US2605328A - Flexible web coated with an ethyl cellulose composition - Google Patents

Description

Patented July 29, 1952 FLEXIBLE. WEBCOATED WITHYAN ETHYL' CELLULOSE COMPOSITION MiltonH. Pintell, Richmond, Va;

. Nonrawi g. LApplication 'Apfil144 19.49, J I ;Seri al No. 87,519 I T object o li he presen i v n qnl sfto. P130? vide an adhesive which may be applied tojpaper nd ot er web labels. crai p si a d us i various other applications; and which is char acterized byfnonblocking atnormal temperatures. which willbefstable for long periods of time and whic h,]when activated by heat," will acquire i strong adhesive. properties' and Willf "retaina'ta'cky and adhesive property for adesired periqd of time, whereupon inherent crystalliza bottles: are placed; in team. a refrigeratoriimmersedvwin a water :talikv maintained atglow temperatures, to efiect -,cooling of v the beverage prior to consumption; and should be essentially non-toxicrand water insoluble; Werethe .{label coating ,solubleain; water, or were -itto contain constituents that; tended toward leaching: Qr; re-

I moval in: the: presence of high humidity 01 3111),-

tion progressively occurs tq emove the tacky characteristic. v u For many years c orts have been f .produce an adhesive composition which will be dry and stable on a carryingweb, which will specifically be non-blocking under normal temperatures, but which, can be rapidly activated by heat to become tacky and strongly adhesive with .adelayed set, and a specific object of the present'invention' ls'to provide an improved adhesive of such type.

Adhesives of the stated type have many useful applications. In the packaging of many products, heat-sealing materials of the general types in use are not, applicable because heating irons cannot'be applied to the laps and folds of the terials, jand' my adhesive composition removes the necessity for such method of heatesealing. A second examplefof'utility ispresent in the use of labelsfor high speed bottle-labeling mawrapperswithout damage to the packaged ma chines; which function at speeds upwards or of the label should be retained :afterthe label has reached room temperature andfor at least several minutes, so that should the necessity arise-for stopping" the labeling machine to remove one or "more "broken bottles or otherwiseclean the labeling unit, labels not yet pressed on their a bottles may be effectively pressed into firm bonding after such'dela'y';

In order'toprovi'de a delayed set adhesive for general u'se, it should be essentially odor-free and water insoluble. 'rhus labeled beyer'ase.

mersiont in a water -cooling-tank,;,=the1 labels would float: off the beverage bottle, causing-floss of identity of: theibeverage: contained therein.

Commercial production ofwrappers andlabels requires that they be printedor otherwise decoratedin'klarg'e sheets'or roll formysubsequent'tp further processing 'and cutting into the; final smaller sizes; Pressures caused by the rollformation-of' webs andthe stacking of.v large sheets or labels or the. web-tension required-dame}; printing processes "toinsure ssatisfactoryare-wind .of the xprinted.:.labels, andw storage conditions under rather: high temperatures, are such that complete absence, oftack; or, adhesive character of the coating. is required- Under-suchmonditions, my adhesive adequately meets these requirements. Furthermore; a large percentage of Wrappers and labels are currently-embossed to provide for a more pleasing eifect. The applied adhesive should, therefore, providesuflicient flexibility to P m t rcsaisaewrwm es m of the coated label stock, and ray-adhesive mposition meets this requirement, Also, the applied labelqcoating should have satisfactoryadhesion to glass -o li-Qother -s urfaces to which, the label is applied, after activation, and should robs- Eviously retain this adhesive character lfpraex tended periods of time, without'material deterioriation' :or its adhesive character even under conditions of high-humidity; I Y i Conventional bottle-washing practices :employ aqueous sodium'hydroxidesolution-to eflect remova'l-"of "the applied label. Labels of aluminum foil or foil-on-paperlabels react-with the sodium hydroxide solution to form wsodium aluminate. My adhesive coating does not react with-'thefso diumaluminate. A 1 i 'Myedelayed tack coatinglconsists'of ia "film former such as ethyl cellulose; together with a plasticizer that is unique'in that it is' normally solid or crystalline at room'-temperature, but possesses the 'pe'cular characteristic of remaining fluid foran extended period of time prior to crystallizingy The "effectbf delayed" crystalliz'ation of solids normally solid at' room' tent-- perature is extremely limited to at -mos't three or four known'substances.v 'I'h'e preferred crystali'ne materiallxhibiting this' unique delayed Percent ortho terphenyl 52.50 Ethyl cellulose (46.8-48.5% contained ethoxyl having a viscosity of 4 cps. when by weight of this cellulose ether is dissolved in a solvent solution consistin e of 80% toluol and 20% ethanol 17.50 V Acetone 18.75 Isopropyl alcohol (80%) 11 -.25;

Although the lower boiling alkyl alcohols are 7 alcohol, The percentage "of selected alcohol is carefully m'aintainedto a" point above which pr'eci'pitatioii of the ortho terphenyl occurs;

* In production practice, the paper,'foil or paper mounted-aluminum foil is coated with the? composition indicated" previously, by any standard means'fand'the coated web is thereupon caused to pass through an oven section, whereupon air maintained atjr'oom temperature (not to exceed 120 {-;F. is thereupon caused to pass over the surrace "of the coated'web, effecting 'removal of the solvent'constituentsi In practice, the mutual solventconstituent, such as acetone, evaporates firstf'leavingacoating containing isopropyl alcoho'l and 'precipitation with spontaneous cryst'allization of the coating occurs.

3 "asecond example:

I V Percent orthoiterphenylngn u 52.50 Ethyl cellulose (46 .8-485 containedv ethoxyl exhibiting a I viscosity ,of 4 cps. i Whe1 i.,20% by weight of this. cellulose 1" other is dissolved in a solution consisting 012.80%, toluol and 20% ethanol) 17. 50 H a e' --,--,-'--.-T.---, 22- Anhydrous ethanol 7.50

' The following means have been developed to provide for acceleration 'of the "crystallization of the coating: I a

f (a) The coating'is :applied to the paper web, dried by passage of heated 'air over the surface of the. coated web, a thin layer of selected lubricant such as oil, wax or soap is applied to the tacky coating by spray application or by coating rolls, and the surface is thereupon subjected to a brushing operation, accelerating the crystallization and permitting immediate re-wind or sheeting of the tack-free web. The employment of alubricant is required to avoid adhesion of the brush to the tacky coated-surface.

"'-i(b) The coating is applied to the paper Web. dried by passage of heated air over the surface of the coated web, and a thin layer of selected solventisapplied over the surface of the dried web, and the solvent is thereupon caused to be :removed 'by passage of air no higher than room temperature (not to exceed 120 F.). Selection of the solvent is of considerable importance. Any solvent in which the ethyl cellulose is soluble but which exhibits poor or no solvent action on the ortho terphenyl has been discovered to be satisfactory. For example, all the lower alkyl alcohols, such as methyl, ethyL-iso-propyl, propyl and others, all of which'exhibit poor solvent action on ortho terphenyl, but which have pronounced solvent action on the ethyl cellulose have been discovered to be satisfactory.

(c) The coating is applied to the paper web, dried by passage of heated air over the surface of the coated web, and finely divided or powdered ortho terphenyl in solid crystalline form is caused to be sprayed over the surface of the web. The solid crystalline ortho terphenyl seeds andefiects rapid crystallization of the coating.

Both formulae are capable of wide variation to effect-a greater. or lesser degree oftack or adhesive character. Thehigherthe ortho] -tor-1. phenyl to ethyl cellulose. ratio, the more; acky will bethe final. product' f'a'nd ,con erse1 lower the ortho terphenyl tofethylcelluloser the less tacky Will be the .fiilalgprodllct, a mi ni mumof 2.5% ethyl cellulosajbalaince orthoterphenyl to l 00% is believed-Ito be the lowestc'o' centration that .would; functio'n successfully; jA maximumof 82.5 ethyl ce1lulose,,b alanoe ortho terphenyl to is believedfltqbethehighest ethyl cellulose concentration that wouldifunction satisfactorily. In practice, although thefhigher character of'orthoterphenyl increases the tack or adhesive character of "they coating, film strength and adhesive-character of the coating reach an optimum when the coating composition follows the formulae indicated previously. Q;

Substitution of the ethyl cellulosevtype can-b effected without materially affecting the adhesive character and properties of the'coating. Forexample any ethyl cellulose containing 43.5 to 50% contained ethoxyl and varying from 2 cps. to 500 cps. (exhibiting this viscosity. when a v20% solution of the cellulose. ether is dissolved in a solvent combination consisting of 80% toluol, 20% ethanol). In addition, it is entirely possible to substitute other filmformers such -.as.nitrocellulose, benzyl or other aryl cellulose, methyl or other alkyl cellulose, -mixed cellulose esters, such as cellulose aceto-butyrate or;- aceto-propionate, vinyl halides, vinyl acetate-mixed vinyl. co-polyvmers, such as vinyl chlor-acetate, acrylic and methacrylic acid esteripolymers, polymers and co-polymers of styrendpolymers and co polymers of vinylidene-halide, abietic acid esters and most other resinous compatible products for the'ethyl cellulose. I 7 I '1 Although the ortho isomer of terphenyl is remarkable and completely'unique in=its exhibition of delayed crystallization at normal room temperatures (35 to "F-.') other substances-also exhibit this delayed crystallization tendency to a lesser degree and in consequence "can-also be employed to produce delayed tack adhesive coat ings. These include diphenyl'and-th 'other two isomers of terphenyl, the meta and para.

The ortho terphenyl-ethyl cellulose preferred composition has functioned successfully on'labels subject to washing in'existing rotary-label and bottle washing equipment employing sodium hydroxide solutions exhibiting no untowardlefiects in the wash tanks. Accelerated removal 'ofsaid labels can be secured by the'incorporation of aluminum, zinc or magnesium .poWderj'to the coating composition and to the extent of from 1 to 25% (perferred 7.5% aluminum powder) which in turn tends towards amor pronounced andajmore rapid reaction-smith the sodiurh hydroxide solution. IIt willzbeiunderstoodthaiisirnany or FofSthe compositions given herein and additional plasticizer: may be. added..whenevenz'='it is desired. to secureincreased-plasticity. further examplawhich "empldys a film other than that specified 1 in he. first tw 'ample's,"is as fo1lows-: A i i Example 3 Percent Ortho terphenyl 28.22 second nitrocellulose containing 10.7 to

11.2% nitrogen 8.71 Methyl ethyl ketone 14.27 Isopropyl alcohol (85%) 48.80

In the following example, the film former selected is polyvinyl acetate:

Example 4 Percent Ortho terphenyl 32.87 Polyvinyl acetate (havinga viscosity of cps. when 5% by weight of this resin is dissolved in methanol) 9.83 Methyl ethyl ketone 2.10 Acetone 8.22 Ethyl alcohol (8.7%) 41.98

'In the following example, the film former proportion substantially exceeds that of the ortho terphenyl or equivalent material having delayed crystallization effect:

Example 5 Percent Ortho terphenyl 11.50 Ethyl cellulose (46.8-48.5% containing eth- Ethyl cellulose (45.8-48.5% containing ethoxyl) having a viscosity of 4 cps. when by Weight is dissolved in a solvent solution consisting of 80% toluol and 20% ethanol 1 15.12

Acetone 18.37 Isopropyl alcohol 15.67

Apply to web at solution temperature of As an additional example:

Ermmple 7 Per cent Ortho terphenyl 33.75 Para terphenyl -1 22.12 Methyl phthalyl ethyl glycolate 4.73

Ethyl cellulose (46.8-48.5% containing ethoxyl) having a viscosity of 7 cpsywhen 20% by weight of this cellulose ether is dissolved in a solvent solution consisting of 80% toluol and 20% ethanol 13.67 Hexane 4.28

Toluol 2.25

Anhydrous ethanol 9.20

ethoxyl) having a' viscosity of 7 cps. "when 20% by weight of this-,cellulose I ether is dissolved in a solvent-solution consisting of toluol and 20% ethanol 14.23

Heptane 21.11 Toluol 2.25

Anhydrous ethanol 6.33

Formulae containing diphenyl may prove advantageous in inhibiting mold growth in products subject to mold growth packaged in wraps prepared with the above coating.

As an additional example:

Example 9 Per cent Para terphenyl 38.75

Ethyl cellulose (46.848.5% containing'ethoxyl) having a viscosity of 4 c. p. s. when 20% by weight of this cellulose ether is dissolved in a solvent solution consisting of 80% toluol and 20% ethanol 15.23 Hexane 24.25 Toluol 3.12 Anhydrous ethanol 18.65

This coating solution should be applied at temperatures from -130 F. because of the low solubility of the para terphenyl in the solvent composition at room temperature and is not a preferred composition.

It will thus be seen that by means of the invention there is provided a homogeneous normallysolid coating for flexible webs and other carriers,

which comprises a film-forming material, and a material normally solid at room temperatures, the composition being capable of activation by heat to assume a tacky adhesive form for an extended period of time and to progressively crystallize to a non-tacky solid.

Further utility of the invention lies in the following characteristic of the coating:

Through the progressive crystallization of the coating after it has assumed adhesive character through the application of heat, adhesive layers of intermediate labels, for example, and containers to which the labels are afiixed, become dry. At the same time the said dry adhesive does not lose its ability to become fluid and tacky when again heated. Thus in the case of labels on bottles, such labels may be removed by stripping after the application of heat. There are many further applications where this characteristic of the adhesive coating finds special utility.

Accelerated crystallization of the initially applied coating, after evaporation of the solvent, by brushing action, as herein specified, may be substituted by any suitable surface agitation of the coating, vibration for example, or by induced crystallization through any other suitable means, as by pressure contact with hard small aggregates bonded to a flexible carrier or bythe solvent film method described herein.

Having described my invention, what I claim' 7 and, desire, to secure by Letters Patent, isas follows:

A flexible web'having au a-surface thereof a normally dry coating composition havingdelayed adhesive properties when subjected to heat above room temperature which comprises a" minor proportion of ethyl cellulose, and ortho terphenyl inmajor proportion.

' MILTON H. PIN'I'ELL REFERENCES 'cnmn y y The following references are of record in the file of this patent:

Number UNITED STATES PATENTS 7 Name Date Hasburg Dec, 11, 1917 McClellan Mar'..7, 1922 Lovell May 7,1929 Charch 1 Oct. 6, 1931 Bradley Feb. '7, 1933 Murray May 15, 1934 Kauppi et a1 Oct. 6, 1942 Sermattei Dec. 28, 1943.

Keller Nov. 6. 1945