WO1980000248A1 - A method of preparing gypsum articles - Google Patents

A method of preparing gypsum articles Download PDF

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Publication number
WO1980000248A1
WO1980000248A1 PCT/SE1979/000154 SE7900154W WO8000248A1 WO 1980000248 A1 WO1980000248 A1 WO 1980000248A1 SE 7900154 W SE7900154 W SE 7900154W WO 8000248 A1 WO8000248 A1 WO 8000248A1
Authority
WO
WIPO (PCT)
Prior art keywords
potassium
slurry
plaster
calcium sulfate
potassium salt
Prior art date
Application number
PCT/SE1979/000154
Other languages
English (en)
French (fr)
Inventor
S Nordqvist
Original Assignee
Tenax Maskin Ab
S Nordqvist
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Tenax Maskin Ab, S Nordqvist filed Critical Tenax Maskin Ab
Priority to DE19792952945 priority Critical patent/DE2952945A1/de
Priority to IN35/CAL/80A priority patent/IN152205B/en
Publication of WO1980000248A1 publication Critical patent/WO1980000248A1/en
Priority to DK105780A priority patent/DK105780A/da

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/02—Sand moulds or like moulds for shaped castings
    • 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
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/14—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements
    • C04B28/141—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements containing dihydrated gypsum before the final hardening step, e.g. forming a dihydrated gypsum product followed by a de- and rehydration step

Definitions

  • a method of preparing gypsum articles This invention relates to a process for the prepara ⁇ tion of gypsum (plaster of Paris) articles, especially plaster board and moulds for the preparation of metallic and ceramic articles.
  • plaster products by suspending gypsum (calcium sulfate se ihydrate) in water, moulding the slurry to the desired product ' (desired shape) and solidifying (setting) this.
  • Various additives can be added to the prepared slurry of calcium sulfate semihydrate in water, such as accelerators, retardants and resins. The solidification is apparently due to the fact that the semihydrate is hydrated forming dihydrate (calcium sulfate dihydrate) .
  • the starting material of the gypsum product preparation i e calcium sulfate semihydrate (hemihydrate, half-hydrate)
  • it is started from calcium sulfate dihydrate (here also called dihydrate gypsum)
  • the content of water of crystallization being reduced by burning. This burning requires large amounts of energy and, moreover, must be carefully controlled so that a correct content of water of crystallization is obtained.
  • plaster (gypsum) products preferably plaster boards and moulds for the production
  • OMPI •, WIPO m . ⁇ of metal articles and ceramic articles can be produced by adding to a water slurry of calcium sulfate dihydrate (dihydrate gypsum) a potassium salt optionally in combina ⁇ tion with a carrier and then, in known manner, the product is moulded and further treated, the slurry being kept below 70 C. preferably below 55°C.
  • the potassium salt consists preferably of potassium hydrogencarbonate or potassium tetraborate but, in the first place, potassium sulfate.
  • the potassium salts can be used as such or mixed with each other, e.g. a mixture of potassium -sulfate and potassium hydrogencarbonate, and optionally dissolved in water or together with a carrier, e.g. sodium sulfate.
  • the density of the resulting plaster product can be adjusted by addition of various additives and through the mixing procedure (air being added) .
  • An addition of a wetting agent is suitable for this adjustment of the density.
  • potassium hydrogencarbonate a foam product is obtained and the expansion (the degree of blowing) can be adjusted by using potassium sulfate together with the potassium hydrogencarbonate, the propor ⁇ tions thereof being varied all according to the desired product.
  • the calcium sulfate dihydrate resulting as waste in the preparation of phosphate fertilizers is- preferably used.
  • This starting material shows usually an analysis of
  • Silicate about 2 % by weight
  • Heavy metals about 2 % by weight
  • starting materials can be used, e.g. dihydrate gypsum, which is obtained at purification of flue gas, and naturally occurring dihydrate gypsum. It is also possible to re-use as starting material the products obtained according to the present invention, which are then crushed and suspended in water.
  • the amount of potassium salt added, especially potassium sulfate can vary, the minimum amount being about 2 or 3 % by weight; 5-40 % , preferably 6-20 % _ calculated on the amount of calcium sulfate dihydrate (CaS0 4 -2 H O) have turned out to be suitable amounts. It has also been found that different agents can be admixed in the present starting slurry, plaster products being obtained with different modifications of the properties.
  • Such additives as create porosity e.g. of silicate type, are of special importance. These additives e.g. consist of perlite or ⁇ 'er iculite.
  • the resulting products e.g. boards or moulds, are heat insulating and have a good stiffness in flexing at a suitable thickness.
  • the potassium hydrogencarbonate is used according to the invention by itself for preparation of solidified, hard plaster foam products.
  • the potassium hydrogencarbonate is preferably used together with potassium sulfate and other of the indicated additives
  • a plaster product according to the invention which is not being provided with a surface layer in said manner can be immersed in or treated with a solution of e.g.
  • potassium sulfate or a borate such as potassium or sodium tetraborate, which increases the hardness and the strength.
  • the hardness can also be increased by using as additive an agent, e.g. a salt, influencing the solubility of the gypsum, such as sodium thiosulfate, methaphosphate and hexamethaphosphate.
  • An additive which has been found to provide surprisingly good plaster products mainly plaster board
  • spent sulfite liquor as additive, the surface layer adhesion, especially of cardboard, to the plaster board is improved to a very large extent.
  • the strength is also improved.
  • Another agent also improving the surface layer adhesion is corn starch.
  • 'Other additives can also be used, e.g. agents retarding the setting rate, such as soda, glycerol , alginate.
  • Other additives are sulfuric acid, hydrogen hexafluorosilicate, citric acid, ammonium carbonate (hartshorn), urea phosphate, ammonia. These agents are i.a. used for adjustment of pH.
  • plaster products very resistant to high temperatures are desired, it is suitable to admix magnesium oxide in the form of a powder.
  • the magnesium oxide can comprise up to 50 % by weight of the calcium sulfate dihydrate. It is also suitable to admix perlite.
  • the water content can also be varied, i.e. you can dilute the calcium sulfate dihydrate slurry with water, e.g. so that 70 % of the slurry consist of water, or admix various wetting agents.
  • the agents giving off gas and already described are used.
  • the process of the invention might also be considered to consist in a "solidification" of the calcium sulfate dihydrate, i.e. the included grains and the whole plaster product prepared will be harder.
  • the grain size of the potassium sulfate is of a certain importance, as the process is quicker the more fine granular the potassium sulfate is.
  • Potassium sulfate with a grain size of down to 70 has been tested and this grain size will provide about the same rate of solidification as an aqueous solution of potassium sulfate.
  • ⁇ - WIPO . sulfate when mixed are equivalent to potassium sulfate.
  • a solution of potassium chloride and a solution of magnesium sulfate can be used by adding them simultaneou ly, for instance.
  • the various indicated additives are usually used in an amount of 1-15 % by weight calculated on the included amount of calcium sulfate dihydrate.
  • the temperature of the water slurry shall be kept below 70 C all the time. In this way no substantial formation of calcium sulfate semihydrate is obtained even in the case where dehydrating agents as sulfuric acid, are present.
  • the temperature of the slurry should preferably be kept below 55 C, as e.g. below 45 C or 50°C, also during the drying and setting steps.
  • Example 1 50 kg K ⁇ SO. were added to 1000 kg slurry of dihydrate gypsum containing 20 % w ⁇ ater. Addition was carried out under vigorous stirring at 1400 rpm. The slurry was immediately cast to a board and cubic test bodies (5 cm x 5 cm x 5 cm) were made. The board having ambient temperature about 20 C solidified in a very short time (some minutes) . The test bodies showed a compression strength of 8 MPa after 24 h.
  • Example 2. 3600 kg of potassium sulfate in solid form were added to 3600 kg of a slurry of dihydrate gypsum under vigorous stirring, such as in example 1. Board and test bodies were prepared as in example 1. The density
  • OM strength of the test bodies was 4.1 MPa as determined after 96 h at 20°C or 48 h at 40°C.
  • Example 3 1000 kg of dihydrate gypsum of 72 % were mixed with 35 kg of ammonium hydrogencarbonate and 60 kg of potassium sulfate. The mixture was cast in plane slabs. After a setting period of 15-20 minutes at 13°C a board with good strength properties was obtained.
  • Example 5 1000 kg of.72 % dihydrate gypsum in the form of a slurry were mixed with 55 kg of potassium sulfate - having a grain size of 70 % less than 80 ' m. Slabs were prepared on a plaster board machine, solidified and dried by microwave radiation for 2 seconds repeated six times in a 4 minutes' period. The temperature of the slurry .was maximum about 44 C; locally it seemed as a slightly higher temperature temporarily was reached.
  • Example 6 A slurry of 72 % dihydrate gypsum containing 1.5 % spent sulfite liquor (dry substance) was continuously moulded to a "thickness of about 13 mm on a running web of paper board on a plaster board machine.
  • Potassium sulfate (7 % by weight based on dry dihydrate gypsum) was added to the -slurry during the moulding. It was in a fine granular form (80 passing a 70 urn mesh sieve) .
  • the moulded slabs were solidified and dried in a conventional way, the slurry having a maximum temperature of about 41°C. Wall board of about 13 mm ⁇ v'ith good strength properties was obtained.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Structural Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)
  • Mold Materials And Core Materials (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)
PCT/SE1979/000154 1978-07-13 1979-07-12 A method of preparing gypsum articles WO1980000248A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
DE19792952945 DE2952945A1 (de) 1978-07-13 1979-07-12 A method of preparing gypsum articles
IN35/CAL/80A IN152205B (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1978-07-13 1980-01-10
DK105780A DK105780A (da) 1978-07-13 1980-03-12 Fremgangsmaade til fremstilling af gipsgenstande

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE7807807 1978-07-13
SE7807807A SE426053C (sv) 1978-07-13 1978-07-13 Sett att framstella gipsprodukter

Publications (1)

Publication Number Publication Date
WO1980000248A1 true WO1980000248A1 (en) 1980-02-21

Family

ID=20335446

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1979/000154 WO1980000248A1 (en) 1978-07-13 1979-07-12 A method of preparing gypsum articles

Country Status (8)

Country Link
JP (1) JPS55500522A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
AU (1) AU528999B2 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
CA (1) CA1135291A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
DK (1) DK105780A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
FR (1) FR2430921A1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
GB (1) GB2047675B (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
SE (1) SE426053C (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
WO (1) WO1980000248A1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1981002010A1 (en) * 1980-01-09 1981-07-23 Tenax Maskin Ab Plaster products and a process for the production thereof

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU2020202788A1 (en) * 2020-04-27 2021-11-11 Pact Renewables Pty Ltd Mineral-based composites
US20230312417A1 (en) * 2020-06-25 2023-10-05 Pact Renewables Pty Ltd Degradable materials containing waste paper products

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE432542C (de) * 1924-04-15 1926-08-09 Morduch E Lewin Verfahren zur Herstellung einer zementaehnlichen Masse
DE1267160B (de) * 1964-03-27 1968-04-25 United States Gypsum Co Verfahren zur Herstellung von gegossenen Formkoerpern aus Gips
DE2324312A1 (de) * 1972-05-15 1973-11-29 Raytheon Co Verfahren zur herstellung von giessformen oder teilen davon aus gips-formmasse
US3841886A (en) * 1972-04-13 1974-10-15 Motus Chem Inc Refractory cement incorporating fluxing component
US4146402A (en) * 1977-03-23 1979-03-27 Mitsubishi Mining & Cement Company, Ltd. Process of producing fiber-reinforced hardened body of gypsum system

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5313629A (en) * 1976-07-23 1978-02-07 Mitsubishi Mining & Cement Co Gypsum series setting material production method
JPS53119918A (en) * 1977-03-28 1978-10-19 Chichibu Cement Kk Light weight hardened body and its manufacture

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE432542C (de) * 1924-04-15 1926-08-09 Morduch E Lewin Verfahren zur Herstellung einer zementaehnlichen Masse
DE1267160B (de) * 1964-03-27 1968-04-25 United States Gypsum Co Verfahren zur Herstellung von gegossenen Formkoerpern aus Gips
US3841886A (en) * 1972-04-13 1974-10-15 Motus Chem Inc Refractory cement incorporating fluxing component
DE2324312A1 (de) * 1972-05-15 1973-11-29 Raytheon Co Verfahren zur herstellung von giessformen oder teilen davon aus gips-formmasse
US4146402A (en) * 1977-03-23 1979-03-27 Mitsubishi Mining & Cement Company, Ltd. Process of producing fiber-reinforced hardened body of gypsum system

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Swedish Ceramic Society, Course concerning plaster and moulds for ceramic industry, Gothenburg 1973, September 17 - 18, Lecture 4, in particular pages 2 - 4 and 11 12 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1981002010A1 (en) * 1980-01-09 1981-07-23 Tenax Maskin Ab Plaster products and a process for the production thereof

Also Published As

Publication number Publication date
CA1135291A (en) 1982-11-09
JPS55500522A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1980-08-14
SE7807807L (sv) 1980-01-14
AU4887979A (en) 1980-01-17
SE426053B (sv) 1982-12-06
DK105780A (da) 1980-03-12
SE426053C (sv) 1985-09-09
FR2430921B1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1984-12-21
GB2047675B (en) 1984-02-29
AU528999B2 (en) 1983-05-19
FR2430921A1 (fr) 1980-02-08
GB2047675A (en) 1980-12-03

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