Method for determining amount of at least one printing bottom applied to at least one paper layer as carrier material by means of x-ray fluorescence analysis

Abstract

The invention relates to a method for determining the amount of at least one printing bottom applied to at least one paper layer as a carrier material by means of X-ray fluorescence analysis, the method comprises the steps of: providing a plurality of reference samples by applying at least one printing bottoming material to at least one carrier material in respectively differently quantificationally defined amounts; recording at least one X-ray fluorescence spectrum of each of the reference samples with at least one X-ray fluorescence measurement head for the divalent cations to be detected respectively contained in the printing bottoming part; associating differently quantificationally defined amounts of the printed bottoming of the reference sample with the recorded X-ray fluorescence spectrum of the mentioned reference sample; and creating a calibration model for a relationship between the recorded X-ray fluorescence spectrum of the reference sample and the affiliated quantificationally defined amount of the printed bottoming; providing at least one sample to be measured by applying at least one layer consisting of at least one printing bottoming part to 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 a quantitative amount of the printed bottoming 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 a calibration model created from the reference sample.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for determining the quantity of at least one primer applied to at least one carrier material using X-ray fluorescence analysis. BACKGROUND

[0002] The carrier material provided with the decor, for example a wood-based panel or a paper layer, is printed mainly in a gravure printing method or a digital printing method.

[0003] The gravure printing method is a printing technique in which the elements to be depicted are present as recesses in a printing form which is dyed before printing. The printing color is first in the recesses and is transferred to the object to be printed, for example the carrier material, due to the contact pressure of the printing form and due to the adhesive force.

[0004] In contrast, in digital printing the printed image is transferred directly from the computer to the printer, for example a laser printer or an inkjet printer. The use of a static printing form is dispensed with here.

[0005] In the further development of the printing technology for different carrier materials, digital printing is increasingly being carried out. The digital printing method was first mainly used in the graphics industry, for example in advertising agencies, advertising medium manufacturers or print shops, and during this period the digital printing method also increasingly appeared in other industrial sectors. There are various reasons for this, however two main arguments can be identified. Thus, digital printing enables the production of printed images with a particularly high quality by means of a higher resolution and, in addition, allows a broader application range with high flexibility. This is illustrated by the fact that the printed image is no longer limited in length.

[0006] Important in all methods for printing media, here paper, but also in other cases wood-based panels, is that a uniform and repeatable printed image is produced for the customer, both in terms of color and shape, which must match the original pattern at every printing. Deviations are not desired and are not accepted.

[0007] That is to say, in order to print paper by means of digital printing ink, the paper needs to be provided with an intermediate layer in advance. A primer or also a pre-priming serves as the intermediate layer in order to keep the color deviations between the printed decor of one production batch or also between identically printed decors of different production batches as small as possible from the outset due to the pigment absorption.

[0008] Here, the primer has two functions, on the one hand, it forms a kind of barrier layer between the ink and the paper, on the other hand, it has reactive components which react with the ink and thus ensure that ink drops which should have a certain size on the paper no longer change this size. The primer reacts with the ink in such a way that the drops immediately come to rest and no longer spread out.

[0009] Furthermore, the use of the primer reduces the amount of ink which has to be used for printing. Without primer, the ink sinks to a large extent into the paper and a larger amount of ink has to be used in order to achieve the desired printing result. Since the primer is significantly cheaper than the printing ink, the use of the primer is associated with a significant cost saving.

[0010] The paper to be printed is provided with primer or print primer in the digital printing facility. The primer is applied to the blanket roll in defined volumetric application amounts by means of a roll (anilox roll; it is also possible to apply the primer by curtain coating or spraying) and then to the paper. Subsequently, the primer is dried before the digital printing ink is applied and the paper is dried again.

[0011] Different disadvantages can arise from this.

[0012] Due to different influences, the application of the primer or print primer can be uneven. This occurs, for example, in the case of (mechanical) damage at the anilox roll, (mechanical) damage at the blanket roll for transferring the primer, tilted installation of one of the rolls, roll wear, wear so that the cell depth and thus the suction volume change, insufficient cleaning of the roll so that the cell depth and thus the suction volume change. Paper cockling can also cause different application amounts.

[0013] High costs arise due to unusable rejects, repeated production (material, personnel), complaints, too high material consumption (ink, primer).

[0014] The production time is increased due to repeated production and / or the time-consuming changing of the rolls, since simple cleaning is no longer sufficient.

[0015] Furthermore, resources in terms of material and personnel are wasted due to the doubled production and rejects and / or due to the too high ink and primer consumption. SUMMARY

[0016] The object on which the invention is based is therefore to create a measuring method with which the primer application or print primer application is monitored both in terms of time, i.e. the number of running meters, and in terms of bandwidth. By controlling the primer application, it is possible to ensure that there are no deviations in the printed image.

[0017] According to the invention, this object is achieved by a method having the features of claim 1.

[0018] According to this, a method for determining the amount of at least one print primer coated on at least one paper layer by means of X-ray fluorescence analysis is provided, wherein the method comprises the following steps:

[0019] - providing a plurality of reference samples by applying at least one print primer containing at least one divalent cation in respectively differently quantitatively defined amounts to at least one carrier material;

[0020] - recording at least one X-ray fluorescence spectrum for each of the reference samples with at least one X-ray fluorescence measuring head for the divalent cations respectively contained in the print primer;

[0021] - correlating the differently quantitatively defined amounts of the print primer of the reference samples with the recorded X-ray fluorescence spectra of the mentioned reference samples; and

[0022] - creating a calibration model for the relationship between the recorded X-ray fluorescence spectra of the reference samples and the quantitatively defined amounts belonging to the print primer;

[0023] - providing at least one sample to be measured by applying at least one layer consisting of at least one print primer to at least one carrier material;

[0024] - recording at least one X-ray fluorescence spectrum of the sample to be measured with at least one X-ray fluorescence measuring head;

[0025] - determining the quantitatively amount of the print 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.

[0026] By means of the X-ray fluorescence analysis applied in the present method, even a small amount of coating of the print primer or primer can be reliably determined.

[0027] X-ray fluorescence analysis (RFA) or X-ray fluorescence spectroscopy (RFS) is a method derived from material analysis and is one of the most frequently used methods for determining the elemental composition of samples qualitatively and quantitatively, since the sample is not destroyed by the measurement and does not have to be decomposed. X-ray fluorescence analysis (RFA) is particularly widely used in the metal processing industry, the investigation of glass, ceramics and building materials and the analysis of lubricating and mineral oil products.

[0028] A large advantage of X-ray fluorescence over other measurement methods is that even a very small amount of coating (<1 g / m2) can be reliably determined. This is the case when coating a print primer.

[0029] By means of the X-ray radiation incident or irradiating the material sample, first the electrons of the element to be determined are knocked out of the inner orbit of the electron shell. Subsequently, electrons from the outer shell fall into the vacancies and here emit characteristic X-ray radiation. The characteristic X-ray radiation is specific for each element and allows the determination of the element quantity. The element-specific X-ray radiation is detected by a suitable radiation detector.

[0030] The element-specifically emitted X-ray radiation is displayed in the form of pulses or counts. Here, the intensity or height of the emitted counts is proportional to the quantity of the primer applied. The counts detected by the detector correspond to the quantity of photons released after irradiation of the sample with high-energy radiation.

[0031] The current method enables the determination of the quantity of the applied print primer or primer quantity continuously, contactlessly and online. Thus, during ongoing production, it is possible to measure the quantity of the applied print primer or primer quantity not only over the web width but also over the web length. Only in this way can deviations that cause problems in printing be identified early.

[0032] Before the measuring technology can be used in the facility, a calibration is first carried out on the basis of reference samples, wherein, on the one hand, the uncoated carrier material, for example untreated raw paper, is measured as a zero point and, on the other hand, a calibration sequence with different quantities of primer is created onto the carrier material. Known different quantities of primer are applied to the carrier material and analyzed by RFA. On the basis of the data taken, a compensation straight line is created, on the basis of which the primer quantity of the sample to be measured can be determined.

[0033] In one embodiment, for calibration purposes, primer with different quantities of divalent cations, for example Ca2+, is applied as reference samples, the total spectrum is recorded and the emitted radiation in the range specific to the divalent cations is analyzed. The quantity of the applied reference samples is between 0.5 g / m2and 10 g / m2, preferably between 1.0 g / m2and 8.0 g / m2, particularly preferably between 2.0 g / m2and 6.0 g / m2of print primer, for example 1.1 g / m2; 2.2 g / m2; 3.3 g / m2. The following correlations can be seen: 24000-26000 counts for the zero sample; 120000-130000 counts for a quantity of 1.1 g / m2; 220000-230000 counts for a quantity of 2.2 g / m2; 310000-320000 counts for a quantity of 3.3 g / m2.

[0034] It is also possible to investigate the emitted radiation for other elements.

[0035] For the sample to be measured in the production facility, an X-ray fluorescence measuring head is installed behind the primer application mechanism and optionally behind a subsequent dryer. Via the measured or detected X-ray radiation, the concentration of primer in the sample to be measured can be indicated. Ideally, the measurement should be constant. If deviations occur, this means that the current primer application quantity does not correspond to the desired one and as a result deviations in the printed image can occur.

[0036] The measuring head can span the commodity web during the measurement or alternatively a plurality of measuring heads can also be installed side by side in the web width range, thus enabling control of the primer application in the web width range.

[0037] Common to all embodiments is that the spectrum is recorded continuously in order to observe the primer application over time. Deviations can thus be identified early and eliminated.

[0038] With the current method it can be ensured that the current actual printed image corresponds to the saved original pattern, i.e. to the desired printed image. It is ensured that the customer's requirements are met.

[0039] Cost savings are generated by timely determination of the wear of the rollers and their replacement, avoidance of false production, optimal use of primer and ink, and by saving time by avoiding false production and large downtimes caused by defects at the application rollers. Resources are also saved by optimal use of primer and ink and avoidance of false production or double production.

[0040] As already mentioned, the currently used print primer (as a basis for digital printing) contains at least one divalent cation, in particular Mg2+, Ca2+, Sr2+, Ba2+, preferably Ca2+. The X-ray fluorescence analysis is particularly effective in elements with a higher atomic number, such as Ca2+, Sr2+or Ba2+. Therefore, the divalent cation serves as an indicator of the amount of primer applied.

[0041] The divalent cation is present in the print primer as a salt, in particular as a chloride, sulfate, formate. Suitable salts are calcium diformate, calcium chloride, barium sulfate, calcium sulfate, of which calcium chloride and calcium diformate are preferred.

[0042] However, the use of calcium carbonate is not desirable, since calcium carbonate has a poor solubility in water.

[0043] The salt is preferably used in a water-based dispersion, which can be completely miscible with water or can be partially soluble in water. Depending on the paper and printing requirements, the dispersion is diluted before being applied to the paper layer.

[0044] The dispersion used as printing primer contains, in addition to the divalent salt, also a small amount of an organic solvent, such as methanol or ethane-1,2-diol (glycol). The primer dispersion or the basecoat dispersion should have a low solvent content of less than 10 wt.%, preferably less than 5 wt.%, particularly preferably less than 3 wt.%, still more preferably less than 2 wt.% or less than 1 wt.%. Typical solvents are ethane-1,2-diol (glycol) or methanol.

[0045] The concentration of the divalent cation salt in the primer dispersion or the basecoat dispersion (before dilution) can be between 5 wt.% and 25 wt.%, preferably between 10 wt.% and 20 wt.%. Thus, for example, a basecoat mixture with 5 wt.% to 10 wt.% calcium diformate and 5 wt.% to 10 wt.% methanol, or a basecoat mixture with 10 wt.% to 20 wt.% calcium chloride and 0.1 wt.% to 1 wt.% methanol is used. The remainder is water.

[0046] The solids content of the dispersion before dilution is 5 wt.% and 25 wt.%, preferably 10 wt.% to 20 wt.%, particularly preferably 13 wt.% to 18 wt.%, more particularly preferably 14 wt.% to 16 wt.%. The viscosity of the undiluted dispersion is 400 mPas to 600 mPas, preferably 450 mPas to 550 mPas (at a shear rate of 1000 s"1at 25°C).

[0047] As mentioned, the printing primer dispersion or the basecoat dispersion is applied to the paper layer in diluted form. Water is preferably used as diluent.

[0048] By means of the dilution, the viscosity of the printing primer to be applied to the paper layer is set to a value between 30 mPas and 100 mPas, preferably between 40 mPas and 80 mPas, particularly preferably between 50 mPas and 70 mPas (measured in a 4 mm flow cup at 22 s to 25 s at 23°C to 26°C).

[0049] The solids content of the diluted dispersion is 1 wt.% to 15 wt.%, preferably 5 wt.% to 12 wt.%, particularly preferably 8 wt.% to 10 wt.%, quite particularly preferably 10 wt.%.

[0050] The amount of the (diluted) printing primer applied to the at least one carrier material is preferably between 0.5 g / m2and 10 g / m2, preferably between 1 g / m2and 8 g / m2, in particular between 2 g / m2and 6 g / m2, more particularly preferably between 4 g / m2and 6 g / m2.

[0051] The other constituents of the printing primer mixture or the basecoat mixture can be polymeric binders, for example from the group 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 sulphate; polyvinyl alcohol; vinyl alcohol copolymers; polyvinyl acetate; polyvinyl acetal; polyvinyl pyrrolidone; polyacrylamide; acrylamide / acrylic acid copolymers; polystyrene, styrene copolymers; acrylic or methacrylic acid polymers; styrene / acrylic acid copolymers; ethylene-vinyl acetate copolymers; vinyl methyl-methyl vinyl acetate copolymers; vinyl methyl ether / maleic acid copolymers; poly(2-acrylamido-2-methylpropanesulfonic acid); poly(diethylenetriamine-co-adipic acid) acid); polyvinyl pyridine; polyvinyl imidazole; epoxide chloropropane-modified polyethylene imine; ethoxylated polyethylene imine; ether bond-containing polymers such as polyoxyethylene (PEO), polyoxypropylene (PPO), polyethylene glycol (PEG) and polyvinyl ether (PVE); polyurethane; melamine resin; gelatin; carrageenan; dextran. Preferred polymers are polyvinyl alcohol (PVA), vinyl alcohol copolymers or modified polyvinyl alcohol. The modified polyvinyl alcohol can be a cationic polyvinyl alcohol.

[0052] In a preferred embodiment, however, the currently used printing primer mixture or basecoat mixture does not contain polymer constituents which, for example, cause an increase in viscosity. In particular, the following are not contained: dextrin, starch, cellulose derivatives, polyurethane, polyamide, polycarbodiimide.

[0053] The basecoat mixture can contain further additives, such as dyes (for example Ti02 as white pigment), surfactants, bactericides, antistatic agents, elastomers, UV absorbers, plasticizers, light stabilizers, pH regulators, antistatic agents, bleaching agents, matting agents and the like. Thus, it is possible to add 2-methyl-2H-isothiazol-3-one and / or 5-chloro-2-methyl-2H-isothiazol-3-one as further constituents of the basecoat mixture, however, the constituents are preferably contained only in small amounts of less than 0.005% by weight.

[0054] As explained above, the X-ray fluorescence spectrum is recorded from each sample to be measured. Preferably, the total spectrum is recorded, so that, in addition to the selected divalent cation, further elements of the primer composition can also be determined. Thus, for example, it is desirable to determine, in addition to the divalent cation salt, also higher valent salts or oxides, for example Ti02.

[0055] To this end, the sample to be measured is first excited (for example by electron bombardment) and the X-ray radiation emitted by the excited elements is determined. In the current method, the emitted X-ray radiation can have an energy in the range between 2000 eV and 6000 eV, preferably in the range between 3000 eV and 5500 eV, still more preferably in the range between 3000 eV and 5000 eV.

[0056] In the case of determining the amount of Ca2+as an indicator of the print primer or base coat application, the energy range between 3600 eV and 3800 eV, preferably between 3620 eV and 3770 eV, is analyzed. In one preferred embodiment, the energy range of Ca2+has a starting energy of 3627 eV and an ending energy of 3763 eV. In the case of Ti02, for example, the energy range between 4200 eV and 4700 eV will be analyzed.

[0057] In one embodiment of the current method, at least one base coat is applied to at least one carrier material as a (diluted) liquid suspension or solution, the base coat having a solids content of 1 to 15% by weight, preferably 5 to 12% by weight, particularly preferably 8 to 10% by weight, completely particularly preferably 10% by weight. The base coat application can be carried out by means of an anilox roll or by means of spraying.

[0058] In another embodiment of the current method, the base coat application is dried and subsequently an X-ray fluorescence spectrum is recorded with at least one X-ray fluorescence measurement head.

[0059] A paper layer is used as a carrier material, in particular a paper layer composed of at least one raw paper or at least one pretreated impregnated paper.

[0060] In the case of using a paper layer, the paper used should have a smooth surface so that the print primer applied on the paper layer does not penetrate into or is not absorbed into the paper.

[0061] Thus, in one embodiment, the at least one carrier material to be printed is at least one raw paper. Here, raw paper is understood to mean a paper which is neither subjected to a substantial amount of sizing nor to impregnation of the surface with resins or sizes. Raw paper is essentially composed of paper pulp, pigments and filler materials, and customary additives. In order to manufacture raw paper, for example decorative paper, coniferous paper pulp, broadleaf paper pulp or a mixture of these two types of paper pulp can be used. In order to color the raw paper, inorganic colored pigments, such as metal oxides, metal hydroxides and metal oxide hydrates, metal sulfides, metal sulfates, metal chromates and metal molybdates, as well as organic colored pigments and / or dyes, for example carbonyl colorants, cyanide colorants and others, can be used.

[0062] In a preferred embodiment, the currently to be printed base paper is at least one non-impregnated paper web.

[0063] In another embodiment, the at least one to be printed carrier material is at least one pre- treated impregnated paper. Here, a pre-treated paper (or cellulose layer) is understood to be a paper or paper web impregnated with a resin solution. The paper can be soaked with different resin solutions, such as melamine resin and urea resin, plastic-acrylate compounds or starch sizing. A mixture of resins can also be present. It is also possible to impregnate the paper with a resin powder. The use of a resin powder will be described in detail hereinafter.

[0064] In a preferred embodiment variant, an impregnated paper is used, which is provided by means of the following method steps (see also EP 2 980 313 A1 ): a) complete soaking of the cellulose layer with a curable resin, such as melamine formaldehyde resin, b) removal of the excess resin formed on the surface (for example by stripping or scraping off), c) drying of the impregnated cellulose layer, so that after the evaporation of the water from the resin, the cellulose fibers on the surface of the resin are at least partially exposed.

[0065] By stripping or scraping off, the resin remaining on the surface of the cellulose layer ends in fiber tips. During drying, the resin retreats into the fibers, so that the fibers are soaked with resin but not surrounded by it. This surface is suitable for printing with aqueous digital printing inks.

[0066] A special device for stripping or scraping off works similarly to a spade machine, in which one or more rollers on the paper are run backwards and absorb the excess resin. By different speeds of the rollers, the amount can be precisely controlled and reproducibility is ensured.

[0067] The paper weight can vary in the range between 30 g / m2and 250 g / m2. Thus, for example, the paper weight of a decorative paper can be between 30 g / m2and 150 g / m2, preferably between 50 g / m2and 120 g / m2, particularly preferably between 80 g / m2and 100 g / m2. In the case of base paper or kraft paper, the paper weight can be between 50 g / m2and 250 g / m2, preferably between 100 g / m2and 200 g / m2, in particular between 120 g / m2and 150 g / m2.

[0068] As mentioned, it is also possible to provide the engineered wood panel as a carrier material to be coated with a primer. In this case, the engineered wood panel can be a chipboard, medium density fiberboard (MDF), high density fiberboard (HDF), oriented strand board (OSB) or plywood composed of a wood-plastic mixture or composite material, or a WPC board (wood plastic composite).

[0069] The current method is performed continuously and in-line in a production line comprising at least one X-ray fluorescence measurement head and at least one control system. It is also possible to provide two or three X-ray fluorescence measurement heads at different positions in the production line. Such a production line can be a production line for processing or finishing paper layers.

[0070] In one embodiment, the production line comprises:

[0071] - at least one coating mechanism for applying a print primer to at least one carrier material, preferably a paper layer,

[0072] - optionally, at least one X-ray fluorescence measurement head arranged downstream of the coating mechanism;

[0073] - at least one dryer arranged downstream of the coating mechanism,

[0074] - at least one X-ray fluorescence measurement head arranged downstream of the dryer;

[0075] - at least one printing device for printing the primed carrier material,

[0076] - further coating mechanisms with respectively corresponding dryers for applying at least one, preferably multiple, resin layers to the printed carrier material and drying.

[0077] In one embodiment, the production line comprises:

[0078] - at least one coating mechanism with an anilox roll for applying a print primer to at least one carrier material, preferably a paper layer,

[0079] - optionally, at least one X-ray fluorescence measurement head arranged downstream of the coating mechanism;

[0080] - at least one dryer arranged downstream of the coating mechanism,

[0081] - at least one X-ray fluorescence measurement head arranged downstream of the dryer;

[0082] - at least one digital printer for printing the primed carrier material,

[0083] - further coating mechanisms with respectively corresponding dryers for applying at least one, preferably multiple, resin layers to the printed carrier material and drying.

[0084] Preferably, the production line travels or runs at a line speed of between 100 m / min and 200 m / min, preferably between 120 m / min and 180 m / min, particularly preferably between 130 m / min and 150 m / min, for example 135 m / min.

[0085] It is proposed in one embodiment to use more than one X-ray fluorescence measurement head, preferably two or three X-ray fluorescence measurement heads.

[0086] During the measurement, the X-ray fluorescence measurement head travels over the sample to be measured, in particular the paper layer provided with the underprint, at 1.0 m / min to 5.0 m / min, preferably 1.5 m / min to 3.5 m / min, particularly preferably 1.5 m / min to 2.5 m / min, for example 2.0 m / min.

[0087] As already mentioned, the carrier material is provided with a decoration in digital printing after the underprint has been applied. In digital printing, the print image is transferred directly from the computer to the printer, for example a laser printer or an inkjet printer. Here, the use of static stamps is dispensed with. The decoration printing takes place in one pass according to the inkjet principle, in which the entire width of the upper side to be printed is traversed, wherein the underprinted carrier material is moved under the printer. However, it is also possible for the carrier material to be printed to be stopped under the printer and for the printer to be driven over the surface at least once when printing.

[0088] The print colors are brought together in separate print head rows in the digital printer, wherein each color can be provided with one or two rows of print heads. The colors of the digital printing ink are, for example, black, blue, red, yellow with a reddish tint, yellow with a greenish tint, optionally also CMYK can be used. The digital printing ink is optionally based on the same pigments that are used for analog and / or digital printing by means of water-based inks. The digital printing ink is preferably based on UV ink. However, it is also possible to use water-based digital printing ink or so-called hybrid ink. After printing, the decoration printing is dried and / or irradiated.

[0089] The print colors are applied in an amount of between 0.5 g / m2and 30 g / m2, preferably between 3 g / m2and 20 g / m2, particularly preferably between 3 g / m2and 15 g / m2, for example between 0.5 g / m2and 13 g / m2.

[0090] Subsequently, at least one, preferably a plurality of resin layers, are applied to the printed decoration as a protective layer or wear layer. The type and number of the layers are known to the person skilled in the art.

[0091] The control system of the production line comprises at least one computer-aided evaluation unit (or processor unit) and a database. In the evaluation unit, the X-ray fluorescence spectra measured for the primer-coated carrier material are aligned or compared with the created calibration model. The data thus determined are stored in the database.

[0092] The data determined by means of the current spectroscopic method can be used to control the production line. As has already been described, the non-contact measured parameter values of the X-ray fluorescence measuring head can be used directly and "in real time" for open-loop or closed-loop control of the associated facility, for example in that the actual values are measured and stored in a database, for example a relational database, and compared with the desired values of the parameters present there. The resulting differences are then used for open-loop or closed-loop control of the production line.

[0093] In one embodiment, in particular the coating mechanism for printing the primer and the subsequent dryer are controlled. If it is derived from the recorded X-ray fluorescence measuring head and the values determined in the evaluation unit that there is an interference in the coating, the method steps can be influenced purposefully or the defect can be eliminated.

[0094] The contact pressure of the coating rollers of the coating mechanism can thus be controlled purposefully in order to compensate for irregularities in the surface of the carrier material as a result. Defective coating can also arise as a result of damage to the coating rollers; the coating rollers can be replaced and / or repaired accordingly. Another cause of defective coating can also be empty containers for printing the primer or a malfunctioning dryer. By means of the current method, the defects can be eliminated simply and quickly.

[0095] In order to align and control the production line, a computer-implemented method and a computer program comprising instructions which, when the program is run by a computer, cause the computer to carry out the computer-implemented method are provided. The computer program is stored in a storage unit of the control system of the production line. BRIEF DESCRIPTION OF DRAWINGS

[0096] The application is explained in more detail in the following with reference to the drawings. The drawings show:

[0097] Figure 1 X-ray fluorescence spectra of carrier material coated with a printed primer and carrier material without a printed primer coating are shown. DETAILED DESCRIPTION

[0098] Calibration

[0099] From the graph of Figure 1 A typical X-ray fluorescence spectrum of a primer layer coated onto a base paper layer is known from the graph. The primer used as a printed primer contains Ca2+ in the form of calcium formate.

[0100] The sample is currently irradiated with rays in the energy range of 2 keV to 5.6 keV, and the output X-ray radiation is determined as pulses or counts.

[0101] The X-ray fluorescence spectrum is recorded using an X-ray fluorescence measuring head from the company Spektro. The measuring head is a silicon drift detector or a silicon PIN detector. The detector is chosen specifically. Care is taken during the measurement that the short spacing between the measuring head and the sample to be measured. The spacing should preferably be only a few millimeters.

[0102] For calibration, different primer quantities (0 g / m2; 1.1 g / m2; 2.2 g / m2; 3.3 g / m2) are applied and measured. Three measurements are carried out for each primer quantity, more precisely at three different measurement points on the primer-coated base paper layer each: A side (AS), B side (BS) and middle (M). For control, the back side (back) is also measured separately.

[0103] The different measurements are shown as peaks in the X-ray fluorescence spectrum each at Figure 1 The signal typical for Ca2+ cations lies in the region between 3.6 keV and 3.8 keV. It can be clearly seen that the primer-coated paper has a significantly increased pulse relative to the uncoated paper. Thus, the peak of the sample coated with 3.3 g / m2 primer reaches a maximum of 4000 pulses (on the x-axis), while the zero sample is 700 pulses.

[0104] The integral of the peak is given as counts. In Table 1, the individual values and the average values of the counts from the three corresponding measurements of each primer quantity are listed.

[0105]

[0106] Table 1: Correlation of primer quantity and counts of detected X-ray fluorescence rays. From the average values, a compensation straight line is created, on the basis of which the primer quantity of the sample to be measured can be determined.

[0107] Example 1:

[0108] In a paper digital printing plant, the raw paper is provided with a primer (base paint) in a first step in order to achieve a connection between the paper and the ink. The primer is applied to the paper by means of an anilox roll and dries immediately thereafter. A transverse X-ray fluorescence measuring head, which determines the primer quantity, is located behind the dryer. The measuring head runs at approximately 2 m / min over the entire web width of maximum 2080 mm (corresponding to the width of the paper web). After maintenance of the primer application mechanism, the plant is put into operation test-wise. After one minute, an alarm sound goes off and a signal light flashes. The plant operator stops the plant manually. The measured values show that the primer application on the left side is significantly lower than desired. The primer application mechanism is then checked again. It is shown that there is a difference in the contact pressure between the sides. After the problem has been eliminated, the plant is put into operation again without problems.

[0109] Example 2:

[0110] In a paper digital printing plant, the raw paper is provided with a primer in a first step in order to achieve a connection between the paper and the ink. The primer is applied to the paper by means of an anilox roll and dries immediately thereafter. Behind the dryer, three X-ray fluorescence measuring heads, which determine the primer quantity, are distributed uniformly over the web width. During production coating of a decor, the plant is stopped and a signal (acoustically and visually) appears. The reason for this is that the primer application on the right side is disturbed. The primer application taken by the X-ray fluorescence measuring heads at this location is 30% less than on the left side and in the middle. Upon inspection of the application mechanism, it is shown that damage is visible on the right side of the primer roll. The doctor blade has damaged the cells so that the application quantity is reduced.

[0111] Example 3:

[0112] In a paper digital printing plant, the raw paper is provided with a primer in a first step in order to achieve a connection between the paper and the ink. The primer is applied to the paper by means of an anilox roll and dries immediately thereafter. A fixedly installed X-ray fluorescence measuring head is located behind the dryer. During a large-scale coating of more than 15 tons, the plant signals (acoustically / visually). The plant is stopped automatically. The X-ray fluorescence measuring head takes a primer application of 0 g / m2. The plant operator then finds that the primer IBC is empty and that no new container is connected.

Claims

1. A method for determining the amount of at least one print primer coated onto at least one paper layer as carrier material by means of X-ray fluorescence analysis, the method comprising the following steps: - providing a plurality of reference samples by applying at least one print primer containing at least one divalent cation in respectively differently quantitatively defined amounts onto at least one of the carrier materials; - recording at least one X-ray fluorescence spectrum of each of the reference samples for the divalent cation to be detected respectively contained in the print primer by means of at least one X-ray fluorescence measuring head; - correlating the differently quantitatively defined amounts of print primer of the reference samples with the recorded X-ray fluorescence spectra of the reference samples; - creating a calibration model for the relationship between the recorded X-ray fluorescence spectra of the reference samples and the quantitatively defined amounts belonging to the print primer; - providing at least one sample to be measured by applying at least one layer consisting of at least one print primer onto at least one of the carrier materials; - recording at least one X-ray fluorescence spectrum of the sample to be measured by means of the at least one X-ray fluorescence measuring head; - determining the quantitatively defined amount of print primer applied onto 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.

2. The method of claim 1, wherein, The at least one print primer comprises at least one salt having a divalent cation, in particular Mg2+, Ca2+, Sr2+, Ba2+, preferably Ca2+.

3. The method according to any of the preceding claims, characterized in that, The at least one print primer is applied as a liquid suspension or solution onto at least one of the carrier materials, the print primer having a solids content of 1 to 15 wt.%, preferably 5 to 12 wt.%, particularly preferably 8 to 10 wt.%, more particularly preferably 10 wt.%.

4. The method according to any of the preceding claims, characterized in that, The print primer is dried and the X-ray fluorescence spectrum is subsequently recorded by means of the X-ray fluorescence measuring head.

5. The method according to any of the preceding claims, characterized in that, The amount of print primer applied onto at least one of the carrier materials is greater than 0.5 g / m2, preferably greater than 1 g / m2.

6. The method according to any of the preceding claims, characterized in that, At least one of the carrier materials comprises at least one raw paper or at least one pretreated impregnated paper.

7. The method according to any of the preceding claims, characterized in that, The determination of the coated primer amount is carried out continuously and in-line.

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