US2179562A - Method of coating webs - Google Patents

Description

Nov. 14, 1939.

P. H. PENNELL METHOD OF COATING WEBS Filed July 24, 1936 Patented Nov. 14, 1939 UNITED STATES PATENT OFFICE METHOD OF COATING WEBS Pennsylvania Application July 24, 1936, Serial No. 92,295 11 Claims. (on. 91-70) My invention relates to a method of coating webs and is directed particularly to a method for use in printing floor or other surface coverings requiring a film of paint of appreciable thickness toserve as a'wear surface. In the manufacture of printed coverings of this class, there are a number of factors which at the present time militate against the observance of certain fundamental criteria, known to the skilled paint technician as being essential to the formation oi a high quality wearing surface from the four These factors arise by reason of the unusually heavy film of paiiit which must be applied in a single application in order to be economically practicable, and by the fact that curing or stoving of the film must be effected to properly condition the film for use as a wear surface. This necessitates that the base, which is generally in the form of a continuous web, with its applied coating paint, must, at some time almost immediately after application of the paint film, assume an inclined or vertical position. These problems, which are inherent in the application of a heavy film of slow drying paint and in the stoving thereof, are amplified when the curing is efiected in the festoon stoves commonly empioyed in the floor covering industry, wherein the material, as it emerges from the'printing machine, is directed into a curing chamber and hung therein in vertically extending festoons on cylindrical battens, the length of the festoon generally being in the order of forty-five feet, although similar problems are present when flat rackstoving is utilized. In such operation, the material must assume a substantially vertical position while being directed from the bed of the machine to those racks which lie above or below the plane of the bed, and paint runs are as common in flat rack stoving as in festoon stoving.

Contrary to one of the fundamental prerequisites of satisfactory wear film formation, it has been common practice in the printed floor covering industry to body up the paint to prevent paint runs. This has been efiected by incorporating relatively large amounts of pigments or other filling agents into the paint. It has been the theory that in such paints the reduction of fiowability is due to increased interfacial frictionai resistance built up by the pigment particles within the film. In some instances the proportion of pigment has been as high as 44% by volume of the nonvolatile portion of the paint,

whereas it has long been known that the ideal pigmentation for wear films should be approximately 30% by volume of the nonvolatile portion of the paint. Any increase in pigmentation inevitably results in lowering of the wear, alkali and acid resistance of the formed film. An equally acute problem is encountered with bodied up paints where the covering material is printed in design. The paint film which is formed by printing with paints having high pigment concentrations will not level out satisfactorily after application but "stands proud, taking the outline of the printing member which applied the film and leaving relatively sharp ribs or ridges where contiguous color patches abut. This condition is aggravated by the'use of peg or line block printing members of the type com monly utilized in the printing of floor coverings to provide air relief. Another disadvantage arising out of the use of high pigment concentration paints, lies in the difiiculty of obtaining a glossy surface. Gloss is imparted to the surface of the film primarily by the vehicle overlying or surrounding the pigment particles and disposed at the surface of the film; If the pigment concentration is too high, there is insumcient vehicle to. adequately wet and coat the pigment particles and, as a result, the dried film is dull and has no appreciable sheen. In addition, the cost of the paint is increased proportionately with any increase in proportion of pigment to vehicle.

The use of bodied up" paints has minimized Paint runs but has not eliminated them completely since the pigment particles will, by their gravitational forces, tend to orient themselves readily upon reduction of viscosity of the vehicle induced by heat, and, the material being. subjected to such heat while in a vertical plane, the tendency still remains for the particles to 40 gravitate downwardly, thus forming regions of thick and thin films. While the print paints heretofore employed have possessed some thixotropic body inherent in pigmented vehicle struc-- tures, movement of the material through a ver- 45 tical path has been effected so soon after the printing step, which applies shearing forces to the paint and thus reduces the viscosity thereof, that any material thickening by thixotropic action cannot be availed of prior to movement of the material into the stoves or curing racks, for, under ordinary temperature conditions, such thixotropic action is so slow that it would require a commercially impracticable time period be- 55 tweenprinting and stoving to avail of such ac tion. 1

It is an object of my invention to provide a method and means whereby low pigment paints, in the order of 30% concentration, may be used in printing floor coverings or other surfaces requiring a relatively heavy film and may be hung in festoon type stoves or otherwise cured without running. The fact that the material will pass through or remain in a vertical plane for an extended period of time does not materially affeet the film when employing the method and apparatus of my invention.

Another object of my invention is to provide a mechanism and method whereby leveling of a film of thixotropic body paint which may be of the usual character and high pigment concentration may be accomplished and paint runs eliminated.

According to a preferred embodiment of my in- .vention, the former object is attained by the use of a vehicle having the characteristic of attaining a false body within the applied film by micelle formation within a relatively short period of time, which micelle formation may be accelerated by the application of heat, and heating the film while maintained in a horizontal plane to reduce the viscosity of the vehicle to thus enhance micelle formation, with consequent thickening and stiffening of the film to a degree sufficient to permit hanging in a festoon, or movement in a vertical plane, substantially immediately after completion of the printing operation and to induce leveling of the applied film into a smooth, plane surface. Leveling, which is dependent upon and results from reduction of the surface tension of the applied film, and gravitational forces, should be accomplished before the creation of the false body" has proceeded too far, since, if the film is rendered stiff and viscous, leveling, without mechanical Working of the film, cannot be accomplished. The false body preferably results from the formation of micelles within the vehicle due to the presence of gel particles and/or resinoid particles therein, and, where the film is pigmented, the pigments may be so chosen that micelle formation is enhanced thereby. The paint thus formed will be in a thixotropic state and will permit of application by the printing machines commonly employed in the floor covering industry.

It'is preferred to create the false body effect but temporarily in order that gloss will not be sacrificed and to insure proper cohesion of the film to the surface to which it is applied. For that reason, the resinoid particles should preferably be soluble in the oil of the vehicle, although they may be only difiicultly so, in order that the resinoid particles will nt,be present as such in the final, cured film. The false bodying, re sulting in immediate but temporary stiffening of the film, will be replaced by permanent setting or coagulation of the vehicle and conversion of the various components of the film into a stable, tough, flexible, alkali-resistant wear surface.

A typical example of a vehicle of the preferred type may comprise a partially regenerated oil gel, a prepared resinoid, and, if desired, a heat bodied oil gel.

The partially regenerated oil gel may be formed in the following manner: A batch consisting of 2000 pounds of a linseed, China-wood oil mixture is heated in an open kettle to about 565 F. and maintained at that temperature until a semi-solid condition is obtained which may be determined by examination for a heavy string on a test paddle immersed in the oil immediately after thorough stirring. The oil is then in such condition that continued heating for a short period of time'would result in complete solidification of the oil mixture. In order to arrest this action, at least temporarily, a paste comprising a mixture of about 20 pounds of litharge and sufiicfnt oil I to produce the proper consistency is incorporated into the batch by stirring. The incorporation of this material results in a regeneration of the gel formed by heating. There is some saponification of the oil structure and, upon incorporation of the litharge, accomplished by stirring, the oils become of fiowable consistency but would normally revert to a solid gel upon cooling. Therefore, immediately after sufficient regenerating agent such as litharge has been incorporated, the batch is thinned with a compatible oil. In the example referred to, approximately 1950 pounds of raw linseed oil are added; the material being incorporated slowly and with constant stirring in order to preserve the regenerated gel particles. The product thus formed. should have a viscosity of about 4.35 poises at 570 F. and contain a fairly large proportion of suspensoids in the form of gel particles thoroughly dispersed throughout the raw oil and the liquid portion of the oil gel resulting from regeneration thereof. Manganese resinate or other suitable drier in the amount of about three pounds is added, and the batch is permitted to cool to room temperature.

A resinoid which is but difiicultly soluble in the above regenerated oil gel may be formed in the following manner: A mixture composed of amberol F-7 and amberol K-12-A and consisting of about 285 pounds of the former resin and 15 pounds of the latter is melted with 114 pounds of regenerated oil gel prepared as above described. The K-12-A amberol is less readily soluble in the regenerated oil gel than the F-7 and the proportions may be varied over a relatively wide range depending upon the amount and rate of micelle formation desired. The temperature of the batch is raised to about 420 F. and maintained at that temperature until the melt is clear. the temperature is rapidly raised to about 550 F. It is desirable to first dissolve the resin in the oil under relatively low temperature conditions in order to prevent charring of the resin in the bottom of the heating kettle which might result if the temperature were too high, and thereafter, elevate the temperature of the batch to obtain the desired consistency. The temperature is then reduced to approximately 450 F., accompanied by continuous stirring. Manganese resinate in the amount of about A of a pound is then added. Thereafter, mineral spirits or other thinning agent are added in the amount of 414 pounds. It is preferred to use a thinning agent in which the resinoid is difficultly soluble, since micelle formation is increased in the final product when a thinner of that type is employed, since by the use of such a thinner the resinoid is broken down into a form in which the particles are capable of rapid micelle formation and are dispersed in the final product ina fetastable condition rather than disposed in solution in the thinner. I have obtained satisfactory results, however, when using hydrogenated naphtha which is a fairly good solvent for the amberol resin in the above example. The resinoid is of a flowable consistency and, under ordinary temperature conditions, is not readily soluble in regenerated oil gel of the type above described.

Thereafter 590 F. until a viscosity of 250 poises at 590 F.

is attained and thereafter the two batches, are blended together. The temperature of the mixture is then permitted to fall to 450 F. and manganese resinate in the amount of about two pounds is added. The product resulting contains a substantial amount of gel which is formed probably by local overheating of the oil in the kettle. In order to maintain a temperature of 590 F., considerable local overheating will occur and this undoubtedly results in the formation of a substantial amount of gel particles. In this heat bodied oil, the litharge is utilized to more rapidly effect gel formation and heat bodying. If the litharge werel'eliminated, then heat thickening'would require a considerably longer period of time and, as a result, the oil would be dark in color and not as satisfactory for some purposes as that prepared in accordance with the preferred procedure.

A typical example of a print paint suitable for use as a wearing surface for floor coverings may be formed by mixing the following ingredients into a paste and then grinding the mixture on a paint mill:

Pounds Lithopone 38 Zinc oxide 25 Whiting 37 Regenerated oil gel 25 With 100 pounds of this paste, is mixed, in a suitable paint mixer, 17 pounds of regenerated oil gel, 16 pounds of resinoid, and 4 pounds of heat bodied oil gel.

The resulting paint contains resinoid particles and gel particles formed from both the re-- generated oil gel and the heat bodied oil gel.

The term particles" is used in a generic sense,

since the resinoidand oil gel particles may be in the form of suspensoids or may be in a colloidal state. The particles are dispersed throughout the vehicle in a metastable condition, and immediately after shearing forces, such as those resulting from the printing operation, cease to be applied, micelle formation begins. This micelle formation is believed to be a direct result of the combined forces of the particles some of which are of an anisotropic character, and gravitational forces. It is probably true that the resinoid and gel particles have some affinity for each other and for themselves audit the pigment be properly chosen, the particles thereof also will have a tendency to group themselves with the other particles within the film. coincidentally with micelle formation, there is a general thicknening of the applied film. The reaction is not completely understood, but it is believed toresult from the fact that with the first formation of micelles, there is immediately an enormous increase in the specific surface of the particles to be wetted and, concomitantly, a diminution in the liquid or vehicle available for wetting. There immediately follows, therefore, a general thick- 2,179,502 The heat bodied oil gel may take the form of a V ening and stiffening oi the whole structure. In order to accelerate this formation, I purpose to apply heat to the paint film disposed upon the surface being coated, while the material rests in a substantially horizontal plane in which run ning of the applied film will not occur. By the application of heat, the viscosity of the vehicle is reduced and the particles within the paint film are released for proper and immediate orientation. This may be accompanied by vaporization of a portion of the thinner for the resinoid which loss will also have some thickening effect on the film. Since leveling of the paint film is dependent upon the reduction in surface tension and gravitational deposition of the pigment and other particles within the film, it is desirable to applythe heat to the film over an extended period of time, in the order of three minutes, and the temperature should. not be so high as to induce micelle formation at too rapid a rate for, as pointed out above, thickening will result before leveling is accomplished. At the present rate of production on fiat block printing machines, a heating chamber about 70 feet long would berequired for athree minute heating period. This may be objectionable from the standpoint of space limitations, but in many instances the heating chamber may be positioned at a point near the bottom of the curing chamher without any major alterations to existing equipment.

I have found that when a film formed as above described is applied to a foundation web of saturated felt of the type commonly employed in the manufacture of felt base floor covering, a general thickening and stiffening of the applied film and satisfactory leveling may be accomplished if the temperature of the web be elevated to 165 F., and maintained at that temperature for a period of thirty seconds while the .material rests in a substantially horizontal plane. heating to this temperature, a relatively short heating time is necessary. The web may then be immediately transferred to a substantially vertical plane without danger of running.

In the accompanying drawing there is illustioned at the exit end of a fiat block printing machine and adapted to properly condition a paint film prior to passage of the web into a curing chamber.

The presetting device 2 is positioned between a fiat block printing machine 3 and a curing chamber 4, and is of relatively short length. The exit end 5 of the presetting device may be positioned within the curing chamber 4 as shown. The presetting device comprises a bank of steam coils 6 fed by a header I communicating with a suitable source of steam supply. In the embodiment shown, the coils 6 extend transversely of the bed of the printing machine and are secured to supporting framework 8. A second battery of steam coils 9 is disposed in a plane parallel to the bed of the printing machine 3 and these coils are secured between the print ng machine frame members l0. The coils 9 are preferably formed of flattened pipes in order to present a relatively fiat surface to support the web of decorated material ll during its travel from the printing machine 3 into the curing chamber 4. It will be observed that the coils 9 lie in a position in advance of the coils 6 in order that the web ll may be brought to the desired temperature prior to the application of radiant heat to the decorated surface of the web by the coils 6. The coils 9 .trated, in side elevation, a presetting device posiare provided with a-steam inlet I2 feeding'into a header l3 to which the coils are connected. A return line [4 is also provided for drainage purposes.

The radiating coils 6 and the supporting framework 8' aremounted for movement in a longitudinal direction parallel with the web in order that, upon the filling of the curing chamber, the mechanism may be moved out of the curing chamber and the door D closed. In order to provide a conveniently movable mechanism, end frame members l5 are provided with rollers l6 engageable with tracks I! attached to the printing machine frame. A roller [8 is secured to the machine frame and engages a track IS on the supporting framework 8. A supporting roller 20, secured to the framework 8, rides on a track 2| attached to wall 22 of the curing chamber 4. A stop 23 is provided to limit movement of the exit end 5 into the curing chamber.

From the foregoing, it will be clear that after decoration of the web I I by the printing machine vweb. After the web ll leaves the flat surface of the coils 9, it rides upon a plate 24 secured at one end to the framework of the presetting device by an angle 25, the other end resting freely upon the coils 9. The decorated material then passes over a batten roll 26 through a vertically extending dip 21 to an upper batten 28 from which it hangs in a festoon in the curing chamber 4 where sufficient heat is applied to properly set or coagulate the vehicle, and, where a paint of my preferred type is employed, to effect conversion of the resinoid with the oil of the vehicle to form a wear resistant surface which has good gloss characteristics and is stable, tough, flexible, and alkali-resistant.

It sometimes happens in printing machine operation that block chokes, shimming adjustments and other causes require stopping the machine for a period of time greater than desirable for the application of heat to the decorated web in the presetting device. In order that the radiant heat applied to the surface may-be rendered less intense, and further in order to avoid the application of heat to the base web during such shut downs, means are provided whereby the radiant heaters may be moved away from the surface of the web a distance to render them sufficiently ineffective, and means are provided for injecting cooling fluid through the steam coils 9. In the embodiment illustrated, the frame-work 8 supporting the coils 6 is suspended from the shaft 29 by cables 30, two shafts 29 and four cables 30 being provided. Each shaft 29 is rotatable by a worm wheel 3| engaged by a worm operated by a handle 32, whereby the cables 30 are wound therearound and the radiant heaters 6 are elevated away from the surface of the decorated web. The connections from the source of steam supply to the header 1 should preferably be made flexible to permit of such movement without the necessity of disjoining of pipes and fittings.

Any suitable connection may be made to the line [2 of the heating coils 9 for the passage of cooling water or other fluid therethrough. For example, a Y connection 33 may be used and a steam line 34 connected to one side thereof and a water line 35 connected to the other side. Valves should be provided in each of these lines to efiect proper control.

An electrically heated presetting device may be conveniently formed along the same general lines as those disclosed in the drawing, radiant heating coils being substituted for the steam coils 6 and anelectrically heated platen replacing the coil 9. The mechanism for elevating the coils 6 may then be dispensed with and a. control switch provided to cut off the heating current in the event of a shut down of the printing machine.

The presetting device could utilize heated air .if the time period for presetting were long enough. Care should, of course, be taken to insure that the velocity of the air coming into contact with the wet film is not so great as to cause rippling or deformation of the applied pattern.

The presetting device illustrated in the drawing has been found to operate very satisfactorily with floor covering paints, both of the pigment bodied up type and of the type in which a false body is created by gel particles, resinoid particles or anisotropic pigment particles or combinations thereof. In the former type, the presetting device effects proper orientation of the pigment and whatever minor amount of micelle formation which may be inherent in any oil paint film, and in the latter type the device operates to effect rapid micelle formation and concomitant thickening and stiffening of the film induced thereby.

While I have illustrated and described, certain preferred embodiments of my invention, it will be understood that the invention is not so limited but may be otherwise embodied within the scope of the, following claims.

I claim:

v1. In the method of printing, the steps consisting in applying a film to a base, said film including oil and a resinoid which is but diflicultly soluble in the oil, said film having a thixothropic body susceptible to rapid micelle formation when shearing forces cease to be applied, applying heat to said film accelerate micelle formation while maintaining the base in a substantially horizontal plane with the film at rest thereon, moving the base with its applied film through an inclined path, and curing said film at a temperature suflicient to effect substantially complete conversion of the resinoid with the oil.

2. In the method of coating a web, the steps consisting in applying a film of coating material to a base, said coating material including a partially regenerated oil gel, applying heat to said film while disposed in a substantially horizontal plane to effect micelle formation of the gel particles and concomitant thickening of the film, passing said base through an inclined path, and curing the film.

3. In the method of coating a web, the steps consisting in applying a film of coating material including an oil vehicle containing resinoid particles dispersed therein to a base, applying heat to the film while disposed in a substantially horizontal plane, passing said base through an inclined path, and curing the film at a temperature sufiicient to effect substantial conversion of the resin with the oil.

4. In the method of coating a Web, the steps consisting in applying a film of coating material hit including a heat bodied oil vehicle containing oil gel particles, resinoid particles and pigment particles in dispersed condition therein to a base, the pigment being present in an amount less than 34% by volume of the nonvolatile constituent of the coating material, applying heat to said film while disposed in a substantially horizontal plane to effect micelle formation of the various particles, passing the base through an inclined path, and curing the film.

5. In the method of coating a web, the steps consisting in applying to a substantially nonabsorptive web a relatively heavy film of coating material including an oil vehicle with particles dispersed therein in a metastable condition, said particles having the characteristic of micelle formation, and being selected from a group consisting of oil gel, resinoid and fiocculant pigments,

said film of coating material when applied being,

of such character that running will occur-if the web be disposed in a substantially vertical plane, applying heat to said film while the same is disposed in a substantially horizontal plane to effect a thinning of the vehicle and a general leveling of the applied film, continuing the application of heat while so disposed to eflect conversion oi said particles into micelles with concomitant thickening of said film in an amount sumcient to prevent running when disposed in a substantially vertical plane, passing said web with said film disposed thereon through an inclined path, and thereafter curing the film.

6. In the method of coating a web, the steps consisting in applying to a substantially nonabbe disposed in a substantially vertical plane, ap-

plying heat to said film while the same is disposed in a substantially horizontal plane to efiect conversion of said particles into micelles with concomitant thickening of said film in an amount sumcient to prevent running when disposed in a substantially vertical plane, passing the web with the film disposed thereon through an inclined path and thereafter curing the film.

7. In the method of coating a web, the steps consisting in applying to a substantially nonabsorptiveweb a film of thixotropic bodied paint'ina plurality of design elements, said paint including an oil vehicle with particles dispersed therein in a metastable condition, said particles havin the characteristic of micelle formation and being selected from a group consisting of oil gel, resinoid and fiocculent pigments, said paint when applied being of such character that running will occur if the web be disposed in a substantially vertical plane, applying heat to said elements while disposed on the base web in a substantially horizontal plane to effect leveling of the elements to a substantially plane, continuous film prior to thickening thereof by thixotropic action, continuing the application of heat while so disposed to ellect" conversion of said particles into micelles with concomitant thickening of said film in an amount sufiicient to prevent running when disposed in a substantially vertical plane, passing said web with said film disposed thereon through an inclined path, and thereafter curing the film.

8. 'In the method of coating a web required to be moved in an inclined path, the steps consisting in applying to a substantially non-absorptive web a relatively heavy film of coating material including an oil vehicle with particles dispersed therein in a metastable condition, said particles having the characteristic of micelle or aggregate formation, and being selected from a group consisting of oilgel, resinoid and fiocculent pigments, disposing said web so that a low viscosity film will not run thereon, while in such position applying heat to the applied film in an amount sufiicient to reduce the viscosity of the film to permit natural leveling of the same, thereafter while the web is disposed in substantially the same manner effecting substantial thickening of the film by the application of additional heat thereto, moving the web in an inclined path and thereafter curing the film by the continued application of heat.

9. In the method of coating aweb, the steps consisting of applying to a substantially 'nonabsorptive web a relatively heavy film of coating material including an oil vehicle with oil gel particles dispersed therein in a metastable condition,

applyng heat to said film while disposed in a substantially horizontal plane to efiect micelle formation of the gel particles and concomitant thickening of the film, passing the web through an inclined path and thereafter curing the film.

10. In the method of coating a web required to be moved in an inclined path, the steps consisting in applying to a substantially non-absorptive web a relatively heavy film of coating material including a vehicle with oil gel particles having the characteristic of micelle or aggregate formation dispersed therein in a metastable condition, said particles resulting from the treatment of a heatbodied oil gel with a regenerating agent and thinning with a compatible oil, applying heat to said film'while disposed in a substantially horizontal plane 'toefiect such micelle or aggregate formation of the oil gel particles and concomitant thickening of the film, passing the web through an inclined path and thereafter curing the film.

11. In the method of coating a web required to be moved in an inclined path, the steps consisting in applying to a substantially non-absorptive web a relatively heavy film of coating material including a vehicle with resinoid particles having the characteristic of micelle or aggregate formation dispersed therein in a. metastable condition,

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