Method using x-ray fluorescence analysis for determining an amount of at least one printing primer applied to at least one paper ply as carrier material

Abstract

The present invention relates to a method using x-ray fluorescence analysis for determining an amount of at least one printing primer applied to at least one paper ply as carrier material, comprising the following steps: providing a plurality of reference samples by applying at least one printing primer in in each case different quantitatively defined amounts to the at least one carrier material; recording at least one x-ray fluorescence spectrum of each of the reference samples using at least one x-ray fluorescence measuring head in a for the respective divalent cation to be detected contained in the printing primer, assigning the different quantitatively defined amounts of printing primer of the reference samples to the recorded x-ray fluorescence spectra of the aforementioned reference samples; and creating a calibration model for the relationship between the recorded x-ray fluorescence spectra of the reference samples and the associated quantitatively defined amounts of printing primer; providing at least one sample to be measured by applying at least one layer of at least one printing primer to the at least one carrier material, recording at least one x-ray fluorescence spectrum of the sample to be measured using the at least one x-ray fluorescence measuring head, and determining the quantitative amount of printing primer applied to the carrier material in the sample to be measured by comparing the x-ray fluorescence spectrum of the sample to be measured with the calibration model created from the reference samples.

Description

[0001] Method for determining an amount of at least one printing primer applied to at least one paper layer as a carrier material using X-ray fluorescence analysis

[0002] The present invention relates to a method for determining the amount of at least one primer applied to at least one support material using X-ray fluorescence analysis.

[0003] Description

[0004] Support materials with a decoration, such as wood-based panels or paper layers, are mainly printed using gravure or digital printing processes.

[0005] The gravure printing process is a printing technique in which the elements to be reproduced are indentations in a printing form, which is inked prior to printing. The printing ink is primarily located in the indentations and is transferred to the object to be printed, such as a substrate, due to the pressure of the printing form and adhesive forces.

[0006] With digital printing, however, the print image is transferred directly from a computer to a printing machine such as a laser or inkjet printer. This eliminates the need for a static printing plate.

[0007] As printing technology for a wide variety of substrates continues to evolve, digital printing is becoming increasingly popular. While digital printing processes were initially used primarily in the graphics industry, such as by advertising agencies, promotional material manufacturers, and printing companies, digital printing processes are now also becoming more common in other industries. There are many reasons for this, but two key arguments can be identified. Digital printing enables the production of a particularly high-quality print image thanks to higher resolution and also allows for a wider range of applications with a high level of flexibility. This is illustrated by the fact that there are no longer any limitations on the length of the print image.The key to all printing processes on a medium (in this case, paper, but also wood-based panels) is to ensure a consistent and repeatable print image for the customer. Both the colors and shapes must match the original sample every time. Deviations are undesirable and will not be accepted.

[0008] To print paper with digital printing ink, it is necessary to first apply an intermediate layer. A primer or pre-coat is used as an intermediate layer to minimize color deviations between the printed designs of a production batch, or even between identical printed designs from different production batches, due to pigment absorption.

[0009] The primer serves two functions: first, it forms a kind of barrier layer between the ink and the paper. Second, this primer contains a reactive component that reacts with the ink, ensuring that an ink droplet of a certain size doesn't change its size on the paper. The primer reacts with the ink in such a way that a droplet immediately stops and doesn't spread.

[0010] Furthermore, the use of a primer reduces the amount of ink needed for a print. Without a primer, the ink would sink deep into the paper, and a larger amount of ink would be required to achieve the desired print result. Since the primer is significantly cheaper than printing ink, its use results in significant cost savings.

[0011] The paper to be printed is coated with a primer in the digital printing system. This primer is applied to a rubber roller using a roller (anilox roller; a curtain or spraying of the primer is also possible) with a defined volume of the primer applied, and then to the paper. The primer is then dried before the digital printing ink is applied, and the paper is dried again.

[0012] This can result in various disadvantages.

[0013] The application of primer or printing undercoat can be uneven due to various factors. This can occur, for example, with (mechanical) damage to the anilox roller, (mechanical) damage to the rubber roller used to transfer the primer, crooked installation of one of the rollers, wear on the rollers, wear and tear resulting in a change in the cell depth and thus the draw volume, or inadequate cleaning of the rollers resulting in a change in the cell depth and thus the draw volume. Wrinkling of the paper can also be responsible for varying application rates.

[0014] High costs arise from non-recyclable waste, from repeating a production (material, personnel), from complaints, from excessive use of materials (ink, primer).

[0015] Production times increase due to repeating a production and / or due to complex roller changes because simple cleaning is no longer sufficient.

[0016] Furthermore, resources are wasted in the use of materials and personnel, through duplicate production and waste and / or through excessive amounts of ink and primer.

[0017] The invention is therefore based on the technical problem of establishing a measuring method with which the primer application can be monitored both over time, i.e., in linear meters, and across the web width. By monitoring the primer application, it can be ensured that there are no deviations in the printed image.

[0018] This object is achieved according to the invention by a method having the features of claim 1.

[0019] Accordingly, a method is provided for determining an amount of at least one printing primer applied to at least one paper layer using X-ray fluorescence analysis, the method comprising the following steps:

[0020] - Providing several reference samples by applying at least one printing primer containing at least one divalent cation in different quantitatively defined amounts to the at least one carrier material;

[0021] - Recording at least one X-ray fluorescence spectrum of each of the reference samples using at least one X-ray fluorescence measuring head in a manner suitable for the divalent cation contained in the printing primer, - Assigning the different quantitatively defined amounts of printing primer of the reference samples to the recorded X-ray fluorescence spectra of said reference samples; and

[0022] - Creation of a calibration model for the relationship between the recorded X-ray fluorescence spectra of the reference samples and the corresponding quantitatively defined amounts of printing primer;

[0023] - Providing at least one sample to be measured by applying at least one layer of at least one printing primer to the at least one carrier material,

[0024] - Recording at least one X-ray fluorescence spectrum of the sample to be measured using at least one X-ray fluorescence measuring head,

[0025] - Determining the quantitative amount of printing primer applied to the substrate in the sample to be measured by comparing the X-ray fluorescence spectrum of the sample to be measured with the calibration model created from the reference samples.

[0026] With the X-ray fluorescence analysis used in this method, it is possible to reliably determine even small application quantities of the printing primer.

[0027] X-ray fluorescence analysis (XRF) or X-ray fluorescence spectroscopy (XRF) is a method used in materials analysis and is one of the most widely used methods for the qualitative and quantitative determination of a sample's elemental composition, as the sample is not destroyed by the measurement and no digestion is required. X-ray fluorescence analysis (XRF) is particularly widely used in the metalworking industry, in the analysis of glass, ceramics, and building materials, as well as in the analysis of lubricants and petroleum products.

[0028] The great advantage of X-ray fluorescence compared to other measuring methods is that even the smallest application quantities (< 1 g / m 2) can still be reliably determined. This is the case when the printing primer is applied. By irradiating or irradiating the material sample with X-rays, the electrons of the element to be determined are first knocked out of the inner orbits of the electron shell. Electrons then fall back from the outer shells into these gaps, emitting characteristic X-rays. This X-ray is specific to each element and allows the element quantity to be determined. The element-specific X-rays are detected by a suitable radiation detector.

[0029] The element-specific X-rays emitted are displayed as pulses or counts. The intensity or height of the emitted counts is proportional to the amount of primer applied. The counts detected by the detector correspond to the number of photons released after irradiating the sample with high-energy radiation.

[0030] This method enables continuous, non-contact online determination of the applied primer quantity. This allows the applied primer quantity to be measured during ongoing production, both across the web width and length. This is the only way to detect deviations that could lead to printing problems at an early stage.

[0031] Before the measurement technology can be used in the system, a calibration is first performed using reference samples. First, an uncoated substrate (such as untreated raw paper) is measured as the zero point. Second, a calibration series is created with different application rates of primer applied to the substrate. Different known amounts of primer are applied to the substrate and analyzed by XRF. Based on the data obtained, a best-fit line is created, which can be used to determine the primer quantity in the samples to be measured.

[0032] In one embodiment, for the purpose of calibration, a primer with different amounts of divalent cation, such as Ca 2+applied, the total spectrum is recorded, and the emitted radiation is analyzed in the range specific to the divalent cation. The amount of the applied reference sample is between 0.5 and 10 g / m 2 , preferably between 1.0 and 8.0 g / m 2 , particularly preferably between 2.0 and 6.0 g / m 2 Print primer, e.g. 1.1 g / m 2 ; 2.2 g / m 2 ; 3.3 g / m 2 The following correlation can be seen: 24,000-26,000 counts for the blank sample; 120,000-130,000 counts for a quantity of 1.1 g / m 2 , 220,000 - 230,000 counts for a quantity of 2.2 g / m 2 , 310,000 - 320,000 counts for a quantity of 3.3 g / m 2 .

[0033] It is also possible to study the emitted radiation for other elements.

[0034] For the samples to be measured in a production facility, an X-ray fluorescence measuring head is installed behind the primer application unit and, if necessary, behind a downstream dryer. The measured or detected X-rays can provide information about the primer concentration in the sample being measured. Ideally, the measured value should be constant. If deviations occur, this means that the current primer application quantities do not correspond to the target, which could lead to deviations in the printed image.

[0035] The measuring head can traverse across the web during the measurement or, alternatively, several measuring heads can be installed next to each other across the web width, so that the primer application can be monitored across the web width.

[0036] What all versions have in common is that the spectra are recorded continuously to monitor the primer application over time. This allows deviations to be detected and corrected early on.

[0037] This process ensures that the current actual print image corresponds to the stored master sample, i.e., the target print image. It ensures that the customer's requirements are met.

[0038] This results in cost savings through timely detection and replacement of roller wear, the avoidance of defective production, and optimal use of primer and ink. Time savings are achieved through the avoidance of defective production and the avoidance of major downtimes due to defects in the form rollers. The optimal use of primer and ink and the avoidance of defective or duplicate production also conserve resources.

[0039] As already mentioned, the printing primer used here (as a basis for digital printing) contains at least one divalent cation, in particular Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , preferably Ca 2+ X-ray fluorescence analysis is particularly effective for elements with higher atomic numbers, such as Ca 2+ , Sr 2+ or Ba 2+ The divalent cation thus serves as an indicator for the amount of primer applied.

[0040] The divalent cations are present in the printing primer in the form of salts, particularly chlorides, sulfates, and formates. Suitable salts are calcium diformate, calcium chloride, barium sulfate, and calcium sulfate, with calcium chloride and calcium diformate being preferred.

[0041] The use of calcium carbonate, however, is not desirable because calcium carbonate has poor solubility in water.

[0042] The salts are preferably used in water-based dispersions that are fully miscible or partially soluble in water. Depending on the paper and printing requirements, these dispersions are diluted before application to the paper layer.

[0043] The dispersions used as printing primers contain, in addition to the divalent salt, small amounts of organic solvents such as methanol or ethane-1,2-diol (glycol). The primer dispersion should have a low solvent content of less than 10 wt%, preferably less than 5 wt%, particularly preferably less than 3 wt%, even more preferably less than 2 wt% or less than 1 wt%. Typical solvents are ethane-1,2-diol (glycol) or methanol.

[0044] The concentration of divalent cation salts in the primer dispersion can be between 5 and 25 wt% (before dilution), preferably between 10 and 20 wt%. For example, primer mixtures containing 5-10 wt% calcium diformate and 5-10 wt% methanol, or 10-20 wt% calcium chloride and 0.1-1 wt% methanol, are used. The remainder is water.

[0045] Before dilution, the solids content of the dispersion is between 5 and 25 wt%, preferably 10-20 wt%, particularly preferably 13-18 wt%, and most preferably 14-16 wt%. The viscosity of the undiluted dispersion is 400-600 mPas, preferably 450-550 mPas (at a shear rate of 1000 s-1 at 25°C).

[0046] As mentioned, the printing primer dispersions or primer dispersions are applied to the paper layer in diluted form. Water is preferably used as the diluent. The viscosity of the printing primer applied to the paper layer is adjusted by dilution to values ​​between 30 and 100 mPas, preferably between 40 and 80 mPas, and particularly preferably between 50 and 70 mPas (measured in a 4 mm flow cup for 22-25 s at 23-26°C).

[0047] The solids content of the diluted dispersion is 1-15 wt%, preferably 5-12 wt%, particularly preferably 8-10 wt%, most particularly preferably 10 wt%.

[0048] The amount of (diluted) printing primer applied to at least one substrate is preferably between 0.5 g / m 2 and 10 gm 2 , preferably between 1 g / m 2 and 8 g / m 2 , especially between 2 g / m 2 and 6 g / m 2, most preferably between 4 and 6 g / m 2 .

[0049] Other components of the printing primer mixture can be polymeric binders, such as those from the group consisting of hydroxyethyl cellulose; hydroxypropyl cellulose; hydroxyethyl methyl cellulose; hydroxypropyl methyl cellulose; hydroxybutyl methyl cellulose; methyl cellulose; sodium carboxymethyl cellulose; sodium carboxymethyl hydroxyethyl cellulose; water-soluble ethyl hydroxyethyl cellulose; cellulose sulfate; polyvinyl alcohol; vinyl alcohol copolymers; polyvinyl acetate; polyvinyl acetal; polyvinylpyrrolidone; polyacrylamide; acrylamide / acrylic acid copolymer; polystyrene, styrene copolymers; acrylic or methacrylic polymers; styrene / acrylic copolymers; ethylene-vinyl acetate copolymer; vinylmethyl methyl vinyl acetate copolymer; vinyl methyl ether / maleic acid copolymer; poly(2-acrylamido-2-methylpropanesulfonic acid); poly(diethylenetriamine-coadipic acid); polyvinylpyridine; polyvinylimidazole; epichlorohydrin-modified polyethyleneimine; ethoxylated polyethyleneimine;Ether-containing polymers such as polyethylene oxide (PEO), polypropylene oxide (PPG), polyethylene glycol (PEG), and polyvinyl ether (PVE); polyurethane; melamine resins; gelatin; carrageenan; dextran. A preferred polymer for the is a polyvinyl alcohol (PVA), a vinyl alcohol copolymer, or modified polyvinyl alcohol. The modified polyvinyl alcohol can be a cationic polyvinyl alcohol.

[0050] In a preferred embodiment, however, the print primer mixture used here does not contain any polymeric components that would, for example, increase viscosity. In particular, the following are not included: dextrins, starch, cellulose derivatives, polyurethanes, polyamides, polycarbodiimide. The primer mixture may contain further additives, such as dyes (e.g., TiO2 as a white pigment), surfactants, biocides, antistatic agents, elastomers, UV absorbers, plasticizers, light stabilizers, pH adjusters, antistatic agents, bleaching agents, matting agents, and the like. 2-methyl-2H-isothiazol-3-one and / or 5-chloro-2-methyl-2H-isothiazol-3-one may be added as further components of primer mixtures, although these are preferably present only in small amounts of less than 0.005% by weight.

[0051] As explained above, an X-ray fluorescence spectrum is recorded for each sample to be measured. Preferably, a complete spectrum is recorded so that, in addition to the selected divalent cation, other elements of the primer composition can be determined. For example, it may be desirable to determine higher-valent salts or oxides such as TiO2 in addition to the divalent cation salt.

[0052] For this purpose, the sample to be measured is first excited (e.g., by electron impact), and the X-rays emitted by the excited element are determined. In the present method, the emitted X-rays can have an energy in a range between 2000 and 6000 eV, preferably in a range between 3000 and 550 eV, and even more preferably in a range between 3000 and 5000 eV.

[0053] In case of determining the amount of Ca 2+As an indicator for the amount of primer applied, an energy range between 3600 and 3800 eV, preferably 3620 and 3770 eV, is analyzed. In a preferred embodiment, the energy range for Ca 2+ with an initial energy of 3627 eV and a final energy of 3763 eV. In the case of TiO2, for example, an energy range between 4200 and 4700 eV would be analyzed.

[0054] In one embodiment of the present process, the at least one primer is applied to the at least one carrier material as a (diluted) liquid suspension or solution with a solids content of 1-15 wt%, preferably 5-12 wt%, particularly preferably 8-10 wt%, and most preferably 10 wt%. The primer can be applied using an anilox roller or by spraying.

[0055] In a further embodiment of the present method, the primer coating is dried, and then the X-ray fluorescence spectrum is recorded using at least one X-ray fluorescence measuring head. A paper layer is used as the carrier material, in particular a paper layer made of at least one base paper or at least one pretreated impregnated paper.

[0056] If a paper layer is used, the paper used should have a smooth surface so that the printing primer applied to the paper layer is not penetrated or absorbed into the paper.

[0057] Thus, in one embodiment, the at least one carrier material to be printed is at least one base paper. Base paper is understood to mean paper that has been neither subjected to sizing in the mass nor to surface impregnation with a resin or glue. Base paper essentially consists of pulp, pigments, fillers, and conventional additives. Softwood pulp, hardwood pulp, or mixtures of both pulp types can be used to produce base papers such as decorative papers. Inorganic color pigments such as metal oxides, metal hydroxides and metal oxide hydrates, metal sulfides, metal sulfates, metal chromates, and metal molybdates, as well as organic color pigments and / or dyes such as carbonyl colorants, cyanine colorants, and others, can be used to color the base paper.

[0058] In a preferred embodiment, the base paper to be printed is at least one paper web without impregnation.

[0059] In a further embodiment, the at least one substrate to be printed is at least one pretreated, impregnated paper. Pretreated paper (or cellulose layer) is understood to mean a paper or paper web impregnated with a resin solution. The paper can be impregnated with a wide variety of resin solutions, for example, melamine resins and urea resins, plastic-acrylate compounds, or starch sizing. Mixtures of the resins can also be present. It is also possible to impregnate the paper using resin powder. The use of resin powder is described in detail below.

[0060] In a preferred embodiment, an impregnated paper is used which is provided with the following process steps (see also EP 2 980 313 A1): a) complete impregnation of the cellulose layer with a curable resin, e.g. melamine-formaldehyde resin), b) removal of the excess resin forming on the surface (e.g. by peeling or doctoring), c) drying the impregnated cellulose layer in such a way that after the water has evaporated from the resin, the cellulose fibers on the surface from which the resin was removed are at least partially exposed.

[0061] By peeling or doctoring, the resin remaining on the surface of the cellulose layer becomes flush with the fiber tips. During the drying process, the resin retracts into the fibers, so that the fibers are saturated with the resin but not enclosed by it. Such a surface is suitable for printing with aqueous digital printing inks.

[0062] The special device used for squeegeeing or doctoring works similarly to a spatula, with one or more rollers running backward on the paper and collecting the excess resin. By varying the roller speeds, the amount can be precisely controlled and repeatability can be ensured.

[0063] The paper weights can range between 30 and 250 g / m 2 For example, the paper weight of decorative papers can vary between 30 and 150 g / m 2 , preferably between 50 and 120 g / m 2 , particularly preferably between 80 and 100 g / m 2 In the case of raw paper or kraft paper, the paper weight can be between 50 and 250 g / m 2 , preferably between 100 and 200 g / m 2 , especially between 120 and 150 g / m 2 be.

[0064] As mentioned, it is also possible to use a wood-based panel as the substrate to be coated with a primer. In this case, the wood-based panel can be a particleboard, medium-density fiberboard (MDF), high-density fiberboard (HDF), oriented strand board (OSB), or plywood, a wood-plastic blend, or a composite material, or a WPC (wood-plastic composite) board.

[0065] The present method is carried out continuously and online in a production line comprising at least one X-ray fluorescence measuring head and at least one control system. Two or three X-ray fluorescence measuring heads can also be provided at different locations in the production line. Such a production line can be a production line for processing or finishing paper layers. In one embodiment, the production line comprises: at least one application unit for applying the printing primer to the at least one carrier material, preferably a paper layer,

[0066] Optionally, at least one X-ray fluorescence measuring head provided after the coating unit; at least one dryer arranged after the coating unit; at least one X-ray fluorescence measuring head provided after the dryer; at least one printing device for printing the primed carrier material,

[0067] - further application units, each with corresponding dryers for applying and drying at least one, preferably several, resin layers onto the printed carrier material.

[0068] In one embodiment, the production line comprises: at least one application unit with anilox roller for applying the printing primer to the at least one carrier material, preferably a paper layer,

[0069] Optionally, at least one X-ray fluorescence measuring head provided after the coating unit; at least one dryer arranged after the coating unit; at least one X-ray fluorescence measuring head provided after the dryer; at least one digital printer for printing the primed carrier material,

[0070] - further application units, each with corresponding dryers for applying and drying at least one, preferably several, resin layers on the printed carrier material.

[0071] The production line is preferably driven or operated at a system speed between 100 and 200 m / min, preferably between 120 and 180 m / min, particularly preferably between 130 and 150 m / min, e.g. 135 m / min.

[0072] In one embodiment, it is provided to use more than one X-ray fluorescence measuring head, preferably two or three X-ray fluorescence measuring heads.

[0073] During the measurement, the X-ray fluorescence measuring head moves over the sample to be measured, in particular the paper layer provided with the primer, at 1.0 to 5.0 m / min, preferably 1.5 - 3.5 m / min, particularly preferably 1.5 - 2.5 m / min, such as 2.0 m / min. As already mentioned, after the printing primer has been applied, the carrier material is provided with a decoration in digital printing. In digital printing, the print image is transferred directly from a computer to a printing machine, such as a laser printer or inkjet printer. This eliminates the need for a static printing form. Decoration printing is carried out according to the inkjet principle in a single-pass, in which the entire width of the top side to be printed is spanned, with the primed carrier material being moved under the printer. However, it is also possible for the carrier material to be printed to be held under the printer, which then passes over the surface at least once during printing.

[0074] The printing inks are grouped into separate rows of print heads in the digital printer, with one or two rows of print heads per color. Digital printing inks are available in colors such as black, blue, red, reddish yellow, and greenish yellow. CMYK is also optionally available. Digital printing inks are optionally based on the same pigments used for analog and / or digital printing with water-based inks. Digital printing inks are preferably based on UV inks. However, water-based digital printing inks or so-called hybrid inks can also be used. After printing, the decorative print is dried and / or irradiated.

[0075] The printing inks are used in quantities between 0.5 and 30 g / m 2 , preferably between 3 and 20 g / m 2 , particularly preferably between 3 and 15 g / m 2 applied, e.g. between 0.5g / m 2 and 13g / m 2 .

[0076] At least one, preferably several, resin layers are then applied to the printed decoration as protective or wear layers. The type and number of these layers are known to those skilled in the art.

[0077] The production line's control system comprises at least one computer-based evaluation unit (or processor unit) and a database. The evaluation unit compares the X-ray fluorescence spectrum measured for the primer-coated substrate with the created calibration model. The resulting data is stored in the database.

[0078] The data determined using this spectroscopic method can be used to control the production line. As previously described, the non-contact measured parameter values ​​of the X-ray fluorescence measuring head can be used directly and in real time to control or regulate the relevant system. For example, by storing the measured actual values ​​in a database, e.g., a relational database, and comparing them with the target values ​​of these parameters available there. The resulting differences are then used to control or regulate the production line.

[0079] In one embodiment, the application unit for the printing primer and the subsequent dryer are controlled. If the values ​​determined by the recorded X-ray fluorescence measuring head and the evaluation unit reveal a defect in the application, process steps can be specifically influenced or deficiencies corrected.

[0080] This allows the contact pressure of the application roller of the applicator unit to be precisely controlled to compensate for irregularities in the surface of the substrate. Defective application can also result from damage to the application roller; the application roller can be replaced and / or repaired accordingly. Another cause of defective application can be an empty primer container or a defective dryer. With this method, these defects can be easily and quickly remedied.

[0081] For the calibration and control of the production line, a computer-implemented method and a computer program comprising instructions that, when executed by a computer, cause the computer to execute the computer-implemented method are provided. The computer program is stored in a memory unit of the production line's control system.

[0082] The invention will be explained in more detail below with reference to an exemplary embodiment of the invention and the accompanying drawings. It shows:

[0083] Figure 1 shows an X-ray fluorescence spectrum of a substrate coated with a printing primer and a substrate without a printing primer coating. Calibration

[0084] The diagram in Figure 1 shows a typical X-ray fluorescence spectrum of a primer layer applied to a base paper layer. The primer used as a printing undercoat contains Ca 2+in the form of calcium formate.

[0085] The samples were irradiated with rays in an energy range from 2 keV to 5.6 eV and the emitted X-rays were determined as pulses or counts.

[0086] An X-ray fluorescence detector from Spektro was used to record the X-ray fluorescence spectra. The detector is a silicon drift or silicon PIN detector. The detector is selected according to the application. During the measurement, it is important to maintain a short distance between the detector and the sample to be measured. This distance should preferably be only a few millimeters.

[0087] For calibration, different primer amounts (0 g / m 2 ; 1.1 g / m 2 ; 2.2 g / m 2 ; 3.3 g / m 2) and measured. Three measurements were taken for each primer quantity, each at three different measuring points on the primed base paper layer: A-side (AS), B-side (BS), and center (center). For control purposes, the reverse side (re) was also measured.

[0088] The different measurements are shown as peaks in the X-ray fluorescence spectrum of Figure 1. The Ca 2+ The typical signal for cations lies in a range between 3.6 and 3.8 keV. It is clearly visible that primer-coated paper exhibits significantly higher pulses than uncoated paper. The peaks for the paper with a weight of 3.3 g / m 2 Primer coated sample shows maximum values ​​of 4000 counts (on the x-axis), while the blank samples are at 700 counts.

[0089] The integrals of the peaks are expressed as counts. Table 1 lists the individual values ​​and mean counts from the three respective measurements for each primer amount.

[0090] Table 1: Correlation of primer quantity and counts of detected X-ray fluorescence rays. A best-fit line is created from the mean values, which can be used to determine the primer quantity of the samples to be measured.

[0091] Example 1 :

[0092] In a digital paper printing system, untreated base paper is first coated with a primer to create a bond between the paper and the ink. The primer is applied to the paper using an anilox roller and then immediately dried. Behind the dryer is a traversing X-ray fluorescence measuring head that determines the amount of primer. The measuring head moves across the entire web width of max. 2080 mm (equivalent to the width of a paper web) at approximately 2 m / min. After maintenance on the primer application unit, the system is run for a test run. After one minute, a warning tone sounds and a signal light flashes. The system operators stop the system manually. The measured values ​​show that the primer application on the left side is significantly below the target. The primer application unit is then checked again. It turns out that there were differences in the contact pressure between the pages.Once the problem was resolved, the system continued to run without any problems. In a digital paper printing system, the base paper is first coated with a primer to create a bond between the paper and the ink. The primer is applied to the paper using an anilox roller and then immediately dried. Behind the dryer, there are three X-ray fluorescence measuring heads evenly distributed across the web width to determine the amount of primer. During the production of a decorative job, the system stopped and a signal (audible and visual) appeared. The reason for this was an incorrect application of the primer on the right side. The X-ray fluorescence measuring head determined that the primer application was 30% lower at this point than on the left and middle. An inspection of the application unit revealed damage to the right side of the primer roller.The squeegee damaged the cells and thus the application quantity was reduced.

[0093] Example 3:

[0094] In a digital paper printing system, the base paper is first primed to create a bond between the paper and the ink. The primer is applied to the paper using an anilox roller and then immediately dried. A permanently installed X-ray fluorescence measuring head is located behind the dryer. During a large print run of more than 15 tons, a signal (audible / visual) is emitted from the system. The system stops automatically. The X-ray fluorescence measuring head detects a primer application of 0 g / m². 2 The plant operators then notice that the primer IBC is empty and no new container has been connected.

Claims

Claims 1. A method for determining an amount of at least one printing primer applied to at least one paper layer as a carrier material using X-ray fluorescence analysis, comprising the steps: - Providing several reference samples by applying at least one printing primer containing at least one divalent cation in different quantitatively defined amounts to the at least one carrier material; - Recording at least one X-ray fluorescence spectrum of each of the reference samples using at least one X-ray fluorescence measuring head in a manner suitable for detecting the divalent cation contained in the printing primer, - Assigning the different quantitatively defined amounts of printing primer of the reference samples to the recorded X-ray fluorescence spectra of the said reference samples; - Creation of a calibration model for the relationship between the recorded X-ray fluorescence spectra of the reference samples and the corresponding quantitatively defined amounts of printing primer; - Providing at least one sample to be measured by applying at least one layer of at least one printing primer to the at least one carrier material, - Recording at least one X-ray fluorescence spectrum of the sample to be measured using at least one X-ray fluorescence measuring head, and - Determining the quantitative amount of printing primer applied to the substrate in the sample to be measured by comparing the X-ray fluorescence spectrum of the sample to be measured with the calibration model created from the reference samples.

2. Method according to claim 1, characterized in that the at least one printing primer contains at least one salt with a divalent cation, in particular Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , preferably Ca 2+ includes.

3. Method according to one of the preceding claims, characterized in that the at least one printing primer is applied to the at least one carrier material as a liquid suspension or solution with a solids content of 1-15% by weight, preferably 5-12% by weight, particularly preferably 8-10% by weight, most particularly preferably 10% by weight.

4. Method according to one of the preceding claims, characterized in that the printing primer is dried and then the X-ray fluorescence spectrum is recorded using the X-ray fluorescence measuring head.

5. Method according to one of the preceding claims, characterized in that the amount of printing primer applied to the at least one carrier material is more than 0.5 g / m 2 , preferably more than 1 g / m 2 amounts.

6. Method according to one of the preceding claims, characterized in that the at least one carrier material comprises at least one raw paper or at least one pretreated, impregnated paper.

7. Method according to one of the preceding claims, characterized in that the determination of the amount of primer applied is carried out continuously and online.

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