Optics: measuring and testing – For optical fiber or waveguide inspection
Patent
1993-06-07
1996-01-23
Limanek, Robert P.
Optics: measuring and testing
For optical fiber or waveguide inspection
356318, 356335, 356441, 250432R, 2504591, G01N 2164, G01N 3334, G01N 1514
Patent
active
054869048
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a method for determining the number and size of resin particles freely distributed in paper stock.
2. Description of the Prior Art
In papermaking by a procedure at neutral pH, the natural resin particles present in the paper stock give rise to problems. In particular, the free resin particles, ie. those which are not bound to the wood fibers, are deposited in the paper machines and hence lead to considerable operating problems, for example tears in the paper, and consequently to expensive downtimes. Assistants which bind the resin particles to the wood fibers and thus ensure that the resin is discharged with the paper from the paper machine are therefore added to the paper stock. The efficiency of such assistants has been tested to date by expensive and not very reliable tests on the paper machines themselves. Furthermore, the literature describes methods which permit determination of the harmful amount of resin in the laboratory. However, the detection of free resin particles and testing of the efficiency of the assistants used is made very difficult on the laboratory scale by virtue of the fact that the unbound resin is present only in very small amounts in the paper stock (about 1 g of free resin to 1 tonne of paper stock). The known, conventional methods of determination of harmful resin, such as the extraction of the paper stock with organic solvents, for example with dichloromethane (Weigl et al., Das Papier 40 (1986), V52), the deposition of the resin on surfaces, for example according to Gustafson (Gustafson C. et al., Paperi ja Puu 34 (1952), 121-127), the flotation method according to Storle and Teves (Storle and Teves, Das Papier 10 (1956), 264-170) and the microscopic counting method (Allen, L. H., Pulp & Paper, Canada, 76 (1975), 70) thus give unsatisfactory and controversial results.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for determining the number and the size of resin particles freely distributed in paper stock, which can be carried out reliably without great expense, even at a very low concentration of dispersed resin in the paper stock.
We have found that this object is achieved by the method according to the invention, wherein a paper stock suspension is first prepared and the resin particles are separated from said suspension by filtration, after which the resin particles are marked with a fluorescent dye, isolated and then excited to produce light emission, the light signals of the individual resin particles are detected and the detection signals are evaluated for counting and size determination of the resin particles.
The method is described in detail below for an example, with reference to the drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows a schematic longitudinal section of a measuring cell for isolating the resin particles,
FIG. 2 shows a measuring arrangement for carrying out the method and
FIG. 3 is a graph showing the dependence of the number of resin particles on the assistant concentration.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
After preparing a suspension from the paper stock to be investigated and water, the suspension is filtered to separate the resin particles from the paper stock.
This is done using a dynamic drainage jar, a Plexiglas container with an integral paper sieve of 80 .mu.m mesh size, by first diluting the paper stock to be investigated to a solids content of about 0.4% (value used in practice) and filtering the stirred stock through the sieve. The assistant for binding the resin particles to the wood fibers is added to the dilute paper stock suspension before filtration, in a concentration of from 0 to 0.5%, based on the fiber solids content. The filtrate obtained, which contains resin particles and fibers smaller than 80 .mu.m, is further diluted (1:10), and a dye solution, preferably the fluorescent dye Fluorol.RTM. from BASF AG (N-(n-butyl)-4-(n-butylamino)naphthalimide) in solution in a concentration of 40 m
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patent: 4837446 (1989-06-01), Renard et al.
patent: 5046853 (1991-09-01), Hemel et al.
patent: 5216483 (1993-06-01), Berthold et al.
Norman, "Flow Cytometry", Nov./Dec. 1980, vol. 7, No. 6, Medical Physics pp. 609-615.
Gierulski Alfred
Horn Dieter
Kroehl Thomas
Lorencak Primoz
Lueddecke Erik
BASF - Aktiengesellschaft
Hardy David B.
Limanek Robert P.
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