US2519728A - Method of eliminating moisture from the surface of moistureabsorbent sheet material - Google Patents

Description

Aug-22, 1950 P. ALEXANDER METHOD OF ELIMINATING MOISTURE FROM THE SURFACE MOISTURE ABSORBENT SHEET MATERIAL Flled Apr1l 5, 1948 Inventor Attorney 8 Patented Aug. 22, 1950 OFFICE I METHOD ELIMINATING MOISTURE FROM THE SURFACE OF MOISTURE- ABSORBENT SHEET .MA'TERIAL Paul Alexander, Berkhamsted, England Application April 1948, Serial No. 19,008 I This; invention relates to methods of eliminating moisture from the surface of moisture absorbent sheet material on which metal is to be deposited by thermal evaporation in a vacuum; and to apparatus for 'so treating the material.

In applicants United States Patent specification Number 2,402,269 there is described a method of eliminating moisture from a moisture absorbent sheet material e. g. paper by heating one surface of the material in a vacuum chamber by radiant heat, whereby the said surface is freed from moisture without so far drying the whole body of the material as to render it undulybrittle. 1 r

The main object of the present invention is to devise an improved method of treating moisture absorbent material .(such aspaper or transparent sheet material sold under the registered trade-mark Cellophane) containing plasticizers, such as g'lycerine which have a very low vapour pressure at atmospheric temperature.

According to the present invention a roll of the absorbent material is gradually unwound and progressivelyexposed in web form in a vacuum chamber (heating chamber) at a moderate vacuum (e. ggata pressure of from 0.05 to 0.5 mm. of mercury) to radiant heat and passed out of the heating chamber whilst hot to a communicating re-rollingchamber adapted to be vacuumized, the pressure in the vacuumized re -rolling chamber being maintained at a higher pressure than that inthe vacuumized heating chamber, whereby one surface only of the web is freed of the plasticizer and the vapour of the plasticizer is prevented from gaining access, to the re-rolling chamber.

By the present invention the is re-rolled without exposing the treated surface when cooled to the vapour evolved from it during the heat treatment, andmay be thereafter coated in a separate vacuum chamber with a metal by the 'known thermal evaporation methods; This deposition cannot be. commercially performed in the re-rolling chamber because the low pressure required could not be economically maintained in theheatin chamber.

ThB present invention also comprises apparatus for depriving one surface of a moisture ab sorbent material in, web form of a plasticizer, such as glycerinawhich has a very low vapour pressur'eat atmospheric temperature character ised by two chambers adapted to be vacuumized, one of said chambers (the heating chamber) con-. taining a heater providing radiant heat for'the web, and the other (the re.-rolling chamber) heated material I 4 Claims. (01. 34 -16) containing a take'up roll, the heating chamber communicating with the re-rolling chamber only by one or twoslits in the wall of the heating chamber through which the web passes, the slit through which the web passes out of the heating chamber being situated so close to the heater that the web leaves the heating chamber whilst still hot, the two chambers being evacuated by exhausting means connected to the heating cham-. ber so that the re-rolling chamber is evacuated solely by flow of gas from it into the heating chamber through the said slit or slits.

The supply roll may be in the heating chamber in which case only one slit will be required in the wall of the heating chamber or may be disposed together with the take up roll in the-rerolling chamber in which latter case two slits are required in the wall of the. heating chamber... By such arrangement the two chambers are simultaneously evacuated whilst maintaining a lower pressure in the heating chamber than in the re-rolling, whereby there is a continual flow of gas from there-rolling to the heating chamber and vapour evolvedin the latter cannot pass .25 to the re-rolling chamber.

The re-rolled material is removed from the re-rolling chamber and then mounted in an independent vacuumchamber on which metal deposition is effected under a very much lower pres sure.

. In order that the invention may be more clearly understood reference will now be made to .the accompanying diagrammatic drawings, which showby way of example preferred embodiments of the presentinvention In the drawings: b a Figures 1 and, 2 are sectional views showing the heating andre-rolling chambers, the supply roll being outside the heating chamber in Figure l and inside the heating chamber in, Figure 2.

' Figure 3 is .a sectional view showing a modificationof the arrangement shown in Figure l. The same reference numerals indicate similar parts in the two figures. v r,, The vacuum chamber l, herein termed the heating chamber, is enclosed within a chamber 2, herein termed there-rolling chamber, the chamber l containsthe source of radiant heat constituted by an electric heater 3. 1

Referring first to Figure 1, a web of material 41in the manufacture of which glycerine has been used as a plasticizer), emanating from a supply roll 5 in the re-rolling chambennpasses over a guide roll Band through a slit 1 in the wall of theheating chamber. In the heating chamber the face of the web intended eventually to be coated, by condensation thereon of the Vapour of metal produced by thermal evaporation in a vacuum, passes in front of the heater 3, thence over a guide roll 8, and out of the heating chamber 1 through a second slit la in the wall of the chamber, hence over a guide roll 9 to the take-up roll H1, in the re-rolling chamber 2, driv en by a clockwork motor indicated at H.

The arrangement is similar in Figure 2, except that the supply roll is in the heating chamber I, and there is, therefore, only one slit, la, in the wall thereof through which slit the strip 4 passes out of the heating chamber into the re-rolling chamber.

The vacuum in the heating chamber I is maintained at a lower pressure than the vacuum in the re-rolling chamber, so that any flow oi air or vapour between the two chambers is in the direct n w i h is from the rerollin chamber .2 to h h ting h mb r 1; his ff c s brou h about by evacuating the two chambers through a ng p ssa e l2 located in t e wa l of the heating chamber I and connected directly to the p mpin ppa t s, A suitable vacuum in the heating chamber is a pressure of about 0.1 min. of mercury.

It may be noted that the web of material passes out of the chamber I while it is still too hot to 3 for carrying out the invention, the two chamhers a e m d by a pa tition wall a within a single vacuum chest which partition divides the chest into the two chambers I, 2. The vacuum pump I2 is connected tg the heating chamber, and the re-rolling chamber 2 is evacuated by flow of gas through two slits, I, "la in the partition Ia into the heating chamber I,

Similarly, the construction shown in Figure 2 m y b m fied y d vi ing the outer chamber by a partition and arranging the supply roll in the heating chamber, as will be readily understood.

By using s h f rms o apparatus lycerine is effectively vapourised from one Surface of absorbent material, for example paper or that transparent material sold on the open market under the registered trade-mark Cellophane, and the vapour is removed from the material whilst hot, so that there is no possibility of glycerine vapours condensing on the cooled material as it is being re-rolled.

I claim:

1. A method of eliminating moisture from the surface of a moisture absorbent. sheet material, on which surface metal is to be deposited by thermal evaporation in a vacuum, comprising p ss v ly u ro l n and expo ing a web of moisture absorbent sheet material to radiant heat in a vacuumised heating chamber, passing the said material into a vacuumised ire-rolling chamber communicating with said heating chamber only by a restricted opening or openings sufficient to permit of passa e of the material from one said chamber to the other, and rolling the said material into roll ,form in said re-rolling chamber whilst it is still hot from heat exposure in said heating chamber, the vacuum. in said heating chamber being maintained by connecting said heating chamber to an evacuating pump, and the said re-rolling chamber being vacuumised solely by flow of gas thereirorn 4 into said heating chamber through said opening or openings, said flow of gas thereby precluding egress of moisture from said heating chamber through said opening or openings into said rerolling chamber.

2. An apparatus of the kind described, comprising a vacuumised heating chamber, a vacuumised ree-rolling chamber immediately adjoining said heatingchamber, a supply roll for supplying moisture absorbent material to be treated, a radiant heat source in said heating chamber, restricted aperture means for establishing communication between said heating chamber and said re-rolling chamber, means for progressively conducting a web of moisture absorbent material gradually unwound from said supply roll past said heat source with one surface thereof exposed to said heat source and through said aperture means int said re-rolling chamber,v said aperture means bein dispo d in uch proximi y to said heat source that said m t rial enters said re-rolling chamber wh ls still hot, a take-up roll in said re -rolling chamher for converting aid hot material into roll form, and exhausting means connected to s heating chamber for maintaining a desired vacuum h r in, said re-rolling chamber bein vacuumised solely by flow of gas therefrom through said aperture means into said heating chamber, said flow of gas thereby precluding egress of moisture from said heating chamber throu h said ap r ure means into said rer 11ine chamber.

3. An appar us of the kind described. mprising. a vacuumised heating chamber, a va mise r -rolling chamber, one of said chambers b in dispo ed wi hin the. other s id chamber, a supply roll in said re rolling chamt for supplying m i ture absorbent materi l to be treated, a radiant heat source in said heatin cham er, first r tricted apertur m a p mitting of the passage of said material from said re-rolling chamber into said heating chamber, second restricted aperture. means for passing said material out of said heatin chamber into said re-rolling chamber, means for progressively conducting a w b of moisture absorbent m t ri l gradually unwound from said Supply roll through said first aperture means past saidv heat source with one surface thereof exposed to said heat source and through said second aperture means into said re-rolling chamber, said secondv aperture means being disposed in such proximity to said heat source that said material enters said re-rolling chamber whilst still hot, a take-up roll in said re-rolling chamber for converting said not material into roll form, and exhausting means connected to said heating chamber for maintaining a desired vacuum therein, said rerolling chamber being vacuumised solely by flow of gas therefrom through said aperture means into said heating chamber, said flow of gas thereby precluding egress of moisture from said heating chamber through said, aperture means into said re-rolling chamber,

4. An apparatus of the kind described, comprising a vacuumised heating chamber, a vacuumised re-rolling chamber, one of said chambers being disposed Within the other said chamber, a pply roll n said heating chamber for supplying oisture absorbent material to be treated, a radiant heat source in said heating chamber, restricted aperture means for estabchamber and said re-roll'ing chamber, means for such proximity to said heat source that said material enters said re-rolling chamber Whilst still hot, a take-up roll in said re-rolling chamber for converting said hot material into roll form, and exhausting means connected to said heating chamber for maintaining a desired vacuum therein, said re-rolling chamber being vacuumised solely by flow of gas therefrom through said aperture means into said heating 5 2,402,269

chamber, said flow of gas thereby precluding egress of moisture from said heating chamber through said aperture means into said re-rolling chamber.

- PAUL ALEXANDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 839,191 Passburg Dec. 25, 1906 921,307 Strohn May 11, 1909 2,384,500 Stoll Sept. 11, 1945 Alexander et a1. June 18, 1946

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