US2053781A - Apparatus for moistureproofing materials - Google Patents

Description

Sept. 8, 1936. F. H. REICHEL 2,053,781.

' APPA ATUS FOR .MOISTUREPROOFING MATERIALS Original Filed June 1932' Sheets-Sheet 1 INVENTQR 1 l JQW.

'ITORNEY5 P 1936 ,F. H. REICHEL 2,053,781

- ABPARATUS MOISTUREPROOFING MATERIALS I Oiiginal Filed June 4, 1932 3 Sheets-Sheet 2 INVENTOP WMM ATTORNEY5 UL o- Patented Sept. 8, 1936 UNITED STATES PATENT OFFICE APPARATUS FOR 'molsruanrnoormo MATERIALS Frank H. l'teicliel, Fredericksburg, Va., assignor to Sylvania Industrial Corporation, New York, N. Y., a corporation of Virginia Original application June '4, 1932. Serial No. 615,353. Divided and this application May 13, 1933, Serial No. 670,866. Renewed June 3, 1936 6 Claims.

This invention relates to coating, and more particularly to an apparatus for coating flexible sheet materials which are adapted to be used.

a thin, transparent, continuous, moistureproof' film in a simple, efiicient and economical manner.

It is a further object of the invention to provide a simple, eflicientand economical apparatus 'for forming a continuous wax coatingon flexible sheet material or on articles supported upon a moving conveyor, whereby a moistureproof coat ing is formed which is extremely thin, transparent and substantially uniform in thickness, without the necessity of resorting to mechanical ma nipulation of the coating.

It is a specific object to provide an apparatus having means to form a cloud of fine particles of a moistureproofing wax material, with means to expose flexible sheet material so that the comminuted material is deposited thereon and means tofiux the deposited material to form a flexible, transparent, moistureprooi and extremely thin film on the sheet material.

It is a further specific object of the invention to provide an apparatus having, in combination, means to form a cloud of fine particles of wax, means to separate particles of a predetermined size from said cloud, means to circulate the-selected particles so as to bring them into contact with flexible sheet material and means to flux the wax particles deposited upon said material to form a flexible, transparent, molstureproof, non-tacky, non greasy and extremely thin film thereon.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the apparatus having the features of construction, combination of elements and arrangement of parts; which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which: 7 9

Figure 1 show diagrammatically a vertical longitudinal sectional view of one modification of tlfi apparatus of the invention for coating flexible sheet materials; f Figure 2 shows a similar view of another and presently preferred form of apparatus taken along the broken line 2-2 in Figure 3, looking in the 19 I direction of the arrows; and,

Figure 3 shows a horizontal sectional view thereof taken along the broken line 3-3 in' Figure 2, looking in the direction of the arrows.

-Heretoiore, in preparing moistureproof wrap- 15 ping materials, either a multioomponent lacquer including wax has been applied, or the base sheet material has been waxed heavily by direct spraying, dipping or rubbing with wax. These latter products are known to the trade as waxed paper! 20 and consist of a sheet of paper stock, pulp, paper, glassine or the like which are provided with a relatively thick, opaque and waterproof coating consisting of wax. Among other reasons, these latter materials are not entirely satisfactory for 25 wrapping purposes because of their relative opacity, inflexibility as evidenced by their thickness and their inability to resist the passage of moisture through creases or fissures after they have been folded during the wrapping operation. 30 Theapplication of wax in a thickness of the neighborhood of one micron, by hot direct spray ing or rubbing followed by subsequent polishing or scraping has also been recently suggested; but principally for purposes other than moisture- 35 proofing, and the suggested amounts are much greater than are permissible to accomplish the ends of my present invention and, moreover, the subsequent rubbing or scraping step is not essential and in some cases indeed is not permissible for the attainment of the correlated essential qualities characteristic of the present invention. Furthermore, when wax is thus applied directly to non-fibrous homogeneous sheet materials, such as regenerated cellulose, the coating will interfere with their transparency, may rub oil through lack of adhesion or may flake 011 in use and ordinary handling because of lack of flexibility.

0n the other hand, the manufacture of those prior moistureprooi wrapping materials by coating with multicomponent lacquers including wax, a cellulose derivative and plasticizers, gums, etc., ordinarily necessitates the use of relatively expensive solvent mixtures and ingredients. Such solvent mixtures not only contain expensive components, but their elimination and recovery are likewise expensive, troublesome and tedious; and with the temperatures usually used in drying the coating, it is necessary to re-impart the flexibility otherwise impaired by the drying out of the base material; and even with all precautions, it happens frequently that the wax present in such lacquers and coatings prevents the elimination of the last traces of the volatile solvents, giving a product which is not odorless and the uses of which are consequently limited.

The apparatus of the present invention is designed to provide a moistureproof coating without the use of expensive solvents or high drying temperatures and the base material is moistureproofed without injuring the properties of flexibility, etc. which it may initially possess. Wrapping materials made with the use of the present apparatus are also to be distinguished from the waxed papers of the prior art, not only by their flexibility, but also by their high transparency, moistureproofness, non-tackiness and nongreasiness.

In general, the present invention contemplates an apparatus for forming on a base material an extremely thin, continuous film of wax such as, for example, paraflin, beeswax, ozokerite, etc.,or mixtures of such waxes with each other or with suitable modifying materials such as stearates, stearic acid, resins, etc., the wax being the major ingredient, and all being referred to hereinafter as wax, in a manner such that the coating is uniformly disposed over the base material in a layer so thin that it is substantially invisible. In a preferred form of the apparatus, this is accomplished by providing means for subjecting the base material to an air borne cloud of finely comminuted wax, to distribute minute particles thereof uniformly over the surface, and means for fluxing these particles together so that they spread to form a thin continuous film which is effectively resistant to the passage of moisture and yet which is highly flexible, and is not opaque, tacky or greasy.

In most or all heretofore known moistureproof I wrapping materials in which wax has been used as the moistureproofing substance, it has been impossible to utilize water soluble glues or adhesives in sealing them or in affixing revenue stamps, la-' bels, etc. thereto. I have found, however, that when flexible base materials, which are water-' absorbent and are non-absorbent for waxes, are moistureproofed in accordance with the principles of myinventionthey exhibit not only all of the desirable characteristics above enum rated but, in addition, may be made to have the remarkable and commercially important property of permitting the use of water soluble adhesives therewith. For example, by proper selection of the wax, regenerated cellulose, moistureproofed in this manner, may be readily sealed with ordinary animal or vegetable glue, or may thus have revenue stamps, etc. afiixed directly thereto, without the use of organic solvents of any kind.

plied shall be of natures such that the former shall spread on the latter when the particles are fiuxed and will sufficiently adhere to its surface after the film is formed. This may be controlled either by the selection of the wax which is to be 5 deposited on the given surface, or by the treatment or coating of the base sheet material. I

have found, for example, that a sheet of regenerated cellulose or other cellulosic sheet material such as, for example, glassine paper or the like, may be advantageously moistureproofed with ozokerite or other suitable wax with the apparatus comprising the present invention without previous treatment.

In speaking of regenerated cellulose, I mean the flexible, transparent sheet material which contains some water and usually a small percentage of hygroscopic material, such as glycerine or the like.

Certain materials such as, for example, 'the 20 commercial grades of gelatin, cellulose acetate or the like whose surfaces may not permit thewax used to spread and adhere suificiently may be first treated or coated with a suitable coating material, not itself necessarily significantly moistureproof. Suitable intermediate coatings may be formed from cellulose derivatives of polymerized vinyl compounds admixed with plesticizers, gums, resins, blown oils, or the like,

' which increase the adherence and the spreading of the wax, and the use of these latter materials alone on the base material, for this purpose is not precluded. Small amounts of dyes, pigments, waxes, etc., may be added to the intermediate layer if desired. The coated or treated sheet is then subjected to the waxing treatment in the manner indicated below. Such procedure may also be used with sheet materials which otherwise would be too highly absorbent for the wax and would consequently tend to prevent the formationof the thin surface film desired.

The lacquer or other intermediate coating or impregnating substance, as aforesaid, may be ap-' plied in any convenient manner, as by passing the base material through a solution of the lacquer and then drying while recovering the solvents (if any) in the usual manner. The article pro,- duced by the use of an intermediate coating comprises a laminated sheet material composed of the base sheet material having a thin, intermediate layer of lacquer or the like and a thin, transparent and moistureproof surface film of Wax.

I have found also that if materials such as regenerated cellulose are first coated in this way 5 and then waxed as aforesaid, a product more adapted for some uses is obtained, particularly in cases when waterproofness is desired, in addition to a high degree of moistureproofness. By this means, exceptionally high moistureproofness can be obtained with the use of much thinner films and consequently with the use of much smaller quantities of coating materials than in moistureproof coatings heretofore known. The product thus produced is superior to any wrapping material heretofore known, and I consider it a preferred embodiment of my invention, as it produces a product of very uniform all-over moistureproof value. I

The ultimate moistureproofness of the finished article is substantially independent of the thickness of this layer of lacquer and hence it may be extremely thin. I have obtained satisfactory results with such a, film of only 0.00025 millimeter in thickness on each side of the base material. 7

A suitable thickness of intermediate coating will be obtained if approximately 10 grams of this mixture is dissolved in approximately 300 cc. of a solvent mixture consisting of 40 parts ethyl acetate and 60 parts benzene, and the regenerated cellulose is coated therewith and dried in the usual manner well known in the art. After the coating is dried, such laminated sheet material may then be coated on one or both sideswith paraifin or other suitable wax, in the apparatus indicated below, to the production of a highly moistureproof wrapping material which is transparent, flexible,

non-tacky and waterproof.

By long experimentation and careful investigation, I have found that the wax coating which is necessary to produce my commercially desirable moistureproof material, when applied to each surface of a regenerated cellulose sheet material,

for example, should uniformly cover the sheet material and need not be of a thickness substantially greater than about one-tenth of a micron on each side. Such films, of a thickness of even as low as one one-hundredth of a micron, have very effective moistureproofing properties, and i prefer a thickness of one-twentieth o one-fiftieth of a micron, although on certain previously coated materials the. thickness may be still further increased without impairing the desired qualities of the film.

While by my improved apparatus thicker coatings may be applied. nevertheless there is no necessity for such added thickness for moistureprooiing purposes, particularly with uncoated materials, and there is a tendency to the production of products of poorer quality in that they are greasy, tacky, smudgy and of reduced fiexibility. With sheet materials which have first been coated with a lacquer as above suggested, the moistureprooi coating is more adherent and therefore subsequent mechanical manipulation thereof is not precluded, although it is not necessary for good results.

By measuring the diameter of and counting the spherical wax particles on the surface of the regenerated cellulose prior to the fluxing operation, and by calculation, I have determined the thickness of the film resulting when they are fluxed to gether. Stated another way, I have found that the operations should in general be so conducted that prior to the fluxing operation, the equivalent of from 500 to 2500 particles of wax having diameters not greater than about 40 microns, and preferably not greater than about 20 microns, and of which preferably from 50% to 90% or above have diameters of less than 8 microns and l preferably less than microns should be uniticles are larger than indicated and are not uniformly distributed are inclined to be opaque and smudgy in spots, and streak and smear through handling in use, and in general do not exhibit the improved correlated properties of the product made in accordance with my invention. With slightly absorbent substances, such as uncoated glassine, and with some previously coated materials, the time of exposure should be increased somewhat so as to give an exposed surface layer of wax of the character indicated.

In accordance with the processes disclosed in my co-pending application, Serial No. 671,012,

' filed May 13, 1933, such a microscopically thin coating of wax can be applied by forming a fine cloud of wax in a closed chamber, exposing the material to be coated in the chamber at a point sufiiciently far removed from the source so that all particles larger than approximately 30 microns in diameter fall to the bottom of the chamber and do not lodge on the sheet; and after the surface has been uniformly and sufiiciently covered with the fine particles of wax, it is heated by passing through a hot zone, or by other suitable means, so as to fiux the wax particles together, whereupon it is cooled, giving a uniform and very thin film of wax over the entire surface. When moistureproofing sheet materials, one or both sides may be coated as desired.

A simple embodiment of my improved apparatus for coating sheet materials is shown diagrammatically in Figure l of the drawings in which the reference numeral i0 designates a closed elongated chamber, at one end of which there, is provided a wax atomizing mechanism designated generally as ii. At the other end, the chamber is provided with spaced slots l2, in a well is through which the sheet material is passed from a mill roll it onto a finished roll it.

The atomizing apparatus may consist of a heated trough l6 containing parafiin ll, which is in liquid condition, .i. e. melted and, if desired, somewhat diluted with toluol or the like, and into which dips a slowly rotating feed wheel l8 which,

as it rotates, carries on its periphery it a thin film of the paraifin. The mechanism is also provided with a tangentially disposed air blast nozzle 20 through which heated air is blown forcibly onto the periphery i9, breaking the thin film of liquid wax and carrying it in atomized form, as indicated at H, across the chamber l0.

Even with the best atomizing apparatus thus far obtained, I have found that the cloud of wax normally contains particles which are too large, and contains too large a proportion of particles which are above the desirable size so that it is now necessary to eliminate these larger particles as, for example, by spacing the exposed material at a distance from the atomizer and by providing a bafiie arrangement indicated generally at 23, which forces the cloud to traverse'a tortuous route in passing from one section of the chamber to the next, thus causing substantially all particles having diameters greater than a predetermined value to be separated from the cloud and to collect at the bottom in piles 2|, which wax may be removed at intervals and re-used. The residual cloud of fine particles is air borne and deposits the desired particles on the material.

Upon leaving the chamber I0, the material then passes through a heating zone 22, in which the deposited particles of wax are fused together to form a uniform and moistureproof film, and which may be provided, if desired, with a suitable air conditioning means to prevent the loss of flexibility of the material during the fluxing of the wax particles. The coated sheet material then passes onto the finished roll 15 which is deposed at such a distance from the heater 22 as to permit the wax coating to cool before the sheet is again rolled, or suitable cooling means is provided. This cooling is indicated in the drawings by the broken away portion 24. To allow for changes in the diameters of the rolls I4 and i5, and to tension, guide and/or stretch the sheet. material properly, there are provided a suflicient number of auxiliary rolls 25.

If toluol or the like is used to dilute the wax, a heated dryer (not shown) is preferably interposed before the heating zone 22 or the zone is made sufficiently long to drive off the solvents. When coating both sides of a base material inthis form of apparatus, the wax, deposited separately on each side, may be fluxed simultaneously if desired, in which case the heating zone 22 is not used during the first passage of the base material through the chamber.

In Figures 2 and 3 is shown another and preferred embodiment of apparatus in which the corresponding parts are similarly designated. A principal difference between this and the previously described form is that the cloud of air borne wax particles is positively circulated by suitable means such as fans 26 in a closed circuit including the cloud-forming section and the treating section. This feature may also, if desired, be incorporated in the form of apparatus shown in Figure 1,but in order to facilitate the diiferential separation of the larger wax particles, the atomizing and separating chamber A is preferably made distinct from the depositing chamber B, as shown in Figure 3, the fans 26 operating to introduce the cloud of fine wax particles into the latter preferably at the top at one end and withdraw the residual cloud at the other end for recirculation through the chamber A. Furthermore, by the use of the positive circulation, it is expedient to deposit wax particles on both sides ofthe sheet material at once and to this end the sheet material may have a double traverse of the chamber B before passing through the heater 22. By routing the sheet in the direction shown by the arrows, the deposited particles are not disturbed by the auxiliary rollers 25 prior to the fluxing operation, because the par-- ticles are deposited substantially only on the upper surface of the sheet during its traverse of the chamber B.

moistureproof wrapping material, which is devoid of odor. When using my preferred apparatus, a study of the deposited particles under a microscope shows also that they might be grouped with regard to, size and percentage distribution as follows:

11% are $5 micron 31% are 1 micron 25% are 1% microns 13% are 2 microns 9% are 3 microns 3% are 4 microns 2% are 5 microns or less and 8% are between a and 20 microns.

I have found that when using such extremely fine particles as are last mentioned, from 1500 to 5000 particles thereof may be distributed per square millimeter of area on a sheet of regenerated cellulose with good results. Obviously with different embodiments of my improved apparatus, different percentage distributions of particle size may be obtained. Theoretically, if the particles were all of one size, the approximate number per square millimeter of area required to give a thickness of wax film of 1/ 10th and 1/ 100th of a micron would be as follows:

Number of parti- Number of parti Diameter of cles per sq. mm. cles per sq. mm. particle of area for film of area for fllm micron thickness of Mo thickness of Moo micron micron In using paraffin wax, I prefer to employ one having a relatively high melting point, e. g. 58-60 C. I have also obtained very good results with a mixture of about 95% purified ozokeritc and 5% purified beeswax applied to uncoated regenerated cellulose. In coating glassine, purified beeswax alone is preferable, but, as indicated above, the deposition period should be somewhat longer because of the slight absorption of the fluxed wax by the surface of the material. For

example, in the apparatus referred to above, the

length of exposure for glassine should be about twice that for regenerated cellulose.

While I have illustrated mechanisms by which the desired coating operations may .he accomplished, it is obvious that oneskilled in the art may devise other modifications of the improved apparatus above described without departing from the spirit of the present invention, and that the herein disclosed embodiments are for the purpose of illustration. It is also obvious that the thickness of film, as well as the size of the deposited particles, may be varied as above described by changing the distances or time of exposure, or by using other atomizing devices in my novel apparatus for applying the coating, without departing from the invention.

With the apparatus described above, I have been able to apply to a sheet of regenerated cellulose one-thousandth of an inch thick a-thin coating of wax which is highly transparent, flexible, and is not tacky or greasy, but which is moistureproof. That is to say, when it is exposed on one side to a dry atmosphere and on the other side to one saturated with water vapor, less than 60 grams of water vapor will permeate per square meter of area, during 24 hoursat a temperature of about 40 C.

While I have referred frequently above to wrapping and flexible'sheet materials, it is to be understood that my invention is not limited thereto, as the apparatus is applicable to coating any suitable material. For example, materials such as packages, containers and cans, as well as other articles or substances of many kinds, can thus be readily rendered moistureproof, either with or ages of tobacco or the like may be closed eifectively and the material per se may be moistureproofed if it is gas pervious. As will be obvious to one skilled in the art, the apparatus may be appropriately modified when treating. small or individual articles so as to substitute a moving conveyor for the sheet materials shown in the drawings, without departing from the spirit of the invention.

This apparatus may also be advantageously used in sealing the cut edges and the outside layer of coated or uncoated hygroscopic sheet materials such as cut rolls or ordinary or moistureproofed regenerated cellulose in order to protect them from changing in moisture content, especially at I the edges with consequent swelling of the film and resultant distortion thereof, or from drying out during storage. 7 It will thus be seen that by means of the present invention there has been provided a novel apparatus for the production of improved and technically important products which may be economically and easily prepared, and since certain modifications in the 'apparatus which embodies the invention may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be inter-,

preted as illustrative and not in a limiting sense. It is also to be understood that in said claims ingredients recited in the singular are intended to include compatible mixtures of such ingredients 1 wherever the sense permits.

This application is a division of my co-pending application, Serial No. 615,353, filed June 4, 1932.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. An apparatus for moistureproofing flexible sheet materials including, in combination, a chamber provided with means to form. a cloud of fine particles of wax having diameters not substantially greater than about 40 microns, a second chamber provided with means for passing a flexible sheet of material therethrough in at least double traverse, means disposed between said chambers for circulating the cloud of wax particles fromthe first mentioned chamber into the second mentioned chamber, whereby they are deposited on one side of the sheet material during one traverse and on the opposite side during another traverse, and means to flux said deposited wax particles.

2. An apparatus for moistureproofing materials including, in combination, a chamber divided into sections, means to form a cloud of fine particles of wax in one section thereof, means to pass the material for treating through a second section of said chamber, means disposed between said sections to force the cloud of wax particles to traverse a tortuous route in passing to said treating section whereby there are separated from said cloud substantially all particles having diameters as greater than about 40 microns and means to flux the wax particles deposited on said material.

3. An apparatus for moistureproofing flexible sheet materials including, in combination, a chamber divided into sections, means to form a cloud of fine particles of wax in one section of said chamber, a baflle disposed between said section and a'second section of said chamber, means for forcing said cloud of wax particles in a tortuous route through said baiile whereby there are sepa-, rated from said cloud substantially all particles having diameters greater than about 40 microns, means to pass said material to be treated through the residual wax particles in said second section whereby the particles are deposited thereon, a heating chamber and means to pass said treated material through said chamber to flux the wax particles deposited on said material.

4.'An apparatus for moistureproofing flexible sheet materials including, in combination, a chamber divided into sections, means to form a cloud of fine particles of Wax in one section of said chamber, a baffie disposed between said section and a second section of said chamber, means for forcing said cloud of wax particles in a tortu-. ous route through said baiile whereby there are separated from said cloud substantially all par-- said chamber, a baflle disposed between said section and a second section of said chamber, means for forcing said cloud of wax particles in a tortuous route through said baffle whereby there are separated from said cloud substantially all particles having diameters greater than about 40 microns, means for passing a flexible sheet material through the residual wax particles in said second section in at least double traverse whereby the particles are deposited on one side of the material during one traverse and on the opposite side during another, traverse, a heating chamber and means to pass said treated material through said chamber to flux the deposited wax particles.

6. An apparatus for moistureproofing materials including, in combination, means to form a cloud of wax particles, means for producing an air current for conveying said cloud, means to force the cloud to traverse a tortuous route in passing to the treating point whereby there are separated from the cloud substantially all particles having diameters greater than a predetermined value, means to pass the'm'aterial to be treated into contact with the residual air-borne wax particles, and means to flux the wax particles deposited on said material.

' FRANK I-I. REICHEL.

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