July 20, 1954 M. F. KRITCHEVER 2,683,894 APPARATUS FOR TREATING PLASTIC FILM Filed June 27, 1951

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4%.e.477 OPNVEYS. efo Patented July 20, 1954 2,683,894

UNITED STATES PATENT OFFICE 2,683,894 APPARATUS FOR TREATING PLASTICFILM Mathew F. Kritchever, Wilmette, Ill., assignor to Traver Corporation, Chicago, Ill., a corporation oflinois Application June 27, 1951, Serial No. 233,829 3 Claims. (CI. 18-) 1. 2 This invention relates &o apparatus for treat vention to overcome the difficulties. Of printing ing plastics, and more particularly to means for or coating onto polyethylene, and it is a related treating resinous films or plastic materials which object to overcome the same type of difficulties have heretofore been considered uneceptive to which are also inherent in plastic film, sheet coating compositions, etc. So as to render then stock and molded products based upon the resin. receptive for such printing, coating, etc. The polyvinylidene chloride and copolymers thereof means is also effective in changing the char with vinylchloride and vinylacetate. acter of the Surface of the films or plastic arti In accordance With this invention, a surface cles, etc., enabling then to be united, bonded, highly receptive to the common ink and coating imprinted, and treated in many other WayS. compositions is developed on polyethylene or The present invention constitutes a continua O tion-in-part of my copending application Serial polyvinylidene chloride by directing a gas flame No. 150,414 for Treating Polyethylene Plastics onto the surfaces to be printed for a relatively for Printing, inow abandoned. short time without raising the mass of the plastic In most respects, anchorage of the printing or to a temperature enabling distortion. If the coating compositions on various types of Surfaces 5 plastic material is in the form of a film of thin depends upon some type of physical or chemical sheet stock, it is expedient to direct the flame bond existing between the coating or printing onto the surfaces of the plastic while the oppo compositions and the surfaces upon which they site wall is being cooled. If the flame directed are to be applied. When printing on paper Or onto the plastic surfaces is in excess of 1300. F., other porous surfaces, anchorage of the print 20 preferably within the range of 1300° to 1600°F., ing ink or coating composition is achieved by almost instantaneous conversion to a highly ink partial impregnation and infiltration of the com receptive surface is secured. Even better results position into the pores of the fibrous structure are obtained when the fame temperature is which enables the development of a firm grip higher, say up to 3600 F., or higher, and the ping relation with the surface in a type of physi 25 period of exposure of the plastic. Surface to the cal interlocking. When printing or coating onto flame is considerably shortened. If lower tem smoother surfaces, such as plastic, glass or the peratures are employed, it may be necessary to like, reliance is usually had upon a physico prolong the flame treatment or to provide suc chemical bond, such as softening of the material cessive treatinents, keeping in mind that the on the plastic surfaces to be printed, as by means 30 plastic should not be heated through to a tem of a mutual solvent, to make possible a type of perature permitting plastic flow. In any event integration of one material with the other. it is seldom that more than a Second or a frac With a material such as polyethylene, the tion of a second is required. possibilities for anchorage in the usual manner At present, beneficial results have been only are substantially absent. This is eSpecially true achieved by direct contact of a flame with the with polyethylene plastics, the molecules of plastic surface. which have been Orientated by stretching while In the cooling of the plastic body it has been in plastic condition and then setting as in the found that adverse results are sometimes ex manufacture of film or sheet Stock. The diffi perienced when a pocket of air is trapped be culties with printing on polyethylene Surfaces 40 tween the polyethylene and the cooling roller. apparently arise from the Smoothness of the Since the air forms an insulating space on the surfaces, which militates against purely physical opposite side of the film, that portion of the film anchorage, and the inertness of the resinous remains uncooled during the flame-treating step. polymers which militates against development 45 Further, the thin wide film of polyethylene is of a bond through the technique of eating into handled with difficulty because of its width and the surfaces to be printed by solvents or the thinness and often irregularities occur which like, usually embodied in the printing or coating prevent the effective codling. composition. I have found that the above difficulties can In view of the increasing use of polyethylene 50 be overcome by providing a liquid cooling bath in the for in of film, sheet Stock, or containe's in conjunction with the roller so as to apply a for packaging, it becomes important to provide film of water or other liquid below the film as a system which perimits printing thereon, on a it is being flame-treated. The liquid film pre mass production basis, characteristic of modern vents the formation of air pockets, etc. and in packaging technique. It is an object of this in 55 fact provides a Surface on which the film seems 2,683,894 t 4. to float. Further, such a liquid film is found inwardly. Since this device is of well-known to be unusually effective in cooling the side of construction, a further detailed description is be the film opposite that exposed to the flame. In lieved unnecessary. Instead of employing Wac conjunction with the above apparatus I pro uum in the drum 3, the felt pad 3fa can be kept vide means for removing the moisture clinging 5 in absorbent condition by the use of heating to the under side of the film So that the film may means, electronic means, etc. then be rolled or otherwise Stacked. The method of flame-treating described above An object of the invention is to provide ap seem to be highly effective when the temperatures paratus and means for treating a polyethylene, are maintained at elevated ranges in the neigh polyvinylidene chloride, or other film Surface to O borhood of 3600° F., while greatly reducing the render the same receptive to ink and other coat moment of exposure of the film to the flame. ings, etc. while providing means for continuous Not only are the results better but also the proc ly rolling or stacking the treated materials. A essing is greatly Speeded up. further object is to provide effective apparatus I have found that certain plastic materials do for directing a gas flame onto the plastic Sur not respond to the flame-treating method and face while providing improved means for cool apparatus described. Polyethylene is highly re ing the opposite surface of the plastic during its sponsive and not only does the treated Surface exposure to the intense heat of the flame. Yet thereafter, even after days and months of delay, another object is to provide a method and means readily receive printing inks, coatings, etc. but for cooling polyethylene, polyvinylidene chloride 20 also the treated surfaces enable sheets of poly or other plastic films or articles While the Same ethylene to be readily laminated. Where prior are being exposed to contact with a flame. Yet to treatment the film or laminae could not be another object is to provide a means and method effectively bonded, after flame treating, Such for applying liquid to an under Surface of Such films or other laminae are secured readily by the plastic films while impinging a flame On the Op 2 5 use of ordinary adhesives. posite side. A still further object is to provide The proposed process and method as to the a method and means for floating Such a plas laimination of plastics applies best to polyethyl tic film upon a liquid cooling film while flame ene and polyvinylidene chloride, permitting poly treating the opposite side of the film and while vinylidene chloride to be laminated to polyethyl providing also means for removing moisture from 30 ene, polyvinylidene chloride to be laminated to the cooled side of the film. Other Specific Ob itself, polyethylene to be laminated to itself, jects and advantages will appear as the Speci polyethylene to be laminated to cellophane, poly fication proceeds. Vinylidene chloride to be laminated to cellophane, The invention is illustrated by the accompany and other combinations of both polyethylene ing drawings, in which and/or polyvinylidene chloride to be laminated In the illustration given in Figs. 1 and 2, I em to standard commercial films. To lender the ploy a liquid bath for feeding a film of Water Or polyvinylidene chloride or the polyethylene Sus other cooling liquid onto the driven roll 23. I ceptible to the adhesive, the film is run over the find that the water forms a film Over the roll cooled rotating drum described, while exposing 23 and prevents the formation of air pockets un the same to the hot flame described. Then the derneath the film. Further, the liquid gives a second film is treated in the same way. The highly effective means for cooling the under side adhesive is then applied to one or both surfaces of the film as it is being Subjected to the flame to be joined. The two films are then brought leaving the pipes 24 thereabove. The water or into contact with each other With the adhesive other cooling liquid is Supported Within an Open or treated sides together, and maximum Sur vessel 25 and the rotation of drum or roll 23 face contact is obtained by rolling the two to causes a film 26 of water or other cooling liquid gether between rolls. Preferably the adhesive to form thereon, as illustrated in Figs. 4 and 5. is one of a polymerizing type with high cohesive In the Specific illustration given, the poly Strength, but satisfactory bonding can be had ethylene film 27 or other film to be treated leaves With a variety of types of adhesive and in some the roll 28, passing under the roll 29. As the instances it is found that ordinary printing inks film 27 approaches the roll 23, it meets the as of a high polymerizing type may be successfully cending water film 26 and the thin Wide sheet of used to lanninate and provide color to the trans film appears to float upon this liquid film as it parent films. Where a film of a type which is follows the upper contour of the roll 23. The presently being Successfully laminated is to be film then passes under the guide roll 30 over a joined to a film which has not heretofore been Vacuum roll 3 and finally is wound upon the bondable, Such as polyethylene or polyvinylidene core 32 carried by mandrel 33. By rotating drum chloride, the heat-treating step need only be 23 at a peripheral speed slightly greater than the applied to the polyethylene or polyvinylidene Surface Speed of film 27, water is packed into the chloride because the adhesive chosen will itself tangential junction space creating a relatively bond to the untreated film. high pressure area, which excludes air. The apparatus and means herein described is A U-shaped support 34 is carried by the vessel also efficacious in enabling color-coding of poly 25 and Within the Support is mounted a doctor ethylene-coated electrical wire or cable. The blade 35 adapted to engage the bottom portion of (55 polyethylene-insulated wire is rapidly passed the film 27 to remove liquid droplets therefrom through a jet of flame so that the flanne envelops and to cause them to return to the tank or ves the wire. Temperatures as high as 2800° to 3200 Sel 25. A vacuum drier roll 3f, which is of well F. have been found very useful, the movement known construction, may be provided for remov of the Wire being So rapid that the critical tem ing any remaining traces of moisture on the film 0. preature of the polyethylene is not reached by prior to the rolling of the film onto the core 32. the body of polyethylene but merely the surface In the Specific illustration given, the roll 3 is is affected. It is believed that this treatment provided with an outer felt or absorbent cloth reorients the Surface molecules, breaking the layer 3 and a slight vacuum is maintained on Surface tension, and creating myriads of mole the inside of the drum for drawing the moisture 75 cule 'chains' to which the subsequently-applied 2,683,894 5 6 ink Will cling. A wide variety of commercially the lower portion of the roller in the liquid car available inks may be used with excellent results. ried by said vessel, means for rotating said roller The Speed of treating is proportional to the num to form a film. On the Outer surface thereof, neans ber of flame jets used or to the temperature of for conveying plastic film to be treated onto the the flame. The treatment may be made at any 5 liquid film carried by said roller, a burner Sup time prior to color application as, for example, ported for directing flame into contact with Said from one second to one year, etc. While I have plastic film on a side directly opposite said liquid Set out Specific uses for the apparatus and means film, and means for removing moisture from the described, it will be understood there are many lower side of said plastic film. Other uses to Which it and the methods herein 10 3. Apparatus for treating plastic film, com may be applied. prising a vessel containing cooling liquid, a roller While in the foregoing specification have Supported for rotation above said vessel and with Set forth Specific steps and elements in consider the lower portion of the roller in the liquid car able detail, for the purpose of illustrating en ried by said vessel, whereby upon rotation of said bodiments of the invention, it will be understood 5 roller, a film of liquid is formed on the Outer that such details may be varied widely by those surface thereof, means for conveying a plastic skilled in the art Without departing from the film to be treated onto the liquid film carried spirit of my invention. by Said rollei, and a burner Supported above said I claim: film and directing flame downwardly into contact l. In apparatuS for treating polyethylene film, 20 With said film. On a side directly opposite said a rotatably mounted roller adapted to convey the liquid film. film, a vessel supported below said roller and adapted to contain cooling fluid in contact with the lower portion of Said roller, imeans for ad AReferences Cited in the file of this patent vancing said film over said roller, means for UNITED STATES PATENTS rotating said roller to convey cooling fluid to the Number Name Date top portion thereof beneath said film, and means 2,248,714 Lytle ------July 8, 1941 for inpinging a flaine upon the upper Side of 2,412,429 Slingluff et al. --- Dec. 10, 1946 said polyethylene film directly opposite said 2,576,317 Toulmin ------Nov. 27, 1951 liquid on Said roller. 30 2. Apparatus for treating plastic film, conn OTHER REFERENCES prising a vessel containing cooling liquid, a roller l?eyers “Polyethylene,' Plastics, Sept. 1944, pp. supported for rotation above said vessel and with 39, 40, 42, 43, 100.