US2019648A - Moistureproof cellulose acetate sheeting - Google Patents

Description

Nov.-5, 1935. N. F. BEACH ET AL 2,019,648

MOISTUREPROOF CELLULOSE ACETATE SHEETING Filed July 17, 1931 Gum 5 Fig.2.

June 450m 1Z0rmaIpEBeach& James m1,

Patented Nov. 5, 1935 I Norman F.

Beach and James G. McNally,

Rochester, N. Y.,.assignors to Eastman Kodak Company, Rochester, N. Y.-,

New York a corporation of Application July 11, 1931,, Serial No. 551,490

is. Claims. (01. 91410) This invention relates the manufacture of thin cellulosic acetate sheeting andmore particularly to a waterproof and moistureproof sheet- 7 ing having superimposed thereon separate layers of gum and wax.

It is known to coat paper, cloth, and other forms of cellulosic material with waxes or gumsfor the purpose of rendering them impenetrable or impermeable to water and other liquids. So

far as we are aware, however, there has been no attempt to waterproof or moistureproof cellulose acetate sheeting by the method hereinaiter described. The present invention is not concerned broadly with either waterproofing or moisture-' proofing, but relates to the treatment of a colloidized' cellulosic base sheet and involves the use of a type of coating material which, due to its peculiar properties, requires a special technique. The resulting moistureprooi coating not onlydiiiers from known coatings in the requirements with respect to its mode of application,

but also diiiers in composition in that it contains only two necessary ingredients and does not require the presence of a base material such as cellulose nitrate, cellulose acetate or other cellulose esters or ethers.

Thin cellulose acetate sheeting has found wide use as wrapping or packaging material, due to the fact that it is comparatively tou h, flexible,

transparent, and impermeable to dust and similar foreign .matter. Its principal drawback for this purpose is that, as ordinarily produced, it is not waterprooi or moistureprooi, and, for this reason cannot be used for wrapping products where substantially-complete exclusion of moisture is important. For example, untreated cellulose acetate sheeting of the order of .001" in thickness will transmit as much as 1.0 to 1.5 milligrams oi water vapor per sq. cm. per hour. The improved product which is the subject of the present invention, however, will in some cases transmit as little as .002 milligrams of water under the same conditions, thus showing a marked improvement in water-resistant properties overuntreated' sheeting.

The principal object of our invention is to produce a highly waterproof and moistureproot formof thin cellulose acetate -sheetiitig. A further object is to provide a wrapping or packaging material which is not only highlywater-resistant but is also transparent, flexible, odorless, and non-tacky. Another object is to provide a simple but effective method for moistureproofing thin cellulose acetate sheeting, while at the same time preserving its flexibility, transparency, and

' sides of the sheet.

ins for forming the gum coating,

other essential and valuable properties. Other objects will appear hereinafter.

These objects are accomplished by the following invention which in its broadest aspect may be said to comprise applying to a thin basesheet 5- of cellulose acetate a first coating of a gum or resin and then applying a second coating of wax'. These materials are preferably applied in the form of solutions in suitable solvents or they may be applied in a molten state, in separate 10 layers, the gum or resin layer in either case being applied first to'form a strongly adhering coat followed by the wax coating which, in turn, is

strongly held by the gum or resin coat. The sheet may be coated onone or both sides. In 15 case it is to be coated on two sides, this may be accomplished in successive operations, or both sides may be coated simultaneously with a given solution, as will more fully appear in the following description in which reference is made to 20 the drawing forming a part 0! this application.

In thedrawing,

Figure 1 is a diagrammatic representation oi I one form of apparatus for carrying out the in vention, in which the sheet is coated on one side with successive layers of coating mate 1 I Figure '2 is a diagrammatic representation oi apparatus similar to, and for use in connection with, that of Figure 1 when it is desired to coat 7 both sides oi the sheet.

Figure 3 is also a diagrammatic representation oi thev equipment for simultaneously coating both variety of game or res= typical examples of these materials being ester gum, dammar, rosin, and sandarak. Natural or synthetiegums or resins are eqhally desirable for this purpose. Any of these gums or resins may-beused alone or in combination with one another or with many 40 other gums or resins of this general nature which are iznown to those skilled in the art. The gun must, of course, adhere well to the base sheet and must hold the wax coating without separation.

The wax coating. may consist of ceresin, beeswax, pimela, lanolin, Montan, bayberry, halowax, japan, oandelilla, Chinese wax and other similar waxes, any of which may, as in thecase of the gums, be used .50 separately or in co 'bination with one another.

Our invention is distinguished by the application of two or more layers of waterproofing material, the first of which is a gum or resin. which adheres closely to the base sheet by virtue We may employ a large of its adhesiveness with respect to cellulose ace-' chloride, ethylene dichloride, and trichiorethyl-- ene, or similar solvents, it only being necessary in choosing the solvents to select one which is a good solvent for the gum, but substantially a non-solvent for cellulose acetate. .A liquid possessing any appreciable solvent power for cellulose acetate would not be desirable, since it would have a tendency to dissolve and weaken the base :0 sheet during coating and thereby render it unfit for use.

With regard to wax solvents, it may be said that the hydrocarbons such as gasoline, kerosene, petroleum ether, and other compounds of this general nature are preferable. Inasmuch as the wax coating is superimposed on the gum or resin coating, the same care in the selection of the solvent is unnecessary, since the first ad-' hesive coating of gum protects the cellulose acetate sheet to a certain extent from the action of the solvent which may be used in the wax solution. It is necessary, however, to selecta solvent which has no pronounced solvent action on the gum, as otherwise the gum coating would be dissolved from the base sheet. As indicated above, the gum and wax need not necessarily be put into solution, although from the standpoint of convenience in handling they can be more readily and conveniently epplied in this way. If desired, each of these materials may be liquefied and app d in a molten condition. In some cases it may be an 'advantage to carry out the operation in this way, since less complicated drying apparatus is required and the drying time may be somewhat shorter. The properties of the finished product, such as waterproofness, moistureproofness, flexibility, and transparency, may be controlled within certain limits in accordance with the particular qualities desired, by varying the amounts of gum and wax making up the composite coating. With regard'to the waterproofing properties of the coating, it may be stated that, in general, the higher the proportion of wax to gum or resin,

the greater will be the water resistant properties, although it is necessary to control the amount of wax in such a way that the transparency of the original acetate sheet is not adversely affected. We have found that if too so thick a coating of wax is applied, the material will have a tendency to feel greasy and show finger marks readily. On the other hand, if the proportion of gum is too high, the material will be objectionably tacky. It should be under- 5 stood, however, that as a general rule the more resinous material present, the' better will be the' adhesion properties of the composite coating.

' In the following examples we have set forth examples of a typical gum, a typical wax solu- 7 tion, anda typical combination gum-wax solution, respectively, but it is to be understood that these formulae are merely illustrative and are not intended as a l mitation of our invention,

since it will be obvious to those skilled in the 75 art that a larger variety of similar compositions of solvent vapors.

sheet I passes to wind up roll I3.

may be made up in accordance with the present description.

Example of typical gum-containing solution Percent by weight 5 Ester gum 80% toluene {20% ethylene dichloride} Example of typical was: solution 10 Percent Paraiiin wax 1 Petroleum distillate boiling between C.

and 70 C. 99

Example of typical gum wax solution 15 Percent Paraffin 3 parts 1 Ester gum 1 part Ethylene dichloride 15 20 Toluene 84 a drying chamber which is preferably provided with suitable means (also not shown) for maintaining the desired temperature and for removal The numeral 1 indicates a 35 second subbing roll having positioned thereover and cooperating therewith squeeze roll 8. Roll I is normally partially immersed in a second bath of coating soution 9 contained in vat I0, which, as in the previous case may be provided with known means for maintaining the coating material in a fluid condition. Numeral II designates a drying chamber similar to chamber 6. Numeral I2 is a guide roll over which the Figure 2 shows additional apparatus for use in connection with the equipment shown in Figure 1, I 4 being a guide roll over which the sheet I passes to a subbing roll I5 having positioned thereover and cooperating therewith squeeze roll IS, the function of rolls I5 and I6, as well as I9 and 20, being the same as rolls 3 and 4, and I and 8, respectively, of Figure l. The vats I8 and 22 also serve a purpose similar to that of 5 and 10. In like manner, drying chambers 23 and 24 55 operate in a manner similar to drying chambers 6 and II. Numeral 25 designates a guide roll over which the finished sheet passes to windup roll 26.

Figure 3 shows an optional form of equipment 60 for simultaneously coating both sides of a base sheet with a series of waterproofing materials according to the invention. Numeral 21 designates asupply roll from which the base sheet I is passed over guide roll 28. Numeral 29 represents an immersion roll normally partially immersed in coating fluid 30 contained in vat I I Numerals 22 and 32 designate a conventional form of scraping device for removing excess coating fiuid from the sheet and insuring uniform application. 7

Numeral 34 is a guide roll over which the sheet I a similar manner by means of rolls 1 and 8, dried up the gum coating fluid I and carrying it. onto the under surface of the base sheet. Roll 0 squeezes oil the excess fluid which eventually returns to the bath. The sheet then passes through the drying chamber 6 where the material applied is merely dried at the proper temperature. The second layer of wax is applied from bath I in in drying chamber ll, passed over guide roll l2,

and finally wound up on roll II; If it is desired to coat both sides of the sheet, instead of being wound up on roll l3, the sheet may be passed around another guide roll ll, thence first through a gum coating operation between rolls l5 and I6, then through a wax coating operation between rolls l9 and 20; and finally wound 'up upon roll 26,

drying of the sheet being accomplished by passage through drying chambers 23 and 24 as in the case of the single coating process of Figure 1.

If it is desired to apply a gain coating to both sides of the sheet simultaneously, the apparatus of Figure 3 may be employed. In this case the sheet I, fed from supply roll 21, passes over guide roll 28, immersion roll 29, between scrapers 32 and 33, over guide roll 34 and thence to drying chamber 35. During the passage of the sheet over roll 29, the vat Si is raised to the proper height which,

places the roll well beneath the surface of the fluid 30 with the result that the coating liquid flows freely into the opening between the downcoming and up-going portions of the sheet, thereby insuring application of the material to both sides thereof at the same time. Excess fluid is removed by scraper bars 32 and 33 which also assist in an even distribution of the material over the surface of the sheet. The single-coated sheet is then dried at the proper temperature by passing through drying chamber and is then subjected to a coating of wax by passage t ugh bath 39, roll 31 and dryingchamber ll perform ing the same functions as previously described, a d the finished sheet is finally wound up on roll It is to be understood that the apparatus herein described is intended to be merely illustrative and that many changes maybe made therein without in any way departing from the scope of our invention. It is conceivable that other t s of apparatus might be used with equally desirable results in carrying out our process. In fact,

the particular apparatus shown and described herein does not of itself form any part of the invention and is intended to be merely conven-'- tional.

As illustrating the highly desirable results to be obtained by the use oi' our process, the following typical examples of coating operations are given below. a Example i v,

A gum solution consisting of ester gum in toluene was applied by hnersion to a'base sheet of cellulose acetate of about .001" thickness hav- 'ing an original capacity for transfusion of of 1.01to 1.5 milligrams per square centimeter per hour. lifter drying at a temperature of 50-105.

tive seal therebetwcen may the points. of contact.

0., a second of solution consisting of 54% ofa 139 paramn,dissolved in a commercial hexane having a boiling point of 60 to 70 C. was thereafter applied in the same mann'e the sheet be- I ing dried at 50 to 105 C. The coated sheet was 5 found to transmit only .005 milligrams per square centimeter per hour.

Example I! A solution containing 1% ester gum dissolved in toluene was applied by a subbing operation to a cellulose acetate base sheet similar to that used in Example 1. After drying at a temperature of 50 to 105 C. a second solution containing 3% candelilla wax dissolved in gasoline was applied in the same manner as'the gum solution and dried at the same temperature as before. The sheet was found to transmit only .026 milligrams of water per square centimeter per hour.

Example III Y 50 0.,the sheet was coated with a second solution consisting of 5% of a 139 paraiiin dissolved in a a commercial hexane having a boiling point of 80 to 70 C. Afterdrying, the double coated sheet was found to transmit only .004- milligrams of water per square-centimeter per hour.

It is a feature of our invention that the double coating of the sheet as it emerges from the bath of wax solution may, if desired-be subjected to a temperature during the last drying operation sufficient to cause the gum and wax layers tounitc or coalesce at their mutual boundary with the result that the coating will range all the way from 100% wax at the outside to 100% gum at the portion in contact with the base sheet.

The-double coated product of our invention is readily susceptible to heat or solvent sealing. For example, when two sheetsare brought to ether with their coated-surfaces in contact, an eifec- I be made merely by the application of heat and pressure, the respec: tivemoistureproof coatings readily softenin and flowing together, to form a satisfactory joint at The application of pressure will enhance the coalescing eifect producm by the heat and serve to ring the sheets into even closer relation and cause them to adhere strongly to'one'another. J

Whilewe prefer to use a base sheet having -a thickness of the order of .001", it is entirely to the purpose of our invention, are plasticisers such as tricresyl phosphate, triphenyl phosphate,

benzyi benmate, and other plasticizing or softeningagents. Furthermore, various spirit.- and oil- 0 soluble dyes, aluminum flake, gold leaf, pearl. essence, and other coloring materials may be included in the composition, or may be incorporated directly-into the original ester dope from which the base sheet'is produced. Perfumes or flavoring 7 whichthe finished product is ultimately to be put.

- Likewise various ultra-violet filters, such, for example, as those described in the co-pending application of Richardson and Stan Serial No. 457,508, filed May 29, 1930, may be advantageously used in the manufacture of moistureproof sheeting which is to be used for the wrapping of delicately tinted articles which have been dyed with dyes which are fugitive to ultra-violet light.

It has also been found that the waterproof sheeting of our invention is readily susceptible of being united or joined by applying various solvents to the portions of the material it is desired to unite and bringing them into close contact. As in the case of simple heat sealing, suchasdescribed above, heat and pressure are advantageously used to cause those portions of the moistureproof sur- 1:

face which have been softened or partially dissolved by the solvents to coalesce and, upon evaporation of the solvent, to form a strong, uniform, and transparent joint or seal. The heat evaporates oi! the solvent and leaves only the mingled or coalesced portion of the coatings of the respective sheets adhering and thereby forming a uniform bond between them..

, Among the solvents which havebeen found suitable for the purpose of solventsealing may be included alcohols of both the aliphatic and aro-' :matic series and containing one or more hydroxyl groups such as methyl, ethyl and normal butyl alcohol, glycerol, benzyl alcohol and cyclohexanol; derivatives of alcohols, such as esters of monoor polyhydric alcohols,- typical examples of which are ethyl acetate, monacetin and diacetin, respectively; keto alcohols, such as diacetone alcohol; aromatic ketones, such as acetophenone, benzophenone, and cyclohexanone; mixed etheresters of aromatic or aliphatic acids, such as ethoxy ethyl phthalate, mixed ether alcohols, such as the monobutyl ether of ethylene glycol and the monoethyl ether of ethylene glycol; diacyl derivatives of dihydroxy alcohols, such as glycol diacetate; monoacyl derivatives .of the monoalkyl ethers of glycol, such as .derived from the monoethyl ether of ethylene glycol and others. The discovery that the abovementioned compounds may be used for this purpose is not to be understood as forming part of our invention, since this is the invention of C. J. Staud and William O. Kenyon, as set forth in their Patent No. 1,925,509.

It is to be understood thatthe terms gum and resin are -used herein and in the claims interchangeably and when reference is made to a gum it is to be taken-for the purposes of our invention as also including both natural and synthetic materials.

Furthermore, although the specific examples above given are directed to, and the foregoing specification is chiefly concerned with, sheeting composed of cellulose acetate, it is to be understood that we are not-to be limited thereby, as our invention is applicable to thin sheeting composed of any cellulosic material to which a gum-wax coating will adhere well; such, for instance, as

cellulose acetate propionate, cellulose acetate butyrate, cellulose propionate or butyrate, or that cellulosic material which is commonly known as Having now particularly described our inven- I tion, what we claim as new and desire to secure 'by letters Patent of the United States is:

2,019,048 materialmay be used, depending upon the use to 1. The process of moistureprooflng thin, flexible, transparentcellulose acetate sheeting adapted for wrappingpurposes which comprises first applying thereto an adhesive layer essentially consisting of gum' and thereafter su- 5 perimposing on said gum layer a second layer consisting predominately of wax.

2. The process of moistureproofing thin, fiexible, transparent cellulose acetate sheeting adapted for wrapping purposes which comprises applying a layer essentially consisting of gum to the sheeting, drying the coating thus formed, thereafter applying a coating consisting predominately of wax, and subjecting the double coating thus formed to a temperature 'suillcient v to cause at least partial coalescing of the gum and wax layers.

3. The process of moistureproofing thin, flexible, transparent cellulose acetate sheeting adapted for wrapping purposes which comprises applying to the sheeting a thin coating essentially consisting of a gum or resin in a molten condition and thereafter superimposing a-coating consisting predominately of wax on said first coating.

4. The process of moistureproofing thin, flexible, transparent cellulose acetate sheeting adapted for wrapping purposes which comprises applying to. the sheeting a thin coating of' ester gum in a molten condition, applying sufficient heat to dry the coating thus produced, and applying on the first coating a second coating of molten paraflin.

5. The process of manufacturing thin cellu lose acetate sheeting of a thickness of the order of .001" which comprises first applying to an untreated cellulose acetate base sheet a solution comprising 1% of ester gum dissolved in a solvent consisting of 80% toluene and 20% ethylene dichloride, subjecting the sheet to a temperature of 50-105 C. for a length of time suflicient to evaporate off the solvents and leave a gum coating closely adhering to said'sheet, and thereafter applying to said gum coating a solution comprising 1% paraflin dissolved in a petroleum distillate boiling between 60 and 70 C., and evaporating off the solvent.

6. The processof moistureproofing thin, flexible, transparent cellulose acetate sheeting adapted for wrapping purposes which comprises first applying to the surface of the sheeting a thin coating essentially consisting of gum and thereafter superimposing on said gum coating a coating comprising a mixture of a gum and. wax. I 5.

7. The process of moistureprooilng thin, flexible, transparent cellulose acetate 'sheeting adapted for wrapping purposes which comprises first applying to the surface thereof a thin coating essentially consisting of gum and thereafter superimposing on said gum coating a second coating comprising a mixture of a gum and wax in which the wax predominates.

8. An article of manufacture comprising a thin, flexible transparent sheet of cellulose acetate adapted for wrapping purposes of a thickness of about .001" having closely adhering to the surface thereof a layer of ester gum, said layer having superimposed thereon and adhering thereto an outer layer consisting predominately of paraiiln.

9. An article of manufacture comprising a thin; flexible, transparent sheet of cellulose acetate adapted for wrapping purposes having a closely adhering coating essentially consisting of a gum, said gum coating having superimposed thereon and adhering thereto an outer coating consisting predominately of wax.

10. An article of manufacture comprising a I thin, flexible, transparent sheet of cellulose acetate adapted for wrapping purposes having a w thin, closely adhering coating essentially consisting of gum, said gum coating having superimposed thereon, and adhering thereto, an outer sisting of gum, "said gum coating having superimposed thereonand adhering thereto an outer coating comprising a mixture of a gum and a wax in which-the wax predominates.

12. The process of 'moistureprooflng sheeting composed oi thin, flexible, transparent cellulosic sheet material adapted for wrapping purposes which comprises first applying an adhesive layer essentially consisting of gum and'thereaiter superimposing on said gum layer a second layer consisting predominately of wax.

13. An article of manufacture comprising a thin, flexible,-transparent sheet of cellulosic mathereon and adhering thereto an outer coating 15 consisting predominately of wax.

" NORMAN F. BEACH. JAMES G. 'MCNALLY

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