US2371710A - Resilient materials - Google Patents

Description

Patented i0,- 1945 UNITED STATES PATENT-Y OFFICE 2,371,710 assmsn'r MATERIALS I George Schneider, Montclair, N. J., and Mervin E.

Martin, Cumberland, MIL, assignorsto Celanese Corporation of America, a corporation of Delaware No Drawing.

Application November 12, 1941 Serial No. 418,861

3 Claims. 1 (Cl. 288- -34) This invention relates to the preparation of resilient materials and relates more particularly to the. production of resilient materials suitable for use as cushion liners in closures, such as those 7 tureand internal pressure of the contents of the I containers on which they are applied.

Other objects of our invention will appear from the following detailed description.

Closures of various types are employed in sealing containers of glass or metal which are used for holding liquids. In the case of carbonated beverages such as soft drinks, beer, etc., where it is important to retain the gas in solution, the closures are usually in the form of a metal cap or shell lined with a disc of some soft, easily deformable material which may be covered with a flexible metal foil. The closures'are put on the filled bottles-by a suitable capping device which serves to bend the edges of the metal closure beneath a lip provided at the top of thebottle and to force the soft, foil-covered disc against the upper or pouring edge of the bottle. .The pressure of the disc against the bottle acts as a seal and serves to prevent the 'bscape of either the gas or the liquid. Ordinarily, the soft disc is formed of a material such as cork, but the quality and availability of this materialvaries from time to time. For this reason, a suitable material having the physical advantages of cork but which is readily" available and whose quality can be controlled has long been sought.

be prepared from cellulose fibers insheet form, it the moisture content of said material is main-- tained at a relatively high level. In accordance with our invention, cellulose fibers compocted into the form of a sheet or web are so treated as to incorporate therein a hygroscopic material. and the sheet material then cut or shaped in any convenient manner into discs or other shapes of suitabledimensions. The hygroscopic material incorporated into the sheet material maintains the moisture content of the discs at the desired relatively high level and thereby imparts to the latter an unusual degree of resiliency. more preferably, after being faced with a film or foil of a suitable inert material having a con- 10 tinuous structure. may then be used as cushion liners for lining container closures. The film or .ioil protects the sheet material from the action of the contents of the container. When the closures are applied by a suitable capping delli vice, the cushion liners of our invention give.

a gasand liquid-tight seal which remains tight through wide fluctuations in both the temperature and internal gas pressure of the container on which the closure is applied, as well as over extended periods of service.

Various hygroscopic materials may be employed for maintaining the moisture content of the cushion liners at the desired level and the hygroscopic materials, which may be liquid or solid, may be incorporated into said materials in many ways. The hygroscopic material may be incorporated into the cellulose fibers before they are formed into sheets, or the cellulose fibers may be treated after the'sheets have already been formed. Preferably, the hygroscopic materials are applied after the fibers have already been fabricated into sheet form, or after the sheets have been cut or shaped into discs of the desired size. In this. way, the .amount incorporated therein may be more closely controlled and the moisture content may be maintained at any desired predetermined level by merely varying the relative amount of hygroscopic material used. Preferably, the moisture content is maintained at from 25 to by weight. Examples ofsuit- V able hygroscopic material which may be employed are organic materials such as glycerine, glycols and sugars, or inorganic materials such as calcium chloride, magnesium chloride and 45. sodium nitrate. The materials are preferably applied in solution in a suitable solvent such as, for example-water or ethyl alcohol. The hygroscopic materials may be employed in amounts varying from 15 to 50% on the weight of the 5 cellulose fiber sheet material, but more or less may be incorporated, as stated, depending upon the particulanmoisture content desired for the particular application of the cushion liner.

The film or toll employed for facing the cello-- I lose iiber cushion liner'm ay be a separate film The discs, when used alone, or

or toll cut to the desired size and then placed in osition, or the sheet material may be coated with a solution of a material in avolatile solvent which forms a film upon evaporation of said solvent. The film or foil over the face of the cushion liner prevents the liquid in the container from coming in contact with the cellulose fibers.

Examples of cellulose derivatives'which may be employed to form the films are cellulose esters such as cellulose acetate, cellulose ropionate and cellulose butyrate, mixed esters such as cellulose acetate-propionate and cellulose acetate-butyrate, inorganic esters; such as cellulose nitrate, and

. cellulose others, such as for example, ethyl cellulose and benzyl cellulose. Any suitable volatile solvent or mixture of solvents may be employed in forming a coating composition suitable for coating the sheet material used to form the cushion "liner. Solvents such as, for example, acetone, chloroform, ethylene dichloride, acetone and ethyl or methyl alcohol, ethyl alcohol,and ethylene dichloride and ethyl or methyl alcohol are suitable. j

The cellulose fiber cushion liner may be employed as a single layer of the desired thickness for'lining the metal closures, or the cushion liner may comprise a plurality of layers sumcient to build up a layer of the desired thickness. The layers may be held in position as by some binding material or else the layers may be held in the metal closure merely by the pressure exerted when the cap or shell is applied to a container.

In order further to illustrate our invention but withoutbeing limited thereto the following examples are given:

Example I Discs of suitable size are cut or punched from a compacted sheet of wood pulp cellulose of about closure of the cap type in register and faced with a cellulose acetate .fllm about 0.004 inch in thickness. The assembled closure is thenapplied to a bottle holding a carbonated beverage by means of a capping device. The sealed bottles are then subjected to a pasteurization treatment during which the internal pressure rises from the usual 35 pounds per square inch to 100 pounds per square. inch. Oncooling, the pressure returns to 35 pounds per square inch and remains there. The seal formed by the cellulose disc remains permanently tight and there is .no loss in pressure due to the escape of gas. I

Exam le II Wood-pulp cellulose discs of proportions similar to those of Example I are prepared, inserted into a bottle cap in register; and faced by an unplasticized cellulose acetate film 0.004 inch in thickness, the whole system being cemented to-- and the resulting seal remains tight to gas and liquid under the varying conditions of temperature and pressure during pasteurization as well as after.

It is to be understood that the foregoing detailed description is given merely by way or illustration and that many variations may bev made therein without departing from the spirit of our invention.

to of an organic hygroscopic material selected from the group consisting of glycerine and diethylene glycol, and a facing of a preformed 4 organic derivative of cellulose foil secured to said a material.

2. A resilient material adapted to be employed to form a pressure seal, comprising a compact material in sheet formhaving a basis of woodpulp cellulose fibers and having incorporated therein an aqueous solution containing from 15 to 50% of an organic hygroscopic material seiected from the group consisting of glycerine and dlethylene glycol, anda facing of a preformed cellulose acetate foil securedtosaid material.

3. A resilient material adapted to be employed to form a pressure seal, comprising a compact material in sheet form having a basis of, wood.-

pulp cellulose fibers and having incorporated therein an aqueous solution containing 50% of an organic hygroscopic materialselected from the group consisting of glycerine and diethylene lycol, and is facing of a preformed cellulose acetate foil secured to saidmaterial.

- GEORGE SCHNEIDER.