Patent Publication Number: US-9890475-B2

Title: Method and device for application of liquid polymeric material onto spinning cords

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a 35 U.S.C. § 371 National Phase conversion of PCT/CZ2012/000019, filed Feb. 27, 2012, which claims benefit of Czech Republic Application No. PV 2011-212, filed Apr. 12, 2011, the disclosure of which is incorporated herein by reference. The PCT International Application was published in the English language. 
     TECHNICAL FIELD 
     The invention relates to a method for application of liquid polymeric material onto active spinning zone of a cord of spinning member of spinning electrode byan application means moving reversibly along the active spinning zone of the cord in a device for production of nanofibres through electrostatic spinning of liquid material in electrostatic field of high intensity between at least one spinning electrode and against it arranged collecting electrode. 
     Further the invention relates to a device for application of liquid polymeric material onto active spinning zone of a cord of a spinning member of a spinning electrode in a device for production of nanofibres through electrostatic spinning of liquid material in electrostatic field of high intensity between at least one spinning electrode and against it arranged collecting electrode, whereas the device comprises a carrying body placed reversibly displaceably along the active spinning zone and coupled with a drive and with a reservoir of the liquid polymeric material. 
     BACKGROUND ART 
     The EP 2173930 describes the device for production of nanofibres through electrostatic spinning of liquid material in electrostatic field between at least one spinning electrode and against it arranged collecting electrode. The spinning electrode comprises at least one spinning member comprising the cord, which comprises the straight section, which is parallel with the plane of depositing of nanofibres and/or with the collecting electrode and it forms an active spinning zone of the cord. The cord of the spinning member is stationary, or it is displaceable along its length, or it is movable continuously or discontinuously along its length and it comprises at least one active spinning zone, which is in stable position with respect to the collecting electrode. To the cord there is assigned a device for applying the liquid material onto the cord in direction of length of the cord, whereas the device is placed reversibly displaceably in the carrying body of the spinning electrode along the active spinning zone of the cord. The EP 2173930 describes number of variants of the arrangement of the cord of the spinning member, in one of them the cord is placed movably in the direction of its length, whereas its final length is several times bigger than the length of the active spinning zone of the cord. The beginning of the cord is placed on the unwinding reel, which is coupled with a drive or with a brake to secure defined tension of the cord. The winding reel is coupled with the winding drive to secure movement speed of the cord. The EP 2173930 describes number of variants of application means, which are arranged reversibly displaceably along the length of the active spinning zone of the cord, for example the capillary application means, into which there is brought liquid material is brought, which is forced out from them and sticks on the active spinning zone of the cord. The capillary application means move under the active spinning zone of the cord and the described variants comprise one or two capillary application means for one cord. The movement of application means is as frequent and fast as to be enough liquid material for spinning in the active spinning zone of the cord. A disadvantage of the capillary application means is possibility of clogging-up of the capillaries, especially with the drying out and ageing liquid polymeric material, which is in contact with air. Another disadvantage of the capillary application means is that it is difficult to regulate it, especially with respect to polymer consumption. Application of Polymeric material onto the active zone of the cord from the bottom side of the cord does not always guarantee the same and uniform polymeric material layer on the top side of the spinning cord. Other variants of application devices comprise the application roller, which is common for several cord active zones, under which is rotatingly mounted in the polymeric material reservoir, whereas is mounted together with reservoir of polymeric material reversibly displaceably along the active spinning zones of cords. The roller by its surface carries out the liquid material from the reservoir and applies it on the active spinning zone of the cords. The disadvantage of this arrangement is the fact that in case of most of polymeric materials the spinning effect probably occurs also on the roller surface off the cords. This disadvantage is eliminated by the next described invention embodiment, where the roller is replaced by a system of disks, whereas one disk is assigned to each cord. Application devices with neither the application roller nor the application disks are able to ensure in long term the constant quality of the polymeric material layer on the top side of the spinning cord, especially because of high quantity of polymer that being in contact with environment. Another disadvantage is free level of polymer in the reservoir from which solvent evaporates, which even in case of mixing results in faster ageing of the polymeric material mixing. 
     The goal of the invention is to eliminate or at least reduce the disadvantages of background art. 
     SUMMARY OF THE INVENTION 
     The goal of the invention is achieved by a method for application of liquid polymeric material according to the invention, which principle consists in that the liquid polymeric material is applied on the cord around its whole circumference without any contact with gaseous environment in the spinning space, where the application means reversibly moves, whereas the thickness of the layer of the liquid polymeric material is being reduced when the cord leaves the application means and immediately after leaving the application means the process of electrostatic spinning of the liquid polymeric material applied on the cord is started. 
     The technique according to the invention prevents evaporation of solvent from the liquid polymeric material during application on the cord and so ageing of the liquid polymeric material is slowed down. The spinning process runs after the cord leaves the application means and only from the layer stuck on the cord, which improves uniformity of produced nanofibres. 
     The thickness of the layer of the liquid polymeric material on the cord is determined by the size of distance between the cord and the wall of application holes of the application means, whereas this distance is determined by qualitative parameters of the liquid polymeric material, mainly its viscosity. 
     To ensure constant quality of the liquid polymeric material in the application holes, the liquid polymeric material in a small amount flows out through the application holes through the distance between the wall of the application hole of the application means and the cord. 
     The goal of the invention is also achieved by a device for application of the liquid polymeric material according to the invention, which principle consists in that there is at least one application means placed in the carrying body of the application device, in which there is made a supply chamber fillable during application with the liquid polymeric material. The supply chamber is connected with external environment by two application holes, through which the cord runs during application without touching its walls, whereas the liquid polymeric material flows out through the distance between the wall of the application hole and the cord to the tank of the application device, from which it is drawn away. 
     The device secures insulation of the place, where the liquid polymeric material is applied on the cord, from environment, where spinning of the liquid polymeric material runs, which eliminates disadvantages of the background art. 
     To secure continuous supply of the liquid polymeric material for long-time maintaining the spinning process, the supply chamber is connected with the reservoir of the liquid polymeric material which is formed by the working reservoir of fresh liquid polymeric material. 
     In case of simpler variant of the device, which is intended for testing of for example ability of spinning of the liquid polymeric materials, the supply chamber is interconnected with the working reservoir of the fresh liquid polymeric material, which is arranged above the supply chamber of the application means, so the liquid polymeric material flows into it by gravity. The outlet of the used liquid polymeric material flowing during application on the cord through the application holes is secured by tank of the application device. 
     For processing of smaller doses of the liquid polymeric material the supply chamber is equipped with a dosing hole, so the working reservoir of the fresh liquid polymeric material is formed. 
     To secure stable supply of the liquid polymeric material, especially during long-term operation it is advantageous if there is the dosing device of the liquid polymeric material arranged between the reservoir or the working reservoir of the liquid polymeric material and the application means or number of application means. 
     With respect to the fact that there is very small amount of the liquid polymeric material needed to supply to the application means, it is advantageous if the dosing device is equipped with a pump capable of supplying with the liquid polymeric material in small separate doses or continuously in small amount. 
     In a concrete embodiment the carrying body comprises a base body, on which there is mounted a tank equipped with a removable cover. The tank has an inclined bottom sloped down to the base body, in which there is formed a retention vessel for collecting of the used liquid polymeric material which is connected with the waste reservoir of the used liquid polymeric material through flexible pipes, whereas the application means arranged in the carrying body are interconnected by a system of tubes, whereas the first of them is connected to the inlet of the liquid polymeric material, every other one is connected to the previous one and the outlet of the last one is connected to the system of returning of the liquid polymeric material. 
     For slowly ageing liquid polymeric materials it is advantageous, if the system for returning of the liquid polymeric material comprises return pipe leading to the working reservoir, from which it is retaken for processing. In this variant the used liquid polymeric material is represented by only a part of the liquid polymeric material flowing through the application holes during application of the liquid polymeric material on the cord. 
     For standard liquid polymeric materials it is sufficient if the system for returning of the liquid polymeric material comprises a constricted overflow or its equivalent, which leads to above of the inclined bottom of the tank. 
     It is advantageous for all embodiments, if the application holes of the application means have the same diameter. 
     In terms of quality of the applied layer, it is advantageous for all embodiments, if the cord meets the axis of the application holes. 
     Other characteristics of the device are specified in the dependent claims. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Examples of the embodiment of the device according to the invention are schematically represented in the attached drawings. 
       The  FIG. 1  shows a longitudinal section of the carrying body of the application device with two application means, 
       The  FIG. 2  shows a schema of supply of the application means by liquid polymeric material, 
       The  FIG. 3 a    shows a view of the arrangement of the application means and the cord, 
       The  FIG. 3 b    shows a section of the  FIG. 3 a    along the cord, 
       The  FIG. 4 a - d    show view, projection and sections of the application means, 
       The  FIG. 5  shows another possible embodiment of the application means, 
       The  FIG. 6 a - c    show the application device comprising the cord guiding mechanism formed by two pulleys and 
       The  FIG. 7 a - b    show the application device comprising the cord guiding mechanism formed by three pulleys. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     The device for application of the liquid polymeric material on the active spinning zone of the cord of the spinning member of the spinning electrode according to the invention in the example of embodiment shown in the  FIG. 1, 3   a ,  3   b  comprises the carrying body  1  common for two cords  2  of the spinning member of the spinning electrode created for example according the EP 2173930 (WO 2009/010020). The carrying body  1  is mounted reversibly displaceably along the active spinning zone of both cords  2  and its main part is the tank  3 , which is firmly mounted on the base body  4  and equipped at the upper section with the removable cover  5 . The tank  3  is arranged perpendicularly to the cords  2  and is formed by a hollow body  31  opened from above, which has an inclined bottom  311  sloped down to the base body  4 . In the cavity of the tank  3  there is arranged a system of tubes  32  whose beginning is connected to an inlet  33  of the liquid polymeric material, which is in the shown embodiment arranged in the base body  4 . In places of the cords  2  there are in the system of tubes  32  arranged application means  6  for application of the liquid polymeric material on the active zones of the cords  2 . After the last application means  6  there is in the system of tubes  32  arranged a constricted overflow  34  which secures constant overpressure, or constant level of the liquid polymeric material in the system of tubes  32  and in the application means  6 . Excess of the liquid polymeric material flows from the constricted overflow  34  to the inclined bottom  311  and, as an effect of sloping, it flows over the bottom  311  into the retention vessel  41 , which is formed in the base body  4 . In the retention vessel  41  there is arranged freely displaceably a float-gauge  42  coupled with a known not represented evaluation and/or control device. The float-gauge  42  lies on the surface of the liquid polymeric material in the retention vessel  41  and prevents the liquid polymeric material from the contact with air. 
     As it is shown in the  FIG. 2 , the liquid polymeric material is led to the inlet  33  through pipes from the reservoir  7  of the liquid polymeric material, which in the shown embodiment comprises the working reservoir  71  of the fresh liquid polymeric material and the waste reservoir  72  of the used liquid polymeric material. 
     The application means  6  in the first example of embodiment shown in  FIG. 1, 3   a ,  3   b ,  4   a - d , is formed by a cylindrical body  61  equipped with faces  62  and  63 . In the longitudinal axis of the body  61  in the faces  62  and  63  there are made co-axial application holes  621 ,  631 , to which an outward opened axial groove  64 , which is parallel to the longitudinal axis of the cylindrical body  61 , tangentially ties together by its bottom or to the bottom equivalent inner surface. In the shown embodiment the axial groove  64  is cylindrical but it can be of any shape allowing insertion of an openable and sealing element  66  and secures its sealing function. The bottom or the inner surface equivalent to the bottom of the axial groove  64  in the faces  62 ,  63  forms the surface tangential to the application holes  621 ,  631  in the faces, whereas the axial groove  64  and the application holes  621 ,  631  are interconnected by insertion grooves  622 ,  632 , which allow insertion of the cord  2  into the application holes  621 ,  631  in the faces  62  and  63  and in a case of a need its removal. Perpendiculary to the axial groove  64  parallel to the longitudinal axis of the cylindrical body  61  there is in the cylindrical body  61  of the application means  6  between the faces  62  and  63  made a supply chamber  65 , which is in the shown embodiment formed by a cylindrical hole. To the supply chamber  65  there are connected tubes  32  for an inlet of the liquid polymeric material. The input side of the supply chamber  65  of the first application means  6  is connected through the first tube  321  to the inlet  33  of the liquid polymeric material, the output side of the supply chamber  65  of the first application means  6  is connected through the second tube  322  to the input side of the supply chamber  65  of the second application means  6  and the output side of the supply chamber  65  is connected through the third tube  323  to the constricted overflow  34 . The axial groove  64  parallel to the longitudinal axis of the cylindrical body  61  of the application means  6  is intended for insertion of the openable and sealing element  66 , which is of the same shape as the axial groove  64  and in the shown embodiment is formed by a sealing cylinder. In a case of a need to apply the liquid polymeric material onto more cords  2 , the device has adequate number of the application means  6 . 
     The diameter of the application holes  621 ,  631  of the application means  6  is bigger than the diameter of the cord  2 , whereas the distance between the outer surface of the cord  2  and the wall of the respective application hole  621  or  631 , determines, together with both pressure and viscosity of the liquid polymeric material in the system, thickness of the layer of the liquid polymeric material applied on the active zone of the cord  2 . The distance is set in a way to avoid trickling. The mutual position of the cord  2  and the application holes  621 ,  631  of the application means  6  is set in a way to avoid contact of the cord  2  and the walls of the application holes  621 ,  631  everywhere during reversible movement of the application means  6  along the active zone of the cord  2 , whereas it is desirable that the cord  2  is in the axis of both application holes  621 ,  631  of the application means  6 . Set up of the cord  2  to the required position is done by setting of its end points, between which the cord  2  is stretched. 
     The application of the liquid polymeric material takes place inside the application means  6  in the cavity of the supply chamber  65 , which is completely filled with the liquid polymeric material and through which the cord  2  passes transversely. Therefore application takes place in closed space in the absence of air or gaseous medium present in the spinning space around the application means  6 , through which the application means  6  reversibly moves during application. during movement of the application means  6  along the active zone of the cord  2 , the cord  2  enters the front application hole  621  or  631  of the application means  6  (depending on direction of movement). At the same time, the liquid polymeric material flows through the distance between the cord  2  and the wall of the front application hole  621  or  631  and the liquid polymeric material partially flushes away the residual polymeric material stuck on the cord  2  and flows to the inclined bottom  311  of the tank  3 . When the cord  2  leaves the back application hole  631  or  621  of the application means  6 , a deposit of the liquid polymeric material is created on the cord  2 . According to the type and quality of the surface of the cord  2  and according to the type and viscosity of the liquid polymeric material, the liquid polymeric material creates on the surface of the cord  2  either a continuous film or a set of droplets. So, the deposit of the liquid polymeric material is created inside the application means  6  and amount of the liquid polymeric material on the cord  2  is reduced to required amount by the back application hole  631  or  621  of the application means  6 , whereas a part of the liquid polymeric material, which does not stuck on the cord  2 , flows down the face of the application means  6  to the inclined bottom  311  of the tank  3  and then down the bottom to the retention vessel  41 , in which its surface is covered by the float-gauge  42 , which prevents air from access to the polymeric material. 
     The system of supply of the liquid polymeric material shown in  FIG. 2  comprises the working reservoir  71  of the fresh liquid polymeric material, which is connected to the application means  6  through the dosing device  8 . The dosing device  8  comprises the pump  81  capable of supplying the liquid polymeric material into the application means  6  in small separate doses or continuously in small amount. Additionally, a mixing pump  83  can be assigned to the working reservoir  71 . In the shown embodiment the dosing device  8  is equipped with the drain pump  82 , which is interconnected with the retention vessel  41  and with the waste reservoir  72  of the used liquid polymeric material and so forms a system of returning of the liquid polymeric material. 
     According to another not represented embodiment, the system of returning of the liquid polymeric material can comprise a return pipe connected to the outlet of the last application means  6  and empties into the working reservoir  71  of the liquid polymeric material. This is optimal for slowly ageing liquid polymeric materials. If the liquid polymeric material is not capable for repeated usage, it is led into the waste reservoir  72 . 
     In a simpler variant of the device intended for testing of for example spinning of the liquid polymeric materials, the supply chamber  65  is interconnected with the working reservoir  71  of the fresh liquid polymeric material, which is arranged above the supply chamber  65  of the application means  6 , so the liquid polymeric material flows into it by gravity. The outlet of the used liquid polymeric material, flowing during application on the cord  2  through the application holes, is secured by the tank  3  of the application means  6 . 
     For processing even smaller doses of the liquid polymeric material the supply chamber  65  is in another not represented embodiment, equipped with the dosing hole, so it forms the working reservoir of the fresh liquid polymeric material. 
     Another possible embodiment of the application means  6  is shown in the  FIG. 5 . In this embodiment, the application holes  621 ,  631  are made in the auxiliary body  610 , which is rotatingly mounted in a cylindrical body  61  of the application means  6 , whereas made in the auxiliary body  610  there is made a guiding groove  611  reaching the application holes  621 ,  631 . The auxiliary body  610  is able to take two positions. At the first position, the guiding groove  611  points out of the body, so the application means can be put on the cord  2 . At the second position, the auxiliary body  610  is turned and the guiding groove  611  is closed, so the cord  2  cannot fall off the application holes  621 ,  631  during application. 
     To secure a stable position of the cord  2  in the application holes  621 , in the application means  6  there is mounted  631  the a guiding mechanism  67  of the cord  2 . 
     In the embodiment shown in the  FIG. 6 a - c   , the supply chamber  65  made inside the application means  6  is extended and two guiding pulleys  671 ,  672  are rotatingly mounted inside it one above the other. The pulleys  671 ,  672  are mounted displaceably in the direction perpendicular to their axis and to the axis of the application holes  621 ,  631  and they are coupled with setting means. The place of the touch of the guiding pulleys  671 ,  672  lays in the axis of the application holes  621 ,  631 . The cylindrical body  61  of the application means  6  is separated into two parts to enable insertion of the cord between the guiding pulleys, whereas the parting line passes through the axis of the application holes  621 ,  631 . The parting line can be either vertical or horizontal. The bottom guiding pulley  671  is equipped with a groove for guiding of the cord  2  and there are holes made in it to allow the liquid polymeric material to pass through the supply chamber  65  to the next application means  6 , whereas the holes serve at the same time for mixing the liquid polymeric material in the supply chamber  65  of the application means  6 . 
     In another embodiment shown in the  FIG. 7 a,b   , the cord guiding mechanism comprises two rotatingly mounted guiding pulleys  673 ,  674  arranged next to each other, whereas their circumferences are arranged tangentially to the axis of the application holes  621 ,  631 . A tentioner pulley  675  reaches between these guiding pulleys  673 ,  674  by its circumference, it is mounted displaceably in the direction perpendicular to the axis of the application holes  621 ,  631  and it is coupled with position setting means. This occurs tension of the cord  2  and its precise guidance through the application holes  621 ,  631 . The cylindrical body  61  of the application means  6  is separated into two parts to enable insertion of the cord between the guiding pulleys, whereas the parting line passes through the axis of the application holes  621 ,  631 . The parting line can be either vertical or horizontal. The guiding pulleys  673  and  674  are equipped with a groove for guiding of the cord  2  and there are holes made in them to allow the liquid polymeric material to pass through the supply chamber  65  to the next application means  6 , whereas the holes serve at the same time for mixing the liquid polymeric material in the supply chamber  65  of the application means  6 . The holes are made also in the tentioner pulley  675 . 
     LIST OF REFERENTIAL MARKINGS 
       1  carrying body 
       2  cord of spinning member of the spinning electrode 
       3  tank 
       31  hollow body opened from above 
       311  inclined bottom 
       32  tube 
       321  first tube 
       322  second tube 
       323  third tube 
       33  inlet of the liquid polymeric material 
       34  constricted overflow 
       4  base body 
       41  retention vessel 
       42  float-gauge 
       5  removable cover of the tank 
       6  application means 
       61  body of the application means 
       610  auxiliary body 
       611  guiding groove 
       62 ,  63  faces of the application means 
       621 ,  631  application holes of faces of the application means 
       622 ,  632  insert grooves in faces of the application means 
       64  axial groove 
       65  supply chamber 
       66  openable and sealing element 
       67  cord guiding mechanism 
       671  bottom guiding pulley 
       672  top guiding pulley 
       673 ,  674  guiding pulleys 
       675  tentioner pulley 
       7  reservoir of the liquid polymeric material 
       71  working reservoir 
       72  waste reservoir 
       8  dosing device 
       81  pump 
       82  drain pump 
       83  mixing pump