US 3194706 A
Description (OCR text may contain errors)
y 1965 w. c. UTSCHIG ET AL 3 94,
IMPREGNA'I'ING, LAMINATING, AND CAST COATING IN ONE OPERATION Filed May 12, 1959 INVENTORS er C. ton Ye Ill/ Wolf U ig Mil mm 3. Mg J. 49mm 6 4.49. 048)- ATTORNEYS United States Patent 3,194,796 I IMPREGNATING, LAMINATHNG, AND CAT COATING IN ONE UPERATIUN Walter C. Utschig and Milton Yezeir, Battle Greek, Mich, assignors to General Foods Corporation, White Plains, N.Y., a corporation of Delaware Filed May 12, 1959, Ser. No. 812,706 3 Ciaims. (Cl. 156-242) This invention relates to a method of continuously producing laminated and at least partly impregnated packaging material having on one side a smooth glossy coating of a thermoplastic material such as wax. In particular, the method makes it possible to produce, at low cost, paper packaging material adapted for making folding cartons having highly glossy surfaces and other protective qualities heretofore available at a considerably higher cost.
The method involves the process steps of impregnating,
laminating, and waxing paper and paper board plies to produce the packaging material, these steps being carried out in one operation on a relatively high speed machine. As practiced heretofore, such steps would require three separate operations. The method further provides econ-' omies in equipment and in the materials used for making the laminated packaging material. Other advantages will become apparent hereinafter.
The invention broadly comprises passing a continuous web of paper through a bath of melted thermoplastic agent to impregnate and coat both sides of the web with agent, after which the web with the coatings thereon in a plastic state is passed through a first nip where the amount of agent on the Web is adjusted or controlled. The web is then moved to a second nip formed by a heated rubber impression roll and a cold casting roll where, in combination with a continuous web of paper board, which may or may not have been previously impregnated and coated with said agent, it is passed through the second nip. The latter exerts a laminating action on the two webs, which are maintained in registering position relatively to each other during passage through the nip. Thereafter the laminated web is subjected to a rapid or shook cooling wherein the exposed coated side of the paper ply is brought into intimate contact with the surface of the cold casting roll so that such coated side adheres thereto. As hereinafter described, the cold casting roll acts to uniformly distribute the thermoplastic agent on the adhering side of the paper ply, to solidify the coatings on the laminated web and, in particular, to impart a smooth glossy finish to the coating on the said adhering side of the paper ply.
The invention may be better understood by referring to the accompanying drawing wherein FIG. 1 diagrammatically illustrates one method of carrying out the invention, and FIG. 2 diagrammatically illustrates a modified method.
Referring to FIG. 1, a continuous web of paper from source 11 is passed around idler roll 12 into the bath 13 of molten thermoplastic agent such as wax contained in tank 14 and then around the idler roll 15 disposed in the bath, after which it is moved at least partially through and then out of the bath and over guide rolls 16 and 17. Coincidently with the movement of web it) through bath 13, a continuous web 18 of paper board from source 19 is introduced to bath 13, being passed around idler roll 15 in contact with, but disposed outwardly of, web 10. Web 18 then continues through the bath for a substantial distance, passes over guide roll 24), leaves the bath, and, in combination with web 16, moves to a pair of nip rolls 21 and 22.
It will be noted that the two webs enter bath 13 separately and separately leave it, and that for the most is conventional and therefore not shown.
part they are kept separate during passage through the bath, the purpose being to facilitate their handling and to reduce or avoid wrinkling, fluttering, and the constant lamination and delamination which may otherwise result. Both webs are impregnated in the bath and coated with wax on both sides. By impregnation is meant the fact that the voids and interstices within each web are filled with wax to a substantial depth beneath the surfaces of the webs. The application of the wax coatings on the webs enables them to be subsequently laminated, and permits a high gloss to be produced on the exposed side of the paper ply by treatment subsequent to lamination.
Webs 1t and 18 are progressively brought to surface contact with each other by movement over rolls 22 and 21., respectively, and are laminated by passage through the nip of rolls 2,1 and 22, the webs being in registering position relatively to each other during such passage. The lower roll 21 is made of steel and the upper roll of rubber; these rolls are commonly referred to as squeeze rolls, serving not only to laminate the two webs but also to meter, that is, regulate or adjust the amount of coating agent on the webs so as to secure a good lamination. By engaging each web with its respective roll at a point well in advance of the nip, as shown, air may be excluded from the laminated web 23 at the laminating surfaces thereof and wrinkles thus avoided. Excess wax may be removed from the lower surface of the board ply by means of the doctor blade 24, the wax being caught on lip 25 of tank 14 and fed back to the bath. The laminated web 23, with the coatings thereon in a plastic state, particularly the coating on the exposed side of the paper ply, is then moved over a heated rubber impression roll 26 and into the nip formed by such roll with a cold casting roll 27 so that the exposed coated side 26a of the paper ply comes into intimate contact with and, by virtue of the plasticity of the coating 26a, adheres to the surface of the casting roll. Web 23 thus becomes immovably disposed relatively to roll 27.
The cold casting roll 27 has a smooth, mirror-finished cooled surface, the roll being cooled by means of a brine which circulates within it. The circulating equipment The temperature of the cooled roll depends on the coating on the laminated web, but in any event is below the fusing point of the coating agent. More particularly, the temperature may range from just above 32 F. to about 70 F. The lower temperature of such range should be such as to avoid the formation of ice on the casting roll surface. Preferably, the upper temperature is F. Cooling of the wax on the web is quite rapid after initial contact with the cold roll. Such cooling step, which may be described as shock cooling, owing to its rapidity, is described in detail in co-pending application Serial No. 663,269, filed June 3, 1957, now United States Patent No. 2,912,347 of which the present application is a continuation-in-part. The impression roll 26 acts to press the coating 26a against the smooth surface of roll 27 to smoothen the coating so that it becomes more uniformly continuous. Coincidently with the smoothening effect, the smooth mirror-finished surface of roll 27 imparts a high gloss to the coating. To insure these results it is essential that the coating shall be in a substantially plastic state at the point of initial contact with cold roll 27; the desired plasticity of the coating may be obtained by keeping the distance traveled by the web 23 between the rolls 2t, 22 and the cold roll 27 as short as practical, and further, by heating the coating through the medium of the heated impression roll 26 to maintain the coating in a plastic state up to its initial contact with roll 27.
Note that the nip of rolls 26 and 27 also acts as a secondary laminating nip.
The coated web travels a substantial distance while in contact with the smooth cooled surface of roll 27, such distance, in combination with the cold bath 2-8, being suiiicient to insure cooling of the coatings to a temperature substantially below their melting point and to effect the smoothening and gloss-producing actions noted. The casting roll 27 rotates in a body 28 of cold water contained in tank 29, and as rotation continues, the laminated web moves downwardly toward and through. the cold water to further cool the coatings on the web. In particular, the coating 26:: on the adhering side of the paper ply is cooled from both sides of the same, that is, by the cold surface of roll 27 and by the water 255 which makes contact with the exposed side of the board ply. Note that the water acts to remove heat from the coating 26a through both the paper ply and the board ply.
The laminated web 23 is submerged in the water for a time sufficient to insure solidification of all coatings, and during such time the web remains immovable disposed on and in contact with the casting roll surface. As the web moves upwardly from the water, it passes through the nip formed by the casting roll and a soft rubber wringer roll 30, the latter serving to remove water which may adhere to the exposed side of the board ply. Wringer roll 30, which is in pressure contact with the web-covered roll 27, also helps to peel the laminated web from roll 27 without damage to the coating 26a. In this connection the rotational axis of roll 30 is substantially parallel to that of roll 27 to avoid any eccentricity in the peeling step and any distortion of the coating or tearing of the Web. The web passes over guide roll 31 and is collected by means not shown.
The cold roll 27, on which is provided the smooth surface necessary to produce the high gloss, preferably has a coating on such surface comprising a continuous and extremely smooth sheet of material such as vinyl acetate. This sheet possesses good release properties, that is, readily permits the coated web to be peeled otl therefrom, and it has sucha high degree of smoothness as to insure production of a continuous surface on the film or coating 26a which is cast onto the paper ply. Instead of vinyl acetate, other compositions capable of offering a smooth, mirror-finished surface and good release properties may be employed, such as a sheet of copper or aluminum foil, or a lacquer of silicone or other resin. If desired, roll2'7 may also comprise a polished metal roll, or a nickelor chromium-plated roll. In general, the casting surface of the cold roll should have a mirror-like finish and should have a surfacewhich, when cooled to substantially below the fusion point of the coating on the paper ply, adheres to such coating with only a slight bond such that the coated web can be readily peeled therefrom.
If desired, the cold roll may be replaced by an endless belt having a smooth mirror-finished surface,'although a roll is preferred.
In the modification of PEG. 2, paper web it? from a source 41 passes over guide roll 42 and then around the guide roll 43 disposed in the bath 44 of thermoplastic agent, such as wax, in tank 45. Both sides of web are impregnated and coated with the wax and the web leaves the bath by passing around guide roll 46, after which it moves through the nip of rolls 4'7 and 48 to adjust the amount of wax thereon. Rolls 4'7 and 4% are like rolls 21 and 22 of FIG. 1. The lip or guard 49 of tank tends to catch any spray resulting from the high v speed movement of the web and to re-introduce the same to the bath. Web 49, with the coating thereon in a plastic state, passes over idler roll 50 to the nip of the cold casting roll 51 and heated rubber impression roll $8 where it is joined by the board web 54 traveling from source 55 around idler rolls 56 and 57. The two Webs, in registering position, pass throughthe nip of rolls 51 and 58 and are thereby laminated. Prior to passage through the nip, the coating on the exposed or upper side of the enc aves roll 26 of PEG. 1, against the web at its contact with the cold roll, thus causing the web to conform to the cold roll surface. The resulting action, as roll 51 ro tates in the bath 52 of cold water disposed in tank53, is substantially the same as described for the roll 27. The laminated web 6t). leaves the bath, passes through the nip of roll 51 and rubber Wringer roll-59, and then over guide roll til to a collecting means not shown.
As is apparent, theonly laminating nip in FIG. 2 is that. provided by rolls 51 and 58. It is desirable that the web strikes the castingiroll 51 at approximately the same instant that it entersthe nip of rolls 51 and 58, the purpose being to keep the coating of war on web 40 warm, and therefore in a plastic state,'as well as to insure that laminating of the plies occurs just prior to cooling on the casting roll. If desired, the thickness of the coatings on web it) may be'regulated as by installing a Mayer rod adjacent'theweb on both' sides and in place of squeeze rolls 47 and d8;
in either modification,conventional equipment is used; whereas if the impregnating, laminating, and Waxing steps were done separately, additional equipment would be required.
Where the final carton product. is required to have a high level of protection against water and water vapor transfer, the packaging material produced by the, method of FIG. 1 would be suitable. Where Waterproofness on too inside or board side of the carton was not a prime requirement, and where only a moderate level of protection against water and water vapor transfer was required, the packaging material produced by the'method of FIG. 2 would be preferred. The product of the latter method would also be advantageous in providing glueable flaps for the cartons since the laminated web 60 of FIG. 2 can be readily dewaxed to provide glueable flaps.
The webs 1i? and d-tlmay comprise any suitable paper, in most cases a paper capable of being printed, and the paper may or may not be printed. Suitably the paper may have a Weight in the range of 8 to lbs. (basis 24 x 36 500:3000 sq. ft.). Various kinds of paper are suitable, and as examples any of the following can be used; papers made from chemical pulps including sulphate papers, sulphite papers, sulphate-sulphite combination papers, and soda pulp papers, these various papers phate papers, and machine finish and machine glazed sulphite-sulphate papers. Other materials are cellulosic films including cellophane and cellulose acetate; also foil of aluminum or tin. I
'By the term paper web it is intended to include webs .of paper of the types noted, plastic films, metal foil,
paperboard, and the like.
Webs it: and 54 may include paper boards made from pure chemical pulps such as bleached and unbleached ltraft; soda and sulphite boards; boards made from semichemical pulp such as corrugating medium board and bleached semi-chemical board;-boards made from waste .materials such as chip board and jute board; and boards made from combinations of waste, groundwood and chemical pulps such; as White Patent coated news board, double manila lined news, groundwood center, and double bleached linedwaste-groundwood center board. Such board isinormally specified in weight per 1000 sq. ft. and
in points thickness (one point=0.001 inch); and on this basis any of the above types of board in the range of to 160 lbs. per 1000 sq. ft. and 5 to points may be suitable for use.
The coating composition is preferably a thermoplastic agent such as paraifin wax, microcrystalline wax, polyethylene of low molecular weight, say in the range of about 2,000 to 21,000, etc. Other thermoplastic resins besides polyethylene are useful, such as polyamides, polyterpenes, petroleum resins, or any resins having thermoplastic properties. Mixtures of two or more of the fore going agents are suitable, such as a combination of paraflin wax and microcrystalline wax or polyethylene. The agent should, of course, be capable of producing gloss and protective characteristics when deposited on the web, and its melting point should not be so high as to injure the web. In general, the particular composition to be used will depend on the particular product desired. For example, for a product having high gloss, moderate WVT (water vapor transfer) properties, and good scufiproofness, a suitable agent is polyethylene having a molecular weight of 2,000 to 21,000, preferably 6,000 to 14,000.
In FIG. 1 the amount of wax used may be up to 100 lbs. per 3000 sq. ft. of surface, whereas in FIG. 2 the amount may be up to 40 lbs. per 3000 sq. ft.
The coated laminated web product on the exposed side of the paper ply has an extremely glossy, smooth, and continuous surface that is entirely free of imperfections such as crows feet. The continuity of the coating means that the packaging material product will have good resistance to the transfer of water vapor therethrough in the subsequent use to which such product is put, particularly for making folding cartons for holding foods such as gelatin, cereal, butter, frozen foods, etc. The cartons are characterized by having a highly glossy attractive appearance and by being resistant to the passage of water and Water vapor through them either in an angular direction relative to the walls of the carton, or in a direction extending longitudinally of a carton wall, as in the phenomenon of edge wicking, wherein water vapor, for example, enters the cut edges of a carton flap and passes longitudinally of the flap through the interstices of the same into the interior of the carton. The cartons are further characterized by their manufacture from low cost materials, including the paper and paper board, and particularly the use of a thermoplastic agent like wax to replace a high cost material such as solvent lacquer. The coating also protects the cartons against scufiing, particularly in the case of paper plies that are inked, because the coating prevents the ink from being transferred over onto non-inked areas as by pressure from a users fingers. In addition, the coating improves the sealing capacity of the carton in respect of air, etc.
It is to be understood that the invention is not restricted to the specific details of the foregoing description but is capable of obvious variations thereof without departing from its scope.
In the light of the foregoing description, the following is claimed.
1. A method for producing laminated packaging material having on one side thereof a smooth, glossy coating of thermoplastic agent, comprising applying a coating of molten thermoplastic agent to opposed surfaces of an elongated first ply, bringing said first ply into contact with a second elongated ply so that the coating on one surface of said first ply is contiguous with a surface of said second ply, forcing said plies into the nip formed by a mirror-finished casting surface and a pressure roll to form a laminated structure in which said molten thermoplastic agent is disposed between said first and second plies and the coating on the exposed surface of said first ply is adhered to said casting surface, said laminated structure thereby being held immovable relative to said casting surface, chilling said laminated structure while it is held on said casting surface to simultaneously harden the laminating layer between said first and second plies and the coating adhered to said casting surface, and peeling the laminated structure from said casting surface.
2. Apparatus for producing laminated packaging material having on one side thereof a smooth, glossy coating of thermoplastic agent, comprising means for applying a coating of molten thermoplastic agent to opposed surfaces of an elongated first ply, a pair of rolls forming a nip therebetween, means for directing said first ply into said nip in registration with a second elongated ply so that the coating on one surface of said first ply is contiguous with a surface of said second ply and forms a laminating layer between said surfaces, means for directing the laminated structure issuing from the nip of said pair of rolls into the nip of said further pair of rolls, one of said further pair of rolls being a mirror-finished casting roll to which the coating on the exposed surface of said first ply adheres to dispose said laminated structure immovable relative to said casting roll, means chilling said laminated structure while same is in contact with said casting roll to harden said laminating layer and the coating on the exposed surface of said first ply, and means for peeling said laminated structure from said casting roll after said coating and said laminating layer have been substantially hardened.
3. Apparatus for producing laminated packaging ma-- terial having on one side thereof a smooth, glossy coating of thermoplastic agent, comprising means for applying a coating of molten thermoplastic agent to opposed surfaces of an elongated first ply, a pair of rolls forming a nip therebetween, means for directing said first ply into said nip in registration with a second elongated ply so that the coating on one surface of said first ply is contiguous with a surface of said second ply and forms a laminating layer between said surfaces, a further pair of rolls forming a nip therebetween, means for directing the laminated structure issuing from the nip of said pair of rolls into the nip of said further pair of rolls, one of said further pair of rolls being a mirror-finished internally cooled casting roll to which the coating on the exposed surface of said first ply adheres to dispose said laminated structure immovable relative to said cold casting roll, means for rotating said cold casting roll and said laminated structure disposed thereon, a cold liquid bath disposed in the path of movement of said laminated structure on said casting roll, and means for peeling said laminated structure from said cold casting roll after said coating and said laminating layer have been substantially hardened.
References Cited by the Examiner UNITED STATES PATENTS 2,264,494 12/41 Wickwire 154-120 2,642,366 6/53 Rumberger 117103 X 2,714,952 8/55 Ireton 15450 X 2,753,275 7/56 Wiles et al 117103 X 2,829,980 4/58 Redd 117103 X 2,912,347 11/ 59 Yezek et al.
2,975,094 3/61 Anderson 156152 EARI. M. BERGERT, Primary Examiner.
A. WYMAN, CARL F. KRAFFT, Examiners.