US1988099A - Process of increasing the moistureproof qualities of sheets of organic matter - Google Patents

Description

Patented Jan. 15, 1935 UNITED STATES PROCESS OF INCREASING THE MOISTURE- PROOF QUALITIES 0F SHEETS .OF OB-,

GANIO MATTER Richard Weingand and Josef Seiberlich, Bomlitz, near Walsrode, Germany Application April 21, 1932, Serial No. 606,717 In Germany December 29, 1931 2 Claims.

This invention has reference to the treatment of thin sheets of solidified cellulose solutions and the like by means of which the objectionable effects of the hygroscopic or moisture-retaining qualities of such material are obviated or entirely eliminated and the adaptability of this kind of material is increased and a great improvement in the quality of the product and of the course of manufacture, particularly for a great many industrial and other purposes may be produced. It is well known that all opaque and transparent-or translucent foils or thin sheets of plates of cellulose, and of cellulose compounds, as well as sheets and plates of gelatine and the like present the very serious drawback that these articles and products made therefrom on account of their hygroscopic nature are more or less permeable for water vapors and steam. In view of these facts articles and objects which are hygroscopic themselves and which have been wrapped up in foils or sheets of the material referred to are dried up in accordance with the amount of moisture in the atmosphere; or such objects absorb moisture very readily, so that in a great number of cases the wrapped up articles become unfit for use. As instances of such articles and objects various alimentary articles may be mentioned, such as biscuit, crackers, pastry, cakes, sweets, candy, cheese, coffee, tea, tobacco products, hygroscopic salts and many other articles. For shipping and packing purposs of such articles and objects and for storage thereof they will have to be packed or wrapped up, so as to be proof against the action of water vapors.

Various suggestions to overcome this difficulty have been made in the'prior art in connection with the wrapping and enclosing means in use. Of these a scheme may be mentioned according to which paper has been impregnated or coated with a layer of oil or of wax; or in accordance with another instance sheets or foils of paper were pasted onto metal foils or thin sheets of metal, for instance in the art of packing or wrapping up crackers and the like. In the case of transparent foils of cellulose-hydrate, ester of cellulose or gelatine it has been suggested to coat foils or sheets thereof with, a solution of a cellulose ester in a volatile organic solvent in which resins, waxes and softening agents have also been dissolved, in order to reduce the permeability thereof for water vapors; the varnish film which remains upon the foils or sheets after the evaporation of the solvent produces the desired imperviousness' against the action of water vapors. However, the carrying out of this method presents certain difficulties. and calls for an extensive, space requiring apparatus, and it is by no means easy to remove'the solvents without any residue, inasmuch as this can only be done by an increase of temperature which is liable to impair the quality of the material. Yet, the absolute freedom from solvent is a necessity, because the sheets and foils, particularly in the case of the wrapping up of foods, must be perfectly inodorous. On the other hand, if the solvents are not removed without residue, the aggregated foils or sheets in a pile are likely to become pasted to each other. There is the additional inconvenience that the coating of varnish very often becomes turbid in consequence of the vaporization of the solvents, so that the required glassy clearness of the transparent foils is seriously interfered with. Moreover, this procedure is rather expensive in view of the fact that even with the most careful recovery a portion of the solvent is lost, and the recovery of the solvent necessitates an expensive series of apparatus which consume heat and energy.

Now, as a result of lengthy investigations and experiments it has been ascertained that a high degree of impermeability against the action of water vapors at least equal to that of a coating of varnishes of cellulose-esters obtained by the aid of solvents may be produced upon sheets or foils of the kind referred to or upon articles comprising the same without the use of a volatile solvent and in a far more simple and less expensive manner than heretofore by applying the coating material in which cellulose-compound are contained, to the base in the liquid or semi-solid condition instead of preparing a volatile solution thereof. This object is accomplished in our invention by making use of the resins or softening means contained in the coating compound or of a combination of these means as solvents for the cellulose compounds. Such resins and softening means reduce the permeability for water vapors of the coating and they also impart to the cellulose-compound and consequently to the coating the desired pliability and hardness, so as to prevent the peelingoif of the varnish otherwise caused .by meohanical strains acting upon the foils, sheets or films.

It has also been found to be of advantage to add waxes, wax-like bodies and the like as additional water repelling agents to the coating material in combination with the components above referred to. In a preferred embodiment of the lose, benzyl-cellulose.

in the resin. Then the further additions, such ing together of the contacting surfaces.

invention we may proceed by adding and incorfeature of our invention the portions of the porating the cellulose compound with the fused sheets or foils to be united are placed upon each resin slowly and by thorough agitation by which other and are heated for a short time to about means the cellulose compound becomes dissolved degrees centigrade, which results in the weld- This as softening agents and waxes are added and fi at o t e Process 18 particularly 0! the mixture is continued to be heated with agii tance o the packin of a tic y tation, until the melt has become homogeneous. chine 'y- As cellulose compounds which have proved to be suitable for our purposes we may mention the following:--nitro-cellulose, acetyl-cellulose, stearyl-cellulose, palmityl-cellulose, ethyl-cellu- Of resins natural and artificial resins are to be used, such as for instance, rosin, dammar-gum or -resin, gum copal and the well known resin-esters. As softening agents we may advantageously make use of all kinds of plasticity imparting agents usually employed in combination with cellulose compounds,

Examples 1. Into one kilogram of rosin or colophony heated to C. grams of benzyl-cellulose are introduced with thorough agitation, thereby causing the latter to be dissolved. 'Ihereuponv 500 grams of beeswax and 100 grams of tricresyl-phosphate are added to the solution and the mass is stirred at 80 C., until a homogeneous melt has been obtained. This product is applied by a roller brush to an endless web of parchment paper. After the coating has been such as f0r instance, camphor, tricresyl-phoseffected, the web is passed through a drying triphenylphosphatei methyl'cyclohexa tunnel or the like which has been heated to 60 1101 and the like. Additions such as beeswax, degrees c. at a speed to allow the web to ceresine, carnauba-wax, paraffine, Vaseline, woolmain therein for about 30 Second3 After 1.

grease in view of their water repelling properties are well adapted to considerably increase 'ing material.

The coating which may comprise a solution of a cellulose compound in one or more resins or softening agents with or without the addition of waxes or wax-like bodies may for instance ing the web is rolled up.

2. The coating mixture comprises the following constituents 100 grams tricresyl-phcsphate, 100 grams nitrocellulose containing 11.5 percent nitrogen,

500 grams gum dammar, 400 grams carnauba wax,

be pp d by passing the s eets. o s a d t the nitrocellulose being kneaded together with k u h the molten mixtu a y existing the softening agent and being then worked into excess in r m v d by Scraping Similar a homogeneous melt with the other ingredients device. The process may, however, be modified t 70 degrees c, vThe resulting compound is ap.

by applying and distributing the molten or semi= solid compound upon the foil or sheet to be coated by means of rotating rollers or brushes. and then smoothening the coat, after it has become solidified, by means of soft brushes. may also apply the molten material to the em W it is smoothened by means of a soft brush.

plied in the molten state by means of a spraying pistol to a transparent sheet or foil of cellulose-hydrate, so as to constitutes. layer of 0.001 millimeter after the solidification of which The accompanying drawing shows by way of e y m a s f sp y rs or p ay pi t sexample several practical embodiments of the inand then, after solidification, smoothen the coat.- ti in Figures 1 3 and 3 in gchematicgl rep.- For the purpose of more thoroughly attaching resentation, in which Rig. 1 is a diagrammatic the at l yer ,to the s ace t e p cu vertical section of the device and Figs. 2 and a sheet or foil may be preheated for a short time. i il r i w of modifications. It has also been found to be of advantage for According to Figure 1 the foil 1 of cellulose the formation of the coating film of varnish hydrate is passed from t 11 4 thrgugh t p n the foil to maintai t Coating 8 ceptacle 2 containing the coating solution 3 and short time after application thereof at an inth th ough the scraping device 5. The foil 1 as d t mp ratu and pa u a at its is coated on its both sides with solution when melting temperature, by which means the union going through the receptacle 2 and any existing 01 the coat with the surface iS also assisted. excess of olution will be removed by the craps s qu t h atin y be produced for ing device 5 from the foil after leaving the reinstenoe y passing the sheets, foils or w s ceptacle. The foil is then conducted away over through a heated room or over heated rollers. the r ll 6 and wound up. According toFigure 2 In accordance with the intended utilization th f il 1 coming from the roll 4 is coated on one of the coated article it may be provided with a id by means of the rotating brush '1 immersing hin or thick v n lay It has been ascerin the coating mass 8 contained in the container tained that a film-like layer of one u thickness 9 and applying coating mass upon the foil 1. is already sufficient to impart the desired imh rotating brush 10 uniformly distributes the perviousness against water-vaporsto the sheets. applied coating mass upon the foil 1 and then The coating may, of course, be applied to one the 1 1 is subjected to the action of at or both sides of the sheet or foil. Inasmuch duced by means of h 11 mm t inteas such coatings of the required thickness are 1 of hi vapor is mt If degired th perfectly transparent, they are particularly suitcoating may be smoothened'betweenthe guidable for the reduction of the permeabilityfor m r ll r 12, 15 by means of the soft rotating water v p s t wis p ss ed by trensperbrush 13, whereupon'the foil 1 is wound upon ent sheets, such as thin sheets dr foils of cellut 11 14, In Figure 3 t 11 1 .ooming ydrat llulose-comp unds, eelatin' a d from the roll 4 is conducted through the electric P y at o PTOdHCtS- Sheets COB-ted in heating device 16 preheating the foil before it cordance with this invention present the addi passes between the two spraying squirts 17, 18 tional advantage that they. may beunited withapplying molten coating mass to both-the sides out the use of adhesives. In carrying out this of the foil 1. Then the foil is subjected to the action of the rotating brushes 19, producin the uniform distribution and the smoothening of thecoating mass applied. Thereafter the foil 1 goes through the drying tunnel 21 heated to degrees C. by being traversed by hot air and finally the toil is wound up on the roller 14.

It should be pointed out that various changes may be made within the scope of this invention, as for example different kinds and proportions of the coat producing agents and diflferent kinds of preferably-flexible sheets may be used, and

' other changes may be made, except as otherwise appears from the annexed claims.

We claim:

1. The process of making moisture-proof wrappers which comprises fusing a mixture consisting'of cellulose derivative, resin, plasticizer and wax, the cellulose derivative being in a minor proportion as to the resin and wax, and applying the mixture to a structureless foil while in a molten condition.

2. The process of making moisture-proof wrappers which comprises fusing a mixture consisting of cellulose derivative, resin, plasticizer and wax and applying the mixture to a structureless foil while in molten condition, said derivative being approximately in the proportion of parts to 500 parts of said other ingredients.

RICHARD WEINGAND. JOSEF SEIBERLICH.

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