introductory:
In the field of offset printing, the drying speed of the ink has a key impact on the printing efficiency and quality. Medium speed offset printing inks show unique advantages in many printing scenarios due to their moderate drying characteristics, which not only avoids the low production efficiency caused by too slow drying, but also prevents the printing quality problems caused by too fast drying. The purpose of this program is to comprehensively introduce the characteristics, application scenarios, technical parameters, usage methods and precautions of medium speed adhesive printing inks.
1. Technical parameters
Drying speed
Under the standard printing environment (temperature 25°C, relative humidity 50%), the dry time is 5-10 minutes, and the drying time is 30-60 minutes, which can not only meet the needs of continuous printing, but also have enough time for post-press processing.
Viscosity
At 25°C, the viscosity range is 30 - 50 Pass, which ensures good transferability and uniformity of the ink during the printing process, ensures clear dots and accurate color reproduction.
Fineness
The fineness of the ink particles does not exceed 15μm, which ensures the smoothness and gloss of the printed matter and reduces the printing defects caused by the coarse particles.
Color saturation
Using high-quality pigments, the color saturation is high, and the color reproduction degree can reach more than 90%, which can meet the printing tasks with strict color requirements.
Lightfastness
It has good lightfastness, and the color fading rate is within 10% under sunlight irradiation, which ensures the color stability of the printed matter in long-term display.
2. Application scenarios
Publication printing
Books, magazines and other publications have comprehensive requirements for printing speed and quality. Medium fast drying offset printing ink can ensure clear text and bright colors at the same time, adapt to the production rhythm of high-speed rotary printing machine, improve production efficiency and reduce costs.
Commercial printing
Commercial printed materials such as posters, leaflets, and business cards need to be printed and put into use in a short period of time. The moderate drying speed of medium speed adhesive printing ink makes it dry quickly after printing, which is convenient for subsequent cutting, binding and other processing, and meets the timeliness needs of commercial activities.
Packaging and printing
For some non-food packaging and printing, such as electronic product packaging boxes, daily necessities packaging boxes, etc., medium-speed adhesive printing inks can be quickly dried on the premise of ensuring ink adhesion and wear resistance, and improving the efficiency of packaging production.
3. Ink selection
According to the printing material
Paper, ordinary offset paper can choose medium fast-drying offset printing ink with good versatility; For coated paper with a smoother surface, choose a medium speed offset printing ink with a higher gloss to show better printing results. When printing plastic films, it is necessary to choose medium quick-drying offset printing inks that are specifically for plastic materials to ensure that the ink has good adhesion to the film.
Combined printing process
Standard medium quick-drying offset printing ink can be selected for conventional lithographic offset printing; Waterless offset printing requires the use of special waterless medium-speed offset printing inks to meet the special requirements of waterless printing.
4. Pre-printing preparation
Equipment cleaning and commissioning
Thoroughly clean the ink fountain, ink roller, blanket and other parts of the printing machine to ensure that there is no residual ink and impurities. Debug the printing pressure to ensure that the ink is transferred evenly; Adjust the water-ink balance, and determine the appropriate amount and concentration of dampening solution according to the characteristics of the printing material and ink.
Ink preparation
Accurately mix ink according to the color requirements of the printing order. Use ink stirring equipment to fully stir to evenly disperse pigments and additives to avoid precipitation and affect the printing quality.
Printing material testing: check the flatness, thickness uniformity, surface roughness and other indicators of the paper to ensure that the paper meets the printing requirements. For plastic films, the surface tension is tested to ensure that the surface tension meets the requirements of ink adhesion.
5. Printing process control
Printing pressure control
Fine adjustment of printing pressure according to the thickness and hardness of the printed material. Excessive pressure can easily lead to the expansion of dots and the accumulation of ink; If the pressure is too small, there will be problems such as insufficient ink transfer and false graphics and texts.
Ink and water balance control
Strictly control the amount and concentration of dampening solution. Too much dampening solution will emulsify the ink, reducing color saturation and drying speed; Too little dampening solution will easily cause the layout to become dirty.
Drying control
In the printing process, the temperature and humidity of the printing workshop are reasonably adjusted according to the drying characteristics of the ink and the actual printing situation. Too high a temperature may cause the ink to dry too quickly and produce crystallization; If the temperature is too low, the drying speed will be slower. It is advisable to control the humidity at 50% - 60% to help the ink dry properly.
6. Quality inspection
Drying speed detection
During the printing process, regularly check the drying of the ink to ensure that the drying speed meets the requirements of technical parameters. You can judge whether there is sticky hand phenomenon by touching the surface of the printed matter; It can also be inspected using a special drying speed test equipment.
Color detection
Use spectrophotometer and other equipment to measure the color of the printed matter and compare it with the standard color sample to ensure that the color deviation is within the allowable range.
Printing quality inspection: visually check the clarity and uniformity of the dots of the printed matter, and whether there are problems such as ghosting and pasting. Use a magnifying glass to check the print quality of small text and lines.
7. Storage & Transportation
Storage
Store in a cool, dry, well-ventilated warehouse, away from direct sunlight and high temperatures. The storage temperature is controlled at 15°C - 25°C, and the relative humidity is 40% - 60%. The ink should be sealed and stored to prevent solvent volatilization and impurities from mixing.
Transportation
Use special means of transport to avoid collisions, crushing and rain. During loading and unloading, handle with care to prevent damage to the package. During transportation, keep the ambient temperature and humidity stable.
8. Precautions
Operator protection
Operators should wear protective gloves, masks and goggles to avoid skin contact and inhalation of volatile gases from ink. The workplace should be well ventilated.
Ink use management
Follow the principle of first-in, first-out, and use ink in strict accordance with the shelf life. Expired ink needs to be tested and can only be used after it is qualified, otherwise it should be properly disposed of.
Environmental management
The printing workshop should be kept clean and the ink residue and waste should be cleaned regularly. Ink-containing wastewater and waste gas should be discharged after treatment to meet the standards to reduce environmental pollution.
9. Recommend products of the same type
Ordinary Economical Offset Ink