US2776234A - Vapor-permeable gypsum board - Google Patents

Description

[MA4 Y 17e/da Mmm/e V2/ende VAPOR-PERMEABLE GYPSUM BOARD w. c. RIDDELL ET Al. 2,776,234

Filed Aug. 4. 1953 Gypsum pre e /wf y 7'/7/ee P/y Paper Fl E E INVENTORS. Wa//ace C Riddell.

BY George B. K/rk.

United States Patent O VAPOR-PERMEABLE GYPSUM BOARD Wallace C. Riddell, Berkeley, and George B. Kirk, Redwood City, Calif., assiguors to Kaiser Gypsum Company, Inc., Oakland, Calif., a corporation of Washington Application August 4, 1953, Serial No. 372,398

Claims. (Cl. 154-86) render them water-repellent.

Gypsum sheathing board, consisting of a core of set gypsum crystals, containing also small amounts of moditying agents, deposited between and adhering to paper liners, has been well known in building construction. However, where this board is desired to be used as sheathing material or where it will come into contact with moisture or the elements, it has been found of practical necessity to treat the paper to render it water-repellent in order to maintain the hardness and strength of the core, to maintain the paper liner intact, and to secure other advantages. A number of methods have been proposed for making the paper water-repellent. These have included the application of various heavy hydrocarbons, water-insoluble soaps and other agents. Some of these earlier methods have required treatment and storage time and others have employed heavy materials which tend to be taken up by the rolls which are now used so generally in continuous processes of wallboard manufacture, raising problems of cleaning the machines before processing other types of boards.

It is an object of this invention to provide a method for making sheathing board water-repellent and waterresistant while employing a treating agent which can be applied directly to the paper or fiber liner during the board-making operation. It is another object of the invention to provide such a method while treating with an agent which does not require an inammable solvent in application, and which does not require melting to apply. It is a further object to provide such a method whereby the paper is rendered water-repellent but simultaneously retains high vapor permeability, and a still further object to render the sheathing water-repellent while avoiding interference with bonding of core to liner.

According to the present invention, water-repellent or water-resistant sheathing board is made by preparing a slurry of calcined gypsum in water in the manner known to the art, depositing the plastic slurry between two flberous or paper liners, and then applying to the outer or exterior surfaces of the liners a small amount, up to about 0.1 gram per square foot of liner surface, of a chromic chloride of a carboxylic acid having at least ten carbon atoms, such as oleato chromic chloride, laurato chromic chloride, palmitato chromic chloride, abietato chromic chloride or of stearato chromic chloride. Preferably, there is added from 0.01 to 0.1 gram per square foot of liner surface, of this agent. In another manner of expressing this, carboxylic acido chromic chloride is added in a small amount, up to about 0.25 lb. per 1000 square feet of board treated, where both sides or surfaces of the board are made water repellent, and preferably in an amount of from about 0.03 to about 0.3 lb. per 1000 square feet of board so treated. Higher amounts can be added but this would increase the cost of production. The acido chromic chloride is added as a water solution and can be of any convenient concentration or strength, but suitably it is added in the form of a 0.3% to 3% solution in water. Mixtures of the carboxylic acido chlorides can be employed. The chromium compounds employed in this invention are complex compounds of the Werner type wherein a trivalent nuclear chromium atom is coordinated with the acido group. After application to the sheathing surface, the board is heated to eect drying, and the nished product is of good water-repellency, but the liner retains approximately its original vapor permeability. The air temperature in the drying zone is from about 210 F. to about 400 F., and preferably does not exceed about 350 F.

An example of the treating agent employed herein, is stearato chromic chloride having the formula It is water-soluble but upon heating becomes hydrophobic, apparently by polymerization. The paper or fibrous liner treated according to the process of this invention is rendered quite water-repellent or water-resistant, but at the same time it retains high vapor permeability, which is particularly advantageous because it is essential that water vapor or the like be able to pass through the sheathing and its liner. The stearato chromic chloride is usually available as a solution containing 30% of the compound, 58% to 60% of isopropanol and 10% to 12% of water. Advantageously, from about 1% to 10% of this solution dissolved in water is employed in treating the board liner.

If it is desired to maintain highest strength in the paper to be treated, or if for any reason it is desired to employ a less acid solution, a neutralizer can be added to the acido chromic chloride solution. For instance, a solution for treating paper can be prepared by admixing 96 parts of water, 2 parts of the above described acido chromic chloride solution in isopropanol and water, and 2 parts of a neutralizing solution consisting of 16.5% urea, 5.0% sodium formate, 0.2% formic acid and 78.3% water. The addition of the neutralizing solution as described raises the pH of the stearato chromic chloride solution from about 2.5 to slightly over 3.0. The other acido chromic chlorides, or one of them, can be employed in the same manner.

Fig. 1 is a cross-sectional View of a sheathing board made according to the invention, showing a gypsum core covered on both faces by paper liners, the latter having acido chromic chloride distributed in their outer surfaces as shown; Fig. 2 is a cross-sectional view of a sheathing board according to this invention, showing in more detail a gypsum core covered on both faces by three-ply paper liners, and having acido chromic chloride distributed predominantly within the outer ply, the thickness of the paper liners being exaggerated for purposes of this illustration.

Where the liner is made water-repellent before the gypsum slurry of the core is dried to the necessary or desired extent, that is, is dried to remove free water but not the characteristic two mols of water of crystallization (CaSo4-2H2O). it is necessary that the liner be vaporpermeable in order to permit the water vapor to escape freely during the drying of the core. After the sheathing board has been installed, it is also necessary that it be Vaponpermeable in order to permit passage of water vapor and to prevent the collecting and depositing of water within the structure wall spaces with consequent damage to studding and the like. That this vapor-permeability is secured by the above-described treating agent in an unexpectedly efficient manner and amount is shown by the following series of tests.

In these tests, a test piece, A, of sheathing paper is sprayed on its outer surface with a 0.6% solution of stearato chromic chloride in water in an amount to apply 0.06 gr. of the chloride per squareY foot of paper and is then dried. at about 220' F. for about 5 minutes. Another test piece, B, ofthe same sheathing paper iswater proofed or made water-repellent by applying uniformly over its outer surface a normally solid. or semi-solid hydrocarbon such as petrolaturn which has been heated to liquify 'the hydrocarbon, and then allowing` theV so'- treated paper to cool, as previously known in lthis art. A third test piece, C, consists ofthe same sheathingv paper but without any waterproofing` or water-repellency treatment. In the tests, each sample piece is clamped` between two funnels atlthe large ends thereof, providing an area of 36.5 sq. om. of paper exposedto now of gas, and thestein of one funnelis connected' with an inlet tube conducting air toward the paper, 'while the stem' of the opposite funnel is connected with an exit tube conducting air away from the paper. Along the exittub'e is placed a manometer by which are measured the relative displacements obtained with each test piece, as a measure of the permeability ofA the piece to the tlow of the gas. Air is admitted lto the inlet tube under about 1.9' grams per square centimeter pressure,- and displacement is measured on thel manometer in centimeters. The tests are run in triplica-te and resul-ts are as follows-z The effectiveness of the treatment `according to this invention in making the liners water-repellent is shown by `the following tests, known as the Cobb paper sizing test. A piece of the liner to be tested, measuring 5" x 5, is weighed and placed in the Cobb test device wherein the paper is held under Water at a depth of one inch, square inches of paper surface being in contact with the water, the water being maintained at 70 F. After five minutes" immersion, the paper is removed, excess Water fwiped from the surfaces, and the paper is t-hen weighed, land the weight of water absorbed by the paper is thus determined. There are shown in Table II the results of tests o'n three :test pieces, wherein A is a piece of paper liner, which piece has been waterproofed by treatment Iwith' a commercial Waterproofing compound comprising a solution of paraffin wax in a light hydrocarbon. B is a piece of the same paper liner, this piece having been treated according to this invention. C is a piece of the same paper liner, but this piece not having been subjected to any waterproofing treatment. Each entire piece of A and B, ythat is, both the inner and the outer ply, has been treated with the water-repellency agent described as to each. Following. are the results of these tests.

The amount ofv agent added inthe matter of the A piece is given. as the wax. component because the lighti hydrocarbonsubstantiall'y entirely volatilizes od. It can be noted that the treatment according to this invention results in a more water-repellent material with the application of only one-half the amount of treatment agent, as compared with paratin wax.

The paper liner usually employed in making gypsum lath, sheathing or wallboard consists of at least three plies of paper. The inner layer is quite absorbent, to take up moisture from the slurry core.y The middle layer is heavily sized but is vapor-permeable. The outer ply or layer is also not as absorbent `as the inner layer but apparently absorbsthe predominant portion of the treating solution herein `described and it is believed' that it is' the outer ply especially which is made water-resistant or water-repellent by the method of the present invention.

Not only is the vapor-permeability retained in very high amount, Abut the treatment agent here employed is especially advantageous in making sheathing or wallboard by the continuous process because the water solution can be :applied during the advancing of the board over rolls toward the drying zone, the solution is readily absorbed by the paper liners, and it does not adhere to or gumv up the rolls. It is a particularly advantageous feature of the invention that the ltreating solution is applied after the board is formed and while it is being forwarded to the dryingl zone, 4because the gypsumslurry, having been deposited between the paper liners, will already have been partially absorbed by the inner surfaces thereof, or inner plies, and no waterproofing agent will have been interposed between the gypsum slurry and Ithe liner prior to contact between these two elements. Better bonding is thus obtained between the slurry and the paper, both by deposition of interlacing gypsum crystals in the interstices of the inner plies and by the bonding etectof any adhesi-ve, such as starch or dextrin, added in the slurry, because direct contact is maintained between the slurry and the inner ply. It is also an advantage of the present process that it enables use in a plant of any standard wallboard or sheathing paper in making the board, lath or sheathing, and the paper can be waterproofed or made Water-repellent during the manufacture of the board.

This obviates the necessity of keeping in stock separatel Example To make a gypsum core sheathing board, a plastic slurry of calcined gypsum in water is prepared in the manner known to the art, by admixing calcined gypsum, smallV amounts of starch or dextrin adhesive, a retarder, if desired a small amount of an :air-entraining agent, or a pre-formed foam, fibers such as organic fiber or asbestos or ceramic fibers etc., and mixing the whole with water to form the desired plastic slurry. The slurry is made according `to any desired method, many methods or variations being known in this art. The slurry is then deposited between paper liners in the known way, in a board-forming machine. The board so formed is drawn forward over rollers toward a drying zone. A 0.6% water solution of stearato chromic chloride is prepared by mixing two parts by weight of the solution in isopropanol described above with 98 parts by Weight of water. The solution so obtained contains from 1.16 to 1.2% of isopropanol and 0.6% stearato chromic chloride and the remainder water, and is therefore an essentially water solution. It is applied to the outer surfaces of the sheathing board as the latter travels over the rollers after leaving the forming machine and before entering Ithe dryer. The treating solutiony is applied to the top ofthe board -by means of one or more felt rollers; and to the bottom surface by a spray gun. Other methods ot applying the agent can be employed. The board then passes throughv `the dryer where the air temperatures vary fromY about.

350 F. at the entrance to the drying zone to about 210 F. at the exit therefrom. Fans maintain a -brisk current of heated air through the drying zone, for example, of #about 45,000 cub-ic feet per minute, corresponding in this example to a linear velocity of yapproximately 1000 feet per minute. The amount of treating lsolution applied to the board in this example provides about 0.06 gram stearato chromic chloride per square foot of paper or about 0.12 gram per square foot -of sheathing, i. e. 0.06 gram yapplied to each of two surfaces. This corresponds to yan application approximately 0.27 lb. per 1000 square feet of board, in this example.

In this specification and claims, percentages `and parts are by weight unless otherwise indicated. It is to be understood that the stearato chromic chloride can be employed in making water-repellent sheathing as applied to a gypsum core of any composition. The treating agent can be applied to the liner, particularly the outer or exterior surface thereof, prior lto use in the board making operation, and, likewise, it can be -applied to a board previously made, `and can then be heated briefly yto 200 F. or slightly more to render the agent hydrophobic. However, it is more economical yand a preferred method of procedure to apply it directly in the board making operation as described fabove. A multi-ply paper having more or less Ithan three plies can be employed in which case preferably the outer ply is made water-repellent by application thereto, or distribution therethrough, of the treatment agent described herein. Where rthe board may be treated -after forming and drying, ya greater penetration of the treating agent may be desirable.

Amounts and percentages shown in Ithis specication Iand the appended claims are by Weight unless otherwise indicated. The paper employed in the above example is sheathing paper, starch-free, having :a rosin size and usually black in color, although paper of any color can be employed. The stearato chromic chloride described above is sold by E. I. du Pont de Nemours & Company, IInc. under the trade name of Quilon.

Having now described the invention, what is claimed is:

`1. Process for producing Water-repellent, vapor-permeable gypsum sheathing board which comprises depositing a slurry consisting essentially of calcined gypsum in vwater between two paper liners, then applying to the outer surfaces of Asaid liners a lwater solution of -a Wernertype Iacido chromic chloride yof a carboxylic acid having vat least 10 carbon atoms in an amount to provide from 0.01 to 0.1 gram of 'said chloride per square foot of paper surface, vthen heating Iand -drying the board at ya temperature of from 210 F. to 400 F.

2. Process Ias in claim 1 wherein said chloride is stearato chromie chloride.

3. Process for preparing water-repellent, vapor-permeable gypsum sheathing board which comprises forming ya board by depositing between two paper liners ya plastic slurry consisting essentially of calcined gypsum Iand water, then while conducting said formed board to a heating zone, lapplying uniformly over the surfaces of said liners a water solution of stearato chromic chloride containing 0.6% of -said chloride and from 1.16% to 1.2% isopropanol, said water `solution being `added in an -amount to provide about 0.06 gram of said chloride per square foot of paper surface, then heating said hoard tto from 350 to 210 IF. in a current of heated air and drying and hardening said board.

4. A vapor-permeable gypsum sheathing board of improved water-repellency having :a core consisting essentially of set interlaced gypsum crystals, multi-ply paper liners enclosing said core, fand uniformly distributed in lthe outer ply of said liners from 0.01 to 0.1 gram per l square foot of said liners, of Ia Werner-type acido chromic chloride of carboxylic -acid having at least ten carbon atoms.

5. Product as `in claim 4 wherein said acido chromic chloride is stearato chromic chloride.

References Cited in the le of this patent UNITED STATES PATENTS 1,278,821 Armstrong Sept. 17, 1918 1,793,810 Levin lFeb. 24, 1931 2,273,040 Iler lFeb. 17, 1942 2,356,161 ller Aug. 22, 1944 2,560,521 Camp July 10, 1951 2,562,859 Camp July 31, 1951 2,673,824 Biefeld et al Mar. 30, 1954

Claims (1)

1. PROCESS FOR PRODUCING WATER-REPELLENT, VAPOR-PREMEABLE GYPSUM SHEATING BOARD WHICH COMPRISES DEPOSITING A SLURRY CONSISTING ESSENTIALLY OF CALCINED GYPSUM IN WATER BETWEEN TWO PAPER LINERS, THEN APPLYING TO THE OUTER SURFACES OF SAID LINERS A WATER SOLUTION OF A WERNERTYPE ACIDO CHROMIC CHLORIDE OF A CARBOXYLIC ACID HAVING AT LEAST 10 CA RBON ATOMS IN AN AMOUNT TO PROVIDE FROM 0.01 TO 0.1 GRAM OF SAID CHLORIDE PER SQUARE FOOT OF PAPER SURFACE, THEN HEATING AND DRYING THE BOARD AT A TEMPERATURE OF FROM 210* F. TO 400* F.

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