Study on Deinking Performance of Water-based Photocurable Ink

The water-based ink is mainly composed of hydrophilic acrylic resin, pigment, water and additives. In the conventional alkaline deinking process, the hydrophilic acrylic resin brings great difficulty to the deinking of waste paper. The main reason is that The ink particles peeled off from the fibers in the pulping stage are dispersed extremely fine, with an average particle size of about 0.2-1.0 microns, and are hydrophilic, which seriously affects the deinking efficiency.

There have been studies to improve the deinking performance of newsprint and magazine paper printed with water-based inks by optimizing the deinking process and using appropriate deinking agents, and then improve the deinking efficiency. However, it is not suitable to use the conventional alkaline flotation washing and deinking technology when processing more than 10% of printing waste paper with water-based ink.

In order to solve this problem, this subject conducted a preliminary discussion from the aspect of changing the ink composition. The prepared water-based photocurable ink was printed and de-inked on newsprint. The ink is a new type of water-based ink and the ink is connected. It has a hydrophilic group and can be dispersed in water under alkaline conditions; when printed on paper, the ink can be quickly cross-linked and cured under ultraviolet (UV) radiation to complete the drying process. The printing production can be completed on the current flexographic printing machine with UV device.

When the newspaper printed with this ink is de-inked under normal alkaline conditions, due to the cross-linking reaction of the binder, the ink particles peeled off from the fiber will not be disintegrated into very fine particles like ordinary aqueous ink. Particles controlled in the range of 20-200 microns suitable for flotation deinking can greatly improve deinking efficiency.

1 Experiment

1.1 Experimental materials and equipment

Newsprint: quantitative 46.3g / m3, whiteness 57.8%, opacity 94.3%, taken from Shandong Huatai Paper Group; water-based photocurable ink: self-made; oil-based news ink: produced by Taiyuan Ink Factory; water-based flexographic ink: Shenzhen cloth Produced by Reiter and Industrial Co., Ltd .; Color wheel: manufactured by Shanghai Printing Technology Research Institute; 518 type reflection densitometer: manufactured by X-Rite, USA; UV curing machine: domestically produced, 15 cm illumination distance, 80W / cm light intensity; YQ-Z-48B whiteness tester: domestically produced; H-272M pulper; L-100 flotation deinking instrument; FI101 square chip reader; residual ink scanner: made in Canada.

1.2 Experimental method

1.2.1 Simulated printing of different types of inks Use a color wheel to print different types of black ink on newsprint, with an ink coverage of 25%. Oil-based news inks and water-based flexographic inks are printed using natural drying, water-based photocurable ink Immediately afterwards, irradiate and dry with a UV curing machine. In order to ensure the consistency of the ink film thickness of different types of inks, the optical density method of printed products is used to control the thickness of the ink film, adjust the amount of ink on each ink, so that the optical density of the product after drying is 1.35-1.45, and the optical density is measured by a reflective densitometer . The printed paper can be stored for 2 months.

1.2.2 Paper shredding

Tear the paper printed in 1.2.1 to 25mm * 25mm and place it in a sealed bag to balance moisture. Pulverize the pulp in the Gao Nong pulper, add a certain amount of hot water to the pulper, adjust the pulp temperature to 55 degrees Celsius, then add the metered NaOH solution, Na2SiO3, deinking agent, H2O2 and 80g dry fiber News paper.

1.2.3 Flotation

Dilute the crushed slurry to 1%, pour it into the waste paper flotation deinking instrument, start the circulating pulp pump for 2min, open the air inlet valve, adjust the gas flow to 0.08-0.12 m3 / h, and float at room temperature.

1.2.4 Washing

The slurry after flotation is washed to a concentration of 0.5%, washed and concentrated once by a 80-mesh copper mesh.

1.2.5 Copying

The crushed slurry or the slurry after flotation was washed on a square tablet, the quantitative is 60g / m2.

1.3 Analysis method

Use a whiteness meter to measure the whiteness of the paper. The residual ink scanner was analyzed according to TAPPI standard T568pm-99, and the resolvable ink particle size was 8-678 microns.

2 Results and discussion

This experiment explores the deinking performance of water-based photocurable inks under conventional alkaline methods. The chemical conditions simulate conventional deinking. The dosage of chemicals (relative to absolutely dry waste paper) is NaOH1%, Na2SiO32%, deinking agent 0.4%, H2O21%.

2.1 According to the data obtained from the experiment, in the conventional alkaline deinking process, the suitable deinking conditions for water-based photocurable inks are 10% pulp concentration, 20min pulping time, stirring speed 1500r / min, and flotation time 15min.

2.2 Under suitable deinking conditions, the deinking efficiency of water-based photocurable inks is close to that of oil-based news inks, which is superior to water-based flexographic inks. 2.3 The water-based photocurable ink has changed the formula and drying method of the traditional water-based ink, and provides a new idea for solving the problem of the difficulty of deinking the water-based ink.

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