FI97558C - Multilayer kraftliner - Google Patents

Description

97558

The present invention relates to a presentation liner, i.e. a multilayer kraftliner. Presentation liner refers to improved liner quality that produces good printability for copy, and evenness of print, brightness, contrast, and sharpness.

10

Presentation liner is used when high-quality printing, halftone printing and multicolor printing are desired. It is also used to print barcodes and lowercase information.

15

The performance liner must have good surface smoothness, matched luminescence, uniform absorption, and high purity. Kraf liners, which form even layers in corrugated boards, also called surface layers, are usually made primarily of kraft pulp in two or three layers to a basis weight of 100 to 440 g / m 2, and are usually read on kraft papers.

Kraftliners, i.e. surface layers, are usually made from the sulphate pulp of softwood and hardwood, whereby the composition of the pulp depends on the requirements for a certain pulp quality. Hardwood produces a better surface than softwood and is somewhat cheaper than softwood. It is also known to mix recycled fibers into the kraftliner, at least in a layer of 30, in which case fine printing waste is usually used as a raw material.

Swiss patent publication CH 633 482 describes a process for producing a high-strength surface layer for corrugated board 35, i.e. a liner comprising at least two layers, one layer of which is a semi-finished waste paper 2 97558 and the other layer or layers of chemimechanical softwood pulp (CMP ). It is said that this production method decisively reduces or completely avoids the use of kraft pulp or kraft recycled fibers, whereby the wood raw material 5 is better utilized.

The patent specification also describes, as part of the prior art, a method of extending kraft pulp with modified hot milling (MTMP) or chemical hot milling (CTMP).

10

As mentioned above, the present invention relates to a so-called presentation liner, i.e. a kraft liner, characterized in that the liner comprises several layers, preferably 2 to 3 layers, that 55 to 100% of the mass forming the surface layer or layers 15 comprises bleached hardwood sulphate pulp, which is free of chlorine chemical and which additionally contains 0 to 15% of a pigment, e.g. calcined clay, the concentrations being calculated as a percentage of the dry mass; and that the remainder of the pulp of the top layer (top layer) comprises unbleached softwood sulphate pulp or bleached softwood sulphate pulp free of chlorine chemical.

It has been found that the luminance (Y-value, SCAN method P 8:75) of the surface layer (top) of the liner according to the invention is 45-25%, or expressed as brightness 32-85% (SCAN method P

3:75).

According to a particular embodiment of the invention, at least 80% of the hardwood pulp of the top layer comprises birch. Hardwood pulp 30 can be oxygen bleached in one or more steps, or bleached in known oxygen and peroxide steps.

The basis weight of the surface layer, i.e. the uppermost layer, is preferably between 30 and 90 g / m 3, and the mass 35 forming this layer is preferably ground to a degree of grinding of 20 to 40 SR.

According to a particular embodiment of the invention, the pulp of the other 3,97558 layers of liner comprises unbleached softwood pulp, in a mixture of 0 to 10% unbleached hardwood sulphate pulp and 0 to 50% recycled fiber. The surface of the surface layer preferably has a Bendtsen roughness number of less than 1000 ml / min (SCAN-P 21:67).

5

Example

The liner according to the present invention was prepared by existing machinery and mainly by conventional methods.

10 The liner comprises two layers, the top layer of which was made of oxygen-bleached hardwood sulphate pulp (> 80% birch) with a kappa number of 12. The pulp was purchased from another manufacturer. The pulp was pure and ground to an SR of 24 to 25. The basis weight of the surface layer was about 60 g / m 2.

15

The base layer was made of softwood sulphate pulp with a Kap number of about 75. The pulp was ground to an SR number of about 21 to 22 and 10% recycled corrugated board was added.

The total basis weight of the prepared product was 186 g / m 2. The Bendtsen roughness number (SCAN-P 21:67) was less than 1000 ml / min and the performance liner luminance was 54% (Y-value, SCAN-P 8:75).

. 25 30 35

Claims (8)

1. Presentation liner in multilayer construction, preferably consisting of 2 to 3 layers, the top layer being formed of 50-100. optionally recycled fiber, characterized in that the top layer of hardwood sulphate pulp 15 consists of 50 - 100% chlorine chemical-free bleached hardwood sulphate pulp with the addition of 0 - 15% pigment, calculated on dry mass, e.g. calcined clay, with the remainder of the pulp for the top layer being bleached or chlorine-chemical-free bleached softwood sulfate pulp, and the liner's top surface having a luminance (Y value, SCAN method P 8:75), of 45 - 85%, or measured as lightness 32 - 85% (SCAN method P 3:75). 2. Liner according to claim 1, characterized in that the top layer is formed of pulp, for which the foliage of more than 80% is made of birch. Liner according to claim 1, characterized in that the deciduous wood pulp is oxygen bleached in one or more steps. 4. Liner according to claim 1, characterized in that the deciduous wood pulp bleached with a combination of oxygen and peroxide steps. 5. Liner according to claim 1, characterized in that the surface weight of the top layer is 30 - 90 g / m2. 35 6. Liner according to claim 1, characterized in that the mass of the top layer is ground to 20 - 40 SR. 97558 7. Liner according to claim 1, characterized in that the Swedish layers except the top layer are formed of unbleached softwood sulphate pulp and 0 - 10% unbleached low sulphate pulp and 0 - 50% recycled fiber. 8. Liner according to claim 1, characterized in that the surface of the top layer has a surface roughness of less than 1000 ml / min according to Bendtsen (SCAN-P 21:67).