3. Offset printing ink for web printing
In the past, the popularity of waterless offset printing on webs has been slow due to the lack of print force and printing ink hiding power of waterless offset printing plates. However, recently, due to the increase in the strength of the non-image portion of the silicone layer, in Japan, more than 20 web offset presses have been converted to waterless offset presses.
In order to cope with the high-speed production of web offset printing presses, inks need to have low viscosity and high fluidity that are resistant to high speed printing, in order to obtain good ink transferability, ink receptivity, and dryness, and to prevent ink stains. One of the most notable technologies is the self-adhesive resin technology led by Japan.
Since the self-adhesive resin has a large molecular weight and a large number of cross-linking points between molecules, it is not necessary to use a metal chelate gelator to obtain a binder having a strong gelling elasticity. The ink using such a binder has lower viscosity than the ink using a resin binder, and thus can maintain high speed while avoiding paper fluffing. In addition, its viscoelasticity is less affected by the temperature, which can reduce the dirt problem caused by the rise in the temperature of the printing press during the long live printing, and shows the superiority of high-speed printing. The aromatic-free inks using these resins have been used in production and will undoubtedly promote the development of web-free offset printing.
4.UV waterless offset ink develops to low viscosity
UV waterless offset inks are characterized by a fast drying and strong dry ink film. Similarly, UV-curing inks have also been improved from high-viscosity type to low-viscosity type, and they are expanding into the field of film printing (PP, PE, PVC, PS, synthetic paper, telephone cards, etc.) after satisfying paper printing.
Fully develop aromatic-free inks
The composition of the waterless offset ink is the same as that of a water offset ink, which is prepared by dispersing rosin modified phenol resin, drying oil, petroleum solvent, coloring material and the like into a binder. After satisfying various printability requirements for waterless offset printing, environmental protection safety has been an important issue in the manufacture of waterless offset inks for the sake of environmental protection.
The following will describe in detail the research and development of aromatic-free petroleum solvents and 100% non-aromatic anhydrous offset inks.
1. Stability and characteristics of aromatic-free solvents
Petroleum solvents contain aromatic components, which are the cause of odors and irritations to the skin. In this regard, inks containing no aromatic solvents (AF) have greatly improved in this respect. The so-called aromatic-free solvent is one in which the aromatic component in the solvent is controlled to be 1% or less. Table 5 shows the performance comparison between the petroleum hydrocarbon solvent (No. solvent) for the original ink manufactured by Japan Oil Corporation and the aromatic-free solvent.
As can be seen from the table, the aromatic-free solvent has a narrower distillation range and a higher aniline point than the No. solvent. From the aspect of components, the No. solvent contains more alkane components and aromatic components, and aromatic solvents are not included. The aromatic components are mainly composed of cyclic hydrocarbons obtained after the addition of hydrogen, and the content of aromatic components is even greater. micro. In addition, the alkane, naphthene, and aromatic components contained in the solvent should have the general structure shown in FIG. 4 .
2. Develop sheet-free water-free offset inks that contain no aromatic solvents
The ink containing no aromatic hydrocarbon solvent is higher in safety than the ink using a petroleum solvent, but the aniline point is also high and the solubility to the resin is deteriorated. The aniline point is the temperature at which white turbidity occurs when the solvent and the aniline are mixed in an equal volume, and the solvent having a low aniline point has a strong ability to dissolve the resin.