Production of prints by the offset heatset process

Details Production of prints by the offset heatset process Production of prints by the offset heatset process

1996-07-31

1999-03-02

Yoon, Tae

Printing

Processes

With heating or cooling

101491, 101492, 106 3162, 523161, 524277, 524489, C09D 1112, B41L 3514, B41F 702

Patent

active

058757201

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to an improved process for the production of prints by the offset heatset process using a printing ink, preferably based on mineral oil, and using an agent for increasing the abrasion resistance of the print. The present invention furthermore relates to certain novel printing inks which are suitable for offset heatset printing, and to oxidized polyethylene having a certain specification.
Offset printing and the printing inks based on mineral oil that are used for this purpose are known in general terms. In addition to pigments, the binder and the mineral oil diluent, these printing inks usually also contain auxiliaries for simplifying the printing operation, increasing the stability of the printing ink and improving the quality of the resultant prints, including, in particular, additives for increasing the abrasion resistance of the prints.
In offset printing technology, there are various methods of drying the printed papers. In the coldset process, in which the print is allowed to dry at room temperature, the abrasion resistance of the prints is increased principally using waxes and wax-like olefin polymers, such as waxlike unoxidized polyethylene.
In the heatset process, in which the printed paper webs are briefly heated to from about 80.degree. to 200.degree. C. in order to set the print, these waxes are, however, unsuitable since they melt and/ or dissolve during this thermal treatment and thus lose the desired action. Use is therefore made of high-melting, wax-like polymers made from fluorinated olefins, in particular polytetrafluoroethylene waxes or mixtures thereof with other natural or synthetic waxes. However, these substances are expensive and have the disadvantage that hydrogen fluoride and volatile organofluorine compounds are liberated when the printed paper is burnt.
DE-A 25 47 967 discloses the addition of finely divided oxidized polyethylene in order to improve printing inks for intaglio, but not for improving offset heatset printing inks based on mineral oil. EP-A 324 077 mentions oxidized polyolefin waxes as additives for intaglio inks.
JP-B 62911/93 recommends the addition of various finely divided resins having a spherical shape, for example nylon, silicone, vinyl, epoxy, olefin and styrene resins, natural waxes, paraffin waxes, polyolefins and general oxidation products of these resins, to offset heatset printing inks.
It is an object of the present invention to improve, in an economical manner, the abrasion resistance of prints produced by offset heatset printing.
We have found that this object is achieved by a process for the production of prints by the offset heatset process using a printing ink based on mineral oil and additionally using an agent for increasing the abrasion resistance of the prints, which comprises using a finely divided oxidized olefin polymer which has an acid number of from 5 to 50 mg of KOH/g of polymer, measured in accordance with DGF M-IV 2 (57), and a melt viscosity of from 100 to 15,000 mm.sup.2 /s, measured in accordance with DGF M-III 8 (75).
Novel printing inks which are suitable for said purpose, and oxidized polyethylene having a certain new specification have furthermore been found.
The oxidized polyolefin waxes as defined, referred to as oxidized waxes below, are known in general terms, some being commercially available and the remainder being obtainable in a known manner, for example by oxidizing the parent olefin polymers in aqueous dispersion using air, as described in greater detail in, for example, DE-A 15 70 652.
Suitable olefin polymers on which the oxidized waxes are based are, in particular: permeation chromatography) in the range from 100,000 to 10,000,000 g/mol, including low- and medium-density polyethylene (LLDPE, LDPE and MDPE), in particular high-density polyethylene (HDPE), ie. having a density of greater than 0.94 g/cm.sup.3, molecular weight in the range from 70,000 to 500,000 g/mol, 10,000,000 comprising from 0.1 to 99.9 mol % of ethylene and from 99.0 to 0.1 mol % of a C.sub.3 - to C.sub.8 -alk-1-ene,

REFERENCES:
patent: Re35229 (1996-05-01), Blanch et al.
patent: 3330684 (1967-07-01), Wheeler
patent: 4338230 (1982-07-01), Ames
JP 05062911--Chem. Abstrst, Sep. 1993.

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