M-real Oyj

Stina Nyg&aring;rd

Markku Leskel&auml;

Maija Pitk&auml;nen

Eeva &angst;n&auml;s

Kaarlo Johannes Niskanen

The present invention concerns a process for preparing a paper web. According to the process a pulp is formed from a fibrous raw material, a web is formed from the pulp and it is dried on a paper machine. According to the invention the pulp is formed from a mechanical pulp produced from a peroxide bleached mechanical wood raw material of the genus Populus, the pH of proportioning of the mechanical pulp being set at 6.8 to 7.2 and the machine pH at 7.1 to 7.5 and the conductivity of the pulp being set at 1000 to 1500 &mgr;S/cm. By using a relatively low pH value and a narrow pH range it is possible to diminish the sensitivity to disturbances of the paper making process. According to the present invention a mechanical aspen pulp can be combined with chemical pulp for preparing base paper of fine paper, whereby the mechanical pulp gives a high conductivity on the machine which improves the stability of the wet end and enhances water removal.

Process for preparing a paper web

The present invention concerns a method for producing a base paper for fine papers, the base paper being produced from a mixture of a mechanical pulp and a chemical pulp. The chemical pulp used comprises a chemical softwood pulp having a elastic modulus close to that of the mechanical pulp and a great bonding strength. It is preferred to use a chemical softwood pulp which produces a sheet having a elastic modulus of less than 6000 N/mm when the bonding strength is 400 J/m . A pulp of this kind has a good ScottBond strength at the same light scattering. The base paper produced by the method can therefore be used in double-coated fine papers which require a large bonding strength of the base paper.

Process for preparing base paper for fine paper

The invention concerns a method for producing a paper web. According to the method a stock is produced from the fibrous raw material and the stock is formed to a web which is dried on a paper machine. According to the invention the stock is formed from a mechanical pulp prepared from wood material of the Populus family and from bleached chemical spruce pulp, whereby the amount of the mechanical pulp is 20 to 70 weight-% and the amount of the bleached chemical softwood pulp is 80 to 30 weight-% of the dry matter of the stock. It is preferred to use an aspen pulp, over 70% of the fiber fractions of which comprise fiber fractions &plus;100, &plus;200 and &minus;200, and the proportion of the &minus;200 fraction is 45% or less. A coated fine paper can be produced from the paper web whose properties are better than those of a traditional fine paper having the corresponding bulk and grammage, on the same capacity level the paper produced by the invention will give a yield gain of up to more than 20%.

Growing community of inventors

Lohja as, Finland

Stina Nygård

Growing community of inventors

Lohja as, Finland

Stina Nyg&aring;rd

Stina Nygård