US3183055A - Process of hardening cellulose paper board with certain alums and polyhydroxyl loweralkanols and products produced therefrom - Google Patents

Description

United States Patent 3,183,055 PROCESS OF HARDENING CELLULOSE PAPER BOARD WITH CERTAIN ALUMS AND POLYHY- DROXYL LOWER ALKANOLS AND PRODUCTS PRODUCED THEREFROM Leonard Mackles, 635 E. 14th St., New York, N.Y. No Drawing. Filed May 15, 1961, Ser. No. 116,227 6 Claims. (Cl. 8--116) This invention relates to a method for preparing a treated novel hardened paper board from untreated paper board as well as to the novel product obtained by the process.

There are innumerable patents and procedures for fireproofing, water-proofing, insect-proofing, coating, hardening, etc., paper and paper products to produce specifically desired results. Clearly the field is a crowded one wherein the room for improvement is usually a matter of degree of improvement over the prior art.

Less commonly are changes made in kind wherein a novel departure from prior art thinking and practice is revealed.

The specific improvement of this invention is an improvement over the prior art both in degree and in kind as will be described hereinafter.

A greatly desired result in the box board and allied fields is the preparation of corrugated paper board having about the crush strength of, for example, sheet steel. Were such a board possible, the packaging of mechandise and the shipping of it great distances would be done with great safety from damage due to the boxes being broken or mutilated by the rough handling normally associated with freight transportation.

Attempts have been made to harden corrugated paper board by the use of inorganic salts, for example, am- 3 monium alum Al (SO .(NH (SO ).24H O but the results have been unsatisfactory. Generally the alum is diluted with water and the paper board is immersed therein for a relatively short time by a dipping procedure. The results of such dipping gave erratic results probably due to the uneven absorption of the water relative to the absorption of the dissolved ammonium alum molecule by the paper at its planar surface and at the interface between the liquid solution and the atmosphere.

In any event the process is not commercially feasible because the water and the alum are not uniformly and consistently absorbed by the paper board in the ratio present in solution. The coated dried board instead of having a uniformly hard planar coating and thus yield uniform test readings had in fact a most non-uniform coating having areas of extreme hardness intermingled among areas of extreme weakness.

This problem of erratic results puzzled the art and the solution of it was urgent.

It is an object of this invention to provide a coat-hardened fibrous board having a uniformly hard coating chemically bonded to a fibrous cellulosic board.

'It is another object to provide a hardened corrugated paper board of exceptional strength.

It is a further object to provide a hardened coated paper board having increased resistence to fire.

It is another object to provide a commercially feasible method for producing a uniformly hardened fibrous board.

It is a further object to provide an inexpensive method for obtaining a superiorly hardened paper board.

These and still other objects of this invention will become apparent upon reading the following descriptive disclosure taken in conjunction with a plurality of illustrative examples, illustrating the wide versatility of the invent both as to its application to industry and as to the ingredients employed.

3,183,055 Patented May 11, 1965 According to this invention ammonium alum and potassium alum (Al SO .K SO 24H O are used to accomplish the desired result, in conjunction with the use of a polyalcohol compound. 7

According to this invention the use of polyalcohols, also called polyhydroxyalcohols, in lieu of water in preparing the ammonium alum or the potassium alum solution results in a process yielding rapid and stablized impregnation of the alum into the cellulosic fibrous material. The product obtained by this invention has a uniform hard coating thereon which is believed to be chemically bonded to the cellulosic molecules.

Contrary to the irregular surface of the dried paper board obtained when ammonium alum dissolved in water is used, the paper board obtained when a polyhydroxyl compound is used as the solvent to make the ammonium alum solution has a smooth glossy surface.

Moreover, the coating obtained on corrugated paper board when using the prior art aqueous solution of ammonium alum is relatively easily pried away from the paper base; but when, for example, a glycol or other polyhydroxyl alcohol is used as the solvent, the coating is strongly bonded to the cellulosic material in a chemical manner so that the coating is believed to be integral with the cellulose molecules constituting the surface of the paper board.

Moreover, because of the presence of the high molecular weight polyhydroxy alcohol unit in the coating absorbed on the paper surface, the hardened coating obtained by drying, yields an over-all product which is excessively resistent to fire. Clearly a high molecular weight high boiling liquid is a better fire retardant than the relative easily volatilized water molecules of the prior art products.

Furthermore, the use of glycols and other polyhydroxyl alcohols effects a rapid wetting of the cellulosic material. Besides, unlike the soggy and limp paper product obtained when a corrugated paper board sheet is dipped in an aqueous solution of alum for any prolonged time, the.

use of a polyhydroxyl alcohol as a solvent for the ammonium alum solution permits a long residence time or absorption time without producing a limp and soggy paperboard. In short, the water of an aqueous alum solution dissolves the aqueous adhesive used in the manufacture of conventional corrugated board. But the high molecular weight polyhydroxyl alcohol solvent do not appreciably dissolve the water soluble adhesives customarily used in making corrugated paper board.

Ammonium alum and potassium alum have high melting points, so that when molten alum solutions are employed the water of hydration is easily driven off and in the prior art it was often condensed and returned to the aqueous solution to keep the solution suitably thin or viscous, lest it become too thick for convenient dipping and absorption of coating by the paper stock being used.

However,-where high boiling point polyhydroxyl alcohols are used in place of water as the solvent, the danger of driving off the solvent at the high temperatures employed of F. to 210 are very small, so that less manual care need be applied to this process making it a relatively inexpensive self-regulating process.

Experience obtained in making many varities of hardened cellulosic paper board leads to the belief that the polyhydroxyl alcohol when used as a solvent is substituted I has its water molecules replaced in whole or in substan tial part by glycol molecules.

Moreover, when such an ammonium alum solution having glycol molecules in lieu of water molecules is heated to the temperatures employed in this invention, namely 180 F. to 210 F. and a cellulose containing board is dipped therein, it is believed that the hydroxyl group on the compounds react with the hydroxyl groups present in cellulose to form an ether-like linkage. Such chemical bonding is impossible where aqueous solutions of alum are employed.

In this invention a large number of polyhydroxyl alcohols are operable as solvents since they are miscible with the alum at the high temperatures employed. Thus ethylene glycol is operable and a preferred solvent. Similarly I also prefer to use propylene glycol and glycerol. Moreover, I have tried hexylene glycol, trimethylene glycol, triethylene glycol and diethylene glycol and found them to be operable. In short, there is a vast number of operable polyhydroxy alcohols which may be substituted for the water of hydration in ammonium alum and yield advantageous results in that a superior paper board product is obtained.

Two tests were performed on the paper stock used. The paper stock used was, (a) 350 Mullen Test double wall corrugated paper board and (b) 200 Mullen Test single wall corrugated paper board. Specimens of a rectangular shape having the dimensions of six inches by fourteen inches were used for a hardness test and for a crush test.

The hardness test consisted of placing the paper board on a pair of parallel disposed knife-like edges disposed 12 inches apart so that the board over-lapped each knife edge by one inch. A plurality of disc weights of four inches in diameter weighing five pounds each were assembled.

The untreated or blank 350 Mullen Test corrugated paper board broke on the application of fifty pounds of weights at the center area located between the two knife edges. In the case of the untreated or blank 200 Mullen Test single wall paper board the specimen broke, i.e. caved in, upon the application of thirty-five pounds of weight in its center.

Another test was made to see how the flutes stand upon the addition of the five pounds weight. This test was a crush test for testing the force necessary to crush the flutes of the above two types of corrugated paper board used.

In the case of the untreated 350 Mullen Test corrugated paper board, it was noted that with the paper board disposed on a flat horizontal surface a load of fifty pounds on a four inch diameter area sagged flutes fifty percent of their original height.

Where 200 Mullen Test single wall untreated paper board was used a load of fifty pounds on a four inch diameter center crushed the flutes substantially completely.

The following examples of this invention illustrates its wide variety and scope.

In all examples used herein, the test specimens of 350 Mullen double wall corrugated paper board and of 200 Mullen single wall paper board were six by fourteen inches in size. And all tests were performed at normal room temperature and humidity conditions.

Example 1 Nine parts by weight i.e. nine pounds of potassium alum and ten parts by weight i.e. ten pounds of ethylene glycol were poured into a container and the mixture was heated carefully to 190 F. to 195 F. A six inch by fourteen inch sheet of conventional 350 Mullen Test double wall corrugated paper board was immersed in this solution for a period of ten seconds after which it was removed and air dried at room temperature. This treated board was tested for its hardness using said five pounds disc weights such as are used in weight lifting devices. This board did not break even upon the application of two hundred pounds on a four inch area located at the center of the specimen.

Clearly a marked improvement over the untreated board that broke upon the application of a fifty pounds load is apparent.

A crush test was performed on this double wall board using the plurality of five pounds weights upon an above treated dried corrugated paper board and no visible sagging of the flutes was noted even upon the application of two hundred pounds of weight on a four inch diameter area. The untreated double wall board showed a fifty percent sagging of flutes with a load of fifty pounds.

Where 200 Mullen single wall paper board was immersed for five seconds in the potassium alum bath at to F. and then dried, the hardness test showed no break even after addition of five pound weights to a total of one hundred pounds. In this case the crush test showed no visible flute sagging even after the addition of weights to a total force of one hundred eighty-five pounds.

The treated potassium alum paper boards of both the 350 Mullen Test and of the 200 Mullen Test specimens were then subjected to flame tests to see if they would sustain a flame. Neither specimen sustained a flame.

The treated product for both the 350 Mullen Test and the 200 Mullen Test specimens were smoothly coated and had a stone hard surface.

Example II The procedure of Example I was repeated exactly as described therein but using 9 parts of ammonium alum in lieu of the nine parts of potassium alum to see what the effect would be. It was learned that the hardness test of the 350 Mullen double wall paper board obtained by the use of ammonium alum also did not break at the application of a two hundred pound load. In the case of the ammonium alum treated 200 Mullen Test single wall paper board a test for hardness showed no break even after one hundred pounds or weights were added.

In the crush test of the treated ammonium alum specimens, a 360 Mullen double wall specimen withstood a two hundred pound load without visible sign of crushing of flutes and the 200 Mullen single all specimen withstood a one hundred eighty-five pounds load without a sign of visible crushing. I

All the ammonium alum specimens also exhibited a smooth uniformly coated high gloss hard coating as in the case of the potassium alum-ethylene glycol mixture.

Example III The procedure of Example I was repeated but using a reflux condenser to return any Water of hydration which may have evaporated during the heating and dipping operation. It was noted that the treated double wall corrugated paper stock and the treated single wall corrugated paper stock gave substantially identical hardness and crush tests as when no provision is made to return the water of hydration to the container of the solution.

Accordingly it was believed that the return of the water of hydration associated with the alum was immaterial to obtain an improved product so long as a substantial amount of polyhydroxyl alcohol was present.

Example IV board hardness test showed no bending at the application of a one hundred pound load and the crush test showed no visible flute sageven on the application of a one hundred eighty-five pound load.

Example V The procedure of above Example IV using propylene glycol was repeated using nine parts of ammonium alum in place of the nine parts of potassium alum and using a thirty second immersion time in lieu of ten seconds. The results of this experiment were as follows:

The double wall corrugated specimen gave a hardness test of no bending even with a load of two hundred pounds.

The coated and air dried single wall corrugated paper board gave a hardness test of no bending even with a two hundred pound load and the single wall coated and dried paper board exhibited no bending even with a one hundred pound load. Also the crush test of the propylene glycol ammonium alum double wall coated corrugated specimen showed no visible flute sag upon the application of a two hundred pound load in the crush test. The single wall corrugated board treated with propylene glycol and ammonium alum showed no visible crush of flutes in the crush test even upon the addition of a one hundred eighty-five pound load.

The tests using nine parts of ammonium alum were repeated with one part hexylene glycol (molecular weight 118.18) for a ten second immersion time. The results with the coated double wall corrugated paper board were as follows:

No bending in the hardness test was noticeable upon applying a load of two hundred pounds. No crushing of flutes even with a two hundred pound load on a four inch diameter area, was observed.

Triethylene glycol (molecular weight 150.18) was then substituted for ethylene glycol in Example I.

The double wall corrugated paper board showed a noticeable sag in the hardness test.

Also the single wall corrugated paper board coated with nine parts ammonium alum using one part triethylene glycol onhardness testing showed a visible sag.

It was concluded that in the preparation of the hard coating of this invention, the lower molecular weight glycols and polyhydroxy alcohols were preferred and particularly propylene glycol and ethylene glycol.

This invention is of generic scope as to the time of immersion of the cellulosic material into the molten bath. The preferred range of immersion time is fromabout ten seconds to about forty seconds, but longer immersion times is operable and clearly where a longer immersion time is employed the amount of coating on the cellulosic material is greater. The operable temperature range is from about F. to about 210 F. but a range of about F. to about 210 F. is preferred and the optimum range desired is from about F. to 200 F.

This invention has been described by means of several embodiments but it is not limited thereto as the weight of the ingredients may be varied from the nine parts of alum to one part of polyhydroxyl alcohol to nine parts of alum (ammonium or potassium) to about one-half part polyhydroxyl alcohol or lessto about three parts said alcohol or more. The amount of polyhydroxy alcohol to be used is determined in part by the cost thereof since such alcohols are relatively expensive. Moreover mixtures of the polyhydroxyl alcohols are operable. Accordingly the scope of this invention is limited only by the claims herein.

I claim:

1. A process of preparing a hard coating on a cellulose paper board comprising preparing a molten mixture of about nine parts by weight of alum selected from the group consisting of ammonium alum and potassium alum with about one-half to about three parts by weight of solvent, low molecular weight, liquid, non-substituted,

polyhydroxyl lower alkanols, maintaining said molten mixture at a temperature between 170 F. to 210 F., immersing said paper board in said bath for about ten to about forty seconds time interval and thereafter removing and air drying said coated paper board to obtain a smooth alum coating bonded to said cellulose paper board.

2. The process of claim 1 wherein the temperature range 1 of the molten bath is from about 185 F. to about 210 3. The process of claim 2 wherein the time of immersion of said paper board is from about ten seconds to about thirty seconds.

4. The process of claim 1 wherein the polyhydroxyl alkanol is selected from the group consisting of ethylene glycol, propylene glycol and glycerol.

5. The product prepared by the process of claim 1.

6. The product prepared by the process of claim 4.

OTHER REFERENCES Chem. Abst., vol. 54, 1960, p. 18957 (b). Chem. Abst., vol. 54, 1960, p. 25822(a).

NORMAN G. TORCHIN, Primary Examiner.

Claims (1)

1. A PROCESS OF PREPARING A HARD COATING ON A CELLULOSE PAPER BOARD COMPRISING PREPARING A MOLTEN MIXTURE OF ABOUT NINE PARTS BY WEIGHT OF ALUM SELECTED FROM THE GROUP CONSISTING OF AMMONIUM ALUM AND POTASSIUM ALUM WITH ABOUT ONE-HALF TO ABOUT THREE PARTS BY WEIGHT OF SOLVENT, LOW MOLECULAR WEIGHT, LIQUID, NON-SUBSTITUTED, POLYHYDROXYL LOWER ALKNOLS, MAINTAINING SAID MOLTEN MIXTURE AT A TEMPERATURE BETWEEN 170*F. TO 210*F., IMMERSING SAID PAPER BOARD IN SAID BATH FOR ABOUT TEN TO ABOUT FORTY SECONDS TIME INTERVAL AND THEREAFTER REMOVING AND AIR DRYING SAID COATED PAPER BOARD TO OBTAIN A SMOOTH ALUM COATING BONDED TO SAID CELLULOSE PAPER BOARD.