Process for making a liquid absorbing thermoplastic material

Abstract

The present invention relates to an improved process for making liquid absorbing thermoplastic materials comprising a thermoplastic polymeric composition and an absorbent material in particle form dispersed in the thermoplastic polymeric composition. Such liquid absorbing thermoplastic material can be utilised in the absorbent cores of disposable absorbent articles, such as sanitary napkins, panty liners, interlabial devices, tampons, disposable diapers, incontinence pads, wound dressings, nursing pads and the like for completely or partially substituting said absorbent cores.

1 . A process for making a liquid absorbing thermoplastic material comprising a matrix of a thermoplastic polymeric composition and particles of an absorbent material dispersed in said matrix, wherein said thermoplastic polymeric composition comprises at least two components, said process comprising the following steps: 
 providing said particles of absorbent material;    mixing said particles of absorbent material with a first component in the liquid state of said at least two components forming a pre-mix; and    mixing said pre-mix with a second component of said thermoplastic polymeric composition in the molten state.    
   
   
       2 . The process according to  claim 1 , wherein said process comprises the further step of grinding said particles of absorbent material into said pre-mix to a selected average particle size.  
   
   
       3 . The process according to  claim 1 , wherein said process comprises the further step of grinding said particles of absorbent material into said thermoplastic polymeric composition to a selected average particle size.  
   
   
       4 . The process according to  claim 1 , wherein said particles of absorbent material include particles of water-insoluble water-swellable absorbent material.  
   
   
       5 . The process according to  claim 1 , wherein said particles of absorbent material include particles of liquid gelling material.  
   
   
       6 . The process according to  claim 1 , wherein said first component of said thermoplastic polymeric composition in said pre-mix is liquid at room temperature.  
   
   
       7 . The process according to  claim 6 , wherein said first component has a viscosity at room temperature below about 30,000 centipoise.  
   
   
       8 . The process according  claim 1 , wherein said particles of absorbent material have an average particle size below about 150μ.  
   
   
       9 . The process according to  claim 1 , wherein said thermoplastic polymeric composition comprises a thermoplastic polymer and a compatible plasticiser.  
   
   
       10 . The process according to  claim 9 , wherein said first component in said pre-mix is said compatible plasticiser.  
   
   
       11 . The process according to  claim 9 , wherein said thermoplastic polymer is selected from the group consisting of: polyurethanes, poly-ether-amides block copolymers, polyethylene-acrylic acid and polyethylene-methacrylic acid copolymers, polyethylene oxide and its copolymers, ethylene acrylic esters and ethylene methacrylic esters copolymers, poly lactide and copolymers, polyamides, polyesters and copolyesters, polyester block copolymers, sulfonated polyesters, poly-ether-ester block copolymers, poly-ether-ester-amide block copolymers, polyacrylates, polyacrylic acids and derivatives, ionomers, polyethylene-vinyl acetate with a vinyl acetate content of at least 28% by weight, polyvinyl alcohol and its copolymers, polyvinyl ethers and their copolymers, poly-2-ethyl-oxazoline and derivatives, polyvinyl pyrrolidone and its copolymers, thermoplastic cellulose derivatives, poly-caprolactone and copolymers, poly glycolide, polyglycolic acid and copolymers, polylactic acid and copolymers, polyureas; and 
 said compatible plasticiser is selected from the group consisting of citric acid esters, tartaric acid esters, glycerol and its esters, sucrose esters, adipates, sebacates, sorbitol, epoxidized vegetal oils, polymerised vegetal oils, polyols, phthalates, liquid polyesters, glycolates, glycols and polyglycols and their derivatives, sorbitan esters, phosphates, monocarboxylic fatty acids (C 8 -C 22 ) and their derivatives, mineral oils, high boiling point alcohols, glycerine, glycol ethers.    
   
   
       12 . The process according to  claim 1 , wherein said pre-mix comprises from about 40% to about 80%, by weight of said pre-mix, of said particles of absorbent material, and from about 20% to about 60%, by weight of said pre-mix, of said first component of said thermoplastic polymeric composition.  
   
   
       13 . The process according to  claim 1 , wherein said liquid absorbing thermoplastic material comprises from about 10% to about 90% by weight of said liquid absorbing thermoplastic material, of said particles of absorbent material.