CA1157893A - Gypsum calcination method and composition - Google Patents
Gypsum calcination method and compositionInfo
- Publication number
- CA1157893A CA1157893A CA000364273A CA364273A CA1157893A CA 1157893 A CA1157893 A CA 1157893A CA 000364273 A CA000364273 A CA 000364273A CA 364273 A CA364273 A CA 364273A CA 1157893 A CA1157893 A CA 1157893A
- Authority
- CA
- Canada
- Prior art keywords
- superplasticizer
- gypsum
- powdered
- rock
- gypsum rock
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B11/00—Calcium sulfate cements
- C04B11/02—Methods and apparatus for dehydrating gypsum
- C04B11/024—Ingredients added before, or during, the calcining process, e.g. calcination modifiers
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
- Phenolic Resins Or Amino Resins (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
This invention relates to a novel method and compositions for reducing the water demand of gypsum plaster which is used in the production of gypsum wallboard. The method comprises adding a super-plasticiser to the powdered gypsum rock before or during calcination to produce the plaster for the wallboard.
The superlasticisers are natural or synthetic polymeric dispersing agents.
This invention relates to a novel method and compositions for reducing the water demand of gypsum plaster which is used in the production of gypsum wallboard. The method comprises adding a super-plasticiser to the powdered gypsum rock before or during calcination to produce the plaster for the wallboard.
The superlasticisers are natural or synthetic polymeric dispersing agents.
Description
~ ~j3~
FIELD OF THE INVENTION
_ _ _ This in~ention relate!s to the calcina-tion of yypsum and the production of g~psum wal:Lboarcl. More particularly, this invention rela-tes to a novel method and compositions for reduciny the water demand o gyps~rn plaster which is used in produciny gypsum wallboard thereby permitting reduced wallboard drying time, increased wallboard production rates and lower clryer energy costs per unit area of wallboard.
BACKGROUND OF THE INVENTION
Calcium sulphate hemihydrate (plaster), which is the core material for gypsum wallboard, is produced by the process of calcining powdered gypsum rock. A
number of processes and apparatus for continuous calcination of powdered gypsum rock are commonly used in the industry. One process and apparatus for continuous calcination of powdered gypsum rock are described in Canadian Patents 779,217 and 779,218, both issued on February 27, 1968 in the name of R.C. Blair, granted to the British Plaster Board (Holdings) Limited.
Alternative equipment and process for -the continuous calcining process are disclosed in U.S.
Patent No. 4,052,149 granted on October 4, 1977 to National Gypsum Company. The continuous calciner has two coaxial cylindrical walls and provides for heating air within the inner cylinder and then directing -the air, for conveying and heating ~ine gypsum particles, along a spiral path between the walls of -the two coaxial cylinders. ~he walls extend from one end of the calciner to an exi-t at the second end.
llhe resultant continuousl.y calcined p]aster i.s commonly usecl in the form of an aqueous slurry, to produce gypsum walIboard. rrhe aqueous plaster slur.ry is spread in a con-tinuous pre-determined arnoun-t between -two parallel con-tinuollsly mov:ing paper sheets and allowed to set to a hardened condition. The h~rde~e~ wet wallboard is then cut to form boards o:E prescr:ibed length, after which they are passed through an oven or kiln to be dried until the excess water ;n -the gypsum board has evaporatecl.
Usually, a large excess of water has to be aclded to the calcined plaster -to ensure that suffic;ent slurry consistency or :Eluidity is obtained to allow a rapicl and even spreading of the sl~lrry across the width between the two continuous moving paper .sheets. The amount of water required by a given plaster to obtain a plaster slurry mix of a standard consistency is known as the water demand.
With rapidly escalating energy prices, the cost of drying wallboard to remove the excess water has become a major undesirable factor in the overall cost of the wallboard manufacturing process. It follows that a lower plaster water demand reduces the excess water used in the wallboard production process and the energy required to drive off the excess water is reduced. With reduced total water requirements for a given boardline production speed, the wallboard can be dried at lower temperatures thereby desirably decreasing energy usage and wallboard drying costs per unit area.
Lower drying temperatures during the drying process 'have the added ad~antage of reclucing -~he incidence of w~llboard edge anrl end b-lrning, which is a major quality control problem :Leading to a substandard wallboard product. This edge burning problem is particularly prevalent in modern high speed wallboard manuEacturing plants where elevated dryer temperatures are normally required in order -to enahle -the wallboard to be dried at a rate corresponding to the wallboard produc-t,ion line speed.
A further advantage is realized if the wallboard dryer is operating at maximum drying capacity for a process uslng a normal water demand plas-ter slurry. In this case the drying stage is the rate limiting factor governing the overall speed of the wallboard manufacturing process. Clearly a lower water demand plaster increases the dryer capacity potential and permits a boardline speed increase thereby improving wallboard production output.
~arious ways to reduce the plaster water demand are known by the gypsum industry. One is the process o~ aridization, in which a gypsum plaster o~
reduced water demand is obtained by calcination in the presence of a salt or other compound of high affinity for water (a so~called 'laridizing agent"). This process is described in Canadian Patent No. 999,118, granted November 2, 1976 to BPB Industries Limited. The preferred aridizing agents claimed in this patent are water-soluble inorganic chlorides such as calcium chloride. Unfortunately, aridized plasters produce undesirable side effects in a wallboard manufacturing ~ .bj ~
process an~l :in the Einlshed wal.l.boclr-1 p:roduct. For these reasons, the proce.ss of plaster ari~ization is no-t generally uLled in the wal.lboa:rd rnanufac-turing ;ndustr~.
Another rnethod o-E reducing water demand and -thereby increasing the -Fluidity of plaster slurries is through the addi-tion of water reducing agents. For several years, it has been a common industry practice -to use na-turally occurring lignin by-produc-t.s of -the pulp and paper industry as water reducing agents for the plaster slurry. Lignosulphonate products known by the trade marks I,ignosol SF and Orzan G are typical.
materials of this type. The major disadvantage with these products is that generally they have a retarding effect on the gypsum setting rate and tend to decrease gypsum board core strength, both oE which are detrimental to the manufacture of good quality ~ypsum wallboard.
Another family of water reducing agents is disclosed in U.S. Patent No. 4,184,887, granted January 22, 1980 to United States Gypsum Company. This patent discloses the use of a potassium salt o:E a condensation product of naphthalene and sulfonic acid as a water reducing agent for a plaster compositon used in making cast or molded products.
SUMMARY OF THE INVENTION
Within the gypsum wallboard industry, it is known that the water demand of a plaster slurry can be reduced whilst maintaining slurry fluidity, by the addition of a synthetic chem:ical di.s~e:rc;ant (superplas-ticizer~ to the sl~.lrry aE-tcr -the calc.inlng process.
Superplasticlzers are na-tural, or synthetic polvmeric, dispersing agents which have found application in the concrete inclustry by improving the workability or fluidi-ty of cemen-t aclmix-ture.s.
Superplasticize:r.s appear -to exer-t -their action by decreasing the surface tension of water, increasing the surface charge o~ the sol.id particles, or producing a lubrica-ting film at the partic].e surface.
Superplasticizers of -the synthe-tic type may be classified into -two main types:
Type 1 - Sulphonated naphthalene-formaldehyde condensates.
Type 2 - Sulphonated melamine-formaldehyde conclensates.
Type 1 superplasticizers sold under the trade marks LOMAR D (a~ailable from Diamond ShamrocX
Corporation) or DARVAN ~6 (available from R.T.
Vanderbilt Company) are usually added to the gypsum plaster after calcination in a concen-tra-tion ranging from about 0.01 to about 1 weigh-t percent of the plaster to reduce water demand. Similarly, a Type 2 super-plasticize.r sold under the trade mark MELMET L10 can be added to the plaster after the continuous calcination process to reduce water demand.
t~
Une~pectedly, it has now been found tha-t the reductlon in plas-ter water demand can be significantly improved by adding -the superplasticizer -to the gypsum before or during calcinakion ra-ther than adcling it after calcination. E'urther, -the ]ow water demand plaster produced by in situ calcination with a superplasticizer surprisingly does not significantly affect the sekting characteristics of the aqueous plaster slurry, nor are the resultant wallboard core properties adversely affected.
The invention i5 directed to a method of reducing water demand of gypsum plaster produced from powdered gypsum rock comprising adding a water demand reducing agent, such as a superplasticizer, to the powdered gypsum rock before or during calcination of the powdered gypsum rock to produce gypsum plaster.
It is understood that the applicant's invention has application in eithar batch or continuous gypsum plaster preparing operations.
me gypsum plaster of the invention may be used in -the production of gypsum wallboard.
In the invention, the water demand reducing agent may be a synthetic polymeric dispersing agent.
In -the invention, the superplasticizer may be selected from the group consisting of sulphonated naphthalene-~ormaldehyde condensates and sulphonated melamine-formaldehyde condensates.
In the invention, the superplasticizer may be selected Erom the group of substances identified by the trade marks LOMAR D and DARVAN ~6.
In the invention, -the superp~lastici~er may be added to -the powclere-l gyps~lrrl rock in a concentration ranging from about 0.01 to abou-t 1.0 percent by weiyht of the powdered gypsum rock.
In the inven-tion, -the superplas-ticizer rnay be added to the powdered gypswn rock in a concentra-tion ranging from abou-t 0.05 to about 0.5 percent by weight of -the powdered gypsum rock.
The application is al.so ~irected to a superplasticizer composition useful for adding to powdered gypsurn rock prior to or during calcina-tiorl oE
-the gypsum rock into gypsum plas-ter in gypsum wallboard selected from the group consisting of sulphonated naph-thalene formaldehyde condensates and sulphonated melamine~formaldehyde condensates.
The composition may be selected particularly from -the group of substances identified by the trade marks LOMAR D and DARVAN #6.
DRAWINGS
In the drawings:
FIGURE 1 illustrates in graphical form -the effect of superplasticizer LOMAR D in powder form added to gypsum plaster, FIGURE 2 illustrates in graphical form the effec-t of superplasticizer LOMAR D in aqueous form added to gypsum plaster; and FIGURE 3 illustrates in graphical form the effect of superplasticizer DARVAN #6 added to gypsum plaster.
~- ,.. .
~ ;3 DETACL,ED D~SC~IPTION OF THE INVE~TIO~
Con-tinuous calcina-tion experimen-ts were carried ou-t in a laboratory ket-t:Le appara-tus which is essentially a scaled down model oE -the ket-tle design described in detail in the aforemerltioned Canadian Patents Nos. 779,217 and 779,218, R.C. ~lair.
The laboratory me-thod comprised dry blending various weigh-ts oE superplasticizer with ground gypsum using a Pa-tterson-Kelly twin shell dry blending apparatus. Each mi~ture was then calcined continuously in the labora-tory kettle appara-tus using a constant gas firing rate and a calcina-tion temperature of 147 + 1C.
The plaster produced by in situ calcination with a superplasticizer was analyzed -to determine:
a) l'he chemical analysis of the plaster;
b) The effect on the fluidity of the aqueous plas-ter slurry, c) The effec-t on the plas-ter water demand;
and d) The percentage of water reduction in the aqueous plaster slurry a-t a s-tandard consistency.
A calcined plaster produced without superplasticizer addi-tion and a plaster containing superplaticizers added after calcina-tion were used as controls.
LOMAR D (POWDER FORM) - SUPERPLASTICIZER ADDITION TO GYPSUM PLASTER
__ ~ _____________ __ _ ._ ____ ~ ___.____ . ___ Che nical Analys s, % _ Water Slurry % Wa-ler Plaster Hemi Soluble Res;dual Demand Fluidity ~eduction Type Hydrate Anhydrite Gypsum mls/100 g mm spread a-t std Consistency ~__ _ .. . _ _ .. .. _ _ __ _ Normal Plaster without addition o superplast-icizer 64.6 7.1 2.5 7068 __ _ __ _ _ . _._ .. __ Normal Plas-ter LOMAR D
superplast-icizer adcled after calcination 0.05%
LOMAR D* 64.6 7.1 2.5 6779 6.
0.1~
LOMAR D* 64.6 7.1 2.5 6688 11.1 0.15%
LOMAR D* 64.6 7~1 2.5 6493 12.6 Plaster with LOMAR D
superplast-icizer added be~ore calcination 0.05%
LOMAR D* 64.3 7.9 2.3 6684 8.9 0.1%
LOMAR D* 62.6 9.5 1.0 6494 16.3 0.15%
LOMAR D* 64.6 7O5 2.5 6210721.6 * LOMAR D Powder Analysis:
84% Naphthalene sul.phonate polymer 11% Sodium sulphate 5% Free moisture TABLF. 2 LOIYAR D (SOLUTION E'ORM) - ~SUPERPLA ~ _ _ ~ ______ ____. _______ Chemica]. Analysis, ~ Wa-ter Slurry % Water Plaster Hemi Solub.Le Resi~lual ~emand E'luidity Reduction Type Hydrate Anhydrite Gypsum mls/100 g mm spread at std Consistenc _ . ._ . . _ __ _____ _ .____ Normal Plaster without addition of superplast-icizer 68.0 5.9 2.8 71 62 __ ._ . ~ _ _ . _ ____ . _____ _____ Normal Plaster LOMAR D
superplast-icizer added after calcination 0.05%
LOMAR D* 68.0 5.9 2.8 70 66 4.6 0.1~
LOMAR D* 68.0 5.9 2.8 69 72 7.2 0.2~
LOMAR D* 68.0 5.9 2.8 67 80 11.8 . . _ _ ___ _ ~ _ _ _. _ Plaster with LOMAR D
superplast-icizer added before calcination 0.05~
LOMAR D* 67.3 6.6 2.9 70 72 6.7 0.1%
LOMAR D* - 65.8 7.0 3.3 68 89 12.8 0.2%
LOMAR D* 59.5 7.8 3.1 65 100 16.4 _ _ ~ . . _ . _ ._ _ _ * LOMAR D Aqueous Solution Analysis:
33% Napthalene sulphona-te polymer <1% Sodium sulphate -- 10 ~
[A~ 3 DA VA 1~6*_= _UPl-,RP:[.~S'['IC Y.~.R Al>l)ITION To_ YP~SI)M PLASTER
_.___ _ __ _____ __ _._ ~ _, __ _______ _ .__ __ _ _ Chemical Analysis, %_ _ Wa-ter Slurry ~ Water Plas-ter Herni Soluble ~esidual Demand Fluidi-ty Keduc-tion Type Hydrate Anhydrite Gypsum mls/100 g mm spread at std Consistency _ _ _ _ .. ___ ___.__ _ ___ _ __ ___._ __ _ .______ Norlna 1 Plaster without addition of superplast-icizer 64.5 7.7 2.1 68 74 ___ ___ .__ _ ____ ___ __ __ ____ _____ _ _ Normal Plaster DARVAN #6*
superplast-icizer added after calcinatior 0.05~
DARVAN #6* 64.5 7.7 2.1 66 82 4.9 0.1%
DARVAN #6* 64.5 7.7 2.1 65 87 8.1 0.15%
DARVAN #6*64.5 7.7 2.1 64 90 9.7 _ ,. _ _ Plaster DARVAN #6*
superplast-icizer added before cal.cination 0.05%
DARVAN #6*59.2 11.7 1.1 64 94 11.9 0.1%
DARVAN #6*64.4 6.6 2.4 63 96 13.0 0.15%
DARVAN #6*64.1 6.8 _ _ 62 _ _ __ . __ * DARVAN #6 - Polyrnerized alkyl naphthalene sulfonic acid, sodium salt a ~
Typical results :Eor LOMAR D Type l super-plasticizer are shown in TA~LES l and 2, which c1early demonstrate the particular eEf/3ctiveness of the superplasticizers added before or du:ring calcination in comparison with addition after calcination. Adding the superplasticizer before or during calcination unexpect-edly produces plasters wi-th a water demand lower than plasters in which the superplasticizer was added after calcination. The results indicate -that the LOMAR D
aqueous solution having only 33~ superplasticizer reduced wa-ter demand more effectively on an equivalent basis than the LOMAR D powder.
The surprising efEec-t of be~ore calcination compared with after calcina-tion addition of super-plasticizers to plaster is also graphically demonstrated in FIGURES l and 2.
A further example of the unexpected advantage of superplasticizer add~tion before or during calcination is presented in TABLE 3 and F'IGURE 3. The superplasticizer used in this case was the powder sold under the trade mark DARVAN ~6.
Surprisingly, the superplasticizer did not lose effectiveness by being subjected to the conditions of the calcination process. Moreover, the fact that the performance of the superplasticizer was superior when added before or during ~alcination compared to adding the superplasticizer after calcination was even more surprising. While the applicants do not wish to be bound to any theories, it appears from preliminary testing that the superplasticizer is advan-tageously ~ J~
modified by the cond:itions of the calcination process, which is completely unexpected. I-t is apparent Erom the foregoing d~-ta tha-t regardless of whether the superplasticizer ls modiEied or not, the performance of the superplasticizer when addec1 beEore or during calcination is distinctly improved.
As will be apparent to those skilled in the art in the light of -the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.
FIELD OF THE INVENTION
_ _ _ This in~ention relate!s to the calcina-tion of yypsum and the production of g~psum wal:Lboarcl. More particularly, this invention rela-tes to a novel method and compositions for reduciny the water demand o gyps~rn plaster which is used in produciny gypsum wallboard thereby permitting reduced wallboard drying time, increased wallboard production rates and lower clryer energy costs per unit area of wallboard.
BACKGROUND OF THE INVENTION
Calcium sulphate hemihydrate (plaster), which is the core material for gypsum wallboard, is produced by the process of calcining powdered gypsum rock. A
number of processes and apparatus for continuous calcination of powdered gypsum rock are commonly used in the industry. One process and apparatus for continuous calcination of powdered gypsum rock are described in Canadian Patents 779,217 and 779,218, both issued on February 27, 1968 in the name of R.C. Blair, granted to the British Plaster Board (Holdings) Limited.
Alternative equipment and process for -the continuous calcining process are disclosed in U.S.
Patent No. 4,052,149 granted on October 4, 1977 to National Gypsum Company. The continuous calciner has two coaxial cylindrical walls and provides for heating air within the inner cylinder and then directing -the air, for conveying and heating ~ine gypsum particles, along a spiral path between the walls of -the two coaxial cylinders. ~he walls extend from one end of the calciner to an exi-t at the second end.
llhe resultant continuousl.y calcined p]aster i.s commonly usecl in the form of an aqueous slurry, to produce gypsum walIboard. rrhe aqueous plaster slur.ry is spread in a con-tinuous pre-determined arnoun-t between -two parallel con-tinuollsly mov:ing paper sheets and allowed to set to a hardened condition. The h~rde~e~ wet wallboard is then cut to form boards o:E prescr:ibed length, after which they are passed through an oven or kiln to be dried until the excess water ;n -the gypsum board has evaporatecl.
Usually, a large excess of water has to be aclded to the calcined plaster -to ensure that suffic;ent slurry consistency or :Eluidity is obtained to allow a rapicl and even spreading of the sl~lrry across the width between the two continuous moving paper .sheets. The amount of water required by a given plaster to obtain a plaster slurry mix of a standard consistency is known as the water demand.
With rapidly escalating energy prices, the cost of drying wallboard to remove the excess water has become a major undesirable factor in the overall cost of the wallboard manufacturing process. It follows that a lower plaster water demand reduces the excess water used in the wallboard production process and the energy required to drive off the excess water is reduced. With reduced total water requirements for a given boardline production speed, the wallboard can be dried at lower temperatures thereby desirably decreasing energy usage and wallboard drying costs per unit area.
Lower drying temperatures during the drying process 'have the added ad~antage of reclucing -~he incidence of w~llboard edge anrl end b-lrning, which is a major quality control problem :Leading to a substandard wallboard product. This edge burning problem is particularly prevalent in modern high speed wallboard manuEacturing plants where elevated dryer temperatures are normally required in order -to enahle -the wallboard to be dried at a rate corresponding to the wallboard produc-t,ion line speed.
A further advantage is realized if the wallboard dryer is operating at maximum drying capacity for a process uslng a normal water demand plas-ter slurry. In this case the drying stage is the rate limiting factor governing the overall speed of the wallboard manufacturing process. Clearly a lower water demand plaster increases the dryer capacity potential and permits a boardline speed increase thereby improving wallboard production output.
~arious ways to reduce the plaster water demand are known by the gypsum industry. One is the process o~ aridization, in which a gypsum plaster o~
reduced water demand is obtained by calcination in the presence of a salt or other compound of high affinity for water (a so~called 'laridizing agent"). This process is described in Canadian Patent No. 999,118, granted November 2, 1976 to BPB Industries Limited. The preferred aridizing agents claimed in this patent are water-soluble inorganic chlorides such as calcium chloride. Unfortunately, aridized plasters produce undesirable side effects in a wallboard manufacturing ~ .bj ~
process an~l :in the Einlshed wal.l.boclr-1 p:roduct. For these reasons, the proce.ss of plaster ari~ization is no-t generally uLled in the wal.lboa:rd rnanufac-turing ;ndustr~.
Another rnethod o-E reducing water demand and -thereby increasing the -Fluidity of plaster slurries is through the addi-tion of water reducing agents. For several years, it has been a common industry practice -to use na-turally occurring lignin by-produc-t.s of -the pulp and paper industry as water reducing agents for the plaster slurry. Lignosulphonate products known by the trade marks I,ignosol SF and Orzan G are typical.
materials of this type. The major disadvantage with these products is that generally they have a retarding effect on the gypsum setting rate and tend to decrease gypsum board core strength, both oE which are detrimental to the manufacture of good quality ~ypsum wallboard.
Another family of water reducing agents is disclosed in U.S. Patent No. 4,184,887, granted January 22, 1980 to United States Gypsum Company. This patent discloses the use of a potassium salt o:E a condensation product of naphthalene and sulfonic acid as a water reducing agent for a plaster compositon used in making cast or molded products.
SUMMARY OF THE INVENTION
Within the gypsum wallboard industry, it is known that the water demand of a plaster slurry can be reduced whilst maintaining slurry fluidity, by the addition of a synthetic chem:ical di.s~e:rc;ant (superplas-ticizer~ to the sl~.lrry aE-tcr -the calc.inlng process.
Superplasticlzers are na-tural, or synthetic polvmeric, dispersing agents which have found application in the concrete inclustry by improving the workability or fluidi-ty of cemen-t aclmix-ture.s.
Superplasticize:r.s appear -to exer-t -their action by decreasing the surface tension of water, increasing the surface charge o~ the sol.id particles, or producing a lubrica-ting film at the partic].e surface.
Superplasticizers of -the synthe-tic type may be classified into -two main types:
Type 1 - Sulphonated naphthalene-formaldehyde condensates.
Type 2 - Sulphonated melamine-formaldehyde conclensates.
Type 1 superplasticizers sold under the trade marks LOMAR D (a~ailable from Diamond ShamrocX
Corporation) or DARVAN ~6 (available from R.T.
Vanderbilt Company) are usually added to the gypsum plaster after calcination in a concen-tra-tion ranging from about 0.01 to about 1 weigh-t percent of the plaster to reduce water demand. Similarly, a Type 2 super-plasticize.r sold under the trade mark MELMET L10 can be added to the plaster after the continuous calcination process to reduce water demand.
t~
Une~pectedly, it has now been found tha-t the reductlon in plas-ter water demand can be significantly improved by adding -the superplasticizer -to the gypsum before or during calcinakion ra-ther than adcling it after calcination. E'urther, -the ]ow water demand plaster produced by in situ calcination with a superplasticizer surprisingly does not significantly affect the sekting characteristics of the aqueous plaster slurry, nor are the resultant wallboard core properties adversely affected.
The invention i5 directed to a method of reducing water demand of gypsum plaster produced from powdered gypsum rock comprising adding a water demand reducing agent, such as a superplasticizer, to the powdered gypsum rock before or during calcination of the powdered gypsum rock to produce gypsum plaster.
It is understood that the applicant's invention has application in eithar batch or continuous gypsum plaster preparing operations.
me gypsum plaster of the invention may be used in -the production of gypsum wallboard.
In the invention, the water demand reducing agent may be a synthetic polymeric dispersing agent.
In -the invention, the superplasticizer may be selected from the group consisting of sulphonated naphthalene-~ormaldehyde condensates and sulphonated melamine-formaldehyde condensates.
In the invention, the superplasticizer may be selected Erom the group of substances identified by the trade marks LOMAR D and DARVAN ~6.
In the invention, -the superp~lastici~er may be added to -the powclere-l gyps~lrrl rock in a concentration ranging from about 0.01 to abou-t 1.0 percent by weiyht of the powdered gypsum rock.
In the inven-tion, -the superplas-ticizer rnay be added to the powdered gypswn rock in a concentra-tion ranging from abou-t 0.05 to about 0.5 percent by weight of -the powdered gypsum rock.
The application is al.so ~irected to a superplasticizer composition useful for adding to powdered gypsurn rock prior to or during calcina-tiorl oE
-the gypsum rock into gypsum plas-ter in gypsum wallboard selected from the group consisting of sulphonated naph-thalene formaldehyde condensates and sulphonated melamine~formaldehyde condensates.
The composition may be selected particularly from -the group of substances identified by the trade marks LOMAR D and DARVAN #6.
DRAWINGS
In the drawings:
FIGURE 1 illustrates in graphical form -the effect of superplasticizer LOMAR D in powder form added to gypsum plaster, FIGURE 2 illustrates in graphical form the effec-t of superplasticizer LOMAR D in aqueous form added to gypsum plaster; and FIGURE 3 illustrates in graphical form the effect of superplasticizer DARVAN #6 added to gypsum plaster.
~- ,.. .
~ ;3 DETACL,ED D~SC~IPTION OF THE INVE~TIO~
Con-tinuous calcina-tion experimen-ts were carried ou-t in a laboratory ket-t:Le appara-tus which is essentially a scaled down model oE -the ket-tle design described in detail in the aforemerltioned Canadian Patents Nos. 779,217 and 779,218, R.C. ~lair.
The laboratory me-thod comprised dry blending various weigh-ts oE superplasticizer with ground gypsum using a Pa-tterson-Kelly twin shell dry blending apparatus. Each mi~ture was then calcined continuously in the labora-tory kettle appara-tus using a constant gas firing rate and a calcina-tion temperature of 147 + 1C.
The plaster produced by in situ calcination with a superplasticizer was analyzed -to determine:
a) l'he chemical analysis of the plaster;
b) The effect on the fluidity of the aqueous plas-ter slurry, c) The effec-t on the plas-ter water demand;
and d) The percentage of water reduction in the aqueous plaster slurry a-t a s-tandard consistency.
A calcined plaster produced without superplasticizer addi-tion and a plaster containing superplaticizers added after calcina-tion were used as controls.
LOMAR D (POWDER FORM) - SUPERPLASTICIZER ADDITION TO GYPSUM PLASTER
__ ~ _____________ __ _ ._ ____ ~ ___.____ . ___ Che nical Analys s, % _ Water Slurry % Wa-ler Plaster Hemi Soluble Res;dual Demand Fluidity ~eduction Type Hydrate Anhydrite Gypsum mls/100 g mm spread a-t std Consistency ~__ _ .. . _ _ .. .. _ _ __ _ Normal Plaster without addition o superplast-icizer 64.6 7.1 2.5 7068 __ _ __ _ _ . _._ .. __ Normal Plas-ter LOMAR D
superplast-icizer adcled after calcination 0.05%
LOMAR D* 64.6 7.1 2.5 6779 6.
0.1~
LOMAR D* 64.6 7.1 2.5 6688 11.1 0.15%
LOMAR D* 64.6 7~1 2.5 6493 12.6 Plaster with LOMAR D
superplast-icizer added be~ore calcination 0.05%
LOMAR D* 64.3 7.9 2.3 6684 8.9 0.1%
LOMAR D* 62.6 9.5 1.0 6494 16.3 0.15%
LOMAR D* 64.6 7O5 2.5 6210721.6 * LOMAR D Powder Analysis:
84% Naphthalene sul.phonate polymer 11% Sodium sulphate 5% Free moisture TABLF. 2 LOIYAR D (SOLUTION E'ORM) - ~SUPERPLA ~ _ _ ~ ______ ____. _______ Chemica]. Analysis, ~ Wa-ter Slurry % Water Plaster Hemi Solub.Le Resi~lual ~emand E'luidity Reduction Type Hydrate Anhydrite Gypsum mls/100 g mm spread at std Consistenc _ . ._ . . _ __ _____ _ .____ Normal Plaster without addition of superplast-icizer 68.0 5.9 2.8 71 62 __ ._ . ~ _ _ . _ ____ . _____ _____ Normal Plaster LOMAR D
superplast-icizer added after calcination 0.05%
LOMAR D* 68.0 5.9 2.8 70 66 4.6 0.1~
LOMAR D* 68.0 5.9 2.8 69 72 7.2 0.2~
LOMAR D* 68.0 5.9 2.8 67 80 11.8 . . _ _ ___ _ ~ _ _ _. _ Plaster with LOMAR D
superplast-icizer added before calcination 0.05~
LOMAR D* 67.3 6.6 2.9 70 72 6.7 0.1%
LOMAR D* - 65.8 7.0 3.3 68 89 12.8 0.2%
LOMAR D* 59.5 7.8 3.1 65 100 16.4 _ _ ~ . . _ . _ ._ _ _ * LOMAR D Aqueous Solution Analysis:
33% Napthalene sulphona-te polymer <1% Sodium sulphate -- 10 ~
[A~ 3 DA VA 1~6*_= _UPl-,RP:[.~S'['IC Y.~.R Al>l)ITION To_ YP~SI)M PLASTER
_.___ _ __ _____ __ _._ ~ _, __ _______ _ .__ __ _ _ Chemical Analysis, %_ _ Wa-ter Slurry ~ Water Plas-ter Herni Soluble ~esidual Demand Fluidi-ty Keduc-tion Type Hydrate Anhydrite Gypsum mls/100 g mm spread at std Consistency _ _ _ _ .. ___ ___.__ _ ___ _ __ ___._ __ _ .______ Norlna 1 Plaster without addition of superplast-icizer 64.5 7.7 2.1 68 74 ___ ___ .__ _ ____ ___ __ __ ____ _____ _ _ Normal Plaster DARVAN #6*
superplast-icizer added after calcinatior 0.05~
DARVAN #6* 64.5 7.7 2.1 66 82 4.9 0.1%
DARVAN #6* 64.5 7.7 2.1 65 87 8.1 0.15%
DARVAN #6*64.5 7.7 2.1 64 90 9.7 _ ,. _ _ Plaster DARVAN #6*
superplast-icizer added before cal.cination 0.05%
DARVAN #6*59.2 11.7 1.1 64 94 11.9 0.1%
DARVAN #6*64.4 6.6 2.4 63 96 13.0 0.15%
DARVAN #6*64.1 6.8 _ _ 62 _ _ __ . __ * DARVAN #6 - Polyrnerized alkyl naphthalene sulfonic acid, sodium salt a ~
Typical results :Eor LOMAR D Type l super-plasticizer are shown in TA~LES l and 2, which c1early demonstrate the particular eEf/3ctiveness of the superplasticizers added before or du:ring calcination in comparison with addition after calcination. Adding the superplasticizer before or during calcination unexpect-edly produces plasters wi-th a water demand lower than plasters in which the superplasticizer was added after calcination. The results indicate -that the LOMAR D
aqueous solution having only 33~ superplasticizer reduced wa-ter demand more effectively on an equivalent basis than the LOMAR D powder.
The surprising efEec-t of be~ore calcination compared with after calcina-tion addition of super-plasticizers to plaster is also graphically demonstrated in FIGURES l and 2.
A further example of the unexpected advantage of superplasticizer add~tion before or during calcination is presented in TABLE 3 and F'IGURE 3. The superplasticizer used in this case was the powder sold under the trade mark DARVAN ~6.
Surprisingly, the superplasticizer did not lose effectiveness by being subjected to the conditions of the calcination process. Moreover, the fact that the performance of the superplasticizer was superior when added before or during ~alcination compared to adding the superplasticizer after calcination was even more surprising. While the applicants do not wish to be bound to any theories, it appears from preliminary testing that the superplasticizer is advan-tageously ~ J~
modified by the cond:itions of the calcination process, which is completely unexpected. I-t is apparent Erom the foregoing d~-ta tha-t regardless of whether the superplasticizer ls modiEied or not, the performance of the superplasticizer when addec1 beEore or during calcination is distinctly improved.
As will be apparent to those skilled in the art in the light of -the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.
Claims (21)
1. A method of reducing water demand of gypsum plaster produced from powdered gypsum rock comprising adding a superplasticizer to the powdered gypsum rock before or during calcination of the powdered gypsum rock to produce gypsum plaster.
2. A method according to Claim 1 wherein the gypsum plaster is used in the production of gypsum wallboard.
3. A method according to Claim 2 wherein the superplasticizer is a synthetic polymeric dispersing agent.
4. A method according to Claim 1 wherein the superplasticizer is selected from the group consisting of sulphonated naphthalene-formaldehyde condensates and sulphonated melamine-formaldehyde condensates.
5. A method according to Claim 1 wherein the superplasticizer is a sulphonated napthalene-formaldehyde condensate.
6. A method according to Claim 1 wherein the superplasticizer is a sulphonated melamine-formaldehyde condensate.
- Page 1 of Claims -
- Page 1 of Claims -
7. A method according to Claim 1 wherein the superplasticizer is selected from the group of substances identified by the trade marks LOMAR D and DARVAN #6.
8. A method according to Claim 1, 3 or 4 wherein the superplasticizer is added to the powdered gypsum rock in a concentration ranging from about 0.01 to about 1.0 percent by weight of the powdered gypsum rock.
9. A method according to Claim 5, 6 or 7 wherein the superplasticizer is added to the powdered gypsum rock in a concentration ranging from about 0.01 to about 1.0 percent by weight of the powdered gypsum rock.
10. A method according to Claim 1, 3 or 4 wherein the superplasticizer is added to the powdered gypsum rock in a concentration ranging from about 0.05 to about 0.5 percent by weight of the powdered gypsum rock.
11. A method according to Claim 5, 6 or 7 wherein the superplasticizer is added to the powdered gypsum rock in a concentration ranging from about 0.05 to about 0.5 percent by weight of the powdered gypsum rock.
12. A method for producing calcined gypsum rock, comprising:
dry calcining powdered gypsum rock in the presence of an effective water demand reducing amount of a superplasticizer selected from the group consisting of - Page 2 of Claims -sulphonated naphthalene-formaldehyde condensates and sulphonatd melamine formaldehyde condensates.
dry calcining powdered gypsum rock in the presence of an effective water demand reducing amount of a superplasticizer selected from the group consisting of - Page 2 of Claims -sulphonated naphthalene-formaldehyde condensates and sulphonatd melamine formaldehyde condensates.
13. A method according to Claim 12 wherein the superplasticizer is added to the powdered gypsum rock in a concentration ranging from about 0.01 to about 1.0 percent by weight of the powdered gypsum rock.
14. A method according to Claim 12 wherein the superplasticizer is added to the powdered gypsum rock in a concentration ranging from about 0.05 to about 0.5 percent by weight of the powdered gypsum rock.
15. A method according to Claim 12, 13 or 14 wherein the superplasticizer is added to the gypsum before calcination.
16. A method according to Claim 12, 13 or 14 wherein the superplasticizer is added to the gypsum during calcination.
17. A method according to Claim 12, 13 or 14 wherein the method comprises dry blending the super-plasticizer with the powdered gypsum rock to form a mixture of the superplasticizer and the gypsum and then calcining the mixture.
18. A method according to Claim 12, 13 or 14 wherein the calcined powdered gypsum is used in the production of wallboard.
- Page 3 of Claims -
- Page 3 of Claims -
19. A method for producing calcined gypsum rock comprising the steps of:
dry blending a superplasticizer selected from the group consisting of sulphonated naphthalene-formaldehyde condensates and sulphonated melamine-formaldehyde condensates with powdered gypsum rock to form a mixture of the superplasticizer and the gypsum and then calcining said mixture.
dry blending a superplasticizer selected from the group consisting of sulphonated naphthalene-formaldehyde condensates and sulphonated melamine-formaldehyde condensates with powdered gypsum rock to form a mixture of the superplasticizer and the gypsum and then calcining said mixture.
20. A superplasticizer composition useful for adding to powdered gypsum rock prior to or during calcination of gypsum wallboard made from the powdered gypsum rock comprising a substance selected from the group consisting of sulphonated naphthalene-formaldehyde condensates and sulphonated melamine-formaldehyde condensates, in combination with water.
21. A composition according to Claim 20 wherein the composition is selected from the group of substances identified by the trade marks LOMAR D and DARVAN #6.
- Page 4 of Claims -
- Page 4 of Claims -
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000364273A CA1157893A (en) | 1980-11-07 | 1980-11-07 | Gypsum calcination method and composition |
| GB8106378A GB2086869B (en) | 1980-11-07 | 1981-02-27 | Reducing water demand of gypsum plaster |
| FR8104018A FR2493827B1 (en) | 1980-11-07 | 1981-02-27 | METHOD AND COMPOSITIONS FOR REDUCING THE DEMAND FOR PLASTER WATER |
| IE45681A IE51013B1 (en) | 1980-11-07 | 1981-03-03 | Gypsum calcination method and composition |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000364273A CA1157893A (en) | 1980-11-07 | 1980-11-07 | Gypsum calcination method and composition |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1157893A true CA1157893A (en) | 1983-11-29 |
Family
ID=4118386
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000364273A Expired CA1157893A (en) | 1980-11-07 | 1980-11-07 | Gypsum calcination method and composition |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1157893A (en) |
| FR (1) | FR2493827B1 (en) |
| GB (1) | GB2086869B (en) |
| IE (1) | IE51013B1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB0708382D0 (en) | 2007-05-01 | 2007-06-06 | Bpb Plc | Gypsum based compositions |
-
1980
- 1980-11-07 CA CA000364273A patent/CA1157893A/en not_active Expired
-
1981
- 1981-02-27 FR FR8104018A patent/FR2493827B1/en not_active Expired
- 1981-02-27 GB GB8106378A patent/GB2086869B/en not_active Expired
- 1981-03-03 IE IE45681A patent/IE51013B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| IE51013B1 (en) | 1986-09-03 |
| GB2086869B (en) | 1984-04-26 |
| FR2493827A1 (en) | 1982-05-14 |
| FR2493827B1 (en) | 1985-12-06 |
| GB2086869A (en) | 1982-05-19 |
| IE810456L (en) | 1982-05-07 |
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