DE3413471A1 - ARRANGEMENT AND METHOD FOR CONNECTING THE END OF TWO TRACKS - Google Patents

Description

Patent attorney

cüUARD K. BAUMANN

Dip !. Phys.

• attlerstr. 1, D-8011 Höhenkirchen-Munich
el. ("8102) 4108 Telex:

Arrangement and method for joining the ends of two webs

The invention relates to an arrangement and a method for joining two oppositely long webs of
flexible material, in particular for joining a web of thermosensitive material to a second web in such a way that the end of the thermosensitive web is protected during subsequent processing in a high temperature environment.

It is known to carbonize polyacrylonitrile or another carbonizable material in that the material
first oxidized and then heated in a protective gas atmosphere to a temperature sufficient to achieve the
Substantially carbonize material. In the case of polyacrylonitrile, such material is often machined in the form of a long web of tow, which run substantially parallel to one another, side by side, for the length of the web thereby formed. The web is under mechanical tension on relatively complex webs, which by rolling in one or
several oxidation ovens are defined, before it enters a carbonation oven. In the oxidation furnace, the path goes several times through different stages of the furnace, the
are kept at temperatures that lead to a
lead to the desired oxidation of the polyacrylonitrile tow.

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The polyacrylonitrile tows are designed so that the web must not remain in the rest position, but must be constantly moved through the oxidation furnace when it is up to the oxidation temperature is heated up. Lingering on the web, even for a short time, would very quickly lead to fiber damage and a possible exothermic reaction of the polyacrylonitrile tow to lead. Even if the web is constantly moving through the oven, there should not be any loose ends or knots in the Tows are present. When such loose ends or knots are present, an exothermic reaction usually takes place the same in the hot oven instead, which leads to a process interruption and often even a breakdown of the entire process Process and re-inserting the web into the oxidation furnace after it has cooled down.

For this reason, the web of polyacrylonitrile tow is typically fed into the cold oxidizer. this takes place by placing the individual tow at various points along the length of a threading device at which opposite ends of ropes are attached, is linked to the threading device. The ropes serve the purpose to pull the threading device with the tow attached to it in and through the oxidation furnace. Because the oven is cold there is no exothermic reaction of the knots and loose ends of the tow at their points of connection with the threading device instead of.

When the threading device has pulled the tow completely through the oxidation furnace, it is switched on and heated to oxidation temperatures while the tow web is moved further through the furnace. Usually it takes two hours for the furnace to reach oxidizing temperatures, during which time the web is constantly being passed through the furnace drawn. As the furnace reaches oxidizing temperatures, there are new sections of web entering and through the furnace are drawn, oxidized in a desired manner. The previous sections of the track, which typically contain approx. 90-180 kg poly-

Acrylonitrile tow must be disposed of as rejects. Since the polyacrylonitrile tows are relatively expensive, this represents a significant cost disadvantage with regard to the overall cost-effectiveness of the process.

It is mostly impractical or even impossible to have processes of this type run continuously because staff would have to be present around the clock for this. Also, power outages and other interruptions usually result this means that the oxidation furnace has to cool down, after which the start-up process explained above must be repeated. They are too Lengths of raw tow on the supply reels limited, so that periodic shutdowns are required. So that is Loss of substantial quantities of polyacrylonitrile tow has become a routine and a necessary component such procedures.

Because fresh polyacrylonitrile tow is used in preparation for oxidation a material web under suitable mechanical tension must be present in the oxidation furnace, is a The method commonly used to shut down the process is to keep the web running through the oven after the oven has been switched off and until it has cooled down enough to bring the web to a standstill can. With the subsequent start-up, the web begins to move through the furnace, and this is brought to the oxidation temperature warmed up. Those sections of the web that are used during cooling and subsequent switching on of the furnace by the Oven are rejected and must be disposed of.

In some cases the individual tows of the web are severed at the inlet to the furnace after the furnace has cooled and the Passage of the web is interrupted. In this case the process can be started again by removing the web to be oxidized is attached to the polyacrylonitrile tow remaining in the oven. In such cases the individual tows the web to be introduced into the oven with the

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linked individual tows of the web remaining in the oven, after which the web begins to run through the oven. To a exothermic reaction of the knots and loose ends at the junctions To avoid the tow, the furnace is switched on in stages, each stage being switched on first after the tow's junctures have passed this stage. In turn, there are considerable quantities involved the polyacrylonitrile tow was lost before the oven was heated to operating temperature and the web was oxidized can begin in the desired manner.

If the web is polyacrylonitrile fabric instead of individual tow comprises, sections of the tissue are connected to one another using different techniques (cf. e.g. U.S. Patent 4,077,822). In this US-PS webs of polyacrylonitrile tow spliced together using multiple layers of silicone rubber adhesive. Such A layer of adhesive is applied between overlapping sections of the webs, and additional layers of adhesive are applied to the outsides of the overlapped web sections. Heat and pressure are then applied to the silicone rubber adhesive layers to harden.

In its own DE patent application P is a

Method specified in which the web of polyacrylonitrile tow is introduced into the oxidation furnace by first placing a precursor in the form of a sheet of silica cloth or a other heat-resistant material is conveyed through the furnace, after which the furnace, if it is still cold, is heated up. That The trailing end of the precursor that remains outside the furnace then becomes more carbonizable with the leading end of the web Tow connected, and the precursor serves the purpose of pulling the tow web in and through the hot oven. By the use of the heat-resistant precursor greatly minimizes the amount of waste of the carbonizable tow web.

In the said DE patent application is a method for Joining the rear end of the precursor to the front end of the polyacrylonitrile filament tow web indicated in which the two The ends are taped off with tape, quilted and folded over to form loops, into which long rods are inserted will. Then the two ends are fixed in a connecting rod, the opposite halves of which have long openings Form inclusion of the two ends with their rods. The connecting rod can be used to release the front end of the web carbonizable tow can be removed from the precursor after the leading end has passed through the oxidizer.

The method of joining the trailing end of the precursor to the leading end of the web of polyacrylonitrile tow of FIG the aforementioned DE patent application has proven to be highly satisfactory; but it is desirable to have an alternative To provide a method and an arrangement for connecting the webs, in general in cases where long Tracks can be flexibly connected to one another, as well as can be used in the special case in which one of the tracks is made thermosensitive material and therefore in high temperature environments must be protected from exothermic reactions and other hazards. U.S. Patent 4,077,822, previously mentioned does not provide any impetus for this, since it is more carbonizable with the different kind of problem of splicing different webs Spinning tow is concerned and not with the protection of such a web, while the other web is made of silica fabric or another heat-resistant material.

The object of the present invention is thus to provide an arrangement and a method for connecting opposing ones long lanes in a flexible manner, with a flexible, heat-protected connection of a long, heat-sensitive Track is to be made with another track.

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In accordance with the arrangement and method of the invention, there is a flexible connection of oppositely long webs intended. If the one sheet of heat-sensitive material exists, it is bonded to the second web in such a way that the former can be used in high temperature environments is protected. When the heat sensitive web is off carbonisable tow is made, the flexible connection covers the free ends of the tow at the end of the web such that the risk of an exothermic reaction of the tow is practically minimized.

The connection of a heat sensitive web with a Heat-resistant sheet according to the invention is achieved by applying an adhesive to a portion of the surface of the heat-resistant Web is applied to form a first adhesive layer. The end of the heat-sensitive web is then only over one Part of the first layer of adhesive laid. Then a protective cover made of heat-resistant material is provided, and theirs The underside is coated with glue so that a second layer of glue is created. The protective cover is then over the The end of the heat-sensitive web is placed in such a way that the second layer of adhesive is attached to the underside of the protective cover with the side of the heat-sensitive sheet opposite the heat-resistant sheet and with the portion of the first Adhesive layer that connects over the end of the heat sensitive Railway extends beyond. Then there is preferably an application of heat and pressure, so that the adhesive layers Harden.

Preferably, the size of the heat-resistant protective cover is approximately the same as the size of the first adhesive layer and is so applied so that it extends substantially the same as the first layer of adhesive. It also covers the heat-sensitive Web prefers about 60% of the first adhesive layer, exposing about 40% of the same over the second layer of adhesive on the underside of the protective cover. The tow ends that form the end of the heat sensitive web

are preferably covered with tape before the thermosensitive sheet is adhered to the first layer of adhesive is connected.

The heat-sensitive web can be made of carbonizable There are tows such as polyacrylonitrile. The heat-resistant sheet and the protective cover can be made of silica fabric or a other heat-resistant material. The adhesive layers preferably consist of silicone rubber adhesive.

The invention is explained in more detail, for example, with the aid of the drawing. Show it:

1 shows a plan view of a device which is used for a method for oxidizing a carbonizable Spinning cable web is used;

Fig. 2 is a perspective view of parts of the filling thread introducer and the tensioning frame of the device according to FIG. 1 adjacent to it;

3 is a block diagram showing the sequential

Steps in a method for introducing a carbonizable tow web into the oxidizing ovens of the device of Fig. 1;

4 is a block diagram showing the sequential Indicating steps in a method for forming a flexible connection according to the invention, this being usable in the method according to FIG. 3;

Figure 5 is an illustrative perspective view of opposing panels and a protective cover the method according to FIG. 4; and

Figure 6 is an end view of the ends of the opposite

Tracks and the protective cover of Fig. 5 together with the adhesive interlayers of the finished flexible connection.

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For a better understanding of the invention, a method and a device for the oxidation of a polyacrylonitrile filament tow web are intended first or another web of carbonizable tows. Because such a procedure or such a device are already described in detail in the aforementioned DE patent application, follows below just a brief explanation.

Fig. 1 shows a device in a continuous process for the oxidation of a web of carbonizable Tow is used. The device comprises a creel 10 with a plurality of slip-on bobbins 12 on which Spinning cables are wound from carbonizable material. In the present case, the tows are made of polyacrylonitrile, Each tow consists of 3,000-12,000 filaments, depending on how tight the tow is in the one formed from them Web are spaced from each other. From Fig. 1 it can be seen that individual tow 14 from the various slip-on bobbins 12 unwound and pulled through a group 18 of top combs into a filling thread insertion device 16. The top combs serve as guides, while the tow 14 unwound from the slip-on bobbins 12 and to a relatively flat, im substantially horizontally extending web 20 can be drawn into the filling thread introducer 16 at the inlet. The width of the Web 20 can be up to approximately 134 cm and the web consists of up to 600 tows 14.

The filling thread insertion device 16 is used to weave a filling thread between the various tow 14, so that the various tow 14 of the web 20 are held together for further processing. A filling thread introducer is z. B. in our own U.S. Pat. No. 4,173,990. The braided by the filling thread insertion device 16 Filler thread is typically used after oxidation and further

machining of the web 20 removed so that the tow 14 individually or in groups and not just as part of the overall web 20 can be wound up.

After the filling thread has been braided in, the web 20 is conveyed into a tensioning frame 22, which consists of several of each other in the There is spaced rollers 24. Within the tensioning frame 22, the track 20 follows an alternating path around the various roles 24 before it emerges from the tensioning frame 22 and enters a first oxidation furnace 26. That The tensioning frame 22 is of conventional construction and ensures the desired mechanical tension of the web 20 when it is enters the oxidation furnace 26.

The oxidation furnace 26 forms together with a second oxidation furnace 28, an oxidation furnace unit 30. In the first oxidation furnace 26, the path 20 follows a relatively winding course by several different rollers 32, which are each arranged at opposite ends of the furnace 26. From the First oxidation furnace 26, the web 20 is drawn into the second oxidation furnace 28, in which it in turn is a relative follows a tortuous path as it travels around a plurality of rollers 34 at opposite ends of the furnace 28, respectively. Typically, the oxidation ovens 26 and 28 are internally divided into several different stages (not in FIG. 1 shown), each of which is kept at a temperature which is somewhat relative to the temperatures in the other stages is different. The roles 32 and 34 in the ovens 26 and maintain in connection with the tensioning frame 22 and a Tensioning frame 35 outside the outlet end of the furnace 28 creates a desired mechanical tension in the web 20 while this is drawn through ovens 26 and 28. At least some of the mechanical stress occurs as a result of shrinkage of the die Polyacrylonitrile material forming web 20 during the oxidation thereof. At the exit end of the second oxidation furnace 28, the web 20 is conveyed through the tensioning frame 35 and wound onto a revolving winding roller 36

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which it is kept before carbonation and further processing. The tensioning frame 35 is similar to that Tensioning frame 22 built up.

FIG. 2 shows in detail a part of the device from FIG. 1, in particular the filling thread insertion device 16 and the like Tensioning frame 22. According to FIG drawn between two opposed rollers 38 and 40 where the web 20 is formed. As in the one already U.S. Pat. No. 4,173,990 mentioned above, alternately successive tows 14, which are positioned between the rollers 38 and 40 run off, from the remaining tow 14 by harnesses 42 and 44, which are part of the filling thread introducer 16, are separated. A gripper unit 46 guides a filling thread 48 between the separated tow 14, immediately before the separated tow 14 again in a single plane to run towards each other with renewed formation of the web 20, which now has the filling thread 48. From FIG. 2 it can be seen that that the filling thread 48 runs back and forth alternately in a zigzag shape over the width of the web 20.

3 illustrates the successive steps of a method for introducing the web 20 into the oxidation ovens 26 and 28; this process is described in detail in the aforementioned DE patent application. First will be a Precursors in the form of a long web of refractory material moved through oxidizing ovens 26 and 28, after which the tail end of the precursor is connected to a leading end of the tow web to be oxidized. Then the forerunner becomes it used to pull the tow web through ovens 26 and 28 where tow of the web is desired be oxidized. When the leading end of the tow web from the tensioning frame 35 adjacent to the exit end of the second Oven 28 has leaked, this end can be severed from the rear end of the precursor. By using a Heat-resistant precursors, the ovens 26 and 28 can already be on the

Oxidation temperatures are brought before the web of carbonizable tow enters and through the ovens this is guided, whereby the loss of carbonizable tow is minimized or even eliminated.

According to the first step 52 in FIG. 3, the refractory precursor, which is a long sheet of refractory material such as Silica or aramid fabric, in oxidizing ovens 26 and 28 until it has completely or substantially completely passed through the ovens, with its rear end remains outside the inlet 50 to the furnace 26 and near it. In a second step 53, the oxidation ovens 26 and 28 are heated to the oxidation temperatures, if this has not yet happened. In a third step 53, the front end of the tow consisting of the tow 14 and through the web 20 formed by the filling thread introducer 16 is connected to the rear end of the precursor. In a fourth step 56, the precursor continues to pass through ovens 26 and 28 so that web 20 is in and through the oxidizing ovens 26 and 28 is performed. When the leading end of the web 20 of carbonizable tow 14 has passed completely through both ovens 26 and 28 and the tensioning frame 35 has run, in a fifth step 58 this front end can be separated from the rear end of the Precursors are separated.

According to the method illustrated in FIG. 3, the Heat-resistant precursors run into the furnaces 26 and 28 when they have already been heated to the oxidation temperature. Of the Precursors can remain in the heated ovens 26 and 28 without being damaged. In a typical case, at which the device of Fig. 1 is to be switched off for a certain period of time, the heat-resistant precursor is in the Ovens 26 and 28 initiated while the process is off and the ovens are cooling. When starting up again, the Furnaces 26 and 28 brought to the oxidation temperatures while the heat-resistant precursor is in them at rest. In the meantime, the trailing edge of the forerunner can be

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Edge of the web 20 are connected, so that when the oxidation temperatures are reached, the precursor and then the web 20 can be promoted through the ovens 26 and 28.

In the already mentioned DE patent application are a method and means for connecting the web 20 of carbonizable tow to the refractory leader 78 is provided, the opposite ends of the webs are covered with mutually opposite tape sections, and wherein the Spinning tow sections of the web 20 extending over the opposite Extend tape sections also to be cut off. Each edge so formed is then along its length Quilted and folded over in such a way that a loop is created into which a long rod is inserted. The opposite Edges and the inserted rods are then inserted between the opposing halves of a long connecting rod, and the opposing halves are with tensioning screws drawn towards each other over the length of the rod, so that the opposite tracks in the Connecting rod are set. When the connecting rod is fully moved through the oxidizers 26 and 28, can the web 20 can be separated from the heat-resistant precursor by loosening the screws along the length of the connecting rod, thereby separating the opposing halves of the connecting rod and the ends of the previously secured therein Lanes are released.

The present invention provides an alternative method or arrangement for forming a flexible joint between the web 20 and the heat-resistant precursor, this method or arrangement also in other cases are applicable, in which the opposite ends of two different long tracks are to be joined together. the successive steps of such a method are shown in Fig. 4 in conjunction with the perspective view of Figs indicated in the end view of FIG.

According to FIG. 4, in a first step 64, a protective cover 66 made of glass fabric, aramid fabric or another is made Heat-resistant flexible material provided. According to Fig. 5, the protective cover 66 has a width W equal to the width of one of the Heat-resistant precursors forming long web 68. The web 68 is also made of glass or aramid fabric or a other heat-resistant material. The width W of both protective cover 66 and web 68 is greater than about 12.7 mm the width of the web 20 of carbonizable tow. The length L of the protective cover 66 is appropriate measured, in the present case it is 25.4 cm.

In the second step 70 of FIG. 4, an adhesive layer 72 is applied to the end of the web at its edge 74. The size the adhesive layer 72 corresponds approximately to the size of the protective cover 66.

In a third step 76 of FIG. 4, an end 78 of the carbonizable tow web 20 is placed on part of the adhesive layer 72 so laid that the sheet 68 and its adhesive layer each about 6.35 mm over each of the opposite Edges of the web 20 extend out. Previously, on opposite sides of the end 78 of the web 20, sections of tape are made applied, wherein the ends of the tow protruding beyond the tape are cut off to form an edge 80 of the web 20. An upper belt section 82 is shown in Figure 5, and the opposite lower belt section is there not visible. The end 78 of the web 20 is placed on the adhesive layer 72 so that the end 78 is only part of the adhesive layer 72 covered. In the present case, the end 78 of the web 20 covers approximately 60% of the area of the adhesive layer 72, so that edge 80 is approximately six inches from edge 74 of web 68. This leaves an approx. 10.1 cm wide strip of the Adhesive layer 72 uncovered.

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In a next step 84 of FIG. 4, a second adhesive layer 86 is applied to the underside of the protective cover 66. Both the adhesive layer 86 and the first adhesive layer 72 can be made of silicone rubber adhesive (e.g. GE RTV No. 31) exist. The adhesive layers 72 and 86 are each approximately 3.2 mm thick in the present case, but they can each be used in individual cases have the required thickness.

In a next step 88 of Fig. 4, the protective cover 66 is on the end 78 of the web 20 and the free Sections of the adhesive layer 72 placed so that both the protective cover 66 and the adhesive layer 86 are in the extend substantially the same as the first adhesive layer 72. This places the adhesive layer 86 on the underside of the protective cover 66 is connected to the end 78 of the web 20 and to the free portions of the adhesive layer 72. The protective cover 66, the width W of which is greater than the width of the web 20 by 12.7 mm, extends over each of the opposing ones Edges of the web by 6.3 mm.

In a next step 90 of FIG. 4, the webs 20 and 68 as well as the protective cover 66 and the associated adhesive layers 72 and 82 applied heat and pressure to cure the adhesive. It has been found that a silicone rubber adhesive by using a hardening accelerator made of tin octoate within 5-15 minutes when exposed to cures essentially completely at a pressure of 0.48-1.03 bar at a temperature of 93.3-149 C. the Heating under pressure can be done in an air press using opposing Teflon release sheets placed on top opposite heating plates are placed in the press.

The completed connection is shown in FIG. It can be seen that the end 78 of the web 20 is between the heat resistant web 68 and the heat-resistant protective cover 66 is enclosed and protected. The ends of the individual web 20 forming

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The tow at the edge 80 is completely separated from the protective cover 66, the web 68 and the adhesive layers therebetween 72 and 86 surrounded and enclosed, reducing the risk of exothermic reactions in the high temperature environment in the Oxidation and similar machining processes are minimized or excluded. At the same time, the connection has proven to be proven to be extremely solid and highly flexible. At the end of the oxidation process or another processing step, the web 20 can be separated from the web 68 by removing the web cut across its width adjacent to the connection or, alternatively, the connection itself, which consists of the web 68, protective cover 66, adhesive layers 72 and 86 and possibly a portion of end 78 of web 20, is severed.

Claims (12)

PoTenian attorney cOUARD K. BAUMANN Dipl. Phys. Patent claims » attlerstr. 1, D-8011 Höhenkirchen-Munich egg. (08102) 4108 Telex ·. 1 / arrangement for connecting the end of a first web to the end of a second web, characterized by a first layer of adhesive (72) covering the end (74) of the second Connects web (68) to the end (80) of the first web (20) on a first side of the first web (20), a piece of material (66) and a second layer of adhesive (86) that the piece of material (66) with the end (80) of the first web (20) on a second side of the first web (20) opposite the first side. 2. Arrangement according to claim 1, characterized in that that a portion of the piece of material (66) overlaps the second web (68) and is secured thereon with a layer of adhesive (72) is. 3. Arrangement according to claim 1, characterized in that that the first web (20) made of heat-sensitive material and the second web (68) and the piece of material (66) made of heat-resistant Material. 4. Arrangement according to claim 1, characterized in that that the first and second adhesive layers (72, 86) consist of silicone rubber adhesive. J4 I J4 / I - 2 ■ 5. Arrangement according to claim 1,
characterized, that the first web (20) is formed from a plurality of tows (14) made of carbonizable material, that the second web (68) and the piece of material (66) consist of silica fabric, and that the first and second adhesive layers (72, 86) consist of silicone rubber adhesive. 6. Arrangement according to claim 1,
characterized, that the first web is a long heat-sensitive web (20), that the second web is a long heat-resistant web (68), the End (74) overlaps a first side of the thermosensitive sheet (20) at the end (80) thereof, that the first adhesive layer (72) is a first layer of flexible material that connects the heat-resistant sheet (68) to the first side of the heat-sensitive web (20) is connected by the fact that the piece of material (66) is a flexible, heat-resistant material section which overlaps an opposite second side of the heat-sensitive sheet (20), and that the second adhesive layer (82) is a second layer of flexible material, which the flexible heat-resistant material piece (66) connects to the second side of the thermosensitive sheet (20). 7. Arrangement according to claim 6,
characterized, that the first and second layers of flexible material (72, 86) consist of silicone rubber adhesive. 8. Arrangement according to claim 7,
characterized, that the heat-sensitive web (20) made of polyacrylonitrile tow consists and that the heat-resistant web (68) and the flexible heat-resistant material piece (66) each made of silica fabric exist. 9. A method of joining a first and a second long sheet of flexible material,
characterized by the following process steps: Providing a protective cover (66) made of flexible material; Applying a first layer of adhesive (72) to a portion of the second web (68) near one end (74) thereof; Laying one end of the first web (20) including an edge (80) thereof on the first adhesive layer (72); Applying a second layer of adhesive (86) to an underside of the protective cover (66); and Placing the protective cover (66) over the first sheet (20) so that the second layer of adhesive is on the underside (86) contacts the first track (20) and the protective cover (66) is on the opposite side of the second track (68) Side of the first web (20) is located. 10. The method according to claim 9,
characterized, that the protective cover (66) is placed on the first web (20) in such a way that a section of the protective cover (66) extends beyond the edge of the first web (20). 11. The method according to claim 9,
characterized by the further step that the first and the second web (20, 68) and the protective cover (66) are subjected to heat and pressure after the laying of the latter (66) on the first web (20), so that the J4 I J4 / I first and second adhesive layers (72, 86) on the second web (68) and the underside of the protective cover (66)
Harden. 12. The method according to claim 9, characterized by the further step, that the edge of the first web (20), including its edge, on the first adhesive layer (72) before it is placed is covered with tape (82).