WO2011067392A1

WO2011067392A1 - Fibers for producing composite materials

Info

Publication number: WO2011067392A1
Application number: PCT/EP2010/068880
Authority: WO
Inventors: Sandra Sitter
Original assignee: Sgl Carbon Se
Priority date: 2009-12-04
Filing date: 2010-12-03
Publication date: 2011-06-09
Also published as: KR20120092649A; EP2507420A1; DE102009047514A1; CA2782750A1; US20120280412A1; JP2013513034A; WO2011067392A9

Abstract

The invention relates to a method for producing carbon-containing fibers, in particular carbon fibers and/or the precursor fibers thereof, comprising the following steps: a) providing one or more starting material fibers; b) bringing the one or more starting material fibers in contact with at least one treatment fluid, wherein a treatment fluid comprises at least one silicon compound and has a content of 0 - 25 wt.% water, in relation to the total weight of the treatment fluid; c) treating the one or more starting material fibers with the treatment fluid during a treatment time having a duration of at least three minutes at a treatment temperature ranging from 126ºC to 450ºC. The invention further relates to carbon fibers and carbon fiber precursor fibers, which can be produced in particular according to the method of the invention, and to the use thereof.

Description

Fibers for the production of composite materials

The present invention relates to fibers which are particularly suitable for the production of C / SiC composite materials, as well as processes for their preparation and their use for the production of composite materials.

Processes for producing composites, and in particular C / SiC composite materials have been known for many years. Typically, in the manufacture of a C / SiC composite material, a carbon body is infiltrated with a suitable infiltrant, such as liquid silicon, and ceramified by a chemical reaction to form silicon carbide.

US 4725635 describes an agent for post-treatment of synthetic fibers. For example, DE 44 38 455 and US Pat. No. 5,486,379 describe processes for the production of C / SiC composite materials, although the fiber material used to produce the composite has hitherto received little or no attention. Likewise, many papers teach carbon fiber and precursor fiber manufacturing processes, but most do not address the issue of how carbon fibers or their precursor fibers can be made and, if desired, surface treated to obtain high quality composites.

The object of the present invention is therefore to provide access to carbon fibers and their precursor fibers, which makes it possible to provide high quality fibers, which are particularly suitable for the production of composite materials, in particular of C / SiC composite materials. Such a process should also allow a reliable, safe conversion of the starting materials into carbon fibers. Furthermore, such a process should in principle also be suitable for the production of fibers from more problematic starting materials from the point of view of process engineering, such as, for example, polyacrylonitrile homopolymers, modacrylics or cellulose, and make it possible to carry out the reaction at comparatively low temperatures. For procedures in Industrial scale is also of great importance that the process can be carried out inexpensively.

Attached figures show in an illustrative and non-restrictive manner inventive fibers, as well as illustrative diagrams:

Fig. 1 shows a SEM micrograph of a polyacrylonitrile fiber, which is used as starting material of the method according to the invention;

Fig. 2 shows an ESEM photograph of a prior art gas phase oxidized and then carbonized 1450 ° C fiber;

Fig. 3 is an ESEM photograph of a carbon fiber precursor fiber of the present invention from which the treatment fluid was not removed by a wash;

4 shows an ESEM image of a carbon fiber precursor fiber according to the invention, from which the treatment fluid with methyl ethyl ketone has been at least partially removed;

Fig. 5 shows an ESEM photograph of a carbon fiber according to the invention, from which the treatment fluid was not removed by a washing process;

Fig. 6 shows an ESEM image of a carbon fiber according to the invention, from which the treatment fluid with methyl ethyl ketone has been at least partially removed; Fig. 7 shows schematically the temperature-time course of a treatment with treatment fluid;

Fig. 8 shows schematically a comparison of the chemical composition and density of precursor fibers according to the invention.

The object of the present invention is achieved by providing a process for producing carbonaceous fibers, in particular carbon fibers and / or their precursor fibers, which comprises: a) providing one or more starting material fibers; b) contacting the one or more source material fibers with at least one treatment fluid, wherein a treatment fluid comprises at least one silicone compound and has a content of 0-25% by weight of water based on the total weight of the treatment fluid; c) treating the one or more starting materials rialfasern with the treatment fluid during a treatment period of a duration of at least three minutes at a treatment temperature in a range of 126 ° C to 450 ° C; d) optionally post-treating the treatment fluid-treated fiber, wherein the aftertreatment comprises one or more mechanical aftertreatment operations and / or one or more wash operations; e) optionally drying the treated and optionally post-treated fiber; f) optionally obtaining the treated, optionally post-treated and / or optionally dried fiber. Furthermore, the present invention provides carbon fibers and their precursor fibers according to claims 15, 19, 23 and 27. In addition, the present invention teaches a use of carbon fibers and their precursor fibers according to claim 32. Preferred embodiments are given in the subclaims, respectively.

During the numerous experiments that led to the present invention, it was surprisingly found that not only carbon fibers and their precursor fibers can be obtained with very advantageous combinations of material properties by the inventive method, but also that the inventive method also the conversion of the starting materials at high process security allows. In particular, it is highly advantageous that the process according to the invention can optionally be carried out at comparatively low temperatures and optionally direct contact of the fibers with an oxygen-containing gas phase at elevated temperature completely or at least partially avoided during the production of the carbon fiber precursor fiber can. In addition, the carbon fibers according to the invention have a high carbon content, an advantageous density, a high content of silicon, in particular on and / or on the surface, and a good tensile strength and are outstandingly suitable for the production of composite materials, in particular for the production of C / SiC Composite materials. In addition, the inventive method on an industrial scale can be realized, as well as reliable and easy to control. Furthermore, the inventive method provides shorter process times and leads to good yields of carbon fibers, the carbon fibers also have a high carbon content and a low number of defects. By treating the In addition, fibers with a treatment fluid are subject to an advantageous heat transfer, so that the method according to the invention has a good utilization of the energy used. An important advantage of the method according to the invention is also that this also allows the production of carbon fibers starting from previously difficult starting materials, such as fibers based on homopolymer polyacrylonitrile or modacrylic and their hybrid fibers, or fibers based on pitch, lignin, viscose or cellulose since the process can provide for carrying out the initial oxidation reaction or the initial thermal stabilization or a portion of the initial oxidation reaction or a portion of the initial thermal stabilization at low temperatures. The process according to the invention for producing carbon-containing fiber, in particular carbon fiber and / or its precursor fiber, comprises in a first step the provision of one or more starting material fibers.

The term "starting material fiber" as used in the present application includes any carbon-containing fiber which can be used in particular for the production of carbon fibers and / or precursor fibers for the production of carbon fibers. In addition to one or more carbon-containing fibers, which may be used in particular for the production of carbon fibers and / or precursor fibers for the production of carbon fibers, the plurality of starting material fibers may additionally comprise one or more fibers based on ceramics.

Particularly good results have been obtained in the process of the invention using one or more starting material fibers comprising or consisting of fibers selected from the group consisting of polyacrylonitrile-based fibers which are homopolymeric and / or polymeric copolymeric polyacrylonitrile, fibers based on polyacetylene, fibers based on polyphenylene, fibers based on cellulose, fibers Base of pitch, fibers based on lignin, fibers based on viscose, fibers based on polypropylene, blends of carbonaceous fibers and fibers based on ceramics, and mixtures thereof. Manufacturing processes for these fibers are each known to a person skilled in the art and are also explained below. For example, in polymer-based raw material fibers, the fibers may be made of the respective homopolymer and / or copolymer.

Furthermore, the method according to the invention comprises contacting the one or more starting material fibers with at least one treatment fluid, wherein a treatment fluid comprises at least one silicone compound and has a content of 0-25% by weight of water, based on the total weight of the treatment fluid and treating the one or more source material fibers with the treatment fluid for a treatment period of at least three minutes at a treatment temperature in a range of from 126 ° C to 450 ° C.

Upon contacting the one or more source material fibers with the treatment fluid, it may either already have a selected treatment temperature in the range of about 126 ° C to 450 ° C, especially in the range of 185 ° C to 282 ° C lower temperature, in particular below the range of treatment temperatures, for example a temperature in the range of 0 ° C to below about 126 ° C, in particular from the range of 0 ° C to below about 185 ° C, and from this temperature to the selected (n) temperature (s) are heated in the treatment temperature range. Optionally, after the end of the treatment period, the one or more source material fibers may be treated with the treatment fluid, which may be at a temperature below the treatment temperature range, eg, a temperature in the range of 0 ° C to below about 126 ° C, especially in the range of 0 ° C remains below about 185 ° C, remain in contact and remain there for a further period of time, for example of at least one minute.

Without limiting the present invention to the accuracy of the theory presented below, it is believed that in this treatment Starting material fibers an at least partial cyclization and at least partial hydrogen abstraction or dehydrogenation, in particular with the formation of H ₂ O, takes place, so that fibers are obtained, which offer in comparison to the starting material fibers in an oxidative attack by oxygen less attack possibilities. In the context of the present application, fibers which have been subjected to a treatment with the at least one treatment fluid and have thereby undergone an at least partial chemical change are also referred to as stabilized fibers. Preferably, the step of treating with the treatment fluid is such that the fibers obtained after this step are no longer fusible.

In particular, in the method according to the invention, it is advantageous that the step of treating the starting material fibers with at least one treatment fluid does not necessarily have to be carried out with exclusion of oxygen or under an atmosphere with reduced oxygen content, but under an ambient air atmosphere (for example an atmosphere comprising about 76 wt % Nitrogen, about 23 wt% oxygen, about 1 wt% noble gases, based on the total weight of the atmosphere). Optionally, an oxygen-comprising gas may be introduced into the treatment fluid. However, no addition of oxygen donors to the mixture or introduction of inert gas and / or oxygen through the mixture during the treatment step is mandatory; Optionally, therefore, can be dispensed with such an addition and / or such an introduction. Without limiting the present invention to the accuracy of the theory presented below, it is believed that by using a treatment fluid, the oxidation proceeds smoothly and is well controllable, with the advantage that the transfer of heat to the fibers is liquid or at least partially liquid treatment fluid. The term "treatment fluid" includes any fluid that comprises at least one silicone compound and is in a liquid or at least flowable state at the selected treatment temperatures. Preferably, the treatment fluid is at 20 ° C, preferably at 125 ° C, more preferably at 150 ° C, in particular at 165 ° C in a liquid or at least flowable state. The term "silicone compound" as used in the present application includes any chemical, in particular any organic chemical

A compound comprising or consisting of silicon, carbon and hydrogen, and optionally, for example, oxygen and nitrogen. suitable

Silicone compounds can be selected by a person skilled in the art on the basis of his specialist knowledge and the treatment temperature depending on the ignition point and / or

Flash point, as well as the occurring decomposition phenomena of

Select treatment fluids.

The term "treating the starting material fibers with at least one treatment fluid" includes not only treatment with a treatment fluid of constant or substantially constant temperature and / or composition, but also treatments in which the temperature or composition of the treatment fluid is varied during the treatment period. In particular, the water content or the content of one or more silicone compounds can be changed. This can be done, for example, by adding water or one or more compounds to the mixture during the treatment period and / or increasing or decreasing the temperature during the treatment period. If desired, however, transfer into at least one further spatially separated, for example in one or more further containers, treatment fluid may take place, in each case at least one silicone compound (which is also available from the silicone compound (s) present in the first treatment fluid (US Pat. en) can differ).

The term "treatment temperature" describes the temperature of the treatment fluid in which the fibers to be treated are located or which surrounds these fibers.

Fibers with very advantageous properties for use in the manufacture of composites can be obtained when the treatment temperature is preferably in the range of 132 ° C to 362 ° C, preferably in the range of 136 ° C to 360 ° C, more preferably in a range of 165 ° C to 320 ° C, in particular in a range of 185 ° C to 282 ° C.

The treatment period may preferably be a duration of at least 5 minutes, preferably at least 9 minutes, preferably from 5 to 750 minutes, more preferably from 5 to 200 minutes, in particular from 3 to 120 minutes, more particularly from 17 to 100 minutes, even further especially from 21 to 65 minutes. The processing of the starting material fibers can be carried out procedurally simply and advantageously by contacting, in particular dipping, the starting material fibers into a treatment fluid which has a temperature in the treatment temperature range or which is heated after contacting, in particular immersion, to a temperature in the treatment temperature range. Preferably, the source material fibers may be immersed in a treatment fluid in a container or bath. Treatment of the starting material fibers can also be effected, for example, by an impregnation process, by brushing, by application by rolling or other methods known to a person skilled in the art.

The treatment fluid may comprise one or more silicone compounds. For example, fibers having very good composite fabrication properties can be obtained when the treatment fluid comprises at least one silicone compound selected from the group consisting of polydialkylsiloxanes, polydiarylsiloxanes, and polymonoalkylmonoarylsiloxanes. In particular, the treatment fluid may be polydimethylsiloxanes, polyphenylmethylsiloxanes, polydiphenylsiloxanes and mixtures thereof. An example of a treatment fluid is available under the trade name UCOTHERM X-BF from FRAGOL Schmierstoff GmbH & Co. KG, D-45481 Mülheim an der Ruhr.

Fibers with very good properties for use in composite materials can be obtained, for example, if the treatment fluid has a water content of 0.001-22% by weight, preferably 0.1-15% by weight, preferably 0.5-12% by weight. % in particular 0.8 to 8 wt.%, in each case based on the total weight of the treatment fluid. The total content of silicone compounds in the treatment fluid may be, for example, at least 65% by weight, preferably 70-100% by weight, preferably 75-99% by weight, in particular 88-98% by weight, based on the total weight of the treatment fluid.

Without limiting the present invention to the accuracy of the theory presented below, it is believed that the presence of water in the treatment fluid promotes the desired conversion of carbonaceous feedstock fibers to precursor fibers. Currently, it is believed that this promotion of conversion of the raw material fibers to the ability of the water to form hydrogen bonds and / or a stabilizing attachment of water, H ₃ O ⁺ and / or OH ^" to a carbonaceous fiber, which is a more energy-efficient transition state in the ongoing reactions, such as oxidation, allows, may be based.

In addition, the treatment fluid may contain one or more additives, such as

for example, one or more lubricants, one or more

Stabilizers, one or more viscosity regulators, one or more oxygen donors, such as manganese dioxide (manganese dioxide) or

Permanganates, such as potassium permanganate, one or more corrosion inhibitors, organic and inorganic acids, organic and inorganic bases, salts, buffer mixtures, and formaldehyde. These additives can be selected by a person skilled in the art on the basis of his general knowledge and depending on the precursor fiber or carbon fiber to be produced and

be adjusted in terms of quantity.

The preparation of the at least one treatment fluid may be accomplished by one skilled in the art on the basis of his general knowledge. For example, the one or more silicone compound (s) and the water, and optionally one or more additives may be mixed by stirring. Fibers of very good quality can be obtained, for example, if the step of treating the one or more source material fibers with the treatment fluid comprises treating the one or more source material fibers in a first temperature range and at least a second temperature range, wherein the lowest temperature of the at least a second temperature range is higher than the highest temperature of the first temperature range and the treatment begins with treating the one or more source material fibers in the first temperature range. Without limiting the present invention to the accuracy of the theory presented below, it is believed that such a reaction regime results in high load fiber having a very small number of defects in the fibers.

The terms "treatment in a first temperature range" and "treatment in at least a second temperature range" encompass that the treatment may be at a particular temperature or in a range of temperatures.

In particular, the first temperature range may be a temperature range selected from the range of 126 ° C to 260 ° C, preferably selected from the range of 152 ° C to 250 ° C, preferably selected from the range of 190 ° C to 240 ° C , and / or the at least one second temperature range, a temperature range selected from the range of 140 ° C to 450 ° C, preferably selected from the range of 180 ° C to 290 ° C, preferably selected from the range of 195 ° C to 282 ° C, his. In this case, the first and / or second temperature range may comprise either the entire range of temperatures specified in each case or a subarea thereof, which may comprise, for example, 10 ° C., preferably 5 ° C., preferably 2 ° C., in particular 1 ° C. The term "the at least one second temperature range" may comprise, for example, a second to tenth temperature range, preferably a second to fifth temperature range, in particular a second to third temperature range. In this case, the lowest temperature of the temperature range with the respective next highest temperature is preferably based on a temperature range with a considered numbering. each numbering higher than the highest temperature of the temperature range with the numbering considered. The treatments preferably begin in the first temperature range, then take place in the second temperature range and are then optionally carried out in the third temperature range, then in the fourth temperature range, as well as in the other temperature ranges according to their numbering.

For example, a first temperature range of 195 to 205 ° C, a second temperature range of 206 to 215 ° C, a third temperature range of 216 to 225 ° C extend. In addition, for example, a first temperature range of 218 to 222 ° C, a second temperature range of 223 to 227 ° C, a third temperature range of 228 to 232 ° C, a fourth temperature range of 233 to 237 ° C, a fifth temperature range of 238 to 242 ° C, a sixth temperature range of 243 to 247 ° C, a seventh temperature range of 248 to 252 ° C extend. Very good results can be obtained, in particular, if the first temperature range extends from 200 to 245 ° C., and the at least one second temperature range extends from 246 ° C. to 260 ° C.

Numerous temperature histories enable the treatment of the one or more source material fibers to occur in a first temperature range and at least a second temperature range, wherein the lowest temperature of the at least one second temperature range is higher than the highest temperature of the first temperature range. A limitation of the present invention to exemplified in the context of the present application

Temperature gradients is not intended.

The temperature of the treatment fluid may increase continuously or discontinuously throughout the treatment period or one or more sections of the treatment period. For example, the temperature may rise throughout the treatment period. The temperature increase can be effected in any desired manner, for example linear or exponential. Preferably, the total duration of the one or more subsections of the treatment period with increasing temperature is at least 5%, preferably at least 30%, preferably at least 45%, in particular 5 to 20% of the total duration of the treatment period.

For example, fibers having a very advantageous property profile can be obtained if periods of constant or essentially constant temperature alternate with periods of increasing temperature during the treatment period. With regard to a treatment with a treatment fluid, the term "constant temperature" can, in addition to keeping the temperature constant, also changes the temperature by, for example, up to + 5 ° C, preferably up to + 3 ° C, preferably up to + 2 ° C, as well as the term "substantially constant temperature" temperature changes by, for example, up to +5 ° C, preferably up to +3 ° C, preferably up to + 2 ° C, and slowly rising or falling temperatures, for example up to below 0.5 ° C per minute, preferably up to 0.3 ° C per minute. Without limiting the present invention to the accuracy of the theory presented below, it is believed that such a reaction regime, in which both periods of time in which the temperature is kept constant or substantially constant, as well as periods at which the temperature changes, is preferably increased, leading to fibers of high load capacity with a very low number of defects in the fibers.

High quality fibers, in particular, can be obtained if the temperature of the treatment fluid is increased stepwise, at least during a portion of the treatment period. In particular, the treatment period may comprise at least one period in which the temperature is kept constant at a temperature or substantially constant and / or comprise at least one further period of time during which the temperature is changed, preferably increased. Preferably, the treatment period comprises at least two, preferably at least three, more preferably at least five, even more preferably at least ten, in particular two to twelve periods during which the temperature is changed. The temperature change can be carried out in any desired manner, for example linear or exponential. Furthermore, the treatment period may be at least two, preferably at least three, more preferably at least five, even more preferably at least ten, in particular two to twelve periods of time during which the temperature is kept constant or substantially constant. In particular, a period of time during which the temperature is kept constant or substantially constant may be a period of at least two minutes, preferably at least 5 minutes, preferably at least 15 minutes, more preferably at least 20 minutes, especially from 2 to 40 minutes especially from three to five minutes. Furthermore, a period of time in which the temperature is changed, a duration of at least two minutes, preferably of at least 5 minutes, preferably of at least 15 minutes, more preferably at least 20 minutes, in particular from two to 15 minutes, more particularly from three to five minutes.

Fibers of very good quality can be obtained if the ratio of the total duration of the time periods at which the temperature is kept constant or substantially constant to the total duration of the time intervals at which the temperature is changed is 1:10 to 15: 1, preferably 1 : 5 to 10: 1, more preferably 1: 2 to 2: 1.

Particularly advantageous results with regard to the fiber quality can be obtained if, during the entire treatment period or at least during 30% of the total duration of the treatment period, time intervals during which the temperature is kept constant or substantially constant, as well as time periods at which the temperature changes , preferably increased, alternate.

The changing of the temperature may, for example, be such that the temperature of the treatment fluid is increased or decreased by 0.5 to 15 ° C for one minute, preferably by 5 to 10 ° C for one minute. The temperature change during a temperature change period can, for example, increase or decrease linearly or exponentially, or can have any profile that can be selected by a person skilled in the art. For example, fibers having a particularly advantageous property profile may be obtained when the fibers are in a stressed state before and / or at least partially during the step of treating with the treatment fluid. It is advantageous in terms of process technology if, for example, the fibers present in a tensioned state are drawn through a mixture comprising at least one silicone compound and water, which is located, for example, in a container. The transfer of the starting material fibers to a tensioned state can be achieved in any manner known to those skilled in the art. It is advantageous in terms of process technology, for example, if this takes place by clamping between one or more devices or by a strain on the train. Procedures by which fibers can be placed in a tensioned state are known to a person skilled in the art.

The treated with the treatment fluid fibers are subjected in a further process step of an optional post-treatment, wherein on the treated fibers remaining treatment fluid, in particular remaining silicone compounds and / or remaining water, at least partially or completely removed from the treated fibers. The aftertreatment may include one or more mechanical aftertreatment operations and / or one or more washes. This can be done, for example, by subjecting the fibers to a pressing operation, for example by passing between rollers or pressing with absorbent material, for example paper, whereby the fluid present on or remaining on the fibers is at least partially removed. From a process engineering point of view, it is advantageous if these separated silicone compounds fertilize and / or this water is collected and optionally further used after cleaning or filtering in the process according to the invention. Furthermore, the aftertreatment may also include dripping of the fibers, for example for at least 1 minute. Suctioning of the treatment fluid can also take place as aftertreatment. In addition, the aftertreatment may include that a washing process with a solvent or a solvent mixture takes place. Such a washing process can be done for example by spraying a solvent or solvent mixture. The washing process can also be carried out by dipping the treated fibers once or several times in a solvent or solvent mixture or by passing or passing through the treated fibers through a container with a solvent or solvent mixture. The solvent or solvent mixture may have a temperature in a washing operation, for example in a range of 0 ° C to the boiling point of the solvent or solvent mixture. In order to obtain high-quality fibers, for example, the washing process can be carried out in the form of an extraction, in particular a Soxhlet-type extraction or a flow-through extraction. Numerous embodiments of Soxhlet-type extractions are known to one skilled in the art and can be adapted to the application-specific problems encountered. A construction of a Soxhlet extraction apparatus is shown, for example, in HGO Becker et al., Organikum, VEB Deutscher Verlag der Wissenschaften, 1988, ISBN 3-326-00076-6, pages 55-56. Other embodiments are possible and can be selected by a person skilled in the art and adapted to the method according to the invention. For example, the fibers can be arranged on a solvent-permeable support and come there in contact with the respective solvent or solvent mixture. In this case, a part of the treatment fluid dissolves in the solvent or solvent mixture or is entrained by this and passes through the solvent-permeable pad. Optionally, the mixture thus separated then passes, after passing through, into a container in which it is heated to boiling. Here, the component with the lowest boiling point, the solvent or solvent mixture is heated to boiling, separated and brought back into contact with the fibers to be extracted. In addition, the fibers may be sonicated in a bath of solvent or solvent mixture. A Post-treatment may also include applying silicone remover to the fiber, such aftertreatment being considered a washing operation in the present invention. Preferably, after an aftertreatment, fluid still remains on the fiber previously treated with the treatment fluid.

As a solvent or a solvent mixture for carrying out the washing process, both organic and inorganic solvents, as well as mixtures thereof, can be used. Fibers of particularly good quality can be obtained if, for a washing process, a solvent or a solvent mixture selected from the group consisting of water, isopropanol, methyl ethyl ketone, ethanol, hexane, pentane, toluene, xylene, benzene, acetone , Silicone remover and mixtures thereof. Optionally, one or more additives, such as one or more lubricants, one or more stabilizers, one or more viscosity control agents, one or more antioxidants, one or more corrosion inhibitors may be added to the solvent or solvent mixture. These additives can be selected and adjusted in volume by a person skilled in the art on the basis of his or her general knowledge and depending on the precursor fiber or carbon fiber to be produced.

The washing process, which is also referred to as desizing in the context of the present invention, is preferably carried out by, for example, bringing the fibers into contact with the chosen solvent, preferably extracted for at least 40 minutes, preferably for 230 to 250 minutes. Preferably, the solvents used are methyl ethyl ketone or silicone remover and their aqueous mixtures. By choosing a solvent or the duration and number of washes, the amount of silicon-containing deposits on and / or on the preoxidized fiber present after treatment with the treatment fluid can be controlled. The exact duration of the wash (s) may be determined by experimentation by a person skilled in the art. It is likewise possible to use fibers which have been subjected to a washing process, optionally after a preceding pressing, draining off or aspiration of the treatment fluid. Optionally, the washing process can also be repeated. In particular, a combination of one or more washes is possible. Such a combination comprises two or more of the washing operations selected from the group consisting of: washing by spraying, washing by immersion, particularly by the action of ultrasound, and washing by extraction.

Post-treatments may be performed one or more times and optionally combined with one another by a person skilled in the art in any order based on general knowledge.

Furthermore, the post-treated, i. For example, a washing process and / or a pressing process and / or a draining and / or a suctioning, stabilized fibers are optionally dried at a temperature in a range of 20 ° C to 170 ° C. Drying can be carried out in a gas mixture in the presence of oxygen, for example at a volume content of 18-35% by volume of oxygen, based on the total volume of the gas mixture, for example in an ambient air mixture or free of or substantially free of oxygen, for example at a volume content of less than 1 vol .-%, preferably less than 0.08 vol .-% of oxygen, each based on the total volume of the gas mixture.

Subsequent to the above-described steps, which include a treatment of the starting material fibers and an optional aftertreatment of the fibers treated in this way, as well as an optional drying, it is possible to obtain fibers which in the context of the present application are referred to as precursor fibers. If a polyacrylonitrile-based fiber was used as the starting material fiber, as the precursor fiber, a pre-oxidized polyacrylonitrile-based fiber, which is commonly referred to as PAN-Ox fiber, can be obtained. Fibers of excellent quality can be obtained, for example, when a polyacrylonitrile-based fiber is used which, in addition to acrylonitrile, comprises 1% by weight of itaconic acid and 4.5% by weight of methyl acrylate.

The starting materials of the invention are preferably alfibers which are so-called endless fibers, that is to say fibers which, for example, can have a length of at least 5 cm, preferably at least 10 cm. Continuous fibers z. B. in the form of a fiber coil may preferably be several kilometers long.

A very advantageous carbon fiber precursor fiber is obtainable, for example, according to a process comprising the process steps a) to c) given above and explained, and further the following steps: d) optionally after-treatment of the fiber treated with the treatment fluid, wherein the aftertreatment consists of a or several mechanical aftertreatment operations, and no washing occurs between step c) of the treatment and step e) of drying; e) drying the treated and optionally post-treated fiber. This carbon fiber precursor fiber is also colloquially referred to as a "non-desized" carbon fiber precursor fiber. A carbon fiber precursor fiber according to the invention may comprise silicon-containing deposits on its surface and may have a silicon content, for example in one

Range of at least 19 wt .-%, preferably from 19.3 to 20.6 wt .-% and / or a carbon content of, for example 49.9 to 63.5 wt .-%, preferably from 50.0 to 63.4 Wt .-% and / or an oxygen content of, for example, 12.4 to 14.0 wt .-%, preferably from 12.5 to 13.9 wt .-% and / or a nitrogen content of, for example, 3.3 to 16.2 Wt .-%, preferably from 3.4 to 16.1 wt .-%, each based on the total weight of the silicon-containing deposits on its surface comprising carbon fiber precursor fiber. The density of this fiber preferably has 1.22 to 1.44 g / cm ³ . Preferably, this fiber is obtainable starting from a fiber based on polyacrylonitrile. In Depending on the duration of the treatment with the treatment fluid and the treatment temperature, the nitrogen content can be lowered and the carbon content increased. Without limiting the present invention to the accuracy of the theory presented below, it is believed that in the case of carbon fiber precursor fibers of the present invention, the silicon is at least partially, especially predominantly, in the form of silicate compounds. Hereupon, the position of the Si peak in X-ray photoelectron spectroscopy (XPS) measurements indicates.

Fig. 3 shows fibers obtainable from polyacrylonitrile-based fibers which, after the step of treating with the treatment fluid, are merely pressed between paper and then dried at 105 ° C. Silicon-based deposits on or on the surface are clearly visible. Such a fiber which has not been subjected to washing is also referred to as non-desized, stabilized fiber in the context of the present invention.

As used in the present application, the term "fiber with deposits on its surface" may include fibers that have deposits on and / or partially or completely in and / or partially or completely below their surface.

After completion of the carbonization (in particular after completion of a temperature treatment according to the inventive method) applied to a carbon fiber finishing, finishing, Präparationsauflagen and / or coatings, and after completion of the stabilizing treatment (especially after completion of the treatment with treatment fluid according to the inventive method) A finish, carbon fiber precursor fiber, finishing pads and / or coatings are preferably not covered by the term "deposits" in the context of the present application. Optionally, however, it is additionally possible to apply size and / or one or more coatings to the fibers according to the invention which may have silicon-containing deposits on their surface become. Preferably, the deposits are wholly or at least partially in the form of particles which adhere to the fiber surface and / or rather do not penetrate, otherwise the fiber is destroyed or no longer present as fiber. The particles may have any shape and may be, for example, flaky or substantially spherical. For example, the largest elongation of the particles smaller than 40 μιτι, preferably less than 8 μιτι, preferably less than 2 μιτι be. In particular, the largest elongation of the particles may be less than the largest fiber diameter, preferably less than one third of the largest fiber diameter, preferably less than one fifth of the largest fiber diameter.

For comparative purposes, Fig. 1 shows a polyacrylonitrile-based fiber used as the starting material fiber, and Fig. 2 illustrates a fiber first oxidized in the gas phase according to a prior art method and then carbonized at 1450 ° C under an inert atmosphere.

In addition, the method according to the invention can optionally be combined with further treatment steps which take place before or after the step of treatment with the treatment fluid in which one or more further treatments are carried out prior to obtaining the precursor fiber, which comprises heating the treated fibers or the starting material fibers to one Temperature of more than 126 ° C, in particular more than 200 ° C include. For example, the method according to the invention may comprise a further treatment step, in which the treated fibers or the starting material fibers are brought into contact with an oxygen-containing gas, for example in an oven, at a temperature of more than 126 ° C., in particular more than 200 ° C.

However, in view of saving labor, energy and process costs, as well as desirable fiber properties and improving process safety, the process of the invention preferably comprises only the step of treatment with the treatment fluid as a single process step at temperatures greater than 126 ° C , in particular more than 200 ° C, before an optional recovery of pre-oxidized carbon fiber precursor fibers and / or a final conversion to carbon fibers by performing a temperature treatment.

In order to obtain fibers which have advantageous properties, in particular for the production of composite materials, the method according to the invention can be carried out in such a way that the one or more fibers are treated after step c) of the treatment and before step g) of the temperature treatment with an atmosphere, which has a content of more than 5% by weight of oxygen and a temperature of 70 ° C or more, preferably 50 ° C or more, preferably 38 ° C or more, not or not more than over a period of, for example, one Minute comes in contact.

For example, fibers that have been subjected to a washing process are shown in FIG. 4. These fibers, which are obtainable from a polyacrylonitrile-based fiber, after the step of treating with the treatment fluid, were pressed with paper, extracted with methyl ethyl ketone in a Soxhlet apparatus for 240 minutes, and then under ambient air atmosphere Dried at 105 ° C. Silicon-containing deposits on or on the surface are clearly visible. Fibers that have been subjected to one or more washes are referred to in the context of the present invention as "desized" fibers. The term ambient air atmosphere may describe any air mixtures that are present in human workspaces and / or outdoors, in particular so-called atmospheric air. Compositions of these atmospheres are known to a person skilled in the art. In particular, the term ambient atmosphere can describe atmospheres containing about 75-76% by weight of nitrogen, about 23-24% by weight of oxygen, about 1-2% by weight of noble gases, and optionally further gases with a content of less than 1 Wt .-%, based on the total weight of the atmosphere, include, as well as their mixtures with water vapor. A very advantageous carbon fiber precursor fiber is obtainable, for example, according to a process comprising the above-mentioned steps a) to c) and further the following steps: d) aftertreatment of the treatment fluid-treated fiber by one or more washes and optional after-treatment by one or more mechanical post-treatment operations; e) optionally drying the post-treated fiber. This fiber is also colloquially referred to as a "desized" carbon fiber precursor fiber. A carbon fiber precursor fiber according to the invention may have silicon-containing deposits on its surface and may have a silicon content, for example in a range of at least 0.5% by weight, preferably from 0.55 to 4.6% by weight, preferably from 2 , 0 to 4.5 wt .-% and / or a carbon content of, for example, 52.9 to 81, 6 wt .-%, preferably from 62.6 to 66.1 wt .-% and / or an oxygen content of, for example, 3 , 3 to 9.7 wt .-%, preferably from 5.6 to 9.6 wt .-% and / or a nitrogen content of, for example, 7.3 to 34.4 wt .-%, preferably from 21, 3 to 23 , 9 wt .-%, each based on the total weight of the silicon-containing deposits on its surface comprising carbon fiber precursor fiber. The density of this fiber is preferably 1.30 to 1.50 g / cm ³ . Depending on the duration of the treatment with the treatment fluid and the treatment temperature, the nitrogen content can be lowered and the carbon content can be increased. Preferably, this fiber is obtainable starting from a fiber based on polyacrylonitrile.

In a treatment with a treatment fluid, the treatment duration and the treatment temperature are preferably selected such that carbon fiber precursor fibers are obtained in which a quantity of heat Q in the range from 175 to 310 J is released in a DSC measurement, determined according to DIN ISO 1 1357-3.

After an optional aftertreatment of the fiber treated with the treatment fluid, as well as an optional drying of the aftertreated fiber, it is optionally possible to obtain a recovery of the treated fiber, and optionally aftertreated and / or optionally dried fiber. This fiber can then be converted into a carbon fiber in one or more further steps. However, if desired, no separate step of recovery is required, but the fiber may be subjected directly to one or more further conversion steps to carbon fiber after treatment with the treatment fluid. In a further process step, which can lead to the carbon fiber, a temperature treatment takes place. This temperature treatment can be carried out with the treated and optionally post-treated and / or optionally dried fiber obtained after the preceding process steps. During the temperature treatment, the fiber is exposed to one or more temperatures in the range of 450 ° C to 1800 ° C, preferably 450 ° C to 1620 ° C, under an inert atmosphere during a temperature treatment period. The temperature treatment may additionally comprise a heating phase in which a heating, for example from 20 ° C, up to 450 ° C takes place and include a cooling phase in which cooling from 450 ° C to lower temperatures, for example up to 20 ° C takes place. The temperature treatment period may be, for example, in the range of 1 to 10 hours, preferably in the range of 3 to 8 hours. Alternatively, in a continuous process, the treatment time may be 1-5 minutes at a temperature of 450 ° -1000 ° C and 1-5min at a temperature of 1000 ° C-1450 ° C.

Continuous process means that the fiber is pulled endlessly through two consecutive ovens. In the first furnace, the fibers are thermally treated at 450 ° -1000 ° C in an inert gas atmosphere. In the second then from 1000 ° -1450 ° C. Dwell times in the furnaces are each between 1 -5min, while the fiber is kept under tension by driven roller mills. The term "inert atmosphere" in the context of the present invention includes any atmosphere that is free of oxygen or an oxygen content of less than 5 wt .-%, preferably less than 1 wt .-%, preferably less than 0, 2 wt .-%, more preferably less than 0.1 wt .-%, in particular less than 0.001 wt .-%, based on the total weight of the atmosphere, up. A preferred inert atmosphere, for example, has a content of at least 99.9 wt .-% of nitrogen and a residue of other gases, based on the total weight of the atmosphere. Preferably, the gases of the rest of noble gases, oxygen and carbon oxides, preferably from noble gases. In addition, as an "inert atmosphere", an atmosphere having a pressure of less than 1 atm, that is, an atmosphere obtained after a partial or substantial evacuation of the atmosphere-containing vessel, may also be used. The inert atmosphere may advantageously comprise nitrogen and / or noble gases.

The temperature treatment is preferably carried out in such a way that a conversion of the fiber subjected to this treatment into a carbon fiber takes place. Optionally, after the temperature treatment, carbon fibers can be recovered.

Optionally, further process steps can be carried out after a temperature treatment, such as, for example, coating of the carbon fibers or surface treatment of the carbon fibers. In addition, it has proven to be advantageous for achieving fibers of good quality if the temperature treatment takes place in such a way that the temperature treatment takes place in a first temperature treatment temperature range and at least a second temperature treatment temperature range, the lowest temperature of the at least one second temperature treatment temperature range. higher than the highest temperature of the first temperature treatment

Temperature range is and the temperature treatment begins in the first temperature treatment temperature range. In particular, the first temperature-treatment temperature range may be, for example, a temperature range selected from the range of 450 ° C. to 1000 ° C. (for which optionally, for example, heating of lower temperatures, for example 20 ° C., can take place), and / or For example, at least one second temperature range

Temperature range selected from the range of 1001 ° C to 1450 ° C, preferably selected from the range of 1001 ° C to 1375 ° C, preferably selected from the range of 1001 ° C to 1320 ° C. In this case, the first and / or second temperature range may comprise either the entire range of temperatures specified in each case or a subarea thereof, which may comprise, for example, 10 ° C., preferably 5 ° C., preferably 2 ° C., in particular 1 ° C. In particular, the temperature treatment may include, at least during a section, increasing the temperature, in particular increasing the temperature step by step. In addition, the temperature treatment may be carried out for at least a period of time at a constant or substantially constant temperature and / or during at least a period of increasing temperature. With regard to the temperature treatment, the term "constant temperature" may include, besides keeping the temperature constant, changes in temperature of, for example, up to + 10 ° C, preferably up to + 3 ° C, preferably up to + 2 ° C, and the term "substantially constant temperature" may include changes in temperature, for example up to + 10 ° C, preferably up to + 3 ° C, preferably up to + 2 ° C, as well as slowly rising or falling temperatures, for example from up to below of 0.5 ° C per minute, preferably up to 0.3 ° C per minute.

A very advantageous carbon fiber is obtainable, for example, according to a method which comprises the above-described steps a) to c) and further the following steps: d) optionally after-treatment of the treated with the treatment fluid fiber, wherein the aftertreatment of one or more mechanical aftertreatment processes and there is no washing between step c) of the treatment and step f) of the temperature treatment; e) optionally drying the treated and optionally post-treated fiber; f) carrying out a temperature treatment of the treated, and optionally post-treated and / or optionally dried fiber, wherein the fiber is exposed during a temperature treatment period to a temperature of at least 450 ° C under an inert atmosphere. A carbon fiber according to the invention may comprise silicon-containing deposits on its surface and may, for example, have a carbon content of from 94.0% by weight to 94.6% by weight, preferably from 94.2% by weight to 94.4% by weight. %, and / or a content of silicon in a range of more than 0.45 wt .-%, preferably from 0.48 wt .-% to 1, 0 wt .-%, preferably of 0.5 wt. % to 0.6 wt .-%, and / or a nitrogen content of 2.4 wt .-% to 2.9 wt .-%, preferably from 2.6 wt .-% to 2.7 wt. % and or have an oxygen content of 1, 5 wt .-% to 2.1 wt .-%, preferably from 1, 7 wt .-% to 1, 9 wt .-%, each based on the total weight of the silicon-containing deposits on their Surface comprising carbon fiber. Such a carbon fiber has a density which is preferably more than 1.20 g / cm ³ , and preferably a density in a range of 1.42 g / cm ³ to 1.82 g / cm ³ . Preferably, this fiber is obtainable starting from a fiber based on polyacrylonitrile. Without limiting the present invention to the accuracy of the theory presented below, it is assumed that in the case of carbon fibers according to the invention, the silicon is present at least partially, in particular predominantly, in the form of silicon dioxide. This is indicated by the position of the Si peak in X-ray photoelectron spectroscopy (XPS) measurements.

In addition, the present invention also includes carbon fibers which have been subjected to one or more washing operations before the temperature treatment and which are obtainable, for example, by a process comprising the above-mentioned steps a) to c) and further the following steps: d) aftertreatment with the treatment fluid treated fiber by one or more washes and optionally aftertreated by one or more mechanical aftertreatment procedures; e) optionally drying the post-treated fiber; f) performing a thermal treatment of the post-treated and optionally dried fiber, wherein the fiber is exposed to a temperature of at least 450 ° C under an inert atmosphere during a temperature treatment period. Such a carbon fiber is colloquially referred to as "desized" carbon fiber. A carbon fiber according to the invention may comprise silicon-containing deposits on its surface. A carbon fiber according to the invention has a density which is preferably more than 1.20 g / cm ³ , preferably a density in a range from 1.42 g / cm ³ to 1.82 g / cm ³ . Preferably, this carbon fiber is obtainable starting from a fiber based on polyacrylonitrile.

Optionally, a surface treatment may be performed on the fiber obtained after the thermal treatment, particularly if the fiber is to be further processed into a composite material to improve the adhesion of the fiber in the matrix.

Carbon fibers which have been produced by the process according to the invention, which may have been subjected to an optional after-treatment, in particular a washing process, may have tensile strengths of more than 800 MPa, preferably a tensile strength of more than 1300 MPa, preferably a tensile strength of more than 1900 MPa, more preferably a tensile strength of more than 2800 MPa, in particular a tensile strength in the range of 1300 to 6560 MPa, determined according to DIN 65382.

Furthermore, carbon fibers produced by the process according to the invention, which may have been subjected to an optional after-treatment, in particular a washing process, have moduli of elasticity of more than 60 GPa, preferably a modulus of elasticity of more than 150 GPa, preferably a modulus of elasticity of more than 210 GPa , in particular have a modulus of elasticity in the range of 150 to 275 GPa, determined according to DIN 65382.

An advantageous property profile, in particular for the production of composite materials, carbon fibers according to the invention, which in combination a

Density of 1, 24 to 1, 81 g / cm ³ and a tensile strength of 250 to 6560 MPa, preferably in combination have a density of 1, 65 to 1, 81 g / cm ³ and a tensile strength of 1900 to 6560 MPa. An advantageous property profile, in particular for the production of composite materials, also have carbon fibers having a density of 1, 64 to 1 82 g / cm ³ and a fiber shrinkage of less than 28% in combination. The carbon fibers according to the invention, which are obtainable for example by the process according to the invention, may have a diameter in the range from 5 to 13 μm, preferably from 6 to 8.6 μm. A fiber suitable as a starting material fiber is a fiber based on polyacrylonitrile, wherein such a fiber is also referred to as "polyacrylonitrile fiber" in the context of the present application. Homopolymer polyacrylonitrile and / or copolymeric polyacrylonitrile can be used as the polyacrylonitrile. For the preparation of homopolymeric polyacrylonitrile or copolymeric polyacrylonitrile, any method of the prior art may be selected by a person skilled in the art. The fiber fineness of a starting material fiber may be, for example, in a range of 0.9 to 2.4 dtex.

According to one embodiment, it is preferred that the polyacrylonitrile is a polymer which comprises at least 50% by weight, preferably at least 95% by weight, in particular from 96 to 99% by weight of acrylonitrile units (as monomer units) , based on the total weight of the polymer. According to a further embodiment, the polyacrylonitrile may be so-called modacrylic, that is to say a polymer which consists of more than 50% by weight and less than 85% by weight of acrylonitrile units, based on the total weight of the polymer. Optionally, a fiber based on polyacrylonitrile may have further components and additives known to the person skilled in the art. The polymer may be an organometallic polymer, that is, a polymer comprising metal atoms in the polymer chain or complexed, but preferably no such polymer is used to make the starting material fibers. Preferably, a starting material fiber comprises a polymer comprising at least 80% by weight of acrylonitrile units (as monomer units), and 1 to 3% by weight of itaconic acid units (as monomer units), and 3 to 5% by weight of methyl acrylate units (as Monomer units), in each case based on the total weight of the polymer.

Methods of producing polyacrylonitrile fibers are described, for example, in the publication by E. Fitzer, LM Manocha, "Carbon Reinforcements and Carbon / Carbon Composites ", Springer Verlag, Berlin, 1998, ISBN 3-540-62933-5, pp. 10-17, as well as in the patents US 4,001, 382 and US 6,054,214 explained.

Co-polymeric polyacrylonitrile can be obtained, for example, by polymerizing acrylonitrile with a (co) monomer copolymerizable therewith, for example by solution polymerization, by redox polymerization or by slurry polymerization.

As a copolymerizable (co) monomer in a production of co-polymeric polyacrylonitrile, for example, may be used

Vinylcarbonsäurederivat such as methacrylic acid, itaconic acid; a halogenated vinyl compound such as, but not limited to, vinyl chloride; a (meth) acrylate derivative such as, but not limited to, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, dimethylaminoethyl (meth ) acrylate; and further, for example, methacrylamide, styrene. In the context of the present invention, more than one co-monomer may also be used. Preferably, a starting material fiber comprises co-polymeric polyacrylonitrile.

Feedstock fibers for making a pitch-based precursor fiber can be both isotropic and anisotropic pitch fibers. To prepare such source material fibers, mesophase pitch is melt-spun and stretched as long as it is plastically deformable to produce pitch fibers having a preferred orientation. Suitable preparation methods are known in the art and are described, for example, in the publication by E. Fitzer, LM Manocha, "Carbon Reinforcements and Carbon / Carbon Composites", Springer Verlag, Berlin, 1998, ISBN 3-540-62933-5, p. 24-34, as well as in the patent DE 697 32 825 T2 explained. Methods of preparation of polyacetylene-based fibers, polyphenylene-based fibers, lignin-based fibers, cellulose-based fibers are known to those skilled in the art. For example, the following cellulose fibers may be used especially regenerated cellulose: viscose, cupro, modal, cellulose residues: acetate and triacetate.

Manufacturing processes for ceramic-based fibers are known to a person skilled in the art. Ceramic fibers may be selected, for example, at least one compound selected from alumina, zirconia, SiNC, SiBNC, SiC, B ₄ C, BN, Si ₃ N _4, TiC, WC, and include mixtures thereof or therefrom completely or at least 90 wt .-%, preferably at least 93 wt .-%, based on the total weight of the fibers consist. In particular, ceramic fibers may be basalt fibers and / or glass fibers or a mixture thereof with other ceramic fibers. For example, fibers, in particular high-temperature fibers, based on Si, C, B, N, Al or compounds thereof in the document DE 197 1 1 829 C1 are described.

Methods a) Density

A determination of the density of fibers can be made in particular according to DIN 65569, Part 1. b) Tensile strength and Young's modulus

A determination of the tensile strength and the modulus of elasticity can be carried out in particular according to DIN 65382. c) fineness of fibers

A determination of the fineness of fibers can be made in particular according to DIN 60905, sheet 1. d) Determination of the content of C, H, N, O

The determination of the content of C, H, N, O can be carried out in particular by an elemental analysis device for determining the content of C, H, N and O, which can be based in particular on the principle of dynamic spontaneous combustion. A sample preparation can be carried out in particular by drying at 105 ° C to constant weight. b) EDX procedure

In particular, an EDX detection can be carried out to determine the silicon content. A sample preparation can preferably be carried out by drying at 105 ° C to constant weight.

EDX detections of carbon fibers can be carried out in particular in SEM (Scanning Electron Microscope). The device used was the model GEMINI DSM 982 of the device manufacturer LEO. All observations on the SEM to determine the content of silicon are made at an acceleration voltage of 5 kV.

In particular, EDX detections of carbon fiber precursor fibers can be performed on the ESEM (Environmental Scanning Electron Microscope). The device used was the model XL 30 ESEM FEG of the device manufacturer FEI Company. All measurements on the ESEM to determine the silicon content are made at an accelerating voltage of 10 kV. d) fineness of fibers

A determination of the fineness of fibers can preferably be made according to DIN 60905, sheet 1. e) fiber shrinkage

A determination of the fiber shrinkage S is made according to the following formula: S = [1 - (I 1 / I 2)] × 100, where = length of the fiber before temperature treatment (carbonization) and \ 2 = length of the fiber after temperature treatment.

The invention will now be explained in more detail with reference to the following, non-limiting examples:

example 1

Treatment with the treatment fluid In each 1000 ml beaker (Simax®), 300 ml of silicone oil (UCOTHERM X-BF from FRAGOL Schmierstoff GmbH & Co. KG, D-45481 Mülheim an der Ruhr) were contained in a 1000 ml beaker (Simax®). The starting material fibers ("SAF", polyacrylonitrile-based fibers comprising 1. 5% by weight of itaconic acid and 4.5% by weight of methyl acrylate were heated in this oil bath.) To ensure a constant heating rate, the MSC basic C used in combination with the temperature controller TC 3, with which a self-contained oil heating could be realized (manufacturer of the plate and the controller: yellow line) .The open design made it possible to use the PAN (polyacrylonitrile) fibers at a defined oil temperature. In order to ensure a homogeneous temperature distribution in the oil, the oil was constantly mixed with the integrated magnetic stirrer during the experiments.Thanks to the strong heat loss to the sides, the oil bath was insulated with ceramic wool, so that the temperature range of 200 ° C to 280 ° C. In order to be able to lower the starting material fiber with a defined length into the oil bath , frames were bent from copper tubes and the fibers were applied to them. The frames could be drained on a tripod over a wire in the oil bath. It was ensured that the fiber had no contact with the beaker wall and a complete covering with oil was ensured. With the thermocouple connected to the Thermologger K204 (voltcraft®), the temperature / time profile was recorded during each test.

For a series of samples A, the oil temperature was kept constant during the heat treatment and only the stabilization time varied. For this purpose, the PAN fiber was immersed at 210 ° C, 220 ° C and 230 ° C oil temperature. The fibers were removed from the oil after 55 minutes, 200 minutes, 300 minutes, 420 minutes and 720 minutes, respectively.

For Sample B, a constant heating rate was approximated with a stepped profile. Each sample of this series of samples was immersed at an oil bath temperature of 200 ° C. After 10 minutes holding time, the temperature was gradually increased by 10 K and held for 10 min after reaching the new target temperature. In this way, the treatment temperature increased successively up to 280 ° C. In order to follow the effects of the incremental temperature increase on the fibers, nine pre-oxidized polyacrylonitrile fibers "PanOx 2" to "PanOx 10" were obtained, as shown in Table 2. Fiber "PanOx 2" was removed after 10 minutes hold at 200 ° C, fiber "PanOx 3" was taken after reaching a temperature of 210 ° C and holding this temperature for 10 minutes, fiber "PanOx 4" became after reaching a temperature taken from 220 ° C and 10 minutes holding this temperature, fiber "PanOx 5" was taken after reaching a temperature of 230 ° C and 10 minutes holding this temperature, etc. Fiber "PanOx 10" was finally reached after reaching a temperature of 280 ° C and 10 minutes holding this temperature removed. Fig. 7 illustrates the temperature profile in a fiber treatment with stepwise increase in temperature.

Example 2 Aftertreatment Process a) Extraction with methyl ethyl ketone

The fibers were blotted with paper after removal from the oil bath and then subjected to Soxhlet extraction with methyl ethyl ketone for 240 minutes. In this case, only the pure solvent reaches the fiber to be desized in each extraction cycle. Subsequently, the fibers were dried in an ambient air atmosphere at 100 ° C. b) Alternative ways of aftertreatment

Some fiber samples were dabbed with paper only after treatment with the treatment fluid to remove the oil remaining on the fibers. In the context of the present application, such fibers are also referred to as "non-desized" fibers.

Further, in some series of experiments, fibers were dropped after draining with paper of Soxhlet extraction with toluene or isopropanol or acetone for 240 hours Minutes. Depending on the particular solvent chosen and the extraction time, the extent of removal of the treatment fluid can be controlled. In addition, cleaning tests were carried out in an ultrasonic bath with the solvents acetone, isopropanol and toluene in some series of experiments.

In addition, the cleaning was tested with a commercially available silicone remover. This viscous mass was applied to the fibers with a brush.

c) Comparison of various post-treatments Various post-treatment operations of PAN fibers ("SAF" fibers as described above) after identical treatment with treatment fluid

(UCOTHERM X-BF from FRAGOL Schmierstoff GmbH & Co. KG) were compared with each other: dab with paper, followed by drying; Dabbing with paper, followed by extraction with methyl ethyl ketone or isopropanol or acetone or toluene, each for 240 minutes, followed by drying at 105 ° C to constant weight, and cleaning with a commercial silicone remover, as in Example 2b above described, with subsequent drying at 105_ ° C to constant weight. EDX measurements showed the following silicon contents, based in each case on the total weight of the silicon-containing deposits on their surface comprising pre-oxidized carbon fiber precursor fiber:

Example 3

Elemental analysis of pre-oxidized PAN fibers

The pre-oxidized polyacrylonitrile fibers "PanOx 2" to "PanOx 10", whose preparation is described in Example 1, were subjected to extraction and drying according to Example 2a. The abbreviation SAF-PAN denotes the starting material fiber described in Example 1.

Depending on the final temperature of a stepwise preparation, the following elemental analytical values were obtained by combustion analysis with a C, H, N, O analyzer for the preoxidized polyacrylonitrile fibers "PanOx 2" to "PanOx 10" (in the following Table Nos. 2 to 10) :

In the second column are values F (X), which indicate the final temperature, after which the fibers were removed from the oil bath after reaching and holding for 10 minutes. Fig. 8 shows a graphical plot of these values.

Example 4

Carbonisation process (temperature treatment)

For temperature treatment (also referred to as "carbonization" in the context of the present application) of the treatment fluid-treated fibers described above, the tube furnace LORA 1800-32-600-1 (HTM Reetz GmbH) was used. During the carbonation, the sample chamber was purged with nitrogen to ensure the lowest possible concentration of oxygen in the furnace during carbonation and to divert the gases produced during sample conversions. In order to obtain an oxygen content of less than 1% by weight, based on the total weight of the atmosphere in the tube furnace, this was measured with a lambda probe (Bosch, model 0258 104 004) in the exhaust gas path. Both the lambda probe voltage signal and the temperatures measured with the thermocouple integrated in the furnace were recorded during each carbonation process. The samples were placed at each carbonation pass as close as possible to the middle of the working tube and thus also in the immediate vicinity of the thermocouple. The fibers were stored either on a piece of graphite or in a 10cm long Zirkonschiffchen so as not to unnecessarily pollute the working tube of the furnace. Various temperature profiles were investigated in series of experiments.

Temperature Profile I is carried out as follows: Heating was carried out at 500 ° C for 1.5 hours, during which the temperature was kept constant at 500 + 25 ° C for the next 30 minutes, then the temperature became 8 during the next 2.75 hours Increased levels to 1450 ° C and then allowed to cool for 2.5 hours at 550 ° C.

Temperature profile II is carried out as follows: first, heating takes place at a heating rate of 250 ° C./h to 1000 ° C., then holding the temperature for 2 minutes. Subsequently, heating takes place at a heating rate of 250 ° C / h to 1375 ° C, then holding the temperature at 1375 ° C for 2 minutes. This is followed by cooling to room temperature. Temperature profile III is carried out as follows: First, it is heated at a heating rate of 250 ° C / h to 1000 ° C, then holding the temperature for 2 minutes. Subsequently, heating takes place at a heating rate of 250 ° C / h to 1320 ° C, then holding the temperature of 1320 ° C for 2 minutes. This is followed by cooling to room temperature.

Example 5

Material properties of carbon fibers

The pre-oxidized polyacrylonitrile fiber "PanOx 10", the preparation of which is described in Example 1, was subjected to extraction and drying according to Example 2a and then to a temperature treatment (carbonization) according to temperature profile I. Since the modulus of elasticity for this fiber is "C fiber 10" low, this fiber was carbonized only up to 1000 ° C.

Example 6 Production of a High Resilience Carbon Fiber

SAF fibers (fibers based on polyacrylonitrile, comprising 1.5% by weight of itaconic acid and 4.5% by weight of methyl acrylate) were introduced into a silicone oil bath (UCOTHERM X-BF from FRAGOL Schmierstoff GmbH & Co. KG, D-45481 Mülheim an der Ruhr) with a temperature of 230 ° C immersed. This oil bath temperature was maintained for 20 minutes, then the temperature was raised to 250 ° C over 10 minutes and the temperature maintained for 30 minutes. After removal from the oil bath, the fibers were blotted with paper and then a Soxhlet extraction with Subjected to methyl ethyl ketone for 240 minutes. Subsequently, the fibers were dried in an ambient air atmosphere at 105 ° C. This was followed by carbonization with a defined temperature profile. The carbon fiber thus produced has the following characteristics: density 1, 753 g / cm ³ , tensile strength 2844 MPa, modulus of elasticity 218 GPa, diameter 7.0 μιτι.

It should be emphasized that use of a step profile, production of high tensile strength fibers with high modulus of elasticity already allows for a comparatively short treatment period of 60 minutes or less. Comparable tests at constant temperature surprisingly lead to carbon fibers of significantly poorer quality, in particular tensile strength.

Claims

claims

A method of producing carbonaceous fiber which comprises: a) providing one or more source material fibers; b) contacting the one or more starting material fibers with at least one treatment fluid, wherein a treatment fluid comprises at least one silicone compound and has a content of 0-25% by weight of water, based on the total weight of the treatment fluid; c) treating the one or more starting material fibers with the treatment fluid for a treatment period of at least three minutes at a treatment temperature in a range of 126 ° C to 450 ° C,

The method of claim 1, further comprising, g) performing a heat treatment of the treated, as well as

optionally aftertreated and / or optionally dried fiber, wherein the fiber is exposed to a temperature of at least 450 ° C under an inert atmosphere for a temperature treatment period.

The method of any one of the preceding claims, wherein the one or more starting material fibers comprises fiber selected from the group consisting of polyacrylonitrile-based fibers, polyacetylene-based fibers, polyphenylene-based fibers, cellulose-based fibers , Pitch-based fibers, lignin-based fibers, fibers Base of viscose, polypropylene-based fibers, blends of carbonaceous fibers and ceramic-based fibers, and blends thereof.

Process according to any one of the preceding claims, wherein the treatment temperature is in the range of preferably 136 ° C to 360 ° C, preferably in the range of 165 ° C to 320 ° C, especially in the range of 185 ° C to 282 ° C.

The method of claim 1, wherein the treatment with the treatment fluid comprises treating in a first temperature range and at least a second temperature range, wherein the lowest temperature of the at least one second temperature range is higher than the highest temperature of the first temperature range and the treatment begins with treating the one or more source material fibers in the first temperature range.

The method of claim 5, wherein the first temperature range is a temperature range selected from the range of 126 ° C to 260 ° C, preferably selected from the range of 152 ° C to 250 ° C, preferably selected from the range of 190 ° C to 240 ° C, and / or the second temperature range is a temperature range selected from the range of 140 ° C to 450 ° C, preferably selected from the range of 180 ° C to 290 ° C, preferably selected from the range of 195 ° C to 282 ° C, is.

Method according to one of the preceding claims, wherein the temperature of the treatment fluid increases continuously or discontinuously during the entire treatment period or one or more periods of the treatment period.

Method according to one of the preceding claims, wherein the treatment period comprises at least a period of time during which the temperature is kept constant or substantially constant at a temperature. and at least one period of time during which the temperature changes, preferably increases.

9. The method according to any one of the preceding claims, wherein the temperature of the treatment fluid at least during a period of the treatment period by 0.5 to 15 ° C / minute, preferably by 5 to 10 ° C / minute, increased or decreased.

A method according to any one of the preceding claims, wherein the treatment fluid comprises at least one silicone compound selected from the group consisting of polydialkylsiloxanes, polydiarylsiloxanes and polymonoalkyl monoarylsiloxanes.

Method according to one of the preceding claims, wherein the treatment fluid has a water content of 0.001-22 wt.%, Preferably 0.1-15 wt.%, Preferably 0.5-12 wt.%, In particular 0, 8 - 8 wt .-%, each based on the total weight of the treatment fluid.

A method according to any one of the preceding claims, further comprising providing the starting material fibers before and / or at least partially during step c) of the treatment in a tensioned state.

The method of any one of the preceding claims, wherein the one or more mechanical aftertreatment operations include subjecting the treated fiber to a pressing operation and / or a suctioning operation and / or a draining operation, and / or wherein the one or more washing operations comprise an extraction and / or a treatment in a bath under the action of ultrasound.

A method according to any one of the preceding claims, wherein the one or more fibers after step c) of the treatment and prior to step g) are subjected to temperature treatment with an atmosphere containing greater than 5% by weight of oxygen and a temperature of 70 ° C or more, preferred of 50 ° C or more, preferably of 38 ° C or more, does not or no longer comes into contact for a period of up to one minute.

A carbon fiber precursor fiber comprising silicon-containing deposits on its surface, the silicon-containing deposits on its surface comprising carbon fiber precursor fiber having a carbon content of from 49.9% to 63.5% by weight, based on the total weight of the silicon-containing deposits their surface comprising carbon fiber precursor fiber.

The carbon fiber precursor fiber of claim 15 which has a density of 1.30-1.5 g / cm ³ .

A carbon fiber precursor fiber according to claim 15 or 16, which has a content of silicon of at least 19% by weight, preferably a content of silicon of 19.3% by weight to 20.6% by weight,

and / or has a nitrogen content of from 3.3% by weight to 16.2% by weight, and / or has an oxygen content of from 12.4% by weight to 14.0% by weight, based in each case on the Total weight of the siliceous deposits on their surface comprising carbon fiber precursor fiber.

The carbon fiber precursor fiber of any one of claims 15 to 17, wherein the carbon fiber precursor fiber is obtainable by a process comprising a) providing one or more source material fibers; b) contacting the one or more starting material fibers with at least one treatment fluid, wherein a treatment fluid comprises at least one silicone compound and has a content of 0-25% by weight of water, based on the total weight of the treatment fluid; c) treating the one or more source material fibers with the treatment fluid for a treatment period of at least three minutes at a treatment temperature in a range of 126 ° C to 450 ° C; d) optionally aftertreating the treatment fluid treated fiber, wherein the aftertreatment consists of one or more mechanical after-treatment operations, and

no washing takes place between step c) of the treatment and step e) of drying; e) drying the treated and optionally post-treated fiber.

19. A carbon fiber precursor fiber comprising silicon-containing deposits on its surface, wherein the silicon-containing deposits on its surface comprising carbon fiber precursor fiber has a carbon content of 52.9 wt .-% to 81, 6 wt .-%, each based on the total weight silicon-containing deposits on their surface comprising carbon fiber precursor fiber.

A carbon fiber precursor fiber according to claim 19 which has a density greater than 1.20 g / cm ³ , which preferably has a density in the range 1.20 g / cm ³ to 1.38 g / cm ³ .

21. A carbon fiber precursor fiber according to claim 19 or 20, which has a content of silicon of at least 0.5 wt.%, Preferably a content of silicon of from 0.55 wt.% To 4.6 wt.%, And / or

has a nitrogen content of from 7.3% by weight to 34.4% by weight, and / or has an oxygen content of from 3.3% by weight to 9.7% by weight,

each based on the total weight of the silicon-containing deposits on their surface comprising carbon fiber precursor fiber.

The carbon fiber precursor fiber of any of claims 19 to 21, wherein the carbon fiber precursor fiber is obtainable by a process comprising a) providing one or more source material fibers; b) contacting the one or more starting material fibers with at least one treatment fluid, wherein a treatment fluid comprises at least one silicone compound and has a content of 0-25% by weight of water, based on the total weight of the treatment fluid; c) treating the one or more source material fibers with the treatment fluid during a treatment period of at least three minutes at a treatment temperature in a range of 126 ° C to 450 ° C; d) post-treating the treatment fluid-treated fiber

by one or more washes and optional

After treatment by one or more mechanical

Post-treatment operations; e) optionally drying the post-treated fiber.

23. A carbon fiber comprising silicon-containing deposits on its surface, wherein the silicon-containing deposits on their surface comprising carbon fiber having a carbon content of 94.0 wt .-% to 94.6 wt .-%, based on the total weight of the silicon-containing deposits on its surface comprehensive carbon fiber.

A carbon fiber according to claim 23, which has a density of more than 1.20 g / cm ³ , preferably a density in a range of 1.42 g / cm ³ to 1.82 g / cm ³ .

25. Carbon fiber according to claim 23 or 24, which has a content of silicon in a range of more than 0.45 wt .-%, preferably from 0.48 wt .-% to 1, 0 wt .-%, and / or

has a nitrogen content of from 2.4% to 2.9% by weight, and / or has an oxygen content of from 2.6% to 2.7% by weight,

in each case based on the total weight of the silicon-containing deposits on their surface comprising carbon fiber.

The carbon fiber according to any one of claims 23 to 25, wherein the carbon fiber is obtainable by a method comprising

a) providing one or more source material fibers; b) contacting the one or more source material fibers with at least one treatment fluid, wherein the treatment fluid comprises at least one silicone compound and the treatment fluid has a content of 0-25% by weight of water based on the total weight of the treatment fluid; c) treating the one or more source material fibers with the treatment fluid during a treatment period of at least three minutes at a treatment temperature in a range of 126 ° C to 450 ° C; d) post-treating the treatment fluid-treated fiber

by one or more washes and optional

After treatment by one or more mechanical

Post-treatment operations; e) optionally drying the post-treated fiber; f) carrying out a temperature treatment of the aftertreated and optionally dried fiber, wherein the fiber during a temperature is exposed to a heat treatment period of a temperature of at least 450 ° C under an inert atmosphere.

27. A carbon fiber comprising silicon-containing deposits on its surface, the silicon-containing deposits having on its surface comprising carbon fiber, a carbon content of 94.0 wt .-% to 94.6 wt .-%, based on the total weight of the silicon-containing deposits on their Surface comprising carbon fiber.

A carbon fiber according to claim 27, which has a density of more than 1.20 g / cm ³ , preferably a density in a range of from 1.42 g / cm ³ to 1.82 g / cm ³ .

29. Carbon fiber according to claim 27 or 28, which has a content of silicon in a range of more than 0.45 wt .-%, preferably from 0.48 wt .-% to 1, 0 wt .-%, and / or

which has a nitrogen content of from 2.4% by weight to 2.9% by weight, and / or has an oxygen content of from 1.5% by weight to 2.1% by weight,

each based on the total weight of the silicon-containing deposits on their surface comprising carbon fiber.

The carbon fiber of any of claims 27 to 29, wherein the carbon fiber is obtainable by a process comprising a) providing one or more source material fibers; b) contacting the one or more starting material fibers with at least one treatment fluid, wherein a treatment fluid comprises at least one silicone compound and has a content of 0-25% by weight of water, based on the total weight of the treatment fluid; c) treating the one or more source material fibers with the treatment fluid for a treatment period of at least three minutes at a treatment temperature in a range of 126 ° C to 450 ° C; d) optionally aftertreating the treatment fluid treated fiber, wherein the aftertreatment consists of one or more mechanical after-treatment operations, and

no washing process takes place between step c) of the treatment and step f) of the temperature treatment; e) optionally drying the treated and optionally post-treated fiber; f) performing a temperature treatment of the treated, as well

31. Precursor fiber according to one of claims 15 to 22 or carbon fiber according to one of claims 23 to 30, wherein the deposits comprise particulate deposits, wherein preferably the greatest length expansion of the particles is less than 40 μιτι, more preferably less than 8 μιτι, preferably less than 2 μιτι ,

32. Use of a precursor fiber according to any one of claims 15 to 22 or 31 or a carbon fiber according to any one of claims 23 to 31 for producing a fabric and / or fiber fabric and / or a composite material, in particular a C / SiC composite material.