between the cellulose and the phosphorous comprising compound.

A benefit of using cellulose-reactive treatments with N-methylol phosphate is that they do not exhibit an exotherm. Hence fabrics or garments treated with said treatment offer better protection against very intensive heat or longer-term flash fires compared to, for instance, non-cellulose reactive treatments. Also articles treated with cellulose-reactive treatments with N-methylol phosphate hardly suffer from an afterflame.

A disadvantage of above described cellulose-reactive treatment is that the phosphorous comprising molecules may detach from the cellulose-containing textile article which leads to a reduction of the flame- resistant properties. This detachment may be the result of washing the treated article, especially when washed using a bleach containing detergent. Also the bonds between the phosphorous molecules and the treated article may hydrolyse due to the presence of free acids in the treated article. As a result of this, treated textile articles have a limited shelf life. Free acids can be removed by washing the article every six months using an alkaline detergent. However, the need to wash articles that are not used is very inconvenient. Also each wash to remove the free acids will to some extent result in lower phosphorous content of the article.

Furthermore it is known that the reaction between the cellulose and the phosphonopropionamide tends to weaken the cellulose fibres and thereby also weakens the textile article comprising said fibre. This weakening of the cellulose fibres can cause the fabric to lose up to 50% tearing strength and up to 20% tensile strength. In addition there is a maximum to the amount of phosphorous that can be grafted onto the cellulose as suitable reaction sites are limited. When all sites are occupied, the cellulose-reactive, flame- retardant compound cannot react with the cellulose and hence will not bind. Treating textile articles and fabrics with above mentioned treatments is known in the art. US 2016/0201236 aims to produce an inexpensive flame-resistant fabric that performs at par with the currently available flame- resistant fabrics in order to facilitate the spread of safer products. In order to produce said fabric, phosphorous containing regenerated cellulose fibre (FR Rayon) is mixed with antimony containing modacrylic fibre. In an alternative embodiment, a fabric comprising a natural cellulose fibre and an antimony containing modacrylic fibre is subjected to a phosphorous treatment.

Whilst the above mentioned treatments can be used to produce garments that provide a reasonable protection against heat and/or flames, there is a need for a textile article that gives superior flame-resistant properties compared to those known from the prior art such that garments with superior flame-resistant properties can be produced. Preferably this treatment uses phosphorous-comprising compounds as these are compatible with cellulose fibres. More specifically there is a need for a textile article that protects against body burns, has a limited after-flame time under substantial thermal exposure and a high activation-energy before it starts to exotherm. In addition this fabric may need to meet some or all other relevant parameters on tensile and tear strength, abrasion resistance, snagging resistance and resistance to penetration by water and liquid chemicals. Furthermore and desirably, the fabric needs to be comfortable, have adequate moisture management and be durable in that it has a long shelf life and can withstand at least 50 washes, and more preferably even more than 100 washes.

SUMMARY OF THE INVENTION

The inventors have surprisingly found a method that can be used on a textile article comprising cellulose- containing fibres to give it a superior flame-resistant performance. This method for making a textile article flame-resistant, wherein the textile article comprises cellulose-containing fibres, comprises: a. providing at least part of the textile article with a non-cellulose-reactive, phosphorous-containing, flame-retardant compound, and b. providing at least part of the textile article with a cellulose-reactive, phosphorous- containing, flame-retardant compound, wherein the parts treated in a. and b. coincide at least partially. In this context, a cellulose-reactive compound may be defined as a compound that reacts with cellulose in such a manner that the compound will be chemically bound to the cellulose. A non-cellulose-reactive compound may be defined as one that does not chemically react with the cellulose.

It will be understood that a non-cellulose-reactive, flame-retardant compound does not react with the cellulose and thus needs to have another mechanism for fixing the compound to the fibre in order to provide the required flame-retardant properties. This mechanism may be the formation of a cross-linked network around and throughout the molecular structure of the cellulose-comprising fibre or it may be that the flame- retardant compound is present throughout the fibre and hence physically enclosed by the cellulose polymers. In one embodiment of the invention, treatments a. and b. are provided on cellulose containing fibres before they are combined to form the textile article. In this context, reference is given to a. and b. as being‘treatments’ but it will be understood that these need not be separate treatments. They may be different steps in a single treatment or parts of a combined process and reference to either a step or a treatment is not intended to be limiting. As will be seen below, what is important is that the product is ‘provided with’ the requisite cellulose-reactive compound and non-cellulose-reactive compound in any suitable manner.

There are several suitable processes to provide a textile article with the flame retardant compounds referred to in a. and/or b.. These processes, which typically rely on bringing the textile article in contact with a flame- retardant compound such that the textile article becomes flame resistant, may be referred to as flame- retardant treatments. A treatment with a cellulose-reactive compound is denoted as a cellulose-reactive treatment. The associated treatment with said non-cellulose-reactive compound is denoted as a non- cellulose-reactive treatment.

Both the non-cellulose-reactive compound and the cellulose-reactive compound may be provided by bringing the textile article in contact with the compound. In this respect, bringing in contact can encompass dipping, padding, soaking, rolling, spraying, coating and the like. Also bringing in contact can refer to printing techniques such as digital printing.

In another embodiment providing a textile article with a compound - usually a non-cellulose-reactive compound - implies that the textile article is provided with fibres or yarns comprising said compound. For example, a regenerated cellulosic spun fibre may be produced by adding non-cellulose-reactive, phosphorous-containing, flame-retardant particulates during production of the fibre prior to spinning. In this case the flame-retardant compound is provided during fibre production. It may be beneficial to also include the cellulose-reactive compound to the spinning solution in such a manner that the spun fibre comprises a non-cellulose-reactive and a cellulose-reactive flame-retardant compound.

It is thus understood that a textile article may be provided with a non-cellulose-reactive, phosphorous- containing, flame-retardant compound by providing it with regenerated cellulosic spun fibres comprising said compound. Hence, in this embodiment, the part of the textile article that has been provided with a non- cellulose-reactive compound is a regenerated cellulose fibre comprising flame-retardant particulates. In a further embodiment said flame-resistant particulates are organic, non-halogenated, phosphorous- containing, flame-retardant particulates. The regenerated cellulose fibre comprising flame-retardant particulates may be Lenzing FR® or a similar equivalent.

It is believed that the method according to the invention wherein different flame retardant compounds are provided and wherein the flame retardant compounds bind to the textile article using different chemical and/or physical bonds, may lead to synergistic effects. For instance, it may lead to the articles having improved durability of their flame-resistant properties. Without being bound by theory, it is believed that the network formed by the non-reactive-cellulose compound may increase the fixation of the cellulose-reactive compound. Hence the cellulose-reactive compound is less likely to be removed rendering the flame- resistant textile article more durable. Depending on the details of the compounds, it may be beneficial to provide one of the compounds before the other. Hence it may be beneficial to first provide the non-cellulose- reactive compound (step a.) and then the cellulose-reactive compound (step b.). However, in other cases the opposite might be true, meaning that it is beneficial to first provide the cellulose-reactive compound (step b.) and then the non-cellulose-reactive compound (step a). In yet another alternative, it might be beneficial to provide the non-cellulose reactive compound (step a.) together with the cellulose-reactive compound (step b.).

In another embodiment steps a. and b. are performed on the textile article. The textile article may be first provided with a non-cellulose-reactive, phosphorous-containing, flame-retardant compound (step a.) and subsequently provided with a cellulose-reactive, phosphorous-containing, flame-retardant compound (step b.). Alternatively it may be beneficial to first provide the textile article with a cellulose-reactive, phosphorous- containing, flame-retardant compound (step b.) and subsequently provide a non-cellulose-reactive, phosphorous-containing, flame-retardant compound (step a.). In yet another alternative, it might be beneficial to apply the non-cellulose-reactive, phosphorous-containing, flame-retardant compound together with the cellulose-reactive, phosphorous-containing, flame-retardant compound.

The non-cellulose-reactive, phosphorous-containing, flame-retardant compound is a tetrakishydroxyalkylphosphonium salt. In an even more specific embodiment the non-cellulose-reactive, phosphorous-containing, flame-retardant compound is Proban® or a similar equivalent. A typical process for performing a Proban® treatment comprises padding a textile article with an aqueous solution comprising tetrakishydroxyalkylphosphonium (THP) salt which is pre-reacted with urea and pH adjusted to 5-8. Alternatively the textile article can be soaked, impregnated, dipped, soaked, rolled, sprayed, coated, printed or the like. After the Proban® has been applied to the textile article, it may be cured using ammonia.

The cellulose-reactive, phosphorous-containing, flame-retardant compound is a N-methylol phosphonate compound such as N-methylol dialkyl phosphonopropionamide. The cellulose-reactive, phosphorous- containing, flame-retardant compound may be Pyrovatex® CP LF, Aflammit® KWB or the like. A process for performing a flame-retardant treatment using Pyrovatex® CP LF is impregnating the textile article with a solution containing the Pyrovatex® until the liquid has sufficiently penetrated the fabric. Alternatively the textile article can be soaked, impregnated, dipped, soaked, rolled, sprayed, coated, printed or similar. To remove the excess liquid, the fabric may be squeezed at a carefully controlled rate. Next the fabric may be pre-dried and heat-treated to help bind the phosphorous compound to the cellulose molecules. This process is also applicable when Aflammit® KWB or the like is used. The concentration of the Pyrovatex® or Aflammit® KWB in the flame-retardant treatment liquid (also referred to as treatment agent) is not particularly limited. In the art concentrations up to 500 g/L of Pyrovatex® or Aflammit® may be found. The method of the current invention will also work with such a high concentration but preferably a lower concentration is used. This may be 50 to 400 g/L, more preferably 50 to 300 g/L, or even more preferably 50 to 100 g/L. It is common to include additional chemicals in the liquid. Phosphoric acid or similar acid is used as additive that promotes the esterification reaction of hydroxyl groups of the cellulosic fibres. Melamine based resins, urea based resins or similar may be used as a cross- linking agent to increase crease resistance of the fabric. As example of such a resin is Knittex® MLF NEW. Penetrants such as Invadine® PBN may be used to increase the ability of the phosphorous to penetrate the fabric.

The textile article that has been made flame-resistant using the method of the invention may have a phosphorous content of at least 1 .5 wt%, more preferable at least 2.0 wt%, even more preferably at least 2.2 wt%, even more preferably at least 2.5 wt% and most preferably at least 3.0 wt%. In the context of the current invention wt% is short for weight percent and - unless indicated differently for specific cases - is used to quantify the relative weight of a chemical in comparison to the weight of the textile article including said relative amount of the chemical. The phosphorous content may be less than 3.0 wt%, or may be less than 5.0 wt%, or may be less than 7.0 wt% or may be less than 10.0 wt%.

According to an important aspect of the invention, the phosphorous may be present both as chemically- bound phosphorous and as non-chemically-bound phosphorous. In this context, chemically-bound is intended to refer to the fact that the phosphorous is chemically reacted either directly or indirectly to the cellulose i.e. phosphorous that has been provided by the cellulose reactive compound. Non-chemically- bound phosphorous is phosphorous that is not chemically reacted to the cellulose although of course, it may be chemically bonded to another molecule as in the case for THP. This phosphorous may be provided by the non-cellulose reactive compound. The amount of phosphorous that has been provided by the noncellulose reactive compound is preferably at least 1 .5 wt%, more preferably at least 1 .7 wt%, even more preferably at least 1 .9 wt% and most preferably at least 2.0 wt%. Alternatively the amount of phosphorous provided by the non-cellulose-reactive compound is between 1 .5 and 2.0 wt%, more preferably between 1 .6 and 1 .9 wt%, and most preferably between 1 .7 and 1 .9 wt%. The amount of phosphorous provided by the cellulose reactive compound is preferably at least 0.1 wt%, more preferred at least 0.2 wt% and most preferred at least 0.3 wt%. Alternatively the amount of phosphorous provided by the cellulose-reactive compound is between 0.1 and 1 .0 wt%, more preferably between 0.2 and 0.7 wt% and even more preferably between 0.3 and 0.5 wt%.

According to an aspect of the invention, 70-90 wt% of the phosphorous may have been provided by the non-cellulose reactive compound and 30-10 wt% by the cellulose-reactive treatment. Without wishing to be bound by theory, it is believed that reducing the absolute amount of both the non-cellulose-reactive compound and the chemically-bound phosphorous may be beneficial to the resultant article. As mentioned above, chemically-bound phosphorous is believed to weaken cellulose fibres and also suffers from detachment of phosphorous containing molecules by hydrolysis. Operating with a lower initial percentage of chemically-bound phosphorous is believed to ensure better long term performance and article strength. After the treatment with the flame-retardant compound or compounds, various finishes which are known in the art can be applied. For instance, a fluorocarbon finish may be applied to increase the water and oil repellence of the article. This can be performed with a (perfluoralkyl) acrylate such as Nuva® 21 10. To increase the ability of the fluorocarbon to penetrate fabric a penetrant such as Invadine® PBN may be used. In addition a smoothing agent such a Perapret® PEP may be used. Also often a weak acid such as acetic acid may be used to control the pH. It will be understood that any number of additional compounds or treatments may be applied to the article according to the required end use.

The method of the invention gives considerable improvements in flame-resistant properties compared to the individual treatments. Hence, a textile article which has been rendered flame-resistant using the method of the invention will normally meet the requirements of ISO 11612. In particular the estimated body burns, after-flame time, exotherm behaviour and/or phosphorous-content are improved. Surprisingly this was improved without further impairing the physical properties, such as tensile and tear strength, as compared with a textile article that has been treated by either of the two treatments individually.

The phosphorous content - as determined by the colour shift following a reduction of the phosphorous with molybdic acid in isobutyl alcohol - of the fabric treated with the method according to the invention is at least 2.0 wt%, preferably at least 2.1 wt%, more preferably at least 2.3 wt% and most preferably at least 2.5 wt% or even at least 3.0 wt%. The abrasion resistance, as measured using ISO 12947 Part 2, is at least 50,000 rubs, more preferably at least 60,000 rubs, even more preferably at least 75,000 rubs and most preferably at least 100,000 rubs.

The flame-resisting textile article obtained by the method according to the invention suitably has tear strength (as measured using ISO 13937-2) and a tensile strength (as measured using ISO 13934-1 ) of at least 80% of that of the corresponding untreated material. More preferably the tear strength and tensile strength are at least 85%, even more preferably 90%, even more preferably 95% and most preferably at least 100% of that of the corresponding untreated material.

T ypically, improvements are durable and are retained even after many washes (up to 100 washes), meaning that the physical and/or thermal resistance properties are largely maintained at the same level as for unwashed fabrics. Also the phosphorous-content is durable and very resilient against washing. This was achieved substantially without increasing the fabric weight, i.e. the weight increase due to the treatment was very limited. Here the term washes relates to a process for cleaning a fabric or garment in either a domestic or an industrial setting. Normally a detergent is used that comprises several chemicals which are beneficial for the cleaning process and/or help to obtain the desired end result. Said chemicals typically include an anionic surfactant such as sodium alkyl benzene sulfonate, a non-ionic surfactant, a carbonate buffer, antiredeposition polymers, phosphonates, optical whiteners, enzymes and a bleach system. To optimize the effectivity of the enzymes and the bleach system the detergent is formulated such that the wash liquor comprising the dissolved detergent will be alkaline. The alkalinity of the wash liquor and/or the presence of bleach in said wash liquor are considered to be detrimental for any flame retardant treatment.

A standardized method of washing, including options for detergents, is available in ISO method 6330. In the context of this application, reference detergent 6 (see Annex N of ISO 6330) is considered the preferred detergent for laboratorial testing as detergent 6 comprises 20% of perborate bleach and 3% TAED bleach activator making it a stress test for any flame resistant fabric or garment. In this context, stable to X washes is intended to denote that the article and property remain at a level exceeding 90% of the original value after X washes of the given type, which in the present context will be a wash according to ISO 6330 6N unless otherwise stated. .

The method according to the invention allows to obtain flame-retardant textile articles that are stable in the sense that the phosphorous content is at a level exceeding 90% of the original value after 5 washes, more preferably 25 washes, more preferably 50 washes or most preferably 100 washes. Also said method allows to obtain flame-retardant textile articles that are stable in the sense that the phosphorous content is at a level exceeding 90% of the original value after 6 months of storage and subsequently after been washed for 5 washes, more preferably 25 washes, more preferably 50 washes or most preferably 100 washes. As a result the flame-resisting properties, and especially the after-flame properties, are maintained at a level exceeding 90% after 5 washes, more preferably 25 washes, more preferably 50 washes or most preferably 100 washes. Also the flame-resistant properties, and especially the after-flame properties, are maintained at 90% of their original value after 6 months of storage and subsequently after been washed for 5 washes, more preferably 25 washes, more preferably 50 washes or most preferably 100 washes.

In a more preferred embodiment, the method allows to obtain flame-retardant textile articles that are stable in the sense that the phosphorous content is at a level exceeding 90% of the original value after 12 months of storage and subsequently after been washed for 5 washes, more preferably 25 washes, more preferably 50 washes or most preferably 100 washes. Also the flame-resistant properties, and especially the afterflame properties, are maintained at 90% of their original value after 12 months of storage and subsequently after been washed for 5 washes, more preferably 25 washes, more preferably 50 washes or most preferably 100 washes. Using the above described method according to the invention, it is possible to obtain a flame-resistant textile article having a very durable high phosphorous content whilst retaining desirable physical properties such as tensile strength, tear strength and elongation at break.

The invention also relates to textile articles produced using any of the above mentioned methods. According to the invention, a textile article can be any useful object such as a garment or other end product, a fabric - which can be woven, non-woven or otherwise - , a yarn or a fibre. Non-limiting examples include personal protective clothing - such as flame-resistant coats, trousers, uniforms, vests and coveralls, as well as helmets, seats, and trims - in particular for military vehicles and welding gloves.

The invention also relates to the use of a non-cellulose-reactive, phosphorous-containing, flame-retardant compound and a cellulose-reactive, phosphorous-containing, flame-retardant compound in any of the above-described methods. Furthermore the invention covers the use of the flame-resistant textile article produced according to any one of the methods described above for protecting individuals from heat and/or flames.

The flame-resistant method according to the invention allows production of textile articles that have a high and durable phosphorous content without having substantial negative effects of the phosphorous system on the physical properties of the textile articles. More specifically, the tensile strength, tear strength, abrasion resistance and/or snagging resistance are no worse than fibres treated by either of the two systems individually. In addition the phosphorous is durably bound to the fibre, yarn and/or fabric and can withstand at least 25, more preferably 50, even more preferably 100, or most preferably 150 washes without significant degradation. Also it is not very susceptible to spontaneous hydrolyzation which results in a long shelf life of the product.

The textile article produced according to the invention with a cellulose content of at least 10 wt%, or at least 25 wt%, or at least 40 wt%, or at least 50 wt%, or at least 60 wt%, or at least 70 wt%, or even at least 75 wt% may have beneficial properties relating to comfort. Alternatively the textile article according to the invention comprising between 30-80 wt% cellulose, more specifically between 50-75 wt% or still more specifically, 60-65 wt% cellulose may have beneficial properties relating to comfort.

In an embodiment, the textile article of the invention may comprise other fibres besides the cellulose fibres. These fibres can include, but are not limited to, meta-Aramid, para-Aramid, polyamide imide, polyamide, modacrylic, melamine, poly(p-phenylene benzobisoxazole) (PBO), polybenzimidazole (PBI), polysulphonamide (PSA), Panox (oxidized acrylic), semicarbon, partially oxidized acrylic (including partially oxidized polyacrylonitrile), rayon , lyocell, phenolic (novoloid), polyphenylene sulphide (PPS), PTFE, polyimide, polyester, acrylic, wool, viscose, flax, hemp, silk, nylon, anti-static fibers, and combinations thereof. In a preferred embodiment the fabric of the invention also comprises para-Aramid, meta-Aramid, modacrylic, acrylic, wool, silk and/or anti-static fibers. In particular, the inclusion of meta-Aramid and/or antistatic fibers may be highly desirable.

The textile article can be a fibre, yarn, fabric or garment. Said fabric may be a woven fabric, a knitted fabric or a non-woven fabric. Woven fabrics consist of two sets of interlocked yarns and are typically produced on a loom. Both sets consist of straight yarns which run in parallel. The set of yarns that runs in the direction of weaving is referred to as the warp. The set of yarns that runs orthogonal to the direction of weaving is referred to as the weft. Depending on how the weft and warp are interlocked, different types of woven fabrics may be produced according to the invention, such as twill or ripstop. Knitted fabrics also consist of interlocked yarns, however in this case the yams are interlocked using loops. A non-woven fabric consists of sheets of entangled fibres that are mechanically, thermally or chemically bonded.

The article is particularly useful in the form of a light weight fabric having a weight of between 100 and 300 g/m2, alternatively from 150 to 250 g/m2 or alternatively in the range of 180 to 210 g/m2. Such a fabric may be ideal for manufacture of protective clothing.

For use in the manufacture of protective clothing, the article may be a fabric having good air permeability, in particular, values of air permeability of more than 100 L/m2/s, or more than 200 L/m2/s or even greater than 300 L/m2/s may be provided, measured according to ISO 9237.

The invention may also be applied to heavier weight fabrics such as fabrics having weights of between 300 and 600 g/m2. In such situations, better comfort may be achieved since the fabric has relatively more cellulose-containing fibre such as cotton for example, and relatively less chemicals than is the case when a single treatment of non-reactive phosphorous is applied.

EXAMPLES

Example 1

A flame-resistant fabric was woven from a fibre blend comprising 64% Lenzing FR® - which is a Rayon fibre that has been made flame retardant by a non-cellulose-reactive treatment -, 24% aramid, 10% polyamide, 2% antistatic fibre to a twill construction at approximately 180 g/m ² . The same type of yarns was used in both directions (warp and weft). Subsequently the fabric was printed with a 100% coverage standard camouflage pattern composed of 7 colours. After the fabric was printed, a cellulose-reactive, phosphorous- containing, flame-retardant compound was applied to the fabric. This compound was applied by impregnating the fabric with an aqueous solution comprising Pyrovatex® CP LF, Knittex® MLF NEW , Phosphoric acid 85% and Invadin® PBN according to the concentrations as indicated in the top half of Table 1 . After the flame-retardant treatment liquid had sufficiently penetrated the fabric, the fabric was squeezed at a predetermined squeezing rate, pre-dried, and heat-treated by curing on a tenter frame for 1 minute at 170°C to help bind the phosphorus compound to cellulose molecules. Subsequently it was neutralized by soaking it in a 12 g/L sodium hydroxide solution at 60°C for 2 minutes and thoroughly rinsed using hot water. Thereafter, the samples received a standard fluorocarbon finish according to the bottom half of Table 1 . This finish improves the water and oil repellent properties of the fabrics. The process of applying the finish consisted of soaking the samples in an aqueous solution comprising the ingredients according to Table 1 and rapid curing of the treated samples on a tenter frame for 1 minute at 170°C.

The resulting fabric was tested and the results of said tests are presented in Table 2. All washes referred to in Table 2 are performed using ISO 6330 using detergent 6 from Annex N and tumble drying. If not specifically indicated, the fabric was not washed.

Table 1: Flame-retardant treatment.

Comparative example 1 was produced by the same procedure as the other samples except that no cellulose-reactive flame-retardant treatments was applied.

Table 2: Flame protection and physical properties.

The flame-retardant treatment resulted in a considerable improvement in flame-resistant properties, particularly in after-flame time and phosphorous content. Both improvements were retained after 5 washings. Surprisingly the tensile strength and elongation at break were not compromised by the treatment but even marginally increased. Also after 5 washings the tensile strength and elongation at break were not compromised. The tensile strength even maintained its increment after 5 washings.

Example 2

The experiment of Example 1 was repeated on a fabric woven to a plain ripstop construction at approximately 210 g/m ² . The yarns used to produce the fabric and the treatment received by the samples are identical to Example 1 . Said fabric was tested for relevant properties. Results of these tests are presented in Table 3. All washes referred to in Table 3 are performed using ISO 6330 using detergent 6 from Annex N and tumble drying. If not specifically indicated, the fabric was not washed.

Table 3: Flame protection and physical properties.

Again, also for the heavier ripstop fabric, considerable improvements in flame-resistant properties were noted, particularly in after-flame time, phosphorous content and LOI. This improvement was retained even after 5 washings. Surprisingly the tensile strength and elongation at break were not compromised directly after the flame-retardant treatment as well as after 5 washed. The tensile strength even marginally increased.

Example 3

Flame-resistant fabric was woven to a twill construction at approximately 180 g/m ² . The same type of yarns were used in both directions (warp and weft), for which the fibre blend comprised 64% Lenzing FR ^® which is a Rayon fibre that has been made frame retardant by a non-cellulose-reactive treatment, 24% aramid, 10% polyamide, 2% antistatic fibre. The fabric was printed with a 100% coverage standard camouflage pattern composed of 7 colours. After the fabric was printed a cellulose-reactive, phosphorous-containing, flame-retardant compound was applied to the fabric according to the conditions given in Table 4: (1 ) in combination with a standard finish with the fluorocarbon (in one step) or (2) before a standard finish with the fluorocarbon had been carried out.

Table 4: Application of a flame-retardant treatment in combination with a fluorocarbon finish (recipe 1) or as a separate process step (recipe 2).

Aflammit ^® KWB was used as the cellulose-reactive, phosphorous-containing, flame-retardant compound. The fabric was impregnated with an aqueous solution comprising Aflammit ^® KWB, Knittex® MLF NEW , Phosphoric acid 85% and Invadin® PBN in the concentrations as indicated in Table 4. After the flame- retardant treatment liquid had sufficiently penetrated the fabric, the fabric was squeezed at a predetermined squeezing rate, pre-dried, and heat-treated to bind the phosphorus compound to cellulose molecules. Phosphoric acid was used as the catalysts that promotes esterification reaction of hydroxyl groups of cellulosic fibres. Knittex® MLF NEW was used as cross-linking agent and to increase crease resistance of the fabric. Invadine® PBN manufactured by Huntsman was used as penetrant in order to increase the ability of the phosphorous compound to penetrate the fabric.

Process step 1 (related to a flame-retardant treatment with or without fluorocarbon finish) consisted of the following steps:

• impregnation according to the steps of Table 4,

• curing on a tenter frame 1 minute at 170°C,

• neutralisation: 12 g/L sodium hydroxide at 60°C, minimum 2 minutes,

• rinsing in hot water,

• drying.

Process step 2 consisted of (related to a fluorocarbon finish alone)

• impregnation according to the steps of Table 4

• rapid curing on a tenter frame 1 minute at 170°C

As can be seen in Table 4, comparative example 3 was produced by the same procedure as the other samples except that no flame-retardant treatments and related process steps were used for this fabric.

Results of these tests are presented in Table 5. All washes referred to in Table 5 are performed using ISO 6330 using detergent 6 from Annex N and tumble drying. If not specifically indicated, the fabric was not washed.

Table 5: Flame protection and physical properties.

As can be seen in Table 5, considerable improvement in flame-resistant properties particularly in after-flame time was noted when the flame-retardant treatment was combined with a fluorocarbon finish in one step or when these were carried out as separate steps. This improvement was retained even after 5 washings. The water and oil repellence along with physical properties were maintained at the same level for both initial and washed fabrics for both routes. The flame-retardant treatment hardly affected the tear strength. Surprisingly the decrease in tear strength due to washing was less for fabrics that did receive a flame-retardant treatment than that of fabrics that only received a fluorocarbon finish.

Example 4

Flame-resistant fabric was woven to a twill construction at approximately 180 g/m ² . The same type of yarns were used in both directions (warp and weft), for which the fibre blend comprised 64% Lenzing FR ^® which is a Rayon fibre that has been made frame retardant by a non-cellulose-reactive treatment, 24% aramid, 10% polyamide, 2% antistatic fibre and was for use in garments offering protection to brief exposure to substantial thermal fluxes. The fabric was printed with a 100% coverage standard camouflage pattern composed of 7 colours. After the fabric was printed a cellulose-reactive phosphorous-containing, flame- retardant compound was applied to the fabric according to the conditions given in Table 6. Also a standard finish with a fluorocarbon was carried out according to the conditions in Table 6.

Table 6: Application of a flame-retardant treatment.

The process steps related to the flame-retardant treatment were as following:

• Impregnation (Table 6)

• Curing on a tenter frame 1 minute at 170°C

• Neutralisation: 12 g/L sodium hydroxide at 60°C, minimum 2 minutes

• Rinsing in hot water

• Drying

Process step related to a fluorocarbon finish consisted of

• impregnation according to the steps of Table 6

• rapid curing on a tenter frame 1 minute at 170°C The comparative example 4 was produced by the same procedure as the other samples except that no flame-retardant treatments and related process steps were used for this fabric.

The fabrics were subjected to storage and washing before being tested for after-flame properties. The washing conditions were according to ISO 6330 using detergent 6 from Annex N, a 40°C program and tumble drying. Results of these tests are showed in Table 7.

Table 7; Flame protection after applying flame-retardant treatment as given in Table 6.

Table 8: LOI and Phosphorous/Nitrogen content after applying flame-retardant treatment as given in Table 6.

Table 9: Physical properties after applying flame-retardant treatment as given in Table 6.

As can be seen from Tables 7-9, considerable improvement in flame-resistant properties, particularly in after-flame time, phosphorous content and LOI were noted. This improvement was retained even after 5 washings. Furthermore the improvement was retained after 6 or 12 months storage even after washing the stored product. The physical properties are maintained at the same level for both initial and washed fabrics, while the fabric weight and air permeability remained unaffected, does maintaining excellent comfort properties.

Example 5

Flame-resistant fabric was woven to a plain ripstop construction at approximately 190 g/m ² . The same type of yams were used in both directions (warp and weft), for which the fibre blend comprised 64% Lenzing FR® which is a Rayon fibre that has been made frame retardant by a non-cellulose-reactive treatment, 24% aramid, 10% polyamide, 2% antistatic fibre and was for use in garments offering protection to brief exposure to substantial thermal fluxes. The fabric was printed with a 100% coverage standard camouflage pattern composed of 7 colours. After the fabric was printed a cellulose-reactive phosphorous-containing, flame-retardant compound was applied to the fabric according to the conditions given in Table 6 of Example 4. Further process steps are also as in Example 4. Thereafter, a standard finish with a fluorocarbon was carried out as in Example 4. The resulting fabric was tested and the results of said tests are presented in Tables 10-13. The washing conditions referred to in any of these tables were according to ISO 6330 using detergent 6 from Annex N, a 40°C program and tumble drying

The comparative example 5 was produced by the same procedure as the other samples except that no flame-retardant treatments and related process steps were used for this fabric. Table 10: Flame protection after applying flame-retardant treatment as given in Table 6.

Table 12: Physical properties after applying flame-retardant treatment as given in Table 6.

As can be seen from Tables 10-12 considerable improvement in flame-resistant properties, particularly in after-flame time, phosphorous content, and LOI were noted. This improvement was retained even after 5 washings. Furthermore the improvement was retained after 6 or 12 months storage even after washing the stored product. The physical properties are maintained at the same level for both initial and washed fabrics, while the fabric weight and air permeability remained unaffected, thus maintaining excellent comfort properties.

Thus, the invention has been described by reference to certain examples discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art. In particular, the fibre blends and weights may be varied according to the intended use. Many modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention