Process for producing sandwich structures with particulate material pattern

Abstract

The present invention is concerned with a process for forming a very well defined pattern of particulate material in a composite material comprising a web material and particulate absorbent material. The present invention relates also to a method for determining the equipment design and process parameter for such a process. In a particular application, the present invention provides a process for preparing liquid absorbent structures, such as may be useful for disposable absorbent articles.

1 . A method for continuously producing a pattern of particulate material in a sandwich structure, the method comprising the steps of: 
 providing 
 a particulate material;  
 a transfer device for receiving said particulate material in a receiving region and transferring it to a discharging region, said transfer device comprising a first pattern forming means;  
 at least one essentially flat web material as carrier and/or cover material;  
 an essentially endless carrier support means for said carrier material having a support pattern corresponding to the pattern of said first pattern forming means of said transfer device;  
 a carrier material holding means for temporarily attaching said carrier material to said surface of said carrier support means;  
 a sandwich fixation means for combining the sandwich structure; executing the process steps of  
 transferring said particulate material to said receiving region of said transfer device, whereby said first pattern forming means defines a particulate cluster pattern;  
 moving said pattern of particulate material to the discharging region of said transfer device;  
 guiding said carrier material over said carrier support means at a carrier speed corresponding to the carrier support speed;  
 deforming said carrier material by said carrier material holding means, such that an indentation is formed in the unsupported regions, thereby forming a pattern corresponding to said particulate cluster pattern;  
 expelling said particulate material from said transfer device towards said carrier material;  
 depositing said expelled particulate material on said deformed carrier material;  
 applying said cover material to said carrier material and said patterned particulate material, thereby forming a sandwich structure; and  
 providing a fixation means for bonding the outer sandwich layers to each other,  
   at least in parts of the bonding area.    
     
     
         2 . A method for determining the equipment design and process parameters for a process for selectively positioning particulate material onto a moving surface, the method comprising the steps of: 
 a.) providing a set of physical equations forming a physical model, said set of physical equations being connected by interaction boundary conditions, optionally including sub-models connected by sub-model connectivity boundary conditions;    b.) selecting a set of fixed boundary conditions, comprising the overall equipment set-up, overall process requirements, and a set of initial operating conditions (fixed model input);    c.) providing a set of predetermined model targets;    d.) selecting a set of variable boundary conditions, which may vary throughout one simulation (variable model input);    e.) performing calculus operations on the physical equations by using the initial operating conditions and variable boundary conditions;    f.) transforming the calculus results into a model output which is readable to a human analyst directly or by a means of a computing device;    g.) comparing the model output to predetermined model targets and determining the deviation there between;    h.) modifying the set of variable boundary conditions using computational equations for minimizing the deviation between said model output to predetermined model targets; and    i.) reiterating steps d.) to h.) until a preset exit criterion is met.    
     
     
         3 . A method for determining the equipment design and process parameter for a process for selectively positioning particulate material onto a moving surface according to  claim 2 , wherein said exit criterion is defined by a preset number of iterations.  
     
     
         4 . A method for determining the equipment design and process parameter for a process for selectively positioning particulate material onto a moving surface according to  claim 2 , wherein said exit criterion is defined by a preset exit deviation criterion between the model output and said predetermined model targets.  
     
     
         5 . A method for determining the equipment design and process parameter for a process for selectively positioning particulate material onto a moving surface according to  claim 2 , wherein said calculations are performed by employing a computer device.  
     
     
         6 . A method for determining the equipment design and process parameter for a process for selectively positioning particulate material onto a moving surface according to  claim 5 , wherein said exit criterion is defined by a preset number of iterations.  
     
     
         7 . A method for determining the equipment design and process parameter for a process for selectively positioning particulate material onto a moving surface according to  claim 5 , wherein said exit criterion is defined by a preset exit deviation criterion between the model output and said predetermined model targets.  
     
     
         8 . A system for determining the equipment design and process parameter for a process for selectively positioning particulate material onto a moving surface, said system comprising a memory device and a processor, disposed in communication with said memory device, said processor being configured to receive virtual simulation programs and overall boundary conditions, simulation targets, and simulation starting parameters, so as to calculate a set of pre-defined output parameters and to transmit the output parameters to an output device.  
     
     
         9 . A system for determining the equipment design and process parameter for a process for selectively positioning particulate material onto a moving surface according to  claim 8 , wherein the deviation of the output parameter from the simulation targets determine the exit criteria.