Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
1999-03-05
2002-07-02
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S339080, C250S339110
Reexamination Certificate
active
06414312
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for controlling a process for the production of a cellulose fibre containing product from cellulose fibre containing raw material, in particular a process for the production of wood based panels such as particleboards.
DESCRIPTION OF THE RELATED ART
The production of cellulose fibre containing products often involve addition of different substances during the production process. The purpose of the addition may be to facilitate the production process per se, or to effect the resulting product, or both. Addition of various glues, often consisting of a glue system comprising a resin and a hardener, in the production of wood based panels is exemplary of an addition in order to effect the resulting product. An important parameter in this connection is often the proportion between the components making up the substance, if more than one, such as e.g. the proportions between resin and hardener in a glue, or the proportions between urea and formaldehyde in a glue containing those components. Another important parameter may be the proportions between different added substances, which are destined to different parts of the panel, e.g. in different layers of the panel.
WO 97/04299 relates to a method for controlling process variables influencing parameters of wood based panels, including glue amounts and wax amounts, which method comprises analysing the raw material by means of a spectrometric method, linking the obtained spectral data into a combination with desired parameters, and comparing said combination with reference combinations consisting of reference data from reference raw material linked with known parameters of said reference material, whereby the reference combinations have been calibrated to known variables by means of multivariate analysis. There is however no suggestion about controlling any proportions relating to those additives.
It would however be desirable to be able to control such proportions, as by doing so, it should be possible to produce cellulose fibre containing product such as wood based panels with very specific properties at optimised technical and economical conditions.
BRIEF SUMMARY OF THE INVENTION
The problem to be solved by the present invention is thus to enable such controlling.
This problem has been solved by the invention as defined by the appended claims. More particularly the present invention involves a method for controlling a process for the production of a cellulose fibre containing product from cellulose fibre containing raw material, during which process various substances are added, at least two of which substantially influence the same property of said product in correspondence to the relation between said substances, whereby a calibration model has been established by way of a procedure comprising linking known reference values for said product property and corresponding known reference relations between the substances, by means of a mathematical function; the method comprises the steps of
I) applying the calibration model on the actual relation between the substances in order to predict the value for said product property;
II) comparing the predicted value for said product property with a desired target value for said product property;
and, if said predicted value is not substantially equal to said target value, adjusting the actual relation between the substances in a predetermined way;
III) repeating steps I and II until said predicted value is substantially equal to said target value.
By the expression “in a predetermined way” is, in the present context, partly meant that it has been determined in advance whether the relation should be adjusted at all in the present turn in the loop defined by steps I to III; partly meant that it has been determined in advance whether the adjustment should be incremental or decremental depending on the fact per se that the predicted value is larger that the target value, irrespective of the size of the difference between those values, and vice versa, and partly meant that the absolute value of the adjustment has been determined in advance.
DETAILED DESCRIPTION OF THE INVENTION
The present method presents a plurality of advantages to the producer of cellulose fibre containing products. By means of the present method a particleboard producer, for instance, can regulate one or more properties of the produced boards in a very fast and economical way.
In a preferred embodiment the calibration model has been established by means of a multivariate analysis; this also implies that the same kind of multivariate analysis is applied when the calibration model is applied on the actual relation. The multivariate analysis may, for instance, be principal component analysis (PCA), partial least squares regression (PLS), principal component regression (PCR), multilinear regression analysis (MLR), discriminant analysis, or any other suitable method for multivariate analysis. The PLS method is disclosed in detail in Carlson R., “Design and optimization in organic synthesis”, B. G. M. Vandeginste, O. M. Kvalheim, Eds., “Data handling in science and technology”, (Elsevier, 1992), vol. 8, incorporated herein by reference. For a tutorial in PCA, PLS and PCR, see P. Geladi et al in “Partial Least-Squares Regression: A Tutorial” in Anal. Chim. Acta, 185, 1-17 (1986), which is incorporated herein by reference in its entirety. By MLR, the best fitting plane for the parameters as a function of the spectra is defined, using least squares techniques to define each boundary of the plane. This plane is then used to recognize and assign a predicted value to an unknown parameter value. Discriminant Analysis is a method whereby, by use of spectral data, the known parameter values are grouped into different clusters, separated by linear decision boundaries. From its spectrum, a sample of unknown parameter values then can be matched to a cluster, and the parameter value can be assigned a value, e.g., the average value of the cluster. Applied generally to the field of chemistry those statistic methods are also termed chemometrics methods. The technique of chemometrics is more fully explained in S. D. Brown, “Chemometrics”, Anal. Chem. 62, 84R-101R (1990), which by reference is incorporated herein in its entirety.
In a preferred embodiment the cellulose fibre containing product is a wood based panel. The wood based panel may comprise two or more layers. One of the substances may for instance be added to substantially stay between the layers, in order to e.g. agglutinate (i.e. glue together) the layers. Alternatively, one substance may be added to be substantially contained within one of the layers, in order to e.g. bind wood based particles in a particle board, or to provide the layer with some property, or to enhance some already present property. The wood based panel is preferably a board, such as a particleboard, a medium density fibre board (MDF), a waferboard, an oriented strand board (OSB), a hardboard, or a board of plywood; in particular, the board is a particleboard. Background information on particleboard and the processes for the manufacturing thereof is set forth in “Modern Particleboard & dry-process fibreboard manufacturing” by Thomas M. Maloney (1993), (cf. especially Chapter 4 and 5), which by reference is incorporated herein in its entirety.
It should be understood that the two (or more) substances which have a substantial influence on the same property of said product in correspondence to the relation between said substances may very well lack any effect, or only have a weak effect on that (or any other) property when used isolated from each other. This, basically, is the case when, for instance, one substance is a resin and another one is a corresponding hardener. On the other hand, the effect of the substances may in another embodiment be of basically the same magnitude, e.g. when using two urea-formaldehyde glues having different U/F proportions. In the latter case the property of interest can be brought towards its target value by controlling the U/F
Engström Björn
Johnsson Bo
Nordin Sofia
Akzo Nobel N.V.
Gagliardi Albert
LandOfFree
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