Causes and Treatments of Post-light Fog on Printing Surfaces

There are also stepwise polymerization reactions to form a film (including polycondensation reaction forms, hydrogen transfer polymerization forms, and addition co-agent curing forms) including room temperature curing, heat curing, and specialty curing film formation.

Looking at the base oil and varnish materials and the film forming mechanism described above, it will be found that the varnish system adopts the easily emulsified resin as the varnish film material material, and during the process of varnish production, storage and use, the temperature When the temperature rises or the humidity is high, the water vapor in the goods and packages will continuously condense on the inner surface of the top layer of the polyethylene hydrocarbon film, generating a lot of fine water droplets, forming an opaque misty white water film, and making it transparent. The lightness is greatly reduced, and the temperature in the film rises quickly. The already emulsified acidic moisture causes the instability of the coating oil, and the white misty gas is released, which affects the coated UV oil material after printing. The surface properties. In serious cases, it caused users to reduce the price of packaging prints, and even be sued for claims.

4. Methods for preventing varnish and polyolefin mist

In the face of aerosol failures, it must be clearly stated that aerosols are caused by the defects of optical oil films and polyolefin films, and can even be extended to the packaging printing substrates containing excessive moisture.

First, the anti-fogging agent is added to the coating oil or polyolefin film system to make full use of the surface activity of the anti-fogging agent to make the above materials hydrophilic, and the resulting fine water droplets gradually develop on the surface of the varnish film or the polyolefin film. Condensation into large water droplets, so that the water droplets down the flow, or reflow back into the packaging printing products, and even goods, so as to restore the transparency of the film. If the coating oil and polyolefin film pass through the mechanism of anti-fogging agent - (1) use of hydrophilic polymer materials; (2) crosslinking additives; (3) surfactants to absorb moisture, Not only can prevent and inhibit the severe failure of packaging and printing products from white frost, but also can greatly increase the water resistance and friction resistance of the resin in coating oil and polyolefin systems. While adding anti-fogging agents to flexible polyolefin film materials, it is recommended to add a small amount of nucleating agent to improve the transparency of the film.

Second, the user should store the packaged goods in a ventilated and dry warehouse as much as possible; according to the different volatilization rates of solvent or water solvent, design a varnish oil product or ink product that can evaporate gradient balance and flow smoothly. The residual solvent content of the varnish oil is reduced to a minimum value; a wax material capable of blocking moisture release is added to the varnish system; and a heat-insulating, heat-resistant mica or silicone resin is introduced into the varnish system to reduce the rise in temperature. At the same time, the stability of packaging and printing substrates; selection of packaging materials with less water content or PH value for printing and finishing substrates; adding catalyst (such as stannous chloride) in the varnish system to increase the transparent hardness value of the varnish film .

In summary, regardless of whether the method of producing a mildew-resistant varnishes or anti-fogging polyolefin plastic film by using a varnish or a polyolefin film or adding a wax, mica, silicone, or a catalyst in a varnish coating process, the respective moisture content is selected. A small method of packaging printed products (substrates) finishes, all of these ways of dealing with this failure have advantages and disadvantages.

(Text / Liu Jiaju)