US1570098A - Process of rendering paper transparent - Google Patents

Description

c. E. SWETT PROCESS OF BENDERI NG PAPER TRANSPARENT Jan. 19,1926.. 1570;098'

Filed May 18,- 1922 liarra K071 6'72an8es Z a/e22 Patented Jan. 19, 1926.

UNITED STATES PATENT OFFICE.

CHARLES E. SWETT, OF "WEST ROXBURY, MASSACHUSETTS, ASSIGNOR TO UNITED STATES ENVELOPE COMPANY,- OF SPRINGFIELD, MASSACHUSETTS, A. CORPORA- TION OF MAINE.

PROCESS OF RENDERING PAPER TRANSPARENT.

Application filed May is;

To all whom it may concern.-

Be it known that I, CHARM-1s E. SWE'LT,

a citizen of the United States, residing at West Roxbury, in the county of Suffolk and 5 Commonwealth of ,Massachusctts. have in-- vented a new and useful Improvement in a Process of Rendering Paper Transparent, of which the following is a specification.

The present invention relates to improvements in the art of treating paper, for the purpose of rendering it transparent. The process is applicable, for instance, to the manufacture of window envelopes of the one piece type, i. e., anenvelope in which an integral part of the material is made pervious to light by treatment with a suitable substance of a resinous or similar nature.

The invention resides in a certain mode of treatment adapted to decrease very materially the time required for completing the transparentizing operation and for bringing the treated blanks or sheets into condition for subsequent operations thereon, such as printing, stacking, folding and the like. In consequence of this, as hereinafter described, it is possible, by the use of the invention, to coordinate, and to perform in a practically continuous manner, the several successive operations required for the production of the finished articles.- without need for any substantial interruption in the entire manufacturing process from beginning to end.

It is well known that the impregnation of paper with various suitable substances of a resinous or similar nature operates, to a greater or less degree. in making the material pervious to light, or transparent; and it is also recognized that for permanence of result, the impregnating substance should remain in the paper in the form substantially of a solid. In the utilization of these principles, the practice, in general, has been to use a solvent for the resinous or similar matter, the liquid mixture being applied to the aper and caused to penetrate its pores; tliereafter, by driving off the solvent and drying the residue, the desired 50 result is obtained.

Heretofore, it has been deemed essential A and indispensable to' the above described process that the sheets or blanks of paper,

following the application of the treating 1922. Serial No. 562,030.

sheets or blanks'are to be subjected. For.

example, in the manufacture of one piece window envelopes, this transparentizing treatment has heretofore been available only as an independent preliminary operation, separate and apart from the other manufacturing steps; the envelope blanks, after application thereto of the treating liquid,

have to be spread out by hand on trays, to

facilitate their disposal in a suitable oven or heating chamber, and then, following the prolonged heating of the treated blanks, they have to be handled a second time, in order to assemble them into stacks, preparatory to their passage through an envelope folding machine.

I have discovered that the above described prolonged application of heat can be dispensed with in the process of transparentizing paper. In the accompanying drawing, the single figure represents, diagrammatically, one form of apparatus which may be used in putting my invention into effect, as hereinafter described. According to my invention. the sheets or blanks, having received their imprints or coatings of the treating liquid. are subjected to alternate short periods of heating and cooling, the aggregate duration of which for the entire process need not, under ordinary circumstances. exceed two minutes,in contrast with the much longer'period, usually an hour or more. that is required when the heating is uninterrupted.

The invention resides essentially in the above described mode of treatment, without regard to the mechanism or apparatus employed for performing the same,since it is obvious that the process is susceptible of utilization in a large variety of ways, as for instance, by causing the treated material, in its progress, either continuous or intermittent, towards those instrumentalities which convert it into the finished product, to par:

on an endless conveying belt 1, for example, through alternate hot and cold zones, the former being constituted, for example, by heated plates or coils, 2, 2, and the latter either by the unheated intervening spaces or by blasts of air 3, 3 directed onto the material in the intervals between its subjections to heat. I Y

The limits and proportions of time and temperature, and also the number and duration of the alternate heating and cooling cycles will vary, for the different conditions and requirements that arise,all of, the above being affected in greater or less degree by such factors as the thickness of the paper, and its condition" as to moisture ll1n materials, sizing and the like, and also y the composition of the treating sub stance. In general, it is found advantageous to give the heating periods a slightly longer duration that the alternatecooling periods, and also to subject the pa er in said heating periods to somewhat igher temperatures than those that are reached when rolonged and uninterrupted heating, accord ing to previous known processes, is employed; this last can be done, without damage to the paper, becausethe beatings are of such short duration. This treatment, giving accelerated impregnation to the paer, coupled with recurring o ortunities .or the condensation and soli i cation of the transparentizing substance, need only be continued for a very short time; its

culmination finds the. sheets or blanks in condition for immediate further operations thereon,the impregnated portions thereof having hardened and dried sufficiently to permit stacking of the sheets or blanks, without danger of sticking. As applied for instance to the manufacture of one piece window envelopes, the invention, by eliminating the necessity for prolonged transarentizing treatment, permits said manu-- iods of s ort duration to obtain accelerated v penetration and solidification of the impregnating substance.

2. In the art of rendering aper transparent, the improvement whlcli consists in applying to the paper an impregnating substance, and heating, the paper at intervals, alternately with ex osures to atmospheric temperature, to obta1n solidification of said impregnating substance.

ated this 16th day of May, 1922.

CHARLES E. swam,

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