US2383096A - Cork composition and products made therefrom - Google Patents

Description

Aug. 21, 1945. A. H. WARTH ETAL 2,333,095

CORK COMPOSITIQN AND PRODUCTS MADE THEREFROM I Filed Aug. 3, 1942 371 511 Raul Gr bw Jr.

Patented Aug. 1 21, 1945 CORK COMPOSITION AND PRODUCTS MADETHEREFBOM Albin H. Warth and Paul Grabus, Jr., Baltimore, Md., assignors to Crown Cork & Seal Company, Inc., Baltimore, Md., a corporation of New Y k A Application August s, 1942, Serial No. 453,462

15 Claims. (01. 215-40) The present invention relates to a new composition of matter, adapted for use as a gasket or sealing material of generalutility. More particularly, the invention relates to a new composition;

of matter adapted to serveas a substitute for cork compositions of thetype extensively used, forinstance, in bottle caps of the crown type, a the sealing disc or cushion liner therein. In view of cation and claims.

of hollyhock, such as is referred to in the specifi- Although thispith does not have the gas imperviousness ofnatural cork, its cell structure resembles cork somewhat, and the material is compressible and somewhat elastic in all directions. ,Zl'he hollyhock pith is considerably softer than cork and, by itself, does not have suflicient strength, body, and-imperviousness to the scarcity at the present time of cork and rubher, it has become important to develop materials capable of serving as substitutes. Materials having the characteristics of cork, as to lightness,

compressibility, resilience, and gas imperviousness, however, are extremely rare or non-existent, and, prior to the present invention, no completely satisfactory substitute for, the standard cork composition discs for crown closures has been disccovered. a K The cell structure of natural cork is funda mentally diiierent from practically all other woods or vegetable substances, since the cells have, theoretically, fourteen facets and have the characteristics of a spheroid, equally balanced in all directions. Hence, cork is substantially equally compressible in all directions,,wher'eas practically all other woods are more compressible transversely of the grain than lengthwise. Because of these characteristics, cork may be, and conventionally is, granulated, mixed with a binder, treated by heat, and sliced into sheets or discs to serve as cushion liners for receptacle closures. In such discs, the relativepositions of the granules are immaterial, since the granules havesubstantially equal compressibility and resiliency in all direc tions.

Practically all other vegetable materials, however, are grainy, stringy, or have a substantial fiber content, whichmake them less compressible in a lengthwise direction than transversely. Hence, when such materials are comminuted or granulated and mixed with a binder, someiof the particles are so positioned as to be less compressible than others, with the result that the sealing pad has varying characteristics as to compressibility, resiliency, and sealing efllciency overdifferent portions ofits surface. An exception to this. general rule occurs inthe case of the pith ofuthe stem of the common hollyhock plant] gllollyhock, is known in various sections of the country by different names, such as Hibiscus coccineus, Walt, ""Hibiscus moscheutos," frequentlydesignated"as seahollyhock,"

"Althaea rosea which is of the cultivatedtype serve, in granulated form, with a binder as a satisfactory cork composition substitute for receptacle closures and the like. It has been discovered, however, that this granulated material, when properly treated as described below, may serve as a filler or extender in cork compositions and, may be employed to replace substantially by volume of the corkgranules, thus making it possible, in commercial practice, to make a given amount of cork go substantially twice as far as heretofore in providingsealing discs for receptacle closures;

An object of the invention, therefore, isto produce a cork compositionhaving substantially all r of the characteristics of standard compositions of the prior art, but employing a lesser amount of cork granules. Totlfis end, the invention aims to conserve the supply of natural cork, by diminishing the amount employed ina given volume of the new composition. i

A further object of the invention is toreduce the cost of cork compositions,bysubstituting for a portion 01' the natural cork, normally employed, a cheaper material. a a 1' a I A further object of the invention is to produce .a cork composition that cannotbe distinguished and Sidalcea"malvdeflora knownto California as the wild hollyhock; the foregoing are typical position cushion ,discs substantially, 11

by casual inspection from the standard cork compositions heretofore employed. To this end,

the invention provides a for dyeing the substitute material to match the cork, whereby the substitute material is substantially indistinguishable in the finished product from the natural cork.

A further object of the invention is toincrease the impermeability of normally porous material mixed with granulated cork, so as tomake the finished product substantially as imperviousto gases as prior art compositions, or at least to make the finished product sumciently impervious to gases as to satisfy commercial requirements.

A further object of the invention is to provide means; for rendering relatively perviousycork com- Other and further, obje 'ts and, ad antages of the invention wint e pp r nt-th ngs skilled in the :art, from a consideration ofthe ri'ollowingldescripti o specific emwd fii etf t,il ef ei tion.

In the drawing:

Figure 1 is a diagrammatic plan view of a cushion disc for a crown closure. made from the cork composition of the present invention. with the pith granules in {heir natural. non-dyed state:

Figure 2 is a similar diagrammatic view with the pith granules indicated as having been dyed to match the cork granules:

Figure 3 is a. bottom plan view of a crown closure in accordance with the present invention. and

Figure 4 is a diametric section taken on line 4-4 of Figure 3.

In carrying out the invention of the present application, hollyhock stem raw material. is gathered from areas where it grows in great abundance, such as in certain sections of Florida. This raw material has a long fibrous, gray bark of extreme thinness. similar to tissue paper. The stems are decorticated by stripping or peeling off the bark which only lightly adheres to the internal pith. in a Ball & Jewel mill, in the same manner that cork is conventionally ground. If the moisture content of the stem material is at the optimum, between 5 and 6%, there is very little loss in grinding, whereas if the material is bone-dry, the loss is greater. Therefore, it is desirable to control the moisture content prior to the grinding operation, for instance, by wetting. if the moisture content is unduly low. Since the hollyhock stems contain none of the dirt, bark dust, and other impurities that are prevalent with cork, the grinding loss is less than with cork in ordinary milling operations.

The ground hollyhock material has adensity much less than cork, i. e., about .1085, as compared with .25-.20 for cork. As stated above. it has a cellular structure. rather than being of fibrous nature and is substantially equally compressible in all directions. It is softer and more compressible than cork, but this disadvantage can be overcome bytreating the granulated pith in suitable ways. such as by impregnating the particles with a thin glue solution containing a wetting agent. Penetratio or impregnation of the particles causes their density to approach that oi cork and decreases their compressibility.

In order to improve the appearance of the finished product, it is desirable to dye the granulated pith, since the material in the natural state is substantially white or light gray in color. Any dyes, such as those employed in the manufacture of artificial chocolate or certain extracts from coffee beans, may be employed. A certified color dye known as chocolate'brown, of the National Analine 8: Chemical Co. has been found to be entirely satisfactory for this purpose.

Preferably, the dye is incorporated in the thin glue solution used to impregnate the hollyhock particles. Asuitable formula for this purpose is as follows: A

Parts Water 50 Gelatin Glycerine Tan color 1 Aerosol 1 The pith is then ground or granulated penetrate the hollyhock particles, carrying the tan dye along, imparting to the particles on appearance similar to cork.

After such treatment with the impre nating agent and the dye, the pith particles are air dried and then thoroughly mixed with the previously ground cork granules. The glue binder may then be added, while the pith and cork particles are tumbling in a dough mixer. The resulting product may be packed into rods or blocks or roll molds and subjected to the usual heat treatment. to set the glue binder. After a suitable seasoning period. the cushion discs may be sliced from the rod or sheets cut from the roll or block in the usual manner. Oi" course. any other known method of making, the liners or gaskets may be employed, substituting the mixture of treated pith particles, granulated cork particles. and glue for the usual granulated cork products alone.

A suitable formula for the binder. employed to secure the hollyhock pith particles and the cork particles together is as follows:

Parts Water 31 Gelatin 22 Sulphonated oil l5 Glycerine 30 Paraffin wax 2 if hexamethylenetetramine is used, about three times that amount should be added.

Approximately 1 part of binder is added to 2 parts of the prepared hollyhock and cork mixture in the dough mixer to produce the agglomeratc for packing, although the amount can be varied, to satisfy particular conditions.

The following formula is suitable for ribbon or sheet blocks or rolls:

Parts Cork (granulated in roller mill) 50 Decorticated hollyhock stems (Ball & Jewel Mill granulated, thin glue processed) 33 Cold glue mix 31 Sulphonated castor oil 5 Insolubilizing agent (1 part hexamethylenetetramine, 2 parts water 2 ,4

, The invention is not limited to specific proportions of pith and cork granules. It has been found that, in general, a proportion of 50% pith and 50% cork by volume is quite satisfactory and produces an efiective sealing pad, capable of withstanding a gas pressure of 70 pounds per square inch, without the use of a center spot liner or other gas impervious layers or coatings. When cork and pith granules are mixed in the proportion of 25 pounds of cork to 15 pounds of hollyhock pith, the volumes of the two materials will be substantially equal and satisfactory sealing pads can be produced.

In the accompanying drawing, a sealing pad is indicated generally at I0, the cork granules being shown at H and the hollyhock pith granules at l2; Although the invention is not limited to any particular relation of particle sizes. it is preferred that all of the granules be ground to substantially the same average size, such as those that will pass screens having eight openings and twelve openings to the inch. The pith granules l2 in Figure 1 are shown in their netura-l, non-dyed condition and appear in the finished product as substantially white or light gray spots. If this is objectionable, the particles may be dyed as indicated in Figure 2. so that the pith particles I substantially match thecork particles IS in the disc l4.

As indicated in Figures 3 and 4, a center spot liner 2!) may be adhesively united to the exposed face of the cushion disc 2 I, in concentric relation to the crown closure 22, as is well understood in the art. The spot liner may be of any of the resin-wax composition, to increase the gas imperviousness of the disc as a whole by sealing the surface cells of the hoilyhock pith granules. The pith of other plants may be substituted cork and granulated hoilyhock pith in substantially equal volumes, and a binder.

7. A cushion disc adapted for use as a sealing pad in a receptacle closure comprising substantially equal volumes or granulated cork and granulated hoilyhock stem pith, and a binder, the cork and pith granules being of substantially the same average size.

8. A cushion disc adapted for use as a sealing pad. in a receptacle closure comprising granulated cork, granulated hoilyhock pith impregnated with glue to decrease its porosity, and a binder.

9. A resilient, substantially gas-impervious sealing disc ioruse in a receptacle closure comprising granulated hollyh'ock pith, the particles of which are impregnated with a cell-sealing agent to decrease their porosity, granulated cork, and

a binder. I

10. A resilient, substantially gas-impervious sealing disc for a receptacle closure comprising particles ofgranulated hoilyhock pith pre-coated with glue to decrease their porosity, granulated for the hoilyhock pith for certain purposes, al-

though not as satisfactory for other purposes. The pith oisuniiower stalk and similar plants has proved satisfactory in cases where equal 0031-, pressibility of the particles in all directions is not essential.

It must be understood, therefore, that the'invention contemplates all variations and changes coming within the scope oi. the appended-claims and their equivalents.

We claim: l. A cork composition comprising cork granules, pith granules from hoilyhock of the Florida type known as Hibiscus coccincus, Walt. inter mixed therewith, and a binder.

2. A cork composition comprising substantially 50% each by volume of granulated cork and granulated pith from hoilyhock of the Florida type known as Hibiscus coccineus, Walt. and a binder.

3. A cork composition comprising granulated cork and granulated hollyh'ock pith material, and a binder.

4. A cork composition comprising equal volumes of granulated cork and granulated hollyhock pith material.

5. A cushion disc adapted for use as a sealing pad in a receptacle closure or the like, comprising granulated cork, granulated hollyhock pith, and a binder.

6. A cushion disc adapted for use as a sealing pad in a receptacle closure comprising granulated cork particles intermixed therewith, and a binder uniting the corkand pith granules.

i 11. A cork composition comprising granulated cork, granulated hoilyhock pith dyed a color to match the cork granules, and a binder.

12. A cork composition comprising granulated cork, granulated hoilyhock pith, the particles of which have been dyed to match the cork and porosity, and a binder.

have been pre-treated with glue to decrease their 13. A cork composition comprising granulated cork and granulated hoilyhock stem pith in substantially equal volumes, the pith granules being characterized by the presence of suflicient brown dye to substantially match the cork, by a cellsubstantially sealing agent which decreases their porosity, and

by being of thesame average size as the cork particles.

14. A receptacle closure having secured therein a cork composition cushion liner comprising granulated cork, granulated h'ollyhockpith, and a binder.

15. In combination, a cap of the crown type, a cushion liner therefor comprising substantially equal volumes of granulated cork and granulated hoilyhock pith material, and a center s t of gasimpervious sheet material adhesively united to the exposed i ace of the liner.

mm H. wsa'rn. PAUL owns, an.

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