US2795521A - Method of calendering a plastic mass - Google Patents

Description

June 11, 1957 B. B. BLACKFORD 2,795,521

METHOD OF VCALENDE RING A PLASTIC MASS Filed June 5, 1953 ATTORNEY tire sheet.

United States Patent 2,795,521 METHOD. OF CALENDERING A PLASTIC MASS Benjamin B. Blackford, Metuchen, N. J., assignor to Johnson & Johnson, a corporation of New Jersey Application June 5, 1953, Serial No. 359,701

3 Claims. (Cl. 154-102) The invention is directed to spreading of adhesive on webs in parallel strip zones leaving parallel uncoated zones on the web between the coated zones. Particular embodiments of the invention are directed to preparation of such zone coated webs for useas backing material for surgical dressings, and in particular, adhesive bandages.

Backing sheets utilized in ordinary adhesive bandages are coated with an adhesive mass which covers the eu- In many instances merely to assure firm anchorage of the bandage to the patient it is not necessary to coat the entire surface of the backing with adhesive, and therefore economy without sacrifice in quality would be realized by coating the backing material with adhesive in zones or strips. In other cases, to produce proper venting of the adhesive bandage it is necessary to perforate the backing in the region of the dressing pad, whereas if regions of the backing were left uncoated with adhesive the natural permeability of the uncoated backing sheet would afiord sufficient venting without the necessity and additional expense of perforation. Hence, one object of the invention is to produce a sheet zone-coated with adhesive which may be used in manufacture of adhesive bandages with particular advantage from the standpoint of economy and improved venting characteristics.

Prior art zone coating procedures have been carried out on the order of 'Gilchrist U. S. P. 2,086,126 which requires the use of raised portions of metal on the roll itself which pick up adhesive from a kiss roll and deposit this adhesive from the raised portion directly onto the web. There are many disadvantages to this type operation among which are the necessity of specialized, highcost equipment, and the tendency of the raised portions on the roll to wear excessively due to direct contact with the kiss roll.

One object of the present invention is to develop a procedure and machinery for zone coating of adhesive on moving webs which is simple and inexpensive and does not involve the use of specialized high-cost equipment.

According to'the present invention, coated and uncoated longitudinal zones are calendered on a continuous web of material by feeding adhesive mass between a pair of adjacent rolls, one of the rolls having raised portions on its periphery and adjacent the other roll, the raised portions being spaced axially from each other. The raised portions on the one roll do not, however, touch the other roll. Said other roll rotates, and the temperature of the rolls is controlled to control in turn the plasticity of the adhesive so that said raised portions, as the adhesive is drawn as sheet or film between the rolls, cause the adhesive film to divide into separate, longitudinal sections which are subsequently deposited on a continuous sheet of material to form longitudinal coated and uncoated zones thereon. The raised portions on the first roll correspond and are substantially coextensive with the uncoated zones of material and, conversely, the unraised portions correspond and are substantially coextensive with the coated zones. It is a particularly notable feature of the invention that division of the adhesive film ice between the rolls and resulting uncoated zones on the fab r-ic are produced without having the'surfaces of the-two rolls forced together or in contact. This is accomplished as indicated utilizing a suitable adhesive so that at theternperature of the operation the plasticity of the adhesive is:

sufiiciently low so that the adhesive film divides spontaneously when it passes between the raised portionsof the. one roll and the second roll. The invention also includes the apparatus for carrying out the operation described. v

In addition to accomplishing the objects set forth above, the advantages of the invention include provision of method and means for manufacture of a product wl n'ch may be made more economically, since it contains less adhesive than the usual calendered product, and also has the desirable property of permittingsome passage'of water vapor so that in use as a backing for adhesive bandages it is not necessary to perforate the backing to pro-' vide for breathing of the bandage. y

The invention may be conveniently understood by ref erence to the attached drawing in which the same reference number refers tocorresponding parts of the various figures.

Fig. l is a side elevation view of a three roll calender constructed according to the invention.

Fig. 2 is a front elevation of the apparatus in Fig. 1'.

Fig. 3 illustrates the top two rolls of Figs. 1 and 2 constructed according to a'modifiedform of, the invention.

Reference number 10 designates a supporting frame for a three roll calender having a top roll 11, a middle roll 12 and a bottom roll 15, respectively. The-top roll is supported on axle 16, the middle roll on axle 17 and the bottom roll on axle 20, each axle being supported in frame 10. Ear blocks 21 and 22 disposed at opposite ends of the top and middle rolls serve to guide adhesive into the nip between these two rolls. Feed roll 25 contains a wind-up of sheet material which may be fabric, non-woven or woven, or may be synthetic material'suc'h as regenerated'cellulose.

Top roll 11 is provided on its periphery with a spiral winding of material 27 such asa sturdy thread of textile fibers anchored at each end to roll 10 or to-fram e 10 at points not shown. Band 27 may be narrow or wide, as will appear hereinafter, depending upon whether it is desired to have narrow or wide areas of uncoated material in the final product. It will be noted that therolls 11 and 12 are not in -contact,but that there is a finite-space designated as A in Figs. land 2 separating these two rolls at the nip 23. A notable feature of this invention is that the band of material '27 does not fill-in'all of the space A but leaves a small but finite clearance between the outermost limits of band 27 and the topmost surface of roll 12. The importance of this feature of the invention apparatus will appear hereinafter. Y

The apparatus is operated as follows. An adhesive mass having suitable plasticity and other properties given below is placed in a bank between ear blocks 21 and 22 and the nip between rolls 11 and12.' ' Rolls 12 and 15 are rotated in the direction indicated in Fig. 1, while roll 11 remains stationary. Alternatively, roll 11 may rotate slowly in which case band 27 may suitably be secured to roll 11 itself rather than to frame 10. *The adhesive from bank 30 tends to be drawn into and out of the nip between rolls 11 and 12 as a thin sheet 31 having a smooth surface and uniform thickness depend ing upon the clearance A between the rolls. "The temperature and speed of the rolls are controlled'as they are in normal calender operations. Near the point where rolls 11 and 12 are closest to contact, the filmof adhesive 31 from bank 30 is divided or split by the raised portion 27 of the-band into individual films 31 which travel around the left side of roll 12 as seen in Fig. 1 and into the nip 32 between rolls1-2-and 15. At this point the individualsheets of adhesive -31-on thesurface of roll 12 meet and contact the upper surface of fabric 26. The adhesive adheres to the surface of fabric 26 and leaves the periphery of roll '12. Theindividual areasof adhesive coated on fabric 26 are shown at on Fig. '2 with parallel uncoated areas of adhesive therebetween at 36. It will belnotedthat-the-uncoated areas 36 correspond and are substantiallycoextensivein width-with the band material 27 in the -nip' between rolls 11 and-12.

To provide the. splitting and dividing action by ridges 28 on roll'll it is importantthat, if roll his not stationary,it should move at 'a rate which is slower than the rateof movement of the film 31 emerging from the nip'23. Movementof rollll may beclockwise or counterclockwise. 'It isimportant only thatanyclockwise directional movement. should be slower than that corresponding witha peripheral speed equal tothe speed of movement, of, film31. .Inthe modified embodiment of the invention illustrated in Fig. 3 top roll40 and middle roll 41 are shown with space A therebetween. ,These rolls are supported on axles 45 and46 mounted in a frame not shownsimilar to frame 10 in Fig.2. Instead of band of material-27 woundspirally around thetop roll, roll 40 is provided with individual bands 47 secured to roll 40 by means not shown. Theseindividual bands 47in the nip between rolls 40 and 41 perform a function corresponding to those portions of. band .27 in the mp2s between rolls Hand 12. .The width,uspacing,. height and clearance between the rolls is :controlled in theFig. .3 embodiment in the same way a nd ffor thesamepurposesas in vthe vease of the; Fig. -2 embodirnent describedabove.

The material of-which the band is made is a factor of considerable importancem thepresent invention. It is preferably made of a material softer. than that of the su'rfaceof roll 12. This affords the'advantage that in the case of inadvertent contact :betweenband 27 ,and roll- 12 there will be no or little wearbetween the parts in contact,;.and in particular, no wear of the surface of roll 12,:therebynecessitating rebuilding of the equipment, or at the very least, expensive maintenance. The bands maybe made suitably of either fabric or metal or other material. *Thevheight of the band-is also important. As indicated; above, it doesnotpcome in contact with the. outer-surface of roll ;12. vHowever, it, should be sufficientlyrhighto cause: splittingor-dividingof the film of adhesive from .bank 30 in theregion of ip; 23. :With this :objectin view the vheight of-band-27 shouldbe at least. about onehalf the dimension A, i.; e. ;one, half :the distance lbetween'rollsill and 12 .at nip.23. It is seen, therefore, .thatthezdepth. of;.groove .24 which is equal to the height of .ridges .28 .is preferably at .least about as :great-as the finitedistanceibetween the radial. eX-

trernity ofridges. 28 and the'sadjacentsurface of roll 12/ The plasticity of the .adhesivemass in .bank 30 will be influenced by the temperature. of T011511 and .12, -.the degree of working onthe rolls controlled in turn by the roll speed, and the internal'friction brought about .by this working. The tendency of the adhesive film from bank-.30 to divide'into separate longitudinal areas as described above is influenced to a degree by this plasticity.

Accordingly, in the present invention the nature of the mass-is suchas to afford under-operating conditions a mass plasticity sufliciently high .to produce the desired dividing of the film.

It is not alwayspredictable from the mass plasticity at room temperature or at any given temperature what the plasticity ofthe mass will be as it isbeingworked-in the bankcon the calender rolls. However, suitable masses forgone coating. according tothe invention may be made bycompounding approximately equal parts of 'elastom-er, taekifierzandzextender. The .elastomer may. benatural rubber, butadiene-slyrene :copolyiner, reclaimed:rubber, onpolyisobutylene fil lstomer. ;-Mix t ures of these various elastomers may be employed. Any of various tackifiers known in the art, may be satisfactorily utilized. iExtenders, as the term is used here, includes also fillers and pigments. Zinc oxide, titanium dioxide, and starch are examples of ingredients falling in this classification. In addition to the above three groups of ingredients the adhesive may also be plasticized with any of several plasticizers known in the art.

According to preferred embodiments. ofthe invention, the masses are so compounded that their plasticities measured under standard conditions of test are ,within a certain preferred: range. 'Plasticityissmeasured on a cylindrical pellet of .adhesivemass 16 mm. in diameter and weighing 2.00 grams. By placing the pellet on a parallel plate plastometer of. the type manufactured, for example, by the Scott Instrument Company, and maintaining the pellet and surroundings at F. and under a 5000 gram load for 14 minutes, the height in millimeters of the pellet-after this time is taken ,as .a measurement' of plasticity. The preferred plasticity. range} is,.approximately 1.5 to 2.5mm. Howeverylower or higher plasticities may beused depending uponthebehav'ior of the'adhesive when it is subjected to the conditions prevailing in the bank-between the calender rolls.

' One satisfactory adhesive mass is composed of .polyisobutylene-according to Wing U. S.-P. 2,484,060, preferably with an average molecular weight (staudingeryofabout 100,000 compounded with effective. amounts :of tackifier, plasticizer, pigment,--etc.- as disclosed in-the patent. *For purposes of theprese'nt -invention,.-it is milled for time to impart plasticity oft-.5 to- 2.5 mm.

Another suitable ma'ss is-based-on natural pale -crepe rubber" (33%) and contains dehydro'genated rosin acid MJP. '70-72 C., tackifier (25%), lanolin (7%) -as plasticizen'TiOa (15%) and Z (15%) aspigment,--a'nd starch (5%) as filler, and is milled'fortime toprovide a plasticity of from'1;5 to 2.5 mm. Blends of-the-syn thetic and natural rubbers may be utilized.

The following is an example of procedure-for manufacture of azone-coated fabric particularly suitable for use as a backing for adhesive bandages. 'A'web 10f woven material having a count of 80x 80' per inch and a weight of 3 ounces per squareiyard isunrolled from roll 25 and fediinto the nip between rolls 12 and 15.

* An adhesive massflhavingithe composition describedin the next preceding. paragraph and 1a plasticity of 1.70 ispreheated to 240 F. and charged to jbankj. 30 from which it is fed into nip 23 betweengste'el v,rollsf 11 and 12. Roll.11 is operated at 250 F. and. ro1l, 12' at F. thereby. to maintain bank 30 at laboutl240" 'F. The spacing between rolls I1 and 12 is 0.004 inch. ;Roll 11 is wound on its outside periphery. with an bqagor copper wire having asquare brossf section 10.003 vinch thick and 0.020 inchwide. The .winding is ,arranged in a spiral fashion andsecured at-the two ends tofstationary par'ts of framelt). Said copper ;ribbo n-;forms ridges28. (With the winding inplace the distance be tween ridges. 28. is- Vz inch. The height of ridges 28 above the surface. of roll 11 ;is.0.003 inch and the, width of each ridge is:0..020 inch. ,Roll v11-.isstationary;;and roll 12;rotates;at-.a peripheral speed of QO -feet' per. minute. The mass divides into-separate individual sheets 35 with intervening parallel zones of no adhesive. The product as itiswithdrawn from-roll lS contains parallel coated zones /2 inch wide and intervening uncoated Zones approximately inch wide. The adhesive strip moves with rotation of roll'l2'fromnip 23 to thdbot tom of roll 12 where contactv is made withfthe upper surface of fabric 26. The fabric picks up the adhesive stripswhich become embedded in fabric 26. 2

Various modifications and equivalents which will now be apparent togthose skilled in theart, .although;,-not specifically recited above, are. intended to be included within the scope of the invention. It-is intended that the invention be limited, not by the above disclosure, but only by the appended claims as fairly interpreted in view of the disclosures of the prior art.

The claims are:

1. A method of calendering a pressure-sensitive adhesive mass having a plasticity at 100 F. in the range of about 1.5 to 2.5 mm. and comprising a tackifier and an elastomer, the latter being selected from the group consisting of natural rubber, reclaimed rubber, butadiene-styrene copolymer and polyisobutylene, which method comprises forming a relatively wide film thereof at a temperature of about 240 F., said film being of a thickness of about 0.004 inch, and pressing parallel grooves therein about 0.003 inch deep and about 0.02 inch wide, said grooves being about 0.5 inch apart, while moving said film in the direction of said grooves, whereby separate parallel films about 0.004 inch thick and about 0.5 inch wide are obtained.

2. A method of claim 1 wherein the parallel films are deposited upon a continuous sheet of material form ing longitudinal coated and uncoated zones thereon, said uncoated zones being about inch wide.

3. A method of claim 2 wherein the plasticity is about 1.7 mm.

References Cited in the file of this patent UNITED STATES PATENTS 1,402,160 Gwozdz Ian. 3, 1922 1,471,588 Bourn Oct. 23, 1923 1,628,836 Gammeter May 17, 1927 1,683,707 Smith Sept. 11, 1928 1,974,209 Fowler Sept. 18, 1934 2,054,115 Abrams et al. Sept. 15, 1936 2,070,600 Jenett Feb. 16, 1937 2,089,525 Abrams et a1. Aug. 10, 1937 2,582,294 Stober Jan. 15, 1952 FOREIGN PATENTS 892,998 France May 25, 1944

Claims (2)

1. A METHOD OF CALENDERING A PRESSURE-SENSITIVE ADHESIVE MASS HAVING A PLASTICITY AT 100*F. IN THE RANGE OF ABOUT 1.5 TO 2.5 MM. AND COMPRISING A TACKIFIER AND AN ELASTOMER, THE LATTER BEING SELECTED FROM THE GROUP CONSISTING OF NATURAL RUBBER, RECLAIMED RUBBER, BUTADIENE-STYRENE COPOLYMER AND POLYISOBUTYLENE, WHICH METHOD COMPRISES FORMING A RELATIVELY WIDE FILM THEREOF AT A TEMPERATURE OF ABOUT 240*F., SAID FILM BEING OF A THICKNESS AT ABOUT 0.004 INCH, AND PRESSING PARALLEL GROOOVES THEREIN ABOUT 0.003 INCH DEEP AND ABOUT 0.02 INCH WIDE, SAID GROOVES BEING ABOUT 0.5 INCH APART, WHILE MOVING SAID FILM IN THE DIRECTION OF SAID GROOVES. WHEREBY SEPARATE PARALLEL FILMS ABOUT 0.004 INCH THICK AND ABOUT 0.5 INCH WIDE ARE OBTAINED.

2. A METHOD OF CLAIM 1 WHEREIN HTE PARALLEL FILMS ARE DEPOSITED UPON A CONTINUOUS SHEET OF MATERIAL FORMING LONGITUDINAL COATED AND UNCOATED ZONES THEREON, SAID UNCOATED ZONES BEING ABOUT 1/16 INCH WIDE.

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