US2367563A - Wrapping foe commodities - Google Patents

Description

Fatentecl Jan. 16, 1945 WRAPPING FOR COMMODITIES William H. Bryce, Memphis, Tenn. 1

No Drawing. Application August 7, 1941, Serial No. 405,882

3 Claims.

The present invention relates to wrappings of the type which have a high degree of transparency, high eificiency in moisture-vapor resistances, heat sealing qualities and which provide a more effective and attractive package, when used for wrapping commodities.

Paper, such as glassine made from stock of highly gelatinized fibers are suited for carrying out the present invention, but the physical properties as well as the visual characteristics of ordinary glassine papers should first be enhanced by highly plasticizing the same and yet the moisture content of such highly plasticized papers is greatly reduced during the coating operations and in time evaporates to such an extent that the desirable physical properties incorporated are somewhat reduced and therefore it is amongst the principal objects of the present invention to provide means for preserving highly plasticized papers whereby their improved physical and visual characteristics will be maintained.

Waxed Wrappers as hitherto used have provided an efiective moisture-resisting covering and are quite transparent, but to increase the moisture-resisting qualities of the papers for such wrappers the thickness of the wax film applied thereto must be increased and as the thickness of the wax film is increased the transparency of the wrapper is reduced and other desirable increased physical properties of the paper as well as the attractiveness of the wrapper are lost. In addition to improving the moisture-resisting qualities of papers it is also necessary that the same have vapor-resisting qualities when employed as wrappings for commodities and therefore it is an equally important object of the invention to provide a coating compound which will render papers for commodities more moisturevapor-proof tha if coated with paraffine without impairing the improved physical properties imparted thereto and yet increase the transparency of the papers and improve the attractiveness of the wrappers.

Another object of the present invention is to provide a coating compound which will melt and liquefy below the boiling point of water without requiring the use of any solvent, and which may be applied to a sheet of paper by running the same through a conventional waxing machine for retaining the improved physical properties and visual characteristics of the paper, rendering the same highly moisture-vapor-proof, and that the so treated paper will be flexible, nontacky and thermoplastic or adhesive.

Other objects of the invention will be in part obvious and in part pointed out in the following description whereby those skilled in the art can readily apprehend and make use of the same.

The invention may be practiced by using paper of the type known commercially as glassine paper made from stock which has been hydrated or gelatinized to the extent that there are practically no cellulose fibres, or only very short fibres,

left in the sheet. The customary method of manufacturing these papers upon a standard Fourdrinier paper making machine is followed and to enhance the physical properties or characteristics of the glassine paper it is highly plasticized by incorporating therein, during its manufacture, small percentages of Cerelose and glycerine as by running the sheet of paper partially dried but while still holding a considerable percentage of moisture through a size-press containing an aqueous solution of these materials. Cerelose as herein referred to is the trade name for anhydrous dextrose manufactured by the Corn Products Refining Co. The Cerelose improves the transparency, glossy surface, silver whiteness, flatness and grease-proof qualities or what may be termed the visual characteristics of the paper, while the glycerine serves as a plasticizer to give to the paper strength and pliability and more or less stretch and the degree of these characteristics in the finished paper can be controlled by varying the percentages of the ingredients and by diluting the solution more or less with water. The moisture retention content serves to increase the strength of the finished highly plasticized paper sheet.

The water retention of the sheet of paper at this stage should be between a minimum of 4.9 percent and a maximum of 25 percent.

For the impregnating bath a solution composed of 15 percent of glycerine, 15 percent of Cerelose and percent of water may be used in the size-press and the water retention content of the finished paper will be 4.9 percent. However, if very good plastic qualities are required, heavier solutions must be employed, but to obtain the maximum water retention content of the finished paper sheet of 25 percent the solution should contain 27 percent of glycerine, 2'7 percent of Cerelose and 46 percent of water. These highly plasticized sheets of glassine paper of this water retention may be waxed by running the same through a waxing machine to render the same waterproof and still more transparent. However, the conventional methods of waxing such highly plasticized papers will not preserve the materials impregnated therein or retain the moisture content of the same unless a very thick 111m of wax is applied which latter would not only reduce the transparency of the paper but would be undesirable in a wrapper for commodities.

A great many foods as well as other articles either give up their natural moisture to the surrounding atmosphere or absorb moisture from the atmosphereand are thereby altered from their natural or desired state by exposure to the atmosphere. Fresh articles of food, such as rolls, bread, pastry and the like which liberate water vapors-when wrapped in highly plasticized wax coated glassine papers, have the tendency to cause the surface of the wrapper to acquire a rough, mottled, crumpled or cockled appearance, as ifit had been rained upon and become dry again, because of the fact that ordinary waxed glassine papers are not moisture-vapor-proof enough or water-proof enough to retain their enhanced physical properties or characteristics.

I have found that by combining paraffin wax with a rubbery hydrocarbon material such as a polymerization product of isobutylene, the resulting compound produces an excellent coating for papers and particularly highly plasticized glassine papers, as not only the improved physical properties are preserved, but the visual characteristics are greatly improved, thereby now making it possible to produce a very attractive wrapper and one which is suitable for enclosing fresh foods and like commodities as it is moisture-vapor-proof.

Hereinafter, the term synthetic rubbery polymerized isobutylene will be used to cover this polymerized product.

This waxy compound should contain about 2 percent of the rubbery hydrocarbon material and when it is desirable to give to the coated papers additional heat sealing properties a thermoplastic rubber derivative may be added to the compound. A meltable wax-like compound containing approximately 2 pounds of the rubbery hydrocarbon material, 6 pounds of the rubber derivative (Pliolite) and 91 pounds of Wax is desirable for coating highly plasticized glassine papers.

The rubbery hydrocarbon material is a rubber hydrocarbon material produced by the polymerization of isobutylene at low temperatures in the presence of an inorganic halide catalyst. It is stretchable and sticky, but unlike natural rubber in that it does not oxidize easily nor does it react readily with sulphur. It has no odor and is nontoxic and is compatible with rubber and paraflin. This material is sold under the name Vistanex. When mixed with paraffin and a thermo-plastic rubber derivative it improves aging, ozone and oxygen resistance, improves resistance to vegetable oils and fats, and lessens permeability to gases and moisture, all of which properties are required in a. coating composition where a moisture-vapor-proof paper is required.

The rubber derivative suitable for this compound is a resinous product compound in powdered form and unmilled, known in the trade as "unmilled Pliolite and is the kind of product made in the primary stages of the process shown in Bruson U. S. Patent 1,846,247, and Gehman U. S. Patent 2,050,209.

Such products are resinous and can be made by treating natural rubber with halides, e. g. stannic chloride, antimony pentachloride, titanium tetrachloride, ferric chloride, etc., then treating with water, alcohol or acetone; or by treating natural rubber with hydrated chlorostannic acid. The

product is steam distilled, forming a whitish powder, this being used in its unmilled condition, in the present invention. The term "unmilled Pliolite" will hereinafter be used to cover this material.

In preparing my coating composition I first mix together one partof the synthetic rubbery polymerized isobutylene with three parts of paraflin wax producing a solid solution of one and the other. This blending or mixing is accomplished by milling with a conventional rubber compounding mill or a heavy duty dough mixer to prevent the paraflln wax from crystallizing in large plates or needles until a solid solution is produced containing 25 percent of the rubbery hydrocarbon material and percent of the paraflin wax. This mixture will be hereinafter referred to as a. rubbery wax product.

I next melt pounds of paraiiln wax by applying heat of about 200 F. While subjecting this molten wax to constant agitation I slowly add thereto 8 pounds of the above referred to rubbery wax product (i. e. synthetic rubbery polymerized isobutylene) and parafiine in solid solution. This mixture is then allowed to cool until it has a temperature of between and F. This molten mixture when so cooled and still being agitated has added thereto 6 /2 pounds of the unmilled condensation derivative of rubber i. e. unmilled Pliolite. This rubbery hydrocarbon material and derivative of rubber are like ordinary rubber when subjected to high temperatures in that they lose many of their desirable properties. By first milling the rubbery hydrocarbon material with wax until the rubbery wax product is formed and subsequently adding the same to the molten wax these materials will be properly blended together. After this mixture is allowed to cool somewhat (i. e. to between 140 and 165 F.), the rubber derivative unmilled Pliolite may be added without impairing any of the desirable properties of these rubber-like products and yet all of the ingredients will be homogeneously mixed together.

This compound may then be used as a coating for papers or it may be allowed to solidify and stored for future use. When using this compound it is only necessary to heat the same at temperatures where it will melt and liquefy without the use of any volatile solvent and the sheet of paper to be coated may be easily dipped therein or the meltable compound applied with any conventional waxing machine. It will be noted that no volatile solvents have been added to this mixture. The use of volatile solvents would be objectionable in this process, giving less desirable products. Also the temperatures required to melt and liquefy this compound are below that required for boiling water and accordingly the improved physical properties imparted to the paper will not be impaired in the coating of the same.

This coating compound when applied to highly plasticized glassine papers will preserve the improved physical properties thereof as the rubbery hydrocarbon material contained therein will, due to its sticky or adhesive nature, seal itself in and on the paper already impregnated with the aqueous solution of Cerelose and glycerine so as to retain the high moisture content of the papers and thereby lessen th permeability of the papers to gases and moisture and at the same time add strength and flexibility to the paper sheet. The wax will add to the moisture proofness of the paper and together with the rubbery aeemee hydrocarbon material add to the transparency of the paper. The rubber derivative will also add to the transparency of the paper, but is primarily included in the compound so as to give to the paper sheet better heat sealing qualities. Therefore, a sheet of highly plasticized glassine paper coated with my improved compound will be strong, flexible, moisture-vapor-proof, have heat sealing qualities and yet have visual characteristics which will render the same ideal as a Wrapping for commodities.

To preserve the improved physical properties and visual characteristics of highly plasticized glassine papers I preferably also coat the same with a composition consisting of paraffin wax and an unmilled resinous thermoplastic powder prepared by treating rubber with a halide of an amphoteric metal (i. e. the unmilled Pliolite) A composition containing 4 to 6 percent of the rubber derivative and between 94 and 96 percent of d parafiin wax is suitable for this purpose, and when these two ingredients are heated below the boiling point of Water readily blend together in all proportions and go into a thin solution without the use of any solvents whereby the paper to be coated may be clipped therein. After the coating is applied to the highly plasticized glassine papers the rubber derivative will seal the pores of the paper as to retain the moisture content thereof whereby the improved physical properties will be retained for a greater length of time, the visual characteristics of the paper improved and yet give to the wrapper the desirable heat sealing qualities. By retaining the moisture content of this highly plasticized paper and using a high percentage of paraffin wax, a highly moisturevapor-proof wrapping for commodities will be produced.

The percentages of the several ingredients used and the temperatures that control the same as herein referred to may be varied to produce a coating compound of a character as conditions or preference may require or dictate. Manifestly,

the wrapping as herein disclosed is capable of considerable modification and such modifications as come withi the scope of my claims, I consider within the spirit of my invention.

I claim:

1. A moisture-vapor-proof wrapper for commodities having heat sealing qualities which comprises a sheet of glassine paper treated with an aqueous solution of anhydrous dextrose and glycerine, coating the so treated paper with a melt containing a major amount of paraffin wax and minor amounts of synthetic rubbery polymerized isobutylene and unmilled thermoplastic rubber derivative prepared by the treatment of rubber with a halide of an amphoteric metal and said melt being applied in a molten state free from volatile solvents.

2. A process of treating plasticized glassine paper which comprises impregnating such paper with an aqueous solution containing anhydrous dextrose and glycerine to render the same highly plasticized, then waxing said highly plasticized paper with a molten mixture of parafiine wax, carrying therewith a synthetic rubbery polymerized isobutylene and unmilled powdered resinous reaction product of rubber and an amphoteric metal halide compound, free from volatile solvents, said mixture being applied at between F. and F.

3. The method of preparing a coating composition for paper which consists in melting parafiin wax and maintaining the temperature of the melted paralfin wax of about 200 F., subjecting said molten wax to constant agitation, slowly adding to said molten and agitated wax a synthetic rubbery polymerized isobutylene milled with parafiin wax in a solid solution, reducing the temperature of the mixed wax and synthetic rubbery polymerized isobutylene to between 140 F. and 165 F., heating unmilled thermoplastic resinous powder prepared by treating rubber with a halide of an amphoteric metal, finally adding the heated unmilled thermoplastic resinous powder to said latter mixture while under agitation and at said reduced temperature, all in the absence of added volatile solvents, the amount of said parafiin wax being in preponderating excess over the sum of the other components, and the amount of Pliolite being about three times greater than the amount of said polymerized isobutylene.

- WILLIAM H. BRYCE.