Heat-sealing barrier paper

Abstract

A paper including a fibrous substrate, a precoat layer including a binder and a mixture of platy filler(s) having a shape factor of at least 15 and of finer filler(s), the size of the particles of which is, for 80% by weight, less than 2 μm (measured according to the ISO 13317-3 SediGraph method) and at least one covering layer applied to the precoat layer, the paper having a water vapour permeability of at most 150 g/m 2 /24 h and preferably of less than 100 g/m 2 /24 h, measured according to the ASTM F1249 standard under so-called tropical conditions of 38° C. and 90% relative humidity.

1 - 37 . (canceled) 
     
     
         38 . Paper comprising:
 a fibrous substrate,   a precoat layer comprising a binder and a mixture of platy filler(s) having a shape factor of at least 15 and of finer filler(s), the size of the particles of which is, for 80% by weight, less than 2 μm (measured according to the ISO 13317-3 SediGraph method),   at least one covering layer applied to the precoat layer,   the paper having a water vapour permeability of at most 150 g/m 2 /24 h, measured according to the ASTM F1249 standard under so-called tropical conditions of 38° C. and 90% relative humidity.   
     
     
         39 . Paper according to  claim 38 , the weight of the covering layer not exceeding 10 g/m 2  when dry. 
     
     
         40 . Paper according to  claim 39 , the covering layer comprising a heat-sealable polymer, or even being constituted by a heat-sealable polymer. 
     
     
         41 . Paper according to  claim 38 , the platy filler(s) and the finer filler(s) being of the same nature. 
     
     
         42 . Paper according to  claim 38 , the shape factor of the platy filler particles being at least 40. 
     
     
         43 . Paper according to  claim 38 , the finer filler(s) having a particle size, for 95% by weight, of less than 2 microns, measured according to the ISO 13317-3 SediGraph method. 
     
     
         44 . Paper according to  claim 38 , the platy filler(s) being mineral filler(s). 
     
     
         45 . Paper according to  claim 38 , the finer filler(s) being mineral filler(s). 
     
     
         46 . Paper according to  claim 38 , the platy filler(s) being selected from kaolins and talc and mixtures thereof. 
     
     
         47 . Paper according to  claim 38 , the finer filler(s) being selected from kaolins, calcium carbonate, barium sulphate, silica, titanium dioxide and mixtures thereof. 
     
     
         48 . Paper according to  claim 38 , the finer filler(s) being selected from kaolins. 
     
     
         49 . Paper according to  claim 38 , the dry weight of platy filler(s) being between 3% and 58% of the total dry weight of the precoat layer. 
     
     
         50 . Paper according to  claim 38 , the dry weight of finer filler(s) being between 3% and 58% of the total dry weight of the precoat layer. 
     
     
         51 . Paper according to  claim 38 , the percentage of platy filler(s), expressed by dry weight, relative to the sum of the fillers, expressed by dry weight, being between 10% and 90%. 
     
     
         52 . Paper according to  claim 38 , the binder having a glass transition temperature T g  below or equal to 25° C. 
     
     
         53 . Paper according to  claim 38 , the binder being selected from latices of styrene-butadiene, styrene-acrylic, acrylic, butyl acrylate, butyl acrylate-styrene-acrylonitrile chemical nature, and mixtures thereof. 
     
     
         54 . Paper according to  claim 38 , the binder being selected from latices of styrene-butadiene chemical nature. 
     
     
         55 . Paper according to  claim 38 , the binder being introduced in latex form. 
     
     
         56 . Paper according to  claim 38 , comprising in the precoat layer at least 15 parts when dry of binder relative to the weight of fillers when dry (100 parts). 
     
     
         57 . Paper according to  claim 38 , the binder comprising a polymer of chemical nature not present in the covering layer. 
     
     
         58 . Paper according to  claim 38 , the covering layer being substantially free of filler. 
     
     
         59 . Paper according to  claim 38 , the covering layer being the only layer that covers the precoat layer. 
     
     
         60 . Paper according to  claim 38 , the covering layer comprising one or more polymers selected from copolymers based on PVdC or on styrene-acrylic and mixtures thereof. 
     
     
         61 . Paper according to  claim 38 , the amount of precoat layer being less than or equal to 12 g/m 2  by dry weight. 
     
     
         62 . Paper according to  claim 38 , comprising a printing layer on the face of the substrate opposite the one bearing the precoat layer and the covering layer. 
     
     
         63 . Paper according to  claim 38 , the substrate bearing two identical precoat layers on its opposite faces. 
     
     
         64 . Paper according to  claim 38 , the substrate bearing two precoat layers of different natures on its opposite faces. 
     
     
         65 . Paper according to  claim 38 , a pore-filling composition being applied to the substrate, and the precoat layer being applied to the pore-filling composition. 
     
     
         66 . Paper according to  claim 38 , the basis weight of the fibrous substrate being between 25 and 180 g/m 2 . 
     
     
         67 . Paper according to  claim 38 , the paper being heat-sealable. 
     
     
         68 . Paper according to  claim 38 , the final basis weight of the paper being between 45 and 200 g/m 2 . 
     
     
         69 . Precoated paper suitable for the manufacture of a paper as defined in  claim 38 , having a water vapour permeability of at most 150 g/m 2 /24 h according to the ASTM F1249 standard at 38° C. and 90% relative humidity, the precoated paper being uncalendered. 
     
     
         70 . Packaging comprising a paper as defined in  claim 38 , the paper being heat-sealed to itself, containing a food product. 
     
     
         71 . Process for manufacturing a paper according to  claim 38 , in which a composition is applied to a fibrous substrate, the composition comprising a binder in latex form and a dispersion of a mixture of platy filler(s) having a shape factor of at least 15 and of finer filler(s), the size of the particles of which is, for 80% by weight, less than 2 μm.