A low-temperature curing environmental protection varnish for iron printing

Abstract

The invention discloses a low-temperature setting environment-friendly overprinting varnish for metal printing. The overprinting varnish comprises, by weight, 55-65 parts of saturated polyester, 4-5 parts of partial methoxylation melamino-formaldehyde resin, 6-8 parts of phenylated melamino-formaldehyde resin, 0.3-0.4 part of flatting agent, 0.5-0.6 part of closed acid drier, 0.3-0.8 part of wax liquor, 0.1-0.3 part of brightener, 0.7-1 part of adhesion promoter and 20-25 parts of environment-friendly solvent; the T-4 cup viscosity of the saturated polyester is 60-80 s, the acid value of the saturated polyester is 2-4 mg KOH / g, the solid content of the saturated polyester is 55-60wt%, the glass transition temperature of the saturated polyester is 40-50 DEG C, and the average molecular weight of the saturated polyester ranges from 4000 to 6000 Da. Compared with the prior art, the environment-friendly overprinting varnish can be set at the low temperature of 125-130 DEG C, the setting time is only 8-10 min, original good performance of the overprinting varnish can be kept without yellowing, roller painting is used as the construction mode, construction is convenient, energy consumption is reduced, and the overprinting varnish is low-carbon, environmentally friendly and good in performance.

Description

technical field [0001] The invention relates to the technical field of iron printing coatings, in particular to a low-temperature-cured environmental-friendly varnish for iron printing. Background technique [0002] Iron printing coatings are commonly used in the field of iron printing packaging, such as moon cake boxes, tea cans, milk powder cans, etc. of various iron cans. Most of the iron printing coatings are cured at high temperature, and are applied to the metal surface by printing or roller coating, and then heated and baked. It cross-links and solidifies to form a tough coating film. Varnish coating is a kind of iron printing coating. It is widely used on the surface of iron coating because of its high hardness and high gloss. It improves the aesthetic effect and scratch resistance of the product, and is beautiful and practical. However, most of the current varnish coatings are cured at high temperature, usually baked and cured at 160-180 degrees Celsius, and the cu...

AI Technical Summary

Problems solved by technology

However, most of the current varnish coatings are cured at high temperature, usually baked and cured at 160-180 degrees Celsius, and the curing time is about 20 minutes, and the way to provide heat is usually gas or coal, which consumes a lot of energy and causes air pollution; Secondly, most of the varnishes currently in use contain some harmful substances such as bisphenol A, organotin, and heavy metals, which are harmful to the human body to varying degrees.

Therefore, the use of such products in the food packaging industry has been restricted both at home and abroad; moreover, varnish is usually used on the surface layer of the product coating, and finally printed. If the baking temperature is too high, it is easy to cause thermal expansion of the cured coating. Cause coating cracking or yellowing, product damage or direct scrapping

[0003] In addition, low-temperature coatings generally have insufficient curing. For varnishes, the curing is insufficient, the surface becomes soft, the scratch resistance deteriorates, and the original excellent performance of varnish is lost; The adhesion between finished products or the adhesion between finished products and packaging materials brings many problems to post-processing, packaging and transportation

Another example of existing patented technology is that the patent of publication number CN102719159A discloses an environment-friendly low-temperature curing varnish coating, which can be cured at 110-120 degrees Celsius, and the curing time is 20 minutes. The resin used is an acrylic resin. The obtained varnish has good hardness and gloss, but it is not conducive to post-processing. The construction method of this varnish is electrostatic painting, which cannot be applied to the field with post-processing. The curing time is 20 minutes, and the curing time is too long. Production less efficient

Another example is CN102408783A patent which discloses a low-temperature curing coating, which is composed of vinyl acetate resin, polyurethane resin, amino group and other additives, and can be cured at low temperature, but does not point out the baking temperature and time, application field and construction of the coating from beginning to end. method, and vinyl acetate resin has defects such as low surface gloss and easy whitening in humid and low temperature environment