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Modifiers for gypsum slurries and method of using them

a technology of gypsum and slurries, which is applied in the field of improving gypsum products, can solve the problems that polycarboxylate dispersants are often one of the most expensive components of products, and achieve the effects of improving the efficacy of dispersants, reducing the amount of water used, and reducing the dosage of dispersants

Inactive Publication Date: 2006-12-14
UNITED STATES GYPSUM CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0018] Lowering the concentration of the dispersant also minimizes the disadvantageous effects of the polycarboxylate dispersant. At a lower dose, there is less retardation of the setting reactions. Less set accelerator would be needed in the product to overcome the effects of set retardation, reducing the price paid for the accelerator.
[0019] Instead of or in addition to reducing the dispersant dosage, the improved efficacy of the dispersant can also be used to reduce the amount of water used to make the gypsum slurry. The manufacturing process can be made more fuel efficient, conserving fossil fuels and realizing the cost savings. Fuel savings can be based on either reduced kiln temperatures or shorter residence time in the kiln.

Problems solved by technology

Polycarboxylate dispersants are often one of the most expensive components in products that use them.

Method used

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  • Modifiers for gypsum slurries and method of using them
  • Modifiers for gypsum slurries and method of using them
  • Modifiers for gypsum slurries and method of using them

Examples

Experimental program
Comparison scheme
Effect test

example i

[0064] Tests were conducted to determine the effect of the addition of potassium carbonate on two different dispersants. In each of the following samples, a gypsum slurry was made from 400 grams of stucco from Southard, Okla., 180 grams of water and 0.2% dispersant based on the dry weight of the stucco. The dispersant type and amount of potassium carbonate are shown in Table I below, together with the results of the patty size and the stiffening rate tests.

TABLE IPotassiumStiffeningDispersantCarbonate, gPatty Size, cmTime2110.630.36:002110.019.82:05Melflux 2500L0.626.010:30 Melflux 2500L0.015.52:35

[0065] As is seen in the data in Table I above, the addition of potassium carbonate increases the slurry fluidity as evidenced by the increase patty size. The modifier addition also retarded the stiffening time compared to the samples where no potassium carbonate was used.

example 2

[0066] Tests were run to determine the effect of lime on dispersant MELFLUX 2500L with two different stuccos.

TABLE IIWater to Stucco Ratio at GivenDispersant DoseStuccoLime0.0%0.05%0.11%0.22%Shoals00.650.640.580.50Shoals0.25%0.680.610.520.41Galena00.600.530.450.39Galena0.25%0.640.500.390.30

[0067] Tests presented above show that lime is an effective modifer with stuccos from Shoals and Galena Park.

example 3

[0068] Soda ash was tested in the laboratory for suitability as a modifier. The amount of water listed in Table III, the water demand, was added to 50 cc of board stucco, a beta-calcined hemihydrate. This amount of water was selected to produce a standard 3-¾″ patty when the stucco, dispersant, modifier and water were combined. The dispersant was added at the rate of 1.5# / MSF on a solids basis as if it were being added to the slurry for a ½″ wallboard. The dispersant was a PCE211, two-repeating unit dispersant, identified as PCE49.

[0069] Sodium carbonate was added at the concentrations shown in Table III, ranging from none to 0.6% by weight based on the weight of the dry stucco. The water demand and the set time are shown in Table III.

TABLE IIINa2CO3cc Water AddedSet Time 0.0%52170.05%47170.10%45170.20%45150.40%47110.60%5011

[0070] Up to and including, 0.2%, the amount of water needed to make a patty of standard diameter decreases as the amount of the modifier increases. At 0.40% ...

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Abstract

An improved gypsum slurry that includes water, calcium sulfate hemihydrate, a polycarboxylate dispersant and a modifier. The modifier is chemically configured to improve the efficacy of the polycarboxylate dispersant. Preferred modifiers include cement, lime, slaked lime, soda ash, carbonates, silicates and phosphates.

Description

CROSS REFERENCES TO RELATED APPLICATIONS [0001] This application is related to co-pending U.S. Ser. No. 11 / ______ (Attorney Ref. No. 2033.72380), entitled “Fast Drying Wallboard”, U.S. Ser. No. 11 / ______ (Attorney Ref. 2033.72699), entitled “High Strength Flooring Compositions”, U.S. Ser. No. 11 / ______ (Attorney Ref. No. 2033.72740), entitled “Gypsum Products Utilizing a Two-Repeating Unit System and Process for Making Them”; U.S. Ser. No. 11 / ______ (Attorney Ref. No. 2033.73064), entitled “Method of Making a Gypsum Slurry with Modifiers and Dispersants” and U.S. Ser. No. 11 / ______ (Attorney Ref. No. 2033.73130), entitled, “Effective Use of Dispersants in Wallboard Containing Foam”, all filed concurrently herewith and all hereby incorporated by reference.BACKGROUND [0002] This invention relates to improved gypsum products. More specifically, it relates to an improved gypsum slurry that is flowable at low water concentrations, with less expense and less retardive effects of using car...

Claims

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Application Information

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IPC IPC(8): C04B28/14C04B11/00B32B1/04
CPCC04B28/14Y10T428/232C04B14/04C04B22/064C04B22/10C04B22/16C04B24/003C04B24/2641C04B2103/408
Inventor LETTKEMAN, DENNIS M.SHAKE, MICHAEL P.LIU, QINGXIAWILSON, JOHN W.RANDALL, BRIAN S.BLACKBURN, DAVID R.
Owner UNITED STATES GYPSUM CO
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