Paper making and fiber liberation – Processes and products – Non-fiber additive
Patent
1999-01-27
2000-07-04
Silverman, Stanley S.
Paper making and fiber liberation
Processes and products
Non-fiber additive
162185, 162216, 162190, 1621681, 1621646, 1621811, D21H 2304, D21H 2100
Patent
active
060833483
DESCRIPTION:
BRIEF SUMMARY
METHOD FOR PRODUCING PAPER
The present invention relates to a process for the production of paper by draining a paper stock containing process chemicals on a paper machine in which a main stream of the paper stock and a dilution stream consisting of white water and amounting to 5-35% by volume of the total head box feed are fed via a head box to the paper machine wire.
BACKGROUND OF THE INVENTION
The process described above is known in the technical literature as the module jet concept, cf. Das Papier, Number 10A (1995), pages V 99-V 105, and Wochenblatt fur Papierfabrikation, 122 (1994), 485-491. With the aid of this special head box, it is possible to produce, inter alia, high-quality supercalandered papers (SC papers) having a high filler content and a uniform formation. However, the papers obtainable by this process have a tendency to dusting.
The paper machines usually have only a single stream for feeding the paper stock to the head box. In addition to the fibers suspended in water, the paper stock contains process chemicals, such as fixing agents, drainage aids, retention aids and flocculants and may contain sizes, dry and wet strength agents, dyes and fillers. The metering of the process chemicals to the paper stock can be carried out by various methods described in the literature. For example, Wochenblatt fur Papierfabrikation 13 (1979), 493-502 discloses the use of cationic polyelectrolytes in combination with bentonite, first bentonite and then the cationic polyelectrolytes being added to the paper stock and it being possible, if required, to subject the paper stock to a shear gradient.
EP-B-0 235 893 discloses that a synthetic cationic polymer having a molar mass of more than 500.000 can initially be added to a paper stock, resulting in the formation of flocks which are then comminuted to microflocks in a subsequent shearing step. Thereafter, bentonite is added and the paper stock containing the process assistants is drained. In the papermaking process disclosed in EP-A-0 335 575, two different water-soluble, cationic polymers are added in succession to the paper stock. Here, a low molecular weight cationic polymer is first metered in as a fixing agent and then a high molecular weight cationic polymer as a flocculant, the paper stock is then subjected to a shear stage with the formation of microflocks, bentonite is added and the paper stock is then drained. However, the formation profile of the papers thus produced is unsatisfactory.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for the production of paper, an increase in the retention, in particular the fiber and crill retention and, if required, the filler retention being achieved in comparison with the known processes and at the same time papers having a uniform formation profile being obtained.
We have found that this object is achieved, according to the invention, by a process for the production of paper by draining a paper stock containing process chemicals and, if required, fillers on a paper machine in which a main stream of the paper stock and a dilution stream consisting of white water and amounting to 5-35% by volume of the total head box feed are fed via a head box to the paper machine wire, if at least 5% by weight of the process chemicals are metered into the dilution stream. The papers thus produced have a uniform formation profile and surprisingly contain a qualitatively very good bond of the crill and fillers to the long fiber, so that these papers exhibit virtually no dusting or exhibit dusting which causes no problems. Moreover, the interfering substances generally contained in the white water, such as wood ingredients or tacky impurities from the paper coat in the case of recycled fibers or with the use of waste paper, are virtually quantitatively fixed to the paper stock and thus rendered harmless for the papermaking process and the subsequent paper recycling.
DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS
The novel process comprises a head box having a
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W. Auhorn, et al., Wochenblatt fur Papierfabrikation, vol. 13, pp. 493-502, "Untersuchung Von Storsubstanzen In Geschlossenen Kreislaufsystemen", 1979 .
Auhorn Werner
Blum Rainer
Dyllick-Brenzinger Rainer
Meixner Hubert
Monch Dietmar
BASF - Aktiengesellschaft
Fortuna Jos'e A.
Silverman Stanley S.
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