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Application Characteristics of Soybean-Based Offset Printing Inks

Published on Mar. 12, 2020

At present, soy based offset ink has different viscosity types for customers to choose from, but the price is higher than that of petroleum-based inks.

The content of soybean oil in the ink varies depending on the purpose of the ink, generally between 25% and 55%. The advantage of soybean-based offset printing inks is high transparency, which is very beneficial for newspaper color printing. Soy-based offset printing inks rarely bleed off, and have higher color rendering than petroleum-based inks. An equivalent amount of soybean-based offset printing inks can print 10% to 15% more prints than traditional inks.

1. Good friction resistance

Soy-based offset printing inks are resistant to friction. Readers will not stain their hands with black when reading newspapers or magazines. At the same time, there is no bad irritating odor. Traditional petroleum-based inks have poor friction resistance. Hands and bad smell.

2.Easy deinking of waste paper

Soybean ink has good deinking performance during the paper recycling process. The recycled paper has good paper quality, less waste, and low recycling cost.

3. Low ink consumption for printing

Soy ink prints are bright in color and high in saturation. Vibrant prints can be obtained with less ink, which reduces ink usage, saves printing costs, and is more economical for color printing.

4. Good inking properties

Compared with cured inks or anhydrous offset printing inks, soybean-based offset printing inks dry more slowly. However, from the practical results, the ink has good transferability, good inking properties in the field, and uniform ink color in the halftone dots of the bright tone. After the ordinary offset printing ink reaches the paper, the solvent penetrates fast, and the ink film will break off in the part close to the paper surface, while the soybean-based offset printing ink is slower and the peeling surface of the ink is closer to the blanket side, which is The thicker ink film is transferred to the paper surface, so the ink transfer amount is increased.

Soy Based Offset Ink

Soy Based Offset Ink

Drying mechanism of soybean-based offset printing inks:

Although soy oil thermal curable ink has a lot of printability better than petroleum-based ink, but its drying performance is poor, after many improvements, the current soybean-based offset printing ink is similar to the general ink, That is, the drying time on coated paper reaches 2 to 4 hours, and that of uncoated paper is 4 to 6 hours. But its on-board anti-drying property is very good, up to 30 hours.

The drying mechanism of the soybean oil offset printing ink is the drying of the oxidized conjunctiva. Therefore, to control the oxidation process of the ink, it is necessary to control the various components of the ink.

1. Composition of soybean-based offset printing ink

Printing ink is mainly composed of resin, binder, filler and auxiliary materials. The binder is composed of oil, solvent, resin and other materials. Among them, soybean oil is a binder that provides ink fluidity. The components of soybean-based offset printing inks include refined soybean oil, clear tung oil, and petroleum synthetic resins.

2.Drying process of soybean-based offset printing ink

Ink drying is generally divided into two stages, that is, penetration drying and oxidative conjunctival drying. First, the ink just transferred to the substrate starts to contact with oxygen to begin curing; the solvent in the ink begins to penetrate into the substrate fibers or coating gaps. The pigment remains in the soybean oil component, and the pigment is fixed on the surface of the printed matter through an oxidative film. However, at this time, the ink was not completely dried. Due to the loss of solvent, the viscosity of the ink film increased, it reacted with oxygen in the air, and the viscosity of the resin in the binder increased. At this stage, the ink on the surface is fixed, but the ink in the middle of the ink film still maintains a certain fluidity. Depending on the composition of the ink, the thickness of the printing ink film, the nature of the paper, and environmental conditions, it takes approximately 1.5 hours for the ink to fully set.

3. Control of drying speed of soybean-based offset printing inks

In order to accelerate the drying speed of soybean-based offset printing inks, oxidation can be accelerated by adding a desiccant. There are three types of desiccants that are used more, namely cobalt (which can accelerate surface drying and fixation), manganese (to accelerate the internal drying process), and lead.

When printing with soy-based offset printing inks, the use of desiccants can speed up and dry the ink surface and interior completely. On the drying of heatset soy based printing ink, the following points should be noted.

(1) When printing on fine and smooth paper surfaces, try to avoid using soy-based offset printing inks. Because soybean oil is a semi-dry oil, the drying speed is slow.

(2) The pH value of the fountain solution should be controlled within the range of 5.0 to 6.0 during printing. Due to the high acidity (low pH value), the drying process of the ink will be prolonged.

(3) When printing a large area of land, the use of a varnish containing a desiccant can speed up the drying, but too much desiccant will plasticize the ink, resulting in slower drying.

(4) You can add some desiccant to the fountain solution to increase the drying speed of the ink, or use large particles to dust, so that more air enters the paper gap to accelerate the drying speed of the ink.

(5) Using an infrared drying device to speed up ink drying is also a better method.