Coated paper
What is described is a coated paper comprising a base paper and at least three coatings applied thereto, wherein the at least three coatings, proceeding from the base paper, in this sequence, comprise a first barrier layer comprising at least one hydrophobic polymer, a second barrier layer comprising at least one hydrophilic polymer, and a third barrier layer comprising at least one hydrophobic polymer, a method for producing such a coated paper, and the use of the coated paper as packaging material.
1 . A coated paper comprising a base paper and at least three coatings applied thereto, wherein the at least three coatings, proceeding from the base paper, in this sequence, comprise a first hydrophobic barrier layer comprising at least one hydrophobic polymer, a second hydrophilic barrier layer comprising at least one hydrophilic polymer, and a third hydrophobic barrier layer comprising at least one hydrophobic polymer, wherein the at least one hydrophobic polymer contained in the third barrier layer is a thermoplastic polymer, and so the third barrier layer is thus heat-sealable, wherein a pre-coat comprising at least one inorganic pigment and a polymer binder is provided between the base paper and the first barrier layer, and wherein the at least one inorganic pigment comprises a silicate, wherein the coated paper has a sealed-seam strength of from 1.5 N/15 mm to 10 N/15 mm, wherein the sealed-seam strength is determined for the coated paper as follows: the coated paper is sealed at 3.3 bar for 0.3 seconds in a temperature range of from 100° C. to 200° C. transversely to the direction of the paper web and the sealed-seam strength is determined in accordance with DIN 55529 (2012).
2 . The coated paper according to claim 1 , wherein the first barrier layer comprises substances which are selected from the group of lipophilic substances, waxes, microcrystalline waxes, waxes based on plant oils or fats, waxes based on animal oils or fats, plant waxes, animal waxes, low-molecular polyolefins, polyterpenes, and mixtures thereof.
3 . The coated paper according to claim 1 , wherein the transfer of hydrophobic substances is reduced or prevented by the second barrier layer.
4 . The coated paper according to claim 1 , wherein the transfer of hydrophobic substances from the first barrier layer or through the first barrier layer, into the third barrier layer or therebeyond is reduced or prevented.
5 . The coated paper according to claim 1 , wherein the transfer of hydrophobic substances from the third barrier layer or through the third barrier layer, into the first barrier layer is prevented.
6 . The coated paper according to claim 1 , wherein the transfer of substances which are selected from the group of lipophilic substances, paraffins, waxes, microcrystalline waxes, waxes based on plant oils or fats, waxes based on animal oils or fats, plant waxes, animal waxes, low-molecular polyolefins, polyterpenes, and mixtures thereof, is reduced or prevented.
7 . The coated paper according to claim 1 , wherein the third barrier layer, apart from unavoidable or admissible impurities, is free from substances which are selected from the group of lipophilic substances, paraffins, waxes, microcrystalline waxes, waxes based on plant oils or fats, waxes based on animal oils or fats, plant waxes, animal waxes, low-molecular polyolefins, polyterpenes, and mixtures thereof.
8 . The coated paper according to claim 1 , wherein the base paper has an area density of from 20 to 120 g/m 2 .
9 . The coated paper according to claim 1 , wherein the first barrier layer comprises a hydrophobic polymer based on a polyacrylate and/or a polyolefin.
10 . The coated paper according to claim 1 , wherein the second barrier layer comprises at least one hydrophilic polymer based on a polyvinyl alcohol.
11 . The coated paper according to claim 1 , wherein the third barrier layer comprises a hydrophobic polymer based on a polyacrylate, a styrene/butadiene copolymer and/or a polyolefin.
12 . The coated paper according to claim 8 , wherein the inorganic pigment further comprises a polymer binder based on a polyacrylate.
13 . The coated paper according to claim 1 , wherein no adhesion promoter is used between the individual barrier layers.
14 . The coated paper according to claim 1 , wherein the coated paper is free from halogen-containing compounds.
15 . The coated paper according to claim 1 , wherein the coated paper does not comprise an aluminium, Al 2 O 3 or SiO 2 layer.
16 . The coated paper according to claim 1 , wherein the base paper has a long-fibre content of from 10 to 80% and a short-fibre content of from 20 to 90 wt. %, a long fibre being a fibre with a fibre length of from 2.6 to 4.4 mm and a short fibre being a fibre with a fibre length of from 0.7 to 2.2 mm.
17 . A method for producing a coated paper according to claim 1 , wherein aqueous suspensions comprising starting materials of the first, second and third barrier layer are applied successively to the base paper, the aqueous application suspensions having a solids content of from 10 to 60 wt. %, and being applied by means of a curtain coating process at an operating speed of the coating plant of at least 200 m/min.
18 . The method according to claim 17 , wherein the first and second or the second and third barrier layer are applied immediately successively wet-on-wet by means of a double curtain coating process.