EP3014002B1 - Method for production of cellulosic filaments - Google Patents

Description

The present invention is a continuous process for producing a high-strength regenerated cellulose filament according to the preamble of claim 1.

State of the art:

Cellulosic regenerated filaments have long been known. They are especially for textiles, but - in a high-strength form - for technical applications, such. B. used as a tire cord. For the purposes of this invention, "regenerated cellulosic fibers" are to be understood as meaning those fibers which are produced from a cellulose-containing spinning solution by spinning into a spinning bath (often called a precipitation bath), the cellulose being present in the spinning solution as a cellulose derivative, in particular as cellulose xanthate Regeneration in the precipitation bath back to pure cellulose takes place. The regenerated fibers and filaments produced via the xanthate are commonly referred to as "viscose" or "rayon". The cellulose-containing spinning solution is also referred to as "viscose" or "viscose spinning solution". The manufacturing process itself is therefore referred to as Viskoseverfahren.

Viscose processes for staple fibers and continuous filaments have been known in principle for many years and, for example, at length K. Götze, man-made fibers by the viscose process, 1967 , described. However, the textile properties of the resulting fibers and filaments are significantly affected by many parameters. In addition, limits are set for many influencing factors due to the design of the existing production facilities, which can not be exceeded for technical or economic reasons, so that any variations in the product range can be exceeded Parameters are often not possible and therefore would not cause the expert to do so.

In the course of time, different variants of the viscose process were developed and partly used industrially to this day. The individual variants differ mainly in the composition of the spinning solution and the precipitation bath, whereby the mechanical properties of the products can be greatly influenced. Examples of these are the modal and polynosic fibers, which are produced on a commercial scale only in the form of staple fibers. The basics of the modal process for the production of staple fibers are in AT 287905 described. In the field of filaments it is now also possible, through improvements in mechanical engineering, to spin continuously, using the so-called "continue" method, instead of the earlier, discontinuous centrifuge methods.

Standard viscose filaments are now widely used in the textile and clothing industry, especially in the field of linings. The low strength, especially when wet, the high elongation and the high surface shrinkage put the use of viscose filaments in the textile sector but limits. In particular, light, d. H. thin, but nevertheless solid textiles, which are also easy to wash, are therefore not possible. Also for more heavily used textiles, eg. As work clothes and uniforms they are not suitable. Although there are possibilities here by synthetic filaments, for example made of polyester or polyamide, but these are in particular in wearing comfort, much worse than the cellulosic materials. There is therefore still a need for high strength cellulosic filaments for textile applications which can not be economically produced by the known processes.

A well-known, commercial, high-strength regenerated filament is, for example, CORDENKA®, which is produced by a modified viscose process. It is manufactured with single fiber titers of approx. 1.8 dtex and strengths (conditioned) of approx. 45 to approx. 52 cN / tex. It is in the technical Range, for the reinforcement of rubber articles, in particular high-quality vehicle tires used. For textile applications, such a filament is too coarse and too expensive to manufacture. Here, the composition of spinning solution and precipitation bath were changed in comparison to standard viscose in particular.

It has also been known for a long time to spin various pigments into cellulosic regenerated fibers, especially into fibers by the viscose process. The pigments may be flame-retardant pigments, in particular those based on phosphorus, or else colorants or matting agents. Such pigment-containing viscose fibers are produced worldwide for standard applications in the textile and nonwovens sector with a single fiber titer between 0.8 and 16 dtex. The pigments are added to the cellulose-containing spinning solution by means of suitable metering devices. This pigment-containing spinning solution is then extruded through spinnerets and precipitated according to the known methods and further treated. The pigments introduced into the fibers in this way are stored very firmly and can not be washed out, for example, by conventional washing processes.

For the flame-retardant finish of viscose fibers various chemicals are described in the literature. Above all, flame retardants based on halogens, silicon and phosphorus are used.

The Patents DE4128638A1 or DE102004059221A1 describe flame retardant dispersions based on a 2,2'-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorinane] 2,2'-disulfide using various dispersant systems and also mention the use of these dispersions for the flame-retardant finish of viscose fibers.

Also the EP1882760 describes the preparation of flame-retarded viscose fibers using flame retardant dispersions based on a 2,2'-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorinane] 2,2'-disulfide. There will described as an important feature of the invention that the particle size may be a maximum of 10 microns and that the spinning mass must therefore be cleaned before spinning through filters with a maximum mesh size of 10 microns. However, it has been found that this criterion is not sufficient to produce fibers that meet the requirements described here. In the EP1882760 described maximum particle size of 10 microns is perhaps for viscose filaments or. Monofilaments with a high titre are sufficient, but by far no longer meet the requirements of a modern staple fiber production with fiber finenesses of about 1 to 4 dtex; a 1.3 dtex fiber has a diameter of about 10 μm.

The fibers described in the prior art or commercially available are all prepared by standard viscose methods. Although they show comparatively good mechanical fiber data for flame-retardant viscose fibers, since the phosphorus contents are very low. Investigations with various flame retardants on the basis of phosphorus have shown, however, that only from a phosphorus content of about 2.8%, a sufficient flame retardant effect is achieved. The flame retardancy correlates very well with the content of flame retardant converted to pure phosphorus.

However, it has been found that, for example, the incorporation of large amounts (15-25%) of a flame-retardant pigment leads to a further deterioration of the textile parameters of the viscose fiber. Therefore, the limitations of the application areas already mentioned for the standard viscose fibers apply a fortiori to flame-retarded viscose fibers.

This is all the more regrettable because flame-retardant fibers could be used to particular advantage in products that are also exposed to heavy mechanical loads, for example in workwear for particularly dangerous activities such as fire departments, foundries, military, petroleum and chemical industries. For such products will be Usually already used synthetic high performance fibers such as (aromatic) polyamides, aramids, polyimides and the like. However, these fibers have a low wearing comfort, since they are not able to absorb moisture sufficiently. A mixture of these fibers with cellulosic fibers, which complement the range of properties by an increased wearing comfort, without the other properties to deteriorate too much, would be desirable.

It is likewise known to incorporate color pigments or matting agents, especially titanium dioxide, into cellulosic regenerated fibers. Basically, the same problems occur due to the solids content. The problems described here by spinning larger amounts of solids apply to viscose staple fibers, but especially for viscose filaments.

In the WO 2011/026159 A1 discloses a process for producing flame-retarded cellulosic staple fibers which is intended to solve these problems. The fiber described there contains as a flame-retardant substance a spun, particulate phosphorus compound, preferably an organophosphorus compound and has a so-called use value between 6 and 35, preferably between 8 and 35 and particularly preferably between 10 and 35. Such a fiber could be produced for the first time by a modified viscose process.

It has been shown that for the production of in the WO 2011/026159 A1 fibers described a cellulose concentration of 4-7% when using a pulp with an R-18 content of 93-98% and an alkali ratio (= cellulose concentration / sodium hydroxide concentration, in g / l) of 0.7 to 1.5 the ideal conditions represent. However, the spinning parameters must be adjusted accordingly due to the addition of the flame-retardant FR pigment.

1. a. das Alkaliverhältnis (= Cellulosekonzentration/Alkaligehalt) der spinnfertigen Viskose 0,7 bis 1,5 beträgt,
2. b. folgende Fällbadkonzentrationen eingesetzt werden:
   • H₂SO₄ 68 - 90 g/l
   • Na₂SO₄ 90 - 160 g/l
   • ZnSO₄ 30 - 65 g/l
3. c. der Endabzug aus dem Fällbad mit einer Geschwindigkeit zwischen 15 und 60 m/min erfolgt und
4. d. als flammhemmende Substanz eine pigmentförmige Organophosphorverbindung in Form einer Pigmentdispersion eingesponnen wird.

The WO 2011/026159 A1 therefore also describes a process for producing a flame retarded regenerated cellulose fiber for textile applications by spinning a viscose containing 4 to 7% cellulose, 5 to 10% NaOH, 36 to 42% (based on cellulose) carbon disulfide and 1 to 5% (based on cellulose) of a modifier in a coagulating bath, stripping off the coagulated filaments using a viscose whose spin gamma value is 50 to 68, preferably 55 to 58, and whose spin viscosity is 50 to 120 fall times; and that the temperature of the precipitation bath is 34 to 48 ° C, wherein

1. a. the alkali ratio (= cellulose concentration / alkali content) of ready-to-use viscose is 0.7 to 1.5,
2. b. following precipitation bath concentrations are used:
   • H ₂ SO ₄ 68-90 g / l
   • Na ₂ SO ₄ 90-160 g / l
   • ZnSO ₄ 30-65 g / l
3. c. the final discharge from the precipitation bath takes place at a speed between 15 and 60 m / min and
4. d. as a flame-retardant substance a pigmented organophosphorus compound is spun in the form of a pigment dispersion.

Suitably, a viscose is used, to which the modifier is added only shortly before the spinning of the viscose.

The in the WO 2011/026159 A1 proposed measures of compliance with a certain spinning maturity for which the spinngammawert is characteristic, the maintenance of a certain viscosity, for which the falling ball values are characteristic, and the observance of certain conditions in the precipitation bath, together effect the desired fiber properties. Spinning gamma is the proportion of carbon disulfide molecules bound to 100 cellulose molecules. The spin gamma value is determined according to Zellcheming leaflet draft by R. Stahn [1958] and leaflet III / F 2. The term "ball drop" is understood to mean the viscosity determined by the falling ball method; it is expressed in terms of bullet seconds. The provision is in K. Götze, Chemiefasern [1951], p. 175 s.

The flame retardant phosphorus compound prepared as a pigment is prepared according to the WO 2011/026159 A1 the Viskosespinnlösung added in the form of a pigment dispersion. In this case, so much of the flame-retardant substance is spun in that the finished fiber contains at least 2.6%, preferably between 3.2% and 6.0%, particularly preferably between 3.5% and 6.0% phosphorus, based on cellulose.

As already stated above, a flame retardant organophosphorus compound which is particularly suitable for the purposes of the present invention is 2,2'-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorinane] 2,2'-disulphide.

In particular, the quality of the pigment dispersion has a significant influence on the fiber properties. This is determined by the average and maximum particle size of the pigments, the concentration of the dispersion in use, d. H. during the addition to the viscose spinning solution, as well as the type and amount of the dispersing aids.

Contrary to the patent EP1882760 described possible upper particle size of 10 microns has been found that an average particle size (x ₅₀ ) smaller than 1 micron and a maximum particle size (x ₉₉ ) smaller than 5 microns, preferably less than 3 microns are necessary. Fig. 3 shows a size distribution of a still suitable pigment dispersion.

Preferably, according to the WO 2011/026159 A1 contain the pigment dispersion between 10 and 50% of the flame retardant substance.

In most prior art documents, the influence of the dispersant is not described as fully as it would be appropriate. However, many chemicals that provide a highly stabilized flame retardant dispersion have a negative impact on the spinning process, as they also have a modifying effect on the viscose, but the fiber strength is in contrast to the used modifiers do not affect positively. As ideal dispersants for the flame retardant dispersion for producing the fibers according to the invention which do not adversely affect the fiber strength, in particular those have been found which have been selected from the group containing modified polycarboxylates, water-soluble polyesters, alkyl ether phosphates, end-capped nonylphenol ethoxylates, castor oil alkoxylates and carboxymethylated alcohol polyglycol ethers. Preferably, the pigment dispersion should contain between 1.5 and 13% of the dispersing aid.

The WO 2011/026159 A1 refers explicitly to the production of staple fibers. Since these usually have a cutting length between about 25 and 90 mm and are mixed intensively several times before their final use in textiles, small differences in the uniformity of the individual fibers as well as small spinning defects do not play a major role in their production. However, the conditions are quite different in the production of (continuous) filaments for textile or technical applications. These are usually spun in thin filament bundles with about 10 to 2000 individual filaments and wound up directly. It takes about 48 hours to fill a bobbin. If, due to a spider error, even a single filament breaks off within 48 hours, this has a significant impact on the product quality and therefore the achievable price. In addition, the filaments are naturally no longer mixed in their use, so that unevenness of the filaments, for example, in textiles are clearly visible. This also affects the product quality and thus the achievable price.

In summary, regenerated cellulose filaments are known in the prior art, which have a high strength, but too coarse titers, on the other hand textile filaments, which are so fine that they offer a textile comfort, but at the same time have only a low strength. In particular, there are no textile regenerated cellulose filaments known which, with high strength, have such a high content of pigment, for example Flame retardant pigment, have that they actually show good flame retardant properties.

Description of the invention

1. a. das Alkaliverhältnis (= Cellulosekonzentration/Alkaligehalt) der spinnfertigen Viskose 0,7 bis 1,5 beträgt,
2. b. folgende Fällbadkonzentrationen eingesetzt werden:
   • H₂SO₄ 68 - 95 g/l
   • Na₂SO₄ 90 - 160 g/l
   • ZnSO₄ 30 - 65 g/l
3. c. der Endabzug aus dem Fällbad und das Aufspulen mit einer Geschwindigkeit zwischen 15 und 180 m/min erfolgt,

wobei

• d. die im Fällbad koagulierten Filamente anschließend durch ein zweites Bad geführt werden, wobei das zweite Bad wässrige, 3 - 7 Gew.-%ige Schwefelsäure bei einer Temperatur von 80 - 98 °C enthält.

The present invention is a continuous process for producing a high-strength regenerated cellulose filament by spinning a viscose containing 4 to 8% cellulose, 5 to 10% NaOH, 36 to 42% (based on cellulose) carbon disulfide and 1 to 5% (relative on cellulose) of a modifier in a coagulation bath, stripping off the coagulated filaments, using a viscose whose spinnegamma value is 50 to 68 and whose spin viscosity is 50 to 150 fall times; and that the temperature of the precipitation bath is 34 to 65 ° C,

1. a. the alkali ratio (= cellulose concentration / alkali content) of ready-to-use viscose is 0.7 to 1.5,
2. b. following precipitation bath concentrations are used:
   • H ₂ SO ₄ 68-95 g / l
   • Na ₂ SO ₄ 90-160 g / l
   • ZnSO ₄ 30-65 g / l
3. c. the final discharge from the coagulation bath and the coiling takes place at a speed of between 15 and 180 m / min,

in which

• d. the filaments coagulated in the precipitation bath are subsequently passed through a second bath, the second bath containing aqueous, 3-7% by weight sulfuric acid at a temperature of 80-98 ° C.

By spinning such a spinning solution with subsequent stretching and fixation in the second bath to obtain high-strength cellulosic Regeneratfilamente that even after incorporation of flame retardant or coloring pigments filament or Garnfestigkeiten that are well above comparable cellulosic Regeneratfilamenten consisting of textile viscose spinning solution according to the prior the technique was spun.

Suitably, a viscose is used, to which the modifier is added only shortly before the spinning of the viscose.

In the context of the process according to the invention, "continuous" is intended to mean that the spinning out of the viscose into the precipitation bath, drawing, washing, drying and winding takes place continuously in the same operation. In contrast, there are the widely used centrifuge spinning processes in which the wet filaments are wound up in centrifuges and then these so-called spin cakes are washed intermittently and dried.

The inventively proposed measures of compliance with a certain spinning maturity, for which the Spinngammawert is characteristic, compliance with a certain viscosity, for which the falling ball values are characteristic, and compliance with certain conditions in the precipitation bath, together effect the desired fiber properties. Spinning gamma is the proportion of carbon disulfide molecules bound to 100 cellulose molecules. The spin gamma value is determined according to Zellcheming leaflet draft by R. Stahn [1958] or leaflet IIIIF 2. The term "ball drop" is understood to mean the viscosity determined by the falling ball method; it is expressed in terms of bullet seconds. The provision is in K. Götze, Chemiefasern [1951], p. 175 s.

In order to reliably achieve the high strength of the filaments, it has proven to be advantageous to use cellulose as the cellulosic raw material with an α content of 93-99%. Such a pulp has only small proportions Low-molecular secondary constituents which, on the one hand, reduce the strength in the finished filament and, on the other hand, can enter into the precipitation bath cycles, where they can be troublesome in many ways as soiling.

An important feature of the method according to the invention is that the filaments in the second bath are stretched by 70% to 105%. In the prior art, on the one hand no second bath is used, which contains only aqueous sulfuric acid and has a temperature of 80-98 ° C, and on the other hand after leaving the precipitation bath in the continue-spinning process only about 5%, in batch processes stretched by about 10-20% for textile filament ..

This process makes it possible to produce both pigment-free high-strength regenerated cellulose filaments and those regenerated cellulose filaments which have a pigment content of more than 20% by weight and a strength of more than 22 cN / tex.

A surprising correlation was found between the strength of a pigment-free regenerated cellulose filament and a pigment-containing regenerated cellulose filament, if only the pigment content in the filament is changed and the other process parameters are kept constant: $${\mathrm{FFK}}_{\mathrm{P}}={\mathrm{FFK}}_{\mathrm{R}}\times {{\mathrm{c}}_{\mathrm{<figure-callout\; id="2"\; label="Cell"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">Cell</figure-callout>}}}^{\mathrm{2}}$$

Therein, FFK _{P is} the fineness-related strength of the pigment-containing regenerated cellulose filament, FFK _{R is} the fineness-related strength of the pigment-free regenerated cellulose filament and C _{Cell is} the cellulose fraction of the pigment-containing regenerated cellulose filament, based on the dry content of the filament and expressed as a fraction.

For example, under process conditions according to the invention, under which pigment-free regenerated cellulose filaments are obtained with a Strength of 35 cN / tex, also pigment-containing regenerated cellulose filaments having a strength of 22 cN / tex and a pigment content of 0.21 (ie a cellulose content of 0.79).

The pigments are preferably spun in the form of a pigment dispersion. It is particularly advantageous if the pigment metering ratio is automatically controlled or adjusted on the basis of the spinning solution flow and adjusted by means of a regulated metering pump. An exact dosage is extremely important, among other things, for a consistent filament quality. Any deviation from the uniformity is clearly visible in the end use in the textile area in the fabric. In the technical field of application, unevenness can lead to failure of the end product.

Therefore, the selection of a suitable controlled metering pump for the success of the method according to the invention is important. For example, eccentric screw pumps have proved to be particularly suitable. Piston pumps, however, are common in large liquid flows, but too imprecise in the present here, low liquid flows because they do not work continuously but impulsively and thus cause a constantly changing pigment concentration. The common in the synthetic fiber range gear pumps are not applicable in the present process, because on the one hand, the pigments used, in particular TiO ₂ , would lead to a very high abrasion of the gear pumps. On the other hand, there is a risk that the pigment settles between the teeth of the pump gears and closes them, so that the delivery rate is lower and the dispersion enters the viscose spinning solution with a lower pigment content.

As pigments, according to the invention, in principle all solids are suitable which do not change undesirably under the conditions in the viscose spinning solution, ie strongly alkaline and CS ₂ -containing. In particular, the pigment is selected from the group consisting of flame-retardant, colored, fluorescent ("high-vis" dyes) and X-ray detectable pigments. It is also intended that mixtures of these pigments for a combination of several properties in the same filament are expressly included in the present invention. In a preferred embodiment of the invention, the pigmented substance is therefore at least partially a flame retardant substance

In order to achieve an effective flame retardant effect, in the process according to the invention so much of the flame-retardant substance is spun in that the finished fiber is at least 2.8%, preferably between 3.2% and 6.0%, particularly preferably between 3.5% and 6 , 0% phosphorus, based on cellulose. The phosphorus is preferably in the form of the organophosphorus compound 2,2'-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorinane] 2,2'-disulfide (I).

The described advantageous mechanical properties of the regenerated cellulose filaments obtained by the process according to the invention are achieved particularly reliably when the pigment dispersion is between 10 and 50% of the flame-retardant substance with an average particle size (x ₉₀ ) smaller than 1.0 μm and a maximum particle size (x ₉₉ ) smaller 5.0 microns, preferably less than 3.0 microns and between 5 and 20% of a dispersing aid.

This dispersant for the flame retardant dispersion is preferably selected from the group comprising modified polycarboxylates, water-soluble polyesters, alkyl ether phosphates, end-capped nonylphenol ethoxylates, castor oil alkoxyl esters and carboxymethylated alcohol polyglycol ethers.

The flame retardant phosphorus compound prepared as a pigment is added to the viscose spinning solution in the form of a pigment dispersion according to the invention. In this case, so much of the flame-retardant substance is spun in that the finished fiber contains at least 2.6%, preferably between 3.2% and 6.0%, particularly preferably between 3.5% and 6.0% phosphorus, based on cellulose.

As already stated above, a flame retardant organophosphorus compound which is particularly suitable for the purposes of the present invention is 2,2'-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorinane] 2,2'-disulphide.

In particular, the quality of the pigment dispersion has a significant influence on the fiber properties. This is determined by the average and maximum particle size of the pigments, the concentration of the dispersion in use, d. H. during the addition to the viscose spinning solution, as well as the type and amount of the dispersing aids.

Contrary to the patent EP1882760 described possible upper particle size of 10 microns has been found that an average particle size (x ₅₀ ) smaller than 1 micron and a maximum particle size (x ₉₉ ) smaller 5.0 microns, preferably less than 3 microns are necessary. Fig. 3 shows a size distribution of a still suitable pigment dispersion.

Preferably, the pigment dispersion should contain between 10 and 50% of the flame retardant.

The process according to the invention achieves the production of regenerated cellulose filaments which have both a pigment content of more than 20% by weight and a strength of more than 22 cN / tex.

These pigments introduce desired additional functionalities into the filaments. This can be z. As a flame retardant, a permanent color or a matting. But for special products, other additives are possible, for example, provide for a particularly good visibility or warning effect, electrical conductivity, absorption of pollutants or radiographic visibility (eg for surgical sewing threads). In principle, all solids are suitable as pigments, which do not change undesirably under the conditions in the viscose spinning solution, ie, strongly alkaline and CS ₂ -containing, and the strongly acidic precipitating bath, in particular partially or completely dissolved. A conceivable exception are substances which are present in a strongly alkaline environment in dissolved form and only pass into a solid aggregate form in the acidic precipitation bath. In particular, the pigment is selected from the group consisting of flame-retardant, colored, fluorescent ("high-vis" dyes) and X-ray detectable pigments. Mixtures of these pigments for a combination of several properties in the same filament should also be expressly encompassed by the present invention, for example the combination of color pigments, high-vis color pigments and flame-retardant pigments for use in lightfast, warning-colored, flame-retardant clothing for fire services and rescue services ,

The described advantageous mechanical properties of the pigment-containing regenerated cellulose filaments according to the invention are achieved particularly reliable when the pigment has a particle size distribution with x ₅₀ smaller 1.0 micron and x ₉₉ smaller than 5.0 microns, preferably less than 3.0 microns.

It is further provided that the regenerated cellulose filaments according to the invention have a fine single fiber titer of between 0.4 and 4 dtex, preferably between 0.8 and 3.0 dtex. Such fine regenerated cellulose filaments, especially if they contain sufficient amounts of pigment, have not yet been produced with the strengths described above.

The spun-in pigments preferably have a particle size distribution with x ₅₀ smaller than 1.0 μm and x ₉₉ smaller than 5.0 μm, preferably smaller than 3.0 μm.

Das erfindungsgemäße Filament enthält in einer bevorzugten Ausführungsform mindestens 2,8%, bevorzugt zwischen 3,2% und 6,0 %, besonders bevorzugt zwischen 3,5% und 6,0 % Phosphor, jeweils bezogen auf Cellulose. Geringere Phosphorgehalte als 2,8 % ergeben keine ausreichende flammhemmende Wirkung. Höhere Phosphorgehalte als 6 % verschlechtern die mechanischen Eigenschaften der Filamente und sind darüber hinaus nicht mehr wirtschaftlich.As the organophosphorus compound, 2,2'-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorinan] 2,2'-disulfide (Formula I) is preferably used. This substance is available under the trade names Exolit and Sandoflam in sufficient quantities and is not washed out of the fibers during the manufacturing process and also in the subsequent application:

In a preferred embodiment, the filament according to the invention contains at least 2.8%, preferably between 3.2% and 6.0%, particularly preferably between 3.5% and 6.0% phosphorus, in each case based on cellulose. Lower phosphorus content than 2.8% does not provide sufficient flame retardancy. Higher phosphorus contents than 6% deteriorate the mechanical properties of the filaments and are also no longer economical.

In most prior art documents, the influence of the dispersant is not described as fully as it would be appropriate. However, many chemicals that provide a highly stabilized flame retardant dispersion, have negative effects on the spinning process, as they also have a modifying effect in the viscose, but do not positively affect the fiber strength, in contrast to the modifiers used. As ideal dispersants for flame retardant dispersion for the preparation of Regeneratcellulosefilamente invention, which do not adversely affect the fiber strength, have been found in particular those selected from the group containing modified polycarboxylates, water-soluble polyesters, alkyl ether, endgruppenverschlossenyl Nonylphenolethoxylate, castor oil alkoxyl and carboxymethylated alcohol polyglycol. Preferably, the pigment dispersion should contain between 1.5 and 13% of the dispersing aid.

The process according to the invention also achieves the production of a pigment-free regenerated cellulose filament which has a strength in the conditioned state of more than 36 cN / tex. The regenerated cellulose filaments according to the invention preferably also have a fine single fiber titer of between 0.4 and 4 dtex, more preferably between 0.8 and 3.0 dtex

A regenerated cellulose filament having such a high strength and fineness can be processed very well into woven fabrics and other textile fabrics, which have an exceptionally high abrasion resistance compared to standard viscose filaments, which has a strength of about 20 cN / tex. Thus, it is particularly well suited for use in sports, for example for motorcycle, Kartbekleidung and sportswear. With abrasion resistance is at this point in particular by the Martindale abrasion test meant measured property. Due to the higher temperature resistance compared to synthetic filaments such as polyester and nylon, the high-strength filament is also used in many technical applications, eg. B. for turbocharger hoses in cars and trucks.

Both (pigment-free) filaments having a conditioned state strength greater than 36 cN / tex and pigment-containing filaments having a pigment content greater than 20% by weight and a strength conditioned greater than 22 cN / tex are intended for the purposes of the present invention Invention also be referred to as "high strength".

When used, the filaments according to the invention are not used individually but in the form of the filament bundles obtained in the spinning process from in each case a single spinneret, also referred to as filament yarns. In the textile sector, a filament yarn usually contains about 30-200 individual filaments. In technical applications, for example for reinforcing car tires, conveyor belts or other rubber articles, about 700 to 2000 individual filaments in the yarn are common.

Also provided is the use of the filaments according to the invention for producing a textile fabric. In addition to the fibers according to the invention, this fabric may also contain other fiber yarns or filament yarns, for example and in particular wool, flame-retardant wool, para-aramides (Kevlar®, Twaron®) and meta-aramids (Nomex®), polybenzimidazole (PBI), p-phenyl 2,6-benzobisoxazole (PBO), polyimide (P84®), polyamideimide (Kermel®), modacrylic, polyamides, flame retarded polyamides, flame retarded acrylic fibers, melamine fibers, polyesters, flame retarded polyesters, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), glass fibers, Cotton, silk, carbon fibers, oxidized thermally stabilized polyacrylonitrile (PANOX®) fibers, elastanes and electrically conductive fibers, as well as blends of these fibers

The fabric is preferably a woven, knitted, knitted or crocheted goods. In the case of a woven or knitted fabric, the mixture of filaments according to the invention with the other fiber or filament yarns either by mixing before yarn production, the so-called intimate mixing, or by sharing each pure yarns of different filament and fiber types in weaving, working, Knitting or crocheting possible.

The process of the invention will now be described with reference to a possible and well suited embodiment, without the invention being limited to this embodiment. Functionally equivalent solutions are expressly included in the invention.

The spinning machine, with which the process is carried out, is in principle Fig. 1 The supply of the viscose or the viscose dispersion mixture via the piping system (1). The metering of the titer-dependent amount of viscose is carried out by means of precision gear pumps (2). In the filters (3), the filtration of the metered viscose takes place. In the variant described here, customary spinnerets (4) are installed submerged on so-called spinning pipes for producing the required filament in the precipitation bath (5). Preference is given in a precipitation bath next to each other spun two filament yarns from separate spinnerets (4) and then guided parallel to each other over the entire spinning machine. These spinnerets (4) contain the number of holes corresponding to the desired number of individual filaments in a filament yarn. The precipitation bath (5) is supplied via a level-regulated feed with precipitation bath liquid which has the composition according to the invention. Via a pipe section, the coagulated filaments with the Fällbadflüssigkeit first to a trough (7), which serves as a drain for the precipitation bath. Such a process is commonly referred to as a tube spinning process. The filaments are guided above the trough (7) onto the first godet (8) of the drawing unit, whereby excess precipitation bath is collected by the trough (7). From the galette (8), the filaments run into the second bath (9), where they are simultaneously stretched and fixed. This second bath has an inlet (10) and a drain (11) for the bath liquid described above. From the arranged in the second bath deflection device, which may be a movable (non-driven) pair of rollers or a rigid glass rod or the like, the filaments are guided on an entangled, with a wash water application (12) and a washing water drain (13) pair of rollers where They are washed first and then dried in a drying zone (14). Subsequently, they are scanned in a finishing unit (15) and finally wound on a Doppelspuleinheit (16). The pair of rollers may additionally be equipped with an exhaust (17) for the resulting water vapor and other gaseous by-products.

The tube spinning process described here allows about 10% higher strength and faster to about three times faster spinning than the conventional dipping spinning process. Without the addition of a pigment dispersion, spinning speeds of up to 180 m / min are possible, with the addition of a pigment dispersion still up to 85 m / min.

A particularly uniform addition of the pigments is, for example, by a metering device according to Fig. 2 possible: This contains a stirring container (18) for the preparation of the pigment dispersion, a Dispersion metering pump (19) for discharging the dispersion, a corresponding flow measurement (20), and two static mixer (21, 22) for mixing the dispersion with the main stream of Visc solution, via a line (23), a booster pump (24) and a Flow measurement (25) to the static mixers (21, 22) passes. After a further flow measurement (27), the viscose pigment dispersion is fed via a further pipeline (28) to the spinning machine. In addition, a temperature control circuit (27) may be provided for controlling the temperature of the main viscous stream.

The invention will now be explained by way of examples. These are to be understood as possible embodiments of the invention. By no means is the invention limited to the scope of these examples.

Example 1:

6 parts by weight of 2,2'-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorinan] 2,2'disulfide, 6 parts by weight of water and 0.55 parts by weight of Alkylpolyglykoletherphosphorsäureester be homogenized by means of a dissolver and milled in a stirred ball mill (Drais, type Perl Mill PML-V / H) with Zirkonoxidmahlkörpern at a temperature of 40-55 ° C until the final dispersion has a x ₉₉ <1.50 microns. Beech pulp (R18 = 97.5%) was alkalized with mash liquor containing 240 g / l NaOH at 35 ° C with stirring and pressed to a Alkalellellulosevlies. The alkali cellulose nonwoven was fiberized, aged and sulfided. The xanthate was dissolved with a dilute sodium hydroxide solution to a viscose with 5.6% cellulose, 6.8% NaOH and 39% CS ₂ , based on cellulose. The viscose was filtered 4 times and vented. The viscose was dosed 1 hour before spinning 3%, based on cellulose, ethoxylated amine, a modifier causing a shell structure. The viscose was ripened to a spinning gamma value of 57. The viscosity during spinning was 80 falling seconds. The finished flame retardant dispersion is added to this ready-to-spin viscose.

The nozzles used have a nozzle hole diameter of 60 microns. The precipitation bath contains 75 g / l of sulfuric acid, 113 g / l of sodium sulfate and 53 g / l of zinc sulfate. The precipitation bath temperature was 39 ° C.
The coagulated and partially regenerated plastic yarn strand of pale yellow color was passed over a galette (G 1) into a second bath whose temperature was 95 ° C. and contains 4.8% by weight sulfuric acid, and there between G 1 and a second godet (G 2) stretched by 100%. The final discharge was 30 m / min. The filament was then washed free of acid with hot water, dried and then wound up. Table 1: Fiber data: fiber Titre [dtex] Single filaments [number] FFk [cN / tex] Fdk [%] BISFA wet module [cN / tex] P content [%] example 1 200 76 23.5 6.1 5.2 3.5

Claims (16)

1. A continuous method for the production of a high-strength regenerated cellulose filament by spinning a viscose containing 4 to 8 % cellulose, 5 to 10 % NaOH, 36 to 42 % (in relation to cellulose) carbon disulphide and 1 to 5 % (in relation to cellulose) of a modifier into a precipitation bath, withdrawing the coagulated filaments, a viscose being used of which the spinning gamma value is 50 to 68, and of which the spinning viscosity is 50 to 150 falling ball seconds; and the temperature of the precipitation bath being 34 to 65°,

   a) the alkali ratio (= cellulose concentration/alkali content) of the ready-to-spin viscose being 0.7 to 1.5,

   b) the following precipitation bath concentrations being used:

   - H₂SO₄ 68-95 g/l

   - Na₂SO₄ 90-160 g/l

   - ZnSO₄ 30-65 g/l

   c) the final withdrawal from the precipitation bath and the reeling up taking place at a speed of between 15 and 180 m/min,

   characterised in that

   d) the filaments coagulated in the precipitation bath are then passed through a second bath, the second bath containing aqueous sulphuric acid, 3-7 % by weight, at a temperature of 80-98°C.
2. The method according to Claim 1, a pulp having an α content of 93-99% being used as a cellulosic raw material.
3. The method according to Claim 1 or 2, the filaments being stretched by 70 % to 105 % in the second bath.
4. The method according to any of the preceding claims, a pigment-type substance in the form of a pigment dispersion being spun into the filaments.
5. The method according to Claim 4, the pigment dosing ratio being controlled and/or adapted automatically based on the spinning solution flow rate and being adjusted by means of a controlled dosing pump.
6. The method according to Claim 5, the controlled dosing pump being an eccentric screw pump.
7. The method according to any of Claims 4 to 6, the pigment-type substance being selected from the group including flame-retardant, coloured, fluorescent and radiographically detectable pigments.
8. The method according to Claim 7, the pigment-type substance being at least partly a flame-retardant substance.
9. The method according to Claim 7 or 8, the flame-retardant substance being spun in to such an extent that the finished fibre contains at least 2.8 %, preferably between 3.2 % and 6.0 %, particularly preferably between 3.5 % and 6.0 % phosphorus in relation to cellulose.
10. The method according to Claim 9, the phosphorus being in the form of the organophosphorus compound 2,2-oxybis[5,5-dimethyl-1,3,2-dioxaphosphorinane]2,2'disulphide (I).
11. The method according to any of Claims 7 to 9, the pigment dispersion containing between 10 and 50 % of the flame-retardant substance with an average particle size (x₉₀) of less than 1.0 µm and a maximum particle size (x₉₉) of less than 5.0 µm and between 1.5 and 20 % of a dispersing agent.
12. The method according to any of Claims 7 to 11, a dispersing agent additionally being used for the flame retardant dispersion that is selected from the group including modified polycarboxylates, water-soluble polyesters, alkyl ether phosphates, end group-capped nonylphenol ethoxylates, castor oil alkoxy esters and carboxymethylated alcohol polyglycol ethers.
13. The method according to any of the preceding claims, the spinning of the viscose into the precipitation bath taking place in the form of a tube spinning method.
14. A method of using a regenerated cellulose filament in technical applications, for example for strengthening car tyres, conveyor belts or other rubber items, characterised in that a regenerated cellulose filament is produced by a method according to any of Claims 1 to 13, and the regenerated cellulose filament that is produced in this way is used.
15. A method of producing a textile fabric, characterised in that a regenerated cellulose filament is produced by a method according to any of Claims 1 to 13, and the textile fabric is produced from the regenerated cellulose filament that is produced in this way.
16. The method according to Claim 15, wherein the fabric contains further fibre yarns or filament yarns, for example and in particular wool, flame-retardant wool, para-aramids (Kevlar®, Twaron® and meta-aramids (Nomex®), polybenzimidazole (PBI), p-phenyl-2,6-bezobisoxazole (PBO), polyimide (P84®), polyamidimide (Kermel®), modacrylic, polyamides, flame-retardant polyamides, flame-retardant acrylic fibres, melamine fibres, polyesters, flame-retardant polyesters, polyphenylene sulphide (PPS), polytetrafluoroethylene (PTFE), glass fibres, cotton, silk, carbon fibres, oxidised thermally stabilised polyacrylonitrile fibres (PANOX®), elastanes and electrically conductive fibres, as well as mixtures of these fibres.

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