US2159108A - Cellulosic material and process for preparing same - Google Patents

Description

Patented May 23, 1939 CELLULOSIO MATERIAL AND PROCESS FOR PREPARING SAME Ambrose W. Staudt, Kenmore, N. Y., assignor, by mesne assignments, to E. L du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application March 23. 1936, Serial No. 70,401

11 Claims.

This invention relates to the application of labels to various articles and more particularly to a method of afiixing the usual gummed labels to thin sheets or films suitable for use as wrapping tissues, including cellulose derivative films such as those of cellulose acetate, cellulose nitrate, cellulose ethers, or the like.

Labels are aflixed to articles and packages of all kinds for various reasons. The usual labels are treated with an adhesive such as glue, dextrine and the like, of such a character that when they are to be afflxed to an article it is only necessary to moisten the adhesive surface and apply the label to the article. The usual labels are provided with an adhesive which is of a water soluble type, or one which is capable of becoming energized by the application of water. With the advent of cellulose derivative wrapping tissues, such as those of cellulose acetate, it has been impossible to afilx the usual gummed labels to such wrapping tissues, in the sealing, closing, labelling or the like of packages wrapped therein because the water energized adhesive will not stick to the cellulose derivative and a firmand useful bond cannot be obtained. Of course, a special gumming composition might be applied to the label which could be energized by some material which would simultaneously modify thecellulose derivative wrapping tissue and enable a firm bond to be obtained. This would require, however, that a separate supply of labels be on hand for each type of cellulose derivative wrapping tissue and the label manufacturer would be put to the serious inconvenience of having to carry a stock of labels provided with a variety of adhesives, depending on the requirements of a large number of customers. The present invention provides means whereby labels gummed with the usual, water energizable adhesives can be firmly and permanently afiixed to cellulose derivative wrapping tissues.

It has been proposed previously (Snyder United States 1,815,365) to ailix gummed labels of the usual type to articles made from or having a coating including a cellulose derivative, such as cellulose acetate, cellulose nitrate, cellulose ethers or the like, by moistening the gummed label with a liquid composition comprising in its preferred form a material capable of rendering the adhesive on the label tacky and also a solvent or softener for the cellulose derivative. Thus, a solution comprising a mixture of water and ethylene glycol monomethyl ether might be used.

The moistening solution described by Snyder is particularly useful in the aflixing of gummedlabels to regenerated cellulose film coated with cellulose derivative compositions because the solvent in the moistening solution modifies only the cellulose derivative coating and the regenerated cellulose base is capable of maintaining the integrity of thefilm until after the solvent has evaporated. In the application of gummed labels to self-sustaining films of cellulose derivatives and particularly those which are sufliciently thin to serve as wrapping tissues, considerable care must be taken to avoid such an attack on the cellulose derivative by the solvent in that the film will be distorted, wrinkled or even .completely destroyed.

The present invention provides an improved moistening solution and an improved method for aflixing gummed labels to self-sustaining sheets or films of cellulose derivatives, particularly cellulose acetate, which are suitable for use as wrapping tissues.

It is therefore an object of this invention to provide an improved method of affixing gummed labels to cellulose derivative wrapping tissue, the bond between the label and the wrapping tissue being strong and permanent and effected without curling, wrinkling, buckling or destruction of the wrapping tissue involved.

Generally speaking, the objects of the invention are accomplished by means of a moistening solution comprising a cellulose derivative, 9. softener for the label gumming material and a solvent or mixture of solvents, with or without a plasticizer for the cellulose derivative, and preferably though not necessarily containing an appreciable quantity of water. In its preferred embodiment the invention contemplates the use of a moistening solution comprising a cellulose derivative in minor proportion, a plasticizer for that cellulose derivative also in minor proportion, and a-softener for the label gumming material in major proportion dissolved in a solvent or mixture of solvents containing up to 40% water.

The cellulose derivative and the softener for the label gumming material are essential in these moistening solutions for the development of a firm, permanentbond between the label and the cellulose derivative material which is used as the wrapper. The preferred modification of the moistening solution includes water in the solvent mixture since by the presence of water, it is possible to secure a quick, initial tackiness so that the labels can be made to adhere immediately after moistening without being held in place while the solvents are permitted to dry.

The cellulose derivatives which are useful in the practice of this invention includes cellulose acetate, cellulose nitrate, cellulose propionate, cellulose butyrate, cellulose aceto-propionate, ethyl cellulose, benzyl cellulose or other cellulose esters or ethers. When using cellulose acetate, an acetone soluble variety having a very low viscosity is preferable. This material usually contains between 42 and 58% combined acetic acid and the viscosity may be made quite low by any of the methods known to the art, either by the direct production of a low viscosity cellulose acetate or by reduction of the viscosity of a previously prepared, dried cellulose acetate flake. A low viscosity cellulose acetate obtained by the treatment of cellulose acetate flake with dry hydrochloric acid gas as described in Reid United States Patent No. 1,874,350 has been used successfully in the practice of the present invention.

Those cellulose derivatives which exhibit a fairly high tolerance for water are particularly useful in the practice of the invention inasmuch as the preferred moistening solutions contain fairly large proportions of water. Thus, cellulose acetate with a low acetyl content has a greater tolerance for water in acetone-water mixtures than does a highly acetylated product, so that it is particularly adaptable to the preparation of moistening solutions containing a high percentage of water in the solvent mixture and by-means of which good initial tackiness can be secured. When nitrocellulose is used, it is preferable to employ the ethyl alcohol soluble type or other low viscosity types possessing a high tolerance for water. The low viscosity solutions are preferred inasmuch as they lend themselves much more readily to use in standard equipment which generally involves application of a moistening solution by means of wicks or brushes.

The softener for the label gumming material is chosen from among such substances as glycerol,

ethylene glycol, monoethylin (glycerol monoethyl ether), mono-acetln (glycerol mono-acetic acid ester), acetamide, heptyl alcohol, glycerol monolactate,polyglycerols,polyglycols and the like. The softener is usually one which will cause the gum to remain soft and prevent it from shrinking too much after the water or other solvent has evaporated. Generally, a rather high proportion of this ingredient is essential in affixing labels to thin sheets of cellulose acetate, for example, in order to avoid as much as possible any wrinkling or distortion which would mar the appearance of the package. Preferably, a softener will be chosen, which in addition to being a softener for the gumming material on the label will also tend to have a softening or plasticizing effect on the cellulose derivative sheet material. Monoethylin and mono-acetin are good examples of such compounds.

Mention has been made of the alternative use of a cellulose derivative plasticlzer to plasticize the cellulose derivative in the moistening solution. Where such a plasticizer is desired, its choice will depend-largely on the cellulose derivative and the following substances may be used singly or in combination with themselves or other cellulose derivative plasticizers:

The solvents used in the preparation of these moistening solutions should be chosen so as to produce clear, low viscosity solutions. They should be highly volatile so that they will dry out of the joint quickly after the moistened label has been aflixed to the desired surface. The solvents or solvent mixture should be of such nature that they will not cause excessive wrinkling, shrinkage or other distortion of the cellulose derivative wrapping tissue to which the label is afllxed. Representative solvents are disclosed in the accompanying, illustrative examples.

As mentioned above, it is preferable to employ water in the solvent mixtures and as much as 40% water can be used, depending on the type of cellulose derivative and the choice of organic "solvents. In some instances more than 40% water can be employed; Although the water is not essential for the permanent bonding of the labels to the cellulose derivative surface, it is preferred a for the development of quick, initial tackiness of the label gumming material so that the labels will adhere to the surface immediately after being placed thereon and will not require need for holding them in position until the solvents have dried. Usually, the water also tends to decrease the activity of the solvents towards the cellulose derivative sheet material and thus assists in avoiding undue wrinkling, shrinkage or other distortion of the sheet.

It is also preferred that the water he used in an amount which will dissolve in the organic solvents present since the preferred moistening compositions, including those of the examples given .below, are homogeneous mixtures or solutions.

The following specific examples are illustrative of typical moistening solutions, prepared in accordance with the present invention. By means of these moistening solutions labels gummed with the usual adhesives such as gelatin, dextrin, fish glue, acacia gum or the like may be firmly and permanently ailixed to thin sheets of cellulose derivatives, such as cellulose acetate wrapping tissue.

Example I Per cent Cellulose acetate (low viscosity) 4 Methoxyethyl phthalate 4 Monoethylin 30 Acetone- 46 Water '16 Example II Per cent Toluol Water Example III Per cent Cellulose acetate (containing 44% combined acetic acid, low viscosity type) 2 Triacetin Glycerol Ar-efnne Example IV Per cent Nitrocellulose (low viscosity ethyl alcohol soluble type) Diethyl phthalate 2 Monoacetin 10 Ethyl alcohol 68 Toluol 8 Water 10 Example V Per cent Cellulose acetate (containing 44% combined '(Note: The alcohol of this example contained about 10% acetone.)

In practicing the invention the gumming material on the gummed label is moistened with a moistening solution, whereupon the label is applied to the sheet of cellulose derivative wrapping tissue and the solvents are permitted to evaporate either by air drying or forced drying, such as by the application of heat. Suflicient pressure is usually employed to hold the label against the surface of the wrapping tissue.

Moistening solutions prepared in accordance with this invention are non-viscous and nonstringing, so that they may be applied to the gummed label quickly and easily by hand or machine operation. These solutions and the constituents thereof may be removed from the hands of operators or machine parts simply by washing with water. The-moistening solutions yield residues which are odorless after drying and when dry, the non-volatile constituents of the solutions are transparent, so that transparent gummed labels may be aflixed without obliterating printed matter or decorative designs that may be under or on the sheeting to which the label is amxed.

The invention has been described in connection with the application of gummed labels to cellulose acetate wrapping tissue. It will be understood, however, that these moistening solutions can be used equally well to aflix gummed labels to thin sheets of nitrocellulose or other cellulose derivative sheeting, to transparent sheet-,

ing or other objects coated with cellulose acetate, cellulose nitrate or other cellulose derivative lacquers including those cellulose derivative lacquers which contain wax or other moistureprooflng agent and likewise to cellulose derivative plastic or molded objects. Gummed labels moistened with these solutions and affixed to a cellulose derivative sheet, object or coating may be used for labelling to identify or advertise by means of printed or written message or notation on the labels, or they may be used to close the package by holding the folded ends or edges of the cellulose derivative wrapping tissue or the cellulose derivative coated sheeting. The labels may be of paper, cloth or any other materials commonly 'used for labelling, instructing or sealing pack- .ages.

Parts and proportions given above are parts and proportions by weight unless otherwise specified.

As many widely different embodiments of the invention are possible, the invention is not to be limited to the above specific description and examples except as indicated in the claims.

I claim:

1. An article comprising, in combination, a body having a surface consisting of a cellulose derivative, a body having a surface consisting of a water-energizable adhesive, said two surfaces of said bodies bonded to each other by means of an agent therebetween, said agent comprising, as the sole adhesion-inducing ingredients, a cellulose derivative and a softener for said water-energizable adhesive.

2. An article comprising, in combination, a thin flexible sheet having a surface consisting of a cellulose derivative, a label having a surface consisting of a water-energizable adhesive, said two surfaces of said two elements bonded to each other by means of an agent therebetween, said agent comprising, as the sole adhesion-inducing ingredients, a cellulose derivative and a softener for said water-energizable adhesive.

3. An article comprising, in combination, a thin, flexible, cellulose derivative sheet, a label having a surface'consisting of a water-energizable adhesive, said surface of said label bonded to said cellulose derivative sheet by means of an agent therebetween, said agent comprising, as the sole adhesion-inducing ingredients, a cellulose derivative and a softener for said water-energizable adhesive.

4. An article comprising, in combination, a thin, flexible, cellulose acetate sheet, a label having a surface consisting of a water-energizable adhesive, said surface of said label bonded to said cellulose acetate sheet by means of an agent therebetween, said agent comprising, as the sole adhesion-inducing ingredients, a cellulose derivative and a softener for said water-energizable adhesive.

5. The method of aiiixing to a cellulose derivative surface of a body a water-energizable adhesive surface of a second body which comprises applying between said cellulose derivative surface and said adhesive surface of said two bodies a liquid composition containing in solution, as the sole adhesion-inducing ingredients, a cellulose derivative and a softener for said adhesive.

6. The method of affixing to a cellulose derivative surface of a thin flexible sheet a water-energizable adhesive surface of a label which comprises applying between said cellulose derivative.

surface and said adhesive surface of said two elements a liquid composition containing in solution, as the sole adhesion-inducing ingredients, a cellulose derivative and a softener for said adhesive.

7. The method of aflixing to a cellulose derivative surface of a thin flexible sheet a water-energizable adhesive surface of a label which comprises applying between said cellulose derivative surface and said adhesive surface of said two elements a liquid composition containing in solution, a cellulose derivative, a plasticizer for said derivative, a softener for said adhesive. and water; said cellulose derivative and said softener being the sole adhesion-inducing ingredients of said composition.

8. The method of affixing to a thin, flexible, cellulose derivative sheet. a water-energizable adhesive surface of a label which com rises applying between said water-energizable adhesive surface of said label and said sheet a liquid composition containing a cellulose derivative. a plasticizer for said derivative, a softener for said adhesive, and water, said cellulose derivative and said softener being the sole adhesion-inducing ingradients of said composition.

9. A composition suitable for adhering the cellulose derivative surface of a body to the waterenergizable adhesive surface of a second body, said composition comprising a cellulose derivative, a solvent for said cellulose derivative, and a softener for said water-energizable adhesive, said cellulose derivative and said softener being the sole adhesion-inducing ingredients of said composition.

10. A composition suitable for adhering the cellulose derivative surface of a body to the waterenergizable adhesive surface of a second body, said composition comprising a cellulose derivative, a solvent and a plasticizer for said cellulose derivative, a softener for said water-energizable adhesive and water, said cellulose derivative and said softener being the sole adhesion-inducing ingredients of said composition.

11. A composition suitable for adhering the cellulose derivative surface of a body to the waterenergizable adhesive surface of a second body, said composition comprising a homogeneous mixture containing a cellulose derivative, a solvent and a, plasticizer for. said cellulose derivative, a softener for said water-energizable adhesive and water, said cellulose derivative and said softener being the sole adhesion-inducing ingredients of said composition.

AMBROSE W. STAUDT.