Method for Determining Adhesive Penetration Into at Least One Porous Coating Material
20240201080 ยท 2024-06-20
Inventors
Cpc classification
International classification
Abstract
Provided is a method for determining the adhesive penetration into at least one porous coating material which is pressed with at least one carrier plate and at least one adhesive layer arranged on the carrier plate. The adhesive penetrates or rises into the at least one porous coating material during the pressing process.
Claims
1. A method for determining the adhesive penetration into at least one porous coating material which is pressed with at least one carrier plate and at least one adhesive layer arranged on the carrier plate, wherein the adhesive penetrates or rises into the at least one porous coating material during the pressing process, comprising the steps of: recording at least one NIR spectrum of several reference samples, each having different values for adhesive penetration into a porous coating material, using at least one NIR measuring head in a wavelength range between 500 nm and 2500 nm, preferably between 700 nm and 2000 nm, particularly preferably between 900 nm and 1700 nm, and especially advantageously between 1000 nm and 1300 nm and/or between 1400 nm and 1550 nm; determining of adhesive penetration into the porous coating material of said reference samples by means of a mechanical removal of the porous material surface; correlating of the adhesive penetration determined by mechanical removal with the recorded NIR spectra of said reference samples; and establishing of a calibration model for the relationship between the spectral data of the NIR spectra and the corresponding adhesive penetrations of the reference samples using multivariate data analysis; pressing of at least one porous coating material with at least one carrier plate and at least one adhesive layer arranged on the carrier plate, recording at least one NIR spectrum of the porous coating material pressed with the carrier plate and the adhesive layer using the at least one NIR measuring head in a wavelength range between 500 nm and 2500 nm, preferably between 700 nm and 2000 nm, in particular preferably between 900 nm and 1700 nm and especially advantageously between 1000 nm and 1300 nm and/or between 1400 nm and 1550 nm; and determining the adhesive penetration into the at least one porous coating material by comparing the NIR spectrum recorded for the porous coating material with the calibration model created.
2. The method according to claim 1, wherein the NIR spectrum is recorded in a wavelength range between 1100 and 1250 nm and 1400 and 1550 nm.
3. The method according claim 1, wherein the at least one adhesive is a polyurethane adhesive.
4. The method according to claim 3, wherein the polyurethane adhesive is based on aromatic polyisocyanates, in particular polydiphenylmethane diisocyanate (PMDI), toluylene diisocyanate (TDI) and/or diphenylmethane diisocyanate (MDI), PMDI being particularly preferred.
5. The method according to claim 1, wherein the adhesive is a polyvinyl ester adhesive, in particular a polyvinyl acetate adhesive.
6. The method according to claim 1, wherein in at least one additive is applied to the at least one adhesive layer.
7. The method according to claim 6, wherein the at least one additive is selected from the following group comprising dyes (e.g. ink), pigments (e.g. color pigments, metallic pigments or reflective pigments) flame retardants (e.g. ammonium polyphosphate, tris(tri-bromo neopentyl) phosphate, zinc borate or boric acid complexes of polyhydric alcohols), agents for increasing conductivity, UV stabilizers, bleaching agents, hydrophobing agents or antimicrobial agents.
8. The method according to claim 6, wherein the at least one additive is a dye.
9. The method according to claim 1, wherein the at least one carrier plate is a plate made of a wood material, in particular a particleboard, medium-density fiberboard (MDF), high-density fiberboard (HDF), (OSB) or plywood board, made of plastic, a wood material-plastic mixture or a composite material, a cement fiberboard, gypsum fiberboard or a WPC board (Wood Plastic Composites) or an SPC board (Stone Plastic Composites).
10. The method according to claim 1, wherein the at least one porous coating material comprises at least one veneer layer, leather material, felt material, nonwoven material and/or such materials which have a porosity in which liquid adhesive can rise during pressing and which are at least partially plastically deformable.
11. The method according to claim 1, wherein the at least one carrier plate, the at least one adhesive layer disposed on the carrier plate, and the at least one porous coating material are compressed at temperatures between 150 and 200? C., preferably between 170 and 180? C., at a pressure of 30 to 50 kg/cm.sup.2, preferably 40 kg/cm.sup.2 for 30-120 seconds, preferably 60 to 90 seconds.
12. The method according to claim 1, wherein spectral data from the entire recorded spectral range are used to create the calibration model.
13. The method according to claim 1, wherein spectral data from the NIR spectral range between 1000 nm and 1300 nm and/or between 1400 nm and 1550 nm, which are pretreated by means of suitable mathematical methods and are subsequently fed to the multivariate data analysis, are used to create the calibration model.
14. The method according to claim 1, wherein the determination of the adhesive penetration into the porous coating material is performed continuously and online.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0071] The solution is explained in more detail below with reference to the FIGURES in the drawings using an example of an embodiment.
[0072]
DESCRIPTION OF THE INVENTION
[0073]
[0074] In the case of the PMDI adhesive, the NIR spectrum shows characteristic peaks in wavelength ranges between 1120 and 1250 nm with maxima at 1130-1150 nm and 1200-1220 nm, and between 1440 and 1540 nm.
[0075] In the case of the PVAc adhesive, the NIR spectrum shows characteristic peaks in wavelength ranges between 1160 and 1220 nm with a maximum at 1180-1200 nm, and between 1420 and 1480 nm.
Example 1
[0076] On two 8 mm HDF (500?500 mm), black colored PMDI (100% system) was applied on one side in quantities of 50 and 100 fl g/m.sup.2. This was done with a roller application unit.
[0077] An oak veneer (thickness: 0.5 mm) was then laid on top of the HDFs. Then the structure was pressed in a laboratory press at 180? C., a pressure of 40 kg/cm.sup.2 and a pressing time of 160 seconds. The veneer was thus compressed to a thickness of 0.35 mm.
[0078] Afterwards, specimens were cut from the plates (100?100 mm, four pieces each). After cooling, the surface was measured with an NIR measuring head at four points, which were marked by a coordinate cross and at which the abrasion/removal by the Taber abraser would later take place. In addition, a zero sample was also measured in which the oak veneer was fixed to the HDF with the aid of an adhesive device.
[0079] The specimens were then tested on a Taber abraser. The test was carried out in accordance with DIN EN 13329. The friction wheels of the taber-abraser were covered with the usual abrasive papers and also loaded with the usual weights. Then, after 200 revolutions in each case, it was visually checked whether black discoloration could already be observed in the veneer. Then, using a dial gauge in the circular recess created by the sandpaper in the four segments of the circle formed by a coordinate cross, the removal in mm was determined and the average value was formed from this. From this mean value, together with the four other samples, an overall mean value was formed. The removal was then subtracted from the veneer thickness, which was determined with the aid of a microscope, and then correlated with the spectra.
[0080] The values obtained are summarized in Table 1 below. It can be seen that at higher amounts (100 g/m.sup.2) of applied PMDI adhesive, the mechanical degradation in Taber-Abraser test is lower than at 50 g/m.sup.2 of PMDI adhesive. This proves that the more PMDI adhesive is applied, the more PMDI adhesive penetrates into the veneer ply and the less has to be removed in the Taber-Abraser test to observe the black discolorations in the veneer ply.
[0081] The mechanical reduction in the Taber-Abraser test corresponds to the reduction determined by the NIR method, so that the NIR method allows verification of the penetration level of the adhesive in the veneer layer.
TABLE-US-00001 TABLE 1 Amount of PMDI Decrease Decrease in mm Difference adhesive applied in mm NIR Taber Abraser in mm Zero sample 0.26 0.29 0.03 50 g PMDI fl/m.sup.2 0.11 0.14 0.03 100 g PMD fl/m.sup.2 0.06 0.06 0
[0082] The measuring head for determining adhesive penetration is installed directly behind the press used. An automated displacement option allows the measuring head to analyze different areas of a panel coated with veneer or it can traverse over the panel. This ensures that areas that can usually be problematic due to different pressing conditions (e.g. panel edges) are also analyzed.
[0083] If the penetration of the adhesive into the veneer is not adequate, an improved adhesive flow can be achieved by changing the pressing temperature and/or the pressing time. The two parameters are changed in opposite directions. If the pressing temperature is reduced, the pressing time is extended. For example, if the pressing temperature is reduced by 10C, the pressing time is extended by 10 to 20 seconds.
Example 2
[0084] To check the accuracy of the calibration, a coating with a leather was carried out instead of a coating of a HWS with a veneer. First, a spectrum of the leather used was created with the aid of an NIR measuring instrument to check whether the PMDI peak at approx. 1500 nm was superimposed by peaks of the leather. This was not confirmed.
[0085] A PMDI coating of 100 g f/m.sup.2 (solids content 100%) was applied to one side of an 8 mm HDF (500?500 mm).
[0086] A brown leather (thickness: 0.75 mm) was then placed on the PMDI. The structure was then compressed in a laboratory press at 180? C., a pressure of 40 kg/cm.sup.2 and a pressing time of 160 seconds. This compressed the leather to a thickness of 0.45 mm.
[0087] Samples were then cut from the plate (100?100 mm, four pieces each). After cooling, the surface was measured with an NIR measuring head at four points marked by a coordinate cross.
[0088] The measurement with the NIR gauge showed a penetration depth of 0.35 mm. This was subsequently checked with the Taber abraser. A value of 0.35 was determined.
[0089] Other porous coating materials such as fabric, felt, fleece, etc. can also be measured using this method.