Non-fibrous regenerated cellulose film containing anchoring-plasticizing agent

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ANCHORING-PLASTICIZING AGENT Filed Jan. 27, 1959

HYDROPHOBIC TOPCOAT

CELLULOSE FILM CONTAINING AS ANCHORING-PLASTICIZING AGENT A WATER-SOLUBLE COMPOUND FROM GROUP OF AMIDES AND AMINES CONTAINING AT LEAST ONE HYDROPHOBIC SUBSTITUENT OF AT LEAST 6 CARBON ATOMS AND AT LEAST o LOWER ALKYLENEOXY GROUPS inventor.

ANTHONY J. GENTILE

CLEMMON PORTER

BY r

ATTORNEY

United States Patent Office Patented Apr. 18, 1961

2,980,554

NON-FIBROUS REGENERATED CELLULOSE FILM CONTAINING ANCHORING-PLASTICIZING AGENT

Anthony J. Gentile, Greenwich, and Clemmon Porter, Stamford, Conn., assignors to American Cyanamid Company, New York, N.Y., a corporation of Maine

Filed Jan. 27, 1959, Ser. No. 789,271

Claims. (CI. 117—76)

The present invention relates to non-fibrous regenerated cellulose film uniformly impregnated with a di- or polysubstituted water-soluble higher nitrogen-base compound as combined anchoring-plasticizing agent for subsequently applied topcoat material. The invention includes methods for applying the anchoring-plasticizing agent to the film and further includes the treated cellulose film with and without the topcoat.

Pure non-fibrous regenerated cellulose film (i.e., uncoated dry film containing no modifying or treating agent) is brittle and therefore has few practical uses. Such film is therefore usually impregnated with a humectant (e.g., glycerol) which acts as a plasticizer. The resulting film is valuable as a wrap. Such film, however, is permeable to water-vapor and is therefore not suitable for wrapping moisture-sensitive products and foods. It is known that cellulose film which contains glycerol as plasticizer can be rendered impervious to water by coating it with hydrophobic topcoat material. However, topcoat material tends to slough from such film in the presence of water, and to prevent this it is customary to pretreat the film with an anchoring agent (usually an aminealdehyde resin). In commercial practice the anchoring agent is dissolved in the glycerol bath and the film is thus impregnated with the two materials; together. The general process is disclosed in Pollard U.S. Patent No. 2,394,009 granted February 5, 1946.

One disadvantage of this process is that the anchoring agent is generally substantive to cellulose whereas the plasticizer is not, so that the two materials exhaust from the bath at different rates. The bath therefore requires periodic chemical analysis and the separate metering of two different agents.

The discovery has now been made that non-fibrous regenerated cellulose film containing a water-soluble compound from the group consisting of amides and amines containing at least 6 lower alkyleneoxy groups and at least one hydrophobic substituent of at least 6 carbon atoms are both plasticized and provided with a content of anchoring agent for subsequently applied hydrophobic topcoat material. The compounds have thus been found to serve a double purpose when present in cellulose film. The term “amides” includes thioureas, ureas, carbazides, and semi-carbizides. The term “amines includes amidines, guanidines, oximes, and ammonium quaternaries.

The invention possesses a number of substantial advantages.

(1) It permits one compound to be used in place or two, and thus permits elimination of the necessity for maintaining a balance between separately added plasticizing and anchoring agents in the film treating bath, and the handling of two different agents.

(2) The agents need not contain formaldehyde, and thus are comparatively odorless. The film of the pres- ent invention is thus particularly suited for wrapping foods of delicate flavor, such as cheese.

(3) Baths containing the agents do not deteriorate when used at elevated temperature, up to at least 60°-75° C. Moreover, the baths rapidly decrease in viscosity as they are heated. As a result, the agents are adapted for use in high-speed film-treating machines.

(4) The process of the present invention manipulatively is performed in customary manner, so that no new techniques need be learned.

According to the process of the present invention nonfibrous regenerated cellulose film is impregnated with an aqueous solution of one or more of the agents described below, withdrawn, and stripped of excess or free solution in any convenient way, after which the film, now containing the anchoring-plasticizing agent, may be dried and used, or topcoated with or without drying as dictated by the characteristics of the topcoating composition.

The agents of the present invention are generally effective over a wide pH range so that there is usually no need to control the pH of the bath within narrow limits. It is a feature of the invention, however, that the agents are effective in the range pH 6-pH 8, so that substantially neutral cellulose film can be produced. Such film does not undergo acid tendering and is consequently more dosira-blo

The bath may contain more than one of the agents of the present invention so long as they are generally mutually compatible. Incompatibility is evidenced by precipitation upon admixture. In addition the bath may contain other agents commonly used in the treatment of non-fibrous regenerated cellulose film: for example, one or more polyhydric alcohols to impart supplementary plasticization; one or more of the numerous known watersoluble cationic anchoring agents for non-fibrous regenerated cellulose film to impart supplementary anchoring properties; and agents to impart still other properties. Thus the bath may contain a methylolcarbamyl polyazaalkane resin of Jen et al. U.S. Patent No. 2,764,507, granted on September 25, 1956; a fire retardant mixture, for example diammonium phosphate and dicyandiamide as shown in Wooding et al. U.S. Patent No. 2,757,102, granted on July 13,1956; a dye; or a scent.

' Amongst those water-repellent topcoats which may be used are nitrocellulose, cellulose acetate, methyl cellulose, polyethylene, deacetylated chitin, rubber, chlorinated rubber, rubber hydrochloride, ethyl cellulose, butyl methacrylate, moisture-resistant lacquers, waxes such as * montan wax, beeswax, carnauba wax and other conventional film-forming waterproofing materials. The topcoat is not necessarily a continuous film, and may and often does consist of printed legends, revenue stamps, or decorative matter.

Such topcoat material is generally applied in the form of a solution in an organic solvent and in such event the film is dried to normal water content before application of the topcoat solution. If desired, the topcoat may be applied by fusing molten thermoplastic resin material thereover, for example molten polyethylene, in which case the. film is likewise dried beforehand. Where the topcoat is applied in the form of a latex or emulsion, however, this preliminary drying is not necessary. .

Laboratory tests so far have shown that a few percent ot a preferred anchor-bonding agent of the present invention imparts a noticeable amount of flexibility and a significant anchoring effect, so that evidently there is no amount however small which does not produce some useful result. The plasticization and anchoring effect imparted by each

2,980,564 increment of agent is pronounced when the agent is present in the film in the range of 5%-15% by weight. Thereafter the increase in plasticization and anchoring tends to level off and the upper economic limit is generally reached when the film contains 25%-3 5% by weight of agent. Our preferred concentration of agent m the film is accordingly between about 10% and 20%, based on the dry weight of the film, corresponding to the amount picked up by the film when impregnated to saturation with a solution containing 5% to 10% by weight of the agent.

The hydrophobic substituents present in the treating agents may be hydrocarbon substituents such as aryl, alkyl, aralkyl, and alkaryl groups containing more than 6 carbon atoms, or chloroalkyl, chloroaryl substituents, or ester substituents. _ One effect of the hydrophobic groups is to impart flexibility to the film, and better results, are obtained when the hydrophobic groups contain more than 12 carbon atoms.

The lower alkyleneoxy groups also present in the treat- 20 ing agents contain not more than 4 carbon atoms each and are such as are formed by condensation of a parent amide or amine with a lower alkylene oxide (e.g., ethylene oxide or propylene oxide) or with a lower chlorohydrin (e.g., epichlorohydrin). When the parent com- 25 pound is water-insoluble, the number of alkyleneoxy groups introduced should be sufficient to confer at least some water-solubility, for example 5%.

In this specification the term “water-soluble,” as applied to the treating agents of the present invention, in- 30 eludes agents which are self-dispersible in water forming cloudy colloidal solutions having the appearance of soap solutions, as well as agents which form clear solutions in water.

Anchor-plasticizing agents suitable for use in the present invention may be prepared by a variety of methods and the invention does not depend upon the particular method which is selected. Thus carboxamide-type agents may be prepared by reacting a higher fatty acid nitrogen2-hydroxyethylamide with sufficient alkylene oxide, at ⁴⁰least 6 mols, to produce solubility. An example of this is the reaction of N-2-hydroxyethyl stearamide with 20 mols of ethylene oxide. Amidine-type agents may be prepared by direct reaction of an alkylene oxide or epichlorohydrin upon a higher fatty guanamine, a melamine 45 which has been reacted with a higher fatty acid chloride, or a higher fatty acid substituted urea, thiourea, guanidine, biguanamide, biuret, or dicyandiamide.

A further class of suitable treating agents may be prepared by reacting an appropriately substituted sulfon- 50 amide with a lower alkylene oxide.

. Anchoring-plasticizing agents according to the invention can further be prepared from high molecular weight polymers. Thus agents having a polyalkylenepolyamine __________{_}__...

structure can be prepared by partially reacting polyethyl- 55 water and adjusting the pH to the value ^shown.^^Excent emmme with a higher fatty chloride or acid chloride and ~~ ·- ” — -· then reacting the resulting amine or amine-amide with ethylene oxide. Additional agents may be prepared by polymerizing a vinyl amide, for example acrylamide and ______ ____. _allu ., methacrylamide, alone or with a vinyl compound copoly- 60 tween water-white and light amber, merizable therewith, partially reacting the polymer with a higher fatty acid chloride and then further reacting with an alkylene oxide, and by reacting a heterocyclic amine, for example 2-dodecylpyridine with ethylene oxide in necessary amount.

Treating agents of the quaternary ammonium type may be prepared by reacting a quaternary ammonium compound containing the necessary hydrophobic substituent and a hydroxyl group with ethylene oxide. Thus p- ________________{U1 uuu}-_uuluui, _icgCu_aa hydroxyphenyl trimethyl ammonium chloride may be 70 cellulose film containing 16% by weight of glycerol reacted with ethylene oxide. Alternatively, a tertiary · — amine may be reacted under acid conditions with ethylene oxide. The ethylene oxide combines directly with the nitrogen atom thereby quaternarizing it. The prod- _______o___.____ _____ uct, starting from Ν,Ν-dimethylamine and using hydro- 75 plasticity and the rating of 4 was given to sheets which chloric acid as the catalyst, is dimethyloctadecyl hydroxy (polyoxyethyl) ammonium chloride.

We have successfully used agents containing 100 alkyleneoxy groups in each molecule so that there does not appear to be any maximum to the number thereof which may be present. In practice we prefer agents which contain more than 20 such groups per molecule. This number of groups generally avoids the danger of the presence of too few and appears to enhance or fortify the plasticizing action of the hydrophobic organic group or groups.

The anchoring agents which contain one or more aldehyde-reactive —NH— substituents may be reacted by known means with formaldehyde to yield metholated ¹ anchor-plasticizing agents which thermoset when heated at film drying temperatures. Film containing one or more of such modified agents is within the scope of the present invention.

The molecular weights of the treating agents, while ¹ considerable, need not be of polymeric magnitude and we have achieved very satisfactory plasticization and anchoring by the use of agents having molecular weights no greater than 600. On the other hand, laboratory evidence indicates that high molecular weight compounds are more permanent in the properties they impart since they display less tendency to migrate when the treated film is pressed against other material in which the agent is soluble. Our evidence indicates that treating agents having molecular weights in excess of 5000 are more permanent for this reason and, where permanence is of chief importance, such agents are therefore preferred.

The invention is illustrated by the drawing, which is a schematic vertical section of non-fibrous regenerated cellulose film containing an anchoring-plasticizing agent a water-soluble compound selected from the group consisting of the amides and amines containing at least one hydrophobic substituent of at least 6 carbon atoms and at least 6 lower alkyleneoxy groups. The film carries an optional hydrophobic topcoat.

The invention will be more particularly described by the examples which follow. These examples constitute specific embodiments of the invention and are not to be construed as limitations thereon.

Example 1

The manufacture and testing of non-fibrous regenerated cellulose film containing a variety of the anchoringplasticizing agents described above is illustrated by the following.

The agents were prepared by reacting a parent amine or amide, as shown in the table below, with 6 or more mols of an alkylene oxide.

A series of anchoring-plasticizing baths was prepared by dissolving the agents in laboratory demineralized as indicated in the table, dilute aqueous sodium hydroxide or hydrochloric acid was used for this adjustment. The baths, when viewed in bulk, ranged in appearance from clear to quite cloudy and their color ranged beSheets of wet swollen washed regenerated cellulose film were immersed in the baths for 5 minutes at room temperature, hung to allow excess bath liquid to drain off, clamped to wooden frames to prevent shrinkage, and 65 oven dried at 200° C. for 10 minutes. The sheets were then removed from the frames. They were water-clear, flexible and odorless.

The flexibility of the sheets was determined using as the reference standard a sheet of non-fibrous regenerated ----1 as plasticizer. The comparisons were made manually, a rating of 0 indicating no plasticization and a rating of 3 indicating plasticization equal to the glycerol standard. Ratings of 1 and 2 were given to sheets of intermediate

2,980,554 were better plasticized then the sample. The plasticity values obtained are shown in the table below.

At the same time, samples of the anchoring-plasticizing baths were aged for 96 hours at 20° C. and 60° C. The temperatures at which these solutions remained stable (as judged by the development of a precipitate) during this period are shown in the table below.

The films were then topcoated by dipping into a standard nitrocellulose topcoat lacquer solution prepared as described in U.S. Patent No. 2,394,009, drained, and oven-dried at 200° F. for the times shown in the table below, three minutes at that temperature being about the minimum necessary to dry the topcoat.

Strips were cut from the resulting topcoated films, all edges of the strips being freshly cut, and the strips immersed in water at 190° F. Resistance to sloughing was determined by rubbing the films which contained one of the anchoring resins every two to four minutes between the fingers and averaging the results.

Results are shown in the table below.

viscosities of these solutions were determined at 20° C.

and 60° C. Results are as follows:

Run No.

Parent Amine or Amide

Mols EtiOi React.

Vise, (cps.)

20° C. 60° O.

Percent Deer.

9..

16.

20.

21.

22.

25.

26.

Octadecylamine_____......

Stearoguanamine...--------Lauroguanamine____________

Lauroguanide...............

(Lauroguanyl) urea--------Octadecyldicyandiamide-... N,N-Dimethylstearamidopropylamine.

i Ethylene oxide.

230

84.5

2.594.0

395.0

558.0

464.6

491.0

498.5

297.5