[1]Patented Dec. 29,,1942 2@3069478 UNITED STATES PATENT OFFICE 2,306,478@. MOISTUREPROOF SHEET WRAPPING XALTEBL4L Harold Stephens Holt, Wflniington, Del., assignor to E. L du Pont de Nemours & Company, Wumington, Del., a corpomtion of Delaware No Drawin g. APPReation November 1, 1939 Serial No. 302,323 .12 Claims. (Cf. 117-146) This invention relates to moisturepiroof sheet moistureproofness of the wrapping. Ptrtherwrapping material, especially .ransparent, flexi, ble, non-l;acky, moistureproofed, non-fibrous cellulosic web. More particularly, it'appertains to moistureproof coatings for regenerated ce'llulose 5 and like film which are not readily scraped from the base sheet by automatic machinery, and which adhere to the base sheet with great tenacity in the vicinity of adhesive bonds. Recentiy there has appeared in coinmerce a 10 transparent, moistureproof' sheet wrapping - material consisting of a base sh(@e# of regenerated ceilulose Mm coated with a moistureprooflng coating composition. The manufacture of such a base sheet is described in U. 8, A. Patent No. 15 1,548,864 (Brandenberger), and the coating of the like with a moistureproofing coating composition is described in U. S. A. Patent No. 1,737,187 (Charch & Prindle). ' The moistureproofing coating comprises essentially a film 20 formet (usually nitrocehulose) and a moistureproofing agent (usually paraffm wax). Oidinarily the coating also contains a blending agent (usually a resin) for the film former and moistureproofihg agent. Frequently a plasticizer for 25 the moistureproofing coating is also present. In spite of the many desirable properties of this wrapping material, it has certain characteristi6s which limit its usefulness, particularly under condition@, of high humidity or actual contact 50 with water. For example, when products containing considerable water (cheese, fish, fresh L vegetables, etc.) are wrapped therein the surface coating loosens in a few hours, with the ,result that the eff6ctiveness ol the wrapping is 35 very mucli reduc@@d. Extensive research has been carried out with the object in view of improving this type of material. One line of endeavor has been the search for new film formers. Among the materials suitable 40 for this purpose previously discovered have been rubber and chlorinated rubber. The moistureproofing coating compositions utilizing these materials as.Lilm formers give a very desirable prodiiet for a wrapping tissue so far as moistureprobf - 45 ness, tralisparency and flexibility are coneemed, but it has been found that such moistureproofing coati-,lg 6ompositions do not adhere to the smooth,' glossy surface of the base sbeet (for example, regenerated cellulose) with sufficient 50 tenacity for all purposes. . Oacasionally- such coatings are found to slough off or be scraped from the surface in certain operations on automatic wrapping machin6s. As a result there is usually a fouling of the apparatus and a loss In 65 more, an undesimbie . appearance may result from the scraping off of the moistureproof coating. Where the wrappings are sealed by means of - adhesives or the appucation of heat and pressure to the coating itself, It frequently happens that the adhesive bond formed is not sufficiently strong because the coating in the area of the adhesive bond separates from the base sheet. If beta-naphthol Is worked on 6 rubber mill (or in a Banbury mixer) with rifaber and a small aniount of di-hydroxy-fluoro-boric acid or sulfuric acid for about 15 minutes at about loo, C.L I there Is obtained a material quite unuke rubber and the heretofore known rubber derivatives and Isomers. 7be riiaterial sb2ks when placed In water, wiil not adhere'to rubber, is more soluble in hydrocarbon solvents than rubber isomers, and when mixed with rubber on a mill and the mixture made Into a thin cement, layers off. It has now been discovered that this m%terial which, for convenience, may be generically described as a phenol-modi:fted rubber, is an excellent fUm former and that moistureproofing coating compositions. employing it in that capacity adhere very satisfactorily to non-fibrous wat6r sensitive ceUuloSieL flIM. It is an excellent adhesive and adhesive base for regenerated cellulose Mm. Ibis invention' had for an object the,manufacture of improved transparent, moistureproof sheet wrapping materials. Parther objects were to provide firmly adhering transparent, molstureproof, flexible, non-tacky coating compositions for non-:fibrous cellullosic sheet- material-, to Provide moistureprooflng coating compositions having a fllm former comprising essenti a Phenol-modified, rubber; to provide a mo prooflng coating COMPosition comprising essentially a i3henol-modified rubber and a moistureproofing agent; and to provide a moistureproofing coating composition comprising essentiauy a Phenol-modified rubber and a moistureproofing wax. A general advance in the art, and other objects which will appear hereinafter, tire also contemplated. In general the objects of this invention are obtained by. coating a non-flbrous, nonporous, cellulosic film with a raoistureproofing coatilig comPosition comprising phenol-modified rubber as a fllm former, tt moigtureproofing wax and, OPtiOnallY, other constituents such as plasticizers, blending agents,,resin, etr,. From the following description and specific examples, in which gre diselo em sed certain bodi-
[2]2 %806,478, ments of the Invention, as weU u detai Is of wlmt pauecl through a dip bath of the solution, then is believed to be the best mode for carrying out between doctor knives and Into a drying chamthe invention, it wiU be apparent how the foreber. In the drier the solvent was evaporated going objects and related ends are accomplished. at a temperature at least approximately eqW Parts are given by weight throughout the SPPli5 to the melting point of the wax in the compoodcatiom tiorl This material had a heat seal bond strength E=inple I volue of NO. Exampze v A mdistureproofing coating composition niixture consisting of: . 10 A moistureproofing coating composition mixPercent ture consisting of: Beta-naphth6l modified rubber ------------ - 88 Per cent Parafdn wax (AL P. 61' C.) ---------------- 12 Beta-naphthol modified rubber ------------ 59 was prepared and dissolved in toluene (B. P. Paraffin wax (M. P. 610 C.) --------------- 6 111- C.). The resultilig solution was sPr&Yed 15 -Dicyclohexyl phthalate ----------- -------- 12.5 on a sheet of regenerated ceuulose. The excess Dibutyl phthalate ------------------------ 12.5 Rosin 2,017,866* ------------------------- 10 of the coating composition was removed by passing the covered sheet under a doctor knife.- The *This Is a I'modilled r6sin" prepared bl. treating rMn In accordance with U. S. A. Patent No. 017,866. In gencoated film was then introduced into a drier eral its properties are much the same as thosd of rosin, tllrough,which air was circulating, 'where, after 2o but with the difference that it has a molecular welght within the range 50/@ to 400% greater than ordinary a rapid rise in tp-mperature, the coating was dried at a temperature approximately equal to the melting point of the wax. Example 11 25 A moistweprooflug coating compodtion mix ture consisting of: Per cent Beta-naphthol modified rubber ------------- 80 Paraflin wax (M. P. 61' C.) ---------------- 10 30 Chlorinated diphenyl (sp. g. 1.646-1.653, - chlorine 62%) -------------------------- 10 was prepared and dissolved in a swtable solvent. A web of regenerated cellulose was passed 35 through a bath of the resulting solution and then through doctor rolls to remove the excess solution. The coating was then dried on the web at a temperature sughtly above the inelting point or crystallization point of the wax material bv 40 passa.ae through a -heated chamber through whicli air was circulating. E, xample III A moistuve-Drooflng coating composition mixture consist'mg of: 45 Percent Beta-naphthol modified rubber ------------- 82 Paraffin wax (M. P. 61' C.) ---------------- 8 Hydrogeriated methyl abietate (Hereolyn ro grade, prepared according to U. S. A. Patent 1,944,241) ----------------------- 10 was prepared and dissolved in a suitable solvent. The composition was applied to & regenerated rosin in its pure state and higher than that of pure abletic acid. That it has a melting point (as determined by the capillary tube method) of about 800 C., and higher than the melting point of ure abietlc acid and of purified rosin when in the reafn state. That it In substantially free from combined sulfur and hardening substances held In combination, and that It has an Iodine value lower than that of pure abietic acid. was prepared and dissolved in a suitable solvent. A continuous sheet of regenerated cellulose was passed through a dip bath of the solution, then between doctor knives and into a drying chamber. In the drier the solvent was evaporated at a temperature at least appro3imately equa@ to the melting point of the wax In the composition, This material had a heat seal bond strength value. of 600. E=mple VI A moistureproofing coating composition mixture consisting of: Per cent Beta-naphthol modified rubber ------------- 59 Paraffln wax (M. P. 611 C.) ---------------6 Dibutyl phthalate ------------------------ 12.5 Dicyclohexyl phathalate ------------------ 12.5 Para cumarone indene resin (M. P. in the range 10'-45' C.) ---------------------- 10 wa@- prepared and dissolved in a suitable solvent. A regenerated cellulose sheet was covered with the resulting solution by spraying, and the coated sheet passed @through doctor knives to remove the excess solution. The coated base sheet was then dried at a lower temperature than the melting point or crystauization pohit of the wax in the composition and then subjected to a heat treatcellulose flhn by spraying. After passage through r).i ment at a temperature at least equal to the doctor rous to remove excess solution, the r-ovmelting point or crystallization point of the wax ered film was passed through a drying chamber in the composition. equipped for air circulation and solvent recovery. 7he temperatare of the covered film was Example VII rapidly raised to the melting point of the wax and A moistureprooflng coating composi tion mixwas held until the solvent had been removed from 60 ture consisting of: the coating on the sheet. Per cent Beta-naphthol modified rubber ----- - ------ 40 Example IV Paraffin wax (M. P. 611 C.) ----------------- 10 A moistureprooflng coating composition mix- 65 RoSin 2,017,866 ---------------------------- 10 ture consisting of: Pliolite* ------------- -- ------------------ 40 Per cent *Pllolite Is a therinoplastic rubber derivative made by Beta-iiaphthol modified rubber ------------ 69 condensing rubber witb a catalyst sueh as tin tetraParaffm wax (X P. 61' C.) --------------- 6chloride L(See Paper Trade Journal Ir ge 96, February 23, 1939. J. I. E. C. XXVI, 125, ana . S. A. Patents No. Dicyclohexyl phthalate ------------------- 7 . 5 1,797, 188, 1,846,247, 1,853,334 and 2,052,391). The . 70 cbemi cal mtrurture Is described In "Rubber Age," April Dibutyl phthalate ----------------------- 7 .5 1939, and J'. 1. E. C. XIX, 1033. Hydrogenated methyl abietate (U. S. A. was prepared and dissolved in a suitable solvent. Patent 1,944,241) ---------------------- 10 A regenerated cellulose fUm was moistureproofed was prepared and dissolved in a suitable solvent. bylcoating it with the resultant solution In the A continuous sheet of regenerated cellulose was 7:) usual manner.
[3]2,806,478 E=MPI9 vizz Exampu xzrz A moistureproofing coating composition mix- A moistureproofing coating composition niixture consisting of: ture consisting of: Per cent Percent Beta-naphthol modified rubber ------------ 29.5 Betanaphthol modilled rubber---- ---- -- 6.48 Pamfftn wax (M. P. 61' C.) --------------- 6Urea formaldehydf, monohydric alcohol Dibutyl phthalate ------------------------ 12-5 (iso-butanol) resin (soUds-basis) ------- 3.24 Dicyclohexyl @hthalate ------------------- 12.5 Maleic acid---- 0.36 - - - - - 6 - & - - - - - - - - - - - - - - - - - Rosin 2,017,866 --------------------------- 10 lo Paraffin wax (M. P. C.) -------------- 0.72 Chlorinated rubber (65%-68% clilorine) --- 29.5 Dewaxed damar-.@ ---- r ------------------ 1.20 was prepared and dissolved in a suitable solvent. Toluene -------------------------------- 74.80 A regenerated cellulose fllm was moistureproofed Isobutanol ---- I -------------------- ------ 13.20 by coating it with the resultant solution in the was prepared 'A regenerafed cellulose sheet was usual manner. The moistureproof sheeb had a 15 coate d with this moistureproofing coating In the heat seal bond strength of 100. In a siniilar usual maiiner. - producti in which only chlorinat@d rubber (59%) The primary film-forming ingredients in the was used as the film former, the heat seal strength foreg6 ing examples are, for convenience, cared was zero. (gener ically) phenol-modified rubbers or phenolExample IX 20 modtft ed rubber 2,158,530. They Are prepared a ccording to U. S. A. Patent No. 2,158,530 A moistureproofin'g coating composition mixture consisting of: (Willia m@). The beta-naphthol modified rubber -of ExPercent ample s I, II, III, IV, V, VI, VH and VIII was Beta-naphtiliol modified rubber -------- : ------- - 93 25 prepa red from beta-naphthol (20 parts) and Paraffin wax (BE P. 61' C.) ---------------- 7rubber (100 parts) with sulfuric acid (4 parts) was prepared and dissolved in a, suitable solvent. as a. catalyst. The Phenol (C6H50H) -modifled A regenerated cellulose fUm was moistureproofed rubber product used.in Example IX was prepared with the resultant solution by the usual methods from beta-naphthol (5 parts) and rubber (100 of applicatidn. 30 'parts) with sulfuric acid (4 parts) as the catalyst. Example X A moistureprooflng coating- composition niixture consisting of.- Percent 35 Beta-naphthol modified rubber ------------- 90 Paraffin wax (M. P. 611 C.) ---------------- 10 was prepared and dissolved in- a, suitable solvent. A regenemted cellulose film was moistureproofed 40 with the resultant solution by the usual methods of application. Example XI A moistureproofing coating composition mixture 45 consisting of Percent Beta-ng,phthol modified rubber ------------- 70 Paraffin@ wax (M. P. 610 C.) ---------------- 6 Dibutyl phthalate -------------------------- 7,50 Dicyclohexyl phthalate--- 7 Hydrogenated met4yl abietate (U. S. A. Patent 1,944,241) ------------------------- 10 .was prepared, and dissolved in a suitable soivent. 55 A regenerated cellulose film was moistureproofed with the resultant solution by the usual methods of application. Example XII A moistureprooflng coating- composition mix . .- 60 ture c6nsisting- of: Percent Phenol modified rubber -------------------- 70 (;5 Parafftn wax (M. P. 61' C.) ---------------- 6 Dibutyl phthalate -------------------------- 7 Dicyclohex@rl phthalate ---------- -----------7 Hydrogenated met4yl abietate (U. S. A. Pgtent 1,944,241) ------------------- ---- 10 @To was prepared and dissolved in a suitable solvent. A regenerated cellulose film was mqistureproofed : with the resultant solution-by the usual methods of the application. 75 The beta-naphthol der,ivative of Example X was prepared from beta-naphthol (10 parts) and rubbeir (100 parts) with sulfuric acid (4 parts) as a catalyst. 'The film foriner o' Example M was 1)repared from beta-naphthol (40 parts) and rubber (100 parts) with sulfuric acid (4 parts) as a catalyst. The phenol derivative of Example XII was prepared from phenol (40 parts), rubber, (100 parts) with di -hydroxy-fluor-boric acid (4 parts) as a catalyst. In the manufacture of th6 phenol-modified rubber, It is customar to mill the rubber with 'Y more of the phenol body than is teqi@ired by the theoretical proportions for the reaction. This excess beta-naphthol, phenol or the like can be removed from the reaction mass at the end of the. reaction by treatment with a suitable solvent therefor. It was such a purifled product that was used in the speciflc examples set out above. The crude.product containing the excess phenolic mat-arial can be used as produted in many instances. In other cases the excess phenolic body can be converted to a phenol-formaldehyde type resin (for exan@le, by'@reating the rubber-phenol reaction mass) with formaldehyde. The formation of this resin renders the phenolic material Inert and more compatible with the coating composition Ingredients so that the characteristic tendenqy of phenol to blush out is obviated. The product prepared by reacting 5 to 20 parts of . beta-naphthol with 100 parts of rubber In the presence of 4 parts of sulfuric acid as a catalyst, and p!lrifying by removing the excess betanaphthol Is preferred for the purposes of this invefition. As pointed out in the patent cbvering the manufacture of these substances, the proportion of beta-naphthoi may vary widely (5%-50%, based on the rubber); and various other phenols, such as ordin@ry phenol, chlorophenol, cresois and di-hydroxy-di-phenyl, and various other catalysts such as organic sulfonic a@cids, borontri-fluoride and hydroxy-fluor-boric Acid may be utilized Minor proportions of other fflm forming Ingredients may replace part of the phenolmodi-
[4]4 :fted rubber when sDeeW effects are desirecl. In addition to the chlorinated rubber and rubber isonief (Pliolite) of the specific examples, mentioil n2sy be made of rubber, rubber dei-ivatives and synthetic rubbers including caoutchoue, gutts 5 percha, and rubbery polymers of isoprene, butadiene, and their hoinologs. Mlm forming resins, both natural and synthetic, and various plastic substances, may be employed. The more common flim formers, such as nitrocellulose aiid cel- 10 lulose acetate, give desirable products. In geneml, use may be made of cellwose substitution derivatives, such as cellulose ethers, cerulose esters, ceu-alose hiixed esters and cenulose @ther esters. 15 As a moistureproofing ingredient, any wax (used genericary to include wax-like substances) capable of moistureproo:ftng, may be employed. Ordinarily the paraffins, preferably the high mately 60' C. or over), are preferred. . Other suitable materials deserving of special mention are ceresin, montan, palm wax, Japan wax, Chinese insect wax, spermaceti, tallow, beeswax, 25 stearyl stearate and synthetic waxes. The waxy substances may be used singly or in combination. In its simplest forin the moistureproofing composition of the present invention contemplates a solution of the new fUm forming material and 30 the wax moistureprooflng agent in the. common solvent. The moistureprooflng coatings resulting from such compositions are usually more or less subject to marking when handled., particularly where the moistureproofing agent is a soft wax 35 such as paraffin, or the softer varieties of ceresin wax. This is not objectionable for all, though it is for a large number of uses. This undesimble property may be overcome by introducing a substance which incteases the hardness of the coat- 40 ing. GeneraUy waxes or resins are used In the moistureoroofing coating compo8ition for this purpose. Among the waxes suitable for inereasIng the hardness of the coating, hard wax such as carnauba wax, candelilla wax, and the Me, 45 are most generally used. The resins employed f6r this purpose are preferably those soluble in hydrocarbons (such as benzene, toluene, xylene, gasoline, and the like), but it will be understood[ that resins soluble in other liquids dissolving In 50 the rubber, or waxes already decided upon for the moistureproofing composition, may be employed. Hard or soft ' resins, for example, rosin, hydrogenated rosin and their derivatives, zinc resinate. alkyd resins, coumarone resins, and the like, are suitable. In some Instances the pr6sence of a hard or soft gum, either natural or synthetic, Including gum damar and gum mastic, may be desirable. Compositions utilizing gums and/or resins in general deposit coatings which possess superior surface co gloss and smoothness characteristics. One or more of the hardening ggents maY be used. Rosin and various forms of modifled and, purified rosins are often used for the Oiirpose of blend- 65 Ing .the wax and fUm forming Ingredients. These particular materials therefore have a double fimction since they also harden the surface. Resins serving only to blend the other ingredients MaY be used if desired. 70 Va,rious softening or plasticizing agents, for ex- ample, dibutyl phthalate, tricresyl phosphate, chlorinated paramn, hydrocarbon oils, and the like, may be used. These materials are particularly useful when it is desired to increase the heat 75 seaung Properties. In order to wcure Particular results, one or inore of these agents inay be present ln'the molstweproofing coating. As the solvent. anY organic Hquid in which both the wax Aiid phenol-modified rubber fUm former are soluble, may be employed. Mustrative materials are benzene, toluene, xylene" tetrachlorethane, and the like. It is advantageous to choose a SOlvent With reference to the wax used, particularly in regard to the bouing poitt of said solvent, which should Dreferably be higher than the melting point of the wax. For example, when a wax having a melting point of 60' C. is used, a solvent such as toluene (having a botling point of 1110 C.) gives good results. F'requently, when the temperatur4e of the coating is to be maintained at or above the melting point of the wax- in the composition while the solvent Is being evaporated, It is preferable to use a n2ixed solvent in which at be obvious, the term "solvent" as employed herein is intended to cover one or -more cherhical compounds with or without diluents. In aU cases the solvent selected should be of such a nature that it wiU not injure the base being coated. The compositions may be modified in many ways to secure other kinds of effects. Pigments or pigment-like materials and inetauic soaps may be included in the coating composition. Oil soluble dyesmay be added where a colored transparent coating is desired. Variegated effects can be secured by the use -of powdered n2ica, flsh scales, metallic salts, etc. Rubber anti-oxidants, aeceleratlve and vulcanizing ag,@nts may be incorporated In the composition. The relative proportions of the solid ingredients constituting the solution or coating may vary within wide Hznits,, depending upon the specifle material used and/or the properties desired in the fl.nal -product. Depending upon the wax used and the Properties of coating desired (surface properties, flexibility, transparency, and the like), the amoimt of wax may range from a relatively sma-H amount (for example, 19'0 to 2%) to a relatively lilgh proportion (such as 80% or even 5%), based on the total solids. When gums or resins are ernployed there is AISG a wide range of compositions which wiR give satisfactory results. In any formulation it Is Possible to use larger amounts of a 's'oft gum than of a hard gum without intrgducing brittleness. The effect of a hard resin may be somewhat counteracted by the presence of rlibber Or RlUed SUbStanCeS Whieh " as a softening agent. In the preferred embodiment of the invention regeneiated cellulose web is the base which is coated. Paper and other cellulosfc materials,- especially those which are nonfibrous, non-porous and (preferably) transparent, such as treated paper, film of cenulose derivatives (for e'xample, low substituted cellulose ethers), materials coated with non-moistureproofing compositions, sheets of albuminous materials (for example, gelatin, agar-agar, etc.), are also contemplated. To prevent oiddation and to insure stability of the coating, the preserice therein of antioxidants may some tiines be desirable. Such compounds as benzyl-para-aminophenoI, 2-ainino-5-hydroXY-toluene, and the like, are preferred for this purpose. They are especiany compatible With'the ingredients of the various compositions of this invention, and may be incorporated satisfactorijy therein, particulariy the specinc coml)ositions of the examples. The amount of anti-Oxidant varies melting parafflns (such as those melting above 20 least one of the components has a boiling point 50' C., or better, 55' C., or stiu better, approxiliigher than the melting point of the Wax. As will
