US2331728A - Container closure - Google Patents

Description

1943' J. w. RAYNOLDS ETAL 2,331,728

CONTAINER CLOSURE Filed May 14, 1942 1&9. 1|-

BACKING MATERIYKL CZHLQRINATED "RUBBER HYDROCHLORIDE CONTAINING 42-52 "7 C/HLORINR JAMES W. REYNOLDS WALTER MKUTZ Patented Oct. 1943 CONTAINER CLOSURE James Wallace Raynolds, Easton, and Walter M.

Kutz, Pittsburgh, Pa... assignors to The Raolin Corporation, New York, N. Y., a corporation of West Virginia Application May" 14, 1942, Serial No. 443,010

3 Claims.

This invention or discovery relates to container closures; and it comprises an improved closure top for containersfor foods, beverages, drugs, cosmetics and the like, said closure top being tution. The reactions which produce these compounds are conveniently carried out in carbon tetrachloride or other chlorine-resistant solvents, and it appears that the addition and substitution of chlorine progress to completion more,or less provided on an inner surface with a layer or film 5 simultaneously. Various modifications of the of chlorinated rubber hydrochloride which adprocess of chlorinating rubber have been disvantageously contains from 42 per cent to 52 per closed heretofore. Useful procedures are decent chlorine, said layer being advantageously scribed in U. S. Patent 2,148,830 to North and in applied to a separable liner of paper. pulp board, a copending application of Raynolds, Serial No. cork sheeting, or the like, which may have gas- 245,293. keting functions; and it comprises liners for such As used herein, the terms rubber chloride closures; all as more fully hereinafter set forth and chlorinated rubber refer to chemical comand as claimed. pounds of the class discussed hereinabove, which Foods, drugs, cosmetics and other commodcharacteristically have a combined chlorine conities are often packaged in bottles, jars and like tent of 64 to 68 per cent; part of the chlorine containers having removable topsor closures. saturating double bonds and part being sub- Such closures are often provided with lugs or stituent.

threads-adapted to engage the neck of the bottle A somewhat similar, or at least related, class or jar, and are usually made of metal or of of compounds areproduced by the reaction of molded plastic material. In practically all cases, rubber'and hydrogen de i the absence of the color, taste and odor of materials packagedv free chlorine. These products, which are known .in containers of this type are important, and it as rubber hydrochlorides, are formed by reaction is therefore frequently necessary to protect the of gaseous or liquid HCl with rubber until the closure and the contents of the container from double bonds in the rubber Have been satisfied. contact with each other. Many varnish coatings 5 The product of this reaction is theoretically ruband coatings of related composition for caps and ber di-hydrochloride,- having a composition corcap-liners have therefore been proposed. responding to the formula C1uH1sC12. This theo- Coatings of rubber chloride are frequently useretical'composition corresponds to a chlorine conful in the protection of packaged materials from tent of 34.8 per cent, but in practice, it is selcontact with container closures, and rubber dom possible to obtain products containing more chloride has many virtues forthis purpose, owing than 31' to 32 per cent of chlorine. to its chemical inertness. It is not affected-by b r ydrochlo ide films a e usefu as li acids, alkalies or alcohols, or by most of the ings for certain foods, drugs, cosmetics and other materials packaged in containers of this type. commodities, and the composition is quite re- Rubber chloride is, however, soluble to a certain 3'5 sistant to acids, alkalies, alcohols and most of extent in the fatty oils, and conversely it takes the-materials which are packaged. Rubber hyup fatty oils. A film or lining of rubber chloride drochloride is also quite resistant to vegetable is not grease proofand caps protected by it are oils, being superior to rubber chloride in this not of universal applicability- Many foods, respect. 7 V drugs and cosmetics contain fats or greasy ma- 40 There are, however, several undesirable factors terials. I which impair the-utility of rubber hydrochloride There are a number of rubber chlorides or for the coating of container closures. One of chlorinated rubbers wn. but all ve the these is the excessive thermoplasticity which is a drawback of susceptibilityto grease. These comgeneral characteristic of rubber hydrochlorides. pounds are products resulting from the reaction. Many. food products and cosmetic preparations of chlorine (usually in the gaseous state) and are packaged and sealed hot; and others are rubber (usually in solution). The most stable packed cold, and then heated to pasteurize or products contain about 64 to 68 per cent of sterilize the packaged material. When used in chlorine and are thought to have compositions such processes, rubber hydrochloride films of corresponding to the formulas CmH aCh or the characteristic chlorine content (belowabout CroHmCls. In .such compositions, four chlorine 32 per cent) soften; andthen as the container atoms have been combined by addition at the and its contents cool, the vacuum created in the double bonds of the caoutchouc, andthree or container causes the rubber hydrochloride to four chlorine atoms have been entered by substibulge and become permanently distended, thus destroying its usefulness and appearance. The

thermoplasticity of rubber hydrochloride also frequently causes liners or closures coated with this material to adhere to the mouth of the jar or other container with which they are employed. Several-other disadvantages also result from the excessive plasticity and stickiness of this material when hot.

Another unfavorable characteristic of rubber hydrochloride is its low solubility. It is only soluble to a small extent in the solvents which are normally desirable for coating purposes, such as benzol and toluol. The symmetrical type of rubber hydrochloride is only soluble to the extent of some 2 or 3 per cent, and the asymmetrical type of rubber hydrochloride, although somewhat more soluble, will notform solutions having a solid concentration above about '7 per cent. Such solutions form very thin films on drying, and are not satisfactory for application as varnish coatings to paper and other materials. Vamishes which are economical for use in such applications should contain more than 20 percent, and advantageously between 25 and 30 percent, of solids in a solution having a viscosity between 1500 cps. and 2500 cps. Rubber hydrochloride cannot be made into solutions or varnishes of this character.

'As a result of this difiiculty, it has been necessary heretofore to resort to some other method of applying rubber hydrochloride films and coatings. For example, films can be formed from benzol solutions of rubberhydrochloride containing up to 7'per cent solids by the process disclosed in Patent No. 2,078,526. The separate film of rubber hydrochloride may then be coated on one side with an adhesive and cemented to paper or pulp board or the like to form closure lining material. Considerable difiiculty has been encountered in producing a permanent bond between the rubber hydrochloride film and V the paper carrier, however, and for this and assmze tion, a coating of this chlorinated rubber hydrochloride has a very low moisture permeability as compared with all other types of closure lining materials.

Still further, the chlorinated rubber hydrochloride does not have the excessive thermoplasticity which, as noted, is an undesirable characteristic of ordinary rubber hydrochloride. The thermoplasticity of rubber hydrochloride is substantially reduced when the product is chlorinated, and when a chlorine content of about 43.7 per cent chlorine is reached, the chlorinated rubber hydrochloride is quite satisfactory for use on hot packs. It does not bulge or deform when the packaged material is cooled, and does not stick to the mouth of a container. The thermoplasticity is still further reduced as the chlorine content is increased. In these'respects, the chlorinated rubber hydrochloride films or coatings are decidedly superior to rubber hydrochloride films or coatings for use on container closures or closure liners.

other reasons, the use of these rubber hydrochloride films in closure liners is not economical.

Rubber hydrochloride can be treated with chlorine gas to yield products having considerably increased chlorine contents. The reaction involved is essentially a substitution reaction, and the HCl which is added in forming the rubber hydrochloride is not easily displaced. Products of this reaction apparently have compositions corresponding to. the formulas cmrmch (containing 43.7 per cent chlorine) and CmHuCli (containing 51.04 per cent chlorine). Such products are known as chlorinated rubber hydrochlorides, and their existence has been .disclosed heretofore.

We have found that certain suitably prepared chlorinated rubber hydrochlorides containing from 42 to 52-per cent of combined chlorine are eminently suitable for use in container closures.

These products, to be hereinafter described more in detail, are soluble in concentrations up to 25 A further advantage of the'foregoing chlorinated rubber hydrochlorides containing about 43.7 per cent to 51.04 per cent chorine is their flexibility. Such chlorinated rubber hydrochlorides do not require the addition of plasticizers before application to paper, etc., in the production of closure liners. Their flexibility is adequate for most purposes without the use of plasticizers. The moderate thermoplasticity of this material and its normal'fiexibility result in the production of coatings on paper and other supporting materials which readily conform to the mouth or finish of the container with which they are used, and thus make an'eflective' seal when the closure is in'place.

The chlorinated rubber hydrochloride products employed in accordance with .the present invention are limited'to a specific range of chlorine content and most advantageously produced in accordancewith the process disclosed in the copending U. S. application Serial No. 332,115, filed April 27, 1940. These products must not be confused with the hydrochlorinated rubber chlorides which, as is well known, are a fundamentally different' class of compounds, formed by first treating rubber with hydrogen chloride and later with chlorine. This reaction produces a totally different-kind of chemical composition having properties unrelated to those of the chlorinated rubber hydrochloride herein employed.

Yet, more specifically, the present materials are conventional materials formed by ordinary hydrochlorination of rubber followed by treatment with chlorine. Thus, as

pointed out above, conventional .hydrochlorihation to Produce a symmetrical rubber hydrochloper cent or more inbenzol or toluol and thus are suitable forapplication as a varnish. The resulting coating possesses sumcient thiclmess for closure liners and the like. The resulting films are free'from the objections noted hereinabove.

We have also found that paper coated with one or two coats of this chlorinated rubber hydrochloride varnish has highlydesirable properties for use as a closure lining or gasket. Such varnish coatings or films are unaffected by acids,

alcohols, mineral voils and alkalies, or by .cottonseed oil and other vegetable oils. In addithan 30 per cent chlorine.

ride seldom results in a product containing more Chlorination of this product even under the most favorable temperature conditions results in a reaction efilciency which is extremely poor. Large excesses of chlorine have been hitherto found necessary and it has been quite unusual to obtain products containing more than 39 or 40per cent fixed chlo-,

rine. The resultant products have had very poor solubility in conventional solvents, have been characterized by undesirable instability and appearance and are generally unsuited for the purposes of the present invention. In accordance with the present invention, however, the chlorinated rubber hydrochlorides employed not only possess a higher combined chlorine content within the range of 40 to 50 percent, but have iniproved properties indicating the possibility of a fundamental difference in chemical structure. Such materials have good solubility in the foregoing commercial'solvents, possess improved stav bility, and are formed as clear solutions.

rubber with gaseous chlorine in the usual manner employed in the manufacture of chlorinated rubber. However, such products do not exhibit sat- "I'he details of the preferred method of making these compounds are disclosed in the aforesaid copending application Serial No. 332,115 and reference is accordingly made to this specification for full and complete disclosure of the process. In general, this process involves the chlorination of a suitably prepared rubber hydrochloride solution or dispersion under the influence of ultraviolet light advantageously within. the wave length range of from 2800A to 3600 A. Ultraviolet radiation results in a better and more efficient absorption of chlorine, a more thorough and uniform chlorination, and products of higher chlorine content.

In general, therefore, a rubber hydrochloride produced as above and having, for example, a combined chlorine content of about 30 per cent, is chlorinated under the influence of ultraviolet light within the above range of wavelength to a fixed chlorine-content of 42 to 52 per. cent. Chlorination proceeds rapidly, and efficiency of utilization of the chlorine is quite high.

Yet more specifically, the reactions are preferably carried out in the presence of a suitable solvent. Thus the rubber is preferably originally prepared for hydrochlorination by dissolvingit in benzene. The resulting cement is dehydrated and the anhydrous product subjected to contact with dry hydrogen chloride gas at a low temperature between and 25 C. fora 24 hour period. The resultant hydrochlorinated product containing about 31 per cent fixed chlorine is then treatedwith gaseous chlorine at a temperature above about 80 C, and -'in a vessel providing for continuous circulation of the fluid past a quartz window opposite which is disposed an ultraviolet. light. Chlorination to a final chlorine containing above 42 per cent'normally does not require more than 2 hours under the stated conditions. The product is then blown to remove residual gases and the solid chlorinated hydrochloride recovered from the solution in any convenient manner,

While other methods may be employed in the production of the present materials it is to be above 51 per cent there is an accompanying increase in the brittleness, rendering necessary the addition of plasticizers'and accompanying im pairment of resistance to vegetable oils or otheringredients of package materials. In short, it has been discovered that those products occurring between the ioregoing limits of chlorine content and more broadly within the range of 42 to 52 per cent encompass a field highly suitable and desirable for use in container closures.

It should be noted that-products of similar I chlorine content can be prepared by reacting isfactory resistance to numerous reagents, and they are inferior to the rubber chlorides described hereinabove containing 64 per cent or more of chlorine. desirable properties, it is necessary to prepare rubber hydrochloride first, and then to chlorinate the hydrochloride to a total chlorine content between 42 per cent and 52 per cent. The chlorinated rubber hydrochlorides of this chlorine content are free from the unfavorable characteristics of both rubber hydrochloride and rubber chloride. to ordinary rubber hydrochlride of about 10 to 20 per cent of substituted chlorine eliminates .the undesirable characteristics of the hydrochloride (low solubility. and excessive thermoplasticity) without impairing its grease-resistance or other desirable properties.

. These chlorinated rubber'hydrochlorides form coatings which are colorless, tasteless, odorless and non-toxic. The coatings may be pigmented if desired, titanium di-oxide being a useful pigment for the production of white coatings. Other pigments may, of course, be used when other colors are'desired. V I

As a specific illustrative example of the present invention, a chlorinated rubber hydrochloride produced in accordance with the process described in copending application Serial No. 332,- 115, containing 47.7 per cent of chlorine is dissolved in toluol to form a solution containing 23 per cent solids. The solution has a viscosity of 2500 cps. at 25 C. and is entirely satisfactory for varnish coating or roller coat application. As a base for the, closure liner employed with this coating, a paper is selected' having suflicient density to minimize permeation by the coating solution or the solvent; Numerous such papers having satisfactory properties in this respect are available and pulp board or cork sheeting are also satisfactory, preferably if first treated with a suitable sizing or sealing coating.

The chlorinated rubber hydrochloride solution or varnish is applied to the selected paper by roller coating, although it could 'equally well beapplied bya knife or spreader, or by spraying or other suitable means. The thus coated paper is dried in an oven at a temperature of 220 F. for 10. minutes.' It will be understood that the time and temperature of baking may be varied in accordance with the type of oven employed and the solvent used resin solution. Multiple coatings are readily applied ,by repeating the process,

if desired.

The resulting coated paper possesses a dry film of chlorinated rubber hydrochloride having athickness of'0.001 inch. ,This film." tested for moisture permeability by the standard moisture vapor transmission method of the New York Paint and Varnish Production Club, using standard Payne cups, showed a specific permeability of 0.0669 mg. at 900 F. and 0 percent relative humidity. As a comparison, normalrubber hydrochloride sold for closure lining material showed a specific'permeability of 0.120 mg. at F. and 0 per cent relative humidity in this test. A rubber chloride-vinyl acetate composition disclosed in a copending application of Reynolds, Serial No. 253,861, showed a specific permeability of 0.1225 mg., and a coating of the co-polymer of vinyl chloride and vinyl acetate showed a specific permeability of 0.33 mg, in v In order to obtain the most' It thus appears that the addition both cases at 100 F. and per cent relative humidity, by this test. It is therefore clear that the chlorinated rubber hydrochloride coatings produced in accordance with this invention have extremely low moisture permeability.

As a further test of the coating produced in accordance with our invention, the coated paper was cut into closure liners, which were assembled with metallic closure bodies. Separate glass jars were then filled with each of the following testing materials:

Sodium hydroxide 2 Ammonia 10 Chlorox (sodium hypochlorite) Phosphoric a 85 Hydrochloric acid 10 Acetic acid and 20% salt brine n} 8 IVIilk of ma nesia Ethanol 50 Ethanol l "Astringosol i 95 Cottonseed nil Hydrogen peroxide 3 Acetic acid l Glacial acetic acid 5o Squibbs sun tan oil (contains methyl salicylate) Ferric chloride Sodium carbonate 1 Salt in distilled water The assembled closures having liners coated as described hereinabove were then placed on the jars with the coating exposed to the contents, and the jars were heated to a temperature of 150 F. for 48 hours. At the end of this time, the coatings on the liners were examined and none of them showed any signs of deterioration. Similar results were obtained with the contents heated to 105 for seven days exposure. Samples were tested by exposure to cottonseed oil for 18 days at 150 F. without any noticeable effect on the coating. Similar results were obtained in testing pigmented coatings.

In addition to the excellent resistance and low moisture permeability of the chlorinated rubber hydrochloride coatings produced in accordance with this invention, they also form products of very attractive appearance. For example, paper coated as described ,hereinabove is not changed in colorby the application of the coating, and when white paper is used, the coated paper has a very clean white appearance. Such coatings,

and liners provided with such coatings, are therefore well adapted for use with containers for food products, beverages, cosmetics, drugs and the like.

In commercial operations employing liners of this yp the coated, paper or other coated material is run through a stamping mechanism which stamps out liners of any desired diameter. .For some special purposes, laminated materials are employed, and these may be made entirely of paper or other cellulosic material, or may include aluminum foil or other material. In any case, the coating produced in accordance with this invention is sufll'ciently flexible to conform to the above; and

Fig. 2 shows the liner associated in operative relation with a conventional type of closure member.

In the drawing, the reference numeral 5 designates the shell of a closure provided with a liner 1 coated with a layer 6 of chlorinated rubber hydrochloride.

While our coating of chlorinated rubber hydrochloride gives especially advantageous results when applied to liners for container closures, it is also useful in many other applications where resistance to greases, solvents, acids, bases and salts is desired. For example, it may be applied directly to the surface of metal and other articles, including closures. As previously noted, pigments may be included in the coating composition ii desired, and are often advantageous in that they reduce the specific permeability of the coating still further. Any compatible pigment may be employed.

This application is a continuation-in-part of U. S. Serial No. 326,803.

What we claim is:

1. In a closure for containers, a substantially insoluble grease-proof film disposed between the inner surface of the closure and the interior of the container and adapted to prevent contact between the closure and the contents of the container, said film consisting principally of chlorinated rubber hydro-chloride containing from 42 per cent to 52 per cent of combined chlorine and being characterized by flexibility, freedom from excessive thermoplasticity, extremely low moisture permeability, and resistance to acids, alkalies, oxidizing agents, salts and esters, including vegetable oils. Q

2. The closure of claim 1, wherein the said film is applied to a liner' provided within the closure body.

3. A liner for container closures comprising a 'base and a'coating applied to said base on the side exposed to the contents of the container, said coating consisting principally of chlorinated rubber hydro-chloride containing from 42 percent to 52 per cent of combined chlorine and being characterized by flexibility, freedom from excessive thermoplasticity, extremely low moisture permeability, and resistance to acids, alkalies, oxidizing agents, salts and esters, including vegetable oils. x

. JAMES W. RAYNOLDS.

WALTER M. KUTZ.

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