Method for reducing water in a gypsum slurry
A method for reducing the water-to-stucco ratio of a gypsum slurry (0.1 – 0.9 range) by pairing a polycarboxylate-family dispersant with a defoamer, so that the foam-bubble distribution is preserved while flow is recovered at lower water.
- Assignee
- United States Gypsum Co
- Inventors
- James R. Wittbold, Bruce Lynn Petersen, Alfred Li
- Jurisdiction
- European Patent Office
- Filed
- 2007-08-17
- Published
- 2020-04-08
- Priority
- 2008-08-05
Every kilogram of water added to the slurry is a kilogram of water the kiln has to remove. Water reduction is therefore the single largest energy lever on a board line. Dispersants make slurries flow at less water, but they also change the way soap-generated bubbles behave — leaving you with a lighter slurry that has the wrong void distribution.
This patent addresses that side-effect head on: it pairs the dispersant with a defoamer, tuned so that the finished bubble population is what the plant actually wants.
- 01The slurry is prepared in a mixer with water, calcined gypsum, a defoamer and a dispersant.
- 02The dispersant belongs to a polycarboxylate-type polymer: two repeating units, one an olefinic unsaturated mono-carboxylic acid (or its ester or salt) or an olefinic unsaturated sulphuric acid unit (or its salt), and the second unit defined by a general formula referenced in the claim.
- 03The defoamer collapses the unwanted micro-foam that the dispersant would otherwise stabilise, leaving the intentional foam-void population intact.
- 04The overall water-to-stucco ratio window is defined between 0.1 and 0.9 by weight of dry stucco.
| Parameter | Value | Source |
|---|---|---|
| Water-to-stucco (W/S) window | 0.1 – 0.9 by weight of dry stucco | claim 1 |
| Dispersant chemistry | polymer with an unsaturated carboxylic/sulphuric first unit + a second unit of general formula (I) | claim 1 |
| Companion additive | defoamer (to control the bubble distribution) | claim 1 |
- 01This is one of the cleanest references for justifying a PCE-family dispersant trial to a plant manager whose comfort zone is naphthalenesulfonate.
- 02A defoamer trial should never be run in isolation — this claim treats defoamer and dispersant as one combined system.
- 03Any water-reduction gain has to be re-validated in the kiln: less free water changes both drying curve and calcination state at the exit.
This invention relates to a foamed gypsum slurry. More specifically, it relates to a foamed gypsum slurry that includes a defoamer to produce a distribution of foam bubbles. The gypsum slurry is useful for making building panels.
A method of reducing water in a gypsum slurry with the water to stucco ratio from 0,1 to 0,9, based on dry weight of the stucco, comprising: preparing a gypsum slurry by mixing in a mixer a mixture comprising water, calcined gypsum, a defoamer and a dispersant, wherein the dispersant consists essentially of a first and a second repeating unit, wherein said first repeating unit is an olefinic unsaturated mono-carboxylic acid repeating unit or an ester or salt thereof, or an olefinic unsaturated sulphuric acid repeating unit or a salt thereof, and said second repeating unit is of the general formula (I) […]
Further claims, drawings, prosecution history and legal status: see the official record.
- [1]EP 2 190 797 B1 — Method for reducing water in a gypsum slurry — Google Patents · 2020-04-08