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For printing companies, it is of great practical significance to explore a scheme for optimizing the formulation of water-based inks with a simple process and low cost. This article is based on a formula for printing water-based ink on the surface of corrugated cardboard boxes. By adjusting the viscosity of water-based ink, it is characterized by the printing effect of kraft paper surface, and explores the range of water-based ink viscosity that is conducive to improving the printing effect of kraft paper surface printing, in order to provide printing companies Certain reference basis.
experiment
In this experiment, four kinds of water-based red inks with different viscosities were prepared by controlling the proportion of the main components of the pigment and binder in the water-based ink formulation unchanged, and adding a neutralizer. It is printed on the surface of kraft paper by flexographic printing, and the coloring power, glossiness and adhesion of the printed pattern are tested to characterize the printing effect of kraft paper.
1 Experimental materials
(1) Paper base : Single-sided kraft paper with a basis weight of 230g / m2 (Shenghe Paper Products Co., Ltd.), tightness of 0.75g / cm3, bursting resistance of 9kPa · m2 / g, and folding endurance of 60 times, suitable Flexo printing.
(2) Color paste : red paste ( X-Rite ASL010312), with a color content of 45%, light resistance of 5 to 6 levels, temperature resistance of 180 ° C, and good color strength, stability and fluidity.
(3) Connection materials : film-forming resin (BASF Joncryl series 8052), non-film-forming resin (BASF Joncryl series 631).
(4) Auxiliaries : water-based defoamer 028 (Germany BYK), anti-scratch agent MONENG-1993 (Moeneng Chemical Co., Ltd.), leveling agent 401LS (Dow Corning), ethylene glycol (Guangzhou Bofeng Technology Co., Ltd.), Neutralizer (urea modified polyurethane solution).
2 Experimental instruments
High-speed dispersion machine T18 (German IKA), 3 # Zahn Cup (TQC), reading stopwatch TF307 (Tianfu Huibo Trading Co., Ltd.), density meter i1 (Acer), gloss meter WG75 (Shenzhen Weifu Optoelectronic Technology) Co., Ltd.), pH meter PHS-3C (Shanghai Yidian Scientific Instrument Co., Ltd.), IGT printing suitability tester (F1 of the Dutch IGT company).
3 Experimental methods
(1) Preparation of water-based ink
The most important components in water-based inks are pigments, resins and additives. Among them, the pigment provides the ink with the required color; the resin provides film formation, water resistance, fluidity and good printability for the ink by uniformly dispersing the pigment; the additive has a specific function to improve the performance of the ink itself Adapt to various printing conditions. Based on a mature formula developed earlier in this article, with viscosity as a breakthrough, through the perspective of higher scientific content and more cost-effective, it solves the printing quality problems caused by water-based inks that many companies face.
â‘ Preparation of linking material
In this experiment, using self-made bonding materials suitable for kraft paper printing, selecting film-forming resins with good water resistance, abrasion resistance, film-forming properties and adhesion, and non-film-forming resins with good rheology and printing suitability According to the proportion of the experimental formula, add to the beaker separately, and then add the defoamer to stir for 15 minutes, and then stand to defoam. Among them, the film-forming resin accounts for 60% of the link material, the non-film-forming resin accounts for 39.8% of the link material, and the defoamer accounts for 0.2% of the link material.
â‘¡ Equipped with water-based kraft paper surface printing red ink
First, add the binder, defoamer and dispersant to the mixing tank according to the recipe. Then, start the disperser and slowly add the red pulp during the stirring process. Finally, add antiwear agent, leveling agent, ethylene glycol, pH adjuster and water, and disperse at high speed for 30 minutes. Among them, the water-based red ink formulation is shown in Table 1.
Table 1 Water-based red ink formula (unit:%)
(2) Ink viscosity adjustment
The viscosity of water-based ink is affected by many factors. The neutralizer selected by the formula reduces the viscosity by enhancing the rheological properties through hydrogen bonding. Its rheological properties do not depend on pH and water content. The slight change of the deionized water in the formula has far less effect on the viscosity than the neutralizer, so it can be ignored in the experiment. It can be seen from Table 1 that the ratio of neutralizing agent is adjusted, and on the premise of keeping the main components in the ink consistent, it is equipped with four water-based kraft paper water-based red inks with different viscosities. , Formula 2 is 23.2 ± 0.5s, Formula 3 is 28.7 ± 0.5s, and Formula 4 is 31.3 ± 0.5s.
(3) Printing
Cut the kraft paper sample into 50mm wide sample strips, set the pressure to 350N / m2, the blade pressure to 150N / m2, the speed to 0.6m / s, and print the single-sided red kraft paper sample by single circle printing.
(4) Performance test
â‘ Viscosity test method
According to GB / T 13217.4-2008 "Inspection Standard for Viscosity of Liquid Ink", it is measured by the 3 # Zahn Cup Viscometer method. Control the temperature of the ink to be tested at 25 ℃ according to the regulations, and adjust the temperature of the ink in time during the test; hold the cleaned and dried Zahn cup horizontally, first block the bottom hole with your fingers, and pour into the sample Water-based ink, the height of the ink is flush with the upper edge of the Zahn cup; hold the Zahn cup height can not be higher than 15cm of the liquid surface, release the finger and start the stopwatch at the same time, when the continuous drop of ink in the sample shows the first drop, stop When timing, the stopwatch display time is the ink viscosity.
â‘¡Coloring force measurement
Weigh 1g of standard red ink and 10g of white ink respectively in the balance, and weigh the same proportion of homemade red and white ink in the same way, and thoroughly mix with an ink-adjusting knife; then dilute the equalized ink, draw the sample and place it on the scrape sample At the top left of the paper, take the ink sample and scrape at the top right; scrape 80mm to 100mm long from top to bottom with a scraper. Observe the ink color of the sample on the standard sample, and change the sample by adding white ink until the dilute sample is consistent with the standard sample.
Color strength.
S = D / C × 100%
Among them, S is the percentage of coloring power (%), D is the amount of white ink used to dilute the sample (g), and C is the amount of white ink used to dilute the standard sample (g).
â‘¢Gloss measurement
According to GB / T 8941-2013 "Determination of Mirror Gloss of Paper and Paperboard", this experiment uses the WG75 gloss meter for measurement. After the kraft paper was printed, the gloss of the surface layer was measured using an angle of 75 °.
â‘£Adhesion measurement
According to the requirements of GB / T 9286-1998 "Cross-cut test for paints and varnishes", first draw 5 × 5 small grids of 1mm2 on the kraft paper printed with water-based red ink, and then use 3M tape Draw a small grid of test area, and then use your fingers to grab one end of the tape and pull it off quickly along the vertical direction of the printing surface. According to the situation of ink shedding, it is graded according to the grade division standard. The specific grades are shown in Table 2.
Table 2 Adhesion level
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