Application technology of common solvent ink

1、 Application technology of solvent ink

 （1） Composition of solvent ink

 Solvent ink has many brands, many series, but no matter which series are made up of resin, solvent, pigment, filler (or additives).

The key factors are: 1. Ink resistance to water. Different series of inks have different resins, which are applied to products of different materials and have different ink properties. No ink can be suitable for all materials. Only by selecting the ink with resin composition suitable for the substrate material can the ink be firmly attached to the substrate.

Several resins commonly used in screen printing ink:

Vinly resin;

Acrylic resin;

Polyurethane;

Bad oxygen resin;

Fiber resin;

Alcohol resin;

(1) The main vinly  resin ink (PVA) are derivatives of polyvinyl acetate;

 It is soluble in acetate and ketone solvents; it is commonly used for printing on plastic substrates, such as PVC, ABS, PC and so on。In order to improve the characteristics of ink, it is often mixed with acrylic resin.

Application of printing ink for vinly resin

PVC self adhesive label;

PETG & PC (also suitable for vacuum molding);

3pc & PS, film switch printing;

Decals for motor vehicles;

Plastic and shoe materials;

(2) Main characteristics of acrylic resin inkAcrylic polymer;

Ideal for outdoor use (over 4 years). Acrylic acid (acrylic acid for outdoor use of acrylic resin

Printing with backlight and vacuum forming board;

Adhesion to PMMA and PVC substrate.

(3) Main characteristics of polyurethane resin

 It has excellent outdoor durability (about 3 years): good elasticity; good hardness of ink layer after reaction with isocyanate;

Packaging materials (thermoforming).

2. Solvent: the main liquid substance in ink. Its functions are as follows:

(1) dissolving the resin to make a connecting material to make the ink printable; 

(2) Disperse pigments, dissolve additives, improve the fluidity of ink, ensure the ink mobility during printing;

(3) Viscosity adjustment: in order to achieve the best printing effect, screen printing ink needs to have the appropriate viscosity. Different grades of ink and different printing require different ink viscosity. The viscosity of screen printing ink is about 6000 ~ 12000cp. The unit of viscosity is Pascal · s (PA · s), poise (P), centipoise (CP), millipascal · second (MPA · s);

1Pa·s=10P=1000mPas=1000cP。 At 20 ℃, the viscosity of water is 1cp, and the viscosity of honey is 3000 ~ 4000cp. The viscosity of each series of ink is greater than 10000 CP, so you need to adjust the viscosity with your own solvent before use;

(4) Adjust drying speed: different printing environment requires different drying speed of ink;

(5) On the substrate of the solution penetration, increase adhesion. As the resin of the ink is a mixed resin, the ink is required to have different drying.

Why is the solvent of each series of ink divided into fast, medium and slow?

Because of different printing environment, different substrate and different printing text, the ink should have different drying speed, and the solvent is mainly used to adjust the drying speed of the ink, which requires that the solvent has different volatilization speed, namely, fast, medium and slow. Fast drying solvent is suitable for low temperature environment or large area printing or substrate which is easy to absorb solvent; slow drying solvent is suitable for printing fine stripes or high temperature in summer. The operating environment and drying speed should be fully considered when choosing the solvent.

Pigment: pigment not only gives ink color, but also determines the covering and weather resistance of ink. The size of pigment particles determines the fineness of ink. Pigments are divided into organic pigments and inorganic pigments. Inorganic pigments are metal oxides or inorganic salts, which have good covering power, light resistance and aging resistance. Organic pigments are organic compounds with bright colors and complete chromatograms, but they usually have poor covering power.

4. Additives: additives can improve the physical properties of ink, adjust the proportion of pigment and resin, change the fluidity of ink, affect the brightness of ink, adjust the viscosity of ink, improve the printability of ink, and improve the printing effect. The properties of various auxiliaries used in screen printing ink should be similar to the properties of the ink used, and can be well mixed with the ink. It can not react with other components of the ink, damage the structure of the ink, and can not affect the color, coloring power, adhesion and other basic properties of the ink.

Common additives are: defoamer, dispersant, firming agent, plasticizer, leveling agent, viscosity reducer, anti drying agent, UV absorber, etc.

As can be seen from the above, the ink is composed of four parts. Because the proportion of different components is different, when the ink is stored and transported for a period of time, the components will be layered or separated, resulting in different contents of components in the ink. Do not stir on the use of ink will affect the various properties of the ink, so before use to thoroughly stir, and then add diluent to adjust to the appropriate viscosity and drying speed.

（2） Characteristics of solvent ink

Solvent curing, the formation of solvent film.

2. It is easy to handle and does not need special equipment.

（3） Usage rules of solvent ink

1. Select the appropriate ink according to the material of the substrate;

2. Mix thoroughly before use;

3. Select special solvent, adjust the ink to the appropriate viscosity;

4. Select special auxiliaries to adjust the printability of ink; 

5. Choose solvent with different drying speed according to different printing environment; 

6. The mixing proportion of two-component ink must be correct, and it must be used on the same day of large-scale matching;

7. Color deployment should be accurate;

8. After the ink is completely dried on the substrate, the performance of the ink can be tested;

9. When heating and drying ink, the drying temperature and drying time must be reached;

10. For soft materials, attention should be paid to complete drying to prevent overpressure to avoid adhesion;

11. When printing fine graphics, slow drying solvent should be used and drying time should be prolonged;

12. Due to the diversity of substrate products, before mass production, all kinds of properties of ink should be tested and confirmed before production.