US2768096A - Paper and paper-like materials having a remoistenable adhesive coating - Google Patents

Description

United States Patent Ofiice PAPER AND PAPER-LIKE MATERIALS HAVING A REMOISTENABLE ADHESIVE COATING Harry A. Toulmin, Jr., Dayton, Ohio, assignor to The Commonwealth Engineering Company of Ohio, Dayton, Ohio, a corporation of Ohio No Drawing. Application November 27, 1953, Serial No. 394,884

8 Claims. (Cl. 117-122) This invention relates to novel pregummed papers, and is more particularly concerned with pre-gummed papers which may be remoistened to develop latent adhesive properties.

Although, as will be understood, the invention is not limited thereto, it will be discussed in detail in connection with pre-gurnmed hanging papers having satisfactory slip characteristics and which, on remoistening, develop latent adhesive and bonding properties, that is hanging papers one side of which carries a coating of adhesive material that is normally substantially non-adhesive but that, on moistening with plain water or aqueous media, becomes adhesive permitting bonding of the paper to other materials such as plaster. Paper or paper articles carrying the potentially adhesive coating or film may be classified as pre-gummed articles, or pre-gummed paper. Wallpaper, poster paper, sealing paper and the like may be described as pre-gummed paper.

The provision of an acceptable pre-gummed hanging paper presents many dilficulties. Such papers would be of particular value for amateur use in the home because the average person is unskilled in hanging paper and is generally not successful in using wallpaper and the like as presently marketed, i. e., without a potentially adhesive coating and requiring the application of an adhesive to it immediately prior to use.

It is known that, to be acceptable, pre-gummed hanging paper must have both good slip characteristics and the capacity to bond strongly to the surface to which it is applied. While becoming adhesive when remoistened, it must also be sufiiciently resistant to atmospheric moisture to remain substantially dry and non-tacky until actually wet with moisture, so that the paper can be rolled up on itself and drawn off from the roll as needed. Once moistened to develop the latest adhesiveness, the paper must be capable of being slipped on a wall while in the remoistened condition so that, in hanging wallpaper for example, the person hanging the paper in the usual way, that is in the form of strips, can slip the newly added strip relatively of others, already in place, before it sets in the bonded condition, for accurate matching of patterns. In addition, after the latent adhesiveness is developed by wetting and the paper is hung and dried in place on a wall or the like, the bond should not be susceptible to loosening by the action of atmospheric moisture on the adhesive. A wholly satisfactory pre-gummed hanging paper having all of these properties and characteristics and meeting all of these requirements, and having the important advantage of low cost, has not been available heretofore. 7

One object of this invention is to provide novel, improved pre-gummed paper carrying a potentially adhesive relatively low-cost coating having the properties and characteristics set forth above and which satisfies the requirements for a commercially acceptable paper of this type.

Other objects and advantages of the invention will appear hereinafter.

2,768,096 Patented Oct. 23, 195

The objects of the invention are achieved by providing paper, for instance, hanging paper, with a coating of dextran or a dextran conversion product that, on remoistening, becomes adhesive and on drying in place on an appropriate surface, such as a wall, becomes and, under normal conditions remains, tightly bonded thereto.

The dextrans are high molecular Weight polysaccharides made up of anhydroglucopyranosidic units and characterized in that the linkages between the units are of both alpha-1,6 and non-aIpha-1,6 type, at least 50% of these linkages being, apparently, of the alpha-1,6 type.

A. striking feature of the deXtrans is the wide variations they exhibit with respect to their physical and structural properties including molecular weight, molecular structural repeating alpha-1,6 to non-alpha-1,6 linkages ratios, and water-sensitivity. As to the latter property, while the so-called native dextrans, being hydroxylbearing substances, are hydrophilic, some of the dextrans are readily soluble in water whereas others are difiicultly soluble in water, are initially swollen thereby and only ultimately, if at all, completely dissolved therein.

A Wide variety of dextrans may be used in practicing this invention which, as stated above, is not limited to the provision of hanging papers. The dextran used as latent or potential adhesive may have a molecular weight of 5000 to x10 as determined by light scattering measurements, a molecular structural repeating alphal,6 to non-alpha-l,6 linkages ratio of 1.9:1 to 30:1 and be soluble or substantially insoluble in water, depending on the use for which the pre-gummed paper product or article is intended.

The dextrans may be obtained by various methods. They may be synthesized from sucrose by enzyme action in the presence or substantial absence of bacteria. For example, an aqueous nutrient medium containing sucrose, particularly nitrogenous compounds and certain inorganic salts, may be inoculated with a culture of an appropriate microorganism such as those of the Leuconostoc meseitteroides and L. dextram'cum types, and incubated at the temperature most favorable to the growth of the microorganism until maximum dextran production is attained. This is synthesis of the dextran from sucrose by the so-called whole culture method, i. e., the synthesis is effected by enzyme action in the presence of the bacteria and cellular debris. Or the culture obtained by cultivating the Leuconostoc bacterium may be filtered to isolate the enzyme (dextransucrase) which occurs in the filtrate, the filtrate, usually after dilution to predetermined enzyme potency, may be mixed with an aqueous sucrose solution, and the mixture may be allowed to stand under controlled conditions of pH and temperature until the dextran is synthesized. The enzyme may be separated from the filtrate and used in powdered condition or in the form of an aqueous solution, usually the latter. This is dextran synthesis by enzyme action in the substantial absence of bacteria and cellular debris.

The dextran obtained initially by these procedures is so-called native dextran which normally has a very high average molecular weight, calculated to be in the millions. It may be precipitated from the medium in which it is synthesized by the addition of an organic liquid which is a non-solvent for the dextran. The nonsolvent, or precipitant, may be a Water-miscible aliphatic alcohol, e. g., methanol, ethanol or isopropanol, or a ketone such as acetone or dioxane. The precipitated dextran may be purified and dried to a substantially white mass which may be reduced to powdered condition for use in preparing the present adhesive composition.

Native or high molecular weight dextran may be hydrolyzed under acid or neutral conditions, or by enzyme action to a molecular weight lower than that of the native material. Thus clinica dextran has an average molecular weight of from 20,000 to 200,000. In clinical dextran production, when the desired molecular weight is obtained by hydrolysis or cleavage of the native material, it is usual to isolate the clinical product from the hydnolyzate by fractional precipitation according to which, by successive addition of increasing amounts of watermiscible alcohol or ketone, the highest molecular weight fraction is first thrown down and separated, and the desired or intermediate molecular fraction is then precipitated and recovered. This procedure leaves a supernatant containing dextran the average molecular weight of which is below the clinical range, and the supernatant is usually discarded as waste. The different dextran fractions may also be isolated from the hydrolyzate by fractional solution methods involving the use of the precipitant in conjunction with a dextran solvent, usually water. It may be noted, here, that when the dextran synthesis is effected by the action of the enzyme on sucrose in the absence of bacteria, it is possible to carry out the synthesis under conditions such as to favor the production of dextran of relatively low molecular weight in at least preponderant proportion. It is possible, therefore, as is now known, to obtain relatively low average molecular weight dextran by direct enzymatic synthesis from sucrose.

When dextran is synthesized from sucrose by enzyme action, in the presence or substantial absence of bacteria and cellular debris, the water-sensitivity of the native dextran obtained is influenced by the microorganism cultivated to obtain the culture, or enzyme isolatable therefrom, introduced into the sucrose-bearing medium in which the dextran is to be synthesized. Thus, native dextrans synthesized by the use of the microorganisms bearingthe following NRRL (Northern Regional Research Laboratories) classifications, or their enzymes, are quite readily soluble in Water: Leuconostoc mesenteroides 13-512, 13-1146, 13-119, and B-1196. These dextrans are, usually, smooth, lustrous, elastic gums which are quite readily soluble in water to give clear or substantially clear solutions.

The native dextrans from the microorganisms (or their enzymes) (NRRL) Leuconostoc mesenteroides B-742, 13-1191, B-l196, B1208, and 13-1216, and from Streptobacterium dextranicum 15-1254 are, generally speaking, rather rough, dull, non-elastic gums which may be regarded as relatively insoluble in water but which are water-swellable and go into solution in water under heating and stirring to give viscous solutions that are somewhat turgid.

A third group of native dextrans is represented by and includes those obtained from microorganisms (or their enzymes) bearing the NRRL classifications: Leuconostoc mesenteroides Bl120, B-ll44, 13-523, and Betabacterium vermiforme Bll39. T hese dextrans are generally more or less flocculent gums which are swellable by water but which are, for all practical purposes, substantially insoluble therein.

The adhesive composition may be prepared by mixing a sufiicient proportion of the selected dextran, preferably high molecular weight or native dextran, with water or an organic solvent which at least swells or partially solvates the dextran, to obtain a thick, viscous, non-running solution or soft paste which can be applied to the surface of a paper sheet, strip or preformed article in any conventional manner, as by brushing or by roller application.

Water-soluble dextrans may be used and may be applied in the form of thick, viscous, non-running aqueous solutions. Or, and often preferably, the difficultly watersoluble to substantially water-insoluble dextrans may be used. These may be mixed with water to a soft paste, if desired in the presence of suitable dispersing agents such as the commercially available Tweens and Spans (partial higher-fatty acid esters of polyhydric alcohols of the type of sorbitan mono-stearate and polyoxylethylene condensates of the polyhydric alcohol esters) or they may be mixed with solvents therefor to obtain soft workable pastes capable of being brushed on the paper. For example, the water-insoluble dextrans are soluble in aqueous alkaline solution, such as aqueous sodium hydroxide, and in such solvents'as morpholine, acylamides such as formamide and the lower monoand di-acylamides such as monoand di-methyl formamide, and these solvents may be used in making the viscous non-running solutions or pastes.

After the coating is applied to the paper and dried, the coated surface is substantially non-tacky. However, when the paper is to be used, remoistening of the coating with a controlled amount of water or swellant or a limited amount of solvent sufficient to effect a partial solvation of the dextran, will render the latter adhesive so that it can be bonded, with moderate pressure, to the surface to be decorated and/ or protected.

The paste can be prepared at room temperature or under heating to temperatures of 50 C. to C., with continued stirring until the mass is substantially homogeneous.

Being inherently hydrophilic, the dextrans have the advantage that when it is desired to remove wallpaper or the like bonded to the wall by dextran, the paper can be readily stripped off by moistening or wetting it with water whereby the dextran is swollen and the bond between it and the surface loosened to permit easy peeling of the paper.

The following examples, in which the parts are by weight, are given to illustrate specific embodiments of the invention, and it is to be understood that these examples are not intended to be limitative.

Example I About 30 parts of particulate native L. m. B-5l2 dextran are mixed with 70 parts of water at room temperature to obtain a soft paste. This paste is applied evenly and uniformly over a surface of a wallpaper raw stock, and dried to obtain a finished pre-gummed wallpaper which requires only moistening of the coated surface before being hung and bonded to the wall. It can he slipped, while the coating is in the moist state, on the wall surface for matching the pattern and on drying is firmly bonded to the wall without the persistence of bulges or blisters formed in the paper while the dextran coating is still in the moist, tacky condition.

Example 11 7 About 25 parts of particulate native L. m. B-523 dextran are mixed with parts of water at about 60 C. whereby the normally substantially water-insoluble dextran is swollen and forms a viscous mass or soft paste which is non-running but has sufficient fluidity for easy application by brushing. The paste is applied as an even, uniform coating to a surface of wallpaper raw stock, and dried. On remoistening with water, the dextran is again swollen and becomes adhesive. While the coating is in the remoistened condition, the paper can be hung, slid on the wall surface as required, and then allowed to dry thereon. It is adhesively bonded to the wall.

The pre-gummed papers carrying the dextran coating have a significant cost advantage over previously proposed pre-gurnmed papers. Whereas other gums have been chemically modified or pre-treated to render them suitable for this purpose, and the chemical modification necessarily adds to the cost of the adhesive and of the final coated paper, the high molecular weight dextrans such as the native dextrans obtained by enzymatic synthesis from sucrose may be used directly for preparing the pastes and are generally preferred.

Auxiliary agents may be mixed with the dry base adhesive comprising dextran, for special purposes, or such materials may be incorporated in the liquid used to remoisten the dextran coating. For instance, it may be desirable to disperse or dissolve in the adhesive or potentially adhesive base, or in the moistening liquid, plasticizing agents, or auxiliary agents which favorably influence the adhesive characteristics of the base. Illustratively, when the dextran paste, viscous solution or dispersion, is to be used in preparing pre-gummed hanging papers it may be desirable to include, as plasticizing agents, such normally solid materials as urea, thiourea, sodium nitrate, sodium thiocyanate, potassium thiocyanate, potassium nitrate, calcium chloride, magnesium chloride, and zinc chloride. Or plasticizing liquids of the type of glycerine, diethylene glycol, ethylene glycol, sodium lactate and others may be used. Additional plasticizers include sodium acetate, sodium chloride, sodium diacetate, sodium monophosphate, ammonium chloride and sugars. Viscosity increasing agents such as borax and sodium aluminate may also be included in the paste or soft, viscous solution or dispersion, as Well as various wetting agents, solvents and filling materials, to attain the special eifects or results for which it is conventional in the art to use those adjuvants. Small amounts of oil, grease of wax may be worked into the adhesive base.

When any of the foregoing or equivalent auxiliary agents are used, the amount thereof may vary but will usually be small, and not more than about 5% of the total solids content of the composition. If oil, grease or wax is used, proportions of 0.5% to 3.0% of the solids content will usually be satisfactory. The amount of any auxiliary substance used should be controlled and such that the coated surface of the base, after drying thereof, is in non-tacky condition.

Although the invention has been described in terms of hanging paper such as Wallpaper and poster paper, it will be evident that the invention is not limited thereto.

The adhesive dextran composition having remoistening characteristics may be applied to paper to be used for a variety of purposes. It may be applied to paper in strip form to be used for sealing paper containers and paper wrappings. The compositions, especially those in which non-aqueous liquids are used in the preparation thereof and for remoistening the coating, may be applied to paper-like products such as transparent sheeting, film or strip, e. g., of regenerated cellulose, to obtain products to be adhesively bonded to a base and including nonfibrous sealing tapes. It will be evident also that various paper articles, such as envelopes, stamps, Christmas and other types of package seals, mailing labels, etc. may be provided with a dextran coating to be rendered adhesive on remoistening. As is known, some of these articles are often remoistened by licking with the tongue. No unpleasant taste or other harm can ensue if this is done to an envelope, stamp or the like the adhesive coating of V which comprises dextran. The dextrans are bland, tasteless, odorless, non-toxic and non-irritating substances which are physiologically harmless and, in fact, edible.

The dextran-containing coating composition may comprise pigments, for instance mineral pigments such as china clay, calcium carbonate, satin white and the like, for specific purposes or uses of the composition.

Since numerous changes and modifications may be made in the details given, in practicing the invention, without departing from its spirit and scope, it will be understood that it is not intended to limit the invention except as defined in the appended claims.

What is claimed is:

1. Pre-gummed paper-like sheet material having a normally substantially non-tacky but potentially adhesive by moistening coating consisting essentially of dextran.

2. A pre-gummed hanging paper having a normally substantially non-tacky but potentially adhesive by moistening coating consisting essentially of dextran.

3. Pre-gummed wallpaper having a normally substantially non-tacky but potentially adhesive by moistening coating consisting essentially of dextran.

4. A pre-gummed paper product having a coating consisting essentially of a ditficultly water-soluble to substantially Water-insoluble but Water-swellable dextran, said coating being normally substantially non-tacky and rendered adhesive by moistening with aqueous media to swell the dextran.

5. A pre-gummed hanging paper having a coating consisting essentially of a ditficultly. water-soluble to substantially water-insoluble dextran, said coating being norm-ally substantially non-tacky and rendered adhesive by moistening with aqueous media to swell the dextran.

6. Pre-gummed wallpaper having a coating consisting essentially of a diliicultly water-soluble to substantially Water-insoluble dextran, said coating being normally substantially non-tacky and rendered adhesive by moistening with aqueous media to swell the dextran.

7. Strip sealing paper-like sheet material having a normally substantially non-tacky but potentially adhesive by moistening coating consisting essentially of dextran.

8. Strip sealing paper-like sheet material having a coating consisting essentially of a diflicultly water-soluble to substantially water-insoluble but water-swellable dextran, said coating being normally substantially non-tacky and rendered adhesive by moistening to swell the dextran.

References Cited in the file of this patent UNITED STATES PATENTS 2,183,736 Bauer Dec. 19, 1939 2,288,527 Humphner June 30, 1942 2,503,624 Luaces Apr. 11, 1950 2,674,584 Deniston Apr. 6, 1954

Claims (1)

1. PRE-GUMMED PAPER-LIKE SHEET MATERIAL HAVING A NORMALLY SUBSTANTIALLY NON-TACKY BUT POTENTIALLY ADHESIVE BY MOISTENING COATING CONSISTING ESSENTIALLY OF DEXTRAN.