NO138700B - PROCEDURES FOR IMPROVING THE FLAME RESISTANT PROPERTIES OF NATURAL OR SYNTHETIC POLYAMIDE FIBERS - Google Patents

Description

The present invention relates to textile treatment,

and more particularly improving the flame resistant properties of natural and synthetic polyamide fibers.

Naturally occurring polyamide fibers, such as wool from sheep, exhibit a high degree of natural flame retardancy as a result of their high content of nitrogen and moisture, high ignition temperature (570 - 600°C), low heat of combustion, low flame temperature and and a high limiting oxygen index.

The behavior of woolen textiles against different test methods depends on the particular test method and textile construction. A horizontal test method is significantly less demanding than a 45° or vertical test. Most woolen textiles will satisfy a horizontal test method, but will not satisfy any 45°'s or vertical tests. The effect of the textile's construction is also very significant, and the heavier and denser the textile, the lower its flammability. E.g. conventional wool carpets will satisfy "the American tablet" test (DOC FF 1-70, DOC FF 2-70), while an open pile of wool or a "Flokati" carpet will not satisfy the same test.

Consequently, wool will in certain cases need a flame-retardant treatment to satisfy a special flammability specification and test method. Wool textiles that may need such treatment will be curtains and wall coverings in public buildings, equipment and carpets in aircraft, equipment and carpets in public transport, protective clothing and carpets with low density (floss).

It is known that titanium compounds, especially titanium tetrachloride, when applied to textile fibers, especially natural cellulosic fibers, such as cotton, improve their flame resistance properties. However, with these known methods, the titanium compound must be applied in an undesirably high amount, up to 20% by weight, and the high proportion of mineral component that is incorporated into the fibers or the textile sheet produced therefrom has an undesired effect on the mechanical properties, for example handles -ing properties. Furthermore, the titanium compound forms a weakly adherent coating on the surface of the fibre, and is therefore not washable, and will not adhere after repeated mechanical deformations.

The present invention provides another method

to improve the flame-resistant properties of natural or synthetic polyamide fibers, in which the fibers are treated at a pH below 4 with an aqueous solution containing an anionic titanium complex formed with an organic chelating agent or with fluoride ions. In order to achieve a fully satisfactory effect, the amount of the titanium compound applied to the wool fibers should preferably be at least 0.2% by weight, and more particularly 0.2 - 2.5% by weight calculated as titanium dioxide of the textile's weight (t.v.).

The inventive method can be used when treating synthetic polyamide fibres, e.g. nylon, but is particularly useful when treating natural polyamide fibres. Preferably, the fibers treated are wool fibers from sheep, but they can also be derived from al-pakka, cashmere, mohair, vicuña, guanaco, camel hair, silk and llama, or mixtures of these materials with sheep's wool. Textiles consisting of a mixture containing a larger proportion of wool and a smaller proportion, usually 30% or less, of synthetic fibers or natural cellulosic fibers, e.g. polyamide, polyester or cotton fibres, can also be treated. The treatment can be carried out on the fibers at any desired step during the textile manufacturing process, and the fibers can e.g. be in the form of fur, tops, carded bands, noils, yarn, threads, woven or knotted textiles, non-woven textiles, fleece textiles or clothing. Preferably, the material to be treated is washed, so that it does not contain more than 0.8% methylene chloride extractables, to remove spinning additives or natural waxes that may contribute to the product's flammability•

The titanium compound can be applied using conventional machinery for the treatment of textiles and clothing with liquids, including string washing machines, staplers, warp dyeing equipment, package dyeing machines, hemp dyeing machines, top dyeing equipment, washing equipment and tube cleaning equipment for batch processing, and including foulard rolling machines, roller spraying units , continuous laundry units, reverse washing machines and solvent cleaning machines for continuous or semi-continuous treatment.

The complex titanium compound can be added directly to the treatment liquid, or optionally it can be formed in situ. Compounds which can be added directly to the treatment liquid include alkalinity salts or ammonium salts of fluorotitanates, or titanium oxalates or titanium citrates. Optionally, the complex can be formed in situ by treating a soluble titanium salt, e.g. titanium tetrachloride, with a source of fluoride ions, or with an organic chelating agent, for example oxalic acid, or preferably citric or tartaric acid. Compounds which can be used as a source of fluoride ions include sodium and potassium fluorides or bifluorides and ammonium bifluoride. A water-soluble fluoroborate, e.g. ammonium fluoroborate, can also be used as a source of fluoride ions.

The treatment can be carried out at temperatures in the range 20 - 130°C, and at a pH of less than 4> preferably less than 3.5. The pH value can be easily adjusted by adding a strong mineral acid, for example hydrochloric acid, or an acidic compound, such as ammonium bifluoride. Although the treatment with the fluoride complexes can be carried out with good results at room temperature, it is preferred to carry out the treatment at an elevated temperature with the organic chelate complexes. By preparing the titanium complexes of hydroxycarboxylic acids by extraction from a hot liquid, and preferably at the boiling point, a high degree of penetration of the titanium cotton complex and a consequent improved flame safety effect can be achieved.

The titanium cotton complex can be applied to the fibers by treatment in any conventional manner, i.e. any previously known method or method described in the literature for applying water-soluble compounds, for example by "pad-dry", "pad-steam", " stray-nip-dry", "drip-nip-dry" or "exhaustion" methods. The term "pad-dry" used includes a method of applying a liquid or paste to the fibers to be treated, either by passing them through a bath and then through press rollers (also including the method whereby the fibers are fed vertically downwards through horizontally* arranged pressing rolls, and having a bath or liquid formed over their point of contact), or passing the fibers through pressing rolls, the lower of which is partially immersed in a bath or liquid, and then drying the fibers. The term "spray-nip-dry" means a method where the fibers to be treated are sprayed with the liquid, after which the fibers are forced through press rollers and then dried. The term "exhaustion" means a method of treating the fibers in a bath with the solution containing the active compound, until the compound is substantially completely absorbed, and then drying the fibers. The term "pad-steam" means application of the treatment liquid by the previously described "pad-dry", followed by a steam treatment at 100 - 120°C. The term "drip-nip-dry" includes the method where the fibers are dipped in a treatment bath and fed through pressure rollers and then dried.

Other flame-retardant agents that are previously known or described in the literature can be applied, provided that they do not affect the titanium treatment. E.g. antimony trifluoride and antimony potassium tartrate can be applied to wool by extraction. Aluminum compounds can also be applied to wool.

The present method can be carried out simultaneously with dyeing provided that the dye is capable of absorbing into wool with consistent results at pH values below 4" Acid, equalizing 1:1 pre-metallized dyes and certain reactive dyes can be used, and it is not necessary to add additional formic acid or sulfuric acid, which is usually necessary when using such dyes, as the pH of the dye bath is already sufficiently low. Sodium sulphate should preferably not be added to the solution, as this affects the absorption of the titanium cotton complex, but organic non-ionic leveling agents, e.g. "Avolan SC" or "Albegal B" can be used.

Acid varnish colors or 1:2 pre-metallized colors cannot be used satisfactorily at the same time as the titanium treatment. When using acid dyes, the dye can first be drained, preferably by boiling from the dye bath, after which the temperature of the dye bath is lowered to, for example, 70°C, after which the complex titanium compound is added, and the bath is further heated until the titanium complex is deposited on the wool. When dyeing with chrome colours, the dyeing operation must be carried out after the titanium treatment, otherwise complex formation between the titanium in the solution and the dye will result in a color change.

The acid colors that can be used are water-soluble compounds, for example of the monoazo type or of triphenylmethane or an anthraquinone derivative.

Acidic dyes form a class of dyes that have a greater molecular weight and fewer solubilizing groups than acid leveling dyes. There is no unequivocal distinction between the class of selection colors and the class of equalizing colors, and many colors have intermediate properties. Wax colors are generally applied at a low . pH of 4 - 5.

Pre-metallized colors comprise a class of dyes which have 0,0'-dihydroxyazo-0-amine-O'hydroxyazo or O-carboxyl-O'hydroxy-azo groups which are coordinated with a metal atom, for example chromium or cobalt. The colors can be used as 1:1 complexes.

The dyes that can be used include reactive dyes, i.e. those that react with the fibers and form covalent bonds with them. Such colors provide a high degree of fixation on the fibres. Dyes that fall within this class may contain the following groups: epoxy-, ethyleneimino-, isocyanate-, isothiocyanate-, carbamide acid arylester-, propiolic acid-amido-, monochloro- and dichlorocrotonyl-amine-, chloroacrylamine-, acrylamino-, sulfohalogen- , sulfuric acid ester, sulfoxy, labile halogen atoms, trichloropyridazino, dichloroquinoxaline, allysulfonyl, as well as certain reactive ammonium or hydroxonium residues.

Particularly good results are obtained with highly reactive dyes, e.g. those containing 2:4-dichlorotriazinyl, vinylsulfonyl, 2:3-dichloroquinoxaline, or bromoacrylamido group.

A large number of dyes within the various classes are commercially available, and can for example be found in color indexes.

The treatment according to the present invention has the further advantage that it is compatible with a fluorocarbon oil and water-repellent treatment for furniture covers, textiles for use in, for example, airplane seats. Fluorocarbon resins such as "FC-214", "FC 208" and FC 218" can preferably be applied in the presence of an extender, for example "Phobotex FTN". The titanium and fluorocarbon compounds can be applied simultaneously in an impregnation machine (Foulard) followed by drying at a temperature of at least 100°C, as well as a further heating for a period of time and at a temperature sufficient to harden the resin, after which the textile is washed and dried.The titanium treatment can also be carried out before or after the treatment to promote the water-oil -repelling properties.

The mechanical properties of wool treated with titanium according to the present method are very similar to the properties of wool dyed with acid dyes. This can be seen from the tests shown in table I which relate to yarn, and table II which relate to upholstery textiles.

Undyed wool which has been treated according to the present invention exhibits a faint yellow colour. Such discolouration is disadvantageous when it is desired to produce products with a natural wool color or pastel-coloured products, but can be reduced or prevented according to the invention by post-treatment of the titanium-treated fibers with a fluoride solution, for example a solution containing an alkali metal or ammonium fluoride or bifluoride. The fibers are first treated with the titanium complex, which can be titanium chloride, potassium titanium oxalate or a complex formed in situ between titanium tetrachloride and a gelling agent, especially oxalic, citric or tartaric acid. It is convenient to apply a liquid to the fibers in a ratio of 1:20, and preferably not more than 1:30, when emptying at a pH of less than 4, preferably less than 3.5. When titanium tetrachloride is used together with citric acid, the citric acid is preferably used at a concentration of 4%. The absorption (exhaustion) of the titanium compound is usually complete after boiling in a period of 5 - 30 min., usually approx. 15 min. A dye can be applied to the fibers in mixture with the titanium compound provided that it is taken up with a uniform result at a pH of less than 4, otherwise the titanium treatment should be carried out as a pre-treatment for dyeing. In particular, chrome dyes should always be applied after the flame resistance treatment, because these form complexes in solution with the titanium compounds, and can therefore cause a change in colour. The fibers are then treated with a fluoride solution, preferably ammonium bifluoride. The treatment is preferably carried out in an acidic solution, preferably at a pH of approx. 4.

When sodium fluoride is used, the pH is set to 4 by adding acid, for example formic acid. The concentration of ammonium bifluoride should preferably be 0.2 - 20 g/l, and the reading is kept in contact with the fibers for 5 - 30 minutes. The treated fibers are cleaned with water, which is then pressed out by passing between press rollers, after which they are dried.

When the desired product is undyed wool, it is advantageous to mix the fluoride with a reducing agent. A suitable aqueous fluoride solution contains 40 g/l ammonium bifluoride and 40 g/l sodium metabisulfite or 40 g/l sodium formaldehyde sulfoxylate, which will give substantially complete removal of the yellow color.

Table 1 below shows the effect of first treating carpet yarn by extraction from a solution containing potassium titanium oxalate or titanium tetrachloride and oxalic acid, citric acid or tartaric acid, and then with a solution containing ammonium bifluoride. The results show that with increasing titanium concentration, the yellowness index increases, which increases most markedly when oxalic acid is used, and least markedly when citric acid is used. In order to achieve minimal yellowing of the fibres, it is preferred to apply a mixture of titanium tetrachloride and citric acid to the fibres, after which the fibers are treated with ammonium bifluoride.

Sample methods

The following test methods are used in the examples or have been referred to elsewhere in the description.

(a) Exhaustion

The degree of extraction of the titanium compound used in the flame resistance treatment can be followed by the reaction between titanium solutions and hydrogen peroxide whereby a yellow color is formed. The reaction is believed to be due to the formation of pertitanic acid H4TiOs.

A 10 ml sample of the dissolution bath, which has been freed of dye if necessary, is treated with 3 ml of 3% hydrogen peroxide solution. A yellow color is formed which indicates the amount of titanium present in the solution. When this test is carried out during the extraction treatment, the degree of extraction can be determined quantitatively by a colorimetric determination at a wavelength of 410 nm.

The amount of titanium and aluminum taken up by the wool during the flame resistance treatment can be determined as the ash content (metal oxides). As wool always contains certain inorganic constituents, the ash content of untreated wool must always be determined, and the difference between the ash content of flame-resistant treated and untreated wool indicates the total amount of metal oxides absorbed by the wool during treatment. This method is particularly useful when the flame retardant treatment is carried out at the same time as dyeing, and where the dye can interfere with the titanium-hydrogen peroxide reaction.

(b) Flame resistance

The flame resistance of textiles is measured by the vertical flame test (A.A.T.C. Test Method 34-1969, Fire Resistance of Textile Fabrics), which involves suspending a conditioned (at 65% relative humidity) strip of the textile to be immersed in the flame of a Bunsen burner for 12 seconds and determine the length of the charred part of the textile and the burning time. The flame resistance of carpets can be determined by the "Tablet test" (U.S. Federal Specification DOC FF 1-70) which involves drying the carpet test at 105°C for 2 hours, after which a "Methenamine" (Hexamethyleneamine) tablet is ignited which burns for a set time of the surface of the carpet and then observe the flame spread on the surface of the carpet. It is the purpose of the present invention to provide a textile material that satisfies these test methods, which are referred to in the following as "Vertical flame test" and "Tablet test" respectively.

Example 1

A wool carpet yarn was treated in the form of a hespe in an aqueous bath with the following composition:

The yarn and the treatment agent were mixed at 40°C, after which the mixture was boiled for 45 min. During the process, the titanium compound formed a chelate with the citric acid which presumably then splits to form a basic titanium compound inside the wool fibres.

After the treatment, the yarn was removed from the bath, washed and dried and converted into a rug. The carpet was then tested according to the "Tablet test" (U.S. Federal specification DOC FF 1-70) and the carpet was found to have excellent flame resistance.

Example 2

This example illustrates a simultaneous treatment of loose wool with the flame retardant, and also the application of a colour.

A sample of loos wool was boiled for 45 minutes in a packing apparatus with a solution containing:

"Neopolar Yellow 4GL" is an acidic leveling color. The loose wool was cleaned, dried and spun into yarn and then converted into a carpet with a 5 cm pile and a weight of o 1.22 kg/m 2.

The carpet was examined with regard to flame resistance according to the "Tablet test", as previously described, both after dyeing and after it had been cleaned 10 times according to the procedure specified in DOC FF 1-70.

The carpet was found to exhibit excellent resistance both before and after cleaning, showing that the effect of the treatment exhibited significant resistance to removal as a result of the cleaning step.

Example 3

This example illustrates the implementation of the flame resistance treatment on a previously manufactured carpet.

A stack of carpets with 5 cm pile and weighing 1.22 kg/m was sprayed with a solution containing potassium titanium oxalate (80 g/l), tartaric acid (10 g/l), antimony trifluoride (20 g/l) and "Tergitol Speedwet"

(Union Carbide; 1 g/l) until the weight of the stack increased by 50%.

The stack was then lightly pressed to ensure solvent-even penetration of the yarns, and then dried. The treated carpet was found to pass the "Tablet test" described above.

Example 4

The following mixture was applied to a woolen textile as an aqueous solution using a foulard roller:

The fabric was dried, then cleaned in water at 30°C for 15 minutes with a liquid ratio of 1:20, squeezed and dried. The treated textile was examined for flame resistance using the "vertical flame test" (A.A.T.C. Test Method 34-1969, Fire Resistance of Textile Fabrics), and showed satisfactory flame resistance. The test involves suspending a conditioned (at 65% relative humidity, 20°C) strip of the textile in the flame of a Bunsen burner for 12 seconds and determining the length of the charred part of the textile, as well as the burning time. The treatment was found to be durable after at least 10 washes (45°C, 15 min. in a Philips automatic washing machine set on the wool programme), and for at least 10 water cleanings (28°C, 15 min., liquid ratio 1:20, " Perklone" launderometer).

Example 5

The following mixture was applied to a woolen textile in the form of an aqueous solution using a foulard roller:

The treated textile was dried and then washed with aqueous sodium bicarbonate, pressed and dried. It showed satisfactory flame resistance in the "vertical flame test" (see example 1). The treatment was effective after 10 washes (each for 15 min., 45°C, Philips automatic washing machine, wool programme). After 10 washes, the charred length in the "vertical flame test" was 40% shorter, which indicated that the flame resistance decreased with washing.

Example 6

The following composition was applied to a woolen textile in the form of an aqueous solution using a foulard roller:

The fabric was then treated as indicated in Example 5. In the "vertical flame test" the charred length was 20% less than that of the fabric according to Example 5. The treatment was resistant to washing by the method indicated in Example 5. After 10 minutes the charred length was 40% shorter, indicating that flame resistance increased with washing. The presence of antimony trichloride in the treatment composition is particularly useful for light fabrics (less than 200 g/m ).

Example 7

The following composition was sprayed onto a ready-made staggered pile carpet:

The treated carpet was pressed and dried. Flammability was measured by the "tablet test" (U.S. Federal Specification DOC FF 1-70) and was satisfactory. The carpet floss didn't burn away, and there

no spread of the flame could be observed on the surface thread of the small, treated carpet. The treatment was effective after 10 washes (each for 15 min., 60°C, liquid ratio 1:20, "Hotpoint" washing machine). In addition to the flame-retardant effect in the composition, the treatment also promotes a dirt-repellent effect which is believed to be caused by the presence of the titanium compounds on the surface of the fibres. This protection is not safe against washing, but is effective after 10 times of water cleaning and 5 times of carpet treatment with shampoo.

Sodium or potassium bifluorides can be used instead of ammonium bifluoride, and can be applied to the carpet as described above.

Example 8

Wool tops (45 kg) were treated by extraction with TiCl3

(SO - 3% of the wool weight and citric acid (4% of the wool weight) simultaneously with dyeing ["Xylene light yellow 29" (acid leveling dye)]. The titanium tetrachloride and the dye were completely extracted after 30 minutes of boiling. The dye extraction was approx. 5 - 10 % higher than when the same dye was used without the addition of

TiCl^ and the discoloration was uniform. The wool top was spun into yarn. A very open, staggered pile carpet, made from the treated and dyed yarn, easily satisfied the "tablet test". The color fastness to light, water, perspiration and washing (40°C) is the same as for dyed but untreated yarn.

Example 9

The procedure according to example 8 was repeated with a sample of undyed wool and in the absence of dye mixed with the titanium compound. A staggered pile carpet made from the treated yarn satisfied the "tablet test" without difficulty. In a normal carpet sample according to Air Registration Board Specification 8, the charring width was 5 cm (untreated 7.5 cm). The same carpet without underlay tested with the "vertical test" showed a charring length of 2.5 cm and a burning time of 0 seconds (untreated: charring length 6.9 cm, burning time: 23 seconds).

Example IO

This example illustrates a simultaneous flame resistance treatment and water and oil resistance treatment of wool.

The following composition was applied to wool using a foulard roll to ICO% moisture absorption:

The fabric was dried at 120°C for 3 minutes and then held at 165°C for 4 minutes to cure the fluorocarbon resin. The fabric was then cleaned in a vat at 20°C with water at a liquid ratio of 1:30 for 15 minutes and then dried at 120°C for 3 minutes.

The dried textile was tested with the "vertical sample" and had a charring length of 6.6 cm, and a burning time of 5 seconds. It showed satisfactory resistance to water and oil in a test according to "the spray-and "oil-rating test".

Example 11

This example illustrates the flame resistance treatment of an already manufactured staggered pile carpet using the foulard-steam technique. The carpet was impregnated with the following solution to an uptake of 4CO%:

The impregnated blanket was steamed in a horizontal position for 10 minutes at 106°C, then cleaned in two separate vats of water and dried.

The "tablet test" showed that the treated carpet easily met the specification, while an untreated one did not meet the specification. After 10 times commercial shampoo treatments, the treated carpet satisfied the "tablet test".

Example 12

This example illustrates the flame resistance treatment of sheepskin used for floor coverings and as car seat covers, using the "drip-nip-dry" technique.

The sheepskin was impregnated with the following solution:

After complete wetting, the sheepskin was squeezed between rollers to a liquid absorption of 150% and then dried at 50°C so as not to spoil or harden the skin. After drying, the leather was cleaned in water at 25°C for 15 minutes to remove any remaining chemicals that could affect the soft wool "feel". After cleaning, the leather was pressed and dried at 50°C.

The treated sheepskin satisfied the "tablet test". The difference between the flammability characteristics of treated and untreated sheepskin was very significant as a result of the very open floss construction and loose fibers that are readily available. In the "tablet sample", no fibers remained on untreated sheepskin, while in the corresponding sample on treated sheepskin, only a surface flap with a diameter of 5 cm appeared, followed by an immediate self-extinguishing of the flame-resistant treated wool fibres.

Example 13

This example describes application by the "dip-nip-dry" technique for a continuous flame resistance treatment of loose wool in the last trough in the raw wool washing machine (leviathan).

The solution in the last (fifth) trough in a commercial washing machine had the following composition:

The loose wool material was continuously passed through this mold for 7 minutes at 30°C and pressed to a liquid absorption of 60% and then continuously dried.

The "tablet sample" showed a significant degree of flame resistance compared to corresponding untreated wool fibres.

In certain cases, residual chemicals can affect the workability of the treated wool, and part of the loose wool material was cleaned in a separate trough with water for 15 minutes at 25°C and dried. The treated and cleaned loose wool material satisfied the "tablet test".

Example 14

This example shows a pull-out treatment of knitted garments made of a wool-nylon blend (80/20). The garment was treated in a side-foulard dryer with the following chemicals for 45 minutes at boiling point:

After boiling, the titanium complex was extracted up to 90% and the garment was cleaned and dried. The "vertical flame test" showed a burning time of 1 second and a charring length of 8.8 cm, which are values that easily satisfy the specification (max. burning time 15 s, max. charring length 20 cm).

Example 15

A woolen carpet containing 15% cotton in the warp direction was treated by extraction in a reeling vessel with the following chemicals:

The temperature of the bath was brought to boiling with a heating rate of 40°C/min. and cooked for 45 minutes. After determining the extraction of the titanium citrate complex, the carpet was cleaned and dried.

No difference in "feel" or mechanical properties could be noticed between treated and untreated carpet. The treated carpet easily met the specifications for the "vertical flame test" when examined in both the warp direction and the weft direction, while an untreated carpet did not meet the specification in either direction.

Example 16

A wool-polyester (80/20) yarn in hemp form was treated with

the extraction technique with the following chemicals:

The citric acid was dissolved in hot water in a vat and the titanium tetrachloride solution added to the dissolved citric acid in the vat with stirring. The titanium citrate complex produced in situ was added to the bath which was brought to the boiling point and kept boiling for 45 minutes. After cleaning and drying, the yarn was used to produce a knitted toy which was tested with the "vertical flame test". The burning time (1 second) and the charring length (6.3 cm) indicated a sufficiently effective flame res i st effect.

Example 17

"Ovnsmannstoy" (pure woven wool, 600 g/m) was treated by the extraction technique with the following chemicals at the boiling point for 45 min:

After removing the titanium cotton patch, the toy was cleaned and dried.

Under current stopping conditions, resistance to radiant heat is much more important than flame resistance, therefore treated and untreated cloth was examined with regard to surface flammability (ASTM E-162-66T) of the materials using a radiant heat energy source. Under the experimental conditions used, the materials were exposed to a temperature of 80°C for 15 minutes, and the charring length was measured. The result of this test shows that flame-resistant treated textiles are more resistant to heat than untreated ones.

Example 18

Carpet wool (approx. 45 kg) in hespe form was treated by extraction with TiCl^ (50%) - 3% of the wool weight and citric acid (4% of the wool weight) and simultaneously dyed ["Xylene light yellow 29" (acid leveling dye)]. The titanium complex and dye were completely extracted after boiling for 30 minutes. The dye extraction was approx. 5 - 10% higher than with the same dye used without the addition of TiCl^, and the discolouration was uniform. A very open, staggered pile carpet, made from the treated and dyed yarn, easily satisfied the "Tablet test". Color fastness to light, water, perspiration and washing (40°C) is the same as for dyed but untreated yarn. About. 10 kg of a mixed yarn (wool/nylon, 80/20) was processed at the same time. The color shade was deeper as a result of the presence of nylon, but a staggered pile carpet made from this yarn also easily satisfied the "Tablet test". However, the burning rate was somewhat higher than for lOO% pure wool.

Example 19

The procedure according to example 18 was repeated with a sample of undyed wool and in the absence of dye mixed with the titanium complex. After the titanium complex treatment, the yarn was treated with a 4% ammonium bifluoride (based on the weight of the wool) for 15 minutes at 50°C. This finishing completely removed the bright yellow color. A staggered frayed carpet made from the fluoride-treated yarn easily satisfied the "Tablet test". The standard carpet sample according to Air Registration Board Specification 8 had a char width of 5 cm (untreated 7.6 cm). The same carpet without underlay tested with the "vertical sample" had a charring length of 2.5 cm and a burning time of 0 s (untreated - charring length 6.9 cm, burning time - 23 s).

A simultaneous post-treatment with 4% NH4F.HF and 4% sodium

metabisulfite or 4% sodium formaldehyde sulfoxylate completely removed the yellowness without affecting the flame resistance properties.

Example 2Q

A carpet yarn in reel form was treated with an aqueous

solution containing:

The solution was then boiled for 45 minutes, and the

purchased yarn cleaned twice, pressed and dried. It was transformed into a very open, staggered pile carpet which easily satisfied the "Tablettproven<1>".

Claims (6)

1. Procedure for improving the flame-resistant properties creation of natural or synthetic polyamide fibers by applying titanium, and optionally also an antimony compound, such as antimony trifluoride or antimony potassium tartrate, or an aluminum compound such as aluminum sulfate or chloride, and optionally also a fluorocarbon resin, characterized in that the fibers are treated at a pH below 4 with an aqueous solution containing an anionic titanium complex formed with an organic chelating agent or with fluoride ions. 2. Method according to claim 1, characterized in that a titanium complex is used which is formed with a carboxylic acid containing at least two carboxyl groups or an aliphatic hydroxycarboxylic acid. 3" Method according to claim 1 or 2, characterized in that a titanium complex is used which is formed by reaction between titanium tetrachloride and an alkali metal or ammonium fluoride or bifluoride. 4> Method according to claim 2 or 3, characterized in that the titanium-treated fibers are further treated with a solution of a fluoride such as an alkali metal or ammonium fluoride or bifluoride. 5. Method according to claim 4, characterized in that a fluoride solution is used which also contains a reducing agent, such as sodium metabisulfite or sodium formaldehyde sulfoxylate. 6. Method according to claims 1-5, characterized in that a compatible dye is applied from the same solution as the titanium complex. 7- Method according to claim 6, characterized in that a dye, such as an acid-equalizing, 1:1-premetallized dye or a reactive dye, and the titanium complex are deposited simultaneously in the fibers. 8- Method according to claim 6, characterized in that acid bleaching-1:2-premetallized or reactive dye is deposited in the fibers by extraction while boiling from a dye bath, the temperature of the dye bath is lowered, the titanium complex is added, and the bath is further heated until the titanium complex has been extracted onto the wool. 9- Method according to claims 1-8, characterized in that the amount of titanium complex deposited in the fibers is 0.2 - 2.5% by weight, calculated as titanium dioxide on the weight of the fibers.