ES2487494T3 - Flame retarded cellulose fiber, its use, as well as a manufacturing process - Google Patents

Abstract

Regenerated regenerated cellulose fiber for textile applications, characterized in that it contains as a flame retardant substance a compound of phosphorus incorporated in spinning, in the form of a particle and presents a useful value - defined as a product of the content and phosphorus and of the wet module, the module being measured in wet according to BISFA (BISFA, Testing methods viscose, modal, lyocell and acetate staple fibers and tows, 2004 edition). Between 10 and 35 and because it was manufactured according to a viscous procedure.

Description

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DESCRIPTION

Flame retarded cellulose fiber, its use, as well as a manufacturing process

[0001] The object of the present invention are fire retarded regenerated cellulose fibers with improved use properties for textile applications, which for example also resist the requirements of an industrial wash, their use for the manufacture of yarns and flat structures, as well as a process for the manufacture of these fibers.

10 State of the art

[0002] Today they are known as regenerated cellulose fibers, especially fibers according to the viscous process and are manufactured worldwide for standard applications in the textile and non-woven fabrics with an individual fiber titer between 0.8 and 16 dtex . For the equipment of flame retardant properties of viscose fibers are described

15 in the bibliography the most diverse chemical substances. Above all, flame retardants based on halogens, silicon and phosphorus are used.

[0003] In US2678330 the use of a bis (2,3-dichloropropyl) chlorophosphonate is described for this purpose. GB 1158231 mentions the use of a tris (1-bromo-3-chloro-2-propyl) phosphate. The document FR2138400 describes the use of liquid polybromobenzenes and especially preferably hexabromobenzene. Since liquid flame retardants are only incorporated into the fiber structure but do not establish any link with the cellulose component, the migration of these chemicals from this fiber is clearly greater than in the case of solid substances. Especially after repeated drying at elevated temperatures (eg in the tunnel dryer) the flame retardant property of the

25 fiber

[0004] Also Soviet document SU661047 describes the use of halogenated compounds, such as, for example, hexachlorocyclohexane, halogenated benzenes and tris (dibromopropyl) phosphate. The use of halogen-containing flame retardants has declined sharply in recent years due to environmental concerns

30 environment and does not represent a sustainable solution for future developments. Tris (dibromo-propyl) phosphate is even registered in the Oeko-Tex® association as a prohibited flame retardant substance.

[0005] Viscose fibers, whose flame retardant effect is based on the use of silicates, which are described eg in patents WO9313249 or CN1847476 are ecologically harmless, but are far from complying with

35 requirements of the modern textile industry regarding the mechanical properties of fiber and washing resistance. According to the current state of knowledge, only solid flame-retardant substances, which contain phosphorus, completely insoluble in water, which do not contain halogens, can meet the desired requirements regarding ecology, fire retardant behavior, textile data and other properties of use.

[0006] Patent EP0836634 describes a fire-retarded regenerated fiber, which was manufactured according to the lyocell process and which theoretically should meet the requirements indicated above. However, the manufacture of the phosphorus compound used there is not possible on an industrial scale, so it is too expensive, so that this fiber does not represent any alternative for practice.

[0007] The manufacture of flame-retarded viscose fibers based on the incorporation of a phosphorus-containing pigment in a standard viscous process is also described in Chinese patents CN101215726, CN101037812 and CN1904156. However, the fibers described in these patents do not meet the strict requirements of the modern textile industry and its customers, as will be shown later with the help of tests (table 1).

[0008] Patents DE4128638A1 or DE102004059221A1 describe dispersions of flame retardant substances based on a 2,2'-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorin] 2,2'isulfide using different dispersant systems and mention also the use of these dispersions for the equipment of flame retardant properties of viscose fibers.

[0009] Also EP1882760 describes the manufacture of flame-retarded viscose fibers using dispersions of flame retardant substances based on a 2,2'-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorin] 2,2'isulfide . There it is described as an important feature of the invention that the particle size must be a maximum of 10 µm and that the spinning mass must therefore be cleared before spinning by means of filters with a maximum mesh opening of 10 µm. However, it has been shown that this criterion is not enough to manufacture fibers that meet the

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requirements described here. The maximum particle size of 10 µm described in EP1882760 may be sufficient for viscose filaments, that is, endless filaments, but it is far from meeting the requirements of a modern production of short fibers with fiber fineness of approx. 1 to 4 dtex; a 1.3 dtex fiber has a diameter of approx. 10 µm

[0010] WO 97/02315 discloses both the manufacture of flame retardant fibers according to the viscous process (example 2) and according to the Lyocell procedure (examples 3 and 4). While phosphorus contents and Bisfa modules are indicated for the lyocell fibers obtained, WO 97/02315 does not disclose these values for viscose fibers.

[0011] Although DE 2532521 discloses the manufacture of flame retardant fibers according to the viscous process with different flame retardant additives, it does not indicate the mechanical properties of the fibers obtained. US 5,766,746 discloses the manufacture of fireproof nonwoven fabrics of fireproof viscose fibers. In the examples a flame retardant viscose fiber with a wet module of 3 cN / tex is used. For the

In the manufacture of this fiber, US 5,766,746 refers to DE 2532521. However, the combination does not say anything about which flame retardant compound has actually been used, nor does it indicate the phosphorus content achieved in the finished fiber.

[0012] Standard viscose fibers are used massively today for light fashion textiles. The

The reduced resistance, especially in the wet state, the high extension and the high surface shrinkage, however, imply restrictions for the use of viscose fibers. These textile properties do not allow for example a use in segments that require frequent washing of textiles (in particular in industrial washes). A measure for the suitability for washing is the shrinkage of the surface. In order to easily determine the shrinkage of the surface from a quantitative point of view, its relationship with the module is used in

25 wet, measured according to BISFA standards and henceforth referred to briefly as wet module BISFA (BISFA, Testing methods viscose, modal, lyocell and acetate staple fibers and tows, 2004 edition).

[0013] The relationship between the surface shrinkage (after washing) and the BISFA wet module has been known since the 1970s for viscose fibers (Szegö, L., Faserforsch. Text. Techn .; twenty-one

30 (10), 1970). In the case of a wet module BISFA of 2, it can start from a shrinkage in the wash between 15 and 20%; in the case of a wet module BISFA of 5, the shrinkage is already reduced to between 4 and 7% (see Figure 1).

[0014] All fibers described in the state of the art or that can be purchased commercially, are manufactured

35 by standard viscous procedures. Although they show mechanical data of the comparatively good fibers for flame-retarded viscose fibers, since the phosphorus contents are very low, studies with the more diverse phosphorus-based flame retardants have shown, however, that a flame retardant effect is not achieved. sufficient even from a phosphorus content greater than 2.8%. The flame retardant capacity correlates very well with the content of flame retardants calculated for pure phosphorus.

[0015] However, it could be detected that for example the incorporation of large amounts (between 15 and 25%) of a flame retardant pigment leads to another worsening of the textile parameters of the viscose fiber. Therefore, the restrictions of the aforementioned fields of application for standard viscose fibers are even more valid for flame retarded viscose fibers.

[0016] This is even more regrettable considering that the flame retardant fibers could be used especially advantageously in products that are also exposed to heavy mechanical loads, for example in work clothes for particularly dangerous activities, such as in the body. of firefighters, foundries, the army, the oil and chemical industry. Synthetic fibers are usually used for products of this type

50 high quality polyamides (aromatic), aramids, polyimides and the like. These fibers, however, have reduced comfort when worn, since they are not able to absorb moisture to a sufficient degree. Therefore, it would be desirable to mix these fibers with cellulose fibers, which complement the spectrum of properties by adding greater comfort when wearing them, without making the remaining properties much worse.

[0017] In summary, the state of the art therefore only discloses flame retardant fibers, which have either been manufactured with ecologically critical chemicals, which do not have a resistance, BISFA wet modules and textile use properties. sufficient, which cannot be used for textile purposes due to their manufacturing method or which cannot be manufactured on an industrial scale. More specifically, some publications disclose only the intention of the authors to manufacture fiber of celluloses (also) fireproof.

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objective

[0018] In view of this state of the art, the objective of making available a fiber of

5 ignifuged cellulose that meets the currently valid requirements of an economically and ecologically sustainable manufacturing process, as well as the strictest mechanical requirements of textiles, as presented for example in an industrial wash of garments made from them .

[0019] The requirements of a flame retardant fiber for modern textile applications can be described in one

10 form close to practice by the product of the phosphorus content (corresponds to the flame retardant capacity) and the wet module measured according to the BISFA standard (correlated with the surface shrinkage). The product of the phosphorus content and the wet module BISFA must therefore be indicated hereinafter as "useful value".

[0020] In addition, there was the objective of making available a suitable manufacturing process for these fibers.

[0021] Surprisingly, this objective could be achieved by means of a fire retarded regenerated cellulose fiber for textile applications, which contains as a flame retardant substance a phosphorus compound incorporated in

The spinning, in particulate form, preferably an organophosphorus compound and having a useful value between 10 and 35 and has been manufactured according to a viscous process. Such a fiber could be manufactured for the first time by a modified viscous process according to the invention.

[0022] This flame retardant substance preferably has a particle size distribution with x50 less than 1.0 µm and x99 less than 5.0 µm.

[0023] As an organophosphorus compound, 2,2′-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorin] 2,2′disulfide (formula I) is preferably used. This substance can be obtained in sufficient quantities, among others, under the trade names Exolit and Sandoflam and is not removed from the fibers by washing or during the process of

30 manufacturing or subsequent application:

image 1

[0024] The fiber according to the invention contains in a preferable embodiment at least 2.8%,

Preferably between 3.2% and 6.0%, especially preferably between 3.5% and 6.0% phosphorus, respectively referred to cellulose. Phosphorus contents below 2.8% do not lead to a sufficient flame retardant effect. Phosphorus contents greater than 6% worsen the mechanical properties of the fibers and are no longer economical:

Especially suitable is a fire retardant fiber according to the invention which has a wet module BISFA Bm greater than or equal to 0.5 · (√T) · 10 / T with an extension of 5%. T is the title of an individual fiber, expressed in dtex; Bm is indicated in cN / tex. The fiber according to the invention is preferably presented as a short fiber, that is, it is cut in the course of the manufacturing process to a uniform length. The usual cutting lengths for short fibers for

45 textile field are located between approx. 20 and 150 mm. It is a uniform length of this type of all the fibers that allows a smooth processing in the high productivity machines nowadays common in the textile chain.

[0025] Object of the present invention is the use of the fiber according to the invention for the manufacture of a thread.

50 A thread of this type is characterized in comparison to the fiber threads that were available so far for a clearly higher strength. In order to present the properties suitable for the intended purpose of application respectively, a thread according to the invention of this type may contain in addition to the fibers according to the

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invention also fibers of another origin, for example wool, flame retardant wool, para-aramides and meta-aramides, polybenzimidazole (PBI), p-phenyl-2,6-benzobisoxazole (PBO), polyimide (P84®), polyamidimide (Kermel® ), modacryl, polyamides, flame retardant polyamides, flame retardant acrylic fibers, melamine fibers, polyesters, flame retardant polyesters, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), glass fibers, cotton, silk, carbon fibers,

5 oxidized, thermally stabilized polyacrylonitrile fibers (PANOX®) and electrically conductive fibers, as well as mixtures of these fibers.

[0026] Another object of the present invention is the use of the fiber according to the invention for the manufacture of a flat textile structure. In addition to the fibers according to the invention, this flat structure may also contain another 10 fibers, for example and in particular wool, fire retardant wool, para-aramids and meta-aramides, polybenzimidazole (PBI), phenyl-2,6-benzobisoxazole (PBO ), polyimide (P84®), polyamidimide (Kermel®), modacryl, polyamides, flame retardant polyamides, flame retardant acrylic fibers, melamine fibers, polyesters, flame retardant polyesters, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), glass fibers, cotton, silk, carbon fibers, thermally stabilized oxidized polyacrylonitrile fibers (PANOX®) and electrically conductive fibers, as well as mixtures of these

15 fibers

[0027] The flat structure is preferably a fabric, knitting or knitwear, although in principle it can also be a non-woven fabric. The use of fibers with a high BISFA wet module and high strength is of decisive importance also for high-quality nonwoven fabrics. In the case of a fabric or

A knitted fabric, the mixing of the fibers according to the invention with the other fibers is possible by mixing before the manufacture of the yarn, the so-called intimate mixing, or is it possible by the common use of respectively pure pure yarns of the different types fiber when knitting, knitting or knitting.

[0028] The fiber according to the invention can be manufactured by a viscous process modified according to the

Invention, which is also the subject of the present invention. Viscous processes for short fibers and endless filaments have been known in principle for many years and are described for example in detail in K. Götze, Chemiefasern nach dem Viskoseverfahren, 1967. However, there are many parameters that greatly influence the textile properties of fibers and filaments obtained therein. In addition, limits are specified for many magnitudes of influence through the conception of production facilities

30 existing, which for technical or economic reasons should not be exceeded, so that in many cases freely chosen variations of the parameters are not possible, so the expert would not see any reason to do so.

[0029] It has been shown that for the manufacture of the fibers according to the invention the ideal conditions are

35 a cellulose concentration between 4 and 7% when using a cellulose with an R18 content between 93 and 98% and an alkalinity ratio (= cellulose concentration / sodium hydroxide concentration, respectively in g / l ) from 0.7 to 1.5. However, the spinning parameters must be adapted accordingly due to the addition of the flame retardant FR pigment.

[0030] Therefore, a process for the manufacture of a fire retarded regenerated cellulose fiber for textile applications is also the subject of the invention by spinning a viscose with a content between 4 and 7% cellulose, between the 5 and 10% NaOH, between 36 and 42% (based on cellulose) of carbon sulphide, as well as between 1 and 5% (based on cellulose) of a modifying agent in a coagulation bath, wound of the coagulated threads, using a viscose, whose gamma spinning value is between 50 and 68,

45 preferably between 55 and 58, and whose

[0031] spinning viscosity is located between 50 to 120 seconds of ball drop and the coagulation bath temperature is between 34 and 48 ° C,

50 a. the alkalinity ratio (= cellulose concentration / alkali content) of the viscose ready to spin between 0.7 and 1.5 being located,

b. using the following coagulation bath concentrations:

• H2SO4 68 -90 g / l 55 • Na2SO4 90 -160 g / l

•

ZnSO4 30 -65 g / l

C.

performing the final winding of the coagulation bath with a speed between 15 and 60 m / min and

d.

incorporating an organophosphorus compound in the form of a flame retardant substance as a flame retardant

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pigment in the form of a dispersion of pigments.

[0032] A viscose is recommended to which the modifying agent is not added until shortly before the viscose spinning.

[0033] The measures proposed according to the invention to respect a determined spin maturity, for which the spinning gamma value is characteristic, to respect a given viscosity, for which the ball drop values are characteristic and to respect certain conditions in the coagulation bath, lead together to the desired properties of the fibers. Gamma value of spinning means the part of

10 carbon sulfide molecules linked to 100 cellulose molecules. The spinning gamma value is determined according to the draft of the Zellcheming fact sheet by R. Stahn [1958] or according to fact sheet III / F2. The ball drop means the viscosity determined according to the ball drop method; It is indicated in seconds of ball drop. The determination is indicated in K. Götze, Chemiefasern [1951], page 175.

[0034] The flame retardant phosphorus compound, which is manufactured as a pigment, is added according to the invention in the form of a dispersion of pigments to the spinning solution. An amount of the flame retardant substance is incorporated into the spinning so that the finished fiber contains at least 2.6%, preferably between 3.2% and 6.0%, especially preferably between 3.5% and 6% phosphorus referred to cellulose.

[0035] As explained above, a flame retardant organophosphorus compound especially suitable for the purposes of the present invention is 2,2'-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorin] 2.2 'disulfide.

[0036] In particular, also the quality of the dispersion of pigments substantially influences the properties of the fibers. This depends on the average and maximum particle size of the pigments, on the concentration of the dispersion in use, that is, when added to the viscose spinning solution, as well as on the type and amounts of the dispersing agents.

[0037] Unlike the largest possible particle size described in patent EP1882760 of 10 µm, it has now been found that an average particle size (x50) of less than 1 µm and a maximum particle size (x99) smaller than x99 are necessary at 5 µm. Figure 2 shows a size distribution of an even suitable pigment dispersion.

[0038] Preferably; The pigment dispersion should contain between 10 and 50% of the flame retardant substance.

[0039] In most documents regarding the state of the art the influence of the dispersing agent is not described as detailed as it would deserve. Many chemical substances that offer a perfectly stabilized dispersion of flame retardant substances, on the contrary, negatively influence the spinning process, since despite having a modifying effect on the viscose thread, they do not positively influence the resistance

40 of the fiber unlike the modifying agents used. They have proved to be ideal dispersants for the dispersion of flame retardant substances for the manufacture of the fibers according to the invention, which do not negatively influence the stability of the fibers, in particular those that have been chosen from the group containing modified polycarboxylates, water-soluble polyesters, alkyl ether phosphates, nonylphenoletoxylates closed at the terminal groups, alkoxylic esters of castor oil and carboxymethylated polyglycolic alcohol ethers. The

Pigment dispersion should preferably contain between 1.5 and 13% dispersing agent.

[0040] Next, the invention will be explained with the help of examples. They are to be understood as possible embodiments of the invention. In no way is the invention restricted to the scope of these examples.

50 Examples:

Example 1:

[0041] 6 parts by weight of 2,2’-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorin] 2,2’sulfide, 6 parts by weight of

Water and 0.55 parts by weight of alkyl polyglycol ether phosphoric acid ester are homogenized by means of a solvent and ground in a ball mill with stirrer (Drais, Perl Mill type PML-V / H) with oxide grinding bodies of zirconium at a temperature of 40-55 ° C, until the finished dispersion has an x99 <1.50 µm. A beech cellulose (R18 = 97.5%) is alkalized by stirring with mixed bleach, which contained 240 g / l of NaOH at 35 ° and is removed by pressure to obtain a nonwoven fabric of alkaline cellulose. Non-woven cellulose fabric

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Alkaline was frayed, matured and sulphidized. The xanthogenate was dissolved with a diluted caustic soda to obtain a viscose with 5.6% cellulose, 6.8% NaOH and 39% CS2 referred to cellulose. The viscose was filtered 4 times and aerated. To the viscose was added 1 h before spinning 3% ethoxylated amine referred to cellulose, a modifying agent that causes an enveloping structure. The viscose was later matured

5 to a spinning gamma value of 57. The viscosity during spinning was 80 seconds of ball drop. The finished flame retardant dispersion was added to this viscose ready to spin. The nozzles used have a nozzle hole diameter of 60 µm. The coagulation bath contains 72 g / l of sulfuric acid, 120 g / l of sodium sulfate and 60 g / l of zinc sulfate. The temperature of the coagulation bath was 38 ° C. The skein of coagulated and partially plastic thread

The regenerated pale yellow color passed through a glassmaker (G 1) to a second bath, whose temperature was 95 ° C and was stretched there between G 1 and a second glassmaker (G 2) 120%. The final winding was 42 m / min. The spinning cable was cut into short fibers of a length of 40 mm, which were completely regenerated in dilute sulfuric acid, then washed with hot water until acid free, desulfurized with diluted caustic soda, washed again, bleached with diluted solution of sodium hypochlorite, washed again,

15 fans, pressurized and dried.

Example 2

[0042] 6 parts by weight of 2,2’-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorin] 2,2’sulfide, 6 parts by weight of

20 water and 0.63 parts by weight of carboxymethylated alcohol polyglycol ether are processed analogously to example 1 to obtain a viscose ready to spin (composition: 5.9% cellulose, 6.7% NaOH, the 41% of CS2 referred to cellulose, 3.5% ethoxylated amine referred to cellulose) and spun in an aqueous coagulation bath. The nozzles used have a nozzle hole diameter of 50 µm. The coagulation bath contains 74 g / l of sulfuric acid, 132 g / l of sodium sulfate and 65 g / l of zinc sulfate.

25

Example 3

[0043] 6 parts by weight of 2,2'-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorin] 2,2 disulfide, 6 parts by weight of water and 1.1 parts by weight of acid ethoxylated phthalic are processed analogously to example 1 to obtain a

30 viscose ready to spin (composition: 5.8% cellulose, 6.5% NaOH, 40% CS2 referred to cellulose, as a modifying agent a mixture of 2% DMA + 1% PEG 2000, respectively referred to cellulose) and spun in an aqueous coagulation bath. The nozzles used have a nozzle hole diameter of 50 µm. The coagulation bath contains 73 g / l of sulfuric acid, 120 g / l of sodium sulfate and 58 g / l of zinc sulfate.

35

Example 4 (comparison example)

[0044] A fiber was manufactured according to the exposure of document CN 101037812. Since no indications about the wet module are made in this publication, the conditions of the example were chosen there

40 exposed with the highest wet strength (example 2, 1.52 cN / tex) of the fiber obtained and the following process conditions were adjusted accordingly: 8.86% cellulose, 6.24% NaOH, the 31% of CS2 referred to cellulose. No modifying agent was added. The viscose was spun with a viscosity of 42 seconds of ball drop. The high phosphorus contents indicated in this publication could not be understood. To get to

45 acceptable resistances, several optimization tests with different contents of flame retardants were carried out under the indicated conditions. The indicated properties could not be achieved until the phosphorus content was reduced to 2.1% by weight based on cellulose. The nozzles used have a nozzle hole diameter of 60 µm. The coagulation bath contains 115 g / l of sulfuric acid, 330 g / l of sodium sulfate and 45 g / l of zinc sulfate.

fifty

Example 5 (comparison example):

[0045] A fiber was manufactured according to the exposure of document CN 1904156, adjusting the procedure conditions specifically recommended there:

55 8.9% cellulose, 5.2% NaOH, 33% CS2 referred to cellulose. No modifying agent was added. The viscose was spun with a viscosity of 55 seconds of ball drop.

Nor could the high phosphorus contents indicated in this publication be understood. To get to

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Acceptable resistances, several optimization tests with different contents of flame retardant substances were carried out under the indicated conditions. Also in this example, the indicated properties could not be achieved until the phosphorus content was reduced to 2.1% by weight based on cellulose. The nozzles used have a nozzle hole diameter of 60 µm. The coagulation bath contains 115 g / l

5 of sulfuric acid, 350 g / l of sodium sulfate and 11 g / l of zinc sulfate. The temperature of the coagulation bath was 49 ° C.

Table 1: Fiber data:

Fiber

Title [dtex] Resistance in conditioned state [cN / tex] Fiber extension [%] BISFA wet module [cN / tex] Phosphorus Content [%] Useful value

Example 1

1.7 28.7 13.3 5.2 3.5 18.2

Example 2

1.7 28.8 14.1 5.3 3.5 18.6

Example 3

1.7 27.3 13.5 5.1 3.5 17.9

Example 4 (comparison)

2.2 18.3 20.2 2.0 2.1 4.2

Example 5 (comparison)

2.4 18.5 19.3 1.8 2.1 3.8

[0046] The comparison of fiber properties clearly shows that the flame retardant viscose fibers that were manufactured according to the standard viscose conditions according to example 4 or 5 showed clearly worse useful values than those manufactured according to the invention.

Claims (10)

E10754846 07-28-2014 1. Regenerated regenerated cellulose fiber for textile applications, characterized in that it contains as a flame retardant substance a phosphorus compound incorporated in spinning, in particle form and has a value 5 useful - defined as the product of the phosphorus content and the wet module, the wet module being measured according to the BISFA standard (BISFA, Testing methods viscose, modal, lyocell and acetate staple fibers and tows, 2004 edition). Between 10 and 35 and because it was manufactured according to a viscous procedure. 2. Fire retardant fiber according to claim 1, containing at least 2.8%, preferably between 10 3.2% and 6.0%, especially preferably between 3.5% and 6.0% of cellulose-related phosphorus. 3. Flame retardant fiber according to claim 1 or 2, the phosphorus compound being 2,2'-oxybis [5,5-dimethyl1,3,2-dioxaphosphorin] 2,2'disulfide (I). Fire retardant fiber according to at least claims 1 to 3, which has a wet module BISFA (Bm)> 0.5 · (√T) · 10 / T with an extension of 5% in the wet state. 5. Flame retardant fiber according to claims 1 to 4, characterized in that the flame retardant substance it presents a distribution of particle sizes with x50 less than 1.0 µm and x99 less than 5.0 µm. twenty 6. Flame retardant fiber according to claims 1 to 5, characterized in that the dispersion of flame retardants contains a dispersing agent chosen from the group containing modified polycarboxylates, water-soluble polyesters, alkyl ether phosphates, nonylphenoxyloxylates closed at the end groups, oil alkoxylic esters of castor and carboxymethylated polyglycol alcohol ethers. 25

7.

Use of the fibers according to claims 1 to 6 for the manufacture of a thread.

8.

Use of the fibers according to claims 1 to 6 for the manufacture of a flat textile structure.

30 9. Procedure for the manufacture of a fire retarded regenerated cellulose fiber for textile applications by spinning a viscose with a content of between 4 and 7% cellulose, between 5 and 10% NaOH, between 36 and 42% (referring to cellulose) of carbon sulphide, as well as between 1 and 5% (referring to cellulose) of a modifying agent in a coagulation bath, wound of coagulated wires, using a viscose, whose value spinning gamma is between 50 and 68, and whose spinning viscosity is between 50 and 35 to 120 seconds of ball drop and the coagulation bath temperature being between 34 and 48 ° C, characterized because to. the alkalinity ratio (= cellulose concentration / alkali content) of the viscose ready for Spinning is between 0.7 and 1.5, 40 b. The following coagulation bath concentrations are used:

•

H2SO4 68 -90 g / l

•

Na2SO4 90-160 g / l

• ZnSO4 30 -65 g / l 45

C.

the final winding of the coagulation bath is carried out with a speed between 15 and 60 m / min and

d.

A phosphorus compound in the form of a pigment dispersion is incorporated as a flame retardant substance as a flame retardant substance.

Method according to claim 9, with a spinning amount of such a flame retardant substance being incorporated so that the finished fiber contains at least 2.8%, preferably between 3.2% and 6.0%, especially preferably between 3.5% and 6.0% phosphorus referred to cellulose. 11. The method according to claim 9, the organophosphorus compound being 2,2'-oxybis [5,5-dimethyl55 1,3,2-dioxaphosphorein] 2,2'disulfide (I). 12. Method according to claim 9, containing the dispersion of pigments between 10 and 50% of the flame retardant substance with an average particle size (x50) of less than 1 µm and a maximum particle size (x99) of less than 5 µm and between 1.5 and 20% of the dispersant. 9 E10754846 07-28-2014 13. Method according to claim 12 using a dispersant for a dispersion of flame retardant substances, selected from the group containing modified polycarboxylates, water-soluble polyesters, alkyl ether phosphates, nonylphenoxyloxylates closed at the end groups, castor oil alkoxylic esters and ethers 5 carboxymethylated polyglycolic alcohol. 10