US 2673799 A
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Patented Mar. 30, 1954 UNITED STATES I'PATLENT OFFICE z-Milton ,0. Schur,Asheville, and Robert M. Levy, Brevard, N. ,C., assignorsto :Ecusta Paper Corporation, a corporation of Delaware No Drawing. Original application November'9,
1951, Serial'No. 255,733. Divided'and this ap- :tplication September 25, 1952, Serial No. 316,804
it has not been uncommon for a cigarette to produce black, curling ashes that fall from the cigarette onto the sm'okers clothing.
In the applicationof RobinsonE. Matthews and Ward D. Harrison, Serial No. 162,402, filed May 16, 1950,now Patent No. 2,580,568, there is disclosed a cigarette paper having the abovementioned desirable ashingproperties, which are obtained by incorporating in the paper approximately 0.1% to 1% of ammonium phosphate.
We have found that it is'important to maintain the ammonium phosphate as such, that is, to prevent its decomposition or reaction with the calcium carbonate filler or free lime in the paper.
.If it is allowed to react with the filler or with the free lime its original property of efiecting the above desired type of ash is greatly reduced or entirely lost, depending upon the extent of the reaction. The ammonium phosphate reacts very slowly with the calcium carbonate form of filler because of the lowsolubility of the latter in water, but will react readily with the free lime, calcium hydroxide, content of the filler which may be present originally "or is produced byhydrolysis of the calcium carbonate.
This hydrolysis and the succeeding reaction of the ammonium phosphate with the calcium hydroxide content is likely to take place during the manufacture of the cigarette paper, particularly The moisture and phate and the calcium hydroxide, namely, incorporating in the cigarette paper sheet, by means of a size press or applicator roll, a small amount of water, which-neutralizes the free lime or calcium hydroxide and thereby prevents it from reacting with the ammonium phosphate. As a result, the ammonium phosphate is maintained as such and produces the desired 'ashing properties in the paper. Practical disadvantages to the use of the. phosphoric acid, as above described are the corrosive effect of the dilute solution on the equipment, e. g., pipe, tanks and pump parts, and the formation of calcium phosphate scale on the drier rolls following the point of application of the ammonium phosphate and phosphoric acid solutions. This is especially true when these chemicals are added by. means of an applicator roll at the press section of thepaper machine because of'the relatively higher concentrationof ammonium phosphate required and the larger amount of water in the cigarette paper sheet after theapplicator roll, as compared with conventional size press application.
In accordance with the present invention, we obtain the desirable effect on the ashing properties of the paper with ammonium phosphate and at the same time avoid the above described operational disadvantages attendant to the use of phosphoric acid. We accomplish this result by incorporating in the filler or in the paper furnish, a small amount of magnesium carbonate which neutralizes .the calcium carbonate'content of the filler and prevents its reaction with the am- "monium phosphate. Apparently the magnesium carbonate reacts with the small amount of free calciumhydroxide. presentin the calcium carbonate, to form magnesium hydroxide and calcium carbonate, thus:
"The 'insolublecalcium carbonate thus formed simply adds to the supply of calcium carbonate filler and the very insoluble magnesium hydroxide is likewise retained as a small adjunct to the original supply of filler with the net result of almost complete reduction of the alkalinity of the system.
As to the amount of the magnesium carbonate to be used in accordance with this invention, it may vary upward from a relatively minute minimum, such as 0.5% based on the weight of filler or 0.1% based on weight of paper. In usual commercial practice the amount of magnesium carbonate used would fall within the range of approximately 0.5% to 2% based on the weight of filler, and a typical percentage used would be 1% for the normal type of precipitated calcium Example I To a paper machine chest containing refined cigarette paper pulp at a consistency of about 2.5% there is added 11 pounds of magnesium carbonate to 80 cubic meters of stock volume in the chest. The stock is then pumped to the J ordan, following which there is added the regular calcium carbonate in th form of a slurry. The
pulp-filler furnish is run over the paper machine in the conventional manner, and the ammonium phosphate is applied to the sheet either by an applicator roll or a size press.
Example 11 Magnesium carbonate is added to the furnish just prior to the paper machine as a 0.5 lb./gal. slurry in water at the rate of ZBO/mL/min. when the paper machine is running at a speed to give lb. cigarette paper per minute. The'paper sheet; is formed and the ammonium phosphate applied a in Example I above.
When the ammonium phosphate solution is applied to the wet paper web containing cellulose fiber and calcium carbonate filler, and no magnesium carbonate is present, the ammonium phosphate appears to decompose by reacting, in the presence of moisture, with the free calcium hydroxide to form calcium phosphate and liberate ammonia. The calcium phosphate does not have the property of producing the desirable type of cigarette paper ash above described. Thus, it is important to prevent the decomposition of the ammonium phosphatewhich results in formation of calcium phosphateand to preserve the ammonium phosphate for controlling the cigarette paper ash. This we have accomplished by use of the minute amount of magnesium carbonate which apparently functions as above described to neutralize the free calcium hydroxide content of the calcium carbonate and prevent it from reacting with the ammonium phosphate.
The filler commonly used in cigarette paper to regulate the porosity, and hence the rate at which it burns on the cigarette, is calcium carbonate. It is ordinarily added to the fiax or other cellulosic pulp furnish in an amount suflicient to give a fillercontent of about %-25% in the finished paper, and it constitutes the principal ash-forming constituent in the cigarette paper.
Cigarettes rolled in the paper, prepared as above-described, burned so as to leave fine, discontinuous flakes of paper ash, which closely adhered to the tobacco ash, and these cigarettes upon storage retained their fine ashing properties, when burned, to a much better extent than when the magnesium carbonate wa not used.
This is a division of our copending application Serial No. 255,733, filed November 9, 1951.
Various modifications and changes may be made in the foregoing process, materials and products, without departing from the spirit and scope of our invention as defined in the appended claims.
1. A rocess of producing desired ashing properties in cigarette paper containing cellulosic fibers and calcium carbonate filler, comprising incorporating in the pulp-filler furnish sufficient magnesium carbonate to provide in the cigarette paper produced therefrom, approximatel 0.5% to 2 magnesium carbonate, based on the weight of filler, sheeting the paper furnish and incorporating in the paper sheet sufficient ammonium phosphate to provide in the cigarette paper approximately 0.1% to 1% ammonium phosphate, said magnesium carbonate functioning to neutralize any free calcium hydroxide content of the calcium carbonate filler and prevent reaction between said calcium hydroxide and said ammonium phosphate, whereby the ammonium phosphate can function effectively to provide the desired ashing properties in the cigarette paper.
2. A process of producing cigarette paper containing cellulosic fibers and calcium carbonate filler, comprising incorporating in refined cigarette paper pulp a controlled amount of magnesium carbonate in the proportion of about 11 pounds of magnesium carbonate to 80 cubic meters of the cigarette paper pulp stock of about 2.5% consistency, sheeting this cigarette paper pulp on a paper machine and incorporating in the wet paper sheet sufiicient ammonium phosphate to provide in the finished cigarette paper approximately 0.1% to 1 ammonium phosphate.
MILTON O. SCHUR.