US1899387A - Process of coating articles with liquid pyroxylin or the like - Google Patents

Description

Patented Feb. 28, 1933,

' UNITED STATES PATENT OFFICE WILLIAM c. nimr'ron, or DAYTON, c1110, ASSIGNOR TO THE cnnwronn MCGREGOR Ann CANBY COMPANY, or DAYTON, 03 0, A CORPORATION or OHIO PROCESS OF COATING ARTICLES WITH LIQUID IPYROXYLIN OR THE LIKE No Drawing.-

rious prior patents describe articles as being coated or encased in celluloid, pyroxylin or analogous material, the actual carrying out of such a process involves numerous difficulties and necessitates special steps and handling for which the necessary teaching and instruction is not found in those prior publications and patents which so nonchalantly refer to such use of liquid celluloid and the coating of articles by dipping therein.

In attempting to coat articles by dipping in a liquid pyroxylin or nitrocellulose material, many baffling failures are encountered, The present method and steps to be followed in utilizing such coating material in liquid form have been discovered only after long experiment and trial. It is quite easy to dissolve the material in a suitable solvent such as alcohol, ether, acetate or acetone, the latter being preferred, and to plunge the article to be coated into such solution, and no difliculty is involved in rotating the article to effect approximately unif Jrm distribution. However, to effect the proper drying and solidification of the material to afford a uniformly smooth surface'having a-high natural polish or gloss has been found to be extremely difiicult and to involve careful control of temperatures and humidity.

The major difficulties encountered are those of moisture condensation upon the coating,

causing it'to become discolored or streaked,

the prevailing-tendency of the coating material while solidifying to become wrinkled,

' and the formation of bubbles or pimples, causing the surface to become unsightly and,

rough.

The present process overcomes these dif- Application filed m 24, 1929. Serial No. 365,781.

ficulties and enables the uniform coating of articles in commercial quantities wherein the coating is formed in situ. A succession of articles may be coated to uniform thiclmess, the depth of which may be quite accurately controlled. The finished product possesses an extremely hard, smooth, unbroken surface having a quite high degree of polish or gloss Without the necessity of further working or treatment. I

One of the primary objects of the present invention is to afford a surface finish or coating for metal and wooden articles of great durability and strength which will not chip,

craze or crack, which can be produced in a wide variety of colors, and will possess wearing qualities under severe usage superior to the usual paint, varnish and lacquer finishes.

Whereas shafts, rods and other articles have heretofore been covered or encased by wrapping thereabout strips of celluloid, pyralin or like material, or by enclosing such bodies in tubular casings formed from sheet material which is then subjected to heat and pressure or by plastic molding such material, one of the dominant features of the present invention is to apply a surface coating or finish which will be formed in situ and which will unite with and adhere to the coated article with such tenacity that it will not be likely to split or peel therefrom.

A further object of the invention is to reduce the cost of coating or encasing articles in celluloid, pyroxylin or analogous material.

' A further and important obJect of the invention is to provide a'surface coating or finish which will possess a natural high polish or gloss without the necessity of grinding, bufiing,'or burnishing.

A further and important object of the invention is to provide a method or process for- 1 controlled.

' pear in the specification, the invention consists of the process, steps and treatment and the method of control of the drying or solidifying of the coating material as hereinafter described or their equivalents as hereinafter described and set forth in the claims.

The present process is applicable to the coating of articles of various shapes and in various lines of manufacture, as for example, the coating of furniture, handles or knobs for various purposes, golf club shafts, fishing rods, polo mallets, tennis racquets and other sporting goods, various articles of household and factory equipment, toilet articles and numerous other articles of both metal and wood. .For purpose of illustration, but without intending to limit or otherwise restrict the application of the process and invention, it will be described in its application to the coating of tubular metallic golf club shafts to which it is now being very successfully and extensively applied.

The material employed is obtainable commercially in sheet form, being generally sold under the name of pyroxylin, pyralin, celluloid and other commercial or trade names for materials having nitrocellulose characteristics. Thismaterial is soluble in alcohol, acetone, or some form of acetate. The material is workable at a consistency of thick cream and when dissolved is of viscous character.

The surface to be coated is thoroughly cleansed to remove any grease, dirt or scale. This cleansing is preferably effected by means of a sand blast which gives to the article a slightly roughened or matte surface. It is found that this cleansing and dulling or matting of the surface greatly facilitates the adherence of the coating material.

The cleansed article, which for example is a tubular metallic golf club shaft, being first plugged at its end to prevent entrance of the material, is immersed in the liquefied material, which is preferably contained in tall cans or tanks permitting the shafts to be dipped vertically. The shaft is lowered slowly into the liquid material in order that air may not be carried downward into the solution by friction of the shaft surface. After being immersed to the desired extent, which in the case of golf club shafts is to a point a short distance above that at which the grip wrapping begins, it is permitted to remain in the coating liquid for a short time, sufficient to allow any air bubbles to escape and the ma terial to adhere to the shaft. The shaft is then withdrawn and the surplus material allowed to drain back into the receptacle until the excess material has been removed. The coated shaft is then slowly rotated in order to distribute the material uniformly and prevent a drainage or sagging of the yet soft or semiliquid material to one side of the shaft.

In commercial operation the coated shafts are mounted upon a power driven apparatus which transmits to them a slow rotation while the shafts are maintained in an inclined position of a proximately twenty to thirty degrees. A ter the shaft has been rotated a few times to distribute any accumulation of material, water or other temperature controlling medium is discharged through the hollow interior of the shaft while the rotation continues until the material is set or hardened. It is during this stage that the major difliculties are encountered. The solvents employed are more or less volatile, and the evaporation is normally quite rapid. It has been found impractical to use retarding agents, which have a tendency to break down the structure of the material and to lessen its strength. The evaporation of the solvents under ordinary conditions, is so rapid as to produce a refrigerating effect and the surface of the coating material becomes so cold as to cause moisture condensation from the atmosphere thereon. The accumulation of water of condensation upon the surface coating distorts and discolors the material. This moisture causes yellow and white streaks to appear upon the darker materials, and prevents the formation of the desired polish or gloss. Such attraction of moisture is termed blushing or watering. Under ordinary atmospheric conditions and temperatures, sufiicient water will be collected to form drops which trickle down the surface. Where drops rest, surface pitting also occurs.

The difficulty of bubbling and pimpling occurs when the exterior film of the material becomes too quickly set, confining within the body of material a portion of the solvent which has not had time to evaporate and which under temperature increase, as the refrigerating effect of surface evaporation is arrested, expands within the deposit of material, causing the material to swell and form bubbles, pimples and other irregularities.

The difficulty of wrinkling occurs at a somewhat later stage in the procedure. Even though the exterior has been maintained sufficiently soft to permit the escape and evaporation of all of the solvent, if it is then allowed to set or dry too rapidly, the outside surface drying first shrinks, causing displacement and distortion of the underlying material, causing it to form wrinkles, lines and ridges, giving to the surface a crinkled appearance. This may be prevented only by controlling the drying operation so that the material will set or harden slowly and uniformly.

The successful application of celluloid, pyroxylin or analgous nitrocellulose materials in liquid form, is thus to a very considerable extent dependent upon accurate control of temperatures, moisture or humidity in their relation to barometric pressures. The

work of dip ing and drying must be done in a room of xed temperature and humidity. This temperature is necessarily rather low to prevent too rapid evaporation of the solvent. 5 The temperature of the thermal medium circulated through the hollow metallic golf shaft after the removal of the plug, which may be water, air or other fluid, bears a definite relationship to the room temperature, being ordinarily about four degrees lower in temperature than that of the roofn. Paradoxical as it may seem, this circulating medium, without change of temperature Within itself, is at one stage of the protedure a warming agent, while at a subsequent stage it becomes a cooling agent. Means may be provided for dehydrating the air hf the work room, preferably by means of refrigeration coils or a chilled surface'lof lower temperature than the work, upon which the condensation will deposit in preference to depositing on the material. The moisture is thus extracted from the air. lVh'en the immersed shaft is lifted from the coating liquid, the rapid evaporation of the solvent very materially lowers the temperature of the shaft and material and would cause collection of condensation or watering even though the humidity of the air is very low.

For the best results, the room temperature should be maintained at from fifty to fiftyfour degrees, the lower temperature being preferable. The temperature of the con- 'densing, surface coil for the extraction of atmospheric moisture is maintained at approximately thirty-two degrees Fahrenheit. As before mentioned, after the excess material has been drained from the dipped shaft, the plug in its lower end is removed and it is mounted in a rotating apparatus in connection with a water supply which is discharged through the interior of the hollow metallic shaft at 'a temperature of approximately forty-six degrees, assuming the room temperature to be fifty degrees. That is'to say, the control medium is maintained at approximately four degrees Fahrenheit below the temperature of the room. The refrigeratin g affect of the rapid evaporation of the solvent is such that the temperature of the coating material is temporarily reduced, and during this period. the circulating water acts-as a warming medium to counteract such refrigerating effect of the evaporation, which would otherwise cause condensation and watering upon the partially dried surface of the shaft. The circulation of the temperature control medium maintains the coating mate- .rial at approximately forty-four degrees coating material, the refrigerating effect is arrested. At this stage, the thermal control Fahrenheit, or sufficiently above the. dew

After the solvent is evaporated from the i oftemperature of t e material to that of the room. The room temperature being maintained comparatively low, at say fifty degrees Fahrenheit, does not permit rapid drying or solidification of the surface film of the material and the circulation of the thermal control medium through the tube at a lower temperature prevents undue expansion of any remaining solvent which would otherwise cause bubbling or pimpling. The water or thermal control medium continues to circulate through the. hollow shaft until the material is well set and hardened. It is thus maintained at sufficiently low temperature that the material hardens uniformly and with uniform shrinkage thereby avoiding the wrinkling of the surface.

By experiment it has been found that the coating process may be successfully carried out within a temperature range of the temperature control medium of forty-two to fiftytwo degrees Fahrenheit, while the range of room temperature may be from fifty-four degrees Fahrenheit downwardlv to the operating temperature of the control medium. If the temperature of the room should fall below that of the control medium, the coating is subjected to two cooling effects, i. e., the refrigerating effect of the evaporating solvent and the low room temperature, and undesirable effects result. i

The temperatures at which best results are obtained fluctuate with barometric pressure. At normal barometric reading the preferable room temperature is fifty degrees Fahrenheit, and the temperature of the circulating thermal control medium is preferably forty-six degrees. As the barometric pressure rises, these temperatures will relatively rise and at a high barometric reading of 29.30 to 29.50 a room temperature of fifty-three to fifty-four degrees Fahrenheit and a temperature of the thermal control medium of forty-eight degrees Fahrenheit is productive of good results. The variation of barometric pressures has a marked influence upon the rate of terial must be maintained below the point at which any solvent yet remaining in the material willexpand and form bubbles or pimples before it can escape.

The normal time requirement for completion of the drying and solidifying process is approximatelythirty' minutes. -While the nor scraped. -Whenfinished in thismanner the surface assumes a natural high polish or gloss superior to that which can be given to the material by bufling or mechanically polishing.

While the heretofore method or process is that preferred, the coating of articles may be carried out by a variation of this process which is desirable especially in those instances wherein it is impractical to subject the coated article to the influence'of a thermal control fluid. In carrying o'ut the alternative process, the material is reduced to liquid form, the liquid being sufficiently heavy that a fairly heavy coating'will be deposited when operating in a room at approximately eighty degrees Fahrenheit. The liquid pyroxylin or analogous materials are very sensitive to temperature change. After being dipped and the surplus material drained, the dipped article is immediately removed to a room having a low temperature of approximately zero Fahrenheit, wherein the liquid becomes sufiiciently solid to greatly retard if not to entirely stop further flow or drain. At such low temperature, any moisture remaining in the air will be deposited as frost, and not as water. Even though the temperature of the coated article is materially lowered by evaporation of the solvent, which process however is much retarded at such low temperature, the temperature of the coated surface will not be less than. the room at zero temperature, and therefore will not tend to attract condensation. In any event, it has been found that frost deposits do not mar the finish. At such low mperature the evaporation progresses slow and there is no inclination for the remaining solvent to expand, and therefore bubbling and pimpling' is entirely obviated. A much greater time is required for the material to set and harden at such low temperature. The time factor may be reduced and the process of evaporation of the solvent and consequent setting of the material may be materially accelerated by employing in such cold room, gases whichwill facilitate evaporation, particularly such gases as helium. hydrogen and the like. The coated article is preferably rotated during the cooled treatment process to insure uniformity of the deposit, as well as inthe process first described. The last described process is more difficult from the production point of view, and the difficulties of handling at low temperatures as well as the increased period of treatment. The control of temueratureof the material posited coating whereby the exterior film is maintained suificiently soft to permit the escape of solvent from the underlying strata and conse uent prevention of premature surface shrin age and resulting wrinkling.- It is to be understood that the specific temperature degrees, ranges of temperature, and relation of temperature, while they are those found by experiment to produce satisfactory results, are here stated for illustrative purposes and with no intent to unduly limit or restrict the scope of the invention to such specific temperature degree, range and relation" beyond the broadest valid and legitimate interpretation of the hereinafter stated claims.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modificatidfi in its form, proportions, detail construction and arrangement of parts without de arting from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific details shown, but that the means and construction herein disclosed comprise the preferred form of several modes of putting the invention into effect and the invention is, therefore, claimed in any of its forms or modifications within' the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim: V

1. The herein described method of coating an article with a nitrocellulose material comprising dissolving the material into a viscous liquid, dipping the article therein, and subjecting the dipped article to the influence of a temperature control medium of greater temperature than the applied coating during the periodof rapid evaporation of the solvent and subsequently oflower temperature than the applied coating to retardevaporation and swelling of the coating by expansion of entrapped solvent.

2. The herein described method of surface coating articles with a liquid coating material containing a volatile solvent comprising dipping the article into a bath of liquid coatdipping the article into a bath of liquid coating material, draining the article and subj ecting it while drying to a temperature control medium having a temperature intermediate that induced by the evaporation of the solvent and the room temperature.

at. The herein described method of surface coating articles with a liquid coating material containing a-volatile solvent including dipping the article into a bath of liquid coating material, draining the article and subjecting it while drying to a temperature influence somewhat less than the room temperature in which the drying is effected.

5. The herein described method of surface coating articles with a liquid coating material containing avolatile solvent including dipping the article into a bath of liquid coating material, draining the article and maintaining the article while drying, under temperature condition less than the room temperature sufficiently high to prevent'moistur'e condensation thereon, and sufliciently low to prevent expansion of entrapped solvent within the coating. I

6. The herein described method of surface coating articles with a liquid coating material containing a volatile solvent, comprising dipping the article into a bath of liquid coating material, and subjecting the article to drying temperature of approximately fifty-two degrees Fahrenheit, and simulta neously subjecting the article to'the influence of a temperature medium of approximately forty-six degrees Fahrenheit.

7. The herein described method of surface coating articles with a liquid coating material containing a volatile solvent, comprising dipping the article into a bath of liquid coating material and drying the coating while subjecting the article to a'temperature influence somewhat lower than the room temperature in which drying is effected.

8. The herein described method of surface coating articles with a liquid coating material containing a volatile solvent, comprising dipping the article into a bath of liquid coating material and subjecting the article While drying to a uniform temperature condition initially of higher degree than the temperature of the coating immediately after dipping while rapid evaporation of the solvent is being efi'ected, and subsequently lower than the temperature of the coatingmaterial subsequent to such period of rapid evaporation during the dryingperiod.

9. The herein describedmethod of surface coating hollow articles with a liquid coating containing a volatile solvent comprising dipping the article into a bath of liquid solvent, draining the dipped article, and circulating through the interior of the hollow coated article a temperature control medium having a lower temperature than the surrounding atmosphere. 1

10. The herein described method of surface coating hollow articles with a liquid coating containing a volatile solvent, comprising dipping the article into a bath of liquid solvent, draining the dipped article, and circulating through the interior of the hollow coated article a temperature control medium having a temperature influence of within the range of forty-two to fifty-two degrees Fahrenheit while maintaining the surrounding atmospheric temperature within a temperature range of from fifty-four degrees Fahrenheit downwardly to that of the control medium. v

11. The herein described method of surface coating hollow articles with a liquid coating containing a volatile solvent, comprising dipping the article into a bath of liquid solvent, draining the dipped article, and circulating through the interior of the hollow coated article a temperature control medium having a temperature, less than that of the surrounding atmosphere but greater than the temperature developed by the evaporation of the solvent.

12. The herein described method of 'surface coating tubular shafts with a liquid coating containing a volatile solvent, comprising dipping the shaft into a bath of liquid coating material, draining the dipped shaft, giving to the shaft a rotary motion during a drying period and simultaneously discharging through the shaft a temperature control medium. of lower temperature than that of the surrounding atmosphere.

13. The herein described method of surface coating tubular shafts with a liquid coating containing a volatile solvent, comprising dipping the shaft into a bath of liquid coating material, draining the dipped shaft, and drying the shaft while circulating therethrough a temperature control medium having a temperature below that of the coating material into which the article has been dipped.

' 14. The herein described method of surface coating articles with liquid coating material containing a volatile solvent, including sand blasting the surface to be coated, dipping the article into a bath of liquid coating material, draining the excess material therefrom and temporarily warming the coating material to counteract the refrigerating effect of rapid evaporation of the solvent, and subsequently mamtaining the temperature of the coating below that of the surrounding atmosphere until such coating has solidified. In testimony whereof, I have hereunto set my hand this 22nd day of May A. D. 1929.

WILLIAM C. HAMPTON.