DE1930713B2 - - Google Patents

Description

The invention relates to a method for producing carbon-1 Ormbodern with excellent mechanical strength.

Carbon moldings are generally produced in that grain or powder aggregates Coke is mixed with pitches or synthetic resins as a binder, the mixture being mixed by extrusion or molding is brought into the desired shape and then the molded mixture is treated at a temperature of about 1000 ° C in a non-oxidizing atmosphere. From CH-PS 4 36 092 it is already known, carbon molded bodies made of carbon fibers and Manufacture binders. For the production of electrodes, collector brushes or the like, they are burned Carbon bodies then heat-treated again at temperatures of 2500 ° C and more in order to to g.-aphitate them. The graphitized materials are either used as they are or for Adaptation to the intended use further processed in various ways.

The disadvantage of the carbon molded bodies which can be produced up to now is that they are fragile and have a low mechanical strength. Since they also work in the manner described is made in the bodies not only during the shaping, but also while choosing When heated, foam is easily formed, causing volatilization and therefore considerable loss Amounts of binder, so that it is difficult to obtain high density bodies. Although Carbon itself has fairly good mechanical properties, it is difficult to to find a suitable manufacturing process, with the application of which the end products are also good Have properties.

Although these difficulties in some cases through selection of raw materials and through improvement the manufacturing processes, for example in the manufacture of small-sized molded bodies or of specialty items that can be eliminated, they are particularly useful in the case of manufacture large moldings or not yet eliminated for those cases in which for economic reasons the costs must be kept low. It is therefore still difficult to produce carbon molded articles with sufficient mechanical strength.

The invention is therefore based on the object

ίο while avoiding the disadvantages described Specify process that can be carried out easily and cheaply technically and carbon molded bodies with high mechanical strength.

The invention relates to a process for the production of carbon moldings from a Mixture of carbonizable binder and a carbonaceous material or of the carbonizable Binder alone by providing this base material with a reinforcing fiber layer and too a body is formed, whereupon this body is heated until charring or graphitization, which is characterized in that the base material made infusible pitch fibers in one Mixing ratio of 1 to 85 ° o, based on the weight of the base material, can be added. The essential feature of the invention thus consists in the use of pitch fibers made infusible as a stiffening material for carbon molded bodies and in the advantage achieved thereby. Until now it was believed that pitch is an extremely brittle and fragile material and that even if it is It was given a certain flexibility by being deformed into fibers, but such fibers nonetheless are very brittle and easy to pulverize between your fingers. Even after making it infusible the fibers remain brittle, so that their mechanical strength is very low and one Suitability as a reinforcement material for carbon moldings was not to be expected. Given the However, the fact that the infusibilized pitch fibers have excellent properties, if they are heated further, they can surprisingly still be used for the stated purpose use with excellent results.

The reinforcing fiber material according to the invention is made by first Pitch spun by melt spinning which 1) can be spun well, 2) easily infusible after spinning can be made and 3) are easily charred.

There are a large number of pitches that can be spinnable well, but these can only then be used according to the invention can be used if they also have the aforementioned properties 2) and 3). A well-suited material is petroleum asphalt, whereas normal pure asphalt or blown asphalt Asphalt in its original state is not suitable for the purposes of the invention if it has not been pretreated in this way that they also receive the other properties mentioned at the same time.

In general, pitches with the three properties given are organic compounds which contain condensed polycyclic aromatics and / or alicyclic compounds as the main ingredient, namely z. B. black or dark brown pitch with a carbon content of 90% and more, based on the total amount of carbon

and hydrogen, and having an average molecular weight of 400 and more, measured according to the Rast method with camphor as solvent. However, it can also be pitch-like or act resinous substances obtained by hydrogenation of condensed polycyclic aromatics, which by pyrolytic decomposition or heat treatment at high temperature from a any hydrocarbon compound and which have a softening point of 30 C and more, a melt viscosity of 0.4 P and more within that set during molding Temperature range and a carbonization yield of 70 ° / o and more, wherein the carbonization yield means the yield in the carbonization of the fiber material.

A melt spinning process, which is extrusion spinning, is used to spin these pitches and centrifugal spinning. Both types of spinning are according to the invention for the production of the suitable pitch fibers to be used.

After completion of the spinning, the fiber material has the same softening temperature as its raw material, with the result that a treatment to render it infusible is necessary in order to maintain its shape consistently, ie in order to prevent melting when subsequently heated. Such a treatment is generally an oxidation of the fiber material in an oxidizing atmosphere. For example, the fiber material is treated in ozone-containing air at a temperature of less than 100 ° C and then further heat-treated in air by gradually increasing the temperature up to about 260 ° C, whereby satisfactory results are obtained. In most cases the treatment with Gzon can be omitted, and sometimes chlorine, bromine, SO _S or a nitrogen oxide can be used instead of ozone in a mixing ratio of 0.5 to almost 100 ° η. Even if the air is completely replaced with one of these gases or a mixture of these gases, the infusibilization treatment will not be affected.

The treatment for rendering infusible is carried out with a temperature rise of 0.1 to 10 C'min carried out for about 30 minutes to 10 hours.

If the fiber material is close to 260 ^! When it is heated to C, it becomes, as experiments have shown, sufficiently infusible that it can be used as a stiffening material. However, since the fiber material is not sufficiently strong during this stage of the heat treatment, further heating in air or an inactive atmosphere up to the range around 500 ° C. is preferred, ie up to a temperature just below the carbonization point, in order to increase its strength raise.

Although, as described above, the infusibilized filaments are still charred must be, because of their high carbonizability, they can also be used in the course of heating the mixture of the infusible threads are carbonized with the carbon material, whereby they are given sufficient mechanical strength. Even if, therefore, their strength still appears low after completion of the treatment to render it infusible, it arises after the burning of the carbon material has a considerable stiffening effect. Surprisingly owns such a stiffening material has a better effect compared to the case that car'-onized Fibers are used. The reason for the better strength is that that which is rendered infusible Fiber material still has active functional groups, on the basis of which it is used as a binder The pitches or synthetic resins used are easily chemically bonded, whereas the carbonized ones Fibers are chemically inactive, so that they only stiffen the end product mechanically. aside from that It is assumed that the least stress remains in the carbon molded body because the infusible fiber material one of the contraction of the carbon material (essentially due to the contraction of the binder) corresponding moderate contraction during firing going through.

Using the infusible fiber material, fibers of desired length can be produced made and the fibers with carbon material, such as coke and graphite in granular or powder form, or with binders such as pitches or synthetic resins, or with both at normal or elevated Temperatures are mixed. The fiber material can, however, also be in the form of woven or non-woven fibers Fabrics or mats or in the form of fiber bundles or the like. Are used in soft the Binder is impregnated. The shape of the fiber material, its mixing ratio with the The base material and the mixing process can vary depending on the molded bodies to be produced be freely chosen. In general, the mixing ratio of that which is made infusible is Fiber material between 1 and 85 percent by weight, based on the total amount of the base material.

When shaping the carbon molded body according to the invention, the same devices and Process as in the production of ordinary carbon bodies or as in shaping in the synthetic resin technique can be used. Extrusion, pressing and impregnation processes are particularly suitable, which can be selected according to the circumstances.

The molded articles are made by ordinary heating methods charred or, if necessary, graphitized. It is generally the case today that at In the manufacture of carbon threads, the heat treatment during graphitization is the most expensive The process step is because the treatment takes a long time takes time and a large amount of equipment is necessary. Although carbon threads have various beneficial properties Having properties of strength, elastic modulus, etc., is industrial Relatively limited use due to manufacturing costs. According to the method according to the invention however, infusible filaments are used prior to their carbonization, thereby reducing manufacturing costs the carbon molded body compared to the case in which expensive carbon threads are used, are significantly smaller.

The carbon moldings which are obtained by the process according to the invention can to a wide variety of coal products, e.g. B. to electrodes, blocks, bricks, processed and also can be used as intermediates.

The invention is explained in more detail below by means of examples.

example 1

Petrol pitch is dry distilled in a nitrogen atmosphere for 2 hours at a temperature of 380 C, giving π yn a black, pitch-like mass with a carbon content of 90.4 ⁿ / o, an average molecular weight of 550 and gloss at room temperature. This pitch-like mass is melted and poured into a cylindrical vessel which rotates at a speed of 1600 rpm and with which the spinning into fiber material takes place at a temperature of 160 to 180 ° C. A mat-shaped object composed of fiber material of different lengths is produced .

This object is then for 3 hours at a temperature of 70 ° C in air with a Treated ozone content of 1.5 ° 0, and then the temperature in air with an increase of 1 ° C / min increased to a value of 260 "C, at which the object is then treated for 1 hour, so that the mat-like structure finally consists of completely infusible, non-melting Fibers.

Phenol-formaldehyde resin is then used in the mat-like object impregnated until the weight ratio of the two substances is adjusted to about 1: 1 is. Then the object is pressed to harden under heat, whereby one about 5 mm thick plate received. The hardened plate is first placed in nitrogen at a temperature of 600 ° C and an increase of 2 ° C / min and then further at a temperature of 1000 ° C and an increase charred at 5 ° C / min.

The mechanical properties of the finished composite panel, shown in Table 1 are in comparison with a normal carbon plate much better; significantly better.

Table 1

Carbon plate Carbon plate also infusible normal made threads quality as a stiffening material tensile strenght 97 (kg / cm «) 407 Flexural strength 189 (kg / cm *) 750 Compressive strength 370 (kg / cm ² ) 1530

extruded in air, for which purpose nitrogen with an excess pressure of 20 mm Hg is applied in the melting vessel, while the extruded mass is spun at a reel speed of 300 m / min. The thread obtained in this way is heat-treated at 40 ° C. in air with an ozone content of 10.4 g / m ^{3 for 2 hours.} The temperature is then raised in air with an increase of 10 ° C./h to 260 ° C., at which temperature the thread is maintained for 1 hour in order to render it completely infusible. Thereafter, in nitrogen with an increase of 3 to 5 C / min heated to 500 "C.

The infusible threads are then processed into short threads 3 to 5 cm in length. 30 g of this are mixed with 1000 g of powdered, calcined petroleum coke and 300 g of coal tar, and the mixture is kneaded in a kneader at a temperature of 160 to 180 ° C. Afterward the kneaded mass is extruded into a round rod 3 cm in diameter.

The shaped body is then carbonized in the usual way and then heated up 2800 C graphitized.

In comparison with a shaped body which does not contain any threads which have been rendered infusible, this results the following differences:

Table 2

40

45

55

Example 2

2 parts by weight of coal tar pitch with a softening point of about 80 ° C. and 1 part by weight of petroleum pitch are mixed and distilled dry for 1 hour at a temperature of 380 ° C in nitrogen. This is followed by 3 hours of treatment at 300 ° C. under reduced pressure of l () ~ 'mm Hg to all components with low Molecular weight and a pitch-like mass with a carbon content of 93.5% to obtain.

This pitch-like mass is transferred to a melting vessel, in which it is kept at a temperature of 2 (SO ° C melted and danacli through a nozzle of 0.3 mm

Specimen Specific
Schütt
weight pressure
strength
(km'cm ² ) Not stiffened through
infusible
Threads 1.59 195 Stiffened by not melting
threads made in cash ... 1.60 298

Example 3

From a tarry mass obtained by flame cracking petroleum naphtha (mixing petroleum naphtha into the flame of burning hydrocarbon, the petroleum naphtha being cracked and the tarry mass obtained as a by-product) at a temperature of 1050 ⁰ C, a pitch-like mass is produced by the light components are removed by distillation under a reduced pressure of 5 mm Hg at 300 ° C. The pitch-like mass has a carbon content of 96.2 and 27% chloroform-insoluble.

This mass is at a temperature between 320 and 340 ° C in the same way as in example 2 melt-spun, formed into long threads with a diameter of 9 to 13 μίτι and then in Air by raising the temperature to 260 ° C with an increase of 1 to 3 ° C / min of a first heat treatment subject. This is followed by a second heat treatment in nitrogen Raise the temperature to 450 ° C. Then some of the threads are heated to 1000 "C wcitcrbchandclt, which results in a network made up of both infusible threads and also consists of carbon fibers of great length.

A bundle of this braid is made in ecschmolz.c-

Nes pitch dipped, which has a softening point of 120 ⁰ C, 47% benzene-insoluble and a degree of carbonization of 33%.

Thereafter, the bundle is shaped into a rod while the material is heated. The molded body is fired by increasing the temperature first with an increase of 0.5 ° C / min to 500 ° C and then is raised to 1000 ° C at an increase of 5 ° C / min, thereby giving a carbon rod. The compressive strength of this carbon rod is entered in Table 3.

Table 3

Specimen Compressive strength
(kg / cm ^a ) Stiffened by infusible
made threads
Stiffened with carbon thread 2100
536

Example 4

Steam at 1800 ° C becomes pyrolytic Decomposition of crude oil from Borneo with the following properties

Specific weight (</ '/) 0.833

Density in ° API 38.4

Viscosity at 30 ° C, cSt 2.46

Sulfur content

(Weight percent) 0.07

Distillate 189 to 190 ° C 35 percent by volume

190 to 250 ° C 18 percent by volume

250 to 275 ° C 11 percent by volume

above 275 ° C 36 percent by volume

given, resulting in a tarry mass which is further distilled to the below of Separate 250 ° C distilling components and produce a pitch-like mass, which is predominantly is aromatic. This pitch-like mass is used along with 5 percent by weight of a nickel system catalyst placed in an autoclave, in which a reaction at a temperature of 300 ° C is excited with hydrogen by adding 2301 hydrogen per kilogram of pitch.

The pitch-like,. blackish brown mass has a softening point of 80 to 100 ⁰ C and a viscosity of about 1.2 P at 250 ° C and can be drawn into threads excellently. It is melted and placed from the upper middle part into a rotating cylinder nozzle which has an inner diameter of 350 mm, a depth of 10 mm and twenty small holes 0.5 mm in diameter in the jacket. After spinning the pitch-like material at a temperature of 230 to 250 ° C with the aid of this cylinder nozzle, which rotates at a speed of 2600 rpm, the mass obtained is first in air containing 17 g / m ^{3 of} chlorine for 3 hours Treated 30 to 40 ° C and then made infusible by first increasing the temperature in air with an increase of 1 to 2 ° C / min to 260 ⁰ C and then in nitrogen to 450 ° C. Some of the threads are heated up to 1000 ° C.

The threads made infusible in this way are processed into a mat in which up to a weight ratio of about 1: 1, a pitch of the same kind as that as the starting material pitch used for the infusibilized threads is impregnated. Then the mat pressed into a plate. The plate is by increasing the temperature to 1000 ° C with an increase of Carbonized 3 to 5 ° C / min in nitrogen, thereby obtaining a carbon plate, the properties thereof are given in Table 4.

Table 4

Specimen Bend
strength
(kg / cm ¹ ) pressure
strength
(kg / cm ⁸ ) Stiffened with at 260 ° C
infusible
Threads 260 480 Stiffened with at 450 ° C
infusible
Threads 280 540 Stiffened with carbon
thread 220 410

β 6.75 509528/2 (

Claims (2)

Patent claims: 1. A process for the production of carbon molded bodies from a mixture of carbonizable binder and a carbonaceous material or from the carbonizable binder alone, by providing this base material with a reinforcing fiber insert and shaping it into a body, whereupon this body is heated to carbonization or graphitization , characterized in that pitch fibers made infusible are added to the base material in a mixing ratio of 1 to 85 ⁰ Zo, based on the weight of the base material. 2. The method according to claim 1, characterized in that the made infusible Pitch fibers in the form of a felt mat or a woven or non-woven cloth with the Binder are impregnated and the impregnated, shaped into a body material is carbonized or is graphitized.