US2215848A - Preparation of pregummed hanging paper - Google Patents

Description

Sept. 24, 1940.

H. F. BAUER PREPARATION OF PREGUMMED HANGING PAPER Filed- April 19, 1959 INVENTOR.

1 Hana fiazzer, BY ATTORNEY.

Patented Se a hi4, 1940 UNITED STATES PREPARATION OF PREGULIMIED HANGING PAPER Hans F. Bauer, Chicago, 111., asslgnor to Stein,- Hall Manufacturing Company, Chicago, 111., a

corporation of Delaware Application April 19, 1939, Serial No. 268,780

Claims.

This invention relates to pregummed hanging papers, more particularly wall papers, poster papers, bill boardpapers and the like, having a .dried coating of adhesive thereon which requires only moistening to be applied to a wall or other surface.

Wall papers and other types of hanging papers, including poster papers and bill boardpapers, are ordinarily applied to a wall or other surface I by a paper hanger who makes up a paste and puts it onto the paper just before applying the paper to the wall or other surface. It has heretofore been proposed to make wall papers having a selfcontained adhesive, but these papers have gen.- erally been unsatisfactory because of the numerous problems involved. Thus, Lobdell, Reissue Patent Nd. 10,430 described a wall paper which is dry sized on its back and according to the patent may be hanged by moistening the sized surface and applying it to a wall. The sizing used is said to be dextrine, glue, paste or gums.

No practical or suitable pregummed hanging paper has ever resulted from the teaching of the Lobdell patent because the problem of making a pregummed hanging paper is not so simple that it may be done merely by adding an ordinary type of sizing material or glue to the back of the paper and drying it. A pregummed hanging paper such as a pregummed wall paper must have certain characteristics whichcannot be obtained withan ordinary adhesive. For instance, it must be flexible, non-curling and the adhesive must 7 not crack or chip ofi of the paper. The adhesive 35 must be spread uniformly on the paper and when applied to the wall must dry and shrink evenly so as to shrink out any blisters or bulges which form on the surface of the paper. In view of the numerous problems involved, little progres M has heretofore been made in the preparation of pregummed. hanging papers or more specifically, in the preparation of pregummed Wall papers.

.In my copending application, Serial No. 252,457, filed January 23, 1939 now matured into M U. S. Patent No. 2,183,532, which in turn is a continuation-impart of my application Serial No. 11.69360 filed October 11, 1937, I have described a new and improved type of pregummed hanging paper. The adhesive on said paper comprises a plurality of amylaceous substances of differing water absorptive capacities and a plasticizing agent having the property of increasing the fluidity of amylaceous dispersions.

One of the objects of the present invention is to provide an improved type of pregummed hanglltli after it is first applied to a surface.

ing paper without the necessity of using a plurality of amylaceous substances to form the dried coating on the back of the paper. Other objects of the invention will appear hereinafter.

It has now been found in accordance with the invention that a pregummed hanging paper may be made by using a specified type of degraded or modified amylaceous substance in forming the adhesive coating for the back of the paper. This degraded or modified amylaceous substance for the purpose of this invention should have a solubility within the range of about 5% to about 30% in water at F. and when mixed with proportions of water in the ratio of 10 parts of water to '1 part of amylaceous material should have a fluidity or viscosity characteristic within the range of 7 seconds to 200 seconds, as determined by the following test on a Stormer viscosimeter.

This test involves determining the number of seconds required for revolutions of the viscosimeter cup containing a given sample of material at 75 E, using a 100 gram weight. The sample of amylaceous material to be tested is made up by heating 1 part of said material in 10 parts of water to a temperature of F. until 25 a homogeneous dispersionis obtained, then cooling to 75 F. The viscosimeter cylinder used in testing the amylaceous substances hereinafter referred to required 2.8 seconds for 100 revolutions running free, using a 100 gram weight, and 5.9 seconds with water at 75 F. This test is herein referred to as the viscosity test for degraded amylaceous substances.

In practicing the invention, it has been found that amylaceous degradation products of the character described when dispersed with a plasticizing agent capable of increasing the fluidity of aqueous amylaceous dispersions are excellent adhesives for the manufacture of pregummed hanging papers. Pregummed hanging papers 40 made up with adhesive compositions of this type have sufficient adhesive power to adhere to plane surfaces when the adhesive coating is moistened.

At the same time they have excellent slip characteristics and may be moved from one point to 45 another after the dried coating of adhesive is remoistened while the adhesive is still wet and Furthermore, blisters, bulges, wrinkles and the like which sometimes form when a hanging paper such as a wall paper is applied in the wet state shrink out or disappear in pregummed hanging papers of the type herein described as the paper dries. Another important feature of the pregummed hanging papers made in accordance with this in- 5 vention is to be found in the fact that the dried adhesive coating does not tend to become tacky and cause the paper to stick together when rolled in the usual manner, nor does the adhesive coating tend to crack or cause the paper to curl when it is properly applied to the paper.

For the purpose of this invention, it is preferable that the total solid content of the adhesive before it is applied to the paper or other base material be such that not less than about 1 part of water and not more than about parts of water per part of solids is required to give a viscosity within the range of about 40 seconds to about 180 seconds at 75 F. using a 1000 gram weight in the above mentioned viscosity test instead of a 100 gram weight. This test is referred to herein as the adhesive composition viscosity test. By total solids content is meant the amylaceous material plus plasticizing agents and any other normally solid materials that may be employed.

The ratio of solids to water should preferably not be less than about 1:1 using an amylaceous degradation product of the type herein referred to, or otherwise the adhesive character of the coating will not be sufiicient upon remoistening to give the required slip characteristics. On the other hand, if the ratio of water to solids is greater than about 5:1, the amount of drying required in order to properly apply the adhesive to the paper or other material which is to be coated will normally be prohibitive.

Inthe coating operation the coating weight is always important because -it determines the amount of adhesive material actually on the paper. If this amount is too great, it may cause the adhesive to crack or check. If it is too small, the adhesive will not have the necessary strength to hold the paper on the wall or other surface to which it is applied. Generally speaking, for the purpose of this invention the amount of water required willpreferably be about 2 to 3 parts of Water per part of solids in order ,to apply the adhesive to the paper or other base material at a suitable or proper coating weight.

The plasticizing agent preferably employed in accordance with this invention in order to prepare the adhesive is a normally solid substance or a plurality of normally solid substances that exert a solubilizing influence on amylaceous materials. The term amylaceous materials is used herein to describe starch and starch degradation products. Degraded amylaceous materials or "amylaceous degradation products as the expressions are used herein, cover dextrinized starches and modified starches. A dextrinized starch is a starch which has been converted either in the wet or dry statein the'presence of an acid or an acid reacting substance. If converted in the dry state, it is referred to herein as a dry converted dextrinized starch. A modified starch is a starch which generally retains its starch structure but has been chemically treated or treated in some other manner, for example, by means of enzymes, so as to break down or modify this starch structure. For example, chlorinated starches and thin boiling starches may be called modified starches.

A raw or undegraded starch alone isv unsuitable for the purpose of this invention for several reasons, one of which is to be found in the fact that this type of starch requires too much water for the proper dispersion. On the other hand, certain types of starch degradationproducts, as, for

example, those containing relatively large amounts of dextrlne are also unsuitable for use alone in the preparation of pregummed hanging papers in accordance with this invention, largely due to the'fact that these products are too tacky when formed into a dried coating and then remoistened. The result is that a pregummed hanging paper made from such materials does not have the necessary slip characteristics.

The adhesive which is used in preparing the pregummed hanging material is prepared by dis-.

persing the ingredients, namely, the degraded amylaceous substance, plasticizing agents and any other auxiliary materials in a dispersion medium such as water in suflicient amount to give the mixture a fluidity corresponding to that mentioned above so that it may be suitably spread or coated upon the paper. The resultant composition is then applied to the paper by any suitable method of surface coating involving the use of a doctor blade or other means such as are well known to'those skilled in the coating art, and the paper is then dried or allowed to dry. The coating weight will vary depending upon the composition of the adhesive, the speed and method of applying, and also upon the type of material treated. With ordinary wall papers good results may be obtained by the use of 2 grams or less (e. g., say about 1.2 grams) of adhesive per square foot of wall paper, calculated on the weight of the dried adhesive coating. For some base materials, as low as 0.5 gram of dried adhesive per square foot may be used while for others it may be desirable to use as high as 5 grams per square foot. Relatively heavy papers, for example, on the order of 12 ounce papers or more, are preferred, but the invention is not limited in this respect, as anyone skilled in the coating art can vary the quantity of adhesive within relatively wide ranges to obtain an adhesive coating suited to the particular type of paper and to the use to which the paper is to be put.

Other features and advantages of the inven- Example 1 A starch conversion product was prepared by converting a high grade wheat starch for 1 hour at 280 F. This conversion was carried out in a substantially dry state, using 2%; lbs. of 18 B.

hydrochloric acid to 1000 lbs. of wheat starch.

The acid was diluted to 6 B. before being added to the wheat starch. After being converted 1' hour at 280 F. the conversion product was removed and was found to be 6.4% soluble in water at 75 F. This product when tested at 75 F. with 10 parts of water per part of said product on a Stormer viscosimeter. using a 100 gram weight in the manner previously described gave a viscosity test of 11 seconds in 100 revolutions of the viscosimeter cylinder. I

The conversion product thus prepared was These-ingredients were blended together dry and then mixed with the starch conversion product in the ratio of 35 lbs. to lbs. of the conversion product. The resultant blend was then blended with 1 parts .of water per part of blend and this mixture was heated to 185 F. until clear.

It was coated on the back, of wall paper in a thin film which was allowed to dry. Wall paper thus prepared was non-curling, non-cracking, flexible and the adhesive was non-tacky under ordinary atmospheric conditions. When this adhesive is moistened, the paper possesses excellent slip characteristics so that it will slide from one place to another after it has been applied to a wall and before the adhesive has dried substantially. At the same time, it possesses sufiicient retack power to hold it to the wall. Blisters,

, wrinkles and the like which sometimes form in the paper when it is applied readily shrink out when the paper dries on the wall.

In this example the amount of sodium acetate may be increased to 15% or decreased to 5%, the amount of urea being correspondingly decreased or increased.

Example II A wheat starch conversion product was prepared irom a lower grade wheat starch known as No. 25, the conversion conditions being otherwise the same as for the wheat starch conversion in Example I. This conversion product had a solubility of 2.6% in water at F. and a Stormer viscosity as determined in the manner previously described at,75" F., with a gram weight of 17.2 seconds in 100 revolutions of the cylinder. Sixty-five parts of this conversion product were blended with 35 parts of a plasticizing composition made up of 25 parts urea, 10 parts sodium acetate and 1% parts of 75% suli'onated castor oil. This blend was then mixed with 2 parts of water per part of blend and the mixture heated while stirring to F; until clear. The resultant compositionhad a.viscosity characteristic of 72 seconds as determined on a Stormer viscosimete'r at 75 F. using a 1000 gram weight for 100 revolutions of the cylinder.

This adhesive composition when applied to the back of wall paper to form a pregummed wall paper gave excellent results similar to those described in Example 1.

Example ill The procedure in this example was the same as in Example I except that the starch conversion product was made from a low grade wheat starch known as No.50. This conversion product had a solubility of 4.4i% at 75 F. and a Storrner viscosity'in 10 parts of water per part or said prodnot at 75 I 013 19 seconds using a 100 gram weight according to the test previously described.

A blend of 65 lbs. of this product with 35 lbs. of a plasticizing composition containing 25% urea, 10% sodium acetate and 1 of 75% sulfonated castor oil when mixed with 2%; parts of water per part of blend and heated to 185 F. until clear gave an excellent adhesive composition for the preparation of pregummed hanging paper. This adhesive composition at 75 it. using a 1000 gram weight with a Stormer vlscosimeter gave a fluidity or viscosity corresponding to '70 seconds for 100 revolutions of the viscosimeter cylinder.

Excellent results were obtained when this com- In Example I, the conversion product was obtained from practically 100% pure wheat starch from which substantially all of the gluten had been removed. In Example II, the conversion product was obtained from a somewhat lower grade of wheat starch, which in Example III a still lower grade of wheat starch was used containing gluten in dispersed form. According to the present example the material used as a starting material was wheat flour in which the gluten was rendered inert by the following conversions; This was convertedfor 1 hour with sodium bisulfite using about 2 lbs. of sodium bi-sulfite to 1200 lbs. of flour at a temperature of about 225 FL, then there was added 50 lbs. of boric acid and 3 lbs. of 18 B. hydrochloric acid diluted to 6 B. hydrochloric acid and the temperature was raised to 280 F. for 1%.; hours to 2 hours more. The conversion product obtained had a solubility within the range of 8% to 12% at about 75 F. and gave a Stormer viscosity test in 10 parts of water per part of said product when Example 17 A rice starch conversion product was prepared by adding to 1000 lbs. of rice 3 lbs. of 18 ne. hydrochloric acid which was diluted to 65 Beand converted at 280 F. for about 2%; hours. This conversion product had a solubility of 1% in water at about 75 F. and gave a Stormer viscosity test in 10 parts of water per part of conversion product of 29.5 seconds using a 100 gram weight according to the test procedure previously described.

This conversion product was blended with urea, sodium acetate and sulfonated castor oil in the proportions of- 65 parts conversion product, 25 parts urea, 10parts sodium acetate and 1% parts 75% sulionated castor oil and the blend mixed with water in proportions of .3 parts of water to 1 part. of blend and heated to 185 F. until clear. The resultant composition gave a viscosity test on a Stormer viscosimeter of 97 seconds using a 1000 gram weight for 100 revolutions of the cylinder at 75 F.

Excellent results were obtained in the preparation of pregummed hanging papers with this adhesive composition.

Example W scribed was about 23; seconds.

This conversion product was mixed with a plasticizing composition containing 25 parts urea, parts sodium acetate and 1%, parts of 75% sulfonated castor oil, the proportions of plasticizing agent to conversion product being 35 lbs. to

A rice starch conversion product was formed according to the general methods of Examples V and VI except that the time of conversion was 4% hours and the conversion product had a solubility of 9.2% at 75 F. with a viscosity-characteristic of 8.5 seconds when tested with 10 parts of water per part of conversion product on a Stormer viscosimeter at 75 F. in the manner previously described. This product was blended with a plasticizing composition made up of parts urea, 10 parts sodium acetate, and 1% parts of sulfonated castor oil, the proportions being such that the total blend consisted of 65% rice conversion product and of the plasticizing composition. This blend was then'mixed with 1 parts of water per part of blend and heated to 185 F. This composition showed a viscosity characteristic of 106 seconds as determined on a Stormer viscosimeter for 100 revolutions of the viscosimeter cylinder at F. using a 1000 gram weight.

Excellent results were obtained with this composition in the preparation of pregummed hanging papers of various types including wall paper, poster paper, bill board paper, etc.

Example VIII In this example the degraded amylaceous substance employed was a No. thin boiling starch, a type of starch well known in the trade, made by the wet conversion of com. This starch had a solubility in water at 75 F. of about 15% and a fluidity or viscosity characteristic of 10.5 seconds when tested on a Stormer viscosimeter in 10 parts of water per part of starch at 75 F. ac-

cording to the test previously given. Sixty-five lbs. of this starch were blended with 35 lbs. of a plasticizing composition made up of 25 parts urea, 10 parts sodium acetate and 1% parts sulfonated castor oil. This blend was then mixed with 1 parts water per part of blend and heated to 185 F. The resultant adhesive composition had a viscosity characteristic of 70 seconds when tested on a Stormer viscosimeter at 75 F. using a 1000 gram weight. Good results were obtained in the use of this composition for the preparation of pregummed wall paper.

Example IX A chlorinated starch sold under the trade name of Hercules and having a solubility of 1.8% in '.with others.

gave an adhesive composition which on cooling to 75 F. and testing in a Stormer viscosimeter had a fluidity or viscosity characteristic of 89 seconds for revolutions of the viscosimeter cylinder using a 1000 gram weight. Good resultswere obtained in the use of this composition "for the preparation of pregummed wall paper. 7

Example X I In this example, the conversion product was a corn starch conversion product having a solubility of about 4.2% and a Stormer viscosity characteristic of 16 seconds at 75 F. when tested with 10 parts of'water per part of conversion product according to the viscosity test for degraded amylaceous substances previously described. This conversion product was blended with a plasticizing composition to produce a blend containing 65% conversion product and 35% of the plasticizing composition. The plasticizing composition contained 25 parts urea, 10 parts sodium acetate and 1% parts 75% sulfonated castor oil. This blend was then mixed with 1% parts water per part of blend and heated to F. until clear. The resultant composition had a viscosity or a fluidity characteristic of 70 seconds when tested on a Stormer viscosimeter at 75 F. using a 1000 gram weight.

This product also is suitable for use in the preparation of pregummed hanging papers.

In a similar manner other types of degraded amylaceous substances may be employed for the preparation of pregummed hanging papers provided they fall within the general range of solubilities and viscosity previously mentioned. For example, a No. 75 thin boiling starch can be employed which has a solubility of about .8% in water at about 75 F. and a Stormer viscosity of about 193.5 seconds when tested in 10 parts of water per part of starch according to the test herein given using a100 gram weight. This starch degradation product starch represents approximately the starchiest type of material which can be used as the sole amylaceous substance in order to obtain suitable results for the purpose of the present invention. Thus, a number 60 thin boiling starch is too starchy in its nature and requires too much water in order to be practical for the purpose of this invention. On the other hand, certain types of dextrines having a solubility of say 75% to 80% or more contain too much dextrine and do not have the proper solubility and fluidity or viscosity characteristics for the preparation of a pregummed wall paper as provided by this invention. Thus, it will be seen that the invention is confined to a specific range of amylaceous degradation products. It will be understood of course that these. products may be blended with other types of amylaceous products or other materials than those specifically de-' scribed herein, but the advantage of the present invention is to be found mainly in the fact that it is no longer necessary to use a blend of amylaceous materials.

This invention is not limited to any particular type of amylaceous degradation product and the starchy materials from which these products are products which are particularly desirable are Among the starch degradation.

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the paper.

those derived from wheat and rice because these conversion products within the limits defined herein form softer pastes which do not tend to gell as distinguished, for example, from certain other grain starches, suchas corn, which can be tuber starches such as tapioca and potato withinthe defined limits can be used but are less desirable because the adhesives made from them are tackler than the grain starch degradation products. This tackiness is offset to a considerable extent by salts of aliphatic carboxylic acids such as sodium acetate which imparts slip to the adhesive.

It will be understood that variations may be made in the composition of the adhesive, in the method of applying the adhesive to the base .material and in the various types of base materials to which it is applied. Many wall papers are unsized or contain very little sizing, while poster papers and bill board papers are often highly sized and the type of adhesive within the range specified herein may vary depending upon the sizing and other factors related to the use of a particular base material.

The plasticizing agent employed is preferably a normally solid material which has the property of increasing the fluidity of dispersions of degraded amylaceous substances. Urea and alkali metal acetates both have this-property and in the examples the urea may be used without the allrali metal acetate, or vice versa, but the combination of both appears to give results which are more than merely additive. Furthermore, the combination of both together apparently tends to prevent curling of the paper. Urea is practically neutral in aqueous solution and sodium acetate in water ordinarily has a pH from "i to a so that neither compound is injurious to Urea and/or sodium acetate may be replaced at least in part by other substances which are not injurious to the paper and which have a solubilizing or dispersing action on starch degradation products, as, for example, the water soluble analogues and homologues of urea, in-

. eluding thiourea, other alkali metal acetates such fid as potassium acetate, other salts of aliphatic carboxylic acids such as sodium propionate and other propionates, and many other materials such, for example, as resorcinol, chloral hydrate, sodium salicylate, calcium chloride, zinc chloride, magnesium chloride, water soluble thiocyanates, including potassium thiocyanate, sodium thiocyanate and ammonium thiocyanate, and water soluble nitrates, including sodium nitrate, po-

tassium nitrate, ammonium nitrate and guanibisulfite or sodium hydrosulfite. Fillers may also be used to give body to the adhesive composition.

If either the urea or sodium acetate is omitted,

the proportion of the ingredient retained is preferably correspondingly increased. In addition to its advantages in preventing curling of the paper, sodium acetate also produced a clear film and tends to prevent crystallization of urea in the film so that,the final appearance of the paper is such that the adhesive is not the casual observer.

The amount of solubilizing or dispersing agent, as already indicated, should preferablybe such that the composition will spread evenly and umformly upon the addition of. about 1 to about 5 parts of water per part of blended solid ingredients. avoided because of a tendency to make the composition hygroscopic. This tendency is less marked with sodium acetate. Generally speaking, of the total solids content, a major portion should be formed by the amylaceous degradation product and the total amount of plasticizing composition should not. be greater than about 4.5% of the total solids. Thus, the total amount of urea and sodium acetate is preferably not greater than about 45% of the total solids preferably within the range of 20% to l5%. The minimum amount of sodium acetate is preferably about 5% and the maximum about 30% of the total solids. The minimum amount of urea is preferably about 5% and the maximum about 40% of the total solids.

In some instances it may be desirable to add an acid, preferably in amounts just sumcient to neutralize any ammonia which may be formed. For this purpose very small quantities of acid are required, being in the neighborhood of around 2% or less. Acids which are normally solid at ordinary temperatures are preferred, for example, citric acid, tartaric acid, malic acid, boric acid and the like. v

The sodium acetate employed may be granular or powdered sodium acetate, either 60%, 90% or anhydrous, the first mentioned being preferred. Sodium diacetate having available acetic acid of from 25% to 35% may also be used.

The mixing of the various ingredients of the adhesive compositions and-the temperature of heating may vary, but ordinarily it will be sufficient to heat the mixture within the range of about 140 F. to about 185 F. until a uniform homogeneous dispersion is obtained.

The expression water soluble urea as employed herein is intended to include and cover urea and its water soluble analogues and homologues, including thiourea, monomethyl urea, monoethyl urea, dimethyl urea and higher water soluble homologues or analogues which have the property of increasing the fluidity of aqueous amylaceous dispersions. The expression lower aliphatic carboxylic acid? is intended to cover members of the fatty acid series which are substantially soluble in water.

The pregummed hanging papers made in accordance with this invention upon being moistened have the desired slip characteristics for application to walls and other plane surfaces. This invention makes possible the preparation of pregummed hanging papers in a simpler manner than it has heretofore been possible to make such materials. At the,same time, this is accomplished while producing pregummed hanging readily visible to The presence of too much urea is to be 7 papers having all of the desirable characteristics It of freedom from tack and stickiness in the dry state, freedom from cracking, checking and curling. The amount of water present initially in the adhesive when it is applied to the paper is such that it does not tend to destroy the paper. Moreover, the adhesive is weakly acid, substantially neutral or mildly alkaline, and the in-' gredients thereof do not tend to injure the paper or the wall to which the paper is applied. The adhesive, furthermore, does not tend to lose its adhesive characteristics over long periods of time, that is to say, the adhesive retains its remoistening adhesive properties when a dried coating thereof is moistened with Water, even though the dried coating had been allowed to stand for a considerable length of time, as would be the case with wall papers or other wall coverings which are not sold immediately.

It will be understood that variations may be made in the composition of the adhesive and in the paper or other base material to which it is applied without departing from the invention, and that in carrying out the inventicn, other variations, modifications and equivalents may be employed. Thus, the base material, instead of being paper, may be a canvas wall covering, or a thin wooden panel, or some other type of fibrous wall covering in which proper slip characteristics of the adhesive are essential to match patterns.

Reference is hereby made to my co-pending application Serial No. 184,929, filed January 14,

v 1938, now matured into United States Patent No.

2,183,736, which covers certain new and improved adhesive compositions including some of the compositions which may be employed for making pregummed hanging papers, as set forth in my United States Patent No. 2,183,532, previ-' completely dextrinizedwheat starch having a solubility in water at 75 F. from about 1% to about 25% and a viscosity characteristic within the range of about 8 seconds to about 30 seconds as determined by the viscosity test for degraded amylaceous substances herein described, intimately dispersed with urea and sodium acetate, the dextrinized wheat starch forming a major part of the adhesive, the total amount of urea and sodium acetate being about to about 45% by weight of the total solids, the minimum and maximum" amounts of sodium acetate being about and about 30%, respectively, and the minimum and maximum amounts of ureabeing about 5% and 40%, respectively, on the basis .of the total solids, said adhesive also containing a small amount of sulfonated oil on the basis of the normally solid ingredients.

2. A pregummed wall paper having a dried coating of adhesive thereon formed from an incompletely dextrinized wheat starch having a solubility 'in water at 75 F. from about 1'%- to and a viscosity characteristic within the range of about 8 seconds to about seconds, as

' determined bythe viscosity test for degraded amylaceous substances herein described, intimately dispersed with urea and an alkali metal acetate, the dextrinized wheat starch forming a major part of the adhesive, the total amount of urea and alkali metal acetate being about 20% to 45% by weight of the total solids, the minimum and maximum amounts of alkali metal acetate being about 5% and about 30%, respectively, and the minimum and maximum amounts of urea being about 5% and about respectively, on the basis of total solids.

3. A pregummed hanging paper having a dried coating of adhesive thereon formed from an incompletely dextrinized wheat starch having a solubility in water at 75 F. from about 1% to about 25% and a viscosity characteristic within the range of about 8 seconds to about 30 seconds,

as determined by the viscosity test for degraded amylaceous substances herein described, intimately dispersed with a water soluble urea and an alkali metal acetate, the total amount of the urea and alkali metal acetate being not more than about by weight of the total solids, the minimum and maximum amounts of alkali metal acetate being about 5% and about 30%; respectively, and the minimum and maximum amounts of urea being about 5% and about 40%, respectively, on the basis of the total solids, said ingredients being present in such proportions that said adhesive coating when moistened possesses retack properties and slip characteristics permitting said material to slide after it has first been moistened and while the adhesive is still wet and after it is first applied to a surface. i

4. A pregummed wall covering having a dried coating of adhesive thereon formed from an incompletely dextrinized rice starch having a solubility in water at 75 F. from about 1% to about 25% and a viscosity characteristic within the range of about 8 seconds to 30 seconds, as determined by the viscosity test for degraded amylaceous substances herein described, intimately dispersed with a water soluble urea and an alkali metal acetate, the total amount of the urea and alkali metal acetate being about 20% to about 45% by weight of the total solids, the minimum and maximum amounts of alkali metal acetate being about 5% and about 30%, respectively, and the minimum and maximum amounts of the ureabeing about 5% and about 40%, respectively,

graded grain starch having a; solubility in water at 75 F. within the range of about .5% to about 30%, and a viscosity characteristic within the range of about 7 seconds to 200 seconds, as determined by the viscosity test fon'degraded amye laceous substances herein described, intimately dispersed with a water soluble urea and an alkali metal acetate, thetotal amount of the urea and the alkali metal acetate being not more than about 45% by weight of the total solids, the minimum and maximum amounts of alkali metal acetate being about 5%, and about 30%, respectively, and the minimum and maximum amounts of the urea being about 5% and about 40%, respectively, on the basis of the total solids, said ingredients being present in such proportions that said adhesive coating when moistened pos- I graded amylaceous substance having a solubility in water at 75 F. from about .5% to about 30% and a viscosity characteristic within the range of about 7 to about 200 seconds, as determined by the viscosity test for degraded amylaceous substance herein described, intimately dispersed with a water soluble urea and a soluble salt of a lower aliphatic carboxyllc acid, the total amount of the urea and said salt being not more than about 45% by weight of the total solids, the minimum and maximum amounts of said salt being about 5% and about 30%, respectively, and the minimum and maximum amounts of the urea being about 5% and about 40%, respectively, on the basis of total solids, said ingredients being present in such proportions that said adhesive coating when moistened possesses retack properties sufficient to hold said paper against a surface to which it is applied and slip characteristics permitting said material to slide against said surface while it is stll wet after it is first applied to said surface.

'7. A pregummed hanging paper having a dried coating of adhesive thereon formed from a degraded amylaceous substance having a solubility in water at 75 F. from about 5% to about 30% and a viscosity characteristic within the range of about 7 seconds to about 200 seconds, as determined by the viscosity test for degraded amylaceous substances herein described, intimately dispersed with a substantially neutral, normally solid compound of such character that it will not injure the paper and having a solubilizing action on said degraded amylaceous substance and an alkali metal acetate, said ingredients being present in such proportions that saidadhesive coating when moistened possesses retack properties and slip characteristics permitting said paper to slide while the adhesive is'still wet and after it is first applied to a surface. 8. A pregummed hanging paper having a dried coating of adhesive thereon formed from a degraded amylaceous substance having a solubility in water at 75 F. within the range of about .5% to about 30% and a viscosity characteristic within the range of about '7 seconds to about 200 seconds, as determined by the viscosity test for degraded amylaceous substances herein described, intimately associated with at least one normally solid compound of such character that it will not injure the paper and having a solubilizing action on degraded amylaceous substances, the proportions of said ingredients being such as to produce an adhesive coating which after being. dried is capable of being remoistened and possesses retack properties and slip characteristics permitting the paper to be moved after paper containing the adhesive has been moistened and first aplied to a plane surface while the adhesive is still wet.

9. A pregummed hanging material comprising a flexible sheet material having thereon a dried coating of an adhesive formed from a degraded amylaceous substance having a solubility in water at 75 F. from about .5% to about 30% and a viscosity characteristic within the range of about 7 seconds to about 200 seconds, as determined by the viscosity test for degraded amylaceous substances herein described, intimately dispersed and associated with at least one plasticizing agent which is noninjurious to the base material and has the property of increasing the fluidity of aqueous amylaceous compositions, said adhesive havingapH within the range -from about 5 to about 9, and said ingredients being present in such proportions that said adhesive coating when moistened possesses retack properties suilicient to cause the sheet material to adhere to a plane surface while permitting said material to slide on said surface while the adhesive is still wet after it is first applied.

10. A pregummed hanging material comprising a base material having thereon a dried coating of an adhesive formed from a degraded amylaceous substance having a solubility in water at 75 F. from about .5% to about 30% and a. viscosity characteristicwithin the range of 7 seconds to about 200 seconds as determined by the viscosity test for degraded amylaceous substances herein described, intimately dispersed and associated with at least one plasticizing agent which is non-injurious to the base material and has the property of increasing the fluidity of dispersions of degraded amylaceous substances, said ingredientsbeing present in such proportions that said adhesive coating when moistened possesses retack properties and slip characteristics permitting said material to slide while the adhesive is still wet after it is first applied to a surface.

HANS F. BAUER.

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