IMPROVED APPLICATOR NOZZLE BACKGROUND OF THE INVENTION The present invention relates to an improved applicator nozzle for applying a liquid coating such as a pressure-sensitive adhesive to a continuous paper web or movable web. Pressure sensitive labels typically consist of a supporting film or paper, a thin layer of a release material typically made of silicones, a layer of pressure-sensitive adhesive and a front layer of paper or plastic, typically referred to as a "paper front". Pressure sensitive labels are typically made of continuous, long rolls of paper for labels that are printed or otherwise marked with the desired signs and then separated into individual labels. Conventional processes for making continuous paper webs for pressure sensitive labels typically take the form illustrated in Figure 1. As shown in this figure, a paper web or web of web paper 10 is continuously unrolled from the web. of paper 12, is passed through the printing station by reinforcement stamping 14, through the silicone coating station 16 and towards the curing furnace 18 where the silicone release layer dries and hardens. In some systems, the stamping station 14 goes behind the silicone coating station 16. Then, the continuous paper web is passed to the coating station 20 where a thin layer of pressure-sensitive adhesive is applied to the layer. of sylicon. The web of continuous paper is then passed to the drying oven 24 where the pressure-sensitive adhesive dries to a sticky state. Alternatively, the pressure sensitive adhesive is solidified by cooling as, for example, when a molten metal adhesive is used. After passing out of the drying oven 24, the web of continuous paper is passed to the rolling station 26 where the web of continuous paper is laminated with a front layer of the paper 28 continuously separated from the front supply of the paper 30. The finished continuous paper web is then wound onto a product roll 31. In order to apply the pressure sensitive adhesive to the web of continuous paper 10 in the coating station 20, an applicator nozzle is typically used, as schematically illustrated in FIG. Figure 2. As shown in this Figure, the continuous paper web 10 is passed over a spare roll 22, such that the silicone layer in the continuous paper web 10 is facing the applicator nozzle. 34. The applicator nozzle 34 includes a coating orifice 36 installed approximately perpendicular to the direction of passage of the continuous paper web 10, with the width of the facing orifice. or 36 being approximately as wide as the width of the continuous paper web 10. In this context, "width" refers to the dimension taken transverse to the direction of movement of the continuous paper web passing the liner orifice of the web. nozzle. The pressure-sensitive adhesive is supplied to the coating orifice 36 from an inlet orifice 38 that communicates with a manifold 40 for distributing the pressure-sensitive adhesive along the full width of the coating orifice 36. The manifold 40 communicates with the orifice. of coating 36 through a "pre-projection" or narrow, elongated slot 44 and then through a "projection" or elongated slot 48. In the applicator nozzles of the type described above, the dispenser 40, the pre-projection 44 and the projection 48 are typically installed substantially parallel to and substantially as wide as the nozzle lining holes. The pre-protrusion 44 is typically too long (i.e., the dimension corresponding to the flow direction of the coating material) in relation to its thickness. For example, the length / thickness ratios in such pre-protrusions are typically between about 25/1 and 50/1, while the length / thickness ratios in the protrusions are typically between about 50/1 and 100/1. In the nozzle illustrated in Figures 1 and 2, the pre-protrusion 44 is approximately 750 μm thick and 1 inch long, while the protrusion 48 is approximately 100 to 200 μm thick and 0.75 inches long. The distributors, pre-protrusions and protrusions installed substantially parallel to and substantially as wide as their corresponding liner holes, are widely used in the applicator nozzles as they facilitate the uniform supply of the liquid coating material across the total width of the paper tape Continued to put on. Also, the projections are typically adjustable so that the applied coating thickness can be adjusted as desired. Conventional manufacturing processes such as those illustrated in Figures 1 and 2 can operate over a wide range of production speeds. For example, it is not exceptional for the commercial modes of the previous installation to operate at speeds of 50 to 500 meters per minute using continuous paper tapes that are one meter or more in width. In addition, many different pressure sensitive adhesives can be used in such processes to make pressure sensitive labels. For example, heat-melt adhesives, solvent-based adhesives and emulsion-based adhesives can be used for this purpose. Also, within each of these categories, many different compositions may be employed. In addition, a wide variety of different liquid coatings, in addition to the pressure sensitive adhesives, can be applied to movable continuous paper tapes using the applicator nozzle and the techniques, as described above. In commercial operation, it is often necessary to change from one pressure-sensitive adhesive to another in order to meet consumer demands and other performance requirements. Currently, this is done by changing the pressure sensitive adhesive previously used to a new pressure-sensitive adhesive upstream of the nozzle inlet orifice. Also, the nozzle is typically closed and sometimes cleaned by passing a suitable cleaning liquid such as soapy water through the nozzle, before a new adhesive is provided therethrough. In some cases, an operator passes a wedge or other accessory through the liner hole to ensure that no adhesive attaches to it. Due to the relatively long mass of the continuous paper web roll 10 and the need to keep the continuous paper web 10 moving at a constant speed in commercial operation, it is usual to keep the continuous paper web 10 moving for two to three minutes typically required to change from one pressure-sensitive adhesive to another. Since the continuous paper tape produced during the period of change will typically have an amount outside the specification of pressure sensitive adhesive or non-fully pressure sensitive adhesive, it is usual to discharge all of this material to the waste every time a change is made. At the production speeds typically found today, this translates as a loss of 100 to 1,000 or more meters of the product for each change. According to the above, there is a need for a new applicator nozzle that will allow a much faster change between pressure sensitive adhesives, than is possible in conventional practice. In this regard, applicator nozzles that are capable of processing two or more pressure sensitive adhesives at the same time are already known. See, for example, the E.U. 3,480,998 by Von Erdberg and the E.U. 4,152,387 of Cloeren. However, these nozzles are made to continuously produce multi-layer coatings, not to alternately produce single layer coating. Therefore, they are not able to completely eliminate the flow of a layer or the rapid change that is necessary to reduce or eliminate the large amount of waste produced under current practice. The U.S. Patent No. 4,756,271 to Gary Maier discloses an applicator nozzle that allows the change from one pressure-sensitive adhesive to another, to alternatively produce single-layer coatings. However, in nozzles of this type, sealing the nozzles to prevent spillage of a pressure-sensitive adhesive on the other can be a problem. The spillage of a pressure-sensitive adhesive on the other in a nozzle capable of processing multiple adhesives, can lead to a product outside the specification. Also, the pressure sensitive adhesives can be captured in the "dead zones" in the nozzle, where they can harden, thus rendering the nozzle inoperative. This problem is compounded when the nozzles, such as those illustrated in the Maier Patent, in which one or more flow channels are closed for extended periods of time. The nozzle shown in the above-noted Maier patent uses a rotating cam to effect the change between the different adhesives. During this change, the main face or edge of the cam slides over the outlet channel leading to the lining hole. With this design, effective sealing can be difficult since any sealing means at the leading edge of the cam rubs constantly as the cam moves between the different coating positions. According to the above, there is a need for a nozzle which not only allows rapid change from one adhesive to another, but also which is capable of operating for extended periods of time with little or no spillage. SUMMARY OF THE INVENTION In accordance with the present invention, an improved applicator nozzle is provided which includes two dispensers for receiving two different coating liquids such as pressure sensitive adhesives, two separate passages communicating between the respective dispensers and the pre-protrusion of the nozzle and a closing means for opening and closing the two different passages to allow the coating liquid in the two distributors to flow alternately towards the pre-projection of the nozzle and the coating orifice. Each of the distributors in the nozzle and each of the respective flow passages communicating with the pre-projection of the nozzle, are installed essentially parallel to and essentially the same width as the coating orifice. In addition, the closure means is adapted to open and close each flow passage by rapid action. In addition, a sealing system is provided to seal the closure means in the nozzle body of the inventive nozzle to prevent spillage of the two coating liquids. Because the distributors and the associated flow passages of the inventive applicator nozzle are parallel to and as wide as the coating orifice, each of the coating liquids is supplied to the coating hole as evenly as possible throughout. of the total length of the coating hole. In addition, because the closing means that opens and closes the respective flow passages operates with a fast action, the change between adhesives occurs very fast, thus minimizing the production of the product outside the specification. Further, because the closure means is mounted in the nozzle body of the inventive applicator nozzle with a sealing system, the spillage of the two coating liquids in another within the nozzle and the spillage of the coating liquids out of the nozzle, it is substantially eliminated. As a result of these characteristics, it is possible with the applicator nozzle to change from one coating liquid to another in periods of time as short as 0.1 to 1.0 seconds. This translates as the production of the product outside the specification of typically one to three meters, instead of 100 to 1,000 meters as it is in current practice. In addition, because the spillage of the coating liquids is essentially eliminated, the inventive applicator nozzle can operate for very long periods of time with little or no maintenance or closure. This also contributes to improved production speeds and lower waste production. BRIEF DESCRIPTION OF THE DRAWINGS The present invention can be easily understood by reference to the following drawings, wherein: Figure 1 is a schematic illustration of a typical establishment of the prior art for manufacturing label paper; and Figure 2 is a schematic illustration of a prior art applicator nozzle used in the setting of Figure 1; and Figure 3 is a schematic illustration of the improved applicator nozzle of the present invention; and Figure 4 is an end view of the improved applicator nozzle of Figure 3; and Figure 5 is a partial schematic perspective view of a change bar or closure means used in the applicator nozzle of Figures 3 and 4; and Figure 6 is a schematic end view illustrating the structure of the preferred sealing means used to seal the shift bar of Figure 5 on the nozzle body of the improved applicator nozzle of Figure 3; and Figure 7 is another schematic perspective view illustrating the relationship of the shift bar of Figure 5 with other elements of the improved nozzle of Figures 3, 4 and 5; and Figure 8 is a schematic perspective view illustrating the shape of the dispensers of the improved applicator nozzle of Figure 3; and Figure 9 is a schematic illustration of a coating system comprising the improved applicator nozzle of the present invention and various peripherals. DETAILED DESCRIPTION As shown in Figure 3, the inventive applicator nozzle generally indicated as 50 is composed of an elongate nozzle body 52 having a width generally as wide as the width of the movable continuous paper web to be coated. The nozzle body 52 is composed of a central section 54, an upper section 56 and a lower section 58. The upper section 56 and the lower section 58 define therebetween a narrow, elongated pre-projection or slot 60. The projection 60 communicates with the projection 62 defined between the upper flange of the nozzle 64 and the lower flange of the nozzle 66. The outer edges of the upper flange of the nozzle 64 and the lower flange of the nozzle 66 define a coating hole 68, from which the liquid material is deposited from the nozzle 50 on a movable continuous paper web to be coated. According to conventional practice, the upper rim of the nozzle 64 and the lower rim of the nozzle 66 can be adjustable so that the thickness of the projection 68 and hence the amount of liquid material deposited on the paper web movable continuous through the cover hole 68, can be adjusted as desired. Alternatively, one or both flanges of the nozzle can be fixed, if desired. In order to alternatively supply the liquid coating materials, first and second, to the coating hole 68, the first inlet 69 and the second inlet hole 70 are defined in the central section 54 of the nozzle body 52. The first the inlet 69 communicates with a first distributor 72 which is defined by an elongated slot in the central section 54 of the nozzle body 52. In the same way, the second inlet 70 communicates with the second distributor 74, which also is defined by an elongated channel or slot in the central section 54 of the nozzle body 52. Each of the distributors, 72 and 74, is substantially parallel to and substantially the same width as the liner hole 68. In addition, each of the distributors, 72 and 74, can be defined in the sections, upper and lower, 56 and 58, of the nozzle instead of the central section 54, if desired. In order to load the liquid coating material in the dispenser 72 towards the pre-projection 60, a passage for liquids or change pre-projection 76 is provided. The first passage for liquids 76 is defined by two congruent surfaces, one of which is defined by a main end 78 of the central section of the nozzle 54 and the other of which is defined by a closing means or closure element, which in the particular embodiment shown consists of a first shift bar 80. In the same way, the second distributor 74 communicates with the pre-protrusion 60 by means of a second passage for liquids or pre-protrusion of change 82, with the second passage for liquids or pre-outgoing change 82 also being defined by two congruent surfaces, one of which is formed at the main end 78 of the central section of the nozzle 54 and the other of which is defined by the second shift bar 84. The passages for liquids, first and second, 76 and 82, as well as the corresponding shift bars, 80 and 84, like the distributors, 72 and 74, are also substantially parallel to and substantially as wide as the liner hole 68. A first actuator 86 includes a piston rod 88 (Figure 5) integrally attached to the first shift bar 80 and a force generator 90 to generate a hydraulic, pneumatic force or magnetic on the piston rod 88. A mechanical actuator such as an asymmetric cam can also be used for this purpose. The force generator 90 is of the double action variety and is therefore capable of moving the shift bar 80 up and down in the upper section of the nozzle 56 to open and close the first passage for liquids 76. Similarly, a second actuator 92 includes a piston rod (not shown) and a force generator 94 for moving the second shift bar 84 between positions, open and closed, to allow and prevent the flow of liquid coating material through. of the second passage for liquids 82. In normal operation, one of the shift bars, 80 and 84, is in an open position while the other is in a closed position. Therefore, only one of the liquid coating materials supplied from the inlet, 69 and 70, will flow to the pre-projection 60, projection 62 and coating orifice 68 at any time. In addition, the change from one liquid coating material to the other can be made extremely fast by inverting the positions of the two shift bars through the actuators, 86 and 92. In other words, the passages for liquids, 76 and 82, are They adapt to open quickly and close quickly due to the short distance of step of the bars of change, 80 and 84, as well as the fast movement of these bars of change is made possible by the generators of force, 90 and 94. In this way , for example, in a nozzle in which the passages for liquids, 76 and 82, are from 500 to 5,000 μm in thickness, the change can occur in as little as 0.01 to 1.0 seconds. Figure 5 illustrates the structure of the shift bars 80 and 84, in more detail. As shown in this Figure, the shift bar 80 is composed of a rigid body member 96 having a main end 98 and a rear end 100. The main end 98 is composed of a flat, angled surface, which together with the main end 78 of the central section of the nozzle 54, it defines the first passage for liquids 76. Further, the rigid body member 96 defines an upstream side surface 102 and a downstream side surface 104, both of which are they are parallel to each other, as well as parallel to the piston 88. With this structure, the shift bar 80 is moved by displacement in the upper section of the nozzle 56 in response to the operation of the actuator 86. The ratio of the bar of change 80 with respect to the other elements of the nozzle 50 is further illustrated in Figure 7, it is understood that the ratio of the change bar 84 to the other corresponding elements in the nozzle is the same As shown in Figure 7, the shift bar 80 is mounted to move by sliding in a direction parallel to the side surfaces 102 and 104 to open and close the first passage for liquids 76. In addition, the downstream end 106 of the liquid passage 76 ends at the upstream end 108 of the pre-protrusion 60. In addition, the first dispenser 72 and the first passage for liquids 76 are connected to each other by the pre-protrusion of the first distributor 107, the first dispenser 72 being adjacent, adjacent to the first passage for liquids 76. For fencing, adjacent it is understood that the first dispenser 72 is as close as possible to the passage for liquids 76 (i.e. first distributor 107 is as short as possible) within reasonable machining tolerances. In other words, the dispenser 72 is not so close to the fluid passage 76 that any other machining outside the specification would cause misuse at the front end of the dispenser, as this would lead to the non-use of the nozzle 50. However, within this restriction, the distributor 72 is as close as possible to the passage for liquids 76. Also, it is desirable that the shift bars, 80 and 84 and in particular the output ends of these shift bars , are machined as accurately as possible since this results in no dead zones being virtually at the exit ends of the passages of the shift bar, 76 and 82, in the pre-boss 60. With In order to prevent the spillage of the liquid materials from being processed by the inventive applicator nozzle 50, a sealing system generally indicated as 110 is provided. See Figures 5, 6 and 7. The sealing system 110 includes a first primary seal 112 and a first secondary seal 114, each of which is defined on the upstream side surface 102 of the side bar 80. Located between the seals, primary and secondary, 112 and 114, there is a fluid seal 116 which is connected to a source of cleaning fluid supplied continuously or intermittently, such as water supplied at a lower pressure, for example 5 psig, which is discharged continuously to be discharged or recirculated through the outlet openings , not shown. The sealing system 110 further includes a second primary seal 118, a second secondary seal 120 and a second fluid seal 122, all defined on the downstream side surface 104 of the shift bar 80. As illustrated in Figure 6, each of the seals, primary and secondary, takes the form of a strip of material 124 installed substantially parallel to and is substantially as long as the liner hole 68. Each of these seals, in cross section, is preferably composed of a member U-shaped made from a flexible material such as plastic or elastomer, the U-shaped member carrying an elongated spring member or an initially soft polymer rope 126 therein to deflect the lower ends, 128 and 130, of the member U-shaped 124 in an outward direction. In the embodiment shown, the end 130 includes teeth 132 to engage the abutment surface 133 of the upper portion of the nozzle 56, in which the shift bar 80 is received by sliding. The sealing system 110 substantially eliminates spills of the liquid coating materials between the change bars 80 and 84 and their associated nozzle body sections. This effectively prevents the forced closing of the nozzle 50 through the hardening of the liquid that is coated in these areas, which can occur when the pressure-sensitive adhesives are used. As shown in Figures 5 and 7, the end surfaces of the shift bar 80 are also installed parallel to the piston 88 and, in the embodiment shown, perpendicular to the side surfaces, 102 and 104, of the shift bar. The upper section of the nozzle 56 also defines the mating surfaces to receive these end surfaces of the shift bar by displacement, these matching surfaces are also installed parallel to the piston 88. To prevent spillage of the liquid coating material between the end surfaces of the shift bar 80 and the mating surfaces of the upper section of the nozzle body 56, the same system can be used. of sealing described above. However, in the preferred embodiment of the invention, these surfaces can be effectively sealed by forming these matching surfaces from a suitable material such as flat sheets of Teflon® reinforced with fiber or a soft metal such as bronze or copper. With the above structure, the inventive applicator nozzle can achieve an extremely rapid change from one liquid coating material to the other. This is due, in part, to the fact that the shift bars, 80 and 84, move by a fast action only at a very small distance between the positions, open and closed. This is also due, however, to the fact that the passages for liquids, 76 and 82, as well as the distributors, 72 and 74, are installed substantially parallel to and are substantially as wide as the coating orifice 68. As illustrated in the Figures 3, 4, 5 and 6, the passages for liquids, 76 and 82, in effect form "pre-protrusions of change" between the pre-protrusion 60 and the distributors, 72 and 74, respectively. In addition, the distributors, 72 and 74, communicate with the passages for liquid, 76 and 82, by the respective pre-projections of the distributor, one of which is illustrated as 107 in Figure 7. As is well known, the pre -supports and the substantially parallel installed distributors a and which are substantially as wide as their associated liner holes, facilitate the uniform distribution and metering of the coating materials across the total width of the continuous paper web to be coated. Therefore, the formation of passages for liquid, 76 and 82, of the inventive nozzle as additional "pre-protrusion", promotes the uniform, immediate flow of the coating material in opening the associated change bar. This substantially reduces the time necessary for the flow of the new coating material to reach the operation of the fixed state and thus further reduces the production of waste. Yet another reason why the inventive applicator nozzle can achieve rapid change between the different coating compositions, resides in the enclosed space between the distributors, 72 and 74, the passages for liquid, 76 and 82 and the pre-projection 60. Due to this enclosed space, there is essentially no dead space in which the unused coating material can be captured or remain behind. According to the above, the inactive time is essentially eliminated to remove the captured solidified coating material from the nozzle. Another important feature of the inventive applicator nozzle is that it is relatively maintenance free. This is mainly due to the elimination of the spill, which in turn is due to the adoption of a number of devices of different design, as described above. For example, the closed space of the distributors and the pre-protrusion to the passages for flow 76 and 82, reduces the dead spaces to trap the liquid coating material. In addition, the sealing system 110, as well as the final front sealing system described above, substantially prevent the liquid coating material from being trapped between the side and the end surfaces of the change bars and the mating surfaces of the body sections. of associated nozzle, in which it is housed. Together, these devices allow the applicator nozzle 50 to operate in an essentially problem-free manner for extended periods of time, while at the same time allowing the extremely rapid change between the different coating liquids in a simple and easy manner. Figure 9 illustrates a preferred embodiment of the present invention, in which the inventive applicator nozzle 50 is provided with a cleaning system for cleaning the distributors, 72 and 74, as well as an automatic control system for controlling the operation of the change nozzle and the cleaning system. As shown in this figure, the first inlet 69 of the nozzle 50 is connected by a suitable pipe to a source 132 of a first liquid coating material and a source 134 of cleaning liquid. The control valves 136 and 138 connected to an automatic controller (not shown), are provided to allow and prevent the flow of the first liquid coating material and the cleaning liquid into the inlet 69, as desired. The outer ends of the dispenser 72 in the applicator nozzle 50 shown in Figure 9 are provided with outlet holes which are connected via the appropriate tubing to the waste discharge openings (not shown), the control valves 140 being provided and 142, to allow and prevent the flow of fluid in the dispenser 72 out of these outlet openings, as desired. As illustrated in Figure 9, the second inlet port 70 is connected to a similar installation to supply a second coating liquid and cleaning liquid to the dispenser 74. In operation, the automatic control system causes the first actuators 86 of the applicator nozzle 50 opens the shift bar 80, as well as the control valve 136 allowing the first liquid coating material from the source 132 to flow to and through the nozzle 50 in the manner described above. to a second coating liquid is desired, the automatic control system causes the first actuators 86 to move the shift bar 80 to close the first passage for liquids 76. Simultaneously, the automatic control system causes the second actuators 92 to move the shift bar 84 to open the second passage for liquids 82. Essentially at the same time, the control valve 136 is closed to stopping the flow of the first coating liquid towards the nozzle 50 and the flow of the second coating liquid towards the nozzle 50 starts upon opening the corresponding control valve attached to the source of the second coating liquid. Essentially at the same time, the cleaning system of the inventive apparatus is operated to remove the liquid coating material from the distributor 72. This is done by opening the control valves of the automatic control system, 138, 140 and 142. As a result, the fountain cleaning solution 134 flows into the distributor 72 from the first inlet 69 and then out of the distributor 72 from the two outlet holes located at its outer ends. After an adequate period of time, the flow of the cleaning solution is terminated by closing the control valves of the automatic control system 138, 140 and 142 to complete the cleaning operation. When it is desired to change the operation of the applicator nozzle back to the first coating liquid, the above operation is conducted in reverse, with the distributor 74 then being cleaned while the distributor 72 is in an operation mode to supply the first coating liquid to the continuous paper tape that is coated. A particular advantage of the inventive applicator nozzle equipped with a cleaning system as illustrated in Figure 9 is that a much greater degree of flexibility than with prior systems is possible. This is because a third coating liquid, different from the first and second, can be introduced into the channel without operation of the nozzle after it has been cleaned and while the other nozzle channel is still operating. In this way, it will be appreciated that the inventive applicator nozzle, when equipped with a cleaning system as illustrated in Figure 9, it can process three, four or in fact an unlimited number of different coating materials without closing between the successive coating streams. Although only a few embodiments of the present invention have been described above, it is appreciated that many modifications can be made without departing from the spirit and scope of the present invention. For example, the inventive applicator nozzle can be provided with a heating element and / or channels for the reception and flow of a thermal transfer fluid as well as an associated temperature control system for controlling the temperature of the liquid coating materials that are process in the mouthpiece. In addition, the nozzle control system can be set to move the shift bars, 80 and 82, at slightly different times, during each change since this can have a beneficial effect or execution in certain cases. Also, the control system can be set to allow both change bars to open or close at the same time. This would not only allow multiple layers of liquid coating to be applied simultaneously, but would also facilitate cleaning and washing the nozzle. All of such modifications are intended to be included within the scope of the present invention, which is limited only by the following claims.