Method of producing cast coated paper

Details Method of producing cast coated paper Method of producing cast coated paper

1984-05-24

1986-04-08

Lusignan, Michael R.

Coating processes

With post-treatment of coating or coating material

Swelling agent or solvent applied to treat coating

427362, 4273742, 4273743, 4273983, B05D 302, B05D 312

Patent

active

045812578

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a method of producing cast coated paper. More particularly, the invention relates to a method of producing cast coated high-gloss paper having substantially no warp or curl at a high speed by a rewet casting method or a gel-casting method.


BACKGROUND ART

Conventional methods of producing cast coated high-gloss paper for printing include a wet casting method adapted to finish a glazed coated layer by pressing the wet state coated layer comprising a mineral pigment and an adhesive on the heated highly polished finishing surface (disclosed, for example, in Japanese Patent Publications Nos. 3407/1953 and 25160/1963), a rewet casting method adapted to once dry a coated layer of wet state, to then plasticize the layer with a rewetting liquid and to press the layer on a heated finishing surface (disclosed, for example, in U.S. Pat. No. 2,759,847, Japanese Patent Publication No. 38,005/1973 and Japanese Patent Laid-open Publication No. 102,111/1976), and a gel-casting method adapted to finish a glazed coated layer by pressing the gel state coated layer on the heated finishing surface (disclosed, for example, in Japanese Patent Publications Nos. 15,751/1963, 7,207/1965, U.S. Pat. No. 3,377,192, Japanese Patent Laid-open Publications Nos. 40,410/1976 and 51,896/1982).
In any of these conventional casting methods, coating composition containing as main components, a mineral pigment and an adhesive is applied to a paper web, the wet and plasticized coating layer on paper web is pressed against the heated highly polished finishing surface of the drum by means of a press roll at a pressure higher than the vapor pressure of water, dried, and released from the drum. However, in the wet casting method, the coated layer is frequently damaged due to abrupt evaporation of water when the paper is pressed against the surface of the drum at a temperature of higher than 90.degree. C. As a result, if the pressing pressure is made considerably higher than the vapor pressure in order to prevent the coated layer from being damaged, it is impossible to maintain a sufficient amount of coating composition on the paper web, and a breakage or crack of paper sometimes occurs. Thus, in the conventional wet casting method, the temperature of the drum cannot be raised higher than 90.degree. C., and the operation has to be made at a low speed.
U.S. Patent No. 2,316,202 discloses a wet casting method using a backing roll, in which method a water pool is retained between a pressing roll having a plane(smooth) surface and the backing roll, thereby cleaning and removing coating composition adhered to the pressing roll. However, since this method prevents the transfer of water to the paper by the nip pressure of the pressing and backing rolls, the paper cannot be wetted. In Canadian Patent No. 888,099, a pressing roll is brought into contact with the wet surface of a roll to clean the surface of the pressing roll, and the back surface of the paper is wetted by the water adhered to the pressing roll, so as to ensure the intimate contact of the paper with the surface of the drum. However, since the surface of the pressing roll is plane in this art, the back surface of the paper cannot be wetted to such a degree as intended by this invention.
On the other hand, in conventional rewet casting method and gel-casting method, the coated layer before being pressed against the highly polished surface of the drum is once dried and gelled. Thus, the coated layer is not damaged as in the wet casting method even if the layer is pressed at a high pressure by the drum heated at a temperature higher than 90.degree. C. Therefore, a cast coated paper of high quality can be produced at a high speed. However, the cast coated paper thus obtained by the high temperature and high pressure casting method forms, after being released from the surface of the drum, a curl such that the paper is curled with the cross direction of the paper as the axis of the curl, the high-gloss cast finished surface being on the outside of the curl

REFERENCES:
patent: 2316202 (1943-04-01), Warner
patent: 2759847 (1956-08-01), Frost et al.
patent: 3377192 (1968-04-01), Kirk et al.
patent: 3676184 (1972-07-01), Spearin et al.
patent: 3982056 (1976-09-01), Holder
Takashi, Kadoya et al., Paper Science, p. 267, Line 14 to p. 269, Line 1, Nov. 25, 1977.

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