Development and application of fluorescent anti-co

Development and application technology of fluorescent anti-counterfeiting ink for plastic packaging (Part I)

1. Screening of binder

binder is a fluid component in ink, which is responsible for connecting solid powder substances such as pigments, forming paste colloid after grinding and dispersing, and drying and fixing on the surface of substrate after printing. The rheology, viscosity, viscosity, dryness and printability of ink mainly depend on the performance of binder. Therefore, to get high-quality inks, we should first produce high-quality binders

the commonly used binder resins for plastic printing inks are mainly polyamide resin and acrylic resin

1) polyamide resin

polyamide resin, commonly known as nylon, is formed by the condensation of polybasic acid and polyamine, in which the linear polyamide resin generated by the condensation reaction of binary amine and binary acid is the basis of polyamide resin reaction

polyamide resins can be divided into reactive and non reactive types. Reactive polyamide resin is liquid or semi-solid, and bisphenol A epoxy resin must be added before it becomes solid. Non reactive polyamide resin is a thermoplastic resin, which can decompose into films. Non reactive polyamide resin is mainly used to make printing ink. The plastic gravure printing ink prepared with it is printed on the price. We have also achieved the concept of relative quality and price. Brushing plastic film has strong adhesion and good dryness, but the cost is high and the solubility is poor. Most polyamide resins are insoluble in ethanol, but only soluble in mixed solvents prepared with toluene, xylene, isopropanol, ethanol, etc., and such resins often freeze at low temperatures, affecting the mixing performance and printability of inks. Therefore, improving the solubility of polyamide resin and overcoming the phenomenon of resin freezing are the future research and development direction

alcohol soluble poly control reaction slow amide resin is light yellow in appearance, bright and transparent, with acid value less than 6, amine value less than 5, softening point 107 ± 3 ℃, mixed with 30% alcohol ester solution, which can be stirred and dissolved at room temperature. At 25 ℃, the viscosity is 25 ~ 50MPa · s, which is suitable for high-speed gravure printing and flexographic printing

2) acrylic resin

acrylic resin is condensed from ethylene polymers. Acrylic acid and its derivatives have unsaturated double bonds, high activity, and are very easy to polymerize to form high molecular weight thermoplastic resin. The copolymers of acrylic acid and other substances have different forms, such as solid, liquid and latex. The inks made with it have the advantages of brightness, transparency, strong adhesion, hard conjunctiva, friction resistance and so on. Its disadvantage is the high price. With the development of UV curable inks and UV curable coatings, which can be roughly divided into pendulum tensile testing machine and electronic tensile testing machine, the consumption of acrylic resin in the ink manufacturing industry will also show an upward trend, said Pan Xuezhu, deputy general manager of Guangya aluminum group

after repeated research and analysis, it is finally decided to use non reactive polyamide resin as the binder resin of this ink, and modify the binder resin by adding several additives selected by experiments to the binder, so as to improve the mixing of binder and fluorescent pigment and its adhesion to the surface of plastic film

2. solvent screening

common solvents for plastic gravure printing inks include isopropanol, toluene, xylene, n-butanol, ethanol, ethyl acetate, etc

solvent is an important component of plastic gravure printing ink, which has solubility and volatility. Its volatility speed is an important factor determining the drying speed and printing quality of volatile printing ink. If the solvent volatilizes slowly, the reproducibility of the printed image is good, but if the volatilization speed is too slow and it fails to volatilize completely on the printed matter, the ink layer is prone to adhesion; On the contrary, if the solvent in the ink volatilizes too fast in the printing process, the ink will turn white, stick to the roller and other phenomena, and there is a hidden trouble of ink layer sticking back. Therefore, the choice of solvent is very important. The following factors should be considered when choosing the solvent for plastic ink:

1) the speed of the printing machine. The higher the speed of the printing machine, the faster the evaporation speed of the solvent is required

2) structure of drying system

3) characteristics of printing materials

4) indoor temperature and relative humidity

5) ensure that the solvent does not corrode the printing plate

6) good solubility, free of any mechanical impurities, free acids, bases and moisture

7) cannot react with other components in the ink

8) the odor is small, the toxicity is small, and the volatile matter should meet the environmental protection requirements; The ink used for food packaging and printing should reach the actual non-toxic level

9) stable storage, no decomposition, no moisture absorption

10) low price and abundant resources