Stora Enso Oyj

Antti Savolainen

Jurkka Kuusipalo

Jari Räsänen

Johanna Lahti

Tapani Penttinen

Isto Heiskanen

Kimmo Nevalainen

Markku Sainio

Erkki Laiho

Esa Koreasalo

Tommi Lehikoinen

The invention relates to a polymer-coated Polymer-coated heat-sealable packaging material, heat-sterilized package formed from the material, and use of the packaging material. The material comprises a fiber base(e.g., packaging board made of bleached pulp) with polymer heat-seal layerslocated on both sides thereof. The package comprises, outside the fiber base, first polymer coating layer, which contains white pigment for covering the fiber base from sight, and second coating layer, which contains light-absorbing pigment. A coating layer pigmented grey inside the fiber base may provide a light shield for the packaged product. Absorbent black pigment may be located outside the fiber base underneath the white layer to stabilize the brightness of the material. A heat-sterilized package is made by providing the packaging material, forming a package containing, e.g., food, and heat-sterilizing the package in an autoclave. Yellowing of the fiber-based material is avoided by means of a white pigment.

Method of making heat-sterilised product package

The invention relates to a method for digitally printing a polymer-coated paper or board (), to a paper or board suitable for the method and to the production of a product package equipped with digital prints. During digital printing, printing ink particles are applied in an electric field to the printing surface formed of a polymer coating at locations corresponding to the print, and the printing ink is adhered to the printing surface by fusion with the aid of infrared radiation. In accordance with the invention, the paper or board () to be printed is equipped with an inner coating layer () containing electrically chargeable ethene acrylate copolymer, such as ethene methyl acrylate copolymer (EMA), and with a polyolefin-based outer shield layer () on top of this, which contains e.g. low-density polyethene (LDPE) and provides mechanical strength, forming the printing surface receiving the printing ink.

Digital printing of polymer-coated paper or board

The invention relates to a digital printing method and a paper or board applicable thereto. In digital printing, the surface of a paper or board is charged electrically, toner particles are brought to the surface in an electric field in accordance with the printing, and the particles are melted fast to the surface with the help of heat for forming the printing. According to the invention, the paper or board () is provided with a coating layer () containing an electrically chargeable acrylate copolymer of ethylene, which receives the toner that is fused to the coating with the help of infrared radiation. Suitable coating polymers are especially methyl, ethyl and butyl acrylate copolymers of ethylene (EMA, EEA and EBA). Especially in packaging boards, besides the digitally printable layer, the polymer coatings can comprise a water vapor or oxygen barrier layer for protecting the packed product, and a heat-sealable layer on the opposite side of the board for sealing the package.

Digital printing method and a paper or board applicable thereto

The invention relates to a digital printing method and a paper or board applicable thereto. In digital printing, the surface of a paper or board is charged electrically, toner particles are brought to the surface in an electric field in accordance with the printing, and the particles are melted fast to the surface with the help of heat for forming the printing. According to the invention, the paper or board () is provided with a coating layer () containing an electrically chargeable acrylate copolymer of ethylene, which receives the toner that is fused to the coating with the help of infra red radiation. Suitable coating polymers are especially methyl, ethyl and butyl acrylate copolymers of ethylene (EMA, EEA and EBA). Especially in packaging boards, besides the digitally printable layer, the polymer coatings can comprise a water vapour or oxygen barrier layer for protecting the packed product, and a heat-sealable layer on the opposite side of the board for sealing the package.

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Kangasala, Finland

Antti Savolainen