US1851509A - Method of coating articles with pyroxylin - Google Patents

Description

March 29, 1932. w. c. HAMPTON METHOD OF COATING ARTICLES WITH PYROXYLIN Filefld Oct. 28, 1929 Patented Mar. 29, 1932 UNITED S ATES- PATENT OFFICE wanna *c. more, or neuron, OHIO, assronoa '10 m cmwronn, monsoon arm cams! column, or narrow, 01:10, a coaroaa'rron or onto mo or coa'rmo mirror-Es wrm rmxrnm ama filed October as, 192a. se-m1 no. 402,831

' This invention relates to a method of coat ing articles of metal, wood or other material with a covering of celluloid or of pyroxyhn applied in a liquid form and subsequently 5 cured thereon to afford a continuous, onepiece, adherent covering of substantially uni-:.

highly polished surface.

While reference is made in. some prior 1 patents to proposed applications of celluloid or pyroxylin as a coating material by dipping articles in a body of the materialm liquid form, such suggestions have been prophetic only andthe necessary teaching for successful workin of nitrocellulose materials in liquid form llas been entirely lacking.l Great difficulty is encountered 1n con-. trolling the material subsequent to the dipping operation and in effecting a curing of the coating which will leave the finished; surform thickness and possessing a smooth and face undistorted and unblemished; Many "unusual problems have been presented in effecting a uniformly smooth, pohshedsurface deposit for which the hereinafter stated method affords 'a commercially practical solution.

The solvents employed in reducing .pyroxylin and celluloid to liquid form are highly volatile, evaporating rapidly and permitting the material -to .set quickly upon withdrawal from the dipping bath. Such rapid evaporation produces a refrigerating effect, causing precipitation of moisture from the surrounding atmosphere upon the-coated surface. If such moisture condensation trickles in streams upon the newly coated surface, it produces streaks and discoloration as well as "distortiojn and a rough or, matte surface. If such condensation stands in the form of dew, ice crystals, or drops upon the freshly coated surface, it produces a rough and pitted surface effect.v If the outer surface of the deposit ispermitted to set too quickly, it forms an impenetrablefilm which prevents the escape of solvent from the inner strata and by un-uniform' shrinkage of such outer surface film upon the inner material while yet in a soft condition, it induces and produces a crinkled surface of intricate design. If the freshly coated body .vide a method or process of is maintained at a moderate temperature suflicient to effect rapid evaporation of the solvent before such surface film can form, the solvent is quite likelyvtofboil er vaporize within the deposit of coating material, thus forming pimples and bubbles and causing the material to swell or balloon often assuming 'odd and grotesque shapes. From the experience of many such failures, the hereinafter method or process of successful treatment of articles by dipping in liquid pyroxylin or v celluloid has been evolved.

The object of'the present invention is to provide a comparatively simple, economical, and commercially practical method for covering various articles of wood, metal and other materials, such as steering wheels for automobiles, door knobs, handles for cutlery, golf club heads and shafts, bathroom fixtures, toilet seats, and numerous other articles of everyday commercial and household use with a covering of celluloid or yroxylin having a uniformly smooth surf cepossessing a natural high polish or luster without the necessity of mechanical polishing or finishing operation, and of increased durability and capable of withstanding hard usage and wear,'and which will provide a continuous one-piece covering without seams or oints,

completely sealing the enclosed body against entrance of moisture or attack by vapors or the like.

A further object of the invention is to provide an improved method or process of applying celluloid and pyroxylin in liquid form and controlling the resulting deposit to prevent watering from rapid evaporatiompitting or eggshell surface affect from dew or ice crystal deposits -'of moisture condensation, pimpling and bubble formation as result-of boiling or vaporization of the con-' tained solvent, and wrinkling or orange peel affect due to un-uniform shrinkage.

A further object of the invention is toprovide a method and process by which various articles may coated with celluloid or pyroxylin of various colors, giving to the articles pleasing and ornamental color 'afiects.

A further object of the invention is to proencasing cracking, chipping, crazing, and 'fracture.n A further object of the invention is to provide a coating or covering material which, when applied to articlespossessing a degree of flexib ility oglqfsll iency su h as shafts or gblf clubgcanes, uinbrella hamd the like, willyield in unison with the coated ar ticle. a l a.

With the above primary and other incidental objects in view, as will more fully appear. in the specification, the invention conslsts of the steps and procedure, the apparatus and the method of operation or their equivalents as hereinafter described and set forth in-the claims.

The accdmpanying drawing more or lessdiagrammatically illustrates the apparatus for carrying out the present process, and the a successive steps and stages of the method.

In out. the present process any suitable solvent for pyroxylin or for cell uloid such as ether, alcohol, acetate, or thelike,

-'may be used. However, acetone is the best known and preferable solvent for this purpose.- The process consists of two major operations, to wit, first the preparation and applicationof a solution ofpyroxylin', and second the evaporation of the solvent while governing such evaporation by temperature control, and by preconditioning the air in which the setting or curing of the material is effected.

Preparatory to the dipping or coating oper-v ation, the pyroxylin or celluloid, asthe case may be, is thoroughly dissolved in a suitable solvent until the material becomes a VISCOIIS heavy liq'uid. This mixing of the material and the initial coating or dipping operation are best and preferably performed in a room of normaltemperature of approximately seventy degrees Fahrenheit. The viscous dip-V ping solution takes approximately the same temperature or one somewhat iower, due to the refrigerating 'afiect of evaporation. In the accompanying drawing the preparation anddipping room is indicated as 1 in which is located the tank or vat 2 containing the acetone solution of pyroxylin, the viscosity ofwhich is approximately of the consistency of a'cake'batt er or a thick molasses. This 1 liquid. proxylin, which asapproximately seventy degrees Fahrenheit is sufliciently viscous -to a slow flowing liquid, will become solidi liquid menace fied into a plastic having considerable resistance to movement at lower temperature.

" The article to be coated, whether it be an automobile steering wheel, a golf club shaft or head, a door knob, a toilet seat or other articles, is dipped rather slowly into this viscous to prevent carrying air bubbles into the hquid, and: is then slowly withdrawn. The dipped article'is held momentarily over the tank or vat '2 to allow the excess material to drain from the article. Because of the rapid evaporation, this drainage period must be quite short, varying from a few seconds to ordinalfly lot more than a minute since the evaporationbf'tlreiclvenifoccurs quite rapidly with deleterious affect. The drip is sev-v ered or cut, and'the article inverted to allow the remaining surplus material to flow reversely over the article and redistribute itself.

' The coated article is slowly revolved, preferably about an axis intersecting the article or closely adjacent thereto, so that displacement of the fiuid material by centrifugal influence is minimized. By this operation the liquid material is evenly distributed over the surface of the article. Whilecontinuing the rotation, the, article is immediately trans ferred to a refrigerating room of very much lower temperature. V

In practice, articles coated with terial at a temperature of approximately seventy degrees Fahrenheit are transferred to a curing room wherein a temperature of liquid maapproximately fifteen to twenty degrees below zero is maintained. This temperature change quite naturally causes a great increase in the viscosity of the coating material and gives it the required set, whereby it is. not inclined to change itsshape orv position. In the curing operation, advantage is taken of two physical conditions, i. e., the.

lowering of the temperature causes a lowering of the vapor tension, consequently theatmosphere can contain less water vapor'at the lower temperaturethan at a high temperature, and advantage is taken also of the latent heat of evaporation. The rotation of the article is preferably continued during the curing or' drying operation ;within the cold room. The acetone or other solvent employed is much less volatile in the cold room,

consequently the solvent escapesmore slowly from the deposited material without expansion, thereb obviating the dangers of pimplmg or bu bling and ballooning by which the deposit would otherwise be distorted.

Even though the temperature of the room he maintained quite low, the evaporation of the solvent nevertheless. produces a refrigcrating efi'ect tending to lower the temperature of the coated article below that of the.

surrounding atmosphere, and thereby induce on the surface coating condensation of moisture in the form of ice crystals. ,This effect,

however, is counteracted by extracting the.

moisture fromthe air to a de ee well below the saturation point before t e air comes in contact with the coated article. To this end the curing room or cold room 3, as illustrated inthe drawing, is divided b a partition 4 into two compartments whic communicate with each other at the top and bottom of the wall 4. In one of these compartments 5,

there are located refrigerating coils 6 by which the'air currents circulating within the -;air after it has passed over the refrigerator 1 coils 6. By raising the temperature of the curing air approximately five to ten degrees,

that is to say, from the temperature of minus twenty to minus fifteen or minus ten Fahrenheit, not only is danger of moisture condensation by the refrigerating effect of the evapcrating solvent removed, but the 'capabilit of the air to absOrb the solvent vapors, whic qhave a great aflinity for moisture, is greatly increased.

v The chilling of the air within' the com partment.5 as it passes over the coils 6 causes a downward'current of air whereas the air' passing from the bottom of the'comwpartmen't through the temperin unit 17, by which its temperature is raisef'is givena tendency to rise within the curing room 3 outside the compartment 5 towhich theair returns through the space 9 above the partition 4 after passing over the coated articles bein cured and absorbing therefrom the vaporized solvent. 'Thus the cold air in afcontinuous circulation;

descending in.the-compartment 5 and the slightly warmer air ascending in the room 3 induces natural convectio'n'currents aflord' e slight warming of the air, after it'has] been lowered to such temperature as to con dense its entrained moisture, so increases its capacity to absorb and retain moisture that none of the small remaining amount ofmois-fl ture in the air will'be condensed upon the surface of the work which, due to the evaporating efiect of the solvent, is somewhat colder-than the air circulating thereabout. The low temperature retards the'evaporation of the solvent, allowing sufficient time for the solvent to escape from the deposited material without causing pimples orbubbles. The subjection of the coated-article to such. lowered temperature also enables a heavier or' deeper deposit to be retained upon the article than would otherwise be possible. This coverings orcoatings of considerable thickness may be effected by .a single dip- Y ing operation: To afiord coverings of maximum thickness, the dipping and curing operations may be repeated several times.

By rotating the article not on} 'while' transferring it from the dipping tan or vat to the chill room but during the curing process, any tendency of the material to change its position or shift upon the .article is obviated. As illustrated in the drawing, a hand trucklOcquipped with an air motor -11 supplied from a pressure reservoir '12 or other suitable driving means maybe provided for rotating a series of removablev supporting bars 13 having thereon studs or pins 14 upon which dipped articles may be'temporarily mounted. In order that the article's mounted upon these supporting bars may be rotated about axes passing thru or'closely adjacent to thearticles, the bars 13 are provided with terminal cranks or oiisettrunnions 15 about which the supporting bars. and articles revolve. These supporting bars are removably engageable in a rack upon the hand truck 10 in which they are operativelyconnected with the driving motorfor slow rotation during transference from the dipping roomto the curing room. In the latter room they may be left upon the truck 10 for continued rotation, or. may be transferred to a suitable rack in such room wherein the supporting bars are rotated by suitabledriving means. I

At 16 there is shown a revoluble 'baror shaft for supporting annular coated bodies such as toilet seats. In this case a straight bar 16 extends through openings in a series of articles which are secured to arms 17 upon such bar. A toilet seat is alwaysprovided' with screw holes for attachment of the hinge connection. These same holes may be utilized for attaching the seat to an arm 17 by which v it is' detachably connected with therotating a shaft or bar16. The present material'must' not be confused with lacquers made from cellulose base which are variously used and applied in liquid form.

Such lacquers although derived from the same base to which are added various gums and solvents diifer' widely from the present mate rial in character being brittle when dry, lacking' the tensile strength and durability, and can be practically applied'only in thin coati'ngs whereas the present material can be ap plied to form a quite thick casing or shell about the article which will be hard but tough and practically unbreakable. "Although he commercial as pyroxylin, pyroxyle, or pyroxyline, otherwise known specifically as celluloid, is" the" preferable material, the invention is not material known I specifically limited to this material but ineludes othernitrocellulose derivatives having the characteristics ofpyroxylin.

While the conditioning of the air in the curing room has been-described as being cooled to an extreme low degree to precipitate'the moisture and the temperature then raised to increase its vapor car g capacity before it reaches the article, suc an is not necessarily colder'than the surface of thecoated article with which the circulating a-ir comes in contact. The evaporation of the solvent produces a refrigei ating efie'ct' which tends to lower the temperature of the surface below that of the surrounding atmosphere even at the low temperature of the curing room.

The various temperatures herein mentioned I are given for illustrative purposes but with no intent to arbitrarily limitthis invention to such stated'temperatures nor relative tfem-' perature ranges. It is to be understood that the temperature and'relative variations thereof may be varied within reasonable limits to meet different conditions of use, differences in the material-composition and solvent em-- ployed, and results desired.

- From the above description it will be ap parent that there is thus provided a method of the character described possessing the'particular features of advantage before enumerated as desirable, but'which obviously is susceptible of modification in its steps, sequence, detail procedure and arrangement of. apparatus without departing from the principle involved or sacrificing'any of its advantages.

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

I articles with material having a nitrocellulose H thus described-my invention,"I claim: n Y i 1; The herein described method of coating I base or the like,=jc onsisting in reducing the s o'material' to asemi-liquid-form by-the,addi-.

tionof a solvent," dipping the article to be I; coated in the liquid material at a temperature ofap roximateIyseVenty degrees Fahrenheit, draining the excess therefrom, severing. the-drip-and-meversing the position of v the article to redistribute the surplus material and slowly-rotating thecoated article to main-- tain distribution, transferring the coated article into a; temperature of approximately Y "minus fifteen degrees Fahrenheit and subjecting the article to the action of circulating air which has been previously chilled to approximately minus twenty degrees Fahrenheit and then warmed to approximatelyminus fifteen degrees Fahrenheit.

( 2. The herein described method of coatthe article into a semi-liquid solution 0 I drying temperature Ofthe article.

ing articles with material havingpyroxylin characteristics or the like, consisting in dippin the article into a semi-liquid solution of t e material, drainin the excess material therefrom, subjecting t e coated article to a temperature materially lower than that at which the article is dipped to effect quick congealing and retard evaporator ofsolvent, and

drying the article at such low temperature in air from which moisture has been extracted to a degree well below the dew point at such temperatu 1 t '3. The herein described method of coating articles with material having pyroxylin characteristics or the like, consisting in dippizlilg material, draining the exce s material therefrom, subjecting the artic e to a lower degree of temperature than that at which it was dipped-to eifect quick congealing, and drying the coated article in an arid atmosphere to prevent condensation of atmospheric moisture thereon.

4; The herein described method of coating atmosphere of lower temperature than thatof the material in which the article. was

dipped whereby the solvent will be permitted to evaporate but slowly, and precipitation of atmospheric moisture will be obviated. 5. The, herein described method of coating articles with material having char acteristics or the like, consisting 1n dipping the article into. a semi-liquidsolution of the material, drainin theexcess material therefrom, and subjecting the article while drying to a temperature, materially lower than that of the material in which it was di ped.

'6. The herein described metho of coating articles with material having the characteristics of pyroxylin or the like, includin dipping the article into a semi-liquid solution of the material at approximately normal atmos pheric temperature, and subjecting the dipped article while drying to a substantially zero Fahrenheit temperature substantially as and for the purpose-specified.

' 7. The herein described method of coating acteristics or the like,jin'cluding dippingthe article to be coated in o a semi-fluid solution of the materiahfdrainmgthe excess material therefrom,- and drying the article at a temperature of approximately zero Fahrenheit, in preconditioned air, the moisture content of articles with materialhavingpyroxylin charwhich is lowered belowthe; dew point atthe 8. The herein describedmethod of coating artlcles with material of pyroxylin characprevent bubbling and ing will be retarded until the solvent has rial, drainingthe excess material therefrom, and drying the coated article at a substantially zeroFahrenheit temperature whereby the solvent will be maintained below boiling to pimpling and the dryevaporated to prevent wrinkling.

9. The herein described method of coating articles with material of pyroxylin characteristics or the like, consisting in dipping the article in a semi-liquid solution of the mate rial, draining the excess material'therefrom, and drying the coated article at a temperature approximately seventy degrees Fahrenheit less than the temperature of the material at the time of dipping.

I 10. The herein described method of coating articles with pyroxylin or the like, consisting in reducing the material to semi-liquid form by the addition of a solvent, and maintained at approximately normal atmospheric-temperature, dipping the article in the liquid coating material, and subjecting the coated article to a' materially lower tempera ture by which the material is quickly 'congealedand loss of solvent retarded in an atmosphere from which excess moisture has the solvent to prevent displacement, and subbeen extracted.

11. The herein described method of coating articles with material having a nitrocellulose base, consisting in reducing the material to semiliquid form by the addition of a solvent, dipping the article therein'at a moderately high temperature, subjecting the dippedarticle to a refrigerating effect in an atmosphere wherein the moisture content is maintained materially below the point of saturation.

12. The herein described method of coating articles with a material having a nitrocellulose base, including reducing the material to a semi-liquid form by the addition of a solvent, dipping therein the article to be coated,

' chilling the coated article to congeal the coating material and retard evaporation of the solvent, and subjecting the article to a dry air treatment'whereby condensation of moisture upon the coated surface will be obviated.

13. The herein described method of coating articles with material having a nitrocellulose base including reducing .the 'material 'to' a semi-liquid form by the addition of a solvent, dipping an article to be coatedtherein at a proximately normal room temperature, su jecting the 'dipped article to a freezing temperature and simultaneously subjecting it to the action of air, the temperature of who has been previously lowered to a lesser degree to effect precipitation of moisture and then raised to a higher degree of temperature before reaching the coated article.

' 14. The herein described method of coating articles with material having a nitrocellulose base including reducing the material to a semi-liquid.form by the addition of a-solvent, i p n an jecting the'dipped article to a substantially zero Fahrenheit temperature, and simultaneously circulating thereaboutair from which moisture has been extracted to a point below the dew point at the temperature of the refrigerating effect produced by evaporation of the solvent from the coated article.

article to be coated therein, sub- 15'. The herein described method of coating articles with material having a nitrocellulose base including reducing the material to a semi-liquid form by theadditi on of a solvent, dipping an article to be coated therein, subjecting the dipped article to a temperature of approximately seventy degrees (Fahrenheit) less than the temperature of the material in which it was dipped, and simultaneously drying the dipped article in air from which moisture has been extracted belowthe dew sequently removing the solvent from the congealed coating material. v

17 The herein described method of coating articles with material having a nitrocellulose base including reducing the material to a semi-liquid form by the addition of a solvent,

y the addition of a solvent,

effect congealing' dipping an article to be coated therein, con-- gealing the coating material prior to remova of the solvent and controlling the subsequent evaporation of solvent whereby the solvent will escape slowly.

18. The herein described method of coating I articles with material having a nitrocellulose base including reducing the material to a semi-liquid form by the addition of a solvent, dipping an article to be coated therein, setting the material prior to removal of the solvent, and subsequently evaporating the solvent therefromm an atmosphere which has that produced moisture and then rewarmed.

19. The herein described method of coating articles with material having a nitrocellulose base including reducing the material to a semi-liquid form by the addition of a h solvent, dipping an article to be coated therein, congealing the material prior to the removal of the solvent and subsequently removing the solvent.

20. The herein described method of coating articles with material having a nitrocellulose been previously cooled to a degree lessthan by the refrigerating efl'ect of I the evaporating solvent to precipitate the 6 I ea-Lace base including reducing the material to a semi-liquid form by the addition of a solvent, dipping an articleto be coated therein, chill in the coating material upon the article to e ect congealment thereof and evaporating the solvent therefrom at a temperature less than that at which the coating material was applied. x v 21. The herein described method of coat- 10 ing articles with material having a nitrocellulose base including reducing the material to a semi-liquid form by the addition of a sol vent, dipping an article to be coated therein, subjecting the coating upon-the article to a congealing treatment prior to the escape of the solvent and subsequently removing the solvent sufiiciently slowly to prevent bubbling, pimples or blisters j in'an atmosphere from which moisture has been extracted to such degree as to avoid condensation at the surface temperature of the coated article.

In testimony whereof, I have hereunto set my hand this 19th day of October, A. D. 1929.- 1 1 WILLIAM G. HAMPTON,

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