PAPER WITH IMPROVED SURFACE PROPERTIES AND METHOD OF MAKING THE SAME

Abstract: Paper with improved surface properties, especially printability and coating properties. The invention is characterized in that the paper comprises a surface layer consisting of highly beaten paper pulp, fine material or fibres separated from highly beaten paper pulp and/or fine material, possibly containing fibres, from white water, in an amount of at maximum 10 g/m<2>, preferably at maximum 5 g/m<2>.

Description: Paper with improved surface properties and method of making the same This invention relates to a paper with improved surface properties, especially printability and coating propert¬ ies. The invention also relates to a method of making such a paper. r- When a paper has been made in a paper aking machine, it is in most cases necessary to treat the paper so as to render it applicable to the purpose in question. Such a treatment can be surface sizing for making the fibre . material hydrophobic,or coating, which implies that a pigment dispersed in a binding agent is applied on - the paper web. The treatment is very expensive, and it is therefore of interest to take measures, which can reduce the investments in this respect. The primary object of the present invention is to bring about a uniform, dense, dustless and printable surface on the paper and paperboard and also to obtain an improvement in the bending stiffness without the disadvantages involved with the present state of art. At the making of printing paper and paperboard it is important, that the product has a uniform and printable surface. The surface is desired to have low dusting tendency and low fibre rise. It is, besides, of great economic value that the product has good rigidity. For single-layer sheets and surface layers in paperboard these properties are achieved to-day by a high energy investment at beating and by admixture of short-fibre pulp. In addition, glazing and in many cases surface sizing and coating are required for obtaining the desired surface quality. Increased beating and admixture of short-fibre pulp result in increased drainage resist¬ ance and thereby reduced production. Glazing always implies reduced bending stiffness. The disadvantages at conventional art are overcome by the present invention. According to the invention, a paper is .produced which comprises a surface layer of highly beaten paper pulp, fine material separated from highly beaten paper pulp and/or fine material from white water in an amount of 2 2 at maximum 10 g/m , preferably at maximum 5 g/m . The material is applied on each side or only one side of a wet sheet already formed. The material can be applied on the wet paper web by means of a head box located separately at the papermaking machine or by means of spray tins. According to a particularly suitable embodiment, the surface, layer consists of a cellulose material with a beating degree exceeding 30°SR, preferably exceeding 6θ°SR. This thin layer has the capacity of together with the base layer to form a smooth and strong surface with improved printability and coating properties compared to the base material. The advantage of this method compared to the present art is, that the base material requires less beating and smaller amounts of short-fibre pulps, which render dewatering difficult, in order to achieve the same surface finish and surface bonding strength. The advantage thereof is that for paperboard the bending stiffness is improved due to a greater thickness and due to the increase in the modulus of elasticity of the surfaces. The invention is not restricted to the applying methods set forth, but can be varied within the scope of the invention idea.

Claims: Claims 1. A paper with improved surface properties, especially printability and coating properties, c h a r a c t e r ¬ i z e d i n that it comprises a surface layer con¬ sisting of highly beaten paper pulp, fine material or fibres separated from highly beaten paper pulp and/or fine material, possible containing fibres, from white water, in an amount of at maximum 10 g/m , preferably at maximum 5 g/m 2 . 2. A paper as defined in claim 1, c h a r a c t e r ¬ i z e d i n that the surface layer consists of a cellulose material with a beating degree exceeding 30°SR, preferably exceeding βO°SR. 3. A method at the making of a paper with improved surface properties, especially printability and coating properties, c h a r a c t e r i z e d i n that a wet paper web already formed is provided with a surface layer consisting of highly beaten paper pulp, fine material or fibres separated from highly beaten paper pulp and/or fine material, possibly containing fibres, 2 from white water, in an amount of at maximum 10 g/m , 2 preferably at maximum 5 g/m , and the web thereafter is treated in a manner previously known per se. -i. A method as defined in claim 3, c h a r a c t e r ¬ i z e d i n that the surface layer is applied in the form of a cellulose material with a beating degree exceeding 30°SR, preferably exceeding 6θ°SR. 5. A method as defined in claim 3 or 4, c h a r a c t ¬ e r i z e d i n that the cellulose material is applied through a head box provided separately at the papermaking machine. 6. A method as defined in claim 3 or •>.,. c h a r a c t ¬ e r i z e d i n that the cellulose material is applied by means of spray tins.

Inventors: FELLERS NILS CHRISTER, HTUN MYAT THOUNG, LILJA JONAS EVERT, NAESLUND OLOF PER, OLOFSSON CLAES GREGER, FELLERS, NILS, CHRISTER, HTUN, MYAT, THOUNG, LILJA, JONAS, EVERT, NAESLUND, OLOF, PER, OLOFSSON, CLAES, GREGER
Applicants: SVENSKA TRAEFORSKNINGSINST, SVENSKA TRAEFORSKNINGSINSTITUTET
Application year: 1984
Main classification: D21H3
IPC codes: D21F11, D21H11, D21H17, D21H27