Continuous fibers based on cellulose and / or cellulose derivatives, methods for manufacturing the same, and uses of the same

Abstract

The present invention relates to continuous fibers based on cellulose and / or cellulose derivatives, particularly continuous fibers based on cellulose and / or cellulose derivatives for the manufacture of flame-retardant textiles or carbon fibers. Cellulose and / or cellulose derivatives are present in the continuous fibers in a dehydrated form. The oxygen content is 29 to 39 weight%, the limiting oxygen index (LOI) is 25 to 40 (according to DIN EN ISO 6941; 2004-05), and the density is 1.3 to 1.45 g / cm³ (according to DIN 65569-1; 1992-10). The continuous fibers can be advantageously manufactured in such a way that the starting fibers are impregnated with an aqueous solution of a special salt that releases a dehydrating acid, particularly under thermal conditions, thereby inducing dehydration of the cellulose and / or cellulose derivatives in a subsequent thermal step. In particular, carbon fibers can be advantageously manufactured by the continuous fibers according to the present invention.

Description

Technology Field

[0001] The present invention relates to continuous fibers based on cellulose and / or cellulose derivatives, more specifically, continuous fibers based on cellulose and / or cellulose derivatives for producing flame-retardant textiles or carbon fibers, methods for producing the same, and advantageous uses thereof. Background Technology

[0002] For example, there are numerous continuous fibers based on polymers that include modified polyacrylonitrile in the form of an acrylonitrile / acrylamidine copolymer and, in certain cases, also represent precursor fibers for carbon fibers used in the manufacture of flame-retardant textiles. In most methods known to date, the extruded precursor fibers of carbon fibers must be converted to an infusible state. This requires an expensive and complex oxidative thermal stabilization step. This step is performed under oxygen or under a protective gas atmosphere, and such an atmosphere may include a gas mixture having various oxygen contents. The gas pressure used for oxidative thermal stabilization is, for example, 0.5 to 1 bar. Thermal stabilization is based on a final temperature of 180 to 300°C. The final temperature is set continuously or in steps in a manner of slow temperature increase.

[0003] This is a general procedure for the known precursor fibers described above. However, when fibers based on cellulose and / or cellulose derivatives are used to manufacture carbon fibers, the following major issues require consideration: One event in the conventional oxidative thermal stabilization of cellulose materials is the removal of water starting at 250°C, which triggers unwanted secondary reactions that reduce quality and carbon yield as a result of liquid, carbon-containing pyrolysis products during carbonization. The solutions used involve particularly slow methods or additional chemical reactions, which make such methods uneconomical and environmentally harmful. Furthermore, additional problems arise in the aforementioned stabilization of cellulose and also affect cellulose derivatives. These include excessive tar content in some of these stabilized fibers. The corresponding products are competitive only when thermal stabilization is optimally managed and can be industrially implemented. Furthermore, it is known that conventionally stabilized cellulose fibers have too low a LOI (Limiting Oxygen Index) (a parameter used to describe flame behavior, representing the minimum oxygen concentration of an oxygen-nitrogen mixture that continues to burn under each test condition) and inadequate strength for use as flame-retardant textiles, and the achievable carbonization yield is insufficient. Furthermore, the obtained stabilized cellulose fibers do not have an optimal elemental composition and, due to initial thermal decomposition, have the disadvantage of not being able to produce flame-retardant textiles or carbon fibers with particularly excellent service properties. The problem to be solved

[0004] Accordingly, the problem to be solved by the present invention is to propose a continuous fiber based on cellulose and / or cellulose derivatives that can be used to manufacture advantageous flame-retardant textiles with particularly improved quality and also carbon fibers. The present invention aims to optimize oxygen content, LOI, and density. The present invention aims to develop an advantageous carbon fiber that is excellent in terms of particularly good density, fiber strength, and elongation at break without adverse oxidative thermal stabilization.

[0005] Furthermore, the present invention aims to propose an advantageous method for manufacturing continuous fibers. The objective of the present invention is to produce competitive cellulose-based carbon fibers having quality that is not inferior to conventional carbon fibers based on oil-based polyacrylonitrile. Additionally, according to the method of the present invention, CO2 balance and energy costs are improved and / or lowered, and sustainability is increased. Furthermore, during manufacturing, toxic offgases such as hydrocyanic acid and nitrogen oxides are not generated. Additionally, the present invention aims to achieve improved flame retardancy. Other possible processes performed in air or atmosphere proceed very slowly, require additives, and, for example, do not achieve the qualities essential for cellulose fibers. A specific problem that the present invention aims to solve is the disadvantage that, due to the very high oxygen content within the continuous fiber, the continuous fiber becomes brittle and porous as a result of oxidation, and consequently cannot be processed through standard processes, for example, into flame-retardant textiles, and high-quality carbon fibers cannot be produced from such continuous fibers. means of solving the problem

[0006] The above-mentioned problem on which the present invention is based is achieved by a continuous fiber based on cellulose and / or a cellulose derivative, more specifically by said continuous fiber for producing flame-retardant textiles or carbon fibers, said continuous fiber in which the cellulose and / or a cellulose derivative exists in a dehydrated form, the oxygen content is 29 to 39 weight%, the limiting oxygen index LOI is 25 to 40 (according to DIN EN ISO 6941; 2004-05), and the density is 1.3 to 1.45 g / cm³ 3 It is characterized by being (according to DIN 65569-1; 1992-10). Specific details for implementing the invention

[0007] The degree of dehydration of the dehydrated cellulose or dehydrated cellulose derivative present in the continuous fiber of the present invention plays a clearly excellent role. In this regard, it is preferable that the degree of dehydration be at least 1.0, preferably at least 1.5, and particularly preferably at least 2.0. The continuous fiber of the present invention is more advantageous when the degree of dehydration is at least 2.5, and particularly 3.0. A specific advantage associated with the degree of dehydration is that the thermal stabilization of the fiber is achieved while maintaining service characteristics.

[0008] The present invention presented above is developed in a particularly advantageous manner when the oxygen content is 29 to 32 weight%, the limiting oxygen index LOI is 28 to 37 and / or the density is 1.35 to 1.45.

[0009] The present invention is characterized by the following additional advantageous properties: fiber strength of 8 to 30 cN / tex, more particularly 10 to 16 cN / tex (according to DIN EN ISO 5079; 1996-02), elongation at break of 12 to 25%, more particularly 10 to 16% (according to DIN EN ISO 5079; 1996-02), and / or linear density of 0.5 to 18 dtex, more particularly 1 to 8 dtex (according to DIN EN ISO 1973; 1995-12).

[0010] In practice, the starting material is cellulose and / or a cellulose derivative, which exists in a dehydrated form in the continuous fiber claimed according to the present invention. The original, undehydrated fiber of cellulose, more particularly regenerated cellulose and / or a cellulose derivative, is processed into a favorable continuous fiber by the method of the present invention described below.

[0011] With respect to cellulose fibers and / or recycled cellulose fibers used as starting materials, the following should be noted: Cellulose fibers are understood to be fibers composed mostly, more particularly, of 80 weight percent, preferably 90 weight percent, more particularly exceeding 98 weight percent of cellulose, and are particularly preferred to be composed entirely of cellulose. Such fibers may be fibers manufactured from cellulose starting materials by the latest technology, which may also be referred to as modified or synthetic cellulose fibers. A notable possible example is viscose fiber, which is manufactured by the viscose process. Such a process utilizes a spinning solution containing NMMO (N-methylmorpholine N-oxide) as a solvent. Particularly advantageous cellulose fibers are those obtained by using an ionic liquid as a solvent to obtain the spinning solution (see WO 2007 / 076979 in this regard). Particularly advantageous recycled cellulose fibers are those manufactured by the air gap spinning process. Tire cord yarn is particularly useful herein.

[0012] Further embodiments of the present invention that are particularly advantageous involve the use of cellulose derivatives for producing continuous fibers of the present invention, wherein the cellulose derivatives are likewise included in a dehydrated form. The continuous fibers containing dehydrated cellulose may be obtained from regenerated cellulose fibers or tire cord yarns, and the continuous fibers containing dehydrated cellulose derivatives may be obtained from continuous fibers of esters or ethers of cellulose. In this invention, cellulose acetate, cellulose propionate, cellulose butyrate, and also mixed esters thereof are particularly considered. This means that in each case, fibers of cellulose acetate, cellulose propionate, cellulose butyrate, and mixed esters thereof may be used in individual fibers, but may also exist in a blended form in yarns. Further advantageous cellulose derivatives may be designated as follows: cellulose formate, cellulose carbamate, and / or cellulose allofanate.

[0013] The continuous fibers of the present invention described above can be advantageously used in the manufacture of flame-retardant textiles. In this regard, the term "textile" should be interpreted broadly. Accordingly, this includes woven fabrics, knitted fabrics, and nonwoven fabrics, etc. The specific characteristics of the continuous fibers of the present invention in the form of textiles provide an opportunity for advantageous use in fire-resistant workwear and fire-resistant leisure wear, for example, as fire-resistant textile materials for industrial use, more particularly in the automotive sector, and for use in filtration or insulation, and also as fire-resistant textile materials in the construction sector.

[0014] The continuous fibers of the present invention can be used to produce carbon fibers by carbonization, optionally by subsequent graphitization, with equivalent advantages. In this regard, it can be noted that the carbon fibers of the present invention, more particularly carbon fibers produced from the continuous fibers of the present invention described above, have the following advantageous physical values: 1.55 to 1.75 g / cm³ 3 , more particularly 1.6 to 1.7 [g / cm² 3 Density of ] (according to DIN 65569-1; 1992-10), fiber strength of 2.0 to 5 GPa, more particularly 2.5 to 4 (according to DIN EN ISO 5079; 1996-02), and elongation at break of 2 to 5%, more particularly 2.5 to 3.5% (according to DIN EN ISO 5079; 1996-02).

[0015] Accordingly, the continuous fiber of the present invention can be advantageously carbonized. This is preferably carried out by heating the continuous fiber under a shielding gas in a temperature range of 600°C to 2400°C, more particularly 1000°C to 2400°C, preferably 1200°C to 1600°C. Heating occurs, particularly preferably, up to 1600°C or lower. The resulting carbon fiber, optionally graphitized, usually has a carbon content of more than 98 weight%. Optional subsequent graphitization occurs through heat treatment under a shielding gas, more particularly nitrogen, preferably at 1700 to 3000°C, more particularly 2000°C to 2500°C. The graphitized carbon fiber has a higher elastic modulus than a fiber that is simply conventionally carbonized.

[0016] Further claims of the present invention are an advantageous method for producing a continuous fiber based on cellulose and / or a cellulose derivative, more particularly an advantageous method for producing a continuous fiber based on cellulose and / or a cellulose derivative for use in the manufacture of flame-retardant textiles and carbon fibers, more particularly, (1) contacting a continuous fiber based on cellulose and / or a cellulose derivative with a solution, more particularly an aqueous solution, and the salt thereof releases a dehydrating acid for dehydrating the cellulose and / or a cellulose derivative under subsequent thermal conditions, more particularly a dehydrating acid in the form of an ammonium salt of a sulfonic acid; (2) A method for producing a continuous fiber according to the present invention, characterized in that the supplied continuous fiber is heated to a temperature of 160°C to 300°C, more particularly 180°C to 240°C, and the temperature is maintained for at least 5 minutes, more particularly at least 10 minutes, particularly preferably at least 20 minutes, and the supplied continuous fiber is placed under a reduced pressure of 5 mbar to 500 mbar, more particularly 50 mbar to 200 mbar in an inert gas atmosphere, more particularly nitrogen atmosphere, during each heating step and between heating steps, and accordingly, dehydration of the cellulose and / or cellulose derivative is induced as a result of the formed dehydrating acid.

[0017] In step (1) according to the present invention, a continuous fiber is impregnated with a suitable salt, so to speak, before the process of the subsequent thermal step (2), and ammonia is removed to form a dehydrating acid, and the resulting acid causes dehydration of the cellulose and / or cellulose derivatives related to the present invention.

[0018] This method is advantageously developed in that in step (2), the supplied continuous fiber of step (1) is heated to a first temperature, more particularly 180 to 240°C, and this first temperature is maintained for at least 5 minutes, and subsequently the supplied continuous fiber is heated to at least one second temperature higher than the first temperature, more particularly 240 to 300°C, and likewise the second temperature is maintained for at least 5 minutes, and the supplied continuous fiber is placed under reduced pressure of 5 mbar to 500 mbar, more particularly 50 mbar to 200 mbar in an inert gas atmosphere, more particularly nitrogen atmosphere, during each heating step and between heating steps, and accordingly, dehydration of cellulose and / or cellulose derivatives is induced as a result of the formed dehydrating acid.

[0019] As mentioned above, the heating step (2) may advantageously be carried out as follows: the supplied continuous fiber is heated in step (2) in stages from a first temperature to at least one additional temperature and then to a second temperature, the temperature difference between the time-sequential heating steps is at least 5°C, more particularly at least 10°C, and it may be desirable to maintain the supplied continuous fiber at at least one temperature for at least 3 minutes. Additionally, it is useful to set the second temperature in step (2) to be at least 30°C, more particularly at least 40°C higher than the first temperature. Additionally, it is considered advantageous to maintain the supplied continuous fiber in step (2) at the first temperature, the second temperature, and at least one optional intermediate temperature for at least 10 minutes, more particularly at least 20 minutes.

[0020] Between step (1) and step (2) of the method of the present invention, it is useful to perform intermediate drying by contact heat on a heated godet, more particularly at 60°C to 140°C, more particularly at 80°C to 139°C, or in a hot air tunnel, preferably at 60°C to 140°C, particularly preferably at 80°C to 120°C. A drying step is performed between steps (1) and (2), and the moisture content of the continuous fiber supplied to step (2) can be controlled to 1 to 4 weight%. This intermediate drying is preferably performed continuously. In the invention, the continuous fiber yarn is wound after step (2). The resulting spool is storable and transportable and is supplied to step (2) at a given time, which is preferably performed continuously.

[0021] It is evident that the method of the present invention is preferably a continuous two-step method comprising the specified steps (1) and (2). In the first step, a continuous fiber based on cellulose and / or a cellulose derivative is treated with a solution, more particularly with an aqueous solution, and its salt releases a dehydrating acid for the dehydration of the cellulose and / or cellulose derivative under the specified thermal conditions described in the subsequent step (2). The agent is more particularly an ammonium salt of a sulfonic acid. It is possible in principle to use other salts that release a dehydrating acid under the conditions of the present invention. Those included herein are particularly possible: ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphonicate, ammonium chloride, ammonium hydrogen sulfate and / or ammonium bicarbonate.

[0022] A suitable salt that releases a dehydrating acid to dehydrate cellulose and / or cellulose derivatives under the thermal conditions specified below preferably takes the form of an ammonium salt of a sulfonic acid.

[0023] Accordingly, the sulfonium salt used according to the present invention preferably has the following chemical formula I:

[0024] [Chemical Formula I]

[0025]

[0026] (during food, R 1 is a hydrocarbon group, and K + is a cation of chemical formula II)

[0027] [Chemical Formula II]

[0028]

[0029] (during food, R 2 to R 5 is an organic group having H atoms or 1 to 20 carbon atoms independently of each other, and therefore the cation is an unsubstituted ammonium ion (NH 4 ) + or is a substituted ammonium ion).

[0030] As indicated, R 1 It is preferable that this hydrocarbon group has 1 to 20 carbon atoms, and it is particularly preferable that the hydrocarbon group contains 2 to 15 carbon atoms, more particularly 2 to 10, and very preferably 2 to 5 carbon atoms. In another preferred embodiment, R 1 is an aromatic group or contains such a group. Therefore, R 1 It may be an optionally substituted aryl group, more particularly an optionally substituted phenyl, biphenyl, or naphthyl group or an alkaryl group, more particularly an optionally substituted phenyl, biphenyl, or naphthyl group bonded to the sulfur atom through an alkylene group.

[0031] The cation of Formula I is not any organic or inorganic cation. Instead, it is desirable to have the advantageous structure specified above. In such a structure, as already observed, R 2 to R 5is an organic group having H atoms and / or 1 to 20 carbon atoms, preferably 2 to 15 carbon atoms, and very preferably 5 to 10 carbon atoms independently of each other. In particular, it may also be an alkyl group having 1 to 4 carbon atoms. Advantageous substituents included by these preferred details are methyl and ethyl substituents.

[0032] Quantification of the sulfonium salt originally present in the continuous fiber can be advantageously specified as the supplied continuous fiber containing 0.1 to 5 weight%, more particularly 0.3 to 2 weight%, of sulfur based on its dry weight when supplied to the heat treatment step (2) described below. It is particularly advantageous for the sulfonium salt of the specified formula I to have a water solubility of at least 10 weight parts per 100 weight parts of water (under standard conditions of 20°C and 1 bar). Particularly advantageously, the sulfonium salt is ammonium tosylate.

[0033] When using a sulfonate salt, a solution in a hydrophilic solvent, more particularly water or a hydrophilic organic solvent, for example, an alcohol, is preferred. The hydrophilic solvent is more preferably water or a mixture of water and other hydrophilic organic solvents having unlimited miscibility in water; in the case of water in the solvent mixture, this mixture preferably contains at least 50 weight percent. A solution entirely based on water and containing a sulfonate salt of Formula I in a dissolved form is particularly preferred.

[0034] The concentration of the sulfonate salt in the solution, more particularly in the aqueous solution, and the contact time of the continuous fiber with the solution are usefully selected in such a way that the dried continuous fiber contains the advantageous sulfonate salt content specified above. To this end, the continuous fiber can pass through the solution for a sufficient time and / or can pass through the solution bath for a sufficiently long time in a continuous operation.

[0035] In a preferred embodiment, the continuous fiber passes continuously through a solution of sulfonate salt. The sulfonate salt content of the solution is preferably 0.05 to 5 mol per liter of solution, more particularly 0.1 mol to 2 mol per liter of solution. The contact time between the continuous fiber and the solution of sulfonate salt is preferably at least 0.5 seconds, more particularly at least 2 seconds, and very preferably at least 10 seconds. This is generally 100 seconds or less, preferably 30 seconds or less.

[0036] The continuous fibers of the present invention based on cellulose and / or cellulose derivatives may be further post-processed by additional auxiliary agents. For this purpose, in particular, a solution of a specified sulfonate salt may contain such additional additive. This may be an auxiliary agent that particularly stabilizes thread transport, preferably a fatty acid, such as a long-chain aliphatic monocarboxylic acid. For example, saturated fatty acids such as palmitic acid or oleic acid are particularly suitable.

[0037] Preferably, this additional additive should have a water solubility of at least 10 parts by weight, preferably at least 20 parts by weight, and more particularly at least 30 parts by weight, per 100 parts by weight of water under standard conditions (20°C, 1 bar). The additive is preferably a low molecular weight compound having a molar weight of 1000 g / mol or less, and more particularly 300 g / mol or less. Specific additives under consideration are soaps or acids, examples of which are inorganic salts, inorganic acids, organic salts or organic acids, such as carboxylic acids or phosphonic acids. In the case of salts, the cation is, for example, a metal cation, preferably an alkali metal cation, such as NH₄ + and K + , or more particularly ammonia (NH 4 ) + It may be. In addition, in a preferred embodiment, the continuous fiber according to the present invention does not contain a suitable amount of additional additives other than the sulfonate salt of Formula I broadly described above.

[0038] For further explanation of the method of the present invention, the following may be generally mentioned: The advantageous properties mentioned in relation to the continuous fibers of the present invention are achieved in a targeted and reliable manner by the generation of a dehydrating acid, which may also be referred to as a "carbonization aid" in the context of carbon fiber manufacturing, during the mentioned thermal step (2). A low-pressure stabilization oven that can be used has recently become known. This is particularly important for the practice of the present invention. The specified values ​​in relation to the thermal step (2) are preferred. In the present invention, first, a plurality of continuous fibers of the present invention, which are extended in parallel with one another and are based on cellulose and / or cellulose derivatives, are passed from a supply device to an operating device through an airlock device. From the operating device, the continuous fibers pass through the airlock device and then pass to a take-up device, where they are taken up again. The operating device is placed under reduced pressure of 5 mbar to 500 mbar, more particularly 50 mbar to 300 mbar. A pressure range of 50 to 200 mbar has proven to be particularly advantageous in the present invention. Through a gas supply, a process gas, preferably an inert gas, preferably nitrogen, is applied to the operating device and discharged again through a vacuum pump. The discharged gas contains ammonia as well as water removed as a result of the dehydration of cellulose and / or cellulose derivatives. The discharged gas is purified through a corresponding post-treatment step.

[0039] Furthermore, the heating element targets the operating device, and thus in each of the bands, the heating element preferably generates a constant temperature, more particularly. For example, in the case of a multi-stage embodiment, in the first band, a temperature of 180°C to 240°C is established. For example, in the subsequent bands, temperatures of 200°C, 220°C, 240°C, and 250°C are established. Subsequently, the continuous fiber passes through the operating device at a set speed, and such speed is advantageously established so that it takes about 20 to 40 minutes for the continuous fiber to pass through the entire heated operating device.

[0040] It can be determined that, in a controlled reduced-pressure atmosphere, it is possible to utilize temperatures higher than those at atmospheric pressure in air without burning the continuous fibers or causing thermal damage. Consequently, in the case of carbon fibers, it is possible to regeneratively produce high-density, uniformly stable precursor fibers comprising dehydrated forms of cellulose and / or cellulose derivatives.

[0041] In summary, regarding the advantages related to the present invention, the following may be mentioned in the present invention:

[0042] The continuous fibers of the present invention, comprising cellulose and / or cellulose derivatives in a dehydrated form, exhibit outstanding advantages in relation to flame-retardant LOI, strength, purity, carbon yield (high carbon yield in carbon fiber manufacturing), density, elongation, and superior characteristics as flame-retardant fibers with advantageous applications, preferably as carbon fibers advantageous due to excellent environmental balance and low cost, as precursors for carbon fibers. The method of the present invention avoids adverse oxidative thermal stabilization steps. It utilizes a low-pressure process and preferably uses an inert gas, more particularly nitrogen. Further features of the method are that it can be performed continuously and scalably, requires short residence times, utilizes only a low temperature range, enables controlled and early dehydration and also low levels of byproduct formation, does not generate any toxic off-gases, and exhibits excellent CO2 balance. Finally, it allows for the advantageous use of cellulose and derivatives and also tire cords.

[0043] The following examples are provided to further explain the present invention. Prior to these examples, the following description is provided:

[0044] The Limiting Oxygen Index (LOI) of a standard cellulose fiber is 20. The LOI is a parameter used to describe flame behavior. The numerical index represents the minimum oxygen concentration of an oxygen-nitrogen mixture at which combustion is maintained under test conditions. Flame-retardant cellulose fibers having an increased LOI of 25 to 40 are produced by the method of the present invention. The flame-retardant cellulose fibers have a density of 1.3 to 1.45 g / cm³ 3 It is characterized by high density and additionally a void-part structure and a smooth surface. The individual fibers do not stick together and have a linear density of 0.90 to 1.45 dtex. The carbon content of the flame-retardant cellulose fiber is 55 to 60 weight%, and the oxygen content is 29 to 39 weight%.

[0045] Cellulose fibers used:

[0046] Examples of their use are two types of cellulose fibers. Both are artificial fibers formed from regenerated cellulose or coagulated cellulose, respectively. The regenerated cellulose fibers used in automobile tires are tire cord fibers. Coagulated cellulose fibers are produced from cellulose dissolved in an ionic liquid (1-ethyl-2-methylimidazolidium octanoate [EMIM][Oct]). These are referred to as IL fibers below. Both types of fibers are characterized by particularly high tensile strength.

[0047] Obtained carbon fiber:

[0048] According to the present invention, flame-retardant cellulose fibers can be further processed into carbon fibers (CF). In such cases, the flame-retardant cellulose fibers are converted into CF by pyrolysis. Pyrolysis is generally carried out at a temperature of 500 to 1400°C. This can be carried out under a shielding gas, for example, nitrogen or helium. The obtained carbon fibers have very excellent mechanical properties, particularly excellent strength and elasticity. The method of the present invention can increase the carbon yield. The carbon yield is 70 to 90%, which means that the carbon fibers contain 70 to 90 weight percent of carbon present in the cellulose fibers.

[0049] Example 1

[0050] The manufacture of flame-retardant cellulose fibers according to the present invention is described. An industrial recycled cellulose fiber yarn is provided for use as a tire cord fiber containing 1,000 filaments and having a single filament density of 2.2 dtex, for post-processing with an additive.

[0051] The fibers are post-processed and dried in a continuous operation on godets. The speed of all godets is 10 m / min. The first godet acts as a winding device for the fibers. Before post-processing, the fibers are washed in a washing bath with water (95°C) and water is sprayed onto the godets. Subsequently, the fibers are passed through an aqueous ammonium tosylate solution (ammonium tosylate concentration: 0.35 mol / kg). Then, they are dried on a heated godet (80°C). The dried fibers are wound using a tension-controlled winder under an initial tension of 0.3 cN / tex (Step 1).

[0052] Subsequently, the regenerated cellulose fibers, post-processed with a dehydration additive, are further processed under shielding gas (nitrogen) and reduced pressure (200 mbar). Processing is performed using a low-pressure oven with 24 heating zones. The fibers are unwound through a triple godet and enter the processing tunnel of the oven through three pressure locks. Each pressure lock is sealed to one another by a pair of rolls. Pressure within the locks and processing tunnel is regulated by a vacuum pump and nitrogen supply. The post-processed cellulose fibers are withdrawn from the oven at a speed of 0.2 m / min, corresponding to a residence time of 60 minutes. The temperature is set to 195 to 240°C. Subsequently, the fibers are withdrawn from the oven again through the three pressure locks and wound with an initial tension of 4 cN / tex (Step 2).

[0053] The residual mass of the fiber is 86 wt%, and the fiber density is 1.42 g / cm³. 3 The strength is 16 cN / tex, the elongation at break is 25%, the LOI is 30.5, and the oxygen content is 30 wt%.

[0054] Example 2

[0055] Fibers are prepared as in Example 1. The residence time in the low-pressure oven is shortened to 30 minutes.

[0056] The residual mass of the fiber is 86 wt%, and the fiber density is 1.40 g / cm³.3 The strength is 16 cN / tex, the elongation at break is 21%, the LOI is 29, and the oxygen content is 32 wt%.

[0057] Example 3

[0058] Fibers are prepared as in Example 1. The residence time in the low-pressure oven is shortened to 15 minutes.

[0059] The residual mass of the fiber is 86 wt%, and the fiber density is 1.39 g / cm³. 3 The strength is 13 cN / tex, the elongation at break is 21%, the LOI is 26, and the oxygen content is 38 wt%.

[0060] Example 4

[0061] The manufacture of carbon fibers from flame-retardant cellulose fibers according to the present invention is described. Flame-retardant cellulose fibers are manufactured as described in Example 1 using additive-treated recycled cellulose fibers, so-called tire cord fibers, which are processed using a low-pressure process. The flame-retardant cellulose fibers thus manufactured are subsequently processed in two stages under a shielding gas to provide carbon fibers. In the first stage, the fibers are treated at a maximum temperature of 750°C. Subsequently, in the second stage, the fibers are further treated at 1400°C.

[0062] The carbon yield is 72 wt%, the carbon fiber strength is 2.5 GPa, the elastic modulus is 96 GPa, the elongation at break is 2.5%, and the density is 1.42 g / cm³. 3 am.

[0063] Example 5

[0064] The manufacture of carbon fibers from flame-retardant cellulose fibers of the present invention is described. Flame-retardant cellulose fibers are manufactured as described in Example 2 by using additive-treated tire cord fibers processed using a low-pressure process. The flame-retardant fibers are then processed in two steps under a shielding gas as described in Example 4 to provide carbon fibers.

[0065] The carbon yield is 72 wt%, the carbon fiber strength is 23.2 GPa, the elastic modulus is 110 GPa, the elongation at break is 2.8%, and the density is 1.7 g / cm³ 3 am.

[0066] Example 6

[0067] The manufacture of carbon fibers from flame-retardant cellulose fibers of the present invention is described. Flame-retardant cellulose fibers are manufactured as described in Example 3 by using additive-treated tire cord fibers processed using a low-pressure process. The flame-retardant fibers are then processed in two steps under a shielding gas as described in Example 4 to provide carbon fibers.

[0068] The carbon yield is 82 wt%, the carbon fiber strength is 2.6 GPa, the elastic modulus is 82 GPa, the elongation at break is 2.5%, and the density is 1.68 g / cm³. 3 am.

[0069] Example 7

[0070] The preparation of the flame-retardant cellulose fiber of the present invention is described. The starting material used is a regenerated cellulose fiber (IL fiber) from an air gap spinning process, directly spun from ethyl-, methyl-imidazolium octanoate, containing 1,000 filaments and having a single-filament density of 2.2 dtex. The flame-retardant cellulose fiber is prepared as in Example 1 after post-processing with an additive (ammonium tosylate) by a low-pressure process.

[0071] The residual mass of the fiber is 78 weight%, and the fiber density is 1.38 to 1.42 g / cm³ 3 The strength is 12 cN / tex, the elongation at break is 13%, and the LOI is 31.

[0072] Example 8

[0073] The preparation of carbon fibers from the flame-retardant IL fibers of the present invention is described. Flame-retardant cellulose fibers are prepared as in Example 7. The flame-retardant fibers are subsequently processed in two steps under a shielding gas as described in Example 4 to provide carbon fibers.

[0074] The carbon yield is 80 wt%, the carbon fiber strength is 2.5 GPa, the elastic modulus is 90 GPa, the elongation at break is 2.5%, and the density is 1.69 g / cm³. 3 am.

Claims

Claim 1 A continuous fiber based on cellulose and / or a cellulose derivative, wherein the cellulose and / or the cellulose derivative exists in a dehydrated form, the oxygen content is 29 to 39 weight%, the limiting oxygen index LOI is 25 to 40 (according to DIN EN ISO 6941; 2004-05), and the density is 1.3 to 1.45 g / cm³ 3 A continuous fiber characterized by being (according to DIN 65569-1; 1992-10). Claim 2 A continuous fiber according to claim 1, characterized in that the degree of dehydration of the cellulose and / or the cellulose derivative is at least 1.

0. Claim 3 A continuous fiber according to paragraph 2, characterized in that the dewatering level is at least 2.

5. Claim 4 A continuous fiber according to claim 1, characterized in that the oxygen content is 29 to 32 weight%, the limiting oxygen index LOI is 28 to 37 and / or the density is 1.35 to 1.

45. Claim 5 A continuous fiber according to claim 1, characterized by having a fiber strength of 5 to 30 cN / tex (according to DIN EN ISO 5079; 1996-02), an elongation at break of 12 to 25% (according to DIN EN ISO 5079; 1996-02), and / or a linear density of 0.5 to 18 dtex (according to DIN EN ISO 1973; 1995-12). Claim 6 A continuous fiber according to claim 1, wherein the continuous fiber containing dehydrated cellulose is obtained from regenerated cellulose fiber or tire cord yarn, and the continuous fiber containing a dehydrated cellulose derivative is obtained from a continuous fiber of cellulose ester or ether. Claim 7 A method for manufacturing a continuous fiber based on cellulose and / or a cellulose derivative, comprising: (1) contacting a continuous fiber based on cellulose and / or a cellulose derivative with a solution of salt that releases a dehydrating acid for dehydrating said cellulose and / or a cellulose derivative under subsequent heating conditions; (2) heating said continuous fiber to a temperature of 180°C to 300°C and maintaining said temperature for at least 5 minutes; and placing said continuous fiber under reduced pressure of 5 mbar to 500 mbar in an inert gas atmosphere during each heating step and between heating steps, thereby causing dehydration of said cellulose and / or a cellulose derivative by the dehydrating acid formed by said. Claim 8 A method for producing a continuous fiber based on cellulose and / or a cellulose derivative according to claim 7, wherein in step (2), the continuous fiber supplied by step (1) is heated to a first temperature and maintained at this temperature for at least 5 minutes, subsequently the supplied continuous fiber is heated to at least one second temperature higher than the first temperature and maintained at the first temperature and the second temperature for at least 5 minutes, and the supplied continuous fiber is placed under reduced pressure of 5 mbar to 500 mbar in an inert gas atmosphere during each heating step and between heating steps, and thereby dehydration of the cellulose and / or the cellulose derivative is induced by the dehydrating acid formed thereby. Claim 9 A method for producing a continuous fiber based on cellulose and / or a cellulose derivative, characterized in that, in claim 7 or 8, a drying step is performed between steps (1) and (2), and the moisture content of the continuous fiber supplied to step (2) is controlled to 1 to 4 weight%. Claim 10 A method for producing a continuous fiber based on cellulose and / or a cellulose derivative according to claim 7 or 8, wherein in step (1), the salt is a sulfonic acid salt having the following chemical formula I: [Chemical Formula I] (during food, R 1 is a hydrocarbon group, and K + is a cation of the following chemical formula II)[Chemical Formula II] (during food, R 2 to R 5 is an organic group having an H atom or 1 to 20 carbon atoms independently of each other, and the cation represents a substituted or unsubstituted ammonium ion). Claim 11 A method for producing a continuous fiber based on cellulose and / or a cellulose derivative, wherein, in claim 10, the supplied continuous fiber contains 0.1 to 5 weight percent of sulfur based on the dry weight of the supplied continuous fiber. Claim 12 A method for producing continuous fibers based on cellulose and / or cellulose derivatives, characterized in that, in claim 10, the sulfonic acid salt of the above formula I has a solubility of at least 10 parts by weight per 100 parts by weight of water (under standard conditions of 20°C and 1 bar). Claim 13 A method for producing continuous fibers based on cellulose and / or cellulose derivatives, characterized in that, in claim 12, the sulfonate salt of the above formula I is ammonium tosylate. Claim 14 A method for producing a continuous fiber based on cellulose and / or a cellulose derivative, wherein in step (2), the supplied continuous fiber is heated stepwise from the first temperature to at least one additional temperature and then to the second temperature, the temperature difference between the time-sequential heating steps is at least 5°C, and the supplied continuous fiber is maintained at the at least one temperature for at least 3 minutes. Claim 15 A method for manufacturing a continuous fiber based on cellulose and / or a cellulose derivative, characterized in that, in step (2) of claim 8 or 14, the second temperature is set at least 30°C higher than the first temperature. Claim 16 A method for producing a continuous fiber based on cellulose and / or a cellulose derivative, characterized in that, in step (2), the supplied continuous fiber is maintained at the first temperature, the second temperature, and at least one optional intermediate temperature for at least 10 minutes. Claim 17 A continuous fiber according to any one of claims 1 to 6, wherein the continuous fiber is used to manufacture a fire-resistant textile for use in fire-resistant workwear or fire-resistant leisure wear, or is used as a fire-resistant textile material for industrial use, or is used as a fire-resistant textile material in the construction field. Claim 18 A continuous fiber used to manufacture carbon fibers by carbonization, optionally by subsequent graphitization, in any one of claims 1 to 6. Claim 19 Carbon fibers manufactured from continuous fibers according to any one of claims 1 to 6, having a g / cm³ of 1.55 to 1.75 g / cm³ 3 Carbon fiber characterized by a density (according to DIN 65569-1; 1992-10), a fiber strength of 2.0 to 5 GPa (according to DIN EN ISO 5079; 1996-02), and an elongation at break of 2 to 5% (according to DIN EN ISO 5079; 1996-02).

Images