EP3006608B1 - Flame retardant regenerated cellulose filamentfibres - Google Patents

Description

The invention relates to viscose spun and twisted multifilaments, and their object is to improve them, in particular with regard to a compromise of good surface properties and good flame retardant properties.

The invention provides a viscose spun and twisted multifilament, which has been produced in particular according to one of the method aspects described below, and in which a number of flakes of 2 flakes per 1000 meters in length is not exceeded, preferably a number of flutes per flute 1000 meters, in particular of 0.5 lint per 1000 meters, and on the other hand, a phosphorus content based on the α-cellulose of 2.8% or higher, preferably 3% or higher, in particular 3.2% or higher and 4.2% or less, preferably 4% or less, more preferably 3.8% or less. The twisting takes place on suitable twisting machines, for example and preferably on ring twisting machines of the brand Ratti on S500.

Microscopically, fractures of individual capillaries as a result of spins are a major cause of a deteriorating surface quality, which is manifested in the form of thick spots on the yarn and commonly referred to as lint. In the course of the downstream textile operations, e.g. when twisting, weaving or knitting, they increase in size continuously. Due to the mechanical stress of the yarn due to friction at e.g. Pulleys, eyelets, Schärgattem etc., these loose capillaries can postpone, whereby the lint gradually increase in size.

Quantitatively, the surface quality of the continuous fiber can thus be determined by the number of lint per unit of quantity of the fiber, for example per 1000 meters of length (or per kilogram of yarn). In the context of this invention, the number of lint per 1000 meters is understood to mean the number of defects on the yarn per 1000 meters of length detectable by a gauge, whereby a single broken single filament may already cause such a defect, two or more single capillaries fractured at the same location but not counted twice or more times. A suitable measuring device is, for example, an Elkometer III from the company Textechno.

Preferably, for the invention can be used a method in which the viscose before wet-spinning a phosphorus-containing solid is added, and in which after the at least partial coagulation of the filaments in the spinning bath following the extrusion of the spinning mass still takes place a stretching in the secondary bath from which the filaments are withdrawn at a final take-off speed, and a dimensionless first parameter formed from the quotient of the draft dimensioned in percent and the final take-off speed measured in meters per minute is less than 2.5, preferably less than 2.0, in particular less than 1.67.

It has been further recognized that on the one hand the addition of solids (for example a flame retardant) and on the other hand by the drawing in the second bath (B-bath) using known process parameters the risk of increased brittleness of the fibers produced, which directly negatively affect the surface properties of the fibers and yarns produced. With such a choice of the first parameter, on the other hand, despite the addition of solids and the strength achieved by stretching, improved surface properties of the fibers produced are achieved, in particular smoother fiber surfaces.

In this way, it is no longer necessary to use economically and ecologically less attractive countermeasures in the form of additional, temporarily modifying the surface work steps such as finishing and Schärölen.

By such a method, upper limits for an untwisted yarn of 4 lint / 1000 meters, but also 2 fluff / 1000 meters, even 1.5 fluff / 1000 meters can be achieved and maintained. This is also possible with spun-in pigments in an amount of more than 15%, in particular also in the range of 18% to 25%, these percentages referring to percentages by weight based on the α-cellulose. In addition, the method can also produce doubled yarns with fluff values of 1 flute per 1000 meters or less, in particular of 0.6 fluff per 1000 meters or less, and this even with a spun-on phosphorus-containing flame retardant with a phosphorus content of 3% based on cellulose. up to 4% and in industrial production.

To illustrate the dimensionless first parameter, the following short example can be used. For example, the second bath is stretched by 80% at a final take-off speed of 70 meters / minute. Then the first parameter is 80/70 = 1.14.

The first parameter is preferably greater than 0.75, in particular greater than 1.0. Also, the first parameter may be more preferably less than 1.5, preferably less than 1.33, in particular 1.25. This makes it possible to produce particularly good surface properties of the fibers.

Preferably, a dimensionless second parameter, which is not formed as the first parameter from the quotient but from the product of the two variables, in the range of 3200 up, preferably greater than 3600, in particular greater than 4000, but preferably in the range of less than 8000 , preferably less than 7500, in particular less than 7000.

In this context, it is provided that at least a value of 40 m / min, preferably at least 50, more preferably at least 60 and in particular at least> 65 m / min is achieved as the absolute value for the final take-off speed. With regard to drawing, it should be at least 60%, preferably more than 70% be stretched, but preferably by not more than 120%, in particular not more than 100%.

In a further advantageous development, the titer of the multifilament formed is specifically taken into account. It is provided that a dimensionless third parameter formed from the quotient of the second parameter and the root of the titer of the multifilament measured in dtex is not smaller than 300, preferably greater than 330, more preferably greater than 360, and in particular greater than 400. The titer specification refers to the total titer of the multifilament, this is 225, for example, and the second parameter is 6300, the third parameter is 420. However, these values of the third parameter relate primarily to multifibers with a total denier of 330 dtex or Less, but can also be used for slightly higher titers to about in the range of 600 dtex. In principle, however, for total titers of greater than 330 dtex, in particular of greater than 600 dtex or even greater than 900 dtex, a lower limit for the third parameter of 160, in particular 200, is preferred.

As the upper limit of the third parameter thus formed, the value 680 is preferable. More preferably, the third parameter should be 600 or smaller, more preferably less than 530 and in particular less than 500.

With regard to the amount of solids added, the total amount of such water-insoluble pigments, based on the percentage of α-cellulose, should preferably not exceed 25%. Furthermore, it is preferred that the final take-off speed measured in meters per minute move below the curve 95 - 0.025 x ² , preferably below the curve 90 - 0.016 x ² .

The addition of the phosphorus-containing flame retardant is preferably carried out by adding a dispersion of the particles. In particular, the addition may be made to the otherwise ready-to-spin mass. The dispersants mentioned below can also be used here.

With regard to the total titer of the multifilament fiber, a fiber thickness of not less than 60 dtex is preferred. Furthermore, it is preferred that the total titre of the fiber is not is greater than 2500 dtex. With respect to the Kapillartiter a range of 1.8 to 2.6 dtex is considered to be preferred, in particular in the range of 2.2 to 2.6 dtex, the latter being particularly advantageous for Gesamtgarntiter of less than 330 dtex. As the average diameter of the single fiber, a range between 10 and 30 microns, preferably between 11 and 20 microns is considered advantageous.

Furthermore, it is preferably provided that the amount x _{FR of} the phosphorus-containing flame retardant solid is metered in at a given total titer T of the multifilament in such a way that it is based on the α-cellulose in percent over 16.5 + (290-T) / 90 is above 17 + (290-T) / 90, and especially below 19 + (290-T) / 90, more preferably below 18.5 + (290-T) / 90. In particular, the flame retardant recited in claim 10 is intended. These quantities for x _FR are primarily for total titers in the range of 330 or less. For total titers in the range of 330 or greater, x _{FR should} preferably be in the range of 17.5 to 19.0%.

In particular, it is preferred that an upper limit for the product of fluff number per 1000 meters in length and in terms of α-cellulose in percent phosphorus content is not greater than 8, more preferably not greater than 6, even more preferably not greater than 4, and in particular not greater than 3.

Dry tensile strengths in the conditioned state in the range of over 25 cN / tex are achieved for the finished fiber. Furthermore, after the initial shrinkage (first to second wash), the fabric produced therefrom remains under 5% further shrinkage after another 50 washes.

The wet strength and thus also the wash resistance of the produced multifilament can be indicated, for example, by the Chord modulus, wet in the twisted state cN / tex with the extension points E1 = 4% and E2 = 3.5%, as in the BISFA, Testing Methods for Viscose, Cupro, Acetate, Triacetate, and Lyocell Filament Yarns, 2007 Edition, Chapter 7 (7.6.1.3). It is preferred that the product of the chord modulus thus measured in cN / tex be in the range of not less than 280, preferably not less than 320, more preferably not less than 360, with the square root of the denier of the fiber expressed in dtex Furthermore, this product should preferably not exceed 560, more preferably 520 and in particular 480 do not exceed. These product values apply in particular to fibers with a total titer of 330 dtex or less. In absolute terms, the chord modulus should preferably be at least 20 cN / tex for yarn titers ≥ 200 dtex, and at least 30 cN / tex for yarn titers of 120 dtex or less.

The roller temperature of the drying rollers is in this aspect of the invention preferably in the range of 40 ° C or higher, preferably 45 ° C or higher, in particular 50 ° C or higher, and preferably 95 ° C or lower, preferably 80 ° C or lower, especially 70 ° C or lower.

Particularly preferred pulp of the viscose is a pulp having an intrinsic viscosity of greater than 560 ml / g and an α-cellulose content of greater than 97.5%, in particular monomodal molecular weight distribution, in particular a kraft-softwood pulp. The intrinsic viscosity should be determined according to ISO / FDIS 5351: 2009 (Limiting Viscosity Number [η]).

In the following, further aspects are explained, which can be applied in particular if particles which lead to the preservation of the phosphorus content are brought into a form whose dimension in a particle main axis is greater than in the two orthogonal particle secondary axes. Then, particle main axes in the fiber can preferably be aligned in a preferred direction parallel to their spin direction.

In such a method, therefore, the main axes of the particles incorporated into the fiber are aligned such that ideally their major axes are aligned parallel to the spinning direction of the filament. In practice, an approximation to this ideal state is that the orientation density function of the incorporated particles in the spinning direction of the filament assumes its maximum. The ratio of the particle diameter in the plane spanned by the two particle secondary axes to the length of the particle measured along the main axis is preferably about 1: 3. Preferably, the shape of the particles is a rotational ellipsoid.

By a suitable choice of the spinning parameters, in particular the take-off speed, flame-retardant regenerated cellulose fibers with an LOI greater than 26, in particular 27 and strengths greater than 25 cN / tex and preferably greater than 26 cN / tex, more preferably greater than 29 and in particular of 30 cN / tex. In particular, the decrease in the tensile strength in the conditioned state of the regenerated cellulose filament fiber-flame retardant fiber compared to a comparable regenerated filament fiber which does not contain flame retardant particles is less than 28%. Preferably, a decrease in strength of less than 25% and particularly preferably a reduction in strength of less than 20% can be achieved.

In a preferred embodiment, it is provided that the particle size distribution of the dispersion used as the starting material of the process is adjusted before being fed to the mixing process in a nozzle-based dispersing device.

For example, the total solids content of a flame-retardant dispersion obtainable under the trade name Viskofil® Exolit 5060 VP2988 is between 51 and 56 percent, depending on the batch and formulation, the proportion of the amount depending on the batch flame-retardant substance varies between 41 to 47, in particular 45 percent, in particular 43 to 47 (45) percent. In the nozzle-based dispersing device, which is preferably a device available under the product name Serendip Dispersion Device, for example Serendip LPN 60 or Serendip 500, agglomerates of this commercially available dispersion formed by transport and / or storage are broken up. After only a short amount of energy, this results in a particle size distribution whose average particle diameter lies in a particularly favorable range between 0.7 and 0.8 μm and which has a very narrow particle size distribution.

Furthermore, it proves to be advantageous that at least one additional dispersant is added to the dispersion used as the starting material of the process before it is fed to the mixing process. The dispersant may be derived from the group of anionic, cationic and nonionic dispersants.

The addition of the additional dispersants favors, in particular, a process procedure in which filtering of the mixture from which the cellulose regenerated fiber is spun is carried out only in two coarse filters in which particles larger than 25 μm are retained. An apparative filter sequence of a 10 micron fine filter and a 30 micron coarse filter, as in the prior art according to EP 1 882 760 is proposed, this is not required. The inventive method is thereby significantly more economical, because only the two cheaper in the purchase and maintenance coarse filters are used.

Particularly preferred is the use of a Kapellartiters of 1.8 dtex and hole diameters of the spinnerets from 40 to 60 microns. The average diameter of the single fiber is between 10 to 30 microns, preferably 11 to 20 microns, a preferred upper limit for the Kapillartiter is 2.6 dtex. For yarn titres less than 330 dtex, the preferred capillary density is in the range of 2.2 to 2.6 dtex.

In the context of the invention it is further provided that the viscose is fed to the mixing process as a flow of a viscous pump, whose delivery rate is controlled in dependence on a measurement of the pressure in the outflowing from the mixing flow. This viscous pump may be, for example, a gear pump.

A further advantageous embodiment of the method consists in that the dispersion is supplied to the mixing process by a metering pump, the delivery rate of which is regulated as a function of a measurement of the mass flow of the dispersion fed to the mixing process. A uniform dosage of the input of dispersion into the cellulose is of particular importance for the strength of the regenerated fiber. The maintenance of a fixed constant ratio of dispersion to viscose could, for example, be realized mechanically in the form of a transmission between the viscose pump and the metering pump. However, this would only keep the ratio of the volume flows constant. In contrast, the mass flow-dependent control of the metering pump allows a uniform metering of the dispersion. As a mass flow meter, a Coriolis mass flow meter is preferably used. As a metering pump, an eccentric screw pump is preferably used, since it enables significantly longer service lives in dispersions with a high solids content.

Preferably, the α-cellulose content of the pulp used is greater than 97.5, in particular 98 percent with a DP greater than 400, in particular greater than 1500 in order to achieve the inventive strengths, and a DP of viscose greater than 400.

More preferably, the pulp is also a kraft softwood pulp having an α-cellulose content of greater than 97.5%, in particular monomodal molecular weight distribution.

The viscosity of the viscose is preferably greater than 100 kfs at 20 ° C and the incorporated, water-insoluble flame-retardant particles have a rotational ellipsoidal shape, the longer major axes are aligned in a preferred direction parallel to the direction of stretching of the fiber. As a result, a particularly high strength can be achieved.

The flame-retardant substance used is preferably a phosphorus-containing substance, in particular 2,2'-oxybis [5,5-dimethyl-1,3,2-dioxaphosphorinane] 2,2'-disulphide. The phosphorus content of the finished fiber is preferably in the range from 2.8% to 4.2%, more preferably from 3% to 4%, based on the α-cellulose.

As an example, the limits of the machine parameters are listed within which a method is suitably possible for the titer 200f100 [corrected: 200f110]. titres cN / 100 dtex Spin bath [° C] B-bath [° C] Roller heating [° C] Drawing [%] Deduction [m / min] 200f110 HT-FR 240-310 50-70 75-98 75-95 > 70 > 60

Also protected by the invention is a textile fabric (in particular according to ISO 11612) which is produced by incorporation of a multifilament according to one of the properties described above.

• Aus einem Rührkessel 1 wird eine Dispersion von Partikeln eines flammhemmenden Feststoffes von einer Dosierpumpe 2 über eine Rückschlagklappe 5 einem statischen Mischer 6 zugeführt. Außerdem wird dem statischen Mischer 6 über eine Viskoseförderpumpe 3 Viskose zugeführt. Aus dem statischen Mischer 6 strömt die darin gebildete Mischung aus Viskose und Dispersion in einen weiteren statischen Mischer 7 und wird dort weiterhin durchmischt.

In the following, the invention and therefore or together with it applicable aspects will be explained with reference to the figures of the drawing by way of example. In Fig. 1 is shown:

• From a stirred tank 1 is a dispersion of particles of a flame-retardant solid from a metering pump 2 via a check valve 5 a static Mixer 6 supplied. In addition, the static mixer 6 is fed via a viscose pump 3 viscose. From the static mixer 6, the mixture of viscose and dispersion formed therein flows into another static mixer 7 and continues to be mixed there.

The flow leaving the static mixer 7 passes through a mass flow meter 8 to a spinning machine in which the cellulose regenerated fiber is spun. A control unit 10 generates in response to the measurement signals of the mass flow meter 8 and 9, a control signal for driving the metering pump 2, by the mass ratio of the two flow rates to a desired value is regulated.

Furthermore, the pressure of the conveyed to the spinning machine flow rate is detected by a pressure sensor 4 and regulated in response to the measurement signal, the delivery rate of the viscose pump 3.

Fig. 2 is an SEM image of a manufactured multifilament. It can be seen, indicated by the arrows, the orientation of the particle main axis in the parallel preferred direction of the fiber.

• Es wird im industriellen Verfahren ein Multifilament mit Titer 200f76 mit kontinuierlicher Spinntechnologie hergestellt. Der Spinnmasse wurde noch das phosphorhaltige Flammschutzpigment Viscofil Exolit 5060VP2988 zugegeben. An dieser Stelle und auch generell zu dieser Anmeldung wird unter einem industriellen Verfahren ein Verfahren verstanden, bei dem die eingesetzte Maschine eine Stundenproduktion von wenigstens 6 oder bevorzugt wenigstens 8, insbesondere wenigstens 10 kg pro Stunde erreicht.

Furthermore, an embodiment of the invention is given as follows:

• In the industrial process a multifilament with titre 200f76 with continuous spinning technology is produced. The spinning mass was added nor the phosphorus-containing flame retardant Viscofil Exolit 5060VP2988. At this point, and also generally for this application, an industrial process is understood to mean a process in which the machine used achieves an hourly production of at least 6 or preferably at least 8, in particular at least 10, kg per hour.

The temperature of the coagulation spinning bath is in the range of 58 to 63 ° C, that of the coagulation bath in the range of 90 to 94 ° C. The addition of the flame retardant is such that a solids content in the yarn (based on the α-cellulose) of 19.8% results.

In the drawing bath is stretched by 85%, the final deduction takes place at a speed of 80 m / min. This results in a first parameter of 1.06.

The dimensionless second parameter is 6800 and the dimensionless third parameter is 480.

The phosphorus content of the fiber relative to the α-cellulose is in the range of 3.5%. Nevertheless, in the conditioned state, the fiber retains a dry tensile strength in the range of 265 to 285 cN / 100dtex.

Despite its good flame retardancy and high strength, this multifilament yarn (S500) has only 0.4 to 0.6 fluff per 1000 meters. It is therefore ideal for further processing, especially as a warp material.

The invention is not limited to the features shown individually in the embodiments. Rather, the features of the following claims and the foregoing description, alone or in combination, may be essential to the practice of the invention in its various embodiments,
in particular for the production of high-quality textile products for use, for example, as protective clothing.

Claims (4)

1. A multifilament spun and twisted from viscose, having a lint piece number of 2 lint pieces per 1000 metres of length or less, preferably 1 lint piece per 1000 metres or less, in particular 0.6 lint piece per 1000 metres or less and a phosphorus content in relation to the alpha cellulose of 2.8 % or higher, preferably 3 % or higher, in particular 3.2 % or higher as well as of 4.2 % or less, preferably 4 % or less, in particular 3.8 % or less.
2. The multifilament according to Claim 1, wherein the product of the chord modulus [3.5 % - 4 % wet] specified in cN/tex in the twisted state with the square root of the titre specified in dtex is 280 or higher, preferably 320 or higher, in particular 360 or higher, and preferably 560 or less, more preferably 520 or less, in particular 480 or less.
3. The multifilament according to either of Claims 1 to 2, wherein the cellulose used is a cellulose having an intrinsic viscosity greater than 560 ml/g and an α cellulose content greater than 97.5 %, its molecular weight distribution being in particular monomodal, in particular being a kraft coniferous pulp.
4. A textile fabric produced with the incorporation of a multifilament according to any of Claims 1 to 3.

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