CA1154883A - Procedure for measuring coating rates - Google Patents
Procedure for measuring coating ratesInfo
- Publication number
- CA1154883A CA1154883A CA000419046A CA419046A CA1154883A CA 1154883 A CA1154883 A CA 1154883A CA 000419046 A CA000419046 A CA 000419046A CA 419046 A CA419046 A CA 419046A CA 1154883 A CA1154883 A CA 1154883A
- Authority
- CA
- Canada
- Prior art keywords
- coating layer
- radiation
- coating
- fluorescence radiation
- primary
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000000576 coating method Methods 0.000 title claims abstract description 37
- 239000011248 coating agent Substances 0.000 title claims abstract description 33
- 238000000034 method Methods 0.000 title claims abstract description 20
- 230000005855 radiation Effects 0.000 claims abstract description 62
- 239000011247 coating layer Substances 0.000 claims abstract description 47
- 239000000463 material Substances 0.000 claims abstract description 31
- 238000005259 measurement Methods 0.000 claims abstract description 13
- 239000011111 cardboard Substances 0.000 claims abstract description 10
- 238000010521 absorption reaction Methods 0.000 claims abstract description 5
- 230000006872 improvement Effects 0.000 claims description 4
- 239000000123 paper Substances 0.000 claims description 3
- 239000010410 layer Substances 0.000 abstract description 7
- 230000001678 irradiating effect Effects 0.000 abstract description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 10
- 229910000019 calcium carbonate Inorganic materials 0.000 description 6
- 235000010216 calcium carbonate Nutrition 0.000 description 5
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 4
- 230000009102 absorption Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 239000000945 filler Substances 0.000 description 2
- 239000002345 surface coating layer Substances 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000003550 marker Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
Abstract
A method of measuring the quantities of material in a first coating layer applied to cardboard or an equivalent base material as well as in a second coating layer applied to said first coating layer, comprises the steps of directing a primary X-ray radiation against the second coating layer so as to excite a characteristic fluorescence radiation in the first coating layer and measuring the intensity of said fluorescence radiation be means of a detector placed above said second coating layer, whereby the measurement of the quantity of material in the second coating layer is based on the absorption of the primary X-ray radiation and the fluorescence radiation while traveling through the second coating layer. The measurements in connection with the process of coating are carried out by measuring the quantity of material in the first coating layer before applying the second coating layer by irradiating the first coating layer with a primary X-ray radiation so as to excite a characteristic fluorescence radiation in the first coating layer itself and by measuring the intensity of this fluorescence radiation with a detector. The quantity of material in the second coating layer is measured after the application of this layer to the first coating layer by utilizing the value of the intensity of the fluorescence radiation from the first coating layer as measured before the application of said second coating layer.
Description
~15~3B3 This invention relates to a method of measuring the ~oating rate or amount of material applied as one or several surface coatings on a base material.
It is known in the prior art, from Finnish Patent No.
53757 in ~he name of Pertti Puumalainen, published March 13, 1978, to measure the base weights of a CaCO3 layer applied as a pre-coating on cardboard or paper and of a caolin-containing surface coating by employing X-ray radiation which excites the characteristic secon~ary X-ray radiation of the Ca in the pre-coat. The intensit~ of this radiation is measured from above and below the cardboard by means of detectors. The absorption of the primary radiation coming from the source of radiation in the various coatings is measured. From the mutually independent results of measurement, the base weights of coatings can be cal-culated by solving three equations with three unknown variables.
It is also known in the art to measure the coating rate in one coating on paper by utilizing the characteristic secon-dary X-ray radiation excited by primary X-ray radiation in a marker substance added to the coating material.
The method described in the above-mentioned Finnish Patent No. 53757 suffers from the drawback that the work involved in tlle calibration of a coating rate meter capable of measuring in on-line conditions two different coating layers is cumber-some. In order to be operative, the method re~uires several difficult to determine constants to be measured before the e~ua~
tions forming the basis of the method can be solved and the dif-ferent base weights determined. The method is moreover sensi-tive to variations in the geometry of measurement, since no pri- ;
mary radiation must be allowed to strike the fluorescence detec-tor on the side opposite from the source.
The method above has the drawback that tlle coating rate of only one coating layer can be measured, and only when . ,. ~ ~ . ~ . .
~5~883 coating layer gives rise to a measura~le amount of secondary X-ray radiation.
An object of the present invention is to avoid the drawbacks mentioned above and to provide a method, having simple operating characteristics and particularly suitable for on-line measurements, for the measuring of the coating rate and amount of material applied as one or several coatinss on a base layer.
The invention is particularly suitable for use in connection with the manufacture of paper, cardboard or like material.
Accordingly, the present invention provides an improve-ment in a method of determining the quantities of material in a first coating layer applied to cardboard or equivalent base ma-terial as well as in a second coating layer applied to said first coating layer, said method comprising the steps of subjecting said first coating layer to a primary X-ray radiation derived from an outside source and travelled via said second coating la-yer, so as to excite a characteristic fluorescence radiation in said first coating layer, and measuring the intensity of said fluorescence radiation by means of a detector placed above said second coating layer, whereby the determination is based on the absorption of the primary X-ray radiation and the fluorescence radiation while travelling through said second coating layer, the improvement comprising that, in addition to exciting the fluorescence radiation of the first coating layer, the primary X-ray radiation is used to excite a characteristic fluorescence radiation in the second coating layer, which is measured by means of a detector and used as the basis for determination of the quantity of material in the second coating layer, while the mea-surement of the fluorescence radiation of the first coating layer is performed for the determination of the quantity of material in the first coating layer, with the aid of the quantity of ma-terial in the second coating layer as determined.
1~54883 The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:-Fig. l shows diagrammatically an arrangement for put-ting into practice the method according to the invention, with a supporting web and coatings therein being shown in section;
Fig. 2 is a view similar to Fig. 1 showing an alter-native arrangement; and Fig. 3 is a view similar to Fig. l showing a further arrangement.
In Fig. l the cardboard web constitutes a base mater-ial l and has formed therèon a precoating layer 2, which may, for instance~ consist of CaCO3, and on the precoating layer 2 a surface coating 3, for instance, of caolin. When subsequent to precoating the combination 1,2 is irradiated ~ith a radiation source 4, which may for instance be a 55-Fe radio isotope -~
source, the Ca atoms in the precoating 2 emit their own charac-teristic secondary X-ray radiation, or fluorescence radiation, the intensity of which is proportional to the amount of material present, or of Ca in this case. When the intensity of Ca fluore-scence radiation arriving at the detector is known as a function of the amount of CaC03 present, the amount of CaCO3 is - 2a -~5~83 calculable from the intensity of the pulses delivered by the detector 5.
The web 1 moves forward to another coating unit, where - the surface coating 3 is applied to the web 1. Hereafter, the combination is irradiated once again with radiation ~rom the radiation source 6. This causes the Ca atoms to emit fluore-scence radiation which passes through the surface coating layer 3 and is measured by the aetector 7 located above the surface coating layer 3. Part of the primary and fluorescence radia-tions is abs~rbed, according to a certain experimentally deter-minable function, in the surface coating, and the number of pulses delivered by the detector 7 decreases. In evaluating the decrease in the number of pulses, one takes into account the ratio of efficiencies of measurement of the two pick-ups, which can be determined by running a web having only a base coating through the apparatus. From the pulse reduction found, the surface coating rate can be calculated.
If the base material contains, in significant amounts, fillers which are able to emit a significant amount of measur-able secondary X-ray ~adiation, or if the base material 1 is coated on the other side as well with a coatiny capable of emit- -ting measurable secondary radiation, these effects may be ac-counted for by irradiating the web with a radiation source 8 prior to the coating step and measuring the secondarv X-ray radiation by means of the detector 9. I~hen this is done, vari-ations of the base material 1 cause no possible sources of er-ror in the measurment of coating rates. The efficiency of measurement of the pick-up monitoring the raw cardboard must, however, be taken into account.
In the arrangement shown in Fig. 2, a CaCO3 coating is applied to the base material 1 and thereupon a coating 3 which contains Tio2 is applied. It is possible, by irradiating with :~lS~883 the source 5 the combination of courses 2 and 3, to measure the coating rates as follows: The quantitY of coatina layer 3 is a -function of the ~uantity of TiO2 contained in the coatin~ layer 3. If the amount of X-ray radiation with energy 4.5 keV emitted by TiO2 is measured, this enables the quantity of the surface coating 3 to be calculated. The primary radiation from the source 5 also excites the Ca in the base coating 2, which emits secondary radiation with energy 3.7 keV. Knowing the absorptions of the primary and secondary radiations in the surface coating 3, of which the quantity is already known, one can calculate which is the quantity of CaCO3 able to give rise from under this surface coating 3 to the measured secondary radiation. If required, the effect of the raw cardboard may be eliminated by the same procedure as was applied in the case of Fig. 1.
In Fig. 3, the base material 1 contains a substance capable of emitting secondary radiation, either as filler, as background coating, or as a material with which the base ma-terial has been impregnated. When the base material is irradia- ~
ted by the source 3 and the secondary radiation is measured with ;
the detector 4, information is gained concerning the secondar~
radiation emitted by the base material.
As the web moves forward to the coating unit, in which the surface coating 2 is applied on the web, the combination is irradiated from the source 5. This causes the atoms in the web to emit fluorescence radiation under the influence of the primary radiation that has penetrated through the surface coat-ing 2. The number of pulses received by the detector 6 then de-creases as part of the primary and fluorescence radiations is absorbed in the surface coating in accordance with a given ex-perimentally determinable function. Qne then calculates thecoating rate on the basis of the pulse reduction, taking into account the ratio of the efficiencies of measurement of the two ~ .
: 4 ~54883 pick-ups.
One advantage of the descri~ed methods is that the sources of error arisiny from the variations of the uncoated base material are eliminated therein, thus achieving an e~ceed-ingly high accuracy of measurement. In addition, the need to repeat the most cumbersome steps in the calibration procedure is minimized because the ratios of the efficiencies of measure-ment of the pick-ups and the isotope activities may be left to the computer to resolve, the former in fact point by point across the web. The accuracy requirements of the traversing beams may be quite appreciably reduced. The two or three con-stants most cumbersome to determine are mainly dependent on the chemical composition of the coating materials and therefore the need to be redetermined then is quite minimal.
It is known in the prior art, from Finnish Patent No.
53757 in ~he name of Pertti Puumalainen, published March 13, 1978, to measure the base weights of a CaCO3 layer applied as a pre-coating on cardboard or paper and of a caolin-containing surface coating by employing X-ray radiation which excites the characteristic secon~ary X-ray radiation of the Ca in the pre-coat. The intensit~ of this radiation is measured from above and below the cardboard by means of detectors. The absorption of the primary radiation coming from the source of radiation in the various coatings is measured. From the mutually independent results of measurement, the base weights of coatings can be cal-culated by solving three equations with three unknown variables.
It is also known in the art to measure the coating rate in one coating on paper by utilizing the characteristic secon-dary X-ray radiation excited by primary X-ray radiation in a marker substance added to the coating material.
The method described in the above-mentioned Finnish Patent No. 53757 suffers from the drawback that the work involved in tlle calibration of a coating rate meter capable of measuring in on-line conditions two different coating layers is cumber-some. In order to be operative, the method re~uires several difficult to determine constants to be measured before the e~ua~
tions forming the basis of the method can be solved and the dif-ferent base weights determined. The method is moreover sensi-tive to variations in the geometry of measurement, since no pri- ;
mary radiation must be allowed to strike the fluorescence detec-tor on the side opposite from the source.
The method above has the drawback that tlle coating rate of only one coating layer can be measured, and only when . ,. ~ ~ . ~ . .
~5~883 coating layer gives rise to a measura~le amount of secondary X-ray radiation.
An object of the present invention is to avoid the drawbacks mentioned above and to provide a method, having simple operating characteristics and particularly suitable for on-line measurements, for the measuring of the coating rate and amount of material applied as one or several coatinss on a base layer.
The invention is particularly suitable for use in connection with the manufacture of paper, cardboard or like material.
Accordingly, the present invention provides an improve-ment in a method of determining the quantities of material in a first coating layer applied to cardboard or equivalent base ma-terial as well as in a second coating layer applied to said first coating layer, said method comprising the steps of subjecting said first coating layer to a primary X-ray radiation derived from an outside source and travelled via said second coating la-yer, so as to excite a characteristic fluorescence radiation in said first coating layer, and measuring the intensity of said fluorescence radiation by means of a detector placed above said second coating layer, whereby the determination is based on the absorption of the primary X-ray radiation and the fluorescence radiation while travelling through said second coating layer, the improvement comprising that, in addition to exciting the fluorescence radiation of the first coating layer, the primary X-ray radiation is used to excite a characteristic fluorescence radiation in the second coating layer, which is measured by means of a detector and used as the basis for determination of the quantity of material in the second coating layer, while the mea-surement of the fluorescence radiation of the first coating layer is performed for the determination of the quantity of material in the first coating layer, with the aid of the quantity of ma-terial in the second coating layer as determined.
1~54883 The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:-Fig. l shows diagrammatically an arrangement for put-ting into practice the method according to the invention, with a supporting web and coatings therein being shown in section;
Fig. 2 is a view similar to Fig. 1 showing an alter-native arrangement; and Fig. 3 is a view similar to Fig. l showing a further arrangement.
In Fig. l the cardboard web constitutes a base mater-ial l and has formed therèon a precoating layer 2, which may, for instance~ consist of CaCO3, and on the precoating layer 2 a surface coating 3, for instance, of caolin. When subsequent to precoating the combination 1,2 is irradiated ~ith a radiation source 4, which may for instance be a 55-Fe radio isotope -~
source, the Ca atoms in the precoating 2 emit their own charac-teristic secondary X-ray radiation, or fluorescence radiation, the intensity of which is proportional to the amount of material present, or of Ca in this case. When the intensity of Ca fluore-scence radiation arriving at the detector is known as a function of the amount of CaC03 present, the amount of CaCO3 is - 2a -~5~83 calculable from the intensity of the pulses delivered by the detector 5.
The web 1 moves forward to another coating unit, where - the surface coating 3 is applied to the web 1. Hereafter, the combination is irradiated once again with radiation ~rom the radiation source 6. This causes the Ca atoms to emit fluore-scence radiation which passes through the surface coating layer 3 and is measured by the aetector 7 located above the surface coating layer 3. Part of the primary and fluorescence radia-tions is abs~rbed, according to a certain experimentally deter-minable function, in the surface coating, and the number of pulses delivered by the detector 7 decreases. In evaluating the decrease in the number of pulses, one takes into account the ratio of efficiencies of measurement of the two pick-ups, which can be determined by running a web having only a base coating through the apparatus. From the pulse reduction found, the surface coating rate can be calculated.
If the base material contains, in significant amounts, fillers which are able to emit a significant amount of measur-able secondary X-ray ~adiation, or if the base material 1 is coated on the other side as well with a coatiny capable of emit- -ting measurable secondary radiation, these effects may be ac-counted for by irradiating the web with a radiation source 8 prior to the coating step and measuring the secondarv X-ray radiation by means of the detector 9. I~hen this is done, vari-ations of the base material 1 cause no possible sources of er-ror in the measurment of coating rates. The efficiency of measurement of the pick-up monitoring the raw cardboard must, however, be taken into account.
In the arrangement shown in Fig. 2, a CaCO3 coating is applied to the base material 1 and thereupon a coating 3 which contains Tio2 is applied. It is possible, by irradiating with :~lS~883 the source 5 the combination of courses 2 and 3, to measure the coating rates as follows: The quantitY of coatina layer 3 is a -function of the ~uantity of TiO2 contained in the coatin~ layer 3. If the amount of X-ray radiation with energy 4.5 keV emitted by TiO2 is measured, this enables the quantity of the surface coating 3 to be calculated. The primary radiation from the source 5 also excites the Ca in the base coating 2, which emits secondary radiation with energy 3.7 keV. Knowing the absorptions of the primary and secondary radiations in the surface coating 3, of which the quantity is already known, one can calculate which is the quantity of CaCO3 able to give rise from under this surface coating 3 to the measured secondary radiation. If required, the effect of the raw cardboard may be eliminated by the same procedure as was applied in the case of Fig. 1.
In Fig. 3, the base material 1 contains a substance capable of emitting secondary radiation, either as filler, as background coating, or as a material with which the base ma-terial has been impregnated. When the base material is irradia- ~
ted by the source 3 and the secondary radiation is measured with ;
the detector 4, information is gained concerning the secondar~
radiation emitted by the base material.
As the web moves forward to the coating unit, in which the surface coating 2 is applied on the web, the combination is irradiated from the source 5. This causes the atoms in the web to emit fluorescence radiation under the influence of the primary radiation that has penetrated through the surface coat-ing 2. The number of pulses received by the detector 6 then de-creases as part of the primary and fluorescence radiations is absorbed in the surface coating in accordance with a given ex-perimentally determinable function. Qne then calculates thecoating rate on the basis of the pulse reduction, taking into account the ratio of the efficiencies of measurement of the two ~ .
: 4 ~54883 pick-ups.
One advantage of the descri~ed methods is that the sources of error arisiny from the variations of the uncoated base material are eliminated therein, thus achieving an e~ceed-ingly high accuracy of measurement. In addition, the need to repeat the most cumbersome steps in the calibration procedure is minimized because the ratios of the efficiencies of measure-ment of the pick-ups and the isotope activities may be left to the computer to resolve, the former in fact point by point across the web. The accuracy requirements of the traversing beams may be quite appreciably reduced. The two or three con-stants most cumbersome to determine are mainly dependent on the chemical composition of the coating materials and therefore the need to be redetermined then is quite minimal.
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An improvement in a method of determining the quantities of material in a first coating layer applied to card-board or equivalent base material as well as in a second coating layer applied to said first coating layer, said method compris-ing the steps of subjecting said first coating layer to a pri-mary X-ray radiation derived from an outside source and travel-led via said second coating layer, so as to excite a character-istic fluorescence radiation in said first coating layer, and measuring the intensity of said fluorescence radiation by means of a detector placed above said second coating layer, whereby the determination is based on the absorption of the primary X-ray radiation and the fluorescence radiation while travelling through said second coating layer, the improvement comprising that, in addition to exciting the fluorescence radiation of the first coating layer, the primary X-ray radiation is used to ex-cite a characteristic fluorescence radiation in the second coat-ing layer, which is measured by means of a detector and used as the basis for determination of the quantity of material in the second coating layer, while the measurement of the fluorescence radiation of the first coating layer is performed for the deter-mination of the quantity of material in the first coating layer, with the aid of the quantity of material in the second coating layer as determined.
2. A method according to claim 1, wherein fluore-scence radiation is excited in the first and second coating la-yers simultaneously by using a primary X-ray radiation derived from a single radiation source.
3. A method according to claim 2, wherein the base material is composed of a web of cardboard or paper, which is transported along a line having locations for applying the coat-ing layers and a pair of radiation source and detector for per-forming the measurements, said pair being placed above said line of transport.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000419046A CA1154883A (en) | 1978-11-21 | 1983-01-06 | Procedure for measuring coating rates |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI783544 | 1978-11-21 | ||
| FI783544A FI59489C (en) | 1978-11-21 | 1978-11-21 | FOERFARANDE FOER MAETNING AV BELAEGGNINGSMAENGDER |
| CA000340244A CA1147870A (en) | 1978-11-21 | 1979-11-20 | Procedure for measuring coating rates |
| CA000419046A CA1154883A (en) | 1978-11-21 | 1983-01-06 | Procedure for measuring coating rates |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1154883A true CA1154883A (en) | 1983-10-04 |
Family
ID=27166496
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000419046A Expired CA1154883A (en) | 1978-11-21 | 1983-01-06 | Procedure for measuring coating rates |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1154883A (en) |
-
1983
- 1983-01-06 CA CA000419046A patent/CA1154883A/en not_active Expired
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |