INVESTIGATION OF QUALITY OF PACKAGING MADE OF LAMINATED MICRO-CORRUGATED CARDBOARD

The reproductive and graphic indicators of liners printed by offset printing are investigated in this work. It was considered the process of their laminating to micro-corrugated cardboard using the adhesive device of a new construction with the further determination of the operational parameters of the packaging material. As a result of the research, graphic dependencies were constructed that allow us to assess the quality reproduction of a color image in the offset printing and the operational stability of laminated micro-corrugated cardboard.

However, apply a relatively thick (from 1 mm and more) material high-quality offset printing, varnish, embossing is difficult technically, and often due to the specifics of the equipment is simply impossible. But print on ordinary cardboard, then attach to the base of a 2-layer micro-corrugated cardboard is easier. The result of the lamination is a 3-layer micro-corrugated cardboard with a top liner, which is processed by virtually any printing technology -offset and screen printing, UV varnish, hot stamping foil, hot stamping, which complies with the most complicated packaging requirements and continues to be affordable. The process of lamination involves several steps ( fig. 1).
Over time, the technology of packaging producing of corrugated and micro-corrugated cardboard has undergone significant changes, since it is environmentally friendly, easy to use, easily print decoration and recycled after use [5][6][7]. Therefore, it is actual to carry out researches on the process of microcorrugated cardboard lamination, to determine its qualitative and in particular performance indicators, to develop new and improved existing devices and machines.

The aim of the research
Investigation of the process of making packages of laminated micro-corrugated cardboard; definition of reproduction and graphic indicators of offset printed liners; lamination of micro-corrugated cardboard with the use of adhesive device of a new design; determination of operational parameters of laminated micro-corrugated cardboard (bunching strength and bonding strength, resistance to double bu-ckling) with further investigation of its structure change due to testing.

Objects and methods of research
The objects of the research were the most widespread in the manufacture of packaging materials: offset printed liner (cardboard 'Arctika'), with a grammar of 180 g/m 2 , 215 g/m 2 and 250 g/m 2 followed by sample No The conduct of experimental research was carried out in accordance with international standards (ISO 13655; ISO 3664; ISO 2846-2; ISO 12647-2; ISO 12647-4) [8]. The means for evaluating the quality of the imprints were the test scales with halftone fields and tones for CMYK colors, as well as a number of scales for quality control of the offset printing method Ugra/Fogra Digital Print Scale Control, which include elements of sliding, unpacking, reproduction of small parts, radial measure, halftone fields, a combination of colors, text items, etc. The spectrocolorimeter Gretag SPM 50 was used to measure the optical density.
The process of lamination was carried out on the developed device (Ukrainian Patent No. 83440) [9], which includes a new, reliable adhesive device for application of glue directly to the peak of the fluting wave. The adhesive roller is made in the form of a set of two discs of different diameters alternating, and the side wall of the adhesive bath is variable and executed in the form of a comb, which enters into close contact with the disks of the adhesive roller, so that the residual glue is removed from their lateral surfaces. After the cardboard blank is applied, the adhesive is applied with the help of adhesive disks to a uniform layer at the peak of the fluting wave, and the clamping roller prevents deformation of the corrugation.
After applying the glue to the micro-corrugated cardboard, the feeding of the top sheet and its combination, the laminated microcorrugated cardboard is fed between the upper and lower clamping rollers. Since the thickness of the obtained product can vary in a wide range, the required shaft clamping is ensured by a uniform change in eccentricity by means of the sleeves, which ensures high-quality compression of the liner to the fluting of the micro-corrugated cardboard.
For researches, cardboard liners procurement and micro-corrugated cardboard of 190×190 mm were selected. The lamination was made at an average speed of 10 sheets per minute (20 samples for each individual variant). Ready-made models were kept for 24 hours until the glue was completely dry.
Definition efforts stratification and bonding strength of laminated micro-corrugated cardboard was carried out on tensile testing machines RMB-30-2M [10]. The research on the stability of laminated microcorrugated cardboard to double bends was carried out using the device 'falser' type DFK. To study the change in the structure of micro-corrugated cardboard after the lamination process, the digital photo method was used (50-350 fold increase in image), which includes: OGME microscope, digital camera CCTV Manuel Camera, program for obtaining an image on the PC FLY 2000 TV monitor. To prevent the occurrence of an error in measurements and reliability of the results, 7-10 studies of each model were foreseen. The analysis of the obtained graphic dependencies showed that the gradation of the blue ink of all studied samples (Fig. 2, a), more or less corresponds to the color proof in light areas, in the halftonnage, the optical density of the sample number 3 begins to increase and the trend continues in dark areas and decreases for the sample number 1, ranging from halftones to dark areas. The optical density is the closest to the color proof in model number 2.

Results of researches
As can be seen from Figure 2, b, a similar pattern is observed for purple ink: the gradation transmis-sion in light areas is close to the color proof, in the half-tonal most approximation in the sample number 3, a slight increase in density in the sample number 2 and a decrease in the sample number 1, which continues and in dark areas. Instead, samples 2 and 3 in dark areas show roughly the same result.
Gradual transmission of the yellow ink (Fig. 2, c) Figure 2, d shows the dependence of the optical density for the black ink. As in the previous figures there is more or less stable transmission of gradation in light areas. In the halftone and dark areas, the optical density increases for samples number 1 and number 3. The sample number 2 is the closest to the color proof.
Thus, as it turned out as a result of the conducted research, the most stable result of the graduation transmission at the printing showed sample No. 2 (cardboard Arctika with a grammar of 215 g/m 2 ).
As a result of elaboration of the research results of the operational indicators of laminated micro-corrugated cardboard, histograms of bonding stability (Fig. 3, a) and double buckling (Fig. 3, b) of the studied samples were constructed.
As can be seen from Figure 3, a the difference between the strength properties in the machine and the transverse direction increases with the increase of the grammars of the studied samples. This phenomenon must be taken into account when designing packages, so the direction should be maintained perpendicular to the height of the package. Thus, the least breakthrough efforts are observed for the sample number 1 in the longitudinal direction of the fibers -245 N. The greatest breakthrough effort was recorded in the sample number 3 in the transverse direction of the fibers -272 N.
From the diagram shown in Figu

Conclusions
As a result of experimental researches, the following conclusions were obtained: in light areas all studied samples showed a result close to the color proof; in the halftones the most volatile transfer of gradations, as seen from graphic dependencies, in the ink magenta; in dark areas there are significant deviations from the color proof in all samples, the most stable gradation is transferred for the yellow ink in sample number 1. Nevertheless, after analyzing the obtained results, it can be said that the most closely approximated to the color proof was the sample number 2 (cardboard Arctika with a grammar of 215 g/m 2 ).
The investigation of the lamination of micro-corrugated cardboard and its quality indicate that particular attention should be paid to parameters such as the adhesive viscosity and the pressure at the lamination, which is determined by the distance between the adhesive and clamping rollers of the lamination device, which provide the contact of the fluting and liner in the process of manufacturing laminated micro-corrugated cardboard.
Considering the results of the study of the technological and operational characteristics of laminated micro-corrugated cardboard, despite the high results of the sample number 3 (Arctika 250 g/m 2 ), we recommend for lamination the sample number 2 (Arctika 215 g/m 2 ), which forms with a micro-corrugated cardboard of the brand 311E with a fluting with a grammar of 140 g/m 2 strong adhesive bond, sufficient for operation of this packaging.