Packaging material having a barrier coating based on starch, and coating mass, method, and device for producing such a barrier coating

Abstract

A packaging material includes a starch-based barrier coating. After deducting an optional filler component, the barrier coating has 30 to 90% by weight of starch, wherein at least >20% of the starch has an average molecular weight of at least 500,000 g/mol, and >20% by weight of the starch are present in the barrier coating in the form of gelatinized starch particles. A content of 0-70% by weight of plasticizer in the barrier coating and a surface weight in the range of 3 to 80 g/m 2 , make it possible to produce a mechanically stable barrier coating, which effectively prevents the diffusion of nonpolar hydrocarbons and hydrocarbon derivatives, for example on the inside of cardboard packaging, and thus protects the packaged food against contaminations. The packaging material can be produced easily and cost-effectively at high process speeds and can be recycled without restrictions and meets possible food regulations.

1 . A packaging material comprising a starch-based barrier layer for preventing the diffusion of nonpolar hydrocarbons and/or hydrocarbon derivatives, wherein the packaging material comprises:
 a planar substrate, preferably chosen from the group consisting of paper, pasteboard and cardboard, as carrier layer, and   at least one starch-based barrier layer, which is applied to the planar substrate,   wherein the barrier layer is characterized in that   the barrier layer, after deducting an optionally comprised filler component, comprises 30-100% by weight of starch, wherein   at least >20% of the starch has an average molecular weight M w  of at least 1,000,000 g/mol, and   >20% by weight of the starch is present in the barrier layer in the form of gelatinized starch particles, and   the barrier layer, based on starch plus plasticizer, comprises 0-70% by weight of plasticizer, and   the barrier layer in the dry compound has a surface weight in the range of 3-80 g/m 2 .   
     
     
         2 . The packaging material according to  claim 1 , wherein the barrier layer is applied to a surface of the planar substrate, which corresponds to the rear side of the packaging material, and thus to the inside of a packaging, which is to be created, wherein the substrate is preferably paper comprising a surface weight in g/m 2  in the range of 30 to 800. 
     
     
         3 . The packaging material according to  claim 1 , wherein more than 50% by weight of the starch of the barrier layer has a molar mass M w  of >2,000,000 g/mol. 
     
     
         4 . The packaging material according to  claim 1 , wherein >25% by weight of the starch is present in the barrier layer in the form of gelatinized starch particles. 
     
     
         5 . The packaging material according to  claim 1 , wherein the starch of the barrier layer, preferably the gelatinized starch particles, comprises/comprise tapioca starch, pea starch, potato starch or any mixture thereof, preferably substituted tapioca starch, substituted pea starch, substituted potato starch or any mixture thereof. 
     
     
         6 . The packaging material according to  claim 5 , wherein the barrier layer contains the starch or the starches at a portion of 30 to 100% by weight, after deducting an optionally comprised filler component. 
     
     
         7 . The packaging material according to  claim 1 , wherein the plasticizer content in the barrier layer in % by weight, based on starch plus plasticizer, is at least 5% by weight. 
     
     
         8 . The packaging material according to  claim 1 , wherein the barrier layer in % by weight, based on starch plus thickening agent, comprises maximally 50% by weight of thickening agent. 
     
     
         9 . The packaging material according to  claim 1 , wherein the thickening agent comprises xanthan and/or polyvinyl alcohol, preferably comprising a portion of 0.01 to <2.5% by weight of xanthan and/or 1 to 30% by weight, preferably 1 to 10% by weight of polyvinyl alcohol. 
     
     
         10 . The packaging material according to  claim 1 , wherein the planar substrate additionally comprises a precoat, preferably a mineral precoat, which is arranged between the substrate surface and the barrier layer. 
     
     
         11 . A method for producing a multi-layer packaging material comprising a starch-based barrier layer, comprising the steps
 a) providing a planar substrate, which is preferably chosen from the group consisting of paper, pasteboard and cardboard, and which optionally has a precoat,   b) providing a coating compound,   c) applying the coating compound of step b) to at least one side of the planar substrate and forming a layer on the planar substrate, and   d) increasing the temperature for drying and solidifying the coating compound, which has been applied and shaped to form a layer,   characterized in that a suspension comprising granular starch suspended therein is used as coating compound, and that this suspension is gelatinized and dried in situ on the substrate.   
     
     
         12 . The method according to  claim 11 , wherein the temperature in ° C. of the coating compound in response to application to the substrate is at least 20 and/or the temperature in response to application, based on the temperature Tv, at which the coating compound has its viscosity minimum, is chosen within the following limits: <11 above Tv and <15 below Tv. 
     
     
         13 . The method according to  claim 11 , wherein at least the surface of the substrate, which is to be coated, is heated up prior to the application of the coating compound, so that, in response to application, at least the surface has a temperature in ° C. of >30 and/or that this temperature in ° C. preferably lies >5 above Tv of the coating compound. 
     
     
         14 . The method according to  claim 11 , wherein steam is applied to the coated surface prior to the drying. 
     
     
         15 . The method according to  claim 11 , wherein the coating compound is sprayed with water prior to the application of the steam. 
     
     
         16 . (canceled) 
     
     
         17 . The method according to  claim 11 , wherein the coating compound comprises:
 a) 10-75% by weight of granular starch,   b) 0-50% by weight of dissolved starch,   c) 0-70% by weight of plasticizer,   d) 25-90% by weight of water,   wherein the preferred weight average of the molecular weight distribution M w  of the granular starch is >500,000, and   at 40° C., the coating compound has a viscosity in the range of 50-3,000 mPas.   
     
     
         18 . The method according to  claim 17 , wherein the weight average of the molecular weight distribution M w  of the granular starch is at least 1,000,000 g/mol. 
     
     
         19 . The method according to  claim 17 , wherein the coating compound comprises tapioca starch, pea starch, potato starch or any mixture thereof. 
     
     
         20 . The method according to  claim 17 , wherein the granular starch comprises tapioca starch, pea starch, potato starch or any mixture thereof. 
     
     
         21 . The method according to  claim 17 , wherein the amylose content of the granular starch is in the range of 0 to less than 60% by weight. 
     
     
         22 . The method according to  claim 17 , wherein the plasticizer content is at least 5% by weight. 
     
     
         23 . The method according to  claim 17 , wherein the coating compound comprises at least 2 plasticizers, wherein at least 5% of the individual plasticizers are represented in the combination. 
     
     
         24 . The method according to  claim 17 , wherein the coating compound in % by weight, based on the total starch plus thickening agent, comprises maximally 50% by weight of thickening agent. 
     
     
         25 . The method according to  claim 17 , wherein the thickening agent comprises xanthan and/or polyvinyl alcohol, preferably comprising a portion of 0.01 to <2.5% by weight of xanthan and/or 1 to 30% by weight of polyvinyl alcohol. 
     
     
         26 - 30 . (canceled)