US3113883A - Impregnating a roll having a deformable porous periphery with varnish - Google Patents

Description

Dec. 10, 1963 A. L. JAMES IMPREGNATING A ROLL HAVING A DEFORMABLE POROUS PERIPHERY WITH VARNISH 2 sheets-sht 1 Filed Feb. 9, 1959 JNVENTOR. ax.

I BY

lam/s4 72,412204/ Dec. 10, 1963 A. L. JAMES 3,113,883 IMPREGNATING A ROLL HAVING A DEFQRMABLE POROUS PERIPHERY WITH VARNISH Filed Feb. 9, 1959 2 Sheets-Sheet 2 INVENTOR.

A r rat/IE Y5 United States Patent INIPREGNATING A ROLL HAVING A REFORM- ABLE POROUS PERHPHERY WITH VARNISH Albert L. James, Port Washington, Wis assignor, by

mesne assignments, to National Distiiiers and Chemical Corporation, New York, N.Y., a corporation of Virginia Filed Feb. 9, 195%, Ser. No. 792,677 5 (Jlairns. (til. 117-8) The present invention relates in general to improvements in the art of producing sheet material, and it rclates more specifically to an improved extrusion roll structure for manufacturing films or webs from thermoplastic materials and to an improved method of fabricating such rolls.

The primary object of this invention is to provide a roll structure especially adapted to effectively convert inherently plastic material into stable sheets or films, and to also provide an improved method of fabricating these rolls, whereby most effective commercial production of such sheeting is made possible.

My prior copending application Serial No. 723,040, filed March 21, 1958, discloses a method of and apparatus for producing sheeting of uniform thickness, by initially extruding a curtain of unsupported thermoplastic material in fluent condition into the nip formed between cooperating arcuate surfaces, by revolving the surfaces at relatively high speed to pull the curtain away from the extruder and to further extrude and convert the same into a web of desired thickness, and by finally cooling the web to solidify the same. Both of the arcuate curtain pulling and converting surfaces are preferably of smooth and glossy texture, but one of these surfaces is hard and cold being formed on an internally cooled cylinder while the other is relatively deformable and is disposed upon a roll of special construction which may also be cooled.

The present application is a continuation-in-part of the above identified original, and relates especially to the improved construction of the deformable surfaced roll, and to the improved method of producing such rolls whereby they will effectively cooperate with a plastic curtain extrusion device and with a hard surfaced body to further extrude the sheet into final uniform thickness.

It is therefore an important object of the present invention to provide an improved plastic material extrusion roll having a deformable but sufficiently smooth and glossy peripheral surface so that it will cooperate with another smooth and glossy but harder and more rigid arcuate surface formed on adjacent revolving body or drum, without permitting the plastic to adhere to the extrusion surfaces of the cooperating members.

Another important object of this invention is to provide an improved method of fabricating such plastic extrusion rolls having smooth and glossy non-adhering pecripheral surfaces, in a simple but expeditious manner and at relatively low cost.

A further important but more specific object of the invention is to provide an improved plastic extrusion roll adapted to produce transparent film of uniform thickness having local semi-transparent areas formed thereon, and to also provide an improved method of constructing such rolls.

Still another important object of the present invention is to provide an improved method of manufacturing rolls for accurately and rapidly finally extruding an initially extruded and unsupported curtain of fluent plastic into sheets of uniform gauge, automatically and at a high rate of speed.

These and other more specific objects and advantages of the invention should be apparent from the following "ice detailed description from which it will also be noted that the gist of the improvement is, a method of fabricating a fluent plastic extrusion roll which is provided with a deformable and relatively porous periphery to which a high temperature resistant but tenacious coating is firmly attached as by heating so as to permit limited deformation of the roll periphery, the coating also being susceptible of being dressed and polished in order to prevent the plastic from adhering thereto, and furthermore being adapted to be locally treated for the production of visible indicia on the otherwise highly transparent plastic films.

A clear conception of the several steps constituting the present improved method, and of one type of extrusion roll embodying the invention, may be had by referring to the drawing accompanying and forming a part of this specification in which like reference characters designate the same or similar parts in the various views.

FIGURE 1 is a diagram illustrating one type of apparatus for extruding plastic film with the aid of an improved rol-l fabricated in accordance with the present method;

FIGURE 2 is a perspective view of one of the improved extrusion rolls before it has been coated;

FIGURE 3 is a view depicting the step of applying the coating to the periphery of a roll such as shown in FIG- URE 2;

FIGURE 4 is a similar view illustrating the step of removing the coated roll from the coating chamber;

FIGURE 5 is a sectional view of an oven for baking the coatings onto several of the rolls upon removal thereof from the apparatus shown in FIGURES 3 and 4;

FIGURE 6 is a perspective view of one of the rolls after removal thereof from the baking oven, showing one mode of brushing the coating in the presence of polishing rouge in order to produce fine lines in the polished surface;

FIGURE 7 is another similar perspective View, showring another mode of applying a brushing wheel to the roll coating in order to produce such lines;

FIGURE 8 is another similar perspective view of a glossy finished roll provided with a masking jacket and being subjected to sand blasting in order to apply a local area adapted to produce relatively non-transparent designs or indicia upon plastic sheets being extruded by the roll; and

FIGURE 9 is still another similar perspective view of a final roll resulting from sand blasting treatment as in FIGURE 8, with the masking jacket removed therefrom.

While the invention has been described as being especially and advantageously applicable to extrusion rolls for converting a curtain of fluent plastic material such as polyethylene into continuous transparent film formation, it is not desired to restrict the use of the improved rolls by virtue of this limited disclosure; and it is also contemplated that certain specific descriptive terms be given a more general interpretation. For example, the term unsupported as applied to the curtain, sheet or film delivered from the initial extruder is intended to denote such a curtain which is not hacked or reenforced as it proceeds toward the arcuate extrusion surfaces; and the terms fluid and fluent are intended to define a condition of heated thermoplastic material wherein it is soft and capable of being drawn and expanded or stretched into sheet formation. The word deformable as applied to the roll periphery is intended to denote resiliency or ability to flex or distort under pressure, and it is contemplated that the inherently plastic material capable of bein extruded by the improved rolls includes not only such film-forming materials as polyethylene, but also Pliofilm, Saran, vinyl, nylon, polyesters, cellulose acetate, cellulose acetate butyrate, ethyl cellulose, polystyrene, as

3 Well as others. As to the formation of the body of the improved extrusion roll of silicone rubber, this term is intended to include other materials such as neoprene or relatively flexible pure rubber, and the coating material specifically defined herein as silicone resin varnish is also intended to include any lacquer, varnish, or rubber which will dry or cure to a glossy finish having release properties relative to the plastic being extruded, and also having sufficient temperature resistance to avoid deterioration and drastic changes in physical properties when subjected to the temperature at which the plastic is being extruded.

Referring to the drawings and especially the diagram of FIGURE 1, the method of extruding thermoplastic sheeting in accordance with the original application, involves the primary delivery of an unsupported curtain of fluent thermoplastic material into the nip between cooperating arcuate and glossy advancing surfaces to con vert the curtain 10 into a ribbon 11 of uniform gauge or thickness. One of these smooth and glossy arcuate surfaces is formed on the rigid or hard periphery of a drum 13, while the other is located upon relatively deformable periphery of a roll 14, and the plastic curtain 10 may be initially formed by ejecting the fluent thermoplastic from an extruder 16 through a die or head 17 downwardly into the nip of the cooperating drum 13 and roll 14. The periphery of the hollow drum 13 is cooled by cooling fluid delivered into this drum through its supporting shaft 19 to thereby harden or set the film 11, and the periphery of the roll 14 may also be cooled by causing it to contact a hollow roller 20 the interior of which may likewise be supplied with cooling fluid through its supporting shaft 21, thereby aiding the setting or stabilizing of the film 11.

The advancing and hardened film 11 is thereafter caused to travel over a series of guide rollers 23 until it reaches a pair of circular trimming knives 24 if it is desired to trim stock 25 from the opposite edges of the ribbon. From the knives 24 the finished film 11 is withdrawn over other guide rollers 27 and is ultimately wound into roll formation 28 upon a spindle reel 29, and the finished product may thereafter be dispensed as needed. The film 11 thus produced from the fluent plastic curtain 10 is normally clear and highly transparent so that it may be utilized as a wrapper for visibly displaying enclosed batches of various kinds of merchandise, but it may also be desirable in some instances to provide the transparent films 11 with semi-transparent local designs or indicia and the present invention contemplates the formation of such local configurations upon the sheeting during extrusion thereof in a manner to be later explained.

In accordance with the present invention, one of the polished arcuate surfaces is formed on the extrusion roll 14 the body of which is rotatably supported by a shaft 30 and may be constructed of a metal core 31 embraced by a layer 32 of deformable material such as relatively soft silicone rubber, neoprene or the like, preferably having minute air spaces therein, see FIGURE 2. This initial roll structure should then be coated with some kind of material which will permit slight deformation of the layer 32 under externally applied pressure, but which is susceptible of flexing slightly without cracking and may be highly polished on its external surface.

In order to effect such coating of the rolls 14, a unit such as shown in FIGURES 3 and 4 may be provided, and this unit comprises a casing 33 for confining coating liquid 34 such as silicone resin varnish or the like adapted to be hardened by baking, and having a liquid level indicating gauge 35 and an upper removable cap 36 associated directly therewith, the closure cap 36 being provided with an evacuating connection 37 and with an air inlet 38 alternately connectible with the casing interior by means of a two-way valve 39, while the bottom of the casing is provided with a valve controlled coating liquid inlet and discharge pipe the lower end of which is immersed in liquid 34 in a basin 41. When the valve 39 is sealed from a vacuum source communicating with the connection 37 and the liquid has been drained from within the casing 33, the cap 36 may be removed to permit insertion of a roll 14 such as shown in FIGURE 2 in upright position within the casing 33 as in FIGURES 3 and 4.

When a roll 14 has been thus inserted, the cap 36 should be applied and secured in place. A vacuum should then be thoroughly applied to the casing interior for a suficient period to allow the varnish solution to flow or be drawn into the evacuated casing 33 so as to completely submerge the roll 14. The varnish 34 will then completely replace the air and fill the voids in the layer 32 embracing the roll core 31 and will leave no entrapped air under the varnish coating. The varnish 34 within the casing 33 should be permitted to remain under reduced pressure for from ten to thirty minutes so as to insure removal of all entrapped air or gas bubbles from the varnish, and the reduced pressure causes such bubbles to expand and come to the surface of the liquid 34 where they break. When the varnish has thus been evacuated, the vacuum should be slowly released, whereupon the valve 40 may be opened to permit the varnish to drain slowly from within the casing at a uniform rate. This slow and uniform drainage is important in order to deposit a uniform, run-free, glossy, smooth, and bubble-free coating 32 on the roll surface, and the rate and uniformity of the removal of the varnish may be controlled either by adjusting the pipe line valve 40 or by utilizing a pump to remove the coating material so as to eliminate runs in the final coatings 32.

The thermoplastic coating 42 thus applied is soft and must be hardened and set by the application of heat in order to permit subsequent finishing thereof, and this step may be accomplished with the aid of a baking oven 44 such as shown in FIGURE 5. This oven 44 is provided with a lower source 45 of heat and with an upper exhaust vent 46, and should preferably have an inlet opening 47 of sufiicient sizes to permit a carriage 48 while supporting several of the pre-coated rolls 14 to be inserted within and removed from the baking chamber 48. During the baking operation, the roll coatings 42 are converted into tenacious but sufiiciently hard and glazed condition. The smooth coatings are subsequently brushed in the presence of very fine powder such as polishing rouge, in order to produce fine lines in the baked and glossy surfaces. These lines do not destroy the polish but merely provide proper coaction between the roll coating 42 and the film of thermoplastic advancing therealong, and the brushing may be effected either by applying a brush 49 as in FIGURE 6, or a brush 50 as in FIGURE 7, or both.

When the extrusion roll 14 has been thus properly fabricated, it may be installed in a system such as shown in FIGURE 1 and utilized to automatically produce a continuous highly-transparent ribbon or film 11 of thermoplastic material having uniform thickness throughout its entire area. It may, however, be desirable in some instances, to provide the film 11 with local areas, designs or indicia which are relatively non-transparent or opaque, without printing or otherwise covering or coating these local areas. In accordance with the present invention, the application of such designs or indicia to the polished coating 42 of the roll 14 may be accomplished by embracing the roll periphery with a mask 52 having one or more local cut-outs 53 therein of the desired shape, and by thereafter lightly sand-blasting the exposed area or areas of the coating with a sand blast nozzle 54 as illustrated in FIGURE 8. Upon removal of the mask 52 after sand-blasting has been effected, a roughened local design or indicia 55 will remain on the coating 42 at each blasted area, and when these roughened indicia 55 are impressed upon the film 11, they produce visible but semi-transparent configurations on the advancing film.

An alternate mode of applying designs on the rolls 14 is to start with a matte finish roll having a freshly ground unvarnished silicone rubber periphery, and by stenciling the desired pattern thereon with silicone varnish or lacquer.

From the foregoing detailed description, it Will be apparent that the present invention, in fact, provides a simple but highly eifective extrusion roll for producing sheets of uniform thickness from fluent plastic materials rapidly and with utmost precision, together with an improved method of fabricating such rolls. The plastic materials Which are capable of being extruded with the improved rolls may be various types adapted to be converted into transparent flexible films 11, and the deformable materials used in the formation of the roll bodies may also be of several types preferably containing minute voids, while the coating materials may likewise be of a number of kinds adapted to be firmly anchored to the deformable roll bodies but capable of being transformed into tenacious and hard coatings susceptible of being baked so as to provide mirror-like surfaces to which the plastic will not adhere. When it is desired to apply semi-transparent visible indicia to the otherwise smooth and highly transparent films 11, this can be accomplished by merely roughening the areas at which these indicia are to be located by sand-blasting the polished surfaces, and the extent of this treatment will depend upon the degree of non-transparency required. The present invention has proven highly satisfactory and successful in actual use, and is especially adapted for cooperation with apparatus such as disclosed in FIGURE 1.

It should be understood that it is not desired to limit this invention to the use of all of the method steps or to the precise construction of the extrusion rolls herein described, for various modifications within the scope of the appended claims may occur to persons skilled in the art.

I claim:

1. The method of fabricating an extrusion roll for producing plastic film, which comprises, providing a roll body having a deformable porous nlbber periphery, immersing the body Within a bath of high temperature resistant varnish while subjecting its periphery to vacuum to remove the air and depositing a coating of the varnish upon the evacuated area, removing the roll from the bath and vacuum zone and baking the coating to produce a hard external surface thereon, and finally brushing said surface to a high gloss while providing hair lines thereon.

2. The method of fabricating an extrusion roll for producing plastic film, which comprises, providing a roll body having a deformable relatively porous periphery, subjecting the roll periphery to vacuum to remove the air while simultaneously applying a coating of high temperature re sistant varnish to the evacuated roll periphery, and baking the applied coating to produce a hard and glossy external surface thereon.

3. The method of fabricating a roll for producing extruded polyethylene film, which comprises, providing a roll body having a silicone rubber peripheral surface, evacuating the surface while coating the same with silicone resin varnish, baking the coating onto the surface, and finally brushing the external surface of the coating to produce a polished surface having hair lines therein.

4. The method of fabricating a roll for producing extruded transparent polyethylene film having a visible surface design thereon, which method comprises, providing the roll body with a peripheral porous surface of deformable material, subjecting the surface to vacuum while si multaneously coating the same with transparent varnish, baking the coating onto the surface, and sand-blasting the pattern onto the coating to produce a semi-transparent design upon the film.

5. An article of manufacture comprising, a polyethylene film extrusion roll having a porous deformable peripheral surface portion coated with silicone resin varnish anchored to the surface pores and which has a highly polished relatively hard but flexible external surface locally roughened to produce visible indicia upon the film extruded by the roll.

References Cited in the file of this patent UNITED STATES PATENTS 1,431,917 Antaramian Oct. 17, 1922 1,563,943 Adams et al Dec. 1, 1925 2,088,470 Freedlander July 27, 1937 2,097,315 Watkins Oct. 26, 1937 2,172,394 Lippicott et a1 Sept. 12, 1939 2,204,383 Safford June 11, 1940 2,262,281 Hagler et al Nov. 1 1, 1941 2,280,208 Wilkie Apr. 21, 1942 2,358,710 Helgeson Sept. 19, 1944 2,639,519- Polk et a1 May 26, 1953 2,684,307 Knapman July 20, 1954 2,741,014 Hubbard t Apr. 10, 1956 2,808,022 Kaulen et-al Oct. 1, 1957 2,827,390 Gari-igus Mar. 18, 1958 2,894,853 Anderson July 14, 1959 2,943,475 Benveniste et al July 5, 1960

Claims (1)

1. THE METHOD OF FABRICATING AN EXTRUSION ROLL FOR PRODUCING PLASTIC FILM, WHICH COMPRISES, PROVIDING A ROLL BODY HAVING A DEFORMABLE POROUS RUBBER PERIPHERY, IMMERSING THE BODY WITHIN A BATH OF HIGH TEMPERATURE RESISTANT VARNISH WHILE SUBJECTING ITS PERIPHERY TO VACUUM TO REMOVE THE AIR AND DEPOSITING A COATING OF THE VARNISH UPON THE EVACUATED AREA, REMOVING THE ROLL FROM THE BATH AND VACUUM ZONE AND BAKING THE COATING TO PRODUCE A HARD EXTERNAL SURFACE THEREON, AND FINALLY BRUSHING SAID SURFACE TO A HIGH GLOSS WHILE PROVIDING HAIR LINES THEREON.

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