Alcohol-based solvents play a crucial role in the printing industry, particularly in gravure and flexographic printing.
These solvents are essential for dissolving various resins and inks and are chosen based on their volatility, solubility, and chemical properties.
Here's an overview of some commonly used alcohol-based solvents in the printing industry:
1. Methylated Spirits (Ethanol)
Name Methylated spirits (Ethanol)
CAS No. 64-17-5
Description
Composed of ethanol and water, with a small percentage of methyl alcohol.
Used
Widely used in gravure and flexographic inks.
Volatility
The fastest drying alcohol among all alcohols.
Other Information
Proof spirit contains 57.1% alcohol by volume (49.3% by weight) and has a relative density of 0.92 at 15.68°C (60.8°F).
Methylated spirits 64 op (density 0.821) contains 9.7% by weight of water.
Methylated spirits 74 op IMS (density 0.797) contains 1.4% water.
2. Normal Propanol (n-propyl alcohol)
Name Normal propanol (n-propyl alcohol)
CAS No. 71-23-8
Description
A highly pure solvent with a sweet distinctive odor. Miscible with water and has a higher boiling point compared to methyl alcohol or isopropanol.
Used
Widely used in gravure and flexographic inks, stamp printing varnishes.
Partial to good solvent for polyamides.
Volatility
More stable than methyl alcohol or isopropanol.
3. Isopropanol (Isopropyl Alcohol)
Name Isopropanol (isopropyl alcohol or secondary propyl alcohol)
CAS No. 67-63-6
Description
A colorless alcohol C3H7OH with chemical and solvent properties similar to ethyl alcohol.
It has two concentrations: 99.7% with a boiling point of 82.38°C and 87% with a boiling point of 80.38°C.
Used
Used as a latent solvent in conjunction with ketones and esters in nitrocellulose lacquers.
A solvent for many natural and synthetic resins including ester gum, rosin, shellac, ethyl cellulose, alcohol-soluble phenolics, amine resins, polyvinyl acetate, and polyvinyl butyral.
Volatility
More stable than methyl alcohol but less than normal propanol.
4. Normal Butanol (n-butyl alcohol)
Name Normal butanol (n-butyl alcohol)
CAS No. 71-36-3
Description
A high-purity solvent that evaporates slowly, with excellent solubility strength but with a lingering odor more than n-propanol or isopropanol, preventing its use in food packaging inks.
Used
Used in metal coatings, some gravure and screen compositions.
Widely used as a latent solvent in nitrocellulose papers and acrylic varnishes.
Volatility
Evaporates slowly.
Other Information
KB stands for "Kauri Butanol Value," a term used to describe the cohesion or durability of varnish.
It is used to measure the resistance of varnish to scratches, corrosion, and peeling.
A higher KB value indicates a more durable and cohesive varnish, while a lower value indicates less durability.
5. Cyclohexanol
Name Cyclohexanol
CAS No. 108-93-0
Description
A slightly oily liquid with a strong but not objectionable odor.
It has somewhat elevated boiling and boiling ranges.
Used
Used as a solvent for cellulose ethers, ester gum, shellac, low viscosity silicones, and polyvinyl chloride.
Limited use in screen inks. It blends with oils and hydrocarbon solvents.
6. Methyl Cyclohexanol
Name Methyl cyclohexanol
CAS No. 583-59-5
Description
An oily liquid with an odor similar to cyclohexanol.
Its solvency strength is less than that of cyclohexanol for the mentioned resins.
Used
Limited use in ink manufacturing in the same manner.
Conclusion
The choice of solvent in the printing industry is crucial for achieving the desired printing quality and performance.
Each solvent has its unique properties in terms of volatility, solubility, and chemical interaction with inks and resins.
Understanding these properties helps in selecting the appropriate solvent for specific printing applications, ensuring optimal results in terms of drying time, print quality, and durability.