Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F5/00—Attaching together sheets, strips or webs; Reinforcing edges
  • B31F5/008—Attaching together sheets, strips or webs; Reinforcing edges by friction, e.g. obtained ultrasonic vibrations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31D—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER, NOT PROVIDED FOR IN SUBCLASSES B31B OR B31C
  • B31D1/00—Multiple-step processes for making flat articles ; Making flat articles
  • B31D1/0006—Multiple-step processes for making flat articles ; Making flat articles the articles being coffee filters

Definitions

• the present invention relates to a method of joining together at least two paper sheets, a device for carrying out the method, and a join produced by means of the method.
• Paper sheets are joined together at present with the aid of different adhesives or fasteners, such as staples. It is also known to join paper together mechanically, by deforming the paper; c.f. coffee filter paper, for instance. Joins of this latter nature are beneficial from an environmental aspect, since paper products that are joined together in this way can be recycled in their existing state, without needing to first remove glue residues or metal elements. Joins of this nature that can be effected easily also constitute a cost saving in comparison with conventional joins, since distinct from conventional joins neither glue nor metal elements need be used.
• the object of the present invention is precisely one of producing paper joins in the absence of glue or metal elements .
• This object is achieved in accordance with the invention by means of a method of joining together at least two paper sheets which is characterised by the steps of moistening or wetting each paper sheet with a determined amount of water in the region of the intended join, placing the sheets together with the moistened regions in abutment with one another, and processing the moistened regions of the thus combined paper sheets in an ultrasound welding device such as to remove at least 80 percent by weight of the added water. Since the only substance added to the paper sheets that are joined together in this way is water, the paper can be recycled directly after use.
• the method can also be carried out in conventional apparatus in a simple and cost-effective manner.
• the paper sheets are calendered prior to being processed in the ultrasound welding device.
• Appropriate moistening of the paper sheets is determined empirically, by moistening the paper sheets to different degrees of wetness, although under the same conditions in other respects, wherewith the strength of the join is determined for each degree of moistening.
• An appropriate degree of processing in the ultrasound welding device is then determined empirically, by processing paper sheets that have been moistened to the same degree with different energy inputs to said ultrasound welding device, wherewith the strength of the join is determined for each energy input value .
• the invention also relates to apparatus for joining together at least two paper sheets in the form of two running paper webs taken from storage reels, said apparatus being characterised by a moistening unit, paper-web combining means, and an ultrasound welding device, these apparatus components being disposed downstream of one another in the direction of web movement, and also by means for feeding the paper webs past the moistening unit and through the web combining means and the ultrasound welding device .
• the web combining means is a calendering device.
• the invention also relates to a join which joins together at least two paper webs in the absence of a binding agent, said join being characterised in that it includes regions that have a greaseproof paper-like structure and a thickness smaller than 50%, preferably smaller than 30%, of the combined thickness of said webs .
• Fig. 1 is a schematic illustration of inventive apparatus for joining paper sheets together
• Fig. 2 illustrates schematically and in perspective part of a paper web comprised of two paper sheets that have been joined together in the apparatus shown in Figure 1;
• Fig. 3 is a graph showing the tensile strength and moistening of the paper sheets as a function of the speed at which the paper sheets are advanced;
• Fig. 4 is a graph showing the tensile strength as a function of ultrasound pressure in respect of different feed speeds and degrees of wetness.
• Fig. 5 is a graph showing the tensile strength as a function of wetness.
• the apparatus shown in Figure 1 for joining together two paper webs 1, 2 taken from storage reels 3, 4 includes a moistening or wetting unit 5, a calendering device 6, an ultrasound welding unit 7, and an anvil roll or counterpressure roll 8, these components being disposed in the above order sequentially in the feed direction of the webs 1 , 2.
• the modus operandi of the apparatus is as follows:
• the paper webs are wetted with a determined amount of water as they pass the moistening unit 5.
• the moistened paper webs 1 , 2 then pass through a calendering device 6 with the moistened regions of the webs in mutual abutment.
• the thus combined webs 1, 2 then pass through the nip defined by the horn of the ultrasound unit 7 and the anvil roll 8. It has surprisingly been found that the two paper webs are mutually joined in those regions moistened by the unit 5, after having passed the ultrasound welding unit and the anvil roll.
• Figure 2 shows in perspective a piece that has been cut from the webs 1, 2 subsequent to passing the ultrasound welding unit 7.
• the anvil roll includes rows of projections that form rows of mutually connected regions 10 in the resultant join 9, as evident from Figure 2.
• the mutually joined paper webs are very thin in the regions 10, and have a so-called greaseproof paper-like structure.
• the strength of the join obtained is contingent on the extent to which the paper has been moistened and also on the mechanical energy applied in the ultrasound processing operation. It would appear that the major part of the join 9 is obtained by chemical bonds (of which hydrogen bonds probably form a predominant part) , although the join will also probably include mechanical bonds. It can be assumed from the greaseproof paper-like structure in the regions 10 that the ultrasound horn disintegrates the paper fibres within the regions of the projections on the anvil roll, such as to obtain short fibres in said regions. The presence of water and the heat generated by the mechanical working process also constitute necessary conditions for obtaining a join.
• the moisture content of the webs is measured by weighing the join region both before and after applying water and is constituted by the weight of the water applied divided by the weight of the paper prior to application of the water, multiplied by one-hundred.
• the conditions in which a join of optimum strength is obtained must therefore be determined empirically.
• Figures 3 and 4 illustrate how the degree of moisturisation and energy input are determined in order to obtain a joint of maximum strength between two paper webs comprised of a paper having a weight per unit area of 60 g/m 2 designated CREPE PAPER WHITE and manufactured by Arjo Wiggins, Paris, France. These paper webs were allowed to run through apparatus constructed in accordance with Figure 1.
• the moisturising unit was designed to deliver to the passing paper webs a determined amount of water per unit of time.
• the calendering pressure was 0.5 bar, which is an optimum pressure for this type of paper. The calendering process is intended to facilitate absorption of surface water into the paper.
• the ultrasound welding unit comprised a unit from Dukane Corp., Illinois, USA, with the designation 20A2000.
• the ultrasound horn had a constant amplitude of 15 ⁇ m during all tests.
• the amount of energy supplied to the ultrasound welding device was varied, by varying its counterpressure (UL pressure) .
• Figure 4 illustrates a number of tests in which the UL pressure, by which is meant the counterpressure of the ultrasound horn, was varied while holding the degree of moisturisation of the paper webs and the speed at which said webs were fed through said welding device constant .
• the curves F and B denote join strength and degree of moisturisation respectively, while the curve UL shows the UL pressure .
• FIG. 5 shows two curves I and II which illustrate the join strength as a function of the moisture content in the join region of the paper webs .
• the webs were advanced at a speed of 30 m/min and the UL pressure was 1.2 bar in respect of curve I and 1.8 bar in respect of curve II. It will be evident from the Figure that good joins can be achieved within a relatively broad moisture-content range.
• the thickness of the greaseproof paper-like regions 10 in the join have been measured and found to be less than 30% of the original paper webs .

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Paper (AREA)
• Replacement Of Web Rolls (AREA)
• Lining Or Joining Of Plastics Or The Like (AREA)
• Machines For Manufacturing Corrugated Board In Mechanical Paper-Making Processes (AREA)

Applications Claiming Priority (3)

Publications (1)

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Family Applications (1)

Country Status (7)

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• 1997
  • 1997-11-17 SE SE9704207A patent/SE512767C2/sv not_active IP Right Cessation
• 1998
  • 1998-11-17 JP JP2000520961A patent/JP2001523595A/ja active Pending
  • 1998-11-17 EP EP98954913A patent/EP1032494A1/en not_active Withdrawn
  • 1998-11-17 WO PCT/SE1998/002074 patent/WO1999025547A1/en not_active Application Discontinuation
  • 1998-11-17 CN CN98811174A patent/CN1278761A/zh active Pending
  • 1998-11-17 PL PL98340495A patent/PL340495A1/xx unknown
  • 1998-11-17 CA CA002309040A patent/CA2309040A1/en not_active Abandoned

Non-Patent Citations (1)

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