Method of Treating a Material

The present invention relates to a method of treating a material. In particular, the invention relates to a method of treating a material to impart flame retardant properties thereto. Suitably, a material thus treated is durable to laundering and/or dry cleaning.

Many materials including, for example, wool and cotton materials require chemical treatment in order to render them flame retardant. Wool is inherently flame retardant although not enough to be used in certain applications, for example mass transit seating or upholstery.

It is desirable that flame retardant materials are low cost, durable, do not impact on the mechanical properties of the fabric, meet health and safety requirements, are environmentally acceptable, and are able to tolerate traditional dyeing and printing processes for all colour ranges when used on dyed materials.

Flame retardant (FR) compositions for wool based materials originally focused on the use of chromium salts, which unfortunately gave the wool material a light green colour. However in the 1970s the International Wool Secretariat (IWS) developed the 'Zirpro' treatments. The generic title of 'Zirpro' covered a range of treatments which were based on potassium hexafluorozirconate and potassium hexafluorotitanate salts.

The 'Zirpro' treatments are based on the 'exhaustion' of the negatively charged complex anions ZrF ₆ ^2" and TiF ₆ ^2" , under acidic conditions onto positively charged sites in wool. Other flame retardants for wool are based upon halogen donors, which tend to interfere with free radical processes that maintain a flame, although these are environmentally unacceptable. Alternative treatments available are based on phosphate / polyphosphate salts, but these have achieved only limited commercial success, and are not usually durable to wet treatments.

The present invention relates in particular to a method of providing wash-durable flame retardant compositions. Each of the known existing wash-durable flame retardant compositions has one or more disadvantages. One existing durable FR composition is the 'Zirpro' system mentioned above, in which a solution containing the relevant complex anion is applied to wool via an exhaustion method. An 'exhaustion' method refers to a process where the material is soaked in the FR solution for a period of time until the active chemical has been absorbed (or 'exhausted') onto the material. However, not all dyed wool materials can be treated with the 'Zirpro' system since the hexafluorozirconate system discolours some dyes. The zirconium and titanium hexafluorozirconate salts are also associated with have serious environmental problems. A further disadvantage of Zirpro is that it can make a fibre more brittle. It is possible to treat wool with Zirpro in top form, but the brittleness will lead to loss of fibre when it is then spun and woven. The same loss of strength is observed when yarn is treated with Zirpro. For this reason it is usually desirable to treat materials with a Zirpro process in fabric form.

Another durable FR composition is Noflan (RTM) supplied by Firestop (UK), which is a phosphorous based chemical that is normally applied using a pad bake system, as is described in US6863846 and US625947. This product however contains a large amount (~30%) of ammonium chloride which has the potential to form hydrochloric acid under humid conditions. This is a significant drawback and limits the potential applications of this product. For example it cannot be used on some seating as it may corrode metal frameworks and its use in the airline industry are restricted.

It is an object of the present invention to provide a flame retardant composition which overcomes at least one disadvantage of the prior art, whether specifically mentioned herein or otherwise.

According to a first aspect of the present invention, there is provided a method of treating a material to improve its flame retardancy, the method comprising applying to the material an acidic composition comprising a polyphosphate compound.

By polyphosphate compound, we mean to refer to a compound comprising at least two phosphorous atoms linked by oxygen atoms.

The composition used in the method of the present invention may comprise a mixture of two or more such compounds and references to polyphosphate compounds in this specification include mixtures thereof.

Suitably the polyphosphate compound is provided as an anionic oligomer or low molecular weight polymer. Preferably it is provided as an alkali metal salt. Suitably the polyphosphate compound is provided as a lithium, sodium or potassium salt. It may be provided as a mixed salt. Preferably it is provided as a sodium salt.

A polyphosphate compound typically has the structure shown in figure I:

in which a M ⁺ is an alkali metal cation.

Suitably n may be from 2 to 20, for example from 3 to 15, preferably from 3 to 10, for example from 3 to 8 or from 4 to 7.

As mentioned above mixtures of oligomers may be present.

Especially preferred polyphosphate compounds for use in the present invention are cyclic compounds, suitably having the structure shown in figure II:

Figure II in which a M ⁺ is an alkali metal cation. Suitably x is from 1 to 20, for example from 2 to 12, preferably from 3 to 8, for example from 3 to 5. Most preferably x is 4.

Thus an especially preferred compound is sodium hexametaphosphate, also known as Graham's salt. This is believed to have the structure shown in figure III although other possible structures have been suggested.

Figure III Preferably the polyphosphate compound has a molecular weight at least 300 including the mass of the counter ions, preferably at least 400, more preferably at least 500, preferably at least 550, most preferably at least 575.

Suitably the polyphosphate compound has a molecular weight of up to 2000 including the mass of the counter ions, preferably up to 1500, suitably up to 1000, preferably up to 800, more preferably up to 700 and most preferably up to 650.

It is especially preferred that the polyphosphate compounds for use in the present invention are of limited solubility.

Preferably the polyphosphate compound has a solubility of less than 500gdm ³ , preferably less than 450gdm ³ in water at 20°C under atmospheric pressure. It is believed that the lower solubility of this compound compared to some comparable linear compounds helps improve the durability of the flame retardant finish.

The composition used in the present invention is an acidic composition. Preferably the composition has a pH of less than 6.5, preferably less than 6, more preferably less than 5.5, suitably less than 5, preferably less than 4.5 and more preferably less than 4. Preferably the composition used in the method of the present invention has a pH of less than 3.5, more preferably it has a pH of less than 3.

Suitably the composition applied to the material has a pH of at least 0.5, for example at least 1 or at least 1 .5. In some preferred embodiments the composition may have a pH of from 2 to 3, suitably from 2.2 to 2.8 for example about pH 2.5. The skilled person will appreciate that varying the pH of the composition may vary the nature of the active species present: increasing the acidity will mean that a higher proportion of the polyphosphate compound will be present in protonated form and a composition of higher pH will include more of the deprotonated species. For the avoidance of doubt, references above to the preferred use of alkali metal salts and the like refer to the compound which is initially included in the preparation of the composition and not necessarily to the active species present, which may be pH-dependent.

In preferred embodiments the method of the present invention involves applying to a material a composition having a pH of less than 4. However it is possible to treat the material according to the present invention with a composition having a higher pH if this material has first been pre-treated with a quaternary ammonium salt using the method described in the applicant's earlier application GB1300385.0. Thus in some embodiments the present invention provides a method of treating a material, the method comprising the steps of:

(i) applying to the material a composition comprising a compound of formula E-L-Q ⁺ wherein E is an electrophile, L is a linking moiety and Q ⁺ is a quaternary ammonium residue; and

(ii) applying to the material an acidic composition comprising a polyphosphate compound.

In such embodiments the composition applied in step (ii) may have a pH of greater than 3, suitably greater than 3.5, for example greater than 4. It may for instance have a pH of from 4 to 6.

Preferred features of step (i) are as defined in the earlier application GB1300385.0. An especially preferred compound for use in step (i) is 3-chloro-2-hydroxy-propyl trimethyl ammonium chloride.

Suitably the composition used in the present invention comprises an acid. Any suitable acid may be used including mineral acids and organic acids. Suitable mineral acids include sulphuric acid, phosphoric acid, hydrochloric acid and nitric acid.

Suitable organic acids include formic acid, acetic acid, trichloroacetic acid and trifluoroacetic acid. Preferred acids include sulphuric acid, formic acid and trichloroacetic acid. Sulphuric acid is especially preferred. The composition used in the present invention may include a mixture of two or more acids. In this specification references to acid refer to all acids present.

Preferably the composition applied to the material in the method of the present invention does not comprise a base. In particular, it is preferred that the composition is substantially free of a nitrogen containing base. Thus in preferred embodiments the composition is substantially free of ammonia and amines.

Preferably the composition is an aqueous composition. It may further comprise other water- miscible solvents. Preferably however water is the only solvent present.

In some embodiments the composition may further comprise a wetting agent. The selection of a suitable wetting agent is within the capabilities of the person skilled in the art. The type of wetting agent used and the amount needed depends upon the nature of the material and the method used to apply the composition. For example a pad-batch method typically involves applying a composition to a dry fabric and contact times are usually short. Thus in such methods a relatively high concentration of wetting agent may be needed. Where an exhaustion method is used the material is immersed in the composition for a long period and thus lower levels of wetting agent are usually needed. In some embodiments the composition may not comprise a wetting agent. For example if the treatment method of the present invention is carried out on a material which is already wet, it may not be necessary to add a further wetting agent to the treatment composition. The method may be carried out on a wet material if the material has been pre-wetted or if it has been subjected to an earlier treatment. For example a material which has been dyed but has not been dried could be treated according to the present invention to provide a flame retardant finish. Carrying out sequential treatments in this manner is highly advantageous as it leads to a reduction in overall treatment time and costs.

In some embodiments the composition may further comprise a swelling agent. Suitable swelling agents include urea and guanidine hydrochloride.

In the method of the present invention the composition may be applied to the material by any suitable means. Typically different methods are used depending on the physical form of the material. For example, wool top may typically be treated in a bump machine; fabric may suitably be treated in a jet machine, beam machine or winch machine; garments or other finished articles may typically be treated using a paddle machine; for worsted yarn a package machine is preferred; and carpet yarn is usually treated in hank form in a hank machine. In some preferred embodiments of the present invention the composition is applied to the material using a padding technique. Such an application method will be well known to those skilled in the art and is most appropriately used to treat rolls of fabric material.

In such a method the material is passed through a pair of squeeze rollers which apply the composition to either side of the material.

After passing through the squeeze rollers the material may be rolled up and covered, for example with a plastics material. It is then left for a period to allow the active ingredients to disperse evenly throughout the material. This is known as a pad-batch method.

In some embodiments the material may be passed through an oven after passing through the squeeze rollers. When the oven is at a relatively low temperature (typically 50 to 130°C) this may be referred to as a pad-dry method. When higher temperatures are used (for example greater than 140°C), the method may be referred to as a pad-bake method. Methods involving both drying and baking steps are also possible and may be referred to as pad-dry-bake methods.

In this specification padding methods or padding techniques may refer to pad-batch, pad-dry, pad-bake and pad-dry-bake methods. All of these terms are well understood by the person skilled in the art.

In some preferred embodiments the composition is applied to the material using an exhaustion technique. This technique involves immersing the material in the composition for a period sufficient to allow uptake ('exhaustion') by the material of the active components. Exhaustion may be described as the transfer of a component from a liquor bath to the fibre. The extent of exhaustion is sometimes given as a percentage. For example, a process involving 60% exhaustion of a component would mean that 60% of the total amount of the component in the composition has attached to the fibre, and the remaining 40% remains in solution. Exhaustion techniques are commonly used in dyeing processes. In some cases reactive dyes and acid dyes may exhaust to the point that the dye liquor becomes nearly colourless. It should be noted that a component which has exhausted onto a material has not necessarily "permanently" bonded to the material. In some instances a component may form a permanent covalent bond with a material but in other instances a more transient electrostatic interaction may exist.

It is desirable to achieve very high levels of exhaustion both for economical reasons and environmental reasons. Any chemical not exhausted would end up being discharged in effluent.

The liquor ratio used in the method of the present invention, that is the weight ratio of composition to material treated depends on the application method employed. However selection of an appropriate application method and a suitable liquor ratio for use in such an application method is well within the capabilities of the person skilled in the art.

The concentration of each component present in the composition may vary according to the liquor ratio used. Suitably the concentrations of the components are selected to provide a specific treatment level defined as % omf (% on mass of fibre). This is the percentage by mass of a component which has been fixed onto the material during the treatment process and is calculated by measuring the dry mass of the material at the start and the end of the process. For example, if 100g of dry material is treated and after processing has dry weight of 103g, then a treatment level of 3% omf has been achieved.

In a preferred embodiment the treatment level of the polyphosphate compound is at least 0.1 % omf, preferably at least 1 % omf, more preferably at least 3% omf, suitably at least 5% omf, for example at least 7% omf. Preferably the treatment level of the polyphosphate compound is up to 50% omf , for example up to 40% omf, preferably up to 30% omf, more preferably up to 20% omf, and most preferably up to 18% omf.

Particularly preferred treatment levels are from 8% omf to 15% omf.

The treatment levels of polyphosphate compounds stated above refer to the total amount of polyphosphate compounds when a mixture is used.

As mentioned above, the method of the present invention preferably comprises applying to a material an aqueous composition comprising a polyphosphate compound and an acid. The composition may suitably be prepared by the addition of an acid to an aqueous solution of the polyphosphate compound until the desired pH is achieved. Preferably the treatment level of acid used in the present invention is at least 0.1 % omf, preferably at least 0.5% omf, for example at least 1 % omf, suitably at least 2% omf.

When a swelling agent is used the treatment level is preferably at least 0.1 % omf, preferably at least 0.5% omf, for example at least 1 % omf.

The swelling agent may be present at a treatment level of up to 15% omf, preferably up to 10% omf, suitably up to 8% omf, for example up to 5% omf. The treatment level of acid may be up to 25% omf, for example up to 20% omf, suitably up to 15% omf or up to 12% omf.

When a wetting agent is used in an exhaustion method, a treatment level of less than 10% omf is preferred, suitably less than 5% omf, preferably less than 2.5% omf or less than 1 % omf.

When a wetting agent is used in a padding method a higher treatment level may typically be used for example from 1 to 20% omf, suitably from 5 to 15% omf.

In some embodiments the composition may further comprise a smoke-reducing compound. Such compounds are well known to those skilled in the art and when present are suitably contained in an amount sufficient to provide a treatment level of from 1 to 25% omf, preferably 15 to 20% omf, more preferably from 7 to 15% omf, for example about 10% omf. Suitable smoke-reducing compounds include halogen-containing materials, for example tetrabromophthalic anhydride which is available from Dixon-Chew in West Yorkshire under the trade mark Flameban; along with smoke-reducing materials sold under the trade mark Cetaflam by Avocet Dye & Chemical Co. Ltd.

In some embodiments the composition used in the present invention may be provided in concentrated form, to be diluted by the user.

The method of the present invention may be used to treat any suitable material, for example a cellulose based material (for example cotton, linen, viscose, wood or paper) or polyamide based materials (e.g. wool, nylon, silk, feathers & down). In some embodiments the method of the present invention is used to treat keratin based materials, for example wool, feathers and down.

Preferably the material treated in the method of the present invention comprises polyamide fibres, for example natural polyamide fibres for example wool, silk, alpaca, angora, leather etc; or synthetic polyamide fibres, for example Nylon 6, Nylon 6, 6 etc. Blends or mixtures including polyamide fibres and non-polyamide fibres are within the scope of the present invention. Preferably the material treated by the present invention comprises wool. It may be pure wool or it may be a mixture or blend comprising wool and one or more other materials. In embodiments in which the material is a mixture or blend, it preferably comprises at least 20wt% wool, preferably at least 30wt%, for example at least 40wt%, more preferably at least 50wt%. Such blends or mixtures may suitably comprise one or more further materials selected from nylon, viscose, lycra, acrylics, cotton and polyester.

The wool material may comprise wool in any suitable form, for example wool yarn, wool top, wool fabric, wool carpet, or loose wool; and may include cashmere or non-sheep origin animal fibres. Alternatively, the wool material may be in the form of a garment or other finished article containing wool or a woven fabric containing wool or non-sheep origin fibres.

In some embodiments the material may be a fabric including a knitted or woven fabric or a non-woven material. Suitably the method of the present invention may comprise the steps of:

(a) preparing an acidic composition comprising a polyphosphate compound;

(b) contacting the material with said composition; and

(c) removing the material from contact with the composition.

There may be a pre-treatment step prior to step (a) involving application of a composition comprising a quaternary ammonium compound as is described in the applicant's earlier application GB1 100455.3.

Suitably step (a) comprises preparing a composition comprising a polyphosphate compound and an acid in an amount appropriate to provide the preferred treatment levels as detailed above, and the necessary pH.

It is well within the capability of the skilled person to select appropriate concentrations based on the amount of material and liquor ratio used to arrive at an appropriate treatment level (as %omf). In some preferred embodiments the material is contacted with a heated composition. The composition may be heated prior to contact with the material or during contact with the material.

In a preferred embodiment in which step (b) comprises immersing the material in the composition in an exhaustion method, the composition is suitably heated after immersion of the material.

In an exhaustion method the composition may suitably be heated to a temperature of at least 30°C, more preferably at least 40°C, for example at least 50°C. It may be heated to a temperature of up to 100°C, for example up to 90°C, preferably up to 80°C, more preferably up to 70°C. In a preferred embodiment a temperature of 55 to 65°C is used, for example about 60°C.

Suitably, in step (b) of such exhaustion methods the material is contacted with the composition for a period of at least one minute, preferably at least five minutes, for example at least 10 minutes, suitably at least 15 minutes, or at least 20 minutes. In step (b) the material may be contacted with the composition for a period of up to six hours, for example up to 4 hours, preferably up to 2 hours, for example up to 1 hour, preferably up to 50 minutes, for example up to 40 minutes.

Exhaustion methods are particularly suitable for the treatment of materials comprising polyamide fibres, for example wool. Exhaustions methods are not usually suitable for the treatment of cellulosic materials, for example cotton, unless the material has first been treated to modify the surface, for example by treatment with a cationic compound.

In some alternative embodiments the composition may be applied to the material using a padding method. Such methods are suitable for the treatment of cellulosic materials. They are also suitable for the treatment of materials comprising polyamide fibres, for example wool. As detailed previously a pad-batch method involves passing the material between a pair of rollers and then keeping the treated material roll covered for several hours, typically at ambient temperature. The composition itself may be heated prior to application to the material but it is usual to apply the composition at ambient temperature. The roll of treated material is preferably left for a period of at least 2 hours, for example at least 4 hours, suitably at least 8 hours or at least 10 hours. It may be left for up to 48 hours, suitably up to 36 hours, for example up to 24 hours. During such a period the roll is suitably rotated so that even distribution of the FR composition is achieved. Step (c) may in some embodiments comprise physical removal of the material from contact with the composition. For example if the material is immersed in the composition, the material may simply be lifted from the composition or the composition drained from the container comprising the material. In some embodiments step (c) may also include rinsing the composition from the material. Such a rinsing step may suitably comprise applying water to the material.

After physical removal of the material from contact with the composition in step (c) the material may suitably be dried. It may optionally be spin dried. Alternatively and/or additionally it may be dried at an elevated temperature by passing through or into an oven. In some embodiments the material is first spin dried to remove excess liquor and then dried in an oven. In some embodiments the drying step may involve passing the material through a radio frequency oven. Any suitable drying step can be used and an appropriate method can be easily selected by the person skilled in the art.

In some embodiments the method may comprise of one or more additional further rinsing and/or drying steps.

In pad-dry and pad-bake methods the material is passed through an oven after passing through squeeze rollers. This may or may not involve an intermediate step of rinsing the material with water. Preferably it does not involve rolling the material up prior to drying or baking.

A material treated by the method of the present invention is suitably provided with flame retardant properties that are durable to dry cleaning and cold water rinsing of the material, and to some warm wash procedures. Materials treated with a flame retardant composition for use in transportation fabrics (for example aircraft, railway and shipping) must meet various international standards for flame testing / type of wash testing / smoke production / toxicity of smoke evaluation and the like. The standard(s) required depends on the intended use of the material. In addition, individual aircraft manufacturers (i.e. Boeing & Airbus etc.) have their own requirements and standards that suppliers must meet.

Thus there are many flame tests which could be described. However a suitable test for use in the laboratory is the method set out in BS5438 (Methods of test for flammability of textile fabrics when subjected to a small igniting flame applied to the face or bottom edge of vertically orientated specimens), where the fabric is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds. The British standard requires that the length of the observed char must not exceed the size of the test frame (approximately 15cm). Afterglow supporting a flame front and a hole in the charred region of the fabric are also observations which result in a test fail.

Suitably materials treated by the method of the present invention pass the flame test described in BS5438.

In an alternative test a small Bunsen burner or a kitchen butane torch may be used to assess the flammability characteristics of a material. The flame can be applied at a 45° angle on the bottom edge of the fabric for 15 seconds. For a test pass, after removal of the flame there must be no more than 5 seconds of after flame on the fabric, preferably no more than 2 seconds.

Suitably materials treated according to the present invention pass this simple test. The method of the present invention may be carried out as a batch process or a continuous process. A batch process is preferred.

According to a second aspect of the present invention there is provided the use of an acidic composition comprising a polyphosphate compound to impart flame retardant properties to a material, preferably a material comprising wool.

According to a third aspect of the present invention there is provided a material treated by the method of the first aspect. In embodiments in which the material of the third aspect is a cellulosic material it is preferably treated by a padding method.

In embodiments in which the material of the third aspect comprises polyamide fibres (for example wool), it may be treated by an exhaustion method or a padding method. Preferably it is treated by an exhaustion method.

Other preferred aspects of the second and third aspects are as defined in relation to the first aspect, where appropriate. The invention will now be further described in relation to the following non-limited examples. In these examples when using the term % omf in relation to a reagent, we mean to refer to the amount of that reagent that will be on the material at the end of the treatment process.

Example 1 - Exhaustion process for wool serge fabric

Ground sodium hexametaphosphate 1 .00g (10% omf.) was added to distilled water (100cm ³ ) and allowed to dissolve. The solution was then added to a 300 cm ³ dyeing tube. The non-ionic surfactant (or wetting agent) Sandozin NIN 0.05g (0.5% omf.) was added to the solution. Sulphuric acid 0.4g (4% omf.) was added to the solution.

Wool serge fabric 10.00g (10:1 liquor ratio) was added to a dyeing tube which contained the solution. The dyeing tube was then sealed and placed in a dye-bath.

The temperature of the dye-bath was set at 60°C for a period of 30 minutes. At the end of the treatment step, the wool serge fabric was removed from the dyeing tube and rinsed in cold running water for 3 minutes. Treated samples were then spin-dried and dried in a microwave.

Before a flame test was carried out all samples were kept in a conditioning cabinet (20°C, 60% humidity) for at least 12 hours.

The fabric was then flame tested using two methods:

The method set out in BS5438, where the fabric is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds.

Using a kitchen butane burner, with the flame applied at a 45° angle on the bottom edge of the fabric for 15 seconds.

The resultant treated fabric passes these two flame tests, by not continuing to burn after the applied flame is removed.

Example 2 - Exhaustion process for wool Crepe fabric

Ground sodium hexametaphosphate 1 .00g (10% omf.) was added to distilled water (200cm ³ ) and allowed to dissolve. The solution was then added to a 300 cm ³ dyeing tube. The non-ionic surfactant Sandozin NIN 0.05g (0.5% omf.) was added to the solution. Sulphuric acid 0.4g (4% omf.) was added to the solution. Wool crepe fabric 10.00g (20:1 liquor ratio) was added to a dyeing tube which contained the prepared solution. The dyeing tube was then sealed and placed in a dye-bath.

The temperature of the dye-bath was set at 60°C for a period of 30 minutes. At the end of the treatment step, the wool crepe fabric was removed from the dyeing tube and rinsed in cold running water for 3 minutes. Treated samples were then spin-dried and dried in a microwave.

Before a flame test was carried out, all samples were kept in a conditioning cabinet (20°C, 60% humidity) for at least 12 hours.

The fabric was then flame tested using two methods:

The method set out in BS5438, where the fabric is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds.

Using a kitchen butane burner, with the flame applied at a 45° angle on the bottom edge of the fabric for 15 seconds.

The resultant treated fabric passes these two flame tests, by not continuing to burn after the applied flame is removed.

Example 3 - Exhaustion process for Wool Top

Ground sodium hexametaphosphate 0.50g (10% omf.) was added to distilled water (150cm ³ ) and allowed to dissolve. The solution was then added to a 300 cm ³ dyeing tube. The non-ionic surfactant Sandozin NIN 0.02g (0.4% omf.) was added to the solution. Sulphuric acid 0.3g (6% omf.) was added to the solution.

Wool top 5.00g (30:1 liquor ratio) was added to a dyeing tube which contained the dyeing solution. The dyeing tube was then sealed and placed in a dye-bath.

The temperature of the dye-bath was set at 60°C for a period of 30 minutes. At the end of the treatment step, the wool top was removed from the dyeing tube and rinsed in cold running water for 3 minutes. Treated samples were then spin-dried and dried in a microwave.

Before a flame test was carried out, all samples were kept in a conditioning cabinet (20°C, 60% humidity) for at least 12 hours. The wool top was then flame tested using the method set out in BS5438, where the wool top is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds. The resultant treated fabric passes this flame test, by not continuing to burn after the applied flame is removed.

Example 4 - Exhaustion process for Wool Yarn Two cones of 100% wool yarn (3Kg total) were added to a package dyeing machine. Water (20 litres) and Sandozin NIN 15g (0.5% omf.) were added to the solution and circulated in order to wet the yarn.

Sodium hexametaphosphate (40%w/w aq soln) 1 1 15g (15% omf.) and sulphuric acid 180g (6% omf.) was added to the liquor, which was then made up to a total of 30 litres with water to give a 10:1 liquor ratio.

The temperature of the package machine liquor was set at 60°C for a period of 40 minutes. At the end of the treatment step, the liquor was drained from the package dyeing machine and rinsed with cold water for 3 minutes.

The cones were then removed from the package dyer and spin dried to remove excess liquor and then dried through a radio frequency oven for ~2 hours at ~75°C. The yarn was then knitted into an open weave fabric and flame tested.

Before a flame test was carried out, all samples were kept in a conditioning cabinet (20°C, 60% humidity) for at least 12 hours. The fabric was then flame tested using two methods:

The method set out in BS5438, where the fabric is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds.

- Using a cigarette lighter, the flame was applied to the end of a single yarn to observe whether the flame travelled along the yarn.

The resultant treated samples passes these two flame tests, by not continuing to burn after the applied flame is removed or travelling along the yarn. Example 5 - Exhaustion process for Wool-Nylon Yarn

Cones of newly dyed 83% wool and 17% nylon yarn (100Kg total) were left in a package dyeing machine after a dyeing process. The machine was then filled with water (~950Kg)

Sodium hexametaphosphate (40%w/w aq soln) 37.5Kg (15% omf.) and sulphuric acid 6Kg (6% omf.) was added to the liquor, which was then made up to a total of 1000 litres with water to give a 10:1 liquor ratio.

The temperature of the package machine liquor was set at 60°C for a period of 30 minutes. At the end of the treatment step, the liquor was drained from the package dyeing machine and rinsed with cold water for 3 minutes. The cones were then removed form the package dyer and then spin dried to remove excess liquor and then dried through a radio frequency oven for ~2 hours at ~75°C.

The yarn was then knitted into an open weave fabric and flame tested. Before a flame test was carried out, all samples were kept in a conditioning cabinet (20°C, 60% humidity) for at least 12 hours.

The fabric was then flame tested using two methods: - The method set out in BS5438, where the fabric is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds.

Using a cigarette lighter, the flame was applied to the end of a single yarn to observe whether the flame travelled along the yarn.

The resultant treated samples passes these two flame tests, by not continuing to burn after the applied flame is removed or travelling along the yarn. Example 6 - Pad-Batch process for wool serge fabric:

Ground sodium hexametaphosphate 10.00g (10% omf) was added to distilled water (79cm ³ ) and allowed to dissolve. The solution was then added to a 250 cm ³ beaker. An anionic surfactant (or wetting agent) Alcopol O 1 g (1 % omf) was added to the solution and formic acid 10.OOg (10% omf) was added. Wool serge fabric was padded with the solution in order to achieve a wet pick-up of 100%. The wool serge fabric was then batched by rolling up freshly padded fabrics and covering with a polyethylene film; the batched samples were then stored at 20°C for 17 hours.

At the end of the batching step, the wool serge fabric was removed from the polyethylene film and rinsed in cold running water for 3 minutes. Treated samples were then spin-dried and dried in a microwave. Before a flame test was carried out, all samples were kept in a conditioning cabinet (20°C, 60% humidity) for at least 12 hours.

The fabric was then flame tested using two methods: - The method set out in BS5438, where the fabric is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds.

Using a kitchen butane burner, with the flame applied at a 45° angle on the bottom edge of the fabric for 15 seconds.

The resultant treated fabric passes these two flame tests, by not continuing to burn after the applied flame is removed.

Example 7 - Pad-batch process for wool crepe fabric:

Ground sodium hexametaphosphate (10.00g 10% omf) was added to distilled water (79cm ³ ) and allowed to dissolve. The solution was then added to a 250 cm ³ beaker. An anionic surfactant Alcopol 0 1 g (1 % omf) was added to the solution and formic acid (10.00g 10% omf) was added.

Wool crepe fabric was padded with the solution in order to achieve a wet pick-up of 100%. The wool crepe fabric was then batched by rolling up freshly padded fabrics and covering with a polyethylene film; the batched samples were then stored at 20°C for 17 hours. At the end of the batching step, the wool crepe fabric was removed from the polyethylene film and rinsed in cold running water for 3 minutes. Treated samples were then spin-dried and dried in a microwave. Before carrying out a flame test all samples were kept in a conditioning cabinet (20°C, 60% humidity) for at least 12 hours.

The fabric was then flame tested using two methods: - The method set out in BS5438, where the fabric is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds.

Using a kitchen butane burner, with the flame applied at a 45° angle on the bottom edge of the fabric for 15 seconds.

The resultant treated fabric passes these two flame tests, by not continuing to burn after the applied flame is removed.

Example 8 - Exhaust Application on Pre-dyed Tops

A bulk scale trial was carried out in a top dyeing machine with a capacity of 2000 litres with a 7:1 liquor ratio.

258.5kg of pre-dyed wool top and nylon top (2 shades - dark and light violet on both the wool and nylon tops) was placed into the vessel. The dyeing vessel was half filled with a mixed fill (cold and hot), and circulated to wet out the top (application would be best carried out on freshly dyed top to avoid a drying stage).

H ₂ S0 ₄ (9.6Kg) (4%omf) was added to cold water (~50Kg) in the addition tank, heated to 40°C and then transferred to the dyeing vessel. The liquor in the vessel was then circulated for 2 minutes.

Sodium hexametaphosphate (40% w/w aq soln) (63.5kg) was then added to the addition tank, heated to 40°C and transferred to the dyeing vessel. The solution in the dyeing vessel was circulated for 2 minutes.

The dyeing vessel was heated to 60°C and maintained at 60°C for 30 minutes.

The pH of the liquor was in the range 2.37-2.44.

The vessel was then drained completely and re-filled with cold water. The cold supply was ~8°C and on circulating rose quickly to ~37°C before rapidly dropping to ~20°C. The water was then circulated for 5 minutes. The pH of this rinse water was pH4.10. The vessel was then drained and treated top was removed from the dyeing machine, spun and dried through a radio frequency (RF) oven.

Before carrying out a flame test all samples were kept in a conditioning cabinet (20°C, 60% humidity) for at least 12 hours.

The top was then flame tested using the method set out in BS5438; where the material is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds.

The resultant treated top passes this flame test, by not continuing to burn after the applied flame is removed.

Example 9 - Exhaust Application on Pre-dyed Yarns

A bulk scale trial was carried out in a Thies package dyeing machine with a capacity of 4500 litres with a 20:1 liquor ratio.

240 Kg of pre-dyed wool/nylon blended yarn (Irish Blue shade) was placed into the vessel. The addition tank was filled with a mixed fill, to which 10.1 Kg of H ₂ S0 ₄ was added. The liquor was then heated to 40°C before being transferred to the dyeing vessel.

The liquor was then circulated for 5 minutes to wet out the top (application would be best carried out on freshly dyed top to avoid a drying stage).

The liquor was then transferred back to the addition tank, where 77Kg of sodium hexametaphosphate (40% w/w aq soln) was added.

The liquor was again heated to 40°C before being transferred back into the dyeing vessel [the transfer was carried out at 40°C due to the machine program parameters].

The dyeing vessel was heated to 60°C and maintained at 60°C for 30 minutes. The pH of the liquor was in the range 2.49 to 2.62. The vessel was then drained completely and re-filled with cold water. The cold supply was ~8°C and on circulating rose quickly to ~35°C before rapidly dropping to ~20°C. The water was then circulated for 5 minutes. The pH of this rinse water was pH4.30.

The vessel was then drained and the treated packages were removed from the dyeing machine, spun and dried through an RF oven. Before carrying out a flame test all samples were kept in a conditioning cabinet (20°C, 60% humidity) for at least 12 hours. The top was then flame tested using the method set out in BS5438; where the material is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds.

The resultant treated top passes this flame test, by not continuing to burn after the applied flame is removed.

Example 10 - Pad-dry process for cotton fabric:

Ground sodium hexametaphosphate 10. Og (10% omf) was added to distilled water (79cm ³ ) and allowed to dissolve. The solution was then added to a 250 cm ³ beaker. A nonionic surfactant (or wetting agent) Hostapal NIN 1 g (1 % omf) was added to the solution and formic acid 2.0g (12% omf) was added.

Cotton fabric was padded with the solution in order to achieve a wet pick-up of 100%. The cotton fabric was then dried at 60°C for 30 seconds effective.

Before a flame test was carried out, all samples were kept in a conditioning cabinet (20°C, 60% humidity) for at least 12 hours. The fabric was then flame tested using the method set out in BS5438, where the fabric is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds.

The resultant treated fabric passed this flame test, by not continuing to burn after the applied flame is removed.

Example 11 - Exhaustion process for wool fabric

1 Kg of pre-dyed wool (75%) / nylon (25%) flat woven fabric was placed into a Mathis Jig dyeing vessel. A liquor ratio of 12:1 was used and the vessel was filled with water which was circulated in order to wet out the fabric.

40g (=4%omf) of H ₂ S0 ₄ was added and then circulated for 15 minutes in order to stabilise the pH of the liquor. During this 15 minute period, small aliquots of H ₂ S0 ₄ were added in order to correct the pH to below pH2.5. 1 L of liquor was drawn from the machine, into which 100g of sodium hexametaphosphate soln (40% w/w aq soln) and 25g of Guanidine hydrochloride were added and stirred. Upon dissolution, the liquor was transferred back into the dyeing vessel and circulated.

The dyeing vessel was heated to 60°C and maintained at 60°C for 30 minutes. The pH of the liquor was in the range 2.2 to 2.5. The pH of the liquor was maintained below pH2 during the 30 minutes using small additions of H2S04.

The vessel was then drained completely, re-filled with cold water, circulated for 5 minutes and then drained completely. This rinse procedure was carried out 2 times to ensure the rinse water was above pH4.5.

The vessel was then drained and the treated fabric was removed from the dyeing machine, spun and dried. Before carrying out a flame test all samples were kept in a conditioning cabinet (20°C, 60% humidity) for at least 12 hours.

The fabric was then flame tested using the method set out in BS5438; where the material is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds.

The resultant fabric passes this flame test, by not continuing to burn after the applied flame is removed. Example 12 - Exhaustion process for wool fabric

1 Kg of pre-dyed wool (75%) / nylon (25%) flat woven fabric was placed into a Mathis Jig dyeing vessel. A liquor ratio of 12:1 was used and the vessel was filled with water which was circulated in order to wet out the fabric.

40g (=4%omf) of H ₂ S0 ₄ was added and then circulated for 15 minutes in order to stabilise the pH of the liquor. During this 15 minute period, small aliquots of H ₂ S0 ₄ were added in order to correct the pH to below pH2.5. 1 L of liquor was drawn from the machine, into which 10Og of sodium hexametaphosphate soln (40% w/w aq soln) and 25g of urea were added and stirred.

Upon dissolution, the liquor was transferred back into the dyeing vessel and circulated.

The dyeing vessel was heated to 60°C and maintained at 60°C for 30 minutes. The pH of the liquor was in the range 2.2 to 2.5.

The pH of the liquor was maintained below pH2 during the 30 minutes using small additions of H ₂ S0 ₄ .

The vessel was then drained completely, re-filled with cold water, circulated for 5 minutes and then drained completely. This rinse procedure was carried out 2 times to ensure the rinse water was above pH4.5.

The vessel was then drained and the treated fabric was removed from the dyeing machine, spun and dried.

Before carrying out a flame test all samples were kept in a conditioning cabinet (20°C, 60% humidity) for at least 12 hours.

The fabric was then flame tested using the method set out in BS5438; where the material is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds.

The resultant fabric passes this flame test, by not continuing to burn after the applied flame is removed.

Example 13 - Exhaustion process for wool fabric

240 Kg of pre-dyed wool (75%) / nylon (25%) flat woven fabric was placed into a Thies Jet dyeing vessel (using a liquor ratio of 7:1).

The addition tank was filled with water, to which 9.6Kg (=4%omf) of H ₂ S0 ₄ was added. The liquor was then heated to 40°C before being transferred to the dyeing vessel.

Upon transfer to the dyeing vessel, the liquor was then circulated for 15 minutes in order to stabilise the pH of the liquor. During this 15 minute period, small aliquots of H ₂ S0 ₄ were added in order to correct the pH to below pH2.5. The liquor was then transferred back to the addition tank, where 24Kg of sodium hexametaphosphate soln (40% w/w aq soln) and 6Kg of Urea were added and stirred. Upon dissolution, the liquor was transferred back into the dyeing vessel.

The dyeing vessel was heated to 60°C and maintained at 60°C for 30 minutes. The pH of the liquor was in the range 2.2 to 2.5. The pH of the liquor was maintained below pH2 during the 30 minutes using small additions of H2S04.

The vessel was then drained completely, re-filled with cold water, circulated for 5 minutes and then drained completely. This rinse procedure was carried out 3 times to ensure the rinse water was above pH4.5.

The vessel was then drained and the treated fabric was removed from the dyeing machine, spun and dried. Before carrying out a flame test all samples were kept in a conditioning cabinet (20°C, 60% humidity) for at least 12 hours.

The fabric was then flame tested using the method set out in BS5438; where the material is supported in a vertical frame with a butane flame of specified length applied perpendicular to the fabric for 15 seconds.

The resultant fabric passes this flame test, by not continuing to burn after the applied flame is removed.