Method and a machine for producing a tissue web

Abstract

The invention relates to a method of producing a structured fibrous web of paper suitable for tissue products. The method comprises forming a fibrous web and conveying the formed fibrous web on a water receiving felt (5) to a dewatering nip. An endless steel belt (11) with a smooth steel surface is passed through the nip together with the fibrous web and the water receiving felt (5) wherein the endless steel belt is heated by heaters (HE_U, HE_L). After the dewatering nip, the fibrous web is conveyed by the endless steel belt (11) to an endless textured fabric (12) which is permeable to air and to which the web is transferred from the endless steel belt (11) in a transfer nip. The textured fabric (12) runs at a lower speed than the endless belt (11). After the transfer to the textured fabric (12), the fibrous web is carried by the textured fabric (12) to a drying cylinder (17). The transfer nip is formed by two rolls of which one is a suction roll within the loop of the textured fabric. The transfer nip has a length which is 5 mm-40 mm. The endless steel belt (11) has a width that exceeds the width of the textured fabric (12). The invention also relates to a corresponding machine.

Description

BACKGROUND OF THE INVENTION[0001]The invention relates to a method and a machine for producing a structured fibrous web, in particular a tissue web. The fibrous web produced may be used as, for example, kitchen towel, toilet paper or facial tissue. In sharp contrast to production of paper where the paper should have high density and printable surface, the tissue paper should have high bulk and optimal absorption using creping technique of the web during production of the web.PRIOR ART[0002]A machine for manufacturing structured soft paper is disclosed in U.S. Pat. No. 6,287,426. The machine disclosed in that patent has a forming section with a head box and two forming fabrics. The formed web is passed on a water receiving felt through a dewatering nip. An impermeable belt is also passed through the dewatering nip and the web is transferred to the impermeable belt. The impermeable belt then conveys the fibrous web to a wire 22 which has a web-contacting side with a structure. A sucti...

AI Technical Summary

Benefits of technology

[0008]In paper production, where rush transfer is not sought for, Valmet has developed the OptiPress™ Metal Belt, using a heated metal belt for pre-calendering, obtaining excellent macro scale smoothness, even topography after coating, better optical properties and excellent macroscale topography with same or better stiffness. The paper grades produced has some 60 to 70 g / m2 base paper. However, these product properties are not sought for when producing tissue paper.

Problems solved by technology

When the speed difference is larger than about 8%, sheet transfer is often lost and the web is damaged.

Such an arrangement requires that three rolls cooperate which is difficult due to deflection of the rolls in the nips as well as possibilities of controlling each individual nip individually.

Moreover, the creping wire may be subjected to wear as it contacts the transfer roll.

However, these product properties are not sought for when producing tissue paper.

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