US2360825A - Coating paper - Google Patents

Description

Patented Oct. 2 4, 1944 I COATING PAPER Philip S. Blickcns derl'er, Hamilton, Qhio, assignor to The Champion Paper and Fibre Company, Hamilton, Ohio. a corporation of Ohio No Drawing. Application December 18, 1942,

Serial No. 469,745

.6 Claims.

This invention relatesto the manufacture of cast-surfaced coated paper. with aqueous coatings, on continuously moving casting surfaces such as endless metal belts or rotating drums.

In the manufacture of cast-surfaced coated paper on such belts or drums, it has been found that coating material tends to spread beyond the edges of the paper web and contaminate the casting surface. In the continuous coating and casting process the same section of the casting drum or belt passes the same point many times and it has been found that where the coating is on the paper it is removed from the casting surface before fresh coating is applied but that beyond the edges of the paper web there is nothing to remove even the relatively small amounts of coating which get on the surface and that this coating therefore tends to build up and become tightly adherent to the casting surface, fouling the surface, renderin it unfit for use, and causing serious difficulties when the web shifts laterally or a wider web is to be coated. 'Such accumulations of coating material on the casting surface beyond the edges of the paper web also damage the press rolls, reduce the speed at which it is possible to operate, and otherwise interfere with the coating and casting operations so thatv in the practice of the process it has been found that a very considerable part of the running time was lost by shut-downs for the purpos -of cleaning the edges of the casting surface.

The primary object of the present invention is therefore to prevent the large losses of running time heretofore required for cleaning the edges of the casting surfaces, by providing a method of preventing the building up of adherent deposits of coating materials, etc. on the casting surface beyond the edges of the paper web. Another object is to make possible sustained operation at higher speeds than are otherwise possible. An allied object of the invention is to provide a continuous process for maintaining the condition of the casting surface beyond the edges of the paper web during the operation of coat- 1 ing and casting continuous webs of paper. Other objects and advantages of the invention will be apparent from the following description.

Washing of the surfaces with water, I have found, is inadequate, as the coating compositions used adhere too tenaciously to the casting surface. Application of oil films to these portions of the casting surface was tried. on the theory that" the coating material would not adhere to an oiled surface, but the oil was found to saturate the coating material and render it water-repellant so that it could not even be wetted by the washing water, and the cleaning operation'accordingly became even more difficult than before.

I have now found it possible to accomplish the aforesaid objects and continuously maintain the condition of the casting surface beyond the edges of the paper web by a series of operations, as follows: First, an extremely thin film of a watersoluble oil, advantageously. in a rather dilute solution e.. g. 5 to 10 per cent, is applied to said portionsof the clean casting surface by any convenient method as by an atomizing spray. Thereafter the travel of thecasting surface with its oil-coated edges brings it to the place where the coating and paper are pressed onto the casting surface and greater or lesser amounts of coating are incidentally deposited on the oiled casting surface beyond the edges of the paper, web. Substantially immediately thereafter these parts of the surface are washed by a forcible water spray which removes or floats most if not all of the coatin material from the oil film. The water carrying the coating material and some of the oil film is then removed from the surface by a suitable air jet.

I have found .that soluble calcium or magneslum salts constituting hardness" in this wash water, react with the sulphonated oils used, to form gummy insoluble compounds. Even if completely soft water isused, the trouble is not ordinarily avoided, because of the usual presence of calciumor magnesium salts in the coating materials themselves. When trouble from such sticky and gummy compounds is encountered, I prefer to follow the washing and blowing operations by a series of steam jets directed at an angle against the surface tending to blow the defits laterally off of the edges of the casting ace. The hot moisture of the steam jets tends to soften these deposits so that they are blown ofi of the surface by the jets. Even in cases where the jets, due to imprope adjustment or to other cause, may not serve to maintain absolute cleanliness of these parts of the casting surface, the deposits are slnall in amount and relatively soft and nonadherent so that they may be readily wiped from the surface without the necessity of the long shut-downs heretofore required for cleaning the edges of the casting surfaces. After passing the steam jets, the surface again passes under the atomizing oil sprays, which preferably apply a solution of the oil in distilled or soft water, and the described process is repeated. The operations are advantageously continuous,

and when once adjusted are substantially automatic, requiring little or no attention from the operators.

The oil used should, as hereinbefore noted, he

water soluble. Oils yielding solutions having detergent properties) are particularly useful in maintaining the cleanliness of the surface. Sulphonated vegetable oils have been found to answer: the requirements, sulphonated castor oil having been used with particularly good eflect. It has further been found advantageous in many cases to use a sulphonated oil neutralized with ammonia rather than one neutralized with other alkali. Oils having impurities, such as gums or resins, which tend to accumulate and build up insoluble deposits on the surface should be avoided. If hard water or coatings containing soluble calcium or magnesium are to be used, it is desirable to choose anoil of which the calcium and magnesium soaps are susceptible to solution or softening by the heat and moisture of the steam jets used.

The casting surfaces are ordinarily of metal, though the present process is also useful when non-metallic casting surfaces are employed, so long as oils are used which are compatible with the material of the casting surface.

The process when carried out as described serves to keepv the casting surfacebeyond the edges of the paper web, free from accumulations of coating materials. I have found that it will also serve, when properly adjusted, to free the surface fromaccumulations of coating material which may have been allowed to build up due to the cleaning process being out of service or to other causes.

In accordance with the present invention the paper coating and casting processes can be operated continuously for much longer periods and at higher speeds than heretofore without the necessity for the frequent protracted shut-downsformerly found necessary.

I claim:

1. In the manufacture of cast surfaced coated paper by hardening an aqueous coating on a 'moving web of paper'in intimate contact with a continuously moving casting surface, the meth-- d of maintaining the condition of the casting surface beyond the edges of the paper web, which comprises maintaining on said portions, of the casting'surface a film of water-soluble oil and continuously washing from said him any coating material which may be deposited thereon.

2. In the manufacture of cast surfaced coated paper by hardening an aqueous coating on a moving web of pa r in intimate contact with a con- 7 'tinuously moving casting surface, the method of maintaining the condition of the casting surface beyond the edges of the paper web, which comprises continuously applying a film of sulphonated vegetable oil to said portions of the mov-- ing; casting surface, then at a location after the possibility of contamination of the surface with coating material continuously washing said portions of the casting surface with water.

3. The method of claim 2 in which the oil used is sulphonated castor oil.

4. In the manufacture of cast surfaced coated paper by hardening an aqueous coating on a moving web of paper in intimate contact with a continuously moving casting surface, the method of maintaining the condition of the casting surface beyond the edges of the paper web, which coniprises continuously applying a layer of sulphonated vegetable oil to said portions of the moving casting surface, then at a location after the possibility of contamination of the surface with coating material, continuously washing said'portions of the casting surface with water, and blowing the water from said portions of the surface. 5. The method of claim 4 in which the oil used is sulphonated castor oil.

6. In the manufacture of-cast surfaced coated paper by hardening an, aqueous coating on a moving web' of paper in intimate contact with a continuously moving casting surface, the method of I maintaining the condition of the casting surface beyond the edges of the paper web, which compris s continuously applying water-soluble oil to said portions .of the moving casting surface, then at a location after the possibility of contamination of the surface with coating material, continuously-washing said portions of the castin surface with water, blowing the water from said portions of the surface, and thereafter directin steam jets against'said surface at an angle directed away from the edges of the paper web thereon.-

PmLI'Ps. BLICKENSDERFER.