PROCESS AND SYSTEM FOR THE PRODUCTION OF A POROUS WEB PROVIDED WITH ADHESIVE ON ONE SIDE

Abstract: The invention relates to a process, system and device for the production of a porous web, especially of nonwoven material, provided on one side with adhesive, in which a liquid adhesive is applied to one side of the web in an application area. According to the invention the side of the web opposite the application area is subjected to a stream of gas, which flows in the direction essentially opposite that in which the adhesive is being applied.

Description: The invention relates to a system and to a process for the production of a porous absorbent web of a nonwoven material, provided on one side with adhesive. Porous, absorbent materials are provided with adhesive on one side during the production, for example of hygienic articles such as sanitary napkins and baby diapers. In particular, a liquified hot-melt adhesive is sprayed onto a web as it passes underneath the adhesive applicator. The material must be porous because it has to be adsorbent, but because of this porosity, the adhesive penetrates to a greater or lesser depth into the material. In the case of highly porous materials such as nonwovens, this can lead to bleed-through; that is, the adhesive penetrates all the way through the web. This leads to considerable processing problems, such as the contamination of the pulleys and support rolls. The necessity of cleaning operations increases the cost of production, but in addition this bleed-through also brings with it the danger that the web material will stick to the rolls or other adhesive-contaminated part of the machinery, which can lead to the rupture of the web. US-A-2 770 216 discloses an apparatus for spraying adhesive onto broadloom carpets, wherein air is directed over a baffle along a duct to both side ends of the carpet. Since the duct extends in parallel to the back of the carpet, the air is thus directed along and in parallel to the back of the web. The purpose of this arrangement is to prevent overspray from drifting around the side ends of the carpet to the back thereof as the spray is being reversed. However, this known apparatus cannot solve the above mentioned problems. Therefore, an object of the invention is to provide a process and a system by means of which the danger is eliminated that the web material will stick to the rolls or other adhesive-contaminated parts of the machinery, which can lead to the rupture of the web, even in the case of highly porous web materials. In order to acomplish this object, according to the invention, a process is provided for the production of a porous absorbent web of a nonwoven material, provided on one side with adhesive, in which a liquid adhesive is applied to one side of the web in an application area, and during the application of the adhesive, a stream of gas is created on the side of the web opposite the application area characterized in that said stream of gas flows in the direction opposite that in which the adhesive is being applied, thereby striking the side of the web opposite the application area. Furthermore, according to the invention, there is provided a system for the production of a porous absorbent web of a nonwoven material, provided with adhesive on one side, said system being provided with devices for moving the web through an adhesive application area of at least one adhesive application device in which one side of the web faces the application device, and devices for creating a stream of gas on the side of the web facing away from the adhesive application device, characterized in that said devices for creating a stream of gas comprise means for directing said stream of gas in the direction opposite that in which the adhesive is applied against the side of the web opposite said application area. Further advantageous embodiments are defined in the subclaims 2 to 6 and 8 to 11. According to the invention, directing a stream of gas against the web on the side opposite that to which the adhesive is applied prevents the adhesive from bleeding through. Thus, the adhesive is prevented from reaching the pulleys or rolls and other parts of the machinery. The contamination of these parts with adhesive is avoided, and web ruptures can be almost completely eliminated. It is advantageous for the gas stream according to the invention to be realized in the form of unheated compressed air, which can be done at little expense. In particular, when an adjustable blower is used, the gas stream can be adjusted easily to prevent excessive penetration of adhesive into the web without at the same time interfering with the uniform application of the adhesive. In the following, a preferred embodiment of the invention is explained in more detail on the basis of the attached drawing, which illustrates a preferred embodiment of a system according to the invention in the form of a schematic diagram. System 1 comprises a flat plate 10, over the top of which a web 14 of porous material, especially nonwoven material, to be provided with adhesive is conveyed in the direction of arrow A. Web 14 can be paid out, for example, from a supply roll and wound up again on another supply roll after the adhesive has been applied and possibly a protective film has been attached. Above plate 10 are spray devices 12, which are shown schematically in the drawing in the form of three individual spray nozzles. The spray nozzles of spray device 12 discharge a hot-melt adhesive which has been liquefied by heat in the direction of arrows B onto web 14 and thus produce a spray pattern 18 in an application area 16 over a certain portion of the width of the web. Plate 10 has a long, rectangular opening 20, the width of which is approximately the same as that of application area 16. Web 14 is guided to travel so closely to plate 10 and thus to opening 20 that it seals opening 20. Underneath plate 20 is a nozzle 22, which is connected by a tubular connector 24 to an adjustable blower (not shown). Unheated, compressed air is conveyed by the blower in the direction of arrow C to nozzle 22. In the area of opening 20, this unheated, compressed air strikes the underside of web 14. In application area 16, therefore, web 14 is subjected on one side to the application of hot-melt adhesive and on the other side to a stream of unheated, compressed air. The compressed air penetrates into the web material and prevents the adhesive being applied simultaneously from the opposite side from penetrating through the web material. The supply rate of the compressed air should be selected so that the bleed-through of adhesive is reliably prevented without at the same time causing any interference with the uniform application of the adhesive. Instead of the nozzle with tubular connector shown in the figure, which is suitable especially for connecting the blower to the connector by means of a compressed air hose, it is also possible to connect the nozzle directly to the blower, which makes it possible to save additional space.

Claims: Process for the production of a porous absorbent web (14) of a nonwoven material, provided on one side with adhesive, in which a liquid adhesive is applied to one side of the web in an application area (16), and during the application of the adhesive, a stream of gas is created on the side of the web (14) opposite the application area (16) characterized in that said stream of gas flows in the direction opposite that in which the adhesive is being applied, thereby striking the side of the web (14) opposite the application area (16). Process according to Claim 1, characterized in that a hot-melt adhesive is used as the adhesive. Process according to Claim 1 or Claim 2, characterized in that the adhesive is sprayed onto the web (14). Process according to one of Claims 1-3, characterized in that unheated compressed air is used as the gas stream. Process according to one of Claims 1-4, characterized in that the gas stream is supplied in a form which is distributed in a uniform manner over the entire extent of the application area (16). Process according to one of Claims 1-5, characterized in that the gas stream is supplied by an adjustable blower. System for the production of a porous absorbent web (14) of a nonwoven material, provided with adhesive on one side, said system being provided with devices for moving the web (14) through an adhesive application area (16) of at least one adhesive application device (12) in which one side of the web (14) faces the application device (12), and devices (20, 22) for creating a stream of gas on the side of the wheb (14) facing away from the adhesive application device (12), characterized in that said devices (20, 22) for creating a stream of gas comprise means (22) for directing said stream of gas in the direction opposite that in which the adhesive is applied against the side of the web (14) opposite said application area (16). System according to Claim 7, characterized in that, in the application area (16), the system (1) has a plate (10) with an opening (20), between which and the adhesive application device (12) the web (14) is transported, and in that, to form the gas-supplying devices, the opening (20) is connected to a nozzle (22), through which the stream of gas is conducted onto the web (14). Device according to Claim 8, characterized in that the opening (20) is approximately rectangular and forms the aperture of the nozzle (22). Device according to Claim 8 or Claim 9, characterized in that the nozzle (22) is connected to the outlet of an adjustable blower. Device according to one of Claims 7-10, characterized in that the adhesive application device is formed by at least one, preferably several, adhesive spray nozzles (12), which are set up a distance away from the web (14), this distance being calculated so that the side facing them is sprayed in the application area (16) with a uniform and complete layer of adhesive.

Inventors: SCHNOEDEWIND, FRANZ-JOSEF, Schnödewind, Franz-Josef
Applicants: NORDSON CORPORATION
Application year: 1989
Main classification: D06N7
IPC codes: B32B37, B05D7, B05B15, D06N7, B32B43, D06N3, D06M17, B05B13, B05C9