Machine for the production of tissue paper

Abstract

This invention relates to a machine for the production of a tissue paper web with a forming section in which the tissue paper web is formed from a pulp suspension on a skin and with a nip which is formed between the cylindrical surface of a drying cylinder, in particular a Yankee drying cylinder, and a mating surface and through which the tissue paper web can be conveyed together with the skin. The configuration of the machine is variable such that, depending on the quality of the tissue paper to be produced, for example its absorbency or tear resistance, the skin is either a three-dimensionally structured skin, a structured mesh, a non-structured skin, or a felt, whereby the mating surface is formed by the cylindrical surface of a press roller which includes a suction zone and in which provision is made for bores communicating with the suction zone.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a paper making machine, and, more particularly, to a machine for the production of tissue paper. [0003] 2. Description of the Related Art [0004] Many different types of production processes for tissue paper are known. [0005] The expensive TAD method or the method described in PCT / EP2005 / 050203, for example, are used for the production of a particularly high-quality and fleecy tissue paper with a higher absorbency and high water absorption capacity coupled with high tear resistance. With the method described in PCT / EP2005 / 050203 the tissue paper web is formed in the forming section on a structured mesh and then dewatered in several dewatering steps under the action of pressure. For example, the tissue paper web is conveyed throughout the dewatering on the structured mesh on which it was formed. In this way a tissue paper with voluminous, less compressed areas, and with compressed soli...

AI Technical Summary

Benefits of technology

[0045] To be able to obtain a good dewatering of the tissue paper web by the mechanical tensioning of the press belt and as the result of the gas flow through the press belt the press belt has an open area of at least 25% and a contact area of at least 10% of its total area facing the upper skin. A uniform mechanical pressure is exerted on the arrangement of the structured upper skin and lower skin by increasing the contact area of the press belt.

[0046] Satisfactory results are obtained with all the values, stipulated below, for the contact area and open area of the press belt. Provision is made accordingly for the press belt to have an open area of between 75% and 85% and a contact area of between 15% and 25% of its total area facing the upper skin. Also, provision is made for the press belt to have an open area of between 68% and 76% and a contact area of between 24% and 32% of its total area facing the upper skin. Very good results with regard to dry content and voluminosity of the tissue paper are obtained when the press belt has an open area of between 51% and 62% and a contact area of between 38% and 49% of its total area facing the upper skin. In particular through the construction of the press belt, with a woven structure, it is possible for the press belt to have an open area of 50% or more and a contact area of 50% or less of its total area facing the upper skin. As such it is possible to provide for a good gas flow through the press belt as well as a homogeneous pressing force by way of the press belt.

Problems solved by technology

In tests, however, rollers with a solid circumferential surface display poor transfer properties of the tissue paper web from the mesh to the Yankee drying cylinder because a vacuum is generated in the opening nip and leads to the tissue paper web adhering to the mesh.

A satisfactory transfer performance is obtained by way of bores in the cylindrical surface of the roller, but the roller casings, known from the prior art with their relatively large bores of more than 3.8 mm, leave unacceptable shadow marks on high-quality tissue paper.

With this method, too, there is a need, due to pressure from costs, to replace the expensive shoe press unit with a cheaper press roller.

However, tests in this connection have shown that rollers with a solid circumferential surface and rollers with blind bores are not suitable for replacing the shoe press unit due to too low a dewatering performance.

Furthermore, manufacturers of tissue paper face changing requirements with regard to the quality and quantity of the tissue paper to be produced.

The provision of production machines for both methods is costly for the tissue paper manufacturer as this means on the one hand that both types of production machines have to be purchased and on the other hand that depending on the current market demands the one or other machine cannot be used for production.

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