Coated papers with a semi-crystalline coating layer as packaging material

Abstract

The application relates to a coated paper comprising a base paper and at least one semi-crystalline coating layer with amorphous regions and crystalline regions, applied directly or indirectly to the base paper, wherein the amorphous regions contain one or more natural polymers and/or one or more derivatives of natural polymers; wherein the crystalline regions comprise one or more crystallizable organic compounds; and wherein the permeability of at least one gas through the coated paper is reduced compared to the base paper. The application further relates to the coating used for producing the coated paper, the production method, as well as packaging for food.

1 . A coated paper comprising a base paper and at least one semi-crystalline coating layer with amorphous regions and crystalline regions, applied directly or indirectly to the base paper:
 wherein the amorphous regions contain one or more natural polymers and/or one or more derivatives of natural polymers;   wherein the crystalline regions comprise one or more crystallizable organic compounds, and   wherein the permeability of the coated paper for at least one gas is reduced compared to the base paper.   
     
     
         2 . The coated paper according to  claim 1 , wherein the at least one crystallizable organic compound has a melting temperature T m  that is lower than the glass transition temperature T g  of the at least one natural polymer and/or its derivative. 
     
     
         3 . The coated paper according to  claim 1 , wherein the permeability of at least one gas is lower than the permeability of a coated paper with the same base paper and each a coating layer of the natural polymer or its derivative and a coating layer of the crystallizable organic compound. 
     
     
         4 . The coated paper according to  claim 1 , wherein the coating layer has a contact angle with water of no more than 150° and/or wherein the coating layer has a roll-off angle with a 4 μL water drop of more than 10°. 
     
     
         5 . The coated paper according to  claim 1 , wherein the crystallinity of the semi-crystalline coating layer is in the range of 10% to 90%. 
     
     
         6 . The coated paper according to  claim 1 , with a water vapor transmission rate (WVTR) of no more than 40 g m −2  d −1  measured at 38° C. and over 90% humidity, and with a coating weight of 10±1 g·m −2 . 
     
     
         7 . The coated paper according to  claim 1 , wherein the proportion of crystallizable organic compounds based on the total mass of the coating layer is in the range of 1 to 60 wt. 
     
     
         8 . The coated paper according to  claim 1 , wherein the proportion of natural polymers or their derivatives based on the total mass of the coating layer is in the range of 40 to 99 wt. %. 
     
     
         9 . The coated paper according to  claim 1 , wherein at least one crystallizable organic compound is selected from fatty acids, hydroxy fatty acids, or dicarboxylic acids or their esters, amides, or salts. 
     
     
         10 . The coated paper according to  claim 1 , wherein the fatty acids are saturated or unsaturated fatty acids with 12 to 40 carbon atoms. 
     
     
         11 . The coated paper according to  claim 10 , wherein the at least one crystallizable organic compound is present as a fatty acid mixture or wax in the coating. 
     
     
         12 . The coated paper according to  claim 1 , wherein the natural polymers are selected from the group consisting of proteins, peptides, nucleic acids, polysaccharides, lipids, polyhydroxyalkanoates (PHA), cutin, suberin, lignin, cellulose, chitosan, and starch. 
     
     
         13 . The coated paper according to  claim 12 , wherein the lignin is derived from conifers, hardwoods, grass plants, or annual plants, and extracted using a method selected from the Kraft process, sulfite process, soda-anthraquinone process, GRANIT process, Alcell™ process, and Organocell process. 
     
     
         14 . The coated paper according to  claim 12 , wherein the derivative of a natural polymer is an ester of a natural polymer. 
     
     
         15 . The coated paper according to  claim 10 , wherein at least one fatty acid in the lignin ester is identical to at least one fatty acid used as a crystallizable organic compound. 
     
     
         16 . The coated paper according to  claim 10 , wherein the crystallizable organic compound is stearic acid and the derivative of a natural polymer is lignin stearate. 
     
     
         17 . The coated paper according to  claim 1 , wherein the coated paper has at least one of the following characteristics:
 the coated paper is biodegradable;   the coated paper is recyclable; or   the coated paper can be approved for direct or indirect food contact.   
     
     
         18 . A coating for coating papers comprising at least one solvent, at least one crystallizable organic compound, and at least one natural polymer and/or derivative of a natural polymer;
 wherein the crystallizable organic compound is selected from fatty acids, hydroxy fatty acids, or dicarboxylic acids or their esters, amides, or salts;   wherein the natural polymer and the derivative of a natural polymer are selected from the group consisting of proteins, peptides, nucleic acids, polysaccharides, lipids, polyhydroxyalkanoates (PHA), cutin, suberin, lignin, cellulose, chitosan, and starch; and   wherein the solvent is selected from water, tetrahydrofuran (THF), toluene, ethyl acetate, and alcohols.   
     
     
         19 . The coating according to  claim 18 , with at least one of the following features:
 the crystallizable organic compound is not in crystalline form;   the proportion of natural polymers and/or their derivatives relative to the total mass of the coating is in the range of 6 to 30 wt. %;   the proportion of crystallizable organic compounds relative to the total mass of the coating is in the range of 2 to 15 wt. %, or   the proportion of the solvent relative to the total mass of the coating is in the range of 60 to 90 wt. %.   
     
     
         20 . A method for producing a coated paper with a base paper and a semi-crystalline coating layer, comprising the steps:
 a) producing a coating according to  claim 18  by melt dispersion, high-pressure dispersion, or spray drying and subsequent mechanical dispersion of the components;   b) providing a base paper;   c) applying the coating to the base paper; and   d) curing the coating to form the semi-crystalline coating layer.   
     
     
         21 . A coated paper produced by the method according to  claim 20 . 
     
     
         22 . A packaging for food comprising the coated paper according to  claim 1 .