US2711377A - Construction material and method of making - Google Patents

Description

CONSTRUCTIONMATERIAL j 1911511101)v or I Wallace C. Riddell, Berkeley," Calif assignor to Kaiser Gypsum Company, Inc; a corporation of Washington No Drawing. Application September-1 5,199,-

. Serial No.309,747'

6 Claims. (Cl. 117 1 s'2 I The present invention relates to an improved plaster- I solving hydrated; tslakedfior ,unslaked i liine'f in? water. 1' V Thepotassium sulfate solution is suitablyfprepared by 1 dissolving th a applied s he su fac tofbe treated independen y abu they -canrc'onveniently be mixed' r p epare 8 9 t board surface, particularly such' surface tof hic l it is intended to pp y a coating ot lastengand s a process j for producing the same. V v

In building or construction operations, where wallboard, or lath, is installed to forrnf a'wall or ceiling, a

finish coat of gypsum plaster is appliedjto the exposed core of cementitious composition, such as set gypsum crystals is formed between fibrous liners. It hasbeena problem in such work that the fibrous? or paper liner has been treated with rosin size which reduces the suc tion,'"

or water-absorption, of the liner. Thisflackof suctionf seriously hindered bonding of the plaster coating to the stood that gypsum plaster adheres to the plasterboard because of the interlocking of the-gypsum crystals'; as they set, within the fib'ers, of the liner intd;which apor-z tion of the wetslurry of'calcium sulfate hemihydr'ate ha penetrated. r

It has been proposed to overcomethis disadvantage and to increase the suction by applying'tothe fibrous or paper surfaces various treating agents, for example,'wet'ting 3o liner surface or to the wallboard, as it is generally u'nder-,

agents, which are intended to enable better penetration of 40 the slurry, or alkalies which saponify and remove some 7 However, where Water absorption is suitably increasedy it has been observed that the application of wet plaster to the surfaces of the board often resulted in deformation or sagging of the board, especially in ceiling installations, because an excessive-amount of water; penetrates into the board, reducing its strength.

It is an object of the invention tofimprove theadhesioii of a plaster coating .to the fibrous surfaceof a wallboard, V lath or the like. It is afurther object to provide a plaster-f receiving fibrous surface of improvedJwater-absorption characteristics; and-it is a still further object to-provide a plaster-receiving fibrous surface which promotesrapid setting of the plaster and prevention of 'deformation of the plaster-receiving base.

hydroxide and a solution of [an alkali sulfate,preferab1y potassium sulfate.

1000 square feet of fibrous or paper surfacejtr'eated; and the alkali sulfate is added in an amount 'to provide'frorn 0 .3 to 0.6 lb. thereof per-1000 squarefeet oftfibrous'orpaper surface treated. Preferably, 0.2 lb."c'alcium' hydroro idc and 0.45 lb. potassium sulfate are added per 1000 square feet of such surface. The invention will be further described below with-special referenc e to potassium J sulfate.- I a The calcium hydroxide solutionean be prepared bydismer t mix, and uniformly j applied fto the" solutionsormi ed solnt-io s';;ca' n-.- be Iapplie after, the .boardorlath orjiother 'fib p V hasf b'een@inanufactured or'after itThasbeen installed V a wall or ceiling Alternatively, the solution or solutions c be a i d a V manufacture ofthe projducg 'for ei(ainple',1 infthefcours of manufacture of gypsum wallboardin th'e mannerfwell r S ftionbe limited by 'thisltheory, that the calcium hydroxide I andpo'tassium sulfate reactrnet'atheticallyto form, in'the', "presen jfifw t i fsiurnjhydroxide; f H

Qform of minutecrystals,' uniform v v fibers of the 'linerfandaupon the; liner; surface, upon H 7 d y ng, rand 1 ere 1prbvides;la e urfaces of seedpenetration} and; also "by r acceleratedi setting time 7 potassium'hydroxide'forined -is believed-ito sapon sizin ofithe paper,"therebytsolubilizing andirjeino' ving a j v portionof the size, enabling improved penetration of the i plasterslurry into the paper surface and v like "slurryyresult the 'size (in? q p I onstrated by examinationgaccordirigltotthe Cobb paper I I According tothepresent invention, ithasbcen found I'f sizing test (Tech. Ass' that the above-disadvantages are, overcomeffandfthe aforesaid and other objects are attained';by treating the plaster-receiving surface with a solution escapism a provide ;0.2 11b; ca' '0H 2 pen-1000 square te 's urface and-0.4 5 lbj K2804 per-1100p square feet surface; I tested iii-ex ctl th rfacefi {The v o the surface coated product t iQ inne fltia r th known to the art, 'Th isipllltlbll lcan be applied brush ing,is'praying,' rolling,for*in:any jdesiredfmanner; and is preferabIyaHoWed to dryv priorgtoiaraplyingz-the plaster I coating. Preferably,a'saturatedwatersolutionof calcium h d i P OY Q'Pn Fa l h X }C1 T(. H)a can be added "to insurelsa'turationg; and it is preferred to" use a' '4Ito 5% waterf'solution'ofipotassium sulfate'.*-=

j It is believed,"iwithout intending that th'e'present in 5 crystals which acce ratefthe settingv of theplasterwhen, it isjapplied, "and'iniprove bonding becau'seof improved stronger bondingfth eretor" In addition t Sfbfilieve'dft some 'of the potasisium sulfatecombmesi with so'mefof the :calcium sulfate to forrn syngenite crystals which are I Y 7 (also deposited in th fib ers 'of rthe liner. Thi's mineral tcargns'on -nzoyf alsoihas an excellent taccelerating effect upon "the; setting time *offcalcined gypsum", slurry; if of the sizing and thereby increase water absorption.

potassium Qsulfate'to a calcined gypsumlslurr'yy or of a small: meant of elenite t, (gypsum) crystals; to? another However, the

additionjof the fs'ame mons er potassium sulfate v and of f thef same amounto offslurry"Leifectsise ng Jthereof-in abou a .Whatever :is theniechanisnifofj ithe ac on,i ;however, :greatly improved resultsare'obtained by th process'and 'elenite icry stalsfto jasingle batch 1 i 4 "minutes;

product of the presentinventiongp 7 J I ,7 i'Ihey-proce'ss qfzthis invention-is" efiec tive in reducing I .paperuline'r fOrFpIa'sterbOa'idQas is Vdeinjandtheni'placed'in the'fCobhTestenand water is added t: to cover the paper tof 'a' depth"; er one inch at: 70, F.

After LSIJ minute sJimme'rSion, the paper is removed and Y The calcium hydroxide isadde'd in T an amount to provide from 0.1 to'0.3 "lb; Ca(OI-I)z per weighed- Theamountof water absorbed I by thefpape'r water. An hi'ch hadb'em hydrated lirne' and potassiumjsulfatef na 'amountgto me manner. and absorbed 1. v a we hljt i f b ibdi y. q

the untreated paper. The Cobb Tester is made by B. F. Perkins and Sons, Inc., of Holyoke, Mass. and it comprises an iron plate base, a rubber gasket superimposed thereon-.anda brass ring .one inch in depth and Of 5-inch inside diameter. The weighed paper to be tested is placed between the gasket and the base of the ring and the ring is then clamped down to effect a'seal, and is filled with water at 70 F. providing a one-inch head of water over the paper.

The effectiveness of the process of this invention is also demonstrated by a test which measures the time required for a plasterboard paper liner to absorb 0.1 cc. water at 70 F. In this test, plasterboard paper which had not been treated by the method of this invention absorbed 0.1 cc. water, as delivered from a calibrated burette, in 45 minutes. Another sample of the same paperis surfacedreatedby brushing-it with a water solution providing 0.1 lb. hydrated lime (Ca(OH)2) and 0.3.lb. potassium sulfate, each per 1000 square feet surface, and allowed to dry. The treated paper absorbed 01cc. water in 11 minutes. Therefore, the absorption rate is approximately 4 times as rapid.

It has also been observed that small gypsum crystals accelerate the set of calcined gypsum with water. For example, when one to two pounds of gypsum or selenite crystals in admixed with one ton of calcined gypsum and the whole is then gauged with water, the mass sets in 7 minutes; whereas without the addition of seed crystals, 35 minutes is required for setting time. if the gypsum or selenite crystals are added to the plaster mix itself, the set is not easily controlled and the plaster often sets up before it can be properly applied. According to the present invention it has been found that by this process and in this product, acceleration of the setting time of the plaster is effected after the plaster coating has been applied, and this is apparently brought about by deposition of the seed crystals within and upon the fibrous liner.

lna plant run, .gypsurncore, paper-lined wallboard is made by preparing a water slurry of calcined gypsum which can also contain minor amounts of modifiers known in this art such as asbestos fibers, foaming agents, waterrepellent agents or other modifiers, and the plastic slurry is deposited between fibrous liners or covers, such as paper liners, in a board-formingrnachine, in the known way. A saturated solution of calcium hydroxide is prepared by thoroughly admixing 9.25 lbs. hydrated lime and 60 gals. of water. In this saturated solution is then dissolved 21.75 lbs. of potassium sulfate. This solution is continuously applied to the surface of the paper to be used for plaster base, as the plasterboard moves down the production line, preferably prior to entering the drier. The solution is applied by means of a felt roll or brush, and at arate to provide about 0.2 lb. calcium hydroxide and about 0.45 lb. potassium sulfate, per 1000 square feet of board surface. The plasterboard so manufactured was tested in a wall and plaster was applied thereto, which was found to harden in approximately 2 hours, whereas without treatment the same plaster required approximately 4 hours.

Alternatively, a calcium hydroxide solution and a potassium sulfate solution can each be applied to the board, separately and in any desired order. If desired, the solution can be applied to the paper surface after the board has passed through'the drier, or at any time prior to application of the plaster. The invention has been described above with reference to potassium sulfate. which is the preferred embodiment because the addition of this salt results in the greatest acceleration of plaster setting, due in partat least, it is'believed, to the providing of previously formed seed crystals of syngenite, as well as of gypsum. However, other alkali sulfates, including ammonium sulfate and the sulfates of other alkali metals, are also useful in this invention, either used alone or inadmixtures or in admixture with potassium sulfate. That is, there can be added at least one sulfate chosen from the group consisting of alkali metal sulfates and ammonium sulfate, in the manner which has been described above with more particular reference to potassium sulfate. Of the alkali sulfates, ammonium sulfate is most efiective, with the exception of potassium sulfate, the preferred species. sulfates provide seed crystalsof selenite by reaction with the calcium hydroxide. The rosin size is reduced and the seed crystals of gypsumtselenite) or of selenite and syngenite are deposited largely, in the outer portion-of the fiber liner. The fiber liner can be applied to any plasterboard or gypsum product including particularly gypsum lath and gypsum wallboard. This invention is useful in hastening or accelerating the setting time of gypsum plaster when applied to any fibrous plaster receiving surface; and exhibits particular advantages in accelerating such setting time and preventing sagging or deformation when applied to fiber or paper coated gypsum lath. The description herein refers to applying solutions but it is to be understood that the solutions can contain some suspended solid material, which can be excess calcium hydroxide to insure saturation of the Ca(OI-I)z solution or it can comprise in the mixed solu' tions some precipitated gypsum.

' In the specification and claims all percentages are by weight unless otherwise indicated. It is to be understood that the above examples have been given for purposes of illustration only and variationsand modifications can be made therein without departing from the spirit and scope of the appended claims. By the term solubilized used herein is meant to render water-soluble-or to con-f solution consisting essentially of calcium hydroxide in an amount to provide from 0.1 to 0.3 lb. of calciumhydroxide per 1000 sq. ft. of said surface and at least one sulfate selected from the group consisting of alkali metal sulfates and ammonium sulfate in an amount toprovide from 0.3 to 0.6 lb. total of said sulfate per 1000 sq. ft.

of said surface.

2. A process as in claim 1 wherein there are applied to the fibrous surface 0.2 lb. of calcium hydroxide and 0.45 lb. of potassium sulfate per 1000 sq. ft. of surface. I

3. Process for improving the plaster-bonding properties of the paper-surface of a paper coated-gypsum product which comprises preparing a saturated water solution consisting essentially of calcium hydroxide, diSSGlV'. ing potassium sulfate in said solution, and applying the said solution directly to the surface of said paper coated gypsum product in amount to provide from 0.1 to 0.3lb. of calcium hydroxide and from 0.3 to 0.6 lb. of potassium sulfate per 1000 sq. ft. of paper surface.

4. Process for improving the plaster-bondingproperties of the paper surface of a papercoated gypsum product which comprises applying directly to the paper surface a water solution consisting essentially of calcium hydroxide in an amount to provide from 0.10 to 0.30 lb. of calcium hydroxide per 1000 sq. ft. of surface, and a water solution consisting essentially of potassium sulfate in an amount to provide from 0.3 to 0.6 lb. of potassium sulfate l per 1000 sq. ft. of surface.

5. Plaster board having an improved plaster-receiving paper surface comprising a rosin-sized paper liner containing a small amount of uniformly dispersed finely divided .gypsum therein, the gypsum having been deposited and the said rosin-size having been partially saponified by a process according to claim 1..

6. Plaster board having an improved plaster-receiving paper surface comprising a rosin-sized paper liner containing a smallamount of uniformly dispersed finely di- The alkali vided syngenite therein, the syngenite having been de- 848,916 *Monin Apr. 2, 1907 posited and the said rosin-size having been partially 1,451,485 WOotton Apr. 10, 1923 I V saponified by a process according to claim 1. f 1,738,976 Viv as'; Dec. 10, 1929 "1,868,372 Swift .July 19, 1932 References Cited in the file of this patent 5 2,034,435 Heritage Mar. 17; 1936 UNITED STATES PATENTS 2 ,526,537 Camp Oct. 17, 1950 107,687 Hudson Sept. 27; 1870 r

Claims (1)

1. PROCESS FOR IMPROVING THE PLASTER-BONDING PROPERTIES OF A FIBROUS PLASTER-RECEIVING SURFACE WHICH COMPRISES APPLYING DIRECTLY TO SAID SURFACE, SUBSTANCES IN AQUEOUS SOLUTION CONSISTING ESSENTIALLY OF CALCIUM HYDROXIDE IN AN AMOUNT TO PROVIDE FROM 0.1 TO 0.3 LB. OF CALCIUM HYDROXIDE PER 1000 SQ. FT. OF SAID SURFACE AND AT LEAST ONE SULFATE SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL SULFATES AND AMMONIUM SULFATE IN AN AMOUNT TO PROVIDE FROM 0.3 TO 0.6 LB. TOTAL OF SAID SULFATE PER 1000 SQ. FT. OF SAID SURFACE.