US2553154A - Method of waterproofing and flameproofing paper - Google Patents

Description

y 2 wm P A P G N T. F O 0 on m L F D N A G N T.. F O O R D.. R E T A W F 0 D 0 un T E M May 15, 1951 E. volGTMAN ETAL 2 Sheets-Sheet 1 Filed Oct. 3, 1945 o o C U QN o ROLQMM May 15, v1951 E. H. volGTMAN ET Al. 2,553,154

METHOD 0F WATERPROOF'ING AND FLAMEPROOFING PAPER Filed 0G12. 3, 1945 2 Sheets-Sheet 2 cAuST/c f Z PROTE/N ASPHALT AMMON/UM OLEATE WA TER STEAM HOT PROTE/N ASPHALT PREPARAT/ON TANK TANK STEAM JOD/UM ASPHALT EMULS/FWN@ PENTAc//Lmcf/gm TANK PAPER 3552A/ EMULS/ON PR//VTER AMMON/UM slE- D/LUT/NG WATER TANKS F/RST /MPREGNA T/NG BA T// SALT PREPARAT/ON PRESS SECT/ON STEAM TANK l GU/DE ROLL PACOL WAX l SECOND WAX E RDATH 5r SALT L MPREGNATNG STORAGE M/X/NG BATH TANK PRESS ROLL l` CREP/N6 DRYER CREP/NG DOCTOR CONVEYOR BELT l cAN DRYER SECT/ON W/NDER jazz/Mx atentecl May 175, 1951 UNTED METHOD F WATRPROFING AND FLAMEPROFING PAPER Edward Hugo Voigtman and John Calvin Bletzinger, Neenah, Wis., assignors to Paper Patents Company, Neenah Wisconsin Wis., a corporation of Application October 3, 1945, Serial No. 619,976

Claims. 1

The invention relates to industrial paper and process of making same and relates particularly to the manufacture of a type of paper which may be used for various industrial purposes, for example as a facing sheet for blanket insulation, or for any other purpose Where there is need a paper Which is relatively strong and flexible and which, at the same time, has substantial Water-resistant and flame inhibiting or reresistant properties. For example, a sheet of the general character herein referred to can lbe employed to great advantage as the top or carrier sheet for a compressed bat of asphaltic multiply cellulose tissue crepe Wadding insulation such as is disclosed in the Fourness et al. Patents Nos. 2,339,326 and 2,341,370, or in the Randall Patent No. 2,254,856.

The manufacture of a sheet having the desirable properties of adequate Water resistance, a f

reasonable degree of plasticity or flexibility, adequate mechanical strength While at the same time possessing such ilaine inhibiting or re resistant properties as to reduce, or, at any rate, not to increase, the re hazard of the structure to which the sheet is applied has here-tofore presented great diiiculties. The principal difficulty is due to the fact that asphaltum, the most generally used Water-resistant substance because of its cheapness and other useful properties and advantages, is not compatible With those flreproofingsubstances Which are commercially available by reason of cost or otherwise. It is understood that when herein We speak of two substances which are compatible, we mean that, when the fireproofing substance is dissolved in an aqueous solution, said aqueous solution can be used as the continuous phase of an emulsion in which the other substance, for example Wax, exists as the discontinuous phase.

Similarly, a material emulsiiiable in Water may be said to be incompatible with a reproofing salt which is usually a strong electrolyte, when a high concentration of the salt renders the emulsion unstable and causes the Water-resistant material, which is the discontinuous phase, to be precipitated.

An asphaltum emulsion is incompatible in respect of strong electrolytes and therefore, when a sufficient amount of reproofing salt to give the desired fire-inhibiting properties to an inflammable material such as paper is dissolved in the emulsion, the emulsion breaks or is rendered very unstable and cannot be used to the best advantage in treating the sheet for the purpose ofA imparting to the sheet those properties which the asphalt treatment is intended to supply.

For the above stated and other reasons, the best results cannot be obtained by the use of a combined asphalt emulsion and aqueous solution of a reproofing salt. Also for other reasons, it is not commercially practicable or desirable to employ a two-step process which involves the use of first an asphaltic emulsion and second a reproof salt solution, or those steps in reverse order.

If the sheet is rst treated with asphalt and then impregnated with a salt solution, the salt will be on the outside of the asphalt particles, and the Waterwresistant properties of the sheet Will be, to a certain extent, impaired. On the other hand, it is desirable to impregnato with the freproofing salt in the second step of the process on account of the fact that, in this manner, the nre-resistant or flame inhibiting properties of the sheet are superior to those of a sheet in which the asphalt treatment constitutes the second step of the process.

Hence, it is seen that the production of a highly Water resistant and highly flame inhibiting sheet of the character described would seem to be practically impossible, because of the contradictory requirements. To obtain proper Water resisting properties, the asphalt should be applied last. On the other hand, in order to obtain proper flame inhibiting properties, the fireproofing salt should be applied last.

Thus the purpose of the present invention is to reconcile the aforesaid contradictory requirements in the manufacture of a sheet which will possess in a satisfactory degree all of the desirable properties above mentioned and to enable such sheet to be manufactured at a reasonable cost by the use of conventional facilities.

General method In general, our improved method of manufacture comprises, rst, the manufacture of a strong bibulous paper sheet having incorporated within the body of the sheet a sufcient amount of asphalt or asphalt-like material in the form of an aqueous emulsion, to impart to the sheet the desired plasticity coupled With other desired mechanical properties, while at the same time of and by itself providing a substantial amount of Water resistance. This asphalt loaded sheet, if necessary, is de-Watered, or rather any excess emulsion is removed. Then the sheet is impregnated With a solution of fireproofing salt in Which there is dispersed in the form of an emulasaitfi s i rsion a wax or wax-like substance, which, in the form oi an emulsion, is stable to high concentrations oi a strong electrolyte such as the flameprooiing salt in solution. The sheet is then dewatered and dried. Before complete drying is eiected, it is desirable to crepe the s'. eet, in the event that a creped final product is needed.

On account oi the fact that waxes, which, in emulsion form, are compatible with strong electrolytes, are more expensive than common waterproofing materials such as asp-halt, itis of .course desirable to use no more wax than is necessary to augment sufficiently the waterproofing properties furnished by the asphalt. On the other hand, waxes of a suitable character are more eiicient as water-repellent agents than asphaltum, and hence it is not necessary to luse as large -a percentage of wax asasphalt. Also, the amount of wax used should not be enough to reduce materially the flame-inhibiting properties supplied by the salt impregnation.

Various types of suitable waxes may be purchased. Any ecient water-resistant wax which can be emulsifled to be stable in the presence of a strong electrolyte may be employed. We have had excellent results with wax emulsions which are colloidal dispersions of petroleum wax in an aqueous medium, stabilized and emulsiiied by a small amount of water-soluble gum and a watersoluble salt of an organic sulphom'c acid. A similar emulsion of petrolatum may also be employed.

In certain cases the wa-x, or part of it, may be incorporated in the irst bath which contains the asphaltum ingredient.

The finished dried sheet may contain from 4 to 18% by weight (based upon the Weight of the inished sheet) of asphalt, from 9 to 16% by weight of a flame retardant such as ammonium sulphate and/or ammonium phosphate, and from 1 to 6% by weight of compatible wax.

Specific example In the manufacture of industrial paper of the character described, for use as the outer cover or face sheet of an insulating blanket made of crepe Wadding, we have obtained excellent results in the use of an apparatus and process such as are illustrated somewhat diagrammatically in the accompanying drawings. In the drawings:

Fig. 1 is a diagrammatic representation of the apparatus employed in the process; and

Fig. 2 is a iiow sheet for said process.

Referring to the drawings, I represents a roll of raw or untreated paper such as unbleached kraft, in the present instance having a basis weight of 26 lbs. per ream of 3,000 sq. ft. This paper should be sized or otherwise treated so that it will retain enough mechanical strength to be fed through the impregnating baths without undue breakage, while at the same time the sheet should be in such condition as to take up the proper amount of emulsions or solutions in the impregnating baths.

If the iinished paper is to bear any words or other markings, the sheet may be printed before it is subjected to the waterprooiing and flameproofing treatment. Such printing can be effected in any appropriate type of web fed press, such a press being indicated at Il in the drawings. From the printing press ll, the paper is directed into a rst impregnating bath l2, which contains a water asphalt emulsion. Said emulsion is produced in the following manner.

The emulsificaton is eiected in a tank I3 which is equipped with a high speed mixer |41. The asphalt which, in this instance, may be of a saturating type, is liquefied in a tank i5 heated by indirect steam through a supply line I6. The stabilizer for said emulsion is prepared in a tank Il into which there are introduced separate supplies of caustic, protein, and ammonium oleate.

The protein used may be about eighteen parts soy bean alpha protein which is iirst suspended in ,about 4 times its weight of water, allowed to swell for one-half hour, and then heated to about F. 2 parts by weight of 50% caustic soda solution are then stirred in, and the temperature is raised to F., after which 9 parts by weight of ammonium oleate are added and stirred. Meanwhile, 72 parts by Weight of the asphalt .have been heated to 160 F. to form the emulsion. Enough of the prepared protein mixture is used to supply 1 part by weight of protein for each 4 parts by weight of hot asphalt, and sufficient water is added to the emulsifying tank to bring the total solids to about 30 to 32% by weight.

In making the emulsion, it is desirable rst to add the protein mixture to the emulsifying tank. Then, while vigorously agitating the protein, the hot asphalt is added slowly. After the protein and asphalt have been thoroughly incorporated each with the other, enough additional water, .at the same temperature, 160 F., is added to bring the total solids to the required 30 lto 32% by weight.

Another type of stabilizer that has been successfully used is one which employs a thermoplastic resin derived from pinewood and containing phenol, aldehyde, and ether groups. A stabilizer of this type is described in Chemical and Metallurgical Engineering, 1934, 41, 589.

' rThis emulsifying agent is employed with a small amount of ammonium oleate or soy bean protein. When using this resin, it is desirable to use about 91A pounds of sodium hydroxide for each 100 pounds of the resin, using considerably higher temperatures, for example about 200 F., when forming the asphalt emulsion.

'Ihe concentrated asphalt emulsion is diluted with water in either one of the diluting tanks I8 or l0. The amount of dilution will depend upon the amount of asphalt which is needed in the sheet. In the present instance, the percentage of asphalt in the diluted solution to be used in the impregnating bath -will be slightly higher than the percentage of asphalt by weight in the finished sheet. For example, if a finished sheet asphalt content of 8% by weight (based upon the weight of the finished sheet) is desired, the impregnating bath should contain about 10% by weight of asphalt, whereas, if the `finished sheet asphalt content is to be as high as 18% by weight, the asphalt impregnating bath should contain about 20% by weight of asphalt.

When forming the diluted emulsion, it is advisable to add a small amount of mold inhibitor, for example sodium pentachlorphenate. A sufcient amount of this material should be dissolved in the diluted mixture to give a 0.4% solution by weight. A small amount of carbon black lalso may be added, in order to give a suliciently into the -second bath 2l Which contains the Wax emulsion in name-procng salt solution. Said Wax-salt bath is made in the following manner.

In the dissolving tank 22, there is prepared a solution consisting of 3 parts of ammonium sulfate and 7 parts by Weight of Water, so that the solution will contain 30% by Weight of ammonium sulphate, the active iameproong substance. It is advisable to inject enough direct steam into the dissolving tank in order towarm up the solution sufficiently to insure complete solution with reasonable rapidity.

The 30% salt solution is then conducted into a mixing tank 23 Where it is mixed by vigorous stirring with a Wax emulsion containing sumcient wax so that the Wax represents about 30% by Weight of the amount of active fireproong salt substance in the solution. Any known appropriate Wax emulsion may be used, provided that it is stable in the presence of a strong electrolyte such as the 30% ammonium sulfate solution into which the Wax emulsion is incorporated. A wax emulsion with Which excellent results have been obtained is one which comprises petroleum wax, a Water-soluble gum, and an organic sulfonic acid.

The asphalt-treated, still-damp Web, upon passing through the second bath containing the salt and wax impregnant, picks up a substantial amount of said Wax-saltimpregnant and is then conducted to a large creping dryer 25. The impregnant web is applied to the creping dryer 24 by means of a roll 25 which subjects the web to suiiicient pressure to squeeze out excess impregnant.

After the web has passed around the active surface of the creping dryer 24, it is removed by a creping doctor 26, it being understood that at this point the web still contains a very substantial amount of moisture, for example 55% by Weight. The creping ratio is not critical. Good results have been obtained with creping ratios of between 1 to 11A; and 1 to 2.0.

The moisture still remaining in the sheet is then removed by drying down to a moisture content representing a normal or stable dry condition for the finished sheet, for example 5% moisture by weight. This drying should be effected Without subjecting the sheet to sufficient tension to stretch out the creping, and to this end the web is propelled through a battery of can dryers 27, provided With the usual dryer felt 28. After the creped sheet has been thoroughly dried, it is Wound up into a roll 2S by means of any suitable Winding arrangement*e represented as a Whole 30.

The .composition of the final product, on a bone dry basis and guring 3,000 sq. ft. of the uncreped material, will be approximately as follows:

It will be understood that the particular ingredients and the percentages of same which are used may be Varied in accordance with working conditions, and also in accordance with the purposes for which the sheet is to be used. Ob-

viously, if a high degree of Water resistance is' desired, it will be advantageous to use a higher percentage of asphalt and of Wax, whereas if the sheet must be name resistant to a high degree, a greater percentage of ameproofing salt will be required.

We claim: l

1. The improved process of manufacturing a water and name resistant paper sheet 'which comprises the steps of nrst applying an aqueous emulsion of asphalt to a sheet of paper, then while said sheet is wet with said asphalt emulsion, applying' a second emulsion, the continuous phase of which comprises an aqueous solution of a re inhibiting salt which is a strong electrolyte and the discontinuous phase of Which comprises a Water resistant Wax, and finally drying the sheet.

2. The improved process of manufacturing a water and flame resistant paper sheet which comprises the steps of rst applying an aqueous emulsion of asphalt to a sheet of paper in an amount more than sufficient to saturate said sheet, removing excess emulsion from said sheet,

. then While said sheet is wet with said asphalt emulsion, applying a second emulsion, the continuous Vphase of which comprises an aqueous solution of a fire inhibiting salt which is a strong electrolyte and the discontinuous phase of which comprises a Water resistant wax, and nally drying the sheet.

3. The improved process of manufacturing a water and flame resistant paper sheet which comprises the steps of first applying an aqueous emulsion of asphalt to a sheet of paper in an amount more than enough to saturate said sheet, removing the excess asphalt emulsion from said sheet to reduce the asphalt content to from 4 to 18% by Weight based upon the weight of the nished sheet, then While the sheet is wet with said asphalt emulsion applying a second emulsion, the continuous phase of which comprises an aqueous solution of a fire inhibiting salt which is a strong electrolyte and the discontinuous phase of which comprises a Water resistant wax, the amount of rire inhibiting salt in said second emulsion being such that said nre inhibiting salt represents from 9 to 16% by Weight of the finished sheet and the amount of Wax in said second emulsion being such that said Wax represents from 1 to 6% by weight of the nished sheet, and then drying the sheet.

4. The improved process of manufacturing a water and iiame resistant paper sheet which comprises the steps of first applying an aqueous emulsion of asphalt to a sheet of paper in an amount more than sufficient to saturate said sheet, removing excess emulsion from said sheet, then while said sheet is Wet with said asphalt emulsion, applying a second emulsion, the continuous phase of which comprises an aqueous solution of ammonium sulphate and the discontinuous phase of which comprises a water resistant wax, and finally drying the sheet.

5. The improved process of manufacturing a Water and name resistant paper sheet which comprises the steps of rst applying an aqueous emulsion of asphalt to a sheet of paper in an amount more than enough to saturate said sheet, removing the excess asphalt emulsion from said sheet to reduce the asphalt content to from 4 to 18% by Weight based upon the weight of the finished sheet, then While the sheet is wet with said asphalt emulsion applying a second emulsion, the continuous phase of which comprises an aqueous assale/4 solution of ammonium sulphate and the discontinuous phase of which comprises a Water resistant wax!A the amount of ammonium sulphate in said .second emulsion being such that said ammonium sulphate represents from 9 to 16 by Weight of the nished sheet and the amount of wax in said second emulsion being such that said Wax represents from 1 to 6% by Weight of the finished sheet, and then drying the sheet.

EDWARD HUGO VOIGTMAN.

JOHN CALVIN BLETZINGER.

REFERENCES CITED The following references vare of record in the file of this patent:

Number Number UNITED ASTATES PATENTS- 'Name Date Frederickson May l28, 1929 Rowe June 6, 1939 Porter Mar. 16, 1943 FOREIGN PATENTS Country Date y AGreat Britain July 14, 1932 Great Britain Apr. 4, 1940

Claims (1)

1. THE IMPROVED PROCESS OF MANUFACTURING A WATER AND FLAME RESISTANT PAPER SHEET WHICH COMPRISES THE STEPS OF FIRST APPLYING AN AQUEOUS EMULSION OF ASPHALT TO A SHEET OF PAPER, THEN WHILE SAID SHEET IS WET WITH SAID ASPHALT EMULSION, APPLYING A SECOND EMULSION, THE CONTINUOUS PHASE OF WHICH COMPRISES AN AQUEOUS SOLUTION OF A FIRE INHIBITING SALT WHICH IS A STRONG ELECTROLYTE AND THE DISCONTINUOUS PHASE OF WHICH COMPRISES A WATER RESISTANT WAX, AND FINALLY DRYING THE SHEET.

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