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Detailed printing auxiliaries – defoamers

66 Published by admin May 28,2018

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Defoamers are produced by Qingyi company have a superior performance,and mainly used for heat transfer printing paste defoamers,with excellent defoaming, and antifoaming effects, which can restrain and eliminate paint application during production, canning and printing process generated bubbles.

Defoamers are mainly used for thinner inks.These inks most can be delivered by a pump. During this process, a large amount of air may be mixed and may appear bubbles. In addition, during printing process, these thin ink scraped from the plate or down from the roller, due to impact between the ink, stirring, also produced a large number of bubbles. Aromatic, alcohol, water-based inks all have this phenomenon, while the latter is the most serious, because the latter are mostly alkali-soluble substances, it’s like soap (or detergent) in the water, so foam is very strong . Ink bubbles not only reduce the printed matter quality, but also, seriously ink fountains will produce a large number of bubbles, lead to printing can’t go on.

1)bubbles formation and destruction a brief mechanism.
Bubbles, that is, gas into group by the liquid membrane wall surrounded by separation formed .Bubble walls themselves can form very uniform geometries, forming 120 degrees when three bubble walls (films) meet together. At least two or more components can form bubbles (pure liquids can’t foam), because foams require a large amount of surface area, production these surfaces is countered by the liquid surface tension. Therefore, when the liquid surface tension is relatively low, formation a certain amount of stable bubbles required energy is relatively low.

When a single-molecule film surfactant-soluble appears on liquid surface, bubbles will generated. Liquid surface elasticity can also cause bubbles.
In general, bubbles is not stable, its destruction is generally due to liquid from bubble wall squeeze into the wall edge to occur it,when membrane wall squeezed to a thickness about 100Ao,molecular motion in the membrane wall is to rupture the bubble structure by destroying liquid membrane.

2)Defoamer function.
Defoamers are generally used to eliminate air bubbles through chemical reactions (such as acid or calcium salts can destroy soap film). However, most of defoamers function are spread out on the foam surface, so that surfactant on the bubble before stabilizing effect is removed or replaced,which requires a surface tension smaller than the original bubble-forming film surface tension. If the foam forming agent is easily desorbed and quickly reprocessed, then its effectiveness against defoamers is very small. If the foam desorption function is poor, the surface viscosity is relatively high, the anti-foaming agent spread slowly.

A good anti-foaming agent should work very fast. Generally speaking, it should have very low solubility,and have a certain reduce surface tension liquid function.The most effective defoamer chemical structure should be: When it is oriented at the bubble’s interface,can be flattened. In aqueous systems, this rearrangement is formed either by chain branch to promoteor or with the volume polar groups in the center proliferation, and introduction just enough methylene then get water insoluble to formed.

In order to assist defoamers in the beginning have a best diffusion, distribution function, most industrial defoamers are applied spreading solvent or emulsifier as a carrier, so as to ensure that defoamers can spread well to reach the surface various parts, and play an effective defoaming effect.
Another approach is to add a good solvent to the system,disperse surfactant into the liquid, thus, greatly reducing bubble formation.

3)Defoamer classification.
General speaking, defoamers can be divided into seven types:
1,Alcohols (2-Ethylhexano,Polyalkylene Glycols). Branched chain alcohols and polyols,can meet the smaller water-soluble and lower surface tension needs. And these two points are good defoamer should have main features.
2,Fatty acids and their derived esters (Sorbitan Trioleate,Diglycol Stearate). Some water-soluble fatty acids and fatty acid esters, mostly used in food defoamers.
3,Amides (Distearoylethylenediamine), this class defoamers generally have a high molecular weight.
4, Phosphate esters (Trioctyl Phosphate, Tributyl PhosPhate,Sodium Octyl Phosphate). Most phosphate esters in very small amount, the effect is very good.
5,Metal soap(Calcium stearate,Magnesium Palmitate). After the water-insoluble metal soap pre-dispersed in the appropriate row materials.
6,Multi-polar group-type chemical crystal (Ditertiaryamyl phenoxyethanol).Many effective defoamers, generally contain two or more polar groups. Castor oil is a natural defoamer containing hydroxyl and ester groups.
7, Silicone oil (Polysiloxane). Such defoamers are significant defoamers for both aqueous and non-aqueous systems.
General speaking, when making ink need add defoamer, better than when used in printing,the latter approach is easy to make the printed product happen spots and other disadvantages.

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