US2380149A - Liquid coating compositions, coated objects, and processes for making same - Google Patents

Description

Patented. July 10, 1945 LIQUID COATING COMPOSITIONS, COATED OBJECTS, AND PROCESSES FOR MAKING SAME Newcomb K. Chaney, Swarthmore, Pa., assignor to The United Gas Improvement Company, a corporation of Pennsylvania No Drawing.

Application December 14, 1940, Serial No. 370,138

'17 Claims. (01.,117-132) This application is a continuation-inpart of my copending application Serial Number 291,007,

filed August 19, 1939, now Patent 2,345,483, granted April 4, 1944. a

This invention pertains generally to the coating of metals and particularly'to the coating of metals .,in sheet form.

The invention pertains more particularly to the coating of sheet metal which is to be fabricated into objects by stamping, bending, drawing, threading, turning, punching, and the like.

Machine operations, such as the foregoing, are particularly severe upon coatings or films adheringto the sheet metal, and in many instances, it is extremely difiicult to obtain a, formed object with a coating or film system adequate for the environment to which the finished article is to be subjected when in use.

To illustrate, many types of films and particularly those made from resinous materials, crack, check, striate, silk and/or peel when subjected to the foregoing mechanical operations.

Because of the great economical advantage of coating the sheet metal prior to the various forming operations, the importance of a film or film system which will withstand the various forming operations without injury cannot be over-estimated.

Another quality of extreme importance, particularly in the case of certain uses to which the finished articles are to be put, is the relative insolubility and/chemical inertness of the film or film system. 7 L

An outstanding example of such a use is in the food packaging field in which metal cans and metal foil wrappings are extensively used.

The term food is employed herein to mean that which is eaten or drunk or absorbed for nourishment or otherwise, and includes not only beverages such as beer, but also substances from which food is prepared, examples of which are coffee beans, whether ground or not, and tea leaves.

In the case of cans, for example, economical considerations make it extremely advantageous to apply the film or film system to the sheet metal while in the fiat. The can parts are then cut, shaped and joinedall in a manner well known in the art] Severe stresses are set up" during the forming operations, particularly in the case of the die-drawing of the can ends. The can ends and portions of the can body are again subjected to severe stresses during the can closing operation, such as by the seaming chuck, seaming rolls, and cooperating parts of the can closing machine during the well known double-seaming can sealing operation.

For instance, the die-drawing step produces in v the canends not only angles of very nearly 90 with relatively sharp bends, but also a peripheral portion which is curled back upon itself.

A film or film system to be successful must withstand such and similar metal working opera tions without peeling or rupturing or otherwise failing in the slightest degree.

Metal caps are used in large quantity not only on glass bottles but also on certain types of metal containerssuch as those for holding beverages.

In many cases, such caps are provided with threads for engaging cooperating threads upon the bottle or other container.

The operation for forming the threads in the metal caps is extremely severe, since the metal is frequently stretched by as much as 100% during the thread-forming operation.

In the food packaging field it is, of course, absolutely essential that the film or film system be not only completely insoluble and chemically inert, but also completely incapable oi: imparting taste or odor to the food product.

In this connection, it is a well known fact that the ordinary tin lining is unsatisfactory in the case of certain foods of which grape juice, orange juice, and beer are outstanding examples.

Some foods develop" hydrogen sulfide upon standing which, in turn, reacts chemically with the tin lining to form tin sulfide. In case any of the iron is exposed, such as through cracks, black iron sulfide is formed); I

Furthermore, in the food packaging field, the packaged food stufi, after sealing of the can,'is in many cases, subjected to a sterilization treatment by the application of heat. Such treatment, by reason of the increased temperatures involved, greatly accelerates any reactions capable of taking place.

Numerous attempts have been made to find a lacquer which might be applied over or substituted for the tin coating. Fihns made with previously known lacquers, as a rule, however, have failed to have suflicient adhesion and cohesion to resist formi g operations, or they have failed I "to resist reaction with foods, or they have failed in that they have foods. I

Ifhis led to the adoption of a procedure whereby a coating composition having good bonding properties was employed as a primer coat for a top coat having proper food resisting and taste and odor characteristics, of which the material known imparted taste or odor to the commercially as Vinylite is an outstanding example. In turn, this presented the further problem not only of finding two such coating compositionswhich would bond properly with each other, but also of finding a primer coat which would not impart taste and odor to the food despite the top coat.

The product known commercially as Vinylite though deficient as a primer coat is nevertheless, satisfactory as a top coat provided a proper bond that will withstand not only the forming operations but also the sterilization treatment can be formed between it and the primer coat.

In this connection, many films and dual film systems develop a cloudiness during the sterilization step, such cloudiness being generally referred to as blushing. The resulting discoloration is very undesirable from the standpoint of market appeal, since the average housewife looks with great disfavor upon any discoloration of the inside surface of a can when removing food therefrom.

It follows that any film or film system to be suitable must not only be capable of resisting cleanliness.

Since films and film systems of the character under consideration are necessarily extremely thin, the primer coat is preferably one capable of direct contact with the foodstuff without chemical reaction and without imparting taste or odor thereto. Certain substances which might otherwise be satisfactory as primer coats fail because they are capable of imparting taste and odor to foodstuffs through the top coat.

In addition to the foregoing, there are certain metals which are extremely difficult to coat with satisfactorily adhering films or film systems of any character. Examples are zinc, zinc plate, magnesium and magnesium alloys, such as the material known commercially as Dow metal." In fact, practically all previously known resinous coating compositions fail to form a satisfactory bond with these materials.

In accordance with my invention, singlefilm systems and multiple film ystems having all of the above desirable properties may be produced by forming (a) said single film system, or (b) the primer coat of a multiple film system provided the top coat is of a satisfactory character, or (c) the top coat of a multiple film system provided the primer coat is of a satisfactory character, with a liquid coating composition having as a base cyclopentadiene which has been first catalytically polymerized in a manner to impart to it desired properties, then admixing one or more additives comprising .sulfur or sulfur-containing substances with said polymerized cyclopentadiene base, and then causing such films of polymerized cyclopentadiene plus additives to dry with or without heat.

Generally speaking, the catalytically polymerized cyclopentadiene employed in my liquid coating composition has the following properties. It is soluble in benzene, toluene, chloroform, carbon tetrachloride and high flash naphtha. and insoluble in alcohol, acetone, ether and water. For the purpos of convenience in the claims, these solubility characteristics will be defined by the term benzene-soluble, though it is to be understood that the actual presence of benzene in the solution or in the applied films is not implied. Preferably, my liquid coating composition, after admixture with sulfur or sulfur-containing substances, has other distinctive properties. Among these properties is the ability to form a smooth, glassy, highly flexible and extensible and tenaciously adhering film upon drying with or without baking.

Methods for preparing benzene-soluble catalytically polymerized cyclopentadiene employed in my invention are described and claimed in copending application Serial Number 290,931, filed August 19, 1939, by Samuel G. Trepp, now Patent 2,359,810, granted October 10, 1944, and copending application Serial Number 204,786, filed April 28, 1938, by Frank J. Soday, now Patent 2,314,904, granted March 30, 1943. Methods have also been described in my said copending application.

The following are specific examples of the preparation of the desired polymer.

Example 1 1500 pounds of toluene were charged to a jacketed, brine cooled kettle provided with an agitator .and a brine cooled reflux condenser, 3 pounds of boron trifluoride-diethyl ether complex were then charged, agitation was started, and the kettle was warmed to 35-40 C. After complete mixing, heating was discontinued and the steam in the jacket replaced with brine.

A previously prepared mixture of 525 pounds of cyclopentadiene and 500 pounds of toluene was gradually added from a mixing tank, maintained at a temperature sufliciently low to prevent the volatilization of the cyclopentadiene. The mixture is preferably below room temperature when it reaches the reaction kettle.

The rate of addition was so regulated that the contents of the reaction kettle were maintained at a temperature between 25-30 C. while circulatin cooling brine through the jacket.

From 20 to 60 minutes were required for the addition of the cyclopentadiene-toluene mixture depending upon the efllciency of the cooling brine. When addition was complete, the brine flow was cut down so as to keep the temperature above 25 C. but below 50 C. and the product was agitated for an additional 1 /2 hours.

5 pounds of water were now added to hydrolyze the catalyst so that the fluorine might later be removed as hydrogen fluoride by lime.

After 30 minutes further agitation, 75 pounds of milk of lime (Ca(OH) 2) were added. The temperature was now kept between 18-30 C.

After an additional agitation of one hour 130 pounds of a good grade of filter aid, such as diatomaceous earth, was added. An additional quantity of 70 pounds of filter aid was placed on a suction filter, and the product pumped through the filter. Any type of filter, such as a plate filter'press, centrifuge, etc., might be employed.

The producet was a 20% solution of the desired polymer.

In the above example, the particular temperatures chosen are more or less for expediency, but it will be noted that at no time did the temperature exceed 100 C. or even C. Constant agitation and brine cooling made it possible to prevent local overheating.

Example 2 0.30 cubic centimeter of aluminum chloridediethyl ether complex is added to 60 grams of toluene with thorough agitation to form a suspension, emulsion or solution.

A mixture of 20 grams of cyclopentadiene and 20 grams of toluene is added to the suspension during the course of 12 minutes, the temperature ranging from 2649 C. during the addition. The mixture is then agitated for an additional hour, after which 1 cubic centimeter of water is added. This is followed by agitation for minutes.

10 grams of quicklime (CaO) are now added to the reaction mixture followed by agitation for an additional hour.

5 grams of a suitable filter aid are then added, and the mixture filtered.

A filtered solution containing 16.4 grams of polycyclopentadiene is thus obtained.

Generally speaking, any other boron trifiuoride-organic solvent complex or aluminum chloride-organic solvent complex might be substituted in the above examples. Other methods for making benzene-soluble catalytically polymerized cyclopentadiene obviously may be employed.

In accordance with my present invention a sulfur-containing material (which term for brevity is to be construed as including sulfur) in suitable quantity is added to benzene-soluble catalytically polymerized cyclopentadiene prior to the final drying (as by baking) of such polycyclopentadiene upon the surface to be protected.

Usually, the addition of the sulfur-containing material is made prior to the application of the catalytically polymerized cyclopentadiene to the surface or object to be coated. Thus a sulfurcontaining material, such as flowers 'of sulfur, may be added to said polycyclopentadiene prior to its application to the surface to be coated.

However, the addition of a sulfur-containing material to the polycyclopentadiene may be made after the latter has been applied to the object to be coated; for instance, by baking said object in an atmosphere comprising hydrogen sulfide or other sulfur-containing material in whi h case the sulfur-containing material is absorbed by the polycyclopentadiene from the atmosphere.

Thus, the coated objects may be said to be coated with a dried film of a liquid coating composition comprising benzene-soluble catalytically polymerized cyclopentadiene in admixture with a sulfur-containing material and the coatings of benzene-soluble catalytically polymerized cyclopentadiene may therefore be said to be dried in admixture with a sulfur-containing material. The completely dried films are generally insoluble, particularly in the ordinary solvents.

Both methods may be combined, if desired,-

that is the object or surface to be protected may be coated with benzene-soluble catalytically polymerized cyclopentadiene which already containsa sulfur-containing material, such as sulfur or hydrogen sulfide, and then the coating may be dried such as by baking in an atmosphere comprising hydrogen sulfide or the like.

I have found that by thus incorporating a sulfur-containing material with benzene-soluble catalytically polymerized cyclopentadiene, the properties of the finished resin film are desirably modified, particularly with respect to their ability to withstand drastic metal-working operations such as the die-drawing steps employed to produce bottle caps or can ends from sheet metal.

polycyclopentadiene present in the coating solution) with improved results, I find generally speaking that concentrations in excess of 8% and particularly those lying in the range of from 10 to 16 give very satisfactory results. The maximum quantity employed preferably depends upon the solubility of the additive in the polymer solution, which in turn depends upon the polycyclosystem in accordance with my invention is as follows:

Example 3 To a 24% solution of catalytically polymerized cyclopentadiene in toluene is added 16% sulfur, calculated on the polymer content. The resulting mixture is applied to sheet metal, such as tin plate, in such quantities that the final polymer film whether applied in one coat, or several coats with or without intermediate drying will have a desired thickness, such as the equivalent of about 2 milligrams per squareinch of dry film.

The coated sheet, after suitable evaporation of solvent. is Placed in an oven and heated to a temperature of 250 F. for a period of 20 minutes for purposes of drying during which time the film takes up oxygen from the air without loss of adhesion, flexibility or extensibility. A suitable baking time is between one-quarter of an hour and one and a half hours. The elevated temperatures employed favor the adding on of oxygen.

Sheet metal thus coated is ready for drastic forming operations, such as encountered in the manufacture of cans Or other containers, bottle capsscrew caps, and the like. It will withstand rough treatment without cracking, checking. striv ating, silking, peeling, loosening, or otherwise in- It also appears that the addition of a sulfurcontaining material such as sulfur tends to reduce the rate of oxidation of the polycyclopentadiene film which may be desirable in some instances.

It will be understood that the optimum ratio of additives to be employed may vary somewhat, depending upon factors such as the particular additive, the manner of drying employed, etc. While I have employed sulfur as additive in concentrations of as low as 0.1% (based upon the juring the coating.

When made into cans the coating is highly resistant to foods, imparts no taste or odor thereto, and is free from blushing during the sterilization treatment. In fact, the coating appears to be improved during sterilization.

The procedure of Example 3 was repeated ex cept that sulfur was successively added to polycyclopentadiene in solution in percentages to polymer of approximately from 8% to 13% in ap proximately one percent increments. In all cases the resulting polymer-coating sheet metal was highly satisfactory for use in manufacturing formed objects such as caps, can ends and food containers in'general. The films were extremely resistant to severe metal Working operations.

Examples of the use of additives in the form of hydrogen sulfide are as follows:

Example 4 A tin plated sheet was coated with a solution of polycyclopentadiene in "toluene of 20% polymer content, in sufilcient quantity to secure a de sired final coating weight for xample, approximately 2 milligrams per square inch after drying, such as by baking.

The coated sheet after suitable evaporation of solvent was placed in an oven and baked at a temperature rising from 85 F. (30 C.) to 266 F. (130 C.) over a period of 15 minutes while inai taining a constant flow of hydrogen sulfide through said oven and in contact with said coated sheet. The arrangement may be such that the hydrogen sulfide atmosphere in the oven is substantially pure HzS, or it may be diluted with substantial quantities of air or an inert gas such as carbon dioxide or nitrogen.

Example 5 The procedure of Example 4 was repeated, except that the polycyclopentadiene solution in toluene was substantially saturated with hydrogen sulfide prior to its application to the sheet metal.

Example 6 The procedure of Example 5 was repeated, ex cept that the hydrogen sulfide-containing film was baked in an inert atmosphere of carbon dioxide instead of hydrogen sulfide and at a temperature rising from 95 F. (35 C.) to 266 F. (130 C.) during a period of 18 minutes.

Example 7 The procedure of Example 5 was repeated except that the baking took place in the presence of air instead of hydrogen sulfide, and at a temperature of 302 F. (150 C.) for minutes.

The result in each case was of the same order of magnitude as when elemental sulfur was employed; namely, the production of a coated metal sheet having a polymer film capable of Withstanding severe metal-forming operations such as those involved in cap-forming etc., without mechanical breakdown.

From the foregoing it will be seen that the benzene-soluble polycyclopentadiene may be treated with hydrogen sulfide or other suitable sulfur containing material, at any stage, that is prior to, during and/or after the application of the polycyclopentadiene to the surface to be coated. Generally speaking, however, when using hydrogen sulfide it is preferred to employ the procedure wherein the polycyclopentadiene coating solution is admixed with hydrogen sulfide prior to coating,

and the coated object is baked in a hydrogen sulfide atmosphere, as in Example 5 above.

An example of the formation of a dual film system in accordance with my invention is as follows:

Example 8 A tin plated or other metal sheet, is coated 'with a hydrogen sulfide-saturated solution of polycyclopentadiene in toluene, say of polymer content, to secure a desired final coating weight, for example, approximately 2 to 3 milligrams per square inch after drying such as by baking.

The coated sheet after suitable evaporation of solvent is placed in an oven and. baked in an atmosphere of hydrogen sulfide at a temperature of approximately 250 F. for a period of from 15 to 20 minutes.

Upon cooling, a solution of Vinylite in a mixture of higher boiling ketones is applied in suflicient quantity such that the dual film system will have a desired thickness after drying of the Vinylite film such a with baking, say a thickness equivalent to 4 to 6 milligrams per square inch of dry dual film.

The coated sheet after suitable evaporation of solvent is then re-baked in the same manner as with a primer coat.

The metal sheet thus coated with the dual film may-be subjected to forming operations such as those involved in the making of caps, can elements and the like, with no resulting injury to the resin layer or layers deposited thereon.

It will .be understood, of course, that broadly speaking, the top coat is not limited to "Vlnylite," which is the co-polymer of vinyl acetate and vinyl chloride, but may be a polymer of any of the vinyl compounds used as raw materials for the several vinyl resins; e. 'g., vinyl acetate, vinyl chloride or vinyl chloracetate. In fact other types of resins may be adapted for application as the top coat over my catalytically polymerized cyclopentadiene resin.

Vinyl resins suitable for use in forming the top coat of my invention may be formed from vinyl esters by known polymerization processes. The polymerization products of inorganic vinyl esters, such as vinyl halides, or those of organic vinyl esters, such as vinyl esters of aliphatic acids, may be used.

I prefer to use vinyl resins resulting from the co-polymerization of two or more vinyl esters. For example, vinyl resins having desirable properties may be prepared by the co-polymerization of a vinyl halide and a vinyl ester of an aliphatic acid.

Products of the inc-polymerization of vinyl chloride and vinyl acetate in proportions ranging from about 10% to 90% .by weight of the chloride are particularly desirable.

The commercial product old under the trade name Vinylite falls in the latter category.

The foregoing vinyl resins are substantially water-white and transparent and they are exceptionally resistant to acids, alkalies, and salts in the presence of moisture and may be used to form flexible top coats which adhere exceptionally well to my primer coat, such top coat (like my primer coat) being odorless and tasteless.

To a certain extent, the characteristics of the preferred vinyl resins are retained when the vinyl resin is modified by the addition of a second resin or gum, a cellulose ester, or a high boiling solvent having plasticizing or softening action on the resin. Due to this property, the vinyl resins may be modified to meet specific requirements without materially altering the chemical properties of the resins employed as the top coat. However, in the food packaging field, the commercial product sold under the trade name Vinylite without modification is well suited for the purpose.

This product is thought to result from the copolymerization of about of viny1 chloride with 15% vinyl acetate.

Since the resin films made from polycyclopentadiene plus sulfur-containing additives not only bond Well to surfaces but also are highly resistant to attack by foods, and do not impart taste or odor thereto, they may be used as top coats over primer coats of other materials, if desired. It is, of course, understood that sulfurcontaining polycyclopentadiene may be used-for both a primer coat and a top coat or in any other number of coats.

It will be understood that other sulfur-containing substances might be employed a additives instead of, or together with, those already described. Examples of these are hydrogen polysulfide, Hzsa: (believed to comprise a mixture of ME2N.CS.S.S.CS .NMe2) or butyl zimate (BuzN.CS.S.Zn.S.CS.NBu2) either separately or in suitable admixture with each other. Thus, for example, 12% hydrogen polysulfide; 0.1% to 5.0% Tuads; and 0.1% to 3% butyl zimate: either alone or with varying amounts such as from 1% and 3% sulfur, are among the additive combinations that have been employed with polycyclopentadiene and found to give resin films on sheet metal capable of withstanding drastic shaping and forming operations.

With respect to the temperature and time of baking, I usually prefer to rarely if ever exceed about 400 F. and at such temperatures a baking time not longer than about 15 minutes to avoid any possible injury to the film. However, while my resin films may be safely subjected to relatively high temperatures for brief periods during baking, in general, I find temperatures up to 350 F. with baking times up to 30 minutes very satisfactory. With higher temperatures the baking time may be correspondingly shortened to yield similarly satisfactory results.

I have found that a particularly satisfactory baking schedule is represented by a temperature of 250 F. for a period of 20 minutes. Another satisfactory baking schedule is represented by a procedure wherein the temperature during the bake is gradually raised from about room temperature to the maximum desired temperature such as about 250 F. over a period such as from 15 to 20 minutes. schedule such as the latter is that the solvent is driven off more gradually, thus minimizing or eliminating any tendency for the resin film to be ruptured by escaping solvent.

While I refer to baking broadly and to heating in the presence of air or an "oxygen-containing gas as a means of drying my coating or film, it is to be understood that the taking on of oxygen by the film need not necessarily take place simultaneously with the heating or baking. On the contrary, I have obtained excellent results by heating or baking the coating or the coated object in an atmosphere devoid of oxygen such as an atmosphere of 100% His and/or in an inert atmosphere as of nitrogen, carbon dioxide, or the like. As an illustration see Example 6.

The advantage of a baking H282 and H233) and other sulfur-containing rubf is used, it is to be understood that other suitable Additional drying or hardening of the film may Vinylite, or (0) baking in an atmosphere devoid I of oxygen, followed by application of a top coat,

and then letting the dual film stand or season in contact with an oxygen-containing atmosphere before using the coated article for its intended purpose (in the last-named case, oxygen evi-- dently penetrates'or seeps through the top coat to the primer coat), or(d) applying and drying the primer coat in an atmosphere devoid of oxygen, coating with' a top coat of another resin such as Vinyli-te, still in an atmosphere devoid of oxygen, and heating the multiple-film system thus formed, still in an atmosphere devoid of oxygen, or (c) any combination of any of the foregoing, or otherwise. It ill be understood that an atmosphere devoid of oxygen may have present a sulfur containing material.

Since the resin coating resulting from (d) wherein the entire series of operations take place in an atmosphere devoid of oxygen is entirely satisfactory for commercial use, it would appear that my sulfur-containing polycyclopentadiene films may be satisfactorily hardened either by heat, or by an oxygen-containing and/or sulfur containing environment or by any combination thereof.

In fact, other drying or hardening methods might be employed.

In coating sheet metal, for instance, excellent results may be obtained by coating one side, baking that coating and then coating the other side,

after which the sheet metal is again baked.

After drying or hardening my sulfur-containing polycyclopentadiene films are, generally speaking, insoluble. v

While the film thicknesses given are found to be extremely suitable for the purpose, and particularly for metal container elements such as food containers and caps, other film thicknesses may obviously be employed without departing from the spirit of the invention.

While in the above specific examples toluene solvents may be employed of which benzene, xylene, ethyl benzene, naphtha, chloroform and carbon tetrachloride are examples.

While the foregoing particular description has been concerned primarily with the application of the protective film or films to metal sheets of a gauge used in the manufacture of articles such as caps and tin cans, it will be obvious that my invention is not limited thereto but may be applied to any metal sheet material, and in fact, to metallic objects in general whether pre-fabricated or not, where a tough strongly adhering film or film system is desired. The fabrication of toys from sheet metal for instance, represents another important field of application for my invention.

Thus, the resin film may be applied to metal foil.

As an illustration, tin foil and aluminum foil, each of which is used to package dairy products like butter and cheese, may be so coatedfl If desired, these materials in molten form may be poured into molds lined with foil coated in accordance with my invention.

So too, lead foil, such as is used to package tea leaves, may be coated in accordance with my invention.

Metal foil may be coated by any desired procedure. For example, the foil may be passed through a solution of the coating material and ,t,he excess removed by means of doctor blades or rolls. Or a conventional roll type coating procedure may be employed and the solvent removed and/or recovered in any suitable manner. Or the coating material may be poured or sprayed on the material to be coated'and the. excess removed by doctor blades or rolls, or simply allowed to drain away.

If desired, metal foil may be strengthened by backing it with paper, or by laminating two or more foil layers. For example, a sheet of metal foil may be" coated on one side and the coated side pressed into contact with a sheet of paper or second sheet of foil before the coating material has completely dried. This may be followed by coating the opposite side of the metal foil and drying the film for contact with foodstuffs. On the other hand, metal foil coated with my dual film system with "Vinylite as the top coat may be hot pressed against paper or foil to effect union of the materials.

While the invention has been more particularly described in connection with the coating of sheet metal including foil in the flat, my resin film or film system may be applied during or after any forming operations for converting the initial material into the finished object. It is generally useful for coating metallic objects in general, whether fabricated from sheet metal or not, or whether pre-fabricated in whole or in part prior to application of the film or film system.

While it is preferred to employ cyclopentadiene as substantially the sole resin-forming hydrocarbon in initially preparing th catalytically polymerized polycyclopentadiene resin which is then modified. by the addition of r sulfurcontaini ng additives in the manner described, the presence or addition of relativelysmall'amounts of still other substances of a resin-forming nature with consequent modified results may be sometimes desirable, provided the outstanding characteristics of the base material are not substantially destroyed. The presence of a homo-polymer of methyl cyclopentadiene or a co-polymer of cyclopentadiene and methyl cyclopentadiene, or both, in amoun s up to of the order of from 10 to 20% and possib y more, appears to have no deleterious effect. Th's does not appl in general and extreme in making an additions.

The presence of upto 20% or more of methyl cyclopentadiene in the starting material from which the polycyclopentadiene, resin is prepared thus appears to have no outstanding deleterious effect. The absence of all other materials poly: .merizable under the conditions employed is preferred. In fact, for the preparation of protective films giving the best results from every standpoint, it is preferred that. there be present in the starting materials no substantial quantities of any to resinous materials re'should be exercised other materials (besides the cyclopentadiene and methyl cyclopentadiene) which will form a resin under the polymerization conditions prevailing.

My sulfur-containing polycyclopentadiene films are attractively colored without any color additive. If desired, suitable coloring materials may be added such as dyes, pigments, and lakes. The same applies with respect to the Vinylite top coat. However, in the food packaging field, care should be exercised with respect to any such added substances so as not to lower or destroy the excellent qualities of the original material for this particular use.

Since in the food packaging field the important consideration is that the resin in contact with the food be chemically inert, insoluble in the foodstuff, incapable of imparting odor and taste thereto, and strongly adherent to the enclosing wall, outside portions of the container or foil may be left uncoated, or may be coated with other materials, particularly if suitable, 01' with my materials with or without modifying agents besides those already mentioned, or otherwise.

In the specification and claims, the term sulfur-containing is intended to embrace elemental sulfur as well as compounds containing one or more sulfur atoms in the molecule.

It is to be understood that the above specific examples ar by way of illustration. Therefore, changes, omissions, additions, substitutions, and/or modifications may be made within the scope of the claims without departing from the spirit of the invention.

I claim:

1. A liquid coating composition comprising benzene-soluble catalytically polymerized cyclopentadiene in admixture with a volatile solvent, and a sulfur-containing rubber vulcanization agent.

2. A liquid coating composition comprising benzene-soluble catalytically polymerized cyclopentadiene, sulfur, and a volatile solvent.

3. A liquid coating composition comprising hydrogen sulfide, benzene-soluble catalytically polymerized cyclopentadiene, and a volatile solvent.

4. A composition of matter comprising the reaction product of hydrogen sulfide and benzenesoluble catalytically polymerized cyclopentadiene.

5. A liquid coating composition comprising benzene soluble catalytically polymerized cyclopentadiene, a volatile solvent and from 8% to 16% sulfur based on said benzene soluble catalytically polymerized cyclopentadiene.

6. A formed film coated article shaped by deformation of a metallic body coated with a dried film comprising the reaction product of a sulfur containing vulcanization agent and a benzene soluble resinous polymer of a material having as substantially the only resin forming content thereof one of a group consisting of (a) cyclopentadiene and (b) cyclopentadiene admixed with up to 20% methyl cyclopentadiene, said formed film adhering tenaciously to the formed metal.

7. A formed film coated article shaped by drawing a metallic sheet coated with a dried film comprising the reaction product of sulfur and a benzene soluble resinous polymer of a material having as substantially the only resin forming content thereof one of a group consisting of (a) cyclopentadiene and (b) cyclopentadiene admixed with up to 20% methyl cyclopentadiene, said dried film adhering tenaciously to the drawn metal.

8. A formed film coated article shaped by deformation of a metallic body coated with a dried film comprising the reaction product of hydrogen sulfide with a benzene soluble resinous polymer of a material having as substantially the only resin forming content thereof one of a group consisting of (a) cyclopentadiene and (b) cyclopentadiene admixed with up to 20% methyl cyclopentadiene, said formed film adhering tenaciously to the formed metal.

9. A formed film coated article shaped by deformation of a metallic body coated with a dried film comprising the reaction product of a sulfur containing vulcanization agent and a benzene soluble resinous polymer of monomeric cyclopentadiene, said formed film adhering tenaciously to the formed metal.

10. A formed film coated article shaped by drawing a metallic sheet coated with a dried film comprising the reaction product of a benzene soluble resinous polymer of a material having as substantially the only resin forming content thereof one of a group consisting of (a) cyclopentadiene and (b) cyclopentadiene admixed with up to 20% methyl cyclopentadiene and from 8 to 1.6% sulfur based on said resinous polymer, said dried film adhering tenaciously to the drawn metal.

11. A formed. film coated article shaped by deformation of a metallic body coated with a dried film comprising the reaction product of a benzene soluble resinous polymer of monomeric cyclopentadiene and from 8% to 16% sulfur based on said resinous polymer, said formed film adhering tenaciously to the formed metal.

12. A process for producing a, formed article coated with a formed protective layer of synthetic resin which comprises coating metallic material from which the article is to be formed with a composition comprising a, sulfur containing rubber vulcanization agent and a benzene soluble resinous polymer of a material having as substantially the only resin forming content thereof one of a group consisting of (a) cyclopentadiene and (b) cyclopentadiene admixed with up to 20% methyl cyclopentadiene, baking said coating under temperature conditions not in excess of 400 F. to hardensaid coating; and subjecting the coated article to shaping operations to produce a formed article.

13. A process for producing a formed article coated with a formed protective layer of synthetic resin which comprises coating metallic material from which the article is to be formed with a composition comprising a sulfur containing rubber vulcanization agent and a benzene soluble resinous polymer of a material having as substantially the only resin forming content thereof one of a group consisting of (a) cyclopentadiene and (b) cyclopentadiene admixed with up to 20% methyl cyclopentadiene, baking said coated metallic material at a temperature of about 250 F. for a period of about twenty minutes, and subjecting the coated metallic material to shaping operations to produce a formed article.

14. A process for producing a formed article coated with a formed protective layer of synthetic resin which comprises coating metallic material and (b) cyclopentadiene admixed with up to 20% methyl cyclopentadiene, subjecting said coated metallic material to a baking schedule wherein the temperature during the bake is gradually and thereafter subjecting said coated metallic material to shaping operations to produce a formed article.

15. A process for producing a formed article coated with a formed protective layer of synthetic resin which comprises coating the metallic material from which the article is to be formed with a composition comprising benzene soluble resinous polymer of a material having as substantially the only resin forming content thereof one of a group consisting of (a) cyclopentadiene and (b) cyclopentadiene admixed with up to 20% methyl cyclopentadiene to which resinous polymer 8% to 16% sulfur based on said polymer has been added, reacting said sulfur'and said polymer by heating said coating, and subjecting the coated article to shaping operations to produce a formed article.

16. A process for producing a formed article coated with a formed protective layer of synthetic resin which comprises coating metallic material from which the article is to be formed with a composition comprising a benzene soluble resinouspolymer of a material having as substantially the only: resin forming content thereof one of a group consisting of (a) cyclopentadiene and (b) cyclopentadiene admixed with up to 20% methyl cyclopentadiene, drying said coating in an atmosphere containing hydrogen sulfide, and subjecting the coated article to shaping operations to produce a formed article.

17. A process for producing a formed article coated-with a formed protective layer of synthetic resin which comprises coating metallic material from which the article is to be formed with a composition comprising a sulfur containing rubber vulcanization agent and a benzene soluble resinous polymer of monomeric cyclopentadiene, reacting said vulcanization agent and said polymer by baking said coating; subjecting the coated material to shaping operations to produce a formed article.

NEWCOMB K. CHANEY.