DE69815993T2 - Process for the production and control of heat-connectable core-sheath polyolefin fibers and nonwovens made from them - Google Patents

Abstract

The first object of the new innovation is both to improve and regulate the production conditions for skin-core type polyolefin fibers so that the product fibers have better physical characteristics than before. The second object of the innovation is to manufacture from the said fibers nonwoven-fabrics with strength and softness characteristics that are better than before. The method is especially adapted for large-scale productional melt spinning apparatuses having a short cooling system. One part of the method is aimed at controlled molten-state polymer oxidation and the other part at the control and modification of the molecular weight distribution of the said polymer, by adding thereto, if necessary, prior to the spinning nozzle, a very short chain polymer of the same quality. Characteristic features of the regulation method are in addition a low draw ratio, temperature and nozzle diameter at spinning, measurement of the dynamic deformation of the molten filament as a function of time and distance, in order to ensure the supply of oxygen to the filament in the correct place, quantity and temperature, carrying out the oxidation of the filament using an oxidation nozzle separate from the quenching nozzle as a targeted oxidation and, if necessary, using oxygen enriched air increase of the dispersion value of the molecular weight distribution of the product filament when the molecular weights decrease as the oxidation degree increases, decrease of the thermobonding temperature for the product fibers, regulation of the product fabric strengths and their relationship as a function of the degradation degree of the polymer.

Description

A first goal of the present Invention is the manufacturing conditions of sheath-core polyolefin fibers to both improve and regulate as well as monitor so that the product fibers maintain physical properties. A second goal of the innovation consists of these polyolefin fibers with improved nonwovens Establish strength and softness properties.

The new manufacturing and control process is based on a considerable improvement and regulation of the polymer molecule chain degration process after an autogenous oxidation of the surface layer of the staple fibers in the molten state. The process is particularly used in melt spinning plants high performance with a short cooling system applied.

• – die Oxidation des geschmolzenen Spinnfilaments als gezielte Oxidation ausgeführt wird, bei der ein oxidierendes Gas aus einer von der Abschreckdüse getrennt angeordneten Oxidationsdüse auf das Filamentbündel gerichtet wird,
• – unter unveränderten Spinnbedingungen eine Gleichung von der Form MFI = c₁v₀₂ – c₂v_i + c₃ als Regelungsgleichung bei der gezielten Oxidation zur Bestimmung des Pegels der oxidativen Degradation benutzt wird, wobei in der Gleichung MFI der Schmelzindexwert des Polymers ist, der durch den Wert für die Spinnschmelzeviskosität ersetzt werden kann, der einer niedrigen Scherrate entspricht, v₀₂ die Geschwindigkeit des Oxidationsgases multipliziert mit dem Sauerstoffpartialdruck ist, das heißt der Partialdruckgeschwindigkeit, v_i die Geschwindigkeit des Abschreckgases ist, und c₁, c₂ und c₃ experimentell ermittelte polymer- und prozeßspezifische Konstanten sind, wobei die Sauerstoffpartialdruckgeschwindigkeit, zusätzlich zur Regelung der Molekülkettendegradation des Polymeroberflächenbereichs des Filaments, auch zur Regelung der Größe der Dispersion der Molekülmassenverteilung benutzt wird.

The aim of the invention is therefore a method for controlling the oxidative degradation of the molecular chains in the surface areas of molten polymer filaments, which is applicable to a polyolefin, in particular a prolypropylene short spinning system for the production of filaments, in which the stabilized polymer extrudes and melt-spins and the shaped Spun filaments are oxidized and quenched, characterized in that

• The oxidation of the molten spun filament is carried out as a targeted oxidation, in which an oxidizing gas is directed onto the filament bundle from an oxidation nozzle which is separate from the quenching nozzle,
• - under unchanged spinning conditions, an equation of the form MFI = c ₁ v ₀₂ - c ₂ v _i + c _{3 is used} as the control equation for the targeted oxidation to determine the level of oxidative degradation, the MFI equation being the melt index value of the polymer, which can be replaced by the spinning melt viscosity value which corresponds to a low shear rate, v _{02 is} the velocity of the oxidizing gas multiplied by the oxygen partial pressure, i.e. the partial pressure velocity, v _{i is} the velocity of the quenching gas, and c ₁ , c ₂ and c _{3 are} experimentally determined polymer- and process-specific constants, whereby the oxygen partial pressure velocity is used, in addition to regulating the molecular chain degradation of the polymer surface area of the filament, also to regulate the size of the dispersion of the molecular weight distribution.

In the above equation, the constant c _{1 is} a function of the position of the oxidation nozzle with respect to both the spinneret and the filament bundle, the dimensions and the temperature of the oxidizing gas jet, the spinning deformation of the molten filament; the constant c _{2 is} a function of the position of the quench gas nozzle, the dimensions, the composition and the temperature of the quench gas jet; the constant c _{3 is} a function of the level of oxidative degradation of the filament caused by the quench gas phase, the nozzle diameter, the spinning temperature, the molecular weight distribution of the polymer matrix and the level and the type of additive addition.

The present invention is particular through the dependent Expectations 2 to 16 defined.

A short-chain polyolefin of the same polymer type, in particular polypropylene, is preferably added to the starting polyolefin, in particular polypropylene with a melt index in the range from 350 to 800 and molecular weight distributions in the range from M _w = 125,000-95,000, M _n = 35,000-20,000 and D = 3.5-5.0, the amount added preferably being 15 percent by weight of the polymer fed.

Preferably, in addition to the conventional Regulation of the temperature and speed of the quenching gas phase the molecular chain degradation, the while quenching of the molten polymer filament occurs Regulation of the oxygen partial pressure of the quenching gas phase is regulated.

According to the invention, the thermal molecular chain degradation of the molten polyolefin in the extruder by regulating the melting temperature and extrusion delay time be regulated, especially so that the polyolefin in a temperature range from 250 to 290 ° C is extruded with the delay time the spinning melt in the extruder and the channels is 5 to 15 minutes.

In the process, the polymer fed to the extruder has a melt index of preferably 1.5 to 15, and the values for the molecular weight distributions are in the range from M _w = 500,000-240,000, M _n = 65,000-50,000 and D = 7 , 0-5.0.

The molten filament is preferably quenched under conditions where the volume, velocity and temperature of the quench gas are each in the range of 400 to 1100 Nm ³ / h, 20-60 m / s and 25 ± 5 ° C and the amount of polymer supplied Is 20-40 kg / h per nozzle plate.

In one embodiment, one is in air and free oxygen-poor gas, for example a combustion gas mixture, used as a quenching gas, the oxygen partial pressure in the range from 0.01-0.21 bar lies.

In the process, a product filament is preferably obtained which, after quenching, has a melt index and molecular weight values in the range from 25-50 and M _w = 185,000-200,000, M _n = 40,000-500,000.

In a further preferred embodiment, the amount, the speed, the temperature and the partial pressure of oxygen of the oxidizing gas which is fed to the oxidizing nozzle are each 0.01 to 0.8 Nm ³ / h, 0.1-48 m / s, 25- 60 ° C and 0.21-0.98 bar. The constant c ₁ for the oxygen partial pressure velocity in the control equation is kept in the range from c ₁ = (–0.2) - (+2.0).

The quantity and speed of the quenching gas are preferably regulated such that the tensile stress exerted on the melt filament at the solidification point is below a value of approximately 30 mN / m ² , so that, depending on the spinneret diameters (0.70-0.25 mm) at a die plate capacity of 30-32 kg / h and a spinning melt temperature of 285-290 ° C, the quantity and speed (25 ° C) of the quenching gas are 350-750 Nm ³ / h and 20-45 m / s and relative in other spinning conditions to these values and the constant c _{2 of} the control equation changes in the range from c ₂ = 0–3. The value of the constant c ₃ is usually ≥ 5.

In one embodiment, provision is preferably made for the number-average molecular weight values of the filament polymer to be reduced by a maximum of 30 and its dispersion values to be increased by a maximum of 40 to produce layers of the desired thickness on the surface of a spun filament with a very low molecular weight and a correspondingly very low melting point. compared to the previous values before the nozzle oxidation, by using an oxygen partial pressure velocity in the oxidizing gas and at the same time a corresponding oxygen partial pressure in the range of 0.1-25 m / s and 40-100 vol% O ₂ and at the same time preventing it, by regulating the velocity of the quenching air , an increase in the maximum values of the filament tension beyond 30 mN / m2.

In the method according to the invention is also for it worried that the oxidation nozzle for the Filaments in position α = 5-20 °, x = 60 ± 5 mm and y = 25 ± 5 mm is set, where α is the Angle between the center plane of the oxidizing gas stream and the Spinnerets level and x and y the distances the center line of the free opening area of the oxidation nozzle from the vertical center plane of the polymer jet (x) and the spinneret plane (y), and that the oxidation nozzle for the Filaments in position α = 5-20 °, x = 60 ± 5 mm and y = 25 ± 5 mm is set, where α is the Angle between the center plane of the oxidizing gas stream and the Spinnerets level and x and y the distances the center line of the free opening area of the oxidation nozzle from the vertical center plane of the polymer jet (x) and the spinneret plane (y) are.

If further with the oxidation nozzle in the Position α = 2 ± 1 °, x = 32 ± 5 mm and y = 2 ± 1 mm in the immediate vicinity oxidized at the level of the spinneret surface becomes the spinneret heated inside, where, for example, the effect of a nozzle plate with a unit weight of 0.25 kW / kg is used to prevent the nozzle from cooling.

The invention further relates to a Device for regulating the oxidative degradation of molecular chains in the surface areas a molten polymer filament surface made of polyolefin, in particular Polypropylene, in a filament manufacturing process, with a Melting device with spinnerets and Means, in particular a quenching nozzle, for quenching the polymer filaments, characterized in that the Device for oxidizing the polymer filaments, in particular an oxidation nozzle that is arranged separately from the quenching means.

The invention further relates to the dependent Expectations 18 to 21

The size of the free openings is preferably the quenching nozzle and the oxidation nozzle corresponding to (10-20) × 480 mm and (0.5-1.5) x 460 mm, d. H. that this relationship their surface areas Is 7-42.

The invention further relates to the Application of the procedure for the regulation of the temperatures and connection strengths in a process for heat connection of fibers after the mentioned Processes have been made, especially the melting point and the melting amount of the partial melts, which from the filament surface at heat bonding were formed, as well as the quality characteristics of the Fabrics made of fibers.

• a. die warm zu verbindenden Fasern nach dem erfindungsgemäßen Regelungsverfahren so hergestellt werden, daß sich Fasern mit der gewünschten Oberflächenschichtstruktur und geschmolzenen Flächen ergeben, die sowohl durch den Schmelzindex als auch den Grad der Oberflächendegradation, die durch die Molekülmassenwerte angezeigt werden, bestimmt sind und
• b. die Wärmeverbindung unter Anwendung polymerspezifischer Regelungsgleichungen geregelt wird, die die Festigkeitswerte der Produktstoffe simulieren, wobei die Gleichungen für die Zugfestigkeit und die Dehnung folgende sind: σ(∈) = c₀₁ × [MFI/(MFI)_o]^{n ( o1 )} × T² × exp(–E₀₁/RT) die gemeinsame Umhüllungsgleichung nach Erreichen der maximalen Werte für die Festigkeiten die folgende ist: σ(∈) = c₀₂ × T² × exp(+E₀₂/RT) und
• c. das Verhältnis zwischen der Zugfestigkeit und der Dehnung des Produktstoffes durch die nachstehende polymerspezifische Regelungsgleichung für die Verbindung geregelt wird: σ_II/∈_II = c₀₃ × [MFI/(MFI)_o]^{n ( o3 )} × exp(–E₀₃/RT).

The invention further relates to a method for regulating the thermal connection of sheath-core fibers which have been produced by degradation of the molecules in a filament surface layer on the basis of controlled autogenous oxidation of filaments spun in the molten state from polyolefin, in particular polypropylene, characterized in that that

• a. the fibers to be hot-bonded are produced according to the control method according to the invention in such a way that fibers with the desired surface layer structure and melted surfaces result, which are determined both by the melt index and the degree of surface degradation, which are indicated by the molecular weight values, and
• b. the heat connection is controlled using polymer-specific control equations that simulate the strength values of the product materials, the equations for the tensile strength and the elongation being as follows: σ (∈) = c ₀₁ × [MFI / (MFI) _o ] ^{n ( o1 )} × T ² × exp (–E ₀₁ / RT) the common envelope equation after reaching the maximum strength values is the following: σ (∈) = c ₀₂ × T ² × exp (+ E ₀₂ / RT) and
• c. the relationship between the tensile strength and the elongation of the product is regulated by the following ^{polymer-specific control equation} for the connection: σ _II / ∈ _II = c ₀₃ × [MFI / (MFI) _o ] ^{n ( o3 )} × exp (-E ₀₃ / RT).

• a. aus einem Ausgangspolymer mit M_w = 255 000, M_n = 49 250, M_v = 209 000 und D = 5,15 eine Faserserie hergestellt werden, bei der das Schmelzindexverhältnis bei 2–4,5 liegt,
• b. aus diesen Fasern wärmeverbundene Produktstoffe (etwa 22 g/m²) mit den folgenden Faktoren in den Regelungsgleichungen zum Verbinden entsprechend den Festigkeitswerten und ihrem Verhältnis (σ_II, σ_II/∈_II) hergestellt werden: c₀₁ = 5,442 × 10¹⁹, n₀₁ = 1,811, E₀₁ 47180; c₀₂ = 2, 377 × 10^–10, E₀₂ = 11920; c₀₃ = 3, 235 × 10⁶, n₀₃ = –0,794 und E₀₃ = 12390, wobei die Regelgleichungen, die den Querfestigkeitswerten entsprechen, aus diesen entsprechenden Parametern gebildet sind, und
• c. die erwähnten Stoffe unterschiedliche maximale Festigkeitswerte haben, wenn die nachstehenden Schmelzindizes benutzt werden: MFI = 1,98 und 2, 90; Δ∈_II = 105%; Δ∈_⊥ = 73%; ΔT = 4,5°C MFI = 1,98 und 4, 07; Δσ_II = 8%; Δσ_⊥ = 39%; ΔT = 11,1°C.

For example, in such a method

• a. from a starting polymer with M _w = 255,000, M _n = 49,250, M _v = 209,000 and D = 5.15 a fiber series is produced in which the melt index ratio is 2-4.5,
• b. Heat-bonded product materials (approx. 22 g / m ² ) can be produced from these fibers with the following factors in the control equations for joining in accordance with the strength values and their ratio (σ _II , σ _II / ∈ _II ): c ₀₁ = 5.442 × 10 ¹⁹ , n ₀₁ = 1.811, E ₀₁ 47180 ; c ₀₂ = 2, 377 x 10 ^-10 , E ₀₂ = 11920; c ₀₃ = 3, 235 × 10 ⁶ , n ₀₃ = -0.794 and E ₀₃ = 12390, the control equations corresponding to the transverse strength values being formed from these corresponding parameters, and
• c. the substances mentioned have different maximum strength values if the following melt indices are used: MFI = 1.98 and 2.90; Δ∈ _II = 105%; Δ∈ _⊥ = 73%; ΔT = 4.5 ° C MFI = 1.98 and 4.07; Δσ _II = 8%; Δσ _⊥ = 39%; ΔT = 11.1 ° C.

• – Bei einem Kurzspinnsystem beträgt der Kühlungs- oder Abschreckabstand des geschmolzenen Polymerfilaments, das aus der Spinndüse austritt, etwa 25 mm (bei einem Langspinnsystem etwa 1500 mm). Bei diesem kurzen Abstand und während einiger Millisekunden wird das Filament beim Spinnen mit einem Düsendurchmesser (von 0,25 –0,8 mm) auf nahezu den endgültigen Faserdurchmesser (15–30 μm) gezogen (Kaltziehverhältnis: 150–1600), d. h. seine volumetrische und Oberflächenverformung und entsprechende Geschwindigkeitsänderungen sind sehr groß. Gleichzeitig mit diesen dynamischen Filamentverformungen nimmt die Filamenttemperatur ab (bei Polypropylen 150–200°C), das Polymer härtet aus und seine Kristallisation setzt ein.
• – Um hochqualitative feine Fasern zu garantieren, strebt das neue Verfahren ein niedriges Spinnverhältnis an, d. h. gleichzeitig mit der Anwendung eines kleinen Spinndüsendurchmessers. Infolgedessen muß die Anzahl der Düsen in der Spinnvorrichtung erhöht werden, um eine hinreichende Produktionskapazität zu erzielen, wodurch die gesteuerte homogene Oxidation und Abschrekkung des Faserbündels in dem sehr kurzen Abstand technisch schwierig wird.
• – Bei dem neuen Verfahren werden die Größe der dynamischen Verformungsoberfläche des Filaments und die Änderung darin als Funktion des Abstands und der Zeit gemessen, um dem geschmolzenen Filament den für die oxidative Oberflächendegradation erforderlichen Sauerstoff in der richtigen Menge, Temperatur und am richtigen Ort zuzuführen. Bei der Verformungsmessung müssen auch die dem Filament erteilte Zugfestigkeit und die entsprechenden Orientierungsänderungen in den Molekülketten des geschmolzenen Filamentpolymers (nach der Post-Düsen-Kettendisorientierung, die durch die Relaxation der Scherkräfte bewirkt wird) ebenso wie die Auswirkungen der Zuführung des Sauerstoffs auf sowohl die Verformungsoberflächen als auch die Filamentspannung berücksichtigt werden.
• – Auf der Basis der durchgeführten Prüfungen ist zu schließen, daß die Sauerstoffdiffusion in die Filamentoberfläche und Matrix bei der Degradation der Molekülketten geschwindigkeitskontrolliert ist, weil die Oxidation thermischer Radikale bei der Schmelztemperatur äußerst rasch erfolgt und ferner die Degradation der erzeugten Oxidationsprodukte (u. a. Hydraperoxide) in einem weiten Temperaturbereich erfolgt, weshalb keine dieser Reaktionen primär insgesamt geschwindigkeitskontrolliert ist.

The new control process is therefore a combination of several sub-processes and is based on a large number of measurements and observations. The regulatory procedure is divided into a main part and a secondary part. One part is directed to the molten state, the control of the oxidation of the polymer and the other part, if necessary, to the control and change, before the spin oxidation, the polymer molecular weight distribution, inter alia in the radial direction of the nozzle filament, by mixing, before the reach the spinneret with a very short chain homopolymer of the same polymer quality. Characteristic features of the new process include:

• - In a short spinning system, the cooling or quenching distance of the molten polymer filament that emerges from the spinneret is approximately 25 mm (in the case of a long spinning system approximately 1500 mm). At this short distance and for a few milliseconds, the filament is drawn with a nozzle diameter (from 0.25-0.8 mm) to almost the final fiber diameter (15-30 µm) (cold drawing ratio: 150-1600), ie its volumetric and surface deformation and corresponding changes in speed are very large. At the same time as these dynamic filament deformations, the filament temperature decreases (150–200 ° C for polypropylene), the polymer hardens and its crystallization begins.
• - In order to guarantee high quality fine fibers, the new process aims at a low spinning ratio, ie at the same time as the use of a small spinneret diameter. As a result, the number of nozzles in the spinning device must be increased in order to achieve a sufficient production capacity, which makes the controlled homogeneous oxidation and quenching of the fiber bundle in the very short distance technically difficult.
• The new method measures the size of the dynamic deformation surface of the filament and the change therein as a function of distance and time in order to supply the molten filament with the right amount, temperature and place of the oxygen required for oxidative surface degradation. When measuring the deformation, the tensile strength imparted to the filament and the corresponding changes in orientation in the molecular chains of the molten filament polymer (after the post-nozzle chain disorientation caused by the relaxation of the shear forces) as well as the effects of the supply of oxygen on both the deformation surfaces must also be taken into account as well as the filament tension are taken into account.
• - On the basis of the tests carried out, it can be concluded that the oxygen diffusion into the filament surface and matrix is speed-controlled during the degradation of the molecular chains, because the oxidation of thermal radicals takes place extremely quickly at the melting temperature and furthermore the degradation of the oxidation products (including hydraperoxides) generated in takes place over a wide temperature range, which is why none of these reactions is primarily overall speed-controlled.

• – Wegen dieses sehr kurzen Abschreckabstands und der kleinen erforderlichen Sauerstoffmenge wird für die Oxidation eine separate Oxidationsdüse benutzt, deren Position eingestellt werden kann und die in der Nähe der Spinndüse unmittelbar über der Abschreckdüse angeordnet ist, wobei die Oxidationsdüse eine Düsenöffnung mit einem sehr kleinen freien Oberflächenbereich hat. Die separate Oxidationsdüse ermöglicht eine gezielte Oxidation, die auf das Filamentbündel gerichtet ist, das aus der Spinndüse austritt. Dabei wird das Oxidationsgas in der richtigen Menge, mit der Richtigen Temperatur und an der richtigen Stelle ausgestoßen und, wenn erforderlich, durch die Abschreckzone hindurch, ohne daß die Gase in höherem Maße vermischt sind, um das Oxidationsgas zu erwärmen oder zu kühlen, um die mit Sauerstoff angereicherte Luft wirtschaftlich zu nutzen, den Sauerstoffkonzentrationsgradienten zu erhöhen und damit den Sauerstoffdiffusionsstrom in der Gasphase und den Filamentoberflächenteil, um die Qualität der Oxidationsprodukte zu steuern, die Wärme zwischen den endothermen Verdampfungsreaktionen und den exothermen Oxidationsreaktionen vollständig auszunutzen und die Oberflächenverformungsänderungen mittels der Sauerstoffkonzentration zu regeln.

Based on the deformation measurements, the oxidation of the filament must always be aimed for: At the beginning of the area of greatest deformation in which the filament oxidation area is greatest, the filament tension is lowest, the decrease in filament temperature is as small as possible, the deformation delay time is longest and the polymer birefringence and accordingly the molecular chain orientation is the lowest.

• - Because of this very short quenching distance and the small amount of oxygen required, a separate oxidation nozzle is used for the oxidation, the position of which can be adjusted and which is arranged in the vicinity of the spinneret immediately above the quenching nozzle, the oxidation nozzle being a nozzle opening with a very small free surface area Has. The separate oxidation nozzle enables targeted oxidation, which is aimed at the filament bundle that emerges from the spinneret. The oxidizing gas is expelled in the right amount, at the right temperature and in the right place and, if necessary, through the quenching zone without the gases in higher amounts Dimensions are mixed to heat or cool the oxidizing gas, to use the oxygen-enriched air economically, to increase the oxygen concentration gradient and thus the oxygen diffusion flow in the gas phase and the filament surface part to control the quality of the oxidation products, the heat between the to fully utilize endothermic evaporation reactions and the exothermic oxidation reactions and to regulate the surface deformation changes by means of the oxygen concentration.

• – Wenn das Maß der oxidativen Degradation anhand des Schmelzindex des Filaments gemessen wird, hat die Regelgleichung für die Filamentschmelzoxidation die Form MFI = c₁v₀₂ – c₂v_i + c₃, wobei v₀₂ die Partialdruckgeschwindigkeit des Sauerstoffs ist, d. h. die Geschwindigkeit des Oxidationsgases multipliziert mit seinem Sauerstoffpartialdruck, v_i die Geschwindigkeit der Abschreckluft und c₁, c₂ und c₃ polymerspezifische Konstanten sind (bei konstanten Spinnbedingungen). Eine Zunahme der Geschwindigkeit des Abschreckgases verringert und eine Zunahme der Sauerstoffpartialdruckgeschwindigkeit erhöht das Maß der Degradation. Der Wert der Konstanten c₁ wird hauptsächlich durch die Position der Oxidationsdüse und die Abmessungen des Oxidationsgasstroms bestimmt, und die Konstante c₂ durch die Position der Abschreckdüse und die Abmessungen des Abschreckgasstroms, die Gastemperaturen usw. Die Konstante c₃ ist eine Funktion des Maßes der Oxidationsdegradation durch das Abschreckgas, des Düsendurchmessers, der Spinntemperatur usw.

The angle of the direction of the oxidation nozzle relative to the surface of the spinneret and its distances from the nozzle surface and the filament bundle are essential for carrying out the oxidation process. If the oxidation nozzle is placed on one or both sides (to oxidize one or both sides of the filament bundle) in close proximity to the spinneret surface, it is possible that the oxidizing gas stream will cool the nozzle surface excessively. In this case, if necessary due to the polymer condensation, the nozzle is provided with a low-power electrical resistor and heated to maintain the nozzle surface at a temperature corresponding to that of the spinning melt.

• - If the degree of oxidative degradation is measured on the basis of the melt index of the filament, the control equation for the filament melt oxidation has the form MFI = c ₁ v ₀₂ - c ₂ v _i + c ₃ , where v _{02 is} the partial pressure velocity of the oxygen, ie the velocity of the oxidizing gas multiplied by its oxygen partial pressure, v _{i is} the velocity of the quenching air and c ₁ , c ₂ and c ₃ are polymer-specific constants (at constant spinning conditions). An increase in the quench gas velocity decreases and an increase in the oxygen partial pressure velocity increases the degree of degradation. The value of the constant c ₁ is mainly determined by the position of the oxidation nozzle and the dimensions of the oxidizing gas flow, and the constant c ₂ by the position of the quenching nozzle and the dimensions of the quenching gas flow, the gas temperatures etc. The constant c ₃ is a function of the measure of Oxidation degradation due to the quenching gas, the nozzle diameter, the spinning temperature, etc.

• – Wenn beim Spinnen große Düsendurchmesser verwendet werden, hat dies eine verzögerte Kühlung des Filaments und entsprechend lange Verzögerungszeiten sowie eine erhebliche Zunahme der oxidativen Degradation durch die Abschreckluft im Polymer zur Folge. Dieses Maß der Degradation kann mittels der Spinntemperatur und auch durch entsprechende Wahl von Polymeradditiven, die beide auch die Regelfunktion beeinflussen, geregelt werden. Bei Verwendung kleiner Düsendurchmesser wird das Filament ausgedünnt, und seine Temperatur nimmt so rasch ab, daß die Verzögerungszeit für die Abschreckdegradation zu kurz ist. Wenn es erwünscht ist, das Spinnpolymer in vorzugsweise langkettiger Form zu belassen und die Geschwindigkeit und den Sauerstoffgehalt des aktuellen Oxidationsgases sinnvoll zu halten, beinhaltet das neue Verfahren die Einbeziehung eines kleinen Zusatzes aus einem sehr kurzkettigen Polymer in das Spinnpolymer als einen Teil des Prozesse. Dabei ergibt sich ein hohes Verhältnis der Schmelzindizes der kurz- und langkettigen Polymere, die für diesen Zusatz verwendet werden, d. h. 100–200. Hierbei wurde festgestellt, daß bei der Produktionskapazität entsprechenden Geschwindigkeiten die auf das Filament in den Düsen bei kleinen Düsendurchmessern ausgeübten Scherkräfte ausreichend sind, um wenigstens einen Teil des grobkettigen Polymers im Oberflächenteil des Filaments anzureichern, so daß in diesem Oberflächenteil u. a. sowohl die Abschreckung als auch die gesteuerte Oxidationsdegradation hinreichend intensiviert werden. Eine wichtige Folge dieses Zusatzes in Bezug auf die Oxidation und den Steuerungsprozeß ist die Tatsache, daß bereits ein ziemlich kleiner Zusatz aus einem kurzkettigen Polymer es ermöglicht, die Spinntemperatur zu senken (um 20–50°C), so daß die thermische Degradation in der Filamentmatrix abnimmt und gleichzeitig das Molekulargewicht der Polymerketten innerhalb des Filaments hoch bleibt und – infolge der intensivierten Degradation – in den Filamentoberflächenteilen stark abnimmt.

The degree of oxidation degradation can of course be measured directly on the basis of changes in the polymer molecular weights or viscosities. In this case, the constants in the rule equation change. The constants of the control equation are experimentally determined polymer-specifically for use in controlling the spinning process in manufacture.

• - If large nozzle diameters are used during spinning, this results in delayed cooling of the filament and correspondingly long delay times, as well as a considerable increase in oxidative degradation due to the quenching air in the polymer. This degree of degradation can be controlled by means of the spinning temperature and also by appropriate choice of polymer additives, both of which also influence the control function. When using small nozzle diameters, the filament is thinned and its temperature drops so quickly that the delay time for quench degradation is too short. If it is desired to leave the spin polymer in preferably long chain form and to keep the velocity and oxygen content of the current oxidizing gas reasonable, the new process involves the inclusion of a small addition of a very short chain polymer in the spin polymer as part of the process. This results in a high ratio of the melt indices of the short- and long-chain polymers used for this additive, ie 100-200. It was found here that at the speeds corresponding to the production capacity, the shear forces exerted on the filament in the nozzles in the case of small nozzle diameters are sufficient to accumulate at least part of the coarse-chain polymer in the surface part of the filament, so that in this part of the surface both the quenching and the quenching controlled oxidation degradation are sufficiently intensified. An important consequence of this addition with regard to the oxidation and the control process is the fact that even a rather small addition from a short-chain polymer makes it possible to lower the spinning temperature (by 20-50 ° C.), so that the thermal degradation in the Filament matrix decreases and at the same time the molecular weight of the polymer chains within the filament remains high and - due to the intensified degradation - in the filament surface parts decreases sharply.

• – Bei dem neuen Verfahren sind die Änderungen der Polymermolekulargewichte (Molekulargewicht-Zahlenmittel) und die Dispersion bei der Extrusion, wie Messungen gezeigt haben, herkömmlich, und sie entsprechen bekannten Mehrfachextrusionen, d. h. alle die erwähnten Werte nehmen in regelmäßiger Weise ab (etwa logarithmisch in linearer Weise), wenn der Schmelzindex zunimmt. Bei der Düsenoxidation nach der Extrusion nehmen die Molekulargewichte weiter ab, wenn der Schmelzindex zunimmt, jedoch in anderer Weise als die vorhergehenden Änderungen. Der Dispersionswert nimmt bei zunehmendem Schmel zindex in einer vom herkömmlichen Verhalten abweichenden Weise zu. Dieses Verhalten ist für die Molekulargewichtsverteilung spezifisch, insbesondere unter dem Einfluß einer peripheren Kurzkettenschicht, was leicht aus statistischen Verteilungswerten abgeleitet werden kann.
• – Die polymerspezifische Verbindungsgleichung, die die Faservliesfestigkeitswerte (ϕ) simuliert, hat die Form ϕ = c × T² exp [–E/RT], wobei ϕ (hier) die Zugfestigkeit oder der Dehnungs- bzw. Längungswert ist. Die Aktivierungsenergiewerte beim Verbinden, die den Festigkeitswerten bei der Wärmeverbindung (Thermobonding) in einer Richtung parallel zur Kardierungsrichtung des Faservlieses oder senkrecht dazu entsprechen, sind gleich groß. Die Aktivierungsenergiewerte, die der Zugfestigkeit und Dehnung entsprechen, sind gewöhnlich unterschiedlich groß.

It can also be concluded that, under the spinning conditions for the homopolymer mixture mentioned, the oxidized product filament cures easily to a smectic structure, which can be used to advantage, in particular in the case of a phase-heat connection, during a controlled matrix crystallization as a substantial increase in the connection strength. This part of the new control method can be used and used in particular when spinning fine fibers with small nozzle diameters, in particular for producing high-quality nonwovens.

• With the new process, the changes in the polymer molecular weights (number average molecular weight) and the dispersion in the extrusion, as measurements have shown, are conventional and they correspond to known multiple extrusions, ie all of the values mentioned take on a regular basis ab (approximately logarithmically in a linear manner) when the melt index increases. In die oxidation after extrusion, the molecular weights continue to decrease as the melt index increases, but in a different way than the previous changes. As the melt index increases, the dispersion value increases in a manner that deviates from conventional behavior. This behavior is specific to the molecular weight distribution, especially under the influence of a peripheral short chain layer, which can easily be derived from statistical distribution values.
• - The polymer-specific connection equation that simulates the nonwoven fabric strength values (ϕ) has the form ϕ = c × T ² exp [–E / RT], where ϕ (here) is the tensile strength or the elongation or elongation value. The activation energy values when connecting, which correspond to the strength values for the thermal connection (thermobonding) in a direction parallel to the carding direction of the nonwoven fabric or perpendicular to it, are the same size. The activation energy values, which correspond to the tensile strength and elongation, are usually of different sizes.

The strength values for the heat connection have a maximum value in terms of temperature. The temperature ranges above and below these maximum values have their own equations in the same form. The theoretical maximum value of the connection strength lies at the intersection of these equations. Has the same polymer within the limits of measurement accuracy, with connection strength values, the different degradation values correspond to the same connection equation in the temperature ranges, that exceed the maximum joint strength values, d. H. the strength values lie on a common envelope. The strength value functions are the result of the oxidative degradation and the maximum strength values at low connection temperatures postponed so that the Connection strengths with increasing degradation accordingly the connection equation increases polymer-specifically and to a limited extent.

The polymer-specific control equation for the relationship between the tensile strength (σ) and the elongation (∈) as a function of the melt index ratio and the temperature results directly from the equations simulating the strength values: σ _II / ∈ _II = MFI / (MFI) / ₀ ] ^{- n} × c ₄ × exp [-ΔE / RT], where the value of the exponent n of the melt index ratio is less than 1.0. A similar type of equation also results for the transverse strength values.

By means of the ratios for elongation and strength of the product substance u. a. the tactile properties (softness, Flexibility, elasticity etc.) and the energy of the substances in turn regulated.

In the method according to the invention a starting polymer is used in a manner known per se has been stabilized, in particular peroxide degradation agents, z. B. phosphite-phosphonite mixtures come into question, as a rule in an amount of no more than about 0.5%.

In order to elucidate the state of the art in melt spinning oxidation of a polymer filament, the scientific principles that relate both to polymer melt spinning and its thermal oxidation are considered. In many innovations, including those from the past few years that relate to spinning and oxidation of melt filaments, the effects of, among other things, increasing the spinning melt temperature, delaying the cooling of the melt filament, increasing the diameter of the spinneret and increasing the capacity are advantageously used in the spinning process , For this reason, the results obtained from known experimental spinning models regarding the type and influence of factors are briefly considered. The differential equations of polymer melt spinning dynamics (before crystallization) (S. Kase, T. Matsuo, 1965, 67) in relation to the heat, force and material equilibria are / 1 / v (δT / δy) + δT / δt) = (2√πh / √A ρ Cp) (T – T x ) /1/ (δv / δy) = F / βA / 2 / v (δA / δy) + δA / δt) = –A (δv / δy) / 3 /

The independent variables in the equations are time: t, s and position: y, cm, measured from the spinning head; the dependent variables are the temperature: T, ° C, the filament speed: v, cm / s and the cross-sectional area: A, cm ² .

The drawing viscosity β, gf · s / cm ² is probably only a function of the temperature and the internal viscosity, | η | and the spinning tension: F, gf only a function of time. The filament density: ρ, g / cm ³ and the isobaric specific heat: C _p , cal / g. Degrees are assumed to be constant.

• – Eine Zunahme des Spinndüsendurchmessers ohne Änderung der Wickelgeschwindigkeit oder
• – des Durchmessers verschiebt die A(y)- und T(y)-Funktionen in Richtung auf die y-Achse und vermindert damit die Kühlung und erhöht die Filamentzugspannung (Meßbereich: D_s = 0,4–1,6 mm).
• – Eine Zunahme der thermischen Aktivierungsenergie für die Ziehviskosität β verschiebt die T(y)-Funktion in Richtung einer Zunahme der Y-Achse und die der A(y)-Funktion in die entgegengesetzte Richtung.
• – Eine Verringerung der Temperatur der Abschreckluft oder einer Erhöhung ihrer Geschwindigkeit bewirkt eine Verschiebung der A(y)- und T(y)-Funktionen in Richtung der y-Achse zu abnehmenden Werten hin, d.h. es wird eine noch raschere Ausdünnung des Filaments und Zunahme der Filamentzugspannung bewirkt.
• – Eine Erhöhung der Strömungsgeschwindigkeit (Kapazität) des Polymers bei konstanter Wickelgeschwindigkeit erhöht den zur Aushärtung des Filaments erfor derlichen Abstand erheblich, so daß sie die Polymerabkühlung und Ausdünnung verringert.
• – Durch Anordnung eines isolierenden Zylinders unter dem Spinnkopf um das Faserbündel herum werden die A(y)- und T(y)-Funktionen in Abhängigkeit von der Länge des isolierenden Zylinders zu hohen y-Werten hin verschoben, d. h. der isolierende Zylinder verlangsamt die Abkühlung und Ausdünnung des Polymers und verringert die F-Werte.
• – Der Barus-Effekt und die Temperaturverteilung in Richtung des Filament-Querschnitts werden bei den Funktionen A(y), T(y) und F(y) nur bei sehr hohen Polymerdurchflußwerten signifikant.

In the past few decades, a number of studies, including 2, of fiber filament formation have been presented. However, the equations mentioned and their solutions / 1 / are connected with a rather abundant experimental reference documentation, which in practice covers the most important spinning phenomena and technical applications. The solutions of the steady state of the differential equations / 1 / to / 3 / give the changes in the cross-sectional area A (y) of the fiber filament and the temperature T (y) as Distance y function, measured from the spinner head, for a variety of spinning conditions. The solutions determined are then correlated with the properties of the filament thread. The following can be said about the essential results obtained from the solutions of the spinning model equations [IBM 1401] in melt spinning polypropylene:

• - An increase in the spinneret diameter without changing the winding speed or
• - The diameter shifts the A (y) and T (y) functions in the direction of the y-axis and thus reduces cooling and increases the filament tension (measuring range: D _s = 0.4-1.6 mm).
• - An increase in the thermal activation energy for the draw viscosity β shifts the T (y) function in the direction of an increase in the Y axis and that of the A (y) function in the opposite direction.
• - A decrease in the temperature of the quenching air or an increase in its speed causes a shift of the A (y) and T (y) functions in the direction of the y-axis towards decreasing values, ie there is an even faster thinning of the filament and an increase of the filament tension.
• - An increase in the flow rate (capacity) of the polymer at a constant winding speed increases the distance necessary for curing the filament considerably, so that it reduces the polymer cooling and thinning.
• - By placing an insulating cylinder under the spinning head around the fiber bundle, the A (y) and T (y) functions are shifted towards high y values depending on the length of the insulating cylinder, ie the insulating cylinder slows down cooling and thinning of the polymer and reducing F values.
• - The Barus effect and the temperature distribution in the direction of the filament cross-section become significant for the functions A (y), T (y) and F (y) only at very high polymer flow values.

The polypropylene filament threads crystallize very quickly during melt spinning, which makes the crystallinity and orientation important. As the molten filament becomes thinner, the birefringence Δn increases rapidly. It can be shown that the birefringence of the thread is directly proportional to the tensile strength at the curing point (F / A). In melt spinning, filament crystallization takes place under molecular orientation under non-isothermal conditions. However, the kinetics of the crystallization mechanism can be described by the following Avrami equation used in isothermal kinetics: κ (t) = 1 - exp {- [∫K (T (t)) dt] n } / 14 / the time exponent of the isothermal case and the rate constant (K (t)) being in a simple relationship to the Avrami rate constant (Ziabicki / 2 /).

• – Wenn die Düsentemperatur zunimmt, nimmt die Doppelbrechung Δn ab, wenn F/A_w (Maximum) abnimmt, und die Dichte ρ(κ) nimmt ab, wenn die Kühlzeit Dt/DT abnimmt.
• – Ein vom Spinnkopf aus unten angeordneter Isolationszylinder sorgt für die Beibehaltung einer hohen Lufttemperatur und einer Luftgeschwindigkeit von nahezu Null in dem Zylinder und verringert alle Werte: ρ(κ), Δn, Dt/DT und F/A_w. Eine Verringerung der Kristallisation durch Verlangsamung der Kühlung des geschmolzenen Polymers läßt sich dadurch erklären (Gleichung 5), daß, während der Isolationszylinder die Kühlung verlangsamt, das Filament ausgedünnt wird und gleichzeitig eine hohe Geschwindigkeit während der Zeit erreicht, in der das Filament auf eine Temperatur von etwa 100°C abkühlt. Dies ergibt eine kürzere Kühlzeit und gleichzeitig weniger kristalline Filamente.
• – Wenn die Geschwindigkeit der Kühlluft zunimmt, nehmen alle Werte ρ, Δn, F/A_w und Dt/Dt zu.

The degree of crystallization (κ) can be determined from the equation for any desired point in time, provided that the speed-temperature dependency and the cooling function of the system are known. The temperature function of the isothermal crystallization rate is a largely symmetrical bell function in relation to the maximum rate value. The maximum value of the crystallization rate is below the polymer curing rate of polyolefins. Filament crystallinity is - in addition to the rate of crystallization - dependent on the duration of polymer output in the temperature range in which it has the highest rate of crystallization. This can be expressed quantitatively as the time it takes the polymer to cool one degree, ie Dt / DT = (ρA / P) (dy / dT)) T * / 5 / where Dt / DT is the "cooling time" and (dy / dT) _{T * is} the temperature change along the spun filament near the maximum temperature for the rate of crystallization. Assuming that the temperature T * at which the crystallization rate of the polymer is maximum is a material constant, the degree of crystallization (density) of the filament can be calculated. Some correlations between the properties of the polypropylene thread and the solutions of the spinning equations in the steady state can be mentioned:

• - As the nozzle temperature increases, the birefringence Δn decreases as F / A _w (maximum) decreases, and the density ρ (κ) decreases as the cooling time Dt / DT decreases.
• - An insulation cylinder arranged at the bottom from the spinning head ensures that a high air temperature and an air speed of almost zero are maintained in the cylinder and reduces all values: ρ (κ), Δn, Dt / DT and F / A _w . A decrease in crystallization by slowing the cooling of the molten polymer can be explained (Equation 5) that while the insulation cylinder slows cooling, the filament is thinned out and at the same time reaches a high speed during the time that the filament is at a temperature cools from about 100 ° C. This results in a shorter cooling time and at the same time less crystalline filaments.
• - When the speed of the cooling air increases, all values ρ, Δn, F / A _w and Dt / Dt increase.

The one for the evaluation of the melt oxidation of the polymer filament and the subsequent chain degradation required and focus on changes the filament cross-sectional (and sheath) areas related information as well as the filament temperature and the course of filament hardening as Function of the nozzle of the measured distance and the time can, according to the above requirement, be based on dynamic investigations of the spinning process can be determined.

The autogenous polymer oxidation at low temperatures (<140 ° C) is intense have been examined / 5 /. In contrast, there are hardly any detailed ones Investigations regarding of the polymer melting range at temperatures below a linear Pyrolysis. The oxidation of polypropylene using molecular oxygen let yourself use the following partial formula to illustrate:

Molecular oxygen oxidizes the Polymers by a free radical chain mechanism. In which considered case, free radicals are mainly under both influence thermal as well as mechanical energy.

Carbon radicals react very quickly with the oxygen molecule (3O ₂ radical) (K ₀₃ ~ 10 ⁸ - 10 ⁹ M ^-1 s ^-1 ). However, the oxidation reaction is reversible, and the reverse reaction becomes important when the oxygen is low, the temperature is high, or the carbon radical is stabilized.

An important speed and Produktüberwachungspartialreaktion (Formula 04) is the formation of hydroperoxides as a product hydrogen removal by peroxy radicals. The hydroperoxides are in most cases primary Main products of a polymer oxidation and play - as initiators an autogenous oxidation - one important role in oxidative degradation.

The rate constants for the main reactions in the oxidation reaction scheme are in the temperature range from 71 to 140 ° C: K (01), see -1 = 5.45 x 10 10 × exp (–25000 / RT) K (04), 1M -1 s -1 = 1.61 x 10 7 × exp (–12080 / RT) K (05), 1M -1 s -1 = 1.11 x 10 13 × exp (–11600 / RT)

Polypropylene oxidation is a first order kinetic kinetic. The apparent rate of oxidative pyrolysis is: - d [RH] / dt = K 04 (K 01 [ROOH] s / K 05 ) 1.2 × [RH] / 6 /

The hydroperoxide concentration under stabilized conditions is: [ROOH) s = K 04 2 [RH] 2 / (K 01 K 02 ) / 7 /

Substituting the values of the rate constants into the equation / 6 / gives the following apparent rate constant for the oxidative degradation: K = 1.128 x 10 6 × exp [-18780 / RT] × [ROOH] s / 6 /

For the simulation of the change in the hydroperoxide concentration in the temperature range from 110 to 289 ° C one obtains the equation: [ROOH] s , M1 -1 = 2.981 × 10 -5 × exp [7381 / RT] / 7 /

The reaction rate constant, which corresponds to the kinetics of the oxidative pyrolysis of a polypropylene melt, measured thermogenometrically / 5 / in the temperature range from 240 to 290 ° C., has the form iPP: K, s -1 = 7.75 × 103 × exp (–15240 / RT) / 61 / aPP: K, s -1 = 4.83 × 10 4 × exp (–17190 / RT) / 62 /

If you compare them in the melting temperature ranges from the rate constants for oxidative degradation a solid polypropylene sample (/ 6, 7 /) calculated numerical Values with the corresponding measured values in the melting range (/ 61, 62 /), then it can be concluded that the values both series of measurements within the measuring accuracy limits are the same size. From this it can be concluded that too the reaction mechanisms in both the melted and in the solid phase polypropylene areas are the same.

For solid polypropylene it has been shown experimentally / 8 / that in the case of a flat sample the maximum rate of oxidation is directly proportional to the oxygen pressure in the oxidative gas phase. It has also been shown that the concentration of the primary oxidation product, the hydroperoxide, is directly proportional to the oxygen concentration. For the flat shape, in the case of thick samples, one gets [O 2 ] = [O 2 ] 0 × exp [- (KD) 1.2 × X] / 81 / [ROOH] = [ROOH] 0 × exp [- (KD) 1.2 × X], / 82 / being the index 0 refers to the initial concentration, X is the distance from the sample surface and D is the oxygen diffusion constant.

The concentration distributions of Oxygen and hydroperoxide are then responsible for the amount and quality of the oxidation product distributed to the oxidation system. Similar phenomena obviously also take place during a melt phase oxidation.

The products of the oxidative polypropylene pyrolysis were determined at a temperature of 289 ° C. by IR spectrophotometry from the GC fractions and partly using mass spectrometry / 5 /. The semi-quantitative order of magnitude of the product yield was: ethanol, acetone, butanol, methyl vinyl ketone, C ₆ ketone, polypropylene, methanal, methanol, propanol 2-methyl propanol, 2-pentanone, C ₅ -aldehyde, 3-methyl-3,5-hexadiene.

There is a mutual variation among the first components as a function of pyrolysis time.

The presence of the hydrocarbon products ethane, propane, polypropylene, etc. in the oxidative degradation indicates that oxygen diffusion limits the process. Many of the hydrocarbon components are conventional products of polypropylene pyrolysis in an inert atmosphere. If the atmosphere contains sufficient oxygen, the primary oxidation products are further oxidized, so that both the magnitude of the occurrence and the product quality change as a function of the oxygen content of the oxidation gas:
5% O ₂ : H ₃ C-CO-CH ₃ , H ₃ C-CHO, H ₂ O, H ₃ C-CH = CH ₂ , H ₃ C-CH-CHO, CO ₂ ...
20% O ₂ : H ₂ O, CO ₂ , H ₃ C-CO-CH ₃ , H ₃ C-CHO, H ₃ C-CH = CH ₂ ...
50% O ₂ : CO ₂ , H ₂ O, H ₃ C-CH = CH ₂ , H ₃ C-CHO, H ₃ C-CO-CH ₃
100% O ₂ : CO ₂ , H ₃ C-CH = CH ₃ , H ₂ O

If the oxygen concentration in the atmosphere increases, ethanol, acetone, butanol and water take on insignificant Amounts decrease, and the carbon dioxide yield increases.

The influence of thermal and thermal oxidative Degradation on the polypropylene molecular weights and their distribution be examined briefly.

A reasonable theoretical and practical connection between the thermal (non-oxidative) degradation kinetics of polypropylene and the changes in molecular weights that correspond to the degradation and its distribution has been established (Chan & Balke, / 6 /). For the practical needs of this study, the equations that simulate the resulting changes in molecular weights in the study are: (M w ) 0 - M w = 1.3662 x 10 8th × T .1316 × exp [-8056 / RT] / 9 / (M n ) 0 - M n = 1.1646 x 10 9 × T .1972 × exp [-12646 / RT] / 10 / where the initial values of the mass and number average molecular weights were: (M _w ) ₀ = 234000, (M _n ) ₀ = 59300, (M _w / M _n ) ₀ = 3.94, τ, h are times. The measurements were carried out in the time and temperature ranges from τ = 0 - 48 h and T = 548–598 K.

From the equations it can be seen that in the very short production extrusion delay times the influence of the process temperature on the degradation of polypropylene is essential.

The influence of multiple extrusion of polypropylene under oxidative conditions (air) on the melt index, the degree of dispersity and the melt viscosity at low shear rates has been elucidated in a fairly recent study: J (H. Hinsken at al. / 7 /). The equations that relate to the relationship between the molecular weights and the melt index and approximate the results of the investigation are: M w = 532300 × [MFI] -0, 2890 / 11 / M n = 73510 × [MFI] -0, 1026 / 12 /

The molecular weights and melt indexes of the starting polymer were; M _w = 418400, M _n = 78350, M _w / M _n = 5.34 and MFI = 3.1. The measurement results correspond to an extrusion temperature of 260 ° C. On the basis of the results of this investigation, it can be concluded that, as a result of the multiple random degradation of polypropylene under oxidative conditions, the values of the molecular weights and dispersion decrease conventionally and regularly as a function of the melt index.

The influence of the molecular mass of the polymer crystal on its melting temperature is briefly examined below, since it significantly interferes with the thermal connection of peripheral oxidized fibers, among other things. It can be shown (inter alia HG. Elias, / 23 /) that the melting point (T _M ) of an imperfect polymer crystal with finite molecular mass satisfies the following equation: T M = T M O - [2 RT M T M O / (AH M ) u] [(lnX) / X] + f (X) / 13 / where T _M ^{o is} the melting point of a perfect crystal with a finite molecular mass, (ΔH _M ) u is the melting enthalpy of the polymer unit and X is the degree of polymerization. By inserting the values corresponding to the polypropylene into the equation, the following approximation equation results (accuracy unknown): T M = 460 - 507.5 [(lnX) / X]

Based on this equation can to be concluded that the Decrease in melting point only significant with polymer values X <103 is.

The development of the state of the art in terms of the production of fibers with a sheath-core structure using the oxidative degradation is shown below using some both older than also more recent patent publications checked.

The procedures according to the US patents 2 335 922, 2 715 077, 3 907 957, 4 303 606, 4 347 206 and 4 909 976 deal with kinetic and other problems, and theirs solutions deal with the handling of polymers in connection with the production of peripherally oxidized fibers. In the procedure after U.S. Patent 2,335,922 / 060341, / 11 / is a synthetic Textile material made by extrusion of a high polymer material. The polymer on which air is harmful at the extrusion temperature Has influence is extruded into a chamber that contains inert gas or steam, and cooled to a temperature at which the air has no harmful Influence on has the extrudate. In this process, the influence of air known to the polymer at the extrusion temperature, as well like its prevention, and both influences, in addition to a "chemical" also from kinetic View.

In the procedure according to US 2,715 077/291152, / 12 /, the adhesion of a polyethylene structure (foil) to paints, metals, paper and polymers with different qualities is improved. In this process, the polymer is exposed to a nitrogen oxide containing air (5-20% N ₂ O) with an extrusion temperature in the range of 150-325 ° C, preferably in the presence of UV light (λ ≤ 3900 Å), and quenched , The description discloses knowledge of the kinetics of treatment with nitric oxide and the treatment speed and time.

In the process according to US Pat. No. 3,907,957 / 180474, / 13 /, the formation of oxidizing layers on the nozzle surface when filaments emerge during a rapid spinning process, which has an adverse effect on the processing, is reduced or prevented. In this method, a blanket of steam is placed in a chamber close to and below the nozzle surface (before quenching with air) a small amount of non-condensing, if necessary preheated interten gas. The spatial height of the gases in the direction of the cable is optimized.

In the process according to the US patents 4 303 606/011281 and 4 347 206/310882, / 14 /, one strives to harmful To prevent drawing resonance caused by (one or more) relaxation swellings (Barus effect) in polypropylene spinning in the melt filament immediately after Nozzle become. In this process, the filaments are cut in a short name is Zone extruded - with the extrusion or lower temperature - before them on the cooling air to meet. The extrusion temperature can also be reduced in this way without increasing the relaxation swelling. The extrusion temperature was 204 ° C in the former method and the latter at 177 ° C.

In the method according to the US patent 4 909 976/090588, / 15 /, is the rapid spinning of synthetic Fibers by an additional Online zone heating at a conventional one Process improved. In this process, this becomes the spinning head emerging filament to a temperature above the glass transition temperature quenched (e.g. a smectic structure for the product phase) and then in a warming zone headed where the desired Fiber properties (degree of crystallinity, Orientation, strength). Finally, the filament is back quenched and wound up. The zone length and Temperature values given that a special winding speed correspond.

The development of the prior art in conventional composite polymer structures is described, inter alia, in US Pat. Nos. 4,680,156, 4,632,861, 4,634,739, 5,066,723, 4,840,847, 5,009,951 and European patent application EP 0 662 533 A1 specified.

By the process according to the US patent 4 680 156/140787, / 16 /, the device-specific production capacity and the product quality of composite fibers with a sheath-core structure. In this process, the is molten, restricted, molecular-oriented Material that forms the fiber core is coated with molten material that forms the cladding layer. The combination achieved is a nozzle tool supplied with such a temperature gradient that the outermost part of the fiber core hardened as long as it is still in the tool. The melted one surface layer forms a protective layer that cracks in the surface of the brittle, a high molecular weight oriented core layer prevented and at the same time acts as a lubricant.

In the procedures according to the US patents 4 632 861/240386 and 4 634 739/221085, / 16 /, are the spinning speed and capacity a rapid spinning process for Two-component fibers in a polyethylene-polypropylene system Values of the end components also improved. With the product fiber achieved the polyethylene forms the continuous and the polypropylene the dispersive phase in the matrix. The product fiber has good thermal bonding properties.

In the method according to the US patent 5 066 723/211290, / 16 /, polymer compositions with high shock resistance in the presence of a Ziegler catalyst manufactured. These polymer compositions contain polypropylene as a continuous phase and as a discontinuous phase a thermoplastic Polymer containing 90% polymerized ethylene and the balance other α-olefins contains. The mixture is heated to in the presence of a free radical the viscosity of the system.

In the method according to the US patent 4 840 847/020588, / 16 /, are conjugated fibers with both higher thermal adhesion as well as absorbency made by melt spinning. The fibers contain as one Component a crystalline α-olefin and as another Component is an ethylene dialkylamino alkyl acrylamide copolymer. In which Methods according to US Pat. No. 4,115,620 / 190177, / 16 / spontangekräuselte conjugated fibers with high strength properties. The one component in the structure, the at least two components has contains Polypropylene and 5-50% a thermosetting thermoplastic (which catalyzes from a hydrocarbon which has at least four carbon atoms or a rosin derivative has) and the other polypropylene and a different Amount of a thermosetting thermoplastic.

In the process after the patent application EP 0 662 533 A1 / 040195, / 16 /, are multi-component polymer filaments made by a high speed quenching unit on the side next to the bottom surface one or more spinning heads with a high nozzle density is arranged to aggregate pre-fibers and / or melted To prevent filaments. In this process, a spinning head be used for spinning several different ones at the same time Filaments can be used (U.S. Patents 4,406,850, 5,162,074). In this process, a short spinning system is therefore used for a complicated one Fast spinning system for several polymer components applied.

The processes according to US Pat. Nos. 3,437,725 and 3,354,250 aim to reduce thermal degradation by shortening the process time and reducing the temperature. In the method according to US Pat. No. 3,437,725 / 290,867, / 17 /, the spinneret device contains between the plate containing the filter space and the current nozzle plate an insulating space through which the polymer flows, the melting temperature being below the temperature a significant degradation occurs due to elongated feed pipes to the nozzles in the nozzle plate. The nozzle plate is elec heated trically to produce a steep temperature gradient (≤ 60 ° C) in the polymer (in the feed tube and the capillary) so that the shear stress on the capillary wall is briefly reduced without polymer degradation.

In the method according to the US patent 3 354 250/260264, / 17 /, becomes a polymer powder by means of a screw pressed against a melting membrane, into which an electrical resistance plate is opened. The worm tube is from a water-cooled Sheath surrounded by the temperature of the polymer powder below the lowest melting point of its components is maintained. To The polymer is melted into the nozzles immediately after the filter directed. In this process, the polymer remains for a short time Time in the molten state.

The process according to the patent EP 0 445 536 ( US 5,281,378 ) and patent applications EP 0 630 996 (FI 043072) and 942889 describe the development work in the current decade in the production of sheath-core structural fibers using an oxidative surface degradation.

In the method according to the US patent 5 281 378/200592, / 18 /, are intended to control the polymer degradation, Spinning and quenching phases improved and a fiber produced by means of which it is possible is a nonwoven product with higher Firmness, elasticity and uniform To produce values. Furthermore, this method is intended to improve the thermal connection properties a fiber that is made from a polyolefin Melt is spun.

• – Die Molekulargewichtsverteilung des zugeführten Polymers ist weit, d. h. die Werte der Dispersion sind 5,5-7,75.
• – Das Polymer enthält ein Material aus der Gruppe, die aus Antioxidanten, Stabilisatoren oder deren Mischungen und gegebenenfalls einer degradierenden Komponente besteht.
• – die Menge der Additive ist so gewählt, daß die Degradation des Polymers im Extruder verhindert oder gesteuert (kontrolliert) wird.
• – Das Polymermaterial (MFI: 5–35) wird mit einer Temperatur von 250–350°C extrudiert.
• – In der zweiten Stufe des Verfahrens wird das heiße Extrudat in einer sauerstoffhaltigen Atmosphäre abgeschreckt, um eine oxidative Molekülkettendegradation der Oberfläche unter folgenden Bedingungen zu bewirken:
• – Es wird eine kontrollierte Abschreckung des Extrudats in einer sauerstoffhaltigen Atmosphäre durch Regelung der Abschreckgeschwindigkeit des heißen Extrudats durchgeführt, um eine oxidative Kettendegradation der Filamentoberfläche zu bewirken.
• – Die kontrollierte Abschreckung umfaßt eine verzögerte Abschreckung des heißen Extrudats.
• – Das Abschrecken in einer sauerstoffhaltigen Atmosphäre umfaßt das Abschrecken durch Anblasen in Querrichtung, und der oberste Teil des Querblasstroms wird bis zu 5,4% gesperrt (d. h. das Abschrecken und Anblasen in Querrichtung wird in dieser Zone nicht durchgeführt).
• – Das kontrollierte Abschrecken umfaßt ferner das Aufrechterhalten einer Temperatur des Extrudats von mehr als 250°C während einer Zeit, in der seine Oberfläche oxidativ degradiert wird.
• – Die Produktfaser enthält eine innere Zone: M_w = 10 000–450 000; eine äußere Zone: M_w = 5 000–10 000 und eine mittlere Zone, in der die Molekulargewichte zwischen den erwähnten Grenzen liegen.
• – Die innere Zone hat eine hohe und die äußere Zone ei ne geringe Doppelbrechung.

According to this method, a high-strength staple fiber is produced using an oxidative chain degradation of the surface of a molten spun filament and a slow quenching phase for the molten filament applied to polypropylene with a wide molecular weight distribution. According to the description, the method can be used in a rapid spinning system. According to the description and the claims, the process has the following essential functions: In a first stage of the process, the polypropylene-containing melt is extruded under the following conditions:

• - The molecular weight distribution of the polymer fed is wide, ie the values of the dispersion are 5.5-7.75.
• - The polymer contains a material from the group consisting of antioxidants, stabilizers or mixtures thereof and optionally a degrading component.
• - The amount of additives is chosen so that the degradation of the polymer in the extruder is prevented or controlled.
• - The polymer material (MFI: 5-35) is extruded at a temperature of 250-350 ° C.
• - In the second stage of the process, the hot extrudate is quenched in an oxygen-containing atmosphere in order to cause oxidative molecular chain degradation of the surface under the following conditions:
• - A controlled quenching of the extrudate is carried out in an oxygen-containing atmosphere by regulating the quenching rate of the hot extrudate in order to cause oxidative chain degradation of the filament surface.
• Controlled quenching involves delayed quenching of the hot extrudate.
• Quenching in an oxygen-containing atmosphere includes quenching by transverse blowing, and the top part of the cross-blowing flow is blocked up to 5.4% (ie transverse quenching and blowing is not performed in this zone).
• Controlled quenching further includes maintaining an extrudate temperature greater than 250 ° C during a time when its surface is oxidatively degraded.
• - The product fiber contains an inner zone: M _w = 10,000-450,000; an outer zone: M _w = 5,000-10,000 and a middle zone in which the molecular weights are between the limits mentioned.
• - The inner zone has a high birefringence and the outer zone has a low birefringence.

• – Die Angabe der Querfestigkeitswerte des Stoffes ohne die Angabe von Längs- oder mittleren Festigkeiten sagt nichts aus über die Wärmeverbindung des Stoffes und die wahren Stoff-Festigkeitswerte, da bereits durch eine einfache Einstellung der Kardierung die Querfestigkeiten in weiteren Grenzen als den in der Beschreibung angegebenen Ergebnissen geändert werden können.
• – In der Ergebnistabelle sind die Stoff-Festigkeiten nur für zwei Temperaturen angegeben (die nicht genau definiert sind), was unzureichend ist. Es ist allgemein bekannt, daß die Festigkeitswerte eines wärmeverbundenen Stoffes in Abhängigkeit von der Verbindungstemperatur ein Maximum durchlaufen.
• – Die Gewichtsunterschiede der Stoffproben in der Ta belle sind zu groß, um den erforderlichen Vergleich durchzuführen. Auf der Basis der angegebenen Stoff-Festigkeiten kann jedoch geschlossen werden, daß keine erhebliche Verbesserung infolge der verlangsamten Abschreckung des Faserfilaments oder der Verbreiterung der Molekulargewichtsverteilung des zugeführten Polymers erkennbar ist.

It is difficult to find a basis for the content of the numerous claims in the method described. A comparison of the described fiber series A, B, C and D (Tables I-III) shows that the strength values of the fibers formed from a polymer with a broad chain distribution decrease with delayed quenching. It is noteworthy that the dispersion values of the polymers in the test series B, C and D decrease from the initial values with different sizes, exactly at the beginning of the oxidation (even with non-delayed quenching), to a final value with practically the same size, from where they do not continue change as the oxidation increases and the melt index increases. A statistical evaluation of the molecular weight distribution does not support the assumption in the patent that short molecular chains accumulate in the filament surface. It should be noted that the description does not specify the diameter of the spinneret, the quantity and speed of the quenching gases, nor the length of the quenching zone. The description also does not contain any information regarding the fiber drawing ratio, which is important with regard to the thermal connection strength. The following can be said about the fabrics made from the fibers of the test series (Table IV):

• - The indication of the transverse strength values of the substance without the specification of longitudinal or average strengths says nothing about the thermal connection of the fabric and the true fabric strength values, since the cross strengths can be changed within a range of the results given in the description by simply adjusting the carding.
• - In the results table, the material strengths are only given for two temperatures (which are not precisely defined), which is insufficient. It is generally known that the strength values of a heat-bonded material run through a maximum as a function of the connection temperature.
• - The weight differences of the fabric samples in the table are too large to make the necessary comparison. On the basis of the stated material strengths, however, it can be concluded that there is no significant improvement due to the slow quenching of the fiber filament or the broadening of the molecular weight distribution of the polymer fed.

In the process according to patent application FI 943072/230694, peripherally oxidized fibers with a sheath-core structure for fabrics with high transverse strength properties are produced in combination with uniform quality and flexibility. In this process, different types of spinneret structures are used to carry out the process. The method is used in particular in connection with short spinning systems. In the process, the polymer composition (including polypropylene: MFI = 0.5-40, M _w / M _n ≥ 4.5) is heated (e.g. inductively) in the spinneret or in the immediate vicinity (e.g. using a electrically heated, provided with an opening, which is arranged directly above the nozzle), so that the composition is partially degraded. The partially degraded polymer composition is extruded to form molten filaments. The melted filaments are immediately quenched in an oxidizing atmosphere (oxygen, ozone, air) in order to subject them to at least surface chain degradation. In the description and the patent claims it is stated that material materials can be produced from the fibers produced by this method (23.9 g / m ² , web speed 76.2 m / min), the transverse strength of which is at least 12.6 N / 50 mm ,

• – Es fehlen Angaben hinsichtlich der Fasermaße, Festigkeitswerte, Struktur, Kristallinitätsgrad, Kettenorientierung, Periodenwerte und anderer Faktoren, durch die die Wärmeverbindung beeinflußt wird.
• – Die Angabe der minimalen Querfestigkeit des Stoffes bedeutet keine Angabe der Stoff-Festigkeit, da die entsprechenden Längsfestigkeiten und Dehnungen nicht angegeben sind. Bei Verwendung herkömmlicher Polypropylenfasern können die erwähnten Querfestigkeiten nur durch Regelung der Kardierung erreicht werden.
• – Der bei dem Verfahren angewandt Mikrofusionsprozeß ist nicht ausreichend, um die Wärmefestigkeitseigenschaften der Fasern oder Faservliese nachzuweisen, noch sind es die Festigkeitswerte der hergestellten Stoffe, da kein Zusammenhang zwischen dem erwähnten Verfahren und den Ergebnissen der direkten Festigkeitsmessungen angegeben ist. Das Fehlen dieser und einiger andere relevanter Angaben verhindert nahezu völlig einen Ver gleich des Oxidationsverfahrens nach der Patentanmeldung mit anderen bekannten Verfahren.

It can be stated that the description of the method does not support the present broad claims, due to the lack of many relevant data. The following can be said about the ambiguities and shortcomings of the description:

• - There is no information regarding the fiber dimensions, strength values, structure, degree of crystallinity, chain orientation, period values and other factors by which the thermal connection is influenced.
• - The specification of the minimum transverse strength of the material means no specification of the material strength, since the corresponding longitudinal strengths and strains are not specified. When using conventional polypropylene fibers, the mentioned transverse strengths can only be achieved by regulating the carding.
• - The microfusion process used in the process is not sufficient to demonstrate the heat resistance properties of the fibers or non-woven fabrics, nor is it the strength values of the materials produced, since there is no connection between the method mentioned and the results of the direct strength measurements. The lack of this and some other relevant information almost completely prevents a comparison of the oxidation process after the patent application with other known processes.

By means of the method according to the patent application FI 942889/160694 / 20 / there is a thermal connection of polyolefin fibers, which in particular for the production of nonwovens by means of heated Rollers are suitable. The process is based on the observation that a Enlargement of the Diameter of the nozzle channel in the injection mold of the extruder to a value ≥ 0.5 mm (0.5-2.0 mm) a significant improvement in the thermal connection properties of the product fibers. After the description is the procedure for the production of staple fibers as well as for spun joining processes suitable. If a winding area in the manufacture of staple fibers from 30-500 m / min is used in spinning, there is a suitable distance for the Melt filaments in the range of 10-350 mm. According to the description the spinning temperature is in the range of 240-310 ° C and the subsequent drawing (<100 ° C) in the draw ratio range from 1.1 to 3.5. The process is based on polyolefins in the melt index range from MFI = 5-25 applied.

The description contains a large number of examples for the production of staple fibers and for spunbonding under the conditions: nozzle channel diameter: 0.4-0.9 mm; Spinning temperature: 280 to 310 ° C; Cooling distance: 5-30 mm and winding speed 60 to 2400 m / min. The description also discloses a new method for measuring the thermal bonding properties of the fibers, which was used only in the examples, among others. The description shows no connection between the results obtained by the new measuring method and those of a conventional direct measuring method of tensile strength, elongation and toughness. It should be noted that the result obtained by the measurement method mentioned is ambiguous due to the connection of the nonwoven fabric with heated rollers with regard to the associated strong shear forces. As an example, it can be mentioned that the use of a draw ratio of 3.5 with mechanical drawing of a fiber according to claims 5 and 6 of the application, using a single tool method, a good heat bond value can be achieved with a fiber known to have extremely poor heat bond properties.

The one with a heat connection according to the description achieved results not more conventional with the prior art of heat bonding Nonwovens are compared.

It can also be mentioned that the in the processes described in US Pat. No. 5,281,378 and FI 942889 can be derived from the melt spinning models (e.g. Kase & Matsuo, / 1 /) and both have the same scientific basis.

Given the limited number of reviews Publications, which deals with the oxidative surface degradation of polymer melt spun filaments is not an all-inclusive process or a rule model for a short spinning system been found.

The following are examples some operating principles regarding the melt spinning process, in which an oxidative degradation is applied is described in detail.

example 1

In example 1, the base for the Invention and essential observations based thereon disclosed more detailed examples.

Subexample 1.1

Subexample 1.1 discloses the Manufacturing facility and its operation for fibers and fabrics that the Examples of the description and the invention correspond to and Development of the process were used.

When producing the fiber sample series to describe the new method according to the invention, the so-called Short spinning process applied and appropriate devices used.

The spinning and drawing test series were generally manufactured with test devices that differ from Production devices only in the number of spinning units, however not differentiated in size. The Test devices were better equipped in terms of measurement technology than the production devices. The nozzle diameter (mm) and number of nozzles in the spinneret plates, the for the test series were used: 0.25 and 0.30 / 30500, 0.40 / 22862 and 0.70 / 12132.

The capacity (g / min) of the spinning device was P = 45.88 × ρ × n _r , where ρ (= F (T)) the polymer density (g / cm ³ ) and n _r the speed of the polymer pump (min ⁻¹ ) is. For comparison (including the spinning ratio) of the hot and cold speeds (nozzle and Godets), the hot speed is calculated as the cold speed (cm / min), ie: V s = 45.88 × ρ (T) × n r / ρ (298) × N × A s / 14 / where ρ (T) is the warm density (g / cm ³ ), N is the number of nozzles and A _{s is} the cross-sectional area of the nozzle (cm ² ). The warm density of the polymer is given by the equation ρ ^-1 = 8, 1383 × 10 ^-4 v + 1.1525, and the cold density is ρ (298) = 0.903.

The parts of the short spinning device used in the tests 1 , were: extruders 1 , Melter 2 , 1-godet 3, Ziehofen 4 , 2-godet 5, 2-finishing (avivage) 6, crimping device 7 , Stabilization and drying oven 8th and staple cutters 9 ,

The deformation changes of the spun filament in the molten state after the nozzle under various spinning conditions were photographed with a CCD camera and the information was recorded on a magnetic tape. The analysis of the recording and measurements was carried out according to image analysis methods. A portion of the samples used to analyze details of the invention were made under controlled conditions on a Haake Rheocord-90, which was also equipped with an oven with a mechanical puller. The fiber structure was determined using X-ray WAXS and SAXS processes (Philips PW 1730/10, PW 1710/00, Kratky-KCSAS), AFM processes (TME rasterscope 200 ) and electron microscope (Cambridge 360 and Cameca Camevax Microbeam). The conventional device used for the production of the nonwovens and connection (consolidation) corresponds to that in 2 shown. The parts of the device were: opener 1 , Fine opener 2 , Storage silo 3 , Feeder 4 , Carding device 5 , Consolidation rollers 6 and winding device 7 ,

All devices shown in the drawing correspond to those used in series production. The production and connection speed (solidification speed) of the fiber web on the connection section was adjustable in the range of 25-100 m / min. The upper roller was provided with crescent or round protrusions, and the temperature and pressure were adjustable on the smooth lower roller of the connector. The diameter of the connecting roller corresponded to that series production, but its width was only 2.2 m.

During the investigations of the fiber connection mechanism, so-called fiber loop connection and direct connection tests were carried out with a mechanical and dynamic-mechanical thermal analyzer (Mettler 3000 / TMA40 and Seiko 5600 / DMS-200). The isothermal and dynamic oxidation evaporation tests were performed thermogravimetrically (Mettler 3000 / T650). The relative positions of the quench, oxidation and spinnerets of the melt spinning device used in the tests are shown in 3 shown. The position of the quenching nozzle was chosen based on the best spinning result. The angle between the center plane of the quench nozzle ( 1 ) and the spinneret surface was about 24 ± 1 °. The distance of the longer center line of the rectangular nozzle opening from the spinneret plane was 42 ± 2 mm and their distance in the direction of the angle of the nozzle from the central plane of the cable bundle ( 6 ) was 49 ± 2 mm, the diameter of the spinneret 0.70 mm. With a spinneret diameter of 0.25 mm, the values for the distance were only 0-10 mm smaller than those mentioned above. The opening width of the quenching nozzle was kept constant during the investigations, ie 11.2 × 478 mm. The positions of the oxidation nozzle ( 2 ) were a, b and c in the experiments ( 3 ). The directional angles, corresponding to the nozzle positions, were 7.5 ± 0.5 °, 17.5 ± 0.5 ° and 2 ± 1 °, the distances in the nozzle direction 62 ± 5, 64 ± 5 and 32 ± 5 mm and in the direction the height (measured from the longer center line of the rectangular nozzle opening) 27.5 ± 3, 27.5 ± 3 and 1 ± 2 mm. The opening width of the oxidation nozzle was 0.6 mm × 640 mm. Targeted oxidation from the nozzle position c with small nozzle spacings and high gas velocities resulted in a decrease in the surface temperature of the spinneret plate and an aggregate formation on the surface of the nozzle plate. For this reason, especially with small nozzle diameters (0.30 mm), the nozzle was electrically heated in order to keep its temperature at the same value as the spinning melt. The electric heater included the arrangement of an adjustable resistor ( 5 ) in a groove of the spinneret. The resistance pack ( 4 Units) had a size of 3.3 mm × 485 mm and a line of 270 W.

Subexample 1.2

In sub-example 1.2 dynamic deformation upon quenching a molten polymer filament examined that from the spinneret of a spinning system used in series production emerges.

Applying the right amount of oxygen on the surface of a filament in the molten state at the right temperature and is in the right place with a procedure based on the thermal oxidative degradation of the filament surface layer based, essential. With a view to generating a suitable one Concentration of oxygen in the surface, its diffusion transport and its regulation it is important to size the most suitable for oxygen transport surface of the filament in the molten state and to know the changes therein. The deformations are found in the present short spinning process because of the short quenching distance. To check the interface changes was the deformation of the molten spun filament by means of a Videoka mera depending from the distance from the nozzle surface in the direction measured on the filament axis.

Table 1 contains the spinning conditions of samples used in a series to measure the deformation of the molten filament and the corresponding results calculated from the filament profile are in 4 shown. In the measurements, the changes in the filament cross-section and the jacket surfaces (A (y) and A _v (y)), the temperature (ϑ (y)) and the spinning delay time (T (y)) as a function of the distance (y) from calculated in the direction of the filament axis.

It can be concluded that the in Table 2 and in 4 the results of the measurements given correspond to the results of the Kase & Matsuo / 1 / spinning model, to which reference has already been made. From the measurement results for the melt filaments it can be concluded that - as with the model / 1 / - an increase in the winding speed (v ₁ ), the spinning temperature (ϑ), the nozzle diameter (D _s ) and the nozzle capacity (P) (the others Conditions remained unchanged) the functions A (y) and ϑ (y) in the direction of an increase on the y-axis and, inter alia, an increase in the speed (V _i ) of the quenching air in the direction of a decrease on the y-axis (measured from the nozzle surface off, y = 0). The change in the surface area A _v (y) of the spinning element is opposite to the changes in A (y) and ϑ (y). A comparison shows that the spinning model / 1 / simulates a Langspinnsy stem, while the subject of the comparison is a short spinning system. As an example, the values of the deformation change of filament No. 1 of the model and filament No. 319 of the 4 specified in the area of filament strengthening temperatures: 10 ³ · P cm ³ : 8.185 (No. 1) = 10.2 × 0.8040 (No. 319); y mm: 200 = 31.7 x 6.3; 10 ² * A _v, cm ^2: 105.2 = 23.0 × 4.58 and τ, ms: 945 = 1.71 × 552nd

The following table shows some comparative values from the filament profile measurements of the 4 specified in the filament strengthening range (ϑ ~ 115 ° C, A (y) standardized). The given in parentheses Values are the filament values that correspond to the distance y = 0.6.

As the table shows, there is one Enlargement of the Nozzle opening width (No. 3 to No. 319) a significant slowdown in the cooling effect and the dilution of the filament, which is why during the difference in the melt deformation increases, particularly in the jacket surfaces, so he significantly larger than is the difference between the nozzle capacities (The production capacities of the samples are the same, but the nozzle capacities of different sizes). In in this case the total delay time of the filament deformation also increases significantly. An enlargement of the Nozzle opening width affected therefore very advantageous the oxygen transport and a cheap implementation the oxidative degradation in the filament.

The force balance equation ( 2 ) of the melt spinning equations had the form δv / δy = F / Aβ, ie the rate of deformation is directly proportional to the line tension and inversely proportional to the drawing viscosity of the polymer melt. The equilibrium equations also result in the dependency F βv ⁿ _y / ρc _p , ie the tensile force exerted on the filament is directly proportional to the drawing viscosity and the quenching air velocity. The dependency dA / dy = v ⁿ _y A / c _p ρ ρ FA / βG also results from the equations, ie the gradient (the slope) of the function A (y) is directly proportional to the line tension and inversely proportional to the nozzle capacity (G = ρ Av) and the drawing viscosity (furthermore, the greater the activation energy of the drawing viscosity (β = K exp (E / RT)), the closer A (y) is to Y = 0 and the faster it becomes Filament thinner below the spinneret). Using the equations it is also possible to show that the birefringence and at the same time the polymer chain orientation are directly proportional (at the filament attachment point) to the line tension, ie

Δn = (F / A) (K / T). According to the tables, the nozzle capacity is constant in Sample Nos. 14-18, while the amount and speed of the quenching air change. For samples Nos. 14-16, the line tension decreases as the quench air velocity decreases, so that the strain rate (δv / δy) and the gradient dA / dy decrease ( 4 ). A separate oxygen nozzle was used for sample No. 18, so that the oxygen dissolved in the filament increased the melt viscosity and accordingly also the line tension force, the deformation rate, the gradient dA / dy and also the polymer chain orientation (Table 2, 4 ).

Below is the diffusional oxygen transport through the molten filament surface, which is the result of spinning is formed and is subject to deformation as a function of time, briefly considered. The lack of sufficiently accurate oxygen solubility and - diffusion data in the molten polymer prevents quantitative measurement of the Diffusion. For diffusional oxygen transport, the amount of per unit of time (dm / dt) transported material directly proportional the diffusion constant (D), to the surface (A), which is perpendicular to the Diffusion current stands, and to the concentration gradient (dc / dx) in the direction of the diffusion current, d. H. according to Fick's law / 21 / dm / dt = D × A × (dc / dx) / 15 / With melt spinning, therefore, the surface of the jacket is above the Deformation zone is formed, which differs from the nozzle temperature expands to the solidification temperature, suitable for diffusion.

Table 2 and 4 show the surface areas of the filaments as a function of time, temperature and distance from the nozzle. In this context, the values of the filament surface and the corresponding deformation time, which result at the distance y = 0.6 and at the solidification point, are compared with one another using the table and the figure. The filaments used for the comparison correspond to the nozzle diameter values 0.70 mm (No. 319) and 0.30 mm (No. 14). The 0.30 mm sample (No. 18) is included in the comparison to establish the influence of oxygen. The following values result for the product N × A _v × τ (cm ² · s), which is proportional to the value of the oxygen transport at the distances mentioned: N × A _v × τ / No .: 3.426 / 319-0.327 / 14-0.742 / 18 and (115 ° C) 30.69 / 319-0.436 / 14-1.615 / 18.

The results show that that at the investigation conditions the influence of oxygen transport on the difference in the deformation surfaces of the filaments that the huge and the small nozzle diameter correspond, is very large. The influence of Oxygen to the diffusion system as a result of the change the deformation surface can increase so that he important is.

It should also be noted that the difference in the oxygen diffusion constants, which correspond to the spinning and solidification temperatures, is about 1.5 to 2 De kaden. As a rough approximation, the value for the amorphous polypropylene phase at low temperature was chosen as the value of the diffusion constant (/ 5 /, Jellinek: D _o = 1.5, E = 8700 cal / mol), without correcting the orientation, the oxygen concentration, etc.

Based on the changes the size of the filament surface, deformation time and molecular chain orientation the results of sub-example 1,2 clearly show that the oxidation nozzle is immediate arranged next to the spinneret surface must become. To get the values of the oxygen concentration in the surface (the Solubility) and according to the concentration gradient (the force behind diffusion) the oxygen partial pressure in the oxidative gas phase should be like this high as possible his.

Subexample 1.3

The sub-example 1.3 concerns the Realization of an autogenous oxidation-degradation process Spinnfilamentoberfläche in the molten state and a corresponding control procedure by means of a series of experiments.

Based on the measurements on the spinning profile a molten filament (subexample 1.2) it is obvious that the Oxidation is aimed directly at the beginning of the largest filament deformation area must become, where the oxidation surface of the filament is the largest the spinning line tension (SLT) is the lowest, the temperature falls deeply the deformation delay time the longest is and the molecular chain orientation of the polymer after the nozzle is the least.

In the case of a short spinning system, the quenching distance of the filament from the nozzle is only 25 mm, ie it is very short in comparison to the 250-1500 mm of a long spinning system. Due to the very small processing space, the oxidation and quenching nozzles for the filament are separated from one another in the method according to the invention. In this process, the oxidation takes place as a targeted oxidation with a very narrow nozzle gap (0.60 mm × 460 mm) and a sufficiently high speed so that the oxidizing gas phase is able, if necessary, to allow the rear part of the quenching gas flow to penetrate into the filament space. The blowing process is based on the poor miscibility of the gases under the conditions mentioned / 22 /. The position of the oxidation nozzle in relation to the filament bundles and the spinneret surface must be carefully adjusted ( 3 ) so that the oxidation is successful.

Although the filament oxidation needed The amount of oxygen and therefore the small amount emerging from the nozzle, is enriched with oxygen during the oxidation and its adjustment if necessary Air used. An increase in the oxygen content in the blown air affected the steepness of the radial oxygen concentration gradient in Filament / 21 / and at the same time the degree and location of the molecular chain degradation. By Reduction of the lack of oxygen in the filament surface and outside Is it possible, the quality and influence the amount of evaporating oxygen compounds. With difficult spinning conditions (small nozzle diameter and production fine filaments) it is possible when spinning the available heat between the oxidation and endothermic evaporation reactions (the one Function of the oxygen concentration) for heating the surface areas effective use of the polymer filament.

Several spinning test series were carried out to improve the spin oxidation and its control system. The measurement results of these test series are in Table 3 and 5 specified.

In test series No. 309, the behavior of the control system according to the invention with regard to the operation of the quenching and oxidation nozzles was investigated. The initial molecular weights and melt index of the polymer used in the series of experiments were: M _w = 255000, M _n = 49250, D = 5.25 and MFI = 13.5. The temperatures of the extruder heating zones and the spinneret were 255-265-265-280-290-290 ° C and 295 ° C. The spinning melt temperature was 286 ° C. The delivery rate of the spinning pump was P = 42.78 dm ³ / h. The diameter of the spinneret was D _s = 0.70 mm, and the corresponding positions of the quenching and oxidation nozzles are in subexample 1.1 and in 3 specified. Sample numbers 7-16 in Table 2 correspond to position b of the oxidation nozzle and sample numbers 21-25 correspond to position a. The following control equations for the oxidation in relation to the velocities of the quenching air and oxygen were derived from the measurement results in Table 2: 309-b: MFI = 1.914 × V 02 - 2.427 × v i + 93.248 / 16 / 309-a: MFI = -0.165 × V 02 - 2.427 × v i + 93.248 / 17 /

The volume and the control speeds in Table 3 are not of the STP type, but correspond to the production conditions (ϑ = 24 ± 1 ° C, p = 1.0 bar). It was found that the simple control equation determined could be applied with sufficient accuracy if the so-called partial pressure velocity was used as the oxygen flow velocity, ie v ₀₂ = P ₀₂ x v, where v is the velocity of the oxygen-enriched air. The quenching gas velocities and corresponding spun thread tensions were approximately the same for samples Nos. 7-12 of the test series, while they differed considerably from one another for samples Nos. 13-16. The values calculated using the equation correspond almost exactly to the directly measured values for all samples. Out 3 of sub-example 1.1 it can be concluded that when the oxidation nozzle is in position a (samples: 309-21-25), the oxidation beam crosses most of the quenching beam. According to Table 2, the flow velocities of the oxidation jet do not exceed those of the quench jet, so that the control equation changes from the previous one to equation / 17 /. The slightly negative factor of the oxygen flow shows the cooling effect of the oxygen in the system.

The same test conditions were used in series No. 314 as in series No. 309, but the spinneret diameter D _{s was} only 0.25 mm. The oxidation nozzle was in position b. The determined oxidation function [MFI = 29.8 + 0.376 × v ₀₂ ] is in 5 been recorded as in 3 , shows an ineffective oxidation (corresponding to the spinning deformation) of the samples in the row. The initial, ie quench, oxidation of the samples was also quite low.

In test series No. 325 and 326, the spinneret diameter D ₂ = 0.30 mm. The oxidation nozzle was moved to position c ( 3 ), and it could be used either on one or both sides (test series No. 325 and No. 326). As the oxidation nozzle, which works very close to the spinneret surface, cools, the same small electrical resistances have been applied to the spinnerets to raise the surface temperature of the spinnerets to match the spinneret temperature and, at the same time, to increase the polymer surface area avoid. As a result of the nozzle and temperature corrections, the oxidation control system essentially corresponds to the result of test series No. 309, but the quenching oxidation is still very low ( 5 ). The oxidation equation for test series No. 325 has the form MFI = 1.914 × V 02 - 0.7363 BC i + 62.645 / 18 /

The application of a two or two sided oxidation nozzle improves the oxidation result. A reduction in the free opening of the oxidation nozzle elevated the flow velocities and accordingly the oxidative degradation, which in particular to be considered as a factor which reduces the oxidizing gas level when a bilateral Nozzle used becomes.

The main factors by which influence the degree of quenching oxidation and the degradation, are the temperature, the nozzle size and the corresponding spin deformation, the feed power, the oxygen content of the quenching gas, the molecular weight distribution, etc.

The use of oxygen-enriched air for quenching to increase degradation is economically unreasonable for the quantities required for a series production plant. In the spinning conditions used for test series No. 309, the total output corresponding to the nozzle plate being constant, the nozzle size had approximately the following influence on the melt index: D _s , mm / MFI: 0.25 / 27-0.30 / 30-0 , 40/35 to 0.70 / 41st Due to the high spinning draw ratio, the use of a nozzle with a large diameter leads to quality problems in the series production of fine fibers.

A high temperature of the spinning melt eases deterrent degradation, but its applicability depends on the rheological properties of the polymer and the quality requirements to the spun product. A high temperature also has a strong one thermal degradation in the extruder resulting in the mechanical Properties of the fiber weaken and also the effect of successfully performing peripheral degradation.

An economical series production high quality fine fibers may require a. one if possible low amount of oxidative air enriched with little oxygen is a small nozzle diameter and a low spinning temperature.

In order to further develop the control method according to the invention, tests were carried out to modify the polymers supplied in order to meet the requirements for peripheral filament oxidation in a short spinning system. At the beginning, however, very low and very high molecular weight polypropylene polymers were mixed, it being assumed that even at low nozzle speeds in the short spinning system, the short-chain polymer would accumulate in the surface area of the filament due to the large difference in viscosity. At the same time, the short-chain polymer would act as a plasticizer in the mixture, particularly during extrusion. In the case of a successful mix, one could Increasing the rate of degradation in the system, which would be caused by non-random molecular chain initiation, can be exploited. The temperature of the spinning melt could also be reduced, so that the degree of thermal degradation during the extrusion decreased and a well degraded fiber surface was achieved without a significant deterioration in the mechanical properties of the product fiber.

Experiment series No. 331 carried out an oxidation of a filament in the molten state in the form of a mixture of two polypropylene polymers with very different chain lengths. In the series of experiments using a one-sided oxidation nozzle in position c, the spinning temperature was 265 (270) ° C and the spinneret was 0.25-30500. The spin mixture contained 5 and 10 weight percent polymer with a melt index of 400 (No. 032) mixed with a polymer (No. 031) with a melt index of 4.4. In the results given in Table 2, the former mixture is designated with sample numbers 5–10 and the latter with sample numbers 1–3 (see also 5 and sub-example 1.4).

As a rule equation for the spin oxidation one obtains a function of the oxygen flow partial pressure speed (without considering the quenching speed) 5% No. 32: MFI = 1.293 BC 02 + 28.61 / 19 / 10% No. 32: MFI = 4.026 V 02 + 47.89 / 20 /

The results show that the existence Add 5% by weight of PP 32 to the degree of quench degradation not (compared to other values from test series with a smaller one Diameter) increased, that the The value of the quench degradation increases rapidly with a larger amount added (where the shear viscosity logarithms dependent on are largely linear in concentration). By suitable modification The spin polymers can be very favorable and desirable control values achieve if with small nozzle diameters and batch production feed capacities worked becomes.

Subexample 1.4

The changes are shown in sub-example 1.4 the polymer molecule distribution and investigated the melt indices used in peripheral oxidation of the filaments of the test series of subexample 1.3 in the molten Condition occur.

The results are shown in the table below GPC analysis (solvent TCB, 135 ° C and columns TS 9S & TS 10S) and melt index values (ASTM D 1238: 21.6 N / 230 ° C) of some in the molten state of oxidized spun filaments and of supplied polymers Test series No. 309 (and 331) from sub-example 1.3.

The following equations were determined to simulate the largely thermomechanical and at the same time slightly chemical degradation that occurs in the extrusion process in a normal air atmosphere in test series No. 309: M _n = 6.602 × 10 ⁴ × (MFI) ^−0.1126 and M _w / M _n = 7.727 x (MFI) ^-0.1485 . The result obtained can be compared with the extrusion results, which were determined both in a protective gas and in an air atmosphere.

From the time-temperature functions that simulate the distribution results of the thermal degradation study by Chan & Balke / 6 / (under the delay time and melting temperature conditions corresponding to the series 309: τ = 5 min, ϑ = 286 ° C), one obtains for the unstabilized Polymer only slightly smaller molecular weight decreases than in test series No. 309 (Δ Mw and Δ Mn: C & B: 69485 and 8111, ie -29.8 and -13.7%; No. 309: 63000 and 5850, ie -24 , 7 and –11.9%). A conventional amount of an oxidant in the series 309 polymer (phosphite-phosphonite mixture + anti-acid agent: 0.2%) is not of great importance in reducing thermal degradation. The degradation results in the test series 309 with an extruder correspond to conventional multiple extrusion results in the presence of air, inter alia from the MWD-MFI measurements by H. Hinsken et al. / 7 /. The steepness of the functions lnM _w , lnM _n and ln (M _w / M _n ) / lnMFI, which simulate the measurement results, are almost the same in both test series.

The degree of chemical degradation by quenching air after the extruder depends on the spinning conditions (sub-example 1.3). With the spinning conditions used in the area examined, this degree is low in comparison to the thermal and mechanical degradation. The use of an oxidation nozzle (a side nozzle) according to the new method results in significant changes in the slope of the functions lnM / lnMFI, which simulate the degradation effects, compared to the functions mentioned above, which result from the measured values from Hinsken / 7 /. The values of the InM _{w of} the samples in test series No. 309 decrease less, and the values of the InM _n are steeper depending on the degree of oxidation than the above-mentioned measured values. The most significant change, however, takes place in the dispersion values, which increase instead of decrease, as in conventional oxidative degradation. In the case of oxidation with a lateral nozzle in test series No. 309, the following equations were determined, which simulate the number average molecular weight and the dispersion results: M n = 2.159 x 10 5 × (MFI) -0.420 and M w / M n = 9.925 × (MFI) +0.411 ; (/ 7 /: M n = 7.351 x 10 4 × (MFI) -0.103 and M w / M n = 6,700 × (MFI) -0, 1635 ). / 21 /

The expansion of the polymer molecular weight distribution as a result of the oxidation is not common. However, it can be based on MWD equilibrium calculations show that at a Non-random degradation, by what degradation after surface oxidation it is also the dispersion of the total distribution in the filament with increasing oxidation increases (the dispersion values of the parts decrease simultaneously in the radial direction of the filament). It can mentioned be that a similar Decrease in dispersion values in the case of surface degradation in the solid state could be determined (S. Girois et al. / 10 /, J.E. Brown et al. / 9 /).

In the examples given in the specification of US Pat. No. 5,281,378 / 17 / which relate to peripheral oxidation, only the M _w / M _n and MFI values for the oxidized samples are given (the M _n and M _w values are missing). In the test series B, C and D, which fall within the scope of protection of the patent claims, the initial values of the ratio M _w / M _{n were} 7.75, 6.59 and 7.14. The ratios M _w / M _n in the test area have almost the same value after oxidation (5.3 ± 0.3) and are independent of the MFI values (or decrease slightly as the melt index increases). The test series A behaves similarly, but the start and end values are: M _w / M _n = 5.35 and 4.49 ± 0.08. The distribution values given in the method were abnormal and do not support the occurrence of surface layer degradation.

It can also be mentioned that, as at is known to expand the molecular weight distribution according to the new Oxidation degradation process is a change that the thermal connection of Product fibers relieved.

6 represents a differential molecular weight graph according to the distributions given in the table above. It shows that the distributions are shifted to lower molecular weights due to the oxidation. On the basis of the distribution graph, however, it is not possible to evaluate the changes in the values of M _n and M _w / M _n during the oxidation, since in particular the influence of the changes in the values of M _n on the overall distribution is small.

7 shows an AFM image of a cross section of an etched (CrO ₃ + H ₂ SO ₄ ) filament sample. From the picture it can be seen that a radial surface layer of the fiber is dissolved, which also shows the weakening of the structure due to the oxidation of the filament surface layer and the change in the molecular weight distribution.

8th shows a BSE image of a cross section of an oxidized filament sample. The picture shows the lighter diffusion surface (depleted zone) of the surface layer caused by the oxidation compared to the internal structure of the filament. The surface layers of the sample are not able to withstand the bombardment of the electron gun sufficiently to carry out a thread analysis (devices: SEM, 360 Cambridge and EPMA, Cameca-camevax microbeam).

Subexample 1.5

In sub-example 1.5 the thermal connection of staple fibers from peripherally oxidized polypropylene filaments in the melted state examined, which is produced according to the invention were.

The basics of the thermal connection of a nonwoven fiber web made of synthetic fibers is described in detail in the patent application FI 961252 / 18.03.96 ( EP 0 799 922 ) disclosed.

The constant terms in the fabric tensile strength and elongation equations, which simulate the test results fairly accurately, are given in Table 4. The logarithmic graphs of the equations, which correspond to the tensile stress values of the examined substances, are in 9 shown. The numbers 1 - 7 and 12 Fibers corresponding to the table and figure are made by oxidation to different degrees of degradation and processing of the same starting polymer. The numbers 8th . 9 . 10 and 11 corresponding substances are used for comparison. Fiber No. 11 is a fiber made in the conventional way by short spinning. Fibers Nos. 8, 9 and 10 are imported sheath-core fibers. These fibers have been made by long spinning and their detailed manufacturing conditions are not known. The properties of the test fibers according to Table 4 are summarized in Table 6.

From the theoretical maximum values of the material strength according to Table 4 and the 9 it can be concluded that if the peripheral degree of oxidation increases (the MFI values increase and the M _w and M _n values decrease: sub-example 1.4), the strength functions of the substances are shifted towards low connection temperatures. The values (E) for the compound activation energies are within the limits of the measurement accuracy with the same size of the fibers produced from the same initial polymer. The tensile strength and elongation (σ _II , ∈ _II ) connection equations at high connection temperature of nonwovens made of the fibers seem to combine and form an envelope of maximum strength ( 9 : No. 00 and Equations No. 1-7, 12). The connection of the equations for the strength values in the direction perpendicular to the carding direction (σ _⊥ , ∈ _⊥ ) is not exact, which can be a consequence of the fact that the measured values are further apart than in the previous case.

The envelope clearly shows that the fabric strength values increase as the connection temperature decreases, the degree of degradation the fiber surface layer increases. The improvement in connection can result from an increase the amount of surface melt the fiber, the easier relaxation of the pulling direction with decreasing chain length (causing the orientation-related shrinkage required for the connection harmful is decreasing), the improvement of the melt-strength contact, etc. is derived become. It can also be assumed that the use of a mechanical Drawing process in the solid state after spinning to increase the Fiber strength also for oberflächendegradierte Fibers an accurate heat treatment requires.

From the values in Table 4 it can be concluded that the difference in the maximum strengths of the substances corresponding to fiber samples No. 1 and No. 5 is 28.3% (σ _II ) and accordingly 175.7% (∈ _II ) corresponds. The increase in tensile strength due to the oxidative degradation between the samples mentioned is therefore moderate, while the increase in elongation is considerable. The tensile strength ratio of the fabrics from the same test series has the shape σ II / ∈ II = [MFI / (MFI) 0 ] -0.7 94 × 3.235 × 10 6 × exp [-12380 / RT] / 22 /

In the test series, an increase in the melt index ratio and the connection temperature therefore has a decreasing influence on the ratio σ _II / ∈ _II , the influence of the change in the melt index ratio being greater than the temperature influence.

As far as the elongation and tensile strength ratios are concerned, it can be concluded from the test _results that the elongation _ratio ∈ _⊥ / ∈ _II decreases slightly in the test series mentioned and accordingly the tensile strength _ratio σ _⊥ / σ _II remains constant or increases slightly if the MFI values increase.

It can be mentioned that the ratios σ _II / ∈ _II for the fabrics corresponding to the comparative fibers No. 10 and No. 11 accordingly have the following form: σ II / ∈ II = 2.443 × 10 7 × exp [-13780 / RT] and σ II / ∈ II = 0.808 / 23 / (ie e.g. T = 433 ° K, (σ _II / ∈ _II ) / no: 1.04 / 1, 2.70 / 10 and 0.81 / 11).

It can generally be concluded from the heat connection results for the nonwovens that the tensile strength and elongation results which can be achieved with the fabrics are very polymer-specific. The increase in tensile strength due to the oxidative surface degradation of the fibers is quite limited (both by the polymer properties and the textile properties of the fibers). The regulation of the material expansion by surface degradation is possible within fairly broad limits. By Changing the polymer quality (M _w , MWD, plasticizers and other adjuvants and additives) is an application system with its control ranges analogous to that described for the influence of fiber surface degradation, but available according to the various strength values.

Subexample 1.6

In sub-example 1.6 this is Behavior of some peripheral according to the inventive method Oxidized product fibers are examined if they are oxidizing Evaporation and loop connection are exposed. The goal is, possible Determine kinematic differences in fibers that are considered melted Filaments are oxidized as a result and. a. of changes of the molecular weight.

Oxidizing evaporation follows a first order reaction kinetics, ie the equation that simulates the evaporation effect is: 1 - α = exp (–k × t) / 24 / where α is the vaporized fraction by weight and the reaction rate constant (K min ^-1 ) has the form: K = k 0 × exp [-E 0 / RT] / 25 /

Table 5 contains constants the reaction rate equations for the oxidation evaporation some peripherally oxidized fibers (and the starting polymer) isothermal evaporation. According to the table is the activation energy for the entire process constant (within the measuring accuracy limits), in both polymer and fiber evaporation. From the results it can be seen that the decrease in the rate of evaporation between the starting polymer and the peripherally oxidized samples is significant. Nevertheless, the differences between the oxidized Filament samples quite small, although the speed of these too decreases with increasing melt index.

The change in the rate of oxidative evaporation as a function of the change in the melt index takes the form: K = 2.195 x 10 7 × [MFI / (MFI) 0 ] -0.172 × exp [–22393 / RT] / 26 /

For comparison, the equation constants of the oxidative evaporation of a polymer with a melt index of MFI = 30 are given in Table 6, using both air and oxygen oxidation (No. 0-1 and 0-2). The molecular weights of the compared polymers (0-0 and 0-1) were very different and were (before oxidation): M _w -M _n -D: 254000-49700-5.1 and 193399-34930-5.53. According to the table, the activation energy values of polymers 0-0 and 0-1 for oxidative evaporation are of the same size (within the measuring accuracy limits). When oxidizing with oxygen, the evaporation process is only four times faster than when oxidizing with air (with different polymers there were differences in the evaporation rate values between air and oxygen oxidation up to twelve times). After the incubation period, the mechanism of the oxidation-evaporation process is similar for all samples. The oxidation of the surface area of the molten filament is so moderate that its influence on the oxidative evaporation in the system under investigation is rather small. It can be mentioned that the kinetic equation for the oxidative evaporation of the comparative polymer, especially at high α values, is the Avrami kinetic equation (1 - α = [exp - (kt) ⁿ ]), which applies to a small time exponent (n = 1.20), corresponded better than the pure form of first order.

The equation for the incubation time in the oxidative evaporation of both the starting polymer and the fiber rows oxidized on the surface was t 0 , min = 1.584 × exp [8163 / RT] / 27 /

Hence, also in the incubation period a surface effect of peripheral oxidation can be seen. The incubation period is essentially a function of the antioxidant and stabilizing agents in the polymer (i.e. a substantial part of the stabilizer content of the polymer is still due to the extremely short delay time present in peripheral oxidation).

The incubation times for the oxidative evaporation of the comparison polymer in the air and oxygen oxidation were accordingly: t 0 , min 7, 112 x 10 -5 × exp [12149 / RT] / 28 / t 0 , min 1.755 × 10 -2 × exp [5450 / RT] / 29 /

Oxygen oxidation is reduced hence the temperature dependence the incubation period and shortens the Incubation times.

Also, from the results the oxidative evaporation can be concluded that the kinetics the peripheral oxidation of the molten filament polymer specific is and not just by the molecular weight distribution, but is also influenced by the polymer additive content.

The influence of nitrogen and carbon dioxide-containing gas phases on the "oxygen-free" evaporation of polypropylene is investigated using a dynamic series of thermogravimetric measurements. The series of experiments also shows the influence of bound oxygen, which is contained in combustion gases from fossil fuels, on the oxygen-free evaporation in the filament quenching stage. The molecular weights of the two experiments using conventional spin polymers were: M _w = 206000, M _n = 33450 and D = 6.15.

The results of the dynamic measurements are not exact, but a comparison of the results shows in qualitative Way the direction of the reactions. When comparing, the results are extrapolated in terms of temperature. This is a consequence the increase in the rate of evaporation as a result of the increase the degree of oxidation of the carrier gas phase, which ensures the optimal temperatures for evaporation at the different Test series fall into different temperature zones in the range of 250-500 ° C.

The equation simulating the change in the vaporized fraction (α) as a function of temperature (dT / dt = 20 ° C / min) has the form α = a × T 2 × exp (-E / RT).

The equation constants a and E (cal / mol), the different compositions of the carrier gas phase match are: N _2: 3.058 x 10 ^4/35499, CO _2: 5,317 / 22072, 2102 + 79N _2: 1.904 x 10 ^-1 / 15434 and 4902 + 51N _2: 8.352 x 10 ^-1 / 16148. Compared to the evaporation values for nitrogen, the following comparative series result according to the temperatures of 300 and 390 ° C: 490 ₂ - 210 ₂ - CO ₂ - N ₂ : 658 - 281 - 23 - 1 and 66 - 26 - 5 - 1.

The result therefore shows that the quenching of the molten filaments with combustion gases (CO ₂ + N ₂ ), in comparison with oxidative evaporation values, almost corresponds to the values for non-oxidizing evaporation.

Table 5 contains results of loop connection tests (including FI application no. 961252/180396: page 29, line 20 to page 30, line 9 ; EP No. 079922) at high (index 2) and low (index 1) temperature for some peripherally oxidized fibers.

The loop connection equation in terms of tensile strength has the form: σ, mN = c 1.2 × T 2 × exp [–E1.2 / RT] / 30 /

From the given in the table Results can be concluded that the connection strengths peripherally oxidized fibers as a function of time do not change much distinguish from each other regardless of different melt indices. This could be a result of the application a low temperature rise rate (10 ° C / min) the experiments, whereby the short - chain partial melt, the is formed at low temperature, again before connection cures. This assumption is also supported by the position of the strength function supported which corresponds to the rather high connection temperature. The strength function a fast spinning fiber (8-735) used as a reference fiber is independent from their higher Molecular weight (12-309: 186000 - 5.2 and 8-735: 220000-5.5) for the lower one Connection temperature of the oxidized fibers positioned. Compared to conventional Fibers is also a joining area at high temperature the thermal connection peripherally oxidized fibers evident when the change in tensile strength in dependence the temperature is low, but the increase in elongation (%) and breaking energy (mN × mm) considerably is. This is a result of the better wettability and spreadability of the Link melt on the solid surfaces of the fiber body.

In the present description the applicability of the new control procedure for both a fiber as well as a substance. It must be taken into account that this very complicated control procedures for the manufacturing process of the fibers and nonwovens, which are to be produced from this, in multiple Way within the operating range specified by the Examples and the claims comprises will be changed can be.

Related publications

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Claims (24)

A method for controlling the oxidative degradation of the molecular chains in the surface areas of molten polymer filaments, which is applicable to a polyolefin, in particular a prolypropylene short spinning system for the production of filaments, in which the stabilized polymer is extruded and melt-spun and the shaped spun filaments are oxidized and quenched that - the oxidation of the molten spun filament is carried out as a targeted oxidation, in which an oxidizing gas is directed onto the filament bundle from an oxidation nozzle which is separate from the quenching nozzle, - under unchanged spinning conditions, an equation of the form MFI = c ₁ v ₀₂ - c ₂ v _i + c _{3 is used} as the control equation for the targeted oxidation to determine the level of the oxidative degradation, the MFI equation being the melt index value of the polymer, which is replaced by the value for the spinning melt viscosity which corresponds to a low shear rate, v _{02 is} the velocity of the oxidizing gas multiplied by the oxygen partial pressure, i.e. the partial pressure velocity, v _{i is} the velocity of the quenching gas, and c ₁ , c ₂ and c _{3 are} experimentally determined polymer- and process-specific constants , wherein the oxygen partial pressure velocity, in addition to controlling the molecular chain degradation of the polymer surface area of the filament, is also used to control the size of the dispersion of the molecular weight distribution. A method according to claim 1, characterized in that the Polyolefin is a short chain polyolefin of the same type of polymer, especially polypropylene, is added. A method according to claim 1 or 2, characterized in that that in addition to the conventional Regulation of the temperature and speed of the quenching gas phase the molecular chain degradation, the while the melted polymer filament is quenched by Regulation of the oxygen partial pressure of the quenching gas phase is regulated becomes. Method according to one of claims 1 to 3, characterized in that that the thermal molecular chain degradation of the molten polyolefin in the extruder by controlling the Melting temperature and the extrusion delay time is regulated, especially so that Polyolefin is extruded in a temperature range of 250-290 ° C and the delay time the spinning melt in the extruder and the channels is 5-15 minutes. A method according to any one of claims 1 to 4, characterized in that the melt index value of the polymer fed to the extruder at 1.5-15 located and the values of the molecular mass distributions in the range of M _w = 500,000 to 240,000, M _n = 65 000- 50,000 and D = 7.0 - 5.0. Method according to one of Claims 2 to 5, characterized in that the polypropylene fed to the extruder is a polypropylene with a melt index in the range from 350-800 and molecular weight distributions in each case in the range from M _w = 125,000-95,000, M _n = 35,000- 20,000 and D = 3.5-5.0 is added, the amount added being at most 15 percent by weight of the polymer fed. Method according to one of claims 1 to 6, characterized in that the molten filament is quenched under conditions in which the volume, the speed and the temperature of the quenching gas each in the range of 400 - 1100 nm ³ / h, 20-60 m / s and 25 ± 5 ° C and the amount of polymer fed is 20-40 kg / h per nozzle plate. Method according to one of claims 1 to 7, characterized in that the existence gas poor in air and free oxygen, for example a combustion gas mixture, is used as a quenching gas and the oxygen partial pressure in Range from 0.01-0.21 bar. Method according to one of claims 1 to 8, characterized in that the melt index and molecular mass values of the product filament after quenching are in the range of 25-50 and M _w = 185,000-200,000, M _n = 40,000-50,000. Method according to one of claims 1 to 9, characterized in that the amount, the speed, the temperature and the partial pressure of oxygen of the oxidizing gas that the oxidizing nozzle is 0.01-0.8 Nm ³ / h, 0.1-48 m / s, 25-60 ° C and 0.21-0.98 bar. Method according to one of claims 1 to 10, characterized in that the constant c ₁ for the oxygen partial pressure velocity is kept in the control equation in the range from c ₁ = (-0.2) - (+2.0). Method according to one of claims 1 to 11, characterized in that the quantity and speed of the quenching gas are controlled so that the tensile stress exerted on the melt filament at the solidification point is below a value of approximately 30 mN / m ² , so that, depending on the spinneret diameters (0.70 - 0.25 mm) with a nozzle plate capacity of 30–32 kg / h and a spinning melt temperature of 285–290 ° C the amount and speed (25 ° C) of the quenching gas 350–750 Nm ³ / h and 20–45 m / s and are relative to these values under other spinning conditions and the constant c _{2 of} the control equation changes in the range from c ₂ = 0–3. Method according to one of claims 1 to 12, characterized in that for the production of layers of the desired thickness on the surface of a spun filament with a very low molecular weight and a correspondingly very low melting point, the number average molecular weight of the filament polymer is reduced by at most 30% and its dispersion values at most 40%, compared to the previous values before the nozzle oxidation, by applying an oxygen partial pressure velocity in the oxidizing gas and at the same time a corresponding oxygen partial pressure in the range of 0.1-25 m / s and 40-100 vol% O ₂ and simultaneous prevention, by regulating the speed of the quenching air, an increase in the maximum values of the filament tension beyond 30 mN / m ² . Method according to one of claims 1 to 13, characterized in that that the oxidation nozzle for the Filaments in position α = 5-20 °, x = 60 ± 5 mm and y = 25 ± 5 mm is set, where a is the angle between the median plane of the oxidizing gas flow and the spinneret plane and x and y the distances of the center line the free opening area of the oxidation nozzle from the vertical center plane of the polymer jet (x) and the spinneret plane (y) are. Method according to one of claims 1 to 13, characterized in that that the oxidation nozzle for the Filaments in position α = 5-20 °, x = 60 ± 5 mm and y = 25 ± 5 mm is set, where a is the angle between the median plane of the oxidizing gas flow and the spinneret plane and x and y the distances of the center line the free opening area of the oxidation nozzle from the vertical center plane of the polymer jet (x) and the spinneret plane (y) are. Method according to one of claims 1 to 13 or 15, characterized characterized in that if with the oxidation nozzle in the position a = 2 ± 1 °, x = 32 ± 5 mm and y = 2 ± 1 mm in the immediate vicinity oxidized at the level of the spinneret surface the spinneret heated inside becomes. Device for regulating oxidative degradation of molecular chains in the surface areas of a melted polymer filament surface of polyolefin, in particular Polypropylene, in a filament manufacturing process, with a Melting device with spinnerets and means, in particular a quenching nozzle, for quenching the polymer filaments, characterized in that the Device for oxidizing the polymer filaments, in particular an oxidation nozzle, which is arranged separately from the quenching means. Apparatus according to claim 17, characterized in that the oxidation nozzle for the Filaments in position α = 5-20 °, x = 60 ± 5 mm and y = 25 ± 5 mm is set, where a is the angle between the median plane of the oxidizing gas flow and the spinneret plane and x and y the distances of the Center line of the free opening area of the oxidation nozzle from the vertical center plane of the polymer jet (x) and the spinneret plane (y) are. Apparatus according to claim 17, characterized in that the Filamentabschreckdüse in the position α = 25 ± 3 °, x = 50-75 mm and y = 40-50 mm is set, where a is the angle between the median plane of the Quenching gas flow and the spinneret level and x and y is the distances the center line of the free opening area of the quenching from the vertical center plane of the polymer stream (x) and the spinneret plane (y) are. Apparatus according to claim 17, characterized in that in the case of an oxidation in which the oxidation nozzle has the position α = 2 ± 1 °, x = 32 ± 5 mm, y = 2 ± 1 mm in the immediate vicinity of the plane of the spinneret takes up the surface, the spinneret is provided with an internal electric heater. Device according to one of claims 17 to 20, characterized in that that the Size of the free openings the quenching nozzle and the oxidation nozzle corresponding to (10-20) × 480 mm and (0.5-1.5) x 460 mm is, this means, that this relationship their surface areas Is 7-42. Application of the method according to one of claims 1 to 16 for regulating the temperatures and connection strengths in a method of thermal connection of fibers after the mentioned Processes have been made, especially the melting point and the melting amount of the partial melts, which from the filament surface at heat bonding were formed, as well as the quality characteristics of the Fabrics made of fibers. Process for regulating the thermal connection of core-sheath fibers which have been produced by degradation of the molecules in a filament surface layer on the basis of controlled autogenous oxidation of filaments spun in the molten state from polyolefin, in particular polypropylene, characterized in that a. the fibers to be hot-bonded are produced according to the control method according to one of claims 1 to 16, so that fibers with the desired surface layer structure and melted surfaces result, which are indicated by both the melt index and the degree of surface degradation, which are indicated by the molecular weight values, are determined and b. the heat connection is controlled using polymer-specific control equations that simulate the strength values of the product materials, the equations for tensile strength and elongation being as follows: σ (∈) = c 01 × [MFI / (MFI) 0 ] n ( o1 ) × T 2 × exp (-E 01 / RT) the common envelope equation after reaching the maximum strength values is the following: σ (∈) = c 02 × T 2 × exp (+ E 02 / RT) and c. the relationship between the tensile strength and the elongation of the product material is regulated by the following polymer-specific regulation equation for the connection: σ II / ∈ II = c 03 × [MFI / (MFI) O ] n ( o3 ) × exp (-E 03 / RT). A method according to claim 23, characterized in that, a. a fiber series is produced from a starting polymer with M _w = 255,000, M _n = 49,250, M _v = 209,000 and D = 5.15, in which the melt index ratio is 2 - 4.5, b. heat-bonded product materials (approx. 22 g / m ² ) can be produced from these fibers with the following factors in the control equations for joining in accordance with the strength values and their ratio (σ _II , σ _II / ∈ _II ): c ₀₁ = 5.442 × 10 ¹⁹ , n ₀₁ = 1.811, E ₀₁ = 47180; c ₀₂ = 2.377 x 10 ^-10 , E ₀₂ = 11920; c ₀₃ = 3.235 × 10 ⁶ , n ₀₃ = -0.794 and E ₀₃ 12390 , the control equations corresponding to the transverse strength values being formed from these corresponding parameters, and c. the substances mentioned have different maximum strength values if the following melt indices are used: MFI = 1.98 and 2.90; Δ∈ II = 105%; Δ∈ ⊥ = 73%; ΔT = 4.5 ° C MFI = 1.98 and 4.07; Δσ II = 8%; Δσ ⊥ = 39%; ΔT = 11.1 ° C.