Process for making a printing paper with binder mixtures for pap

Details Process for making a printing paper with binder mixtures for pap Process for making a printing paper with binder mixtures for pap

1996-03-29

1998-12-08

Chin, Peter

Paper making and fiber liberation

Processes and products

With coating after drying

1621647, 1621681, 427121, D21H 1116, D21H 1928

Patent

active

058463810

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to the use of papers, which are coated with a paper coating slip based on a binder containing esters of methacrylic acid with C.sub.4 -C.sub.12 -alkanols, having a glass transition temperature of from -80.degree. to +25.degree. C., and weights being based on the sum A)+B), said paper being used for offset printing.
In offset printing on coated papers, the problem of nonuniformity of the print, which is specific to this printing process, frequently occurs and is referred to in the trade as mottling. It is still one of the unsolved problems in this area and occupies both paper manufacturers and printers. This phenomenon is an effect which occurs especially in multicolor offset printing in halftones and appears as a sort of cloudiness in the perceived color. The nonuniformity in the print is very evidently due to the fact that the printing ink is more readily accepted in some parts of the paper and less readily in other parts.
The causes of this nonuniform ink acceptance are still not clearly understood today.
The reasons why a better understanding of this phenomenon has not been achieved to date in spite of intensive efforts certainly relate on the one hand to the complicated process of offset printing and, on the other hand, to the structure of paper as printing material, which is no less complicated.
In addition to optimizing the properties of the paper and the printing ink, these components must both be tailored to one another and adapted to the offset printing process.
From the point of view of the paper manufacturer, not only do process engineering parameters in the paper coating process have a major influence in the case of the coated papers, but the physicochemical properties of the coating components also play a decisive role here. The binders used in the coating slips are particularly important.
In addition to natural products, such as starch, predominantly polymer emulsions based on styrene and butadiene or styrene and acrylates are used as binders for paper coating slips.
It is known that there is substantially higher tendency to mottling when binders based on butadiene (co)polymers, for example styrene/butadiene copolymers, are used for coated offset papers, in comparison with acrylate (co)polymers, such as styrene/acrylate copolymers.
It is also known that emulsions based on styrene/butadiene can be mixed with acrylate emulsions.
2. Description of Related Art
Japanese Preliminary Published Application 90/169 800 describes latex mixtures for paper coating comprising butadiene copolymers and acrylate copolymers, which are said to result in homogeneous printing ink acceptance in the paper coat. The latex mixtures (contain acrylate copolymers having an alkyl acrylate content of from 20 to 50% by weight and a minimum film formation temperature of from 35.degree. to 80.degree. C.
Japanese Preliminary Published Application 82/191 392 discloses polymer blends for paper coating which consist of a butadiene copolymer and an acrylonitrile copolymer and give the coated paper high print gloss.
Furthermore, EP-A 099 792 discloses aqueous polymer emulsions containing a mixture of butadiene/styrene copolymers and acrylates with C.sub.1 -C.sub.8 -alkanols, and the use thereof in adhesives.
Japanese Preliminary Published Application 63-27579 from the year 1988 discloses binders for paper coating slips, which contain copolymers A) and B) of the type defined above. The papers coated in this manner are suitable for the gravure printing process. However, the gravure printing process differs in principle from the offset printing process and consequently the requirements for the paper and paper coating slips also differ. In the offset printing process, the printing and nonprinting parts of the printing plate are in one plane. When the printing plate is inked, use is made of the incompatibility of the printing inks with water (damping of the nonprinting parts). The paper to be printed is therefore exposed to a printing ink/water system,

REFERENCES:
patent: 4064304 (1977-12-01), Fujita et al.
patent: 4092457 (1978-05-01), Fujita et al.
patent: 4245689 (1981-01-01), Grard et al.
patent: 4503184 (1985-03-01), Marongiu
patent: 5500191 (1996-03-01), DeMatte

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