US2737540A - Paper coated with cold-milled mixture of crepe rubber and hydrogenated fatty oil - Google Patents

Description

March 6, 1956 EGLER U M. M, 2,737,540 PAPER COATED WITH CoLwMILLED MIXT oF CREPE RUBBER AND HYDROGENATED EATT 1L Filed Dec. 24, 1952 INVENToR.

United States Patent O PAPER- coATED WITH coLD-MiLLED oF eREPE RUBBER- AND HYDROGEN'ATED FATTY' on.

Margery M.. Egler, Chicago, lll., assigner, by mesne as sgnments, to PhillipsA Coating. Corporation, a: corporation of Illinois Applicationccember 24,1952, Serial No.327`,739

4 Claims. (Cl. Zlle-752) -The present invention relates to coated paper and coating compositions therefor which form impervious lms having selective pressure-sensitive adhesive cold-sealing properties. It includes among its other objects and advantages a high degree of impermeability and outstanding permanence and resistance to decay and contamination. In thel type of wrappings commonly' employed to wrap vegetable and: animal food products, iti includes complete freedom from odor ofitsV own', combined with only a slight tendency to assume the odor of the substance wrapped..

The advantage of wrapping material' coated with cold sealingr as distinguished from hotse'aling coating compositions has been recognized for some time. However, prior attempts to provide' cold sealing compositions have called forthe` use of relatively expensive'adhesive mixtures and'have proven unsatisfactory'due to the cost' factor plus the factV that the resultingcompositions lack the desired coatingv or film-forming characteristics; These disadvan tages are-avoided bythe present invention;

The coating or film-forming compositions ofthe present invention consist essentially of Sti-70% by weight., of hydrogenated fatty oil and 30"-50% by Weight of.v rubber. One of thepreferred compositions consists ofabout' 60% by weight of hydrogenated fatty oil and' about' 40% by Weight of crepe rubber'. At least' 30% ofV rubbefwith the hydrogenated fatty oil is necessary toprovide a satisfactory coating capable of cold sealing, i; e., sealing of the coating' to coating when pressed together at room' temperature; Also,` it lia-sheen found' necessary to coltiv mill the hydrogenated fatty oil-rubber mixture as' described below before applying heat for` the' coating operation.. If the mixture is heated (fused) before cold millingl. the resultingl composition on cooling is' brittle and willnot form'th'e desiredv cold sealing flexible-type coating or filtri when applied to-paper or other base' sheet material'.

It has previously been proposed to coat'l paper with a composition made upofa minor amount of' alrubber and a major amount ofv hydrogenated fatty oil. An illustra tive-prior art composition made* up of 14 parts by weight of rubber and 86 parts by weightV of hydrogenated oil' is described inthe FergusonU. S. Patent 2,082,278". This composition does not contain enough rubber` to produce a cold sealing film and as it is made byheating'or fusing a mixture of the ingredients instead of heating the previously' cold milled; product as specifically called for in the present invention, the Ferguson process isalso not capable of producing a composition having thev desired coldv sealing` properties. It has also been proposed to coat paper with a rubber-parain wax composition. Compositions of this type are described in Abrams et al. Patents.2,054, 112 and 2,054,115. These compositions 'employingparain wax' or the like in place of the hydrogenated fatty oil; i. e., glyceridesof hydrogenated higher fatty acids, arel alsov not capableof cold` sealing. Application. of suicientlheat to soften or melt the paraflin Wax type compositions, for example, is necessary to obtain'. a seal. Inv other words,- the-Abrams et al. cormgfositionsv are'heat sealing` asfdistin- 2,737,540 Patented Mar. 6, 1956 ICC 2 guished from the improved cold sealing compositions. of the presentinvention.

In the accompanying drawings,

Figure l' is' a diagram of an installation of coatingequipment' according. to the invention;

Figure 2 is a hypothetical cross section of a porous paper on the hot roll before the coating.. contacts it; and

Figure 3 is a hypothetical cross section ofthe finished coated paper.

In the' embodiment of equipment selected for illustration, the uncoated paper is withdrawn-from a conventional roll 10' and passed over a heatedroller 12V havinga long arcV of contact with the paper. Where the paper is travelingvertically downward, it is pinched between the heated roller 12 anda companion dragroller 14, also heated and turning about one-tentli` as fast` as theV roller 12. Conventional adjustment means for the roller 14 are used to calibrate the thickness ofthe issuing strip.

A supply of coatingmaterial i'smaintained in a steam jacketed kettle 16' having a gate valveV at. 17 for controlling the rate of discharge into the crotch lor bight between the. pinch rolls 12 and 14.

From the pinch rolls the hot paper carryingy the hot coating passes through. a short path. onto a large cold chill. roller. 18 which engages the paper on its uncoated side. This reducesthe temperature of the paper abruptly and forcibly.

Thereafter the cool paper passes through` a horizontal reach 20`to`equipment for surfacingthe coating to prevent adhesion and then rolling the strip into a nished roll. I have indicated a turnover roll-22 which delivers the strip into the horizontal reach 24. Above the reach 24 is the hopper`26 provided with an'Y adjustable gate 28 and afdischarge? roller 30; from which'a thin coating of iinely'p'owdered' starch oreq'uival'ent material is sprinkled on the moving` strip. The-striplthen passes over the' guide rollers 32 andi34intoanf inverted reach`-3"6 and; to the storageroll 38. In passing around the rollers 32 andy 34- tliestrip is again inverted sothatf excess powdercarriedl by the strip can fall olf'. The excesspowder may bev collected in a receivingy tro`ughl40-`y The strip' may be agitated above the trough 40, as by a beater'42. Finally' the paper is coiled on-the receivingroll'SS-f'and'theprocessingis complete.

I have found that' tliedegree of permanent union'betweenthef'coatin'g and the paper'dep'ends" on the temperature history of-the`coating' and of they paper. It is not particularlydifficulttol operate within the preferred limits, but staying Within tli'e'preferred'flimit's appears to` be essen'- tial for obtaining an optimum product. I prefer tokeep the temperature of'thel materialk in the rkettle 16 'as hot as the material willfstand'y without thermal injury; Forna blend'of 30`-S0`%'V rubber and`50-70% hydrogenat'edl oil, thistemperature is* advantageously about 300' F.. It' is desirable to maintain this temperature to within about 5` F. eitherway and even closer control is advantageous'. Both rolls12 and 1'4 Vare' heatedy to about the same' tem'- perature as the coating and preferably aboutH 5 F. more. The strip ofv paper'itsel'f in thestorage roll 10, should not be kept in a' coldwarehouse and thrown immediately into thel coating" equipment at temperaturesv below the' d'ew point ofthe air in the room. l

The roller llishould be cooled, asby Coldwater running through it, at least about as low as' 50l F., and 40 FQ is better: It is customarily at a' temperature' below the dew point of the air in theA roomv and may tend to collect a film of water when not in use.

In Figures 2'l an'd'S-I haveindicated ina diagrammatic way what Ii believe tol be onepossible'reason` or explanation forv some of the superiorqualities of coated paper thus produced:v Referring nismo Figure 2; theipaperxat 46- came fromftlie'- folli-I0 at aboutf'ro'om temperatureand. is: suddenly nirown` intol close contact withl the" het metal 12. The types of paper or backing used are preferably porous and the air in the pores undergoes a large volumetric expansion as the temperature rises. As it cannot nd any exit toward the metal of the roll, all of the expansion has to be accommodated by air blowing out of the upper surface of the paper. The result is that loose fibers, indicated at 48, of varying lengths, are lifted up approximately as indicated in Figure 2. It may be that there is also electrostatic action between the moving strip and the metal, which action contributes to this lifting of a nap on the surface of the paper which is going to Contact the coating material.

By the time the paper reaches the coating material it is thoroughly heated through and the air in it has expanded to substantial equilibrium at high temperature. Then contact with the hot gob of coating composition and passage through the pinch rolls causes the sheet to come out as indicated in the left hand section of Figure 3 with a layer of solid coating material at 50 and the pores of the paper adjacent the coated surface impregnated approximately to the extent indicated at 52. Immediately thereafter, contact with the chill roll 18 seals the air cavities below those filled by the impregnation 52 and reduces their temperature to such an extent that a vacuum f from three to five pounds may result. The mechanical force of such a vacuum may compress the paper a trile, but its primary action, because the cold proceeds from the bottom and the air gets cooled first, is to suck the impregnation 54 a little deeper into the interstices of the paper. And because the integument 50 is an air seal, the mechanical compressive force will act to push the material at 50 down into the paper. Theoriginal nap 4S eventually ends up felted into the lower portion of the integurnent S0.

Example In a standard rubber mill place 40 pounds of pure Ceylon crepe rubber and mill it for about l0 minutes until it is thoroughly broken down. Then add slowly 60 pounds of fully hydrogenated cottonseed oil, without the application of heat. The cottonseed oil should be added a little at a time. During the addition a stage is soon reached where the material crumbles and breaks up into a mass of large flakes. At this stage it is necessary to keep picking up the akes and feeding them back into the mill and adding additional oil a little at a time. By processing in this way, a second condition is reached when the material forms itself into a unitary mass which is rubbery. If this mass is stored for a matter of days at room temperature, it takes a slight set. But a short working in the mill restores it to its original condition, at least with no apparent deterioration so far as subsequent use in the process is concerned.

This is the material employed in the kettle 16. It is preferably not cooked or strongly heated in any Way prior to the heating at the time of application, and the heating at the time of application need only be long enough to get the material uniformly heated. It is essential, however, that the hydrogenated fatty oil-rubber mixture not be previously heated until after the completion of the cold milling operation, i. e., until the hydrogenated fatty oil-rubber akes produced initially on milling form a unitary rubbery mass with continued milling with additional hydrogenated fatty oil. As pointed out above, heating or fusing of the mixture before milling results in a product lacking not only in the cold sealing characteristie but also other desired properties. The milling of the previously unheated mixture followed by heating of the resulting milled product are essential steps for obtaining the desired cold sealing film-forming compositions of the present invention. As pointed out above, the milled product is preferably not subjected to heat until ready for the coating operation, i. e., at the time of the coating operation.

For paper to be used in packaging products of vegetable origin, I have so far secured best results with cottonseed oil having a specified melting point of 136 F. and soya bean oil melting at 170 F. For meat and other products of animal origin, I have produced material using completely hydrogenated lard akes having a specified melting point of 155 F. However, I have been able to produce the distinctive results securable according to the invention with a large number of other substances, and believe that any ester of glycerine and a long chain hydrogenated fatty acid, will secure the desired result. If any such material is not completely hydrogenated before use, the uniformity of the product is impaired at the outset, and the product tends to become rancid and develop objectionable odors of its own as well as blends of objectionable odors wida the material wrapped. For packaging foods I have prepared coating exhibiting the charactertistics of the invention with completely hydrogenated products having the following specified melting points:

But for packaging any ordinary food the best results have so far been obtained with cottonseed or soya bean oil for vegetable products and hydrogenated lard for animal products.

The coating according to the invention may be applied to any grade of sulte, kraft or other type paper. It can also be applied if desired to metal foil and to plastic material, such as Pliofilm. With metal foil the material from the hopper should still be at about 300 F. but the rolls 14 and 12 are kept about 50 degrees cooler to avoid discoloration. With metal foil the adhesion is somewhat less, but the layers cannot be separated in large pieces. With plastic sheets the rollers 14 and 12 must be cool enough not to destroy the sheets by melting. The roll temperature varies from about F. to about 160 F. depending on the sheet used. The product is a sheet in which the original plastic and the added layer are welded into each other so that the weld is at least as strong as the rest of the material and-no layer separation at all is possible.

On any base strip, the coating lm has a strong pressure-sensitive adhesion. Dusting reduces the pressuresensitive action sufficiently to permit the coated base strip to be stored on storage rolls but does not materially affect the desired cold sealing obtained by pressing coated surfaces together.

The coating is very effective on any textile base, either felted or woven. Applied to textile ribbon it is useful for surgical bandages and will stick effectively to itself but not to the skin.

It is possible to make up the coating material as a self-sustaining film by itself, and satisfactory thicknesses are from about two-hundredths of an inch up. If there need be no very sharp flexure, thicknesses up to vehundredths of an inch or more also work very Well.

The ypresent application is a continuation-in-part of my prior application Serial No. 96,687, tiled on June 2, 1949 now abandoned.

Others may readily adapt the invention for use under various conditions of service by employing one or more of the novel features involved, or equivalents thereof.

As at present advised with respect to the apparent scope of my invention, I desire to claim the following subject matter.

I claim:

1. A cold milled composition consisting essentially of 30-50 per cent by weight of rubber and 50-70 per cent by weight of hydrogenated fatty oil, said milled composition being a unitary rubbery mass characterized by its ability to form cold sealing films when heated and applied a as a coating to a base sheet.

2. A composition characterizedbyvits ability to form cold sealing films when heated and applied as a coating, consisting of a cold milled previously unheated mixture of about 40 per cent by weight of crepe rubber and about 60 per cent by weight of hydrogenated fatty oil.

3. A base sheet having a cold sealing coating lm thereon consisting essentially of a hot coated cold milled composition consisting essentially of 30-50 per cent by weight of rubber and 50-70 per cent by weight of hydrogenated fatty oil.

4. A paper sheet having a cold sealing coating lm thereon consisting of a hot coated cold milled previously unheated mixture of about 40 per cent by weight of crepe rubber and about 60 per cent by weight of hydrogenated fatty oil.

References Cited in the le of this patent UNITED STATES PATENTS 2,051,944 Hershberger Aug. 25, 1936 2,054,115 Abrams et al Sept. 15, 1936 2,073,630 Gardthausen Mar. 16, 1937 2,082,278 Ferguson June l, 1937

Claims (1)

1. A COLD MILLED COMPOSITION COMSISTING ESSENTIALLY OF 30-50 PER CENT BY WEIGHT OF RUBBER AND 50-70 PER CENT BY WEIGHT OF HYDROGENERATED FATTY OIL, SAID MILLED COMPOSITION BEING A UNITARY RUBBER MASS CHARACTERIZED BY ITS ABILITY TO FORM COLD SEALING FILMS WHEN HEATED AND APPLIED AS A COATING TO A BASE SHEET.

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