Barrier layer for cellulose substrate
In a method for the production of coated substrates, a flowable, biologically degradable first coating which enhances gas tightness is applied to a cellulose-containing substrate. To obtain a packaging consisting only of natural components and offering good tightness, a second watertight coating made of animal and/or vegetable waxes and/or lipids is applied to the first coating.
1. A method for the production of coated substrates, comprising:
molding a three dimensional cellulose-containing substrate using a pulp molding process;
preparing a flowable and biodegradable first coating comprising cellulose and denatured casein, wherein the denatured casein is obtained by reacting casein with a denaturing agent, wherein the denaturing agent is calcium hydroxide, wherein the denatured casein is water-repellent, wherein the cellulose and the denatured casein are dissolved in water;
applying the flowable and biodegradable first coating increasing gas-tightness to the cellulose-containing substrate;
solidifying and drying the first coating; and
applying a second waterproof coating comprising an oil and/or wax composition, wherein the oil and/or wax composition comprises animal and/or vegetable waxes, and/or lipids, to the first coating.
2. The method according to claim 1 , wherein the second coating contains at least one component selected from the group consisting of:
linseed oil,
carnauba wax, and
beeswax.
3. The method according to claim 2 , wherein the second coating contains:
20 to 30% by weight linseed oil,
40 to 60% by weight carnauba wax and
30 to 40% by weight beeswax.
4. The method according to claim 1 , wherein the flowable first coating further comprises at least one-component selected from the group consisting of:
whey;
agar-agar; and
psyllium husks.
5. The method according to claim 1 , wherein the cellulose of the first coating comprises cellulose microfibrils with a median diameter in a range from 30 to 100 nm and/or cellulose nanofibrils with a median diameter in a range from 5 to 20 nm.
6. The method according to claim 1 , wherein the cellulose of the first coating and the denatured casein of the first coating are applied in one or more application processes.
7. The method according to claim 6 , wherein the cellulose of the first coating is applied in a first application process and the denatured casein of the first coating is applied in a second application process.